linux-kernel - [PATCH 04/41] nohz: Move nohz load balancer selection into idle logic

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Date:	Tue,  1 May 2012 01:54:38 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>,
	linaro-sched-sig@...ts.linaro.org
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Alessio Igor Bogani <abogani@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Avi Kivity <avi@...hat.com>,
	Chris Metcalf <cmetcalf@...era.com>,
	Christoph Lameter <cl@...ux.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Geoff Levand <geoff@...radead.org>,
	Gilad Ben Yossef <gilad@...yossef.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Ingo Molnar <mingo@...nel.org>, Kevin Hilman <khilman@...com>,
	Max Krasnyansky <maxk@...lcomm.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Stephen Hemminger <shemminger@...tta.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sven-Thorsten Dietrich <thebigcorporation@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 04/41] nohz: Move nohz load balancer selection into idle logic

[ ** BUGGY PATCH: I need to put more thinking into this ** ]

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: Alessio Igor Bogani <abogani@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Avi Kivity <avi@...hat.com>
Cc: Chris Metcalf <cmetcalf@...era.com>
Cc: Christoph Lameter <cl@...ux.com>
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Geoff Levand <geoff@...radead.org>
Cc: Gilad Ben Yossef <gilad@...yossef.com>
Cc: Hakan Akkan <hakanakkan@...il.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Kevin Hilman <khilman@...com>
Cc: Max Krasnyansky <maxk@...lcomm.com>
Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Stephen Hemminger <shemminger@...tta.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
---
 kernel/time/tick-sched.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index fc9f687..b79dea2 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -398,8 +398,6 @@ static void tick_nohz_stop_sched_tick(struct tick_sched *ts, 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;
 		}
@@ -449,8 +447,10 @@ static void __tick_nohz_idle_enter(struct tick_sched *ts)
 	now = tick_nohz_start_idle(smp_processor_id(), ts);
 	tick_nohz_stop_sched_tick(ts, now);
 
-	if (!was_stopped && ts->tick_stopped)
+	if (!was_stopped && ts->tick_stopped) {
 		ts->idle_jiffies = ts->last_jiffies;
+		select_nohz_load_balancer(1);
+	}
 }
 
 /**
@@ -552,7 +552,6 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
 static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
 {
 	/* Update jiffies first */
-	select_nohz_load_balancer(0);
 	tick_do_update_jiffies64(now);
 
 	touch_softlockup_watchdog();
@@ -610,6 +609,7 @@ void tick_nohz_idle_exit(void)
 		tick_nohz_stop_idle(cpu, now);
 
 	if (ts->tick_stopped) {
+		select_nohz_load_balancer(0);
 		tick_nohz_restart_sched_tick(ts, now);
 		tick_nohz_account_idle_ticks(ts);
 	}
-- 
1.7.5.4

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