From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B1F7EC4360C for ; Tue, 8 Oct 2019 09:06:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9035E206C2 for ; Tue, 8 Oct 2019 09:06:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730016AbfJHJGl (ORCPT ); Tue, 8 Oct 2019 05:06:41 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:3219 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729926AbfJHJGk (ORCPT ); Tue, 8 Oct 2019 05:06:40 -0400 Received: from DGGEMS404-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 6B4501630ADD6AEE8753; Tue, 8 Oct 2019 17:06:37 +0800 (CST) Received: from [127.0.0.1] (10.202.227.179) by DGGEMS404-HUB.china.huawei.com (10.3.19.204) with Microsoft SMTP Server id 14.3.439.0; Tue, 8 Oct 2019 17:06:31 +0800 Subject: Re: [PATCH V3 0/5] blk-mq: improvement on handling IO during CPU hotplug To: Ming Lei , Jens Axboe References: <20191008041821.2782-1-ming.lei@redhat.com> CC: , Bart Van Assche , Hannes Reinecke , Christoph Hellwig , "Thomas Gleixner" , Keith Busch From: John Garry Message-ID: Date: Tue, 8 Oct 2019 10:06:26 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <20191008041821.2782-1-ming.lei@redhat.com> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.227.179] X-CFilter-Loop: Reflected Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 08/10/2019 05:18, Ming Lei wrote: > Hi, > > Thomas mentioned: > " > That was the constraint of managed interrupts from the very beginning: > > The driver/subsystem has to quiesce the interrupt line and the associated > queue _before_ it gets shutdown in CPU unplug and not fiddle with it > until it's restarted by the core when the CPU is plugged in again. > " > > But no drivers or blk-mq do that before one hctx becomes dead(all > CPUs for one hctx are offline), and even it is worse, blk-mq stills tries > to run hw queue after hctx is dead, see blk_mq_hctx_notify_dead(). > > This patchset tries to address the issue by two stages: > > 1) add one new cpuhp state of CPUHP_AP_BLK_MQ_ONLINE > > - mark the hctx as internal stopped, and drain all in-flight requests > if the hctx is going to be dead. > > 2) re-submit IO in the state of CPUHP_BLK_MQ_DEAD after the hctx becomes dead > > - steal bios from the request, and resubmit them via generic_make_request(), > then these IO will be mapped to other live hctx for dispatch > > Please comment & review, thanks! > > John, I don't add your tested-by tag since V3 have some changes, > and I appreciate if you may run your test on V3. > Will do, Thanks > V3: > - re-organize patch 2 & 3 a bit for addressing Hannes's comment > - fix patch 4 for avoiding potential deadlock, as found by Hannes > > V2: > - patch4 & patch 5 in V1 have been merged to block tree, so remove > them > - addres