drivers/cpufreq/cpufreq_conservative.c

   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);