drivers/cpufreq/cpufreq_ondemand.c

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