linux-kernel - [PATCH 06/32] nohz: Move idle ticks stats tracking out of nohz handlers

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Date:	Mon, 15 Aug 2011 17:52:03 +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 06/32] nohz: Move idle ticks stats tracking out of nohz handlers

Idle ticks time tracking is merged into nohz stop/restart
handlers. Pull it out into idle entry/exit handlers instead,
so that nohz APIs is more idle independant.

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 |   34 +++++++++++++++++++---------------
 1 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 8937d4a..21b187c 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -384,7 +384,6 @@ static void tick_nohz_stop_sched_tick(ktime_t now)
 
 			ts->idle_tick = hrtimer_get_expires(&ts->sched_timer);
 			ts->tick_stopped = 1;
-			ts->idle_jiffies = last_jiffies;
 		}
 
 		ts->idle_sleeps++;
@@ -433,8 +432,10 @@ static void __tick_nohz_enter_idle(struct tick_sched *ts, int cpu)
 	now = tick_nohz_start_idle(cpu, ts);
 	tick_nohz_stop_sched_tick(now);
 
-	if (!was_stopped && ts->tick_stopped)
+	if (!was_stopped && ts->tick_stopped) {
+		ts->idle_jiffies = ts->last_jiffies;
 		rcu_enter_nohz();
+	}
 }
 
 void tick_nohz_enter_idle(void)
@@ -498,16 +499,26 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
 static void tick_nohz_restart_sched_tick(ktime_t now, struct tick_sched *ts)
 {
 	int cpu = smp_processor_id();
-#ifndef CONFIG_VIRT_CPU_ACCOUNTING
-	unsigned long ticks;
-#endif
 
 	/* Update jiffies first */
 	select_nohz_load_balancer(0);
 	tick_do_update_jiffies64(now);
 	cpumask_clear_cpu(cpu, nohz_cpu_mask);
 
+	touch_softlockup_watchdog();
+	/*
+	 * Cancel the scheduled timer and restore the tick
+	 */
+	ts->tick_stopped  = 0;
+	ts->idle_exittime = now;
+
+	tick_nohz_restart(ts, now);
+}
+
+static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
+{
 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
+	unsigned long ticks;
 	/*
 	 * We stopped the tick in idle. Update process times would miss the
 	 * time we slept as update_process_times does only a 1 tick
@@ -520,15 +531,6 @@ static void tick_nohz_restart_sched_tick(ktime_t now, struct tick_sched *ts)
 	if (ticks && ticks < LONG_MAX)
 		account_idle_ticks(ticks);
 #endif
-
-	touch_softlockup_watchdog();
-	/*
-	 * Cancel the scheduled timer and restore the tick
-	 */
-	ts->tick_stopped  = 0;
-	ts->idle_exittime = now;
-
-	tick_nohz_restart(ts, now);
 }
 
 void tick_nohz_exit_idle(void)
@@ -551,6 +553,7 @@ void tick_nohz_exit_idle(void)
 	if (ts->tick_stopped) {
 		rcu_exit_nohz();
 		tick_nohz_restart_sched_tick(now, ts);
+		tick_nohz_account_idle_ticks(ts);
 	}
 
 	local_irq_enable();
@@ -766,7 +769,8 @@ static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
 		 */
 		if (ts->tick_stopped) {
 			touch_softlockup_watchdog();
-			ts->idle_jiffies++;
+			if (idle_cpu(cpu))
+				ts->idle_jiffies++;
 		}
 		update_process_times(user_mode(regs));
 		profile_tick(CPU_PROFILING);
-- 
1.7.5.4

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