From patchwork Wed Mar 20 02:34:46 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 13597214 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 26EFDF9D3 for ; Wed, 20 Mar 2024 02:35:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710902106; cv=none; b=HJgaioUdInQ8CM+0XNHvHZ3tyexdI4MiEwlb6pomtXlDm4JkmDC17xk2WHpamzk+51CSvaBCqKgo0dtWCcAM6XhKeUxU9dQWBJ+u/t3AIskyk7FGRI41upZFp1gtaCbBxA7ewMqOVAgmxWchDyzAMZb+l7q0heZBcaarkmA0gBk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710902106; c=relaxed/simple; bh=+FtuJcZDjYoxsHOkuHssLwtOO/q/pOEiv8h2bj3wQ3s=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=dlohffZ6JTWqrgnwIHoPeIUoz9cLYd6MfK8gKYwAeMi9a3ur4s47FuaFP/AQRvE40OYVBzSlv05RhqdKEhbJCGtAOJKy5InCC1yTs6fZ2OBEWbGwUQ4ujJeS9EdEFvRbfJ9+9auIPQrVzjONhe+zvl+nBGKt+0EduAs6RG8ydGg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=I+CvgoHt; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="I+CvgoHt" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1710902104; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=iVOnpgBiHQNqWMYuUycLlmKFbOhzuiuFaGVkmq39BWM=; b=I+CvgoHtUUDKdT0yFNVrbJFduB7RJLWD7aVfyxYgYQb6dwPi4oYDfHpeypJxIxZYwO9GCt BUU7PgNWiGlUnjG62vH0HFddllyWN3HltKO1SNBPXRZFaZYzUywn8PFi9nNFBLPzU5+Q9w z5KEK+YXQRr4SZYmCu0oqOuZHLorlo4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-385-OXVIwTu-PCOkEDm8GDOAyw-1; Tue, 19 Mar 2024 22:35:00 -0400 X-MC-Unique: OXVIwTu-PCOkEDm8GDOAyw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id E7A938007A1; Wed, 20 Mar 2024 02:34:59 +0000 (UTC) Received: from localhost (hp-dl380g10-01.lab.eng.pek2.redhat.com [10.73.196.69]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8CED5492BD3; Wed, 20 Mar 2024 02:34:58 +0000 (UTC) From: Ming Lei To: Jens Axboe , linux-block@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Ming Lei , Tim Chen , Juri Lelli , Andrew Theurer , Joe Mario , Sebastian Jug , Frederic Weisbecker , Bart Van Assche , Tejun Heo Subject: [PATCH V4] blk-mq: don't schedule block kworker on isolated CPUs Date: Wed, 20 Mar 2024 10:34:46 +0800 Message-ID: <20240320023446.882006-1-ming.lei@redhat.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.9 Kernel parameter of `isolcpus=` or 'nohz_full=' are used to isolate CPUs for specific task, and it isn't expected to let block IO disturb these CPUs. blk-mq kworker shouldn't be scheduled on isolated CPUs. Also if isolated CPUs is run for blk-mq kworker, long block IO latency can be caused. Kernel workqueue only respects CPU isolation for WQ_UNBOUND, for bound WQ, the responsibility is on user because CPU is specified as WQ API parameter, such as mod_delayed_work_on(cpu), queue_delayed_work_on(cpu) and queue_work_on(cpu). So not run blk-mq kworker on isolated CPUs by removing isolated CPUs from hctx->cpumask. Meantime use queue map to check if all CPUs in this hw queue are offline instead of hctx->cpumask, this way can avoid any cost in fast IO code path, and is safe since hctx->cpumask are only used in the two cases. Cc: Tim Chen Cc: Juri Lelli Cc: Andrew Theurer Cc: Joe Mario Cc: Sebastian Jug Cc: Frederic Weisbecker Cc: Bart Van Assche Cc: Tejun Heo Tested-by: Joe Mario Signed-off-by: Ming Lei --- V4: - improve comment & commit log as suggested by Tim V3: - avoid to check invalid cpu as reported by Bart - take current cpu(to be offline, not done yet) into account - simplify blk_mq_hctx_has_online_cpu() V2: - remove module parameter, meantime use queue map to check if all cpus in one hctx are offline block/blk-mq.c | 51 ++++++++++++++++++++++++++++++++++++++++---------- 1 file changed, 41 insertions(+), 10 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 555ada922cf0..187fbfacb397 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -28,6 +28,7 @@ #include #include #include +#include #include @@ -2179,7 +2180,11 @@ static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx) bool tried = false; int next_cpu = hctx->next_cpu; - if (hctx->queue->nr_hw_queues == 1) + /* + * Switch to unbound work if all CPUs in this hw queue fall + * into isolated CPUs + */ + if (hctx->queue->nr_hw_queues == 1 || next_cpu >= nr_cpu_ids) return WORK_CPU_UNBOUND; if (--hctx->next_cpu_batch <= 0) { @@ -3488,14 +3493,30 @@ static bool blk_mq_hctx_has_requests(struct blk_mq_hw_ctx *hctx) return data.has_rq; } -static inline bool blk_mq_last_cpu_in_hctx(unsigned int cpu, - struct blk_mq_hw_ctx *hctx) +static bool blk_mq_hctx_has_online_cpu(struct blk_mq_hw_ctx *hctx, + unsigned int this_cpu) { - if (cpumask_first_and(hctx->cpumask, cpu_online_mask) != cpu) - return false; - if (cpumask_next_and(cpu, hctx->cpumask, cpu_online_mask) < nr_cpu_ids) - return false; - return true; + enum hctx_type type = hctx->type; + int cpu; + + /* + * hctx->cpumask has rule out isolated CPUs, but userspace still + * might submit IOs on these isolated CPUs, so use queue map to + * check if all CPUs mapped to this hctx are offline + */ + for_each_online_cpu(cpu) { + struct blk_mq_hw_ctx *h = blk_mq_map_queue_type(hctx->queue, + type, cpu); + + if (h != hctx) + continue; + + /* this hctx has at least one online CPU */ + if (this_cpu != cpu) + return true; + } + + return false; } static int blk_mq_hctx_notify_offline(unsigned int cpu, struct hlist_node *node) @@ -3503,8 +3524,7 @@ 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); - if (!cpumask_test_cpu(cpu, hctx->cpumask) || - !blk_mq_last_cpu_in_hctx(cpu, hctx)) + if (blk_mq_hctx_has_online_cpu(hctx, cpu)) return 0; /* @@ -3912,6 +3932,8 @@ static void blk_mq_map_swqueue(struct request_queue *q) } queue_for_each_hw_ctx(q, hctx, i) { + int cpu; + /* * If no software queues are mapped to this hardware queue, * disable it and free the request entries. @@ -3938,6 +3960,15 @@ static void blk_mq_map_swqueue(struct request_queue *q) */ sbitmap_resize(&hctx->ctx_map, hctx->nr_ctx); + /* + * Rule out isolated CPUs from hctx->cpumask to avoid + * running run wq worker on isolated CPU + */ + for_each_cpu(cpu, hctx->cpumask) { + if (cpu_is_isolated(cpu)) + cpumask_clear_cpu(cpu, hctx->cpumask); + } + /* * Initialize batch roundrobin counts */