[RFC PATCH 00/11] mm/damon: advance DAMOS-based LRU sorting

[RFC PATCH 00/11] mm/damon: advance DAMOS-based LRU sorting

[SeongJae Park]

DAMOS_LRU_[DE]PRIO actions were added to DAMOS for more access-aware LRU
lists sorting.  For simple usage, a specialized kernel module, namely
DAMON_LRU_SORT, has also introduced.  After the introduction of
DAMON_LRU_SORT, DAMON got a few important new features, including the
aim-based quota auto-tuning, young page filter, and monitoring intervals
auto-tuning.  But DAMOS-based LRU sorting had no many updates.  Now we
show some rooms to advance for DAMOS-based LRU sorting.

DAMON sysfs interface users can utilize all the features, but
DAMON_LRU_SORT is not updated for such modern features.  Also, even in
case of DAMON sysfs interface usage, there is no good quota auto-tuning
goal metric for LRU sorting.  Since it is a sort of balancing of active
and inactive pages, a metric that represents the size ratio between the
active and the inactive pages could be useful.  Also, internal behaviors
of DAMOS_LRU_[DE]PRIO are not very symmetric.

Advance DAMOS-based LRU sorting by introducing a new DAMOS quota
auto-tuning target metric for [in]active memory size ratio, making
DAMOS_LRU_[DE]PRIO behavior more intuitive and symmetric.  Also update
DAMON_LRU_SORT module to be able to fully utilize the modern features
including the [in]active memory size ratio, young page filter, and
monitoring intervals auto-tuning.

With these changes, for example, users can now ask DAMON to "find
hot/cold memory regions with auto-tuned monitoring intervals, do one
more page level access check for found hot/cold memory, and move pages
of those to active or inactive LRU lists accordingly, aiming 50:50
active to inactive memory ratio."

Plan for none-RFC Version
-------------------------

I'm planning to do more tests and add the results by the final version.

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

First four patches extend DAMOS quota auto-tuning to support [in]active
memory ratio target metric type.  The patches introduce new metrics
(patch 1), DAMON sysfs support
(patch 2), and add the document (patch 3).

Following patch (patch 4) makes DAMOS_LRU_PRIO action to directly move
target pages to active LRU list, instead of marking accessed and
incrementally be moved to active lists.

Following seven patches (patches 5-11) updates DAMON_LRU_SORT to support
modern DAMON features.  Patch 5 makes it to use not only access
frequency but also age at under-quota regions prioritization.  Patch
6-11 add the support and document it for young page filtering,
active:inactive memory ratio based quota auto-tuning, and monitoring
intervals auto-tuning, respectively.

SeongJae Park (11):
  mm/damon/core: introduce [in]active memory ratio damos quota goal
    metric
  mm/damon/sysfs-schemes: support DAMOS_QUOTA_[IN]ACTIVE_MEM_BP
  Docs/mm/damon/design: document DAMOS_QUOTA_[IN]ACTIVE_MEM_BP
  mm/damon/paddr: activate DAMOS_LRU_PRIO targets instead of marking
    accessed
  mm/damon/lru_sort: consider age for quota prioritization
  mm/damon/lru_sort: support young page filters
  Docs/admin-guide/mm/damon/lru_sort: document filter_young_pages
  mm/damon/lru_sort: support active:inactive memory ratio based
    auto-tuning
  Docs/admin-guide/mm/damon/lru_sort: document active_mem_bp parameter
  mm/damon/lru_sort: add monitoring intervals auto-tuning parameter
  Docs/admin-guide/mm/damon/lru_sort: document intervals autotuning

 .../admin-guide/mm/damon/lru_sort.rst         |  37 ++++++
 Documentation/mm/damon/design.rst             |   4 +
 include/linux/damon.h                         |   4 +
 mm/damon/core.c                               |  22 ++++
 mm/damon/lru_sort.c                           | 110 +++++++++++++++++-
 mm/damon/paddr.c                              |  18 ++-
 mm/damon/sysfs-schemes.c                      |   8 ++
 7 files changed, 189 insertions(+), 14 deletions(-)


base-commit: cd5e995caa32062e89e340acb4acbcbe09ad709e
-- 
2.39.5

[RFC PATCH 03/11] Docs/mm/damon/design: document DAMOS_QUOTA_[IN]ACTIVE_MEM_BP

[SeongJae Park]

Update design document for newly added DAMOS_QUOTA_[IN]ACTIVE_MEM_BP
metrics.  Note that API document is automatically updated by kernel-doc
comment, and the usage document points to the design document which uses
keywords same to that for sysfs inputs.  Hence updating only design
document is sufficient.

