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Date: Fri, 07 Nov 2008 09:31:30 +0100
From: Kevin Wolf <kwolf@suse.de>
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Subject: Re: [Qemu-devel] [PATCH 0/4] qcow2: Improve cluster refcount update
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To: qemu-devel@nongnu.org
Cc: Laurent Vivier <Laurent.Vivier@libertysurf.fr>

Anthony Liguori schrieb:
> Laurent Vivier wrote:
>> This series of patches improves qcow2 performance with O_DIRECT
>> when the qcow2 file is empty and we begin to fill it.
>>   
> 
> I really dislike this series and any future series that does similar
> things.  The real problem is that non-aligned accesses are so slow, but
> there's no reason that they must be so slow.  It's because we're doing
> synchronous IO operations instead of using posix-aio like we should. 
> That's the real problem.  Just doing a memory copy to an aligned buffer
> is not going to cause that much performance delay.

Even if you don't like the alignment part, patches 1 and 2 are still
useful, IMHO.

Kevin