Re: [RFC PATCH 0/7] sched: cpufreq: Remove magic margins

Lukasz Luba
2023-09-12T11:57:04Z

Hi Daniel,

On 9/8/23 13:51, Daniel Bristot de Oliveira wrote:
> On 9/7/23 15:45, Lukasz Luba wrote:
>>>>> RT literatur mostly methinks. Replacing WCET with a statistical model of
>>>>> sorts is not uncommon, the argument goes that not everybody will have
>>>>> their worst case at the same time and lows and highs can commonly cancel
>>>>> out and this way we can cram a little more on the system.
>>>>>
>>>>> Typically this is proposed in the context of soft-realtime systems.
>>>>
>>>> Thanks Peter, I will dive into some books...
>>>
>>> I would look at academic papers, not sure any of that ever made it to
>>> books, Daniel would know I suppose.
>>
>> Good hint, thanks!
>
> The key-words that came to my mind are:
>
> - mk-firm, where you accept m tasks will make their deadline
> every k execution - like, because you run too long.
> - mixed criticality with pWCET (probabilistic execution time) or
> average execution time + an sporadic tail execution time for
> the low criticality part.
>
> mk-firm smells like 2005's.. mixed criticality as 2015's..present.
>
> You will probably find more papers than books. Read the papers
> as a source for inspiration... not necessarily as a definitive
> solution. They generally proposed too restrictive task models.
>
> -- Daniel
>

Thanks for describing this context! That would save my time and avoid
maybe sinking in this unknown water. As you said I might tread that
as inspiration, since I don't fight with life-critical system,
but a phone which needs 'nice user experience' (hopefully there are
no people who disagree) ;)

Regards,
Lukasz