1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Pressure stall information for CPU, memory and IO 4 * 5 * Copyright (c) 2018 Facebook, Inc. 6 * Author: Johannes Weiner <hannes@cmpxchg.org> 7 * 8 * Polling support by Suren Baghdasaryan <surenb@google.com> 9 * Copyright (c) 2018 Google, Inc. 10 * 11 * When CPU, memory and IO are contended, tasks experience delays that 12 * reduce throughput and introduce latencies into the workload. Memory 13 * and IO contention, in addition, can cause a full loss of forward 14 * progress in which the CPU goes idle. 15 * 16 * This code aggregates individual task delays into resource pressure 17 * metrics that indicate problems with both workload health and 18 * resource utilization. 19 * 20 * Model 21 * 22 * The time in which a task can execute on a CPU is our baseline for 23 * productivity. Pressure expresses the amount of time in which this 24 * potential cannot be realized due to resource contention. 25 * 26 * This concept of productivity has two components: the workload and 27 * the CPU. To measure the impact of pressure on both, we define two 28 * contention states for a resource: SOME and FULL. 29 * 30 * In the SOME state of a given resource, one or more tasks are 31 * delayed on that resource. This affects the workload's ability to 32 * perform work, but the CPU may still be executing other tasks. 33 * 34 * In the FULL state of a given resource, all non-idle tasks are 35 * delayed on that resource such that nobody is advancing and the CPU 36 * goes idle. This leaves both workload and CPU unproductive. 37 * 38 * SOME = nr_delayed_tasks != 0 39 * FULL = nr_delayed_tasks != 0 && nr_productive_tasks == 0 40 * 41 * What it means for a task to be productive is defined differently 42 * for each resource. For IO, productive means a running task. For 43 * memory, productive means a running task that isn't a reclaimer. For 44 * CPU, productive means an oncpu task. 45 * 46 * Naturally, the FULL state doesn't exist for the CPU resource at the 47 * system level, but exist at the cgroup level. At the cgroup level, 48 * FULL means all non-idle tasks in the cgroup are delayed on the CPU 49 * resource which is being used by others outside of the cgroup or 50 * throttled by the cgroup cpu.max configuration. 51 * 52 * The percentage of wallclock time spent in those compound stall 53 * states gives pressure numbers between 0 and 100 for each resource, 54 * where the SOME percentage indicates workload slowdowns and the FULL 55 * percentage indicates reduced CPU utilization: 56 * 57 * %SOME = time(SOME) / period 58 * %FULL = time(FULL) / period 59 * 60 * Multiple CPUs 61 * 62 * The more tasks and available CPUs there are, the more work can be 63 * performed concurrently. This means that the potential that can go 64 * unrealized due to resource contention *also* scales with non-idle 65 * tasks and CPUs. 66 * 67 * Consider a scenario where 257 number crunching tasks are trying to 68 * run concurrently on 256 CPUs. If we simply aggregated the task 69 * states, we would have to conclude a CPU SOME pressure number of 70 * 100%, since *somebody* is waiting on a runqueue at all 71 * times. However, that is clearly not the amount of contention the 72 * workload is experiencing: only one out of 256 possible execution 73 * threads will be contended at any given time, or about 0.4%. 74 * 75 * Conversely, consider a scenario of 4 tasks and 4 CPUs where at any 76 * given time *one* of the tasks is delayed due to a lack of memory. 77 * Again, looking purely at the task state would yield a memory FULL 78 * pressure number of 0%, since *somebody* is always making forward 79 * progress. But again this wouldn't capture the amount of execution 80 * potential lost, which is 1 out of 4 CPUs, or 25%. 81 * 82 * To calculate wasted potential (pressure) with multiple processors, 83 * we have to base our calculation on the number of non-idle tasks in 84 * conjunction with the number of available CPUs, which is the number 85 * of potential execution threads. SOME becomes then the proportion of 86 * delayed tasks to possible threads, and FULL is the share of possible 87 * threads that are unproductive due to delays: 88 * 89 * threads = min(nr_nonidle_tasks, nr_cpus) 90 * SOME = min(nr_delayed_tasks / threads, 1) 91 * FULL = (threads - min(nr_productive_tasks, threads)) / threads 92 * 93 * For the 257 number crunchers on 256 CPUs, this yields: 94 * 95 * threads = min(257, 256) 96 * SOME = min(1 / 256, 1) = 0.4% 97 * FULL = (256 - min(256, 256)) / 256 = 0% 98 * 99 * For the 1 out of 4 memory-delayed tasks, this yields: 100 * 101 * threads = min(4, 4) 102 * SOME = min(1 / 4, 1) = 25% 103 * FULL = (4 - min(3, 4)) / 4 = 25% 104 * 105 * [ Substitute nr_cpus with 1, and you can see that it's a natural 106 * extension of the single-CPU model. ] 107 * 108 * Implementation 109 * 110 * To assess the precise time spent in each such state, we would have 111 * to freeze the system on task changes and start/stop the state 112 * clocks accordingly. Obviously that doesn't scale in practice. 113 * 114 * Because the scheduler aims to distribute the compute load evenly 115 * among the available CPUs, we can track task state locally to each 116 * CPU and, at much lower frequency, extrapolate the global state for 117 * the cumulative stall times and the running averages. 