Revert "cpuidle: Quickly notice prediction failure in general case"

Revert commit e11538d1 (cpuidle: Quickly notice prediction failure in
general case), since it depends on commit 69a37be (cpuidle: Quickly
notice prediction failure for repeat mode) that has been identified
as the source of a significant performance regression in v3.8 and
later.

Requested-by: Jeremy Eder <jeder@redhat.com>
Tested-by: Len Brown <len.brown@intel.com>
Cc: 3.8+ <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index fe343a0..b69a87e 100644 (file)
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -34,7 +34,7 @@
 static DEFINE_PER_CPU(struct hrtimer, menu_hrtimer);
 static DEFINE_PER_CPU(int, hrtimer_status);
 /* menu hrtimer mode */
-enum {MENU_HRTIMER_STOP, MENU_HRTIMER_REPEAT, MENU_HRTIMER_GENERAL};
+enum {MENU_HRTIMER_STOP, MENU_HRTIMER_REPEAT};
 
 /*
  * Concepts and ideas behind the menu governor
@@ -116,13 +116,6 @@ enum {MENU_HRTIMER_STOP, MENU_HRTIMER_REPEAT, MENU_HRTIMER_GENERAL};
  *
  */
 
-/*
- * The C-state residency is so long that is is worthwhile to exit
- * from the shallow C-state and re-enter into a deeper C-state.
- */
-static unsigned int perfect_cstate_ms __read_mostly = 30;
-module_param(perfect_cstate_ms, uint, 0000);
-
 struct menu_device {
        int             last_state_idx;
        int             needs_update;
@@ -223,16 +216,6 @@ EXPORT_SYMBOL_GPL(menu_hrtimer_cancel);
 static enum hrtimer_restart menu_hrtimer_notify(struct hrtimer *hrtimer)
 {
        int cpu = smp_processor_id();
-       struct menu_device *data = &per_cpu(menu_devices, cpu);
-
-       /* In general case, the expected residency is much larger than
-        *  deepest C-state target residency, but prediction logic still
-        *  predicts a small predicted residency, so the prediction
-        *  history is totally broken if the timer is triggered.
-        *  So reset the correction factor.
-        */
-       if (per_cpu(hrtimer_status, cpu) == MENU_HRTIMER_GENERAL)
-               data->correction_factor[data->bucket] = RESOLUTION * DECAY;
 
        per_cpu(hrtimer_status, cpu) = MENU_HRTIMER_STOP;
 
@@ -389,7 +372,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
        /* not deepest C-state chosen for low predicted residency */
        if (low_predicted) {
                unsigned int timer_us = 0;
-               unsigned int perfect_us = 0;
 
                /*
                 * Set a timer to detect whether this sleep is much
@@ -400,28 +382,13 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
                 */
                timer_us = 2 * (data->predicted_us + MAX_DEVIATION);
 
-               perfect_us = perfect_cstate_ms * 1000;
-
                if (repeat && (4 * timer_us < data->expected_us)) {
                        RCU_NONIDLE(hrtimer_start(hrtmr,
                                ns_to_ktime(1000 * timer_us),
                                HRTIMER_MODE_REL_PINNED));
                        /* In repeat case, menu hrtimer is started */
                        per_cpu(hrtimer_status, cpu) = MENU_HRTIMER_REPEAT;
-               } else if (perfect_us < data->expected_us) {
-                       /*
-                        * The next timer is long. This could be because
-                        * we did not make a useful prediction.
-                        * In that case, it makes sense to re-enter
-                        * into a deeper C-state after some time.
-                        */
-                       RCU_NONIDLE(hrtimer_start(hrtmr,
-                               ns_to_ktime(1000 * timer_us),
-                               HRTIMER_MODE_REL_PINNED));
-                       /* In general case, menu hrtimer is started */
-                       per_cpu(hrtimer_status, cpu) = MENU_HRTIMER_GENERAL;
                }
-
        }
 
        return data->last_state_idx;