[PATCH 1/5] nohz: Separate idle sleeping time accounting from nohz logic

Frederic Weisbecker
2012-06-11T16:53:42Z

As we plan to be able to stop the tick outside the idle task, we
need to prepare for separating nohz logic from idle. As a start,
this pulls the idle sleeping time accounting out of the tick
stop/restart API to the callers on idle entry/exit.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Avi Kivity <avi@redhat.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Kevin Hilman <khilman@ti.com>
Cc: Max Krasnyansky <maxk@qualcomm.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sven-Thorsten Dietrich <thebigcorporation@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
---
kernel/time/tick-sched.c | 78 +++++++++++++++++++++++++--------------------
1 files changed, 43 insertions(+), 35 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index da70c6d..6321a20 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -271,10 +271,10 @@ u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
}
EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);

-static void tick_nohz_stop_sched_tick(struct tick_sched *ts)
+static void tick_nohz_stop_sched_tick(struct tick_sched *ts, ktime_t now)
{
unsigned long seq, last_jiffies, next_jiffies, delta_jiffies;
- ktime_t last_update, expires, now;
+ ktime_t last_update, expires;
struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
u64 time_delta;
int cpu;
@@ -282,8 +282,6 @@ static void tick_nohz_stop_sched_tick(struct tick_sched *ts)
cpu = smp_processor_id();
ts = &per_cpu(tick_cpu_sched, cpu);

- now = tick_nohz_start_idle(cpu, ts);
-
/*
* If this cpu is offline and it is the one which updates
* jiffies, then give up the assignment and let it be taken by
@@ -444,6 +442,14 @@ out:
ts->sleep_length = ktime_sub(dev->next_event, now);
}

+static void __tick_nohz_idle_enter(struct tick_sched *ts)
+{
+ ktime_t now;
+
+ now = tick_nohz_start_idle(smp_processor_id(), ts);
+ tick_nohz_stop_sched_tick(ts, now);
+}
+
/**
* tick_nohz_idle_enter - stop the idle tick from the idle task
*
@@ -479,7 +485,7 @@ void tick_nohz_idle_enter(void)
* update of the idle time accounting in tick_nohz_start_idle().
*/
ts->inidle = 1;
- tick_nohz_stop_sched_tick(ts);
+ __tick_nohz_idle_enter(ts);

local_irq_enable();
}
@@ -499,7 +505,7 @@ void tick_nohz_irq_exit(void)
if (!ts->inidle)
return;

- tick_nohz_stop_sched_tick(ts);
+ __tick_nohz_idle_enter(ts);
}

/**
@@ -540,39 +546,11 @@ static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
}
}

-/**
- * tick_nohz_idle_exit - restart the idle tick from the idle task
- *
- * Restart the idle tick when the CPU is woken up from idle
- * This also exit the RCU extended quiescent state. The CPU
- * can use RCU again after this function is called.
- */
-void tick_nohz_idle_exit(void)
+static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
{
- int cpu = smp_processor_id();
- struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
#ifndef CONFIG_VIRT_CPU_ACCOUNTING
unsigned long ticks;
#endif
- ktime_t now;
-
- local_irq_disable();
-
- WARN_ON_ONCE(!ts->inidle);
-
- ts->inidle = 0;
-
- if (ts->idle_active || ts->tick_stopped)
- now = ktime_get();
-
- if (ts->idle_active)
- tick_nohz_stop_idle(cpu, now);
-
- if (!ts->tick_stopped) {
- local_irq_enable();
- return;
- }
-
/* Update jiffies first */
select_nohz_load_balancer(0);
tick_do_update_jiffies64(now);
@@ -600,6 +578,36 @@ void tick_nohz_idle_exit(void)
ts->idle_exittime = now;

tick_nohz_restart(ts, now);
+}
+
+/**
+ * tick_nohz_idle_exit - restart the idle tick from the idle task
+ *
+ * Restart the idle tick when the CPU is woken up from idle
+ * This also exit the RCU extended quiescent state. The CPU
+ * can use RCU again after this function is called.
+ */
+void tick_nohz_idle_exit(void)
+
+{
+ int cpu = smp_processor_id();
+ struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+ ktime_t now;
+
+ local_irq_disable();
+
+ WARN_ON_ONCE(!ts->inidle);
+
+ ts->inidle = 0;
+
+ if (ts->idle_active || ts->tick_stopped)
+ now = ktime_get();
+
+ if (ts->idle_active)
+ tick_nohz_stop_idle(cpu, now);
+
+ if (ts->tick_stopped)
+ tick_nohz_restart_sched_tick(ts, now);

local_irq_enable();
}
--
1.7.5.4