sched/numa: Resist moving tasks towards nodes with fewer hinting faults

Just as "sched: Favour moving tasks towards the preferred node" favours
moving tasks towards nodes with a higher number of recorded NUMA hinting
faults, this patch resists moving tasks towards nodes with lower faults.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-24-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6ffddca687fe..89431248d33d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4107,12 +4107,43 @@ static bool migrate_improves_locality(struct task_struct *p, struct lb_env *env)
 
         return false;
 }
+
+
+static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
+{
+        int src_nid, dst_nid;
+
+        if (!sched_feat(NUMA) || !sched_feat(NUMA_RESIST_LOWER))
+                return false;
+
+        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;
+
+        if (p->numa_faults[dst_nid] < p->numa_faults[src_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
 
 /*
@@ -4177,6 +4208,8 @@ 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, rq_clock_task(env->src_rq), env->sd);
+        if (!tsk_cache_hot)
+                tsk_cache_hot = migrate_degrades_locality(p, env);
 
         if (migrate_improves_locality(p, env)) {
 #ifdef CONFIG_SCHEDSTATS