cpufreq_conservative.c revision e08f5f5bb5dfaaa28d69ffe37eb774533297657f
1/* 2 * drivers/cpufreq/cpufreq_conservative.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 * (C) 2004 Alexander Clouter <alex-kernel@digriz.org.uk> 8 * 9 * This program is free software; you can redistribute it and/or modify 10 * it under the terms of the GNU General Public License version 2 as 11 * published by the Free Software Foundation. 12 */ 13 14#include <linux/kernel.h> 15#include <linux/module.h> 16#include <linux/smp.h> 17#include <linux/init.h> 18#include <linux/interrupt.h> 19#include <linux/ctype.h> 20#include <linux/cpufreq.h> 21#include <linux/sysctl.h> 22#include <linux/types.h> 23#include <linux/fs.h> 24#include <linux/sysfs.h> 25#include <linux/cpu.h> 26#include <linux/sched.h> 27#include <linux/kmod.h> 28#include <linux/workqueue.h> 29#include <linux/jiffies.h> 30#include <linux/kernel_stat.h> 31#include <linux/percpu.h> 32#include <linux/mutex.h> 33/* 34 * dbs is used in this file as a shortform for demandbased switching 35 * It helps to keep variable names smaller, simpler 36 */ 37 38#define DEF_FREQUENCY_UP_THRESHOLD (80) 39#define DEF_FREQUENCY_DOWN_THRESHOLD (20) 40 41/* 42 * The polling frequency of this governor depends on the capability of 43 * the processor. Default polling frequency is 1000 times the transition 44 * latency of the processor. The governor will work on any processor with 45 * transition latency <= 10mS, using appropriate sampling 46 * rate. 47 * For CPUs with transition latency > 10mS (mostly drivers 48 * with CPUFREQ_ETERNAL), this governor will not work. 49 * All times here are in uS. 50 */ 51static unsigned int def_sampling_rate; 52#define MIN_SAMPLING_RATE_RATIO (2) 53/* for correct statistics, we need at least 10 ticks between each measure */ 54#define MIN_STAT_SAMPLING_RATE \ 55 (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10)) 56#define MIN_SAMPLING_RATE \ 57 (def_sampling_rate / MIN_SAMPLING_RATE_RATIO) 58#define MAX_SAMPLING_RATE (500 * def_sampling_rate) 59#define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000) 60#define DEF_SAMPLING_DOWN_FACTOR (1) 61#define MAX_SAMPLING_DOWN_FACTOR (10) 62#define TRANSITION_LATENCY_LIMIT (10 * 1000) 63 64static void do_dbs_timer(void *data); 65 66struct cpu_dbs_info_s { 67 struct cpufreq_policy *cur_policy; 68 unsigned int prev_cpu_idle_up; 69 unsigned int prev_cpu_idle_down; 70 unsigned int enable; 71 unsigned int down_skip; 72 unsigned int requested_freq; 73}; 74static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info); 75 76static unsigned int dbs_enable; /* number of CPUs using this policy */ 77 78/* 79 * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug 80 * lock and dbs_mutex. cpu_hotplug lock should always be held before 81 * dbs_mutex. If any function that can potentially take cpu_hotplug lock 82 * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then 83 * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock 84 * is recursive for the same process. -Venki 85 */ 86static DEFINE_MUTEX (dbs_mutex); 87static DECLARE_WORK (dbs_work, do_dbs_timer, NULL); 88 89struct dbs_tuners { 90 unsigned int sampling_rate; 91 unsigned int sampling_down_factor; 92 unsigned int up_threshold; 93 unsigned int down_threshold; 94 unsigned int ignore_nice; 95 unsigned int freq_step; 96}; 97 98static struct dbs_tuners dbs_tuners_ins = { 99 .up_threshold = DEF_FREQUENCY_UP_THRESHOLD, 100 .