118 * 119 * For each runqueue, we track: 120 * 121 * tSOME[cpu] = time(nr_delayed_tasks[cpu] != 0) 122 * tFULL[cpu] = time(nr_delayed_tasks[cpu] && !nr_productive_tasks[cpu]) 123 * tNONIDLE[cpu] = time(nr_nonidle_tasks[cpu] != 0) 124 * 125 * and then periodically aggregate: 126 * 127 * tNONIDLE = sum(tNONIDLE[i]) 128 * 129 * tSOME = sum(tSOME[i] * tNONIDLE[i]) / tNONIDLE 130 * tFULL = sum(tFULL[i] * tNONIDLE[i]) / tNONIDLE 131 * 132 * %SOME = tSOME / period 133 * %FULL = tFULL / period 134 * 135 * This gives us an approximation of pressure that is practical 136 * cost-wise, yet way more sensitive and accurate than periodic 137 * sampling of the aggregate task states would be. 138 */ 139 140 static int psi_bug __read_mostly; 141 142 DEFINE_STATIC_KEY_FALSE(psi_disabled); 143 DEFINE_STATIC_KEY_TRUE(psi_cgroups_enabled); 144 145 #ifdef CONFIG_PSI_DEFAULT_DISABLED 146 static bool psi_enable; 147 #else 148 static bool psi_enable = true; 149 #endif 150 static int __init setup_psi(char *str) 151 { 152 return kstrtobool(str, &psi_enable) == 0; 153 } 154 __setup("psi=", setup_psi); 155 156 /* Running averages - we need to be higher-res than loadavg */ 157 #define PSI_FREQ (2*HZ+1) /* 2 sec intervals */ 158 #define EXP_10s 1677 /* 1/exp(2s/10s) as fixed-point */ 159 #define EXP_60s 1981 /* 1/exp(2s/60s) */ 160 #define EXP_300s 2034 /* 1/exp(2s/300s) */ 161 162 /* PSI trigger definitions */ 163 #define WINDOW_MIN_US 500000 /* Min window size is 500ms */ 164 #define WINDOW_MAX_US 10000000 /* Max window size is 10s */ 165 #define UPDATES_PER_WINDOW 10 /* 10 updates per window */ 166 167 /* Sampling frequency in nanoseconds */ 168 static u64 psi_period __read_mostly; 169 170 /* System-level pressure and stall tracking */ 171 static DEFINE_PER_CPU(struct psi_group_cpu, system_group_pcpu); 172 struct psi_group psi_system = { 173 .pcpu = &system_group_pcpu, 174 }; 175 176 static void psi_avgs_work(struct work_struct *work); 177 178 static void poll_timer_fn(struct timer_list *t); 179 180 static void group_init(struct psi_group *group) 181 { 182 int cpu; 183 184 for_each_possible_cpu(cpu) 185 seqcount_init(&per_cpu_ptr(group->pcpu, cpu)->seq); 186 group->avg_last_update = sched_clock(); 187 group->avg_next_update = group->avg_last_update + psi_period; 188 INIT_DELAYED_WORK(&group->avgs_work, psi_avgs_work); 189 mutex_init(&group->avgs_lock); 190 /* Init trigger-related members */ 191 mutex_init(&group->trigger_lock); 192 INIT_LIST_HEAD(&group->triggers); 193 group->poll_min_period = U32_MAX; 194 group->polling_next_update = ULLONG_MAX; 195 init_waitqueue_head(&group->poll_wait); 196 timer_setup(&group->poll_timer, poll_timer_fn, 0); 197 rcu_assign_pointer(group->poll_task, NULL); 198 } 199 200 void __init psi_init(void) 201 { 202 if (!psi_enable) { 203 static_branch_enable(&psi_disabled); 204 return; 205 } 206 207 if (!cgroup_psi_enabled()) 208 static_branch_disable(&psi_cgroups_enabled); 209 210 psi_period = jiffies_to_nsecs(PSI_FREQ); 211 group_init(&psi_system); 212 } 213 214 static bool test_state(unsigned int *tasks, enum psi_states state) 215 { 216 switch (state) { 217 case PSI_IO_SOME: 218 return unlikely(tasks[NR_IOWAIT]); 219 case PSI_IO_FULL: 220 return unlikely(tasks[NR_IOWAIT] && !tasks[NR_RUNNING]); 221 case PSI_MEM_SOME: 222 return unlikely(tasks[NR_MEMSTALL]); 223 case PSI_MEM_FULL: 224 return unlikely(tasks[NR_MEMSTALL] && 225 tasks[NR_RUNNING] == tasks[NR_MEMSTALL_RUNNING]); 226 case PSI_CPU_SOME: 227 return unlikely(tasks[NR_RUNNING] > tasks[NR_ONCPU]); 228 case PSI_CPU_FULL: 229 return unlikely(tasks[NR_RUNNING] && !tasks[NR_ONCPU]); 230 case PSI_NONIDLE: 231 return tasks[NR_IOWAIT] || tasks[NR_MEMSTALL] || 232 tasks[NR_RUNNING]; 233 default: 234 return false; 235 } 236 } 237 238 static void get_recent_times(struct psi_group *group, int cpu, 239 enum psi_aggregators aggregator, u32 *times, 240 u32 *pchanged_states) 241 { 242 struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu); 243 u64 now, state_start; 244 enum psi_states s; 245 unsigned int seq; 246 u32 state_mask; 247 248 *pchanged_states = 0; 249 250 /* Snapshot a coherent view of the CPU state */ 251 do { 252 seq = read_seqcount_begin(&groupc->seq); 253 now = cpu_clock(cpu); 254 memcpy(times, groupc->times, sizeof(groupc->times)); 255 state_mask = groupc->state_mask; 256 state_start = groupc->state_start; 257 } while (read_seqcount_retry(&groupc->seq, seq)); 258 259 /* Calculate state time deltas against the previous snapshot */ 260 for (s = 0; s < NR_PSI_STATES; s++) { 261 u32 delta; 262 /* 263 * In addition to already concluded states, we also 264 * incorporate currently active states on the CPU, 265 * since states may last for many sampling periods. 266 * 267 * This way we keep our delta sampling buckets small 268 * (u32) and our reported pressure close to what's 269 * actually happening. 