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Re: [xougen] Arch specific optimizations [XAA]

From: emmanuel ALLAUD
Subject: Re: [xougen] Arch specific optimizations [XAA]
Date: Fri, 5 Sep 2003 18:25:31 +0200 (CEST)

 --- ">> G-LiTe /" <address@hidden> a écrit : >
emmanuel ALLAUD wrote:
> >    Hi all,
> >I've read on this list (was RENDER extension
> thread)
> >that part of XFree were actually much slower than
> >imlib2 IIRC. The problems boiled down to the fact
> that
> >imlib2 uses MMX or other x586 specific asm
> >instructions which allowes to be like 3 times
> faster
> >(this is not an average, I don't think there is a
> >global benchmark).
> >My question is is that feasible (and desirable) to
> >borrow some of this code (perhaps also from others
> >good image manipualtion libs) and use it in XFree.
> >I know this will be more troubles for portability,
> but
> >if the functions to be arch-specific are well
> chosen
> >(that's the hard part) ie only a few small
> functions
> >with well determined purpose, this would give us
> good
> >optimization without much hassle for the
> portability
> >(the fallback being the old function if the arch
> has
> >no specific version of the opt. function).
> >Bye
> >Manu
> >  
> >
> First of all: slashdot is great, isn't it? ;)
> Second: x586 is not an architecture, but it should
> be pretty obvious 
> what you actually meant. ;)
> And finally: That article was indeed a comparison
> between Rasterman's 
> IMLib 2 and XRender. The problem, however, was that
> XRender wasn't 
> accelerated by most video drivers and thus not at
> all. It doesn't even 
> use architecture specific optimizations, or it
> would've been as fast as 
> IMLib. If I recall correctly, only nvidia and some
> other card's drivers 
> have accelerated XRender. It would indeed be very
> nice to have this 
> accelerated by the video drivers and possibly using
> OpenGL as described 
> on the wiki somewhere. Architecture specific
> optimizations sound 
> interesting too. Software XRender is one of the
> things we can optimize 
> with this, I guess. (for X servers using VESA and
> the likes) I think we 
> can definitly use some of IMLib's code for that and
> maybe even ask 
> Rasterman himself to help. Portability shouldn't be
> a problem: it should 
> be possible to just have it detect the architecture
> at some point, 
> either at runtime or during the build process. An
> option for runtime 
> would be nice for distributions.

Actually I have followed the thread on XFree devel
list between Rasterman and X people. They were moslty
talking of XRender, but at some point I've quite of
understood that Rasterman was arguing that software
XRender functions were really suboptimal, and he
confirmed that to me adding that even before doing any
arch specific optimization, we should first optimize
the way these functions are handling things (sorry to
be so imprecise, I hope I can have precisions on the
actual issues).
So basically there is room for improvment, and we can
certainly have hints looking at the code from images
manipulations libs such as Imlib2 and others.
I'm still discussing that on XFree-devel list.

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