[Bug 21649] New: EXA cannot allocate memory for OpenGL

bugzilla-daemon at freedesktop.org bugzilla-daemon at freedesktop.org
Sat May 9 13:08:18 PDT 2009


           Summary: EXA cannot allocate memory for OpenGL
           Product: xorg
           Version: unspecified
          Platform: x86 (IA32)
        OS/Version: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Driver/Radeon
        AssignedTo: xorg-driver-ati at lists.x.org
        ReportedBy: hramrach at centrum.cz
         QAContact: xorg-team at lists.x.org

I was trying to run an OpenGL application on a i440BX + Radeon 9200 system with
Xorg 1.6, and it turned out that it is almost fast enough but not quite.

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)

I also tried page flipping but if anything it made things worse.

The X log suggests to reduce Virtual, and indeed I could save a few megs there
.. but the memory is divided as follows:

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.

There is an option that allows changing the percentage of VRAM allocated to the
GL textures, I set it to 90 and the X server would merrily inform me that the
option was ignored.

Switching to XAA resolves the problem. I get ~ 100M for GL textures which is
enough to mitigate FPS drops.

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. With EXA I
do not get that information at all.

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