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Commit 228b3023 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

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 69a37bea (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: default avatarJeremy Eder <jeder@redhat.com>
Tested-by: default avatarLen Brown <len.brown@intel.com>
Cc: 3.8+ <stable@vger.kernel.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 5ae90d8e

drivers/cpuidle/governors/menu.c

+1 −34
Original line number Diff line number Diff line
@@ -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;