[PATCH v2 00/10] mm/damon: extend DAMOS filters for inclusion

[PATCH v2 00/10] mm/damon: extend DAMOS filters for inclusion

[SeongJae Park]

DAMOS fitlers are exclusive filters.  It only excludes memory of given
criterias from the DAMOS action targets.  This has below limitations.

First, the name is not explicitly explaining the behavior.  This
actually resulted in users' confusions[1].  Secondly, combined uses of
multiple filters provide only restriced coverages.  For example,
building a DAMOS scheme that applies the action to memory that belongs
to cgroup A "or" cgroup B is impossible.  A workaround would be using
two schemes that fitlers out memory that not belong to cgroup A and
cgroup B, respectively.  It is cumbersome, and difficult to control
quota-like per-scheme features in an orchestration.  Monitoring of
filters-passed memory statistic will also be complicated.

Extend DAMOS filters to support not only exclusion (rejecting), but also
inclusion (allowing) behavior.  For this, add a new damos_filter struct
field called 'allow' for DAMON kernel API users.  The filter works as an
inclusion or exclusion filter when it is set or unset, respectively.
For DAMON user-space ABI users, add a DAMON sysfs file of same name
under DAMOS filter sysfs directory.  To prevent exposing a behavioral
change to old users, set rejecting as the default behavior.

Note that allow-filters work for only inclusion, not exclusion of memory
that not satisfying the criteria.  And the default behavior of DAMOS for
memory that no filter has involved is that the action can be applied to
those memory.  Also, filters-passed memory statistics are for any memory
that passed through the DAMOS filters check stage.  These implies
installing allow-filters at the endof the filter list is useless.  Refer
to the design doc change of this series for more details.

[1] https://lore.kernel.org/20240320165619.71478-1-sj@kernel.org

Revision History
================

Changes from v1
(https://lore.kernel.org/20250107201739.79484-1-sj@kernel.org)
- Correct wrong comments and documents about pass filters without
  successing block filters
- Rename 'pass/block' to 'allow/reject'
  (to avoid confusion with sz_[ops]_filter_pass)

Changes from RFC v2
(https://lore.kernel.org/20241227210819.63776-1-sj@kernel.org)
- Wordsmith messages
- Wordsmith design documentation about monitoring-purpose usage
- Rebase on latest mm-unstable

Changes from RFC v1
(https://lore.kernel.org/20241226221445.78433-1-sj@kernel.org)
- Fix encoding issue on the last patch

SeongJae Park (10):
  mm/damon: fixup damos_filter kernel-doc
  mm/damon/core: add damos_filter->allow field
  mm/damon/core: support damos_filter->allow
  mm/damon/paddr: support damos_filter->allow
  mm/damon: add 'allow' argument to damos_new_filter()
  mm/damon/sysfs-schemes: add a file for setting damos_filter->allow
  Docs/mm/damon/design: document allow/reject DAMOS filter behaviors
  Docs/ABI/damon: document DAMOS filter allow sysfs file
  Docs/admin-guide/mm/damon/usage: omit DAMOS filter details in favor of
    design doc
  Docs/admin-guide/mm/damon/usage: document DAMOS filter 'allow' sysfs
    file

 .../ABI/testing/sysfs-kernel-mm-damon         | 13 +++--
 Documentation/admin-guide/mm/damon/usage.rst  | 54 ++++++++++---------
 Documentation/mm/damon/design.rst             | 33 ++++++++++--
 include/linux/damon.h                         | 15 +++---
 mm/damon/core.c                               | 12 +++--
 mm/damon/paddr.c                              |  9 ++--
 mm/damon/reclaim.c                            |  2 +-
 mm/damon/sysfs-schemes.c                      | 32 ++++++++++-
 mm/damon/tests/core-kunit.h                   | 14 ++---
 9 files changed, 127 insertions(+), 57 deletions(-)

-- 
2.39.5

[PATCH v2 07/10] Docs/mm/damon/design: document allow/reject DAMOS filter behaviors

[SeongJae Park]

Update DAMOS filters design document to describe the allow/reject
behavior of filters.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/mm/damon/design.rst | 33 +++++++++++++++++++++++++++----
 1 file changed, 29 insertions(+), 4 deletions(-)

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 449eb33688c2..667775bab86c 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -504,9 +504,34 @@ have a list of latency-critical processes.
 
