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
setup_psi(char * str)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
group_init(struct psi_group * group)180 static void group_init(struct psi_group *group)
181 {
182 int cpu;
183
184 group->enabled = true;
185 for_each_possible_cpu(cpu)
186 seqcount_init(&per_cpu_ptr(group->pcpu, cpu)->seq);
187 group->avg_last_update = sched_clock();
188 group->avg_next_update = group->avg_last_update + psi_period;
189 INIT_DELAYED_WORK(&group->avgs_work, psi_avgs_work);
190 mutex_init(&group->avgs_lock);
191 /* Init trigger-related members */
192 mutex_init(&group->trigger_lock);
193 INIT_LIST_HEAD(&group->triggers);
194 group->poll_min_period = U32_MAX;
195 group->polling_next_update = ULLONG_MAX;
196 init_waitqueue_head(&group->poll_wait);
197 timer_setup(&group->poll_timer, poll_timer_fn, 0);
198 rcu_assign_pointer(group->poll_task, NULL);
199 }
200
psi_init(void)201 void __init psi_init(void)
202 {
203 if (!psi_enable) {
204 static_branch_enable(&psi_disabled);
205 static_branch_disable(&psi_cgroups_enabled);
206 return;
207 }
208
209 if (!cgroup_psi_enabled())
210 static_branch_disable(&psi_cgroups_enabled);
211
212 psi_period = jiffies_to_nsecs(PSI_FREQ);
213 group_init(&psi_system);
214 }
215
test_state(unsigned int * tasks,enum psi_states state,bool oncpu)216 static bool test_state(unsigned int *tasks, enum psi_states state, bool oncpu)
217 {
218 switch (state) {
219 case PSI_IO_SOME:
220 return unlikely(tasks[NR_IOWAIT]);
221 case PSI_IO_FULL:
222 return unlikely(tasks[NR_IOWAIT] && !tasks[NR_RUNNING]);
223 case PSI_MEM_SOME:
224 return unlikely(tasks[NR_MEMSTALL]);
225 case PSI_MEM_FULL:
226 return unlikely(tasks[NR_MEMSTALL] &&
227 tasks[NR_RUNNING] == tasks[NR_MEMSTALL_RUNNING]);
228 case PSI_CPU_SOME:
229 return unlikely(tasks[NR_RUNNING] > oncpu);
230 case PSI_CPU_FULL:
231 return unlikely(tasks[NR_RUNNING] && !oncpu);
232 case PSI_NONIDLE:
233 return tasks[NR_IOWAIT] || tasks[NR_MEMSTALL] ||
234 tasks[NR_RUNNING];
235 default:
236 return false;
237 }
238 }
239
get_recent_times(struct psi_group * group,int cpu,enum psi_aggregators aggregator,u32 * times,u32 * pchanged_states)240 static void get_recent_times(struct psi_group *group, int cpu,
241 enum psi_aggregators aggregator, u32 *times,
242 u32 *pchanged_states)
243 {
244 struct psi_group_cpu *groupc = per_cpu_ptr(group->pcpu, cpu);
245 u64 now, state_start;
246 enum psi_states s;
247 unsigned int seq;
248 u32 state_mask;
249
250 *pchanged_states = 0;
251
252 /* Snapshot a coherent view of the CPU state */
253 do {
254 seq = read_seqcount_begin(&groupc->seq);
255 now = cpu_clock(cpu);
256 memcpy(times, groupc->times, sizeof(groupc->times));
257 state_mask = groupc->state_mask;
258 state_start = groupc->state_start;
259 } while (read_seqcount_retry(&groupc->seq, seq));
260
261 /* Calculate state time deltas against the previous snapshot */
262 for (s = 0; s < NR_PSI_STATES; s++) {
263 u32 delta;
264 /*
265 * In addition to already concluded states, we also
266 * incorporate currently active states on the CPU,
267 * since states may last for many sampling periods.
268 *
269 * This way we keep our delta sampling buckets small
270 * (u32) and our reported pressure close to what's
271 * actually happening.
