[net-next-2.6.git] / drivers / cpuidle / governors / menu.c

/*
 * menu.c - the menu idle governor
 *
 * Copyright (C) 2006-2007 Adam Belay <abelay@novell.com>
 * Copyright (C) 2009 Intel Corporation
 * Author:
 *        Arjan van de Ven <arjan@linux.intel.com>
 *
 * This code is licenced under the GPL version 2 as described
 * in the COPYING file that acompanies the Linux Kernel.
 */

#include <linux/kernel.h>
#include <linux/cpuidle.h>
#include <linux/pm_qos_params.h>
#include <linux/time.h>
#include <linux/ktime.h>
#include <linux/hrtimer.h>
#include <linux/tick.h>
#include <linux/sched.h>
#include <linux/math64.h>

#define BUCKETS 12
#define INTERVALS 8
#define RESOLUTION 1024
#define DECAY 8
#define MAX_INTERESTING 50000
#define STDDEV_THRESH 400


/*
 * Concepts and ideas behind the menu governor
 *
 * For the menu governor, there are 3 decision factors for picking a C
 * state:
 * 1) Energy break even point
 * 2) Performance impact
 * 3) Latency tolerance (from pmqos infrastructure)
 * These these three factors are treated independently.
 *
 * Energy break even point
 * -----------------------
 * C state entry and exit have an energy cost, and a certain amount of time in
 * the  C state is required to actually break even on this cost. CPUIDLE
 * provides us this duration in the "target_residency" field. So all that we
 * need is a good prediction of how long we'll be idle. Like the traditional
 * menu governor, we start with the actual known "next timer event" time.
 *
 * Since there are other source of wakeups (interrupts for example) than
 * the next timer event, this estimation is rather optimistic. To get a
 * more realistic estimate, a correction factor is applied to the estimate,
 * that is based on historic behavior. For example, if in the past the actual
 * duration always was 50% of the next timer tick, the correction factor will
 * be 0.5.
 *
 * menu uses a running average for this correction factor, however it uses a
 * set of factors, not just a single factor. This stems from the realization
 * that the ratio is dependent on the order of magnitude of the expected
 * duration; if we expect 500 milliseconds of idle time the likelihood of
 * getting an interrupt very early is much higher than if we expect 50 micro
 * seconds of idle time. A second independent factor that has big impact on
 * the actual factor is if there is (disk) IO outstanding or not.
 * (as a special twist, we consider every sleep longer than 50 milliseconds
 * as perfect; there are no power gains for sleeping longer than this)
 *
 * For these two reasons we keep an array of 12 independent factors, that gets
 * indexed based on the magnitude of the expected duration as well as the
 * "is IO outstanding" property.
 *
 * Repeatable-interval-detector
 * ----------------------------
 * There are some cases where "next timer" is a completely unusable predictor:
 * Those cases where the interval is fixed, for example due to hardware
 * interrupt mitigation, but also due to fixed transfer rate devices such as
 * mice.
 * For this, we use a different predictor: We track the duration of the last 8
 * intervals and if the stand deviation of these 8 intervals is below a
 * threshold value, we use the average of these intervals as prediction.
 *
 * Limiting Performance Impact
 * ---------------------------
 * C states, especially those with large exit latencies, can have a real
 * noticeable impact on workloads, which is not acceptable for most sysadmins,
 * and in addition, less performance has a power price of its own.
 *
 * As a general rule of thumb, menu assumes that the following heuristic
 * holds:
 *     The busier the system, the less impact of C states is acceptable
 *
 * This rule-of-thumb is implemented using a performance-multiplier:
 * If the exit latency times the performance multiplier is longer than
 * the predicted duration, the C state is not considered a candidate
 * for selection due to a too high performance impact. So the higher
 * this multiplier is, the longer we need to be idle to pick a deep C
 * state, and thus the less likely a busy CPU will hit such a deep
 * C state.
 *
 * Two factors are used in determing this multiplier:
 * a value of 10 is added for each point of "per cpu load average" we have.
 * a value of 5 points is added for each process that is waiting for
 * IO on this CPU.
 * (these values are experimentally determined)
 *
 * The load average factor gives a longer term (few seconds) input to the
 * decision, while the iowait value gives a cpu local instantanious input.
 * The iowait factor may look low, but realize that this is also already
 * represented in the system load average.
 *
 */

struct menu_device {
	int		last_state_idx;
	int             needs_update;

	unsigned int	expected_us;
	u64		predicted_us;
	unsigned int	exit_us;
	unsigned int	bucket;
	u64		correction_factor[BUCKETS];
	u32		intervals[INTERVALS];
	int		interval_ptr;
};


