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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 |
10 | * in the COPYING file that acompanies the Linux Kernel. | |
4f86d3a8 LB |
11 | */ |
12 | ||
13 | #include <linux/kernel.h> | |
14 | #include <linux/cpuidle.h> | |
e8db0be1 | 15 | #include <linux/pm_qos.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> |
4f17722c | 21 | #include <linux/sched/loadavg.h> |
03441a34 | 22 | #include <linux/sched/stat.h> |
5787536e | 23 | #include <linux/math64.h> |
9908859a | 24 | #include <linux/cpu.h> |
4f86d3a8 | 25 | |
decd51bb TT |
26 | /* |
27 | * Please note when changing the tuning values: | |
28 | * If (MAX_INTERESTING-1) * RESOLUTION > UINT_MAX, the result of | |
29 | * a scaling operation multiplication may overflow on 32 bit platforms. | |
30 | * In that case, #define RESOLUTION as ULL to get 64 bit result: | |
31 | * #define RESOLUTION 1024ULL | |
32 | * | |
33 | * The default values do not overflow. | |
34 | */ | |
69d25870 | 35 | #define BUCKETS 12 |
ae779300 MG |
36 | #define INTERVAL_SHIFT 3 |
37 | #define INTERVALS (1UL << INTERVAL_SHIFT) | |
69d25870 | 38 | #define RESOLUTION 1024 |
1f85f87d | 39 | #define DECAY 8 |
69d25870 | 40 | #define MAX_INTERESTING 50000 |
1f85f87d | 41 | |
69d25870 AV |
42 | |
43 | /* | |
44 | * Concepts and ideas behind the menu governor | |
45 | * | |
46 | * For the menu governor, there are 3 decision factors for picking a C | |
47 | * state: | |
48 | * 1) Energy break even point | |
49 | * 2) Performance impact | |
50 | * 3) Latency tolerance (from pmqos infrastructure) | |
51 | * These these three factors are treated independently. | |
52 | * | |
53 | * Energy break even point | |
54 | * ----------------------- | |
55 | * C state entry and exit have an energy cost, and a certain amount of time in | |
56 | * the C state is required to actually break even on this cost. CPUIDLE | |
57 | * provides us this duration in the "target_residency" field. So all that we | |
58 | * need is a good prediction of how long we'll be idle. Like the traditional | |
59 | * menu governor, we start with the actual known "next timer event" time. | |
60 | * | |
61 | * Since there are other source of wakeups (interrupts for example) than | |
62 | * the next timer event, this estimation is rather optimistic. To get a | |
63 | * more realistic estimate, a correction factor is applied to the estimate, | |
64 | * that is based on historic behavior. For example, if in the past the actual | |
65 | * duration always was 50% of the next timer tick, the correction factor will | |
66 | * be 0.5. | |
67 | * | |
68 | * menu uses a running average for this correction factor, however it uses a | |
69 | * set of factors, not just a single factor. This stems from the realization | |
70 | * that the ratio is dependent on the order of magnitude of the expected | |
71 | * duration; if we expect 500 milliseconds of idle time the likelihood of | |
72 | * getting an interrupt very early is much higher than if we expect 50 micro | |
73 | * seconds of idle time. A second independent factor that has big impact on | |
74 | * the actual factor is if there is (disk) IO outstanding or not. | |
75 | * (as a special twist, we consider every sleep longer than 50 milliseconds | |
76 | * as perfect; there are no power gains for sleeping longer than this) | |
77 | * | |
78 | * For these two reasons we keep an array of 12 independent factors, that gets | |
79 | * indexed based on the magnitude of the expected duration as well as the | |
80 | * "is IO outstanding" property. | |
81 | * | |
1f85f87d AV |
82 | * Repeatable-interval-detector |
83 | * ---------------------------- | |
