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/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)
  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 /************************** sysfs interface ************************/
 120 static ssize_t show_sampling_rate_max(struct cpufreq_policy *policy, char *buf)
 121 {
 122         return sprintf (buf, "%u\n", MAX_SAMPLING_RATE);
 123 }
 124
 125 static ssize_t show_sampling_rate_min(struct cpufreq_policy *policy, char *buf)
 126 {
 127         return sprintf (buf, "%u\n", MIN_SAMPLING_RATE);
 128 }
 129
 130 #define define_one_ro(_name)                                    \
 131 static struct freq_attr _name =                                 \
 132 __ATTR(_name, 0444, show_##_name, NULL)
 133
 134 define_one_ro(sampling_rate_max);
 135 define_one_ro(sampling_rate_min);
 136
 137 /* cpufreq_conservative Governor Tunables */
 138 #define show_one(file_name, object)                                     \
 139 static ssize_t show_##file_name                                         \
 140 (struct cpufreq_policy *unused, char *buf)                              \
 141 {                                                                       \
 142         return sprintf(buf, "%u\n", dbs_tuners_ins.object);             \
 143 }
 144 show_one(sampling_rate, sampling_rate);
 145 show_one(sampling_down_factor, sampling_down_factor);
 146 show_one(up_threshold, up_threshold);
 147 show_one(down_threshold, down_threshold);
 148 show_one(ignore_nice_load, ignore_nice);
 149 show_one(freq_step, freq_step);
 150
 151 static ssize_t store_sampling_down_factor(struct cpufreq_policy *unused,
 152                 const char *buf, size_t count)
 153 {
 154         unsigned int input;
 155         int ret;
 156         ret = sscanf (buf, "%u", &input);
 157         if (ret != 1 || input > MAX_SAMPLING_DOWN_FACTOR || input < 1)
 158                 return -EINVAL;
 159
 160         mutex_lock(&dbs_mutex);
 161         dbs_tuners_ins.sampling_down_factor = input;
 162         mutex_unlock(&dbs_mutex);
 163
 164         return count;
 165 }
 166
 167 static ssize_t store_sampling_rate(struct cpufreq_policy *unused,
 168                 const char *buf, size_t count)
 169 {
 170         unsigned int input;
 171         int ret;
 172         ret = sscanf (buf, "%u", &input);
 173
 174         mutex_lock(&dbs_mutex);
 175         if (ret != 1 || input > MAX_SAMPLING_RATE || input < MIN_SAMPLING_RATE) {
 176                 mutex_unlock(&dbs_mutex);
 177                 return -EINVAL;
 178         }
 179
 180         dbs_tuners_ins.sampling_rate = input;
 181         mutex_unlock(&dbs_mutex);
 182
 183         return count;
 184 }
 185
 186 static ssize_t store_up_threshold(struct cpufreq_policy *unused,
 187                 const char *buf, size_t count)
 188 {
 189         unsigned int input;
 190         int ret;
 191         ret = sscanf (buf, "%u", &input);
 192
 193         mutex_lock(&dbs_mutex);
 194         if (ret != 1 || input > 100 || input <= dbs_tuners_ins.down_threshold) {
 195                 mutex_unlock(&dbs_mutex);
 196                 return -EINVAL;
 197         }
 198
 199         dbs_tuners_ins.up_threshold = input;
 200         mutex_unlock(&dbs_mutex);
 201
 202         return count;
 203 }
 204
 205 static ssize_t store_down_threshold(struct cpufreq_policy *unused,
 206                 const char *buf, size_t count)
 207 {
 208         unsigned int input;
 209         int ret;
 210         ret = sscanf (buf, "%u", &input);
 211
 212         mutex_lock(&dbs_mutex);
 213         if (ret != 1 || input > 100 || input >= dbs_tuners_ins.up_threshold) {
 214                 mutex_unlock(&dbs_mutex);
 215                 return -EINVAL;
 216         }
 217
 218         dbs_tuners_ins.down_threshold = input;
 219         mutex_unlock(&dbs_mutex);
 220
 221         return count;
