cpufreq_ondemand.c 16 KB

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  1. /*
  2. * drivers/cpufreq/cpufreq_ondemand.c
  3. *
  4. * Copyright (C) 2001 Russell King
  5. * (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>.
  6. * Jun Nakajima <jun.nakajima@intel.com>
  7. *
  8. * This program is free software; you can redistribute it and/or modify
  9. * it under the terms of the GNU General Public License version 2 as
  10. * published by the Free Software Foundation.
  11. */
  12. #include <linux/kernel.h>
  13. #include <linux/module.h>
  14. #include <linux/init.h>
  15. #include <linux/cpufreq.h>
  16. #include <linux/cpu.h>
  17. #include <linux/jiffies.h>
  18. #include <linux/kernel_stat.h>
  19. #include <linux/mutex.h>
  20. /*
  21. * dbs is used in this file as a shortform for demandbased switching
  22. * It helps to keep variable names smaller, simpler
  23. */
  24. #define DEF_FREQUENCY_UP_THRESHOLD (80)
  25. #define MIN_FREQUENCY_UP_THRESHOLD (11)
  26. #define MAX_FREQUENCY_UP_THRESHOLD (100)
  27. /*
  28. * The polling frequency of this governor depends on the capability of
  29. * the processor. Default polling frequency is 1000 times the transition
  30. * latency of the processor. The governor will work on any processor with
  31. * transition latency <= 10mS, using appropriate sampling
  32. * rate.
  33. * For CPUs with transition latency > 10mS (mostly drivers with CPUFREQ_ETERNAL)
  34. * this governor will not work.
  35. * All times here are in uS.
  36. */
  37. static unsigned int def_sampling_rate;
  38. #define MIN_SAMPLING_RATE_RATIO (2)
  39. /* for correct statistics, we need at least 10 ticks between each measure */
  40. #define MIN_STAT_SAMPLING_RATE \
  41. (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10))
  42. #define MIN_SAMPLING_RATE \
  43. (def_sampling_rate / MIN_SAMPLING_RATE_RATIO)
  44. #define MAX_SAMPLING_RATE (500 * def_sampling_rate)
  45. #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000)
  46. #define TRANSITION_LATENCY_LIMIT (10 * 1000)
  47. static void do_dbs_timer(struct work_struct *work);
  48. /* Sampling types */
  49. enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE};
  50. struct cpu_dbs_info_s {
  51. cputime64_t prev_cpu_idle;
  52. cputime64_t prev_cpu_wall;
  53. struct cpufreq_policy *cur_policy;
  54. struct delayed_work work;
  55. struct cpufreq_frequency_table *freq_table;
  56. unsigned int freq_lo;
  57. unsigned int freq_lo_jiffies;
  58. unsigned int freq_hi_jiffies;
  59. int cpu;
  60. unsigned int enable:1,
  61. sample_type:1;
  62. };
  63. static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
  64. static unsigned int dbs_enable; /* number of CPUs using this policy */
  65. /*
  66. * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
  67. * lock and dbs_mutex. cpu_hotplug lock should always be held before
  68. * dbs_mutex. If any function that can potentially take cpu_hotplug lock
  69. * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
  70. * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
  71. * is recursive for the same process. -Venki
  72. */
  73. static DEFINE_MUTEX(dbs_mutex);
  74. static struct workqueue_struct *kondemand_wq;
  75. static struct dbs_tuners {
  76. unsigned int sampling_rate;
  77. unsigned int up_threshold;
  78. unsigned int ignore_nice;
  79. unsigned int powersave_bias;
  80. } dbs_tuners_ins = {
  81. .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
  82. .ignore_nice = 0,
  83. .powersave_bias = 0,
  84. };
  85. static inline cputime64_t get_cpu_idle_time(unsigned int cpu)
  86. {
  87. cputime64_t retval;
  88. retval = cputime64_add(kstat_cpu(cpu).cpustat.idle,
  89. kstat_cpu(cpu).cpustat.iowait);
  90. if (dbs_tuners_ins.ignore_nice)
  91. retval = cputime64_add(retval, kstat_cpu(cpu).cpustat.nice);
  92. return retval;
  93. }
  94. /*
  95. * Find right freq to be set now with powersave_bias on.
  96. * Returns the freq_hi to be used right now and will set freq_hi_jiffies,
  97. * freq_lo, and freq_lo_jiffies in percpu area for averaging freqs.
