[Intel-gfx] [PATCH igt] igt/perf_pmu: Recalibrate interrupt loop.

[Chris Wilson]

Quoting Tvrtko Ursulin (2017-11-24 09:52:23)
> 
> On 24/11/2017 09:28, Chris Wilson wrote:
> > Quoting Tvrtko Ursulin (2017-11-24 09:11:06)
> >>
> >> On 23/11/2017 15:03, Chris Wilson wrote:
> >>> We have to be careful in our calibration loop, too slow and we timeout,
> >>> too fast and we don't emit an interrupt! On fast legacy devices, we
> >>> would overflow the calibration calcuation...
> >>>
> >>> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> >>> Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>> ---
> >>> -     sz = ALIGN(sz, sizeof(uint32_t));
> >>> +     sz = calibrate_nop(gem_fd, 1e6 / target);
> >>> +     gem_quiescent_gpu(gem_fd);
> >>> +
> >>> +     fd = open_pmu(I915_PMU_INTERRUPTS);
> >>> +     spin = igt_spin_batch_new(gem_fd, 0, 0, 0);
> >>
> >> What's the spin batch for?
> > 
> > It's just a plug to ensure that the queue of calibrated execs don't start
> > executing before we're waiting on them. Instead of doing exec + sync, we
> > want to switch to exec[N] + sync.
> 
> Of course, makes sense.
> 
> Only improvement I can think of is to define the target time (1e6) and 
> poll timeout (2000ms) from a common local variable.

Called it test_duration_ms. Thanks,
-Chris