linux-kernel - [PATCH 08/32] nohz: Move nohz load balancer selection into idle logic

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Date:	Mon, 15 Aug 2011 17:52:05 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Anton Blanchard <anton@....ibm.com>,
	Avi Kivity <avi@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
	Paul Menage <menage@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Stephen Hemminger <shemminger@...tta.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tim Pepper <lnxninja@...ux.vnet.ibm.com>
Subject: [PATCH 08/32] nohz: Move nohz load balancer selection into idle logic

We want the nohz load balancer to be an idle CPU, thus
move that selection to strict dyntick idle logic.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Anton Blanchard <anton@....ibm.com>
Cc: Avi Kivity <avi@...hat.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Lai Jiangshan <laijs@...fujitsu.com>
Cc: Paul E . McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Paul Menage <menage@...gle.com>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Stephen Hemminger <shemminger@...tta.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Tim Pepper <lnxninja@...ux.vnet.ibm.com>
---
 kernel/time/tick-sched.c |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index bca1519..de1b629 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -380,8 +380,6 @@ static void tick_nohz_stop_sched_tick(ktime_t now)
 		 * the scheduler tick in nohz_restart_sched_tick.
 		 */
 		if (!ts->tick_stopped) {
-			select_nohz_load_balancer(1);
-
 			ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
 			ts->tick_stopped = 1;
 		}
@@ -434,6 +432,7 @@ static void __tick_nohz_enter_idle(struct tick_sched *ts, int cpu)
 
 	if (!was_stopped && ts->tick_stopped) {
 		ts->idle_jiffies = ts->last_jiffies;
+		select_nohz_load_balancer(1);
 		rcu_enter_nohz();
 	}
 }
@@ -501,7 +500,6 @@ static void tick_nohz_restart_sched_tick(ktime_t now, struct tick_sched *ts)
 	int cpu = smp_processor_id();
 
 	/* Update jiffies first */
-	select_nohz_load_balancer(0);
 	tick_do_update_jiffies64(now);
 	cpumask_clear_cpu(cpu, nohz_cpu_mask);
 
@@ -552,6 +550,7 @@ void tick_nohz_exit_idle(void)
 
 	if (ts->tick_stopped) {
 		rcu_exit_nohz();
+		select_nohz_load_balancer(0);
 		tick_nohz_restart_sched_tick(now, ts);
 		tick_nohz_account_idle_ticks(ts);
 	}
-- 
1.7.5.4

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