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b=A1EuXLLmgt9jXZn2tSu3WzLjEbZru4Lcta2QCZYFNqTUj0Zah/bIhU5rNG6q5iby2 S5JWxRB6HxLhaBMdF/px4nMxQXtcwZmvommDDJGFYcbroMNZgakb7tWLKL5t6Bcnuq LnezLGbUFkNd2L2hqZ54EjeGEqQ/g057yYHc3kdPemIyCqAmfU/gBnyBmOdYwpnkP7 q8J4CJtNZdQMoYaArjtUHNmyOSWwRUIgxFVrHfK6WPGNlk00If5pDJS3nqpnv4yv2P DYKvJ1jQ9DHtk3hArDac4OYuyiQmoddZSjfBoAS0WPNT+aiV8DfAuGpBPBCNVTFrdQ Hy6XkPeBAQLpQ== From: SJ Park To: David Carlier Cc: SJ Park , Aveline Noir , Andrew Morton , 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: Sun, 15 Nov 2026 09:33:42 -0800 Message-ID: <20261115173343.82437-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261114181034.2665113-1-devnexen@gmail.com> References: X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: nhahd6rbc779xjtefq8g7nupqwfctyw4 X-Rspam-User: X-Spam-Status: No, score=-8.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 1B32D80002 X-HE-Tag: 1794764030-895639 X-HE-Meta: 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 Pjd8kCE9 gvWqD3fmB4ySbGzedvCkRrewk+xOC+y58Og54I/MgnsM0FBKqCC98sOh+eHVaRfiVN7gfKQ+Gni4cmx3+10G4bH/ZFq05knR9OEc0eez/mLxJeIETdT8YWK8xGEmLZRFvHQLKA2bmaiquStyYE2LL5co9snJN7SqAqVtWko5+VNWaI5eedAoT+lyaZKoUTiLv78aM9sgwjEafw0ljwQ0yrT2ZcC2/rpTLZji98EaupaX+TnFj+nh6E5M06KTMyfec19a5 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Hello David, On Sat, 14 Nov 2026 18:10:34 +0000 David Carlier wrote: > 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 ! Yes, this is helpful. Thank you for sharing. Would you like to send a patch for this issue? Thanks, SJ [...]