From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753238AbdJMTIx (ORCPT ); Fri, 13 Oct 2017 15:08:53 -0400 Received: from mail-it0-f54.google.com ([209.85.214.54]:53423 "EHLO mail-it0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752853AbdJMTIt (ORCPT ); Fri, 13 Oct 2017 15:08:49 -0400 X-Google-Smtp-Source: ABhQp+RxD2M2qBhU8eCkBUiV4yuzg4mNLeAJ8U1AEZQeyASKGB88w2XmLc2cBYAr0M6mKdyjbhoUpQ== Subject: Re: [PATCH V9 0/7] blk-mq-sched: improve sequential I/O performance 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> From: Jens Axboe Message-ID: <03fc0b94-8463-3f3d-9d75-be3e05d88987@kernel.dk> Date: Fri, 13 Oct 2017 13:08:46 -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: <20171013180532.29304-1-ming.lei@redhat.com> 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 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