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

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

2026-08-05T02:18:53+00:00

Update DAMON usage document for newly added probe weight file.

Link: https://lore.kernel.org/20260710134651.18084-19-sj@kernel.org
Signed-off-by: SJ Park 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam R. Howlett 
Cc: Lorenzo Stoakes 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

Docs/mm/damon/design: document attrs-only monitoring

2026-08-05T02:18:52+00:00

Update DAMON design document for the attributes only monitoring mode.

Link: https://lore.kernel.org/20260710134651.18084-18-sj@kernel.org
Signed-off-by: SJ Park 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam R. Howlett 
Cc: Lorenzo Stoakes 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

Docs/mm/damon/design: update for DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP

2026-07-31T02:40:25+00:00

Patch series "mm/damon: update, optimize, and clean up doc, tests, and
code".

Patches 1 and 2 update the design and ABI documents for recently added
DAMON features.  Patches 3-7 add or update more unit and self tests for
DAMON to cover recently changed or added functions and sysfs files.  Patch
8 optimizes damon_commit_target_regions() to skip unnecessary adjacent
ranges setup.  Patches 9-11 clean and fix up recently added DAMON sysfs
interface code for readability.


This patch (of 11):

Commit 9138e27a3bc3 ("mm/damon: add node_eligible_mem_bp goal metric")
introduced DAMOS_QUOTA_NODE_ELIGIBLE_MEM_BP but forgot updating the DAMON
design document for that.  Update.

Link: https://lore.kernel.org/20260630141726.92246-1-sj@kernel.org
Link: https://lore.kernel.org/20260630141726.92246-2-sj@kernel.org
Signed-off-by: SJ Park 
Cc: Brendan Higgins 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam R. Howlett 
Cc: Lorenzo Stoakes 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: SeongJae Park 
Cc: Shuah Khan 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

Docs/{admin-guide,mm}/damon: fix DAMON documentation details

2026-07-31T02:40:22+00:00

Fix minor DAMON documentation issues.  Correct the sysfs scheme file name
apply_interval_us, the DAMON_STAT module count, a malformed reference, a
misplaced label indentation, and a few typos.

Link: https://lore.kernel.org/20260629145538.134832-4-sj@kernel.org
Signed-off-by: Doehyun Baek 
Signed-off-by: SJ Park 
Reviewed-by: SJ Park 
Cc: David Hildenbrand 
Cc: Lorenzo Stoakes 
Cc: "Liam R. Howlett" 
Cc: Vlastimil Babka 
Cc: Mike Rapoport 
Cc: Suren Baghdasaryan 
Cc: Michal Hocko 
Cc: Jonathan Corbet 
Cc: Shuah Khan 
Cc: Akinobu Mita 
Cc: Asier Gutierrez 
Cc: Brendan Higgins 
Cc: Philippe Laferriere 
Cc: Sailesh Nandanavanam 
Signed-off-by: Andrew Morton

Docs/mm/damon/design: fix three typos

2026-06-02T22:22:34+00:00

L140: "unsinged" -> "unsigned"
L371: "sampleing" -> "sampling"
L387: "multipled" -> "multiplied"

Link: https://lore.kernel.org/20260520012104.93602-3-sj@kernel.org
Signed-off-by: Sakurai Shun 
Signed-off-by: SeongJae Park 
Reviewed-by: Lorenzo Stoakes 
Acked-by: Mike Rapoport (Microsoft) 
Reviewed-by: SeongJae Park 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam R. Howlett 
Cc: Michal Hocko 
Cc: niecheng 
Cc: Shuah Khan 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Cc: Zenghui Yu 
Signed-off-by: Andrew Morton

Docs/mm/damon/design: update for memcg damon filter

2026-06-02T22:22:31+00:00

Update DAMON design document for the newly added belonging memory cgroup
attribute monitoring feature.

Link: https://lore.kernel.org/20260518234119.97569-28-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam R. Howlett 
Cc: Lorenzo Stoakes 
Cc: "Masami Hiramatsu (Google)" 
Cc: Mathieu Desnoyers 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Shuah Khan 
Cc: Steven Rostedt 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

Docs/admin-guide/mm/damon/usage: document data attributes monitoring

2026-06-02T22:22:29+00:00

Update DAMON usage document for the newly added data attributes monitoring
feature.