#define LOAD_INT(x) ((x) >> FSHIFT)
#define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100)

static int get_loadavg(void)
{
	unsigned long this = this_cpu_load();


	return LOAD_INT(this) * 10 + LOAD_FRAC(this) / 10;
}

static inline int which_bucket(unsigned int duration)
{
	int bucket = 0;

	/*
	 * We keep two groups of stats; one with no
	 * IO pending, one without.
	 * This allows us to calculate
	 * E(duration)|iowait
	 */
	if (nr_iowait_cpu(smp_processor_id()))
		bucket = BUCKETS/2;

	if (duration < 10)
		return bucket;
	if (duration < 100)
		return bucket + 1;
	if (duration < 1000)
		return bucket + 2;
	if (duration < 10000)
		return bucket + 3;
	if (duration < 100000)
		return bucket + 4;
	return bucket + 5;
}

/*
 * Return a multiplier for the exit latency that is intended
 * to take performance requirements into account.
 * The more performance critical we estimate the system
 * to be, the higher this multiplier, and thus the higher
 * the barrier to go to an expensive C state.
 */
static inline int performance_multiplier(void)
{
	int mult = 1;

	/* for higher loadavg, we are more reluctant */

	mult += 2 * get_loadavg();

	/* for IO wait tasks (per cpu!) we add 5x each */
	mult += 10 * nr_iowait_cpu(smp_processor_id());

	return mult;
}

static DEFINE_PER_CPU(struct menu_device, menu_devices);

static void menu_update(struct cpuidle_device *dev);

/* This implements DIV_ROUND_CLOSEST but avoids 64 bit division */
static u64 div_round64(u64 dividend, u32 divisor)
{
	return div_u64(dividend + (divisor / 2), divisor);
}

/*
 * Try detecting repeating patterns by keeping track of the last 8
 * intervals, and checking if the standard deviation of that set
 * of points is below a threshold. If it is... then use the
 * average of these 8 points as the estimated value.
 */
static void detect_repeating_patterns(struct menu_device *data)
{
	int i;
	uint64_t avg = 0;
	uint64_t stddev = 0; /* contains the square of the std deviation */

	/* first calculate average and standard deviation of the past */
	for (i = 0; i < INTERVALS; i++)
		avg += data->intervals[i];
	avg = avg / INTERVALS;

	/* if the avg is beyond the known next tick, it's worthless */
	if (avg > data->expected_us)
		return;

	for (i = 0; i < INTERVALS; i++)
		stddev += (data->intervals[i] - avg) *
			  (data->intervals[i] - avg);

	stddev = stddev / INTERVALS;

	/*
	 * now.. if stddev is small.. then assume we have a
	 * repeating pattern and predict we keep doing this.
	 */

	if (avg && stddev < STDDEV_THRESH)
		data->predicted_us = avg;
}

/**
 * menu_select - selects the next idle state to enter
 * @dev: the CPU
 */
static int menu_select(struct cpuidle_device *dev)
{
	struct menu_device *data = &__get_cpu_var(menu_devices);
	int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
	unsigned int power_usage = -1;
	int i;
	int multiplier;

	if (data->needs_update) {
		menu_update(dev);
		data->needs_update = 0;
	}

	data->last_state_idx = 0;
	data->exit_us = 0;

	/* Special case when user has set very strict latency requirement */
	if (unlikely(latency_req == 0))
		return 0;

	/* determine the expected residency time, round up */
	data->expected_us =
	    DIV_ROUND_UP((u32)ktime_to_ns(tick_nohz_get_sleep_length()), 1000);


	data->bucket = which_bucket(data->expected_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.
	 */
	if (data->correction_factor[data->bucket] == 0)
		data->correction_factor[data->bucket] = RESOLUTION * DECAY;

	/* Make sure to round up for half microseconds */
	data->predicted_us = div_round64(data->expected_us * data->correction_factor[data->bucket],
					 RESOLUTION * DECAY);

	detect_repeating_patterns(data);

