[PATCH v15 00/14] Introduce Data Access MONitor (DAMON)

[PATCH v15 00/14] Introduce Data Access MONitor (DAMON)

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

Introduction
============

DAMON is a data access monitoring framework subsystem for the Linux kernel.
The core mechanisms of DAMON called 'region based sampling' and 'adaptive
regions adjustment' (refer to 'mechanisms.rst' in the 11th patch of this
patchset for the detail) make it

 - accurate (The monitored information is useful for DRAM level memory
   management. It might not appropriate for Cache-level accuracy, though.),
 - light-weight (The monitoring overhead is low enough to be applied online
   while making no impact on the performance of the target workloads.), and
 - scalable (the upper-bound of the instrumentation overhead is controllable
   regardless of the size of target workloads.).

Using this framework, therefore, the kernel's core memory management mechanisms
such as reclamation and THP can be optimized for better memory management.  The
experimental memory management optimization works that incurring high
instrumentation overhead will be able to have another try.  In user space,
meanwhile, users who have some special workloads will be able to write
personalized tools or applications for deeper understanding and specialized
optimizations of their systems.

Evaluations
===========

We evaluated DAMON's overhead, monitoring quality and usefulness using 25
realistic workloads on my QEMU/KVM based virtual machine running a kernel that
v13 DAMON patchset is applied.

DAMON is lightweight.  It increases system memory usage by only -0.39% and
consumes less than 1% CPU time in most case.  It slows target workloads down by
only 0.63%.

DAMON is accurate and useful for memory management optimizations.  An
experimental DAMON-based operation scheme for THP, 'ethp', removes 69.43% of
THP memory overheads while preserving 37.11% of THP speedup.  Another
experimental DAMON-based 'proactive reclamation' implementation, 'prcl',
reduces 89.30% of residential sets and 22.40% of system memory footprint while
incurring only 1.98% runtime overhead in the best case (parsec3/freqmine).

NOTE that the experimentail THP optimization and proactive reclamation are not
for production, just only for proof of concepts.

Please refer to the official document[1] or "Documentation/admin-guide/mm: Add
a document for DAMON" patch in this patchset for detailed evaluation setup and
results.

[1] https://damonitor.github.io/doc/html/latest-damon

More Information
================

We prepared a showcase web site[1] that you can get more information.  There
are

- the official documentations[2],
- the heatmap format dynamic access pattern of various realistic workloads for
  heap area[3], mmap()-ed area[4], and stack[5] area,
- the dynamic working set size distribution[6] and chronological working set
  size changes[7], and
- the latest performance test results[8].

[1] https://damonitor.github.io/_index
[2] https://damonitor.github.io/doc/html/latest-damon
[3] https://damonitor.github.io/test/result/visual/latest/heatmap.0.html
[4] https://damonitor.github.io/test/result/visual/latest/heatmap.1.html
[5] https://damonitor.github.io/test/result/visual/latest/heatmap.2.html
[6] https://damonitor.github.io/test/result/visual/latest/wss_sz.html
[7] https://damonitor.github.io/test/result/visual/latest/wss_time.html
[8] https://damonitor.github.io/test/result/perf/latest/html/index.html

Baseline and Complete Git Trees
===============================

The patches are based on the v5.7.  You can also clone the complete git
tree:

    $ git clone git://github.com/sjp38/linux -b damon/patches/v15

The web is also available:
https://github.com/sjp38/linux/releases/tag/damon/patches/v15

There are a couple of trees for entire DAMON patchset series.  It includes
future features.  The first one[1] contains the changes for latest release,
while the other one[2] contains the changes for next release.

[1] https://github.com/sjp38/linux/tree/damon/master
[2] https://github.com/sjp38/linux/tree/damon/next

Sequence Of Patches
===================

The 1st patch exports 'lookup_page_ext()' to GPL modules so that it can be used
by DAMON even though it is built as a loadable module.

Next four patches implement the core of DAMON and it's programming interface.
The 2nd patch introduces DAMON module, it's data structures, and data structure
related common functions.  Following three patches (3rd to 5th) implements the
core mechanisms of DAMON, namely regions based sampling (patch 3), adaptive
regions adjustment (patch 4), and dynamic memory mapping chage adoption
(patch 5).

Following four patches are for low level users of DAMON.  The 6th patch
implements callbacks for each of monitoring steps so that users can do whatever
they want with the access patterns.  The 7th one implements recording of access
patterns in DAMON for better convenience and efficiency.  Each of next two
patches (8th and 9th) respectively adds a debugfs interface for privileged
people and/or programs in user space, and a tracepoint for other tracepoints
supporting tracers such as perf.

Two patches for high level users of DAMON follows.  To provide a minimal
reference to the debugfs interface and for high level use/tests of the DAMON,
the next patch (10th) implements an user space tool.  The 11th patch adds a
document for administrators of DAMON.

Next two patches are for tests.  The 12th patch provides unit tests (based on
the kunit) while the 13th patch adds user space tests (based on the kselftest).

Finally, the last patch (14th) updates the MAINTAINERS file.

Patch History
=============

Changes from v14
(https://lore.kernel.org/linux-mm/20200602130125.20467-1-sjpark@amazon.com/)
 - Directly pass region and task to tracepoint (Steven Rostedt)
 - Refine comments for better read
 - Add more 'Reviewed-by's (Leonard Foerster, Brendan Higgins)

Changes from v13
(https://lore.kernel.org/linux-mm/20200525091512.30391-1-sjpark@amazon.com/)
 - Fix a typo (Leonard Foerster)
 - Fix wring condition of three sub ranges split (Leonard Foerster)
 - Rebase on v5.7

Changes from v12
(https://lore.kernel.org/linux-mm/20200518100018.2293-1-sjpark@amazon.com/)
 - Avoid races between debugfs readers and writers
 - Add kernel-doc comments in damon.h

Changes from v11
(https://lore.kernel.org/linux-mm/20200511123302.12520-1-sjpark@amazon.com/)
 - Rewrite the document (Stefan Nuernberger)
 - Make 'damon_for_each_*' argument order consistent (Leonard Foerster)
 - Fix wrong comment in 'kdamond_merge_regions()' (Leonard Foerster)

Changes from v10
(https://lore.kernel.org/linux-mm/20200505110815.10532-1-sjpark@amazon.com/)
 - Reduce aggressive split overhead by doing it only if required

Changes from v9
(https://lore.kernel.org/linux-mm/20200427120442.24179-1-sjpark@amazon.com/)
 - Split each region into 4 subregions if possible (Jonathan Cameraon)
 - Update kunit test for the split code change

Changes from v8
(https://lore.kernel.org/linux-mm/20200406130938.14066-1-sjpark@amazon.com/)
 - Make regions always aligned by minimal region size that can be changed
   (Stefan Nuernberger)
 - Store binary format version in the recording file (Stefan Nuernberger)
 - Use 'int' for pid instead of 'unsigned long' (Stefan Nuernberger)
 - Fix a race condition in damon thread termination (Stefan Nuernberger)
 - Optimize random value generation and recording (Stefan Nuernberger)
 - Clean up commit messages and comments (Stefan Nuernberger)
 - Clean up code (Stefan Nuernberger)
 - Use explicit signalling and 'do_exit()' for damon thread termination 
 - Add more typos to spelling.txt
 - Update the performance evaluation results
 - Describe future plans in the cover letter

Please refer to the v8 patchset to get older history.

SeongJae Park (14):
  mm/page_ext: Export lookup_page_ext() to GPL modules
  mm: Introduce Data Access MONitor (DAMON)
  mm/damon: Implement region based sampling
  mm/damon: Adaptively adjust regions
  mm/damon: Apply dynamic memory mapping changes
  mm/damon: Implement callbacks
  mm/damon: Implement access pattern recording
  mm/damon: Add debugfs interface
  mm/damon: Add tracepoints
  tools: Add a minimal user-space tool for DAMON
  Documentation/admin-guide/mm: Add a document for DAMON
  mm/damon: Add kunit tests
  mm/damon: Add user space selftests
  MAINTAINERS: Update for DAMON

 Documentation/admin-guide/mm/damon/api.rst    |   20 +
 .../admin-guide/mm/damon/damon_heatmap.png    |  Bin 0 -> 8366 bytes
 .../admin-guide/mm/damon/damon_wss_change.png |  Bin 0 -> 7211 bytes
 .../admin-guide/mm/damon/damon_wss_dist.png   |  Bin 0 -> 6173 bytes
 Documentation/admin-guide/mm/damon/eval.rst   |  215 +++
 Documentation/admin-guide/mm/damon/faq.rst    |   46 +
 .../admin-guide/mm/damon/freqmine_heatmap.png |  Bin 0 -> 8687 bytes
 .../admin-guide/mm/damon/freqmine_wss_sz.png  |  Bin 0 -> 4986 bytes
 .../mm/damon/freqmine_wss_time.png            |  Bin 0 -> 6283 bytes
 Documentation/admin-guide/mm/damon/guide.rst  |  196 +++
 Documentation/admin-guide/mm/damon/index.rst  |   36 +
 .../admin-guide/mm/damon/mechanisms.rst       |  111 ++
 Documentation/admin-guide/mm/damon/plans.rst  |   49 +
 Documentation/admin-guide/mm/damon/start.rst  |  119 ++
 .../mm/damon/streamcluster_heatmap.png        |  Bin 0 -> 37916 bytes
 .../mm/damon/streamcluster_wss_sz.png         |  Bin 0 -> 5522 bytes
 .../mm/damon/streamcluster_wss_time.png       |  Bin 0 -> 6322 bytes
 Documentation/admin-guide/mm/damon/usage.rst  |  305 ++++
 Documentation/admin-guide/mm/index.rst        |    1 +
 MAINTAINERS                                   |   12 +
 include/linux/damon.h                         |  136 ++
 include/trace/events/damon.h                  |   43 +
 mm/Kconfig                                    |   23 +
 mm/Makefile                                   |    1 +
 mm/damon-test.h                               |  635 +++++++
 mm/damon.c                                    | 1554 +++++++++++++++++
 mm/page_ext.c                                 |    1 +
 tools/damon/.gitignore                        |    1 +
 tools/damon/_dist.py                          |   36 +
 tools/damon/_recfile.py                       |   23 +
 tools/damon/bin2txt.py                        |   67 +
 tools/damon/damo                              |   37 +
 tools/damon/heats.py                          |  362 ++++
 tools/damon/nr_regions.py                     |   91 +
 tools/damon/record.py                         |  217 +++
 tools/damon/report.py                         |   45 +
 tools/damon/wss.py                            |   97 +
 tools/testing/selftests/damon/Makefile        |    7 +
 .../selftests/damon/_chk_dependency.sh        |   28 +
 tools/testing/selftests/damon/_chk_record.py  |  108 ++
 .../testing/selftests/damon/debugfs_attrs.sh  |  139 ++
 .../testing/selftests/damon/debugfs_record.sh |   50 +
 42 files changed, 4811 insertions(+)
 create mode 100644 Documentation/admin-guide/mm/damon/api.rst
 create mode 100644 Documentation/admin-guide/mm/damon/damon_heatmap.png
 create mode 100644 Documentation/admin-guide/mm/damon/damon_wss_change.png
 create mode 100644 Documentation/admin-guide/mm/damon/damon_wss_dist.png
 create mode 100644 Documentation/admin-guide/mm/damon/eval.rst
 create mode 100644 Documentation/admin-guide/mm/damon/faq.rst
 create mode 100644 Documentation/admin-guide/mm/damon/freqmine_heatmap.png
 create mode 100644 Documentation/admin-guide/mm/damon/freqmine_wss_sz.png
 create mode 100644 Documentation/admin-guide/mm/damon/freqmine_wss_time.png
 create mode 100644 Documentation/admin-guide/mm/damon/guide.rst
 create mode 100644 Documentation/admin-guide/mm/damon/index.rst
 create mode 100644 Documentation/admin-guide/mm/damon/mechanisms.rst
 create mode 100644 Documentation/admin-guide/mm/damon/plans.rst
 create mode 100644 Documentation/admin-guide/mm/damon/start.rst
 create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_heatmap.png
 create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_wss_sz.png
 create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_wss_time.png
 create mode 100644 Documentation/admin-guide/mm/damon/usage.rst
 create mode 100644 include/linux/damon.h
 create mode 100644 include/trace/events/damon.h
 create mode 100644 mm/damon-test.h
 create mode 100644 mm/damon.c
 create mode 100644 tools/damon/.gitignore
 create mode 100644 tools/damon/_dist.py
 create mode 100644 tools/damon/_recfile.py
 create mode 100644 tools/damon/bin2txt.py
 create mode 100755 tools/damon/damo
 create mode 100644 tools/damon/heats.py
 create mode 100644 tools/damon/nr_regions.py
 create mode 100644 tools/damon/record.py
 create mode 100644 tools/damon/report.py
 create mode 100644 tools/damon/wss.py
 create mode 100644 tools/testing/selftests/damon/Makefile
 create mode 100644 tools/testing/selftests/damon/_chk_dependency.sh
 create mode 100644 tools/testing/selftests/damon/_chk_record.py
 create mode 100755 tools/testing/selftests/damon/debugfs_attrs.sh
 create mode 100755 tools/testing/selftests/damon/debugfs_record.sh

-- 
2.17.1

[PATCH v15 01/14] mm/page_ext: Export lookup_page_ext() to GPL modules

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit exports 'lookup_page_ext()' to GPL modules.  This will be
used by DAMON.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 mm/page_ext.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/page_ext.c b/mm/page_ext.c
index a3616f7a0e9e..9d802d01fcb5 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -131,6 +131,7 @@ struct page_ext *lookup_page_ext(const struct page *page)
 					MAX_ORDER_NR_PAGES);
 	return get_entry(base, index);
 }
+EXPORT_SYMBOL_GPL(lookup_page_ext);
 
 static int __init alloc_node_page_ext(int nid)
 {
-- 
2.17.1

[PATCH v15 02/14] mm: Introduce Data Access MONitor (DAMON)

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit introduces a kernel module named DAMON.  Note that this
commit is implementing only the stub for the module load/unload, basic
data structures, and simple manipulation functions of the structures to
keep the size of commit small.  The core mechanisms of DAMON will be
implemented one by one by following commits.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 include/linux/damon.h |  54 ++++++++++++
 mm/Kconfig            |  12 +++
 mm/Makefile           |   1 +
 mm/damon.c            | 188 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 255 insertions(+)
 create mode 100644 include/linux/damon.h
 create mode 100644 mm/damon.c

diff --git a/include/linux/damon.h b/include/linux/damon.h
new file mode 100644
index 000000000000..135633334929
--- /dev/null
+++ b/include/linux/damon.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * DAMON api
+ *
+ * Copyright 2019-2020 Amazon.com, Inc. or its affiliates.
+ *
+ * Author: SeongJae Park <sjpark@amazon.de>
+ */
+
+#ifndef _DAMON_H_
+#define _DAMON_H_
+
+#include <linux/random.h>
+#include <linux/types.h>
+
+/**
+ * struct damon_region - Represents a monitoring target region of
+ * [@vm_start, @vm_end).
+ *
+ * @vm_start:		Start address of the region (inclusive).
+ * @vm_end:		End address of the region (exclusive).
+ * @sampling_addr:	Address of the sample for the next access check.
+ * @nr_accesses:	Access frequency of this region.
+ * @list:		List head for siblings.
+ */
+struct damon_region {
+	unsigned long vm_start;
+	unsigned long vm_end;
+	unsigned long sampling_addr;
+	unsigned int nr_accesses;
+	struct list_head list;
+};
+
+/**
+ * struct damon_task - Represents a monitoring target task.
+ * @pid:		Process id of the task.
+ * @regions_list:	Head of the monitoring target regions of this task.
+ * @list:		List head for siblings.
+ */
+struct damon_task {
+	int pid;
+	struct list_head regions_list;
+	struct list_head list;
+};
+
+/**
+ * struct damon_ctx - Represents a context for each monitoring.
+ * @tasks_list:		Head of monitoring target tasks (&damon_task) list.
+ */
+struct damon_ctx {
+	struct list_head tasks_list;	/* 'damon_task' objects */
+};
+
+#endif
diff --git a/mm/Kconfig b/mm/Kconfig
index c1acc34c1c35..ecea0889ea35 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -867,4 +867,16 @@ config ARCH_HAS_HUGEPD
 config MAPPING_DIRTY_HELPERS
         bool
 
+config DAMON
+	tristate "Data Access Monitor"
+	depends on MMU
+	help
+	  Provides data access monitoring.
+
+	  DAMON is a kernel module that allows users to monitor the actual
+	  memory access pattern of specific user-space processes.  It aims to
+	  be 1) accurate enough to be useful for performance-centric domains,
+	  and 2) sufficiently light-weight so that it can be applied online.
+	  If unsure, say N.
+
 endmenu
diff --git a/mm/Makefile b/mm/Makefile
index fccd3756b25f..230e545b6e07 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -112,3 +112,4 @@ obj-$(CONFIG_MEMFD_CREATE) += memfd.o
 obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o
 obj-$(CONFIG_PTDUMP_CORE) += ptdump.o
 obj-$(CONFIG_PAGE_REPORTING) += page_reporting.o
+obj-$(CONFIG_DAMON) += damon.o
diff --git a/mm/damon.c b/mm/damon.c
new file mode 100644
index 000000000000..170e8a694dbe
--- /dev/null
+++ b/mm/damon.c
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Data Access Monitor
+ *
+ * Copyright 2019-2020 Amazon.com, Inc. or its affiliates.
+ *
+ * Author: SeongJae Park <sjpark@amazon.de>
+ *
+ * This file is constructed in below parts.
+ *
+ * - Functions and macros for DAMON data structures
+ * - Functions for the module loading/unloading
+ *
+ * The core parts are not implemented yet.
+ */
+
+#define pr_fmt(fmt) "damon: " fmt
+
+#include <linux/damon.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+/*
+ * Functions and macros for DAMON data structures
+ */
+
+#define damon_get_task_struct(t) \
+	(get_pid_task(find_vpid(t->pid), PIDTYPE_PID))
+
+#define damon_next_region(r) \
+	(container_of(r->list.next, struct damon_region, list))
+
+#define damon_prev_region(r) \
+	(container_of(r->list.prev, struct damon_region, list))
+
+#define damon_for_each_region(r, t) \
+	list_for_each_entry(r, &t->regions_list, list)
+
+#define damon_for_each_region_safe(r, next, t) \
+	list_for_each_entry_safe(r, next, &t->regions_list, list)
+
+#define damon_for_each_task(t, ctx) \
+	list_for_each_entry(t, &(ctx)->tasks_list, list)
+
+#define damon_for_each_task_safe(t, next, ctx) \
+	list_for_each_entry_safe(t, next, &(ctx)->tasks_list, list)
+
+/* Get a random number in [l, r) */
+#define damon_rand(l, r) (l + prandom_u32() % (r - l))
+
+/*
+ * Construct a damon_region struct
+ *
+ * Returns the pointer to the new struct if success, or NULL otherwise
+ */
+static struct damon_region *damon_new_region(struct damon_ctx *ctx,
+				unsigned long vm_start, unsigned long vm_end)
+{
+	struct damon_region *region;
+
+	region = kmalloc(sizeof(*region), GFP_KERNEL);
+	if (!region)
+		return NULL;
+
+	region->vm_start = vm_start;
+	region->vm_end = vm_end;
+	region->nr_accesses = 0;
+	INIT_LIST_HEAD(&region->list);
+
+	return region;
+}
+
+/*
+ * Add a region between two other regions
+ */
+static inline void damon_insert_region(struct damon_region *r,
+		struct damon_region *prev, struct damon_region *next)
+{
+	__list_add(&r->list, &prev->list, &next->list);
+}
+
+static void damon_add_region(struct damon_region *r, struct damon_task *t)
+{
+	list_add_tail(&r->list, &t->regions_list);
+}
+
+static void damon_del_region(struct damon_region *r)
+{
+	list_del(&r->list);
+}
+
+static void damon_free_region(struct damon_region *r)
+{
+	kfree(r);
+}
+
+static void damon_destroy_region(struct damon_region *r)
+{
+	damon_del_region(r);
+	damon_free_region(r);
+}
+
+/*
+ * Construct a damon_task struct
+ *
+ * Returns the pointer to the new struct if success, or NULL otherwise
+ */
+static struct damon_task *damon_new_task(int pid)
+{
+	struct damon_task *t;
+
+	t = kmalloc(sizeof(*t), GFP_KERNEL);
+	if (!t)
+		return NULL;
+
+	t->pid = pid;
+	INIT_LIST_HEAD(&t->regions_list);
+
+	return t;
+}
+
+static void damon_add_task(struct damon_ctx *ctx, struct damon_task *t)
+{
+	list_add_tail(&t->list, &ctx->tasks_list);
+}
+
+static void damon_del_task(struct damon_task *t)
+{
+	list_del(&t->list);
+}
+
+static void damon_free_task(struct damon_task *t)
+{
+	struct damon_region *r, *next;
+
+	damon_for_each_region_safe(r, next, t)
+		damon_free_region(r);
+	kfree(t);
+}
+
+static void damon_destroy_task(struct damon_task *t)
+{
+	damon_del_task(t);
+	damon_free_task(t);
+}
+
+static unsigned int nr_damon_tasks(struct damon_ctx *ctx)
+{
+	struct damon_task *t;
+	unsigned int nr_tasks = 0;
+
+	damon_for_each_task(t, ctx)
+		nr_tasks++;
+
+	return nr_tasks;
+}
+
+static unsigned int nr_damon_regions(struct damon_task *t)
+{
+	struct damon_region *r;
+	unsigned int nr_regions = 0;
+
+	damon_for_each_region(r, t)
+		nr_regions++;
+
+	return nr_regions;
+}
+
+/*
+ * Functions for the module loading/unloading
+ */
+
+static int __init damon_init(void)
+{
+	return 0;
+}
+
+static void __exit damon_exit(void)
+{
+}
+
+module_init(damon_init);
+module_exit(damon_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("SeongJae Park <sjpark@amazon.de>");
+MODULE_DESCRIPTION("DAMON: Data Access MONitor");
-- 
2.17.1

[PATCH v15 03/14] mm/damon: Implement region based sampling

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit implements DAMON's basic access check and region based
sampling mechanisms.  This change would seems make no sense, mainly
because it is only a part of the DAMON's logics.  Following two commits
will make more sense.

Basic Access Check
------------------

DAMON basically reports what pages are how frequently accessed.  Note
that the frequency is not an absolute number of accesses, but a relative
frequency among the pages of the target workloads.

Users can control the resolution of the reports by setting two time
intervals, ``sampling interval`` and ``aggregation interval``.  In
detail, DAMON checks access to each page per ``sampling interval``,
aggregates the results (counts the number of the accesses to each page),
and reports the aggregated results per ``aggregation interval``.  For
the access check of each page, DAMON uses the Accessed bits of PTEs.

This is thus similar to common periodic access checks based access
tracking mechanisms, which overhead is increasing as the size of the
target process grows.

Region Based Sampling
---------------------

To avoid the unbounded increase of the overhead, DAMON groups a number
of adjacent pages that assumed to have same access frequencies into a
region.  As long as the assumption (pages in a region have same access
frequencies) is kept, only one page in the region is required to be
checked.  Thus, for each ``sampling interval``, DAMON randomly picks one
page in each region and clears its Accessed bit.  After one more
``sampling interval``, DAMON reads the Accessed bit of the page and
increases the access frequency of the region if the bit has set
meanwhile.  Therefore, the monitoring overhead is controllable by
setting the number of regions.

