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cpuidle: menu: Avoid computations for very close timers

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If the next timer event (not including the tick) is closer than the
target residency of the second state or the PM QoS latency constraint
is below its exit latency, state[0] will be used regardless of any
other factors, so skip the computations in menu_select() then and
return 0 straight away from it.

Still, do that after the bucket has been determined to avoid
updating the correction factor for a stale bucket.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
This commit is contained in:
Rafael J. Wysocki 2018-10-02 23:46:28 +02:00
parent eb40a380bf
commit 8b007ebec9
1 changed files with 12 additions and 0 deletions
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12
drivers/cpuidle/governors/menu.c
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@ -309,6 +309,18 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
get_iowait_load(&nr_iowaiters, &cpu_load);
data->bucket = which_bucket(data->next_timer_us, nr_iowaiters);
if (unlikely(drv->state_count <= 1) ||
((data->next_timer_us < drv->states[1].target_residency ||
latency_req < drv->states[1].exit_latency) &&
!drv->states[0].disabled && !dev->states_usage[0].disable)) {
/*
* In this case state[0] will be used no matter what, so return
* it right away and keep the tick running.
*/
*stop_tick = false;
return 0;
}
/*
* Force the result of multiplication to be 64 bits even if both
* operands are 32 bits.