Re: [Intel-gfx] [PATCH 1/5] drm/i915: Track per-context engine busyness

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 16/12/2019 12:40, Chris Wilson wrote:
> Quoting Tvrtko Ursulin (2019-12-16 12:07:00)
>> @@ -1389,6 +1415,9 @@ static void execlists_submit_ports(struct intel_engine_cs *engine)
>>                  write_desc(execlists,
>>                             rq ? execlists_update_context(rq) : 0,
>>                             n);
>> +
>> +               if (n == 0)
>> +                       intel_context_stats_start(&rq->hw_context->stats);
> 
> Too early? (Think preemption requests that may not begin for a few
> hundred ms.) Mark it as started on promotion instead (should be within a
> few microseconds, if not ideally a few 10 ns)? Then you will also have
> better symmetry in process_csb, suggesting that we can have a routine
> that takes the current *execlists->active with fewer code changes.

Good point, I was disliking the csb latencies and completely missed the 
preemption side of things. Symmetry will be much better in more than one 
aspect.

Regards,

Tvrtko

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