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/sched.h> 22 #include <linux/slab.h> 23 24 #include "cpufreq_governor.h" 25 26 static DEFINE_PER_CPU(struct cpu_dbs_info, cpu_dbs); 27 28 static DEFINE_MUTEX(gov_dbs_data_mutex); 29 30 /* Common sysfs tunables */ 31 /** 32 * store_sampling_rate - update sampling rate effective immediately if needed. 33 * 34 * If new rate is smaller than the old, simply updating 35 * dbs.sampling_rate might not be appropriate. For example, if the 36 * original sampling_rate was 1 second and the requested new sampling rate is 10 37 * ms because the user needs immediate reaction from ondemand governor, but not 38 * sure if higher frequency will be required or not, then, the governor may 39 * change the sampling rate too late; up to 1 second later. Thus, if we are 40 * reducing the sampling rate, we need to make the new value effective 41 * immediately. 42 * 43 * This must be called with dbs_data->mutex held, otherwise traversing 44 * policy_dbs_list isn't safe. 45 */ 46 ssize_t store_sampling_rate(struct gov_attr_set *attr_set, const char *buf, 47 size_t count) 48 { 49 struct dbs_data *dbs_data = to_dbs_data(attr_set); 50 struct policy_dbs_info *policy_dbs; 51 unsigned int rate; 52 int ret; 53 ret = sscanf(buf, "%u", &rate); 54 if (ret != 1) 55 return -EINVAL; 56 57 dbs_data->sampling_rate = max(rate, dbs_data->min_sampling_rate); 58 59 /* 60 * We are operating under dbs_data->mutex and so the list and its 61 * entries can't be freed concurrently. 62 */ 63 list_for_each_entry(policy_dbs, &attr_set->policy_list, list) { 64 mutex_lock(&policy_dbs->timer_mutex); 65 /* 66 * On 32-bit architectures this may race with the 67 * sample_delay_ns read in dbs_update_util_handler(), but that 68 * really doesn't matter. If the read returns a value that's 69 * too big, the sample will be skipped, but the next invocation 70 * of dbs_update_util_handler() (when the update has been 71 * completed) will take a sample. 72 * 73 * If this runs in parallel with dbs_work_handler(), we may end 74 * up overwriting the sample_delay_ns value that it has just 75 * written, but it will be corrected next time a sample is 76 * taken, so it shouldn't be significant. 77 */ 78 gov_update_sample_delay(policy_dbs, 0); 79 mutex_unlock(&policy_dbs->timer_mutex); 80 } 81 82 return count; 83 } 84 EXPORT_SYMBOL_GPL(store_sampling_rate); 85 86 /** 87 * gov_update_cpu_data - Update CPU load data. 88 * @dbs_data: Top-level governor data pointer. 89 * 90 * Update CPU load data for all CPUs in the domain governed by @dbs_data 91 * (that may be a single policy or a bunch of them if governor tunables are 92 * system-wide). 93 * 94 * Call under the @dbs_data mutex. 95 */ 96 void gov_update_cpu_data(struct dbs_data *dbs_data) 97 { 98 struct policy_dbs_info *policy_dbs; 99 100 list_for_each_entry(policy_dbs, &dbs_data->attr_set.policy_list, list) { 101 unsigned int j; 102 103 for_each_cpu(j, policy_dbs->policy->cpus) { 104 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); 105 106 j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_update_time, 107 dbs_data->io_is_busy); 108 if (dbs_data->ignore_nice_load) 109 j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE]; 110 } 111 } 112 } 113 EXPORT_SYMBOL_GPL(gov_update_cpu_data); 114 115 unsigned int dbs_update(struct cpufreq_policy *policy) 116 { 117 struct policy_dbs_info *policy_dbs = policy->governor_data; 118 struct dbs_data *dbs_data = policy_dbs->dbs_data; 119 unsigned int ignore_nice = dbs_data->ignore_nice_load; 120 unsigned int max_load = 0; 121 unsigned int sampling_rate, io_busy, j; 122 123 /* 124 * Sometimes governors may use an additional multiplier to increase 125 * sample delays temporarily. Apply that multiplier to sampling_rate 126 * so as to keep the wake-up-from-idle detection logic a bit 127 * conservative. 