From: SJ Park <sj@kernel.org>
To: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Cc: SJ Park <sj@kernel.org>,
akpm@linux-foundation.org, damon@lists.linux.dev,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 1/2] mm/damon/core: charge only the part of a region the filter left
Date: Wed, 16 Sep 2026 18:24:19 -0700 [thread overview]
Message-ID: <20260917012420.101087-1-sj@kernel.org> (raw)
In-Reply-To: <20260917003553.2465523-2-donggeunyoo.kernel@gmail.com>
On Thu, 17 Sep 2026 09:35:52 +0900 Donggeun Yoo <donggeunyoo.kernel@gmail.com> wrote:
> An address range DAMOS filter that partially overlaps a monitoring
> region splits the region at the filter boundary, so the scheme action is
> applied to only one side of it. damos_apply_scheme() reads the region
> size once on entry, before damos_core_filter_out() performs that split.
>
> The quota charge and the statistics update therefore account for the
> region as it was before the trim. schemes/<S>/stats/sz_tried counts
> memory the filter excluded, which Documentation/mm/damon/design.rst says
> is not counted as tried, and with quotas/bytes set the excluded part is
> charged against the budget, throttling the scheme to a fraction of what
> was configured.
The user impact is that DAMOS could work unexpectedly slow, due to over-charged
quota. Also DAMOS stat could be confusing. No critical events such as crashes
or leask happen.
If above is not incorrect, I will add that to the commit message when I add
this patch to damon/next tree. Let me know if anything is incorrect.
>
> Re-read the region size after the core filters have run.
Thank you for finding and fixing this bug!
>
> Fixes: ab9bda001b68 ("mm/damon/core: introduce address range type damos filter")
> Cc: <stable@vger.kernel.org> # 6.6.x
> Signed-off-by: Donggeun Yoo <donggeunyoo.kernel@gmail.com>
Reviewed-by: SJ Park <sj@kernel.org>
Thanks,
SJ
[...]
next prev parent reply other threads:[~2026-09-17 1:24 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-17 0:35 [PATCH v1 0/2] mm/damon/core: fix the size charged for a filter-trimmed region Donggeun Yoo
2026-09-17 0:35 ` [PATCH v1 1/2] mm/damon/core: charge only the part of a region the filter left Donggeun Yoo
2026-09-17 0:43 ` sashiko-bot
2026-09-17 1:24 ` SJ Park [this message]
2026-09-17 1:38 ` Donggeun Yoo
2026-09-17 0:35 ` [PATCH v1 2/2] mm/damon/tests/core-kunit: test the size charged for a filter-trimmed region Donggeun Yoo
2026-09-17 0:42 ` sashiko-bot
2026-09-17 1:26 ` SJ Park
2026-09-17 1:28 ` [PATCH v1 0/2] mm/damon/core: fix " SJ Park
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