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD, 101 .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR, 102 .ignore_nice = 0, 103 .freq_step = 5, 104}; 105 106static inline unsigned int get_cpu_idle_time(unsigned int cpu) 107{ 108 unsigned int add_nice = 0, ret; 109 110 if (dbs_tuners_ins.ignore_nice) 111 add_nice = kstat_cpu(cpu).cpustat.nice; 112 113 ret = kstat_cpu(cpu).cpustat.idle + 114 kstat_cpu(cpu).cpustat.iowait + 115 add_nice; 116 117 return ret; 118} 119 120/************************** sysfs interface ************************/ 121static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf) 122{ 123 return sprintf (buf, "%u\n", MAX_SAMPLING_RATE); 124} 125 126static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf) 127{ 128 return sprintf (buf, "%u\n", MIN_SAMPLING_RATE); 129} 130 131#define define_one_ro(_name) \ 132static struct freq_attr _name = \ 133__ATTR(_name, 0444, show_##_name, NULL) 134 135define_one_ro(sampling_rate_max); 136define_one_ro(sampling_rate_min); 137 138/* cpufreq_conservative Governor Tunables */ 139#define show_one(file_name, object) \ 140static ssize_t show_##file_name \ 141(struct cpufreq_policy *unused, char *buf) \ 142{ \ 143 return sprintf(buf, "%u\n", dbs_tuners_ins.object); \ 144} 145show_one(sampling_rate, sampling_rate); 146show_one(sampling_down_factor, sampling_down_factor); 147show_one(up_threshold, up_threshold); 148show_one(down_threshold, down_threshold); 149show_one(ignore_nice_load, ignore_nice); 150show_one(freq_step, freq_step); 151 152static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused, 153 const char *buf, size_t count) 154{ 155 unsigned int input; 156 int ret; 157 ret = sscanf (buf, "%u", &input); 158 if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1) 159 return -EINVAL; 160 161 mutex_lock(&dbs_mutex); 162 dbs_tuners_ins.sampling_down_factor = input; 163 mutex_unlock(&dbs_mutex); 164 165 return count; 166} 167 168static ssize_t store_sampling_rate(struct cpufreq_policy *unused, 169 const char *buf, size_t count) 170{ 171 unsigned int input; 172 int ret; 173 ret = sscanf (buf, "%u", &input); 174 175 mutex_lock(&dbs_mutex); 176 if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) { 177 mutex_unlock(&dbs_mutex); 178 return -EINVAL; 179 } 180 181 dbs_tuners_ins.sampling_rate = input; 182 mutex_unlock(&dbs_mutex); 183 184 return count; 185} 186 187static ssize_t store_up_threshold(struct cpufreq_policy *unused, 188 const char *buf, size_t count) 189{ 190 unsigned int input; 191 int ret; 192 ret = sscanf (buf, "%u", &input); 193 194 mutex_lock(&dbs_mutex); 195 if (ret != 1 || input > 100 || input <= dbs_tuners_ins.down_threshold) { 196 mutex_unlock(&dbs_mutex); 197 return -EINVAL; 198 } 199 200 dbs_tuners_ins.up_threshold = input; 201 mutex_unlock(&dbs_mutex); 202 203 return count; 204} 205 206static ssize_t store_down_threshold(struct cpufreq_policy *unused, 207 const char *buf, size_t count) 208{ 209 unsigned int input; 210 int ret; 211 ret = sscanf (buf, "%u", &input); 212 213 mutex_lock(&dbs_mutex); 214 if (ret != 1 || input > 100 || input >= dbs_tuners_ins.up_threshold) { 215 mutex_unlock(&dbs_mutex); 216 return -EINVAL; 217 } 218 219 dbs_tuners_ins.down_threshold = input; 220 mutex_unlock(&dbs_mutex); 221 222 return count; 223} 224 