Commit 525705d1 authored by Byungchul Park's avatar Byungchul Park Committed by Ingo Molnar
Browse files

sched/fair: Consider missed ticks in NOHZ_FULL in update_cpu_load_nohz() 



Usually the tick can be stopped for an idle CPU in NOHZ. However in NOHZ_FULL
mode, a non-idle CPU's tick can also be stopped. However, update_cpu_load_nohz()
does not consider the case a non-idle CPU's tick has been stopped at all.

This patch makes the update_cpu_load_nohz() know if the calling path comes
from NOHZ_FULL or idle NOHZ.

Signed-off-by: default avatarByungchul Park <byungchul.park@lge.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1447115762-19734-3-git-send-email-byungchul.park@lge.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 59543275

include/linux/sched.h

+2 −2
Original line number Diff line number Diff line
@@ -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);

kernel/sched/fair.c

+6 −4
Original line number Diff line number Diff line
@@ -4397,10 +4397,11 @@ 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);

	unsigned long load = active ? weighted_cpuload(cpu_of(this_rq)) : 0;

	unsigned long pending_updates;



	if (curr_jiffies == this_rq->last_load_update_tick)
@@ -4411,10 +4412,11 @@ void update_cpu_load_nohz(void) 
	if (pending_updates) {

		this_rq->last_load_update_tick = curr_jiffies;

		/*

		 * We were idle, this means load 0, the current load might be

		 * !0 due to remote wakeups and the sort.

		 * In the regular NOHZ case, we were idle, this means load 0.

		 * In the NOHZ_FULL case, we were non-idle, we should consider

		 * its weighted load.

		 */

		__update_cpu_load(this_rq, 0, pending_updates, 0);

		__update_cpu_load(this_rq, load, pending_updates, active);

	}

	raw_spin_unlock(&this_rq->lock);

}

kernel/time/tick-sched.c

+4 −4
Original line number Diff line number Diff line
@@ -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);

	}

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