Re: [PATCH 0/2] sched/eevdf: sched_attr::sched_runtime slice hint

[Qais Yousef]

On 09/15/23 14:43, peterz@xxxxxxxxxxxxx wrote:
> Hi,
> 
> As promised a while ago, here is a new version of the variable slice length
> hint stuff.  Back when I asked for comments on the latency-nice vs slice length
> thing, there was very limited feedback on-list, a number of people have
> expressed interrest in the slice length hint.

I did try to give feedback then, but I don't see my email on lore and not sure
if it arrived.

As it stands having any interface to help describe latency sensitive tasks is
much desired! So I am desperate enough to take whatever.

But at the same time, I do see that we will not stop here. And we get a lot of
conflicting requirements from different workloads that I think we need
a framework to help provide sensible way to allow us describe those needs to
help the scheduler manage resources better.

I wasn't sure if you're still planning to send an interface or not, so was
working on this potential way (patch below) to provide a generic framework for
sched-qos. It's only a shell as I didn't get a chance yet to implement the
WAKEUP_LATENCY hint yet.

I did add the concept of grouping the hint to be meaningful for a group of
tasks sharing a cookie. Borrowing the concept from core scheduling. I've seen
many times how priorities (or nice) was used incorrectly with the assumption
that it applies to the apps tasks only. Which might be the case with autogroup
on some systems. But it struck a chord then that there's a perception/desire
not to apply it globally but only relative to a group of tasks they care about.
So I catered to allow describing such cases.

I was still trying to wrap my head around implementing WAKEUP_LATENCY hint, but
the idea I had is to represent WAKEUP_LATENCY in us time and somehow translate
this into lag. Which what I thought is our admission control. Based on your
patch it seems it might be simpler than this.

Was still thinking this through to be honest. But it seems it's either speak
now or forever hold, so here you go :)


Cheers

--
Qais Yousef

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