linux-kernel - [PATCH v2 1/8] sched: Add a comment to get_cpu_idle_time

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Message-ID: <20100509082208.7cb721f0@infradead.org>
Date:	Sun, 9 May 2010 08:22:08 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, davej@...hat.com
Subject: [PATCH v2  1/8] sched: Add a comment to get_cpu_idle_time_us()

From: Arjan van de Ven <arjan@...ux.intel.com>

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>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Reviewed-by: Rik van Riel <riel@...hat.com>

---

 kernel/time/tick-sched.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff -puN kernel/time/tick-sched.c~sched-add-a-comment-to-get_cpu_idle_time_us kernel/time/tick-sched.c
--- a/kernel/time/tick-sched.c~sched-add-a-comment-to-get_cpu_idle_time_us
+++ a/kernel/time/tick-sched.c
@@ -179,6 +179,20 @@ static ktime_t tick_nohz_start_idle(stru
 	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);
_
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