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Date: Wed, 30 Mar 2011 21:11:48 +0200
From: Stefan Weil <weil@mail.berlios.de>
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Subject: Re: [Qemu-devel] GSoC: Improved image format compatibility
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To: Lyu Mitnick <mitnick.lyu@gmail.com>
Cc: Stefan Hajnoczi <stefanha@gmail.com>, qemu-devel@nongnu.org

Am 30.03.2011 20:40, schrieb Lyu Mitnick:
> Hello Stefan,
>
> I have spent a whole night to trace the code of block/vpc.c and 
> compare against the VHD specifications
> (at 
> http://www.microsoft.com/downloads/en/details.aspx?FamilyID=C2D03242-2FFB-48EF-A211-F0C44741109E&amp;displaylang=en 
> <http://www.microsoft.com/downloads/en/details.aspx?FamilyID=C2D03242-2FFB-48EF-A211-F0C44741109E&amp;displaylang=en>).
> It seems that there isn't Fixed hard disk image and Differencing hard 
> disk image support now. I am wondering whether what I has
> learned from tracing code is true or false? I also found some 
> possibility of optimization in block/vpc.c. Should I contact mentor
> assigned to this project in private or post the whole idea on the 
> mailing list??
>
> thanks very much
>
> Mitnick
>


Hello Mitnick,

asynchronous i/o is also missing in block/vpc.c.

All newer block drivers support asynchronous reads and writes,
only some old drivers don't.

So adding asynchronous i/o to at least some of the old drivers
would improve their usability.

Look for "aio" in block/*.c to get a starting point.

Regards
Stefan (W.)