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 56CF8C3A5A1 for ; Thu, 22 Aug 2019 17:40:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3600C23405 for ; Thu, 22 Aug 2019 17:40:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392837AbfHVRkG (ORCPT ); Thu, 22 Aug 2019 13:40:06 -0400 Received: from szxga04-in.huawei.com ([45.249.212.190]:5202 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2392832AbfHVRkF (ORCPT ); Thu, 22 Aug 2019 13:40:05 -0400 Received: from DGGEMS401-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 0396EF9CAEFA3B24BC08; Fri, 23 Aug 2019 01:40:00 +0800 (CST) Received: from [127.0.0.1] (10.202.227.238) by DGGEMS401-HUB.china.huawei.com (10.3.19.201) with Microsoft SMTP Server id 14.3.439.0; Fri, 23 Aug 2019 01:39:49 +0800 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> CC: , Minwoo Im , "Bart Van Assche" , Hannes Reinecke , "Christoph Hellwig" , Thomas Gleixner , Keith Busch , chenxiang From: John Garry Message-ID: Date: Thu, 22 Aug 2019 18:39:43 +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: <20190812134312.16732-1-ming.lei@redhat.com> 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 14:43, 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 Hi Ming, This looks to fix the hotplug issue for me. Previously I could manufacture a scenario while running fio where I got IO timeouts, like this: root@(none)$ echo 0 > ./sys/devices/system/cpu/cpu0/online [ 296.897627] process 891 (fio) no longer affine to cpu0 [ 296.898488] process 893 (fio) no longer affine to cpu0 [ 296.910270] process 890 (fio) no longer affine to cpu0 [ 296.927322] IRQ 775: no longer affine to CPU0 [ 296.932762] CPU0: shutdown [ 296.935469] psci: CPU0 killed. root@(none)$ [ 326.971962] sas: Enter sas_scsi_recover_host busy: 61 failed: 61 [ 326.977978] sas: sas_scsi_find_task: aborting task 0x00000000e2cdc79b root@(none)$ [ 333.047964] hisi_sas_v3_hw 0000:74:02.0: internal task abort: timeout and not done. [ 333.055616] hisi_sas_v3_hw 0000:74:02.0: abort task: internal abort (-5) [ 333.062306] sas: sas_scsi_find_task: querying task 0x00000000e2cdc79b [ 333.068776] sas: sas_scsi_find_task: task 0x00000000e2cdc79b not at LU [ 333.075295] sas: task 0x00000000e2cdc79b is not at LU: I_T recover [ 333.081464] sas: I_T nexus reset for dev 5000c500a7b95a49 Please notice the 30-second delay for the SCSI IO timeout. And now I don't see it; here's a sample for irq shutdown: root@(none)$ echo 0 > ./sys/devices/system/cpu/cpu0/online [ 344.608148] process 849 (fio) no longer affine to cpu0 [ 344.608639] process 848 (fio) no longer affine to cpu0 [ 344.609454] process 850 (fio) no longer affine to cpu0 [ 344.643481] process 847 (fio) no longer affine to cpu0 [ 346.213842] IRQ 775: no longer affine to CPU0 [ 346.219712] CPU0: shutdown [ 346.222425] psci: CPU0 killed. Please notice the ~1.5s pause, which would be the queue draining. So FWIW: Tested-by: John Garry JFYI, I tested on 5.3-rc5 and cherry-picked https://github.com/ming1/linux/commit/0d2cd3c99bb0fe81d2c0ca5d68e02bdc4521d4d6 and "blk-mq: add callback of .cleanup_rq". Cheers, John > > 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 >