270 */ 271 if (state_mask & (1 << s)) 272 times[s] += now - state_start; 273 274 delta = times[s] - groupc->times_prev[aggregator][s]; 275 groupc->times_prev[aggregator][s] = times[s]; 276 277 times[s] = delta; 278 if (delta) 279 *pchanged_states |= (1 << s); 280 } 281 } 282 283 static void calc_avgs(unsigned long avg[3], int missed_periods, 284 u64 time, u64 period) 285 { 286 unsigned long pct; 287 288 /* Fill in zeroes for periods of no activity */ 289 if (missed_periods) { 290 avg[0] = calc_load_n(avg[0], EXP_10s, 0, missed_periods); 291 avg[1] = calc_load_n(avg[1], EXP_60s, 0, missed_periods); 292 avg[2] = calc_load_n(avg[2], EXP_300s, 0, missed_periods); 293 } 294 295 /* Sample the most recent active period */ 296 pct = div_u64(time * 100, period); 297 pct *= FIXED_1; 298 avg[0] = calc_load(avg[0], EXP_10s, pct); 299 avg[1] = calc_load(avg[1], EXP_60s, pct); 300 avg[2] = calc_load(avg[2], EXP_300s, pct); 301 } 302 303 static void collect_percpu_times(struct psi_group *group, 304 enum psi_aggregators aggregator, 305 u32 *pchanged_states) 306 { 307 u64 deltas[NR_PSI_STATES - 1] = { 0, }; 308 unsigned long nonidle_total = 0; 309 u32 changed_states = 0; 310 int cpu; 311 int s; 312 313 /* 314 * Collect the per-cpu time buckets and average them into a 315 * single time sample that is normalized to wallclock time. 316 * 317 * For averaging, each CPU is weighted by its non-idle time in 318 * the sampling period. This eliminates artifacts from uneven 319 * loading, or even entirely idle CPUs. 320 */ 321 for_each_possible_cpu(cpu) { 322 u32 times[NR_PSI_STATES]; 323 u32 nonidle; 324 u32 cpu_changed_states; 325 326 get_recent_times(group, cpu, aggregator, times, 327 &cpu_changed_states); 328 changed_states |= cpu_changed_states; 329 330 nonidle = nsecs_to_jiffies(times[PSI_NONIDLE]); 331 nonidle_total += nonidle; 332 333 for (s = 0; s < PSI_NONIDLE; s++) 334 deltas[s] += (u64)times[s] * nonidle; 335 } 336 337 /* 338 * Integrate the sample into the running statistics that are 339 * reported to userspace: the cumulative stall times and the 340 * decaying averages. 341 * 342 * Pressure percentages are sampled at PSI_FREQ. We might be 343 * called more often when the user polls more frequently than 344 * that; we might be called less often when there is no task 345 * activity, thus no data, and clock ticks are sporadic. The 346 * below handles both. 347 */ 348 349 /* total= */ 350 for (s = 0; s < NR_PSI_STATES - 1; s++) 351 group->total[aggregator][s] += 352 div_u64(deltas[s], max(nonidle_total, 1UL)); 353 354 if (pchanged_states) 355 *pchanged_states = changed_states; 356 } 357 358 static u64 update_averages(struct psi_group *group, u64 now) 359 { 360 unsigned long missed_periods = 0; 361 u64 expires, period; 362 u64 avg_next_update; 363 int s; 364 365 /* avgX= */ 366 expires = group->avg_next_update; 367 if (now - expires >= psi_period) 368 missed_periods = div_u64(now - expires, psi_period); 369 370 /* 371 * The periodic clock tick can get delayed for various 372 * reasons, especially on loaded systems. To avoid clock 373 * drift, we schedule the clock in fixed psi_period intervals. 374 * But the deltas we sample out of the per-cpu buckets above 375 * are based on the actual time elapsing between clock ticks. 376 */ 377 avg_next_update = expires + ((1 + missed_periods) * psi_period); 378 period = now - (group->avg_last_update + (missed_periods * psi_period)); 379 group->avg_last_update = now; 380 381 for (s = 0; s < NR_PSI_STATES - 1; s++) { 382 u32 sample; 383 384 sample = group->total[PSI_AVGS][s] - group->avg_total[s]; 385 /* 386 * Due to the lockless sampling of the time buckets, 387 * recorded time deltas can slip into the next period, 388 * which under full pressure can result in samples in 389 * excess of the period length. 390 * 391 * We don't want to report non-sensical pressures in 392 * excess of 100%, nor do we want to drop such events 393 * on the floor. Instead we punt any overage into the 394 * future until pressure subsides. By doing this we 395 * don't underreport the occurring pressure curve, we 396 * just report it delayed by one period length. 397 * 398 * The error isn't cumulative. As soon as another 399 * delta slips from a period P to P+1, by definition 400 * it frees up its time T in P. 401 */ 402 if (sample > period) 403 sample = period; 404 group->avg_total[s] += sample; 405 calc_avgs(group->avg[s], missed_periods, sample, period); 406 } 407 408 return avg_next_update; 409 } 410 411 static void psi_avgs_work(struct work_struct *work) 412 { 413 struct delayed_work *dwork; 414 struct psi_group *group; 415 u32 changed_states; 416 bool nonidle; 417 u64 now; 418 419 dwork = to_delayed_work(work); 420 group = container_of(dwork, struct psi_group, avgs_work); 421 422 mutex_lock(&group->avgs_lock); 423 424 now = sched_clock(); 425 426 collect_percpu_times(group, PSI_AVGS, &changed_states); 427 nonidle = changed_states & (1 << PSI_NONIDLE); 428 /* 429 * If there is task activity, periodically fold the per-cpu 430 * times and feed samples into the running averages. If things 431 * are idle and there is no data to process, stop the clock. 432 * Once restarted, we'll catch up the running averages in one 433 * go - see calc_avgs() and missed_periods. 434 */ 435 if (now >= group->avg_next_update) 436 group->avg_next_update = update_averages(group, now); 437 438 if (nonidle) { 439 schedule_delayed_work(dwork, nsecs_to_jiffies( 440 group->avg_next_update - now) + 1); 441 } 442 443 mutex_unlock(&group->avgs_lock); 444 } 445 446 /* Trigger tracking window manipulations */ 447 static void window_reset(struct psi_window *win, u64 now, u64 value, 448 u64 prev_growth) 449 { 450 win->start_time = now; 451 win->start_value = value; 452 win->prev_growth = prev_growth; 453 } 454 455 /* 456 * PSI growth tracking window update and growth calculation routine. 