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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 3AC01C4338F for ; Wed, 18 Aug 2021 10:33:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 253A86108F for ; Wed, 18 Aug 2021 10:33:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234505AbhHRKeD (ORCPT ); Wed, 18 Aug 2021 06:34:03 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:39046 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234893AbhHRKdm (ORCPT ); Wed, 18 Aug 2021 06:33:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1629282776; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=P4ECR/7LCl11DZMmIx24paVmBtUy1mAPExnwlhk9tCY=; b=aVy6CQSTlahkO/GkXqqFwXs/NGGVBQYjYoYCzpYwLgYJlOC7FN4WHjgGr09CvBiX5xiUgS RKRjawpcut8vm/CuJdXDDWUC7GXTVX8UXNnESS+ATxRyz/R21MxbvrLFq8Slm8J+GoaJZU G2Ch6kRxbGguINRK3wzFC6IlKJA7uD8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-269-n5v49ef6MlejYgF0sNhzKw-1; Wed, 18 Aug 2021 06:32:54 -0400 X-MC-Unique: n5v49ef6MlejYgF0sNhzKw-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id F066687D543; Wed, 18 Aug 2021 10:32:52 +0000 (UTC) Received: from T590 (ovpn-8-40.pek2.redhat.com [10.72.8.40]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BBC3A369A; Wed, 18 Aug 2021 10:32:43 +0000 (UTC) Date: Wed, 18 Aug 2021 18:32:38 +0800 From: Ming Lei To: John Garry Cc: Jens Axboe , Christoph Hellwig , linux-block@vger.kernel.org, Thomas Gleixner , Greg Kroah-Hartman , Sagi Grimberg , Daniel Wagner , Wen Xiong , Hannes Reinecke Subject: Re: [PATCH V6 3/3] blk-mq: don't deactivate hctx if managed irq isn't used Message-ID: References: <20210722095246.1240526-1-ming.lei@redhat.com> <20210722095246.1240526-4-ming.lei@redhat.com> <23acd521-dac3-068d-b82a-424c078e0ac0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <23acd521-dac3-068d-b82a-424c078e0ac0@huawei.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Wed, Aug 18, 2021 at 10:38:15AM +0100, John Garry wrote: > On 22/07/2021 10:52, Ming Lei wrote: > > blk-mq deactivates one hctx when the last CPU in hctx->cpumask become > > offline by draining all requests originated from this hctx and moving new > > allocation to other active hctx. This way is for avoiding inflight IO in > > case of managed irq because managed irq is shutdown when the last CPU in > > the irq's affinity becomes offline. > > > > However, lots of drivers(nvme fc, rdma, tcp, loop, ...) don't use managed > > irq, so they needn't to deactivate hctx when the last CPU becomes offline. > > Also, some of them are the only user of blk_mq_alloc_request_hctx() which > > is used for connecting io queue. And their requirement is that the connect > > request needs to be submitted successfully via one specified hctx even though > > all CPUs in this hctx->cpumask have become offline. > > > > Addressing the requirement for nvme fc/rdma/loop by allowing to > > allocate request from one hctx when all CPUs in this hctx are offline, > > since these drivers don't use managed irq. > > > > Finally don't deactivate one hctx when it doesn't use managed irq. > > > > Reviewed-by: Christoph Hellwig > > Signed-off-by: Ming Lei > > Sorry for lateness. Just a few minor comments below, regardless: > > Reviewed-by: John Garry > > > --- > > block/blk-mq.c | 27 +++++++++++++++++---------- > > block/blk-mq.h | 8 ++++++++ > > 2 files changed, 25 insertions(+), 10 deletions(-) > > > > diff --git a/block/blk-mq.c b/block/blk-mq.c > > index 2c4ac51e54eb..591ab07c64d8 