 222 }
 223
 224 static ssize_t store_ignore_nice_load(struct cpufreq_policy *policy,
 225                 const char *buf, size_t count)
 226 {
 227         unsigned int input;
 228         int ret;
 229
 230         unsigned int j;
 231
 232         ret = sscanf (buf, "%u", &input);
 233         if ( ret != 1 )
 234                 return -EINVAL;
 235
 236         if ( input > 1 )
 237                 input = 1;
 238
 239         mutex_lock(&dbs_mutex);
 240         if ( input == dbs_tuners_ins.ignore_nice ) { /* nothing to do */
 241                 mutex_unlock(&dbs_mutex);
 242                 return count;
 243         }
 244         dbs_tuners_ins.ignore_nice = input;
 245
 246         /* we need to re-evaluate prev_cpu_idle_up and prev_cpu_idle_down */
 247         for_each_online_cpu(j) {
 248                 struct cpu_dbs_info_s *j_dbs_info;
 249                 j_dbs_info = &per_cpu(cpu_dbs_info, j);
 250                 j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(j);
 251                 j_dbs_info->prev_cpu_idle_down = j_dbs_info->prev_cpu_idle_up;
 252         }
 253         mutex_unlock(&dbs_mutex);
 254
 255         return count;
 256 }
 257
 258 static ssize_t store_freq_step(struct cpufreq_policy *policy,
 259                 const char *buf, size_t count)
 260 {
 261         unsigned int input;
 262         int ret;
 263
 264         ret = sscanf (buf, "%u", &input);
 265
 266         if ( ret != 1 )
 267                 return -EINVAL;
 268
 269         if ( input > 100 )
 270                 input = 100;
 271
 272         /* no need to test here if freq_step is zero as the user might actually
 273          * want this, they would be crazy though :) */
 274         mutex_lock(&dbs_mutex);
 275         dbs_tuners_ins.freq_step = input;
 276         mutex_unlock(&dbs_mutex);
 277
 278         return count;
 279 }
 280
 281 #define define_one_rw(_name) \
 282 static struct freq_attr _name = \
 283 __ATTR(_name, 0644, show_##_name, store_##_name)
 284
 285 define_one_rw(sampling_rate);
 286 define_one_rw(sampling_down_factor);
 287 define_one_rw(up_threshold);
 288 define_one_rw(down_threshold);
 289 define_one_rw(ignore_nice_load);
 290 define_one_rw(freq_step);
 291
 292 static struct attribute * dbs_attributes[] = {
 293         &sampling_rate_max.attr,
 294         &sampling_rate_min.attr,
 295         &sampling_rate.attr,
 296         &sampling_down_factor.attr,
 297         &up_threshold.attr,
 298         &down_threshold.attr,
 299         &ignore_nice_load.attr,
 300         &freq_step.attr,
 301         NULL
 302 };
 303
 304 static struct attribute_group dbs_attr_group = {
 305         .attrs = dbs_attributes,
 306         .name = "conservative",
 307 };
 308
 309 /************************** sysfs end ************************/
 310
 311 static void dbs_check_cpu(int cpu)
 312 {
 313         unsigned int idle_ticks, up_idle_ticks, down_idle_ticks;
 314         unsigned int tmp_idle_ticks, total_idle_ticks;
 315         unsigned int freq_step;
 316         unsigned int freq_down_sampling_rate;
 317         struct cpu_dbs_info_s *this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 318         struct cpufreq_policy *policy;
 319
 320         if (!this_dbs_info->enable)
 321                 return;
 322
 323         policy = this_dbs_info->cur_policy;
 324
 325         /*
 326          * The default safe range is 20% to 80%
 327          * Every sampling_rate, we check
 328          *      - If current idle time is less than 20%, then we try to
 329          *        increase frequency
 330          * Every sampling_rate*sampling_down_factor, we check
 331          *      - If current idle time is more than 80%, then we try to
 332          *        decrease frequency
 333          *
 334          * Any frequency increase takes it to the maximum frequency.