Nonetheless, this scheme cannot preserve the quality of the output if
the assumption is not kept.  Following commit will introduce how we can
make the guarantee with best effort.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 include/linux/damon.h |  48 +++-
 mm/damon.c            | 615 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 660 insertions(+), 3 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 135633334929..f0fe4520a4e9 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -11,6 +11,8 @@
 #define _DAMON_H_
 
 #include <linux/random.h>
+#include <linux/mutex.h>
+#include <linux/time64.h>
 #include <linux/types.h>
 
 /**
@@ -44,11 +46,55 @@ struct damon_task {
 };
 
 /**
- * struct damon_ctx - Represents a context for each monitoring.
+ * struct damon_ctx - Represents a context for each monitoring.  This is the
+ * main interface that allows users to set the attributes and get the results
+ * of the monitoring.
+ *
+ * For each monitoring request (damon_start()), a kernel thread for the
+ * monitoring is created.  The pointer to the thread is stored in @kdamond.
+ *
+ * @sample_interval:		The time between access samplings.
+ * @aggr_interval:		The time between monitor results aggregations.
+ * @min_nr_regions:		The number of initial monitoring regions.
+ *
+ * For each @sample_interval, DAMON checks whether each region is accessed or
+ * not.  It aggregates and keeps the access information (number of accesses to
+ * each region) for @aggr_interval time.  All time intervals are in
+ * micro-seconds.
+ *
+ * @kdamond:		Kernel thread who does the monitoring.
+ * @kdamond_stop:	Notifies whether kdamond should stop.
+ * @kdamond_lock:	Mutex for the synchronizations with @kdamond.
+ *
+ * The monitoring thread sets @kdamond to NULL when it terminates.  Therefore,
+ * users can know whether the monitoring is ongoing or terminated by reading
+ * @kdamond.  Also, users can ask @kdamond to be terminated by writing non-zero
+ * to @kdamond_stop.  Reads and writes to @kdamond and @kdamond_stop from
+ * outside of the monitoring thread must be protected by @kdamond_lock.
+ *
+ * Note that the monitoring thread protects only @kdamond and @kdamond_stop via
+ * @kdamond_lock.  Accesses to other fields must be protected by themselves.
+ *
  * @tasks_list:		Head of monitoring target tasks (&damon_task) list.
  */
 struct damon_ctx {
+	unsigned long sample_interval;
+	unsigned long aggr_interval;
+	unsigned long min_nr_regions;
+
+	struct timespec64 last_aggregation;
+
+	struct task_struct *kdamond;
+	bool kdamond_stop;
+	struct mutex kdamond_lock;
+
 	struct list_head tasks_list;	/* 'damon_task' objects */
 };
 
+int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
+int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
+		unsigned long aggr_int, unsigned long min_nr_reg);
+int damon_start(struct damon_ctx *ctx);
+int damon_stop(struct damon_ctx *ctx);
+
 #endif
diff --git a/mm/damon.c b/mm/damon.c
index 170e8a694dbe..fa14ff7dd31a 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -9,18 +9,29 @@
  * This file is constructed in below parts.
  *
  * - Functions and macros for DAMON data structures
+ * - Functions for the initial monitoring target regions construction
+ * - Functions for the access checking of the regions
+ * - Functions for DAMON core logics and features
+ * - Functions for the DAMON programming interface
  * - Functions for the module loading/unloading
- *
- * The core parts are not implemented yet.
  */
 
 #define pr_fmt(fmt) "damon: " fmt
 
 #include <linux/damon.h>
+#include <linux/delay.h>
+#include <linux/kthread.h>
 #include <linux/mm.h>
 #include <linux/module.h>
+#include <linux/page_idle.h>
+#include <linux/random.h>
+#include <linux/sched/mm.h>
+#include <linux/sched/task.h>
 #include <linux/slab.h>
 
+/* Minimal region size.  Every damon_region is aligned by this. */
+#define MIN_REGION PAGE_SIZE
+
 /*
  * Functions and macros for DAMON data structures
  */
@@ -167,6 +178,606 @@ static unsigned int nr_damon_regions(struct damon_task *t)
 	return nr_regions;
 }
 
+/*
+ * Get the mm_struct of the given task
+ *
+ * Caller _must_ put the mm_struct after use, unless it is NULL.
+ *
+ * Returns the mm_struct of the task on success, NULL on failure
+ */
+static struct mm_struct *damon_get_mm(struct damon_task *t)
+{
+	struct task_struct *task;
+	struct mm_struct *mm;
+
+	task = damon_get_task_struct(t);
+	if (!task)
+		return NULL;
+
+	mm = get_task_mm(task);
+	put_task_struct(task);
+	return mm;
+}
+
+/*
+ * Functions for the initial monitoring target regions construction
+ */
+
+/*
+ * Size-evenly split a region into 'nr_pieces' small regions
+ *
+ * Returns 0 on success, or negative error code otherwise.
+ */
+static int damon_split_region_evenly(struct damon_ctx *ctx,
+		struct damon_region *r, unsigned int nr_pieces)
+{
+	unsigned long sz_orig, sz_piece, orig_end;
+	struct damon_region *n = NULL, *next;
+	unsigned long start;
+
+	if (!r || !nr_pieces)
+		return -EINVAL;
+
+	orig_end = r->vm_end;
+	sz_orig = r->vm_end - r->vm_start;
+	sz_piece = ALIGN_DOWN(sz_orig / nr_pieces, MIN_REGION);
+
+	if (!sz_piece)
+		return -EINVAL;
+
+	r->vm_end = r->vm_start + sz_piece;
+	next = damon_next_region(r);
+	for (start = r->vm_end; start + sz_piece <= orig_end;
+			start += sz_piece) {
+		n = damon_new_region(ctx, start, start + sz_piece);
+		if (!n)
+			return -ENOMEM;
+		damon_insert_region(n, r, next);
+		r = n;
+	}
+	/* complement last region for possible rounding error */
+	if (n)
+		n->vm_end = orig_end;
+
+	return 0;
+}
+
+struct region {
+	unsigned long start;
+	unsigned long end;
+};
+
+static unsigned long sz_region(struct region *r)
+{
+	return r->end - r->start;
+}
+
+static void swap_regions(struct region *r1, struct region *r2)
+{
+	struct region tmp;
+
+	tmp = *r1;
+	*r1 = *r2;
+	*r2 = tmp;
+}
+
+/*
+ * Find three regions separated by two biggest unmapped regions
+ *
+ * vma		the head vma of the target address space
+ * regions	an array of three 'struct region's that results will be saved
+ *
+ * This function receives an address space and finds three regions in it which
+ * separated by the two biggest unmapped regions in the space.  Please refer to
+ * below comments of 'damon_init_regions_of()' function to know why this is
+ * necessary.
+ *
+ * Returns 0 if success, or negative error code otherwise.
+ */
+static int damon_three_regions_in_vmas(struct vm_area_struct *vma,
+		struct region regions[3])
+{
+	struct region gap = {0}, first_gap = {0}, second_gap = {0};
+	struct vm_area_struct *last_vma = NULL;
+	unsigned long start = 0;
+
+	/* Find two biggest gaps so that first_gap > second_gap > others */
+	for (; vma; vma = vma->vm_next) {
+		if (!last_vma) {
+			start = vma->vm_start;
+			last_vma = vma;
+			continue;
+		}
+		gap.start = last_vma->vm_end;
+		gap.end = vma->vm_start;
+		if (sz_region(&gap) > sz_region(&second_gap)) {
+			swap_regions(&gap, &second_gap);
+			if (sz_region(&second_gap) > sz_region(&first_gap))
+				swap_regions(&second_gap, &first_gap);
+		}
+		last_vma = vma;
+	}
+
+	if (!sz_region(&second_gap) || !sz_region(&first_gap))
+		return -EINVAL;
+
+	/* Sort the two biggest gaps by address */
+	if (first_gap.start > second_gap.start)
+		swap_regions(&first_gap, &second_gap);
+
+	/* Store the result */
+	regions[0].start = ALIGN(start, MIN_REGION);
+	regions[0].end = ALIGN(first_gap.start, MIN_REGION);
+	regions[1].start = ALIGN(first_gap.end, MIN_REGION);
+	regions[1].end = ALIGN(second_gap.start, MIN_REGION);
+	regions[2].start = ALIGN(second_gap.end, MIN_REGION);
+	regions[2].end = ALIGN(last_vma->vm_end, MIN_REGION);
+
+	return 0;
+}
+
+/*
+ * Get the three regions in the given task
+ *
+ * Returns 0 on success, negative error code otherwise.
+ */
+static int damon_three_regions_of(struct damon_task *t,
+				struct region regions[3])
+{
+	struct mm_struct *mm;
+	int rc;
+
+	mm = damon_get_mm(t);
+	if (!mm)
+		return -EINVAL;
+
+	down_read(&mm->mmap_sem);
+	rc = damon_three_regions_in_vmas(mm->mmap, regions);
+	up_read(&mm->mmap_sem);
+
+	mmput(mm);
+	return rc;
+}
+
+/*
+ * Initialize the monitoring target regions for the given task
+ *
+ * t	the given target task
+ *
+ * Because only a number of small portions of the entire address space
+ * is actually mapped to the memory and accessed, monitoring the unmapped
+ * regions is wasteful.  That said, because we can deal with small noises,
+ * tracking every mapping is not strictly required but could even incur a high
+ * overhead if the mapping frequently changes or the number of mappings is
+ * high.  Nonetheless, this may seems very weird.  DAMON's dynamic regions
+ * adjustment mechanism, which will be implemented with following commit will
+ * make this more sense.
+ *
+ * For the reason, we convert the complex mappings to three distinct regions
+ * that cover every mapped area of the address space.  Also the two gaps
+ * between the three regions are the two biggest unmapped areas in the given
+ * address space.  In detail, this function first identifies the start and the
+ * end of the mappings and the two biggest unmapped areas of the address space.
+ * Then, it constructs the three regions as below:
+ *
+ *     [mappings[0]->start, big_two_unmapped_areas[0]->start)
+ *     [big_two_unmapped_areas[0]->end, big_two_unmapped_areas[1]->start)
+ *     [big_two_unmapped_areas[1]->end, mappings[nr_mappings - 1]->end)
+ *
+ * As usual memory map of processes is as below, the gap between the heap and
+ * the uppermost mmap()-ed region, and the gap between the lowermost mmap()-ed
+ * region and the stack will be two biggest unmapped regions.  Because these
+ * gaps are exceptionally huge areas in usual address space, excluding these
+ * two biggest unmapped regions will be sufficient to make a trade-off.
+ *
+ *   <heap>
+ *   <BIG UNMAPPED REGION 1>
+ *   <uppermost mmap()-ed region>
+ *   (other mmap()-ed regions and small unmapped regions)
+ *   <lowermost mmap()-ed region>
+ *   <BIG UNMAPPED REGION 2>
+ *   <stack>
+ */
+static void damon_init_regions_of(struct damon_ctx *c, struct damon_task *t)
+{
+	struct damon_region *r, *m = NULL;
+	struct region regions[3];
+	int i;
+
+	if (damon_three_regions_of(t, regions)) {
+		pr_err("Failed to get three regions of task %d\n", t->pid);
+		return;
+	}
+
+	/* Set the initial three regions of the task */
+	for (i = 0; i < 3; i++) {
+		r = damon_new_region(c, regions[i].start, regions[i].end);
+		if (!r) {
+			pr_err("%d'th init region creation failed\n", i);
+			return;
+		}
+		damon_add_region(r, t);
+		if (i == 1)
+			m = r;
+	}
+
+	/* Split the middle region into 'min_nr_regions - 2' regions */
+	if (damon_split_region_evenly(c, m, c->min_nr_regions - 2))
+		pr_warn("Init middle region failed to be split\n");
+}
+
+/* Initialize '->regions_list' of every task */
+static void kdamond_init_regions(struct damon_ctx *ctx)
+{
+	struct damon_task *t;
+
+	damon_for_each_task(t, ctx)
+		damon_init_regions_of(ctx, t);
+}
+
+/*
+ * Functions for the access checking of the regions
+ */
+
+static void damon_mkold(struct mm_struct *mm, unsigned long addr)
+{
+	pte_t *pte = NULL;
+	pmd_t *pmd = NULL;
+	spinlock_t *ptl;
+
+	if (follow_pte_pmd(mm, addr, NULL, &pte, &pmd, &ptl))
+		return;
+
+	if (pte) {
+		if (pte_young(*pte)) {
+			clear_page_idle(pte_page(*pte));
+			set_page_young(pte_page(*pte));
+		}
+		*pte = pte_mkold(*pte);
+		pte_unmap_unlock(pte, ptl);
+		return;
+	}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	if (pmd_young(*pmd)) {
+		clear_page_idle(pmd_page(*pmd));
+		set_page_young(pmd_page(*pmd));
+	}
+	*pmd = pmd_mkold(*pmd);
+	spin_unlock(ptl);
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+}
+
+static void damon_prepare_access_check(struct damon_ctx *ctx,
+			struct mm_struct *mm, struct damon_region *r)
+{
+	r->sampling_addr = damon_rand(r->vm_start, r->vm_end);
+
+	damon_mkold(mm, r->sampling_addr);
+}
+
+static void kdamond_prepare_access_checks(struct damon_ctx *ctx)
+{
+	struct damon_task *t;
+	struct mm_struct *mm;
+	struct damon_region *r;
+
+	damon_for_each_task(t, ctx) {
+		mm = damon_get_mm(t);
+		if (!mm)
+			continue;
+		damon_for_each_region(r, t)
+			damon_prepare_access_check(ctx, mm, r);
+		mmput(mm);
+	}
+}
+
+static bool damon_young(struct mm_struct *mm, unsigned long addr,
+			unsigned long *page_sz)
+{
+	pte_t *pte = NULL;
+	pmd_t *pmd = NULL;
+	spinlock_t *ptl;
+	bool young = false;
+
+	if (follow_pte_pmd(mm, addr, NULL, &pte, &pmd, &ptl))
+		return false;
+
+	*page_sz = PAGE_SIZE;
+	if (pte) {
+		young = pte_young(*pte);
+		pte_unmap_unlock(pte, ptl);
+		return young;
+	}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	young = pmd_young(*pmd);
+	spin_unlock(ptl);
+	*page_sz = ((1UL) << HPAGE_PMD_SHIFT);
+#endif	/* CONFIG_TRANSPARENT_HUGEPAGE */
+
+	return young;
+}
+
+/*
+ * Check whether the region was accessed after the last preparation
+ *
+ * mm	'mm_struct' for the given virtual address space
+ * r	the region to be checked
+ */
+static void damon_check_access(struct damon_ctx *ctx,
+			       struct mm_struct *mm, struct damon_region *r)
+{
+	static struct mm_struct *last_mm;
+	static unsigned long last_addr;
+	static unsigned long last_page_sz = PAGE_SIZE;
+	static bool last_accessed;
+
+	/* If the region is in the last checked page, reuse the result */
+	if (mm == last_mm && (ALIGN_DOWN(last_addr, last_page_sz) ==
+				ALIGN_DOWN(r->sampling_addr, last_page_sz))) {
+		if (last_accessed)
+			r->nr_accesses++;
+		return;
+	}
+
+	last_accessed = damon_young(mm, r->sampling_addr, &last_page_sz);
+	if (last_accessed)
+		r->nr_accesses++;
+
+	last_mm = mm;
+	last_addr = r->sampling_addr;
+}
+
+static void kdamond_check_accesses(struct damon_ctx *ctx)
+{
+	struct damon_task *t;
+	struct mm_struct *mm;
+	struct damon_region *r;
+
+	damon_for_each_task(t, ctx) {
+		mm = damon_get_mm(t);
+		if (!mm)
+			continue;
+		damon_for_each_region(r, t)
+			damon_check_access(ctx, mm, r);
+		mmput(mm);
+	}
+}
+
+/*
+ * Functions for DAMON core logics and features
+ */
+
+/*
+ * damon_check_reset_time_interval() - Check if a time interval is elapsed.
+ * @baseline:	the time to check whether the interval has elapsed since
+ * @interval:	the time interval (microseconds)
+ *
+ * See whether the given time interval has passed since the given baseline
+ * time.  If so, it also updates the baseline to current time for next check.
+ *
+ * Return:	true if the time interval has passed, or false otherwise.
+ */
+static bool damon_check_reset_time_interval(struct timespec64 *baseline,
+		unsigned long interval)
+{
+	struct timespec64 now;
+
+	ktime_get_coarse_ts64(&now);
+	if ((timespec64_to_ns(&now) - timespec64_to_ns(baseline)) <
+			interval * 1000)
+		return false;
+	*baseline = now;
+	return true;
+}
+
+/*
+ * Check whether it is time to flush the aggregated information
+ */
+static bool kdamond_aggregate_interval_passed(struct damon_ctx *ctx)
+{
+	return damon_check_reset_time_interval(&ctx->last_aggregation,
+			ctx->aggr_interval);
+}
+
+/*
+ * Reset the aggregated monitoring results
+ */
+static void kdamond_reset_aggregated(struct damon_ctx *c)
+{
+	struct damon_task *t;
+	struct damon_region *r;
+
+	damon_for_each_task(t, c) {
+		damon_for_each_region(r, t)
+			r->nr_accesses = 0;
+	}
+}
+
+/*
+ * Check whether current monitoring should be stopped
+ *
+ * The monitoring is stopped when either the user requested to stop, or all
+ * monitoring target tasks are dead.
+ *
+ * Returns true if need to stop current monitoring.
+ */
+static bool kdamond_need_stop(struct damon_ctx *ctx)
+{
+	struct damon_task *t;
+	struct task_struct *task;
+	bool stop;
+
+	mutex_lock(&ctx->kdamond_lock);
+	stop = ctx->kdamond_stop;
+	mutex_unlock(&ctx->kdamond_lock);
+	if (stop)
+		return true;
+
+	damon_for_each_task(t, ctx) {
+		task = damon_get_task_struct(t);
+		if (task) {
+			put_task_struct(task);
+			return false;
+		}
+	}
+
+	return true;
+}
+
+/*
+ * The monitoring daemon that runs as a kernel thread
+ */
+static int kdamond_fn(void *data)
+{
+	struct damon_ctx *ctx = (struct damon_ctx *)data;
+	struct damon_task *t;
+	struct damon_region *r, *next;
+
+	pr_info("kdamond (%d) starts\n", ctx->kdamond->pid);
+	kdamond_init_regions(ctx);
+	while (!kdamond_need_stop(ctx)) {
+		kdamond_prepare_access_checks(ctx);
+
+		usleep_range(ctx->sample_interval, ctx->sample_interval + 1);
+
+		kdamond_check_accesses(ctx);
+
+		if (kdamond_aggregate_interval_passed(ctx))
+			kdamond_reset_aggregated(ctx);
+
+	}
+	damon_for_each_task(t, ctx) {
+		damon_for_each_region_safe(r, next, t)
+			damon_destroy_region(r);
+	}
+	pr_debug("kdamond (%d) finishes\n", ctx->kdamond->pid);
+	mutex_lock(&ctx->kdamond_lock);
+	ctx->kdamond = NULL;
+	mutex_unlock(&ctx->kdamond_lock);
+
+	do_exit(0);
+}
+
+/*
+ * Functions for the DAMON programming interface
+ */
+
+static bool damon_kdamond_running(struct damon_ctx *ctx)
+{
+	bool running;
+
+	mutex_lock(&ctx->kdamond_lock);
+	running = ctx->kdamond != NULL;
+	mutex_unlock(&ctx->kdamond_lock);
+
+	return running;
+}
+
+/**
+ * damon_start() - Starts monitoring with given context.
+ * @ctx:	monitoring context
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_start(struct damon_ctx *ctx)
+{
+	int err = -EBUSY;
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (!ctx->kdamond) {
+		err = 0;
+		ctx->kdamond_stop = false;
+		ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond");
+		if (IS_ERR(ctx->kdamond))
+			err = PTR_ERR(ctx->kdamond);
+	}
+	mutex_unlock(&ctx->kdamond_lock);
+
+	return err;
+}
+
+/**
+ * damon_stop() - Stops monitoring of given context.
+ * @ctx:	monitoring context
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_stop(struct damon_ctx *ctx)
+{
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond) {
+		ctx->kdamond_stop = true;
+		mutex_unlock(&ctx->kdamond_lock);
+		while (damon_kdamond_running(ctx))
+			usleep_range(ctx->sample_interval,
+					ctx->sample_interval * 2);
+		return 0;
+	}
+	mutex_unlock(&ctx->kdamond_lock);
+
+	return -EPERM;
+}
+
+/**
+ * damon_set_pids() - Set monitoring target processes.
+ * @ctx:	monitoring context
+ * @pids:	array of target processes pids
+ * @nr_pids:	number of entries in @pids
+ *
+ * This function should not be called while the kdamond is running.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids)
+{
+	ssize_t i;
+	struct damon_task *t, *next;
+
+	damon_for_each_task_safe(t, next, ctx)
+		damon_destroy_task(t);
+
+	for (i = 0; i < nr_pids; i++) {
+		t = damon_new_task(pids[i]);
+		if (!t) {
+			pr_err("Failed to alloc damon_task\n");
+			return -ENOMEM;
+		}
+		damon_add_task(ctx, t);
+	}
+
+	return 0;
+}
+
+/**
+ * damon_set_attrs() - Set attributes for the monitoring.
+ * @ctx:		monitoring context
+ * @sample_int:		time interval between samplings
+ * @aggr_int:		time interval between aggregations
+ * @min_nr_reg:		minimal number of regions
+ *
+ * This function should not be called while the kdamond is running.
+ * Every time interval is in micro-seconds.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
+		unsigned long aggr_int, unsigned long min_nr_reg)
+{
+	if (min_nr_reg < 3) {
+		pr_err("min_nr_regions (%lu) must be at least 3\n",
+				min_nr_reg);
+		return -EINVAL;
+	}
+
+	ctx->sample_interval = sample_int;
+	ctx->aggr_interval = aggr_int;
+	ctx->min_nr_regions = min_nr_reg;
+
+	return 0;
+}
+
 /*
  * Functions for the module loading/unloading
  */
-- 
2.17.1

[PATCH v15 04/14] mm/damon: Adaptively adjust regions

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

At the beginning of the monitoring, DAMON constructs the initial regions
by evenly splitting the memory mapped address space of the process into
the user-specified minimal number of regions.  In this initial state,
the assumption of the regions (pages in same region have similar access
frequencies) is normally not kept and thus the monitoring quality could
be low.  To keep the assumption as much as possible, DAMON adaptively
merges and splits each region.

For each ``aggregation interval``, it compares the access frequencies of
adjacent regions and merges those if the frequency difference is small.
Then, after it reports and clears the aggregated access frequency of
each region, it splits each region into two regions if the total number
of regions is smaller than the half of the user-specified maximum number
of regions.

In this way, DAMON provides its best-effort quality and minimal overhead
while keeping the bounds users set for their trade-off.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 include/linux/damon.h |   7 +-
 mm/damon.c            | 174 +++++++++++++++++++++++++++++++++++++++---
 2 files changed, 169 insertions(+), 12 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index f0fe4520a4e9..babdba6b5c47 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -56,6 +56,7 @@ struct damon_task {
  * @sample_interval:		The time between access samplings.
  * @aggr_interval:		The time between monitor results aggregations.
  * @min_nr_regions:		The number of initial monitoring regions.
+ * @max_nr_regions:		The maximum number of monitoring regions.
  *
  * For each @sample_interval, DAMON checks whether each region is accessed or
  * not.  It aggregates and keeps the access information (number of accesses to
@@ -81,6 +82,7 @@ struct damon_ctx {
 	unsigned long sample_interval;
 	unsigned long aggr_interval;
 	unsigned long min_nr_regions;
+	unsigned long max_nr_regions;
 
 	struct timespec64 last_aggregation;
 
@@ -92,8 +94,9 @@ struct damon_ctx {
 };
 
 int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
-int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
-		unsigned long aggr_int, unsigned long min_nr_reg);
+int damon_set_attrs(struct damon_ctx *ctx,
+		unsigned long sample_int, unsigned long aggr_int,
+		unsigned long min_nr_reg, unsigned long max_nr_reg);
 int damon_start(struct damon_ctx *ctx);
 int damon_stop(struct damon_ctx *ctx);
 
diff --git a/mm/damon.c b/mm/damon.c
index fa14ff7dd31a..8c05be03db3c 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -349,9 +349,12 @@ static int damon_three_regions_of(struct damon_task *t,
  * regions is wasteful.  That said, because we can deal with small noises,
  * tracking every mapping is not strictly required but could even incur a high
  * overhead if the mapping frequently changes or the number of mappings is
- * high.  Nonetheless, this may seems very weird.  DAMON's dynamic regions
- * adjustment mechanism, which will be implemented with following commit will
- * make this more sense.
+ * high.  The adaptive regions adjustment mechanism will further help to deal
+ * with the noise by simply identifying the unmapped areas as a region that
+ * has no access.  Moreover, applying the real mappings that would have many
+ * unmapped areas inside will make the adaptive mechanism quite complex.  That
+ * said, too huge unmapped areas inside the monitoring target should be removed
+ * to not take the time for the adaptive mechanism.
  *
  * For the reason, we convert the complex mappings to three distinct regions
  * that cover every mapped area of the address space.  Also the two gaps
@@ -529,20 +532,25 @@ static void damon_check_access(struct damon_ctx *ctx,
 	last_addr = r->sampling_addr;
 }
 
-static void kdamond_check_accesses(struct damon_ctx *ctx)
+static unsigned int kdamond_check_accesses(struct damon_ctx *ctx)
 {
 	struct damon_task *t;
 	struct mm_struct *mm;
 	struct damon_region *r;
+	unsigned int max_nr_accesses = 0;
 
 	damon_for_each_task(t, ctx) {
 		mm = damon_get_mm(t);
 		if (!mm)
 			continue;
-		damon_for_each_region(r, t)
+		damon_for_each_region(r, t) {
 			damon_check_access(ctx, mm, r);
+			max_nr_accesses = max(r->nr_accesses, max_nr_accesses);
+		}
+
 		mmput(mm);
 	}
+	return max_nr_accesses;
 }
 
 /*
@@ -595,6 +603,141 @@ static void kdamond_reset_aggregated(struct damon_ctx *c)
 	}
 }
 
