The scheduler already favours moving tasks towards its preferred node but
does nothing special if the destination node is anything else. This patch
favours moving tasks towards a destination node if more NUMA hinting faults
were recorded on it. Similarly if migrating to a destination node would
degrade locality based on NUMA hinting faults then it will be resisted.
Signed-off-by: Peter Zijlstra <pet...@infradead.org>
Signed-off-by: Mel Gorman <mgor...@suse.de>
---
kernel/sched/fair.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 48 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e8d9b3e..e451859 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3967,22 +3967,54 @@ task_hot(struct task_struct *p, u64 now, struct
sched_domain *sd)
}
#ifdef CONFIG_NUMA_BALANCING
+
+static bool migrate_locality_prepare(struct task_struct *p, struct lb_env *env,
+ int *src_nid, int *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 ||
+ p->numa_migrate_seq >= sysctl_numa_balancing_settle_count)
+ return false;
+
+ return true;
+}
+
/* 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))
+ if (!migrate_locality_prepare(p, env, &src_nid, &dst_nid))
return false;
- src_nid = cpu_to_node(env->src_cpu);
- dst_nid = cpu_to_node(env->dst_cpu);
+ /* Move towards node if it is the preferred node */
+ if (p->numa_preferred_nid == dst_nid)
+ return true;
- if (src_nid == dst_nid ||
- p->numa_migrate_seq >= sysctl_numa_balancing_settle_count)
+ /*
+ * Move towards node if there were a higher number of private
+ * NUMA hinting faults recorded on it
+ */
+ if (p->numa_faults[task_faults_idx(dst_nid, 1)] >
+ p->numa_faults[task_faults_idx(src_nid, 1)])
+ return true;
+
+ return false;
+}
+
+static bool migrate_degrades_locality(struct task_struct *p, struct lb_env
*env)
+{
+ int src_nid, dst_nid;
+
+ if (!migrate_locality_prepare(p, env, &src_nid, &dst_nid))
return false;
- if (p->numa_preferred_nid == dst_nid)
+ if (p->numa_faults[src_nid] > p->numa_faults[dst_nid])
return true;
return false;
@@ -3993,6 +4025,14 @@ static inline bool migrate_improves_locality(struct
task_struct *p,
{
return false;
}
+
+
+static inline bool migrate_degrades_locality(struct task_struct *p,
+ struct lb_env *env)
+{
+ return false;
+}
+
#endif
/*
@@ -4048,6 +4088,8 @@ int can_migrate_task(struct task_struct *p, struct lb_env
*env)
* 3) too many balance attempts have failed.
*/
tsk_cache_hot = task_hot(p, env->src_rq->clock_task, env->sd);
+ if (!tsk_cache_hot)
+ tsk_cache_hot = migrate_degrades_locality(p, env);
if (migrate_improves_locality(p, env)) {
#ifdef CONFIG_SCHEDSTATS
--
1.8.1.4
--
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