From mboxrd@z Thu Jan 1 00:00:00 1970 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 29155136A for ; Sun, 9 Mar 2025 00:17:12 +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=1741479434; cv=none; b=mO1XLAbpZwd8T+0FR6a4tYIBBbGaHgl3TqGDZuGNFDJBakEyT8D9kb2zBzeJWk6D7B7cN7E/TiA12MP9qC3gSHrY+4UlS0Qgwwbi3MGxl2dJrC0Bqn0Dtk6sjwiu5k7daT9rGEFG1xO9YqqIOSUWXt5ACFlxCFIiU4GzahVx5Y4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741479434; c=relaxed/simple; bh=THtDhScMln822aq4Vmu3UXX6XJfr22NYp7F82DStE0o=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KGVJh3X1tpMyzH71zq2yf6LNCurtSumnmaLySy+MfZj51CFnXTC8mWs7z8CNqa79+t82V9VHWX6hWvaJXLeGksi9bxfyNQ1czCdAWj5kwoVHc/Lvd6BzA5a0bnAa5wUJR6cXQeiwKafWxPB8ss7ahpGTkJxz1LILS0IF6p30fm8= 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=SiGOxgqa; 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="SiGOxgqa" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1741479431; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=cDsahH8DeVAVtVpMyFzohcPlKXp1v4nXuT8Fv8DeuVM=; b=SiGOxgqa1w4AZYOIfeHWvqnb0AdzcBTR7vuaa6pPW1+nmp1U1p0AZfx9xqReda0nN7Hj5m piSB9UzKGSKT/TR4mf6Ki482pDsJSrP7DToo6kicrPrxgl/LvwKM7TemOSdwwxyq3LGHfT /QdOHmWC9QhgpQre6TT7Z/BwNHLwwuQ= Received: from mx-prod-mc-08.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-463-zCNv-e6dO1CSX27mJyXhQA-1; Sat, 08 Mar 2025 19:17:08 -0500 X-MC-Unique: zCNv-e6dO1CSX27mJyXhQA-1 X-Mimecast-MFC-AGG-ID: zCNv-e6dO1CSX27mJyXhQA_1741479427 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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 0D4E618004A9; Sun, 9 Mar 2025 00:17:07 +0000 (UTC) Received: from fedora (unknown [10.72.120.5]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E852C300019E; Sun, 9 Mar 2025 00:16:57 +0000 (UTC) Date: Sun, 9 Mar 2025 08:16:51 +0800 From: Ming Lei To: Mikulas Patocka Cc: Dave Chinner , Christoph Hellwig , Jens Axboe , Jooyung Han , Alasdair Kergon , Mike Snitzer , Heinz Mauelshagen , zkabelac@redhat.com, dm-devel@lists.linux.dev, linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] the dm-loop target Message-ID: References: <7d6ae2c9-df8e-50d0-7ad6-b787cb3cfab4@redhat.com> <8adb8df2-0c75-592d-bc3e-5609bb8de8d8@redhat.com> <1fde6ab6-bfba-3dc4-d7fb-67074036deb0@redhat.com> <81b037c8-8fea-2d4c-0baf-d9aa18835063@redhat.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <81b037c8-8fea-2d4c-0baf-d9aa18835063@redhat.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 On Fri, Mar 07, 2025 at 04:21:58PM +0100, Mikulas Patocka wrote: > > I didn't say you were. I said the concept that dm-loop is based on > > is fundamentally flawed and that your benchmark setup does not > > reflect real world usage of loop devices. > > > Where are the bug reports about the loop device being slow and the > > analysis that indicates that it is unfixable? > > So, I did benchmarks on an enterprise nvme drive (SAMSUNG > MZPLJ1T6HBJR-00007). I stacked ext4/loop/ext4, xfs/loop/xfs (using losetup > --direct-io=on), ext4/dm-loop/ext4 and xfs/dm-loop/xfs. And loop is slow. > > synchronous I/O: > fio --direct=1 --bs=4k --runtime=10 --time_based --numjobs=12 --ioengine=psync --iodepth=1 --group_reporting=1 --filename=/mnt/test2/l -name=job --rw=rw > raw block device: > READ: bw=399MiB/s (418MB/s), 399MiB/s-399MiB/s (418MB/s-418MB/s), io=3985MiB (4179MB), run=10001-10001msec > WRITE: bw=399MiB/s (418MB/s), 399MiB/s-399MiB/s (418MB/s-418MB/s), io=3990MiB (4184MB), run=10001-10001msec > ext4/loop/ext4: > READ: bw=223MiB/s (234MB/s), 223MiB/s-223MiB/s (234MB/s-234MB/s), io=2232MiB (2341MB), run=10002-10002msec > WRITE: bw=223MiB/s (234MB/s), 223MiB/s-223MiB/s (234MB/s-234MB/s), io=2231MiB (2339MB), run=10002-10002msec > xfs/loop/xfs: > READ: bw=220MiB/s (230MB/s), 220MiB/s-220MiB/s (230MB/s-230MB/s), io=2196MiB (2303MB), run=10001-10001msec > WRITE: bw=219MiB/s (230MB/s), 219MiB/s-219MiB/s (230MB/s-230MB/s), io=2193MiB (2300MB), run=10001-10001msec > ext4/dm-loop/ext4: > READ: bw=338MiB/s (355MB/s), 338MiB/s-338MiB/s (355MB/s-355MB/s), io=3383MiB (3547MB), run=10002-10002msec > WRITE: bw=338MiB/s (355MB/s), 338MiB/s-338MiB/s (355MB/s-355MB/s), io=3385MiB (3549MB), run=10002-10002msec > xfs/dm-loop/xfs: > READ: bw=375MiB/s (393MB/s), 375MiB/s-375MiB/s (393MB/s-393MB/s), io=3752MiB (3934MB), run=10002-10002msec > WRITE: bw=376MiB/s (394MB/s), 376MiB/s-376MiB/s (394MB/s-394MB/s), io=3756MiB (3938MB), run=10002-10002msec > > asynchronous I/O: > fio --direct=1 --bs=4k --runtime=10 --time_based --numjobs=12 --ioengine=libaio --iodepth=16 --group_reporting=1 --filename=/mnt/test2/l -name=job --rw=rw > raw block device: > READ: bw=1246MiB/s (1306MB/s), 1246MiB/s-1246MiB/s (1306MB/s-1306MB/s), io=12.2GiB (13.1GB), run=10001-10001msec > WRITE: bw=1247MiB/s (1308MB/s), 1247MiB/s-1247MiB/s (1308MB/s-1308MB/s), io=12.2GiB (13.1GB), run=10001-10001msec BTW, raw device is supposed to be xfs or ext4 over raw block device, right? Otherwise, please provide test data for this case, then it becomes one fair comparison because there should be lock contention for FS write IOs on same file. Thanks, Ming