Aim-oriented DAMOS quota auto-tuning uses a single tuning algorithm.
The algorithm is designed to find a quota value that should be
consistently kept for achieving the aimed goal for long term.  It is
useful and reliable at automatically operating systems that have dynamic
environments in the long term.

As always, however, no single algorithm fits all.  When the environment
has static characteristics or there are control towers in not only the
kernel space but also the user space, the algorithm shows some
limitations.  In such environments, users want kernel work in a more
short term deterministic way.  Actually there were at least two reports
[1,2] of such cases.

Extend DAMOS quotas goal to support multiple quota tuning algorithms
that users can select.  Keep the current algorithm as the default one,
to not break the old users.  Also give it a name, "consist", as it is
designed to "consistently" apply the DAMOS action.  And introduce a new
tuning algorithm, namely "temporal".  It is designed to apply the DAMOS
action only temporally, in a deterministic way.  In more detail, as long
as the goal is under-achieved, it uses the maximum quota available.
Once the goal is over-achieved, it sets the quota zero.

Tests
=====

I confirmed the feature is working as expected using the latest version
of DAMON user-space tool, like below.

    $ # start DAMOS for reclaiming memory aiming 30% free memory
    $ sudo ./damo/damo start --damos_action pageout \
            --damos_quota_goal_tuner temporal \
            --damos_quota_goal node_mem_free_bp 30% 0 \
            --damos_quota_interval 1s \
            --damos_quota_space 100M

Note that >=3.1.8 version of DAMON user-space tool supports this feature
(--damos_quota_goal_tuner).  As expected, DAMOS stops reclaiming memory
as soon as the goal amount of free memory is made.  When 'consist' tuner
is used, the reclamation was continued even after the goal amount of
free memory is made, resulting in more than goal amount of free memory,
as expected.

Patch Sequence
==============

First four patches implement the features.  Patch 1 extends core API to
allow multiple tuners and make the current tuner as the default and only
available tuner, namely 'consist'.  Patch 2 allows future tuners setting
zero effective quota.  Patch 3 introduces the second tuner, namely
'temporal'.  Patch 4 further extends DAMON sysfs API to let users use
that.

Three following patches (patches 5-7) update design, usage, and ABI
documents, respectively.

Final three patches (patches 8-10) are for adding selftests.  The eighth
and the ninth patches extend the testing-purpose DAMON sysfs control
helper and DAMON status dumping tool to support the newly added feature.
The tenth patch extends the existing online commit test to cover the new
feature.

References
==========

[1] https://lore.kernel.org/CALa+Y17__d=ZsM1yX+MXx0ozVdsXnFqF4p0g+kATEitrWyZFfg@mail.gmail.com
[2] https://lore.kernel.org/20260204022537.814-1-yunjeong.mun@sk.com

Changelog
=========

Changes from RFC v1
(https://lore.kernel.org/20260212062314.69961-1-sj@kernel.org)
- Add selftest for goal_tuner commitment.
- Set goal tuner inside damon_new_scheme().
- Allow zero size effective size quota.
- Update the ABI document.
- Wordsmith change descriptions.

SeongJae Park (10):
  mm/damon/core: introduce damos_quota_goal_tuner
  mm/damon/core: allow quota goals set zero effective size quota
  mm/damon/core: introduce DAMOS_QUOTA_GOAL_TUNER_TEMPORAL
  mm/damon/sysfs-schemes: implement quotas->goal_tuner file
  Docs/mm/damon/design: document the goal-based quota tuner selections
  Docs/admin-guide/mm/damon/usage: document goal_tuner sysfs file
  Docs/ABI/damon: update for goal_tuner
  selftests/damon/_damon_sysfs: support goal_tuner setup
  selftests/damon/drgn_dump_damon_status: support quota goal_tuner
    dumping
  selftests/damon/sysfs.py: test goal_tuner commit

 .../ABI/testing/sysfs-kernel-mm-damon         |  6 ++
 Documentation/admin-guide/mm/damon/usage.rst  | 16 +++--
 Documentation/mm/damon/design.rst             | 12 ++++
 include/linux/damon.h                         | 11 ++++
 mm/damon/core.c                               | 60 +++++++++++++++----
 mm/damon/sysfs-schemes.c                      | 58 ++++++++++++++++++
 tools/testing/selftests/damon/_damon_sysfs.py | 12 +++-
 .../selftests/damon/drgn_dump_damon_status.py |  1 +
 tools/testing/selftests/damon/sysfs.py        |  7 +++
 9 files changed, 166 insertions(+), 17 deletions(-)


base-commit: bbba4ca6322dd5c4f66fe31b1b374f77a8d2b2e5
-- 
2.47.3

On Tue,  3 Mar 2026 20:41:09 -0800 SeongJae Park <sj@kernel.org> wrote:

