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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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