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authorArjan van de Ven <arjan@linux.intel.com>2010-05-09 08:22:08 -0700
committerIngo Molnar <mingo@elte.hu>2010-05-09 19:35:25 +0200
commitb1f724c3055fa75a31d272222213647547a2d3d4 (patch)
tree9f9e9105a01405e252b5214e83bdbfcd10921f43 /kernel/time
parente7858f52a5cb868289a72264534a1f05f3340c6c (diff)
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@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Rik van Riel <riel@redhat.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: davej@redhat.com LKML-Reference: <20100509082208.7cb721f0@infradead.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/time')
-rw-r--r--kernel/time/tick-sched.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index f25735a767a..358822ee32d 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);