[RFC PATCH v2 00/11] implement DAMOS filtering for anon pages and

[RFC PATCH v2 00/11] implement DAMOS filtering for anon pages and

[SeongJae Park]

Changes from RFC v1
(https://lore.kernel.org/damon/20221124212114.136863-1-sj@kernel.org/)
- sysfs: Clean up filters directory from scheme directory cleanup path
- sysfs: Link newly created filter to the scheme
- sysfs: Ignore removed memcg when checking path
- sysfs: Guard 'struct mem_cgroup' access with CONFIG_MEMCG
  (kernel test robot)

----

DAMOS let users do system operations in a data access pattern oriented
way.  The data access pattern, which is extracted by DAMON, is somewhat
accurate more than what user space could know in many cases.  However,
in some situation, users could know something more than the kernel about
the pattern or some special requirements for some types of memory or
processes.  For example, some users would have slow swap devices and
knows latency-ciritical processes and therefore want to use DAMON-based
proactive reclamation (DAMON_RECLAIM) for only non-anonymous pages of
non-latency-critical processes.

For such restriction, users could exclude the memory regions from the
initial monitoring regions and use non-dynamic monitoring regions update
monitoring operations set including fvaddr and paddr.  They could also
adjust the DAMOS target access pattern.  For dynamically changing memory
layout and access pattern, those would be not enough.

To help the case, add an interface, namely DAMOS filters, which can be
used to avoid the DAMOS actions be applied to specific types of memory,
to DAMON kernel API (damon.h).  At the moment, it supports filtering
anonymous pages and/or specific memory cgroups in or out for each DAMOS
scheme.

This patchset adds the support for all DAMOS actions that 'paddr'
monitoring operations set supports ('pageout', 'lru_prio', and
'lru_deprio'), and the functionality is exposed via DAMON kernel API
(damon.h) the DAMON sysfs interface (/sys/kernel/mm/damon/admins/), and
DAMON_RECLAIM module parameters.

Patches Sequence
----------------

First patch implements DAMOS filter interface to DAMON kernel API.
Second patch makes the physical address space monitoring operations set
to support the filters from all supporting DAMOS actions.  Third patch
adds anonymous pages filter support to DAMON_RECLAIM, and the fourth
patch documents the DAMON_RECLAIM's new feature.  Fifth to seventh
patches implement DAMON sysfs files for support of the filters, and
eighth patch connects the file to use DAMOS filters feature.  Ninth
patch adds simple self test cases for DAMOS filters of the sysfs
interface.  Finally, following two patches (tenth and eleventh) document
the new features and interfaces.

SeongJae Park (11):
  mm/damon/core: implement damos filter
  mm/damon/paddr: support DAMOS filters
  mm/damon/reclaim: add a parameter called skip_anon for avoiding
    anonymous pages reclamation
  Docs/admin-guide/damon/reclaim: document 'skip_anon' parameter
  mm/damon/sysfs-schemes: implement filters directory
  mm/damon/sysfs-schemes: implement filter directory
  mm/damon/sysfs-schemes: connect filter directory and filters directory
  mm/damon/sysfs-schemes: implement scheme filters
  selftests/damon/sysfs: test filters directory
  Docs/admin-guide/mm/damon/usage: document DAMOS filters of sysfs
  Docs/ABI/damon: document scheme filters files

 .../ABI/testing/sysfs-kernel-mm-damon         |  29 ++
 .../admin-guide/mm/damon/reclaim.rst          |   9 +
 Documentation/admin-guide/mm/damon/usage.rst  |  48 ++-
 include/linux/damon.h                         |  51 +++
 mm/damon/core.c                               |  39 ++
 mm/damon/paddr.c                              |  71 +++-
 mm/damon/reclaim.c                            |  19 +
 mm/damon/sysfs-schemes.c                      | 370 +++++++++++++++++-
 tools/testing/selftests/damon/sysfs.sh        |  29 ++
 9 files changed, 652 insertions(+), 13 deletions(-)

-- 
2.25.1

[RFC PATCH v2 04/11] Docs/admin-guide/damon/reclaim: document 'skip_anon' parameter

[SeongJae Park]

Document the newly added 'skip_anon' parameter of DAMON_RECLAIM, which
can be used to avoid anonymous pages reclamation.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/admin-guide/mm/damon/reclaim.rst | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Documentation/admin-guide/mm/damon/reclaim.rst b/Documentation/admin-guide/mm/damon/reclaim.rst
index 4f1479a11e63..ff335e96e0d8 100644
--- a/Documentation/admin-guide/mm/damon/reclaim.rst
+++ b/Documentation/admin-guide/mm/damon/reclaim.rst
@@ -205,6 +205,15 @@ The end physical address of memory region that DAMON_RECLAIM will do work
 against.  That is, DAMON_RECLAIM will find cold memory regions in this region
 and reclaims.  By default, biggest System RAM is used as the region.
 