	/*
	 * We want to default to C1 (hlt), not to busy polling
	 * unless the timer is happening really really soon.
	 */
	if (data->expected_us > 5)
		data->last_state_idx = CPUIDLE_DRIVER_STATE_START;

	/*
	 * Find the idle state with the lowest power while satisfying
	 * our constraints.
	 */
	for (i = CPUIDLE_DRIVER_STATE_START; i < dev->state_count; i++) {
		struct cpuidle_state *s = &dev->states[i];

		if (s->flags & CPUIDLE_FLAG_IGNORE)
			continue;
		if (s->target_residency > data->predicted_us)
			continue;
		if (s->exit_latency > latency_req)
			continue;
		if (s->exit_latency * multiplier > data->predicted_us)
			continue;

		if (s->power_usage < power_usage) {
			power_usage = s->power_usage;
			data->last_state_idx = i;
			data->exit_us = s->exit_latency;
		}
	}

	return data->last_state_idx;
}

/**
 * menu_reflect - records that data structures need update
 * @dev: the CPU
 *
 * NOTE: it's important to be fast here because this operation will add to
 *       the overall exit latency.
 */
static void menu_reflect(struct cpuidle_device *dev)
{
	struct menu_device *data = &__get_cpu_var(menu_devices);
	data->needs_update = 1;
}

/**
 * menu_update - attempts to guess what happened after entry
 * @dev: the CPU
 */
static void menu_update(struct cpuidle_device *dev)
{
	struct menu_device *data = &__get_cpu_var(menu_devices);
	int last_idx = data->last_state_idx;
	unsigned int last_idle_us = cpuidle_get_last_residency(dev);
	struct cpuidle_state *target = &dev->states[last_idx];
	unsigned int measured_us;
	u64 new_factor;

	/*
	 * Ugh, this idle state doesn't support residency measurements, so we
	 * are basically lost in the dark.  As a compromise, assume we slept
	 * for the whole expected time.
	 */
	if (unlikely(!(target->flags & CPUIDLE_FLAG_TIME_VALID)))
		last_idle_us = data->expected_us;


	measured_us = last_idle_us;

	/*
	 * We correct for the exit latency; we are assuming here that the
	 * exit latency happens after the event that we're interested in.
	 */
	if (measured_us > data->exit_us)
		measured_us -= data->exit_us;


	/* update our correction ratio */

	new_factor = data->correction_factor[data->bucket]
			* (DECAY - 1) / DECAY;

	if (data->expected_us > 0 && measured_us < MAX_INTERESTING)
		new_factor += RESOLUTION * measured_us / data->expected_us;
	else
		/*
		 * we were idle so long that we count it as a perfect
		 * prediction
		 */
		new_factor += RESOLUTION;

	/*
	 * We don't want 0 as factor; we always want at least
	 * a tiny bit of estimated time.
	 */
	if (new_factor == 0)
		new_factor = 1;

	data->correction_factor[data->bucket] = new_factor;

	/* update the repeating-pattern data */
	data->intervals[data->interval_ptr++] = last_idle_us;
	if (data->interval_ptr >= INTERVALS)
		data->interval_ptr = 0;
}

/**
 * menu_enable_device - scans a CPU's states and does setup
 * @dev: the CPU
 */
static int menu_enable_device(struct cpuidle_device *dev)
{
	struct menu_device *data = &per_cpu(menu_devices, dev->cpu);

	memset(data, 0, sizeof(struct menu_device));

	return 0;
}

static struct cpuidle_governor menu_governor = {
	.name =		"menu",
	.rating =	20,
	.enable =	menu_enable_device,
	.select =	menu_select,
	.reflect =	menu_reflect,
	.owner =	THIS_MODULE,
};

/**
 * init_menu - initializes the governor
 */
static int __init init_menu(void)
{
	return cpuidle_register_governor(&menu_governor);
}

/**
 * exit_menu - exits the governor
 */
static void __exit exit_menu(void)
{
	cpuidle_unregister_governor(&menu_governor);
}

