6.6-stable review patch. If anyone has any objections, please let me know.
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From: SeongJae Park sj@kernel.org
commit 8e7bde615f634a82a44b1f3d293c049fd3ef9ca9 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/damon/core.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
--- a/mm/damon/core.c +++ b/mm/damon/core.c @@ -989,7 +989,7 @@ 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) @@ -1089,7 +1089,7 @@ 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) @@ -1109,9 +1109,9 @@ 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; }