Stephane Marchesin wrote: > On 5/18/08, Thomas Hellström <[EMAIL PROTECTED]> wrote: > > >> > Yes, that was really my point. If the memory manager we use (whatever >> > it is) does not allow this kind of behaviour, that'll force all cards >> > to use a kernel-validated command submission model, which might not be >> > too fast, and more difficult to implement on such hardware. >> > >> > I'm not in favor of having multiple memory managers, but if the chosen >> > one is both slower and more complex to support in the future, that'll >> > be a loss for everyone. Unless we want to have another memory manager >> > implementation in 2 years from now... >> > >> > Stephane >> > >> >> First, TTM does not enforce kernel command submission, but it forces you >> to tell the kernel about command completion status in order for the >> kernel to be able to move and delete buffers. >> > > Yes, emitting the moves from the kernel is not a necessity. If your > card can do memory protection, you can setup the protection bits in > the kernel and ask user space to do the moves. Doing so means in-order > execution in the current context, which means that in the normal case > rendering does not need to synchronize with fences at all. > > >> I'm not sure how you could avoid that with ANY kernel based memory >> manager, but I would be interested to know how you expect to solve that >> problem. >> > > See above, if the kernel controls the memory protection bits, it can > pretty much enforce things on use space anyway. > > Well, the primary reason for the kernel to sync and move a buffer object would be to evict it from VRAM, in which case I don't think the user-space approach would be a valid solution, unless, of course, you plan to use VRAM as a cache and back it all with system memory.
Just out of interest (I think this is a valid thing to know, and I'm not being TTM / GEM specific here): 1) I've never seen a kernel round-trip per batchbuffer as a huge performance-problem, and it surely simplifies things for an in-kernel memory manger. Do you have any data to back this? 2) What do the Nvidia propriety drivers do w r t this? /Thomas ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ -- _______________________________________________ Dri-devel mailing list Dri-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/dri-devel
