Question

is it possible to learn the allocated memory range of an OpenGL context? Supposedly this memory range should then be accessed with mmap() from another process. Can this technique work, or are there fundamental problems with it?

Update We’re using a GNU/Linux system with a modern X11 installation and can pick the video card manufacturer whose drivers support such a trick.

Answer 1

Well, there are innumerable reasons why it won’t work.

First, the “allocated memory range of an OpenGL context” is always changing. OpenGL contexts allocate new memory and deallocate it as it decides to.

Second, I would not trust an OpenGL driver to survive under memory mapped conditions like this. Multiple OpenGL contexts can coexist, but only because they all know about each other and the driver can therefore compensate for them. It is highly unlikely that a context can assimilate changes made by another context.

Third, GPUs often work with graphics memory. Even if you can use mmap on GPU memory (which itself is unlikely), you’re probably going to lose a lot of performance when you do. And GPU memory gets shuffled around a lot more than CPU memory.

You appear to be trying to do IPC-based graphics. Your best bet would be to have the graphics system be its own process that you communicate with via IPC methods, rather than trying to talk to OpenGL via IPC.