From: Kevin Wolf <kwolf@redhat.com>
To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Avi Kivity <avi@redhat.com>, Christoph Hellwig <hch@lst.de>,
Qemu-devel@nongnu.org,
Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Subject: Re: [Qemu-devel] Default cache mode
Date: Wed, 29 Jun 2011 14:16:07 +0200 [thread overview]
Message-ID: <4E0B1787.30709@redhat.com> (raw)
In-Reply-To: <4E0B152B.1000201@codemonkey.ws>
Am 29.06.2011 14:06, schrieb Anthony Liguori:
> On 06/29/2011 06:59 AM, Kevin Wolf wrote:
>> Hi,
>>
>> I think we have touched this topic before during some IRC discussions or
>> somewhere deep in a mailing list thread, but I think it hasn't been
>> discussed on the list.
>>
>> Our default cache mode of cache=writethrough is extremely conservative
>> and provides absolute safety at the cost of performance,
>
> But for the most part, we track bare metal fairly well in terms of block
> performance, no?
>
> Or are you really referring to qcow2 as a specific example? In the
> past, we used a different default caching mode for qcow2. I think that
> could be done again if there was a compelling reason.
No, people are also complaining about bad performance with raw. Which
isn't really surprising when you do a flush after each single write
request. O_SYNC is really much more than is needed in the average case.
Kevin
next prev parent reply other threads:[~2011-06-29 12:13 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-29 11:59 [Qemu-devel] Default cache mode Kevin Wolf
2011-06-29 12:06 ` Anthony Liguori
2011-06-29 12:16 ` Kevin Wolf [this message]
2011-06-29 12:23 ` Anthony Liguori
2011-06-29 12:32 ` Kevin Wolf
2011-06-29 13:51 ` Christoph Hellwig
2011-06-29 14:17 ` Michael Tokarev
2011-06-29 14:50 ` Christoph Hellwig
2011-06-29 15:07 ` Michael Tokarev
2011-06-29 13:50 ` Christoph Hellwig
2011-06-29 14:13 ` Anthony Liguori
2011-06-29 14:47 ` Christoph Hellwig
2011-06-29 16:03 ` Stefan Hajnoczi
2011-06-29 13:53 ` Frediano Ziglio
2011-06-29 14:11 ` Kevin Wolf
2011-06-29 14:12 ` Christoph Hellwig
2011-06-29 14:21 ` Kevin Wolf
2011-06-29 13:49 ` Christoph Hellwig
2011-06-29 12:08 ` Anthony Liguori
2011-06-29 13:55 ` Christoph Hellwig
2011-06-29 14:20 ` Anthony Liguori
2011-06-29 14:52 ` Christoph Hellwig
2011-06-29 15:26 ` Anthony Liguori
2011-06-29 12:21 ` Alexander Graf
2011-06-29 13:57 ` Stefan Hajnoczi
2011-06-29 14:05 ` Alexander Graf
2011-06-29 12:52 ` Stefan Hajnoczi
2011-06-29 13:56 ` Christoph Hellwig
2011-06-29 13:00 ` Avi Kivity
2011-06-29 13:05 ` Anthony Liguori
2011-06-29 13:30 ` Avi Kivity
2011-06-29 13:11 ` Kevin Wolf
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