Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757980Ab0HQQ1Y (ORCPT ); Tue, 17 Aug 2010 12:27:24 -0400 Received: from hera.kernel.org ([140.211.167.34]:53355 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757545Ab0HQQ1X (ORCPT ); Tue, 17 Aug 2010 12:27:23 -0400 Message-ID: <4C6AB74E.7080909@kernel.org> Date: Tue, 17 Aug 2010 18:22:38 +0200 From: Tejun Heo User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); en-US; rv:1.9.2.8) Gecko/20100802 Thunderbird/3.1.2 MIME-Version: 1.0 To: Christoph Hellwig CC: jaxboe@fusionio.com, linux-fsdevel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, James.Bottomley@suse.de, tytso@mit.edu, chris.mason@oracle.com, swhiteho@redhat.com, konishi.ryusuke@lab.ntt.co.jp, dm-devel@redhat.com, vst@vlnb.net, jack@suse.cz, rwheeler@redhat.com, hare@suse.de, neilb@suse.de, rusty@rustcorp.com.au, mst@redhat.com Subject: Re: [PATCH 2/5] virtio_blk: implement REQ_FLUSH/FUA support References: <1281977523-19335-1-git-send-email-tj@kernel.org> <1281977523-19335-3-git-send-email-tj@kernel.org> <20100816183317.GA28171@lst.de> <4C6A458B.5040407@kernel.org> <20100817132327.GA3347@lst.de> In-Reply-To: <20100817132327.GA3347@lst.de> X-Enigmail-Version: 1.1.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.3 (hera.kernel.org [127.0.0.1]); Tue, 17 Aug 2010 16:25:51 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1132 Lines: 31 Hello, On 08/17/2010 03:23 PM, Christoph Hellwig wrote: >> Hmmm... the underlying storage could be md/dm RAIDs in which case FUA >> should be cheaper than FLUSH. > > If someone ever wrote a virtio-blk backend that sits directly ontop > of the Linux block layer that would be true. Of the five known > virtio-blk backends all operate on normal files using the Posix I/O > APIs, or the Linux aio API (optionally in qemu) or in-kernel > vfs_read/vfs_write (vhost-blk). Right. > Given how little testing lguest gets compared to qemu I really don't > want a protocol addition for it unless it really buys us something. > Once we're done with this barrier conversion I plan into benchmarking > FUA and a pre-flush tag on the command for virtio in real life setups, > and see if it actually buys us anything. Hmmm... yeah, we can drop it. Michael, what do you think? Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/