Messages in this thread | | | From | Vincent Guittot <> | Date | Tue, 6 Apr 2021 17:33:30 +0200 | Subject | Re: [PATCH v3] sched/fair: bring back select_idle_smt, but differently |
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On Tue, 6 Apr 2021 at 17:31, Vincent Guittot <vincent.guittot@linaro.org> wrote: > > On Tue, 6 Apr 2021 at 17:26, Rik van Riel <riel@surriel.com> wrote: > > > > On Tue, 2021-04-06 at 17:10 +0200, Vincent Guittot wrote: > > > On Fri, 26 Mar 2021 at 20:19, Rik van Riel <riel@surriel.com> wrote: > > > > > > > -static int select_idle_cpu(struct task_struct *p, struct > > > > sched_domain *sd, int target) > > > > +static int select_idle_cpu(struct task_struct *p, struct > > > > sched_domain *sd, int prev, int target) > > > > { > > > > struct cpumask *cpus = > > > > this_cpu_cpumask_var_ptr(select_idle_mask); > > > > int i, cpu, idle_cpu = -1, nr = INT_MAX; > > > > @@ -6136,23 +6163,32 @@ static int select_idle_cpu(struct > > > > task_struct *p, struct sched_domain *sd, int t > > > > > > > > cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr); > > > > > > > > - if (sched_feat(SIS_PROP) && !smt) { > > > > - u64 avg_cost, avg_idle, span_avg; > > > > + if (!smt) { > > > > + if (cpus_share_cache(prev, target)) { > > > > > > Have you checked the impact on no smt system ? would worth a static > > > branch. > > > > > > Also, this doesn't need to be in select_idle_cpu() which aims to loop > > > the sched_domain becaus you only compare target and prev. So you can > > > move this call to select_idle_smt() in select_idle_sibling() > > > > After Mel's rewrite, there no longer are calls to > > select_idle_core() or select_idle_smt() in select_idle_sibling(). > > select_idle_smt() had even disappeared that why it was not in > select_idle_sibling > > > > > Everything got folded into one single loop in select_idle_cpu() > > but this is done completely out of the loop so we don't need to > complify the function with unrelated stuff
s/complify/complexify/
> > > > > I would be happy to pull the static branch out of select_idle_smt() > > and place it into this if condition, though. You are right that > > would save some overhead on non-smt systems. > > > > Peter, would you prefer a follow-up patch for that or a version 4 > > of the patch? > > > > -- > > All Rights Reversed.
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