272 */
273 if (state_mask & (1 << s))
274 times[s] += now - state_start;
275
276 delta = times[s] - groupc->times_prev[aggregator][s];
277 groupc->times_prev[aggregator][s] = times[s];
278
279 times[s] = delta;
280 if (delta)
281 *pchanged_states |= (1 << s);
282 }
283 }
284
calc_avgs(unsigned long avg[3],int missed_periods,u64 time,u64 period)285 static void calc_avgs(unsigned long avg[3], int missed_periods,
286 u64 time, u64 period)
287 {
288 unsigned long pct;
289
290 /* Fill in zeroes for periods of no activity */
291 if (missed_periods) {
292 avg[0] = calc_load_n(avg[0], EXP_10s, 0, missed_periods);
293 avg[1] = calc_load_n(avg[1], EXP_60s, 0, missed_periods);
294 avg[2] = calc_load_n(avg[2], EXP_300s, 0, missed_periods);
295 }
296
297 /* Sample the most recent active period */
298 pct = div_u64(time * 100, period);
299 pct *= FIXED_1;
300 avg[0] = calc_load(avg[0], EXP_10s, pct);
301 avg[1] = calc_load(avg[1], EXP_60s, pct);
302 avg[2] = calc_load(avg[2], EXP_300s, pct);
303 }
304
collect_percpu_times(struct psi_group * group,enum psi_aggregators aggregator,u32 * pchanged_states)305 static void collect_percpu_times(struct psi_group *group,
306 enum psi_aggregators aggregator,
307 u32 *pchanged_states)
308 {
309 u64 deltas[NR_PSI_STATES - 1] = { 0, };
310 unsigned long nonidle_total = 0;
311 u32 changed_states = 0;
312 int cpu;
313 int s;
314
315 /*
316 * Collect the per-cpu time buckets and average them into a
317 * single time sample that is normalized to wallclock time.
318 *
319 * For averaging, each CPU is weighted by its non-idle time in
320 * the sampling period. This eliminates artifacts from uneven
321 * loading, or even entirely idle CPUs.
322 */
323 for_each_possible_cpu(cpu) {
324 u32 times[NR_PSI_STATES];
325 u32 nonidle;
326 u32 cpu_changed_states;
327
328 get_recent_times(group, cpu, aggregator, times,
329 &cpu_changed_states);
330 changed_states |= cpu_changed_states;
331
332 nonidle = nsecs_to_jiffies(times[PSI_NONIDLE]);
333 nonidle_total += nonidle;
334
335 for (s = 0; s < PSI_NONIDLE; s++)
336 deltas[s] += (u64)times[s] * nonidle;
337 }
338
339 /*
340 * Integrate the sample into the running statistics that are
341 * reported to userspace: the cumulative stall times and the
342 * decaying averages.
343 *
344 * Pressure percentages are sampled at PSI_FREQ. We might be
345 * called more often when the user polls more frequently than
346 * that; we might be called less often when there is no task
347 * activity, thus no data, and clock ticks are sporadic. The
348 * below handles both.
349 */
350
351 /* total= */
352 for (s = 0; s < NR_PSI_STATES - 1; s++)
353 group->total[aggregator][s] +=
354 div_u64(deltas[s], max(nonidle_total, 1UL));
355
356 if (pchanged_states)
357 *pchanged_states = changed_states;
358 }
359
update_averages(struct psi_group * group,u64 now)360 static u64 update_averages(struct psi_group *group, u64 now)
361 {
362 unsigned long missed_periods = 0;
363 u64 expires, period;
364 u64 avg_next_update;
365 int s;
366
367 /* avgX= */
368 expires = group->avg_next_update;
369 if (now - expires >= psi_period)
370 missed_periods = div_u64(now - expires, psi_period);
371
372 /*
373 * The periodic clock tick can get delayed for various
374 * reasons, especially on loaded systems. To avoid clock
375 * drift, we schedule the clock in fixed psi_period intervals.
376 * But the deltas we sample out of the per-cpu buckets above
377 * are based on the actual time elapsing between clock ticks.
378 */
379 avg_next_update = expires + ((1 + missed_periods) * psi_period);
380 period = now - (group->avg_last_update + (missed_periods * psi_period));
381 group->avg_last_update = now;
382
383 for (s = 0; s < NR_PSI_STATES - 1; s++) {
384 u32 sample;
385
386 sample = group->total[PSI_AVGS][s] - group->avg_total[s];
387 /*
388 * Due to the lockless sampling of the time buckets,
389 * recorded time deltas can slip into the next period,
390 * which under full pressure can result in samples in
391 * excess of the period length.
