[Intel-gfx] [PATCH 03/23] drm/i915: Remove lrc default desc from GEM context

[Chris Wilson]

Quoting Chris Wilson (2019-08-01 11:57:06)
> Quoting Tvrtko Ursulin (2019-08-01 09:53:15)
> > We could store it in ce then. We already have well defined control 
> > points for when vm changes when all are updated.
> 
> We are storing it in ce; it's not like we recompute it all that often,
> and when we do it's because we have rebound the vma.
> 
> > If done like this then it looks like assigning ctx->hw_id could also do 
> > the default_desc update, so that we can avoid even more work done at pin 
> > time.
> 
> What ctx->hw_id? You are imagining things again :-p
> 
> Remember that we only do this on first pin from idle, not every pin.

Fwiw, I quickly looked at only doing it if the vma is rebound, but
that's move branches just to save a couple. The low frequency at which
we have to actually compute this (walk a few more branches inside an
already branchy contxt_pin) doesn't seem to justify the extra storage for
me. It's not like we are recomputing lrc_desc on every submit as it once
was.
-Chris