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Commit 0224cf4c authored by Arjan van de Ven's avatar Arjan van de Ven Committed by Ingo Molnar
Browse files

sched: Intoduce get_cpu_iowait_time_us() 



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: default avatarArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: davej@redhat.com
LKML-Reference: <20100509082523.284feab6@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent e0e37c20

include/linux/tick.h

+4 −0
Original line number Diff line number Diff line
@@ -42,6 +42,7 @@ enum tick_nohz_mode { 
 * @idle_waketime:	Time when the idle was interrupted

 * @idle_exittime:	Time when the idle state was left

 * @idle_sleeptime:	Sum of the time slept in idle with sched tick stopped

 * @iowait_sleeptime:	Sum of the time slept in idle with sched tick stopped, with IO outstanding

 * @sleep_length:	Duration of the current idle sleep

 * @do_timer_lst:	CPU was the last one doing do_timer before going idle

 */
@@ -60,6 +61,7 @@ struct tick_sched { 
	ktime_t				idle_waketime;

	ktime_t				idle_exittime;

	ktime_t				idle_sleeptime;

	ktime_t				iowait_sleeptime;

	ktime_t				sleep_length;

	unsigned long			last_jiffies;

	unsigned long			next_jiffies;
@@ -123,6 +125,7 @@ extern void tick_nohz_stop_sched_tick(int inidle); 
extern void tick_nohz_restart_sched_tick(void);

extern ktime_t tick_nohz_get_sleep_length(void);

extern u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time);

extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time);

# else

static inline void tick_nohz_stop_sched_tick(int inidle) { }

static inline void tick_nohz_restart_sched_tick(void) { }
@@ -133,6 +136,7 @@ static inline ktime_t tick_nohz_get_sleep_length(void) 
	return len;

}

static inline u64 get_cpu_idle_time_us(int cpu, u64 *unused) { return -1; }

static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; }

# endif /* !NO_HZ */



#endif

kernel/time/tick-sched.c

+28 −0
Original line number Diff line number Diff line
@@ -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

 *

kernel/time/timer_list.c

+1 −0
Original line number Diff line number Diff line
@@ -176,6 +176,7 @@ static void print_cpu(struct seq_file *m, int cpu, u64 now) 
		P_ns(idle_waketime);

		P_ns(idle_exittime);

		P_ns(idle_sleeptime);

		P_ns(iowait_sleeptime);

		P(last_jiffies);

		P(next_jiffies);

		P_ns(idle_expires);