+#define sz_damon_region(r) (r->vm_end - r->vm_start)
+
+/*
+ * Merge two adjacent regions into one region
+ */
+static void damon_merge_two_regions(struct damon_region *l,
+				struct damon_region *r)
+{
+	l->nr_accesses = (l->nr_accesses * sz_damon_region(l) +
+			r->nr_accesses * sz_damon_region(r)) /
+			(sz_damon_region(l) + sz_damon_region(r));
+	l->vm_end = r->vm_end;
+	damon_destroy_region(r);
+}
+
+#define diff_of(a, b) (a > b ? a - b : b - a)
+
+/*
+ * Merge adjacent regions having similar access frequencies
+ *
+ * t		task affected by merge operation
+ * thres	'->nr_accesses' diff threshold for the merge
+ */
+static void damon_merge_regions_of(struct damon_task *t, unsigned int thres)
+{
+	struct damon_region *r, *prev = NULL, *next;
+
+	damon_for_each_region_safe(r, next, t) {
+		if (!prev || prev->vm_end != r->vm_start ||
+		    diff_of(prev->nr_accesses, r->nr_accesses) > thres) {
+			prev = r;
+			continue;
+		}
+		damon_merge_two_regions(prev, r);
+	}
+}
+
+/*
+ * Merge adjacent regions having similar access frequencies
+ *
+ * threshold	'->nr_accesses' diff threshold for the merge
+ *
+ * This function merges monitoring target regions which are adjacent and their
+ * access frequencies are similar.  This is for minimizing the monitoring
+ * overhead under the dynamically changeable access pattern.  If a merge was
+ * unnecessarily made, later 'kdamond_split_regions()' will revert it.
+ */
+static void kdamond_merge_regions(struct damon_ctx *c, unsigned int threshold)
+{
+	struct damon_task *t;
+
+	damon_for_each_task(t, c)
+		damon_merge_regions_of(t, threshold);
+}
+
+/*
+ * Split a region in two
+ *
+ * r		the region to be split
+ * sz_r		size of the first sub-region that will be made
+ */
+static void damon_split_region_at(struct damon_ctx *ctx,
+				  struct damon_region *r, unsigned long sz_r)
+{
+	struct damon_region *new;
+
+	new = damon_new_region(ctx, r->vm_start + sz_r, r->vm_end);
+	r->vm_end = new->vm_start;
+
+	damon_insert_region(new, r, damon_next_region(r));
+}
+
+/* Split every region in the given task into 'nr_subs' regions */
+static void damon_split_regions_of(struct damon_ctx *ctx,
+				     struct damon_task *t, int nr_subs)
+{
+	struct damon_region *r, *next;
+	unsigned long sz_region, sz_sub = 0;
+	int i;
+
+	damon_for_each_region_safe(r, next, t) {
+		sz_region = r->vm_end - r->vm_start;
+
+		for (i = 0; i < nr_subs - 1 &&
+				sz_region > 2 * MIN_REGION; i++) {
+			/*
+			 * Randomly select size of left sub-region to be at
+			 * least 10 percent and at most 90% of original region
+			 */
+			sz_sub = ALIGN_DOWN(damon_rand(1, 10) *
+					sz_region / 10, MIN_REGION);
+			/* Do not allow blank region */
+			if (sz_sub == 0 || sz_sub >= sz_region)
+				continue;
+
+			damon_split_region_at(ctx, r, sz_sub);
+			sz_region = sz_sub;
+		}
+	}
+}
+
+/*
+ * splits every target region into two randomly-sized regions
+ *
+ * This function splits every target region into two random-sized regions if
+ * current total number of the regions is equal or smaller than half of the
+ * user-specified maximum number of regions.  This is for maximizing the
+ * monitoring accuracy under the dynamically changeable access patterns.  If a
+ * split was unnecessarily made, later 'kdamond_merge_regions()' will revert
+ * it.
+ */
+static void kdamond_split_regions(struct damon_ctx *ctx)
+{
+	struct damon_task *t;
+	unsigned int nr_regions = 0;
+	static unsigned int last_nr_regions;
+	int nr_subregions = 2;
+
+	damon_for_each_task(t, ctx)
+		nr_regions += nr_damon_regions(t);
+
+	if (nr_regions > ctx->max_nr_regions / 2)
+		return;
+
+	/* If number of regions is not changed, we are maybe in corner case */
+	if (last_nr_regions == nr_regions &&
+			nr_regions < ctx->max_nr_regions / 3)
+		nr_subregions = 3;
+
+	damon_for_each_task(t, ctx)
+		damon_split_regions_of(ctx, t, nr_subregions);
+
+	last_nr_regions = nr_regions;
+}
+
 /*
  * Check whether current monitoring should be stopped
  *
@@ -634,6 +777,7 @@ static int kdamond_fn(void *data)
 	struct damon_ctx *ctx = (struct damon_ctx *)data;
 	struct damon_task *t;
 	struct damon_region *r, *next;
+	unsigned int max_nr_accesses = 0;
 
 	pr_info("kdamond (%d) starts\n", ctx->kdamond->pid);
 	kdamond_init_regions(ctx);
@@ -642,11 +786,13 @@ static int kdamond_fn(void *data)
 
 		usleep_range(ctx->sample_interval, ctx->sample_interval + 1);
 
-		kdamond_check_accesses(ctx);
+		max_nr_accesses = kdamond_check_accesses(ctx);
 
-		if (kdamond_aggregate_interval_passed(ctx))
+		if (kdamond_aggregate_interval_passed(ctx)) {
+			kdamond_merge_regions(ctx, max_nr_accesses / 10);
 			kdamond_reset_aggregated(ctx);
-
+			kdamond_split_regions(ctx);
+		}
 	}
 	damon_for_each_task(t, ctx) {
 		damon_for_each_region_safe(r, next, t)
@@ -756,24 +902,32 @@ int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids)
  * @sample_int:		time interval between samplings
  * @aggr_int:		time interval between aggregations
  * @min_nr_reg:		minimal number of regions
+ * @max_nr_reg:		maximum number of regions
  *
  * This function should not be called while the kdamond is running.
  * Every time interval is in micro-seconds.
  *
  * Return: 0 on success, negative error code otherwise.
  */
-int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
-		unsigned long aggr_int, unsigned long min_nr_reg)
+int damon_set_attrs(struct damon_ctx *ctx,
+		    unsigned long sample_int, unsigned long aggr_int,
+		    unsigned long min_nr_reg, unsigned long max_nr_reg)
 {
 	if (min_nr_reg < 3) {
 		pr_err("min_nr_regions (%lu) must be at least 3\n",
 				min_nr_reg);
 		return -EINVAL;
 	}
+	if (min_nr_reg > max_nr_reg) {
+		pr_err("invalid nr_regions.  min (%lu) > max (%lu)\n",
+				min_nr_reg, max_nr_reg);
+		return -EINVAL;
+	}
 
 	ctx->sample_interval = sample_int;
 	ctx->aggr_interval = aggr_int;
 	ctx->min_nr_regions = min_nr_reg;
+	ctx->max_nr_regions = max_nr_reg;
 
 	return 0;
 }
-- 
2.17.1

[PATCH v15 05/14] mm/damon: Apply dynamic memory mapping changes

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

Only a number of parts in the virtual address space of the processes is
mapped to physical memory and accessed.  Thus, tracking the unmapped
address regions is just wasteful.  However, tracking every memory
mapping change might incur an overhead.  For the reason, DAMON applies
the dynamic memory mapping changes to the tracking regions only for each
of a user-specified time interval (``regions update interval``).

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 include/linux/damon.h |  13 ++++--
 mm/damon.c            | 106 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 113 insertions(+), 6 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index babdba6b5c47..5afcb2bb7f77 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -55,13 +55,16 @@ struct damon_task {
  *
  * @sample_interval:		The time between access samplings.
  * @aggr_interval:		The time between monitor results aggregations.
+ * @regions_update_interval:	The time between monitor regions updates.
  * @min_nr_regions:		The number of initial monitoring regions.
  * @max_nr_regions:		The maximum number of monitoring regions.
  *
  * For each @sample_interval, DAMON checks whether each region is accessed or
  * not.  It aggregates and keeps the access information (number of accesses to
- * each region) for @aggr_interval time.  All time intervals are in
- * micro-seconds.
+ * each region) for @aggr_interval time.  DAMON also checks whether the target
+ * memory regions need update (e.g., by ``mmap()`` calls from the application,
+ * in case of virtual memory monitoring) and applies the changes for each
+ * @regions_update_interval.  All time intervals are in micro-seconds.
  *
  * @kdamond:		Kernel thread who does the monitoring.
  * @kdamond_stop:	Notifies whether kdamond should stop.
@@ -81,10 +84,12 @@ struct damon_task {
 struct damon_ctx {
 	unsigned long sample_interval;
 	unsigned long aggr_interval;
+	unsigned long regions_update_interval;
 	unsigned long min_nr_regions;
 	unsigned long max_nr_regions;
 
 	struct timespec64 last_aggregation;
+	struct timespec64 last_regions_update;
 
 	struct task_struct *kdamond;
 	bool kdamond_stop;
@@ -94,8 +99,8 @@ struct damon_ctx {
 };
 
 int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
-int damon_set_attrs(struct damon_ctx *ctx,
-		unsigned long sample_int, unsigned long aggr_int,
+int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
+		unsigned long aggr_int, unsigned long regions_update_int,
 		unsigned long min_nr_reg, unsigned long max_nr_reg);
 int damon_start(struct damon_ctx *ctx);
 int damon_stop(struct damon_ctx *ctx);
diff --git a/mm/damon.c b/mm/damon.c
index 8c05be03db3c..778f4d87042d 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -10,6 +10,7 @@
  *
  * - Functions and macros for DAMON data structures
  * - Functions for the initial monitoring target regions construction
+ * - Functions for the dynamic monitoring target regions update
  * - Functions for the access checking of the regions
  * - Functions for DAMON core logics and features
  * - Functions for the DAMON programming interface
@@ -418,6 +419,91 @@ static void kdamond_init_regions(struct damon_ctx *ctx)
 		damon_init_regions_of(ctx, t);
 }
 
+/*
+ * Functions for the dynamic monitoring target regions update
+ */
+
+/*
+ * Check whether regions are intersecting
+ *
+ * Note that this function checks 'struct damon_region' and 'struct region'.
+ *
+ * Returns true if it is.
+ */
+static bool damon_intersect(struct damon_region *r, struct region *re)
+{
+	return !(r->vm_end <= re->start || re->end <= r->vm_start);
+}
+
+/*
+ * Update damon regions for the three big regions of the given task
+ *
+ * t		the given task
+ * bregions	the three big regions of the task
+ */
+static void damon_apply_three_regions(struct damon_ctx *ctx,
+		struct damon_task *t, struct region bregions[3])
+{
+	struct damon_region *r, *next;
+	unsigned int i = 0;
+
+	/* Remove regions which are not in the three big regions now */
+	damon_for_each_region_safe(r, next, t) {
+		for (i = 0; i < 3; i++) {
+			if (damon_intersect(r, &bregions[i]))
+				break;
+		}
+		if (i == 3)
+			damon_destroy_region(r);
+	}
+
+	/* Adjust intersecting regions to fit with the three big regions */
+	for (i = 0; i < 3; i++) {
+		struct damon_region *first = NULL, *last;
+		struct damon_region *newr;
+		struct region *br;
+
+		br = &bregions[i];
+		/* Get the first and last regions which intersects with br */
+		damon_for_each_region(r, t) {
+			if (damon_intersect(r, br)) {
+				if (!first)
+					first = r;
+				last = r;
+			}
+			if (r->vm_start >= br->end)
+				break;
+		}
+		if (!first) {
+			/* no damon_region intersects with this big region */
+			newr = damon_new_region(ctx,
+					ALIGN_DOWN(br->start, MIN_REGION),
+					ALIGN(br->end, MIN_REGION));
+			if (!newr)
+				continue;
+			damon_insert_region(newr, damon_prev_region(r), r);
+		} else {
+			first->vm_start = ALIGN_DOWN(br->start, MIN_REGION);
+			last->vm_end = ALIGN(br->end, MIN_REGION);
+		}
+	}
+}
+
+/*
+ * Update regions for current memory mappings
+ */
+static void kdamond_update_regions(struct damon_ctx *ctx)
+{
+	struct region three_regions[3];
+	struct damon_task *t;
+
+	damon_for_each_task(t, ctx) {
+		if (damon_three_regions_of(t, three_regions))
+			continue;
+		damon_apply_three_regions(ctx, t, three_regions);
+	}
+}
+
 /*
  * Functions for the access checking of the regions
  */
@@ -738,6 +824,17 @@ static void kdamond_split_regions(struct damon_ctx *ctx)
 	last_nr_regions = nr_regions;
 }
 
+/*
+ * Check whether it is time to check and apply the dynamic mmap changes
+ *
+ * Returns true if it is.
+ */
+static bool kdamond_need_update_regions(struct damon_ctx *ctx)
+{
+	return damon_check_reset_time_interval(&ctx->last_regions_update,
+			ctx->regions_update_interval);
+}
+
 /*
  * Check whether current monitoring should be stopped
  *
@@ -793,6 +890,9 @@ static int kdamond_fn(void *data)
 			kdamond_reset_aggregated(ctx);
 			kdamond_split_regions(ctx);
 		}
+
+		if (kdamond_need_update_regions(ctx))
+			kdamond_update_regions(ctx);
 	}
 	damon_for_each_task(t, ctx) {
 		damon_for_each_region_safe(r, next, t)
@@ -900,6 +1000,7 @@ int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids)
  * damon_set_attrs() - Set attributes for the monitoring.
  * @ctx:		monitoring context
  * @sample_int:		time interval between samplings
+ * @regions_update_int:	time interval between vma update checks
  * @aggr_int:		time interval between aggregations
  * @min_nr_reg:		minimal number of regions
  * @max_nr_reg:		maximum number of regions
@@ -909,8 +1010,8 @@ int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids)
  *
  * Return: 0 on success, negative error code otherwise.
  */
-int damon_set_attrs(struct damon_ctx *ctx,
-		    unsigned long sample_int, unsigned long aggr_int,
+int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
+		    unsigned long aggr_int, unsigned long regions_update_int,
 		    unsigned long min_nr_reg, unsigned long max_nr_reg)
 {
 	if (min_nr_reg < 3) {
@@ -926,6 +1027,7 @@ int damon_set_attrs(struct damon_ctx *ctx,
 
 	ctx->sample_interval = sample_int;
 	ctx->aggr_interval = aggr_int;
+	ctx->regions_update_interval = regions_update_int;
 	ctx->min_nr_regions = min_nr_reg;
 	ctx->max_nr_regions = max_nr_reg;
 
-- 
2.17.1

[PATCH v15 06/14] mm/damon: Implement callbacks

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit implements callbacks for DAMON.  Using this, DAMON users can
install their callbacks for each step of the access monitoring so that
they can do something interesting with the monitored access patterns
online.  For example, callbacks can report the monitored patterns to
users or do some access pattern based memory management such as
proactive reclamations or access pattern based THP promotions/demotions
decision makings.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 include/linux/damon.h | 13 +++++++++++++
 mm/damon.c            |  4 ++++
 2 files changed, 17 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 5afcb2bb7f77..12536d9d2f74 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -80,6 +80,15 @@ struct damon_task {
  * @kdamond_lock.  Accesses to other fields must be protected by themselves.
  *
  * @tasks_list:		Head of monitoring target tasks (&damon_task) list.
+ *
+ * @sample_cb:			Called for each sampling interval.
+ * @aggregate_cb:		Called for each aggregation interval.
+ *
+ * @sample_cb and @aggregate_cb are called from @kdamond for each of the
+ * sampling intervals and aggregation intervals, respectively.  Therefore,
+ * users can safely access to the monitoring results via @tasks_list without
+ * additional protection of @kdamond_lock.  For the reason, users are
+ * recommended to use these callback for the accesses to the results.
  */
 struct damon_ctx {
 	unsigned long sample_interval;
@@ -96,6 +105,10 @@ struct damon_ctx {
 	struct mutex kdamond_lock;
 
 	struct list_head tasks_list;	/* 'damon_task' objects */
+
+	/* callbacks */
+	void (*sample_cb)(struct damon_ctx *context);
+	void (*aggregate_cb)(struct damon_ctx *context);
 };
 
 int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
diff --git a/mm/damon.c b/mm/damon.c
index 778f4d87042d..1978ec4114bf 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -880,6 +880,8 @@ static int kdamond_fn(void *data)
 	kdamond_init_regions(ctx);
 	while (!kdamond_need_stop(ctx)) {
 		kdamond_prepare_access_checks(ctx);
+		if (ctx->sample_cb)
+			ctx->sample_cb(ctx);
 
 		usleep_range(ctx->sample_interval, ctx->sample_interval + 1);
 
@@ -887,6 +889,8 @@ static int kdamond_fn(void *data)
 
 		if (kdamond_aggregate_interval_passed(ctx)) {
 			kdamond_merge_regions(ctx, max_nr_accesses / 10);
+			if (ctx->aggregate_cb)
+				ctx->aggregate_cb(ctx);
 			kdamond_reset_aggregated(ctx);
 			kdamond_split_regions(ctx);
 		}
-- 
2.17.1

[PATCH v15 07/14] mm/damon: Implement access pattern recording

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit implements the recording feature of DAMON. If this feature
is enabled, DAMON writes the monitored access patterns in its binary
format into a file which specified by the user. This is already able to
be implemented by each user using the callbacks.  However, as the
recording is expected to be used widely, this commit implements the
feature in the DAMON, for more convenience and efficiency.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 include/linux/damon.h |  15 +++++
 mm/damon.c            | 131 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 143 insertions(+), 3 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 12536d9d2f74..c4796a10cb1a 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -66,6 +66,14 @@ struct damon_task {
  * in case of virtual memory monitoring) and applies the changes for each
  * @regions_update_interval.  All time intervals are in micro-seconds.
  *
+ * @rbuf: In-memory buffer for monitoring result recording.
+ * @rbuf_len: The length of @rbuf.
+ * @rbuf_offset: The offset for next write to @rbuf.
+ * @rfile_path: Record file path.
+ *
+ * If @rbuf, @rbuf_len, and @rfile_path are set, the monitored results are
+ * automatically stored in @rfile_path file.
+ *
  * @kdamond:		Kernel thread who does the monitoring.
  * @kdamond_stop:	Notifies whether kdamond should stop.
  * @kdamond_lock:	Mutex for the synchronizations with @kdamond.
@@ -100,6 +108,11 @@ struct damon_ctx {
 	struct timespec64 last_aggregation;
 	struct timespec64 last_regions_update;
 
+	unsigned char *rbuf;
+	unsigned int rbuf_len;
+	unsigned int rbuf_offset;
+	char *rfile_path;
+
 	struct task_struct *kdamond;
 	bool kdamond_stop;
 	struct mutex kdamond_lock;
@@ -115,6 +128,8 @@ int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
 int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
 		unsigned long aggr_int, unsigned long regions_update_int,
 		unsigned long min_nr_reg, unsigned long max_nr_reg);
+int damon_set_recording(struct damon_ctx *ctx,
+				unsigned int rbuf_len, char *rfile_path);
 int damon_start(struct damon_ctx *ctx);
 int damon_stop(struct damon_ctx *ctx);
 
diff --git a/mm/damon.c b/mm/damon.c
index 1978ec4114bf..43f47755967e 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -58,6 +58,9 @@
 #define damon_for_each_task_safe(t, next, ctx) \
 	list_for_each_entry_safe(t, next, &(ctx)->tasks_list, list)
 
+#define MAX_RECORD_BUFFER_LEN	(4 * 1024 * 1024)
+#define MAX_RFILE_PATH_LEN	256
+
 /* Get a random number in [l, r) */
 #define damon_rand(l, r) (l + prandom_u32() % (r - l))
 
@@ -676,16 +679,80 @@ static bool kdamond_aggregate_interval_passed(struct damon_ctx *ctx)
 }
 
 /*
- * Reset the aggregated monitoring results
+ * Flush the content in the result buffer to the result file
+ */
+static void damon_flush_rbuffer(struct damon_ctx *ctx)
+{
+	ssize_t sz;
+	loff_t pos = 0;
+	struct file *rfile;
+
+	rfile = filp_open(ctx->rfile_path, O_CREAT | O_RDWR | O_APPEND, 0644);
+	if (IS_ERR(rfile)) {
+		pr_err("Cannot open the result file %s\n",
+				ctx->rfile_path);
+		return;
+	}
+
+	while (ctx->rbuf_offset) {
+		sz = kernel_write(rfile, ctx->rbuf, ctx->rbuf_offset, &pos);
+		if (sz < 0)
+			break;
+		ctx->rbuf_offset -= sz;
+	}
+	filp_close(rfile, NULL);
+}
+
+/*
+ * Write a data into the result buffer
+ */
+static void damon_write_rbuf(struct damon_ctx *ctx, void *data, ssize_t size)
+{
+	if (!ctx->rbuf_len || !ctx->rbuf)
+		return;
+	if (ctx->rbuf_offset + size > ctx->rbuf_len)
+		damon_flush_rbuffer(ctx);
+
+	memcpy(&ctx->rbuf[ctx->rbuf_offset], data, size);
+	ctx->rbuf_offset += size;
+}
+
+/*
+ * Flush the aggregated monitoring results to the result buffer
+ *
+ * Stores current tracking results to the result buffer and reset 'nr_accesses'
+ * of each region.  The format for the result buffer is as below:
+ *
+ *   <time> <number of tasks> <array of task infos>
+ *
+ *   task info: <pid> <number of regions> <array of region infos>
+ *   region info: <start address> <end address> <nr_accesses>
  */
 static void kdamond_reset_aggregated(struct damon_ctx *c)
 {
 	struct damon_task *t;
-	struct damon_region *r;
+	struct timespec64 now;
+	unsigned int nr;
+
+	ktime_get_coarse_ts64(&now);
+
+	damon_write_rbuf(c, &now, sizeof(struct timespec64));
+	nr = nr_damon_tasks(c);
+	damon_write_rbuf(c, &nr, sizeof(nr));
 
 	damon_for_each_task(t, c) {
-		damon_for_each_region(r, t)
+		struct damon_region *r;
+
+		damon_write_rbuf(c, &t->pid, sizeof(t->pid));
+		nr = nr_damon_regions(t);
+		damon_write_rbuf(c, &nr, sizeof(nr));
+		damon_for_each_region(r, t) {
+			damon_write_rbuf(c, &r->vm_start, sizeof(r->vm_start));
+			damon_write_rbuf(c, &r->vm_end, sizeof(r->vm_end));
+			damon_write_rbuf(c, &r->nr_accesses,
+					sizeof(r->nr_accesses));
 			r->nr_accesses = 0;
+		}
 	}
 }
 
@@ -866,6 +933,14 @@ static bool kdamond_need_stop(struct damon_ctx *ctx)
 	return true;
 }
 
+static void kdamond_write_record_header(struct damon_ctx *ctx)
+{
+	int recfmt_ver = 1;
+
+	damon_write_rbuf(ctx, "damon_recfmt_ver", 16);
+	damon_write_rbuf(ctx, &recfmt_ver, sizeof(recfmt_ver));
+}
+
 /*
  * The monitoring daemon that runs as a kernel thread
  */
@@ -878,6 +953,9 @@ static int kdamond_fn(void *data)
 
 	pr_info("kdamond (%d) starts\n", ctx->kdamond->pid);
 	kdamond_init_regions(ctx);
+
+	kdamond_write_record_header(ctx);
+
 	while (!kdamond_need_stop(ctx)) {
 		kdamond_prepare_access_checks(ctx);
 		if (ctx->sample_cb)
@@ -898,6 +976,7 @@ static int kdamond_fn(void *data)
 		if (kdamond_need_update_regions(ctx))
 			kdamond_update_regions(ctx);
 	}
+	damon_flush_rbuffer(ctx);
 	damon_for_each_task(t, ctx) {
 		damon_for_each_region_safe(r, next, t)
 			damon_destroy_region(r);
@@ -1000,6 +1079,52 @@ int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids)
 	return 0;
 }
 
+/**
+ * damon_set_recording() - Set attributes for the recording.
+ * @ctx:	target kdamond context
+ * @rbuf_len:	length of the result buffer
+ * @rfile_path:	path to the monitor result files
+ *
+ * Setting 'rbuf_len' 0 disables recording.
+ *
+ * This function should not be called while the kdamond is running.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_set_recording(struct damon_ctx *ctx,
+			unsigned int rbuf_len, char *rfile_path)
+{
+	size_t rfile_path_len;
+
+	if (rbuf_len > MAX_RECORD_BUFFER_LEN) {
+		pr_err("too long (>%d) result buffer length\n",
+				MAX_RECORD_BUFFER_LEN);
+		return -EINVAL;
+	}
+	rfile_path_len = strnlen(rfile_path, MAX_RFILE_PATH_LEN);
+	if (rfile_path_len >= MAX_RFILE_PATH_LEN) {
+		pr_err("too long (>%d) result file path %s\n",
+				MAX_RFILE_PATH_LEN, rfile_path);
+		return -EINVAL;
+	}
+	ctx->rbuf_len = rbuf_len;
+	kfree(ctx->rbuf);
+	kfree(ctx->rfile_path);
+	ctx->rfile_path = NULL;
+	if (!rbuf_len) {
+		ctx->rbuf = NULL;
+	} else {
+		ctx->rbuf = kvmalloc(rbuf_len, GFP_KERNEL);
+		if (!ctx->rbuf)
+			return -ENOMEM;
+	}
+	ctx->rfile_path = kmalloc(rfile_path_len + 1, GFP_KERNEL);
+	if (!ctx->rfile_path)
+		return -ENOMEM;
+	strncpy(ctx->rfile_path, rfile_path, rfile_path_len + 1);
+	return 0;
+}
+
 /**
  * damon_set_attrs() - Set attributes for the monitoring.
  * @ctx:		monitoring context
-- 
2.17.1

[PATCH v15 08/14] mm/damon: Add debugfs interface

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit adds a debugfs interface for DAMON.

DAMON exports four files, ``attrs``, ``pids``, ``record``, and
``monitor_on`` under its debugfs directory, ``<debugfs>/damon/``.

Attributes
----------

Users can read and write the ``sampling interval``, ``aggregation
interval``, ``regions update interval``, and min/max number of
monitoring target regions by reading from and writing to the ``attrs``
file.  For example, below commands set those values to 5 ms, 100 ms,
1,000 ms, 10, 1000 and check it again::

    # cd <debugfs>/damon
    # echo 5000 100000 1000000 10 1000 > attrs
    # cat attrs
    5000 100000 1000000 10 1000

Target PIDs
-----------

Users can read and write the pids of current monitoring target processes
by reading from and writing to the ``pids`` file.  For example, below
commands set processes having pids 42 and 4242 as the processes to be
monitored and check it again::

    # cd <debugfs>/damon
    # echo 42 4242 > pids
    # cat pids
    42 4242

Note that setting the pids doesn't start the monitoring.

Record
------

DAMON supports direct monitoring result record feature.  The recorded
results are first written to a buffer and flushed to a file in batch.
Users can set the size of the buffer and the path to the result file by
reading from and writing to the ``record`` file.  For example, below
commands set the buffer to be 4 KiB and the result to be saved in
'/damon.data'.

