Re: [PATCH v2 0/8] Engine Busyness

[Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>]

On Thu, Dec 14, 2023 at 08:06:46AM +0000, Tvrtko Ursulin wrote:
>
>On 14/12/2023 01:56, Umesh Nerlige Ramappa wrote:
>>On Thu, Dec 07, 2023 at 02:45:47PM +0000, Tvrtko Ursulin wrote:
>>>
>>>Hi,
>>>
>>>On 07/12/2023 12:57, Riana Tauro wrote:
>>>>GuC provides engine busyness ticks as a 64 bit counter which count
>>>>as clock ticks. These counters are maintained in a
>>>>shared memory buffer and internally updated on a continuous basis.
>>>>
>>>>GuC also provides a periodically total active ticks that GT has been
>>>>active for. This counter is exposed to the user such that busyness can
>>>>be calculated as a percentage using
>>>>
>>>>busyness % = (engine active ticks/total active ticks) * 100.
>>>
>>>I think I've asked this before but don't remember it was clarified 
>>>- what are the semantics of "active" with total active ticks? In 
>>>other words considering activity timelines like:
>>>
>>>1)
>>>    0          1s
>>>rcs0 |xxxxx-----|
>>>bcs0 |-----xxxxx|
>>>
>>>2)
>>>    0          1s
>>>rcs0 |xxxxx-----|
>>>bcs0 |xxxxx-----|
>>>
>>>Assuming 1s sampling, would the above formula correctly say 50% 
>>>for both engines in both cases?
>>
>>Yes. What is the significance of case 2? Are you saying rcs and bcs 
>>are executing in parallel?
>
>In parallel yes. Complete overlap, no overlap, or any overlap of 
>activity in between the two.

GuC accumulates this on context switches, so the overlap does not 
matter.

>
>>Either ways, when total active ticks is queried it would provide the 
>>latest value of the active time (does not depend on gt park/unpark 
>>since the value is either obtained on demand from GuC or is a value 
>>that is frequently updated by GuC.
>>
>>The duration of context (in to out) is accumulated for the each engine.
>
>But why is the total *active* tick moving during the 0.5s - 1s time of 
>the 2nd diagram though? What does it mean by "active" if nothing was 
>active during that period?

VF was still using it's allotted time and hence was active.

Regards,
Umesh

>
>>>I am also curious if there are plans to add support to 
>>>intel_gpu_top in which case please copy me on the required 
>>>refactorings.
>>>
>>
>>Certainly. It's in the works.
>
>Cool.
>
>Regards,
>
>Tvrtko