225static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy, 226 const char *buf, size_t count) 227{ 228 unsigned int input; 229 int ret; 230 231 unsigned int j; 232 233 ret = sscanf (buf, "%u", &input); 234 if ( ret != 1 ) 235 return -EINVAL; 236 237 if ( input > 1 ) 238 input = 1; 239 240 mutex_lock(&dbs_mutex); 241 if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */ 242 mutex_unlock(&dbs_mutex); 243 return count; 244 } 245 dbs_tuners_ins.ignore_nice = input; 246 247 /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */ 248 for_each_online_cpu(j) { 249 struct cpu_dbs_info_s *j_dbs_info; 250 j_dbs_info = &per_cpu(cpu_dbs_info, j); 251 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j); 252 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up; 253 } 254 mutex_unlock(&dbs_mutex); 255 256 return count; 257} 258 259static ssize_t store_freq_step(struct cpufreq_policy *policy, 260 const char *buf, size_t count) 261{ 262 unsigned int input; 263 int ret; 264 265 ret = sscanf (buf, "%u", &input); 266 267 if ( ret != 1 ) 268 return -EINVAL; 269 270 if ( input > 100 ) 271 input = 100; 272 273 /* no need to test here if freq_step is zero as the user might actually 274 * want this, they would be crazy though :) */ 275 mutex_lock(&dbs_mutex); 276 dbs_tuners_ins.freq_step = input; 277 mutex_unlock(&dbs_mutex); 278 279 return count; 280} 281 282#define define_one_rw(_name) \ 283static struct freq_attr _name = \ 284__ATTR(_name, 0644, show_##_name, store_##_name) 285 286define_one_rw(sampling_rate); 287define_one_rw(sampling_down_factor); 288define_one_rw(up_threshold); 289define_one_rw(down_threshold); 290define_one_rw(ignore_nice_load); 291define_one_rw(freq_step); 292 293static struct attribute * dbs_attributes[] = { 294 &sampling_rate_max.attr, 295 &sampling_rate_min.attr, 296 &sampling_rate.attr, 297 &sampling_down_factor.attr, 298 &up_threshold.attr, 299 &down_threshold.attr, 300 &ignore_nice_load.attr, 301 &freq_step.attr, 302 NULL 303}; 304 305static struct attribute_group dbs_attr_group = { 306 .attrs = dbs_attributes, 307 .name = "conservative", 308}; 309 310/************************** sysfs end ************************/ 311 312static void dbs_check_cpu(int cpu) 313{ 314 unsigned int idle_ticks, up_idle_ticks, down_idle_ticks; 315 unsigned int tmp_idle_ticks, total_idle_ticks; 316 unsigned int freq_step; 317 unsigned int freq_down_sampling_rate; 318 struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info, cpu); 319 struct cpufreq_policy *policy; 320 321 if (!this_dbs_info->enable) 322 return; 323 324 policy = this_dbs_info->cur_policy; 325 326 /* 327 * The default safe range is 20% to 80% 328 * Every sampling_rate, we check 329 * - If current idle time is less than 20%, then we try to 330 * increase frequency 331 * Every sampling_rate*sampling_down_factor, we check 332 * - If current idle time is more than 80%, then we try to 333 * decrease frequency 334 * 335 * Any frequency increase takes it to the maximum frequency. 