MODULE_LICENSE("GPL");
module_init(init_menu);
module_exit(exit_menu);
Commit	Line	Data
4f86d3a8 LB	1	/*
	2	* menu.c - the menu idle governor
	3	*
	4	* Copyright (C) 2006-2007 Adam Belay <abelay@novell.com>
69d25870 AV	5	* Copyright (C) 2009 Intel Corporation
	6	* Author:
	7	* Arjan van de Ven <arjan@linux.intel.com>
4f86d3a8	8	*
69d25870 AV	9	* This code is licenced under the GPL version 2 as described
69d25870 AV	10	* in the COPYING file that acompanies the Linux Kernel.
4f86d3a8 LB	11	*/
	12
	13	#include <linux/kernel.h>
	14	#include <linux/cpuidle.h>
d82b3518	15	#include <linux/pm_qos_params.h>
4f86d3a8 LB	16	#include <linux/time.h>
	17	#include <linux/ktime.h>
	18	#include <linux/hrtimer.h>
	19	#include <linux/tick.h>
69d25870	20	#include <linux/sched.h>
5787536e	21	#include <linux/math64.h>
4f86d3a8	22
69d25870	23	#define BUCKETS 12
1f85f87d	24	#define INTERVALS 8
69d25870	25	#define RESOLUTION 1024
1f85f87d	26	#define DECAY 8
69d25870	27	#define MAX_INTERESTING 50000
1f85f87d AV	28	#define STDDEV_THRESH 400
1f85f87d AV	29
69d25870 AV	30
	31	/*
	32	* Concepts and ideas behind the menu governor
	33	*
	34	* For the menu governor, there are 3 decision factors for picking a C
	35	* state:
	36	* 1) Energy break even point
	37	* 2) Performance impact
	38	* 3) Latency tolerance (from pmqos infrastructure)
	39	* These these three factors are treated independently.
	40	*
	41	* Energy break even point
	42	* -----------------------
	43	* C state entry and exit have an energy cost, and a certain amount of time in
	44	* the C state is required to actually break even on this cost. CPUIDLE
	45	* provides us this duration in the "target_residency" field. So all that we
	46	* need is a good prediction of how long we'll be idle. Like the traditional
	47	* menu governor, we start with the actual known "next timer event" time.
	48	*
	49	* Since there are other source of wakeups (interrupts for example) than
	50	* the next timer event, this estimation is rather optimistic. To get a
	51	* more realistic estimate, a correction factor is applied to the estimate,
	52	* that is based on historic behavior. For example, if in the past the actual
	53	* duration always was 50% of the next timer tick, the correction factor will
	54	* be 0.5.
	55	*
	56	* menu uses a running average for this correction factor, however it uses a
	57	* set of factors, not just a single factor. This stems from the realization
	58	* that the ratio is dependent on the order of magnitude of the expected
	59	* duration; if we expect 500 milliseconds of idle time the likelihood of
	60	* getting an interrupt very early is much higher than if we expect 50 micro
	61	* seconds of idle time. A second independent factor that has big impact on
	62	* the actual factor is if there is (disk) IO outstanding or not.
	63	* (as a special twist, we consider every sleep longer than 50 milliseconds
	64	* as perfect; there are no power gains for sleeping longer than this)
	65	*
	66	* For these two reasons we keep an array of 12 independent factors, that gets
	67	* indexed based on the magnitude of the expected duration as well as the
	68	* "is IO outstanding" property.
	69	*
1f85f87d AV	70	* Repeatable-interval-detector
	71	* ----------------------------
	72	* There are some cases where "next timer" is a completely unusable predictor:
	73	* Those cases where the interval is fixed, for example due to hardware
	74	* interrupt mitigation, but also due to fixed transfer rate devices such as
	75	* mice.
	76	* For this, we use a different predictor: We track the duration of the last 8
	77	* intervals and if the stand deviation of these 8 intervals is below a
	78	* threshold value, we use the average of these intervals as prediction.
	79	*
