The patch titled Subject: mm/damon/core: handle zero schemes apply interval has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-damon-core-handle-zero-schemes-apply-interval.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

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@kernel.org Subject: mm/damon/core: handle zero schemes apply interval Date: Thu, 31 Oct 2024 11:37:57 -0700

DAMON's logics to determine if this is the time to apply damos schemes assumes next_apply_sis is always set larger than current passed_sample_intervals. And therefore assume continuously incrementing passed_sample_intervals will make it reaches to the next_apply_sis in future. The logic hence does apply the scheme and update next_apply_sis only if passed_sample_intervals is same to next_apply_sis.

If Schemes apply interval is set as zero, however, next_apply_sis is set same to current passed_sample_intervals, respectively. And passed_sample_intervals is incremented before doing the next_apply_sis check. Hence, next_apply_sis becomes larger than next_apply_sis, and the logic says it is not the time to apply schemes and update next_apply_sis. In other words, DAMON stops applying schemes until passed_sample_intervals overflows.

Based on the documents and the common sense, a reasonable behavior for such inputs would be applying the schemes for every sampling interval. Handle the case by removing the assumption.

Link: https://lkml.kernel.org/r/20241031183757.49610-3-sj@kernel.org Fixes: 42f994b71404 ("mm/damon/core: implement scheme-specific apply interval") Signed-off-by: SeongJae Park sj@kernel.org Cc: stable@vger.kernel.org [6.7.x] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/damon/core.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)

--- a/mm/damon/core.c~mm-damon-core-handle-zero-schemes-apply-interval +++ a/mm/damon/core.c @@ -1412,7 +1412,7 @@ static void damon_do_apply_schemes(struc damon_for_each_scheme(s, c) { struct damos_quota *quota = &s->quota;

- if (c->passed_sample_intervals != s->next_apply_sis) + if (c->passed_sample_intervals < s->next_apply_sis) continue;

if (!s->wmarks.activated) @@ -1622,7 +1622,7 @@ static void kdamond_apply_schemes(struct bool has_schemes_to_apply = false;

damon_for_each_scheme(s, c) { - if (c->passed_sample_intervals != s->next_apply_sis) + if (c->passed_sample_intervals < s->next_apply_sis) continue;

if (!s->wmarks.activated) @@ -1642,9 +1642,9 @@ static void kdamond_apply_schemes(struct }

damon_for_each_scheme(s, c) { - if (c->passed_sample_intervals != s->next_apply_sis) + if (c->passed_sample_intervals < s->next_apply_sis) continue; - s->next_apply_sis += + s->next_apply_sis = c->passed_sample_intervals + (s->apply_interval_us ? s->apply_interval_us : c->attrs.aggr_interval) / sample_interval; } _

Patches currently in -mm which might be from sj@kernel.org are

mm-damon-core-handle-zero-aggregationops_update-intervals.patch mm-damon-core-handle-zero-schemes-apply-interval.patch selftests-damon-huge_count_read_write-remove-unnecessary-debugging-message.patch selftests-damon-_debugfs_common-hide-expected-error-message-from-test_write_result.patch selftests-damon-debugfs_duplicate_context_creation-hide-errors-from-expected-file-write-failures.patch mm-damon-kconfig-update-dbgfs_kunit-prompt-copy-for-sysfs_kunit.patch mm-damon-tests-dbgfs-kunit-fix-the-header-double-inclusion-guarding-ifdef-comment.patch