Re: [RFC][PATCH 13/16] sched: Add core wide task selection and scheduling.

[Peter Zijlstra]

On Thu, Apr 11, 2019 at 11:05:41AM +0800, Aaron Lu wrote:
> On Wed, Apr 10, 2019 at 04:44:18PM +0200, Peter Zijlstra wrote:
> > When core_cookie==0 we shouldn't schedule the other siblings at all.
> 
> Not even with another untagged task?
> 
> I was thinking to leave host side tasks untagged, like kernel threads,
> init and other system daemons or utilities etc., and tenant tasks tagged.
> Then at least two untagged tasks can be scheduled on the same core.
> 
> Kindly let me know if you see a problem with this.

Let me clarify; when the rq->core->core_cookie == 0, each sibling should
schedule independently.

As Julien found, there were some issues here, but the intent was:

  core_cookie 0, independent scheduling
  core_cookie 0->n, core scheduling
  core_cookie n->0, one last core schedule to kick possibly forced idle siblings