Messages in this thread | | | Date | Fri, 28 Jun 2019 11:54:41 +0000 | From | Srikar Dronamraju <> | Subject | Re: [PATCH v3 3/7] sched: rotate the cpu search window for better spread |
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* subhra mazumdar <subhra.mazumdar@oracle.com> [2019-06-26 18:29:15]:
> Rotate the cpu search window for better spread of threads. This will ensure > an idle cpu will quickly be found if one exists.
While rotating the cpu search window is good, not sure if this can find a idle cpu quickly. The probability of finding an idle cpu still should remain the same. No?
> > Signed-off-by: subhra mazumdar <subhra.mazumdar@oracle.com> > --- > kernel/sched/fair.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > @@ -6219,9 +6219,15 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t > } > } > > + if (per_cpu(next_cpu, target) != -1) > + target_tmp = per_cpu(next_cpu, target); > + else > + target_tmp = target; > + > time = local_clock(); > > - for_each_cpu_wrap(cpu, sched_domain_span(sd), target) { > + for_each_cpu_wrap(cpu, sched_domain_span(sd), target_tmp) { > + per_cpu(next_cpu, target) = cpu;
Shouldn't this assignment be outside the for loop. With the current code, 1. We keep reassigning multiple times. 2. The last assignment happes for idle_cpu and sometimes the assignment is for non-idle cpu.
> if (!--nr) > return -1; > if (!cpumask_test_cpu(cpu, &p->cpus_allowed)) > -- > 2.9.3 >
-- Thanks and Regards Srikar Dronamraju
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