84 | * There are some cases where "next timer" is a completely unusable predictor: | |
85 | * Those cases where the interval is fixed, for example due to hardware | |
86 | * interrupt mitigation, but also due to fixed transfer rate devices such as | |
87 | * mice. | |
88 | * For this, we use a different predictor: We track the duration of the last 8 | |
89 | * intervals and if the stand deviation of these 8 intervals is below a | |
90 | * threshold value, we use the average of these intervals as prediction. | |
91 | * | |
69d25870 AV |
92 | * Limiting Performance Impact |
93 | * --------------------------- | |
94 | * C states, especially those with large exit latencies, can have a real | |
20e3341b | 95 | * noticeable impact on workloads, which is not acceptable for most sysadmins, |
69d25870 AV |
96 | * and in addition, less performance has a power price of its own. |
97 | * | |
98 | * As a general rule of thumb, menu assumes that the following heuristic | |
99 | * holds: | |
100 | * The busier the system, the less impact of C states is acceptable | |
101 | * | |
102 | * This rule-of-thumb is implemented using a performance-multiplier: | |
103 | * If the exit latency times the performance multiplier is longer than | |
104 | * the predicted duration, the C state is not considered a candidate | |
105 | * for selection due to a too high performance impact. So the higher | |
106 | * this multiplier is, the longer we need to be idle to pick a deep C | |
107 | * state, and thus the less likely a busy CPU will hit such a deep | |
108 | * C state. | |
109 | * | |
110 | * Two factors are used in determing this multiplier: | |
111 | * a value of 10 is added for each point of "per cpu load average" we have. | |
112 | * a value of 5 points is added for each process that is waiting for | |
113 | * IO on this CPU. | |
114 | * (these values are experimentally determined) | |
115 | * | |
116 | * The load average factor gives a longer term (few seconds) input to the | |
117 | * decision, while the iowait value gives a cpu local instantanious input. | |
118 | * The iowait factor may look low, but realize that this is also already | |
119 | * represented in the system load average. | |
120 | * | |
121 | */ | |
4f86d3a8 LB |
122 | |
123 | struct menu_device { | |
124 | int last_state_idx; | |
672917dc | 125 | int needs_update; |
4f86d3a8 | 126 | |
5dc2f5a3 | 127 | unsigned int next_timer_us; |
51f245b8 | 128 | unsigned int predicted_us; |
69d25870 | 129 | unsigned int bucket; |
51f245b8 | 130 | unsigned int correction_factor[BUCKETS]; |
939e33b7 | 131 | unsigned int intervals[INTERVALS]; |
1f85f87d | 132 | int interval_ptr; |
4f86d3a8 LB |
133 | }; |
134 | ||
69d25870 AV |
135 | |
136 | #define LOAD_INT(x) ((x) >> FSHIFT) | |
137 | #define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100) | |
138 | ||
372ba8cb | 139 | static inline int get_loadavg(unsigned long load) |
69d25870 | 140 | { |
372ba8cb | 141 | return LOAD_INT(load) * 10 + LOAD_FRAC(load) / 10; |
69d25870 AV |
142 | } |
143 | ||
64b4ca5c | 144 | static inline int which_bucket(unsigned int duration, unsigned long nr_iowaiters) |
69d25870 AV |
145 | { |
146 | int bucket = 0; | |
147 | ||
148 | /* | |
149 | * We keep two groups of stats; one with no | |
150 | * IO pending, one without. | |
151 | * This allows us to calculate | |
152 | * E(duration)|iowait | |
153 | */ | |
64b4ca5c | 154 | if (nr_iowaiters) |
69d25870 AV |
155 | bucket = BUCKETS/2; |
156 | ||
157 | if (duration < 10) | |
158 | return bucket; | |
159 | if (duration < 100) | |
160 | return bucket + 1; | |
161 | if (duration < 1000) | |
162 | return bucket + 2; | |
163 | if (duration < 10000) | |
