Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752414AbdHCKIg (ORCPT ); Thu, 3 Aug 2017 06:08:36 -0400 Received: from mail-ua0-f171.google.com ([209.85.217.171]:38754 "EHLO mail-ua0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752217AbdHCJ5w (ORCPT ); Thu, 3 Aug 2017 05:57:52 -0400 MIME-Version: 1.0 In-Reply-To: <20170803094242.wol67mmga3om4gjp@techsingularity.net> References: <20170803085115.r2jfz2lofy5spfdb@techsingularity.net> <20170803094242.wol67mmga3om4gjp@techsingularity.net> From: Ming Lei Date: Thu, 3 Aug 2017 17:57:50 +0800 Message-ID: Subject: Re: Switching to MQ by default may generate some bug reports To: Mel Gorman Cc: Christoph Hellwig , Jens Axboe , Linux Kernel Mailing List , linux-block , Paolo Valente Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1346 Lines: 31 On Thu, Aug 3, 2017 at 5:42 PM, Mel Gorman wrote: > On Thu, Aug 03, 2017 at 05:17:21PM +0800, Ming Lei wrote: >> Hi Mel Gorman, >> >> On Thu, Aug 3, 2017 at 4:51 PM, Mel Gorman wrote: >> > Hi Christoph, >> > >> > I know the reasons for switching to MQ by default but just be aware that it's >> > not without hazards albeit it the biggest issues I've seen are switching >> > CFQ to BFQ. On my home grid, there is some experimental automatic testing >> > running every few weeks searching for regressions. Yesterday, it noticed >> > that creating some work files for a postgres simulator called pgioperf >> > was 38.33% slower and it auto-bisected to the switch to MQ. This is just >> > linearly writing two files for testing on another benchmark and is not >> > remarkable. The relevant part of the report is >> >> We saw some SCSI-MQ performance issue too, please see if the following >> patchset fixes your issue: >> >> http://marc.info/?l=linux-block&m=150151989915776&w=2 >> > > That series is dealing with problems with legacy-deadline vs mq-none where > as the bulk of the problems reported in this mail are related to > legacy-CFQ vs mq-BFQ. The serials deals with none and all mq schedulers, and you can see the improvement on mq-deadline in cover letter, :-) Thanks, Ming Lei