Quoting Tvrtko Ursulin (2019-09-23 11:44:01)
>
> On 23/09/2019 11:32, Chris Wilson wrote:
> > diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
> > index 0a4812ebd184..8c1ea5c315ac 100644
> > --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
> > +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
> > @@ -799,6 +799,17 @@ static bool can_merge_rq(const struct i915_request *prev,
> > GEM_BUG_ON(prev == next);
> > GEM_BUG_ON(!assert_priority_queue(prev, next));
> >
> > + /*
> > + * We not submit known completed requests. Therefore if the next
>
> "We _do_ not submit"?
Verbs are for the weak.
> > + * request is already completed, we can pretend to merge it in
> > + * with the previous context (and we will skip updating the ELSP
> > + * and tracking). Thus hopefully keeping the ELSP full with active
> > + * contexts, despite the best efforts of preempt-to-busy to confuse
> > + * us.
> > + */
> > + if (i915_request_completed(next))
> > + return true;
>
> It works with the current use of can_merge_rq but leaves a bit of a
> concern for the future. I did not come up with any interesting
> GEM_BUG_ONs to add. I was thinking along the lines of making sure we
> never end up coalescing different contexts to the same port. But no
> ideas how to do that.
That should just be
diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
index 96dd95d8252c..924cd51e1140 100644
--- a/drivers/gpu/drm/i915/gt/intel_lrc.c
+++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
@@ -1322,7 +1322,13 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
if (!merge) {
*port = execlists_schedule_in(last, port - execlists->pending);
port++;
+ last = NULL;
}
+
+ GEM_BUG_ON(last &&
+ !can_merge_ctx(last->hw_context,
+ rq->hw_context));
+
submit = true;
last = rq;
}
> > @@ -1249,11 +1245,23 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
> > GEM_BUG_ON(ve->siblings[0] != engine);
> > }
> >
> > - __i915_request_submit(rq);
> > - if (!i915_request_completed(rq)) {
> > + if (__i915_request_submit(rq)) {
> > submit = true;
> > last = rq;
> > }
> > +
> > + /*
> > + * Hmm, we have a bunch of virtual engine requests,
> > + * but the first one was already complete (thanks
>
> Complete or completed? Not sure myself..
Hmm. I suppose you can treat it as complete == "whole", completed ==
"finished". +d for consistency.
-Chris
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