Re: [PATCH 2/2] sched/fair: Improve the for loop in select_idle_core()

[Viresh Kumar]

On 11-02-19, 10:30, Peter Zijlstra wrote:
> On Thu, Feb 07, 2019 at 04:16:06PM +0530, Viresh Kumar wrote:
> > @@ -6081,10 +6082,14 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int
> >  	for_each_cpu_wrap(core, cpus, target) {
> >  		bool idle = true;
> >  
> > -		for_each_cpu(cpu, cpu_smt_mask(core)) {
> > -			cpumask_clear_cpu(cpu, cpus);
> > -			if (!available_idle_cpu(cpu))
> > +		smt = cpu_smt_mask(core);
> > +		cpumask_andnot(cpus, cpus, smt);
> 
> So where the previous code was like 1-2 stores, you just added 16.

Is the max number of possible threads per core just 2? That's what I
read just now and I wasn't aware of that earlier. This commit doesn't
improve anything then. Sorry for the noise.

-- 
viresh