Messages in this thread | | | From | Vincent Guittot <> | Date | Thu, 3 Dec 2020 17:38:03 +0100 | Subject | Re: [PATCH 06/10] sched/fair: Clear the target CPU from the cpumask of CPUs searched |
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On Thu, 3 Dec 2020 at 15:11, Mel Gorman <mgorman@techsingularity.net> wrote: > > The target CPU is definitely not idle in both select_idle_core and > select_idle_cpu. For select_idle_core(), the SMT is potentially > checked unnecessarily as the core is definitely not idle if the > target is busy. For select_idle_cpu(), the first CPU checked is > simply a waste.
> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> > --- > kernel/sched/fair.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 68dd9cd62fbd..1d8f5c4b4936 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -6077,6 +6077,7 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int > return -1; > > cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr); > + __cpumask_clear_cpu(target, cpus);
should clear cpu_smt_mask(target) as we are sure that the core will not be idle
> > for_each_cpu_wrap(core, cpus, target) { > bool idle = true; > @@ -6181,6 +6182,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t > time = cpu_clock(this); > > cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr); > + __cpumask_clear_cpu(target, cpus); > > for_each_cpu_wrap(cpu, cpus, target) { > schedstat_inc(this_rq()->sis_scanned); > -- > 2.26.2 >
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