[Xquartz-dev] Main kumppa's CPU eater (XScreenSaver being slow)

[Jeremy Huddleston]

On Jul 26, 2009, at 12:26, Platon Fomichev wrote:

> Hi Everybody
>
> Jeremy, thanks for answer I will profile the hack on Leopard with  
> latest X11 to see the bottleneck.
> Meanwhile I can right away name the main X11 API that's drives this  
> hack - it's XCopyArea - previously
> it was specifically accelerated. The source and destination are the  
> same window, that's why theoretically
> this hack should be very fast - we take pixels from window and copy  
> them in the same window.
>
> P.S.
>
> XCopyArea emulation (window->window) is the major bottleneck for  
> pure OS X port as well btw because there is no low level API in OS X  
> that can do such blits.

Those blits are exposed via libXplugin and are used in rlAccel.  This  
XCopyArea issue was the main reason I suspected that rlAccel being  
removed was the primary culprit.  But when I re-enabled rlAccel, I  
only got a ~30% performance boost (from 7 to 9 fps).  Granted 30% is a  
big gain, but seeing those numbers so low makes me think there is a  
bigger bottleneck somewhere else.