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=-7.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 54B37C31E40 for ; Mon, 12 Aug 2019 16:22:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1019B2075B for ; Mon, 12 Aug 2019 16:22:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726463AbfHLQWB (ORCPT ); Mon, 12 Aug 2019 12:22:01 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:4662 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725887AbfHLQWB (ORCPT ); Mon, 12 Aug 2019 12:22:01 -0400 Received: from DGGEMS407-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id 809D92F126BC02611484; Tue, 13 Aug 2019 00:21:57 +0800 (CST) Received: from [127.0.0.1] (10.202.227.238) by DGGEMS407-HUB.china.huawei.com (10.3.19.207) with Microsoft SMTP Server id 14.3.439.0; Tue, 13 Aug 2019 00:21:51 +0800 From: John Garry Subject: Re: [PATCH V2 0/5] blk-mq: improvement on handling IO during CPU hotplug To: Ming Lei , Jens Axboe References: <20190812134312.16732-1-ming.lei@redhat.com> <20190812134608.GA16803@ming.t460p> CC: , Minwoo Im , "Bart Van Assche" , Hannes Reinecke , "Christoph Hellwig" , Thomas Gleixner , Keith Busch , chenxiang , "linux-scsi@vger.kernel.org" Message-ID: <658b0e7f-72f6-3673-d35e-4d8078069258@huawei.com> Date: Mon, 12 Aug 2019 17:21:44 +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: <20190812134608.GA16803@ming.t460p> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.202.227.238] X-CFilter-Loop: Reflected Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 12/08/2019 14:46, Ming Lei wrote: > Hi John, > > On Mon, Aug 12, 2019 at 09:43:07PM +0800, 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! >> >> V2: >> - patch4 & patch 5 in V1 have been merged to block tree, so remove >> them >> - address comments from John Garry and Minwoo >> >> >> Ming Lei (5): >> blk-mq: add new state of BLK_MQ_S_INTERNAL_STOPPED >> blk-mq: add blk-mq flag of BLK_MQ_F_NO_MANAGED_IRQ >> blk-mq: stop to handle IO before hctx's all CPUs become offline >> blk-mq: re-submit IO in case that hctx is dead >> blk-mq: handle requests dispatched from IO scheduler in case that hctx >> is dead >> >> block/blk-mq-debugfs.c | 2 + >> block/blk-mq-tag.c | 2 +- >> block/blk-mq-tag.h | 2 + >> block/blk-mq.c | 143 +++++++++++++++++++++++++++++++++---- >> block/blk-mq.h | 3 +- >> drivers/block/loop.c | 2 +- >> drivers/md/dm-rq.c | 2 +- >> include/linux/blk-mq.h | 5 ++ >> include/linux/cpuhotplug.h | 1 + >> 9 files changed, 146 insertions(+), 16 deletions(-) >> >> Cc: Bart Van Assche >> Cc: Hannes Reinecke >> Cc: Christoph Hellwig >> Cc: Thomas Gleixner >> Cc: Keith Busch >> -- >> 2.20.1 >> > > Sorry for forgetting to Cc you. Already subscribed :) I don't mean to hijack this thread, but JFYI we're getting around to test https://github.com/ming1/linux/commits/v5.2-rc-host-tags-V2 - unfortunately we're still seeing a performance regression. I can't see where it's coming from. We're double-checking the test though. Thanks, John > > > Thanks, > Ming > > . >