From patchwork Sat Mar 22 01:26:14 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ming Lei X-Patchwork-Id: 14026135 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 3536A200B0 for ; Sat, 22 Mar 2025 01:27:03 +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=1742606824; cv=none; b=AP3zUa7GHmLwSa7k8jNEK/GTqfKKecPEvHsT7/cMsgIY6Z2gzfep260gouSxsE+aFd5/oDIZ7FXn9hsahLUklrQSGhYKEK6TCPgvRIch/3PQUPYLU73Ks1C85Lsbp9L1KTSw+Q1C2Xb07NNs15Du11dlvcHd2W3t9eu3oTXaluY= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742606824; c=relaxed/simple; bh=MfuJx2JFE7rySp1wL8KWaIeNvk+j4K/SO9XmQTgbmDM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=C2wDw/K9WHKevUqPxkCvEvfcvkTFdK8YujWiPm6TQX9g08kDiH9vEpL5pqPlwjGJH2VvhK5qh00eZizuSCcp+LXS8/vLIF/NPkGUm+MTCTgA94m4H5zJh8owMzNnyofIodvQ4pVPYqwtjXfNuOW5u5rMlg+hoipNmod9K7JubHs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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=A39lNMWl; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine 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="A39lNMWl" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1742606822; 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=V5AkDzj9Edwtpo2uTQ1fy7/wklQm03FMr+RqJXBF5uA=; b=A39lNMWlcozoHFJRK37OfhRQ3VS2EKRVXDGNXF8IUKNVzehA6ATUlxTPBHLIWC4Ig4ZKWP Z1D0LnDlCDCebQtngWxTEgopltgX+qc/EKicxJpDUhcECk2z3DrG1/b/UPhj+Xc0oB0Wrb wwWQ8nf81Y7/n5d7HaUuJgUolzbDDGU= Received: from mx-prod-mc-04.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-191-aI3_AqM_PwCNMa_S-NhfFw-1; Fri, 21 Mar 2025 21:26:59 -0400 X-MC-Unique: aI3_AqM_PwCNMa_S-NhfFw-1 X-Mimecast-MFC-AGG-ID: aI3_AqM_PwCNMa_S-NhfFw_1742606818 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (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-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E786E1903081; Sat, 22 Mar 2025 01:26:57 +0000 (UTC) Received: from localhost (unknown [10.72.120.2]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 4934D180174E; Sat, 22 Mar 2025 01:26:55 +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 , Mikulas Patocka , Ming Lei Subject: [PATCH V3 5/5] loop: add hint for handling aio via IOCB_NOWAIT Date: Sat, 22 Mar 2025 09:26:14 +0800 Message-ID: <20250322012617.354222-6-ming.lei@redhat.com> In-Reply-To: <20250322012617.354222-1-ming.lei@redhat.com> References: <20250322012617.354222-1-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 10.30.177.93 Add hint for using IOCB_NOWAIT to handle loop aio command for avoiding to cause write(especially randwrite) perf regression on sparse backed file. Try IOCB_NOWAIT in the following situations: - backing file is block device OR - READ aio command OR - there isn't any queued blocking async WRITEs, because NOWAIT won't cause contention with blocking WRITE, which often implies exclusive lock With this simple policy, perf regression of randwrite/write on sparse backing file is fixed. Link: https://lore.kernel.org/dm-devel/7d6ae2c9-df8e-50d0-7ad6-b787cb3cfab4@redhat.com/ Signed-off-by: Ming Lei --- drivers/block/loop.c | 56 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 56 insertions(+) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 3baabf150488..e1b01285da2a 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -68,6 +68,7 @@ struct loop_device { struct rb_root worker_tree; struct timer_list timer; bool sysfs_inited; + unsigned lo_nr_blocking_writes; struct request_queue *lo_queue; struct blk_mq_tag_set tag_set; @@ -514,6 +515,33 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd) return 0; } +static inline bool lo_aio_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 without contending with + * blocking WRITE + */ + 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->lo_nr_blocking_writes) == 0; +} + static blk_status_t lo_rw_aio_nowait(struct loop_device *lo, struct loop_cmd *cmd) { @@ -523,6 +551,9 @@ static blk_status_t lo_rw_aio_nowait(struct loop_device *lo, if (unlikely(ret < 0)) return BLK_STS_IOERR; + if (!lo_aio_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) @@ -820,12 +851,19 @@ 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_blocking_writes_show(struct loop_device *lo, + char *buf) +{ + return sysfs_emit(buf, "%u\n", lo->lo_nr_blocking_writes); +} + 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_blocking_writes); static struct attribute *loop_attrs[] = { &loop_attr_backing_file.attr, @@ -834,6 +872,7 @@ static struct attribute *loop_attrs[] = { &loop_attr_autoclear.attr, &loop_attr_partscan.attr, &loop_attr_dio.attr, + &loop_attr_nr_blocking_writes.attr, NULL, }; @@ -909,6 +948,19 @@ static inline int queue_on_root_worker(struct cgroup_subsys_state *css) } #endif +static inline void loop_update_blocking_writes(struct loop_device *lo, + struct loop_cmd *cmd, bool inc) +{ + lockdep_assert_held(&lo->lo_mutex); + + if (req_op(blk_mq_rq_from_pdu(cmd)) == REQ_OP_WRITE) { + if (inc) + lo->lo_nr_blocking_writes += 1; + else + lo->lo_nr_blocking_writes -= 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); @@ -991,6 +1043,8 @@ static void loop_queue_work(struct loop_device *lo, struct loop_cmd *cmd) work = &lo->rootcg_work; cmd_list = &lo->rootcg_cmd_list; } + if (cmd->use_aio) + loop_update_blocking_writes(lo, cmd, true); list_add_tail(&cmd->list_entry, cmd_list); queue_work(lo->workqueue, work); spin_unlock_irq(&lo->lo_work_lock); @@ -2057,6 +2111,8 @@ static void loop_process_work(struct loop_worker *worker, cond_resched(); spin_lock_irq(&lo->lo_work_lock); + if (cmd->use_aio) + loop_update_blocking_writes(lo, cmd, false); } /*