Re: [RFC PATCH v3 00/16] Core scheduling v3

[Vineeth Remanan Pillai]

> I didn't see why we need do this.
>
> We only need to have the root level sched entities' vruntime become core
> wide since we will compare vruntime for them across hyperthreads. For
> sched entities on sub cfs_rqs, we never(at least, not now) compare their
> vruntime outside their cfs_rqs.
>
The reason we need to do this is because, new tasks that gets created will
have a vruntime based on the new min_vruntime and old tasks will have it
based on the old min_vruntime and it can cause starvation based on how
you set the min_vruntime. With this new patch, we normalize the whole
tree so that new tasks and old tasks compare with the same min_vruntime.

Thanks,
Vineeth