Messages in this thread | | | From | Vincent Guittot <> | Date | Thu, 5 Dec 2019 19:52:40 +0100 | Subject | Re: [PATCH] sched/fair: Optimize select_idle_core |
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On Thu, 5 Dec 2019 at 18:52, Srikar Dronamraju <srikar@linux.vnet.ibm.com> wrote: > > * Vincent Guittot <vincent.guittot@linaro.org> [2019-12-05 18:27:51]: > > > 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 > > > > > > > That goal we still continue to maintain by the way of cpumask_andnot. > i.e instead of clearing CPUs one at a time, we clear all the CPUs in the > core at one shot.
ah yes sorry, I have been to quick and overlooked the cpumask_andnot line
> > > > 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 > > > > > -- > Thanks and Regards > Srikar Dronamraju >
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