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Wed, 04 Mar 2026 06:24:31 -0800 (PST) From: Jialin Wang To: wjl.linux@gmail.com Cc: axboe@kernel.dk, lenohou@gmail.com, lianux.mm@gmail.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, yukuai@fnnas.com Subject: Re: [PATCH] block: fix race in update_io_ticks causing inflated disk statistics Date: Wed, 4 Mar 2026 14:24:26 +0000 Message-ID: <20260304142426.446360-1-wjl.linux@gmail.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260228100144.254436-1-wjl.linux@gmail.com> References: <20260228100144.254436-1-wjl.linux@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Sat, Feb 28, 2026 at 06:01:44PM +0800, Jialin Wang wrote: > When multiple threads issue I/O requests concurrently after a period of > disk idle time, iostat can report abnormal %util spikes (100%+) even > when the actual I/O load is extremely light. > > This issue can be reproduced using fio. By binding 8 fio threads to > different CPUs, and having them issue 4KB I/Os every 1 second: > > fio --name=test --ioengine=sync --rw=randwrite --direct=1 --bs=4k \ > --numjobs=8 --cpus_allowed=0-7 --cpus_allowed_policy=split \ > --thinktime=1s --time_based --runtime=60 --group_reporting \ > --filename=/mnt/sdb/test > > The iostat -d sda 1 output will show a false 100%+ %util randomly: Sorry, I made a typo. It should be 'iostat -d sdb -x 1'. [...] -- Regards, Jialin