457 * 458 * This approximates a sliding tracking window by interpolating 459 * partially elapsed windows using historical growth data from the 460 * previous intervals. This minimizes memory requirements (by not storing 461 * all the intermediate values in the previous window) and simplifies 462 * the calculations. It works well because PSI signal changes only in 463 * positive direction and over relatively small window sizes the growth 464 * is close to linear. 465 */ 466 static u64 window_update(struct psi_window *win, u64 now, u64 value) 467 { 468 u64 elapsed; 469 u64 growth; 470 471 elapsed = now - win->start_time; 472 growth = value - win->start_value; 473 /* 474 * After each tracking window passes win->start_value and 475 * win->start_time get reset and win->prev_growth stores 476 * the average per-window growth of the previous window. 477 * win->prev_growth is then used to interpolate additional 478 * growth from the previous window assuming it was linear. 479 */ 480 if (elapsed > win->size) 481 window_reset(win, now, value, growth); 482 else { 483 u32 remaining; 484 485 remaining = win->size - elapsed; 486 growth += div64_u64(win->prev_growth * remaining, win->size); 487 } 488 489 return growth; 490 } 491 492 static void init_triggers(struct psi_group *group, u64 now) 493 { 494 struct psi_trigger *t; 495 496 list_for_each_entry(t, &group->triggers, node) 497 window_reset(&t->win, now, 498 group->total[PSI_POLL][t->state], 0); 499 memcpy(group->polling_total, group->total[PSI_POLL], 500 sizeof(group->polling_total)); 501 group->polling_next_update = now + group->poll_min_period; 502 } 503 504 static u64 update_triggers(struct psi_group *group, u64 now) 505 { 506 struct psi_trigger *t; 507 bool update_total = false; 508 u64 *total = group->total[PSI_POLL]; 509 510 /* 511 * On subsequent updates, calculate growth deltas and let 512 * watchers know when their specified thresholds are exceeded. 513 */ 514 list_for_each_entry(t, &group->triggers, node) { 515 u64 growth; 516 bool new_stall; 517 518 new_stall = group->polling_total[t->state] != total[t->state]; 519 520 /* Check for stall activity or a previous threshold breach */ 521 if (!new_stall && !t->pending_event) 522 continue; 523 /* 524 * Check for new stall activity, as well as deferred 525 * events that occurred in the last window after the 526 * trigger had already fired (we want to ratelimit 527 * events without dropping any). 528 */ 529 if (new_stall) { 530 /* 531 * Multiple triggers might be looking at the same state, 532 * remember to update group->polling_total[] once we've 533 * been through all of them. Also remember to extend the 534 * polling time if we see new stall activity. 535 */ 536 update_total = true; 537 538 /* Calculate growth since last update */ 539 growth = window_update(&t->win, now, total[t->state]); 540 if (growth < t->threshold) 541 continue; 542 543 t->pending_event = true; 544 } 545 /* Limit event signaling to once per window */ 546 if (now < t->last_event_time + t->win.size) 547 continue; 548 549 /* Generate an event */ 550 if (cmpxchg(&t->event, 0, 1) == 0) 551 wake_up_interruptible(&t->event_wait); 552 t->last_event_time = now; 553 /* Reset threshold breach flag once event got generated */ 554 t->pending_event = false; 555 } 556 557 if (update_total) 558 memcpy(group->polling_total, total, 559 sizeof(group->polling_total)); 560 561 return now + group->poll_min_period; 562 } 563 564 /* Schedule polling if it's not already scheduled. */ 565 static void psi_schedule_poll_work(struct psi_group *group, unsigned long delay) 566 { 567 struct task_struct *task; 568 569 /* 570 * Do not reschedule if already scheduled. 571 * Possible race with a timer scheduled after this check but before 572 * mod_timer below can be tolerated because group->polling_next_update 573 * will keep updates on schedule. 574 */ 575 if (timer_pending(&group->poll_timer)) 576 return; 577 578 rcu_read_lock(); 579 580 task = rcu_dereference(group->poll_task); 581 /* 582 * kworker might be NULL in case psi_trigger_destroy races with 583 * psi_task_change (hotpath) which can't use locks 584 */ 585 if (likely(task)) 586 mod_timer(&group->poll_timer, jiffies + delay); 587 588 rcu_read_unlock(); 589 } 590 591 static void psi_poll_work(struct psi_group *group) 592 { 593 u32 changed_states; 594 u64 now; 595 596 mutex_lock(&group->trigger_lock); 597 598 now = sched_clock(); 599 600 collect_percpu_times(group, PSI_POLL, &changed_states); 601 602 if (changed_states & group->poll_states) { 603 /* Initialize trigger windows when entering polling mode */ 604 if (now > group->polling_until) 605 init_triggers(group, now); 606 607 /* 608 * Keep the monitor active for at least the duration of the 609 * minimum tracking window as long as monitor states are 610 * changing. 