pbuffer memory problem

[anitak]

Hi:

I have a program with a float pbuffer used to composit images and then display the result on the screen. Everything is fine untill I start running 2 copies of this program. Then everything, including my desktop slows to a crawl if my images are large enough. These images are being composited in Cg through texturing (fragment program). The size of the pbuffer I create equals the bounding box of all images.

Is the slowness due to texture memory swapping? ie: is the second program swapping memory that is getting used by the pbuffer or the textures? Do pbuffers and textures get allocated in the same memory pool, ie: in the graphics card's texture memory?

If there isn't enough texture memory, then my textures maps should appear white, but in the above case I can see the composit result, except that its dog slow. I have tried using texture proxies, but didn't help much.

Assuming I am not doing anything stupid in my code, any insight regarding how graphics cards allocate pbuffer/texture memory would be really helpfull.

My system info:

RH Linux 7.3
Quadro FX1000
GLX 1.3

Thanks
-anita