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Subject[tip:sched/urgent] sched/fair: Fix wake_affine_llc() balancing rules
Commit-ID:  a731ebe6f17bff9e7ca12ef227f9da4d5bdf8425
Gitweb: http://git.kernel.org/tip/a731ebe6f17bff9e7ca12ef227f9da4d5bdf8425
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Wed, 6 Sep 2017 12:51:31 +0200
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 7 Sep 2017 09:29:31 +0200

sched/fair: Fix wake_affine_llc() balancing rules

Chris Wilson reported that the SMT balance rules got the +1 on the
wrong side, resulting in a bias towards the current LLC; which the
load-balancer would then try and undo.

Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Tested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Fixes: 90001d67be2f ("sched/fair: Fix wake_affine() for !NUMA_BALANCING")
Link: http://lkml.kernel.org/r/20170906105131.gqjmaextmn3u6tj2@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8d58687..9dd2ce1 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5435,7 +5435,7 @@ wake_affine_llc(struct sched_domain *sd, struct task_struct *p,
return false;

/* if this cache has capacity, come here */
- if (this_stats.has_capacity && this_stats.nr_running < prev_stats.nr_running+1)
+ if (this_stats.has_capacity && this_stats.nr_running+1 < prev_stats.nr_running)
return true;

/*
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