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[PATCH 1/4] sched,numa: override part of migrate_degrades_locality when idle balancing

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From: Rik van Riel <riel@redhat.com>

Several tests in the NAS benchmark seem to run a lot slower with
NUMA balancing enabled, than with NUMA balancing disabled. The
slower run time corresponds with increased idle time.

Overriding the final test of migrate_degrades_locality (but still
doing the other NUMA tests first) seems to improve performance
of those benchmarks.

Reported-by: Jirka Hladky <jhladky@redhat.com>
Signed-off-by: Rik van Riel <riel@surriel.com>
Signed-off-by: Rik van Riel <riel@redhat.com>
---
 kernel/sched/fair.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2a0e71034e36..2180c8591e16 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6635,6 +6635,10 @@ static int migrate_degrades_locality(struct task_struct *p, struct lb_env *env)
 	if (dst_nid == p->numa_preferred_nid)
 		return 0;
 
+	/* Leaving a core idle is often worse than degrading locality. */
+	if (env->idle != CPU_NOT_IDLE)
+		return -1;
+
 	if (numa_group) {
 		src_faults = group_faults(p, src_nid);
 		dst_faults = group_faults(p, dst_nid);
-- 
2.9.4

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[PATCH 0/4] NUMA improvements with task wakeup and load balancing riel@redhat.com - 2017-06-23 19:00 +0200
  [PATCH 1/4] sched,numa: override part of migrate_degrades_locality when idle balancing riel@redhat.com - 2017-06-23 19:00 +0200
    Re: [PATCH 1/4] sched,numa: override part of  migrate_degrades_locality when idle balancing Ingo Molnar <mingo@kernel.org> - 2017-06-24 09:00 +0200
      Re: [PATCH 1/4] sched,numa: override part of  migrate_degrades_locality when idle balancing Rik van Riel <riel@redhat.com> - 2017-06-25 01:50 +0200
    [tip:sched/core] sched/numa: Override part of  migrate_degrades_locality() when idle balancing tip-bot for Rik van Riel <tipbot@zytor.com> - 2017-06-24 09:30 +0200
  [PATCH 2/4] sched: simplify wake_affine for single socket case riel@redhat.com - 2017-06-23 19:00 +0200
    [tip:sched/core] sched/fair: Simplify wake_affine() for the single  socket case tip-bot for Rik van Riel <tipbot@zytor.com> - 2017-06-24 09:30 +0200

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