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Commit 529c7726 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

sched: improve rq-clock overflow logic 



improve the rq-clock overflow logic: limit the absolute rq->clock
delta since the last scheduler tick, instead of limiting the delta
itself.

tested by Arjan van de Ven - whole laptop was misbehaving due to
an incorrectly calibrated cpu_khz confusing sched_clock().

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
parent ac078602

kernel/sched.c

+13 −2
Original line number Diff line number Diff line
@@ -263,6 +263,7 @@ struct rq { 


	unsigned int clock_warps, clock_overflows;

	unsigned int clock_unstable_events;

	u64 tick_timestamp;



	atomic_t nr_iowait;
@@ -341,7 +342,10 @@ static void __update_rq_clock(struct rq *rq) 
		/*

		 * Catch too large forward jumps too:

		 */

		if (unlikely(delta > 2*TICK_NSEC)) {

		if (unlikely(clock + delta > rq->tick_timestamp + TICK_NSEC)) {

			if (clock < rq->tick_timestamp + TICK_NSEC)

				clock = rq->tick_timestamp + TICK_NSEC;

			else

				clock++;

			rq->clock_overflows++;

		} else {
@@ -3308,9 +3312,16 @@ void scheduler_tick(void) 
	int cpu = smp_processor_id();

	struct rq *rq = cpu_rq(cpu);

	struct task_struct *curr = rq->curr;

	u64 next_tick = rq->tick_timestamp + TICK_NSEC;



	spin_lock(&rq->lock);

	__update_rq_clock(rq);

	/*

	 * Let rq->clock advance by at least TICK_NSEC:

	 */

	if (unlikely(rq->clock < next_tick))

		rq->clock = next_tick;

	rq->tick_timestamp = rq->clock;

	update_cpu_load(rq);

	if (curr != rq->idle) /* FIXME: needed? */

		curr->sched_class->task_tick(rq, curr);