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    Subject[PATCH v4 2/2] sched: consider missed ticks in full NOHZ
    Date
    From: Byungchul Park <byungchul.park@lge.com>

    Even though the cpu is non-idle when its tick is stoped in full NOHZ,
    current "update_cpu_load" code considers as if the cpu has been idle
    unconditionally. It's wrong. This patch makes the "update_cpu_load"
    code know if the calling path comes from full NOHZ or idle NOHZ.

    Signed-off-by: Byungchul Park <byungchul.park@lge.com>
    ---
    include/linux/sched.h | 4 ++--
    kernel/sched/fair.c | 4 ++--
    kernel/time/tick-sched.c | 8 ++++----
    3 files changed, 8 insertions(+), 8 deletions(-)

    diff --git a/include/linux/sched.h b/include/linux/sched.h
    index 699228b..f1b59aa 100644
    --- a/include/linux/sched.h
    +++ b/include/linux/sched.h
    @@ -177,9 +177,9 @@ extern void get_iowait_load(unsigned long *nr_waiters, unsigned long *load);
    extern void calc_global_load(unsigned long ticks);

    #if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
    -extern void update_cpu_load_nohz(void);
    +extern void update_cpu_load_nohz(int active);
    #else
    -static inline void update_cpu_load_nohz(void) { }
    +static inline void update_cpu_load_nohz(int active) { }
    #endif

    extern unsigned long get_parent_ip(unsigned long addr);
    diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
    index 26473fc..63c5ffd 100644
    --- a/kernel/sched/fair.c
    +++ b/kernel/sched/fair.c
    @@ -4428,7 +4428,7 @@ static void update_idle_cpu_load(struct rq *this_rq)
    /*
    * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
    */
    -void update_cpu_load_nohz(void)
    +void update_cpu_load_nohz(int active)
    {
    struct rq *this_rq = this_rq();
    unsigned long curr_jiffies = READ_ONCE(jiffies);
    @@ -4445,7 +4445,7 @@ void update_cpu_load_nohz(void)
    * We were idle, this means load 0, the current load might be
    * !0 due to remote wakeups and the sort.
    */
    - __update_cpu_load(this_rq, 0, pending_updates, 0);
    + __update_cpu_load(this_rq, 0, pending_updates, active);
    }
    raw_spin_unlock(&this_rq->lock);
    }
    diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
    index 7c7ec45..515edf3 100644
    --- a/kernel/time/tick-sched.c
    +++ b/kernel/time/tick-sched.c
    @@ -694,11 +694,11 @@ out:
    return tick;
    }

    -static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
    +static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now, int active)
    {
    /* Update jiffies first */
    tick_do_update_jiffies64(now);
    - update_cpu_load_nohz();
    + update_cpu_load_nohz(active);

    calc_load_exit_idle();
    touch_softlockup_watchdog();
    @@ -725,7 +725,7 @@ static void tick_nohz_full_update_tick(struct tick_sched *ts)
    if (can_stop_full_tick())
    tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
    else if (ts->tick_stopped)
    - tick_nohz_restart_sched_tick(ts, ktime_get());
    + tick_nohz_restart_sched_tick(ts, ktime_get(), 1);
    #endif
    }

    @@ -916,7 +916,7 @@ void tick_nohz_idle_exit(void)
    tick_nohz_stop_idle(ts, now);

    if (ts->tick_stopped) {
    - tick_nohz_restart_sched_tick(ts, now);
    + tick_nohz_restart_sched_tick(ts, now, 0);
    tick_nohz_account_idle_ticks(ts);
    }

    --
    1.7.9.5


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