Re: [PATCH 13/13] sched: Account for the number of preferred tasksrunning on a node when selecting a preferred node

From: Peter Zijlstra
Date: Thu Jul 04 2013 - 10:07:05 EST


On Thu, Jul 04, 2013 at 02:54:15PM +0100, Mel Gorman wrote:
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 9247345..387f28d 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -863,9 +863,13 @@ find_idlest_cpu_node(int this_cpu, int nid)
> load = weighted_cpuload(i);
>
> if (load < min_load) {
> - /* Do not preempt a task running on a preferred node */
> + /*
> + * Do not preempt a task running on a preferred node or
> + * tasks are are pinned to their current CPU
> + */
> struct task_struct *p = cpu_rq(i)->curr;
> - if (p->numa_preferred_nid != nid) {
> + if (p->numa_preferred_nid != nid &&
> + cpumask_weight(tsk_cpus_allowed(p)) > 1) {

We have p->nr_cpus_allowed for that.

> min_load = load;
> idlest_cpu = i;
> }
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