Commit f1d1be8a authored Jun 20, 2018 by Xunlei Pang Committed by Ingo Molnar Jul 03, 2018

sched/fair: Advance global expiration when period timer is restarted



When period gets restarted after some idle time, start_cfs_bandwidth()
doesn't update the expiration information, expire_cfs_rq_runtime() will
see cfs_rq->runtime_expires smaller than rq clock and go to the clock
drift logic, wasting needless CPU cycles on the scheduler hot path.

Update the global expiration in start_cfs_bandwidth() to avoid frequent
expire_cfs_rq_runtime() calls once a new period begins.

Signed-off-by: Xunlei Pang <xlpang@linux.alibaba.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Ben Segall <bsegall@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180620101834.24455-2-xlpang@linux.alibaba.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 512ac999

kernel/sched/fair.c

+10 −5

Original line number	Original line	Diff line number	Diff line
	@@ -5204,14 +5204,19 @@ static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq)

	void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)		void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
	{		{
			u64 overrun;

	lockdep_assert_held(&cfs_b->lock);		lockdep_assert_held(&cfs_b->lock);

	if (!cfs_b->period_active) {		if (cfs_b->period_active)
			return;

	cfs_b->period_active = 1;		cfs_b->period_active = 1;
	hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);		overrun = hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period);
			cfs_b->runtime_expires += (overrun + 1) * ktime_to_ns(cfs_b->period);
			cfs_b->expires_seq++;
	hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);		hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED);
	}		}
	}

	static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)		static void destroy_cfs_bandwidth(struct cfs_bandwidth *cfs_b)
	{		{