392 *
393 * We don't want to report non-sensical pressures in
394 * excess of 100%, nor do we want to drop such events
395 * on the floor. Instead we punt any overage into the
396 * future until pressure subsides. By doing this we
397 * don't underreport the occurring pressure curve, we
398 * just report it delayed by one period length.
399 *
400 * The error isn't cumulative. As soon as another
401 * delta slips from a period P to P+1, by definition
402 * it frees up its time T in P.
403 */
404 if (sample > period)
405 sample = period;
406 group->avg_total[s] += sample;
407 calc_avgs(group->avg[s], missed_periods, sample, period);
408 }
409
410 return avg_next_update;
411 }
412
psi_avgs_work(struct work_struct * work)413 static void psi_avgs_work(struct work_struct *work)
414 {
415 struct delayed_work *dwork;
416 struct psi_group *group;
417 u32 changed_states;
418 bool nonidle;
419 u64 now;
420
421 dwork = to_delayed_work(work);
422 group = container_of(dwork, struct psi_group, avgs_work);
423
424 mutex_lock(&group->avgs_lock);
425
426 now = sched_clock();
427
428 collect_percpu_times(group, PSI_AVGS, &changed_states);
429 nonidle = changed_states & (1 << PSI_NONIDLE);
430 /*
431 * If there is task activity, periodically fold the per-cpu
432 * times and feed samples into the running averages. If things
433 * are idle and there is no data to process, stop the clock.
434 * Once restarted, we'll catch up the running averages in one
435 * go - see calc_avgs() and missed_periods.
436 */
437 if (now >= group->avg_next_update)
438 group->avg_next_update = update_averages(group, now);
439
440 if (nonidle) {
441 schedule_delayed_work(dwork, nsecs_to_jiffies(
442 group->avg_next_update - now) + 1);
443 }
444
445 mutex_unlock(&group->avgs_lock);
446 }
447
448 /* Trigger tracking window manipulations */
window_reset(struct psi_window * win,u64 now,u64 value,u64 prev_growth)449 static void window_reset(struct psi_window *win, u64 now, u64 value,
450 u64 prev_growth)
451 {
452 win->start_time = now;
453 win->start_value = value;
454 win->prev_growth = prev_growth;
455 }
456
457 /*
458 * PSI growth tracking window update and growth calculation routine.
459 *
460 * This approximates a sliding tracking window by interpolating
461 * partially elapsed windows using historical growth data from the
462 * previous intervals. This minimizes memory requirements (by not storing
463 * all the intermediate values in the previous window) and simplifies
464 * the calculations. It works well because PSI signal changes only in
465 * positive direction and over relatively small window sizes the growth
466 * is close to linear.
467 */
window_update(struct psi_window * win,u64 now,u64 value)468 static u64 window_update(struct psi_window *win, u64 now, u64 value)
469 {
470 u64 elapsed;
471 u64 growth;
472
473 elapsed = now - win->start_time;
474 growth = value - win->start_value;
475 /*
476 * After each tracking window passes win->start_value and
477 * win->start_time get reset and win->prev_growth stores
478 * the average per-window growth of the previous window.
479 * win->prev_growth is then used to interpolate additional
480 * growth from the previous window assuming it was linear.
481 */
482 if (elapsed > win->size)
483 window_reset(win, now, value, growth);
484 else {
485 u32 remaining;
486
487 remaining = win->size - elapsed;
488 growth += div64_u64(win->prev_growth * remaining, win->size);
489 }
490
491 return growth;
492 }
493
init_triggers(struct psi_group * group,u64 now)494 static void init_triggers(struct psi_group *group, u64 now)
495 {
496 struct psi_trigger *t;
497
498 list_for_each_entry(t, &group->triggers, node)
499 window_reset(&t->win, now,
500 group->total[PSI_POLL][t->state], 0);
501 memcpy(group->polling_total, group->total[PSI_POLL],
502 sizeof(group->polling_total));
503 group->polling_next_update = now + group->poll_min_period;
504 }
505
update_triggers(struct psi_group * group,u64 now)506 static u64 update_triggers(struct psi_group *group, u64 now)
507 {
508 struct psi_trigger *t;
509 bool update_total = false;
510 u64 *total = group->total[PSI_POLL];
511
512 /*
513 * On subsequent updates, calculate growth deltas and let
514 * watchers know when their specified thresholds are exceeded.
