From patchwork Fri Mar 22 02:12:44 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 13599555 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 D8A2A3D9E for ; Fri, 22 Mar 2024 02:13:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711073587; cv=none; b=m3/kWRC5IfeUoInDxZSRI3tG31jNpAjD35EhQugDVdtapwa1D/ulixvdKihRtnAWZDIihA6SzIyYCScxaU2ZFbjuuv+RoJ0mSlnsjhlvNGYkcIKepzpL78WBdKecWq/Q46Wwbp5P9Nre9X5VvK/Rl3Kl6Vpuf58uZUNs7fOXxE0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711073587; c=relaxed/simple; bh=rmNODrghnbesIeDPV/RTWbbPsoPevkCrra+Ef1UEf/g=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=HzF8vktTW/pd0LdiBOcpAEEKSsqgknQUdSuw2dZHKI+IroDS+9vch4WJLq1o/XIeDfAP1KEASdVpBnhedV9fzNXbTLChk79iVKDXYqLxrO+F2fckojjX4udEwPG/veO5JuePzb/PUesb+Nc0SCoXQr+9cBX3vXW97D1oDqPHwWg= 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=hMJt+3gA; arc=none smtp.client-ip=170.10.133.124 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="hMJt+3gA" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1711073584; 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=u24w++o8Fciu+sjJN4D74nc+aztaWjGLyppfVLTmswY=; b=hMJt+3gAIE0j0X0BX1FF677R0XiICByQQ7lIkiIhsJb2d+FNh4egYmoggwnLmyopWxuRmd ADzRmuSvoJ++FHORmlUHdJ0IiWjFRobShf/CtEFMVKyHpVFAV2o8Ggln5m/OOIu94EHmee JpxTtJ2r4EKosAlBZJc7ETR+x17K2ko= 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-664-bbBtsjmNMqywz7c-g3W3Pw-1; Thu, 21 Mar 2024 22:12:59 -0400 X-MC-Unique: bbBtsjmNMqywz7c-g3W3Pw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (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 100698007A2; Fri, 22 Mar 2024 02:12:59 +0000 (UTC) Received: from localhost (unknown [10.72.116.75]) by smtp.corp.redhat.com (Postfix) with ESMTP id B72C4107AA; Fri, 22 Mar 2024 02:12:57 +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 V5] blk-mq: don't schedule block kworker on isolated CPUs Date: Fri, 22 Mar 2024 10:12:44 +0800 Message-ID: <20240322021244.1056223-1-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 10.11.54.5 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 Tesed-by: Joe Mario Signed-off-by: Ming Lei Reviewed-by: Ewan D. Milne --- V5: - fix comment - add one helper for document benefit - all are suggested by Jens 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 | 57 +++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 47 insertions(+), 10 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 555ada922cf0..06cd9c8068fc 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -28,6 +28,7 @@ #include #include #include +#include #include @@ -2168,6 +2169,15 @@ static inline int blk_mq_first_mapped_cpu(struct blk_mq_hw_ctx *hctx) return cpu; } +/* + * ->next_cpu is always calculated from hctx->cpumask, so simply use + * it for speeding up the check + */ +static bool blk_mq_hctx_empty_cpumask(struct blk_mq_hw_ctx *hctx) +{ + return hctx->next_cpu >= nr_cpu_ids; +} + /* * It'd be great if the workqueue API had a way to pass * in a mask and had some smarts for more clever placement. @@ -2179,7 +2189,8 @@ 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 if no allowable CPUs in this hctx */ + if (hctx->queue->nr_hw_queues == 1 || blk_mq_hctx_empty_cpumask(hctx)) return WORK_CPU_UNBOUND; if (--hctx->next_cpu_batch <= 0) { @@ -3488,14 +3499,30 @@ 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 to rule out isolated CPUs, but userspace still + * might submit IOs on these isolated CPUs, so use the 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 +3530,7 @@ 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 +3938,8 @@ 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 +3966,15 @@ 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 block kworker on isolated CPUs + */ + for_each_cpu(cpu, hctx->cpumask) { + if (cpu_is_isolated(cpu)) + cpumask_clear_cpu(cpu, hctx->cpumask); + } + /* * Initialize batch roundrobin counts */