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