From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from [140.186.70.92] (port=58577 helo=eggs.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1OxiRq-00039W-1f
	for qemu-devel@nongnu.org; Mon, 20 Sep 2010 11:38:31 -0400
Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69)
	(envelope-from <avi@redhat.com>) id 1OxiRo-0005ca-Pc
	for qemu-devel@nongnu.org; Mon, 20 Sep 2010 11:38:29 -0400
Received: from mx1.redhat.com ([209.132.183.28]:40173)
	by eggs.gnu.org with esmtp (Exim 4.69)
	(envelope-from <avi@redhat.com>) id 1OxiRo-0005cI-Ca
	for qemu-devel@nongnu.org; Mon, 20 Sep 2010 11:38:28 -0400
Received: from int-mx01.intmail.prod.int.phx2.redhat.com
	(int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11])
	by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id o8KFcRYT011611
	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK)
	for <qemu-devel@nongnu.org>; Mon, 20 Sep 2010 11:38:27 -0400
Message-ID: <4C977FF0.40208@redhat.com>
Date: Mon, 20 Sep 2010 17:38:24 +0200
From: Avi Kivity <avi@redhat.com>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] [RFC] block-queue: Delay and batch metadata writes
References: <1284991010-10951-1-git-send-email-kwolf@redhat.com>	<4C977028.3050602@codemonkey.ws>	<4C9778EC.9060704@redhat.com>
	<4C977ECF.4000907@redhat.com>
In-Reply-To: <4C977ECF.4000907@redhat.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.nongnu.org/archive/html/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-devel@nongnu.org

  On 09/20/2010 05:33 PM, Avi Kivity wrote:
>  On 09/20/2010 05:08 PM, Kevin Wolf wrote:
>> >
>> >  Let's expand it a bit more:
>> >
>> >  1. Update refcount table
>> >  2. bdrv_flush
>> >  3. Update L2 entry
>> >  4. Write data to disk
>> >  5. Report write complete
>> >
>> >  I'm struggling to understand how a thread helps out.
>>
>> This sequence becomes:
>>
>> 1. Update refcount table
>> 2. Write data to disk
>> 3. Report write complete
>>
>> And only later:
>>
>> 4. Update L2 entry
>> 5. bdrv_flush (possibly merged with other flushes)
>>
>
> The L2 update needs to happen after we're sure the refcount update is 
> stable, so need a bdrv_flush between them.
>
> Still, the basic idea looks sound.  You can do many refcount updates, 
> flush, many L2 updates, flush.
>


Oh, your original RFC has that flush in place, so all is good.

-- 
error compiling committee.c: too many arguments to function