linux-kernel - [PATCH 1/7] sched: add a comment to get_cpu_idle_time

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Message-ID: <20100418120050.562d63a6@infradead.org>
Date:	Sun, 18 Apr 2010 12:00:50 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	linux-kernel@...r.kernel.org
Cc:	Arjan van de Ven <arjan@...radead.org>, akpm@...ux-foundation.org,
	mingo@...e.hu, peterz@...radead.org, tglx@...utronix.de,
	davej@...hat.com, cpufreq@...r.kernel.org
Subject: [PATCH 1/7] sched: add a comment to get_cpu_idle_time_us()

>From 6f9df3bc6571d6545c552151f408d69265e15f92 Mon Sep 17 00:00:00 2001
From: Arjan van de Ven <arjan@...ux.intel.com>
Date: Sun, 18 Apr 2010 10:25:19 -0700
Subject: [PATCH 1/7] sched: add a comment to get_cpu_idle_time_us()

The exported function get_cpu_idle_time_us() has no comment
describing it; add a kerneldoc comment

Signed-off-by: Arjan van de Ven <arjan@...ux.intel.com>
---
 kernel/time/tick-sched.c |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index f992762..54dc155 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -179,6 +179,20 @@ static ktime_t tick_nohz_start_idle(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
+ *
+ * Return the cummulative idle time (since boot) for a given
+ * CPU, in microseconds. The idle time returned includes
+ * the iowait time (unlike what "top" and co report).
+ *
+ * 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)
 {
 	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
-- 
1.6.2.5

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