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: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
This commit is contained in:
Ingo Molnar 2007-08-10 23:05:11 +02:00
parent ac07860264
commit 529c77261b

View File

@ -263,6 +263,7 @@ struct rq {
unsigned int clock_warps, clock_overflows;
unsigned int clock_unstable_events;
u64 tick_timestamp;
atomic_t nr_iowait;
@ -341,8 +342,11 @@ static void __update_rq_clock(struct rq *rq)
/*
* Catch too large forward jumps too:
*/
if (unlikely(delta > 2*TICK_NSEC)) {
clock++;
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 {
if (unlikely(delta > rq->clock_max_delta))
@ -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);