[Bug 21649] EXA cannot allocate memory for OpenGL

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Sat May 16 10:13:16 PDT 2009


--- Comment #3 from Michal Suchanek <hramrach at centrum.cz>  2009-05-16 10:13:16 PST ---
(In reply to comment #2)
> > Looking at the performance options available I tried to switch between 16bit
> > and 32bit textures in the application itself (32bit was faster but it's
> > somewhat expected since I did not switch the X server to 16bit)
> Actually, I'd expect 16 bit textures to always be faster... However, the screen
> depth may indeed override the application hint depending on the value of the
> driconf option texture_depth.

I would expect the texture format matching the framebuffer format to be the
fastest which is also what I have seen.

> > front, back, depth buffer ~ 3*8 = 24M
> > 
> > GL textures ~ 52M
> > EXA offscreen ~ 52M
> > 
> > which suggests I could save perhaps 12M on the screen buffers but I have 52M
> > of completely unused memory.
> If by 'completely unused memory' you mean the EXA offscreen memory, EXA needs
> it for 2D acceleration. Unfortunately, we can't really do better than this
> static partitioning of video RAM without a graphics memory manager, which will
> only come with kernel modesetting.

I guess I don't need EXA acceleration for OpenGL.

> > With XAA the X server also informs that it uses 8M of GART memory although I
> > have set up 128M in the BIOS. Changing to 64M there has no effect.
> Again, without a graphics memory manager the X driver can only allocate GART
> memory statically, and unused GART memory is wasted system memory, which is why
> the driver doesn't allocate the full GART aperture size by default. Current
> versions of the driver use 32 by default though. So maybe you're using an old
> driver, which may also explain why Option "FBTexPercent" isn't working.
> Note that the Mesa r200 driver doesn't use GART memory for textures unless
> there is no video RAM available for textures at all, which requires

So the allocated GART texture memory is also unused. I am not sure how much
memory X allcates, though.

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