From: Avi Kivity <avi@redhat.com>
To: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [RFC] block-queue: Delay and batch metadata writes
Date: Mon, 20 Sep 2010 17:38:24 +0200 [thread overview]
Message-ID: <4C977FF0.40208@redhat.com> (raw)
In-Reply-To: <4C977ECF.4000907@redhat.com>
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
next prev parent reply other threads:[~2010-09-20 15:38 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-20 13:56 [Qemu-devel] [RFC] block-queue: Delay and batch metadata writes Kevin Wolf
2010-09-20 14:31 ` Anthony Liguori
2010-09-20 14:56 ` Anthony Liguori
2010-09-20 15:33 ` Kevin Wolf
2010-09-20 15:48 ` Anthony Liguori
2010-09-20 15:08 ` Kevin Wolf
2010-09-20 15:33 ` Avi Kivity
2010-09-20 15:38 ` Avi Kivity [this message]
2010-09-20 15:46 ` Kevin Wolf
2010-09-20 15:40 ` Anthony Liguori
2010-09-20 15:55 ` Kevin Wolf
2010-09-20 16:34 ` Anthony Liguori
2010-09-20 15:51 ` Anthony Liguori
2010-09-20 16:05 ` Avi Kivity
2010-09-21 9:13 ` Kevin Wolf
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