1 /* 2 * drivers/cpufreq/cpufreq_governor.c 3 * 4 * CPUFREQ governors common code 5 * 6 * Copyright (C) 2001 Russell King 7 * (C) 2003 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>. 8 * (C) 2003 Jun Nakajima <jun.nakajima@intel.com> 9 * (C) 2009 Alexander Clouter <alex@digriz.org.uk> 10 * (c) 2012 Viresh Kumar <viresh.kumar@linaro.org> 11 * 12 * This program is free software; you can redistribute it and/or modify 13 * it under the terms of the GNU General Public License version 2 as 14 * published by the Free Software Foundation. 15 */ 16 17 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 18 19 #include <linux/export.h> 20 #include <linux/kernel_stat.h> 21 #include <linux/slab.h> 22 23 #include "cpufreq_governor.h" 24 25 #define CPUFREQ_DBS_MIN_SAMPLING_INTERVAL (2 * TICK_NSEC / NSEC_PER_USEC) 26 27 static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs); 28 29 static DEFINE_MUTEX(gov_dbs_data_mutex); 30 31 /* Common sysfs tunables */ 32 /** 33 * store_sampling_rate - update sampling rate effective immediately if needed. 34 * 35 * If new rate is smaller than the old, simply updating 36 * dbs.sampling_rate might not be appropriate. For example, if the 37 * original sampling_rate was 1 second and the requested new sampling rate is 10 38 * ms because the user needs immediate reaction from ondemand governor, but not 39 * sure if higher frequency will be required or not, then, the governor may 40 * change the sampling rate too late; up to 1 second later. Thus, if we are 41 * reducing the sampling rate, we need to make the new value effective 42 * immediately. 43 * 44 * This must be called with dbs_data->mutex held, otherwise traversing 45 * policy_dbs_list isn't safe. 46 */ 47 ssize_t store_sampling_rate(struct gov_attr_set *attr_set, const char *buf, 48 size_t count) 49 { 50 struct dbs_data *dbs_data = to_dbs_data(attr_set); 51 struct policy_dbs_info *policy_dbs; 52 unsigned int sampling_interval; 53 int ret; 54 55 ret = sscanf(buf, "%u", &sampling_interval); 56 if (ret != 1 || sampling_interval < CPUFREQ_DBS_MIN_SAMPLING_INTERVAL) 57 return -EINVAL; 58 59 dbs_data->sampling_rate = sampling_interval; 60 61 /* 62 * We are operating under dbs_data->mutex and so the list and its 63 * entries can't be freed concurrently. 64 */ 65 list_for_each_entry(policy_dbs, &attr_set->policy_list, list) { 66 mutex_lock(&policy_dbs->update_mutex); 67 /* 68 * On 32-bit architectures this may race with the 69 * sample_delay_ns read in dbs_update_util_handler(), but that 70 * really doesn't matter. If the read returns a value that's 71 * too big, the sample will be skipped, but the next invocation 72 * of dbs_update_util_handler() (when the update has been 73 * completed) will take a sample. 74 * 75 * If this runs in parallel with dbs_work_handler(), we may end 76 * up overwriting the sample_delay_ns value that it has just 77 * written, but it will be corrected next time a sample is 78 * taken, so it shouldn't be significant. 79 */ 80 gov_update_sample_delay(policy_dbs, 0); 81 mutex_unlock(&policy_dbs->update_mutex); 82 } 83 84 return count; 85 } 86 EXPORT_SYMBOL_GPL(store_sampling_rate); 87 88 /** 89 * gov_update_cpu_data - Update CPU load data. 90 * @dbs_data: Top-level governor data pointer. 91 * 92 * Update CPU load data for all CPUs in the domain governed by @dbs_data 93 * (that may be a single policy or a bunch of them if governor tunables are 94 * system-wide). 95 * 96 * Call under the @dbs_data mutex. 