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 13 #include <linux/kernel.h> 14 #include <linux/module.h> 15 #include <linux/smp.h> 16 #include <linux/init.h> 17 #include <linux/interrupt.h> 18 #include <linux/ctype.h> 19 #include <linux/cpufreq.h> 20 #include <linux/sysctl.h> 21 #include <linux/types.h> 22 #include <linux/fs.h> 23 #include <linux/sysfs.h> 24 #include <linux/sched.h> 25 #include <linux/kmod.h> 26 #include <linux/workqueue.h> 27 #include <linux/jiffies.h> 28 #include <linux/kernel_stat.h> 29 #include <linux/percpu.h> 30 31 /* 32 * dbs is used in this file as a shortform for demandbased switching 33 * It helps to keep variable names smaller, simpler 34 */ 35 36 #define DEF_FREQUENCY_UP_THRESHOLD (80) 37 #define MIN_FREQUENCY_UP_THRESHOLD (11) 38 #define MAX_FREQUENCY_UP_THRESHOLD (100) 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 (def_sampling_rate / 2) 52 #define MAX_SAMPLING_RATE (500 * def_sampling_rate) 53 #define DEF_SAMPLING_RATE_LATENCY_MULTIPLIER (1000) 54 #define DEF_SAMPLING_DOWN_FACTOR (1) 55 #define MAX_SAMPLING_DOWN_FACTOR (10) 56 #define TRANSITION_LATENCY_LIMIT (10 * 1000) 57 58 static void do_dbs_timer(void *data); 59 60 struct cpu_dbs_info_s { 61 struct cpufreq_policy *cur_policy; 62 unsigned int prev_cpu_idle_up; 63 unsigned int prev_cpu_idle_down; 64 unsigned int enable; 65 }; 66 static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info); 67 68 static unsigned int dbs_enable; /* number of CPUs using this policy */ 69 70 static DECLARE_MUTEX (dbs_sem); 71 static DECLARE_WORK (dbs_work, do_dbs_timer, NULL); 72 73 struct dbs_tuners { 74 unsigned int sampling_rate; 75 unsigned int sampling_down_factor; 76 unsigned int up_threshold; 77 unsigned int ignore_nice; 78 }; 79 80 static struct dbs_tuners dbs_tuners_ins = { 81 .up_threshold = DEF_FREQUENCY_UP_THRESHOLD, 82 .sampling_down_factor = DEF_SAMPLING_DOWN_FACTOR, 83 }; 84 85 static inline unsigned int get_cpu_idle_time(unsigned int cpu) 86 { 87 return kstat_cpu(cpu).cpustat.idle + 88 kstat_cpu(cpu).cpustat.iowait + 89 ( !dbs_tuners_ins.ignore_nice ? 90 kstat_cpu(cpu).cpustat.nice : 91 0); 92 } 93 94 /************************** sysfs interface ************************/ 95 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf) 96 { 97 return sprintf (buf, "%u\n", MAX_SAMPLING_RATE); 98 } 99 100 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf) 101 { 102 return sprintf (buf, "%u\n", MIN_SAMPLING_RATE); 103 } 104 105 #define define_one_ro(_name) \ 106 static struct freq_attr _name = \ 107 __ATTR(_name, 0444, show_##_name, NULL) 108 109 define_one_ro(sampling_rate_max); 110 define_one_ro(sampling_rate_min); 111 112 /* cpufreq_ondemand Governor Tunables */ 113 #define show_one(file_name, object) \ 114 static ssize_t show_##file_name \ 115 (struct cpufreq_policy *unused, char *buf) \ 116 { \ 117 return sprintf(buf, "%u\n", dbs_tuners_ins.object); \ 118 } 119 show_one(sampling_rate, sampling_rate); 120 show_one(sampling_down_factor, sampling_down_factor); 121 show_one(up_threshold, up_threshold); 122 show_one(ignore_nice, ignore_nice); 123 124 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused, 125 const char *buf, size_t count) 126 { 127 unsigned int input; 128 int ret; 129 ret = sscanf (buf, "%u", &input); 130 if (ret != 1 ) 131 return -EINVAL; 