From 5a52395af9f30aadd5a81813fd9a69dd3ab2df8f Mon Sep 17 00:00:00 2001 From: Daniel Lezcano Date: Fri, 14 Dec 2012 13:57:35 +0000 Subject: [PATCH 2/2] cpuidle - optimize the select function for the 'menu' governor As the power is backward sorted in the states array and we are looking for the state consuming the little power as possible, instead of looking from the beginning of the array, we look from the end. That should save us some iterations in the loop each time we select a state at idle time. Signed-off-by: Daniel Lezcano --- drivers/cpuidle/governors/menu.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index fe343a0..05b8998 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -367,24 +367,24 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) * Find the idle state with the lowest power while satisfying * our constraints. */ - for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++) { + for (i = drv->state_count - 1; i >= CPUIDLE_DRIVER_STATE_START; i--) { struct cpuidle_state *s = &drv->states[i]; struct cpuidle_state_usage *su = &dev->states_usage[i]; if (s->disabled || su->disable) continue; - if (s->target_residency > data->predicted_us) { - low_predicted = 1; - continue; - } if (s->exit_latency > latency_req) continue; + if (s->target_residency > data->predicted_us) + continue; if (s->exit_latency * multiplier > data->predicted_us) continue; + low_predicted = i - CPUIDLE_DRIVER_STATE_START; data->last_state_idx = i; data->exit_us = s->exit_latency; - } + break; + } /* not deepest C-state chosen for low predicted residency */ if (low_predicted) { -- 1.7.9.5