Re: [PATCH] sched: cgroup SCHED_IDLE support

[Tejun Heo]

Hello,

On Wed, Jun 16, 2021 at 06:01:59PM -0700, Josh Don wrote:
> Consider a tree like
> 
>                   root
>              /             \
>             A              C
>         /      \             |
>       B       idle       t4
>      |           |     \
>      t1         t2   t3
> 
> Here, 'idle' is our cpu.idle cgroup. The following properties would
> not be possible if we moved t2/t3 into SCHED_IDLE without the cgroup
> interface:
> - t1 always preempts t2/t3 on wakeup, but t4 does not
> - t2 and t3 have different, non-minimum weights. Technically we could
> also achieve this by adding another layer of nested cgroups, but that
> starts to make the hierarchy much more complex.
> - I've also discussed with Peter a possible extension (vruntime
> adjustments) to the current SCHED_IDLE semantics. Similarly to the
> first bullet here, we'd need a cgroup idle toggle to achieve certain
> scheduling behaviors with this.

Would you care to share some concrete use cases?

Thank you.

-- 
tejun