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

[Peter Zijlstra]

On Tue, Aug 06, 2019 at 10:03:29AM -0700, Tim Chen wrote:
> On 8/5/19 8:24 PM, Aaron Lu wrote:
> 
> > I've been thinking if we should consider core wide tenent fairness?
> > 
> > Let's say there are 3 tasks on 2 threads' rq of the same core, 2 tasks
> > (e.g. A1, A2) belong to tenent A and the 3rd B1 belong to another tenent
> > B. Assume A1 and B1 are queued on the same thread and A2 on the other
> > thread, when we decide priority for A1 and B1, shall we also consider
> > A2's vruntime? i.e. shall we consider A1 and A2 as a whole since they
> > belong to the same tenent? I tend to think we should make fairness per
> > core per tenent, instead of per thread(cpu) per task(sched entity). What
> > do you guys think?
> > 
> > Implemention of the idea is a mess to me, as I feel I'm duplicating the
> > existing per cpu per sched_entity enqueue/update vruntime/dequeue logic
> > for the per core per tenent stuff.
> 
> I'm wondering if something simpler will work.  It is easier to maintain fairness
> between the CPU threads.  A simple scheme may be if the force idle deficit
> on a CPU thread exceeds a threshold compared to its sibling, we will
> bias in choosing the task on the suppressed CPU thread.  
> The fairness among the tenents per run queue is balanced out by cfq fairness,
> so things should be fair if we maintain fairness in CPU utilization between
> the two CPU threads.

IIRC pjt once did a simle 5ms flip flop between siblings.