    # cd <debugfs>/damon
    # echo 4096 /damon.data > pids
    # cat record
    4096 /damon.data

Turning On/Off
--------------

You can check current status, start and stop the monitoring by reading
from and writing to the ``monitor_on`` file.  Writing ``on`` to the file
starts DAMON to monitor the target processes with the attributes.
Writing ``off`` to the file stops DAMON.  DAMON also stops if every
target processes is terminated.  Below example commands turn on, off,
and check status of DAMON::

    # cd <debugfs>/damon
    # echo on > monitor_on
    # echo off > monitor_on
    # cat monitor_on
    off

Please note that you cannot write to the ``attrs`` and ``pids`` files
while the monitoring is turned on.  If you write to the files while
DAMON is running, ``-EINVAL`` will be returned.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 mm/damon.c | 362 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 361 insertions(+), 1 deletion(-)

diff --git a/mm/damon.c b/mm/damon.c
index 43f47755967e..010806b7f92e 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -14,12 +14,14 @@
  * - Functions for the access checking of the regions
  * - Functions for DAMON core logics and features
  * - Functions for the DAMON programming interface
+ * - Functions for the DAMON debugfs interface
  * - Functions for the module loading/unloading
  */
 
 #define pr_fmt(fmt) "damon: " fmt
 
 #include <linux/damon.h>
+#include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/kthread.h>
 #include <linux/mm.h>
@@ -64,6 +66,15 @@
 /* Get a random number in [l, r) */
 #define damon_rand(l, r) (l + prandom_u32() % (r - l))
 
+/* A monitoring context for debugfs interface users. */
+static struct damon_ctx damon_user_ctx = {
+	.sample_interval = 5 * 1000,
+	.aggr_interval = 100 * 1000,
+	.regions_update_interval = 1000 * 1000,
+	.min_nr_regions = 10,
+	.max_nr_regions = 1000,
+};
+
 /*
  * Construct a damon_region struct
  *
@@ -1163,17 +1174,366 @@ int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
 	return 0;
 }
 
+/*
+ * Functions for the DAMON debugfs interface
+ */
+
+static ssize_t debugfs_monitor_on_read(struct file *file,
+		char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char monitor_on_buf[5];
+	bool monitor_on;
+	int len;
+
+	monitor_on = damon_kdamond_running(ctx);
+	len = snprintf(monitor_on_buf, 5, monitor_on ? "on\n" : "off\n");
+
+	return simple_read_from_buffer(buf, count, ppos, monitor_on_buf, len);
+}
+
+static ssize_t debugfs_monitor_on_write(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	ssize_t ret;
+	char cmdbuf[5];
+	int err;
+
+	ret = simple_write_to_buffer(cmdbuf, 5, ppos, buf, count);
+	if (ret < 0)
+		return ret;
+
+	if (sscanf(cmdbuf, "%s", cmdbuf) != 1)
+		return -EINVAL;
+	if (!strncmp(cmdbuf, "on", 5))
+		err = damon_start(ctx);
+	else if (!strncmp(cmdbuf, "off", 5))
+		err = damon_stop(ctx);
+	else
+		return -EINVAL;
+
+	if (err)
+		ret = err;
+	return ret;
+}
+
+static ssize_t damon_sprint_pids(struct damon_ctx *ctx, char *buf, ssize_t len)
+{
+	struct damon_task *t;
+	int written = 0;
+	int rc;
+
+	damon_for_each_task(t, ctx) {
+		rc = snprintf(&buf[written], len - written, "%d ", t->pid);
+		if (!rc)
+			return -ENOMEM;
+		written += rc;
+	}
+	if (written)
+		written -= 1;
+	written += snprintf(&buf[written], len - written, "\n");
+	return written;
+}
+
+static ssize_t debugfs_pids_read(struct file *file,
+		char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	ssize_t len;
+	char pids_buf[320];
+
+	mutex_lock(&ctx->kdamond_lock);
+	len = damon_sprint_pids(ctx, pids_buf, 320);
+	mutex_unlock(&ctx->kdamond_lock);
+	if (len < 0)
+		return len;
+
+	return simple_read_from_buffer(buf, count, ppos, pids_buf, len);
+}
+
+/*
+ * Converts a string into an array of unsigned long integers
+ *
+ * Returns an array of unsigned long integers if the conversion success, or
+ * NULL otherwise.
+ */
+static int *str_to_pids(const char *str, ssize_t len, ssize_t *nr_pids)
+{
+	int *pids;
+	const int max_nr_pids = 32;
+	int pid;
+	int pos = 0, parsed, ret;
+
+	*nr_pids = 0;
+	pids = kmalloc_array(max_nr_pids, sizeof(pid), GFP_KERNEL);
+	if (!pids)
+		return NULL;
+	while (*nr_pids < max_nr_pids && pos < len) {
+		ret = sscanf(&str[pos], "%d%n", &pid, &parsed);
+		pos += parsed;
+		if (ret != 1)
+			break;
+		pids[*nr_pids] = pid;
+		*nr_pids += 1;
+	}
+	if (*nr_pids == 0) {
+		kfree(pids);
+		pids = NULL;
+	}
+
+	return pids;
+}
+
+static ssize_t debugfs_pids_write(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char *kbuf;
+	int *targets;
+	ssize_t nr_targets;
+	ssize_t ret;
+	int err;
+
+	kbuf = kmalloc(count, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+
+	ret = simple_write_to_buffer(kbuf, count, ppos, buf, count);
+	if (ret < 0)
+		goto out;
+
+	targets = str_to_pids(kbuf, ret, &nr_targets);
+	if (!targets) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond) {
+		ret = -EINVAL;
+		goto unlock_out;
+	}
+
+	err = damon_set_pids(ctx, targets, nr_targets);
+	if (err)
+		ret = err;
+unlock_out:
+	mutex_unlock(&ctx->kdamond_lock);
+	kfree(targets);
+out:
+	kfree(kbuf);
+	return ret;
+}
+
+static ssize_t debugfs_record_read(struct file *file,
+		char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char record_buf[20 + MAX_RFILE_PATH_LEN];
+	int ret;
+
+	mutex_lock(&ctx->kdamond_lock);
+	ret = snprintf(record_buf, ARRAY_SIZE(record_buf), "%u %s\n",
+			ctx->rbuf_len, ctx->rfile_path);
+	mutex_unlock(&ctx->kdamond_lock);
+	return simple_read_from_buffer(buf, count, ppos, record_buf, ret);
+}
+
+static ssize_t debugfs_record_write(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char *kbuf;
+	unsigned int rbuf_len;
+	char rfile_path[MAX_RFILE_PATH_LEN];
+	ssize_t ret;
+	int err;
+
+	kbuf = kmalloc(count + 1, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+	kbuf[count] = '\0';
+
+	ret = simple_write_to_buffer(kbuf, count, ppos, buf, count);
+	if (ret < 0)
+		goto out;
+	if (sscanf(kbuf, "%u %s",
+				&rbuf_len, rfile_path) != 2) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond) {
+		ret = -EBUSY;
+		goto unlock_out;
+	}
+
+	err = damon_set_recording(ctx, rbuf_len, rfile_path);
+	if (err)
+		ret = err;
+unlock_out:
+	mutex_unlock(&ctx->kdamond_lock);
+out:
+	kfree(kbuf);
+	return ret;
+}
+
+
+static ssize_t debugfs_attrs_read(struct file *file,
+		char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char kbuf[128];
+	int ret;
+
+	mutex_lock(&ctx->kdamond_lock);
+	ret = snprintf(kbuf, ARRAY_SIZE(kbuf), "%lu %lu %lu %lu %lu\n",
+			ctx->sample_interval, ctx->aggr_interval,
+			ctx->regions_update_interval, ctx->min_nr_regions,
+			ctx->max_nr_regions);
+	mutex_unlock(&ctx->kdamond_lock);
+
+	return simple_read_from_buffer(buf, count, ppos, kbuf, ret);
+}
+
+static ssize_t debugfs_attrs_write(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	unsigned long s, a, r, minr, maxr;
+	char *kbuf;
+	ssize_t ret;
+	int err;
+
+	kbuf = kmalloc(count, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+
+	ret = simple_write_to_buffer(kbuf, count, ppos, buf, count);
+	if (ret < 0)
+		goto out;
+
+	if (sscanf(kbuf, "%lu %lu %lu %lu %lu",
+				&s, &a, &r, &minr, &maxr) != 5) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond) {
+		ret = -EBUSY;
+		goto unlock_out;
+	}
+
+	err = damon_set_attrs(ctx, s, a, r, minr, maxr);
+	if (err)
+		ret = err;
+unlock_out:
+	mutex_unlock(&ctx->kdamond_lock);
+out:
+	kfree(kbuf);
+	return ret;
+}
+
+static const struct file_operations monitor_on_fops = {
+	.owner = THIS_MODULE,
+	.read = debugfs_monitor_on_read,
+	.write = debugfs_monitor_on_write,
+};
+
+static const struct file_operations pids_fops = {
+	.owner = THIS_MODULE,
+	.read = debugfs_pids_read,
+	.write = debugfs_pids_write,
+};
+
+static const struct file_operations record_fops = {
+	.owner = THIS_MODULE,
+	.read = debugfs_record_read,
+	.write = debugfs_record_write,
+};
+
+static const struct file_operations attrs_fops = {
+	.owner = THIS_MODULE,
+	.read = debugfs_attrs_read,
+	.write = debugfs_attrs_write,
+};
+
+static struct dentry *debugfs_root;
+
+static int __init damon_debugfs_init(void)
+{
+	const char * const file_names[] = {"attrs", "record",
+		"pids", "monitor_on"};
+	const struct file_operations *fops[] = {&attrs_fops, &record_fops,
+		&pids_fops, &monitor_on_fops};
+	int i;
+
+	debugfs_root = debugfs_create_dir("damon", NULL);
+	if (!debugfs_root) {
+		pr_err("failed to create the debugfs dir\n");
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(file_names); i++) {
+		if (!debugfs_create_file(file_names[i], 0600, debugfs_root,
+					NULL, fops[i])) {
+			pr_err("failed to create %s file\n", file_names[i]);
+			return -ENOMEM;
+		}
+	}
+
+	return 0;
+}
+
+static int __init damon_init_user_ctx(void)
+{
+	int rc;
+
+	struct damon_ctx *ctx = &damon_user_ctx;
+
+	ktime_get_coarse_ts64(&ctx->last_aggregation);
+	ctx->last_regions_update = ctx->last_aggregation;
+
+	rc = damon_set_recording(ctx, 1024 * 1024, "/damon.data");
+	if (rc)
+		return rc;
+
+	mutex_init(&ctx->kdamond_lock);
+
+	INIT_LIST_HEAD(&ctx->tasks_list);
+
+	return 0;
+}
+
 /*
  * Functions for the module loading/unloading
  */
 
 static int __init damon_init(void)
 {
-	return 0;
+	int rc;
+
+	rc = damon_init_user_ctx();
+	if (rc)
+		return rc;
+
+	rc = damon_debugfs_init();
+	if (rc)
+		pr_err("%s: debugfs init failed\n", __func__);
+
+	return rc;
 }
 
 static void __exit damon_exit(void)
 {
+	damon_stop(&damon_user_ctx);
+	debugfs_remove_recursive(debugfs_root);
+
+	kfree(damon_user_ctx.rbuf);
+	kfree(damon_user_ctx.rfile_path);
 }
 
 module_init(damon_init);
-- 
2.17.1

[PATCH v15 09/14] mm/damon: Add tracepoints

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit adds a tracepoint for DAMON.  It traces the monitoring
results of each region for each aggregation interval.  Using this, DAMON
will be easily integrated with any tracepoints supporting tools such as
perf.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 include/trace/events/damon.h | 43 ++++++++++++++++++++++++++++++++++++
 mm/damon.c                   |  4 ++++
 2 files changed, 47 insertions(+)
 create mode 100644 include/trace/events/damon.h

diff --git a/include/trace/events/damon.h b/include/trace/events/damon.h
new file mode 100644
index 000000000000..fd260463d5b8
--- /dev/null
+++ b/include/trace/events/damon.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM damon
+
+#if !defined(_TRACE_DAMON_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_DAMON_H
+
+#include <linux/damon.h>
+#include <linux/types.h>
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(damon_aggregated,
+
+	TP_PROTO(struct damon_task *t, struct damon_region *r,
+		unsigned int nr_regions),
+
+	TP_ARGS(t, r, nr_regions),
+
+	TP_STRUCT__entry(
+		__field(int, pid)
+		__field(unsigned int, nr_regions)
+		__field(unsigned long, vm_start)
+		__field(unsigned long, vm_end)
+		__field(unsigned int, nr_accesses)
+	),
+
+	TP_fast_assign(
+		__entry->pid = t->pid;
+		__entry->nr_regions = nr_regions;
+		__entry->vm_start = r->vm_start;
+		__entry->vm_end = r->vm_end;
+		__entry->nr_accesses = r->nr_accesses;
+	),
+
+	TP_printk("pid=%d nr_regions=%u %lu-%lu: %u", __entry->pid,
+			__entry->nr_regions, __entry->vm_start,
+			__entry->vm_end, __entry->nr_accesses)
+);
+
+#endif /* _TRACE_DAMON_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/mm/damon.c b/mm/damon.c
index 010806b7f92e..1ebf9af40499 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -20,6 +20,8 @@
 
 #define pr_fmt(fmt) "damon: " fmt
 
+#define CREATE_TRACE_POINTS
+
 #include <linux/damon.h>
 #include <linux/debugfs.h>
 #include <linux/delay.h>
@@ -31,6 +33,7 @@
 #include <linux/sched/mm.h>
 #include <linux/sched/task.h>
 #include <linux/slab.h>
+#include <trace/events/damon.h>
 
 /* Minimal region size.  Every damon_region is aligned by this. */
 #define MIN_REGION PAGE_SIZE
@@ -762,6 +765,7 @@ static void kdamond_reset_aggregated(struct damon_ctx *c)
 			damon_write_rbuf(c, &r->vm_end, sizeof(r->vm_end));
 			damon_write_rbuf(c, &r->nr_accesses,
 					sizeof(r->nr_accesses));
+			trace_damon_aggregated(t, r, nr);
 			r->nr_accesses = 0;
 		}
 	}
-- 
2.17.1

[PATCH v15 10/14] tools: Add a minimal user-space tool for DAMON

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit adds a shallow wrapper python script, ``/tools/damon/damo``
that provides more convenient interface.  Note that it is only aimed to
be used for minimal reference of the DAMON's debugfs interfaces and for
debugging of the DAMON itself.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 tools/damon/.gitignore    |   1 +
 tools/damon/_dist.py      |  36 ++++
 tools/damon/_recfile.py   |  23 +++
 tools/damon/bin2txt.py    |  67 +++++++
 tools/damon/damo          |  37 ++++
 tools/damon/heats.py      | 362 ++++++++++++++++++++++++++++++++++++++
 tools/damon/nr_regions.py |  91 ++++++++++
 tools/damon/record.py     | 217 +++++++++++++++++++++++
 tools/damon/report.py     |  45 +++++
 tools/damon/wss.py        |  97 ++++++++++
 10 files changed, 976 insertions(+)
 create mode 100644 tools/damon/.gitignore
 create mode 100644 tools/damon/_dist.py
 create mode 100644 tools/damon/_recfile.py
 create mode 100644 tools/damon/bin2txt.py
 create mode 100755 tools/damon/damo
 create mode 100644 tools/damon/heats.py
 create mode 100644 tools/damon/nr_regions.py
 create mode 100644 tools/damon/record.py
 create mode 100644 tools/damon/report.py
 create mode 100644 tools/damon/wss.py

