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cpuidle: teo: Skip tick_nohz_get_sleep_length() call in some cases

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Make teo_select() avoid calling tick_nohz_get_sleep_length() if the
candidate idle state to return is state 0 or if state 0 is a polling
one and the target residency of the current candidate one is below
a certain threshold, in which cases it may be assumed that the CPU will
be woken up immediately by a non-timer wakeup source and the timers
are not likely to matter.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Kajetan Puchalski <kajetan.puchalski@arm.com>
Tested-by: Anna-Maria Behnsen <anna-maria@linutronix.de>
This commit is contained in:
Rafael J. Wysocki 2023-08-03 23:09:18 +02:00
parent 21d28cd2fa
commit 6da8f9ba5a
1 changed files with 22 additions and 0 deletions
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22
drivers/cpuidle/governors/teo.c
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@ -166,6 +166,12 @@
*/
#define NR_RECENT 9
/*
* Idle state target residency threshold used for deciding whether or not to
* check the time till the closest expected timer event.
*/
#define RESIDENCY_THRESHOLD_NS (15 * NSEC_PER_USEC)
/**
* struct teo_bin - Metrics used by the TEO cpuidle governor.
* @intercepts: The "intercepts" metric.
@ -542,6 +548,22 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
idx = i;
}
/*
* Skip the timers check if state 0 is the current candidate one,
* because an immediate non-timer wakeup is expected in that case.
*/
if (!idx)
goto out_tick;
/*
* If state 0 is a polling one, check if the target residency of
* the current candidate state is low enough and skip the timers
* check in that case too.
*/
if ((drv->states[0].flags & CPUIDLE_FLAG_POLLING) &&
drv->states[idx].target_residency_ns < RESIDENCY_THRESHOLD_NS)
goto out_tick;
duration_ns = tick_nohz_get_sleep_length(&delta_tick);
cpu_data->sleep_length_ns = duration_ns;