Re: [PATCH 6.18.y] mm/damon/ops-common: use nr_accesses moving sum for quota score

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The commit message claims to fix the issue by using a new helper function `damon_nr_accesses_mvsum()`, but this function is never defined or called.
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commit 3c964119e352fe243aaf217b238b33be4fa99148
Author: SJ Park <sj@kernel.org>

mm/damon/ops-common: use nr_accesses moving sum for quota score

Since commit 42f994b71404 ("mm/damon/core: implement scheme-specific apply
interval"), DAMOS scheme can be applied at any time.  At that time,
nr_accesses may not be fully aggregated.  But the quota prioritization
score is calculated using the not fully aggregated count.  As a result,
the performance of DAMOS could be degraded.  Fix by using
damon_nr_accesses_mvsum() instead.

Link: https://lore.kernel.org/20260719161136.90191-1-sj@kernel.org

> diff --git a/mm/damon/ops-common.c b/mm/damon/ops-common.c
> index ceaa2a6e1c9a3..929aab600c745 100644
> --- a/mm/damon/ops-common.c
> +++ b/mm/damon/ops-common.c
> @@ -101,8 +101,9 @@ int damon_hot_score(struct damon_ctx *c, struct damon_region *r,
>  	unsigned int age_weight = s->quota.weight_age;
>  	int hotness;
>  
> -	freq_subscore = r->nr_accesses * DAMON_MAX_SUBSCORE /
> -		damon_max_nr_accesses(&c->attrs);
> +	freq_subscore = mult_frac(r->nr_accesses_bp / 10000,
> +			DAMON_MAX_SUBSCORE,
> +			damon_max_nr_accesses(&c->attrs));

[Severity: Medium]
The commit message claims to fix the issue by using a new helper function
damon_nr_accesses_mvsum(), but this function is never defined or called.

Instead, the implementation in damon_hot_score() manually inlines the moving
sum calculation (r->nr_accesses_bp / 10000).

Is there a missing patch that adds damon_nr_accesses_mvsum(), or should the
commit message be updated to match the inline calculation?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260909050521.225965-1-sj@kernel.org?part=1