diff --git a/tools/damon/.gitignore b/tools/damon/.gitignore
new file mode 100644
index 000000000000..96403d36ff93
--- /dev/null
+++ b/tools/damon/.gitignore
@@ -0,0 +1 @@
+__pycache__/*
diff --git a/tools/damon/_dist.py b/tools/damon/_dist.py
new file mode 100644
index 000000000000..9851ec964e5c
--- /dev/null
+++ b/tools/damon/_dist.py
@@ -0,0 +1,36 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import os
+import struct
+import subprocess
+
+def access_patterns(f):
+    nr_regions = struct.unpack('I', f.read(4))[0]
+
+    patterns = []
+    for r in range(nr_regions):
+        saddr = struct.unpack('L', f.read(8))[0]
+        eaddr = struct.unpack('L', f.read(8))[0]
+        nr_accesses = struct.unpack('I', f.read(4))[0]
+        patterns.append([eaddr - saddr, nr_accesses])
+    return patterns
+
+def plot_dist(data_file, output_file, xlabel, ylabel):
+    terminal = output_file.split('.')[-1]
+    if not terminal in ['pdf', 'jpeg', 'png', 'svg']:
+        os.remove(data_file)
+        print("Unsupported plot output type.")
+        exit(-1)
+
+    gnuplot_cmd = """
+    set term %s;
+    set output '%s';
+    set key off;
+    set xlabel '%s';
+    set ylabel '%s';
+    plot '%s' with linespoints;""" % (terminal, output_file, xlabel, ylabel,
+            data_file)
+    subprocess.call(['gnuplot', '-e', gnuplot_cmd])
+    os.remove(data_file)
+
diff --git a/tools/damon/_recfile.py b/tools/damon/_recfile.py
new file mode 100644
index 000000000000..331b4d8165d8
--- /dev/null
+++ b/tools/damon/_recfile.py
@@ -0,0 +1,23 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import struct
+
+fmt_version = 0
+
+def set_fmt_version(f):
+    global fmt_version
+
+    mark = f.read(16)
+    if mark == b'damon_recfmt_ver':
+        fmt_version = struct.unpack('i', f.read(4))[0]
+    else:
+        fmt_version = 0
+        f.seek(0)
+    return fmt_version
+
+def pid(f):
+    if fmt_version == 0:
+        return struct.unpack('L', f.read(8))[0]
+    else:
+        return struct.unpack('i', f.read(4))[0]
diff --git a/tools/damon/bin2txt.py b/tools/damon/bin2txt.py
new file mode 100644
index 000000000000..8b9b57a0d727
--- /dev/null
+++ b/tools/damon/bin2txt.py
@@ -0,0 +1,67 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import argparse
+import os
+import struct
+import sys
+
+import _recfile
+
+def parse_time(bindat):
+    "bindat should be 16 bytes"
+    sec = struct.unpack('l', bindat[0:8])[0]
+    nsec = struct.unpack('l', bindat[8:16])[0]
+    return sec * 1000000000 + nsec;
+
+def pr_region(f):
+    saddr = struct.unpack('L', f.read(8))[0]
+    eaddr = struct.unpack('L', f.read(8))[0]
+    nr_accesses = struct.unpack('I', f.read(4))[0]
+    print("%012x-%012x(%10d):\t%d" %
+            (saddr, eaddr, eaddr - saddr, nr_accesses))
+
+def pr_task_info(f):
+    pid = _recfile.pid(f)
+    print("pid: ", pid)
+    nr_regions = struct.unpack('I', f.read(4))[0]
+    print("nr_regions: ", nr_regions)
+    for r in range(nr_regions):
+        pr_region(f)
+
+def set_argparser(parser):
+    parser.add_argument('--input', '-i', type=str, metavar='<file>',
+            default='damon.data', help='input file name')
+
+def main(args=None):
+    if not args:
+        parser = argparse.ArgumentParser()
+        set_argparser(parser)
+        args = parser.parse_args()
+
+    file_path = args.input
+
+    if not os.path.isfile(file_path):
+        print('input file (%s) is not exist' % file_path)
+        exit(1)
+
+    with open(file_path, 'rb') as f:
+        _recfile.set_fmt_version(f)
+        start_time = None
+        while True:
+            timebin = f.read(16)
+            if len(timebin) != 16:
+                break
+            time = parse_time(timebin)
+            if not start_time:
+                start_time = time
+                print("start_time: ", start_time)
+            print("rel time: %16d" % (time - start_time))
+            nr_tasks = struct.unpack('I', f.read(4))[0]
+            print("nr_tasks: ", nr_tasks)
+            for t in range(nr_tasks):
+                pr_task_info(f)
+                print("")
+
+if __name__ == '__main__':
+    main()
diff --git a/tools/damon/damo b/tools/damon/damo
new file mode 100755
index 000000000000..58e1099ae5fc
--- /dev/null
+++ b/tools/damon/damo
@@ -0,0 +1,37 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import argparse
+
+import record
+import report
+
+class SubCmdHelpFormatter(argparse.RawDescriptionHelpFormatter):
+    def _format_action(self, action):
+        parts = super(argparse.RawDescriptionHelpFormatter,
+                self)._format_action(action)
+        # skip sub parsers help
+        if action.nargs == argparse.PARSER:
+            parts = '\n'.join(parts.split('\n')[1:])
+        return parts
+
+parser = argparse.ArgumentParser(formatter_class=SubCmdHelpFormatter)
+
+subparser = parser.add_subparsers(title='command', dest='command',
+        metavar='<command>')
+subparser.required = True
+
+parser_record = subparser.add_parser('record',
+        help='record data accesses of the given target processes')
+record.set_argparser(parser_record)
+
+parser_report = subparser.add_parser('report',
+        help='report the recorded data accesses in the specified form')
+report.set_argparser(parser_report)
+
+args = parser.parse_args()
+
+if args.command == 'record':
+    record.main(args)
+elif args.command == 'report':
+    report.main(args)
diff --git a/tools/damon/heats.py b/tools/damon/heats.py
new file mode 100644
index 000000000000..99837083874e
--- /dev/null
+++ b/tools/damon/heats.py
@@ -0,0 +1,362 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"""
+Transform binary trace data into human readable text that can be used for
+heatmap drawing, or directly plot the data in a heatmap format.
+
+Format of the text is:
+
+    <time> <space> <heat>
+    ...
+
+"""
+
+import argparse
+import os
+import struct
+import subprocess
+import sys
+import tempfile
+
+import _recfile
+
+class HeatSample:
+    space_idx = None
+    sz_time_space = None
+    heat = None
+
+    def __init__(self, space_idx, sz_time_space, heat):
+        if sz_time_space < 0:
+            raise RuntimeError()
+        self.space_idx = space_idx
+        self.sz_time_space = sz_time_space
+        self.heat = heat
+
+    def total_heat(self):
+        return self.heat * self.sz_time_space
+
+    def merge(self, sample):
+        "sample must have a space idx that same to self"
+        heat_sum = self.total_heat() + sample.total_heat()
+        self.heat = heat_sum / (self.sz_time_space + sample.sz_time_space)
+        self.sz_time_space += sample.sz_time_space
+
+def pr_samples(samples, time_idx, time_unit, region_unit):
+    display_time = time_idx * time_unit
+    for idx, sample in enumerate(samples):
+        display_addr = idx * region_unit
+        if not sample:
+            print("%s\t%s\t%s" % (display_time, display_addr, 0.0))
+            continue
+        print("%s\t%s\t%s" % (display_time, display_addr, sample.total_heat() /
+            time_unit / region_unit))
+
+def to_idx(value, min_, unit):
+    return (value - min_) // unit
+
+def read_task_heats(f, pid, aunit, amin, amax):
+    pid_ = _recfile.pid(f)
+    nr_regions = struct.unpack('I', f.read(4))[0]
+    if pid_ != pid:
+        f.read(20 * nr_regions)
+        return None
+    samples = []
+    for i in range(nr_regions):
+        saddr = struct.unpack('L', f.read(8))[0]
+        eaddr = struct.unpack('L', f.read(8))[0]
+        eaddr = min(eaddr, amax - 1)
+        heat = struct.unpack('I', f.read(4))[0]
+
+        if eaddr <= amin:
+            continue
+        if saddr >= amax:
+            continue
+        saddr = max(amin, saddr)
+        eaddr = min(amax, eaddr)
+
+        sidx = to_idx(saddr, amin, aunit)
+        eidx = to_idx(eaddr - 1, amin, aunit)
+        for idx in range(sidx, eidx + 1):
+            sa = max(amin + idx * aunit, saddr)
+            ea = min(amin + (idx + 1) * aunit, eaddr)
+            sample = HeatSample(idx, (ea - sa), heat)
+            samples.append(sample)
+    return samples
+
+def parse_time(bindat):
+    sec = struct.unpack('l', bindat[0:8])[0]
+    nsec = struct.unpack('l', bindat[8:16])[0]
+    return sec * 1000000000 + nsec
+
+def apply_samples(target_samples, samples, start_time, end_time, aunit, amin):
+    for s in samples:
+        sample = HeatSample(s.space_idx,
+                s.sz_time_space * (end_time - start_time), s.heat)
+        idx = sample.space_idx
+        if not target_samples[idx]:
+            target_samples[idx] = sample
+        else:
+            target_samples[idx].merge(sample)
+
+def __pr_heats(f, pid, tunit, tmin, tmax, aunit, amin, amax):
+    heat_samples = [None] * ((amax - amin) // aunit)
+
+    start_time = 0
+    end_time = 0
+    last_flushed = -1
+    while True:
+        start_time = end_time
+        timebin = f.read(16)
+        if (len(timebin)) != 16:
+            break
+        end_time = parse_time(timebin)
+        nr_tasks = struct.unpack('I', f.read(4))[0]
+        samples_set = {}
+        for t in range(nr_tasks):
+            samples = read_task_heats(f, pid, aunit, amin, amax)
+            if samples:
+                samples_set[pid] = samples
+        if not pid in samples_set:
+            continue
+        if start_time >= tmax:
+            continue
+        if end_time <= tmin:
+            continue
+        start_time = max(start_time, tmin)
+        end_time = min(end_time, tmax)
+
+        sidx = to_idx(start_time, tmin, tunit)
+        eidx = to_idx(end_time - 1, tmin, tunit)
+        for idx in range(sidx, eidx + 1):
+            if idx != last_flushed:
+                pr_samples(heat_samples, idx, tunit, aunit)
+                heat_samples = [None] * ((amax - amin) // aunit)
+                last_flushed = idx
+            st = max(start_time, tmin + idx * tunit)
+            et = min(end_time, tmin + (idx + 1) * tunit)
+            apply_samples(heat_samples, samples_set[pid], st, et, aunit, amin)
+
+def pr_heats(args):
+    binfile = args.input
+    pid = args.pid
+    tres = args.tres
+    tmin = args.tmin
+    ares = args.ares
+    amin = args.amin
+
+    tunit = (args.tmax - tmin) // tres
+    aunit = (args.amax - amin) // ares
+
+    # Compensate the values so that those fit with the resolution
+    tmax = tmin + tunit * tres
+    amax = amin + aunit * ares
+
+    with open(binfile, 'rb') as f:
+        _recfile.set_fmt_version(f)
+        __pr_heats(f, pid, tunit, tmin, tmax, aunit, amin, amax)
+
+class GuideInfo:
+    pid = None
+    start_time = None
+    end_time = None
+    lowest_addr = None
+    highest_addr = None
+    gaps = None
+
+    def __init__(self, pid, start_time):
+        self.pid = pid
+        self.start_time = start_time
+        self.gaps = []
+
+    def regions(self):
+        regions = []
+        region = [self.lowest_addr]
+        for gap in self.gaps:
+            for idx, point in enumerate(gap):
+                if idx == 0:
+                    region.append(point)
+                    regions.append(region)
+                else:
+                    region = [point]
+        region.append(self.highest_addr)
+        regions.append(region)
+        return regions
+
+    def total_space(self):
+        ret = 0
+        for r in self.regions():
+            ret += r[1] - r[0]
+        return ret
+
+    def __str__(self):
+        lines = ['pid:%d' % self.pid]
+        lines.append('time: %d-%d (%d)' % (self.start_time, self.end_time,
+                    self.end_time - self.start_time))
+        for idx, region in enumerate(self.regions()):
+            lines.append('region\t%2d: %020d-%020d (%d)' %
+                    (idx, region[0], region[1], region[1] - region[0]))
+        return '\n'.join(lines)
+
+def is_overlap(region1, region2):
+    if region1[1] < region2[0]:
+        return False
+    if region2[1] < region1[0]:
+        return False
+    return True
+
+def overlap_region_of(region1, region2):
+    return [max(region1[0], region2[0]), min(region1[1], region2[1])]
+
+def overlapping_regions(regions1, regions2):
+    overlap_regions = []
+    for r1 in regions1:
+        for r2 in regions2:
+            if is_overlap(r1, r2):
+                r1 = overlap_region_of(r1, r2)
+        if r1:
+            overlap_regions.append(r1)
+    return overlap_regions
+
+def get_guide_info(binfile):
+    "Read file, return the set of guide information objects of the data"
+    guides = {}
+    with open(binfile, 'rb') as f:
+        _recfile.set_fmt_version(f)
+        while True:
+            timebin = f.read(16)
+            if len(timebin) != 16:
+                break
+            monitor_time = parse_time(timebin)
+            nr_tasks = struct.unpack('I', f.read(4))[0]
+            for t in range(nr_tasks):
+                pid = _recfile.pid(f)
+                nr_regions = struct.unpack('I', f.read(4))[0]
+                if not pid in guides:
+                    guides[pid] = GuideInfo(pid, monitor_time)
+                guide = guides[pid]
+                guide.end_time = monitor_time
+
+                last_addr = None
+                gaps = []
+                for r in range(nr_regions):
+                    saddr = struct.unpack('L', f.read(8))[0]
+                    eaddr = struct.unpack('L', f.read(8))[0]
+                    f.read(4)
+
+                    if not guide.lowest_addr or saddr < guide.lowest_addr:
+                        guide.lowest_addr = saddr
+                    if not guide.highest_addr or eaddr > guide.highest_addr:
+                        guide.highest_addr = eaddr
+
+                    if not last_addr:
+                        last_addr = eaddr
+                        continue
+                    if last_addr != saddr:
+                        gaps.append([last_addr, saddr])
+                    last_addr = eaddr
+
+                if not guide.gaps:
+                    guide.gaps = gaps
+                else:
+                    guide.gaps = overlapping_regions(guide.gaps, gaps)
+    return sorted(list(guides.values()), key=lambda x: x.total_space(),
+                    reverse=True)
+
+def pr_guide(binfile):
+    for guide in get_guide_info(binfile):
+        print(guide)
+
+def region_sort_key(region):
+    return region[1] - region[0]
+
+def set_missed_args(args):
+    if args.pid and args.tmin and args.tmax and args.amin and args.amax:
+        return
+    guides = get_guide_info(args.input)
+    guide = guides[0]
+    if not args.pid:
+        args.pid = guide.pid
+    for g in guides:
+        if g.pid == args.pid:
+            guide = g
+            break
+
+    if not args.tmin:
+        args.tmin = guide.start_time
+    if not args.tmax:
+        args.tmax = guide.end_time
+
+    if not args.amin or not args.amax:
+        region = sorted(guide.regions(), key=lambda x: x[1] - x[0],
+                reverse=True)[0]
+        args.amin = region[0]
+        args.amax = region[1]
+
+def plot_heatmap(data_file, output_file):
+    terminal = output_file.split('.')[-1]
+    if not terminal in ['pdf', 'jpeg', 'png', 'svg']:
+        os.remove(data_file)
+        print("Unsupported plot output type.")
+        exit(-1)
+
+    gnuplot_cmd = """
+    set term %s;
+    set output '%s';
+    set key off;
+    set xrange [0:];
+    set yrange [0:];
+    set xlabel 'Time (ns)';
+    set ylabel 'Virtual Address (bytes)';
+    plot '%s' using 1:2:3 with image;""" % (terminal, output_file, data_file)
+    subprocess.call(['gnuplot', '-e', gnuplot_cmd])
+    os.remove(data_file)
+
+def set_argparser(parser):
+    parser.add_argument('--input', '-i', type=str, metavar='<file>',
+            default='damon.data', help='input file name')
+    parser.add_argument('--pid', metavar='<pid>', type=int,
+            help='pid of target task')
+    parser.add_argument('--tres', metavar='<resolution>', type=int,
+            default=500, help='time resolution of the output')
+    parser.add_argument('--tmin', metavar='<time>', type=lambda x: int(x,0),
+            help='minimal time of the output')
+    parser.add_argument('--tmax', metavar='<time>', type=lambda x: int(x,0),
+            help='maximum time of the output')
+    parser.add_argument('--ares', metavar='<resolution>', type=int, default=500,
+            help='space address resolution of the output')
+    parser.add_argument('--amin', metavar='<address>', type=lambda x: int(x,0),
+            help='minimal space address of the output')
+    parser.add_argument('--amax', metavar='<address>', type=lambda x: int(x,0),
+            help='maximum space address of the output')
+    parser.add_argument('--guide', action='store_true',
+            help='print a guidance for the min/max/resolution settings')
+    parser.add_argument('--heatmap', metavar='<file>', type=str,
+            help='heatmap image file to create')
+
+def main(args=None):
+    if not args:
+        parser = argparse.ArgumentParser()
+        set_argparser(parser)
+        args = parser.parse_args()
+
+    if args.guide:
+        pr_guide(args.input)
+    else:
+        set_missed_args(args)
+        orig_stdout = sys.stdout
+        if args.heatmap:
+            tmp_path = tempfile.mkstemp()[1]
+            tmp_file = open(tmp_path, 'w')
+            sys.stdout = tmp_file
+
+        pr_heats(args)
+
+        if args.heatmap:
+            sys.stdout = orig_stdout
+            tmp_file.flush()
+            tmp_file.close()
+            plot_heatmap(tmp_path, args.heatmap)
+
+if __name__ == '__main__':
+    main()
diff --git a/tools/damon/nr_regions.py b/tools/damon/nr_regions.py
new file mode 100644
index 000000000000..655ee50a7b8d
--- /dev/null
+++ b/tools/damon/nr_regions.py
@@ -0,0 +1,91 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"Print out distribution of the number of regions in the given record"
+
+import argparse
+import struct
+import sys
+import tempfile
+
+import _dist
+import _recfile
+
+def set_argparser(parser):
+    parser.add_argument('--input', '-i', type=str, metavar='<file>',
+            default='damon.data', help='input file name')
+    parser.add_argument('--range', '-r', type=int, nargs=3,
+            metavar=('<start>', '<stop>', '<step>'),
+            help='range of percentiles to print')
+    parser.add_argument('--sortby', '-s', choices=['time', 'size'],
+            help='the metric to be used for sorting the number of regions')
+    parser.add_argument('--plot', '-p', type=str, metavar='<file>',
+            help='plot the distribution to an image file')
+
+def main(args=None):
+    if not args:
+        parser = argparse.ArgumentParser()
+        set_argparser(parser)
+        args = parser.parse_args()
+
+    percentiles = [0, 25, 50, 75, 100]
+
+    file_path = args.input
+    if args.range:
+        percentiles = range(args.range[0], args.range[1], args.range[2])
+    nr_regions_sort = True
+    if args.sortby == 'time':
+        nr_regions_sort = False
+
+    pid_pattern_map = {}
+    with open(file_path, 'rb') as f:
+        _recfile.set_fmt_version(f)
+        start_time = None
+        while True:
+            timebin = f.read(16)
+            if len(timebin) != 16:
+                break
+            nr_tasks = struct.unpack('I', f.read(4))[0]
+            for t in range(nr_tasks):
+                pid = _recfile.pid(f)
+                if not pid in pid_pattern_map:
+                    pid_pattern_map[pid] = []
+                pid_pattern_map[pid].append(_dist.access_patterns(f))
+
+    orig_stdout = sys.stdout
+    if args.plot:
+        tmp_path = tempfile.mkstemp()[1]
+        tmp_file = open(tmp_path, 'w')
+        sys.stdout = tmp_file
+
+    print('# <percentile> <# regions>')
+    for pid in pid_pattern_map.keys():
+        # Skip firs 20 regions as those would not adaptively adjusted
+        snapshots = pid_pattern_map[pid][20:]
+        nr_regions_dist = []
+        for snapshot in snapshots:
+            nr_regions_dist.append(len(snapshot))
+        if nr_regions_sort:
+            nr_regions_dist.sort(reverse=False)
+
+        print('# pid\t%s' % pid)
+        print('# avr:\t%d' % (sum(nr_regions_dist) / len(nr_regions_dist)))
+        for percentile in percentiles:
+            thres_idx = int(percentile / 100.0 * len(nr_regions_dist))
+            if thres_idx == len(nr_regions_dist):
+                thres_idx -= 1
+            threshold = nr_regions_dist[thres_idx]
+            print('%d\t%d' % (percentile, nr_regions_dist[thres_idx]))
+
+    if args.plot:
+        sys.stdout = orig_stdout
+        tmp_file.flush()
+        tmp_file.close()
+        xlabel = 'runtime (percent)'
+        if nr_regions_sort:
+            xlabel = 'percentile'
+        _dist.plot_dist(tmp_path, args.plot, xlabel,
+                'number of monitoring target regions')
+
+if __name__ == '__main__':
+    main()
diff --git a/tools/damon/record.py b/tools/damon/record.py
new file mode 100644
index 000000000000..1e201d788bee
--- /dev/null
+++ b/tools/damon/record.py
@@ -0,0 +1,217 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"""
+Record data access patterns of the target process.
+"""
+
+import argparse
+import copy
+import os
+import signal
+import subprocess
+import time
+
+debugfs_attrs = None
+debugfs_record = None
+debugfs_pids = None
+debugfs_monitor_on = None
+
+def set_target_pid(pid):
+    return subprocess.call('echo %s > %s' % (pid, debugfs_pids), shell=True,
+            executable='/bin/bash')
+
+def turn_damon(on_off):
+    return subprocess.call("echo %s > %s" % (on_off, debugfs_monitor_on),
+            shell=True, executable="/bin/bash")
+
+def is_damon_running():
+    with open(debugfs_monitor_on, 'r') as f:
+        return f.read().strip() == 'on'
+
+def do_record(target, is_target_cmd, attrs, old_attrs):
+    if os.path.isfile(attrs.rfile_path):
+        os.rename(attrs.rfile_path, attrs.rfile_path + '.old')
+
+    if attrs.apply():
+        print('attributes (%s) failed to be applied' % attrs)
+        cleanup_exit(old_attrs, -1)
+    print('# damon attrs: %s' % attrs)
+    if is_target_cmd:
+        p = subprocess.Popen(target, shell=True, executable='/bin/bash')
+        target = p.pid
+    if set_target_pid(target):
+        print('pid setting (%s) failed' % target)
+        cleanup_exit(old_attrs, -2)
+    if turn_damon('on'):
+        print('could not turn on damon' % target)
+        cleanup_exit(old_attrs, -3)
+    while not is_damon_running():
+        time.sleep(1)
+    print('Press Ctrl+C to stop')
+    if is_target_cmd:
+        p.wait()
+    while True:
+        # damon will turn it off by itself if the target tasks are terminated.
+        if not is_damon_running():
+            break
+        time.sleep(1)
+
+    cleanup_exit(old_attrs, 0)
+
+class Attrs:
+    sample_interval = None
+    aggr_interval = None
+    regions_update_interval = None
+    min_nr_regions = None
+    max_nr_regions = None
+    rbuf_len = None
+    rfile_path = None
+
+    def __init__(self, s, a, r, n, x, l, f):
+        self.sample_interval = s
+        self.aggr_interval = a
+        self.regions_update_interval = r
+        self.min_nr_regions = n
+        self.max_nr_regions = x
+        self.rbuf_len = l
+        self.rfile_path = f
+
+    def __str__(self):
+        return "%s %s %s %s %s %s %s" % (self.sample_interval, self.aggr_interval,
+                self.regions_update_interval, self.min_nr_regions,
+                self.max_nr_regions, self.rbuf_len, self.rfile_path)
+
+    def attr_str(self):
+        return "%s %s %s %s %s " % (self.sample_interval, self.aggr_interval,
+                self.regions_update_interval, self.min_nr_regions,
+                self.max_nr_regions)
+
+    def record_str(self):
+        return '%s %s ' % (self.rbuf_len, self.rfile_path)
+
+    def apply(self):
+        ret = subprocess.call('echo %s > %s' % (self.attr_str(), debugfs_attrs),
+                shell=True, executable='/bin/bash')
+        if ret:
+            return ret
+        return subprocess.call('echo %s > %s' % (self.record_str(),
+            debugfs_record), shell=True, executable='/bin/bash')
+
+def current_attrs():
+    with open(debugfs_attrs, 'r') as f:
+        attrs = f.read().split()
+    attrs = [int(x) for x in attrs]
+
+    with open(debugfs_record, 'r') as f:
+        rattrs = f.read().split()
+    attrs.append(int(rattrs[0]))
+    attrs.append(rattrs[1])
+    return Attrs(*attrs)
+
+def cmd_args_to_attrs(args):
+    "Generate attributes with specified arguments"
+    sample_interval = args.sample
+    aggr_interval = args.aggr
+    regions_update_interval = args.updr
+    min_nr_regions = args.minr
+    max_nr_regions = args.maxr
+    rbuf_len = args.rbuf
+    if not os.path.isabs(args.out):
+        args.out = os.path.join(os.getcwd(), args.out)
+    rfile_path = args.out
+    return Attrs(sample_interval, aggr_interval, regions_update_interval,
+            min_nr_regions, max_nr_regions, rbuf_len, rfile_path)
+
+def cleanup_exit(orig_attrs, exit_code):
+    if is_damon_running():
+        if turn_damon('off'):
+            print('failed to turn damon off!')
+        while is_damon_running():
+            time.sleep(1)
+    if orig_attrs:
+        if orig_attrs.apply():
+            print('original attributes (%s) restoration failed!' % orig_attrs)
+    exit(exit_code)
+
+def sighandler(signum, frame):
+    print('\nsignal %s received' % signum)
+    cleanup_exit(orig_attrs, signum)
+
+def chk_update_debugfs(debugfs):
+    global debugfs_attrs
+    global debugfs_record
+    global debugfs_pids
+    global debugfs_monitor_on
+
+    debugfs_damon = os.path.join(debugfs, 'damon')
+    debugfs_attrs = os.path.join(debugfs_damon, 'attrs')
+    debugfs_record = os.path.join(debugfs_damon, 'record')
+    debugfs_pids = os.path.join(debugfs_damon, 'pids')
+    debugfs_monitor_on = os.path.join(debugfs_damon, 'monitor_on')
+
+    if not os.path.isdir(debugfs_damon):
+        print("damon debugfs dir (%s) not found", debugfs_damon)
+        exit(1)
+
+    for f in [debugfs_attrs, debugfs_record, debugfs_pids, debugfs_monitor_on]:
+        if not os.path.isfile(f):
+            print("damon debugfs file (%s) not found" % f)
+            exit(1)
+
+def chk_permission():
+    if os.geteuid() != 0:
+        print("Run as root")
+        exit(1)
+
+def set_argparser(parser):
+    parser.add_argument('target', type=str, metavar='<target>',
+            help='the target command or the pid to record')
+    parser.add_argument('-s', '--sample', metavar='<interval>', type=int,
+            default=5000, help='sampling interval')
+    parser.add_argument('-a', '--aggr', metavar='<interval>', type=int,
+            default=100000, help='aggregate interval')
+    parser.add_argument('-u', '--updr', metavar='<interval>', type=int,
+            default=1000000, help='regions update interval')
+    parser.add_argument('-n', '--minr', metavar='<# regions>', type=int,
+            default=10, help='minimal number of regions')
+    parser.add_argument('-m', '--maxr', metavar='<# regions>', type=int,
+            default=1000, help='maximum number of regions')
+    parser.add_argument('-l', '--rbuf', metavar='<len>', type=int,
+            default=1024*1024, help='length of record result buffer')
+    parser.add_argument('-o', '--out', metavar='<file path>', type=str,
+            default='damon.data', help='output file path')
+    parser.add_argument('-d', '--debugfs', metavar='<debugfs>', type=str,
+            default='/sys/kernel/debug', help='debugfs mounted path')
+
+def main(args=None):
+    global orig_attrs
+    if not args:
+        parser = argparse.ArgumentParser()
+        set_argparser(parser)
+        args = parser.parse_args()
+
+    chk_permission()
+    chk_update_debugfs(args.debugfs)
+
+    signal.signal(signal.SIGINT, sighandler)
+    signal.signal(signal.SIGTERM, sighandler)
+    orig_attrs = current_attrs()
+
+    new_attrs = cmd_args_to_attrs(args)
+    target = args.target
+
+    target_fields = target.split()
+    if not subprocess.call('which %s > /dev/null' % target_fields[0],
+            shell=True, executable='/bin/bash'):
+        do_record(target, True, new_attrs, orig_attrs)
+    else:
+        try:
+            pid = int(target)
+        except:
+            print('target \'%s\' is neither a command, nor a pid' % target)
+            exit(1)
+        do_record(target, False, new_attrs, orig_attrs)
+
+if __name__ == '__main__':
+    main()
diff --git a/tools/damon/report.py b/tools/damon/report.py
new file mode 100644
index 000000000000..c661c7b2f1af
--- /dev/null
+++ b/tools/damon/report.py
@@ -0,0 +1,45 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import argparse
+
+import bin2txt
+import heats
+import nr_regions
+import wss
+
+def set_argparser(parser):
+    subparsers = parser.add_subparsers(title='report type', dest='report_type',
+            metavar='<report type>', help='the type of the report to generate')
+    subparsers.required = True
+
+    parser_raw = subparsers.add_parser('raw', help='human readable raw data')
+    bin2txt.set_argparser(parser_raw)
+
+    parser_heats = subparsers.add_parser('heats', help='heats of regions')
+    heats.set_argparser(parser_heats)
+
+    parser_wss = subparsers.add_parser('wss', help='working set size')
+    wss.set_argparser(parser_wss)
+
+    parser_nr_regions = subparsers.add_parser('nr_regions',
+            help='number of regions')
+    nr_regions.set_argparser(parser_nr_regions)
+
+def main(args=None):
+    if not args:
+        parser = argparse.ArgumentParser()
+        set_argparser(parser)
+        args = parser.parse_args()
+
+    if args.report_type == 'raw':
+        bin2txt.main(args)
+    elif args.report_type == 'heats':
+        heats.main(args)
+    elif args.report_type == 'wss':
+        wss.main(args)
+    elif args.report_type == 'nr_regions':
+        nr_regions.main(args)
+
+if __name__ == '__main__':
+    main()
diff --git a/tools/damon/wss.py b/tools/damon/wss.py
new file mode 100644
index 000000000000..b43065176cfd
--- /dev/null
+++ b/tools/damon/wss.py
@@ -0,0 +1,97 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"Print out the distribution of the working set sizes of the given trace"
+
+import argparse
+import struct
+import sys
+import tempfile
+
+import _dist
+import _recfile
+
+def set_argparser(parser):
+    parser.add_argument('--input', '-i', type=str, metavar='<file>',
+            default='damon.data', help='input file name')
+    parser.add_argument('--range', '-r', type=int, nargs=3,
+            metavar=('<start>', '<stop>', '<step>'),
+            help='range of wss percentiles to print')
+    parser.add_argument('--sortby', '-s', choices=['time', 'size'],
+            help='the metric to be used for the sort of the working set sizes')
+    parser.add_argument('--plot', '-p', type=str, metavar='<file>',
+            help='plot the distribution to an image file')
+
+def main(args=None):
+    if not args:
+        parser = argparse.ArgumentParser()
+        set_argparser(parser)
+        args = parser.parse_args()
+
+    percentiles = [0, 25, 50, 75, 100]
+
+    file_path = args.input
+    if args.range:
+        percentiles = range(args.range[0], args.range[1], args.range[2])
+    wss_sort = True
+    if args.sortby == 'time':
+        wss_sort = False
+
+    pid_pattern_map = {}
+    with open(file_path, 'rb') as f:
+        _recfile.set_fmt_version(f)
+        start_time = None
+        while True:
+            timebin = f.read(16)
+            if len(timebin) != 16:
+                break
+            nr_tasks = struct.unpack('I', f.read(4))[0]
+            for t in range(nr_tasks):
+                pid = _recfile.pid(f)
+                if not pid in pid_pattern_map:
+                    pid_pattern_map[pid] = []
+                pid_pattern_map[pid].append(_dist.access_patterns(f))
+
+    orig_stdout = sys.stdout
+    if args.plot:
+        tmp_path = tempfile.mkstemp()[1]
+        tmp_file = open(tmp_path, 'w')
+        sys.stdout = tmp_file
+
+    print('# <percentile> <wss>')
+    for pid in pid_pattern_map.keys():
+        # Skip first 20 snapshots as regions may not adjusted yet.
+        snapshots = pid_pattern_map[pid][20:]
+        wss_dist = []
+        for snapshot in snapshots:
+            wss = 0
+            for p in snapshot:
+                # Ignore regions not accessed
+                if p[1] <= 0:
+                    continue
+                wss += p[0]
+            wss_dist.append(wss)
+        if wss_sort:
+            wss_dist.sort(reverse=False)
+
+        print('# pid\t%s' % pid)
+        print('# avr:\t%d' % (sum(wss_dist) / len(wss_dist)))
+        for percentile in percentiles:
+            thres_idx = int(percentile / 100.0 * len(wss_dist))
+            if thres_idx == len(wss_dist):
+                thres_idx -= 1
+            threshold = wss_dist[thres_idx]
+            print('%d\t%d' % (percentile, wss_dist[thres_idx]))
+
+    if args.plot:
+        sys.stdout = orig_stdout
+        tmp_file.flush()
+        tmp_file.close()
+        xlabel = 'runtime (percent)'
+        if wss_sort:
+            xlabel = 'percentile'
+        _dist.plot_dist(tmp_path, args.plot, xlabel,
+                'working set size (bytes)')
+
+if __name__ == '__main__':
+    main()
-- 
2.17.1

[PATCH v15 12/14] mm/damon: Add kunit tests

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit adds kunit based unit tests for DAMON.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
---
 mm/Kconfig      |  11 +
 mm/damon-test.h | 635 ++++++++++++++++++++++++++++++++++++++++++++++++
 mm/damon.c      |   6 +
 3 files changed, 652 insertions(+)
 create mode 100644 mm/damon-test.h

diff --git a/mm/Kconfig b/mm/Kconfig
index ecea0889ea35..91473ed9e7c7 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -879,4 +879,15 @@ config DAMON
 	  and 2) sufficiently light-weight so that it can be applied online.
 	  If unsure, say N.
 
