From: David Carlier <devnexen@gmail.com>
To: SJ Park <sj@kernel.org>
Cc: Aveline Noir <jm5905938@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
damon@lists.linux.dev, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/9] mm/damon/stat: avoid 32-bit overflow in idle percentiles
Date: Sat, 14 Nov 2026 18:10:34 +0000 [thread overview]
Message-ID: <20261114181034.2665113-1-devnexen@gmail.com> (raw)
In-Reply-To: <20261102150757.93058-5-sj@kernel.org>
Hi SJ, Aveline,
The value stored a few lines below has the same problem on 32-bit:
damon_stat_idletime(region) *
(long)c->attrs.aggr_interval / USEC_PER_MSEC;
The product is the region's idle time in microseconds, held in a 32-bit
long, so it wraps once a region has been idle for more than about 36
minutes, whatever the intervals are. The cold-end percentiles then come
out negative or wrong. Doing the multiply in s64 with div_s64() would
keep the sign and avoid it.
Hope it helps !
next prev parent reply other threads:[~2026-11-14 18:10 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-02 15:07 [PATCH 0/9] mm/damon: various fixes and cleanup of code, test, and docs SJ Park
2026-11-02 15:07 ` [PATCH 1/9] mm/damon/core: remove unnecessary zero-initialization in damon_new_ctx() SJ Park
2026-11-02 15:10 ` sashiko-bot
2026-11-02 15:07 ` [PATCH 2/9] mm/damon/ops-common: align MMU notifier range when clearing PTE young bit SJ Park
2026-11-02 15:22 ` sashiko-bot
2026-11-02 15:07 ` [PATCH 3/9] mm/damon/ops-common: align MMU notifier range when clearing PMD " SJ Park
2026-11-02 15:29 ` sashiko-bot
2026-11-02 15:07 ` [PATCH 4/9] mm/damon/stat: avoid 32-bit overflow in idle percentiles SJ Park
2026-11-02 15:31 ` sashiko-bot
2026-11-14 18:10 ` David Carlier [this message]
2026-11-02 15:07 ` [PATCH 5/9] mm/damon/{p,v}addr: skip folios already on the migration target node SJ Park
2026-11-02 15:33 ` sashiko-bot
2026-11-03 14:09 ` SJ Park
2026-11-02 15:07 ` [PATCH 6/9] selftests/damon/sysfs.py: stop obsolete_target shells hanging the test SJ Park
2026-11-02 15:34 ` sashiko-bot
2026-11-02 15:07 ` [PATCH 7/9] mm/damon/reclaim: fix typo and grammar SJ Park
2026-11-02 15:35 ` sashiko-bot
2026-11-02 15:07 ` [PATCH 8/9] Docs/admin-guide/mm/damon/lru_sort: fix grammar and stlye SJ Park
2026-11-02 15:36 ` sashiko-bot
2026-11-03 2:37 ` Daniel Pereira
2026-11-02 15:07 ` [PATCH 9/9] Docs/admin-guide/mm/damon/reclaim: document how to disable watermarks SJ Park
2026-11-02 15:37 ` sashiko-bot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20261114181034.2665113-1-devnexen@gmail.com \
--to=devnexen@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=damon@lists.linux.dev \
--cc=jm5905938@gmail.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=sj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.