+skip_anon
+---------
+
+Skip anonymous pages reclamation.
+
+If this parameter is set as ``Y``, DAMON_RECLAIM does not reclaim anonymous
+pages.  By default, ``N``.
+
+
 kdamond_pid
 -----------
 
-- 
2.25.1

[RFC PATCH v2 10/11] Docs/admin-guide/mm/damon/usage: document DAMOS filters of sysfs

[SeongJae Park]

Document about the newly added files for DAMOS filters on the DAMON
usage document.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/admin-guide/mm/damon/usage.rst | 48 +++++++++++++++++++-
 1 file changed, 46 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
index 1a5b6b71efa1..3d82ca6a17ff 100644
--- a/Documentation/admin-guide/mm/damon/usage.rst
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -87,6 +87,8 @@ comma (","). ::
     │ │ │ │ │ │ │ quotas/ms,bytes,reset_interval_ms
     │ │ │ │ │ │ │ │ weights/sz_permil,nr_accesses_permil,age_permil
     │ │ │ │ │ │ │ watermarks/metric,interval_us,high,mid,low
+    │ │ │ │ │ │ │ filters/nr_filters
+    │ │ │ │ │ │ │ │ 0/type,matching,memcg_id
     │ │ │ │ │ │ │ stats/nr_tried,sz_tried,nr_applied,sz_applied,qt_exceeds
     │ │ │ │ │ │ │ tried_regions/
     │ │ │ │ │ │ │ │ 0/start,end,nr_accesses,age
@@ -151,6 +153,8 @@ number (``N``) to the file creates the number of child directories named as
 moment, only one context per kdamond is supported, so only ``0`` or ``1`` can
 be written to the file.
 
+.. _sysfs_contexts:
+
 contexts/<N>/
 -------------
 
@@ -268,8 +272,8 @@ schemes/<N>/
 ------------
 
 In each scheme directory, five directories (``access_pattern``, ``quotas``,
-``watermarks``, ``stats``, and ``tried_regions``) and one file (``action``)
-exist.
+``watermarks``, ``filters``, ``stats``, and ``tried_regions``) and one file
+(``action``) exist.
 
 The ``action`` file is for setting and getting what action you want to apply to
 memory regions having specific access pattern of the interest.  The keywords
@@ -347,6 +351,46 @@ as below.
 
 The ``interval`` should written in microseconds unit.
 
+schemes/<N>/filters/
+--------------------
+
+Users could know something more than the kernel for specific types of memory.
+In the case, users could do their own management for the memory and hence
+doesn't want DAMOS bothers that.  Users could limit DAMOS by setting the access
+pattern of the scheme and/or the monitoring regions for the purpose, but that
+can be inefficient in some cases.  In such cases, users could set non-access
+pattern driven filters using files in this directory.
+
+In the beginning, this directory has only one file, ``nr_filters``.  Writing a
+number (``N``) to the file creates the number of child directories named ``0``
+to ``N-1``.  Each directory represents each filter.  The filters are evaluated
+in the numeric order.
+
+Each filter directory contains three files, namely ``type``, ``matcing``, and
+``memcg_path``.  You can write one of two special keywords, ``anon`` for
+anonymous pages, or ``memcg`` for specific memory cgroup filtering.  In case of
+the memory cgroup filtering, you can specify the memory cgroup of the interest
+by writing the path of the memory cgroup from the cgroups mount point to
+``memcg_path`` file.  You can write ``Y`` or ``N`` to ``matching`` file to
+filter out pages that does or does not match to the type, respectively.  Then,
+the scheme's action will not be applied to the pages that specified to be
+filtered out.
+
+For example, below restricts a DAMOS action to be applied to only non-anonymous
+pages of all memory cgroups except ``/having_care_already``.::
+
+    # echo 2 > nr_filters
+    # # filter out anonymous pages
+    echo anon > 0/type
+    echo Y > 0/matching
+    # # further filter out all cgroups except one at '/having_care_already'
+    echo memcg > 1/type
+    echo /having_care_already > 1/memcg_path
+    echo N > 1/matching
+
+Note that filters could be ignored depend on the running DAMON operations set
+`implementation <sysfs_contexts>`.
+
 .. _sysfs_schemes_stats:
 
 schemes/<N>/stats/
-- 
2.25.1