Re: [Xen-devel] [PATCH][HVM] remove qemu shadow_vram patch forperformance

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

I punted on this one. :-) Christian wasn't sure about it either, hence it's
not been checked in.

 -- Keir

On 20/3/07 08:38, "Li, Xin B" <xin.b.li@xxxxxxxxx> wrote:

> Keir, do you think this patch is OK?
> -Xin 
> 
>> -----Original Message-----
>> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
>> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Zhai, Edwin
>> Sent: Friday, March 16, 2007 11:04 AM
>> To: Keir Fraser
>> Cc: Ian Pratt; xen-devel@xxxxxxxxxxxxxxxxxxx; Zhai, Edwin
>> Subject: Re: [Xen-devel] [PATCH][HVM] remove qemu shadow_vram
>> patch forperformance
>> 
>> On Thu, Mar 15, 2007 at 10:50:13AM +0000, Keir Fraser wrote:
>>> 
>>> 
>>> 
>>> On 15/3/07 03:30, "Zhai, Edwin" <edwin.zhai@xxxxxxxxx> wrote:
>>> 
>>>> remove qemu shadow_vram patch and force a whole screen
>> update each time for
>>>> performance.
>>>> 
>>>> W/O this patch, there is huge performance drop in HVM
>> domain when adding other
>>>> guest(windows or linux with xwindow).
>>>> 
>>>> shadow_vram_revert.patch - revert the shadow_vram patch
>>>> shadow_vram_force_update.patch - explictly redraw screen each time
>>> 
>>> How can updating the whole screen 30 times a second be
>> faster than the
>>> memcmp() that we do currently?
>> 
>> as far as i can tell, the bottle neck is that orig method does
>> memcmp and memcpy
>> byte by byte. furthermore, orig method can void a update by
>> multiple memcmp only
>> if all bytes are equal, which is in the minority.
>> 
>> there is no doubt we need a vram dirty for qemu, but current
>> one is not the 
>> best. we can make a new one in future by shadow or something else.
>> 
>> thanks,
>> 
>>> 
>>>  -- Keir
>>> 
>> 
>> -- 
>> best rgds,
>> edwin
>> 
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>> 
> 
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