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, 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 E4611C2D0F9 for ; Wed, 13 May 2020 07:34:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C76D020673 for ; Wed, 13 May 2020 07:34:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730363AbgEMHe4 (ORCPT ); Wed, 13 May 2020 03:34:56 -0400 Received: from lhrrgout.huawei.com ([185.176.76.210]:2202 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730353AbgEMHe4 (ORCPT ); Wed, 13 May 2020 03:34:56 -0400 Received: from lhreml724-chm.china.huawei.com (unknown [172.18.7.108]) by Forcepoint Email with ESMTP id 60E0559CC7C969C9A2C3; Wed, 13 May 2020 08:34:54 +0100 (IST) Received: from [127.0.0.1] (10.210.165.35) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.1913.5; Wed, 13 May 2020 08:34:53 +0100 Subject: Re: [PATCH V11 00/12] blk-mq: improvement CPU hotplug To: Ming Lei , Jens Axboe CC: References: <20200513034803.1844579-1-ming.lei@redhat.com> From: John Garry Message-ID: <2b4b0a75-c9c0-27de-77e8-85ada602b18f@huawei.com> Date: Wed, 13 May 2020 08:34:01 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: <20200513034803.1844579-1-ming.lei@redhat.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.210.165.35] X-ClientProxiedBy: lhreml701-chm.china.huawei.com (10.201.108.50) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 13/05/2020 04:47, 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 inactive(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 > > Thanks John Garry for running lots of tests on arm64 with this patchset > and co-working on investigating all kinds of issues. > > Thanks Christoph's review on V7 & V8. > > Please consider it for v5.8. > > https://github.com/ming1/linux/commits/v5.7-rc-blk-mq-improve-cpu-hotplug > > V11: > - drop new callback from blk_mq_all_tag_busy_iter, add new helper > of blk_mq_all_tag_iter (5/12), as suggested by Bart > - fix request allocation hang in case of queue freeze(11/12), as > reported by Bart > > V10: > - fix double bio complete in request resubmission(10/11) > - add tested-by tag > > V9: > - add Reviewed-by tag > - document more on memory barrier usage between getting driver tag > and handling cpu offline(7/11) > - small code cleanup as suggested by Chritoph(7/11) > - rebase against for-5.8/block(1/11, 2/11) > V8: > - add patches to share code with blk_rq_prep_clone > - code re-organization as suggested by Christoph, most of them are > in 04/11, 10/11 > - add reviewed-by tag > > V7: > - fix updating .nr_active in get_driver_tag > - add hctx->cpumask check in cpuhp handler > - only drain requests which tag is >= 0 > - pass more aggressive cpuhotplug&io test > > V6: > - simplify getting driver tag, so that we can drain in-flight > requests correctly without using synchronize_rcu() > - handle re-submission of flush & passthrough request correctly > > V5: > - rename BLK_MQ_S_INTERNAL_STOPPED as BLK_MQ_S_INACTIVE > - re-factor code for re-submit requests in cpu dead hotplug handler > - address requeue corner case > > 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 > > > *** BLURB HERE *** :) So my tested-by tags have been dropped. I'll test again, since the changes are non-trivial. Tip commit of https://github.com/ming1/linux/commits/v5.7-rc-blk-mq-improve-cpu-hotplug at this moment is b55e97a4 > > Ming Lei (12): > block: clone nr_integrity_segments and write_hint in blk_rq_prep_clone > block: add helper for copying request > blk-mq: mark blk_mq_get_driver_tag as static > blk-mq: assign rq->tag in blk_mq_get_driver_tag > blk-mq: add blk_mq_all_tag_iter > 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 inactive > block: add blk_end_flush_machinery > blk-mq: add blk_mq_hctx_handle_dead_cpu for handling cpu dead > block: add request allocation flag of BLK_MQ_REQ_FORCE > blk-mq: re-submit IO in case that hctx is inactive > block: deactivate hctx when the hctx is actually inactive > > block/blk-core.c | 32 +++- > block/blk-flush.c | 141 ++++++++++++--- > block/blk-mq-debugfs.c | 2 + > block/blk-mq-tag.c | 33 +++- > block/blk-mq-tag.h | 2 + > block/blk-mq.c | 356 +++++++++++++++++++++++++++++-------- > block/blk-mq.h | 22 ++- > block/blk.h | 11 +- > drivers/block/loop.c | 2 +- > drivers/md/dm-rq.c | 2 +- > include/linux/blk-mq.h | 14 ++ > include/linux/cpuhotplug.h | 1 + > 12 files changed, 494 insertions(+), 124 deletions(-) >