From: Ming Lei <ming.lei@redhat.com>
To: Dexuan Cui <decui@microsoft.com>
Cc: Jens Axboe <axboe@kernel.dk>, 'Christoph Hellwig' <hch@lst.de>,
"'linux-block@vger.kernel.org'" <linux-block@vger.kernel.org>,
Long Li <longli@microsoft.com>,
"Michael Kelley (LINUX)" <mikelley@microsoft.com>,
"'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>
Subject: Re: Random high CPU utilization in blk-mq with the none scheduler
Date: Mon, 13 Dec 2021 11:23:08 +0800 [thread overview]
Message-ID: <Yba8nL4x9R6rmTYL@T590> (raw)
In-Reply-To: <BYAPR21MB1270B5DAD526C42C070ECB9EBF729@BYAPR21MB1270.namprd21.prod.outlook.com>
Hi Dexuan,
On Sat, Dec 11, 2021 at 03:10:43AM +0000, Dexuan Cui wrote:
> > From: Jens Axboe <axboe@kernel.dk>
> > Sent: Friday, December 10, 2021 6:05 PM
> > ...
> > It's more likely the real fix is avoiding the repeated plug list scan,
> > which I guess makes sense. That is this commit:
> >
> > commit d38a9c04c0d5637a828269dccb9703d42d40d42b
> > Author: Jens Axboe <axboe@kernel.dk>
> > Date: Thu Oct 14 07:24:07 2021 -0600
> >
> > block: only check previous entry for plug merge attempt
> >
> > If that's the case, try 5.15.x again and do:
> >
> > echo 2 > /sys/block/<dev>/queue/nomerges
> >
> > for each drive you are using in the IO test, and see if that gets
> > rid of the excess CPU usage.
> >
> > --
> > Jens Axboe
>
> Thanks for the reply! Unluckily this does not work.
>
> I tried the below command:
>
> for i in `ls /sys/block/*/queue/nomerges`; do echo 2 > $i; done
>
> and verified that the "nomerges" are changed to "2", but the
> excess CPU usage can still reproduce easily.
Can you provide the following blk-mq debugfs log?
(cd /sys/kernel/debug/block/dm-N && find . -type f -exec grep -aH . {} \;)
(cd /sys/kernel/debug/block/sdN && find . -type f -exec grep -aH . {} \;)
And it is enough to just collect log from one dm-mpath & one underlying iscsi disk,
so we can understand basic blk-mq setting, such as nr_hw_queues, queue depths, ...
Thanks,
Ming
next prev parent reply other threads:[~2021-12-13 3:23 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-10 3:30 Random high CPU utilization in blk-mq with the none scheduler Dexuan Cui
2021-12-11 1:29 ` Dexuan Cui
2021-12-11 2:04 ` Jens Axboe
2021-12-11 3:10 ` Dexuan Cui
2021-12-11 3:15 ` Jens Axboe
2021-12-11 3:44 ` Dexuan Cui
2021-12-11 7:09 ` Dexuan Cui
2021-12-11 14:21 ` Jens Axboe
2021-12-11 18:54 ` Dexuan Cui
2021-12-13 18:43 ` Jens Axboe
2021-12-14 0:43 ` Dexuan Cui
2021-12-13 3:23 ` Ming Lei [this message]
2021-12-13 4:20 ` Dexuan Cui
2021-12-13 7:38 ` Ming Lei
2021-12-14 0:31 ` Dexuan Cui
2021-12-14 0:53 ` Ming Lei
2021-12-14 3:09 ` Dexuan Cui
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