From patchwork Fri Mar 14 02:11:45 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 14016156 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 E7A2E38DD8 for ; Fri, 14 Mar 2025 02:12:26 +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=1741918348; cv=none; b=r07nuUzRrXkJb/jX/B0bh/Qpz/V+Z4YUgXcWppqSHNJaSCyhQoQNpWJQ0MYcuu4BXpmpfaKNLU57PBhFDpItOErAX7rwuIU/5/Rc6pi057Omr70HMvYxqmlLPULf0em++P4yCYlDH/9QnT5RnO3IHzl+vIVKgAZ+eSADmmw4o6c= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741918348; c=relaxed/simple; bh=menII101TGojYykHQ6b+MfZFAVmDh/is6WcbZSElUuI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JoR+iADNiN/x6a5BBu9/CkZ4T+xqNjwUJ3wJwUk7HyBGzcNpJmiYBrF+6HLg7qBNX9Rzj59fYC1ucQNzSWb8H5k6xBvwBZJnmU/0Edl1by2YMLcj6H92shy9rgUx56EOR6EwholiJ2NupuGZ36G8szv+KW+cjLTY2Fek7/dCBMw= 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=MO9D9FFt; 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="MO9D9FFt" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1741918345; 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: in-reply-to:in-reply-to:references:references; bh=wWBFjWQhhDx9tAlh9GEaUJkOGUMPicNbteHnVS/NWDs=; b=MO9D9FFtoOJ/Kgp9Ent2oyPlS/O8f2gKXEIL1xRKF2YKUx6u77O84iMgWLarnTpGGlb1mb 6ZZhq/eYGx/kxiQyiDiliOFu6E1XgmJS3giCeHGJ0XeeAukIXq6hWTFNDWB46g7KCPgqLp QMbfwzukiFo74z8bHL0kLQSUDfsXCWw= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-27-So7hWVESM3q-NwN3DmOVSA-1; Thu, 13 Mar 2025 22:12:22 -0400 X-MC-Unique: So7hWVESM3q-NwN3DmOVSA-1 X-Mimecast-MFC-AGG-ID: So7hWVESM3q-NwN3DmOVSA_1741918341 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (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 mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3A10D180034D; Fri, 14 Mar 2025 02:12:21 +0000 (UTC) Received: from localhost (unknown [10.72.120.27]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id C851B3003770; Fri, 14 Mar 2025 02:12:19 +0000 (UTC) From: Ming Lei To: Jens Axboe , linux-block@vger.kernel.org Cc: Christoph Hellwig , Jooyung Han , Mike Snitzer , zkabelac@redhat.com, dm-devel@lists.linux.dev, Alasdair Kergon , Ming Lei Subject: [PATCH V2 5/5] loop: add hint for handling aio via IOCB_NOWAIT Date: Fri, 14 Mar 2025 10:11:45 +0800 Message-ID: <20250314021148.3081954-6-ming.lei@redhat.com> In-Reply-To: <20250314021148.3081954-1-ming.lei@redhat.com> References: <20250314021148.3081954-1-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 10.30.177.4 Add hint for using IOCB_NOWAIT to handle loop aio command for avoiding to cause write(especially randwrite) perf regression on sparse file. Try IOCB_NOWAIT in the following situations: - backing file is block device - READ aio command - there isn't queued aio non-NOWAIT WRITE, since retry of NOWAIT won't cause contention on WRITE and non-NOWAIT WRITE often implies exclusive lock. With this simple policy, perf regression of randwrte/write on sparse backing file is fixed. Meantime this way addresses perf problem[1] in case of stable FS block mapping via NOWAIT. Link: https://lore.kernel.org/dm-devel/7d6ae2c9-df8e-50d0-7ad6-b787cb3cfab4@redhat.com/ Signed-off-by: Ming Lei --- drivers/block/loop.c | 61 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 542b1fe938a7..5bf14549cf8e 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -70,6 +70,7 @@ struct loop_device { struct rb_root worker_tree; struct timer_list timer; bool sysfs_inited; + unsigned queued_wait_write; struct request_queue *lo_queue; struct blk_mq_tag_set tag_set; @@ -522,6 +523,30 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd) return 0; } +static inline bool lo_aio_need_try_nowait(struct loop_device *lo, + struct loop_cmd *cmd) +{ + struct file *file = lo->lo_backing_file; + struct inode *inode = file->f_mapping->host; + struct request *rq = blk_mq_rq_from_pdu(cmd); + + /* NOWAIT works fine for backing block device */ + if (S_ISBLK(inode->i_mode)) + return true; + + /* NOWAIT is supposed to be fine for READ */ + if (req_op(rq) == REQ_OP_READ) + return true; + + /* + * If there is any queued non-NOWAIT async WRITE , don't try new + * NOWAIT WRITE for avoiding contention + * + * Here we focus on handling stable FS block mapping via NOWAIT + */ + return READ_ONCE(lo->queued_wait_write) == 0; +} + static blk_status_t lo_rw_aio_nowait(struct loop_device *lo, struct loop_cmd *cmd) { @@ -531,6 +556,9 @@ static blk_status_t lo_rw_aio_nowait(struct loop_device *lo, if (unlikely(ret < 0)) return BLK_STS_IOERR; + if (!lo_aio_need_try_nowait(lo, cmd)) + return BLK_STS_AGAIN; + cmd->iocb.ki_flags |= IOCB_NOWAIT; ret = lo_submit_rw_aio(lo, cmd, nr_bvec); if (ret == -EAGAIN) @@ -821,12 +849,18 @@ static ssize_t loop_attr_dio_show(struct loop_device *lo, char *buf) return sysfs_emit(buf, "%s\n", dio ? "1" : "0"); } +static ssize_t loop_attr_nr_wait_write_show(struct loop_device *lo, char *buf) +{ + return sysfs_emit(buf, "%u\n", lo->queued_wait_write); +} + LOOP_ATTR_RO(backing_file); LOOP_ATTR_RO(offset); LOOP_ATTR_RO(sizelimit); LOOP_ATTR_RO(autoclear); LOOP_ATTR_RO(partscan); LOOP_ATTR_RO(dio); +LOOP_ATTR_RO(nr_wait_write); static struct attribute *loop_attrs[] = { &loop_attr_backing_file.attr, @@ -835,6 +869,7 @@ static struct attribute *loop_attrs[] = { &loop_attr_autoclear.attr, &loop_attr_partscan.attr, &loop_attr_dio.attr, + &loop_attr_nr_wait_write.attr, NULL, }; @@ -910,6 +945,30 @@ static inline int queue_on_root_worker(struct cgroup_subsys_state *css) } #endif +static inline void loop_inc_wait_write(struct loop_device *lo, struct loop_cmd *cmd) +{ + lockdep_assert_held(&lo->lo_mutex); + + if (cmd->use_aio){ + struct request *rq = blk_mq_rq_from_pdu(cmd); + + if (req_op(rq) == REQ_OP_WRITE) + lo->queued_wait_write += 1; + } +} + +static inline void loop_dec_wait_write(struct loop_device *lo, struct loop_cmd *cmd) +{ + lockdep_assert_held(&lo->lo_mutex); + + if (cmd->use_aio){ + struct request *rq = blk_mq_rq_from_pdu(cmd); + + if (req_op(rq) == REQ_OP_WRITE) + lo->queued_wait_write -= 1; + } +} + static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd) { struct request __maybe_unused *rq = blk_mq_rq_from_pdu(cmd); @@ -992,6 +1051,7 @@ static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd) work = &lo->rootcg_work; cmd_list = &lo->rootcg_cmd_list; } + loop_inc_wait_write(lo, cmd); list_add_tail(&cmd->list_entry, cmd_list); queue_work(lo->workqueue, work); spin_unlock_irq(&lo->lo_work_lock); @@ -2051,6 +2111,7 @@ static void loop_process_work(struct loop_worker *worker, cond_resched(); spin_lock_irq(&lo->lo_work_lock); + loop_dec_wait_write(lo, cmd); } /*