Re: [External] Re: Subject: [PATCH] sched/fair: prioritize normal task over sched_idle task with vruntime offset

[chenying]

在 2022/3/15 8:30, Josh Don 写道:
> On Sun, Mar 13, 2022 at 3:07 AM chenying <chenying.kernel@xxxxxxxxxxxxx> wrote:
> > If I set the sched_idle_vruntime_offset to a relatively small value
> > (e.g. 10 minutes), can this issues be avoided?
>
> That's still long enough to cause lockups.
>
> Is the issue that you have a large number of sched_idle entities, and
> the occasional latency sensitive thing that wakes up for a short
> duration? Have you considered approaching this from the other
> direction (ie. if we have a latency sensitive thing wake onto a cpu
> running only sched idle stuff, we could change entity placement to
> position the latency sensitive thing further left on the timeline,
> akin to !GENTLE_FAIR_SLEEPERS).

I think this may not guarantee that latency sensitive tasks are always 
to the left of idle tasks. And it may get complicated if a 
latency-sensitive task is woken up onto a cpu which there are already 
multiple latency-sensitive tasks and sched_idle tasks.