164 | return bucket + 3; | |
165 | if (duration < 100000) | |
166 | return bucket + 4; | |
167 | return bucket + 5; | |
168 | } | |
169 | ||
170 | /* | |
171 | * Return a multiplier for the exit latency that is intended | |
172 | * to take performance requirements into account. | |
173 | * The more performance critical we estimate the system | |
174 | * to be, the higher this multiplier, and thus the higher | |
175 | * the barrier to go to an expensive C state. | |
176 | */ | |
372ba8cb | 177 | static inline int performance_multiplier(unsigned long nr_iowaiters, unsigned long load) |
69d25870 AV |
178 | { |
179 | int mult = 1; | |
180 | ||
181 | /* for higher loadavg, we are more reluctant */ | |
182 | ||
372ba8cb | 183 | mult += 2 * get_loadavg(load); |
69d25870 AV |
184 | |
185 | /* for IO wait tasks (per cpu!) we add 5x each */ | |
64b4ca5c | 186 | mult += 10 * nr_iowaiters; |
69d25870 AV |
187 | |
188 | return mult; | |
189 | } | |
190 | ||
4f86d3a8 LB |
191 | static DEFINE_PER_CPU(struct menu_device, menu_devices); |
192 | ||
46bcfad7 | 193 | static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev); |
672917dc | 194 | |
1f85f87d AV |
195 | /* |
196 | * Try detecting repeating patterns by keeping track of the last 8 | |
197 | * intervals, and checking if the standard deviation of that set | |
198 | * of points is below a threshold. If it is... then use the | |
199 | * average of these 8 points as the estimated value. | |
200 | */ | |
e132b9b3 | 201 | static unsigned int get_typical_interval(struct menu_device *data) |
1f85f87d | 202 | { |
4cd46bca | 203 | int i, divisor; |
3b99669b RV |
204 | unsigned int max, thresh, avg; |
205 | uint64_t sum, variance; | |
0e96d5ad TT |
206 | |
207 | thresh = UINT_MAX; /* Discard outliers above this value */ | |
1f85f87d | 208 | |
c96ca4fb | 209 | again: |
1f85f87d | 210 | |
0e96d5ad | 211 | /* First calculate the average of past intervals */ |
4cd46bca | 212 | max = 0; |
3b99669b | 213 | sum = 0; |
4cd46bca | 214 | divisor = 0; |
c96ca4fb | 215 | for (i = 0; i < INTERVALS; i++) { |
0e96d5ad | 216 | unsigned int value = data->intervals[i]; |
c96ca4fb | 217 | if (value <= thresh) { |
3b99669b | 218 | sum += value; |
c96ca4fb YS |
219 | divisor++; |
220 | if (value > max) | |
221 | max = value; | |
222 | } | |
223 | } | |
ae779300 | 224 | if (divisor == INTERVALS) |
3b99669b | 225 | avg = sum >> INTERVAL_SHIFT; |
ae779300 | 226 | else |
3b99669b | 227 | avg = div_u64(sum, divisor); |
c96ca4fb | 228 | |
7024b18c RV |
229 | /* Then try to determine variance */ |
230 | variance = 0; | |
c96ca4fb | 231 | for (i = 0; i < INTERVALS; i++) { |
0e96d5ad | 232 | unsigned int value = data->intervals[i]; |
c96ca4fb | 233 | if (value <= thresh) { |
3b99669b | 234 | int64_t diff = (int64_t)value - avg; |
7024b18c | 235 | variance += diff * diff; |
c96ca4fb YS |
236 | } |
237 | } | |
ae779300 | 238 | if (divisor == INTERVALS) |
7024b18c | 239 | variance >>= INTERVAL_SHIFT; |
ae779300 | 240 | else |
7024b18c | 241 | do_div(variance, divisor); |
ae779300 | 242 | |
1f85f87d | 243 | /* |
7024b18c RV |
244 | * The typical interval is obtained when standard deviation is |
245 | * small (stddev <= 20 us, variance <= 400 us^2) or standard | |
246 | * deviation is small compared to the average interval (avg > | |
247 | * 6*stddev, avg^2 > 36*variance). The average is smaller than | |
248 | * UINT_MAX aka U32_MAX, so computing its square does not | |
249 | * overflow a u64. We simply reject this candidate average if | |
250 | * the standard deviation is greater than 715 s (which is | |
251 | * rather unlikely). | |
0d6a7ffa | 252 | * |
330647a9 | 253 | * Use this result only if there is no timer to wake us up sooner. |