97 */ 98 void gov_update_cpu_data(struct dbs_data *dbs_data) 99 { 100 struct policy_dbs_info *policy_dbs; 101 102 list_for_each_entry(policy_dbs, &dbs_data->attr_set.policy_list, list) { 103 unsigned int j; 104 105 for_each_cpu(j, policy_dbs->policy->cpus) { 106 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); 107 108 j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_update_time, 109 dbs_data->io_is_busy); 110 if (dbs_data->ignore_nice_load) 111 j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE]; 112 } 113 } 114 } 115 EXPORT_SYMBOL_GPL(gov_update_cpu_data); 116 117 unsigned int dbs_update(struct cpufreq_policy *policy) 118 { 119 struct policy_dbs_info *policy_dbs = policy->governor_data; 120 struct dbs_data *dbs_data = policy_dbs->dbs_data; 121 unsigned int ignore_nice = dbs_data->ignore_nice_load; 122 unsigned int max_load = 0, idle_periods = UINT_MAX; 123 unsigned int sampling_rate, io_busy, j; 124 125 /* 126 * Sometimes governors may use an additional multiplier to increase 127 * sample delays temporarily. Apply that multiplier to sampling_rate 128 * so as to keep the wake-up-from-idle detection logic a bit 129 * conservative. 130 */ 131 sampling_rate = dbs_data->sampling_rate * policy_dbs->rate_mult; 132 /* 133 * For the purpose of ondemand, waiting for disk IO is an indication 134 * that you're performance critical, and not that the system is actually 135 * idle, so do not add the iowait time to the CPU idle time then. 136 */ 137 io_busy = dbs_data->io_is_busy; 138 139 /* Get Absolute Load */ 140 for_each_cpu(j, policy->cpus) { 141 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); 142 u64 update_time, cur_idle_time; 143 unsigned int idle_time, time_elapsed; 144 unsigned int load; 145 146 cur_idle_time = get_cpu_idle_time(j, &update_time, io_busy); 147 148 time_elapsed = update_time - j_cdbs->prev_update_time; 149 j_cdbs->prev_update_time = update_time; 150 151 idle_time = cur_idle_time - j_cdbs->prev_cpu_idle; 152 j_cdbs->prev_cpu_idle = cur_idle_time; 153 154 if (ignore_nice) { 155 u64 cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE]; 156 157 idle_time += div_u64(cur_nice - j_cdbs->prev_cpu_nice, NSEC_PER_USEC); 158 j_cdbs->prev_cpu_nice = cur_nice; 159 } 160 161 if (unlikely(!time_elapsed)) { 162 /* 163 * That can only happen when this function is called 164 * twice in a row with a very short interval between the 165 * calls, so the previous load value can be used then. 166 */ 167 load = j_cdbs->prev_load; 168 } else if (unlikely((int)idle_time > 2 * sampling_rate && 169 j_cdbs->prev_load)) { 170 /* 171 * If the CPU had gone completely idle and a task has 172 * just woken up on this CPU now, it would be unfair to 173 * calculate 'load' the usual way for this elapsed 174 * time-window, because it would show near-zero load, 175 * irrespective of how CPU intensive that task actually 176 * was. This is undesirable for latency-sensitive bursty 177 * workloads. 178 * 179 * To avoid this, reuse the 'load' from the previous 180 * time-window and give this task a chance to start with 181 * a reasonably high CPU frequency. However, that 182 * shouldn't be over-done, lest we get stuck at a high 183 * load (high frequency) for too long, even when the 184 * current system load has actually dropped down, so 185 * clear prev_load to guarantee that the load will be 186 * computed again next time. 187 * 188 * Detecting this situation is easy: an unusually large 189 * 'idle_time' (as compared to the sampling rate) 190 * indicates this scenario. 