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: 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>

diff --git a/include/linux/tick.h b/include/linux/tick.h
index 0343eed..b232ccc 100644 (file)
--- a/include/linux/tick.h
+++ b/include/linux/tick.h
@@ -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

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 50953f4..1d7b9bc 100644 (file)
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -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
  *

diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c
index 1a4a7dd..ab8f5e3 100644 (file)
--- a/kernel/time/timer_list.c
+++ b/kernel/time/timer_list.c
@@ -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);