On Wed, Jun 26, 2013 at 03:38:04PM +0100, Mel Gorman wrote:
> +/* 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;
> +}
Also, until I just actually _read_ that function; I assumed it would
compare p->numa_faults[src_nid] and p->numa_faults[dst_nid]. Because
even when the dst_nid isn't the preferred nid; it might still have more
pages than where we currently are.
Idem with the proposed migrate_degrades_locality().
Something like so I suppose
---
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3969,6 +3969,7 @@ task_hot(struct task_struct *p, u64 now,
return delta < (s64)sysctl_sched_migration_cost;
}
+#ifdef CONFIG_NUMA_BALANCING
/* Returns true if the destination node has incurred more faults */
static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
{
@@ -3983,13 +3984,50 @@ static bool migrate_improves_locality(st
if (src_nid == dst_nid)
return false;
- if (p->numa_migrate_seq < sysctl_numa_balancing_settle_count &&
- p->numa_preferred_nid == dst_nid)
+ if (p->numa_migrate_seq >= sysctl_numa_balancing_settle_count)
+ return false;
+
+ if (p->numa_preferred_nid == dst_nid)
+ return true;
+
+ if (p->numa_faults[src_nid] < p->numa_faults[dst_nid])
+ return true;
+
+ return false;
+}
+
+static vool migrate_degrades_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_faults[src_nid] > p->numa_faults[dst_nid])
return true;
return false;
}
+#else
+
+static inline bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
+{
+ return false;
+}
+
+static inline bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
+{
+ return false;
+}
+
+#endif /* CONFIG_NUMA_BALANCING */
/*
* can_migrate_task - may task p from runqueue rq be migrated to this_cpu?
@@ -4055,8 +4093,10 @@ int can_migrate_task(struct task_struct
return 1;
tsk_cache_hot = task_hot(p, rq_clock_task(env->src_rq), env->sd);
+ if (!tsk_cache_hot)
+ tsk_cache_hot = migrate_degrades_locality(p, env);
if (!tsk_cache_hot ||
- env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
+ env->sd->nr_balance_failed > env->sd->cache_nice_tries) {
if (tsk_cache_hot) {
schedstat_inc(env->sd, lb_hot_gained[env->idle]);
--
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