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Subject[PATCH] sched, numa: migrates_degrades_locality()

Subject: sched, numa: migrates_degrades_locality()
From: Peter Zijlstra <peterz@infradead.org>
Date: Mon Jul 22 14:02:54 CEST 2013

It just makes heaps of sense; so add it and make both it and
migrate_improve_locality() a sched_feat().

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-fwfjk3f8a29o3zx03h1ejb0y@git.kernel.org
---
kernel/sched/fair.c | 35 +++++++++++++++++++++++++++++++++--
kernel/sched/features.h | 2 ++
2 files changed, 35 insertions(+), 2 deletions(-)

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4323,7 +4323,7 @@ static bool migrate_improves_locality(st
{
int src_nid, dst_nid;

- if (!sched_feat(NUMA_BALANCE))
+ if (!sched_feat(NUMA_BALANCE) || !sched_feat(NUMA_FAULTS_UP))
return false;

if (!p->numa_faults || !(env->sd->flags & SD_NUMA))
@@ -4336,7 +4336,30 @@ static bool migrate_improves_locality(st
p->numa_migrate_seq >= sysctl_numa_balancing_settle_count)
return false;

- if (p->numa_preferred_nid == dst_nid)
+ if (task_faults(p, dst_nid) > task_faults(p, src_nid))
+ return true;
+
+ return false;
+}
+
+static bool migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
+{
+ int src_nid, dst_nid;
+
+ if (!sched_feat(NUMA_BALANCE) || !sched_feat(NUMA_FAULTS_DOWN))
+ 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 (task_faults(p, dst_nid) < task_faults(p, src_nid))
return true;

return false;
@@ -4347,6 +4370,12 @@ static inline bool migrate_improves_loca
{
return false;
}
+
+static inline bool migrate_degrades_locality(struct task_struct *p,
+ struct lb_env *env)
+{
+ return false;
+}
#endif

/*
@@ -4409,6 +4438,8 @@ int can_migrate_task(struct task_struct
* 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
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -70,4 +70,6 @@ SCHED_FEAT(LB_MIN, false)
SCHED_FEAT(NUMA, false)
SCHED_FEAT(NUMA_FORCE, false)
SCHED_FEAT(NUMA_BALANCE, true)
+SCHED_FEAT(NUMA_FAULTS_UP, true)
+SCHED_FEAT(NUMA_FAULTS_DOWN, false)
#endif

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