132 133 if (input > MAX_SAMPLING_DOWN_FACTOR || input < 1) 134 return -EINVAL; 135 136 down(&dbs_sem); 137 dbs_tuners_ins.sampling_down_factor = input; 138 up(&dbs_sem); 139 140 return count; 141 } 142 143 static ssize_t store_sampling_rate(struct cpufreq_policy *unused, 144 const char *buf, size_t count) 145 { 146 unsigned int input; 147 int ret; 148 ret = sscanf (buf, "%u", &input); 149 150 down(&dbs_sem); 151 if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) { 152 up(&dbs_sem); 153 return -EINVAL; 154 } 155 156 dbs_tuners_ins.sampling_rate = input; 157 up(&dbs_sem); 158 159 return count; 160 } 161 162 static ssize_t store_up_threshold(struct cpufreq_policy *unused, 163 const char *buf, size_t count) 164 { 165 unsigned int input; 166 int ret; 167 ret = sscanf (buf, "%u", &input); 168 169 down(&dbs_sem); 170 if (ret != 1 || input > MAX_FREQUENCY_UP_THRESHOLD || 171 input < MIN_FREQUENCY_UP_THRESHOLD) { 172 up(&dbs_sem); 173 return -EINVAL; 174 } 175 176 dbs_tuners_ins.up_threshold = input; 177 up(&dbs_sem); 178 179 return count; 180 } 181 182 static ssize_t store_ignore_nice(struct cpufreq_policy *policy, 183 const char *buf, size_t count) 184 { 185 unsigned int input; 186 int ret; 187 188 unsigned int j; 189 190 ret = sscanf (buf, "%u", &input); 191 if ( ret != 1 ) 192 return -EINVAL; 193 194 if ( input > 1 ) 195 input = 1; 196 197 down(&dbs_sem); 198 if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */ 199 up(&dbs_sem); 200 return count; 201 } 202 dbs_tuners_ins.ignore_nice = input; 203 204 /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */ 205 for_each_online_cpu(j) { 206 struct cpu_dbs_info_s *j_dbs_info; 207 j_dbs_info = &per_cpu(cpu_dbs_info, j); 208 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j); 209 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up; 210 } 211 up(&dbs_sem); 212 213 return count; 214 } 215 216 #define define_one_rw(_name) \ 217 static struct freq_attr _name = \ 218 __ATTR(_name, 0644, show_##_name, store_##_name) 219 220 define_one_rw(sampling_rate); 221 define_one_rw(sampling_down_factor); 222 define_one_rw(up_threshold); 223 define_one_rw(ignore_nice); 224 225 static struct attribute * dbs_attributes[] = { 226 &sampling_rate_max.attr, 227 &sampling_rate_min.attr, 228 &sampling_rate.attr, 229 &sampling_down_factor.attr, 230 &up_threshold.attr, 231 &ignore_nice.attr, 232 NULL 233 }; 234 235 static struct attribute_group dbs_attr_group = { 236 .attrs = dbs_attributes, 237 .name = "ondemand", 238 }; 239 240 /************************** sysfs end ************************/ 241 242 static void dbs_check_cpu(int cpu) 243 { 244 unsigned int idle_ticks, up_idle_ticks, total_ticks; 245 unsigned int freq_next; 246 unsigned int freq_down_sampling_rate; 247 static int down_skip[NR_CPUS]; 248 struct cpu_dbs_info_s *this_dbs_info; 249 250 struct cpufreq_policy *policy; 251 unsigned int j; 252 253 this_dbs_info = &per_cpu(cpu_dbs_info, cpu); 254 if (!this_dbs_info->enable) 255 return; 256 257 policy = this_dbs_info->cur_policy; 258 /* 259 * Every sampling_rate, we check, if current idle time is less 260 * than 20% (default), then we try to increase frequency 261 * Every sampling_rate*sampling_down_factor, we look for a the lowest 262 * frequency which can sustain the load while keeping idle time over 263 * 30%. If such a frequency exist, we try to decrease to this frequency. 