> Aim-oriented DAMOS quota auto-tuning uses a single tuning algorithm.
> The algorithm is designed to find a quota value that should be
> consistently kept for achieving the aimed goal for long term.  It is
> useful and reliable at automatically operating systems that have dynamic
> environments in the long term.
> 
> As always, however, no single algorithm fits all.  When the environment
> has static characteristics or there are control towers in not only the
> kernel space but also the user space, the algorithm shows some
> limitations.  In such environments, users want kernel work in a more
> short term deterministic way.  Actually there were at least two reports
> [1,2] of such cases.
> 
> Extend DAMOS quotas goal to support multiple quota tuning algorithms
> that users can select.  Keep the current algorithm as the default one,
> to not break the old users.  Also give it a name, "consist", as it is
> designed to "consistently" apply the DAMOS action.  And introduce a new
> tuning algorithm, namely "temporal".  It is designed to apply the DAMOS
> action only temporally, in a deterministic way.  In more detail, as long
> as the goal is under-achieved, it uses the maximum quota available.
> Once the goal is over-achieved, it sets the quota zero.
> 
> Tests
> =====
> 
> I confirmed the feature is working as expected using the latest version
> of DAMON user-space tool, like below.
> 
>     $ # start DAMOS for reclaiming memory aiming 30% free memory
>     $ sudo ./damo/damo start --damos_action pageout \
>             --damos_quota_goal_tuner temporal \
>             --damos_quota_goal node_mem_free_bp 30% 0 \
>             --damos_quota_interval 1s \
>             --damos_quota_space 100M
> 
> Note that >=3.1.8 version of DAMON user-space tool supports this feature
> (--damos_quota_goal_tuner).  As expected, DAMOS stops reclaiming memory
> as soon as the goal amount of free memory is made.  When 'consist' tuner
> is used, the reclamation was continued even after the goal amount of
> free memory is made, resulting in more than goal amount of free memory,
> as expected.
> 
> Patch Sequence
> ==============
> 
> First four patches implement the features.  Patch 1 extends core API to
> allow multiple tuners and make the current tuner as the default and only
> available tuner, namely 'consist'.  Patch 2 allows future tuners setting
> zero effective quota.  Patch 3 introduces the second tuner, namely
> 'temporal'.  Patch 4 further extends DAMON sysfs API to let users use
> that.
> 
> Three following patches (patches 5-7) update design, usage, and ABI
> documents, respectively.
> 
> Final three patches (patches 8-10) are for adding selftests.  The eighth
> and the ninth patches extend the testing-purpose DAMON sysfs control
> helper and DAMON status dumping tool to support the newly added feature.
> The tenth patch extends the existing online commit test to cover the new
> feature.
> 
> References
> ==========
> 
> [1] https://lore.kernel.org/CALa+Y17__d=ZsM1yX+MXx0ozVdsXnFqF4p0g+kATEitrWyZFfg@mail.gmail.com
> [2] https://lore.kernel.org/20260204022537.814-1-yunjeong.mun@sk.com
> 
> Changelog
> =========
> 
> Changes from RFC v1
> (https://lore.kernel.org/20260212062314.69961-1-sj@kernel.org)
> - Add selftest for goal_tuner commitment.
> - Set goal tuner inside damon_new_scheme().
> - Allow zero size effective size quota.
> - Update the ABI document.
> - Wordsmith change descriptions.
> 
> SeongJae Park (10):
>   mm/damon/core: introduce damos_quota_goal_tuner
>   mm/damon/core: allow quota goals set zero effective size quota
>   mm/damon/core: introduce DAMOS_QUOTA_GOAL_TUNER_TEMPORAL
>   mm/damon/sysfs-schemes: implement quotas->goal_tuner file
>   Docs/mm/damon/design: document the goal-based quota tuner selections
>   Docs/admin-guide/mm/damon/usage: document goal_tuner sysfs file
>   Docs/ABI/damon: update for goal_tuner
>   selftests/damon/_damon_sysfs: support goal_tuner setup
>   selftests/damon/drgn_dump_damon_status: support quota goal_tuner
>     dumping
>   selftests/damon/sysfs.py: test goal_tuner commit

Maybe it is better to add a kunit test for the goal_tuner online commit, like
below.  I will add it to the next spin of this series.


