mirror of
https://github.com/torvalds/linux
synced 2024-09-06 18:01:05 +00:00
cpuidle: menu: Avoid selecting shallow states with stopped tick
If the scheduler tick has been stopped already and the governor selects a shallow idle state, the CPU can spend a long time in that state if the selection is based on an inaccurate prediction of idle time. That effect turns out to be relevant, so it needs to be mitigated. To that end, modify the menu governor to discard the result of the idle time prediction if the tick is stopped and the predicted idle time is less than the tick period length, unless the tick timer is going to expire soon. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
This commit is contained in:
parent
296bb1e51a
commit
87c9fe6ee4
|
@ -352,13 +352,28 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
|
|||
*/
|
||||
data->predicted_us = min(data->predicted_us, expected_interval);
|
||||
|
||||
/*
|
||||
* Use the performance multiplier and the user-configurable
|
||||
* latency_req to determine the maximum exit latency.
|
||||
*/
|
||||
interactivity_req = data->predicted_us / performance_multiplier(nr_iowaiters, cpu_load);
|
||||
if (latency_req > interactivity_req)
|
||||
latency_req = interactivity_req;
|
||||
if (tick_nohz_tick_stopped()) {
|
||||
/*
|
||||
* If the tick is already stopped, the cost of possible short
|
||||
* idle duration misprediction is much higher, because the CPU
|
||||
* may be stuck in a shallow idle state for a long time as a
|
||||
* result of it. In that case say we might mispredict and try
|
||||
* to force the CPU into a state for which we would have stopped
|
||||
* the tick, unless a timer is going to expire really soon
|
||||
* anyway.
|
||||
*/
|
||||
if (data->predicted_us < TICK_USEC)
|
||||
data->predicted_us = min_t(unsigned int, TICK_USEC,
|
||||
ktime_to_us(delta_next));
|
||||
} else {
|
||||
/*
|
||||
* Use the performance multiplier and the user-configurable
|
||||
* latency_req to determine the maximum exit latency.
|
||||
*/
|
||||
interactivity_req = data->predicted_us / performance_multiplier(nr_iowaiters, cpu_load);
|
||||
if (latency_req > interactivity_req)
|
||||
latency_req = interactivity_req;
|
||||
}
|
||||
|
||||
expected_interval = data->predicted_us;
|
||||
/*
|
||||
|
|
Loading…
Reference in a new issue