From: Song Liu <song@kernel.org>
To: Christoph Hellwig <hch@infradead.org>
Cc: linux-block@vger.kernel.org,
linux-raid <linux-raid@vger.kernel.org>,
Jens Axboe <axboe@kernel.dk>,
stable@vger.kernel.org, Larkin Lowrey <llowrey@nuclearwinter.com>,
Wilson Jonathan <i400sjon@gmail.com>,
Roger Heflin <rogerheflin@gmail.com>
Subject: Re: [PATCH] block: check more requests for multiple_queues in blk_attempt_plug_merge
Date: Wed, 9 Mar 2022 23:23:54 -0800 [thread overview]
Message-ID: <CAPhsuW4DJbvH5QZ5YMC4Ms4bd66UOFsLL=-yK8tQKrwreCfKDQ@mail.gmail.com> (raw)
In-Reply-To: <YimfLJoWLKnnhLfR@infradead.org>
On Wed, Mar 9, 2022 at 10:48 PM Christoph Hellwig <hch@infradead.org> wrote:
>
> On Tue, Mar 08, 2022 at 10:42:09PM -0800, Song Liu wrote:
> > RAID arrays check/repair operations benefit a lot from merging requests.
> > If we only check the previous entry for merge attempt, many merge will be
> > missed. As a result, significant regression is observed for RAID check
> > and repair.
> >
> > Fix this by checking more than just the previous entry when
> > plug->multiple_queues == true.
>
> But this also means really significant CPU overhead for all other
> workloads.
Would the following check help with these workloads?
if (!plug->multiple_queues)
break;
>
> >
> > This improves the check/repair speed of a 20-HDD raid6 from 19 MB/s to
> > 103 MB/s.
>
> What driver uses multiple queues for HDDs?
>
> Can you explain the workload submitted by a md a bit better? I wonder
> if we can easily do the right thing straight in the md driver.
It is the md sync_thread doing check and repair. Basically, the md
thread reads all
the disks and computes parity from data.
Maybe we should add a new flag to struct blk_plug for this special case?
Song
next prev parent reply other threads:[~2022-03-10 7:24 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-09 6:42 [PATCH] block: check more requests for multiple_queues in blk_attempt_plug_merge Song Liu
2022-03-10 6:48 ` Christoph Hellwig
2022-03-10 7:23 ` Song Liu [this message]
2022-03-10 22:10 ` Song Liu
2022-03-10 22:12 ` Song Liu
2022-03-10 22:15 ` Jens Axboe
2022-03-10 22:37 ` Song Liu
2022-03-10 23:02 ` Jens Axboe
2022-03-10 23:33 ` Song Liu
2022-03-11 0:07 ` Jens Axboe
2022-03-11 0:31 ` Song Liu
2022-03-11 0:36 ` Jens Axboe
2022-03-11 0:38 ` Jens Axboe
2022-03-11 1:14 ` Ming Lei
2022-03-11 1:21 ` Jens Axboe
2022-03-11 1:32 ` Ming Lei
2022-03-11 1:35 ` Jens Axboe
2022-03-11 8:09 ` Wols Lists
2022-03-11 14:16 ` Jens Axboe
2022-03-11 16:59 ` Song Liu
2022-03-11 21:41 ` Paul Menzel
2022-03-11 22:40 ` Song Liu
2022-03-11 11:30 ` Wilson Jonathan
2022-03-11 15:58 ` Wols Lists
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