Thanks,
SJ

[...]
=== >8 ===
From 15d87f41d0d960e3c337899629cf4e05d09dc042 Mon Sep 17 00:00:00 2001
From: SeongJae Park <sj@kernel.org>
Date: Fri, 6 Mar 2026 16:27:45 -0800
Subject: [PATCH] mm/damon/tests/core-kunit: test goal_tuner commit

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/tests/core-kunit.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/damon/tests/core-kunit.h b/mm/damon/tests/core-kunit.h
index d759314df00d8..28e5de749db04 100644
--- a/mm/damon/tests/core-kunit.h
+++ b/mm/damon/tests/core-kunit.h
@@ -791,6 +791,7 @@ static void damos_test_commit_quota(struct kunit *test)
 		.reset_interval = 1,
 		.ms = 2,
 		.sz = 3,
+		.goal_tuner = DAMOS_QUOTA_GOAL_TUNER_CONSIST,
 		.weight_sz = 4,
 		.weight_nr_accesses = 5,
 		.weight_age = 6,
@@ -799,6 +800,7 @@ static void damos_test_commit_quota(struct kunit *test)
 		.reset_interval = 7,
 		.ms = 8,
 		.sz = 9,
+		.goal_tuner = DAMOS_QUOTA_GOAL_TUNER_TEMPORAL,
 		.weight_sz = 10,
 		.weight_nr_accesses = 11,
 		.weight_age = 12,
@@ -812,6 +814,7 @@ static void damos_test_commit_quota(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, dst.reset_interval, src.reset_interval);
 	KUNIT_EXPECT_EQ(test, dst.ms, src.ms);
 	KUNIT_EXPECT_EQ(test, dst.sz, src.sz);
+	KUNIT_EXPECT_EQ(test, dst.goal_tuner, src.goal_tuner);
 	KUNIT_EXPECT_EQ(test, dst.weight_sz, src.weight_sz);
 	KUNIT_EXPECT_EQ(test, dst.weight_nr_accesses, src.weight_nr_accesses);
 	KUNIT_EXPECT_EQ(test, dst.weight_age, src.weight_age);
-- 
2.47.3

Hi SeongJae!

Nice idea for dynamic environments.

On 3/4/2026 7:41 AM, SeongJae Park wrote:
> Aim-oriented DAMOS quota auto-tuning uses a single tuning algorithm.
> The algorithm is designed to find a quota value that should be
> consistently kept for achieving the aimed goal for long term.  It is
> useful and reliable at automatically operating systems that have dynamic
> environments in the long term.
> 
> As always, however, no single algorithm fits all.  When the environment
> has static characteristics or there are control towers in not only the
> kernel space but also the user space, the algorithm shows some
> limitations.  In such environments, users want kernel work in a more
> short term deterministic way.  Actually there were at least two reports
> [1,2] of such cases.
> 
> Extend DAMOS quotas goal to support multiple quota tuning algorithms
> that users can select.  Keep the current algorithm as the default one,
> to not break the old users.  Also give it a name, "consist", as it is
> designed to "consistently" apply the DAMOS action.  And introduce a new
> tuning algorithm, namely "temporal".  It is designed to apply the DAMOS
> action only temporally, in a deterministic way.  In more detail, as long
> as the goal is under-achieved, it uses the maximum quota available.
> Once the goal is over-achieved, it sets the quota zero.

I'm not sure "temporal" is the best name for this type of behaviour.

How about "by_score?". For example, "damos_goal_tune_esz_bp_by_score" and
DAMOS_QUOTA_GOAL_TUNER_BY_SCORE.