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

diff --git a/Documentation/mm/damon/design.rst b/Documentation/mm/damon/design.rst
index 2290ebefc648..ce8c389f0c68 100644
--- a/Documentation/mm/damon/design.rst
+++ b/Documentation/mm/damon/design.rst
@@ -570,6 +570,10 @@ tries to make ``current_value`` of ``target_metric`` be same to
   set by users at the initial time.  In other words, DAMOS does self-feedback.
 - ``node_mem_used_bp``: Specific NUMA node's used memory ratio in bp (1/10,000).
 - ``node_mem_free_bp``: Specific NUMA node's free memory ratio in bp (1/10,000).
+- ``active_mem_bp``: Active to active + inactive (LRU) memory size ratio in bp
+  (1/10,000).
+- ``inactive_mem_bp``: Inactive to active + inactive (LRU) memory size ratio in
+  bp (1/10,000).
 
 ``nid`` is optionally required for only ``node_mem_used_bp`` and
 ``node_mem_free_bp`` to point the specific NUMA node.
-- 
2.39.5

[RFC PATCH 07/11] Docs/admin-guide/mm/damon/lru_sort: document filter_young_pages

[SeongJae Park]

Document the new DAMON_LRU_SORT parameter, filter_young_pages.  It can
be used to use page level access re-check for the LRU sorting.

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

diff --git a/Documentation/admin-guide/mm/damon/lru_sort.rst b/Documentation/admin-guide/mm/damon/lru_sort.rst
index 7b0775d281b4..18fa73a59f62 100644
--- a/Documentation/admin-guide/mm/damon/lru_sort.rst
+++ b/Documentation/admin-guide/mm/damon/lru_sort.rst
@@ -79,6 +79,20 @@ of parametrs except ``enabled`` again.  Once the re-reading is done, this
 parameter is set as ``N``.  If invalid parameters are found while the
 re-reading, DAMON_LRU_SORT will be disabled.
 
+filter_young_pages
+------------------
+
+Filter [none-]young pages accordingly for LRU [de]prioritizations.
+
+If this is set, check page level access (youngness) once again before each
+LRU [de]prioritization operation.  LRU prioritization operation is skipped
+if the page has not accessed since the last check (not young).  LRU
+deprioritization operation is skipped if the page has accessed since the
+last check (young).  The feature is enabled or disabled if this parameter is
+set as ``Y`` or ``N``, respectively.
+
+Disabled by default.
+
 hot_thres_access_freq
 ---------------------
 
-- 
2.39.5

[RFC PATCH 09/11] Docs/admin-guide/mm/damon/lru_sort: document active_mem_bp parameter

[SeongJae Park]

Document a newly added DAMON_LRU_SORT parameter for doing auto-tuning
aiming an active to inactive memory size ratio.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/admin-guide/mm/damon/lru_sort.rst | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/Documentation/admin-guide/mm/damon/lru_sort.rst b/Documentation/admin-guide/mm/damon/lru_sort.rst
index 18fa73a59f62..ca4e071b3159 100644
--- a/Documentation/admin-guide/mm/damon/lru_sort.rst
+++ b/Documentation/admin-guide/mm/damon/lru_sort.rst
@@ -79,6 +79,18 @@ of parametrs except ``enabled`` again.  Once the re-reading is done, this
 parameter is set as ``N``.  If invalid parameters are found while the
 re-reading, DAMON_LRU_SORT will be disabled.
 
+active_mem_bp
+-------------
+
+Desired active to [in]active memory ratio in bp (1/10,000).
+
+While keeping the caps that set by other quotas, DAMON_LRU_SORT automatically
+increases and decreases the effective level of the quota aiming the LRU
+[de]prioritizations of the hot and cold memory resulting in this active to
+[in]active memory ratio.  Value zero means disabling this auto-tuning feature.
+
+Disabled by default.
+
 filter_young_pages
 ------------------
 
-- 
2.39.5

[RFC PATCH 11/11] Docs/admin-guide/mm/damon/lru_sort: document intervals autotuning

[SeongJae Park]

Document a newly added DAMON_LRU_SORT module parameter for using
monitoring intervals auto-tuning feature of DAMON.

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 Documentation/admin-guide/mm/damon/lru_sort.rst | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/Documentation/admin-guide/mm/damon/lru_sort.rst b/Documentation/admin-guide/mm/damon/lru_sort.rst
index ca4e071b3159..f9dfa8255dda 100644
--- a/Documentation/admin-guide/mm/damon/lru_sort.rst
+++ b/Documentation/admin-guide/mm/damon/lru_sort.rst
@@ -91,6 +91,17 @@ increases and decreases the effective level of the quota aiming the LRU
 
 Disabled by default.
 
+Auto-tune monitoring intervals
+------------------------------
+
+If this parameter is set as ``Y``, DAMON_LRU_SORT automatically tune DAMON's
+sampling and aggregation intervals.  The auto-tuning aims to capture meaningful
+amount of access events in each DAMON-snapshot, while keeping the sampling
+interval 5 milliseconds in minimu, and 10 seconds in maximum.  Setting this as
+``Y`` disables the auto-tuning.
+
+Disabled by default.
+
 filter_young_pages
 ------------------
 
-- 
2.39.5