1f85f87d | 254 | */ |
7024b18c | 255 | if (likely(variance <= U64_MAX/36)) { |
3b99669b | 256 | if ((((u64)avg*avg > variance*36) && (divisor * 4 >= INTERVALS * 3)) |
7024b18c | 257 | || variance <= 400) { |
e132b9b3 | 258 | return avg; |
0d6a7ffa | 259 | } |
69a37bea | 260 | } |
017099e2 TT |
261 | |
262 | /* | |
263 | * If we have outliers to the upside in our distribution, discard | |
264 | * those by setting the threshold to exclude these outliers, then | |
265 | * calculate the average and standard deviation again. Once we get | |
266 | * down to the bottom 3/4 of our samples, stop excluding samples. | |
267 | * | |
268 | * This can deal with workloads that have long pauses interspersed | |
269 | * with sporadic activity with a bunch of short pauses. | |
270 | */ | |
271 | if ((divisor * 4) <= INTERVALS * 3) | |
e132b9b3 | 272 | return UINT_MAX; |
017099e2 TT |
273 | |
274 | thresh = max - 1; | |
275 | goto again; | |
1f85f87d AV |
276 | } |
277 | ||
4f86d3a8 LB |
278 | /** |
279 | * menu_select - selects the next idle state to enter | |
46bcfad7 | 280 | * @drv: cpuidle driver containing state data |
4f86d3a8 LB |
281 | * @dev: the CPU |
282 | */ | |
46bcfad7 | 283 | static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) |
4f86d3a8 | 284 | { |
229b6863 | 285 | struct menu_device *data = this_cpu_ptr(&menu_devices); |
9908859a | 286 | struct device *device = get_cpu_device(dev->cpu); |
ed77134b | 287 | int latency_req = pm_qos_request(PM_QOS_CPU_DMA_LATENCY); |
4f86d3a8 | 288 | int i; |
3ed09c94 NP |
289 | int first_idx; |
290 | int idx; | |
96e95182 | 291 | unsigned int interactivity_req; |
e132b9b3 | 292 | unsigned int expected_interval; |
372ba8cb | 293 | unsigned long nr_iowaiters, cpu_load; |
6dbf5cea | 294 | int resume_latency = dev_pm_qos_raw_read_value(device); |
69d25870 | 295 | |
672917dc | 296 | if (data->needs_update) { |
46bcfad7 | 297 | menu_update(drv, dev); |
672917dc CZ |
298 | data->needs_update = 0; |
299 | } | |
300 | ||
0759e80b RW |
301 | if (resume_latency < latency_req && |
302 | resume_latency != PM_QOS_RESUME_LATENCY_NO_CONSTRAINT) | |
9908859a AS |
303 | latency_req = resume_latency; |
304 | ||
a2bd9202 | 305 | /* Special case when user has set very strict latency requirement */ |
69d25870 | 306 | if (unlikely(latency_req == 0)) |
a2bd9202 | 307 | return 0; |
a2bd9202 | 308 | |
69d25870 | 309 | /* determine the expected residency time, round up */ |
107d4f46 | 310 | data->next_timer_us = ktime_to_us(tick_nohz_get_sleep_length()); |
69d25870 | 311 | |
372ba8cb | 312 | get_iowait_load(&nr_iowaiters, &cpu_load); |
64b4ca5c | 313 | data->bucket = which_bucket(data->next_timer_us, nr_iowaiters); |
69d25870 | 314 | |
51f245b8 TT |
315 | /* |
316 | * Force the result of multiplication to be 64 bits even if both | |
317 | * operands are 32 bits. | |
318 | * Make sure to round up for half microseconds. | |
319 | */ | |
ee3c86f3 | 320 | data->predicted_us = DIV_ROUND_CLOSEST_ULL((uint64_t)data->next_timer_us * |
51f245b8 | 321 | data->correction_factor[data->bucket], |
5787536e | 322 | RESOLUTION * DECAY); |
69d25870 | 323 | |
e132b9b3 RR |
324 | expected_interval = get_typical_interval(data); |
325 | expected_interval = min(expected_interval, data->next_timer_us); | |
96e95182 | 326 | |
dc2251bf RW |
327 | first_idx = 0; |
328 | if (drv->states[0].flags & CPUIDLE_FLAG_POLLING) { | |
329 | struct cpuidle_state *s = &drv->states[1]; | |
0c313cb2 RW |
330 | unsigned int polling_threshold; |
331 | ||
9c4b2867 RW |
332 | /* |
333 | * We want to default to C1 (hlt), not to busy polling | |
e132b9b3 RR |
334 | * unless the timer is happening really really soon, or |