191 */ 192 load = j_cdbs->prev_load; 193 j_cdbs->prev_load = 0; 194 } else { 195 if (time_elapsed >= idle_time) { 196 load = 100 * (time_elapsed - idle_time) / time_elapsed; 197 } else { 198 /* 199 * That can happen if idle_time is returned by 200 * get_cpu_idle_time_jiffy(). In that case 201 * idle_time is roughly equal to the difference 202 * between time_elapsed and "busy time" obtained 203 * from CPU statistics. Then, the "busy time" 204 * can end up being greater than time_elapsed 205 * (for example, if jiffies_64 and the CPU 206 * statistics are updated by different CPUs), 207 * so idle_time may in fact be negative. That 208 * means, though, that the CPU was busy all 209 * the time (on the rough average) during the 210 * last sampling interval and 100 can be 211 * returned as the load. 212 */ 213 load = (int)idle_time < 0 ? 100 : 0; 214 } 215 j_cdbs->prev_load = load; 216 } 217 218 if (unlikely((int)idle_time > 2 * sampling_rate)) { 219 unsigned int periods = idle_time / sampling_rate; 220 221 if (periods < idle_periods) 222 idle_periods = periods; 223 } 224 225 if (load > max_load) 226 max_load = load; 227 } 228 229 policy_dbs->idle_periods = idle_periods; 230 231 return max_load; 232 } 233 EXPORT_SYMBOL_GPL(dbs_update); 234 235 static void dbs_work_handler(struct work_struct *work) 236 { 237 struct policy_dbs_info *policy_dbs; 238 struct cpufreq_policy *policy; 239 struct dbs_governor *gov; 240 241 policy_dbs = container_of(work, struct policy_dbs_info, work); 242 policy = policy_dbs->policy; 243 gov = dbs_governor_of(policy); 244 245 /* 246 * Make sure cpufreq_governor_limits() isn't evaluating load or the 247 * ondemand governor isn't updating the sampling rate in parallel. 248 */ 249 mutex_lock(&policy_dbs->update_mutex); 250 gov_update_sample_delay(policy_dbs, gov->gov_dbs_update(policy)); 251 mutex_unlock(&policy_dbs->update_mutex); 252 253 /* Allow the utilization update handler to queue up more work. */ 254 atomic_set(&policy_dbs->work_count, 0); 255 /* 256 * If the update below is reordered with respect to the sample delay 257 * modification, the utilization update handler may end up using a stale 258 * sample delay value. 259 */ 260 smp_wmb(); 261 policy_dbs->work_in_progress = false; 262 } 263 264 static void dbs_irq_work(struct irq_work *irq_work) 265 { 266 struct policy_dbs_info *policy_dbs; 267 268 policy_dbs = container_of(irq_work, struct policy_dbs_info, irq_work); 269 schedule_work_on(smp_processor_id(), &policy_dbs->work); 270 } 271 272 static void dbs_update_util_handler(struct update_util_data *data, u64 time, 273 unsigned int flags) 274 { 275 struct cpu_dbs_info *cdbs = container_of(data, struct cpu_dbs_info, update_util); 276 struct policy_dbs_info *policy_dbs = cdbs->policy_dbs; 277 u64 delta_ns, lst; 278 279 if (!cpufreq_this_cpu_can_update(policy_dbs->policy)) 280 return; 281 282 /* 283 * The work may not be allowed to be queued up right now. 284 * Possible reasons: 285 * - Work has already been queued up or is in progress. 286 * - It is too early (too little time from the previous sample). 287 */ 288 if (policy_dbs->work_in_progress) 289 return; 290 291 /* 292 * If the reads below are reordered before the check above, the value 293 * of sample_delay_ns used in the computation may be stale. 294 */ 295 smp_rmb(); 296 lst = READ_ONCE(policy_dbs->last_sample_time); 297 delta_ns = time - lst; 298 if ((s64)delta_ns < policy_dbs->sample_delay_ns) 299 return; 300 301 /* 302 * If the policy is not shared, the irq_work may be queued up right away 303 * at this point. Otherwise, we need to ensure that only one of the 304 * CPUs sharing the policy will do that. 305 */ 306 if (policy_dbs->is_shared) { 307 if (!atomic_add_unless(&policy_dbs->work_count, 1, 1)) 308 return; 309 310 /* 311 * If another CPU updated last_sample_time in the meantime, we 312 * shouldn't be here, so clear the work counter and bail out. 313 */ 314 if (unlikely(lst != READ_ONCE(policy_dbs->last_sample_time))) { 315 atomic_set(&policy_dbs->work_count, 