+config DAMON_KUNIT_TEST
+	bool "Test for damon"
+	depends on DAMON=y && KUNIT
+	help
+	  This builds the DAMON Kunit test suite.
+
+	  For more information on KUnit and unit tests in general, please refer
+	  to the KUnit documentation.
+
+	  If unsure, say N.
+
 endmenu
diff --git a/mm/damon-test.h b/mm/damon-test.h
new file mode 100644
index 000000000000..5b18619efe72
--- /dev/null
+++ b/mm/damon-test.h
@@ -0,0 +1,635 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Data Access Monitor Unit Tests
+ *
+ * Copyright 2019 Amazon.com, Inc. or its affiliates.  All rights reserved.
+ *
+ * Author: SeongJae Park <sjpark@amazon.de>
+ */
+
+#ifdef CONFIG_DAMON_KUNIT_TEST
+
+#ifndef _DAMON_TEST_H
+#define _DAMON_TEST_H
+
+#include <kunit/test.h>
+
+static void damon_test_str_to_pids(struct kunit *test)
+{
+	char *question;
+	int *answers;
+	int expected[] = {12, 35, 46};
+	ssize_t nr_integers = 0, i;
+
+	question = "123";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)1, nr_integers);
+	KUNIT_EXPECT_EQ(test, 123, answers[0]);
+	kfree(answers);
+
+	question = "123abc";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)1, nr_integers);
+	KUNIT_EXPECT_EQ(test, 123, answers[0]);
+	kfree(answers);
+
+	question = "a123";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)0, nr_integers);
+	KUNIT_EXPECT_PTR_EQ(test, answers, (int *)NULL);
+
+	question = "12 35";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)2, nr_integers);
+	for (i = 0; i < nr_integers; i++)
+		KUNIT_EXPECT_EQ(test, expected[i], answers[i]);
+	kfree(answers);
+
+	question = "12 35 46";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)3, nr_integers);
+	for (i = 0; i < nr_integers; i++)
+		KUNIT_EXPECT_EQ(test, expected[i], answers[i]);
+	kfree(answers);
+
+	question = "12 35 abc 46";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)2, nr_integers);
+	for (i = 0; i < 2; i++)
+		KUNIT_EXPECT_EQ(test, expected[i], answers[i]);
+	kfree(answers);
+
+	question = "";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)0, nr_integers);
+	KUNIT_EXPECT_PTR_EQ(test, (int *)NULL, answers);
+	kfree(answers);
+
+	question = "\n";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)0, nr_integers);
+	KUNIT_EXPECT_PTR_EQ(test, (int *)NULL, answers);
+	kfree(answers);
+}
+
+static void damon_test_regions(struct kunit *test)
+{
+	struct damon_region *r;
+	struct damon_task *t;
+
+	r = damon_new_region(&damon_user_ctx, 1, 2);
+	KUNIT_EXPECT_EQ(test, 1ul, r->vm_start);
+	KUNIT_EXPECT_EQ(test, 2ul, r->vm_end);
+	KUNIT_EXPECT_EQ(test, 0u, r->nr_accesses);
+
+	t = damon_new_task(42);
+	KUNIT_EXPECT_EQ(test, 0u, nr_damon_regions(t));
+
+	damon_add_region(r, t);
+	KUNIT_EXPECT_EQ(test, 1u, nr_damon_regions(t));
+
+	damon_del_region(r);
+	KUNIT_EXPECT_EQ(test, 0u, nr_damon_regions(t));
+
+	damon_free_task(t);
+}
+
+static void damon_test_tasks(struct kunit *test)
+{
+	struct damon_ctx *c = &damon_user_ctx;
+	struct damon_task *t;
+
+	t = damon_new_task(42);
+	KUNIT_EXPECT_EQ(test, 42, t->pid);
+	KUNIT_EXPECT_EQ(test, 0u, nr_damon_tasks(c));
+
+	damon_add_task(&damon_user_ctx, t);
+	KUNIT_EXPECT_EQ(test, 1u, nr_damon_tasks(c));
+
+	damon_destroy_task(t);
+	KUNIT_EXPECT_EQ(test, 0u, nr_damon_tasks(c));
+}
+
+static void damon_test_set_pids(struct kunit *test)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	int pids[] = {1, 2, 3};
+	char buf[64];
+
+	damon_set_pids(ctx, pids, 3);
+	damon_sprint_pids(ctx, buf, 64);
+	KUNIT_EXPECT_STREQ(test, (char *)buf, "1 2 3\n");
+
+	damon_set_pids(ctx, NULL, 0);
+	damon_sprint_pids(ctx, buf, 64);
+	KUNIT_EXPECT_STREQ(test, (char *)buf, "\n");
+
+	damon_set_pids(ctx, (int []){1, 2}, 2);
+	damon_sprint_pids(ctx, buf, 64);
+	KUNIT_EXPECT_STREQ(test, (char *)buf, "1 2\n");
+
+	damon_set_pids(ctx, (int []){2}, 1);
+	damon_sprint_pids(ctx, buf, 64);
+	KUNIT_EXPECT_STREQ(test, (char *)buf, "2\n");
+
+	damon_set_pids(ctx, NULL, 0);
+	damon_sprint_pids(ctx, buf, 64);
+	KUNIT_EXPECT_STREQ(test, (char *)buf, "\n");
+}
+
+static void damon_test_set_recording(struct kunit *test)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+
+	damon_set_recording(ctx, 4242, "foo.bar");
+	KUNIT_EXPECT_EQ(test, ctx->rbuf_len, 4242u);
+	KUNIT_EXPECT_STREQ(test, ctx->rfile_path, "foo.bar");
+	damon_set_recording(ctx, 42, "foo");
+	KUNIT_EXPECT_EQ(test, ctx->rbuf_len, 42u);
+	KUNIT_EXPECT_STREQ(test, ctx->rfile_path, "foo");
+}
+
+/*
+ * Test damon_three_regions_in_vmas() function
+ *
+ * DAMON converts the complex and dynamic memory mappings of each target task
+ * to three discontiguous regions which cover every mapped areas.  However, the
+ * three regions should not include the two biggest unmapped areas in the
+ * original mapping, because the two biggest areas are normally the areas
+ * between 1) heap and the mmap()-ed regions, and 2) the mmap()-ed regions and
+ * stack.  Because these two unmapped areas are very huge but obviously never
+ * accessed, covering the region is just a waste.
+ *
+ * 'damon_three_regions_in_vmas() receives an address space of a process.  It
+ * first identifies the start of mappings, end of mappings, and the two biggest
+ * unmapped areas.  After that, based on the information, it constructs the
+ * three regions and returns.  For more detail, refer to the comment of
+ * 'damon_init_regions_of()' function definition in 'mm/damon.c' file.
+ *
+ * For example, suppose virtual address ranges of 10-20, 20-25, 200-210,
+ * 210-220, 300-305, and 307-330 (Other comments represent this mappings in
+ * more short form: 10-20-25, 200-210-220, 300-305, 307-330) of a process are
+ * mapped.  To cover every mappings, the three regions should start with 10,
+ * and end with 305.  The process also has three unmapped areas, 25-200,
+ * 220-300, and 305-307.  Among those, 25-200 and 220-300 are the biggest two
+ * unmapped areas, and thus it should be converted to three regions of 10-25,
+ * 200-220, and 300-330.
+ */
+static void damon_test_three_regions_in_vmas(struct kunit *test)
+{
+	struct region regions[3] = {0,};
+	/* 10-20-25, 200-210-220, 300-305, 307-330 */
+	struct vm_area_struct vmas[] = {
+		(struct vm_area_struct) {.vm_start = 10, .vm_end = 20},
+		(struct vm_area_struct) {.vm_start = 20, .vm_end = 25},
+		(struct vm_area_struct) {.vm_start = 200, .vm_end = 210},
+		(struct vm_area_struct) {.vm_start = 210, .vm_end = 220},
+		(struct vm_area_struct) {.vm_start = 300, .vm_end = 305},
+		(struct vm_area_struct) {.vm_start = 307, .vm_end = 330},
+	};
+	vmas[0].vm_next = &vmas[1];
+	vmas[1].vm_next = &vmas[2];
+	vmas[2].vm_next = &vmas[3];
+	vmas[3].vm_next = &vmas[4];
+	vmas[4].vm_next = &vmas[5];
+	vmas[5].vm_next = NULL;
+
+	damon_three_regions_in_vmas(&vmas[0], regions);
+
+	KUNIT_EXPECT_EQ(test, 10ul, regions[0].start);
+	KUNIT_EXPECT_EQ(test, 25ul, regions[0].end);
+	KUNIT_EXPECT_EQ(test, 200ul, regions[1].start);
+	KUNIT_EXPECT_EQ(test, 220ul, regions[1].end);
+	KUNIT_EXPECT_EQ(test, 300ul, regions[2].start);
+	KUNIT_EXPECT_EQ(test, 330ul, regions[2].end);
+}
+
+/* Clean up global state of damon */
+static void damon_cleanup_global_state(void)
+{
+	struct damon_task *t, *next;
+
+	damon_for_each_task_safe(t, next, &damon_user_ctx)
+		damon_destroy_task(t);
+
+	damon_user_ctx.rbuf_offset = 0;
+}
+
+/*
+ * Test kdamond_reset_aggregated()
+ *
+ * DAMON checks access to each region and aggregates this information as the
+ * access frequency of each region.  In detail, it increases '->nr_accesses' of
+ * regions that an access has confirmed.  'kdamond_reset_aggregated()' flushes
+ * the aggregated information ('->nr_accesses' of each regions) to the result
+ * buffer.  As a result of the flushing, the '->nr_accesses' of regions are
+ * initialized to zero.
+ */
+static void damon_test_aggregate(struct kunit *test)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	int pids[] = {1, 2, 3};
+	unsigned long saddr[][3] = {{10, 20, 30}, {5, 42, 49}, {13, 33, 55} };
+	unsigned long eaddr[][3] = {{15, 27, 40}, {31, 45, 55}, {23, 44, 66} };
+	unsigned long accesses[][3] = {{42, 95, 84}, {10, 20, 30}, {0, 1, 2} };
+	struct damon_task *t;
+	struct damon_region *r;
+	int it, ir;
+	ssize_t sz, sr, sp;
+
+	damon_set_recording(ctx, 256, "damon.data");
+	damon_set_pids(ctx, pids, 3);
+
+	it = 0;
+	damon_for_each_task(t, ctx) {
+		for (ir = 0; ir < 3; ir++) {
+			r = damon_new_region(ctx,
+					saddr[it][ir], eaddr[it][ir]);
+			r->nr_accesses = accesses[it][ir];
+			damon_add_region(r, t);
+		}
+		it++;
+	}
+	kdamond_reset_aggregated(ctx);
+	it = 0;
+	damon_for_each_task(t, ctx) {
+		ir = 0;
+		/* '->nr_accesses' should be zeroed */
+		damon_for_each_region(r, t) {
+			KUNIT_EXPECT_EQ(test, 0u, r->nr_accesses);
+			ir++;
+		}
+		/* regions should be preserved */
+		KUNIT_EXPECT_EQ(test, 3, ir);
+		it++;
+	}
+	/* tasks also should be preserved */
+	KUNIT_EXPECT_EQ(test, 3, it);
+
+	/* The aggregated information should be written in the buffer */
+	sr = sizeof(r->vm_start) + sizeof(r->vm_end) + sizeof(r->nr_accesses);
+	sp = sizeof(t->pid) + sizeof(unsigned int) + 3 * sr;
+	sz = sizeof(struct timespec64) + sizeof(unsigned int) + 3 * sp;
+	KUNIT_EXPECT_EQ(test, (unsigned int)sz, ctx->rbuf_offset);
+
+	damon_set_recording(ctx, 0, "damon.data");
+	damon_cleanup_global_state();
+}
+
+static void damon_test_write_rbuf(struct kunit *test)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char *data;
+
+	damon_set_recording(&damon_user_ctx, 256, "damon.data");
+
+	data = "hello";
+	damon_write_rbuf(ctx, data, strnlen(data, 256));
+	KUNIT_EXPECT_EQ(test, ctx->rbuf_offset, 5u);
+
+	damon_write_rbuf(ctx, data, 0);
+	KUNIT_EXPECT_EQ(test, ctx->rbuf_offset, 5u);
+
+	KUNIT_EXPECT_STREQ(test, (char *)ctx->rbuf, data);
+	damon_set_recording(&damon_user_ctx, 0, "damon.data");
+}
+
+static struct damon_region *__nth_region_of(struct damon_task *t, int idx)
+{
+	struct damon_region *r;
+	unsigned int i = 0;
+
+	damon_for_each_region(r, t) {
+		if (i++ == idx)
+			return r;
+	}
+
+	return NULL;
+}
+
+/*
+ * Test 'damon_apply_three_regions()'
+ *
+ * test			kunit object
+ * regions		an array containing start/end addresses of current
+ *			monitoring target regions
+ * nr_regions		the number of the addresses in 'regions'
+ * three_regions	The three regions that need to be applied now
+ * expected		start/end addresses of monitoring target regions that
+ *			'three_regions' are applied
+ * nr_expected		the number of addresses in 'expected'
+ *
+ * The memory mapping of the target processes changes dynamically.  To follow
+ * the change, DAMON periodically reads the mappings, simplifies it to the
+ * three regions, and updates the monitoring target regions to fit in the three
+ * regions.  The update of current target regions is the role of
+ * 'damon_apply_three_regions()'.
+ *
+ * This test passes the given target regions and the new three regions that
+ * need to be applied to the function and check whether it updates the regions
+ * as expected.
+ */
+static void damon_do_test_apply_three_regions(struct kunit *test,
+				unsigned long *regions, int nr_regions,
+				struct region *three_regions,
+				unsigned long *expected, int nr_expected)
+{
+	struct damon_task *t;
+	struct damon_region *r;
+	int i;
+
+	t = damon_new_task(42);
+	for (i = 0; i < nr_regions / 2; i++) {
+		r = damon_new_region(&damon_user_ctx,
+				regions[i * 2], regions[i * 2 + 1]);
+		damon_add_region(r, t);
+	}
+	damon_add_task(&damon_user_ctx, t);
+
+	damon_apply_three_regions(&damon_user_ctx, t, three_regions);
+
+	for (i = 0; i < nr_expected / 2; i++) {
+		r = __nth_region_of(t, i);
+		KUNIT_EXPECT_EQ(test, r->vm_start, expected[i * 2]);
+		KUNIT_EXPECT_EQ(test, r->vm_end, expected[i * 2 + 1]);
+	}
+
+	damon_cleanup_global_state();
+}
+
+/*
+ * This function test most common case where the three big regions are only
+ * slightly changed.  Target regions should adjust their boundary (10-20-30,
+ * 50-55, 70-80, 90-100) to fit with the new big regions or remove target
+ * regions (57-79) that now out of the three regions.
+ */
+static void damon_test_apply_three_regions1(struct kunit *test)
+{
+	/* 10-20-30, 50-55-57-59, 70-80-90-100 */
+	unsigned long regions[] = {10, 20, 20, 30, 50, 55, 55, 57, 57, 59,
+				70, 80, 80, 90, 90, 100};
+	/* 5-27, 45-55, 73-104 */
+	struct region new_three_regions[3] = {
+		(struct region){.start = 5, .end = 27},
+		(struct region){.start = 45, .end = 55},
+		(struct region){.start = 73, .end = 104} };
+	/* 5-20-27, 45-55, 73-80-90-104 */
+	unsigned long expected[] = {5, 20, 20, 27, 45, 55,
+				73, 80, 80, 90, 90, 104};
+
+	damon_do_test_apply_three_regions(test, regions, ARRAY_SIZE(regions),
+			new_three_regions, expected, ARRAY_SIZE(expected));
+}
+
+/*
+ * Test slightly bigger change.  Similar to above, but the second big region
+ * now require two target regions (50-55, 57-59) to be removed.
+ */
+static void damon_test_apply_three_regions2(struct kunit *test)
+{
+	/* 10-20-30, 50-55-57-59, 70-80-90-100 */
+	unsigned long regions[] = {10, 20, 20, 30, 50, 55, 55, 57, 57, 59,
+				70, 80, 80, 90, 90, 100};
+	/* 5-27, 56-57, 65-104 */
+	struct region new_three_regions[3] = {
+		(struct region){.start = 5, .end = 27},
+		(struct region){.start = 56, .end = 57},
+		(struct region){.start = 65, .end = 104} };
+	/* 5-20-27, 56-57, 65-80-90-104 */
+	unsigned long expected[] = {5, 20, 20, 27, 56, 57,
+				65, 80, 80, 90, 90, 104};
+
+	damon_do_test_apply_three_regions(test, regions, ARRAY_SIZE(regions),
+			new_three_regions, expected, ARRAY_SIZE(expected));
+}
+
+/*
+ * Test a big change.  The second big region has totally freed and mapped to
+ * different area (50-59 -> 61-63).  The target regions which were in the old
+ * second big region (50-55-57-59) should be removed and new target region
+ * covering the second big region (61-63) should be created.
+ */
+static void damon_test_apply_three_regions3(struct kunit *test)
+{
+	/* 10-20-30, 50-55-57-59, 70-80-90-100 */
+	unsigned long regions[] = {10, 20, 20, 30, 50, 55, 55, 57, 57, 59,
+				70, 80, 80, 90, 90, 100};
+	/* 5-27, 61-63, 65-104 */
+	struct region new_three_regions[3] = {
+		(struct region){.start = 5, .end = 27},
+		(struct region){.start = 61, .end = 63},
+		(struct region){.start = 65, .end = 104} };
+	/* 5-20-27, 61-63, 65-80-90-104 */
+	unsigned long expected[] = {5, 20, 20, 27, 61, 63,
+				65, 80, 80, 90, 90, 104};
+
+	damon_do_test_apply_three_regions(test, regions, ARRAY_SIZE(regions),
+			new_three_regions, expected, ARRAY_SIZE(expected));
+}
+
+/*
+ * Test another big change.  Both of the second and third big regions (50-59
+ * and 70-100) has totally freed and mapped to different area (30-32 and
+ * 65-68).  The target regions which were in the old second and third big
+ * regions should now be removed and new target regions covering the new second
+ * and third big regions should be crated.
+ */
+static void damon_test_apply_three_regions4(struct kunit *test)
+{
+	/* 10-20-30, 50-55-57-59, 70-80-90-100 */
+	unsigned long regions[] = {10, 20, 20, 30, 50, 55, 55, 57, 57, 59,
+				70, 80, 80, 90, 90, 100};
+	/* 5-7, 30-32, 65-68 */
+	struct region new_three_regions[3] = {
+		(struct region){.start = 5, .end = 7},
+		(struct region){.start = 30, .end = 32},
+		(struct region){.start = 65, .end = 68} };
+	/* expect 5-7, 30-32, 65-68 */
+	unsigned long expected[] = {5, 7, 30, 32, 65, 68};
+
+	damon_do_test_apply_three_regions(test, regions, ARRAY_SIZE(regions),
+			new_three_regions, expected, ARRAY_SIZE(expected));
+}
+
+static void damon_test_split_evenly(struct kunit *test)
+{
+	struct damon_ctx *c = &damon_user_ctx;
+	struct damon_task *t;
+	struct damon_region *r;
+	unsigned long i;
+
+	KUNIT_EXPECT_EQ(test, damon_split_region_evenly(c, NULL, 5), -EINVAL);
+
+	t = damon_new_task(42);
+	r = damon_new_region(&damon_user_ctx, 0, 100);
+	KUNIT_EXPECT_EQ(test, damon_split_region_evenly(c, r, 0), -EINVAL);
+
+	damon_add_region(r, t);
+	KUNIT_EXPECT_EQ(test, damon_split_region_evenly(c, r, 10), 0);
+	KUNIT_EXPECT_EQ(test, nr_damon_regions(t), 10u);
+
+	i = 0;
+	damon_for_each_region(r, t) {
+		KUNIT_EXPECT_EQ(test, r->vm_start, i++ * 10);
+		KUNIT_EXPECT_EQ(test, r->vm_end, i * 10);
+	}
+	damon_free_task(t);
+
+	t = damon_new_task(42);
+	r = damon_new_region(&damon_user_ctx, 5, 59);
+	damon_add_region(r, t);
+	KUNIT_EXPECT_EQ(test, damon_split_region_evenly(c, r, 5), 0);
+	KUNIT_EXPECT_EQ(test, nr_damon_regions(t), 5u);
+
+	i = 0;
+	damon_for_each_region(r, t) {
+		if (i == 4)
+			break;
+		KUNIT_EXPECT_EQ(test, r->vm_start, 5 + 10 * i++);
+		KUNIT_EXPECT_EQ(test, r->vm_end, 5 + 10 * i);
+	}
+	KUNIT_EXPECT_EQ(test, r->vm_start, 5 + 10 * i);
+	KUNIT_EXPECT_EQ(test, r->vm_end, 59ul);
+	damon_free_task(t);
+
+	t = damon_new_task(42);
+	r = damon_new_region(&damon_user_ctx, 5, 6);
+	damon_add_region(r, t);
+	KUNIT_EXPECT_EQ(test, damon_split_region_evenly(c, r, 2), -EINVAL);
+	KUNIT_EXPECT_EQ(test, nr_damon_regions(t), 1u);
+
+	damon_for_each_region(r, t) {
+		KUNIT_EXPECT_EQ(test, r->vm_start, 5ul);
+		KUNIT_EXPECT_EQ(test, r->vm_end, 6ul);
+	}
+	damon_free_task(t);
+}
+
+static void damon_test_split_at(struct kunit *test)
+{
+	struct damon_task *t;
+	struct damon_region *r;
+
+	t = damon_new_task(42);
+	r = damon_new_region(&damon_user_ctx, 0, 100);
+	damon_add_region(r, t);
+	damon_split_region_at(&damon_user_ctx, r, 25);
+	KUNIT_EXPECT_EQ(test, r->vm_start, 0ul);
+	KUNIT_EXPECT_EQ(test, r->vm_end, 25ul);
+
+	r = damon_next_region(r);
+	KUNIT_EXPECT_EQ(test, r->vm_start, 25ul);
+	KUNIT_EXPECT_EQ(test, r->vm_end, 100ul);
+
+	damon_free_task(t);
+}
+
+static void damon_test_merge_two(struct kunit *test)
+{
+	struct damon_task *t;
+	struct damon_region *r, *r2, *r3;
+	int i;
+
+	t = damon_new_task(42);
+	r = damon_new_region(&damon_user_ctx, 0, 100);
+	r->nr_accesses = 10;
+	damon_add_region(r, t);
+	r2 = damon_new_region(&damon_user_ctx, 100, 300);
+	r2->nr_accesses = 20;
+	damon_add_region(r2, t);
+
+	damon_merge_two_regions(r, r2);
+	KUNIT_EXPECT_EQ(test, r->vm_start, 0ul);
+	KUNIT_EXPECT_EQ(test, r->vm_end, 300ul);
+	KUNIT_EXPECT_EQ(test, r->nr_accesses, 16u);
+
+	i = 0;
+	damon_for_each_region(r3, t) {
+		KUNIT_EXPECT_PTR_EQ(test, r, r3);
+		i++;
+	}
+	KUNIT_EXPECT_EQ(test, i, 1);
+
+	damon_free_task(t);
+}
+
+static void damon_test_merge_regions_of(struct kunit *test)
+{
+	struct damon_task *t;
+	struct damon_region *r;
+	unsigned long sa[] = {0, 100, 114, 122, 130, 156, 170, 184};
+	unsigned long ea[] = {100, 112, 122, 130, 156, 170, 184, 230};
+	unsigned int nrs[] = {0, 0, 10, 10, 20, 30, 1, 2};
+
+	unsigned long saddrs[] = {0, 114, 130, 156, 170};
+	unsigned long eaddrs[] = {112, 130, 156, 170, 230};
+	int i;
+
+	t = damon_new_task(42);
+	for (i = 0; i < ARRAY_SIZE(sa); i++) {
+		r = damon_new_region(&damon_user_ctx, sa[i], ea[i]);
+		r->nr_accesses = nrs[i];
+		damon_add_region(r, t);
+	}
+
+	damon_merge_regions_of(t, 9);
+	/* 0-112, 114-130, 130-156, 156-170 */
+	KUNIT_EXPECT_EQ(test, nr_damon_regions(t), 5u);
+	for (i = 0; i < 5; i++) {
+		r = __nth_region_of(t, i);
+		KUNIT_EXPECT_EQ(test, r->vm_start, saddrs[i]);
+		KUNIT_EXPECT_EQ(test, r->vm_end, eaddrs[i]);
+	}
+	damon_free_task(t);
+}
+
+static void damon_test_split_regions_of(struct kunit *test)
+{
+	struct damon_task *t;
+	struct damon_region *r;
+
+	t = damon_new_task(42);
+	r = damon_new_region(&damon_user_ctx, 0, 22);
+	damon_add_region(r, t);
+	damon_split_regions_of(&damon_user_ctx, t, 2);
+	KUNIT_EXPECT_EQ(test, nr_damon_regions(t), 2u);
+	damon_free_task(t);
+
+	t = damon_new_task(42);
+	r = damon_new_region(&damon_user_ctx, 0, 220);
+	damon_add_region(r, t);
+	damon_split_regions_of(&damon_user_ctx, t, 4);
+	KUNIT_EXPECT_EQ(test, nr_damon_regions(t), 4u);
+	damon_free_task(t);
+}
+
+static struct kunit_case damon_test_cases[] = {
+	KUNIT_CASE(damon_test_str_to_pids),
+	KUNIT_CASE(damon_test_tasks),
+	KUNIT_CASE(damon_test_regions),
+	KUNIT_CASE(damon_test_set_pids),
+	KUNIT_CASE(damon_test_set_recording),
+	KUNIT_CASE(damon_test_three_regions_in_vmas),
+	KUNIT_CASE(damon_test_aggregate),
+	KUNIT_CASE(damon_test_write_rbuf),
+	KUNIT_CASE(damon_test_apply_three_regions1),
+	KUNIT_CASE(damon_test_apply_three_regions2),
+	KUNIT_CASE(damon_test_apply_three_regions3),
+	KUNIT_CASE(damon_test_apply_three_regions4),
+	KUNIT_CASE(damon_test_split_evenly),
+	KUNIT_CASE(damon_test_split_at),
+	KUNIT_CASE(damon_test_merge_two),
+	KUNIT_CASE(damon_test_merge_regions_of),
+	KUNIT_CASE(damon_test_split_regions_of),
+	{},
+};
+
+static struct kunit_suite damon_test_suite = {
+	.name = "damon",
+	.test_cases = damon_test_cases,
+};
+kunit_test_suite(damon_test_suite);
+
+#endif /* _DAMON_TEST_H */
+
+#endif	/* CONFIG_DAMON_KUNIT_TEST */
diff --git a/mm/damon.c b/mm/damon.c
index 1ebf9af40499..c390a0cbc54a 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -36,7 +36,11 @@
 #include <trace/events/damon.h>
 
 /* Minimal region size.  Every damon_region is aligned by this. */
+#ifndef CONFIG_DAMON_KUNIT_TEST
 #define MIN_REGION PAGE_SIZE
+#else
+#define MIN_REGION 1
+#endif
 
 /*
  * Functions and macros for DAMON data structures
@@ -1546,3 +1550,5 @@ module_exit(damon_exit);
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("SeongJae Park <sjpark@amazon.de>");
 MODULE_DESCRIPTION("DAMON: Data Access MONitor");
+
+#include "damon-test.h"
-- 
2.17.1

