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 76B81221547 for ; Mon, 10 Mar 2025 11:20:46 +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=1741605648; cv=none; b=E5U6boHM34JwulvevN6yRT33V/55iCSsjC6tyUqA/uOAw5Pn06cFVEKyBAsKVbqQBGzSD7dQT9ohzgaIMWzgeeFjfddfS2K6ydbakfIBGSwOrJcrQFcPGyRDzvyx4ZhI5JyKArwmOrJeqfmfvA7femEWv4Kf/3BFRl4m2UtFy7E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741605648; c=relaxed/simple; bh=fGr3BNhMVOr7TeVMqln/q9SDeGXkyalVL4FjxkOB3jM=; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References: MIME-Version:Content-Type; b=vDtVRb4N7t3TfyLwjWZqPgZhlCeo6FaXle9O7CZ0H6/BruewzhkTgvcNM5nXF2S7erNg1veMvT4ZBXzolrXOjM6I1tNo3kYJ5vlt4Csq07uxdIgQHSRdOrwXmRMzmPOsbBvN62/DcgtfEEIKYlNUGEkqvqFGw/mmYbIiLgb005Q= 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=ffEYzZHd; 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="ffEYzZHd" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1741605645; 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=tIGJRRONDUfWtW53ChawtWMmz7c8o56oFPc2hHVQKfM=; b=ffEYzZHdQMzagAY/QKar1ToD8/LmrxxXC7J38ukfg92e/4L03cDhV3AxROru2gxiRn1H77 lyw/DfjIzmOfsAF6Dz0+aW16c0GZCKHezxVb+eZ/Rz2OsBFfAV1cJIG4+U9nmpATpbN/F9 +R1EGknEsT45xOXqsomuNMY7kyc3TzI= Received: from mx-prod-mc-02.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-344-bcOjqFFfOgCy9g5ksPa7zg-1; Mon, 10 Mar 2025 07:20:41 -0400 X-MC-Unique: bcOjqFFfOgCy9g5ksPa7zg-1 X-Mimecast-MFC-AGG-ID: bcOjqFFfOgCy9g5ksPa7zg_1741605640 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-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7448F19560AB; Mon, 10 Mar 2025 11:20:39 +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 3ACCB1956094; Mon, 10 Mar 2025 11:20:35 +0000 (UTC) Date: Mon, 10 Mar 2025 12:20:32 +0100 (CET) From: Mikulas Patocka To: Ming Lei 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: 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-fsdevel@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 Sun, 9 Mar 2025, Ming Lei 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. > > > > 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? No - raw device means fio directly on /dev/nvme0n1 > 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 Mikulas