515 */
516 list_for_each_entry(t, &group->triggers, node) {
517 u64 growth;
518 bool new_stall;
519
520 new_stall = group->polling_total[t->state] != total[t->state];
521
522 /* Check for stall activity or a previous threshold breach */
523 if (!new_stall && !t->pending_event)
524 continue;
525 /*
526 * Check for new stall activity, as well as deferred
527 * events that occurred in the last window after the
528 * trigger had already fired (we want to ratelimit
529 * events without dropping any).
530 */
531 if (new_stall) {
532 /*
533 * Multiple triggers might be looking at the same state,
534 * remember to update group->polling_total[] once we've
535 * been through all of them. Also remember to extend the
536 * polling time if we see new stall activity.
537 */
538 update_total = true;
539
540 /* Calculate growth since last update */
541 growth = window_update(&t->win, now, total[t->state]);
542 if (!t->pending_event) {
543 if (growth < t->threshold)
544 continue;
545
546 t->pending_event = true;
547 }
548 }
549 /* Limit event signaling to once per window */
550 if (now < t->last_event_time + t->win.size)
551 continue;
552
553 /* Generate an event */
554 if (cmpxchg(&t->event, 0, 1) == 0)
555 wake_up_interruptible(&t->event_wait);
556 t->last_event_time = now;
557 /* Reset threshold breach flag once event got generated */
558 t->pending_event = false;
559 }
560
561 if (update_total)
562 memcpy(group->polling_total, total,
563 sizeof(group->polling_total));
564
565 return now + group->poll_min_period;
566 }
567
568 /* Schedule polling if it's not already scheduled. */
psi_schedule_poll_work(struct psi_group * group,unsigned long delay)569 static void psi_schedule_poll_work(struct psi_group *group, unsigned long delay)
570 {
571 struct task_struct *task;
572
573 /*
574 * Do not reschedule if already scheduled.
575 * Possible race with a timer scheduled after this check but before
576 * mod_timer below can be tolerated because group->polling_next_update
577 * will keep updates on schedule.
578 */
579 if (timer_pending(&group->poll_timer))
580 return;
581
582 rcu_read_lock();
583
584 task = rcu_dereference(group->poll_task);
585 /*
586 * kworker might be NULL in case psi_trigger_destroy races with
587 * psi_task_change (hotpath) which can't use locks
588 */
589 if (likely(task))
590 mod_timer(&group->poll_timer, jiffies + delay);
591
592 rcu_read_unlock();
593 }
594
psi_poll_work(struct psi_group * group)595 static void psi_poll_work(struct psi_group *group)
596 {
597 u32 changed_states;
598 u64 now;
599
600 mutex_lock(&group->trigger_lock);
601
602 now = sched_clock();
603
604 collect_percpu_times(group, PSI_POLL, &changed_states);
605
606 if (changed_states & group->poll_states) {
607 /* Initialize trigger windows when entering polling mode */
608 if (now > group->polling_until)
609 init_triggers(group, now);
610
611 /*
612 * Keep the monitor active for at least the duration of the
613 * minimum tracking window as long as monitor states are
614 * changing.