 335          * Frequency reduction happens at minimum steps of
 336          * 5% (default) of max_frequency
 337          */
 338
 339         /* Check for frequency increase */
 340         idle_ticks = UINT_MAX;
 341
 342         /* Check for frequency increase */
 343         total_idle_ticks = get_cpu_idle_time(cpu);
 344         tmp_idle_ticks = total_idle_ticks -
 345                 this_dbs_info->prev_cpu_idle_up;
 346         this_dbs_info->prev_cpu_idle_up = total_idle_ticks;
 347
 348         if (tmp_idle_ticks < idle_ticks)
 349                 idle_ticks = tmp_idle_ticks;
 350
 351         /* Scale idle ticks by 100 and compare with up and down ticks */
 352         idle_ticks *= 100;
 353         up_idle_ticks = (100 - dbs_tuners_ins.up_threshold) *
 354                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate);
 355
 356         if (idle_ticks < up_idle_ticks) {
 357                 this_dbs_info->down_skip = 0;
 358                 this_dbs_info->prev_cpu_idle_down =
 359                         this_dbs_info->prev_cpu_idle_up;
 360
 361                 /* if we are already at full speed then break out early */
 362                 if (this_dbs_info->requested_freq == policy->max)
 363                         return;
 364
 365                 freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
 366
 367                 /* max freq cannot be less than 100. But who knows.... */
 368                 if (unlikely(freq_step == 0))
 369                         freq_step = 5;
 370
 371                 this_dbs_info->requested_freq += freq_step;
 372                 if (this_dbs_info->requested_freq > policy->max)
 373                         this_dbs_info->requested_freq = policy->max;
 374
 375                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 376                         CPUFREQ_RELATION_H);
 377                 return;
 378         }
 379
 380         /* Check for frequency decrease */
 381         this_dbs_info->down_skip++;
 382         if (this_dbs_info->down_skip < dbs_tuners_ins.sampling_down_factor)
 383                 return;
 384
 385         /* Check for frequency decrease */
 386         total_idle_ticks = this_dbs_info->prev_cpu_idle_up;
 387         tmp_idle_ticks = total_idle_ticks -
 388                 this_dbs_info->prev_cpu_idle_down;
 389         this_dbs_info->prev_cpu_idle_down = total_idle_ticks;
 390
 391         if (tmp_idle_ticks < idle_ticks)
 392                 idle_ticks = tmp_idle_ticks;
 393
 394         /* Scale idle ticks by 100 and compare with up and down ticks */
 395         idle_ticks *= 100;
 396         this_dbs_info->down_skip = 0;
 397
 398         freq_down_sampling_rate = dbs_tuners_ins.sampling_rate *
 399                 dbs_tuners_ins.sampling_down_factor;
 400         down_idle_ticks = (100 - dbs_tuners_ins.down_threshold) *
 401                 usecs_to_jiffies(freq_down_sampling_rate);
 402
 403         if (idle_ticks > down_idle_ticks) {
 404                 /*
 405                  * if we are already at the lowest speed then break out early
 406                  * or if we 'cannot' reduce the speed as the user might want
 407                  * freq_step to be zero
 408                  */
 409                 if (this_dbs_info->requested_freq == policy->min
 410                                 || dbs_tuners_ins.freq_step == 0)
 411                         return;
 412
 413                 freq_step = (dbs_tuners_ins.freq_step * policy->max) / 100;
 414
 415                 /* max freq cannot be less than 100. But who knows.... */
 416                 if (unlikely(freq_step == 0))
 417                         freq_step = 5;
 418
 419                 this_dbs_info->requested_freq -= freq_step;
 420                 if (this_dbs_info->requested_freq < policy->min)
 421                         this_dbs_info->requested_freq = policy->min;
 422
 423                 __cpufreq_driver_target(policy, this_dbs_info->requested_freq,
 424                                 CPUFREQ_RELATION_H);
 425                 return;
 426         }
 427 }
 428
 429 static void do_dbs_timer(struct work_struct *work)
 430 {
 431         int i;
 432         mutex_lock(&dbs_mutex);
 433         for_each_online_cpu(i)
 434                 dbs_check_cpu(i);
 435         schedule_delayed_work(&dbs_work,
 436                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 437         mutex_unlock(&dbs_mutex);
 438 }
 439
 440 static inline void dbs_timer_init(void)
 441 {
 442         schedule_delayed_work(&dbs_work,
 443                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
 444         return;
 445 }
 446
 447 static inline void dbs_timer_exit(void)
 448 {
 449         cancel_delayed_work(&dbs_work);
 450         return;
 451 }
 452
 453 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 454                                    unsigned int event)
 455 {
 456         unsigned int cpu = policy->cpu;
 457         struct cpu_dbs_info_s *this_dbs_info;