[PATCH v15 13/14] mm/damon: Add user space selftests

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit adds a simple user space tests for DAMON.  The tests are
using kselftest framework.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 tools/testing/selftests/damon/Makefile        |   7 +
 .../selftests/damon/_chk_dependency.sh        |  28 ++++
 tools/testing/selftests/damon/_chk_record.py  | 108 ++++++++++++++
 .../testing/selftests/damon/debugfs_attrs.sh  | 139 ++++++++++++++++++
 .../testing/selftests/damon/debugfs_record.sh |  50 +++++++
 5 files changed, 332 insertions(+)
 create mode 100644 tools/testing/selftests/damon/Makefile
 create mode 100644 tools/testing/selftests/damon/_chk_dependency.sh
 create mode 100644 tools/testing/selftests/damon/_chk_record.py
 create mode 100755 tools/testing/selftests/damon/debugfs_attrs.sh
 create mode 100755 tools/testing/selftests/damon/debugfs_record.sh

diff --git a/tools/testing/selftests/damon/Makefile b/tools/testing/selftests/damon/Makefile
new file mode 100644
index 000000000000..cfd5393a4639
--- /dev/null
+++ b/tools/testing/selftests/damon/Makefile
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0
+# Makefile for damon selftests
+
+TEST_FILES = _chk_dependency.sh _chk_record_file.py
+TEST_PROGS = debugfs_attrs.sh debugfs_record.sh
+
+include ../lib.mk
diff --git a/tools/testing/selftests/damon/_chk_dependency.sh b/tools/testing/selftests/damon/_chk_dependency.sh
new file mode 100644
index 000000000000..814dcadd5e96
--- /dev/null
+++ b/tools/testing/selftests/damon/_chk_dependency.sh
@@ -0,0 +1,28 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+DBGFS=/sys/kernel/debug/damon
+
+if [ $EUID -ne 0 ];
+then
+	echo "Run as root"
+	exit $ksft_skip
+fi
+
+if [ ! -d $DBGFS ]
+then
+	echo "$DBGFS not found"
+	exit $ksft_skip
+fi
+
+for f in attrs record pids monitor_on
+do
+	if [ ! -f "$DBGFS/$f" ]
+	then
+		echo "$f not found"
+		exit 1
+	fi
+done
diff --git a/tools/testing/selftests/damon/_chk_record.py b/tools/testing/selftests/damon/_chk_record.py
new file mode 100644
index 000000000000..5cfcf4161404
--- /dev/null
+++ b/tools/testing/selftests/damon/_chk_record.py
@@ -0,0 +1,108 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"Check whether the DAMON record file is valid"
+
+import argparse
+import struct
+import sys
+
+fmt_version = 0
+
+def set_fmt_version(f):
+    global fmt_version
+
+    mark = f.read(16)
+    if mark == b'damon_recfmt_ver':
+        fmt_version = struct.unpack('i', f.read(4))[0]
+    else:
+        fmt_version = 0
+        f.seek(0)
+    return fmt_version
+
+def read_pid(f):
+    if fmt_version == 0:
+        pid = struct.unpack('L', f.read(8))[0]
+    else:
+        pid = struct.unpack('i', f.read(4))[0]
+def err_percent(val, expected):
+    return abs(val - expected) / expected * 100
+
+def chk_task_info(f):
+    pid = read_pid(f)
+    nr_regions = struct.unpack('I', f.read(4))[0]
+
+    if nr_regions > max_nr_regions:
+        print('too many regions: %d > %d' % (nr_regions, max_nr_regions))
+        exit(1)
+
+    nr_gaps = 0
+    eaddr = 0
+    for r in range(nr_regions):
+        saddr = struct.unpack('L', f.read(8))[0]
+        if eaddr and saddr != eaddr:
+            nr_gaps += 1
+        eaddr = struct.unpack('L', f.read(8))[0]
+        nr_accesses = struct.unpack('I', f.read(4))[0]
+
+        if saddr >= eaddr:
+            print('wrong region [%d,%d)' % (saddr, eaddr))
+            exit(1)
+
+        max_nr_accesses = aint / sint
+        if nr_accesses > max_nr_accesses:
+            if err_percent(nr_accesses, max_nr_accesses) > 15:
+                print('too high nr_access: expected %d but %d' %
+                        (max_nr_accesses, nr_accesses))
+                exit(1)
+    if nr_gaps != 2:
+        print('number of gaps are not two but %d' % nr_gaps)
+        exit(1)
+
+def parse_time_us(bindat):
+    sec = struct.unpack('l', bindat[0:8])[0]
+    nsec = struct.unpack('l', bindat[8:16])[0]
+    return (sec * 1000000000 + nsec) / 1000
+
+def main():
+    global sint
+    global aint
+    global min_nr
+    global max_nr_regions
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument('file', metavar='<file>',
+            help='path to the record file')
+    parser.add_argument('--attrs', metavar='<attrs>',
+            default='5000 100000 1000000 10 1000',
+            help='content of debugfs attrs file')
+    args = parser.parse_args()
+    file_path = args.file
+    attrs = [int(x) for x in args.attrs.split()]
+    sint, aint, rint, min_nr, max_nr_regions = attrs
+
+    with open(file_path, 'rb') as f:
+        set_fmt_version(f)
+        last_aggr_time = None
+        while True:
+            timebin = f.read(16)
+            if len(timebin) != 16:
+                break
+
+            now = parse_time_us(timebin)
+            if not last_aggr_time:
+                last_aggr_time = now
+            else:
+                error = err_percent(now - last_aggr_time, aint)
+                if error > 15:
+                    print('wrong aggr interval: expected %d, but %d' %
+                            (aint, now - last_aggr_time))
+                    exit(1)
+                last_aggr_time = now
+
+            nr_tasks = struct.unpack('I', f.read(4))[0]
+            for t in range(nr_tasks):
+                chk_task_info(f)
+
+if __name__ == '__main__':
+    main()
diff --git a/tools/testing/selftests/damon/debugfs_attrs.sh b/tools/testing/selftests/damon/debugfs_attrs.sh
new file mode 100755
index 000000000000..d5188b0f71b1
--- /dev/null
+++ b/tools/testing/selftests/damon/debugfs_attrs.sh
@@ -0,0 +1,139 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+source ./_chk_dependency.sh
+
+# Test attrs file
+file="$DBGFS/attrs"
+
+ORIG_CONTENT=$(cat $file)
+
+echo 1 2 3 4 5 > $file
+if [ $? -ne 0 ]
+then
+	echo "$file write failed"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo 1 2 3 4 > $file
+if [ $? -eq 0 ]
+then
+	echo "$file write success (should failed)"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+CONTENT=$(cat $file)
+if [ "$CONTENT" != "1 2 3 4 5" ]
+then
+	echo "$file not written"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo $ORIG_CONTENT > $file
+
+# Test record file
+file="$DBGFS/record"
+
+ORIG_CONTENT=$(cat $file)
+
+echo "4242 foo.bar" > $file
+if [ $? -ne 0 ]
+then
+	echo "$file writing sane input failed"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo abc 2 3 > $file
+if [ $? -eq 0 ]
+then
+	echo "$file writing insane input 1 success (should failed)"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo 123 > $file
+if [ $? -eq 0 ]
+then
+	echo "$file writing insane input 2 success (should failed)"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+CONTENT=$(cat $file)
+if [ "$CONTENT" != "4242 foo.bar" ]
+then
+	echo "$file not written"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo "0 null" > $file
+if [ $? -ne 0 ]
+then
+	echo "$file disabling write fail"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+CONTENT=$(cat $file)
+if [ "$CONTENT" != "0 null" ]
+then
+	echo "$file not disabled"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo "4242 foo.bar" > $file
+if [ $? -ne 0 ]
+then
+	echo "$file writing sane data again fail"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo $ORIG_CONTENT > $file
+
+# Test pids file
+file="$DBGFS/pids"
+
+ORIG_CONTENT=$(cat $file)
+
+echo "1 2 3 4" > $file
+if [ $? -ne 0 ]
+then
+	echo "$file write fail"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo "1 2 abc 4" > $file
+if [ $? -ne 0 ]
+then
+	echo "$file write fail"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo abc 2 3 > $file
+if [ $? -eq 0 ]
+then
+	echo "$file write success (should failed)"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+CONTENT=$(cat $file)
+if [ "$CONTENT" != "1 2" ]
+then
+	echo "$file not written"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo $ORIG_CONTENT > $file
+
+echo "PASS"
diff --git a/tools/testing/selftests/damon/debugfs_record.sh b/tools/testing/selftests/damon/debugfs_record.sh
new file mode 100755
index 000000000000..fa9e07eea258
--- /dev/null
+++ b/tools/testing/selftests/damon/debugfs_record.sh
@@ -0,0 +1,50 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+source ./_chk_dependency.sh
+
+restore_attrs()
+{
+	echo $ORIG_ATTRS > $DBGFS/attrs
+	echo $ORIG_PIDS > $DBGFS/pids
+	echo $ORIG_RECORD > $DBGFS/record
+}
+
+ORIG_ATTRS=$(cat $DBGFS/attrs)
+ORIG_PIDS=$(cat $DBGFS/pids)
+ORIG_RECORD=$(cat $DBGFS/record)
+
+rfile=$pwd/damon.data
+
+rm -f $rfile
+ATTRS="5000 100000 1000000 10 1000"
+echo $ATTRS > $DBGFS/attrs
+echo 4096 $rfile > $DBGFS/record
+sleep 5 &
+echo $(pidof sleep) > $DBGFS/pids
+echo on > $DBGFS/monitor_on
+sleep 0.5
+killall sleep
+echo off > $DBGFS/monitor_on
+
+sync
+
+if [ ! -f $rfile ]
+then
+	echo "record file not made"
+	restore_attrs
+
+	exit 1
+fi
+
+python3 ./_chk_record.py $rfile --attrs "$ATTRS"
+if [ $? -ne 0 ]
+then
+	echo "record file is wrong"
+	restore_attrs
+	exit 1
+fi
+
+rm -f $rfile
+restore_attrs
+echo "PASS"
-- 
2.17.1

[PATCH v15 14/14] MAINTAINERS: Update for DAMON

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit updates MAINTAINERS file for DAMON related files.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 MAINTAINERS | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 50659d76976b..2396a9098715 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4686,6 +4686,18 @@ F:	net/ax25/ax25_out.c
 F:	net/ax25/ax25_timer.c
 F:	net/ax25/sysctl_net_ax25.c
 
+DATA ACCESS MONITOR
+M:	SeongJae Park <sjpark@amazon.de>
+L:	linux-mm@kvack.org
+S:	Maintained
+F:	Documentation/admin-guide/mm/damon/*
+F:	include/linux/damon.h
+F:	include/trace/events/damon.h
+F:	mm/damon-test.h
+F:	mm/damon.c
+F:	tools/damon/*
+F:	tools/testing/selftests/damon/*
+
 DAVICOM FAST ETHERNET (DMFE) NETWORK DRIVER
 L:	netdev@vger.kernel.org
 S:	Orphan
-- 
2.17.1

Re: [PATCH v15 01/14] mm/page_ext: Export lookup_page_ext() to GPL modules

[David Hildenbrand]

On 08.06.20 13:40, SeongJae Park wrote:
> From: SeongJae Park <sjpark@amazon.de>
> 
> This commit exports 'lookup_page_ext()' to GPL modules.  This will be
> used by DAMON.
> 
> Signed-off-by: SeongJae Park <sjpark@amazon.de>
> Reviewed-by: Leonard Foerster <foersleo@amazon.de>
> ---
>  mm/page_ext.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/page_ext.c b/mm/page_ext.c
> index a3616f7a0e9e..9d802d01fcb5 100644
> --- a/mm/page_ext.c
> +++ b/mm/page_ext.c
> @@ -131,6 +131,7 @@ struct page_ext *lookup_page_ext(const struct page *page)
>  					MAX_ORDER_NR_PAGES);
>  	return get_entry(base, index);
>  }
> +EXPORT_SYMBOL_GPL(lookup_page_ext);
>  
>  static int __init alloc_node_page_ext(int nid)
>  {
> 

I've been told to always smuggle new EXPORTs into the patch that
actually needs it (and cc relevant people on that patch instead).

-- 
Thanks,

David / dhildenb

Re: Re: [PATCH v15 01/14] mm/page_ext: Export lookup_page_ext() to GPL modules

[SeongJae Park]

On Mon, 8 Jun 2020 13:53:23 +0200 David Hildenbrand <david@redhat.com> wrote:

> On 08.06.20 13:40, SeongJae Park wrote:
> > From: SeongJae Park <sjpark@amazon.de>
> > 
> > This commit exports 'lookup_page_ext()' to GPL modules.  This will be
> > used by DAMON.
> > 
> > Signed-off-by: SeongJae Park <sjpark@amazon.de>
> > Reviewed-by: Leonard Foerster <foersleo@amazon.de>
> > ---
> >  mm/page_ext.c | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/mm/page_ext.c b/mm/page_ext.c
> > index a3616f7a0e9e..9d802d01fcb5 100644
> > --- a/mm/page_ext.c
> > +++ b/mm/page_ext.c
> > @@ -131,6 +131,7 @@ struct page_ext *lookup_page_ext(const struct page *page)
> >  					MAX_ORDER_NR_PAGES);
> >  	return get_entry(base, index);
> >  }
> > +EXPORT_SYMBOL_GPL(lookup_page_ext);
> >  
> >  static int __init alloc_node_page_ext(int nid)
> >  {
> > 
> 
> I've been told to always smuggle new EXPORTs into the patch that
> actually needs it (and cc relevant people on that patch instead).

Sorry for didn't noticing that.  I will do so in the next spin.


Thanks,
SeongJae Park

> 
> -- 
> Thanks,
> 
> David / dhildenb

Re: [PATCH v15 01/14] mm/page_ext: Export lookup_page_ext() to GPL modules

[Christoph Hellwig]

On Mon, Jun 08, 2020 at 01:53:23PM +0200, David Hildenbrand wrote:
> > @@ -131,6 +131,7 @@ struct page_ext *lookup_page_ext(const struct page *page)
> >  					MAX_ORDER_NR_PAGES);
> >  	return get_entry(base, index);
> >  }
> > +EXPORT_SYMBOL_GPL(lookup_page_ext);
> >  
> >  static int __init alloc_node_page_ext(int nid)
> >  {
> > 
> 
> I've been told to always smuggle new EXPORTs into the patch that
> actually needs it (and cc relevant people on that patch instead).

A separate patch for anything remotely controversial really helps it
to stick out, so I think keeping it separate is a very good practice.

Re: Re: [PATCH v15 01/14] mm/page_ext: Export lookup_page_ext() to GPL modules

[SeongJae Park]

On Mon, 8 Jun 2020 08:49:17 -0700 Christoph Hellwig <hch@infradead.org> wrote:

> On Mon, Jun 08, 2020 at 01:53:23PM +0200, David Hildenbrand wrote:
> > > @@ -131,6 +131,7 @@ struct page_ext *lookup_page_ext(const struct page *page)
> > >  					MAX_ORDER_NR_PAGES);
> > >  	return get_entry(base, index);
> > >  }
> > > +EXPORT_SYMBOL_GPL(lookup_page_ext);
> > >  
> > >  static int __init alloc_node_page_ext(int nid)
> > >  {
> > > 
> > 
> > I've been told to always smuggle new EXPORTs into the patch that
> > actually needs it (and cc relevant people on that patch instead).
> 
> A separate patch for anything remotely controversial really helps it
> to stick out, so I think keeping it separate is a very good practice.

I have no strong preference here.  So if no further comments are given, in the
next spin, I will keep this separate, but will mention exactly what future
commit needs this change, so that it can be easily squashed later, if
necessary.


Thanks,
SeongJae Park

Re: [PATCH v15 01/14] mm/page_ext: Export lookup_page_ext() to GPL modules

[David Hildenbrand]

> Am 08.06.2020 um 18:11 schrieb Christoph Hellwig <hch@infradead.org>:
> 
> On Mon, Jun 08, 2020 at 01:53:23PM +0200, David Hildenbrand wrote:
>>> @@ -131,6 +131,7 @@ struct page_ext *lookup_page_ext(const struct page *page)
>>>                    MAX_ORDER_NR_PAGES);
>>>    return get_entry(base, index);
>>> }
>>> +EXPORT_SYMBOL_GPL(lookup_page_ext);
>>> 
>>> static int __init alloc_node_page_ext(int nid)
>>> {
>>> 
>> 
>> I've been told to always smuggle new EXPORTs into the patch that
>> actually needs it (and cc relevant people on that patch instead).
> 
> A separate patch for anything remotely controversial really helps it
> to stick out, so I think keeping it separate is a very good practice.
> 

That used to be my approach until Michal told me to do it differently. And there is a good point for it: Reviewers actually understand in which context it is used and if it is really required.

Having that said, I don‘t have a strong opinion on this.

Re: [PATCH v15 04/14] mm/damon: Adaptively adjust regions

[SeongJae Park]

On Mon, 8 Jun 2020 13:40:37 +0200 SeongJae Park <sjpark@amazon.com> wrote:

> From: SeongJae Park <sjpark@amazon.de>
> 
> At the beginning of the monitoring, DAMON constructs the initial regions
> by evenly splitting the memory mapped address space of the process into
> the user-specified minimal number of regions.  In this initial state,
> the assumption of the regions (pages in same region have similar access
> frequencies) is normally not kept and thus the monitoring quality could
> be low.  To keep the assumption as much as possible, DAMON adaptively
> merges and splits each region.
> 
> For each ``aggregation interval``, it compares the access frequencies of
> adjacent regions and merges those if the frequency difference is small.
> Then, after it reports and clears the aggregated access frequency of
> each region, it splits each region into two regions if the total number
> of regions is smaller than the half of the user-specified maximum number
> of regions.

I recently realized that only the 'maximum number of regions' is respected,
meanwhile the 'minimum number of regions' isn't.  In the next spin, I will
update the code to 1) set new internal variable, 'max_sz_region' as size of
entire monitoring target regions divided by the 'minimum number of regions',
and 2) avoid merging regions if it results in region of size larger than that.

This change would make DAMON more flexible for special cases.  For example,
some use cases would need static granularity monitoring.  In such case, users
will be able to adjust the granularity by controlling the 'minimum number of
regions', and avoid the split/merge of regions by setting the 'maximum number
of regions' as same to the 'minimum number of regions'.


Thanks,
SeongJae Park

> 
> In this way, DAMON provides its best-effort quality and minimal overhead
> while keeping the bounds users set for their trade-off.
> 
> Signed-off-by: SeongJae Park <sjpark@amazon.de>
> Reviewed-by: Leonard Foerster <foersleo@amazon.de>

Re: [PATCH v15 01/14] mm/page_ext: Export lookup_page_ext() to GPL modules

[vrd]

On 6/8/20 1:40 PM, SeongJae Park wrote:
> From: SeongJae Park <sjpark@amazon.de>
> 
> This commit exports 'lookup_page_ext()' to GPL modules.  This will be
> used by DAMON.
> 
> Signed-off-by: SeongJae Park <sjpark@amazon.de>
> Reviewed-by: Leonard Foerster <foersleo@amazon.de>

Reviewed-by: Varad Gautam <vrd@amazon.de>

> ---
>  mm/page_ext.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/mm/page_ext.c b/mm/page_ext.c
> index a3616f7a0e9e..9d802d01fcb5 100644
> --- a/mm/page_ext.c
> +++ b/mm/page_ext.c
> @@ -131,6 +131,7 @@ struct page_ext *lookup_page_ext(const struct page *page)
>  					MAX_ORDER_NR_PAGES);
>  	return get_entry(base, index);
>  }
> +EXPORT_SYMBOL_GPL(lookup_page_ext);
>  
>  static int __init alloc_node_page_ext(int nid)
>  {
> 




Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879

Re: [PATCH v15 03/14] mm/damon: Implement region based sampling

[vrd]

On 6/8/20 1:40 PM, SeongJae Park wrote:
> From: SeongJae Park <sjpark@amazon.de>
> 
> This commit implements DAMON's basic access check and region based
> sampling mechanisms.  This change would seems make no sense, mainly
> because it is only a part of the DAMON's logics.  Following two commits
> will make more sense.
> 
> Basic Access Check
> ------------------
> 
> DAMON basically reports what pages are how frequently accessed.  Note
> that the frequency is not an absolute number of accesses, but a relative
> frequency among the pages of the target workloads.
> 
> Users can control the resolution of the reports by setting two time
> intervals, ``sampling interval`` and ``aggregation interval``.  In
> detail, DAMON checks access to each page per ``sampling interval``,
> aggregates the results (counts the number of the accesses to each page),
> and reports the aggregated results per ``aggregation interval``.  For
> the access check of each page, DAMON uses the Accessed bits of PTEs.
> 
> This is thus similar to common periodic access checks based access
> tracking mechanisms, which overhead is increasing as the size of the
> target process grows.
> 
> Region Based Sampling
> ---------------------
> 
> To avoid the unbounded increase of the overhead, DAMON groups a number
> of adjacent pages that assumed to have same access frequencies into a
> region.  As long as the assumption (pages in a region have same access
> frequencies) is kept, only one page in the region is required to be
> checked.  Thus, for each ``sampling interval``, DAMON randomly picks one
> page in each region and clears its Accessed bit.  After one more
> ``sampling interval``, DAMON reads the Accessed bit of the page and
> increases the access frequency of the region if the bit has set
> meanwhile.  Therefore, the monitoring overhead is controllable by
> setting the number of regions.
> 
> Nonetheless, this scheme cannot preserve the quality of the output if
> the assumption is not kept.  Following commit will introduce how we can
> make the guarantee with best effort.
> 
> Signed-off-by: SeongJae Park <sjpark@amazon.de>
> Reviewed-by: Leonard Foerster <foersleo@amazon.de>
> ---
>  include/linux/damon.h |  48 +++-
>  mm/damon.c            | 615 +++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 660 insertions(+), 3 deletions(-)
> 
> diff --git a/include/linux/damon.h b/include/linux/damon.h
> index 135633334929..f0fe4520a4e9 100644
> --- a/include/linux/damon.h
> +++ b/include/linux/damon.h
> @@ -11,6 +11,8 @@
>  #define _DAMON_H_
>  
>  #include <linux/random.h>
> +#include <linux/mutex.h>
> +#include <linux/time64.h>
>  #include <linux/types.h>
>  
>  /**
> @@ -44,11 +46,55 @@ struct damon_task {
>  };
>  
>  /**
> - * struct damon_ctx - Represents a context for each monitoring.
> + * struct damon_ctx - Represents a context for each monitoring.  This is the
> + * main interface that allows users to set the attributes and get the results
> + * of the monitoring.
> + *
> + * For each monitoring request (damon_start()), a kernel thread for the
> + * monitoring is created.  The pointer to the thread is stored in @kdamond.
> + *
> + * @sample_interval:		The time between access samplings.
> + * @aggr_interval:		The time between monitor results aggregations.
> + * @min_nr_regions:		The number of initial monitoring regions.
> + *
> + * For each @sample_interval, DAMON checks whether each region is accessed or
> + * not.  It aggregates and keeps the access information (number of accesses to
> + * each region) for @aggr_interval time.  All time intervals are in
> + * micro-seconds.
> + *
> + * @kdamond:		Kernel thread who does the monitoring.
> + * @kdamond_stop:	Notifies whether kdamond should stop.
> + * @kdamond_lock:	Mutex for the synchronizations with @kdamond.
> + *
> + * The monitoring thread sets @kdamond to NULL when it terminates.  Therefore,
> + * users can know whether the monitoring is ongoing or terminated by reading
> + * @kdamond.  Also, users can ask @kdamond to be terminated by writing non-zero
> + * to @kdamond_stop.  Reads and writes to @kdamond and @kdamond_stop from
> + * outside of the monitoring thread must be protected by @kdamond_lock.
> + *
> + * Note that the monitoring thread protects only @kdamond and @kdamond_stop via
> + * @kdamond_lock.  Accesses to other fields must be protected by themselves.
> + *
>   * @tasks_list:		Head of monitoring target tasks (&damon_task) list.
>   */
>  struct damon_ctx {
> +	unsigned long sample_interval;
> +	unsigned long aggr_interval;
> +	unsigned long min_nr_regions;
> +
> +	struct timespec64 last_aggregation;
> +
> +	struct task_struct *kdamond;
> +	bool kdamond_stop;
> +	struct mutex kdamond_lock;
> +
>  	struct list_head tasks_list;	/* 'damon_task' objects */
>  };
>  
> +int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
> +int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
> +		unsigned long aggr_int, unsigned long min_nr_reg);
> +int damon_start(struct damon_ctx *ctx);
> +int damon_stop(struct damon_ctx *ctx);
> +
>  #endif
> diff --git a/mm/damon.c b/mm/damon.c
> index 170e8a694dbe..fa14ff7dd31a 100644
> --- a/mm/damon.c
> +++ b/mm/damon.c
> @@ -9,18 +9,29 @@
>   * This file is constructed in below parts.
>   *
>   * - Functions and macros for DAMON data structures
> + * - Functions for the initial monitoring target regions construction
> + * - Functions for the access checking of the regions
> + * - Functions for DAMON core logics and features
> + * - Functions for the DAMON programming interface
>   * - Functions for the module loading/unloading
> - *
> - * The core parts are not implemented yet.
>   */
>  
>  #define pr_fmt(fmt) "damon: " fmt
>  
>  #include <linux/damon.h>
> +#include <linux/delay.h>
> +#include <linux/kthread.h>
>  #include <linux/mm.h>
>  #include <linux/module.h>
> +#include <linux/page_idle.h>
> +#include <linux/random.h>
> +#include <linux/sched/mm.h>
> +#include <linux/sched/task.h>
>  #include <linux/slab.h>
>  
> +/* Minimal region size.  Every damon_region is aligned by this. */
> +#define MIN_REGION PAGE_SIZE
> +
>  /*
>   * Functions and macros for DAMON data structures
>   */
> @@ -167,6 +178,606 @@ static unsigned int nr_damon_regions(struct damon_task *t)
>  	return nr_regions;
>  }
>  
> +/*
> + * Get the mm_struct of the given task
> + *
> + * Caller _must_ put the mm_struct after use, unless it is NULL.
> + *
> + * Returns the mm_struct of the task on success, NULL on failure
> + */
> +static struct mm_struct *damon_get_mm(struct damon_task *t)
> +{
> +	struct task_struct *task;
> +	struct mm_struct *mm;
> +
> +	task = damon_get_task_struct(t);
> +	if (!task)
> +		return NULL;
> +
> +	mm = get_task_mm(task);
> +	put_task_struct(task);
> +	return mm;
> +}
> +
> +/*
> + * Functions for the initial monitoring target regions construction
> + */
> +
> +/*
> + * Size-evenly split a region into 'nr_pieces' small regions
> + *
> + * Returns 0 on success, or negative error code otherwise.
> + */
> +static int damon_split_region_evenly(struct damon_ctx *ctx,
> +		struct damon_region *r, unsigned int nr_pieces)
> +{
> +	unsigned long sz_orig, sz_piece, orig_end;
> +	struct damon_region *n = NULL, *next;
> +	unsigned long start;
> +
> +	if (!r || !nr_pieces)
> +		return -EINVAL;
> +
> +	orig_end = r->vm_end;
> +	sz_orig = r->vm_end - r->vm_start;
> +	sz_piece = ALIGN_DOWN(sz_orig / nr_pieces, MIN_REGION);
> +
> +	if (!sz_piece)
> +		return -EINVAL;
> +
> +	r->vm_end = r->vm_start + sz_piece;
> +	next = damon_next_region(r);
> +	for (start = r->vm_end; start + sz_piece <= orig_end;
> +			start += sz_piece) {
> +		n = damon_new_region(ctx, start, start + sz_piece);
> +		if (!n)
> +			return -ENOMEM;
> +		damon_insert_region(n, r, next);
> +		r = n;
> +	}
> +	/* complement last region for possible rounding error */
> +	if (n)
> +		n->vm_end = orig_end;
> +
> +	return 0;
> +}
> +
> +struct region {
> +	unsigned long start;
> +	unsigned long end;
> +};
> +
> +static unsigned long sz_region(struct region *r)
> +{
> +	return r->end - r->start;
> +}
> +
> +static void swap_regions(struct region *r1, struct region *r2)
> +{
> +	struct region tmp;
> +
> +	tmp = *r1;
> +	*r1 = *r2;
> +	*r2 = tmp;
> +}
> +
> +/*
> + * Find three regions separated by two biggest unmapped regions
> + *
> + * vma		the head vma of the target address space
> + * regions	an array of three 'struct region's that results will be saved
> + *
> + * This function receives an address space and finds three regions in it which
> + * separated by the two biggest unmapped regions in the space.  Please refer to
> + * below comments of 'damon_init_regions_of()' function to know why this is
> + * necessary.
> + *
> + * Returns 0 if success, or negative error code otherwise.
> + */
> +static int damon_three_regions_in_vmas(struct vm_area_struct *vma,
> +		struct region regions[3])
> +{
> +	struct region gap = {0}, first_gap = {0}, second_gap = {0};
> +	struct vm_area_struct *last_vma = NULL;
> +	unsigned long start = 0;
> +
> +	/* Find two biggest gaps so that first_gap > second_gap > others */
> +	for (; vma; vma = vma->vm_next) {

Since vm_area_struct already maintains information about the largest gap below this vma
in the mm_rb rbtree, walking the vma via mm_rb instead of the linked list, and skipping
the ones with don't fit the gap requirement via vma->rb_subtree_gap helps avoid the
extra comparisons in this function.