128 */ 129 sampling_rate = dbs_data->sampling_rate * policy_dbs->rate_mult; 130 /* 131 * For the purpose of ondemand, waiting for disk IO is an indication 132 * that you're performance critical, and not that the system is actually 133 * idle, so do not add the iowait time to the CPU idle time then. 134 */ 135 io_busy = dbs_data->io_is_busy; 136 137 /* Get Absolute Load */ 138 for_each_cpu(j, policy->cpus) { 139 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); 140 u64 update_time, cur_idle_time; 141 unsigned int idle_time, time_elapsed; 142 unsigned int load; 143 144 cur_idle_time = get_cpu_idle_time(j, &update_time, io_busy); 145 146 time_elapsed = update_time - j_cdbs->prev_update_time; 147 j_cdbs->prev_update_time = update_time; 148 149 idle_time = cur_idle_time - j_cdbs->prev_cpu_idle; 150 j_cdbs->prev_cpu_idle = cur_idle_time; 151 152 if (ignore_nice) { 153 u64 cur_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE]; 154 155 idle_time += cputime_to_usecs(cur_nice - j_cdbs->prev_cpu_nice); 156 j_cdbs->prev_cpu_nice = cur_nice; 157 } 158 159 if (unlikely(!time_elapsed)) { 160 /* 161 * That can only happen when this function is called 162 * twice in a row with a very short interval between the 163 * calls, so the previous load value can be used then. 164 */ 165 load = j_cdbs->prev_load; 166 } else if (unlikely(time_elapsed > 2 * sampling_rate && 167 j_cdbs->prev_load)) { 168 /* 169 * If the CPU had gone completely idle and a task has 170 * just woken up on this CPU now, it would be unfair to 171 * calculate 'load' the usual way for this elapsed 172 * time-window, because it would show near-zero load, 173 * irrespective of how CPU intensive that task actually 174 * was. This is undesirable for latency-sensitive bursty 175 * workloads. 176 * 177 * To avoid this, reuse the 'load' from the previous 178 * time-window and give this task a chance to start with 179 * a reasonably high CPU frequency. However, that 180 * shouldn't be over-done, lest we get stuck at a high 181 * load (high frequency) for too long, even when the 182 * current system load has actually dropped down, so 183 * clear prev_load to guarantee that the load will be 184 * computed again next time. 185 * 186 * Detecting this situation is easy: the governor's 187 * utilization update handler would not have run during 188 * CPU-idle periods. Hence, an unusually large 189 * 'time_elapsed' (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 (load > max_load) 219 max_load = load; 220 } 221 return max_load; 222 } 223 EXPORT_SYMBOL_GPL(dbs_update); 224 225 static void dbs_work_handler(struct work_struct *work) 226 { 227 struct policy_dbs_info *policy_dbs; 228 struct cpufreq_policy *policy; 229 struct dbs_governor *gov; 230 231 policy_dbs = container_of(work, struct policy_dbs_info, work); 232 policy = policy_dbs->policy; 233 gov = dbs_governor_of(policy); 234 235 /* 236 * Make sure cpufreq_governor_limits() isn't evaluating load or the 237 * ondemand governor isn't updating the sampling rate in parallel. 238 */ 239 mutex_lock(&policy_dbs->timer_mutex); 240 gov_update_sample_delay(policy_dbs, gov->gov_dbs_timer(policy)); 241 mutex_unlock(&policy_dbs->timer_mutex); 242 243 /* Allow the utilization update handler to queue up more work. */ 244 atomic_set(&policy_dbs->work_count, 0); 245 /* 246 * If the update below is reordered with respect to the sample delay 247 * modification, the utilization update handler may end up using a stale 248 * sample delay value. 249 */ 250 smp_wmb(); 251 policy_dbs->work_in_progress = false; 252 } 253 254 static void dbs_irq_work(struct irq_work *irq_work) 255 { 256 struct policy_dbs_info *policy_dbs; 257 258 policy_dbs = container_of(irq_work, struct policy_dbs_info, irq_work); 259 schedule_work_on(smp_processor_id(), &policy_dbs->work); 260 } 261 262 static void dbs_update_util_handler(struct update_util_data *data, u64 time, 263 unsigned int flags) 264 { 265 struct cpu_dbs_info *cdbs = container_of(data, struct cpu_dbs_info, update_util); 266 struct policy_dbs_info *policy_dbs = cdbs->policy_dbs; 267 u64 delta_ns, lst; 268 269 /* 270 * The work may not be allowed to be queued up right now. 271 * Possible reasons: 272 * - Work has already been queued up or is in progress. 273 * - It is too early (too little time from the previous sample). 