Commit 8e7bde61 authored by SeongJae Park's avatar SeongJae Park Committed by Andrew Morton
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mm/damon/core: handle zero schemes apply interval 

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: 42f994b7 ("mm/damon/core: implement scheme-specific apply interval")
Signed-off-by: default avatarSeongJae Park <sj@kernel.org>
Cc: <stable@vger.kernel.org>	[6.7.x]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 3488af09

mm/damon/core.c

+4 −4
Original line number Diff line number Diff line
@@ -1412,7 +1412,7 @@ 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)
@@ -1622,7 +1622,7 @@ 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)
@@ -1642,9 +1642,9 @@ 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;

	}