336 * Frequency reduction happens at minimum steps of 337 * 5% (default) of max_frequency 338 */ 339 340 /* Check for frequency increase */ 341 idle_ticks = UINT_MAX; 342 343 /* Check for frequency increase */ 344 total_idle_ticks = get_cpu_idle_time(cpu); 345 tmp_idle_ticks = total_idle_ticks - 346 this_dbs_info->prev_cpu_idle_up; 347 this_dbs_info->prev_cpu_idle_up = total_idle_ticks; 348 349 if (tmp_idle_ticks < idle_ticks) 350 idle_ticks = tmp_idle_ticks; 351 352 /* Scale idle ticks by 100 and compare with up and down ticks */ 353 idle_ticks *= 100; 354 up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) * 355 usecs_to_jiffies(dbs_tuners_ins.sampling_rate); 356 357 if (idle_ticks < up_idle_ticks) { 358 this_dbs_info->down_skip = 0; 359 this_dbs_info->prev_cpu_idle_down = 360 this_dbs_info->prev_cpu_idle_up; 361 362 /* if we are already at full speed then break out early */ 363 if (this_dbs_info->requested_freq == policy->max) 364 return; 365 366 freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100; 367 368 /* max freq cannot be less than 100. But who knows.... */ 369 if (unlikely(freq_step == 0)) 370 freq_step = 5; 371 372 this_dbs_info->requested_freq += freq_step; 373 if (this_dbs_info->requested_freq > policy->max) 374 this_dbs_info->requested_freq = policy->max; 375 376 __cpufreq_driver_target(policy, this_dbs_info->requested_freq, 377 CPUFREQ_RELATION_H); 378 return; 379 } 380 381 /* Check for frequency decrease */ 382 this_dbs_info->down_skip++; 383 if (this_dbs_info->down_skip < dbs_tuners_ins.sampling_down_factor) 384 return; 385 386 /* Check for frequency decrease */ 387 total_idle_ticks = this_dbs_info->prev_cpu_idle_up; 388 tmp_idle_ticks = total_idle_ticks - 389 this_dbs_info->prev_cpu_idle_down; 390 this_dbs_info->prev_cpu_idle_down = total_idle_ticks; 391 392 if (tmp_idle_ticks < idle_ticks) 393 idle_ticks = tmp_idle_ticks; 394 395 /* Scale idle ticks by 100 and compare with up and down ticks */ 396 idle_ticks *= 100; 397 this_dbs_info->down_skip = 0; 398 399 freq_down_sampling_rate = dbs_tuners_ins.sampling_rate * 400 dbs_tuners_ins.sampling_down_factor; 401 down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) * 402 usecs_to_jiffies(freq_down_sampling_rate); 403 404 if (idle_ticks > down_idle_ticks) { 405 /* 406 * if we are already at the lowest speed then break out early 407 * or if we 'cannot' reduce the speed as the user might want 408 * freq_step to be zero 409 */ 410 if (this_dbs_info->requested_freq == policy->min 411 || dbs_tuners_ins.freq_step == 0) 412 return; 413 414 freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100; 415 416 /* max freq cannot be less than 100. But who knows.... */ 417 if (unlikely(freq_step == 0)) 418 freq_step = 5; 419 420 this_dbs_info->requested_freq -= freq_step; 421 if (this_dbs_info->requested_freq < policy->min) 422 this_dbs_info->requested_freq = policy->min; 423 424 __cpufreq_driver_target(policy, this_dbs_info->requested_freq, 425 CPUFREQ_RELATION_H); 426 return; 427 } 428} 429 430static void do_dbs_timer(void *data) 431{ 432 int i; 433 lock_cpu_hotplug(); 434 mutex_lock(&dbs_mutex); 435 for_each_online_cpu(i) 436 dbs_check_cpu(i); 437 schedule_delayed_work(&dbs_work, 438 usecs_to_jiffies(dbs_tuners_ins.sampling_rate)); 439 mutex_unlock(&dbs_mutex); 440 unlock_cpu_hotplug(); 441} 442 443static inline void dbs_timer_init(void) 444{ 445 INIT_WORK(&dbs_work, do_dbs_timer, NULL); 446 schedule_delayed_work(&dbs_work, 447 usecs_to_jiffies(dbs_tuners_ins.sampling_rate)); 448 return; 449} 450 451static inline void dbs_timer_exit(void) 452{ 453 cancel_delayed_work(&dbs_work); 454 return; 455} 456 457static int cpufreq_governor_dbs(struct cpufreq_policy *policy, 458 unsigned int event) 