  98. */
  99. static unsigned int powersave_bias_target(struct cpufreq_policy *policy,
  100. unsigned int freq_next,
  101. unsigned int relation)
  102. {
  103. unsigned int freq_req, freq_reduc, freq_avg;
  104. unsigned int freq_hi, freq_lo;
  105. unsigned int index = 0;
  106. unsigned int jiffies_total, jiffies_hi, jiffies_lo;
  107. struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, policy->cpu);
  108. if (!dbs_info->freq_table) {
  109. dbs_info->freq_lo = 0;
  110. dbs_info->freq_lo_jiffies = 0;
  111. return freq_next;
  112. }
  113. cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_next,
  114. relation, &index);
  115. freq_req = dbs_info->freq_table[index].frequency;
  116. freq_reduc = freq_req * dbs_tuners_ins.powersave_bias / 1000;
  117. freq_avg = freq_req - freq_reduc;
  118. /* Find freq bounds for freq_avg in freq_table */
  119. index = 0;
  120. cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
  121. CPUFREQ_RELATION_H, &index);
  122. freq_lo = dbs_info->freq_table[index].frequency;
  123. index = 0;
  124. cpufreq_frequency_table_target(policy, dbs_info->freq_table, freq_avg,
  125. CPUFREQ_RELATION_L, &index);
  126. freq_hi = dbs_info->freq_table[index].frequency;
  127. /* Find out how long we have to be in hi and lo freqs */
  128. if (freq_hi == freq_lo) {
  129. dbs_info->freq_lo = 0;
  130. dbs_info->freq_lo_jiffies = 0;
  131. return freq_lo;
  132. }
  133. jiffies_total = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
  134. jiffies_hi = (freq_avg - freq_lo) * jiffies_total;
  135. jiffies_hi += ((freq_hi - freq_lo) / 2);
  136. jiffies_hi /= (freq_hi - freq_lo);
  137. jiffies_lo = jiffies_total - jiffies_hi;
  138. dbs_info->freq_lo = freq_lo;
  139. dbs_info->freq_lo_jiffies = jiffies_lo;
  140. dbs_info->freq_hi_jiffies = jiffies_hi;
  141. return freq_hi;
  142. }
  143. static void ondemand_powersave_bias_init(void)
  144. {
  145. int i;
  146. for_each_online_cpu(i) {
  147. struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, i);
  148. dbs_info->freq_table = cpufreq_frequency_get_table(i);
  149. dbs_info->freq_lo = 0;
  150. }
  151. }
  152. /************************** sysfs interface ************************/
  153. static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
  154. {
  155. return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
  156. }
  157. static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
  158. {
  159. return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
  160. }
  161. #define define_one_ro(_name) \
  162. static struct freq_attr _name = \
  163. __ATTR(_name, 0444, show_##_name, NULL)
  164. define_one_ro(sampling_rate_max);
  165. define_one_ro(sampling_rate_min);
  166. /* cpufreq_ondemand Governor Tunables */
  167. #define show_one(file_name, object) \
  168. static ssize_t show_##file_name \
  169. (struct cpufreq_policy *unused, char *buf) \
  170. { \
  171. return sprintf(buf, "%u\n", dbs_tuners_ins.object); \
  172. }
  173. show_one(sampling_rate, sampling_rate);
  174. show_one(up_threshold, up_threshold);
  175. show_one(ignore_nice_load, ignore_nice);
  176. show_one(powersave_bias, powersave_bias);
  177. static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
  178. const char *buf, size_t count)
  179. {
  180. unsigned int input;
  181. int ret;
  182. ret = sscanf(buf, "%u", &input);
  183. mutex_lock(&dbs_mutex);
  184. if (ret != 1 || input > MAX_SAMPLING_RATE
  185. || input < MIN_SAMPLING_RATE) {
  186. mutex_unlock(&dbs_mutex);
  187. return -EINVAL;
  188. }
  189. dbs_tuners_ins.sampling_rate = input;
  190. mutex_unlock(&dbs_mutex);