335 | * C1's exit latency exceeds the user configured limit. | |
9c4b2867 | 336 | */ |
0c313cb2 RW |
337 | polling_threshold = max_t(unsigned int, 20, s->target_residency); |
338 | if (data->next_timer_us > polling_threshold && | |
339 | latency_req > s->exit_latency && !s->disabled && | |
dc2251bf RW |
340 | !dev->states_usage[1].disable) |
341 | first_idx = 1; | |
9c4b2867 | 342 | } |
4f86d3a8 | 343 | |
e132b9b3 RR |
344 | /* |
345 | * Use the lowest expected idle interval to pick the idle state. | |
346 | */ | |
347 | data->predicted_us = min(data->predicted_us, expected_interval); | |
348 | ||
349 | /* | |
350 | * Use the performance multiplier and the user-configurable | |
351 | * latency_req to determine the maximum exit latency. | |
352 | */ | |
353 | interactivity_req = data->predicted_us / performance_multiplier(nr_iowaiters, cpu_load); | |
354 | if (latency_req > interactivity_req) | |
355 | latency_req = interactivity_req; | |
356 | ||
71abbbf8 AL |
357 | /* |
358 | * Find the idle state with the lowest power while satisfying | |
359 | * our constraints. | |
360 | */ | |
3ed09c94 NP |
361 | idx = -1; |
362 | for (i = first_idx; i < drv->state_count; i++) { | |
46bcfad7 | 363 | struct cpuidle_state *s = &drv->states[i]; |
dc7fd275 | 364 | struct cpuidle_state_usage *su = &dev->states_usage[i]; |
4f86d3a8 | 365 | |
cbc9ef02 | 366 | if (s->disabled || su->disable) |
3a53396b | 367 | continue; |
3ed09c94 NP |
368 | if (idx == -1) |
369 | idx = i; /* first enabled state */ | |
14851912 | 370 | if (s->target_residency > data->predicted_us) |
8e37e1a2 | 371 | break; |
a2bd9202 | 372 | if (s->exit_latency > latency_req) |
8e37e1a2 | 373 | break; |
71abbbf8 | 374 | |
3ed09c94 | 375 | idx = i; |
4f86d3a8 LB |
376 | } |
377 | ||
3ed09c94 NP |
378 | if (idx == -1) |
379 | idx = 0; /* No states enabled. Must use 0. */ | |
380 | ||
381 | data->last_state_idx = idx; | |
382 | ||
69d25870 | 383 | return data->last_state_idx; |
4f86d3a8 LB |
384 | } |
385 | ||
386 | /** | |
672917dc | 387 | * menu_reflect - records that data structures need update |
4f86d3a8 | 388 | * @dev: the CPU |
e978aa7d | 389 | * @index: the index of actual entered state |
4f86d3a8 LB |
390 | * |
391 | * NOTE: it's important to be fast here because this operation will add to | |
392 | * the overall exit latency. | |
393 | */ | |
e978aa7d | 394 | static void menu_reflect(struct cpuidle_device *dev, int index) |
672917dc | 395 | { |
229b6863 | 396 | struct menu_device *data = this_cpu_ptr(&menu_devices); |
a802ea96 | 397 | |
e978aa7d | 398 | data->last_state_idx = index; |
a802ea96 | 399 | data->needs_update = 1; |
672917dc CZ |
400 | } |
401 | ||
402 | /** | |
403 | * menu_update - attempts to guess what happened after entry | |
46bcfad7 | 404 | * @drv: cpuidle driver containing state data |
672917dc CZ |
405 | * @dev: the CPU |
406 | */ | |
46bcfad7 | 407 | static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev) |
4f86d3a8 | 408 | { |
229b6863 | 409 | struct menu_device *data = this_cpu_ptr(&menu_devices); |
4f86d3a8 | 410 | int last_idx = data->last_state_idx; |
46bcfad7 | 411 | struct cpuidle_state *target = &drv->states[last_idx]; |
320eee77 | 412 | unsigned int measured_us; |
51f245b8 | 413 | unsigned int new_factor; |
4f86d3a8 LB |
414 | |
415 | /* | |
61c66d6e | 416 | * Try to figure out how much time passed between entry to low |
417 | * power state and occurrence of the wakeup event. | |
418 | * | |
419 | * If the entered idle state didn't support residency measurements, | |
4108b3d9 LB |
420 | * we use them anyway if they are short, and if long, |
421 | * truncate to the whole expected time. | |
61c66d6e | 422 | * |