I measured the following implementation to be considerably faster as the number of
vmas grows for a process damon would attach to:

-static int damon_three_regions_in_vmas(struct vm_area_struct *vma,
+static int damon_three_regions_in_vmas(struct rb_root *root,
 		struct region regions[3])
 {
+	struct rb_node *nd = NULL;
 	struct region gap = {0}, first_gap = {0}, second_gap = {0};
-	struct vm_area_struct *last_vma = NULL;
+	struct vm_area_struct *vma = NULL;
 	unsigned long start = 0;
 
 	/* Find two biggest gaps so that first_gap > second_gap > others */
-	for (; vma; vma = vma->vm_next) {
-		if (!last_vma) {
-			start = vma->vm_start;
-			last_vma = vma;
+	for (nd = rb_first(root); nd; nd = rb_next(nd)) {
+		vma = rb_entry(nd, struct vm_area_struct, vm_rb);
+
+		if (vma->rb_subtree_gap < sz_region(&second_gap)) {
+			/*
+			 * Skip this vma if the largest gap at this vma is still
+			 * smaller than what we have encountered so far.
+			 */
 			continue;
 		}
-		gap.start = last_vma->vm_end;
+		if (!vma->vm_prev) {
+			/* This is the first vma. */
+			start = vma->vm_start;
+			continue;
+		}
+		gap.start = vma->vm_prev->vm_end;
 		gap.end = vma->vm_start;
 		if (sz_region(&gap) > sz_region(&second_gap)) {
 			swap_regions(&gap, &second_gap);
 			if (sz_region(&second_gap) > sz_region(&first_gap))
 				swap_regions(&second_gap, &first_gap);
 		}
-		last_vma = vma;
 	}
 
 	if (!sz_region(&second_gap) || !sz_region(&first_gap))
@@ -35,7 +44,7 @@
 	regions[1].start = ALIGN(first_gap.end, MIN_REGION);
 	regions[1].end = ALIGN(second_gap.start, MIN_REGION);
 	regions[2].start = ALIGN(second_gap.end, MIN_REGION);
-	regions[2].end = ALIGN(last_vma->vm_end, MIN_REGION);
+	regions[2].end = ALIGN(vma->vm_end, MIN_REGION);
 
 	return 0;
 }


> +		if (!last_vma) {
> +			start = vma->vm_start;
> +			last_vma = vma;
> +			continue;
> +		}
> +		gap.start = last_vma->vm_end;
> +		gap.end = vma->vm_start;
> +		if (sz_region(&gap) > sz_region(&second_gap)) {
> +			swap_regions(&gap, &second_gap);
> +			if (sz_region(&second_gap) > sz_region(&first_gap))
> +				swap_regions(&second_gap, &first_gap);
> +		}
> +		last_vma = vma;
> +	}
> +
> +	if (!sz_region(&second_gap) || !sz_region(&first_gap))
> +		return -EINVAL;
> +
> +	/* Sort the two biggest gaps by address */
> +	if (first_gap.start > second_gap.start)
> +		swap_regions(&first_gap, &second_gap);
> +
> +	/* Store the result */
> +	regions[0].start = ALIGN(start, MIN_REGION);
> +	regions[0].end = ALIGN(first_gap.start, MIN_REGION);
> +	regions[1].start = ALIGN(first_gap.end, MIN_REGION);
> +	regions[1].end = ALIGN(second_gap.start, MIN_REGION);
> +	regions[2].start = ALIGN(second_gap.end, MIN_REGION);
> +	regions[2].end = ALIGN(last_vma->vm_end, MIN_REGION);
> +
> +	return 0;
> +}
> +
> +/*
> + * Get the three regions in the given task
> + *
> + * Returns 0 on success, negative error code otherwise.
> + */
> +static int damon_three_regions_of(struct damon_task *t,
> +				struct region regions[3])
> +{
> +	struct mm_struct *mm;
> +	int rc;
> +
> +	mm = damon_get_mm(t);
> +	if (!mm)
> +		return -EINVAL;
> +
> +	down_read(&mm->mmap_sem);
> +	rc = damon_three_regions_in_vmas(mm->mmap, regions);
> +	up_read(&mm->mmap_sem);
> +
> +	mmput(mm);
> +	return rc;
> +}
> +
> +/*
> + * Initialize the monitoring target regions for the given task
> + *
> + * t	the given target task
> + *
> + * Because only a number of small portions of the entire address space
> + * is actually mapped to the memory and accessed, monitoring the unmapped
> + * regions is wasteful.  That said, because we can deal with small noises,
> + * tracking every mapping is not strictly required but could even incur a high
> + * overhead if the mapping frequently changes or the number of mappings is
> + * high.  Nonetheless, this may seems very weird.  DAMON's dynamic regions
> + * adjustment mechanism, which will be implemented with following commit will
> + * make this more sense.
> + *
> + * For the reason, we convert the complex mappings to three distinct regions
> + * that cover every mapped area of the address space.  Also the two gaps
> + * between the three regions are the two biggest unmapped areas in the given
> + * address space.  In detail, this function first identifies the start and the
> + * end of the mappings and the two biggest unmapped areas of the address space.
> + * Then, it constructs the three regions as below:
> + *
> + *     [mappings[0]->start, big_two_unmapped_areas[0]->start)
> + *     [big_two_unmapped_areas[0]->end, big_two_unmapped_areas[1]->start)
> + *     [big_two_unmapped_areas[1]->end, mappings[nr_mappings - 1]->end)
> + *
> + * As usual memory map of processes is as below, the gap between the heap and
> + * the uppermost mmap()-ed region, and the gap between the lowermost mmap()-ed
> + * region and the stack will be two biggest unmapped regions.  Because these
> + * gaps are exceptionally huge areas in usual address space, excluding these
> + * two biggest unmapped regions will be sufficient to make a trade-off.
> + *
> + *   <heap>
> + *   <BIG UNMAPPED REGION 1>
> + *   <uppermost mmap()-ed region>
> + *   (other mmap()-ed regions and small unmapped regions)
> + *   <lowermost mmap()-ed region>
> + *   <BIG UNMAPPED REGION 2>
> + *   <stack>
> + */
> +static void damon_init_regions_of(struct damon_ctx *c, struct damon_task *t)
> +{
> +	struct damon_region *r, *m = NULL;
> +	struct region regions[3];
> +	int i;
> +
> +	if (damon_three_regions_of(t, regions)) {
> +		pr_err("Failed to get three regions of task %d\n", t->pid);
> +		return;
> +	}
> +
> +	/* Set the initial three regions of the task */
> +	for (i = 0; i < 3; i++) {
> +		r = damon_new_region(c, regions[i].start, regions[i].end);
> +		if (!r) {
> +			pr_err("%d'th init region creation failed\n", i);
> +			return;
> +		}
> +		damon_add_region(r, t);
> +		if (i == 1)
> +			m = r;
> +	}
> +
> +	/* Split the middle region into 'min_nr_regions - 2' regions */
> +	if (damon_split_region_evenly(c, m, c->min_nr_regions - 2))
> +		pr_warn("Init middle region failed to be split\n");
> +}
> +
> +/* Initialize '->regions_list' of every task */
> +static void kdamond_init_regions(struct damon_ctx *ctx)
> +{
> +	struct damon_task *t;
> +
> +	damon_for_each_task(t, ctx)
> +		damon_init_regions_of(ctx, t);
> +}
> +
> +/*
> + * Functions for the access checking of the regions
> + */
> +
> +static void damon_mkold(struct mm_struct *mm, unsigned long addr)
> +{
> +	pte_t *pte = NULL;
> +	pmd_t *pmd = NULL;
> +	spinlock_t *ptl;
> +
> +	if (follow_pte_pmd(mm, addr, NULL, &pte, &pmd, &ptl))
> +		return;
> +
> +	if (pte) {
> +		if (pte_young(*pte)) {
> +			clear_page_idle(pte_page(*pte));
> +			set_page_young(pte_page(*pte));
> +		}
> +		*pte = pte_mkold(*pte);
> +		pte_unmap_unlock(pte, ptl);
> +		return;
> +	}
> +
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +	if (pmd_young(*pmd)) {
> +		clear_page_idle(pmd_page(*pmd));
> +		set_page_young(pmd_page(*pmd));
> +	}
> +	*pmd = pmd_mkold(*pmd);
> +	spin_unlock(ptl);
> +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
> +}
> +
> +static void damon_prepare_access_check(struct damon_ctx *ctx,
> +			struct mm_struct *mm, struct damon_region *r)
> +{
> +	r->sampling_addr = damon_rand(r->vm_start, r->vm_end);
> +
> +	damon_mkold(mm, r->sampling_addr);
> +}
> +
> +static void kdamond_prepare_access_checks(struct damon_ctx *ctx)
> +{
> +	struct damon_task *t;
> +	struct mm_struct *mm;
> +	struct damon_region *r;
> +
> +	damon_for_each_task(t, ctx) {
> +		mm = damon_get_mm(t);
> +		if (!mm)
> +			continue;
> +		damon_for_each_region(r, t)
> +			damon_prepare_access_check(ctx, mm, r);
> +		mmput(mm);
> +	}
> +}
> +
> +static bool damon_young(struct mm_struct *mm, unsigned long addr,
> +			unsigned long *page_sz)
> +{
> +	pte_t *pte = NULL;
> +	pmd_t *pmd = NULL;
> +	spinlock_t *ptl;
> +	bool young = false;
> +
> +	if (follow_pte_pmd(mm, addr, NULL, &pte, &pmd, &ptl))
> +		return false;
> +
> +	*page_sz = PAGE_SIZE;
> +	if (pte) {
> +		young = pte_young(*pte);
> +		pte_unmap_unlock(pte, ptl);
> +		return young;
> +	}
> +
> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
> +	young = pmd_young(*pmd);
> +	spin_unlock(ptl);
> +	*page_sz = ((1UL) << HPAGE_PMD_SHIFT);
> +#endif	/* CONFIG_TRANSPARENT_HUGEPAGE */
> +
> +	return young;
> +}
> +
> +/*
> + * Check whether the region was accessed after the last preparation
> + *
> + * mm	'mm_struct' for the given virtual address space
> + * r	the region to be checked
> + */
> +static void damon_check_access(struct damon_ctx *ctx,
> +			       struct mm_struct *mm, struct damon_region *r)
> +{
> +	static struct mm_struct *last_mm;
> +	static unsigned long last_addr;
> +	static unsigned long last_page_sz = PAGE_SIZE;
> +	static bool last_accessed;
> +
> +	/* If the region is in the last checked page, reuse the result */
> +	if (mm == last_mm && (ALIGN_DOWN(last_addr, last_page_sz) ==
> +				ALIGN_DOWN(r->sampling_addr, last_page_sz))) {
> +		if (last_accessed)
> +			r->nr_accesses++;
> +		return;
> +	}
> +
> +	last_accessed = damon_young(mm, r->sampling_addr, &last_page_sz);
> +	if (last_accessed)
> +		r->nr_accesses++;
> +
> +	last_mm = mm;
> +	last_addr = r->sampling_addr;
> +}
> +
> +static void kdamond_check_accesses(struct damon_ctx *ctx)
> +{
> +	struct damon_task *t;
> +	struct mm_struct *mm;
> +	struct damon_region *r;
> +
> +	damon_for_each_task(t, ctx) {
> +		mm = damon_get_mm(t);
> +		if (!mm)
> +			continue;
> +		damon_for_each_region(r, t)
> +			damon_check_access(ctx, mm, r);
> +		mmput(mm);
> +	}
> +}
> +
> +/*
> + * Functions for DAMON core logics and features
> + */
> +
> +/*
> + * damon_check_reset_time_interval() - Check if a time interval is elapsed.
> + * @baseline:	the time to check whether the interval has elapsed since
> + * @interval:	the time interval (microseconds)
> + *
> + * See whether the given time interval has passed since the given baseline
> + * time.  If so, it also updates the baseline to current time for next check.
> + *
> + * Return:	true if the time interval has passed, or false otherwise.
> + */
> +static bool damon_check_reset_time_interval(struct timespec64 *baseline,
> +		unsigned long interval)
> +{
> +	struct timespec64 now;
> +
> +	ktime_get_coarse_ts64(&now);
> +	if ((timespec64_to_ns(&now) - timespec64_to_ns(baseline)) <
> +			interval * 1000)
> +		return false;
> +	*baseline = now;
> +	return true;
> +}
> +
> +/*
> + * Check whether it is time to flush the aggregated information
> + */
> +static bool kdamond_aggregate_interval_passed(struct damon_ctx *ctx)
> +{
> +	return damon_check_reset_time_interval(&ctx->last_aggregation,
> +			ctx->aggr_interval);
> +}
> +
> +/*
> + * Reset the aggregated monitoring results
> + */
> +static void kdamond_reset_aggregated(struct damon_ctx *c)
> +{
> +	struct damon_task *t;
> +	struct damon_region *r;
> +
> +	damon_for_each_task(t, c) {
> +		damon_for_each_region(r, t)
> +			r->nr_accesses = 0;
> +	}
> +}
> +
> +/*
> + * Check whether current monitoring should be stopped
> + *
> + * The monitoring is stopped when either the user requested to stop, or all
> + * monitoring target tasks are dead.
> + *
> + * Returns true if need to stop current monitoring.
> + */
> +static bool kdamond_need_stop(struct damon_ctx *ctx)
> +{
> +	struct damon_task *t;
> +	struct task_struct *task;
> +	bool stop;
> +
> +	mutex_lock(&ctx->kdamond_lock);
> +	stop = ctx->kdamond_stop;
> +	mutex_unlock(&ctx->kdamond_lock);
> +	if (stop)
> +		return true;
> +
> +	damon_for_each_task(t, ctx) {
> +		task = damon_get_task_struct(t);
> +		if (task) {
> +			put_task_struct(task);
> +			return false;
> +		}
> +	}
> +
> +	return true;
> +}
> +
> +/*
> + * The monitoring daemon that runs as a kernel thread
> + */
> +static int kdamond_fn(void *data)
> +{
> +	struct damon_ctx *ctx = (struct damon_ctx *)data;
> +	struct damon_task *t;
> +	struct damon_region *r, *next;
> +
> +	pr_info("kdamond (%d) starts\n", ctx->kdamond->pid);
> +	kdamond_init_regions(ctx);
> +	while (!kdamond_need_stop(ctx)) {
> +		kdamond_prepare_access_checks(ctx);
> +
> +		usleep_range(ctx->sample_interval, ctx->sample_interval + 1);
> +
> +		kdamond_check_accesses(ctx);
> +
> +		if (kdamond_aggregate_interval_passed(ctx))
> +			kdamond_reset_aggregated(ctx);
> +
> +	}
> +	damon_for_each_task(t, ctx) {
> +		damon_for_each_region_safe(r, next, t)
> +			damon_destroy_region(r);
> +	}
> +	pr_debug("kdamond (%d) finishes\n", ctx->kdamond->pid);
> +	mutex_lock(&ctx->kdamond_lock);
> +	ctx->kdamond = NULL;
> +	mutex_unlock(&ctx->kdamond_lock);
> +
> +	do_exit(0);
> +}
> +
> +/*
> + * Functions for the DAMON programming interface
> + */
> +
> +static bool damon_kdamond_running(struct damon_ctx *ctx)
> +{
> +	bool running;
> +
> +	mutex_lock(&ctx->kdamond_lock);
> +	running = ctx->kdamond != NULL;
> +	mutex_unlock(&ctx->kdamond_lock);
> +
> +	return running;
> +}
> +
> +/**
> + * damon_start() - Starts monitoring with given context.
> + * @ctx:	monitoring context
> + *
> + * Return: 0 on success, negative error code otherwise.
> + */
> +int damon_start(struct damon_ctx *ctx)
> +{
> +	int err = -EBUSY;
> +
> +	mutex_lock(&ctx->kdamond_lock);
> +	if (!ctx->kdamond) {
> +		err = 0;
> +		ctx->kdamond_stop = false;
> +		ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond");
> +		if (IS_ERR(ctx->kdamond))
> +			err = PTR_ERR(ctx->kdamond);
> +	}
> +	mutex_unlock(&ctx->kdamond_lock);
> +
> +	return err;
> +}
> +
> +/**
> + * damon_stop() - Stops monitoring of given context.
> + * @ctx:	monitoring context
> + *
> + * Return: 0 on success, negative error code otherwise.
> + */
> +int damon_stop(struct damon_ctx *ctx)
> +{
> +	mutex_lock(&ctx->kdamond_lock);
> +	if (ctx->kdamond) {
> +		ctx->kdamond_stop = true;
> +		mutex_unlock(&ctx->kdamond_lock);
> +		while (damon_kdamond_running(ctx))
> +			usleep_range(ctx->sample_interval,
> +					ctx->sample_interval * 2);
> +		return 0;
> +	}
> +	mutex_unlock(&ctx->kdamond_lock);
> +
> +	return -EPERM;
> +}
> +
> +/**
> + * damon_set_pids() - Set monitoring target processes.
> + * @ctx:	monitoring context
> + * @pids:	array of target processes pids
> + * @nr_pids:	number of entries in @pids
> + *
> + * This function should not be called while the kdamond is running.
> + *
> + * Return: 0 on success, negative error code otherwise.
> + */
> +int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids)
> +{
> +	ssize_t i;
> +	struct damon_task *t, *next;
> +
> +	damon_for_each_task_safe(t, next, ctx)
> +		damon_destroy_task(t);
> +
> +	for (i = 0; i < nr_pids; i++) {
> +		t = damon_new_task(pids[i]);
> +		if (!t) {
> +			pr_err("Failed to alloc damon_task\n");
> +			return -ENOMEM;
> +		}
> +		damon_add_task(ctx, t);
> +	}
> +
> +	return 0;
> +}
> +
> +/**
> + * damon_set_attrs() - Set attributes for the monitoring.
> + * @ctx:		monitoring context
> + * @sample_int:		time interval between samplings
> + * @aggr_int:		time interval between aggregations
> + * @min_nr_reg:		minimal number of regions
> + *
> + * This function should not be called while the kdamond is running.
> + * Every time interval is in micro-seconds.
> + *
> + * Return: 0 on success, negative error code otherwise.
> + */
> +int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
> +		unsigned long aggr_int, unsigned long min_nr_reg)
> +{
> +	if (min_nr_reg < 3) {
> +		pr_err("min_nr_regions (%lu) must be at least 3\n",
> +				min_nr_reg);
> +		return -EINVAL;
> +	}
> +
> +	ctx->sample_interval = sample_int;
> +	ctx->aggr_interval = aggr_int;
> +	ctx->min_nr_regions = min_nr_reg;
> +
> +	return 0;
> +}
> +
>  /*
>   * Functions for the module loading/unloading
>   */
> 




Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879

Re: Re: [PATCH v15 03/14] mm/damon: Implement region based sampling

[SeongJae Park]

On Wed, 10 Jun 2020 22:36:00 +0200 <vrd@amazon.com> wrote:

> On 6/8/20 1:40 PM, SeongJae Park wrote:
> > From: SeongJae Park <sjpark@amazon.de>
> > 
> > This commit implements DAMON's basic access check and region based
> > sampling mechanisms.  This change would seems make no sense, mainly
> > because it is only a part of the DAMON's logics.  Following two commits
> > will make more sense.
> > 
[...]
> > +
> > +/*
> > + * Find three regions separated by two biggest unmapped regions
> > + *
> > + * vma		the head vma of the target address space
> > + * regions	an array of three 'struct region's that results will be saved
> > + *
> > + * This function receives an address space and finds three regions in it which
> > + * separated by the two biggest unmapped regions in the space.  Please refer to
> > + * below comments of 'damon_init_regions_of()' function to know why this is
> > + * necessary.
> > + *
> > + * Returns 0 if success, or negative error code otherwise.
> > + */
> > +static int damon_three_regions_in_vmas(struct vm_area_struct *vma,
> > +		struct region regions[3])
> > +{
> > +	struct region gap = {0}, first_gap = {0}, second_gap = {0};
> > +	struct vm_area_struct *last_vma = NULL;
> > +	unsigned long start = 0;
> > +
> > +	/* Find two biggest gaps so that first_gap > second_gap > others */
> > +	for (; vma; vma = vma->vm_next) {
> 
> Since vm_area_struct already maintains information about the largest gap below this vma
> in the mm_rb rbtree, walking the vma via mm_rb instead of the linked list, and skipping
> the ones with don't fit the gap requirement via vma->rb_subtree_gap helps avoid the
> extra comparisons in this function.

Thanks for the idea!

> 
> I measured the following implementation to be considerably faster as the number of
> vmas grows for a process damon would attach to:
> 
> -static int damon_three_regions_in_vmas(struct vm_area_struct *vma,
> +static int damon_three_regions_in_vmas(struct rb_root *root,
>  		struct region regions[3])
>  {
> +	struct rb_node *nd = NULL;
>  	struct region gap = {0}, first_gap = {0}, second_gap = {0};
> -	struct vm_area_struct *last_vma = NULL;

I like this cleanup.  I'm so wonder how I forgot using '->vm_prev'. :)

> +	struct vm_area_struct *vma = NULL;
>  	unsigned long start = 0;
>  
>  	/* Find two biggest gaps so that first_gap > second_gap > others */
> -	for (; vma; vma = vma->vm_next) {
> -		if (!last_vma) {
> -			start = vma->vm_start;
> -			last_vma = vma;
> +	for (nd = rb_first(root); nd; nd = rb_next(nd)) {
> +		vma = rb_entry(nd, struct vm_area_struct, vm_rb);

This seems meaningless to me.  This will iterate the vma tree in address order,
as same to the old code.  Moreover, 'rb_next()' and 'rb_entry()' might be
slower than the direct reference of '->vm_next'.

> +
> +		if (vma->rb_subtree_gap < sz_region(&second_gap)) {
> +			/*
> +			 * Skip this vma if the largest gap at this vma is still
> +			 * smaller than what we have encountered so far.
> +			 */
>  			continue;

This means we are skipping this node only.  It would make no big difference
from the old code, as we still iterate all nodes.

Rather than that, by the definition of the '->rb_subtree_gap', we could skip
all vmas in the subtree.  For example:

	vma = rb_entry(rb_last(vma->vm_rb), struct vm_area_struct, vm_rb);
	continue;

Nevertheless, this function is not the performance critical point, as this will
be called only once for the initial time in this patch, and the followup
patches will make this function to be called for every regions update interval,
which defaults to 1 second.  The followup patches will also allow users set the
interval large enough and even configure their own optimized version.  For the
reason, I concern simpleness ratherthan performance here.

That said, your fundamental idea obviously makes sense and the changes for that
would be subtle.  I will update this patch in abovely modified way and do some
test.

If I missed something, please let me know.


Thanks,
SeongJae Park