linux-kernel - [PATCH 3/4] nohz: Consolidate sleep time stats read code

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Date:	Fri, 16 Aug 2013 17:42:32 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Fernando Luis Vazquez Cao <fernando_b1@....ntt.co.jp>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: [PATCH 3/4] nohz: Consolidate sleep time stats read code

get_cpu_idle_time_us() and get_cpu_iowait_time_us() mostly share
the same code. Lets consolidate both implementations.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Fernando Luis Vazquez Cao <fernando_b1@....ntt.co.jp>
Cc: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Arjan van de Ven <arjan@...ux.intel.com>
---
 kernel/time/tick-sched.c |   76 ++++++++++++++++++++--------------------------
 1 files changed, 33 insertions(+), 43 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index f7fc27b..017bec2 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -440,24 +440,10 @@ static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts)
 	return now;
 }
 
-/**
- * get_cpu_idle_time_us - get the total idle time of a cpu
- * @cpu: CPU number to query
- * @last_update_time: variable to store update time in. Do not update
- * counters if NULL.
- *
- * Return the cummulative idle time (since boot) for a given
- * CPU, in microseconds.
- *
- * This time is measured via accounting rather than sampling,
- * and is as accurate as ktime_get() is.
- *
- * This function returns -1 if NOHZ is not enabled.
- */
-u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
+static u64 get_cpu_sleep_time_us(int cpu, bool io, u64 *last_update_time)
 {
 	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
-	ktime_t now, idle;
+	ktime_t now, sleep;
 	unsigned int seq;
 
 	if (!tick_nohz_enabled)
@@ -469,16 +455,41 @@ u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
 
 	do {
 		seq = read_seqcount_begin(&ts->sleeptime_seq);
-		if (ts->idle_active && !nr_iowait_cpu(cpu)) {
+		if (io)
+			sleep = ts->iowait_sleeptime;
+		else
+			sleep = ts->idle_sleeptime;
+
+		if (ts->idle_active)
+			continue;
+
+		if ((io && nr_iowait_cpu(cpu)) || (!io && !nr_iowait_cpu(cpu))) {
 			ktime_t delta = ktime_sub(now, ts->idle_entrytime);
-			idle = ktime_add(ts->idle_sleeptime, delta);
-		} else {
-			idle = ts->idle_sleeptime;
+			sleep = ktime_add(sleep, delta);
 		}
 	} while (read_seqcount_retry(&ts->sleeptime_seq, seq));
 
-	return ktime_to_us(idle);
+	return ktime_to_us(sleep);
+
+}
 
+/**
+ * get_cpu_idle_time_us - get the total idle time of a cpu
+ * @cpu: CPU number to query
+ * @last_update_time: variable to store update time in. Do not update
+ * counters if NULL.
+ *
+ * Return the cummulative idle time (since boot) for a given
+ * CPU, in microseconds.
+ *
+ * This time is measured via accounting rather than sampling,
+ * and is as accurate as ktime_get() is.
+ *
+ * This function returns -1 if NOHZ is not enabled.
+ */
+u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
+{
+	return get_cpu_sleep_time_us(cpu, false, last_update_time);
 }
 EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
 
@@ -498,28 +509,7 @@ EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
  */
 u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
 {
-	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
-	ktime_t now, iowait;
-	unsigned int seq;
-
-	if (!tick_nohz_enabled)
-		return -1;
-
-	now = ktime_get();
-	if (last_update_time)
-		*last_update_time = ktime_to_us(now);
-
-	do {
-		seq = read_seqcount_begin(&ts->sleeptime_seq);
-		if (ts->idle_active && nr_iowait_cpu(cpu) > 0) {
-			ktime_t delta = ktime_sub(now, ts->idle_entrytime);
-			iowait = ktime_add(ts->iowait_sleeptime, delta);
-		} else {
-			iowait = ts->iowait_sleeptime;
-		}
-	} while (read_seqcount_retry(&ts->sleeptime_seq, seq));
-
-	return ktime_to_us(iowait);
+	return get_cpu_sleep_time_us(cpu, true, last_update_time);
 }
 EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
 
-- 
1.7.5.4

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