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bh=lluNge2cWGquXLKIKjAjPmT4YYpm8dK1DV0H182H8zE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=nlj+MY03Ri0+qCpt6vlRjDsttq+/Tpvtz0u7ivy1P1So/s98IONLh5iE18yM/xUnn zVGoSQ1Th6Apgif30FDi42/4ue2M/7HZwJBB7yGFnlBLi4ct6gxRyhCnJB7Q2dvnnR lscIiFco7yEwKKRbM636Zs4vXI+y9EyDnFwO3WVKrMsrO0VB2pdpVh8TPO5OyUa9rI UuyMk1jiP1syw0EIma0xOUy7atHBezZ1lH2R3/5CBZ6pfvWm79OMYFeFFAvT2qhb0p OrWrLsUxZ5ovod1iYxqeY8VdQZoe43RNSWO3lucjmmzvWaxq8H8hhlnwRl7LYhX2td eno4p/QFg7o+Q== From: SeongJae Park To: Quanmin Yan Cc: SeongJae Park , akpm@linux-foundation.org, damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org, wangkefeng.wang@huawei.com, zuoze1@huawei.com, apanyaki@amazon.com Subject: Re: [PATCH] mm/damon/core: prevent unnecessary overflow in damos_set_effective_quota() Date: Thu, 21 Aug 2025 09:59:11 -0700 Message-Id: <20250821165911.79204-1-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250821125555.3020951-1-yanquanmin1@huawei.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 320D7160013 X-Stat-Signature: 189jfspy7gpz3k7w41bg9rd6tyggcfqk X-Rspam-User: X-HE-Tag: 1755795554-932164 X-HE-Meta: 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 IjSOagNx ZXl2b X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, 21 Aug 2025 20:55:55 +0800 Quanmin Yan wrote: > On 32-bit systems, the throughput calculation in function > damos_set_effective_quota() is prone to unnecessary multiplication > overflow. Using mult_frac() to fix it. > > Andrew Paniakin also recently found and privately reported this > issue, on 64 bit systems. This can also happen on 64-bit systems, > once the charged size exceeds ~17 TiB. On systems running for long > time in production, this issue can actually happen. > > More specifically, when a DAMOS scheme having the time quota run > for longtime, throughput calculation can overflow and set esz too > small. As a result, speed of the scheme get unexpectedly slow. > > Fixes: 1cd243030059 ("mm/damon/schemes: implement time quota") > Cc: # 5.16.x > Signed-off-by: Quanmin Yan > Reported-by: Andrew Paniakin > Closes: N/A # privately reported Reviewed-by: SeongJae Park Thanks, SJ [...]