linux.git/Documentation/mm/damon, branch master

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/design: document DAMON actions when TRANSPARENT_HUGEPAGE is off

2026-04-05T20:53:31+00:00

MADV_HUGEPAGE and MADV_NOHUGEPAGE are guarded and they are not available
when compiling the kernel without TRANSPARENT_HUGEPAGE option.  The DAMON
behaviour is to silently fail [1] in when DAMOS_HUGEPAGE or
DAMOS_NOHUGEPAGE are used, but TRANSPARENT_HUGEPAGE is disabled.  Update
the DAMON documentation to reflect this behaviour.

Link: https://lkml.kernel.org/r/20260318035349.88715-1-sj@kernel.org
Link: https://lore.kernel.org/66131775-180b-4b9f-b7ce-61a3e077b6e6@huawei-partners.com/ [1]
Signed-off-by: Asier Gutierrez 
Reviewed-by: SeongJae Park 
Signed-off-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/mm/damon/design: document the goal-based quota tuner selections

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

Update the design document for the newly added goal-based quota tuner
selection feature.

Link: https://lkml.kernel.org/r/20260310010529.91162-6-sj@kernel.org
Signed-off-by: SeongJae Park 
Signed-off-by: Andrew Morton

Docs/mm/damon/index: fix typo: autoamted -> automated

2026-04-05T20:53:23+00:00

There is an obvious typo.  Fix it (s/autoamted/automated/).

Link: https://lkml.kernel.org/r/20260307195356.203753-8-sj@kernel.org
Fixes: 32d11b320897 ("Docs/mm/damon/index: simplify the intro")
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/mm/damon/maintainer-profile: use flexible review cadence

2026-04-05T20:53:23+00:00

The document mentions the maitainer is working in the usual 9-5 fashion. 
The maintainer nowadays prefers working in a more flexible way.  Update
the document to avoid contributors having a wrong time expectation.

Link: https://lkml.kernel.org/r/20260307195356.203753-7-sj@kernel.org
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/mm/damon/design: document the power-of-two limitation for addr_unit

2026-04-05T20:53:21+00:00

The min_region_sz is set as max(DAMON_MIN_REGION_SZ / addr_unit, 1). 
DAMON_MIN_REGION_SZ is the same to PAGE_SIZE, and addr_unit is what the
user can arbitrarily set.  Commit c80f46ac228b ("mm/damon/core: disallow
non-power of two min_region_sz") made min_region_sz to always be a power
of two.  Hence, addr_unit should be a power of two when it is smaller than
PAGE_SIZE.  While 'addr_unit' is a user-exposed parameter, the rule is not
documented.  This can confuse users.  Specifically, if the user sets
addr_unit as a value that is smaller than PAGE_SIZE and not a power of
two, the setup will explicitly fail.

Document the rule on the design document.  Usage documents reference the
design document for detail, so updating only the design document should
suffice.

Link: https://lkml.kernel.org/r/20260307194222.202075-3-sj@kernel.org
Signed-off-by: SeongJae Park 
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: Suren Baghdasaryan 
Signed-off-by: Andrew Morton

Docs/mm/damon/maintainer-profile: remove damon-tests/perf suggestion

2026-01-31T22:22:49+00:00

The DAMON performance tests [1] use PARSEC 3.0 as its major test
workloads.  But the official web site for PARSEC 3.0 has gone, so there is
no easy way to get the benchmark.  Mainly due to the fact, DAMON
performance tests are difficult to run, and effectively broken.  Do not
request running it for now.  Instead, suggest running any benchmarks or
real world workloads that make sense for performance changes.

[1] https://github.com/damonitor/damon-tests/tree/master/perf

Link: https://lkml.kernel.org/r/20260118180305.70023-9-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/mm/damon/maintainer-profile: fix wrong MAITNAINERS section name

2026-01-31T22:22:49+00:00

Commit 9044cbe50a70 ("MAINTAINERS: rename DAMON section") renamed the
section for DAMON from "DATA ACCESS MONITOR" to "DAMON".  But the commit
forgot updating the name on the maintainer-profile document.  Update.

Link: https://lkml.kernel.org/r/20260118180305.70023-8-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