[Intel-gfx] [PATCH 2/5] drm/i915/perf: allow holding preemption on filtered ctx

[Lionel Landwerlin]

On 21/05/2019 17:36, Chris Wilson wrote:
> Quoting Lionel Landwerlin (2019-05-21 15:08:52)
>> diff --git a/drivers/gpu/drm/i915/gt/intel_lrc.c b/drivers/gpu/drm/i915/gt/intel_lrc.c
>> index f263a8374273..2ad95977f7a8 100644
>> --- a/drivers/gpu/drm/i915/gt/intel_lrc.c
>> +++ b/drivers/gpu/drm/i915/gt/intel_lrc.c
>> @@ -2085,7 +2085,7 @@ static int gen9_emit_bb_start(struct i915_request *rq,
>>          if (IS_ERR(cs))
>>                  return PTR_ERR(cs);
>>   
>> -       *cs++ = MI_ARB_ON_OFF | MI_ARB_ENABLE;
>> +       *cs++ = MI_ARB_ON_OFF | rq->hw_context->arb_enable;
> My prediction is that this will result in this context being reset due
> to preemption timeouts and the context under profile being banned. Note
> that preemption timeouts will be the primary means for hang detection
> for endless batches.
> -Chris
>

Another thought :

What if we ran with the max priority?
It would be fine to have the hangcheck preempt the workload (it's pretty 
short and shouldn't affect perf counters from 3d/compute pipeline much) 
as long as ensure nothing else runs.

-Lionel