From 739294fb03f590401bbd7faa6d31a507e3ffada5 Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Fri, 23 Jun 2017 12:55:27 -0400 Subject: [PATCH] sched/numa: Override part of migrate_degrades_locality() when idle balancing 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 Signed-off-by: Rik van Riel Cc: Linus Torvalds Cc: Mel Gorman Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Link: http://lkml.kernel.org/r/20170623165530.22514-2-riel@redhat.com Signed-off-by: Ingo Molnar --- kernel/sched/fair.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 694c258b8771..6e0c0524131e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6688,6 +6688,10 @@ 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);