[igt-dev] [PATCH i-g-t 03/17] benchmarks/gem_wsim: fix scaling of period steps

[Tvrtko Ursulin]

On 29/09/2023 10:31, Bernatowicz, Marcin wrote:
> Hi,
> 
> On 9/29/2023 10:01 AM, Tvrtko Ursulin wrote:
>>
>> On 28/09/2023 18:45, Marcin Bernatowicz wrote:
>>> Period steps take scale time (-F) command line option into account.
>>
>> "Make period steps.."?
>>
>> "Periods steps should take.."?
>>
>>> This allows to scale workload without need to modify .wsim file
>>>
>>> ex. having following example.wsim
>>>
>>> 1.VCS1.3000.0.1
>>> 1.RCS.500-1000.-1.0
>>> 1.RCS.3700.0.0
>>> 1.RCS.1000.-2.0
>>> 1.VCS2.2300.-2.0
>>> 1.RCS.4700.-1.0
>>> 1.VCS2.600.-1.1
>>> p.16000
>>>
>>> we can scale the whole workload x10 with:
>>>
>>> gem_wsim -w example.wsim -f 10 -F 10
>>>
>>> -f is for batch duration steps, -F for period and delay steps
>>
>> Actually I am having a little bit of a second thought here. Thinking 
>> that perhaps it was deliberate to not scale periods.
>>
>> Think of it like this. -f 0.5 simulates a twice as fast GPU. -F 2 
>> simulates a twice as slow CPU.
>>
>> In both cases if something wants to hit 60 fps, it still wants to hit 
>> 60 fps. What use case for scaling the period do you have in mind?
>>
> 
> That gives another view on the matter.
> 
> I thought about it more like having a common unit, so giving -F 1000 -> 
> makes all CPU values (Period/Duration) are given in ms.

I lost you here. -F is also a scaling factor and not a time value.

> -f option may be used to calibrate for difference between GPU and CPU 
> ex. if wrongly reported freq makes a real GPU duration 10x faster than 
> CPU measured (ex. 10ms specified batch duration takes 1ms in reality) we 
> can provide -f 10 and still have GPU durations correspond to CPU time.

Hm but in either case nothing of this relates to framerate.

My current thinking is to drop this patch unless you can think of a good 
use case for scaling period. Or we need a new command option for scaling 
only periods.

Regards,

Tvrtko

> 
> Regards,
> marcin
> 
> 
>> Regards,
>>
>> Tvrtko
>>
>>> v2:
>>> - apply same approach as with DELAY step (Tvrtko)
>>>
>>> Signed-off-by: Marcin Bernatowicz <marcin.bernatowicz at linux.intel.com>
>>> ---
>>>   benchmarks/gem_wsim.c | 2 ++
>>>   1 file changed, 2 insertions(+)
>>>
>>> diff --git a/benchmarks/gem_wsim.c b/benchmarks/gem_wsim.c
>>> index 42690d3d0..41557517c 100644
>>> --- a/benchmarks/gem_wsim.c
>>> +++ b/benchmarks/gem_wsim.c
>>> @@ -1186,6 +1186,8 @@ parse_workload(struct w_arg *arg, unsigned int 
>>> flags, double scale_dur,
>>>   add_step:
>>>           if (step.type == DELAY)
>>>               step.delay = __duration(step.delay, scale_time);
>>> +        else if (step.type == PERIOD)
>>> +            step.period = __duration(step.period, scale_time);
>>>           step.idx = nr_steps++;
>>>           step.request = -1;