459{ 460 unsigned int cpu = policy->cpu; 461 struct cpu_dbs_info_s *this_dbs_info; 462 unsigned int j; 463 int rc; 464 465 this_dbs_info = &per_cpu(cpu_dbs_info, cpu); 466 467 switch (event) { 468 case CPUFREQ_GOV_START: 469 if ((!cpu_online(cpu)) || 470 (!policy->cur)) 471 return -EINVAL; 472 473 if (policy->cpuinfo.transition_latency > 474 (TRANSITION_LATENCY_LIMIT * 1000)) 475 return -EINVAL; 476 if (this_dbs_info->enable) /* Already enabled */ 477 break; 478 479 mutex_lock(&dbs_mutex); 480 481 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group); 482 if (rc) { 483 mutex_unlock(&dbs_mutex); 484 return rc; 485 } 486 487 for_each_cpu_mask(j, policy->cpus) { 488 struct cpu_dbs_info_s *j_dbs_info; 489 j_dbs_info = &per_cpu(cpu_dbs_info, j); 490 j_dbs_info->cur_policy = policy; 491 492 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(cpu); 493 j_dbs_info->prev_cpu_idle_down 494 = j_dbs_info->prev_cpu_idle_up; 495 } 496 this_dbs_info->enable = 1; 497 this_dbs_info->down_skip = 0; 498 this_dbs_info->requested_freq = policy->cur; 499 500 dbs_enable++; 501 /* 502 * Start the timerschedule work, when this governor 503 * is used for first time 504 */ 505 if (dbs_enable == 1) { 506 unsigned int latency; 507 /* policy latency is in nS. Convert it to uS first */ 508 latency = policy->cpuinfo.transition_latency / 1000; 509 if (latency == 0) 510 latency = 1; 511 512 def_sampling_rate = 10 * latency * 513 DEF_SAMPLING_RATE_LATENCY_MULTIPLIER; 514 515 if (def_sampling_rate < MIN_STAT_SAMPLING_RATE) 516 def_sampling_rate = MIN_STAT_SAMPLING_RATE; 517 518 dbs_tuners_ins.sampling_rate = def_sampling_rate; 519 520 dbs_timer_init(); 521 } 522 523 mutex_unlock(&dbs_mutex); 524 break; 525 526 case CPUFREQ_GOV_STOP: 527 mutex_lock(&dbs_mutex); 528 this_dbs_info->enable = 0; 529 sysfs_remove_group(&policy->kobj, &dbs_attr_group); 530 dbs_enable--; 531 /* 532 * Stop the timerschedule work, when this governor 533 * is used for first time 534 */ 535 if (dbs_enable == 0) 536 dbs_timer_exit(); 537 538 mutex_unlock(&dbs_mutex); 539 540 break; 541 542 case CPUFREQ_GOV_LIMITS: 543 mutex_lock(&dbs_mutex); 544 if (policy->max < this_dbs_info->cur_policy->cur) 545 __cpufreq_driver_target( 546 this_dbs_info->cur_policy, 547 policy->max, CPUFREQ_RELATION_H); 548 else if (policy->min > this_dbs_info->cur_policy->cur) 549 __cpufreq_driver_target( 550 this_dbs_info->cur_policy, 551 policy->min, CPUFREQ_RELATION_L); 552 mutex_unlock(&dbs_mutex); 553 break; 554 } 555 return 0; 556} 557 558static struct cpufreq_governor cpufreq_gov_dbs = { 559 .name = "conservative", 560 .governor = cpufreq_governor_dbs, 561 .owner = THIS_MODULE, 562}; 563 564static int __init cpufreq_gov_dbs_init(void) 565{ 566 return cpufreq_register_governor(&cpufreq_gov_dbs); 567} 568 569static void __exit cpufreq_gov_dbs_exit(void) 570{ 571 /* Make sure that the scheduled work is indeed not running */ 572 flush_scheduled_work(); 573 574 cpufreq_unregister_governor(&cpufreq_gov_dbs); 575} 576 577 578MODULE_AUTHOR ("Alexander Clouter <alex-kernel@digriz.org.uk>"); 579MODULE_DESCRIPTION ("'cpufreq_conservative' - A dynamic cpufreq governor for " 580 "Low Latency Frequency Transition capable processors " 581 "optimised for use in a battery environment"); 582MODULE_LICENSE ("GPL"); 583 584module_init(cpufreq_gov_dbs_init); 585module_exit(cpufreq_gov_dbs_exit); 586