On Sunday, August 12, 2018 6:09:30 PM CEST Leo Yan wrote: > To avoid staying in a shallow state for a long time, the menu governor > relies on not stopping tick when detects the prediction is shorter than > the tick event. This is just luckily to cover most cases but cannot say > it is completely safe. For example, if the prediction is 2000us and the > TICK_USEC=1000 so it's impossible to meet the condition > 'data->predicted_us < TICK_USEC' and this lead to stop the tick for a > shallow state; finally the CPU is possible to stay in this shallow state > for very long time. > > This patch checks the candidate idle state isn't deepest one and find if > the timer will come after more than 2 times of the maximum target > residency, though the governor selects a shallow state according to > prediction, due the timer is most reliable waken up source but it will > come very late, so the CPU has chance to stay in the shallow state > for a long time; the patch doesn't stop the tick for this case so can > avoid powernightmares issue. > > Signed-off-by: Leo Yan <[email protected]> > --- > drivers/cpuidle/governors/menu.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/drivers/cpuidle/governors/menu.c > b/drivers/cpuidle/governors/menu.c > index 4f02207..566c65c 100644 > --- a/drivers/cpuidle/governors/menu.c > +++ b/drivers/cpuidle/governors/menu.c > @@ -284,6 +284,10 @@ static unsigned int get_typical_interval(struct > menu_device *data) > static bool menu_decide_stopping_tick(struct cpuidle_driver *drv, > struct menu_device *data, int idx) > { > + int max_target_residency; > + > + max_target_residency = drv->states[drv->state_count-1].target_residency;
But this state may be disabled, may it not? Thanks, Rafael