 458         unsigned int j;
 459         int rc;
 460
 461         this_dbs_info = &per_cpu(cpu_dbs_info, cpu);
 462
 463         switch (event) {
 464         case CPUFREQ_GOV_START:
 465                 if ((!cpu_online(cpu)) ||
 466                     (!policy->cur))
 467                         return -EINVAL;
 468
 469                 if (policy->cpuinfo.transition_latency >
 470                                 (TRANSITION_LATENCY_LIMIT * 1000))
 471                         return -EINVAL;
 472                 if (this_dbs_info->enable) /* Already enabled */
 473                         break;
 474
 475                 mutex_lock(&dbs_mutex);
 476
 477                 rc = sysfs_create_group(&policy->kobj, &dbs_attr_group);
 478                 if (rc) {
 479                         mutex_unlock(&dbs_mutex);
 480                         return rc;
 481                 }
 482
 483                 for_each_cpu_mask(j, policy->cpus) {
 484                         struct cpu_dbs_info_s *j_dbs_info;
 485                         j_dbs_info = &per_cpu(cpu_dbs_info, j);
 486                         j_dbs_info->cur_policy = policy;
 487
 488                         j_dbs_info->prev_cpu_idle_up = get_cpu_idle_time(cpu);
 489                         j_dbs_info->prev_cpu_idle_down
 490                                 = j_dbs_info->prev_cpu_idle_up;
 491                 }
 492                 this_dbs_info->enable = 1;
 493                 this_dbs_info->down_skip = 0;
 494                 this_dbs_info->requested_freq = policy->cur;
 495
 496                 dbs_enable++;
 497                 /*
 498                  * Start the timerschedule work, when this governor
 499                  * is used for first time
 500                  */
 501                 if (dbs_enable == 1) {
 502                         unsigned int latency;
 503                         /* policy latency is in nS. Convert it to uS first */
 504                         latency = policy->cpuinfo.transition_latency / 1000;
 505                         if (latency == 0)
 506                                 latency = 1;
 507
 508                         def_sampling_rate = 10 * latency *
 509                                         DEF_SAMPLING_RATE_LATENCY_MULTIPLIER;
 510
 511                         if (def_sampling_rate < MIN_STAT_SAMPLING_RATE)
 512                                 def_sampling_rate = MIN_STAT_SAMPLING_RATE;
 513
 514                         dbs_tuners_ins.sampling_rate = def_sampling_rate;
 515
 516                         dbs_timer_init();
 517                 }
 518
 519                 mutex_unlock(&dbs_mutex);
 520                 break;
 521
 522         case CPUFREQ_GOV_STOP:
 523                 mutex_lock(&dbs_mutex);
 524                 this_dbs_info->enable = 0;
 525                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
 526                 dbs_enable--;
 527                 /*
 528                  * Stop the timerschedule work, when this governor
 529                  * is used for first time
 530                  */
 531                 if (dbs_enable == 0)
 532                         dbs_timer_exit();
 533
 534                 mutex_unlock(&dbs_mutex);
 535
 536                 break;
 537
 538         case CPUFREQ_GOV_LIMITS:
 539                 mutex_lock(&dbs_mutex);
 540                 if (policy->max < this_dbs_info->cur_policy->cur)
 541                         __cpufreq_driver_target(
 542                                         this_dbs_info->cur_policy,
 543                                         policy->max, CPUFREQ_RELATION_H);
 544                 else if (policy->min > this_dbs_info->cur_policy->cur)
 545                         __cpufreq_driver_target(
 546                                         this_dbs_info->cur_policy,
 547                                         policy->min, CPUFREQ_RELATION_L);
 548                 mutex_unlock(&dbs_mutex);
 549                 break;
 550         }
 551         return 0;
 552 }
 553
 554 static struct cpufreq_governor cpufreq_gov_dbs = {
 555         .name           = "conservative",
 556         .governor       = cpufreq_governor_dbs,
 557         .owner          = THIS_MODULE,
 558 };
 559
 560 static int __init cpufreq_gov_dbs_init(void)
 561 {
 562         return cpufreq_register_governor(&cpufreq_gov_dbs);
 563 }
 564
 565 static void __exit cpufreq_gov_dbs_exit(void)
 566 {
 567         /* Make sure that the scheduled work is indeed not running */
 568         flush_scheduled_work();
 569
 570         cpufreq_unregister_governor(&cpufreq_gov_dbs);
 571 }
 572
 573
 574 MODULE_AUTHOR ("Alexander Clouter <alex-kernel@digriz.org.uk>");
 575 MODULE_DESCRIPTION ("'cpufreq_conservative' - A dynamic cpufreq governor for "
 576                 "Low Latency Frequency Transition capable processors "
 577                 "optimised for use in a battery environment");
 578 MODULE_LICENSE ("GPL");
 579
 580 module_init(cpufreq_gov_dbs_init);
 581 module_exit(cpufreq_gov_dbs_exit);