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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 8C10AC76191 for ; Tue, 16 Jul 2019 03:03:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4E2972171F for ; Tue, 16 Jul 2019 03:03:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730284AbfGPDDU (ORCPT ); Mon, 15 Jul 2019 23:03:20 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:36350 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1728256AbfGPDDU (ORCPT ); Mon, 15 Jul 2019 23:03:20 -0400 Received: from DGGEMS412-HUB.china.huawei.com (unknown [172.30.72.60]) by Forcepoint Email with ESMTP id C7AF8FF383205C9B2B50; Tue, 16 Jul 2019 11:03:16 +0800 (CST) Received: from [127.0.0.1] (10.74.223.225) by DGGEMS412-HUB.china.huawei.com (10.3.19.212) with Microsoft SMTP Server id 14.3.439.0; Tue, 16 Jul 2019 11:03:13 +0800 Subject: Re: [RFC PATCH 3/7] blk-mq: stop to handle IO before hctx's all CPUs become offline To: Ming Lei , Jens Axboe CC: , "James E . J . Bottomley" , "Martin K . Petersen" , , Bart Van Assche , "Hannes Reinecke" , Christoph Hellwig , Thomas Gleixner , Keith Busch References: <20190712024726.1227-1-ming.lei@redhat.com> <20190712024726.1227-4-ming.lei@redhat.com> From: John Garry Message-ID: <91f2a5ce-614a-1e4d-6830-81750cf7f708@huawei.com> Date: Tue, 16 Jul 2019 11:03:14 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190712024726.1227-4-ming.lei@redhat.com> Content-Type: text/plain; charset="gbk"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.74.223.225] X-CFilter-Loop: Reflected Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org ÔÚ 12/07/2019 10:47, Ming Lei дµÀ: > Most of blk-mq drivers depend on managed IRQ's auto-affinity to setup > up queue mapping. Thomas mentioned the following point[1]: > > " > 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. > " > > However, current blk-mq implementation doesn't quiesce hw queue before > the last CPU in the hctx is shutdown. Even worse, CPUHP_BLK_MQ_DEAD is > one cpuhp state handled after the CPU is down, so there isn't any chance > to quiesce hctx for blk-mq wrt. CPU hotplug. > > Add new cpuhp state of CPUHP_AP_BLK_MQ_ONLINE for blk-mq to stop queues > and wait for completion of in-flight requests. > > [1] https://lore.kernel.org/linux-block/alpine.DEB.2.21.1904051331270.1802@nanos.tec.linutronix.de/ > > Cc: Bart Van Assche > Cc: Hannes Reinecke > Cc: Christoph Hellwig > Cc: Thomas Gleixner > Cc: Keith Busch > Signed-off-by: Ming Lei > --- > block/blk-mq-tag.c | 2 +- > block/blk-mq-tag.h | 2 ++ > block/blk-mq.c | 67 ++++++++++++++++++++++++++++++++++++++ > include/linux/blk-mq.h | 1 + > include/linux/cpuhotplug.h | 1 + > 5 files changed, 72 insertions(+), 1 deletion(-) > > diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c > index da19f0bc8876..bcefb213ad69 100644 > --- a/block/blk-mq-tag.c > +++ b/block/blk-mq-tag.c > @@ -324,7 +324,7 @@ static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt, > * true to continue iterating tags, false to stop. > * @priv: Will be passed as second argument to @fn. > */ > -static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, > +void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, > busy_tag_iter_fn *fn, void *priv) > { > if (tags->nr_reserved_tags) > diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h > index 61deab0b5a5a..321fd6f440e6 100644 > --- a/block/blk-mq-tag.h > +++ b/block/blk-mq-tag.h > @@ -35,6 +35,8 @@ extern int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx, > extern void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool); > void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, > void *priv); > +void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, > + busy_tag_iter_fn *fn, void *priv); > > static inline struct sbq_wait_state *bt_wait_ptr(struct sbitmap_queue *bt, > struct blk_mq_hw_ctx *hctx) > diff --git a/block/blk-mq.c b/block/blk-mq.c > index e5ef40c603ca..028c5d78e409 100644 > --- a/block/blk-mq.c > +++ b/block/blk-mq.c > @@ -2205,6 +2205,64 @@ int blk_mq_alloc_rqs(struct blk_mq_tag_set *set, struct blk_mq_tags *tags, > return -ENOMEM; > } > > +static bool blk_mq_count_inflight_rq(struct request *rq, void *data, > + bool reserved) > +{ > + unsigned *count = data; > + > + if ((blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT)) > + (*count)++; > + > + return true; > +} > + > +unsigned blk_mq_tags_inflight_rqs(struct blk_mq_tags *tags) > +{ > + unsigned count = 0; > + > + blk_mq_all_tag_busy_iter(tags, blk_mq_count_inflight_rq, &count); > + > + return count; > +} > + > +static void blk_mq_drain_inflight_rqs(struct blk_mq_hw_ctx *hctx) > +{ > + while (1) { > + if (!blk_mq_tags_inflight_rqs(hctx->tags)) > + break; > + msleep(5); > + } > +} > + > +static int blk_mq_hctx_notify_online(unsigned int cpu, struct hlist_node *node) > +{ > + struct blk_mq_hw_ctx *hctx = hlist_entry_safe(node, > + struct blk_mq_hw_ctx, cpuhp_online); > + unsigned prev_cpu = -1; > + > + if (hctx->flags & BLK_MQ_F_NO_MANAGED_IRQ) > + return 0; is it possible to make this check at registration, such that we don't even register for when (hctx->flags & BLK_MQ_F_NO_MANAGED_IRQ)? > + > + while (true) { > + unsigned other_cpu = cpumask_next_and(prev_cpu, hctx->cpumask, nit: to me name next_cpu seems better > + cpu_online_mask); > + > + if (other_cpu >= nr_cpu_ids) > + break; > + > + /* return if there is other online CPU on this hctx */ > + if (other_cpu != cpu) > + return 0; > + > + prev_cpu = other_cpu; > + } > + > + set_bit(BLK_MQ_S_INTERNAL_STOPPED, &hctx->state); > + blk_mq_drain_inflight_rqs(hctx); > + > + return 0; > +} > + > /* > * 'cpu' is going away. splice any existing rq_list entries from this > * software queue to the hw queue dispatch list, and ensure that it > @@ -2221,6 +2279,9 @@ static int blk_mq_hctx_notify_dead(unsigned int cpu, struct hlist_node *node) > ctx = __blk_mq_get_ctx(hctx->queue, cpu); > type = hctx->type; > > + if (test_bit(BLK_MQ_S_INTERNAL_STOPPED, &hctx->state)) > + clear_bit(BLK_MQ_S_INTERNAL_STOPPED, &hctx->state); can you just always clear the bit without the test? > + > spin_lock(&ctx->lock); > if (!list_empty(&ctx->rq_lists[type])) { > list_splice_init(&ctx->rq_lists[type], &tmp); > @@ -2243,6 +2304,8 @@ static void blk_mq_remove_cpuhp(struct blk_mq_hw_ctx *hctx) > { > cpuhp_state_remove_instance_nocalls(CPUHP_BLK_MQ_DEAD, > &hctx->cpuhp_dead); > + cpuhp_state_remove_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE, > + &hctx->cpuhp_online); > } > > /* hctx->ctxs will be freed in queue's release handler */ > @@ -2301,6 +2364,8 @@ static int blk_mq_init_hctx(struct request_queue *q, > hctx->queue_num = hctx_idx; > > cpuhp_state_add_instance_nocalls(CPUHP_BLK_MQ_DEAD, &hctx->cpuhp_dead); > + cpuhp_state_add_instance_nocalls(CPUHP_AP_BLK_MQ_ONLINE, > + &hctx->cpuhp_online); > > hctx->tags = set->tags[hctx_idx]; > > @@ -3536,6 +3601,8 @@ static int __init blk_mq_init(void) > { > cpuhp_setup_state_multi(CPUHP_BLK_MQ_DEAD, "block/mq:dead", NULL, > blk_mq_hctx_notify_dead); > + cpuhp_setup_state_multi(CPUHP_AP_BLK_MQ_ONLINE, "block/mq:online", > + NULL, blk_mq_hctx_notify_online); > return 0; > } > subsys_initcall(blk_mq_init); > diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h > index 911cdc6479dc..dc86bdac08f4 100644 > --- a/include/linux/blk-mq.h > +++ b/include/linux/blk-mq.h > @@ -59,6 +59,7 @@ struct blk_mq_hw_ctx { > atomic_t nr_active; > > struct hlist_node cpuhp_dead; > + struct hlist_node cpuhp_online; I'd reorder with cpuhp_dead > struct kobject kobj; > > unsigned long poll_considered; > diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h > index 87c211adf49e..5177f7bbcb88 100644 > --- a/include/linux/cpuhotplug.h > +++ b/include/linux/cpuhotplug.h > @@ -147,6 +147,7 @@ enum cpuhp_state { > CPUHP_AP_SMPBOOT_THREADS, > CPUHP_AP_X86_VDSO_VMA_ONLINE, > CPUHP_AP_IRQ_AFFINITY_ONLINE, > + CPUHP_AP_BLK_MQ_ONLINE, > CPUHP_AP_ARM_MVEBU_SYNC_CLOCKS, > CPUHP_AP_X86_INTEL_EPB_ONLINE, > CPUHP_AP_PERF_ONLINE, >