0); 316 return; 317 } 318 } 319 320 policy_dbs->last_sample_time = time; 321 policy_dbs->work_in_progress = true; 322 irq_work_queue(&policy_dbs->irq_work); 323 } 324 325 static void gov_set_update_util(struct policy_dbs_info *policy_dbs, 326 unsigned int delay_us) 327 { 328 struct cpufreq_policy *policy = policy_dbs->policy; 329 int cpu; 330 331 gov_update_sample_delay(policy_dbs, delay_us); 332 policy_dbs->last_sample_time = 0; 333 334 for_each_cpu(cpu, policy->cpus) { 335 struct cpu_dbs_info *cdbs = &per_cpu(cpu_dbs, cpu); 336 337 cpufreq_add_update_util_hook(cpu, &cdbs->update_util, 338 dbs_update_util_handler); 339 } 340 } 341 342 static inline void gov_clear_update_util(struct cpufreq_policy *policy) 343 { 344 int i; 345 346 for_each_cpu(i, policy->cpus) 347 cpufreq_remove_update_util_hook(i); 348 349 synchronize_rcu(); 350 } 351 352 static struct policy_dbs_info *alloc_policy_dbs_info(struct cpufreq_policy *policy, 353 struct dbs_governor *gov) 354 { 355 struct policy_dbs_info *policy_dbs; 356 int j; 357 358 /* Allocate memory for per-policy governor data. */ 359 policy_dbs = gov->alloc(); 360 if (!policy_dbs) 361 return NULL; 362 363 policy_dbs->policy = policy; 364 mutex_init(&policy_dbs->update_mutex); 365 atomic_set(&policy_dbs->work_count, 0); 366 init_irq_work(&policy_dbs->irq_work, dbs_irq_work); 367 INIT_WORK(&policy_dbs->work, dbs_work_handler); 368 369 /* Set policy_dbs for all CPUs, online+offline */ 370 for_each_cpu(j, policy->related_cpus) { 371 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); 372 373 j_cdbs->policy_dbs = policy_dbs; 374 } 375 return policy_dbs; 376 } 377 378 static void free_policy_dbs_info(struct policy_dbs_info *policy_dbs, 379 struct dbs_governor *gov) 380 { 381 int j; 382 383 mutex_destroy(&policy_dbs->update_mutex); 384 385 for_each_cpu(j, policy_dbs->policy->related_cpus) { 386 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); 387 388 j_cdbs->policy_dbs = NULL; 389 j_cdbs->update_util.func = NULL; 390 } 391 gov->free(policy_dbs); 392 } 393 394 int cpufreq_dbs_governor_init(struct cpufreq_policy *policy) 395 { 396 struct dbs_governor *gov = dbs_governor_of(policy); 397 struct dbs_data *dbs_data; 398 struct policy_dbs_info *policy_dbs; 399 int ret = 0; 400 401 /* State should be equivalent to EXIT */ 402 if (policy->governor_data) 403 return -EBUSY; 404 405 policy_dbs = alloc_policy_dbs_info(policy, gov); 406 if (!policy_dbs) 407 return -ENOMEM; 408 409 /* Protect gov->gdbs_data against concurrent updates. */ 410 mutex_lock(&gov_dbs_data_mutex); 411 412 dbs_data = gov->gdbs_data; 413 if (dbs_data) { 414 if (WARN_ON(have_governor_per_policy())) { 415 ret = -EINVAL; 416 goto free_policy_dbs_info; 417 } 418 policy_dbs->dbs_data = dbs_data; 419 policy->governor_data = policy_dbs; 420 421 gov_attr_set_get(&dbs_data->attr_set, &policy_dbs->list); 422 goto out; 423 } 424 425 dbs_data = kzalloc(sizeof(*dbs_data), GFP_KERNEL); 426 if (!dbs_data) { 427 ret = -ENOMEM; 428 goto free_policy_dbs_info; 429 } 430 431 gov_attr_set_init(&dbs_data->attr_set, &policy_dbs->list); 432 433 ret = gov->init(dbs_data); 434 if (ret) 435 goto free_policy_dbs_info; 436 437 /* 438 * The sampling interval should not be less than the transition latency 439 * of the CPU and it also cannot be too small for dbs_update() to work 440 * correctly. 