On Wed, Jun 26, 2013 at 03:38:04PM +0100, Mel Gorman wrote:
> @@ -3897,6 +3907,28 @@ task_hot(struct task_struct *p, u64 now, struct
> sched_domain *sd)
> return delta < (s64)sysctl_sched_migration_cost;
> }
>
> +/* Returns true if the destination node has incurred more faults */
> +static bool migrate_improves_locality(struct task_struct *p, struct lb_env
> *env)
> +{
> + int src_nid, dst_nid;
> +
> + if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
> + return false;
> +
> + src_nid = cpu_to_node(env->src_cpu);
> + dst_nid = cpu_to_node(env->dst_cpu);
> +
> + if (src_nid == dst_nid)
> + return false;
> +
> + if (p->numa_migrate_seq < sysctl_numa_balancing_settle_count &&
> + p->numa_preferred_nid == dst_nid)
> + return true;
> +
> + return false;
> +}
> +
> +
> /*
> * can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
> */
> @@ -3945,10 +3977,14 @@ int can_migrate_task(struct task_struct *p, struct
> lb_env *env)
>
> /*
> * Aggressive migration if:
> - * 1) task is cache cold, or
> - * 2) too many balance attempts have failed.
> + * 1) destination numa is preferred
> + * 2) task is cache cold, or
> + * 3) too many balance attempts have failed.
> */
>
> + if (migrate_improves_locality(p, env))
> + return 1;
> +
> tsk_cache_hot = task_hot(p, env->src_rq->clock_task, env->sd);
> if (!tsk_cache_hot ||
> env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
Should we not also do the reverse; make it harder to worsen locality?
Similar to the task_hot() thing; do not allow to migrate a task on low
nr_balance_failed when it makes the locality worse.
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