Link: https://lore.kernel.org/20260518234119.97569-22-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam R. Howlett 
Cc: Lorenzo Stoakes 
Cc: "Masami Hiramatsu (Google)" 
Cc: Mathieu Desnoyers 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Shuah Khan 
Cc: Steven Rostedt 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

Docs/mm/damon/design: document data attributes monitoring

2026-06-02T22:22:29+00:00

Update DAMON design document for newly added data attributes monitoring
feature.

Link: https://lore.kernel.org/20260518234119.97569-21-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam R. Howlett 
Cc: Lorenzo Stoakes 
Cc: "Masami Hiramatsu (Google)" 
Cc: Mathieu Desnoyers 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Shuah Khan 
Cc: Steven Rostedt 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

Docs/mm/damon/design: update for context pause/resume feature

2026-05-29T04:04:58+00:00

Update DAMON design document for the context execution pause/resume
feature.

Link: https://lore.kernel.org/20260427151231.113429-4-sj@kernel.org
Signed-off-by: SeongJae Park 
Cc: Brendan Higgins 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam R. Howlett 
Cc: Lorenzo Stoakes 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Shuah Khan 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton

mm/damon: support MADV_COLLAPSE via DAMOS_COLLAPSE scheme action

2026-05-29T04:04:56+00:00

This patch set introces a new action:  DAMOS_COLLAPSE.

For DAMOS_HUGEPAGE and DAMOS_NOHUGEPAGE to work, khugepaged should be
working, since it relies on hugepage_madvise to add a new slot.  This slot
should be picked up by khugepaged and eventually collapse (or not, if we
are using DAMOS_NOHUGEPAGE) the pages.  If THP is not enabled, khugepaged
will not be working, and therefore no collapse will happen.

DAMOS_COLLAPSE eventually calls madvise_collapse, which will collapse the
address range synchronously.  In cases where there is a large VMA
(databases, for example), DAMOS_COLLAPSE allows us to collapse only the
hot region, and not the entire VMA.

This new action may be required to support autotuning with hugepage
as a goal[1].

=========
Benchmarks:
=========

MySQL
=====

Tests were performed in an ARM physical server with MariaDB 10.5 and
sysbench. Read only benchmark was perform with gaussian row hitting,
which follows a normal distribution.

T n, D h: THP set to never, DAMON action set to hugepage
T m, D h: THP set to madvise, DAMON action set to hugepage
T n, D c: THP set to never, DAMON action set to collapse

Memory consumption. Lower is better.

+------------------+----------+----------+----------+
|                  | T n, D h | T m, D h | T n, D c |
+------------------+----------+----------+----------+
| Total memory use | 2.13     | 2.20     | 2.20     |
| Huge pages       | 0        | 1.3      | 1.27     |
+------------------+----------+----------+----------+

Performance in TPS (Transactions Per Second). Higher is better.

T n, D h: 18225.58
T m, D h 18252.93
T n, D c: 18270.21

Performance counter

I got the number of L1 D/I TLB accesses and the number a D/I TLB
accesses that triggered a page walk. I divided the second by the
first to get the percentage of page walkes per TLB access. The
lower the better.

+---------------+--------------+--------------+--------------+
|               | T n, D h     | T m, D h     | T n, D c     |
+---------------+--------------+--------------+--------------+
| L1 DTLB       | 127248242753 | 125431020479 | 125327001821 |
| L1 ITLB       | 80332558619  | 79346759071  | 79298139590  |
| DTLB walk     | 75011087     | 52800418     | 55895794     |
| ITLB walk     | 71577076     | 71505137     | 67262140     |
| DTLB % misses | 0.058948623  | 0.042095183  | 0.044599961  |
| ITLB % misses | 0.089100954  | 0.090117275  | 0.084821839  |
+---------------+--------------+--------------+--------------+

Masim
=====

I used masim with the "demo" configuration, but changing the times
to 100 seconds for the initial phase and 50 seconds for the rest of
the phases.

