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mm/damon/core: handle zero schemes apply interval

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BugLink: https://bugs.launchpad.net/bugs/2100292

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: 42f994b714 ("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>
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
This commit is contained in:
SeongJae Park
2025-02-26 22:49:14 +09:00
committed by Stefan Bader
parent 7bff7ce482
commit 7d26e8d971
1 changed files with 4 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files
mm/damon/core.c
+4 -4
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@@ -1026,7 +1026,7 @@ static void damon_do_apply_schemes(struct damon_ctx *c,
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)
@@ -1190,7 +1190,7 @@ static void kdamond_apply_schemes(struct damon_ctx *c)
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)
@@ -1210,9 +1210,9 @@ static void kdamond_apply_schemes(struct damon_ctx *c)
}
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;
}