linux-kernel - [tip:sched/urgent] sched: Fix rebalance interval calculation

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Message-ID: <tip-3436ae1298cb22d722a6520fc97f112dd767a9e1@git.kernel.org>
Date:	Thu, 31 Mar 2011 12:40:39 GMT
From:	tip-bot for Sisir Koppaka <sisir.koppaka@...il.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, mingo@...e.hu,
	sisir.koppaka@...il.com
Subject: [tip:sched/urgent] sched: Fix rebalance interval calculation

Commit-ID:  3436ae1298cb22d722a6520fc97f112dd767a9e1
Gitweb:     http://git.kernel.org/tip/3436ae1298cb22d722a6520fc97f112dd767a9e1
Author:     Sisir Koppaka <sisir.koppaka@...il.com>
AuthorDate: Sat, 26 Mar 2011 18:22:55 +0530
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Thu, 31 Mar 2011 13:00:37 +0200

sched: Fix rebalance interval calculation

The interval for checking scheduling domains if they are due to be
balanced currently depends on boot state NR_CPUS, which may not
accurately reflect the number of online CPUs at the time of check.

Thus replace NR_CPUS with num_online_cpus().

 (ed: Should only affect those who set NR_CPUS really high, such as 4096
      or so :-)

Signed-off-by: Sisir Koppaka <sisir.koppaka@...il.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
LKML-Reference: <AANLkTikqHWid2Q93F5U5Qw5snJH8C5PXoa7J6=6hYO94@...l.gmail.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/sched_fair.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 3f7ec9e..c7ec5c8 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -22,6 +22,7 @@
 
 #include <linux/latencytop.h>
 #include <linux/sched.h>
+#include <linux/cpumask.h>
 
 /*
  * Targeted preemption latency for CPU-bound tasks:
@@ -3850,8 +3851,8 @@ static void rebalance_domains(int cpu, enum cpu_idle_type idle)
 		interval = msecs_to_jiffies(interval);
 		if (unlikely(!interval))
 			interval = 1;
-		if (interval > HZ*NR_CPUS/10)
-			interval = HZ*NR_CPUS/10;
+		if (interval > HZ*num_online_cpus()/10)
+			interval = HZ*num_online_cpus()/10;
 
 		need_serialize = sd->flags & SD_SERIALIZE;
 
--
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