 To let users optimize DAMOS schemes with such special knowledge, DAMOS provides
 a feature called DAMOS filters.  The feature allows users to set an arbitrary
-number of filters for each scheme.  Each filter specifies the type of target
-memory, and whether it should exclude the memory of the type (filter-out), or
-all except the memory of the type (filter-in).
+number of filters for each scheme.  Each filter specifies
+
+- a type of memory (``type``),
+- whether it is for the memory of the type or all except the type
+  (``matching``), and
+- whether it is to allow (include) or reject (exclude) applying
+  the scheme's action to the memory (``allow``).
+
+When multiple filters are installed, each filter is evaluated in the installed
+order.  If a part of memory is matched to one of the filter, next filters are
+ignored.  If the memory passes through the filters evaluation stage because it
+is not matched to any of the filters, applying the scheme's action to it is
+allowed, same to the behavior when no filter exists.
+
+For example, let's assume 1) a filter for allowing anonymous pages and 2)
+another filter for rejecting young pages are installed in the order.  If a page
+of a region that eligible to apply the scheme's action is an anonymous page,
+the scheme's action will be applied to the page regardless of whether it is
+young or not, since it matches with the first allow-filter.  If the page is
+not anonymous but young, the scheme's action will not be applied, since the
+second reject-filter blocks it.  If the page is neither anonymous nor young,
+the page will pass through the filters evaluation stage since there is no
+matching filter, and the action will be applied to the page.
+
+Note that the action can equally be applied to memory that either explicitly
+filter-allowed or filters evaluation stage passed.  It means that installing
+allow-filters at the end of the list makes no practical change but only
+filters-checking overhead.
 
 For efficient handling of filters, some types of filters are handled by the
 core layer, while others are handled by operations set.  In the latter case,
@@ -516,7 +541,7 @@ filter are not counted as the scheme has tried to the region.  In contrast, if
 a memory regions is filtered by an operations set layer-handled filter, it is
 counted as the scheme has tried.  This difference affects the statistics.
 
-Below types of filters are currently supported.
+Below ``type`` of filters are currently supported.
 
 - anonymous page
     - Applied to pages that containing data that not stored in files.
-- 
2.39.5

[PATCH v2 09/10] Docs/admin-guide/mm/damon/usage: omit DAMOS filter details in favor of design doc

[SeongJae Park]

DAMON usage document is describing some details about DAMOS filters,
which are also documented on the design doc.  Deduplicate the details in
favor of the design doc.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/admin-guide/mm/damon/usage.rst | 29 ++++++++++----------
 1 file changed, 14 insertions(+), 15 deletions(-)

diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
index 71cf29ae8502..8df3357dcfa3 100644
--- a/Documentation/admin-guide/mm/damon/usage.rst
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -411,13 +411,17 @@ Each filter directory contains six files, namely ``type``, ``matcing``,
 file, you can write one of five special keywords: ``anon`` for anonymous pages,
 ``memcg`` for specific memory cgroup, ``young`` for young pages, ``addr`` for
 specific address range (an open-ended interval), or ``target`` for specific
-DAMON monitoring target 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.  In case of the
-address range filtering, you can specify the start and end address of the range
-to ``addr_start`` and ``addr_end`` files, respectively.  For the DAMON
-monitoring target filtering, you can specify the index of the target between
-the list of the DAMON context's monitoring targets list to ``target_idx`` file.
+DAMON monitoring target filtering.  Meaning of the types are same to the
+description on the :ref:`design doc <damon_design_damos_filters>`.
+
+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.  In case of the address range filtering, you can
+specify the start and end address of the range to ``addr_start`` and
+``addr_end`` files, respectively.  For the DAMON monitoring target filtering,
+you can specify the index of the target between the list of the DAMON context's
+monitoring targets list to ``target_idx`` 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.
@@ -434,14 +438,9 @@ pages of all memory cgroups except ``/having_care_already``.::
     echo /having_care_already > 1/memcg_path
     echo Y > 1/matching
 
-Note that ``anon`` and ``memcg`` filters are currently supported only when
-``paddr`` :ref:`implementation <sysfs_context>` is being used.
-
-Also, memory regions that are filtered out by ``addr`` or ``target`` filters
-are not counted as the scheme has tried to those, while regions that filtered
-out by other type filters are counted as the scheme has tried to.  The
-difference is applied to :ref:`stats <damos_stats>` and
-:ref:`tried regions <sysfs_schemes_tried_regions>`.
+Refer to the :ref:`DAMOS filters design documentation
+<damon_design_damos_filters>` for more details including when each of the
+filters are supported and differences on stats.
 