611 */ 612 group->polling_until = now + 613 group->poll_min_period * UPDATES_PER_WINDOW; 614 } 615 616 if (now > group->polling_until) { 617 group->polling_next_update = ULLONG_MAX; 618 goto out; 619 } 620 621 if (now >= group->polling_next_update) 622 group->polling_next_update = update_triggers(group, now); 623 624 psi_schedule_poll_work(group, 625 nsecs_to_jiffies(group->polling_next_update - now) + 1); 626 627 out: 628 mutex_unlock(&group->trigger_lock); 629 } 630 631 static int psi_poll_worker(void *data) 632 { 633 struct psi_group *group = (struct psi_group *)data; 634 635 sched_set_fifo_low(current); 636 637 while (true) { 638 wait_event_interruptible(group->poll_wait, 639 atomic_cmpxchg(&group->poll_wakeup, 1, 0) || 640 kthread_should_stop()); 641 if (kthread_should_stop()) 642 break; 643 644 psi_poll_work(group); 645 } 646 return 0; 647 } 648 649 static void poll_timer_fn(struct timer_list *t) 650 { 651 struct psi_group *group = from_timer(group, t, poll_timer); 652 653 atomic_set(&group->poll_wakeup, 1); 654 wake_up_interruptible(&group->poll_wait); 655 } 656 657 static void record_times(struct psi_group_cpu *groupc, u64 now) 658 { 659 u32 delta; 660 661 delta = now - groupc->state_start; 662 groupc->state_start = now; 663 664 if (groupc->state_mask & (1 << PSI_IO_SOME)) { 665 groupc->times[PSI_IO_SOME] += delta; 666 if (groupc->state_mask & (1 << PSI_IO_FULL)) 667 groupc->times[PSI_IO_FULL] += delta; 668 } 669 670 if (groupc->state_mask & (1 << PSI_MEM_SOME)) { 671 groupc->times[PSI_MEM_SOME] += delta; 672 if (groupc->state_mask & (1 << PSI_MEM_FULL)) 673 groupc->times[PSI_MEM_FULL] += delta; 674 } 675 676 if (groupc->state_mask & (1 << PSI_CPU_SOME)) { 677 groupc->times[PSI_CPU_SOME] += delta; 678 if (groupc->state_mask & (1 << PSI_CPU_FULL)) 679 groupc->times[PSI_CPU_FULL] += delta; 680 } 681 682 if (groupc->state_mask & (1 << PSI_NONIDLE)) 683 groupc->times[PSI_NONIDLE] += delta; 684 } 685 686 static void psi_group_change(struct psi_group *group, int cpu, 687 unsigned int clear, unsigned int set, u64 now, 688 bool wake_clock) 689 { 690 struct psi_group_cpu *groupc; 691 u32 state_mask = 0; 692 unsigned int t, m; 693 enum psi_states s; 694 695 groupc = per_cpu_ptr(group->pcpu, cpu); 696 697 /* 698 * First we assess the aggregate resource states this CPU's 699 * tasks have been in since the last change, and account any 700 * SOME and FULL time these may have resulted in. 701 * 702 * Then we update the task counts according to the state 703 * change requested through the @clear and @set bits. 704 */ 705 write_seqcount_begin(&groupc->seq); 706 707 record_times(groupc, now); 708 709 for (t = 0, m = clear; m; m &= ~(1 << t), t++) { 710 if (!(m & (1 << t))) 711 continue; 712 if (groupc->tasks[t]) { 713 groupc->tasks[t]--; 714 } else if (!psi_bug) { 715 printk_deferred(KERN_ERR "psi: task underflow! cpu=%d t=%d tasks=[%u %u %u %u %u] clear=%x set=%x\n", 716 cpu, t, groupc->tasks[0], 717 groupc->tasks[1], groupc->tasks[2], 718 groupc->tasks[3], groupc->tasks[4], 719 clear, set); 720 psi_bug = 1; 721 } 722 } 723 724 for (t = 0; set; set &= ~(1 << t), t++) 725 if (set & (1 << t)) 726 groupc->tasks[t]++; 727 728 /* Calculate state mask representing active states */ 729 for (s = 0; s < NR_PSI_STATES; s++) { 730 if (test_state(groupc->tasks, s)) 731 state_mask |= (1 << s); 732 } 733 734 /* 735 * Since we care about lost potential, a memstall is FULL 736 * when there are no other working tasks, but also when 737 * the CPU is actively reclaiming and nothing productive 738 * could run even if it were runnable. So when the current 739 * task in a cgroup is in_memstall, the corresponding groupc 740 * on that cpu is in PSI_MEM_FULL state. 741 */ 742 if (unlikely(groupc->tasks[NR_ONCPU] && cpu_curr(cpu)->in_memstall)) 743 state_mask |= (1 << PSI_MEM_FULL); 744 745 groupc->state_mask = state_mask; 746 747 write_seqcount_end(&groupc->seq); 748 749 if (state_mask & group->poll_states) 750 psi_schedule_poll_work(group, 1); 751 752 if (wake_clock && !delayed_work_pending(&group->avgs_work)) 753 schedule_delayed_work(&group->avgs_work, PSI_FREQ); 754 } 755 756 static struct psi_group *iterate_groups(struct task_struct *task, void **iter) 757 { 758 if (*iter == &psi_system) 759 return NULL; 760 761 #ifdef CONFIG_CGROUPS 762 if (static_branch_likely(&psi_cgroups_enabled)) { 763 struct cgroup *cgroup = NULL; 764 765 if (!*iter) 766 cgroup = task->cgroups->dfl_cgrp; 767 else 768 cgroup = cgroup_parent(*iter); 769 770 if (cgroup && cgroup_parent(cgroup)) { 771 *iter = cgroup; 772 return cgroup_psi(cgroup); 773 } 774 } 775 #endif 776 *iter = &psi_system; 777 return &psi_system; 778 } 779 780 static void psi_flags_change(struct task_struct *task, int clear, int set) 781 { 782 if (((task->psi_flags & set) || 783 (task->psi_flags & clear) != clear) && 784 !psi_bug) { 785 printk_deferred(KERN_ERR "psi: inconsistent task state! task=%d:%s cpu=%d psi_flags=%x clear=%x set=%x\n", 786 task->pid, task->comm, task_cpu(task), 787 task->psi_flags, clear, set); 788 psi_bug = 1; 789 } 790 791 task->psi_flags &= ~clear; 792 task->psi_flags |= set; 793 } 794 795 void psi_task_change(struct task_struct *task, int clear, int set) 796 { 797 int cpu = task_cpu(task); 798 struct psi_group *group; 799 bool wake_clock = true; 800 void *iter = NULL; 801 u64 now; 802 803 if (!task->pid) 804 return; 805 806 psi_flags_change(task, clear, set); 807 808 now = cpu_clock(cpu); 809 /* 810 * Periodic aggregation shuts off if there is a period of no 811 * task changes, so we wake it back up if necessary. However, 812 * don't do this if the task change is the aggregation worker 813 * itself going to sleep, or we'll ping-pong forever. 814 */ 815 if (unlikely((clear & TSK_RUNNING) && 816 (task->flags & PF_WQ_WORKER) && 817 wq_worker_last_func(task) == psi_avgs_work)) 818 wake_clock = false; 819 820 while ((group = iterate_groups(task, &iter))) 821 psi_group_change(group, cpu, clear, set, now, wake_clock); 822 } 823 824 void psi_task_switch(struct task_struct *prev, struct task_struct *next, 825 bool sleep) 826 { 827 struct psi_group *group, *common = NULL; 828 int cpu = task_cpu(prev); 829 void *iter; 830 u64 now = cpu_clock(cpu); 831 832 if (next->pid) { 833 bool identical_state; 834 835 psi_flags_change(next, 0, TSK_ONCPU); 836 /* 837 * When switching between tasks that have an identical 838 * runtime state, the cgroup that contains both tasks 839 * we reach the first common ancestor. Iterate @next's 840 * ancestors only until we encounter @prev's ONCPU. 