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sched: Intoduce get_cpu_iowait_time_us()

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For the ondemand cpufreq governor, it is desired that the iowait
time is microaccounted in a similar way as idle time is.

This patch introduces the infrastructure to account and expose
this information via the get_cpu_iowait_time_us() function.

[akpm@linux-foundation.org: fix CONFIG_NO_HZ=n build]
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: <20100509082523.284feab6@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Arjan van de Ven
2010-05-09 08:25:23 -07:00
committed by Ingo Molnar
parent e0e37c200f
commit 0224cf4c5e
3 changed files with 33 additions and 0 deletions
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28
kernel/time/tick-sched.c
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@@ -161,6 +161,8 @@ update_ts_time_stats(struct tick_sched *ts, ktime_t now, u64 *last_update_time)
if (ts->idle_active) {
delta = ktime_sub(now, ts->idle_entrytime);
ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
if (nr_iowait_cpu() > 0)
ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
ts->idle_entrytime = now;
}
@@ -220,6 +222,32 @@ u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
}
EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
/*
* get_cpu_iowait_time_us - get the total iowait time of a cpu
* @cpu: CPU number to query
* @last_update_time: variable to store update time in
*
* Return the cummulative iowait time (since boot) for a given
* CPU, in microseconds.
*
* 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_iowait_time_us(int cpu, u64 *last_update_time)
{
struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
if (!tick_nohz_enabled)
return -1;
update_ts_time_stats(ts, ktime_get(), last_update_time);
return ktime_to_us(ts->iowait_sleeptime);
}
EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
/**
* tick_nohz_stop_sched_tick - stop the idle tick from the idle task
*