[RFC] improve memory placement for radeon

[Marek Olšák]

On Thu, Nov 29, 2012 at 4:35 PM,  <j.glisse at gmail.com> wrote:
> So as a followup is 2 patch. The first one just stop trying to move
> object at each cs ioctl i believe it could be included in 3.7 as it
> improve performances (especialy with vram change from userspace).
>
> The second one implement a vram eviction policy. It's a simple one,
> buffer used for write operation are more important than buffer used
> for read operation. Buffer get evicted from vram only if they haven't
> been use in the last 50ms (so in the last few frames) and only if
> there is buffer that have been recently use and that could be move
> into vram. This is mostly were i believe discussion should be,
> what kind of heuristic would work better than tat.

First off, I didn't review the patches, because I'm not as familiar
with the DRM. Just some comments.

Isn't 50ms too little? You always need at least 20 fps for that to
make sense. I think 200ms would be more reasonable, but still that
isn't perfect either.

Another option would be to use something else than elapsed time,
something that's based on actual usage.

This weekend, I'll try to make a Mesa patch that sends an end-of-frame
flag to the kernel through the CS ioctl. I think there would be at
most 2 end-of-frame flags received by the kernel each frame: one from
the GL app and the other one from the compositor.

Marek