264 * 265 * Any frequency increase takes it to the maximum frequency. 266 * Frequency reduction happens at minimum steps of 267 * 5% (default) of current frequency 268 */ 269 270 /* Check for frequency increase */ 271 idle_ticks = UINT_MAX; 272 for_each_cpu_mask(j, policy->cpus) { 273 unsigned int tmp_idle_ticks, total_idle_ticks; 274 struct cpu_dbs_info_s *j_dbs_info; 275 276 j_dbs_info = &per_cpu(cpu_dbs_info, j); 277 total_idle_ticks = get_cpu_idle_time(j); 278 tmp_idle_ticks = total_idle_ticks - 279 j_dbs_info->prev_cpu_idle_up; 280 j_dbs_info->prev_cpu_idle_up = total_idle_ticks; 281 282 if (tmp_idle_ticks < idle_ticks) 283 idle_ticks = tmp_idle_ticks; 284 } 285 286 /* Scale idle ticks by 100 and compare with up and down ticks */ 287 idle_ticks *= 100; 288 up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) * 289 usecs_to_jiffies(dbs_tuners_ins.sampling_rate); 290 291 if (idle_ticks < up_idle_ticks) { 292 down_skip[cpu] = 0; 293 for_each_cpu_mask(j, policy->cpus) { 294 struct cpu_dbs_info_s *j_dbs_info; 295 296 j_dbs_info = &per_cpu(cpu_dbs_info, j); 297 j_dbs_info->prev_cpu_idle_down = 298 j_dbs_info->prev_cpu_idle_up; 299 } 300 /* if we are already at full speed then break out early */ 301 if (policy->cur == policy->max) 302 return; 303 304 __cpufreq_driver_target(policy, policy->max, 305 CPUFREQ_RELATION_H); 306 return; 307 } 308 309 /* Check for frequency decrease */ 310 down_skip[cpu]++; 311 if (down_skip[cpu] < dbs_tuners_ins.sampling_down_factor) 312 return; 313 314 idle_ticks = UINT_MAX; 315 for_each_cpu_mask(j, policy->cpus) { 316 unsigned int tmp_idle_ticks, total_idle_ticks; 317 struct cpu_dbs_info_s *j_dbs_info; 318 319 j_dbs_info = &per_cpu(cpu_dbs_info, j); 320 /* Check for frequency decrease */ 321 total_idle_ticks = j_dbs_info->prev_cpu_idle_up; 322 tmp_idle_ticks = total_idle_ticks - 323 j_dbs_info->prev_cpu_idle_down; 324 j_dbs_info->prev_cpu_idle_down = total_idle_ticks; 325 326 if (tmp_idle_ticks < idle_ticks) 327 idle_ticks = tmp_idle_ticks; 328 } 329 330 down_skip[cpu] = 0; 331 /* if we cannot reduce the frequency anymore, break out early */ 332 if (policy->cur == policy->min) 333 return; 334 335 /* Compute how many ticks there are between two measurements */ 336 freq_down_sampling_rate = dbs_tuners_ins.sampling_rate * 337 dbs_tuners_ins.sampling_down_factor; 338 total_ticks = usecs_to_jiffies(freq_down_sampling_rate); 339 340 /* 341 * The optimal frequency is the frequency that is the lowest that 342 * can support the current CPU usage without triggering the up 343 * policy. To be safe, we focus 10 points under the threshold. 344 */ 345 freq_next = ((total_ticks - idle_ticks) * 100) / total_ticks; 346 freq_next = (freq_next * policy->cur) / 347 (dbs_tuners_ins.up_threshold - 10); 348 349 if (freq_next <= ((policy->cur * 95) / 100)) 350 __cpufreq_driver_target(policy, freq_next, CPUFREQ_RELATION_L); 351 } 352 353 static void do_dbs_timer(void *data) 354 { 355 int i; 356 down(&dbs_sem); 357 for_each_online_cpu(i) 358 dbs_check_cpu(i); 359 schedule_delayed_work(&dbs_work, 360 usecs_to_jiffies(dbs_tuners_ins.sampling_rate)); 361 up(&dbs_sem); 362 } 363 364 static inline void dbs_timer_init(void) 365 { 366 INIT_WORK(&dbs_work, do_dbs_timer, NULL); 367 