69d25870 AV	80	* Limiting Performance Impact
	81	* ---------------------------
	82	* C states, especially those with large exit latencies, can have a real
20e3341b	83	* noticeable impact on workloads, which is not acceptable for most sysadmins,
69d25870 AV	84	* and in addition, less performance has a power price of its own.
	85	*
	86	* As a general rule of thumb, menu assumes that the following heuristic
	87	* holds:
	88	* The busier the system, the less impact of C states is acceptable
	89	*
	90	* This rule-of-thumb is implemented using a performance-multiplier:
	91	* If the exit latency times the performance multiplier is longer than
	92	* the predicted duration, the C state is not considered a candidate
	93	* for selection due to a too high performance impact. So the higher
	94	* this multiplier is, the longer we need to be idle to pick a deep C
	95	* state, and thus the less likely a busy CPU will hit such a deep
	96	* C state.
	97	*
	98	* Two factors are used in determing this multiplier:
	99	* a value of 10 is added for each point of "per cpu load average" we have.
	100	* a value of 5 points is added for each process that is waiting for
	101	* IO on this CPU.
	102	* (these values are experimentally determined)
	103	*
	104	* The load average factor gives a longer term (few seconds) input to the
	105	* decision, while the iowait value gives a cpu local instantanious input.
	106	* The iowait factor may look low, but realize that this is also already
	107	* represented in the system load average.
	108	*
	109	*/
4f86d3a8 LB	110
	111	struct menu_device {
	112	int last_state_idx;
672917dc	113	int needs_update;
4f86d3a8 LB	114
4f86d3a8 LB	115	unsigned int expected_us;
56e6943b	116	u64 predicted_us;
69d25870 AV	117	unsigned int exit_us;
	118	unsigned int bucket;
	119	u64 correction_factor[BUCKETS];
1f85f87d AV	120	u32 intervals[INTERVALS];
1f85f87d AV	121	int interval_ptr;
4f86d3a8 LB	122	};
4f86d3a8 LB	123
69d25870 AV	124
	125	#define LOAD_INT(x) ((x) >> FSHIFT)
	126	#define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100)
	127
	128	static int get_loadavg(void)
	129	{
	130	unsigned long this = this_cpu_load();
	131
	132
	133	return LOAD_INT(this) * 10 + LOAD_FRAC(this) / 10;
	134	}
	135
	136	static inline int which_bucket(unsigned int duration)
	137	{
	138	int bucket = 0;
	139
	140	/*
	141	* We keep two groups of stats; one with no
	142	* IO pending, one without.
	143	* This allows us to calculate
	144	* E(duration)\|iowait
	145	*/
8c215bd3	146	if (nr_iowait_cpu(smp_processor_id()))
69d25870 AV	147	bucket = BUCKETS/2;
	148
	149	if (duration < 10)
	150	return bucket;
	151	if (duration < 100)
	152	return bucket + 1;
	153	if (duration < 1000)
	154	return bucket + 2;
	155	if (duration < 10000)
	156	return bucket + 3;
	157	if (duration < 100000)
	158	return bucket + 4;
	159	return bucket + 5;
	160	}
	161
	162	/*
	163	* Return a multiplier for the exit latency that is intended
	164	* to take performance requirements into account.
	165	* The more performance critical we estimate the system
	166	* to be, the higher this multiplier, and thus the higher
	167	* the barrier to go to an expensive C state.
	168	*/
	169	static inline int performance_multiplier(void)
	170	{
	171	int mult = 1;
	172
	173	/* for higher loadavg, we are more reluctant */
	174
	175	mult += 2 * get_loadavg();
	176
	177	/* for IO wait tasks (per cpu!) we add 5x each */
8c215bd3	178	mult += 10 * nr_iowait_cpu(smp_processor_id());
69d25870 AV	179
	180	return mult;
	181	}
	182
4f86d3a8 LB	183	static DEFINE_PER_CPU(struct menu_device, menu_devices);
4f86d3a8 LB	184
672917dc CZ	185	static void menu_update(struct cpuidle_device *dev);
672917dc CZ	186
5787536e SH	187	/* This implements DIV_ROUND_CLOSEST but avoids 64 bit division */
