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

[Chris Wilson]

Quoting Tvrtko Ursulin (2018-01-19 11:45:24)
> 
> On 18/01/2018 11:57, Chris Wilson wrote:
> > 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).
> 
> Glad to hear positive feedback!
> 
> > 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).
> 
> Hm, what is that? You are suggesting some relative stats? Exposed as 
> another counter? It can be calculated in userspace easily.

Just trying to think of better names than engine->queued.
I like 'stats' as it says "this is not part of the normal engine
management, but some auxiliary information we tracked for user
convenience"; then I was just trying to think of a more apropos name
than 'queued'. I definitely think we want to let the reader know what's
queued :)
-Chris