841 */ 842 identical_state = prev->psi_flags == next->psi_flags; 843 iter = NULL; 844 while ((group = iterate_groups(next, &iter))) { 845 if (identical_state && 846 per_cpu_ptr(group->pcpu, cpu)->tasks[NR_ONCPU]) { 847 common = group; 848 break; 849 } 850 851 psi_group_change(group, cpu, 0, TSK_ONCPU, now, true); 852 } 853 } 854 855 if (prev->pid) { 856 int clear = TSK_ONCPU, set = 0; 857 858 /* 859 * When we're going to sleep, psi_dequeue() lets us 860 * handle TSK_RUNNING, TSK_MEMSTALL_RUNNING and 861 * TSK_IOWAIT here, where we can combine it with 862 * TSK_ONCPU and save walking common ancestors twice. 863 */ 864 if (sleep) { 865 clear |= TSK_RUNNING; 866 if (prev->in_memstall) 867 clear |= TSK_MEMSTALL_RUNNING; 868 if (prev->in_iowait) 869 set |= TSK_IOWAIT; 870 } 871 872 psi_flags_change(prev, clear, set); 873 874 iter = NULL; 875 while ((group = iterate_groups(prev, &iter)) && group != common) 876 psi_group_change(group, cpu, clear, set, now, true); 877 878 /* 879 * TSK_ONCPU is handled up to the common ancestor. If we're tasked 880 * with dequeuing too, finish that for the rest of the hierarchy. 881 */ 882 if (sleep) { 883 clear &= ~TSK_ONCPU; 884 for (; group; group = iterate_groups(prev, &iter)) 885 psi_group_change(group, cpu, clear, set, now, true); 886 } 887 } 888 } 889 890 /** 891 * psi_memstall_enter - mark the beginning of a memory stall section 892 * @flags: flags to handle nested sections 893 * 894 * Marks the calling task as being stalled due to a lack of memory, 895 * such as waiting for a refault or performing reclaim. 896 */ 897 void psi_memstall_enter(unsigned long *flags) 898 { 899 struct rq_flags rf; 900 struct rq *rq; 901 902 if (static_branch_likely(&psi_disabled)) 903 return; 904 905 *flags = current->in_memstall; 906 if (*flags) 907 return; 908 /* 909 * in_memstall setting & accounting needs to be atomic wrt 910 * changes to the task's scheduling state, otherwise we can 911 * race with CPU migration. 912 */ 913 rq = this_rq_lock_irq(&rf); 914 915 current->in_memstall = 1; 916 psi_task_change(current, 0, TSK_MEMSTALL | TSK_MEMSTALL_RUNNING); 917 918 rq_unlock_irq(rq, &rf); 919 } 920 921 /** 922 * psi_memstall_leave - mark the end of an memory stall section 923 * @flags: flags to handle nested memdelay sections 924 * 925 * Marks the calling task as no longer stalled due to lack of memory. 926 */ 927 void psi_memstall_leave(unsigned long *flags) 928 { 929 struct rq_flags rf; 930 struct rq *rq; 931 932 if (static_branch_likely(&psi_disabled)) 933 return; 934 935 if (*flags) 936 return; 937 /* 938 * in_memstall clearing & accounting needs to be atomic wrt 939 * changes to the task's scheduling state, otherwise we could 940 * race with CPU migration. 941 */ 942 rq = this_rq_lock_irq(&rf); 943 944 current->in_memstall = 0; 945 psi_task_change(current, TSK_MEMSTALL | TSK_MEMSTALL_RUNNING, 0); 946 947 rq_unlock_irq(rq, &rf); 948 } 949 950 #ifdef CONFIG_CGROUPS 951 int psi_cgroup_alloc(struct cgroup *cgroup) 952 { 953 if (static_branch_likely(&psi_disabled)) 954 return 0; 955 956 cgroup->psi = kzalloc(sizeof(struct psi_group), GFP_KERNEL); 957 if (!cgroup->psi) 958 return -ENOMEM; 959 960 cgroup->psi->pcpu = alloc_percpu(struct psi_group_cpu); 961 if (!cgroup->psi->pcpu) { 962 kfree(cgroup->psi); 963 return -ENOMEM; 964 } 965 group_init(cgroup->psi); 966 return 0; 967 } 968 969 void psi_cgroup_free(struct cgroup *cgroup) 970 { 971 if (static_branch_likely(&psi_disabled)) 972 return; 973 974 cancel_delayed_work_sync(&cgroup->psi->avgs_work); 975 free_percpu(cgroup->psi->pcpu); 976 /* All triggers must be removed by now */ 977 WARN_ONCE(cgroup->psi->poll_states, "psi: trigger leak\n"); 978 kfree(cgroup->psi); 979 } 980 981 /** 982 * cgroup_move_task - move task to a different cgroup 983 * @task: the task 984 * @to: the target css_set 985 * 986 * Move task to a new cgroup and safely migrate its associated stall 987 * state between the different groups. 988 * 989 * This function acquires the task's rq lock to lock out concurrent 990 * changes to the task's scheduling state and - in case the task is 991 * running - concurrent changes to its stall state. 992 */ 993 void cgroup_move_task(struct task_struct *task, struct css_set *to) 994 { 995 unsigned int task_flags; 996 struct rq_flags rf; 997 struct rq *rq; 998 999 if (static_branch_likely(&psi_disabled)) { 1000 /* 1001 * Lame to do this here, but the scheduler cannot be locked 1002 * from the outside, so we move cgroups from inside sched/. 1003 */ 1004 rcu_assign_pointer(task->cgroups, to); 1005 return; 1006 } 1007 1008 rq = task_rq_lock(task, &rf); 1009 1010 /* 1011 * We may race with schedule() dropping the rq lock between 1012 * deactivating prev and switching to next. Because the psi 1013 * updates from the deactivation are deferred to the switch 1014 * callback to save cgroup tree updates, the task's scheduling 1015 * state here is not coherent with its psi state: 1016 * 1017 * schedule() cgroup_move_task() 1018 * rq_lock() 1019 * deactivate_task() 1020 * p->on_rq = 0 1021 * psi_dequeue() // defers TSK_RUNNING & TSK_IOWAIT updates 1022 * pick_next_task() 1023 * rq_unlock() 1024 * rq_lock() 1025 * psi_task_change() // old cgroup 1026 * task->cgroups = to 1027 * psi_task_change() // new cgroup 1028 * rq_unlock() 1029 * rq_lock() 1030 * psi_sched_switch() // does deferred updates in new cgroup 1031 * 1032 * Don't rely on the scheduling state. Use psi_flags instead. 