From: Ming Lei <ming.lei@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org,
Christoph Hellwig <hch@infradead.org>,
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: Sat, 14 Oct 2017 13:23:27 +0800 [thread overview]
Message-ID: <20171014052321.GA21519@ming.t460p> (raw)
In-Reply-To: <3598a2f6-6305-372c-36a3-7813cbe04a77@kernel.dk>
On Fri, Oct 13, 2017 at 02:23:07PM -0600, Jens Axboe wrote:
> On 10/13/2017 01:21 PM, Jens Axboe wrote:
> > On 10/13/2017 01:08 PM, Jens Axboe wrote:
> >> 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?
> >
> > Or it might be something with kyber, my laptop defaults to that. Test
> > box seems to boot (which is SCSI), and nvme loads fine by default,
> > but not with kyber.
> >
> > I don't have time to look into this more today, but the above might
> > help you figure out what is going on.
>
> Verified that the laptop boots just fine if I remove the kyber udev
> rule.
I can reproduce this issue with kyber switched to, and will figure out
it soon.
--
Ming
next prev parent reply other threads:[~2017-10-14 5:23 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 ` [PATCH V9 0/7] blk-mq-sched: improve sequential I/O performance Jens Axboe
2017-10-13 19:21 ` Jens Axboe
2017-10-13 20:23 ` Jens Axboe
2017-10-14 5:23 ` Ming Lei [this message]
2017-10-14 7:10 ` Ming Lei
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