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SubjectRe: [PATCH 08/18] sched: Reschedule task on preferred NUMA node once selected
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On Mon, Jul 15, 2013 at 11:20 PM, Mel Gorman <mgorman@suse.de> wrote:
> +static int
> +find_idlest_cpu_node(int this_cpu, int nid)
> +{
> + unsigned long load, min_load = ULONG_MAX;
> + int i, idlest_cpu = this_cpu;
> +
> + BUG_ON(cpu_to_node(this_cpu) == nid);
> +
> + rcu_read_lock();
> + for_each_cpu(i, cpumask_of_node(nid)) {

Check allowed CPUs first if task is given?

> + load = weighted_cpuload(i);
> +
> + if (load < min_load) {
> + min_load = load;
> + idlest_cpu = i;
> + }
> + }
> + rcu_read_unlock();
> +
> + return idlest_cpu;
> +}
> +
[...]
> + /*
> + * Record the preferred node as the node with the most faults,
> + * requeue the task to be running on the idlest CPU on the
> + * preferred node and reset the scanning rate to recheck
> + * the working set placement.
> + */
> if (max_faults && max_nid != p->numa_preferred_nid) {
> + int preferred_cpu;
> +
> + /*
> + * If the task is not on the preferred node then find the most
> + * idle CPU to migrate to.
> + */
> + preferred_cpu = task_cpu(p);
> + if (cpu_to_node(preferred_cpu) != max_nid) {
> + preferred_cpu = find_idlest_cpu_node(preferred_cpu,
> + max_nid);
> + }
> +
> + /* Update the preferred nid and migrate task if possible */
> p->numa_preferred_nid = max_nid;
> p->numa_migrate_seq = 0;
> + migrate_task_to(p, preferred_cpu);
> }


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