274 */ 275 if (policy_dbs->work_in_progress) 276 return; 277 278 /* 279 * If the reads below are reordered before the check above, the value 280 * of sample_delay_ns used in the computation may be stale. 281 */ 282 smp_rmb(); 283 lst = READ_ONCE(policy_dbs->last_sample_time); 284 delta_ns = time - lst; 285 if ((s64)delta_ns < policy_dbs->sample_delay_ns) 286 return; 287 288 /* 289 * If the policy is not shared, the irq_work may be queued up right away 290 * at this point. Otherwise, we need to ensure that only one of the 291 * CPUs sharing the policy will do that. 292 */ 293 if (policy_dbs->is_shared) { 294 if (!atomic_add_unless(&policy_dbs->work_count, 1, 1)) 295 return; 296 297 /* 298 * If another CPU updated last_sample_time in the meantime, we 299 * shouldn't be here, so clear the work counter and bail out. 300 */ 301 if (unlikely(lst != READ_ONCE(policy_dbs->last_sample_time))) { 302 atomic_set(&policy_dbs->work_count, 0); 303 return; 304 } 305 } 306 307 policy_dbs->last_sample_time = time; 308 policy_dbs->work_in_progress = true; 309 irq_work_queue(&policy_dbs->irq_work); 310 } 311 312 static void gov_set_update_util(struct policy_dbs_info *policy_dbs, 313 unsigned int delay_us) 314 { 315 struct cpufreq_policy *policy = policy_dbs->policy; 316 int cpu; 317 318 gov_update_sample_delay(policy_dbs, delay_us); 319 policy_dbs->last_sample_time = 0; 320 321 for_each_cpu(cpu, policy->cpus) { 322 struct cpu_dbs_info *cdbs = &per_cpu(cpu_dbs, cpu); 323 324 cpufreq_add_update_util_hook(cpu, &cdbs->update_util, 325 dbs_update_util_handler); 326 } 327 } 328 329 static inline void gov_clear_update_util(struct cpufreq_policy *policy) 330 { 331 int i; 332 333 for_each_cpu(i, policy->cpus) 334 cpufreq_remove_update_util_hook(i); 335 336 synchronize_sched(); 337 } 338 339 static struct policy_dbs_info *alloc_policy_dbs_info(struct cpufreq_policy *policy, 340 struct dbs_governor *gov) 341 { 342 struct policy_dbs_info *policy_dbs; 343 int j; 344 345 /* Allocate memory for per-policy governor data. */ 346 policy_dbs = gov->alloc(); 347 if (!policy_dbs) 348 return NULL; 349 350 policy_dbs->policy = policy; 351 mutex_init(&policy_dbs->timer_mutex); 352 atomic_set(&policy_dbs->work_count, 0); 353 init_irq_work(&policy_dbs->irq_work, dbs_irq_work); 354 INIT_WORK(&policy_dbs->work, dbs_work_handler); 355 356 /* Set policy_dbs for all CPUs, online+offline */ 357 for_each_cpu(j, policy->related_cpus) { 358 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); 359 360 j_cdbs->policy_dbs = policy_dbs; 361 } 362 return policy_dbs; 363 } 364 365 static void free_policy_dbs_info(struct policy_dbs_info *policy_dbs, 366 struct dbs_governor *gov) 367 { 368 int j; 369 370 mutex_destroy(&policy_dbs->timer_mutex); 371 372 for_each_cpu(j, policy_dbs->policy->related_cpus) { 373 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); 374 375 j_cdbs->policy_dbs = NULL; 376 j_cdbs->update_util.func = NULL; 377 } 378 gov->free(policy_dbs); 379 } 380 381 int cpufreq_dbs_governor_init(struct cpufreq_policy *policy) 382 { 383 struct dbs_governor *gov = dbs_governor_of(policy); 384 struct dbs_data *dbs_data; 385 struct policy_dbs_info *policy_dbs; 386 unsigned int latency; 387 int ret = 0; 388 389 /* State should be equivalent to EXIT */ 390 if (policy->governor_data) 391 return -EBUSY; 392 393 policy_dbs = alloc_policy_dbs_info(policy, gov); 394 if (!policy_dbs) 395 return -ENOMEM; 396 397 /* Protect gov->gdbs_data against concurrent updates. */ 398 mutex_lock(&gov_dbs_data_mutex); 399 400 dbs_data = gov->gdbs_data; 401 if (dbs_data) { 402 if (WARN_ON(have_governor_per_policy())) { 403 ret = -EINVAL; 404 goto free_policy_dbs_info; 405 } 406 policy_dbs->dbs_data = dbs_data; 407 policy->governor_data = policy_dbs; 408 409 gov_attr_set_get(&dbs_data->attr_set, &policy_dbs->list); 410 goto out; 411 } 412 413 dbs_data = kzalloc(sizeof(*dbs_data), GFP_KERNEL); 414 if (!dbs_data) { 415 ret = -ENOMEM; 416 goto free_policy_dbs_info; 417 } 418 419 gov_attr_set_init(&dbs_data->attr_set, &policy_dbs->list); 420 421 ret = gov->init(dbs_data); 