  191. return count;
  192. }
  193. static ssize_t store_up_threshold(struct cpufreq_policy *unused,
  194. const char *buf, size_t count)
  195. {
  196. unsigned int input;
  197. int ret;
  198. ret = sscanf(buf, "%u", &input);
  199. mutex_lock(&dbs_mutex);
  200. if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD ||
  201. input < MIN_FREQUENCY_UP_THRESHOLD) {
  202. mutex_unlock(&dbs_mutex);
  203. return -EINVAL;
  204. }
  205. dbs_tuners_ins.up_threshold = input;
  206. mutex_unlock(&dbs_mutex);
  207. return count;
  208. }
  209. static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
  210. const char *buf, size_t count)
  211. {
  212. unsigned int input;
  213. int ret;
  214. unsigned int j;
  215. ret = sscanf(buf, "%u", &input);
  216. if ( ret != 1 )
  217. return -EINVAL;
  218. if ( input > 1 )
  219. input = 1;
  220. mutex_lock(&dbs_mutex);
  221. if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
  222. mutex_unlock(&dbs_mutex);
  223. return count;
  224. }
  225. dbs_tuners_ins.ignore_nice = input;
  226. /* we need to re-evaluate prev_cpu_idle */
  227. for_each_online_cpu(j) {
  228. struct cpu_dbs_info_s *dbs_info;
  229. dbs_info = &per_cpu(cpu_dbs_info, j);
  230. dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
  231. dbs_info->prev_cpu_wall = get_jiffies_64();
  232. }
  233. mutex_unlock(&dbs_mutex);
  234. return count;
  235. }
  236. static ssize_t store_powersave_bias(struct cpufreq_policy *unused,
  237. const char *buf, size_t count)
  238. {
  239. unsigned int input;
  240. int ret;
  241. ret = sscanf(buf, "%u", &input);
  242. if (ret != 1)
  243. return -EINVAL;
  244. if (input > 1000)
  245. input = 1000;
  246. mutex_lock(&dbs_mutex);
  247. dbs_tuners_ins.powersave_bias = input;
  248. ondemand_powersave_bias_init();
  249. mutex_unlock(&dbs_mutex);
  250. return count;
  251. }
  252. #define define_one_rw(_name) \
  253. static struct freq_attr _name = \
  254. __ATTR(_name, 0644, show_##_name, store_##_name)
  255. define_one_rw(sampling_rate);
  256. define_one_rw(up_threshold);
  257. define_one_rw(ignore_nice_load);
  258. define_one_rw(powersave_bias);
  259. static struct attribute * dbs_attributes[] = {
  260. &sampling_rate_max.attr,
  261. &sampling_rate_min.attr,
  262. &sampling_rate.attr,
  263. &up_threshold.attr,
  264. &ignore_nice_load.attr,
  265. &powersave_bias.attr,
  266. NULL
  267. };
  268. static struct attribute_group dbs_attr_group = {
  269. .attrs = dbs_attributes,
  270. .name = "ondemand",
  271. };
  272. /************************** sysfs end ************************/
  273. static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
  274. {
  275. unsigned int idle_ticks, total_ticks;
  276. unsigned int load;
  277. cputime64_t cur_jiffies;
  278. struct cpufreq_policy *policy;
  279. unsigned int j;
  280. if (!this_dbs_info->enable)
  281. return;
  282. this_dbs_info->freq_lo = 0;
  283. policy = this_dbs_info->cur_policy;
  284. cur_jiffies = jiffies64_to_cputime64(get_jiffies_64());
  285. total_ticks = (unsigned int) cputime64_sub(cur_jiffies,
  286. this_dbs_info->prev_cpu_wall);
  287. this_dbs_info->prev_cpu_wall = cur_jiffies;
  288. if (!total_ticks)
  289. return;
  290. /*
  291. * Every sampling_rate, we check, if current idle time is less
  292. * than 20% (default), then we try to increase frequency
  293. * Every sampling_rate, we look for a the lowest
  294. * frequency which can sustain the load while keeping idle time over
  295. * 30%. If such a frequency exist, we try to decrease to this frequency.
  296. *
  297. * Any frequency increase takes it to the maximum frequency.
