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authorPallipadi, Venkatesh <venkatesh.pallipadi@intel.com>2008-12-30 14:46:02 -0800
committerLen Brown <len.brown@intel.com>2008-12-30 18:48:01 -0500
commit816bb611e41be29b476dc16f6297eb551bf4d747 (patch)
treefe48f23db073e47a83de5e9e08796c252c7a307d /drivers/cpuidle
parent4a6908a3a050aacc9c3a2f36b276b46c0629ad91 (diff)
downloadop-kernel-dev-816bb611e41be29b476dc16f6297eb551bf4d747.zip
op-kernel-dev-816bb611e41be29b476dc16f6297eb551bf4d747.tar.gz
cpuidle: Add decaying history logic to menu idle predictor
Add decaying history of predicted idle time, instead of using the last early wakeup. This logic helps menu governor do better job of predicting idle time. With this change, we also measured noticable (~8%) power savings on a DP server system with CPUs supporting deep C states, when system was lightly loaded. There was no change to power or perf on other load conditions. Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'drivers/cpuidle')
-rw-r--r--drivers/cpuidle/governors/menu.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index 8d7cf3f..f1df59f 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -15,12 +15,14 @@
#include <linux/tick.h>
#define BREAK_FUZZ 4 /* 4 us */
+#define PRED_HISTORY_PCT 50
struct menu_device {
int last_state_idx;
unsigned int expected_us;
unsigned int predicted_us;
+ unsigned int current_predicted_us;
unsigned int last_measured_us;
unsigned int elapsed_us;
};
@@ -47,6 +49,12 @@ static int menu_select(struct cpuidle_device *dev)
data->expected_us =
(u32) ktime_to_ns(tick_nohz_get_sleep_length()) / 1000;
+ /* Recalculate predicted_us based on prediction_history_pct */
+ data->predicted_us *= PRED_HISTORY_PCT;
+ data->predicted_us += (100 - PRED_HISTORY_PCT) *
+ data->current_predicted_us;
+ data->predicted_us /= 100;
+
/* find the deepest idle state that satisfies our constraints */
for (i = CPUIDLE_DRIVER_STATE_START + 1; i < dev->state_count; i++) {
struct cpuidle_state *s = &dev->states[i];
@@ -97,7 +105,7 @@ static void menu_reflect(struct cpuidle_device *dev)
measured_us = -1;
/* Predict time until next break event */
- data->predicted_us = max(measured_us, data->last_measured_us);
+ data->current_predicted_us = max(measured_us, data->last_measured_us);
if (last_idle_us + BREAK_FUZZ <
data->expected_us - target->exit_latency) {
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