The patch titled
Subject: mm/damon/core: ensure max threshold attempt for max_nr_regions violation
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-damon-core-merge-regions-aggressively-when-max_nr_regions-is-unmet-fix-2.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-damon-core-merge-regions-aggressively-when-max_nr_regions-is-unmet-fix-2.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: SeongJae Park <sj@xxxxxxxxxx>
Subject: mm/damon/core: ensure max threshold attempt for max_nr_regions violation
Date: Thu, 27 Jun 2024 09:31:52 -0700
Since commit ed6cb9d022c8 ("mm/damon/core: increase regions merge
aggressiveness while respecting min_nr_regions") of mm-unstable,
kdamond_merge_regions() stops the repeated merge attempts for meeting
max_nr_regions if the merge threshold that increased for next iteration is
higher than the possible maximum threshold. Hence, it can skip a merge
attempt with the maximum threshold depending on the amount of the
threshold increase, the maximum threshold, and the last-used threshold
value. In extreme situations (e.g., region 1 has 100% access frequency,
region 2 has 0% access frequency, so on), this can degrade the
max_nr_regions violation recovery.
Fix this by stopping the loop by comparing the last-used threshold instead
of the to-be-used threshold, and if the last-used threshold is same to or
higher than the maximum possible threshold.
Link: https://lkml.kernel.org/r/20240627163153.75969-1-sj@xxxxxxxxxx
Fixes: ed6cb9d022c8 ("mm/damon/core: increase regions merge aggressiveness while respecting min_nr_regions") # mm-unstable
Signed-off-by: SeongJae Park <sj@xxxxxxxxxx>
Closes: https://lore.kernel.org/20240626214954.46143-1-sj@xxxxxxxxxx
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/damon/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/damon/core.c~mm-damon-core-merge-regions-aggressively-when-max_nr_regions-is-unmet-fix-2
+++ a/mm/damon/core.c
@@ -1382,7 +1382,7 @@ static void kdamond_merge_regions(struct
}
threshold = max(1, threshold * 2);
} while (nr_regions > c->attrs.max_nr_regions &&
- threshold <= max_thres);
+ threshold / 2 < max_thres);
}
/*
_
Patches currently in -mm which might be from sj@xxxxxxxxxx are
mm-damon-core-merge-regions-aggressively-when-max_nr_regions-is-unmet.patch
mm-damon-core-merge-regions-aggressively-when-max_nr_regions-is-unmet-fix.patch
mm-damon-core-merge-regions-aggressively-when-max_nr_regions-is-unmet-fix-2.patch
docs-mm-damon-maintainer-profile-introduce-hackermail.patch
docs-mm-damon-maintainer-profile-document-damon-community-meetups.patch
selftests-damon-access_memory-use-user-defined-region-size.patch
selftests-damon-_damon_sysfs-support-schemes_update_tried_regions.patch
selftests-damon-implement-a-program-for-even-numbered-memory-regions-access.patch
selftests-damon-implement-damos-tried-regions-test.patch
selftests-damon-_damon_sysfs-implement-kdamonds-stop-function.patch
selftests-damon-implement-test-for-min-max_nr_regions.patch
_damon_sysfs-implement-commit-for-online-parameters-update.patch
selftests-damon-damon_nr_regions-test-online-tuned-max_nr_regions.patch
