From: Anthony Liguori <anthony@codemonkey.ws>
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 10:51:47 -0500 [thread overview]
Message-ID: <4C978313.9060402@codemonkey.ws> (raw)
In-Reply-To: <4C9778EC.9060704@redhat.com>
On 09/20/2010 10:08 AM, Kevin Wolf wrote:
>
>> If you're comfortable with a writeback cache for metadata, then you
>> should also be comfortable with a writeback cache for data in which
>> case, cache=writeback is the answer.
>>
> Well, there is a difference: We don't pollute the host page cache with
> guest data and we don't get a virtual "disk cache" as big as the host
> RAM, but only a very limited queue of metadata.
>
Would it be a mortal sin to open the file twice and have a cache=none
version for data and cache=writeback for metadata?
The two definitely aren't consistent with each other but I think the
whole point here is that we don't care.
It opens up some other possibilities too like cache=none for data and
cache=writethrough for metadata which may be a useful combination.
Regards,
Anthony Liguori
next prev parent reply other threads:[~2010-09-20 15:52 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
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 [this message]
2010-09-20 16:05 ` Avi Kivity
2010-09-21 9:13 ` Kevin Wolf
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