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/kmod.h> 27 #include <linux/workqueue.h> 28 #include <linux/jiffies.h> 29 #include <linux/kernel_stat.h> 30 #include <linux/percpu.h> 31 #include <linux/mutex.h> 32 /* 33 * dbs is used in this file as a shortform for demandbased switching 34 * It helps to keep variable names smaller, simpler 35 */ 36 37 #define DEF_FREQUENCY_UP_THRESHOLD (80) 38 #define DEF_FREQUENCY_DOWN_THRESHOLD (20) 39 40 /* 41 * The polling frequency of this governor depends on the capability of 42 * the processor. Default polling frequency is 1000 times the transition 43 * latency of the processor. The governor will work on any processor with 44 * transition latency <= 10mS, using appropriate sampling 45 * rate. 46 * For CPUs with transition latency > 10mS (mostly drivers 47 * with CPUFREQ_ETERNAL), this governor will not work. 48 * All times here are in uS. 49 */ 50 static unsigned int def_sampling_rate; 51 #define MIN_SAMPLING_RATE_RATIO (2) 52 /* for correct statistics, we need at least 10 ticks between each measure */ 53 #define MIN_STAT_SAMPLING_RATE \ 54 (MIN_SAMPLING_RATE_RATIO * jiffies_to_usecs(10)) 55 #define MIN_SAMPLING_RATE \ 56 (def_sampling_rate / MIN_SAMPLING_RATE_RATIO) 57 #define MAX_SAMPLING_RATE (500 * def_sampling_rate) 58 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000) 59 #define DEF_SAMPLING_DOWN_FACTOR (1) 60 #define MAX_SAMPLING_DOWN_FACTOR (10) 61 #define TRANSITION_LATENCY_LIMIT (10 * 1000 * 1000) 62 63 static void do_dbs_timer(struct work_struct *work); 64 65 struct cpu_dbs_info_s { 66 struct cpufreq_policy *cur_policy; 67 unsigned int prev_cpu_idle_up; 68 unsigned int prev_cpu_idle_down; 69 unsigned int enable; 70 unsigned int down_skip; 71 unsigned int requested_freq; 72 }; 73 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info); 74 75 static unsigned int dbs_enable; /* number of CPUs using this policy */ 76 77 /* 78 * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug 79 * lock and dbs_mutex. cpu_hotplug lock should always be held before 80 * dbs_mutex. If any function that can potentially take cpu_hotplug lock 81 * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then 82 * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock 83 * is recursive for the same process. -Venki 84 */ 85 static DEFINE_MUTEX (dbs_mutex); 86 static DECLARE_DELAYED_WORK(dbs_work, do_dbs_timer); 87 88 struct dbs_tuners { 89 unsigned int sampling_rate; 90 unsigned int sampling_down_factor; 91 unsigned int up_threshold; 92 unsigned int down_threshold; 93 unsigned int ignore_nice; 94 unsigned int freq_step; 95 }; 96 97 static struct dbs_tuners dbs_tuners_ins = { 98 .up_threshold = DEF_FREQUENCY_UP_THRESHOLD, 99 .down_threshold = DEF_FREQUENCY_DOWN_THRESHOLD, 100 .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR, 101 .ignore_nice = 0, 102 .freq_step = 5, 103 }; 104 105 static inline unsigned int get_cpu_idle_time(unsigned int cpu) 106 { 107 unsigned int add_nice = 0, ret; 108 109 if (dbs_tuners_ins.ignore_nice) 110 add_nice = kstat_cpu(cpu).cpustat.nice; 111 112 ret = kstat_cpu(cpu).cpustat.idle + 113 kstat_cpu(cpu).cpustat.iowait + 114 add_nice; 115 116 return ret; 117 } 118 119 /* keep track of frequency transitions */ 120 static int 121 dbs_cpufreq_notifier(struct notifier_block *nb, unsigned long val, 122 void *data) 123 { 124 struct cpufreq_freqs *freq = data; 125 struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info, 126 freq->cpu); 127 128 if (!this_dbs_info->enable) 129 return 0; 130 131 this_dbs_info->requested_freq = freq->new; 132 133 return 0; 134 } 135 136 static struct notifier_block dbs_cpufreq_notifier_block = { 137 .notifier_call = dbs_cpufreq_notifier 138 }; 139 140 /************************** sysfs interface ************************/ 141 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf) 142 { 143 return sprintf (buf, "%u\n", MAX_SAMPLING_RATE); 144 } 145 146 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf) 147 { 148 return sprintf (buf, "%u\n", MIN_SAMPLING_RATE); 149 } 150 151 #define define_one_ro(_name) \ 152 static struct freq_attr _name = \ 153 __ATTR(_name, 0444, show_##_name, NULL) 154 155 define_one_ro(sampling_rate_max); 156 define_one_ro(sampling_rate_min); 157 158 /* cpufreq_conservative Governor Tunables */ 159 #define show_one(file_name, object) \ 160 static ssize_t show_##file_name \ 161 (struct cpufreq_policy *unused, char *buf) \ 162 { \ 163 return sprintf(buf, "%u\n", dbs_tuners_ins.object); \ 164 } 165 show_one(sampling_rate, sampling_rate); 166 show_one(sampling_down_factor, sampling_down_factor); 167 show_one(up_threshold, up_threshold); 168 show_one(down_threshold, down_threshold); 169 show_one(ignore_nice_load, ignore_nice); 170 show_one(freq_step, freq_step); 171 172 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused, 173 const char *buf, size_t count) 174 { 175 unsigned int input; 176 int ret; 177 ret = sscanf (buf, "%u", &input); 178 if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1) 179 return -EINVAL; 180 181 mutex_lock(&dbs_mutex); 182 dbs_tuners_ins.sampling_down_factor = input; 183 mutex_unlock(&dbs_mutex); 184 185 return count; 186 } 187 188 static ssize_t store_sampling_rate(struct cpufreq_policy *unused, 189 const char *buf, size_t count) 190 { 191 unsigned int input; 192 int ret; 193 ret = sscanf (buf, "%u", &input); 194 195 mutex_lock(&dbs_mutex); 196 if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) { 197 mutex_unlock(&dbs_mutex); 198 return -EINVAL; 199 } 200 201 dbs_tuners_ins.sampling_rate = input; 202 mutex_unlock(&dbs_mutex); 203 204 return count; 205 } 206 207 static ssize_t store_up_threshold(struct cpufreq_policy *unused, 208 const char *buf, size_t count) 209 { 210 unsigned int input; 211 int ret; 212 ret = sscanf (buf, "%u", &input); 213 214 mutex_lock(&dbs_mutex); 215 if (ret != 1 || input > 100 || input <= dbs_tuners_ins.down_threshold) { 216 mutex_unlock(&dbs_mutex); 217 return -EINVAL; 218 } 219 220 dbs_tuners_ins.up_threshold = input; 221 mutex_unlock(&dbs_mutex); 222 223 return count; 224 } 225 226 static ssize_t store_down_threshold(struct cpufreq_policy *unused, 227 const char *buf, size_t count) 228 { 229 unsigned int input; 230 int ret; 231 ret = sscanf (buf, "%u", &input); 232 233 mutex_lock(&dbs_mutex); 234 if (ret != 1 || input > 100 || input >= dbs_tuners_ins.up_threshold) { 235 mutex_unlock(&dbs_mutex); 236 return -EINVAL; 237 } 238 239 dbs_tuners_ins.down_threshold = input; 240 mutex_unlock(&dbs_mutex); 241 242 return count; 243 } 244 245 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy, 246 const char *buf, size_t count) 247 { 248 unsigned int input; 249 int ret; 250 251 unsigned int j; 252 253 ret = sscanf(buf, "%u", &input); 254 if (ret != 1) 255 return -EINVAL; 256 257 if (input > 1) 258 input = 