linux-kernel - [PATCH] scheduler: domain: correctly initialize 'next

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Date:	Wed, 7 Mar 2012 14:44:26 -0800
From:	Diwakar Tundlam <dtundlam@...dia.com>
To:	Ingo Molnar <mingo@...e.hu>,
	'Peter Zijlstra' <peterz@...radead.org>,
	'Jens Axboe' <jaxboe@...ionio.com>,
	'Randy Dunlap' <randy.dunlap@...cle.com>
CC:	Peter De Schrijver <pdeschrijver@...dia.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	'Linus Torvalds' <torvalds@...ux-foundation.org>
Subject: [PATCH] scheduler: domain: correctly initialize 'next_balance' in
 'nohz' idle balancer

scheduler: domain: init next_balance in nohz_idle_balancer with jiffies

The 'next_balance' field of 'nohz' idle balancer must be initialized
to jiffies. Since jiffies is initialized to negative 300 seconds the
'nohz' idle balancer does not run for the first 300s (5mins) after
bootup. If no new processes are spawed or no idle cycles happen, the
load on the cpus will remain unbalanced for that duration.

Signed-off-by: Diwakar Tundlam <dtundlam@...dia.com>
---
 1 files changed, 1 insertions(+), 0 deletions(-)

diff -up sched/fair.c{.orig,}
--- sched/fair.c.orig	2012-03-07 08:33:03.000000000 -0800
+++ sched/fair.c	2012-03-07 13:50:30.787265795 -0800
@@ -5614,6 +5614,7 @@ __init void init_sched_fair_class(void)
 	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);
 
 #ifdef CONFIG_NO_HZ
+	nohz.next_balance = jiffies;
 	zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
 	cpu_notifier(sched_ilb_notifier, 0);
 #endif
--
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