 .. _sysfs_schemes_stats:
 
-- 
2.39.5

[PATCH v2 10/10] Docs/admin-guide/mm/damon/usage: document DAMOS filter 'allow' sysfs file

[SeongJae Park]

Update DAMON usage document for the newly added 'allow' sysfs file for
DAMOS filters.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/admin-guide/mm/damon/usage.rst | 33 +++++++++++---------
 1 file changed, 19 insertions(+), 14 deletions(-)

diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
index 8df3357dcfa3..f0d0c20711d6 100644
--- a/Documentation/admin-guide/mm/damon/usage.rst
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -83,7 +83,7 @@ comma (",").
     │ │ │ │ │ │ │ │ │ 0/target_metric,target_value,current_value
     │ │ │ │ │ │ │ :ref:`watermarks <sysfs_watermarks>`/metric,interval_us,high,mid,low
     │ │ │ │ │ │ │ :ref:`filters <sysfs_filters>`/nr_filters
-    │ │ │ │ │ │ │ │ 0/type,matching,memcg_id
+    │ │ │ │ │ │ │ │ 0/type,matching,memcg_id,allow
     │ │ │ │ │ │ │ :ref:`stats <sysfs_schemes_stats>`/nr_tried,sz_tried,nr_applied,sz_applied,sz_ops_filter_passed,qt_exceeds
     │ │ │ │ │ │ │ :ref:`tried_regions <sysfs_schemes_tried_regions>`/total_bytes
     │ │ │ │ │ │ │ │ 0/start,end,nr_accesses,age,sz_filter_passed
@@ -406,13 +406,14 @@ 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 six files, namely ``type``, ``matcing``,
-``memcg_path``, ``addr_start``, ``addr_end``, and ``target_idx``.  To ``type``
-file, you can write one of five special keywords: ``anon`` for anonymous pages,
-``memcg`` for specific memory cgroup, ``young`` for young pages, ``addr`` for
-specific address range (an open-ended interval), or ``target`` for specific
-DAMON monitoring target filtering.  Meaning of the types are same to the
-description on the :ref:`design doc <damon_design_damos_filters>`.
+Each filter directory contains seven files, namely ``type``, ``matching``,
+``allow``, ``memcg_path``, ``addr_start``, ``addr_end``, and ``target_idx``.
+To ``type`` file, you can write one of five special keywords: ``anon`` for
+anonymous pages, ``memcg`` for specific memory cgroup, ``young`` for young
+pages, ``addr`` for specific address range (an open-ended interval), or
+``target`` for specific DAMON monitoring target filtering.  Meaning of the
+types are same to the description on the :ref:`design doc
+<damon_design_damos_filters>`.
 
 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
@@ -422,25 +423,29 @@ specify the start and end address of the range to ``addr_start`` and
 you can specify the index of the target between the list of the DAMON context's
 monitoring targets list to ``target_idx`` 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.
+You can write ``Y`` or ``N`` to ``matching`` file to specify whether the filter
+is for memory that matches the ``type``.  You can write ``Y`` or ``N`` to
+``allow`` file to specify if applying the action to the memory that satisfies
+the ``type`` and ``matching`` should be allowed or not.
 
 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
+    # # disallow anonymous pages
     echo anon > 0/type
     echo Y > 0/matching
+    echo N > 0/allow
     # # further filter out all cgroups except one at '/having_care_already'
     echo memcg > 1/type
     echo /having_care_already > 1/memcg_path
     echo Y > 1/matching
+    echo N > 1/allow
 
 Refer to the :ref:`DAMOS filters design documentation
-<damon_design_damos_filters>` for more details including when each of the
-filters are supported and differences on stats.
+<damon_design_damos_filters>` for more details including how multiple filters
+of different ``allow`` works, when each of the filters are supported, and
+differences on stats.
 
 .. _sysfs_schemes_stats:
 
-- 
2.39.5