From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793716458; b=wzNndmRw6zhvChu909Zl993LuFgusCN9z8j+gA3pBeC/Qm9Ze8VqCbl81hU5kjMKv14N BxwFie37qTad0kzdDWNbJl4OqlUfMrB+DXrTIQfUBNmh7KSKOnejixH4d4B3XIfwZ4Jm/ hlNoFuZrLouZa9eR33MZMfT6dxY9PQE3Id4x3JNbmWjN/P3MAOfaz4msY73TtiTev/c7T D5WV3ciVt0X3zKXBwzRF4PSNWuedbdOXPejYPXTgwmma+7PhU1rf2L9DyPI1/PHzGRhmI kJ9kFDHzfa0F2P7imKlfCnS3PaYrhY4VBbdBZUwKvNRZmYzT0FmQElaf4R2rOGxFtpQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793716458; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:MIME-Version:Content-Transfer-Encoding; bh=0ajyy7n+0qSH1YTBPHJg2ZBD7XeUrxHy6Kcj1EJImYg=; b=d4qipvW2A4OYPJiwkHIbLdVR93dTIQWGh2tPxIBWRgTGg4VIooNs3B6wTRNdoFTE/D+/ Aa0MJEGEAWNvN3OGOshlsKlnsT8YjbQfKs9bqIKkxGFsSu/+Kt9EnX8D36P6h2a1rBviK 0vLB/qfOXWFHb9zFgLxXEL+xzKzokRjdpyh5wW0+1OVaIZrNAizkibanymrkJt969DdcT Z4m9YtnoBoFeKN8erZkdYKlCMcPynxgkTvyRy0LTa5crDTeSIFcdEY7faJLrogE9cdom5 8eyGrRrNCRChTpf6el95pyZwgK5gXMAJGS1IaG1OWGjNPGcHp8HvD+uimuynbX/FBvw== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=TPTCykYL; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F20F0606D83E; Tue, 3 Nov 2026 14:34:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=TPTCykYL Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5DC6E1F0093A; Tue, 3 Nov 2026 14:34:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793716457; bh=0ajyy7n+0qSH1YTBPHJg2ZBD7XeUrxHy6Kcj1EJImYg=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=TPTCykYLb7YyiJfftqIjfbRil9UPgYWqaphUQv4SNzGMIybk7zut1L7O8CycL0PEv Smo0NgFZGhnE+mBm7d9Btecxf57Ahxs29iz8mkXeRHCPAETLHr85sZIyWoN6caU4eI Ol7GIqDjsQJNf1roys0/r/YwrfJP37d3aGtuBGDBHiKYgYoKHl7VVo5s8XPI5BOU3q Jlv+0oj6r42VtAZvavVTNp0T2saIeiOJ1iLja14RovmpDMdwqr8eAnzS0XW8QkM8Lw 887397wb8fvNkInSWSXM7qeWGxayhLmWhlLO+BDB2X2DhcHaVwnIi73BFArxarkNqm vJrNG4eH9MRIg== From: SJ Park To: Wang Guangke Cc: SJ Park , akpm@linux-foundation.org, damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH v2] mm/damon/stat: avoid overflow in estimated_memory_bandwidth calculation Date: Tue, 3 Nov 2026 06:34:09 -0800 Message-ID: <20261103143410.87235-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261103034034.7978-1-gkwang@linx-info.com> References: X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Wang, On Tue, 3 Nov 2026 11:40:34 +0800 Wang Guangke wrote: > estimated_memory_bandwidth is calculated by access_bytes * > USEC_PER_MSEC * MSEC_PER_SEC (= USEC_PER_SEC) / aggr_interval, > and users read it via > /sys/module/damon_stat/parameters/estimated_memory_bandwidth. > > On 32-bit systems, access_bytes * USEC_PER_SEC overflows unsigned > long once access_bytes exceeds about 4294 (U32_MAX / USEC_PER_SEC), > so users get a wrong value. > > Fix it by doing the calculation in 64-bit and splitting the division > into quotient and remainder. > > The issue was reproduced on a 32-bit system (qemu-system-i386): the > parameter estimated_memory_bandwidth reported 362 instead of the > expected 1926150; with the fix, the value matches the expectation. Looks good to me. > > Fixes: fabdd1e911da ("mm/damon/stat: calculate and expose estimated memory bandwidth") > Cc: > Signed-off-by: Wang Guangke Reviewed-by: SJ Park This patch is applied to damon/next [1] tree. I will repost it soon (~1 week) as an mm.git merge request. So, no action from your side is needed for now. [1] https://origin.kernel.org/doc/html/latest/mm/damon/maintainer-profile.html#scm-trees Thanks, SJ [...]