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From: Arjan van de Ven on 9 May 2010 11:30
From: Arjan van de Ven <arjan(a)linux.intel.com>

Right now, get_cpu_idle_time_us() only reports the idle statistics
upto the point the CPU entered last idle; not what is valid right now.

This patch adds an update of the idle statistics to get_cpu_idle_time_us(),
so that calling this function always returns statistics that are accurate
at the point of the call.

This includes resetting the start of the idle time for accounting purposes
to avoid double accounting.

Signed-off-by: Arjan van de Ven <arjan(a)linux.intel.com>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
Reviewed-by: Rik van Riel <riel(a)redhat.com>
---

kernel/time/tick-sched.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff -puN kernel/time/tick-sched.c~sched-update-the-idle-statistics-in-get_cpu_idle_time_us kernel/time/tick-sched.c
--- a/kernel/time/tick-sched.c~sched-update-the-idle-statistics-in-get_cpu_idle_time_us
+++ a/kernel/time/tick-sched.c
@@ -161,6 +161,7 @@ static void update_ts_time_stats(struct
if (ts->idle_active) {
delta = ktime_sub(now, ts->idle_entrytime);
ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
+ ts->idle_entrytime = now;
}
}

@@ -205,14 +206,18 @@ static ktime_t tick_nohz_start_idle(stru
u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
{
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
+ ktime_t now;

if (!tick_nohz_enabled)
return -1;

+ now = ktime_get();
+ update_ts_time_stats(ts, now);
+
if (ts->idle_active)
*last_update_time = ktime_to_us(ts->idle_lastupdate);
else
- *last_update_time = ktime_to_us(ktime_get());
+ *last_update_time = ktime_to_us(now);

return ktime_to_us(ts->idle_sleeptime);
}
_
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Prev: [PATCH v2 1/8] sched: Add a comment to get_cpu_idle_time_us()
Next: [PATCH v2 5/8] sched: Eliminate the ts->idle_lastupdate field