441 */ 442 dbs_data->sampling_rate = max_t(unsigned int, 443 CPUFREQ_DBS_MIN_SAMPLING_INTERVAL, 444 cpufreq_policy_transition_delay_us(policy)); 445 446 if (!have_governor_per_policy()) 447 gov->gdbs_data = dbs_data; 448 449 policy_dbs->dbs_data = dbs_data; 450 policy->governor_data = policy_dbs; 451 452 gov->kobj_type.sysfs_ops = &governor_sysfs_ops; 453 ret = kobject_init_and_add(&dbs_data->attr_set.kobj, &gov->kobj_type, 454 get_governor_parent_kobj(policy), 455 "%s", gov->gov.name); 456 if (!ret) 457 goto out; 458 459 /* Failure, so roll back. */ 460 pr_err("initialization failed (dbs_data kobject init error %d)\n", ret); 461 462 kobject_put(&dbs_data->attr_set.kobj); 463 464 policy->governor_data = NULL; 465 466 if (!have_governor_per_policy()) 467 gov->gdbs_data = NULL; 468 gov->exit(dbs_data); 469 kfree(dbs_data); 470 471 free_policy_dbs_info: 472 free_policy_dbs_info(policy_dbs, gov); 473 474 out: 475 mutex_unlock(&gov_dbs_data_mutex); 476 return ret; 477 } 478 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_init); 479 480 void cpufreq_dbs_governor_exit(struct cpufreq_policy *policy) 481 { 482 struct dbs_governor *gov = dbs_governor_of(policy); 483 struct policy_dbs_info *policy_dbs = policy->governor_data; 484 struct dbs_data *dbs_data = policy_dbs->dbs_data; 485 unsigned int count; 486 487 /* Protect gov->gdbs_data against concurrent updates. */ 488 mutex_lock(&gov_dbs_data_mutex); 489 490 count = gov_attr_set_put(&dbs_data->attr_set, &policy_dbs->list); 491 492 policy->governor_data = NULL; 493 494 if (!count) { 495 if (!have_governor_per_policy()) 496 gov->gdbs_data = NULL; 497 498 gov->exit(dbs_data); 499 kfree(dbs_data); 500 } 501 502 free_policy_dbs_info(policy_dbs, gov); 503 504 mutex_unlock(&gov_dbs_data_mutex); 505 } 506 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_exit); 507 508 int cpufreq_dbs_governor_start(struct cpufreq_policy *policy) 509 { 510 struct dbs_governor *gov = dbs_governor_of(policy); 511 struct policy_dbs_info *policy_dbs = policy->governor_data; 512 struct dbs_data *dbs_data = policy_dbs->dbs_data; 513 unsigned int sampling_rate, ignore_nice, j; 514 unsigned int io_busy; 515 516 if (!policy->cur) 517 return -EINVAL; 518 519 policy_dbs->is_shared = policy_is_shared(policy); 520 policy_dbs->rate_mult = 1; 521 522 sampling_rate = dbs_data->sampling_rate; 523 ignore_nice = dbs_data->ignore_nice_load; 524 io_busy = dbs_data->io_is_busy; 525 526 for_each_cpu(j, policy->cpus) { 527 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); 528 529 j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_update_time, io_busy); 530 /* 531 * Make the first invocation of dbs_update() compute the load. 532 */ 533 j_cdbs->prev_load = 0; 534 535 if (ignore_nice) 536 j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE]; 537 } 538 539 gov->start(policy); 540 541 gov_set_update_util(policy_dbs, sampling_rate); 542 return 0; 543 } 544 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_start); 545 546 void cpufreq_dbs_governor_stop(struct cpufreq_policy *policy) 547 { 548 struct policy_dbs_info *policy_dbs = policy->governor_data; 549 550 gov_clear_update_util(policy_dbs->policy); 551 irq_work_sync(&policy_dbs->irq_work); 552 cancel_work_sync(&policy_dbs->work); 553 atomic_set(&policy_dbs->work_count, 0); 554 policy_dbs->work_in_progress = false; 555 } 556 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_stop); 557 558 void cpufreq_dbs_governor_limits(struct cpufreq_policy *policy) 559 { 560 struct policy_dbs_info *policy_dbs; 561 562 /* Protect gov->gdbs_data against cpufreq_dbs_governor_exit() */ 563 mutex_lock(&gov_dbs_data_mutex); 564 policy_dbs = policy->governor_data; 565 if (!policy_dbs) 566 goto out; 567 568 mutex_lock(&policy_dbs->update_mutex); 569 cpufreq_policy_apply_limits(policy); 570 gov_update_sample_delay(policy_dbs, 0); 571 mutex_unlock(&policy_dbs->update_mutex); 572 573 out: 574 mutex_unlock(&gov_dbs_data_mutex); 575 } 576 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_limits); 577