[Intel-gfx] [PATCH i-g-t v2] tests/perf_pmu: Test busyness reporting in face of GPU hangs

[Chris Wilson]

Quoting Tvrtko Ursulin (2018-03-01 09:21:52)
> 
> On 01/03/2018 08:08, Chris Wilson wrote:
> > Quoting Tvrtko Ursulin (2018-02-28 17:15:19)
> >> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> >>
> >> Verify that the reported busyness is in line with what would we expect
> >> from a batch which causes a hang and gets kicked out from the engine.
> >>
> >> v2: Change to explicit igt_force_gpu_reset instead of guessing when a spin
> >>      batch will hang. (Chris Wilson)
> >>
> >> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
> > 
> > It's nice and quick, yes. However, sometime the opposite is true and you
> > have to wait for the batch you want to start before pulling the trigger.
> > 
> > I'd put a usleep(100) in there /* Wait for batch to execute */ and we
> 
> Hm, but reset is triggered after the first sleep (which checks for 100% 
> busy). So even the non-hanging test flavour could be affect if the delay 
> before execution is so long. So by this logic this usleep(100) (or more 
> for small core CI) should then go to many tests. Only difference in the 
> hang flavour is that if it completely failed to run until after the 
> reset, then the idle assert would fail. So maybe I should just add an 
> assert that the batch is idle before sampling pmu after reset?

Sneaky. Yes, that will work, just add a comment for the case where it
may fail (reset before batch execution).
-Chris