1; 259 260 mutex_lock(&dbs_mutex); 261 if (input == dbs_tuners_ins.ignore_nice) { /* nothing to do */ 262 mutex_unlock(&dbs_mutex); 263 return count; 264 } 265 dbs_tuners_ins.ignore_nice = input; 266 267 /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */ 268 for_each_online_cpu(j) { 269 struct cpu_dbs_info_s *j_dbs_info; 270 j_dbs_info = &per_cpu(cpu_dbs_info, j); 271 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j); 272 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up; 273 } 274 mutex_unlock(&dbs_mutex); 275 276 return count; 277 } 278 279 static ssize_t store_freq_step(struct cpufreq_policy *policy, 280 const char *buf, size_t count) 281 { 282 unsigned int input; 283 int ret; 284 285 ret = sscanf(buf, "%u", &input); 286 287 if (ret != 1) 288 return -EINVAL; 289 290 if (input > 100) 291 input = 100; 292 293 /* no need to test here if freq_step is zero as the user might actually 294 * want this, they would be crazy though :) */ 295 mutex_lock(&dbs_mutex); 296 dbs_tuners_ins.freq_step = input; 297 mutex_unlock(&dbs_mutex); 298 299 return count; 300 } 301 302 #define define_one_rw(_name) \ 303 static struct freq_attr _name = \ 304 __ATTR(_name, 0644, show_##_name, store_##_name) 305 306 define_one_rw(sampling_rate); 307 define_one_rw(sampling_down_factor); 308 define_one_rw(up_threshold); 309 define_one_rw(down_threshold); 310 define_one_rw(ignore_nice_load); 311 define_one_rw(freq_step); 312 313 static struct attribute * dbs_attributes[] = { 314 &sampling_rate_max.attr, 315 &sampling_rate_min.attr, 316 &sampling_rate.attr, 317 &sampling_down_factor.attr, 318 &up_threshold.attr, 319 &down_threshold.attr, 320 &ignore_nice_load.attr, 321 &freq_step.attr, 322 NULL 323 }; 324 325 static struct attribute_group dbs_attr_group = { 326 .attrs = dbs_attributes, 327 .name = "conservative", 328 }; 329 330 /************************** sysfs end ************************/ 331 332 static void dbs_check_cpu(int cpu) 333 { 334 unsigned int idle_ticks, up_idle_ticks, down_idle_ticks; 335 unsigned int tmp_idle_ticks, total_idle_ticks; 336 unsigned int freq_target; 337 unsigned int freq_down_sampling_rate; 338 struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info, cpu); 339 struct cpufreq_policy *policy; 340 341 if (!this_dbs_info->enable) 342 return; 343 344 policy = this_dbs_info->cur_policy; 345 346 /* 347 * The default safe range is 20% to 80% 348 * Every sampling_rate, we check 349 * - If current idle time is less than 20%, then we try to 350 * increase frequency 351 * Every sampling_rate*sampling_down_factor, we check 352 * - If current idle time is more than 80%, then we try to 353 * decrease frequency 354 * 355 * Any frequency increase takes it to the maximum frequency. 356 * Frequency reduction happens at minimum steps of 357 * 5% (default) of max_frequency 358 */ 359 360 /* Check for frequency increase */ 361 idle_ticks = UINT_MAX; 362 363 /* Check for frequency increase */ 364 total_idle_ticks = get_cpu_idle_time(cpu); 365 tmp_idle_ticks = total_idle_ticks - 366 this_dbs_info->prev_cpu_idle_up; 367 this_dbs_info->prev_cpu_idle_up = total_idle_ticks; 368 369 if (tmp_idle_ticks < idle_ticks) 370 idle_ticks = tmp_idle_ticks; 371 372 /* Scale idle ticks by 100 and compare with up and down ticks */ 373 idle_ticks *= 100; 374 up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) * 375 usecs_to_jiffies(dbs_tuners_ins.sampling_rate); 