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Date: Tue, 22 Feb 2011 17:15:56 +0100
From: Kevin Wolf <kwolf@redhat.com>
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Subject: Re: [Qemu-devel] Re: Strategic decision: COW format
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: Chunqiang Tang <ctang@us.ibm.com>, Markus Armbruster <armbru@redhat.com>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, qemu-devel@nongnu.org

Am 22.02.2011 16:57, schrieb Anthony Liguori:
> On 02/22/2011 02:56 AM, Kevin Wolf wrote:
>>
>> *sigh*
>>
>> It starts to get annoying, but if you really insist, I can repeat it
>> once more: These features that you don't need (this is the correct
>> description for what you call "misfeatures") _are_ implemented in a way
>> that they don't impact the "normal" case.
> 
> Except that they require a refcount table that adds additional metadata 
> that needs to be updated in the fast path.  I consider that impacting 
> the normal case.

Like it or not, this requirement exists anyway, without any of your
"misfeatures".

You chose to use the dirty flag in QED in order to avoid having to flush
metadata too often, which is an approach that any other format, even one
using refcounts, can take as well.

Kevin