[igt-dev] [PATCH i-g-t 3/3] tests/perf_pmu: Give sampling more time

[Tvrtko Ursulin]

On 08/02/2018 08:13, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2018-02-08 08:01:31)
>> From: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
>>
>> We get occasional errors like:
>>
>>   (perf_pmu:21315) CRITICAL: Test assertion failure function sema_wait, file perf_pmu.c:631:
>>   (perf_pmu:21315) CRITICAL: Failed assertion: (double)(val[1] - val[0]) <= (1.0 + (tolerance)) * (double)(slept) && (double)(val[1] - val[0]) >= (1.0 - (tolerance)) * (double)(slept)
>>   (perf_pmu:21315) CRITICAL: 'val[1] - val[0]' != 'slept' (450000000.000000 not within 5.000000% tolerance of 500129618.000000)
> 
> Something to remember when reporting pmu errors is whether it's
> sampling. In this case sema_wait is always sampling... But I wonder if
> we can report it from pmu somehow?

Theoretically I think we could add our own file to sysfs, alongside 
<counter-name>(.unit|.scale) etc.. like ".resolution" or something. Not 
sure how polite that would be though.. not very I think. Alternative 
would be to create additional pmu hierarchy in debugfs with this data.

Regards,

Tvrtko