376 377 if (idle_ticks < up_idle_ticks) { 378 this_dbs_info->down_skip = 0; 379 this_dbs_info->prev_cpu_idle_down = 380 this_dbs_info->prev_cpu_idle_up; 381 382 /* if we are already at full speed then break out early */ 383 if (this_dbs_info->requested_freq == policy->max) 384 return; 385 386 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100; 387 388 /* max freq cannot be less than 100. But who knows.... */ 389 if (unlikely(freq_target == 0)) 390 freq_target = 5; 391 392 this_dbs_info->requested_freq += freq_target; 393 if (this_dbs_info->requested_freq > policy->max) 394 this_dbs_info->requested_freq = policy->max; 395 396 __cpufreq_driver_target(policy, this_dbs_info->requested_freq, 397 CPUFREQ_RELATION_H); 398 return; 399 } 400 401 /* Check for frequency decrease */ 402 this_dbs_info->down_skip++; 403 if (this_dbs_info->down_skip < dbs_tuners_ins.sampling_down_factor) 404 return; 405 406 /* Check for frequency decrease */ 407 total_idle_ticks = this_dbs_info->prev_cpu_idle_up; 408 tmp_idle_ticks = total_idle_ticks - 409 this_dbs_info->prev_cpu_idle_down; 410 this_dbs_info->prev_cpu_idle_down = total_idle_ticks; 411 412 if (tmp_idle_ticks < idle_ticks) 413 idle_ticks = tmp_idle_ticks; 414 415 /* Scale idle ticks by 100 and compare with up and down ticks */ 416 idle_ticks *= 100; 417 this_dbs_info->down_skip = 0; 418 419 freq_down_sampling_rate = dbs_tuners_ins.sampling_rate * 420 dbs_tuners_ins.sampling_down_factor; 421 down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) * 422 usecs_to_jiffies(freq_down_sampling_rate); 423 424 if (idle_ticks > down_idle_ticks) { 425 /* 426 * if we are already at the lowest speed then break out early 427 * or if we 'cannot' reduce the speed as the user might want 428 * freq_target to be zero 429 */ 430 if (this_dbs_info->requested_freq == policy->min 431 || dbs_tuners_ins.freq_step == 0) 432 return; 433 434 freq_target = (dbs_tuners_ins.freq_step * policy->max) / 100; 435 436 /* max freq cannot be less than 100. But who knows.... */ 437 if (unlikely(freq_target == 0)) 438 freq_target = 5; 439 440 this_dbs_info->requested_freq -= freq_target; 441 if (this_dbs_info->requested_freq < policy->min) 442 this_dbs_info->requested_freq = policy->min; 443 444 __cpufreq_driver_target(policy, this_dbs_info->requested_freq, 445 CPUFREQ_RELATION_H); 446 return; 447 } 448 } 449 450 static void do_dbs_timer(struct work_struct *work) 451 { 452 int i; 453 mutex_lock(&dbs_mutex); 454 for_each_online_cpu(i) 455 dbs_check_cpu(i); 456 schedule_delayed_work(&dbs_work, 457 usecs_to_jiffies(dbs_tuners_ins.sampling_rate)); 458 mutex_unlock(&dbs_mutex); 459 } 460 461 static inline void dbs_timer_init(void) 462 { 463 init_timer_deferrable(&dbs_work.timer); 464 schedule_delayed_work(&dbs_work, 465 usecs_to_jiffies(dbs_tuners_ins.sampling_rate)); 466 return; 467 } 468 469 static inline void dbs_timer_exit(void) 470 { 471 cancel_delayed_work(&dbs_work); 472 return; 473 } 474 475 static int cpufreq_governor_dbs(struct cpufreq_policy *policy, 476 unsigned int event) 477 { 478 unsigned int cpu = policy->cpu; 479 struct cpu_dbs_info_s *this_dbs_info; 480 unsigned int j; 481 int rc; 482 483 this_dbs_info = &per_cpu(cpu_dbs_info, cpu); 484 485 switch (event) { 486 case CPUFREQ_GOV_START: 487 if ((!cpu_online(cpu)) || (!policy->cur)) 488 return -EINVAL; 489 490 if (this_dbs_info->enable) /* Already enabled */ 491 break; 492 493 