Re: [RFC PATCH V2 0/3] sched/fair: Fix nr-running vs delayed-dequeue

[Xuewen Yan]

Hi Peter

On Mon, Mar 3, 2025 at 8:00 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> On Mon, Mar 03, 2025 at 06:52:38PM +0800, Xuewen Yan wrote:
> > Delayed dequeued feature keeps a sleeping sched_entitiy enqueued until its
> > lag has elapsed. As a result, it stays also visible in rq->nr_running.
> > However, sometimes when using nr-running, we should not consider
> > sched-delayed tasks.
> > This serie fixes those by adding a helper function which return the
> > number of sched-delayed tasks. And when we should get the real runnable
> > tasks, we sub the nr-delayed tasks.
> >
>
> Is there an actual performance improvement? Because when a runqueue
> looses competition, delayed tasks very quickly dissipate.

At the moment, I don't have very detailed test data. I've been
studying delay-dequeue carefully recently, and these are the issues I
feel might need modification as I go through the code.

Thanks!

BR