From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751817AbdJMUXY (ORCPT ); Fri, 13 Oct 2017 16:23:24 -0400 Received: from mail-pg0-f42.google.com ([74.125.83.42]:54688 "EHLO mail-pg0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750907AbdJMUXW (ORCPT ); Fri, 13 Oct 2017 16:23:22 -0400 X-Google-Smtp-Source: AOwi7QCfCXXtSgXdK4A+W1U267uWRylIH0dORcKsKkOPzJZi8GTSDIQ1RAP+44W68bP26kaIZBKGtg== Subject: Re: [PATCH V9 0/7] blk-mq-sched: improve sequential I/O performance From: Jens Axboe To: Ming Lei , linux-block@vger.kernel.org, Christoph Hellwig Cc: 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 References: <20171013180532.29304-1-ming.lei@redhat.com> <03fc0b94-8463-3f3d-9d75-be3e05d88987@kernel.dk> <95fe2831-12a9-3346-5fc7-9259ff988669@kernel.dk> Message-ID: <3598a2f6-6305-372c-36a3-7813cbe04a77@kernel.dk> Date: Fri, 13 Oct 2017 14:23:07 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 MIME-Version: 1.0 In-Reply-To: <95fe2831-12a9-3346-5fc7-9259ff988669@kernel.dk> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. -- Jens Axboe