mutex_lock(&dbs_mutex); 494 495 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group); 496 if (rc) { 497 mutex_unlock(&dbs_mutex); 498 return rc; 499 } 500 501 for_each_cpu_mask_nr(j, policy->cpus) { 502 struct cpu_dbs_info_s *j_dbs_info; 503 j_dbs_info = &per_cpu(cpu_dbs_info, j); 504 j_dbs_info->cur_policy = policy; 505 506 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(cpu); 507 j_dbs_info->prev_cpu_idle_down 508 = j_dbs_info->prev_cpu_idle_up; 509 } 510 this_dbs_info->enable = 1; 511 this_dbs_info->down_skip = 0; 512 this_dbs_info->requested_freq = policy->cur; 513 514 dbs_enable++; 515 /* 516 * Start the timerschedule work, when this governor 517 * is used for first time 518 */ 519 if (dbs_enable == 1) { 520 unsigned int latency; 521 /* policy latency is in nS. Convert it to uS first */ 522 latency = policy->cpuinfo.transition_latency / 1000; 523 if (latency == 0) 524 latency = 1; 525 526 def_sampling_rate = 10 * latency * 527 DEF_SAMPLING_RATE_LATENCY_MULTIPLIER; 528 529 if (def_sampling_rate < MIN_STAT_SAMPLING_RATE) 530 def_sampling_rate = MIN_STAT_SAMPLING_RATE; 531 532 dbs_tuners_ins.sampling_rate = def_sampling_rate; 533 534 dbs_timer_init(); 535 cpufreq_register_notifier( 536 &dbs_cpufreq_notifier_block, 537 CPUFREQ_TRANSITION_NOTIFIER); 538 } 539 540 mutex_unlock(&dbs_mutex); 541 break; 542 543 case CPUFREQ_GOV_STOP: 544 mutex_lock(&dbs_mutex); 545 this_dbs_info->enable = 0; 546 sysfs_remove_group(&policy->kobj, &dbs_attr_group); 547 dbs_enable--; 548 /* 549 * Stop the timerschedule work, when this governor 550 * is used for first time 551 */ 552 if (dbs_enable == 0) { 553 dbs_timer_exit(); 554 cpufreq_unregister_notifier( 555 &dbs_cpufreq_notifier_block, 556 CPUFREQ_TRANSITION_NOTIFIER); 557 } 558 559 mutex_unlock(&dbs_mutex); 560 561 break; 562 563 case CPUFREQ_GOV_LIMITS: 564 mutex_lock(&dbs_mutex); 565 if (policy->max < this_dbs_info->cur_policy->cur) 566 __cpufreq_driver_target( 567 this_dbs_info->cur_policy, 568 policy->max, CPUFREQ_RELATION_H); 569 else if (policy->min > this_dbs_info->cur_policy->cur) 570 __cpufreq_driver_target( 571 this_dbs_info->cur_policy, 572 policy->min, CPUFREQ_RELATION_L); 573 mutex_unlock(&dbs_mutex); 574 break; 575 } 576 return 0; 577 } 578 579 #ifndef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE 580 static 581 #endif 582 struct cpufreq_governor cpufreq_gov_conservative = { 583 .name = "conservative", 584 .governor = cpufreq_governor_dbs, 585 .max_transition_latency = TRANSITION_LATENCY_LIMIT, 586 .owner = THIS_MODULE, 587 }; 588 589 static int __init cpufreq_gov_dbs_init(void) 590 { 591 return cpufreq_register_governor(&cpufreq_gov_conservative); 592 } 593 594 static void __exit cpufreq_gov_dbs_exit(void) 595 { 596 /* Make sure that the scheduled work is indeed not running */ 597 flush_scheduled_work(); 598 599 cpufreq_unregister_governor(&cpufreq_gov_conservative); 600 } 601 602 603 MODULE_AUTHOR ("Alexander Clouter <alex-kernel@digriz.org.uk>"); 604 MODULE_DESCRIPTION ("'cpufreq_conservative' - A dynamic cpufreq governor for " 605 "Low Latency Frequency Transition capable processors " 606 "optimised for use in a battery environment"); 607 MODULE_LICENSE ("GPL"); 608 609 #ifdef CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE 610 fs_initcall(cpufreq_gov_dbs_init); 611 #else 612 module_init(cpufreq_gov_dbs_init); 613 #endif 614 module_exit(cpufreq_gov_dbs_exit); 615