	188	static u64 div_round64(u64 dividend, u32 divisor)
	189	{
	190	return div_u64(dividend + (divisor / 2), divisor);
	191	}
	192
1f85f87d AV	193	/*
	194	* Try detecting repeating patterns by keeping track of the last 8
	195	* intervals, and checking if the standard deviation of that set
	196	* of points is below a threshold. If it is... then use the
	197	* average of these 8 points as the estimated value.
	198	*/
	199	static void detect_repeating_patterns(struct menu_device *data)
	200	{
	201	int i;
	202	uint64_t avg = 0;
	203	uint64_t stddev = 0; /* contains the square of the std deviation */
	204
	205	/* first calculate average and standard deviation of the past */
	206	for (i = 0; i < INTERVALS; i++)
	207	avg += data->intervals[i];
	208	avg = avg / INTERVALS;
	209
	210	/* if the avg is beyond the known next tick, it's worthless */
	211	if (avg > data->expected_us)
	212	return;
	213
	214	for (i = 0; i < INTERVALS; i++)
	215	stddev += (data->intervals[i] - avg) *
	216	(data->intervals[i] - avg);
	217
	218	stddev = stddev / INTERVALS;
	219
	220	/*
	221	* now.. if stddev is small.. then assume we have a
	222	* repeating pattern and predict we keep doing this.
	223	*/
	224
	225	if (avg && stddev < STDDEV_THRESH)
	226	data->predicted_us = avg;
	227	}
	228
4f86d3a8 LB	229	/**
	230	* menu_select - selects the next idle state to enter
	231	* @dev: the CPU
	232	*/
	233	static int menu_select(struct cpuidle_device *dev)
	234	{
	235	struct menu_device *data = &__get_cpu_var(menu_devices);
ed77134b	236	int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY);
71abbbf8	237	unsigned int power_usage = -1;
4f86d3a8	238	int i;
69d25870 AV	239	int multiplier;
69d25870 AV	240
672917dc CZ	241	if (data->needs_update) {
	242	menu_update(dev);
	243	data->needs_update = 0;
	244	}
	245
1c6fe036 AV	246	data->last_state_idx = 0;
	247	data->exit_us = 0;
	248
a2bd9202	249	/* Special case when user has set very strict latency requirement */
69d25870	250	if (unlikely(latency_req == 0))
a2bd9202	251	return 0;
a2bd9202	252
69d25870	253	/* determine the expected residency time, round up */
4f86d3a8	254	data->expected_us =
69d25870 AV	255	DIV_ROUND_UP((u32)ktime_to_ns(tick_nohz_get_sleep_length()), 1000);
	256
	257
	258	data->bucket = which_bucket(data->expected_us);
	259
	260	multiplier = performance_multiplier();
	261
	262	/*
	263	* if the correction factor is 0 (eg first time init or cpu hotplug
	264	* etc), we actually want to start out with a unity factor.
	265	*/
	266	if (data->correction_factor[data->bucket] == 0)
	267	data->correction_factor[data->bucket] = RESOLUTION * DECAY;
	268
	269	/* Make sure to round up for half microseconds */
5787536e SH	270	data->predicted_us = div_round64(data->expected_us * data->correction_factor[data->bucket],
5787536e SH	271	RESOLUTION * DECAY);
69d25870	272
1f85f87d AV	273	detect_repeating_patterns(data);
1f85f87d AV	274
69d25870 AV	275	/*
	276	* We want to default to C1 (hlt), not to busy polling
	277	* unless the timer is happening really really soon.
	278	*/
	279	if (data->expected_us > 5)
	280	data->last_state_idx = CPUIDLE_DRIVER_STATE_START;
4f86d3a8	281
71abbbf8 AL	282	/*
	283	* Find the idle state with the lowest power while satisfying
	284	* our constraints.
	285	*/
69d25870	286	for (i = CPUIDLE_DRIVER_STATE_START; i < dev->state_count; i++) {
4f86d3a8 LB	287	struct cpuidle_state *s = &dev->states[i];
4f86d3a8 LB	288
71abbbf8 AL	289	if (s->flags & CPUIDLE_FLAG_IGNORE)
71abbbf8 AL	290	continue;
4f86d3a8	291	if (s->target_residency > data->predicted_us)
71abbbf8	292	continue;
a2bd9202	293	if (s->exit_latency > latency_req)
71abbbf8	294	continue;
69d25870	295	if (s->exit_latency * multiplier > data->predicted_us)
71abbbf8 AL	296	continue;
