[Intel-gfx] [RFC 6/6] drm/i915/pmu: Add running counter

[Chris Wilson]

Quoting Tvrtko Ursulin (2018-01-18 10:41:36)
> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> 
> We add a PMU counter to expose the number of requests currently executing
> on the GPU.
> 
> This is useful to analyze the overall load of the system.
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>

Ok, the split between queued (unmet dependencies),
submitted (met dependencies, ready for hw) and running (on hw) look good
to me. The usual slight inaccuracies that may arise due to trying to
sample across async hw + engines, but those should be minor. And the
counters seem very useful (at least for the trivial overlay).

The only suggestion I would make is perhaps

	engine->stats.unready_requests / requests_queued;
	engine->stats.requests_ready / requests_submitted;

(doesn't have to be stats, but I think we want a bit more verbosity
here).

Oh, the second suggestion is perhaps not to use 1e-2 :) Talk about
giving me a fright!
-Chris