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authorLen Brown <len.brown@intel.com>2014-12-16 01:52:06 -0500
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2014-12-17 02:26:28 +0100
commit4108b3d96273784f697dd6d8e59ef9203a10a02d (patch)
tree38e187ed6a4b853c43b601fde3bbc0d42962c902 /drivers/cpuidle
parent0c570c183ace73f06e42d65432bf938fbdde6524 (diff)
cpuidle: menu: Better idle duration measurement without using CPUIDLE_FLAG_TIME_INVALID
When menu sees CPUIDLE_FLAG_TIME_INVALID, it ignores its timestamps, and assumes that idle lasted as long as the time till next predicted timer expiration. But if an interrupt was seen and serviced before that duration, it would actually be more accurate to use the measured time rather than rounding up to the next predicted timer expiration. And if an interrupt is seen and serviced such that the mesured time exceeds the time till next predicted timer expiration, then truncating to that expiration is the right thing to do -- since we can never stay idle past that timer expiration. So the code can do a better job without checking for CPUIDLE_FLAG_TIME_INVALID. Signed-off-by: Len Brown <len.brown@intel.com> Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org> Reviewed-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.c25
1 files changed, 10 insertions, 15 deletions
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 659d7b0c9ebf..40580794e23d 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -396,8 +396,8 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
* power state and occurrence of the wakeup event.
*
* If the entered idle state didn't support residency measurements,
- * we are basically lost in the dark how much time passed.
- * As a compromise, assume we slept for the whole expected time.
+ * we use them anyway if they are short, and if long,
+ * truncate to the whole expected time.
*
* Any measured amount of time will include the exit latency.
* Since we are interested in when the wakeup begun, not when it
@@ -405,22 +405,17 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
* the measured amount of time is less than the exit latency,
* assume the state was never reached and the exit latency is 0.
*/
- if (unlikely(target->flags & CPUIDLE_FLAG_TIME_INVALID)) {
- /* Use timer value as is */
- measured_us = data->next_timer_us;
- } else {
- /* Use measured value */
- measured_us = cpuidle_get_last_residency(dev);
+ /* measured value */
+ measured_us = cpuidle_get_last_residency(dev);
- /* Deduct exit latency */
- if (measured_us > target->exit_latency)
- measured_us -= target->exit_latency;
+ /* Deduct exit latency */
+ if (measured_us > target->exit_latency)
+ measured_us -= target->exit_latency;
- /* Make sure our coefficients do not exceed unity */
- if (measured_us > data->next_timer_us)
- measured_us = data->next_timer_us;
- }
+ /* Make sure our coefficients do not exceed unity */
+ if (measured_us > data->next_timer_us)
+ measured_us = data->next_timer_us;
/* Update our correction ratio */
new_factor = data->correction_factor[data->bucket];