> Tests
> =====
> 
> I confirmed the feature is working as expected using the latest version
> of DAMON user-space tool, like below.
> 
>     $ # start DAMOS for reclaiming memory aiming 30% free memory
>     $ sudo ./damo/damo start --damos_action pageout \
>             --damos_quota_goal_tuner temporal \
>             --damos_quota_goal node_mem_free_bp 30% 0 \
>             --damos_quota_interval 1s \
>             --damos_quota_space 100M
> 
> Note that >=3.1.8 version of DAMON user-space tool supports this feature
> (--damos_quota_goal_tuner).  As expected, DAMOS stops reclaiming memory
> as soon as the goal amount of free memory is made.  When 'consist' tuner
> is used, the reclamation was continued even after the goal amount of
> free memory is made, resulting in more than goal amount of free memory,
> as expected.
> 
> Patch Sequence
> ==============
> 
> First four patches implement the features.  Patch 1 extends core API to
> allow multiple tuners and make the current tuner as the default and only
> available tuner, namely 'consist'.  Patch 2 allows future tuners setting
> zero effective quota.  Patch 3 introduces the second tuner, namely
> 'temporal'.  Patch 4 further extends DAMON sysfs API to let users use
> that.
> 
> Three following patches (patches 5-7) update design, usage, and ABI
> documents, respectively.
> 
> Final three patches (patches 8-10) are for adding selftests.  The eighth
> and the ninth patches extend the testing-purpose DAMON sysfs control
> helper and DAMON status dumping tool to support the newly added feature.
> The tenth patch extends the existing online commit test to cover the new
> feature.
> 
> References
> ==========
> 
> [1] https://lore.kernel.org/CALa+Y17__d=ZsM1yX+MXx0ozVdsXnFqF4p0g+kATEitrWyZFfg@mail.gmail.com
> [2] https://lore.kernel.org/20260204022537.814-1-yunjeong.mun@sk.com
> 
> Changelog
> =========
> 
> Changes from RFC v1
> (https://lore.kernel.org/20260212062314.69961-1-sj@kernel.org)
> - Add selftest for goal_tuner commitment.
> - Set goal tuner inside damon_new_scheme().
> - Allow zero size effective size quota.
> - Update the ABI document.
> - Wordsmith change descriptions.
> 
> SeongJae Park (10):
>   mm/damon/core: introduce damos_quota_goal_tuner
>   mm/damon/core: allow quota goals set zero effective size quota
>   mm/damon/core: introduce DAMOS_QUOTA_GOAL_TUNER_TEMPORAL
>   mm/damon/sysfs-schemes: implement quotas->goal_tuner file
>   Docs/mm/damon/design: document the goal-based quota tuner selections
>   Docs/admin-guide/mm/damon/usage: document goal_tuner sysfs file
>   Docs/ABI/damon: update for goal_tuner
>   selftests/damon/_damon_sysfs: support goal_tuner setup
>   selftests/damon/drgn_dump_damon_status: support quota goal_tuner
>     dumping
>   selftests/damon/sysfs.py: test goal_tuner commit
> 
>  .../ABI/testing/sysfs-kernel-mm-damon         |  6 ++
>  Documentation/admin-guide/mm/damon/usage.rst  | 16 +++--
>  Documentation/mm/damon/design.rst             | 12 ++++
>  include/linux/damon.h                         | 11 ++++
>  mm/damon/core.c                               | 60 +++++++++++++++----
>  mm/damon/sysfs-schemes.c                      | 58 ++++++++++++++++++
>  tools/testing/selftests/damon/_damon_sysfs.py | 12 +++-
>  .../selftests/damon/drgn_dump_damon_status.py |  1 +
>  tools/testing/selftests/damon/sysfs.py        |  7 +++
>  9 files changed, 166 insertions(+), 17 deletions(-)
> 
> 
> base-commit: bbba4ca6322dd5c4f66fe31b1b374f77a8d2b2e5

-- 
Asier Gutierrez
Huawei

On Wed, 4 Mar 2026 13:15:29 +0300 Gutierrez Asier <gutierrez.asier@huawei-partners.com> wrote:

> Hi SeongJae!
> 
> Nice idea for dynamic environments.

Thank you :)

> 
> On 3/4/2026 7:41 AM, SeongJae Park wrote:
> > Aim-oriented DAMOS quota auto-tuning uses a single tuning algorithm.
> > The algorithm is designed to find a quota value that should be
> > consistently kept for achieving the aimed goal for long term.  It is
> > useful and reliable at automatically operating systems that have dynamic
> > environments in the long term.
> > 
> > As always, however, no single algorithm fits all.  When the environment
> > has static characteristics or there are control towers in not only the
> > kernel space but also the user space, the algorithm shows some
> > limitations.  In such environments, users want kernel work in a more
> > short term deterministic way.  Actually there were at least two reports
> > [1,2] of such cases.
> > 
> > Extend DAMOS quotas goal to support multiple quota tuning algorithms
> > that users can select.  Keep the current algorithm as the default one,
> > to not break the old users.  Also give it a name, "consist", as it is
> > designed to "consistently" apply the DAMOS action.  And introduce a new
> > tuning algorithm, namely "temporal".  It is designed to apply the DAMOS
> > action only temporally, in a deterministic way.  In more detail, as long
> > as the goal is under-achieved, it uses the maximum quota available.
> > Once the goal is over-achieved, it sets the quota zero.
> 
> I'm not sure "temporal" is the best name for this type of behaviour.

I agree there could be a better name.

> 
> How about "by_score?". For example, "damos_goal_tune_esz_bp_by_score" and
> DAMOS_QUOTA_GOAL_TUNER_BY_SCORE.

And thank you for the suggestion!

But... I don't think "by_score" is much better, because all tuners are assumed
to, and actually do the tuning of the quota based on the score.  Or, maybe you
mean it makes non-zero quota only until the score becomes the goal?  That makes
sense, but again, in a sense, that's same for "consistent" tuner.

Naming is difficult...

I was also thinking about a few more names, but my conclusion after the self
discussion was that some of ambitious names are inevitable here.  Otherwise,
the name will be too long.  I therefore picked the shortest and simplest ones
on my list, which at least contrasts the current two tuners.  I agree that
could still be difficult to understand.  But as long as there is a good
documentation, I think difficult-to-understnd names that encourage users to
read the document is ok and might even be better in some cases.

I'm of course open to other suggestions.


Thanks,
SJ

[...]