linux-toradex.git/Documentation/admin-guide/mm/damon, branch master

Docs/admin-guide/mm/damon/lru_sort: warn commit_inputs vs param updates race

2026-04-18T07:10:51+00:00

DAMON_LRU_SORT handles commit_inputs request inside kdamond thread,
reading the module parameters.  If the user updates the module
parameters while the kdamond thread is reading those, races can happen.
To avoid this, the commit_inputs parameter shows whether it is still in
the progress, assuming users wouldn't update parameters in the middle of
the work.  Some users might ignore that.  Add a warning about the
behavior.

The issue was discovered in [1] by sashiko.

Link: https://lore.kernel.org/20260329153052.46657-3-sj@kernel.org
Link: https://lore.kernel.org/20260319161620.189392-2-objecting@objecting.org [1]
Fixes: 6acfcd0d7524 ("Docs/admin-guide/damon: add a document for DAMON_LRU_SORT")
Signed-off-by: SeongJae Park 
Cc:  # 6.0.x
Signed-off-by: Andrew Morton

Docs/admin-guide/mm/damon/reclaim: warn commit_inputs vs param updates race

2026-04-18T07:10:51+00:00

Patch series "Docs/admin-guide/mm/damon: warn commit_inputs vs other
params race".

Writing 'Y' to the commit_inputs parameter of DAMON_RECLAIM and
DAMON_LRU_SORT, and writing other parameters before the commit_inputs
request is completely processed can cause race conditions.  While the
consequence can be bad, the documentation is not clearly describing that. 
Add clear warnings.

The issue was discovered [1,2] by sashiko.


This patch (of 2):

DAMON_RECLAIM handles commit_inputs request inside kdamond thread,
reading the module parameters.  If the user updates the module
parameters while the kdamond thread is reading those, races can happen.
To avoid this, the commit_inputs parameter shows whether it is still in
the progress, assuming users wouldn't update parameters in the middle of
the work.  Some users might ignore that.  Add a warning about the
behavior.

The issue was discovered in [1] by sashiko.

Link: https://lore.kernel.org/20260329153052.46657-2-sj@kernel.org
Link: https://lore.kernel.org/20260319161620.189392-3-objecting@objecting.org [1]
Link: https://lore.kernel.org/20260319161620.189392-2-objecting@objecting.org [3]
Fixes: 81a84182c343 ("Docs/admin-guide/mm/damon/reclaim: document 'commit_inputs' parameter")
Signed-off-by: SeongJae Park 
Cc:  # 5.19.x
Signed-off-by: Andrew Morton

Docs/mm/damon: document min_nr_regions constraint and rationale

2026-04-05T20:53:34+00:00

The current DAMON implementation requires 'min_nr_regions' to be at least
3.  However, this constraint is not explicitly documented in the
admin-guide documents, nor is its design rationale explained in the design
document.

Add a section in design.rst to explain the rationale: the virtual address
space monitoring design needs to handle at least three regions to
accommodate two large unmapped areas.  While this is specific to 'vaddr',
DAMON currently enforces it across all operation sets for consistency.

Also update reclaim.rst and lru_sort.rst by adding cross-references to
this constraint within their respective 'min_nr_regions' parameter
description sections, ensuring users are aware of the lower bound.

This change is motivated from a recent discussion [1].

Link: https://lkml.kernel.org/r/20260320052428.213230-1-aethernet65535@gmail.com
Link: https://lore.kernel.org/damon/20260319151528.86490-1-sj@kernel.org/T/#t [1]
Signed-off-by: Liew Rui Yan 
Reviewed-by: SeongJae Park 
Signed-off-by: Andrew Morton

Docs/mm/damon: document exclusivity of special-purpose modules

2026-04-05T20:53:30+00:00

Add a section in design.rst to explain that DAMON special-purpose kernel
modules (LRU_SORT, RECLAIM, STAT) run in an exclusive manner and return
-EBUSY if another is already running.

Update lru_sort.rst, reclaim.rst and stat.rst by adding cross-references
to this exclusivity rule at the end of their respective Example sections.

This change is motivated from another discussion [1].

Link: https://lkml.kernel.org/r/20260315162945.80994-1-sj@kernel.org
Link: https://lore.kernel.org/damon/20260314002119.79742-1-sj@kernel.org/T/#t [1]
Signed-off-by: Liew Rui Yan 
Reviewed-by: SeongJae Park 
Signed-off-by: SeongJae Park 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes (Oracle) 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Shuah Khan 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

Docs/admin-guide/mm/damon/usage: document goal_tuner sysfs file

2026-04-05T20:53:26+00:00

Update the DAMON usage document for the new sysfs file for the goal based
quota auto-tuning algorithm selection.

Link: https://lkml.kernel.org/r/20260310010529.91162-7-sj@kernel.org
Signed-off-by: SeongJae Park 
Signed-off-by: Andrew Morton

Docs/admin-guide/mm/damn/lru_sort: fix intervals autotune parameter name

2026-04-05T20:53:22+00:00

The section name should be the same as the parameter name.  Fix it.

Link: https://lkml.kernel.org/r/20260307195356.203753-6-sj@kernel.org
Fixes: ed581147a417 ("Docs/admin-guide/mm/damon/lru_sort: document intervals autotuning")
Signed-off-by: SeongJae Park 
Acked-by: wang lian 
Cc: Brendan Higgins 
Cc: David Gow 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes (Oracle) 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Shuah Khan 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

Docs/admin-guide/mm/damon/usage: update stats update process for refresh_ms

2026-01-31T22:22:48+00:00

DAMOS stats on sysfs was only manually updated.  Recent addition of
'refresh_ms' knob enabled periodic and automated updates of the stats. 
The document for stats update process is not updated for the change,
however.  Update.

Link: https://lkml.kernel.org/r/20260118180305.70023-7-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

Docs/admin-guide/mm/damon/usage: introduce DAMON modules at the beginning

2026-01-31T22:22:48+00:00

DAMON usage document provides a list of available DAMON interfaces with
brief introduction at the beginning of the doc.  The list is missing DAMON
modules for special purposes, while it is one of the major suggested
interfaces.  Add an item for those to the list.

Link: https://lkml.kernel.org/r/20260118180305.70023-6-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

Docs/admin-guide/mm/damon/lru_sort: document intervals autotuning

2026-01-27T04:02:31+00:00

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

Link: https://lkml.kernel.org/r/20260113152717.70459-12-sj@kernel.org
Signed-off-by: SeongJae Park 
Acked-by: wang lian 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

Docs/admin-guide/mm/damon/lru_sort: document active_mem_bp parameter

2026-01-27T04:02:31+00:00

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

Link: https://lkml.kernel.org/r/20260113152717.70459-10-sj@kernel.org
Signed-off-by: SeongJae Park 
Acked-by: wang lian 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam Howlett 
Cc: Lorenzo Stoakes 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton