Re: [POC][RFC][PATCH] sched: Extended Scheduler Time Slice

Daniel Bristot de Oliveira
2023-10-26T16:32:10Z

On 10/26/23 17:49, Steven Rostedt wrote:
> On Thu, 26 Oct 2023 09:40:35 -0400
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
>> Hence, why I don't want to associate this with priority inheritance. The
>> time constraint is a fundamental difference.
>
> Let me add one more fundamental difference here that makes this solution
> different than priority inheritance and ceiling.
>
> PI and ceiling define the correctness of the system. If you get it wrong or
> remove it, the system can be incorrect and lock up, fail deadlines, etc.
> There's hundreds, if not thousands of papers mathematically defining the
> correctness of PI, ceiling and proxy execution, as they are complex and
> critical for the system to behave properly.
>
> This feature is a performance boost only, and has nothing to do with
> "correctness". That's because it has that arbitrary time where it can run a
> little more. It's more like the difference between having something in
> cache and a cache miss. This would cause many academics to quit and find a
> job in sales if they had to prove the correctness of an algorithm that gave
> you a boost for some random amount of time. The idea here is to help with
> performance. If it exists, great, your application will likely perform
> better. If it doesn't, no big deal, you may just have to deal with longer
> wait times on critical sections.

terminologies, terminologies.... those academic people :-)

I think that this can also be seen as an extension of the non-preemptive
mode to the user space, but... not entirely, it is a ceiling to the
[ higher than fair/lower than RT ] prior?

and it is not global. It is partitioned: once the section starts, it stays
there, being preempted by RT/DL?

[ trying to understand the implications of it ]

>
> This is why I do not want to associate this as another form of PI or
> ceiling.
>
> -- Steve