Memory consumption:

+------------------+----------+----------+----------+
|                  | T n, D h | T m, D h | T n, D c |
+------------------+----------+----------+----------+
| Total memory use | 2.38 GB  | 2.36 GB  | 2.37 GB  |
| Huge pages       | 0        | 190 MB   | 188 MB   |
+------------------+----------+----------+----------+

Performance:

THP never, DAMOS_HUGEPAGE
initial phase:                40,491 accesses/msec, 100001 msecs run
low phase 0:                  39,658 accesses/msec, 50002 msecs run
high phase 0:                 41,678 accesses/msec, 50000 msecs run
low phase 1:                  39,625 accesses/msec, 50003 msecs run
high phase 1:                 41,658 accesses/msec, 50002 msecs run
low phase 2:                  39,642 accesses/msec, 50002 msecs run
high phase 2:                 41,640 accesses/msec, 50001 msecs run

THP madvise, DAMOS_HUGEPAGE
initial phase:                51,977 accesses/msec, 100000 msecs run
low phase 0:                  86,953 accesses/msec, 50000 msecs run
high phase 0:                 94,812 accesses/msec, 50000 msecs run
low phase 1:                 101,017 accesses/msec, 50000 msecs run
high phase 1:                 94,841 accesses/msec, 50000 msecs run
low phase 2:                 100,993 accesses/msec, 50000 msecs run
high phase 2:                 94,791 accesses/msec, 50001 msecs run

THP never, DAMOS_COLLAPSE
initial phase:                93,678 accesses/msec, 100001 msecs run
low phase 0:                 101,475 accesses/msec, 50000 msecs run
high phase 0:                 98,589 accesses/msec, 50000 msecs run
low phase 1:                 101,531 accesses/msec, 50001 msecs run
high phase 1:                 98,506 accesses/msec, 50001 msecs run
low phase 2:                 101,458 accesses/msec, 50001 msecs run
high phase 2:                 98,555 accesses/msec, 50000 msecs run

Memory consumption dynamic (how quickly collapses occur):

It shows in seconds how many huge pages are allocated.

+----+----------+----------+
|    | T m, D h | T n, D c |
+----+----------+----------+
| 5  | 32       | 188      |
| 10 | 48       | 188      |
| 15 | 64       | 188      |
| 20 | 96       | 188      |
| 30 | 112      | 188      |
| 35 | 144      | 188      |
| 40 | 160      | 188      |
| 45 | 190      | 188      |
| 50 | 190      | 188      |
| 55 | 190      | 188      |
| 60 | 190      | 188      |
+----+----------+----------+

=========

- We can see that DAMOS "hugepage" action works only when THP is set
  to madvise. "collapse" action works even when THP is set to never.
- Performance for "collapse" action is slightly lower than "hugepage"
  action and THP madvise. This is due to the fact that collapases
  occur synchronously. With "hugepage" they may occur during page
  faults.
- Memory consumption is slighly lower for "collapse" than "hugepage"
  with THP madvise. This is due to the khugepage collapses all VMAs,
  while "collapse" action only collapses the VMAs in the hot region.
- There is an improvement in TLB utilization when collapse through
  "hugepage" or "collapse" actions are triggered. The amount of
  TLB misses is lower.
- "collapse" action is performance synchronously, which means that
  page collapses happen earlier and more rapidly. This can be
  useful or not, depending on the scenario.
- "hugepage" action may trigger a VMA split in some scenarios, since
  it needs to change the flag of the VMA to THP enabled. This may
  lead to additional overhead.

Collapse action just adds a new option to chose the correct system
balance.

Link: https://lore.kernel.org/20260426231619.107231-5-sj@kernel.org
Link: https://lore.kernel.org/damon/20260313000816.79933-1-sj@kernel.org/ [1]
Signed-off-by: Asier Gutierrez 
Signed-off-by: SeongJae Park 
Reviewed-by: SeongJae Park 
Cc: Cheng-Han Wu 
Cc: David Hildenbrand 
Cc: Jonathan Corbet 
Cc: Liam R. Howlett 
Cc: Liew Rui Yan 
Cc: Lorenzo Stoakes 
Cc: Michal Hocko 
Cc: Mike Rapoport 
Cc: Shuah Khan 
Cc: Suren Baghdasaryan 
Cc: Vlastimil Babka 
Signed-off-by: Andrew Morton