Re: [PATCH] sched/fair: Prefer idle CPU to cache affinity

[Srikar Dronamraju]

* Dietmar Eggemann <dietmar.eggemann@xxxxxxx> [2021-03-02 10:53:06]:

> On 26/02/2021 17:40, Srikar Dronamraju wrote:
> 
> [...]
> 
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index 8a8bd7b13634..d49bfcdc4a19 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -5869,6 +5869,36 @@ wake_affine_weight(struct sched_domain *sd, struct task_struct *p,
> >  	return this_eff_load < prev_eff_load ? this_cpu : nr_cpumask_bits;
> >  }
> > 
> > +static int prefer_idler_llc(int this_cpu, int prev_cpu, int sync)
> > +{
> > +	struct sched_domain_shared *tsds, *psds;
> > +	int pnr_busy, pllc_size, tnr_busy, tllc_size, diff;
> > +
> > +	tsds = rcu_dereference(per_cpu(sd_llc_shared, this_cpu));
> > +	tnr_busy = atomic_read(&tsds->nr_busy_cpus);
> > +	tllc_size = per_cpu(sd_llc_size, this_cpu);
> > +
> > +	psds = rcu_dereference(per_cpu(sd_llc_shared, prev_cpu));
> > +	pnr_busy = atomic_read(&psds->nr_busy_cpus);
> > +	pllc_size = per_cpu(sd_llc_size, prev_cpu);
> > +
> > +	/* No need to compare, if both LLCs are fully loaded */
> > +	if (pnr_busy == pllc_size && tnr_busy == pllc_size)
> 
>                                                      ^
>                                            shouldn't this be tllc_size ?

Yes, thanks for pointing out.

-- 
Thanks and Regards
Srikar Dronamraju