From b1f724c3055fa75a31d272222213647547a2d3d4 Mon Sep 17 00:00:00 2001 From: Arjan van de Ven Date: Sun, 9 May 2010 08:22:08 -0700 Subject: 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 Signed-off-by: Andrew Morton Reviewed-by: Rik van Riel Acked-by: Peter Zijlstra Cc: davej@redhat.com LKML-Reference: <20100509082208.7cb721f0@infradead.org> Signed-off-by: Ingo Molnar --- kernel/time/tick-sched.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'kernel/time') diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index f25735a767af..358822ee32d5 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); -- cgit v1.2.3-70-g09d2