[RFC 0/3] TTM priority queue logic

[Lauri Kasanen]

Hi list, Thomas,

I'd like to know if this is going in the right direction.

I've implemented a priority queue on top of the kernel rb tree and
linked list. It's been tested well in userspace.

I hardcoded radeon to input the buffer size as the score. Nothing blew
up, games ran fine, and even got ~2% more fps on average*.

The only thing missing from this code is the "if score is too low, and
there is no room without eviction, tell driver so" logic.

- Lauri

* This is a fairly bad strategy, and according to my simulator achieves
16% worse results compared to LRU in heavier situations. The games
tested here all fit in VRAM, which should explain the improvement.