	297
	298	if (s->power_usage < power_usage) {
	299	power_usage = s->power_usage;
	300	data->last_state_idx = i;
	301	data->exit_us = s->exit_latency;
	302	}
4f86d3a8 LB	303	}
4f86d3a8 LB	304
69d25870	305	return data->last_state_idx;
4f86d3a8 LB	306	}
	307
	308	/**
672917dc	309	* menu_reflect - records that data structures need update
4f86d3a8 LB	310	* @dev: the CPU
	311	*
	312	* NOTE: it's important to be fast here because this operation will add to
	313	* the overall exit latency.
	314	*/
	315	static void menu_reflect(struct cpuidle_device *dev)
672917dc CZ	316	{
	317	struct menu_device *data = &__get_cpu_var(menu_devices);
	318	data->needs_update = 1;
	319	}
	320
	321	/**
	322	* menu_update - attempts to guess what happened after entry
	323	* @dev: the CPU
	324	*/
	325	static void menu_update(struct cpuidle_device *dev)
4f86d3a8 LB	326	{
	327	struct menu_device *data = &__get_cpu_var(menu_devices);
	328	int last_idx = data->last_state_idx;
320eee77	329	unsigned int last_idle_us = cpuidle_get_last_residency(dev);
4f86d3a8	330	struct cpuidle_state *target = &dev->states[last_idx];
320eee77	331	unsigned int measured_us;
69d25870	332	u64 new_factor;
4f86d3a8 LB	333
	334	/*
	335	* Ugh, this idle state doesn't support residency measurements, so we
	336	* are basically lost in the dark. As a compromise, assume we slept
69d25870	337	* for the whole expected time.
4f86d3a8	338	*/
320eee77	339	if (unlikely(!(target->flags & CPUIDLE_FLAG_TIME_VALID)))
69d25870 AV	340	last_idle_us = data->expected_us;
	341
	342
	343	measured_us = last_idle_us;
4f86d3a8	344
320eee77	345	/*
69d25870 AV	346	* We correct for the exit latency; we are assuming here that the
69d25870 AV	347	* exit latency happens after the event that we're interested in.
320eee77	348	*/
69d25870 AV	349	if (measured_us > data->exit_us)
	350	measured_us -= data->exit_us;
	351
	352
	353	/* update our correction ratio */
	354
	355	new_factor = data->correction_factor[data->bucket]
	356	* (DECAY - 1) / DECAY;
	357
1c6fe036	358	if (data->expected_us > 0 && measured_us < MAX_INTERESTING)
69d25870	359	new_factor += RESOLUTION * measured_us / data->expected_us;
320eee77	360	else
69d25870 AV	361	/*
	362	* we were idle so long that we count it as a perfect
	363	* prediction
	364	*/
	365	new_factor += RESOLUTION;
320eee77	366
69d25870 AV	367	/*
	368	* We don't want 0 as factor; we always want at least
	369	* a tiny bit of estimated time.
	370	*/
	371	if (new_factor == 0)
	372	new_factor = 1;
320eee77	373
69d25870	374	data->correction_factor[data->bucket] = new_factor;
1f85f87d AV	375
	376	/* update the repeating-pattern data */
	377	data->intervals[data->interval_ptr++] = last_idle_us;
	378	if (data->interval_ptr >= INTERVALS)
	379	data->interval_ptr = 0;
4f86d3a8 LB	380	}
	381
	382	/**
	383	* menu_enable_device - scans a CPU's states and does setup
	384	* @dev: the CPU
	385	*/
	386	static int menu_enable_device(struct cpuidle_device *dev)
	387	{
	388	struct menu_device *data = &per_cpu(menu_devices, dev->cpu);
	389
	390	memset(data, 0, sizeof(struct menu_device));
	391
	392	return 0;
	393	}
	394
	395	static struct cpuidle_governor menu_governor = {
	396	.name = "menu",
	397	.rating = 20,
	398	.enable = menu_enable_device,
	399	.select = menu_select,
	400	.reflect = menu_reflect,
	401	.owner = THIS_MODULE,
	402	};
	403
	404	/**
	405	* init_menu - initializes the governor
	406	*/
	407	static int __init init_menu(void)
	408	{
	409	return cpuidle_register_governor(&menu_governor);
	410	}
	411
	412	/**
	413	* exit_menu - exits the governor
	414	*/
	415	static void __exit exit_menu(void)
	416	{
	417	cpuidle_unregister_governor(&menu_governor);
	418	}
	419
	420	MODULE_LICENSE("GPL");
	421	module_init(init_menu);
	422	module_exit(exit_menu);