100644 > > --- a/block/blk-mq.c > > +++ b/block/blk-mq.c > > @@ -427,6 +427,15 @@ struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op, > > } > > EXPORT_SYMBOL(blk_mq_alloc_request); > > +static inline int blk_mq_first_mapped_cpu(struct blk_mq_hw_ctx *hctx) > > I don't see why it needs to be inline. I think generally we leave it to the > compiler to decide. Usually if one function is called more than two times, it will not be inlined. blk_mq_first_mapped_cpu() is called in fast path, so we need to inline it. > > > +{ > > + int cpu = cpumask_first_and(hctx->cpumask, cpu_online_mask); > > + > > + if (cpu >= nr_cpu_ids) > > + cpu = cpumask_first(hctx->cpumask); > > + return cpu; > > +} > > + > > struct request *blk_mq_alloc_request_hctx(struct request_queue *q, > > unsigned int op, blk_mq_req_flags_t flags, unsigned int hctx_idx) > > { > > @@ -468,7 +477,10 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q, > > data.hctx = q->queue_hw_ctx[hctx_idx]; > > if (!blk_mq_hw_queue_mapped(data.hctx)) > > goto out_queue_exit; > > - cpu = cpumask_first_and(data.hctx->cpumask, cpu_online_mask); > > + > > + WARN_ON_ONCE(blk_mq_hctx_use_managed_irq(data.hctx)); > > + > > + cpu = blk_mq_first_mapped_cpu(data.hctx); > > data.ctx = __blk_mq_get_ctx(q, cpu); > > if (!q->elevator) > > @@ -1501,15 +1513,6 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx) > > hctx_unlock(hctx, srcu_idx); > > } > > -static inline int blk_mq_first_mapped_cpu(struct blk_mq_hw_ctx *hctx) > > -{ > > - int cpu = cpumask_first_and(hctx->cpumask, cpu_online_mask); > > - > > - if (cpu >= nr_cpu_ids) > > - cpu = cpumask_first(hctx->cpumask); > > - return cpu; > > -} > > - > > /* > > * It'd be great if the workqueue API had a way to pass > > * in a mask and had some smarts for more clever placement. > > @@ -2556,6 +2559,10 @@ static int blk_mq_hctx_notify_offline(unsigned int cpu, struct hlist_node *node) > > struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node, > > struct blk_mq_hw_ctx, cpuhp_online); > > + /* hctx needn't to be deactivated in case managed irq isn't used */ > > + if (!blk_mq_hctx_use_managed_irq(hctx)) > > + return 0; > > In a previous version (v2) I think that we just didn't register the cpu > hotplug handlers, so not sure why that changed. Sorry, forget to mention the change, inside blk_mq_realloc_hw_ctxs() we may grab one cached hctx without initializing it, so use managed irq info change may not be visible in blk_mq_init_hctx(). Given blk_mq_hctx_notify_offline() isn't in fast path, I'd rather to check in blk_mq_hctx_notify_offline(), which is more reliable than running the check in blk_mq_init_hctx(). > > > + > > if (!cpumask_test_cpu(cpu, hctx->cpumask) || > > !blk_mq_last_cpu_in_hctx(cpu, hctx)) > > return 0; > > diff --git a/block/blk-mq.h b/block/blk-mq.h > > index d08779f77a26..7333b659d8f5 100644 > > --- a/block/blk-mq.h > > +++ b/block/blk-mq.h > > @@ -119,6 +119,14 @@ static inline struct blk_mq_hw_ctx *blk_mq_map_queue(struct request_queue *q, > > return ctx->hctxs[type]; > > } > > +static inline bool blk_mq_hctx_use_managed_irq(struct blk_mq_hw_ctx *hctx) > > +{ > > + if (hctx->type == HCTX_TYPE_POLL) > > + return false; > > + > > + return hctx->queue->tag_set->map[hctx->type].use_managed_irq; > > +} > > This function only seems to be used in blk-mq.c, so not sure why you put it > in .h file. oops, the helper must be used in early version, I will send a new version soon. Thanks, Ming