[Intel-gfx] [PATCH 3/6] drm/i915: Split the batch pool by engine

[Chris Wilson]

On Thu, Mar 19, 2015 at 09:36:14AM +0000, Tvrtko Ursulin wrote:
> Oh right, I got it, but not sure I like it that much. I don't think
> batch pool implementation is well enough decoupled from the users.

"batch pool" Splitting it this way actually improves decoupling.

> Well in a way at least where when we talk about LRU ordering, it
> depends on retiring working properly and that is not obvious from
> code layout and module separation.

I've lost you. The list is in LRU submission order. With this split, the
list is both in LRU submission and LRU retirememnt order. That the two
are not the same originally is not a fault of retiring not working
properly, but that the hardware is split into different units and
timelines.
 
> And then with this me move traversal inefficiency to possible more
> resource use. Would it be better to fix the cause rather than
> symptoms? Is it feasible? What would be the downside of retiring all
> rings before submission?

Not really. Inefficient userspace is inefficient. All we want to be sure
is that one abusive client doesn't cause a DoS on another, whilst making
sure that good clients are not penalized.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre