Commit 09a1d34f authored by Michal Hocko's avatar Michal Hocko Committed by Thomas Gleixner
Browse files

nohz: Make idle/iowait counter update conditional 



get_cpu_{idle,iowait}_time_us update idle/iowait counters
unconditionally if the given CPU is in the idle loop.

This doesn't work well outside of CPU governors which are singletons
so nobody (except for IRQ) can race with them.

We will need to use both functions from /proc/stat handler to properly
handle nohz idle/iowait times.

Make the update depend on a non NULL last_update_time argument.

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/11f23179472635ce52e78921d47a20216b872f23.1314172057.git.mhocko@suse.cz


Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent 6beea0cd

kernel/time/tick-sched.c

+35 −6
Original line number Diff line number Diff line
@@ -198,7 +198,8 @@ static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts) 
/**

 * 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

 * @last_update_time: variable to store update time in. Do not update

 * counters if NULL.

 *

 * Return the cummulative idle time (since boot) for a given

 * CPU, in microseconds.
@@ -211,20 +212,35 @@ static ktime_t tick_nohz_start_idle(int cpu, struct tick_sched *ts) 
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, idle;



	if (!tick_nohz_enabled)

		return -1;



	update_ts_time_stats(cpu, ts, ktime_get(), last_update_time);

	now = ktime_get();

	if (last_update_time) {

		update_ts_time_stats(cpu, ts, now, last_update_time);

		idle = ts->idle_sleeptime;

	} else {

		if (ts->idle_active && !nr_iowait_cpu(cpu)) {

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



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

		} else {

			idle = ts->idle_sleeptime;

		}

	}



	return ktime_to_us(idle);



	return ktime_to_us(ts->idle_sleeptime);

}

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

 * @last_update_time: variable to store update time in. Do not update

 * counters if NULL.

 *

 * Return the cummulative iowait time (since boot) for a given

 * CPU, in microseconds.
@@ -237,13 +253,26 @@ EXPORT_SYMBOL_GPL(get_cpu_idle_time_us); 
u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)

{

	struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);

	ktime_t now, iowait;



	if (!tick_nohz_enabled)

		return -1;



	update_ts_time_stats(cpu, ts, ktime_get(), last_update_time);

	now = ktime_get();

	if (last_update_time) {

		update_ts_time_stats(cpu, ts, now, last_update_time);

		iowait = ts->iowait_sleeptime;

	} else {

		if (ts->idle_active && nr_iowait_cpu(cpu) > 0) {

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



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

		} else {

			iowait = ts->iowait_sleeptime;

		}

	}



	return ktime_to_us(ts->iowait_sleeptime);

	return ktime_to_us(iowait);

}

EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);

CRA Git | Maintained and supported by SUSTech CRA and CCSE