422 if (ret) 423 goto free_policy_dbs_info; 424 425 /* policy latency is in ns. Convert it to us first */ 426 latency = policy->cpuinfo.transition_latency / 1000; 427 if (latency == 0) 428 latency = 1; 429 430 /* Bring kernel and HW constraints together */ 431 dbs_data->min_sampling_rate = max(dbs_data->min_sampling_rate, 432 MIN_LATENCY_MULTIPLIER * latency); 433 dbs_data->sampling_rate = max(dbs_data->min_sampling_rate, 434 LATENCY_MULTIPLIER * latency); 435 436 if (!have_governor_per_policy()) 437 gov->gdbs_data = dbs_data; 438 439 policy_dbs->dbs_data = dbs_data; 440 policy->governor_data = policy_dbs; 441 442 gov->kobj_type.sysfs_ops = &governor_sysfs_ops; 443 ret = kobject_init_and_add(&dbs_data->attr_set.kobj, &gov->kobj_type, 444 get_governor_parent_kobj(policy), 445 "%s", gov->gov.name); 446 if (!ret) 447 goto out; 448 449 /* Failure, so roll back. */ 450 pr_err("initialization failed (dbs_data kobject init error %d)\n", ret); 451 452 policy->governor_data = NULL; 453 454 if (!have_governor_per_policy()) 455 gov->gdbs_data = NULL; 456 gov->exit(dbs_data); 457 kfree(dbs_data); 458 459 free_policy_dbs_info: 460 free_policy_dbs_info(policy_dbs, gov); 461 462 out: 463 mutex_unlock(&gov_dbs_data_mutex); 464 return ret; 465 } 466 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_init); 467 468 void cpufreq_dbs_governor_exit(struct cpufreq_policy *policy) 469 { 470 struct dbs_governor *gov = dbs_governor_of(policy); 471 struct policy_dbs_info *policy_dbs = policy->governor_data; 472 struct dbs_data *dbs_data = policy_dbs->dbs_data; 473 unsigned int count; 474 475 /* Protect gov->gdbs_data against concurrent updates. */ 476 mutex_lock(&gov_dbs_data_mutex); 477 478 count = gov_attr_set_put(&dbs_data->attr_set, &policy_dbs->list); 479 480 policy->governor_data = NULL; 481 482 if (!count) { 483 if (!have_governor_per_policy()) 484 gov->gdbs_data = NULL; 485 486 gov->exit(dbs_data); 487 kfree(dbs_data); 488 } 489 490 free_policy_dbs_info(policy_dbs, gov); 491 492 mutex_unlock(&gov_dbs_data_mutex); 493 } 494 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_exit); 495 496 int cpufreq_dbs_governor_start(struct cpufreq_policy *policy) 497 { 498 struct dbs_governor *gov = dbs_governor_of(policy); 499 struct policy_dbs_info *policy_dbs = policy->governor_data; 500 struct dbs_data *dbs_data = policy_dbs->dbs_data; 501 unsigned int sampling_rate, ignore_nice, j; 502 unsigned int io_busy; 503 504 if (!policy->cur) 505 return -EINVAL; 506 507 policy_dbs->is_shared = policy_is_shared(policy); 508 policy_dbs->rate_mult = 1; 509 510 sampling_rate = dbs_data->sampling_rate; 511 ignore_nice = dbs_data->ignore_nice_load; 512 io_busy = dbs_data->io_is_busy; 513 514 for_each_cpu(j, policy->cpus) { 515 struct cpu_dbs_info *j_cdbs = &per_cpu(cpu_dbs, j); 516 517 j_cdbs->prev_cpu_idle = get_cpu_idle_time(j, &j_cdbs->prev_update_time, io_busy); 518 /* 519 * Make the first invocation of dbs_update() compute the load. 520 */ 521 j_cdbs->prev_load = 0; 522 523 if (ignore_nice) 524 j_cdbs->prev_cpu_nice = kcpustat_cpu(j).cpustat[CPUTIME_NICE]; 525 } 526 527 gov->start(policy); 528 529 gov_set_update_util(policy_dbs, sampling_rate); 530 return 0; 531 } 532 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_start); 533 534 void cpufreq_dbs_governor_stop(struct cpufreq_policy *policy) 535 { 536 struct policy_dbs_info *policy_dbs = policy->governor_data; 537 538 gov_clear_update_util(policy_dbs->policy); 539 irq_work_sync(&policy_dbs->irq_work); 540 cancel_work_sync(&policy_dbs->work); 541 atomic_set(&policy_dbs->work_count, 0); 542 policy_dbs->work_in_progress = false; 543 } 544 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_stop); 545 546 void cpufreq_dbs_governor_limits(struct cpufreq_policy *policy) 547 { 548 struct policy_dbs_info *policy_dbs = policy->governor_data; 549 550 mutex_lock(&policy_dbs->timer_mutex); 551 cpufreq_policy_apply_limits(policy); 552 gov_update_sample_delay(policy_dbs, 0); 553 554 mutex_unlock(&policy_dbs->timer_mutex); 555 } 556 EXPORT_SYMBOL_GPL(cpufreq_dbs_governor_limits); 557