From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 0A1BE1917F1 for ; Sat, 8 Mar 2025 20:45:28 +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=1741466730; cv=none; b=JIa9KFLUB5/E4A19dgNIzaFLmGKY3IxBpricpmaftlmO1VVkfFWH1emmpsp/vku2fOX/TX2qRTi6vaOgw3a0HVNrp5kbKuJnaMat6E5xIbOH9/n7g6eK6VFaLmL5MhoIOQgAW1UioZlZ4Tm0IXSmZP3G+q7hweOyliImXJKVdw4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741466730; c=relaxed/simple; bh=PPyvufgAWR7rNTCyTZMjT4tPhN/1t/o73atSQ21maOM=; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References: MIME-Version:Content-Type; b=dEr2txLe0OoJTgXSWcmVbn2FivaTcVGK9DlO7m9/u+taaVAWiQNtcket0+qRyptG3mgKLxavX9NSNzXSJB0vWRYteEgP/5QGlIBg23h+TNI2F3W9h0UjonM5iOgVSaVP45vD0kd+mcWP4YBYyed9rH2cehAVlxox2i40Ri/UN08= 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=aEtOHZjD; 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="aEtOHZjD" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1741466727; 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=tI7vJWycCZb7O/jK+mzUBHYszZSb9B4nRDxa4wUAFKY=; b=aEtOHZjDBY8XlFjpY57VlhIkIkBa188iSuoST3bsGjlzdxzc21ll/A4g8Y/2SASVY2wTsM 51wQ33AgcE7c1t94iu/kO4SBfx1XrGZOs6J/bF1YTBirXE6YrRKqGPwKXNKpJlxrdeCFjJ kTCECdBylOucDlIbWCJiAGsUNNwd9uw= Received: from mx-prod-mc-05.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-390-ciook4O9M_GnLhMBfsuEHQ-1; Sat, 08 Mar 2025 15:45:24 -0500 X-MC-Unique: ciook4O9M_GnLhMBfsuEHQ-1 X-Mimecast-MFC-AGG-ID: ciook4O9M_GnLhMBfsuEHQ_1741466723 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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 93EC7195608B; Sat, 8 Mar 2025 20:45:22 +0000 (UTC) Received: from [10.45.224.17] (unknown [10.45.224.17]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id DDB6C1956094; Sat, 8 Mar 2025 20:45:18 +0000 (UTC) Date: Sat, 8 Mar 2025 21:45:15 +0100 (CET) From: Mikulas Patocka To: "Darrick J. Wong" 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 In-Reply-To: <20250308034945.GG2803740@frogsfrogsfrogs> Message-ID: <747a3ac0-8c5c-64d4-8857-df63112e6b72@redhat.com> 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> <20250308034945.GG2803740@frogsfrogsfrogs> 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 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 On Fri, 7 Mar 2025, Darrick J. Wong wrote: > 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. > > Are you running the loop device in directio mode? The default is to use > buffered io, which wastes pagecache /and/ sometimes trips dirty limits > throttling. The loopdev tests in fstests get noticeably faster if I > force directio mode. Yes, I am. I set it up with: losetup --direct-io=on /dev/loop0 /mnt/test/l mount -t xfs /dev/loop0 /mnt/test2 I double checked it and I got the same results. Mikulas > --D > > > 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 > > ext4/loop/ext4: > > READ: bw=274MiB/s (288MB/s), 274MiB/s-274MiB/s (288MB/s-288MB/s), io=2743MiB (2877MB), run=10001-10001msec > > WRITE: bw=275MiB/s (288MB/s), 275MiB/s-275MiB/s (288MB/s-288MB/s), io=2747MiB (2880MB), run=10001-10001msec > > xfs/loop/xfs: > > READ: bw=276MiB/s (289MB/s), 276MiB/s-276MiB/s (289MB/s-289MB/s), io=2761MiB (2896MB), run=10002-10002msec > > WRITE: bw=276MiB/s (290MB/s), 276MiB/s-276MiB/s (290MB/s-290MB/s), io=2765MiB (2899MB), run=10002-10002msec > > ext4/dm-loop/ext4: > > READ: bw=1189MiB/s (1247MB/s), 1189MiB/s-1189MiB/s (1247MB/s-1247MB/s), io=11.6GiB (12.5GB), run=10002-10002msec > > WRITE: bw=1190MiB/s (1248MB/s), 1190MiB/s-1190MiB/s (1248MB/s-1248MB/s), io=11.6GiB (12.5GB), run=10002-10002msec > > xfs/dm-loop/xfs: > > READ: bw=1209MiB/s (1268MB/s), 1209MiB/s-1209MiB/s (1268MB/s-1268MB/s), io=11.8GiB (12.7GB), run=10001-10001msec > > WRITE: bw=1210MiB/s (1269MB/s), 1210MiB/s-1210MiB/s (1269MB/s-1269MB/s), io=11.8GiB (12.7GB), run=10001-10001msec > > > > Mikulas