TTM's role in score-based eviction

[Michel Dänzer]

On Die, 2013-12-10 at 12:03 +0100, Maarten Lankhorst wrote:
> op 10-12-13 01:49, Michel Dänzer schreef:
> > On Mon, 2013-12-09 at 23:45 +0100, Marek Olšák wrote:
> >> On Mon, Dec 9, 2013 at 9:30 PM, Lauri Kasanen <cand at gmx.com> wrote:
> >>> Note that the hotness calculation will be in userspace, as only there
> >>> are the necessary counters available. So the finished hotness score
> >>> will be passed to the kernel, instead of sending all the necessary data
> >>> there. Ought to be less context switches that way.
> > Sounds like this could be abused by userspace though...
> Of all the worries that exist, this is a non-issue. Userspace can
> simply queue a lot of draw calls that take 1 second each through the
> normal command submission methods, why would it need to tweak some
> obscure number to cause some eviction?

That's not what I'm concerned about.

Consider e.g. a multiseat environment: Some users could patch their
userspace drivers such that their buffers are more likely to stay in
VRAM than those of other users.

I agree it's not a huge issue, I'm just saying we should try to make the
score calculation as much as possible based on the actual usage of the
buffers instead of on meta data provided by userspace.


-- 
Earthling Michel Dänzer            |                  http://www.amd.com
Libre software enthusiast          |                Mesa and X developer