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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2016-03-20 01:33:35 +0100
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2016-03-21 15:50:28 +0100
commit0c313cb207326f759a58f486214288411b25d4cf (patch)
tree57ae8bbc8c73539174eb6f026e8592d9d31893df /drivers/cpuidle/governors
parentcpuidle: menu: use high confidence factors only when considering polling (diff)
downloadlinux-0c313cb207326f759a58f486214288411b25d4cf.tar.xz
linux-0c313cb207326f759a58f486214288411b25d4cf.zip
cpuidle: menu: Fall back to polling if next timer event is near
Commit a9ceb78bc75c (cpuidle,menu: use interactivity_req to disable polling) changed the behavior of the fallback state selection part of menu_select() so it looks at interactivity_req instead of data->next_timer_us when it makes its decision. That effectively caused polling to be used more often as fallback idle which led to significant increases of energy consumption in some cases. Commit e132b9b3bc7f (cpuidle: menu: use high confidence factors only when considering polling) changed that logic again to be more predictable, but that didn't help with the increased energy consumption problem. For this reason, go back to making decisions on which state to fall back to based on data->next_timer_us which is the time we know for sure something will happen rather than a prediction (which may be inaccurate and turns out to be so often enough to be problematic). However, take the target residency of the first proper idle state (C1) into account, so that state is not used as the fallback one if its target residency is greater than data->next_timer_us. Fixes: a9ceb78bc75c (cpuidle,menu: use interactivity_req to disable polling) Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Reported-and-tested-by: Doug Smythies <dsmythies@telus.net>
Diffstat (limited to 'drivers/cpuidle/governors')
-rw-r--r--drivers/cpuidle/governors/menu.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 00c5f891e352..03d38c291de6 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -315,17 +315,21 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
expected_interval = min(expected_interval, data->next_timer_us);
if (CPUIDLE_DRIVER_STATE_START > 0) {
- data->last_state_idx = CPUIDLE_DRIVER_STATE_START - 1;
+ struct cpuidle_state *s = &drv->states[CPUIDLE_DRIVER_STATE_START];
+ unsigned int polling_threshold;
+
/*
* We want to default to C1 (hlt), not to busy polling
* unless the timer is happening really really soon, or
* C1's exit latency exceeds the user configured limit.
*/
- if (expected_interval > drv->states[CPUIDLE_DRIVER_STATE_START].target_residency &&
- latency_req > drv->states[CPUIDLE_DRIVER_STATE_START].exit_latency &&
- !drv->states[CPUIDLE_DRIVER_STATE_START].disabled &&
+ polling_threshold = max_t(unsigned int, 20, s->target_residency);
+ if (data->next_timer_us > polling_threshold &&
+ latency_req > s->exit_latency && !s->disabled &&
!dev->states_usage[CPUIDLE_DRIVER_STATE_START].disable)
data->last_state_idx = CPUIDLE_DRIVER_STATE_START;
+ else
+ data->last_state_idx = CPUIDLE_DRIVER_STATE_START - 1;
} else {
data->last_state_idx = CPUIDLE_DRIVER_STATE_START;
}