Re: [PATCH v3] drm/i915/execlists: Set queue priority from secondary port

[Chris Wilson <chris@chris-wilson.co.uk>]

Quoting Tvrtko Ursulin (2018-04-11 13:03:00)
> 
> On 11/04/2018 12:34, Chris Wilson wrote:
> > Quoting Chris Wilson (2018-04-11 11:39:29)
> >> We can refine our current execlists->queue_priority if we inspect
> >> ELSP[1] rather than the head of the unsubmitted queue. Currently, we use
> >> the unsubmitted queue and say that if a subsequent request is more
> >> important than the current queue, we will rerun the submission tasklet
> >> to evaluate the need for preemption. However, we only want to preempt if
> >> we need to jump ahead of a currently executing request in ELSP. The
> >> second reason for running the submission tasklet is amalgamate requests
> >> into the active context on ELSP[0] to avoid a stall when ELSP[0] drains.
> >> (Though repeatedly amalgamating requests into the active context and
> >> triggering many lite-restore is off question gain, the goal really is to
> >> put a context into ELSP[1] to cover the interrupt.) So if instead of
> >> looking at the head of the queue, we look at the context in ELSP[1] we
> >> can answer both of the questions more accurately -- we don't need to
> >> rerun the submission tasklet unless our new request is important enough
> >> to feed into, at least, ELSP[1].
> >>
> >> v2: Add some comments from the discussion with Tvrtko.
> >> v3: More commentary to cross-reference queue_request()
> >>
> >> References: f6322eddaff7 ("drm/i915/preemption: Allow preemption between submission ports")
> >> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> >> Cc: Michał Winiarski <michal.winiarski@intel.com>
> >> Cc: Michel Thierry <michel.thierry@intel.com>
> >> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> >> Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> > 
> >  From the discussion thread,
> > 
> > Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> > 
> > I assume Tvrtko is happy with the comments added based on that
> > conversation.
> 
> Yes, all fine!

Forgot to say, thanks and pushed.

If you are feeling better, there's the igt that purports to hit the issue
as well: https://patchwork.freedesktop.org/series/41535/
Or one of the Ms!
-Chris
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