  298. * Frequency reduction happens at minimum steps of
  299. * 5% (default) of current frequency
  300. */
  301. /* Get Idle Time */
  302. idle_ticks = UINT_MAX;
  303. for_each_cpu_mask(j, policy->cpus) {
  304. cputime64_t total_idle_ticks;
  305. unsigned int tmp_idle_ticks;
  306. struct cpu_dbs_info_s *j_dbs_info;
  307. j_dbs_info = &per_cpu(cpu_dbs_info, j);
  308. total_idle_ticks = get_cpu_idle_time(j);
  309. tmp_idle_ticks = (unsigned int) cputime64_sub(total_idle_ticks,
  310. j_dbs_info->prev_cpu_idle);
  311. j_dbs_info->prev_cpu_idle = total_idle_ticks;
  312. if (tmp_idle_ticks < idle_ticks)
  313. idle_ticks = tmp_idle_ticks;
  314. }
  315. load = (100 * (total_ticks - idle_ticks)) / total_ticks;
  316. /* Check for frequency increase */
  317. if (load > dbs_tuners_ins.up_threshold) {
  318. /* if we are already at full speed then break out early */
  319. if (!dbs_tuners_ins.powersave_bias) {
  320. if (policy->cur == policy->max)
  321. return;
  322. __cpufreq_driver_target(policy, policy->max,
  323. CPUFREQ_RELATION_H);
  324. } else {
  325. int freq = powersave_bias_target(policy, policy->max,
  326. CPUFREQ_RELATION_H);
  327. __cpufreq_driver_target(policy, freq,
  328. CPUFREQ_RELATION_L);
  329. }
  330. return;
  331. }
  332. /* Check for frequency decrease */
  333. /* if we cannot reduce the frequency anymore, break out early */
  334. if (policy->cur == policy->min)
  335. return;
  336. /*
  337. * The optimal frequency is the frequency that is the lowest that
  338. * can support the current CPU usage without triggering the up
  339. * policy. To be safe, we focus 10 points under the threshold.
  340. */
  341. if (load < (dbs_tuners_ins.up_threshold - 10)) {
  342. unsigned int freq_next, freq_cur;
  343. freq_cur = __cpufreq_driver_getavg(policy);
  344. if (!freq_cur)
  345. freq_cur = policy->cur;
  346. freq_next = (freq_cur * load) /
  347. (dbs_tuners_ins.up_threshold - 10);
  348. if (!dbs_tuners_ins.powersave_bias) {
  349. __cpufreq_driver_target(policy, freq_next,
  350. CPUFREQ_RELATION_L);
  351. } else {
  352. int freq = powersave_bias_target(policy, freq_next,
  353. CPUFREQ_RELATION_L);
  354. __cpufreq_driver_target(policy, freq,
  355. CPUFREQ_RELATION_L);
  356. }
  357. }
  358. }
  359. static void do_dbs_timer(struct work_struct *work)
  360. {
  361. struct cpu_dbs_info_s *dbs_info =
  362. container_of(work, struct cpu_dbs_info_s, work.work);
  363. unsigned int cpu = dbs_info->cpu;
  364. int sample_type = dbs_info->sample_type;
  365. /* We want all CPUs to do sampling nearly on same jiffy */
  366. int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
  367. delay -= jiffies % delay;
  368. if (lock_policy_rwsem_write(cpu) < 0)
  369. return;
  370. if (!dbs_info->enable) {
  371. unlock_policy_rwsem_write(cpu);
  372. return;
  373. }
  374. /* Common NORMAL_SAMPLE setup */
  375. dbs_info->sample_type = DBS_NORMAL_SAMPLE;
  376. if (!dbs_tuners_ins.powersave_bias ||
  377. sample_type == DBS_NORMAL_SAMPLE) {
  378. dbs_check_cpu(dbs_info);
  379. if (dbs_info->freq_lo) {
  380. /* Setup timer for SUB_SAMPLE */
  381. dbs_info->sample_type = DBS_SUB_SAMPLE;
  382. delay = dbs_info->freq_hi_jiffies;
  383. }
  384. } else {
  385. __cpufreq_driver_target(dbs_info->cur_policy,
  386. dbs_info->freq_lo,
  387. CPUFREQ_RELATION_H);
  388. }
  389. queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work, delay);
  390. unlock_policy_rwsem_write(cpu);
  391. }
  392. static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
  393. {
  394. /* We want all CPUs to do sampling nearly on same jiffy */
  395. int delay = usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
  396. delay -= jiffies % delay;
  397. dbs_info->enable = 1;
  398. ondemand_powersave_bias_init();
  399. dbs_info->sample_type = DBS_NORMAL_SAMPLE;
  400. INIT_DELAYED_WORK(&dbs_info->work, do_dbs_timer);
