[PATCH v5 0/2] mm/damon/core: iterate over installed probes instead of DAMON_MAX_PROBES

[SJ Park <sj@kernel.org>]

From: Suhaas Joshi <suhaas@s-joshi.in>

There were two "todo: " items of the same nature in mm/damon/core.c.
Both of these suggested that we should iterate over only installed
probes while updating (last_)probe_hits[] during merging/splitting
regions, instead of iterating over the entire array, which may have
empty/unused indices.

So this patch series does exactly that. It replaces the for-loop over
[0, DAMON_MAX_PROBES) with a damon_for_each_probe() over the probe list
of the context.

Reviewer note.

These patches are based off mm-new. They pass all KUnit tests related to
damon. I have boot tested (but nothing beyond) on qemu-x86_64. Please do
let me know if I should do any specific tests and link the logs here.

The series has been tested with mm-new fetched on Oct 14, 2026.

Changes from v4
- v4: https://lore.kernel.org/20261015135533.18761-1-suhaas@s-joshi.in
- Collect R-b: from SJ.
- Remove/separate messages in cover letter that not suitable for commit
  message.
- Wrap cover letter for 75 columns length.
- Rebase to latest mm-new.

Changes v3 -> v4:
1. In some places, kunit_skip() was being called before freeing
   resources.  This is correctly ordered now.
2. In some places, regions were not being freed. In v4, they are being
   freed.
Link to v3: https://lore.kernel.org/damon/20261012145636.168436-1-suhaas@s-joshi.in/T/#t

Changes v2 -> v3:
1. In test functions, new probe and context allocations happen after
   target, region etc have been allocated. Further, target is added to
   the context.  These 2 changes help in reducing allocation code and
   improving simplicity and readability of the patches. This change is
   true for both patches.  (on SJ suggestion)
2. Earlier, if a function's argument list required multiple lines, I was
   aligning these lines to the opening paranthesis of the function. In
   v3, these begin after 2 tab spaces. (On SJ suggestion)
3. damon_test_last_region_quota_reset() uses the older version of
   damos_skip_charged_region().  Make it use the new version.
Link to v2: https://lore.kernel.org/damon/20261008151944.113714-1-suhaas@s-joshi.in/

Changes v1 -> v2:
1. simplified commit message of patch 1 (on Liew's suggestion)
2. wrapped all lines at 80 characters (on SJ's suggestion)
3. added comments for new argument in function (on SJ's suggestion)
4. added damon_ctx_destroy() in r2 failure case in
   damon_test_merge_two() (on SJ/Sashiko/Liew suggestion)
Link to v1: https://lore.kernel.org/damon/20261007154851.45368-1-suhaas@s-joshi.in/

SJ Park (1):
  mm/damon/core: copy only installed probe in damon_split_region_at()

Suhaas Joshi (1):
  mm/damon/core: use only installed probe in damon_merge_two_regions()

 mm/damon/core.c             | 57 +++++++++++++++----------
 mm/damon/tests/core-kunit.h | 84 +++++++++++++++++++++++++++++++------
 2 files changed, 106 insertions(+), 35 deletions(-)


base-commit: 79e2e91bd5a4b213cf40819c2711a9364b2c0f86
-- 
2.47.3