1033 */ 1034 task_flags = task->psi_flags; 1035 1036 if (task_flags) 1037 psi_task_change(task, task_flags, 0); 1038 1039 /* See comment above */ 1040 rcu_assign_pointer(task->cgroups, to); 1041 1042 if (task_flags) 1043 psi_task_change(task, 0, task_flags); 1044 1045 task_rq_unlock(rq, task, &rf); 1046 } 1047 #endif /* CONFIG_CGROUPS */ 1048 1049 int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res) 1050 { 1051 int full; 1052 u64 now; 1053 1054 if (static_branch_likely(&psi_disabled)) 1055 return -EOPNOTSUPP; 1056 1057 /* Update averages before reporting them */ 1058 mutex_lock(&group->avgs_lock); 1059 now = sched_clock(); 1060 collect_percpu_times(group, PSI_AVGS, NULL); 1061 if (now >= group->avg_next_update) 1062 group->avg_next_update = update_averages(group, now); 1063 mutex_unlock(&group->avgs_lock); 1064 1065 for (full = 0; full < 2; full++) { 1066 unsigned long avg[3] = { 0, }; 1067 u64 total = 0; 1068 int w; 1069 1070 /* CPU FULL is undefined at the system level */ 1071 if (!(group == &psi_system && res == PSI_CPU && full)) { 1072 for (w = 0; w < 3; w++) 1073 avg[w] = group->avg[res * 2 + full][w]; 1074 total = div_u64(group->total[PSI_AVGS][res * 2 + full], 1075 NSEC_PER_USEC); 1076 } 1077 1078 seq_printf(m, "%s avg10=%lu.%02lu avg60=%lu.%02lu avg300=%lu.%02lu total=%llu\n", 1079 full ? "full" : "some", 1080 LOAD_INT(avg[0]), LOAD_FRAC(avg[0]), 1081 LOAD_INT(avg[1]), LOAD_FRAC(avg[1]), 1082 LOAD_INT(avg[2]), LOAD_FRAC(avg[2]), 1083 total); 1084 } 1085 1086 return 0; 1087 } 1088 1089 struct psi_trigger *psi_trigger_create(struct psi_group *group, 1090 char *buf, enum psi_res res) 1091 { 1092 struct psi_trigger *t; 1093 enum psi_states state; 1094 u32 threshold_us; 1095 u32 window_us; 1096 1097 if (static_branch_likely(&psi_disabled)) 1098 return ERR_PTR(-EOPNOTSUPP); 1099 1100 if (sscanf(buf, "some %u %u", &threshold_us, &window_us) == 2) 1101 state = PSI_IO_SOME + res * 2; 1102 else if (sscanf(buf, "full %u %u", &threshold_us, &window_us) == 2) 1103 state = PSI_IO_FULL + res * 2; 1104 else 1105 return ERR_PTR(-EINVAL); 1106 1107 if (state >= PSI_NONIDLE) 1108 return ERR_PTR(-EINVAL); 1109 1110 if (window_us < WINDOW_MIN_US || 1111 window_us > WINDOW_MAX_US) 1112 return ERR_PTR(-EINVAL); 1113 1114 /* Check threshold */ 1115 if (threshold_us == 0 || threshold_us > window_us) 1116 return ERR_PTR(-EINVAL); 1117 1118 t = kmalloc(sizeof(*t), GFP_KERNEL); 1119 if (!t) 1120 return ERR_PTR(-ENOMEM); 1121 1122 t->group = group; 1123 t->state = state; 1124 t->threshold = threshold_us * NSEC_PER_USEC; 1125 t->win.size = window_us * NSEC_PER_USEC; 1126 window_reset(&t->win, sched_clock(), 1127 group->total[PSI_POLL][t->state], 0); 1128 1129 t->event = 0; 1130 t->last_event_time = 0; 1131 init_waitqueue_head(&t->event_wait); 1132 t->pending_event = false; 1133 1134 mutex_lock(&group->trigger_lock); 1135 1136 if (!rcu_access_pointer(group->poll_task)) { 1137 struct task_struct *task; 1138 1139 task = kthread_create(psi_poll_worker, group, "psimon"); 1140 if (IS_ERR(task)) { 1141 kfree(t); 1142 mutex_unlock(&group->trigger_lock); 1143 return ERR_CAST(task); 1144 } 1145 atomic_set(&group->poll_wakeup, 0); 1146 wake_up_process(task); 1147 rcu_assign_pointer(group->poll_task, task); 1148 } 1149 1150 list_add(&t->node, &group->triggers); 1151 group->poll_min_period = min(group->poll_min_period, 1152 div_u64(t->win.size, UPDATES_PER_WINDOW)); 1153 group->nr_triggers[t->state]++; 1154 group->poll_states |= (1 << t->state); 1155 1156 mutex_unlock(&group->trigger_lock); 1157 1158 return t; 1159 } 1160 1161 void psi_trigger_destroy(struct psi_trigger *t) 1162 { 1163 struct psi_group *group; 1164 struct task_struct *task_to_destroy = NULL; 1165 1166 /* 1167 * We do not check psi_disabled since it might have been disabled after 1168 * the trigger got created. 1169 */ 1170 if (!t) 1171 return; 1172 1173 group = t->group; 1174 /* 1175 * Wakeup waiters to stop polling. Can happen if cgroup is deleted 1176 * from under a polling process. 1177 */ 1178 wake_up_interruptible(&t->event_wait); 1179 1180 mutex_lock(&group->trigger_lock); 1181 1182 if (!list_empty(&t->node)) { 1183 struct psi_trigger *tmp; 1184 u64 period = ULLONG_MAX; 1185 1186 list_del(&t->node); 1187 group->nr_triggers[t->state]--; 1188 if (!group->nr_triggers[t->state]) 1189 group->poll_states &= ~(1 << t->state); 1190 /* reset min update period for the remaining triggers */ 1191 list_for_each_entry(tmp, &group->triggers, node) 1192 period = min(period, div_u64(tmp->win.size, 1193 UPDATES_PER_WINDOW)); 1194 group->poll_min_period = period; 1195 /* Destroy poll_task when the last trigger is destroyed */ 1196 if (group->poll_states == 0) { 1197 group->polling_until = 0; 1198 task_to_destroy = rcu_dereference_protected( 1199 group->poll_task, 1200 lockdep_is_held(&group->trigger_lock)); 1201 rcu_assign_pointer(group->poll_task, NULL); 1202 del_timer(&group->poll_timer); 1203 } 1204 } 1205 1206 mutex_unlock(&group->trigger_lock); 1207 1208 /* 1209 * Wait for psi_schedule_poll_work RCU to complete its read-side 1210 * critical section before destroying the trigger and optionally the 1211 * poll_task. 1212 */ 1213 synchronize_rcu(); 1214 /* 1215 * Stop kthread 'psimon' after releasing trigger_lock to prevent a 1216 * deadlock while waiting for psi_poll_work to acquire trigger_lock 1217 */ 1218 if (task_to_destroy) { 1219 /* 1220 * After the RCU grace period has expired, the worker 1221 * can no longer be found through group->poll_task. 1222 */ 1223 kthread_stop(task_to_destroy); 1224 } 1225 kfree(t); 1226 } 1227 1228 __poll_t psi_trigger_poll(void **trigger_ptr, 1229 struct file *file, poll_table *wait) 1230 { 1231 __poll_t ret = DEFAULT_POLLMASK; 1232 struct psi_trigger *t; 1233 1234 if (static_branch_likely(&psi_disabled)) 1235 return DEFAULT_POLLMASK | EPOLLERR | EPOLLPRI; 1236 1237 t = smp_load_acquire(trigger_ptr); 1238 if (!t) 1239 return DEFAULT_POLLMASK | EPOLLERR | EPOLLPRI; 1240 1241 poll_wait(file, &t->event_wait, wait); 1242 1243 if (cmpxchg(&t->event, 1, 0) == 1) 1244 ret |= EPOLLPRI; 1245 1246 return ret; 1247 } 1248 1249 #ifdef CONFIG_PROC_FS 1250 static int psi_io_show(struct seq_file *m, void *v) 1251 { 1252 return psi_show(m, &psi_system, PSI_IO); 1253 } 1254 1255 static int psi_memory_show(struct seq_file *m, void *v) 1256 { 1257 return psi_show(m, &psi_system, PSI_MEM); 1258 } 1259 1260 static int psi_cpu_show(struct seq_file *m, void *v) 1261 { 1262 return psi_show(m, &psi_system, PSI_CPU); 1263 } 1264 1265 static int psi_open(struct file *file, int (*psi_show)(struct seq_file *, void *)) 1266 { 1267 if (file->f_mode & FMODE_WRITE && !capable(CAP_SYS_RESOURCE)) 1268 return -EPERM; 1269 1270 return single_open(file, psi_show, NULL); 1271 } 1272 1273 static int psi_io_open(struct inode *inode, struct file *file) 1274 { 1275 return psi_open(file, psi_io_show); 1276 } 1277 1278 static int psi_memory_open(struct inode *inode, struct file *file) 1279 { 1280 return psi_open(file, psi_memory_show); 1281 } 1282 1283 static int psi_cpu_open(struct inode *inode, struct file *file) 1284 { 1285 return psi_open(file, psi_cpu_show); 1286 } 1287 1288 static ssize_t psi_write(struct file *file, const char __user *user_buf, 1289 size_t nbytes, enum psi_res res) 1290 { 1291 char buf[32]; 1292 size_t buf_size; 1293 struct seq_file *seq; 1294 struct psi_trigger *new; 1295 1296 if (static_branch_likely(&psi_disabled)) 1297 return -EOPNOTSUPP; 1298 1299 if (!nbytes) 1300 return -EINVAL; 1301 1302 buf_size = min(nbytes, sizeof(buf)); 1303 if (copy_from_user(buf, user_buf, buf_size)) 1304 return -EFAULT; 1305 1306 buf[buf_size - 1] = '\0'; 1307 1308 seq = file->private_data; 1309 1310 /* Take seq->lock to protect seq->private from concurrent writes */ 1311 mutex_lock(&seq->lock); 1312 1313 /* Allow only one trigger per file descriptor */ 1314 if (seq->private) { 1315 mutex_unlock(&seq->lock); 1316 return -EBUSY; 1317 } 1318 1319 new = psi_trigger_create(&psi_system, buf, res); 1320 if (IS_ERR(new)) { 1321 mutex_unlock(&seq->lock); 1322 return PTR_ERR(new); 1323 } 1324 1325 smp_store_release(&seq->private, new); 1326 mutex_unlock(&seq->lock); 1327 1328 return nbytes; 1329 } 1330 1331 static ssize_t psi_io_write(struct file *file, const char __user *user_buf, 1332 size_t nbytes, loff_t *ppos) 1333 { 1334 return psi_write(file, user_buf, nbytes, PSI_IO); 1335 } 1336 1337 static ssize_t psi_memory_write(struct file *file, const char __user *user_buf, 1338 size_t nbytes, loff_t *ppos) 1339 { 1340 return psi_write(file, user_buf, nbytes, PSI_MEM); 1341 } 1342 1343 static ssize_t psi_cpu_write(struct file *file, const char __user *user_buf, 1344 size_t nbytes, loff_t *ppos) 1345 { 1346 return psi_write(file, user_buf, nbytes, PSI_CPU); 1347 } 1348 1349 static __poll_t psi_fop_poll(struct file *file, poll_table *wait) 1350 { 1351 struct seq_file *seq = file->private_data; 1352 1353 return psi_trigger_poll(&seq->private, file, wait); 1354 } 1355 1356 static int psi_fop_release(struct inode *inode, struct file *file) 1357 { 1358 struct seq_file *seq = file->private_data; 1359 1360 psi_trigger_destroy(seq->private); 1361 return single_release(inode, file); 1362 } 1363 1364 static const struct proc_ops psi_io_proc_ops = { 1365 .proc_open = psi_io_open, 1366 .proc_read = seq_read, 1367 .proc_lseek = seq_lseek, 1368 .proc_write = psi_io_write, 1369 .proc_poll = psi_fop_poll, 1370 .proc_release = psi_fop_release, 1371 }; 1372 1373 static const struct proc_ops psi_memory_proc_ops = { 1374 .proc_open = psi_memory_open, 1375 .proc_read = seq_read, 1376 .proc_lseek = seq_lseek, 1377 .proc_write = psi_memory_write, 1378 .proc_poll = psi_fop_poll, 1379 .proc_release = psi_fop_release, 1380 }; 1381 1382 static const struct proc_ops psi_cpu_proc_ops = { 1383 .proc_open = psi_cpu_open, 1384 .proc_read = seq_read, 1385 .proc_lseek = seq_lseek, 1386 .proc_write = psi_cpu_write, 1387 .proc_poll = psi_fop_poll, 1388 .proc_release = psi_fop_release, 1389 }; 1390 1391 static int __init psi_proc_init(void) 1392 { 1393 if (psi_enable) { 1394 proc_mkdir("pressure", NULL); 1395 proc_create("pressure/io", 0666, NULL, &psi_io_proc_ops); 1396 proc_create("pressure/memory", 0666, NULL, &psi_memory_proc_ops); 1397 proc_create("pressure/cpu", 0666, NULL, &psi_cpu_proc_ops); 1398 } 1399 return 0; 1400 } 1401 module_init(psi_proc_init); 1402 1403 #endif /* CONFIG_PROC_FS */ 1404