615 */
616 group->polling_until = now +
617 group->poll_min_period * UPDATES_PER_WINDOW;
618 }
619
620 if (now > group->polling_until) {
621 group->polling_next_update = ULLONG_MAX;
622 goto out;
623 }
624
625 if (now >= group->polling_next_update)
626 group->polling_next_update = update_triggers(group, now);
627
628 psi_schedule_poll_work(group,
629 nsecs_to_jiffies(group->polling_next_update - now) + 1);
630
631 out:
632 mutex_unlock(&group->trigger_lock);
633 }
634
psi_poll_worker(void * data)635 static int psi_poll_worker(void *data)
636 {
637 struct psi_group *group = (struct psi_group *)data;
638
639 sched_set_fifo_low(current);
640
641 while (true) {
642 wait_event_interruptible(group->poll_wait,
643 atomic_cmpxchg(&group->poll_wakeup, 1, 0) ||
644 kthread_should_stop());
645 if (kthread_should_stop())
646 break;
647
648 psi_poll_work(group);
649 }
650 return 0;
651 }
652
poll_timer_fn(struct timer_list * t)653 static void poll_timer_fn(struct timer_list *t)
654 {
655 struct psi_group *group = from_timer(group, t, poll_timer);
656
657 atomic_set(&group->poll_wakeup, 1);
658 wake_up_interruptible(&group->poll_wait);
659 }
660
record_times(struct psi_group_cpu * groupc,u64 now)661 static void record_times(struct psi_group_cpu *groupc, u64 now)
662 {
663 u32 delta;
664
665 delta = now - groupc->state_start;
666 groupc->state_start = now;
667
668 if (groupc->state_mask & (1 << PSI_IO_SOME)) {
669 groupc->times[PSI_IO_SOME] += delta;
670 if (groupc->state_mask & (1 << PSI_IO_FULL))
671 groupc->times[PSI_IO_FULL] += delta;
672 }
673
674 if (groupc->state_mask & (1 << PSI_MEM_SOME)) {
675 groupc->times[PSI_MEM_SOME] += delta;
676 if (groupc->state_mask & (1 << PSI_MEM_FULL))
677 groupc->times[PSI_MEM_FULL] += delta;
678 }
679
680 if (groupc->state_mask & (1 << PSI_CPU_SOME)) {
681 groupc->times[PSI_CPU_SOME] += delta;
682 if (groupc->state_mask & (1 << PSI_CPU_FULL))
683 groupc->times[PSI_CPU_FULL] += delta;
684 }
685
686 if (groupc->state_mask & (1 << PSI_NONIDLE))
687 groupc->times[PSI_NONIDLE] += delta;
688 }
689
psi_group_change(struct psi_group * group,int cpu,unsigned int clear,unsigned int set,u64 now,bool wake_clock)690 static void psi_group_change(struct psi_group *group, int cpu,
691 unsigned int clear, unsigned int set, u64 now,
692 bool wake_clock)
693 {
694 struct psi_group_cpu *groupc;
695 unsigned int t, m;
696 enum psi_states s;
697 u32 state_mask;
698
699 groupc = per_cpu_ptr(group->pcpu, cpu);
700
701 /*
702 * First we update the task counts according to the state
703 * change requested through the @clear and @set bits.
704 *
705 * Then if the cgroup PSI stats accounting enabled, we
706 * assess the aggregate resource states this CPU's tasks
707 * have been in since the last change, and account any
708 * SOME and FULL time these may have resulted in.
709 */
710 write_seqcount_begin(&groupc->seq);
711
712 /*
713 * Start with TSK_ONCPU, which doesn't have a corresponding
714 * task count - it's just a boolean flag directly encoded in
715 * the state mask. Clear, set, or carry the current state if
716 * no changes are requested.
717 */
718 if (unlikely(clear & TSK_ONCPU)) {
719 state_mask = 0;
720 clear &= ~TSK_ONCPU;
721 } else if (unlikely(set & TSK_ONCPU)) {
722 state_mask = PSI_ONCPU;
723 set &= ~TSK_ONCPU;
724 } else {
725 state_mask = groupc->state_mask & PSI_ONCPU;
726 }
727
728 /*
729 * The rest of the state mask is calculated based on the task
730 * counts. Update those first, then construct the mask.
731 */
732 for (t = 0, m = clear; m; m &= ~(1 << t), t++) {
733 if (!(m & (1 << t)))
734 continue;
735 if (groupc->tasks[t]) {
736 groupc->tasks[t]--;
737 } else if (!psi_bug) {
738 printk_deferred(KERN_ERR "psi: task underflow! cpu=%d t=%d tasks=[%u %u %u %u] clear=%x set=%x\n",
739 cpu, t, groupc->tasks[0],
740 groupc->tasks[1], groupc->tasks[2],
741 groupc->tasks[3], clear, set);
742 psi_bug = 1;
743 }
744 }
745
746 for (t = 0; set; set &= ~(1 << t), t++)
747 if (set & (1 << t))
748 groupc->tasks[t]++;
749
750 if (!group->enabled) {
751 /*
752 * On the first group change after disabling PSI, conclude
753 * the current state and flush its time. This is unlikely
754 * to matter to the user, but aggregation (get_recent_times)
755 * may have already incorporated the live state into times_prev;
756 * avoid a delta sample underflow when PSI is later re-enabled.
