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