From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ming Lei Subject: Re: [PATCH V9 0/7] blk-mq-sched: improve sequential I/O performance Date: Sat, 14 Oct 2017 13:23:27 +0800 Message-ID: <20171014052321.GA21519@ming.t460p> References: <20171013180532.29304-1-ming.lei@redhat.com> <03fc0b94-8463-3f3d-9d75-be3e05d88987@kernel.dk> <95fe2831-12a9-3346-5fc7-9259ff988669@kernel.dk> <3598a2f6-6305-372c-36a3-7813cbe04a77@kernel.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mx1.redhat.com ([209.132.183.28]:38610 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751678AbdJNFXo (ORCPT ); Sat, 14 Oct 2017 01:23:44 -0400 Content-Disposition: inline In-Reply-To: <3598a2f6-6305-372c-36a3-7813cbe04a77@kernel.dk> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Jens Axboe Cc: linux-block@vger.kernel.org, Christoph Hellwig , Bart Van Assche , Laurence Oberman , Paolo Valente , Oleksandr Natalenko , Tom Nguyen , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, Omar Sandoval , John Garry 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