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authortuukka.tikkanen@linaro.org <tuukka.tikkanen@linaro.org>2014-02-24 08:29:35 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-03-06 01:45:59 +0100
commit96e95182e95fd4e0069ff4d6ee1888fe9031d154 (patch)
treedfb20bf37e38982972b7fde9a0e7e8729aa3db22 /drivers/cpuidle
parent61c66d6efa23759f1061d80ced668977fd28337d (diff)
downloadlinux-96e95182e95fd4e0069ff4d6ee1888fe9031d154.tar.bz2
cpuidle: Move perf multiplier calculation out of the selection loop
The menu governor performance multiplier defines a minimum predicted idle duration to latency ratio. Instead of checking this separately in every iteration of the state selection loop, adjust the overall latency restriction for the whole loop if this restriction is tighter than what is set by the QoS subsystem. The original test s->exit_latency * multiplier > data->predicted_us becomes s->exit_latency > data->predicted_us / multiplier by dividing both sides of the comparison by "multiplier". While division is likely to be several times slower than multiplication, the minor performance hit allows making a generic sleep state selection function based on (sleep duration, maximum latency) tuple. Signed-off-by: Tuukka Tikkanen <tuukka.tikkanen@linaro.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/cpuidle')
-rw-r--r--drivers/cpuidle/governors/menu.c15
1 files changed, 10 insertions, 5 deletions
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index b347c101c1f7..71b523293354 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -288,7 +288,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
struct menu_device *data = &__get_cpu_var(menu_devices);
int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
int i;
- int multiplier;
+ unsigned int interactivity_req;
struct timespec t;
if (data->needs_update) {
@@ -310,8 +310,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
data->bucket = which_bucket(data->next_timer_us);
- multiplier = performance_multiplier();
-
/*
* if the correction factor is 0 (eg first time init or cpu hotplug
* etc), we actually want to start out with a unity factor.
@@ -331,6 +329,15 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
get_typical_interval(data);
/*
+ * Performance multiplier defines a minimum predicted idle
+ * duration / latency ratio. Adjust the latency limit if
+ * necessary.
+ */
+ interactivity_req = data->predicted_us / performance_multiplier();
+ if (latency_req > interactivity_req)
+ latency_req = interactivity_req;
+
+ /*
* We want to default to C1 (hlt), not to busy polling
* unless the timer is happening really really soon.
*/
@@ -353,8 +360,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
continue;
if (s->exit_latency > latency_req)
continue;
- if (s->exit_latency * multiplier > data->predicted_us)
- continue;
data->last_state_idx = i;
}