Re: [PATCH v2 0/8] Engine Busyness

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

On 20/12/2023 05:36, Umesh Nerlige Ramappa wrote:
> 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.

And if we leave SR-IOV out for a moment?

"GuC also provides a periodically total active ticks that GT has been 
active for."

How many time worth of total GT active ticks does GuC report in diagram 
2 above?

Regards,

Tvrtko

> 
> 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