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Date: Tue, 23 Sep 2008 09:47:17 -0500
From: Anthony Liguori <aliguori@us.ibm.com>
MIME-Version: 1.0
Subject: Re: [Qemu-devel] Re: [PATCH 0/3] Refactor AIO to allow multiple AIO
	implementations
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To: Ryan Harper <ryanh@us.ibm.com>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org

Ryan Harper wrote:
> * Anthony Liguori <aliguori@us.ibm.com> [2008-09-22 22:44]:
>   
>> Can you run the same performance tests with the following patches (using 
>> sync=on instead of cache=off)?
>>
>> You'll need my aio_init fix too.  I suspect this will give equally good 
>> performance to your patch set.  That's not saying your patch set isn't 
>> useful, but I would like to get performance to be better for the case 
>> that we're going through the page cache.
>>     
>
> I can run the test, but it is orthogonal to the patchset which is
> focused on using O_DIRECT and linux-aio.
>   

Yes, I'm trying to understand where the performance is coming from.  The 
hunch is that supporting multiple simultaneous requests along is what 
did it.  O_SYNC should give similar completion behavior to O_DIRECT.

Regards,

Anthony Liguori