From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965671AbeEIRB6 (ORCPT ); Wed, 9 May 2018 13:01:58 -0400 Received: from mail-it0-f42.google.com ([209.85.214.42]:50537 "EHLO mail-it0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935516AbeEIRBz (ORCPT ); Wed, 9 May 2018 13:01:55 -0400 X-Google-Smtp-Source: AB8JxZpTBho4Ly/txyOGdWQ/8OrxNgRgDEZwfr8mSg6TsRG4avB2JmKczmxDql9t6XPv+e6f78714Q== Subject: Re: bug in tag handling in blk-mq? To: Mike Galbraith , Paolo Valente Cc: Christoph Hellwig , linux-block , Ulf Hansson , LKML , Linus Walleij , Oleksandr Natalenko References: <999DF2B3-4EE8-4BDF-89C5-EB0C2D8BF69E@linaro.org> <7760d23b-7a4c-a645-1c7a-da7569bb44dc@kernel.dk> <84145CD7-B917-4B32-8A5C-310C1910DB71@linaro.org> <1525755090.24338.1.camel@gmx.de> <1525768632.5208.4.camel@gmx.de> <1525797766.5204.2.camel@gmx.de> <3692ce7d-a767-72e6-65ae-6178b6c2e7d8@kernel.dk> <57952405-bdeb-f4e4-1aef-a7c0a8a68674@kernel.dk> <1525839089.15732.1.camel@gmx.de> <1525885030.15732.6.camel@gmx.de> From: Jens Axboe Message-ID: <1e51eb57-6d9b-a53c-9cd6-2adfc86b21b5@kernel.dk> Date: Wed, 9 May 2018 11:01:52 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <1525885030.15732.6.camel@gmx.de> Content-Type: text/plain; charset=iso-8859-15 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 5/9/18 10:57 AM, Mike Galbraith wrote: > On Wed, 2018-05-09 at 09:18 -0600, Jens Axboe wrote: >> On 5/8/18 10:11 PM, Mike Galbraith wrote: >>> On Tue, 2018-05-08 at 19:09 -0600, Jens Axboe wrote: >>>> >>>> Alright, I managed to reproduce it. What I think is happening is that >>>> BFQ is limiting the inflight case to something less than the wake >>>> batch for sbitmap, which can lead to stalls. I don't have time to test >>>> this tonight, but perhaps you can give it a go when you are back at it. >>>> If not, I'll try tomorrow morning. >>>> >>>> If this is the issue, I can turn it into a real patch. This is just to >>>> confirm that the issue goes away with the below. >>> >>> Confirmed. Impressive high speed bug stomping. >> >> Well, that's good news. Can I get you to try this patch? > > Sure thing. The original hang (minus provocation patch) being > annoyingly non-deterministic, this will (hopefully) take a while. You can verify with the provocation patch as well first, if you wish. Just need to hand-apply since it'll conflict with this patch in bfq. But it's a trivial resolve. -- Jens Axboe