Commit 6beea0cd authored by Michal Hocko's avatar Michal Hocko Committed by Thomas Gleixner
Browse files

nohz: Fix update_ts_time_stat idle accounting 



update_ts_time_stat currently updates idle time even if we are in
iowait loop at the moment. The only real users of the idle counter
(via get_cpu_idle_time_us) are CPU governors and they expect to get
cumulative time for both idle and iowait times.
The value (idle_sleeptime) is also printed to userspace by print_cpu
but it prints both idle and iowait times so the idle part is misleading.

Let's clean this up and fix update_ts_time_stat to account both counters
properly and update consumers of idle to consider iowait time as well.
If we do this we might use get_cpu_{idle,iowait}_time_us from other
contexts as well and we will get expected values.

Signed-off-by: default avatarMichal Hocko <mhocko@suse.cz>
Cc: Dave Jones <davej@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Link: http://lkml.kernel.org/r/e9c909c221a8da402c4da07e4cd968c3218f8eb1.1314172057.git.mhocko@suse.cz


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent ef0e0f5e

drivers/cpufreq/cpufreq_conservative.c

+3 −1
Original line number Diff line number Diff line
@@ -120,10 +120,12 @@ static inline cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu, 


static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)

{

	u64 idle_time = get_cpu_idle_time_us(cpu, wall);

	u64 idle_time = get_cpu_idle_time_us(cpu, NULL);



	if (idle_time == -1ULL)

		return get_cpu_idle_time_jiffy(cpu, wall);

	else

		idle_time += get_cpu_iowait_time_us(cpu, wall);



	return idle_time;

}

drivers/cpufreq/cpufreq_ondemand.c

+3 −1
Original line number Diff line number Diff line
@@ -144,10 +144,12 @@ static inline cputime64_t get_cpu_idle_time_jiffy(unsigned int cpu, 


static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall)

{

	u64 idle_time = get_cpu_idle_time_us(cpu, wall);

	u64 idle_time = get_cpu_idle_time_us(cpu, NULL);



	if (idle_time == -1ULL)

		return get_cpu_idle_time_jiffy(cpu, wall);

	else

		idle_time += get_cpu_iowait_time_us(cpu, wall);



	return idle_time;

}

kernel/time/tick-sched.c

+4 −4
Original line number Diff line number Diff line
@@ -159,9 +159,10 @@ update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_upda 


	if (ts->idle_active) {

		delta = ktime_sub(now, ts->idle_entrytime);

		ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);

		if (nr_iowait_cpu(cpu) > 0)

			ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);

		else

			ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);

		ts->idle_entrytime = now;

	}
@@ -200,8 +201,7 @@ static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts) 
 * @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).

 * CPU, in microseconds.

 *

 * This time is measured via accounting rather than sampling,

 * and is as accurate as ktime_get() is.
@@ -221,7 +221,7 @@ 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

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