The quilt patch titled
Subject: Docs/mm/damon/design: document for intervals auto-tuning
has been removed from the -mm tree. Its filename was
docs-mm-damon-design-document-for-intervals-auto-tuning.patch
This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------
From: SeongJae Park <sj@xxxxxxxxxx>
Subject: Docs/mm/damon/design: document for intervals auto-tuning
Date: Mon, 3 Mar 2025 14:17:24 -0800
Document the design of DAMON sampling and aggregation intervals
auto-tuning.
[sj@xxxxxxxxxx: fix a typo on 'intervals auto-tuning' section]
Link: https://lkml.kernel.org/r/20250305182744.56125-1-sj@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20250303221726.484227-7-sj@xxxxxxxxxx
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/mm/damon/design.rst | 46 ++++++++++++++++++++++++++++
1 file changed, 46 insertions(+)
--- a/Documentation/mm/damon/design.rst~docs-mm-damon-design-document-for-intervals-auto-tuning
+++ a/Documentation/mm/damon/design.rst
@@ -313,6 +313,10 @@ sufficient for the given purpose, it sho
lowered. It is recommended to be set proportional to ``aggregation interval``.
By default, the ratio is set as ``1/20``, and it is still recommended.
+Based on the manual tuning guide, DAMON provides more intuitive knob-based
+intervals auto tuning mechanism. Please refer to :ref:`the design document of
+the feature <damon_design_monitoring_intervals_autotuning>` for detail.
+
Refer to below documents for an example tuning based on the above guide.
.. toctree::
@@ -321,6 +325,48 @@ Refer to below documents for an example
monitoring_intervals_tuning_example
+.. _damon_design_monitoring_intervals_autotuning:
+
+Monitoring Intervals Auto-tuning
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+DAMON provides automatic tuning of the ``sampling interval`` and ``aggregation
+interval`` based on the :ref:`the tuning guide idea
+<damon_design_monitoring_params_tuning_guide>`. The tuning mechanism allows
+users to set the aimed amount of access events to observe via DAMON within
+given time interval. The target can be specified by the user as a ratio of
+DAMON-observed access events to the theoretical maximum amount of the events
+(``access_bp``) that measured within a given number of aggregations
+(``aggrs``).
+
+The DAMON-observed access events are calculated in byte granularity based on
+DAMON :ref:`region assumption <damon_design_region_based_sampling>`. For
+example, if a region of size ``X`` bytes of ``Y`` ``nr_accesses`` is found, it
+means ``X * Y`` access events are observed by DAMON. Theoretical maximum
+access events for the region is calculated in same way, but replacing ``Y``
+with theoretical maximum ``nr_accesses``, which can be calculated as
+``aggregation interval / sampling interval``.
+
+The mechanism calculates the ratio of access events for ``aggrs`` aggregations,
+and increases or decrease the ``sampleing interval`` and ``aggregation
+interval`` in same ratio, if the observed access ratio is lower or higher than
+the target, respectively. The ratio of the intervals change is decided in
+proportion to the distance between current samples ratio and the target ratio.
+
+The user can further set the minimum and maximum ``sampling interval`` that can
+be set by the tuning mechanism using two parameters (``min_sample_us`` and
+``max_sample_us``). Because the tuning mechanism changes ``sampling interval``
+and ``aggregation interval`` in same ratio always, the minimum and maximum
+``aggregation interval`` after each of the tuning changes can automatically set
+together.
+
+The tuning is turned off by default, and need to be set explicitly by the user.
+As a rule of thumbs and the Parreto principle, 4% access samples ratio target
+is recommended. Note that Parreto principle (80/20 rule) has applied twice.
+That is, assumes 4% (20% of 20%) DAMON-observed access events ratio (source)
+to capture 64% (80% multipled by 80%) real access events (outcomes).
+
+
.. _damon_design_damos:
Operation Schemes
_
Patches currently in -mm which might be from sj@xxxxxxxxxx are
mm-damon-sysfs-schemes-let-damon_sysfs_scheme_set_filters-be-used-for-different-named-directories.patch
mm-damon-sysfs-schemes-implement-core_filters-and-ops_filters-directories.patch
mm-damon-sysfs-schemes-commit-filters-in-coreops_filters-directories.patch
mm-damon-core-expose-damos_filter_for_ops-to-damon-kernel-api-callers.patch
mm-damon-sysfs-schemes-record-filters-of-which-layer-should-be-added-to-the-given-filters-directory.patch
mm-damon-sysfs-schemes-return-error-when-for-attempts-to-install-filters-on-wrong-sysfs-directory.patch
docs-abi-damon-document-coreops_filters-directories.patch
docs-admin-guide-mm-damon-usage-update-for-coreops_filters-directories.patch
mm-damon-sysfs-validate-user-inputs-from-damon_sysfs_commit_input.patch
mm-damon-core-invoke-kdamond_call-after-merging-is-done-if-possible.patch
mm-damon-core-make-damon_set_attrs-be-safe-to-be-called-from-damon_call.patch
mm-damon-sysfs-handle-commit-command-using-damon_call.patch
mm-damon-sysfs-remove-damon_sysfs_cmd_request-code-from-damon_sysfs_handle_cmd.patch
mm-damon-sysfs-remove-damon_sysfs_cmd_request_callback-and-its-callers.patch
mm-damon-sysfs-remove-damon_sysfs_cmd_request-and-its-readers.patch
mm-damon-sysfs-schemes-remove-obsolete-comment-for-damon_sysfs_schemes_clear_regions.patch
mm-damon-remove-damon_callback-private.patch
mm-damon-remove-before_start-of-damon_callback.patch
mm-damon-remove-damon_callback-after_sampling.patch
mm-damon-remove-damon_callback-before_damos_apply.patch
mm-damon-remove-damon_operations-reset_aggregated.patch
mm-damon-sysfs-schemes-avoid-wformat-security-warning-on-damon_sysfs_access_pattern_add_range_dir.patch
mm-madvise-use-is_memory_failure-from-madvise_do_behavior.patch
mm-madvise-split-out-populate-behavior-check-logic.patch
mm-madvise-deduplicate-madvise_do_behavior-skip-case-handlings.patch
mm-madvise-remove-len-parameter-of-madvise_do_behavior.patch
