From: Jens Axboe <axboe@kernel.dk>
To: Ming Lei <ming.lei@redhat.com>,
linux-block@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>
Cc: Bart Van Assche <bart.vanassche@sandisk.com>,
Laurence Oberman <loberman@redhat.com>,
Paolo Valente <paolo.valente@linaro.org>,
Oleksandr Natalenko <oleksandr@natalenko.name>,
Tom Nguyen <tom81094@gmail.com>,
linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org,
Omar Sandoval <osandov@fb.com>,
John Garry <john.garry@huawei.com>
Subject: Re: [PATCH V9 0/7] blk-mq-sched: improve sequential I/O performance
Date: Fri, 13 Oct 2017 13:08:46 -0600 [thread overview]
Message-ID: <03fc0b94-8463-3f3d-9d75-be3e05d88987@kernel.dk> (raw)
In-Reply-To: <20171013180532.29304-1-ming.lei@redhat.com>
On 10/13/2017 12:05 PM, Ming Lei wrote:
> Hi Jens,
>
> In Red Hat internal storage test wrt. blk-mq scheduler, we found that I/O
> performance is much bad with mq-deadline, especially about sequential I/O
> on some multi-queue SCSI devcies(lpfc, qla2xxx, SRP...)
>
> Turns out one big issue causes the performance regression: requests are
> still dequeued from sw queue/scheduler queue even when ldd's queue is
> busy, so I/O merge becomes quite difficult to make, then sequential IO
> performance degrades a lot.
>
> This issue becomes one of mains reasons for reverting default SCSI_MQ
> in V4.13.
>
> This 8 patches improve this situation, and brings back performance loss.
>
> With this change, SCSI-MQ sequential I/O performance is improved much, Paolo
> reported that mq-deadline performance improved much[2] in his dbench test
> wrt V2. Also performance improvement on lpfc/qla2xx was observed with V1.[1]
>
> [1] http://marc.info/?l=linux-block&m=150151989915776&w=2
> [2] https://marc.info/?l=linux-block&m=150217980602843&w=2
I wanted to run some sanity testing on this series before committing it,
and unfortunately it doesn't even boot for me. Just hangs after loading
the kernel. Maybe an error slipped in for v8/9?
--
Jens Axboe
next prev parent reply other threads:[~2017-10-13 19:08 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-13 18:05 [PATCH V9 0/7] blk-mq-sched: improve sequential I/O performance Ming Lei
2017-10-13 18:05 ` [PATCH V9 1/7] blk-mq-sched: dispatch from scheduler only after progress is made on ->dispatch Ming Lei
2017-10-13 18:05 ` [PATCH V9 2/7] blk-mq-sched: move actual dispatching into one helper Ming Lei
2017-10-13 18:05 ` [PATCH V9 3/7] sbitmap: introduce __sbitmap_for_each_set() Ming Lei
2017-10-13 18:05 ` [PATCH V9 4/7] blk-mq: introduce .get_budget and .put_budget in blk_mq_ops Ming Lei
2017-10-13 23:43 ` Bart Van Assche
2017-10-14 7:34 ` Ming Lei
2017-10-13 18:05 ` [PATCH V9 5/7] blk-mq-sched: improve dispatching from sw queue Ming Lei
2017-10-13 18:05 ` [PATCH V9 6/7] SCSI: allow to pass null rq to scsi_prep_state_check() Ming Lei
2017-10-13 23:16 ` Bart Van Assche
2017-10-14 8:06 ` Ming Lei
2017-10-13 18:05 ` [PATCH V9 7/7] SCSI: implement .get_budget and .put_budget for blk-mq Ming Lei
2017-10-13 19:08 ` Jens Axboe [this message]
2017-10-13 19:21 ` [PATCH V9 0/7] blk-mq-sched: improve sequential I/O performance Jens Axboe
2017-10-13 20:23 ` Jens Axboe
2017-10-14 5:23 ` Ming Lei
2017-10-14 7:10 ` Ming Lei
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