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Subject[PATCH 6/7] sched: introduce get_cpu_iowait_time_us()
From c4dd11703034f2ecbc3180603663fab14c292d7c Mon Sep 17 00:00:00 2001
From: Arjan van de Ven <arjan@linux.intel.com>
Date: Sun, 18 Apr 2010 10:57:43 -0700
Subject: [PATCH 6/7] sched: introduce 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.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
---
include/linux/tick.h | 4 ++++
kernel/time/tick-sched.c | 28 ++++++++++++++++++++++++++++
kernel/time/timer_list.c | 1 +
3 files changed, 33 insertions(+), 0 deletions(-)
diff --git a/include/linux/tick.h b/include/linux/tick.h
index 0343eed..4aa3703 100644
--- 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(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 326f5f8..a6104a8 100644
--- 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
--- 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);
--
1.6.2.5


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