[Intel-gfx] [PATCH 6/6] drm/i915: Store the vma in an rbtree under the object

[Chris Wilson]

On Tue, Nov 01, 2016 at 08:54:09AM +0000, Tvrtko Ursulin wrote:
> 
> On 01/11/2016 08:50, Chris Wilson wrote:
> >On Tue, Nov 01, 2016 at 08:41:01AM +0000, Tvrtko Ursulin wrote:
> >>
> >>On 31/10/2016 10:26, Chris Wilson wrote:
> >>>With full-ppgtt one of the main bottlenecks is the lookup of the VMA
> >>>underneath the object. For execbuf there is merit in having a very fast
> >>>direct lookup of ctx:handle to the vma using a hashtree, but that still
> >>>leaves a large number of other lookups. One way to speed up the lookup
> >>>would be to use a rhashtable, but that requires extra allocations and
> >>>may exhibit poor worse case behaviour. An alternative is to use an
> >>>embedded rbtree, i.e. no extra allocations and deterministic behaviour,
> >>>but at the slight cost of O(lgN) lookups (instead of O(1) for
> >>>rhashtable). The major of such tree will be very shallow and so not much
> >>>slower, and still scales much, much better than the current unsorted
> >>>list.
> >>>
> >>>References: https://bugs.freedesktop.org/show_bug.cgi?id=87726
> >>>Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> >>
> >>I suggest leaving this out of the mini-series which fixes the
> >>recently introduced bugs.
> >
> >Just review it now, it's a two year old bug that was impacting the test
> >cases I was running... :-p Then we won't have to review it next week ;)
> 
> I'll review it, just split it out please so the CI fire can be
> extinguished first.

Sure, I'm pushing the fixes as soon as they've been baked. There's a
regression fix that builds upon this patch for multiple timelines (the
linear walk in reservation_object is particularly nasty for scaling).
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre