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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 523CCC4360C for ; Wed, 16 Oct 2019 08:58:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3158A20872 for ; Wed, 16 Oct 2019 08:58:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389107AbfJPI6i (ORCPT ); Wed, 16 Oct 2019 04:58:38 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:45330 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2388817AbfJPI6i (ORCPT ); Wed, 16 Oct 2019 04:58:38 -0400 Received: from DGGEMS403-HUB.china.huawei.com (unknown [172.30.72.58]) by Forcepoint Email with ESMTP id 18EE1BDB72AB2273BE37; Wed, 16 Oct 2019 16:58:36 +0800 (CST) Received: from [127.0.0.1] (10.202.227.179) by DGGEMS403-HUB.china.huawei.com (10.3.19.203) with Microsoft SMTP Server id 14.3.439.0; Wed, 16 Oct 2019 16:58:33 +0800 Subject: Re: [PATCH V4 0/5] blk-mq: improvement on handling IO during CPU hotplug To: Ming Lei , Jens Axboe References: <20191014015043.25029-1-ming.lei@redhat.com> CC: , Bart Van Assche , Hannes Reinecke , Christoph Hellwig , "Thomas Gleixner" , Keith Busch From: John Garry Message-ID: Date: Wed, 16 Oct 2019 09:58:27 +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: <20191014015043.25029-1-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 14/10/2019 02:50, 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. Hi Ming, So I got around to doing some testing. The good news is that issue which we were experiencing in v3 series seems to have has gone away - alot more stable. However, unfortunately, I did notice some SCSI timeouts: 15508.615074] CPU2: shutdown [15508.617778] psci: CPU2 killed. [15508.651220] CPU1: shutdown [15508.653924] psci: CPU1 killed. [15518.406229] sas: Enter sas_scsi_recover_host busy: 63 failed: 63 Jobs: 1 (f=1): [R] [0.0% done] [0[15518.412239] sas: sas_scsi_find_task: aborting task 0x00000000a7159744 KB/0KB/0KB /s] [0/0/0 iops] [eta [15518.421708] sas: sas_eh_handle_sas_errors: task 0x00000000a7159744 is done [15518.431266] sas: sas_scsi_find_task: aborting task 0x00000000d39731eb [15518.442539] sas: sas_eh_handle_sas_errors: task 0x00000000d39731eb is done [15518.449407] sas: sas_scsi_find_task: aborting task 0x000000009f77c9bd [15518.455899] sas: sas_eh_handle_sas_errors: task 0x000000009f77c9bd is done A couple of things to note: - I added some debug prints in blk_mq_hctx_drain_inflight_rqs() for when inflights rqs !=0, and I don't see them for this timeout - 0 datarate reported from fio I'll have a look... Thanks, John > > V4: > - resubmit IOs in dispatch list in case that this hctx is dead > > 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 > - address comments from John Garry and Minwoo > > > > Ming Lei (5): > blk-mq: add new state of BLK_MQ_S_INTERNAL_STOPPED > blk-mq: prepare for draining IO when hctx's all CPUs are offline > blk-mq: stop to handle IO and drain IO before hctx becomes dead > 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 | 137 ++++++++++++++++++++++++++++++++++--- > 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, 141 insertions(+), 15 deletions(-) > > Cc: John Garry > Cc: Bart Van Assche > Cc: Hannes Reinecke > Cc: Christoph Hellwig > Cc: Thomas Gleixner > Cc: Keith Busch >