Re: [Qemu-devel] Re: Qemu 2D performance plunges below acceptable levels

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

Paul Brook wrote:

>>      SDL_BlitSurface(guest_screen, &rec, real_screen, &rec);
>> -    SDL_UpdateRect(real_screen, x, y, w, h);
>> +    SDL_UpdateRects(real_screen, 1, &rec);
> 
> Have you actually tried this? I'd be amazed and dismayed if it made any 
> difference. I can believe that SDL_UpdateRects is better that *multiple* 
> calls to SDL_UpdateRect. However I see absolutely no justification for this 
> change.
> 

Of course I didn't: I don't have any MacOSX available and this is the
main reason I am asking other people to test this patch and doing it myself.

>From the documentation I thought they were implemented differently
somehow but now that you make me think about it I went through the
actual code and SDL_UpdateRect is implemented using SDL_UpdateRects :(

Also I don't how to explain the fact that SDL_Flip is faster than
SDL_UpdateRect on MacOSX according to malc: the same libsdl macosx faq I
 linked before claims that SDL_DOUBLEBUF is not even supported on MacOsX.