  401. queue_delayed_work_on(dbs_info->cpu, kondemand_wq, &dbs_info->work,
  402. delay);
  403. }
  404. static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
  405. {
  406. dbs_info->enable = 0;
  407. cancel_delayed_work(&dbs_info->work);
  408. }
  409. static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
  410. unsigned int event)
  411. {
  412. unsigned int cpu = policy->cpu;
  413. struct cpu_dbs_info_s *this_dbs_info;
  414. unsigned int j;
  415. int rc;
  416. this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
  417. switch (event) {
  418. case CPUFREQ_GOV_START:
  419. if ((!cpu_online(cpu)) || (!policy->cur))
  420. return -EINVAL;
  421. if (policy->cpuinfo.transition_latency >
  422. (TRANSITION_LATENCY_LIMIT * 1000)) {
  423. printk(KERN_WARNING "ondemand governor failed to load "
  424. "due to too long transition latency\n");
  425. return -EINVAL;
  426. }
  427. if (this_dbs_info->enable) /* Already enabled */
  428. break;
  429. mutex_lock(&dbs_mutex);
  430. dbs_enable++;
  431. rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
  432. if (rc) {
  433. dbs_enable--;
  434. mutex_unlock(&dbs_mutex);
  435. return rc;
  436. }
  437. for_each_cpu_mask(j, policy->cpus) {
  438. struct cpu_dbs_info_s *j_dbs_info;
  439. j_dbs_info = &per_cpu(cpu_dbs_info, j);
  440. j_dbs_info->cur_policy = policy;
  441. j_dbs_info->prev_cpu_idle = get_cpu_idle_time(j);
  442. j_dbs_info->prev_cpu_wall = get_jiffies_64();
  443. }
  444. this_dbs_info->cpu = cpu;
  445. /*
  446. * Start the timerschedule work, when this governor
  447. * is used for first time
  448. */
  449. if (dbs_enable == 1) {
  450. unsigned int latency;
  451. /* policy latency is in nS. Convert it to uS first */
  452. latency = policy->cpuinfo.transition_latency / 1000;
  453. if (latency == 0)
  454. latency = 1;
  455. def_sampling_rate = latency *
  456. DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
  457. if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
  458. def_sampling_rate = MIN_STAT_SAMPLING_RATE;
  459. dbs_tuners_ins.sampling_rate = def_sampling_rate;
  460. }
  461. dbs_timer_init(this_dbs_info);
  462. mutex_unlock(&dbs_mutex);
  463. break;
  464. case CPUFREQ_GOV_STOP:
  465. mutex_lock(&dbs_mutex);
  466. dbs_timer_exit(this_dbs_info);
  467. sysfs_remove_group(&policy->kobj, &dbs_attr_group);
  468. dbs_enable--;
  469. mutex_unlock(&dbs_mutex);
  470. break;
  471. case CPUFREQ_GOV_LIMITS:
  472. mutex_lock(&dbs_mutex);
  473. if (policy->max < this_dbs_info->cur_policy->cur)
  474. __cpufreq_driver_target(this_dbs_info->cur_policy,
  475. policy->max,
  476. CPUFREQ_RELATION_H);
  477. else if (policy->min > this_dbs_info->cur_policy->cur)
  478. __cpufreq_driver_target(this_dbs_info->cur_policy,
  479. policy->min,
  480. CPUFREQ_RELATION_L);
  481. mutex_unlock(&dbs_mutex);
  482. break;
  483. }
  484. return 0;
  485. }
  486. static struct cpufreq_governor cpufreq_gov_dbs = {
  487. .name = "ondemand",
  488. .governor = cpufreq_governor_dbs,
  489. .owner = THIS_MODULE,
  490. };
  491. static int __init cpufreq_gov_dbs_init(void)
  492. {
  493. kondemand_wq = create_workqueue("kondemand");
  494. if (!kondemand_wq) {
  495. printk(KERN_ERR "Creation of kondemand failed\n");
  496. return -EFAULT;
  497. }
  498. return cpufreq_register_governor(&cpufreq_gov_dbs);
  499. }
  500. static void __exit cpufreq_gov_dbs_exit(void)
  501. {
  502. cpufreq_unregister_governor(&cpufreq_gov_dbs);
  503. destroy_workqueue(kondemand_wq);
  504. }
  505. MODULE_AUTHOR("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>");
  506. MODULE_AUTHOR("Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>");
  507. MODULE_DESCRIPTION("'cpufreq_ondemand' - A dynamic cpufreq governor for "
  508. "Low Latency Frequency Transition capable processors");
  509. MODULE_LICENSE("GPL");
  510. module_init(cpufreq_gov_dbs_init);
  511. module_exit(cpufreq_gov_dbs_exit);