423 | * Any measured amount of time will include the exit latency. | |
424 | * Since we are interested in when the wakeup begun, not when it | |
2fba5376 | 425 | * was completed, we must subtract the exit latency. However, if |
61c66d6e | 426 | * the measured amount of time is less than the exit latency, |
427 | * assume the state was never reached and the exit latency is 0. | |
4f86d3a8 | 428 | */ |
69d25870 | 429 | |
4108b3d9 LB |
430 | /* measured value */ |
431 | measured_us = cpuidle_get_last_residency(dev); | |
4f86d3a8 | 432 | |
4108b3d9 | 433 | /* Deduct exit latency */ |
efddfd90 | 434 | if (measured_us > 2 * target->exit_latency) |
4108b3d9 | 435 | measured_us -= target->exit_latency; |
efddfd90 RR |
436 | else |
437 | measured_us /= 2; | |
69d25870 | 438 | |
4108b3d9 LB |
439 | /* Make sure our coefficients do not exceed unity */ |
440 | if (measured_us > data->next_timer_us) | |
441 | measured_us = data->next_timer_us; | |
69d25870 | 442 | |
51f245b8 TT |
443 | /* Update our correction ratio */ |
444 | new_factor = data->correction_factor[data->bucket]; | |
445 | new_factor -= new_factor / DECAY; | |
69d25870 | 446 | |
5dc2f5a3 | 447 | if (data->next_timer_us > 0 && measured_us < MAX_INTERESTING) |
448 | new_factor += RESOLUTION * measured_us / data->next_timer_us; | |
320eee77 | 449 | else |
69d25870 AV |
450 | /* |
451 | * we were idle so long that we count it as a perfect | |
452 | * prediction | |
453 | */ | |
454 | new_factor += RESOLUTION; | |
320eee77 | 455 | |
69d25870 AV |
456 | /* |
457 | * We don't want 0 as factor; we always want at least | |
51f245b8 TT |
458 | * a tiny bit of estimated time. Fortunately, due to rounding, |
459 | * new_factor will stay nonzero regardless of measured_us values | |
460 | * and the compiler can eliminate this test as long as DECAY > 1. | |
69d25870 | 461 | */ |
51f245b8 | 462 | if (DECAY == 1 && unlikely(new_factor == 0)) |
69d25870 | 463 | new_factor = 1; |
320eee77 | 464 | |
69d25870 | 465 | data->correction_factor[data->bucket] = new_factor; |
1f85f87d AV |
466 | |
467 | /* update the repeating-pattern data */ | |
61c66d6e | 468 | data->intervals[data->interval_ptr++] = measured_us; |
1f85f87d AV |
469 | if (data->interval_ptr >= INTERVALS) |
470 | data->interval_ptr = 0; | |
4f86d3a8 LB |
471 | } |
472 | ||
473 | /** | |
474 | * menu_enable_device - scans a CPU's states and does setup | |
46bcfad7 | 475 | * @drv: cpuidle driver |
4f86d3a8 LB |
476 | * @dev: the CPU |
477 | */ | |
46bcfad7 DD |
478 | static int menu_enable_device(struct cpuidle_driver *drv, |
479 | struct cpuidle_device *dev) | |
4f86d3a8 LB |
480 | { |
481 | struct menu_device *data = &per_cpu(menu_devices, dev->cpu); | |
bed4d597 | 482 | int i; |
4f86d3a8 LB |
483 | |
484 | memset(data, 0, sizeof(struct menu_device)); | |
485 | ||
bed4d597 CK |
486 | /* |
487 | * if the correction factor is 0 (eg first time init or cpu hotplug | |
488 | * etc), we actually want to start out with a unity factor. | |
489 | */ | |
490 | for(i = 0; i < BUCKETS; i++) | |
491 | data->correction_factor[i] = RESOLUTION * DECAY; | |
492 | ||
4f86d3a8 LB |
493 | return 0; |
494 | } | |
495 | ||
496 | static struct cpuidle_governor menu_governor = { | |
497 | .name = "menu", | |
498 | .rating = 20, | |
499 | .enable = menu_enable_device, | |
500 | .select = menu_select, | |
501 | .reflect = menu_reflect, | |
4f86d3a8 LB |
502 | }; |
503 | ||
504 | /** | |
505 | * init_menu - initializes the governor | |
506 | */ | |
507 | static int __init init_menu(void) | |
508 | { | |
509 | return cpuidle_register_governor(&menu_governor); | |
510 | } | |
511 | ||
137b944e | 512 | postcore_initcall(init_menu); |