From patchwork Fri Mar 14 02:11:44 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 14016149 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 73C2717588 for ; Fri, 14 Mar 2025 02:12:24 +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=1741918346; cv=none; b=EeJYDFMraTODjFUZkxTyK9Du/jazGCRrA91zKZ2gnoK1CABU9e4dJpkNmGLNt2IGaYaGQh98xL6UcVwDHvUsTEjNST8f1BjGPG9iSvOvXfrrc7CG1BA3Kw+izEK7T9nC3RSBQ48DQJukK9VyyPRZfdKF1eW9uODHPGDu9SEhn+8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741918346; c=relaxed/simple; bh=gHm1+9Fr63yZCGuLdER1Pl9STie7jx/U5SsqUMMDIVw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=ca0PbfcIXvHwIPD9GEW38ZMSy0VuYB2XBPdzP0yC+eGVZ2PAiUvtpdqDCSlSaUmpCapKBCOAK5d3qbYFZZRIHwgfL6fVACRwYUzUzqAEb6z48qm0yP+tP14du+QEYuBEkuCDzEdesKRr8qFt78NAeYNaJNrhXoIaH4YNH8XG908= 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=UMvdJHOF; 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="UMvdJHOF" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1741918343; 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=AjF5jQkybIwVeLwRpnIgYis0nR2Ur+KxbDfyjyny6iM=; b=UMvdJHOFJr1Si5fWbETcLYQH5yNYlyPKBmC5qaIoK1FSBAqP1JZfhwuU/FQJ+7Uhlmwveh LaHOH37NftBoAVJwe7VIyqRtCx+ZBlHHBhycQu4mKqtQJAXfuXxN0cBFqG7ehEH7MA8mJz QVfnIo94kaQGf5x9EUt7zAi8QCHfWug= Received: from mx-prod-mc-01.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-556-B7LZZ9wwM3mlBvjxq2r0kA-1; Thu, 13 Mar 2025 22:12:18 -0400 X-MC-Unique: B7LZZ9wwM3mlBvjxq2r0kA-1 X-Mimecast-MFC-AGG-ID: B7LZZ9wwM3mlBvjxq2r0kA_1741918336 Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A8F4B1956055; Fri, 14 Mar 2025 02:12:16 +0000 (UTC) Received: from localhost (unknown [10.72.120.27]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id BAC1319373D7; Fri, 14 Mar 2025 02:12:15 +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 4/5] loop: try to handle loop aio command via NOWAIT IO first Date: Fri, 14 Mar 2025 10:11:44 +0800 Message-ID: <20250314021148.3081954-5-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: dm-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 Try to handle loop aio command via NOWAIT IO first, then we can avoid to queue the aio command into workqueue. This is usually one big win in case that FS block mapping is stable, Mikulas verified [1] that this way improves IO perf by close to 5X in 12jobs sequential read/write test. Fallback to workqueue in case of -EAGAIN. This way may bring a little cost from the 1st retry, but when running the following write test over loop/sparse_file, the actual effect on randwrite is obvious: ``` truncate -s 4G 1.img #1.img is created on XFS/virtio-scsi losetup -f 1.img --direct-io=on fio --direct=1 --bs=4k --runtime=40 --time_based --numjobs=1 --ioengine=libaio \ --iodepth=16 --group_reporting=1 --filename=/dev/loop0 -name=job --rw=$RW ``` - RW=randwrite: obvious IOPS drop observed - RW=write: a little drop(%5 - 10%) This perf drop on randwrite over sparse file will be addressed in the following patch. BLK_MQ_F_BLOCKING has to be set for calling into .read_iter() or .write_iter() which might sleep even though it is NOWAIT, and the only effect is that rcu read lock is replaced with srcu read lock. Link: https://lore.kernel.org/linux-block/a8e5c76a-231f-07d1-a394-847de930f638@redhat.com/ [1] Signed-off-by: Ming Lei --- drivers/block/loop.c | 51 ++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 47 insertions(+), 4 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 81f6ba9bc911..542b1fe938a7 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -92,6 +92,8 @@ struct loop_cmd { #define LOOP_IDLE_WORKER_TIMEOUT (60 * HZ) #define LOOP_DEFAULT_HW_Q_DEPTH 128 +static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd); + static DEFINE_IDR(loop_index_idr); static DEFINE_MUTEX(loop_ctl_mutex); static DEFINE_MUTEX(loop_validate_mutex); @@ -393,6 +395,15 @@ static void lo_rw_aio_do_completion(struct loop_cmd *cmd) if (!atomic_dec_and_test(&cmd->ref)) return; + + /* -EAGAIN could be returned from bdev's ->ki_complete */ + if (cmd->ret == -EAGAIN) { + struct loop_device *lo = rq->q->queuedata; + + loop_queue_work(lo, cmd); + return; + } + kfree(cmd->bvec); if (likely(!blk_should_fake_timeout(rq->q))) blk_mq_complete_request(rq); @@ -498,15 +509,38 @@ static int lo_submit_rw_aio(struct loop_device *lo, struct loop_cmd *cmd, static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd) { unsigned int nr_bvec = lo_cmd_nr_bvec(cmd); - int ret = lo_rw_aio_prep(lo, cmd, nr_bvec); + int ret; - if (ret >= 0) - ret = lo_submit_rw_aio(lo, cmd, nr_bvec); + /* + * This command is prepared, and we have tried IOCB_NOWAIT, but got + * -EAGAIN, so clear it now + */ + cmd->iocb.ki_flags &= ~IOCB_NOWAIT; + ret = lo_submit_rw_aio(lo, cmd, nr_bvec); if (ret != -EIOCBQUEUED) lo_rw_aio_complete(&cmd->iocb, ret); return 0; } +static blk_status_t lo_rw_aio_nowait(struct loop_device *lo, + struct loop_cmd *cmd) +{ + unsigned int nr_bvec = lo_cmd_nr_bvec(cmd); + int ret = lo_rw_aio_prep(lo, cmd, nr_bvec); + + if (unlikely(ret < 0)) + return BLK_STS_IOERR; + + cmd->iocb.ki_flags |= IOCB_NOWAIT; + ret = lo_submit_rw_aio(lo, cmd, nr_bvec); + if (ret == -EAGAIN) + return BLK_STS_AGAIN; + + if (ret != -EIOCBQUEUED) + lo_rw_aio_complete(&cmd->iocb, ret); + return BLK_STS_OK; +} + static int do_req_filebacked(struct loop_device *lo, struct request *rq) { struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq); @@ -1937,6 +1971,14 @@ static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx, break; } + if (cmd->use_aio) { + blk_status_t res = lo_rw_aio_nowait(lo, cmd); + + if (res != BLK_STS_AGAIN) + return res; + /* fallback to workqueue for handling aio */ + } + loop_queue_work(lo, cmd); return BLK_STS_OK; @@ -2087,7 +2129,8 @@ static int loop_add(int i) lo->tag_set.queue_depth = hw_queue_depth; lo->tag_set.numa_node = NUMA_NO_NODE; lo->tag_set.cmd_size = sizeof(struct loop_cmd); - lo->tag_set.flags = BLK_MQ_F_STACKING | BLK_MQ_F_NO_SCHED_BY_DEFAULT; + lo->tag_set.flags = BLK_MQ_F_STACKING | BLK_MQ_F_NO_SCHED_BY_DEFAULT | + BLK_MQ_F_BLOCKING; lo->tag_set.driver_data = lo; err = blk_mq_alloc_tag_set(&lo->tag_set);