Messages in this thread | | | From | Vincent Guittot <> | Date | Thu, 5 Dec 2019 18:27:51 +0100 | Subject | Re: [PATCH] sched/fair: Optimize select_idle_core |
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Hi Srikar,
On Thu, 5 Dec 2019 at 18:23, Srikar Dronamraju <srikar@linux.vnet.ibm.com> wrote: > > Currently we loop through all threads of a core to evaluate if the core > is idle or not. This is unnecessary. If a thread of a core is not > idle, skip evaluating other threads of a core.
I think that the goal is also to clear all CPUs of the core from the cpumask of the loop above so it will not try the same core next time
> > Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com> > --- > kernel/sched/fair.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 69a81a5709ff..b9d628128cfc 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5872,10 +5872,12 @@ static int select_idle_core(struct task_struct *p, struct sched_domain *sd, int > bool idle = true; > > for_each_cpu(cpu, cpu_smt_mask(core)) { > - __cpumask_clear_cpu(cpu, cpus); > - if (!available_idle_cpu(cpu)) > + if (!available_idle_cpu(cpu)) { > idle = false; > + break; > + } > } > + cpumask_andnot(cpus, cpus, cpu_smt_mask(core)); > > if (idle) > return core; > -- > 2.18.1 >
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