schedule_delayed_work(&dbs_work, 368 usecs_to_jiffies(dbs_tuners_ins.sampling_rate)); 369 return; 370 } 371 372 static inline void dbs_timer_exit(void) 373 { 374 cancel_delayed_work(&dbs_work); 375 return; 376 } 377 378 static int cpufreq_governor_dbs(struct cpufreq_policy *policy, 379 unsigned int event) 380 { 381 unsigned int cpu = policy->cpu; 382 struct cpu_dbs_info_s *this_dbs_info; 383 unsigned int j; 384 385 this_dbs_info = &per_cpu(cpu_dbs_info, cpu); 386 387 switch (event) { 388 case CPUFREQ_GOV_START: 389 if ((!cpu_online(cpu)) || 390 (!policy->cur)) 391 return -EINVAL; 392 393 if (policy->cpuinfo.transition_latency > 394 (TRANSITION_LATENCY_LIMIT * 1000)) 395 return -EINVAL; 396 if (this_dbs_info->enable) /* Already enabled */ 397 break; 398 399 down(&dbs_sem); 400 for_each_cpu_mask(j, policy->cpus) { 401 struct cpu_dbs_info_s *j_dbs_info; 402 j_dbs_info = &per_cpu(cpu_dbs_info, j); 403 j_dbs_info->cur_policy = policy; 404 405 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j); 406 j_dbs_info->prev_cpu_idle_down 407 = j_dbs_info->prev_cpu_idle_up; 408 } 409 this_dbs_info->enable = 1; 410 sysfs_create_group(&policy->kobj, &dbs_attr_group); 411 dbs_enable++; 412 /* 413 * Start the timerschedule work, when this governor 414 * is used for first time 415 */ 416 if (dbs_enable == 1) { 417 unsigned int latency; 418 /* policy latency is in nS. Convert it to uS first */ 419 420 latency = policy->cpuinfo.transition_latency; 421 if (latency < 1000) 422 latency = 1000; 423 424 def_sampling_rate = (latency / 1000) * 425 DEF_SAMPLING_RATE_LATENCY_MULTIPLIER; 426 dbs_tuners_ins.sampling_rate = def_sampling_rate; 427 dbs_tuners_ins.ignore_nice = 0; 428 429 dbs_timer_init(); 430 } 431 432 up(&dbs_sem); 433 break; 434 435 case CPUFREQ_GOV_STOP: 436 down(&dbs_sem); 437 this_dbs_info->enable = 0; 438 sysfs_remove_group(&policy->kobj, &dbs_attr_group); 439 dbs_enable--; 440 /* 441 * Stop the timerschedule work, when this governor 442 * is used for first time 443 */ 444 if (dbs_enable == 0) 445 dbs_timer_exit(); 446 447 up(&dbs_sem); 448 449 break; 450 451 case CPUFREQ_GOV_LIMITS: 452 down(&dbs_sem); 453 if (policy->max < this_dbs_info->cur_policy->cur) 454 __cpufreq_driver_target( 455 this_dbs_info->cur_policy, 456 policy->max, CPUFREQ_RELATION_H); 457 else if (policy->min > this_dbs_info->cur_policy->cur) 458 __cpufreq_driver_target( 459 this_dbs_info->cur_policy, 460 policy->min, CPUFREQ_RELATION_L); 461 up(&dbs_sem); 462 break; 463 } 464 return 0; 465 } 466 467 static struct cpufreq_governor cpufreq_gov_dbs = { 468 .name = "ondemand", 469 .governor = cpufreq_governor_dbs, 470 .owner = THIS_MODULE, 471 }; 472 473 static int __init cpufreq_gov_dbs_init(void) 474 { 475 return cpufreq_register_governor(&cpufreq_gov_dbs); 476 } 477 478 static void __exit cpufreq_gov_dbs_exit(void) 479 { 480 /* Make sure that the scheduled work is indeed not running */ 481 flush_scheduled_work(); 482 483 cpufreq_unregister_governor(&cpufreq_gov_dbs); 484 } 485 486 487 MODULE_AUTHOR ("Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>"); 488 MODULE_DESCRIPTION ("'cpufreq_ondemand' - A dynamic cpufreq governor for " 489 "Low Latency Frequency Transition capable processors"); 490 MODULE_LICENSE ("GPL"); 491 492 module_init(cpufreq_gov_dbs_init); 493 module_exit(cpufreq_gov_dbs_exit); 494