757 */
758 if (unlikely(groupc->state_mask & (1 << PSI_NONIDLE)))
759 record_times(groupc, now);
760
761 groupc->state_mask = state_mask;
762
763 write_seqcount_end(&groupc->seq);
764 return;
765 }
766
767 for (s = 0; s < NR_PSI_STATES; s++) {
768 if (test_state(groupc->tasks, s, state_mask & PSI_ONCPU))
769 state_mask |= (1 << s);
770 }
771
772 /*
773 * Since we care about lost potential, a memstall is FULL
774 * when there are no other working tasks, but also when
775 * the CPU is actively reclaiming and nothing productive
776 * could run even if it were runnable. So when the current
777 * task in a cgroup is in_memstall, the corresponding groupc
778 * on that cpu is in PSI_MEM_FULL state.
779 */
780 if (unlikely((state_mask & PSI_ONCPU) && cpu_curr(cpu)->in_memstall))
781 state_mask |= (1 << PSI_MEM_FULL);
782
783 record_times(groupc, now);
784
785 groupc->state_mask = state_mask;
786
787 write_seqcount_end(&groupc->seq);
788
789 if (state_mask & group->poll_states)
790 psi_schedule_poll_work(group, 1);
791
792 if (wake_clock && !delayed_work_pending(&group->avgs_work))
793 schedule_delayed_work(&group->avgs_work, PSI_FREQ);
794 }
795
task_psi_group(struct task_struct * task)796 static inline struct psi_group *task_psi_group(struct task_struct *task)
797 {
798 #ifdef CONFIG_CGROUPS
799 if (static_branch_likely(&psi_cgroups_enabled))
800 return cgroup_psi(task_dfl_cgroup(task));
801 #endif
802 return &psi_system;
803 }
804
psi_flags_change(struct task_struct * task,int clear,int set)805 static void psi_flags_change(struct task_struct *task, int clear, int set)
806 {
807 if (((task->psi_flags & set) ||
808 (task->psi_flags & clear) != clear) &&
809 !psi_bug) {
810 printk_deferred(KERN_ERR "psi: inconsistent task state! task=%d:%s cpu=%d psi_flags=%x clear=%x set=%x\n",
811 task->pid, task->comm, task_cpu(task),
812 task->psi_flags, clear, set);
813 psi_bug = 1;
814 }
815
816 task->psi_flags &= ~clear;
817 task->psi_flags |= set;
818 }
819
psi_task_change(struct task_struct * task,int clear,int set)820 void psi_task_change(struct task_struct *task, int clear, int set)
821 {
822 int cpu = task_cpu(task);
823 struct psi_group *group;
824 u64 now;
825
826 if (!task->pid)
827 return;
828
829 psi_flags_change(task, clear, set);
830
831 now = cpu_clock(cpu);
832
833 group = task_psi_group(task);
834 do {
835 psi_group_change(group, cpu, clear, set, now, true);
836 } while ((group = group->parent));
837 }
838
psi_task_switch(struct task_struct * prev,struct task_struct * next,bool sleep)839 void psi_task_switch(struct task_struct *prev, struct task_struct *next,
840 bool sleep)
841 {
842 struct psi_group *group, *common = NULL;
843 int cpu = task_cpu(prev);
844 u64 now = cpu_clock(cpu);
845
846 if (next->pid) {
847 psi_flags_change(next, 0, TSK_ONCPU);
848 /*
849 * Set TSK_ONCPU on @next's cgroups. If @next shares any
850 * ancestors with @prev, those will already have @prev's
851 * TSK_ONCPU bit set, and we can stop the iteration there.
852 */
853 group = task_psi_group(next);
854 do {
855 if (per_cpu_ptr(group->pcpu, cpu)->state_mask &
856 PSI_ONCPU) {
857 common = group;
858 break;
859 }
860
861 psi_group_change(group, cpu, 0, TSK_ONCPU, now, true);
862 } while ((group = group->parent));
863 }
864
865 if (prev->pid) {
866 int clear = TSK_ONCPU, set = 0;
867 bool wake_clock = true;
868
869 /*
870 * When we're going to sleep, psi_dequeue() lets us
871 * handle TSK_RUNNING, TSK_MEMSTALL_RUNNING and
872 * TSK_IOWAIT here, where we can combine it with
873 * TSK_ONCPU and save walking common ancestors twice.
874 */
875 if (sleep) {
876 clear |= TSK_RUNNING;
877 if (prev->in_memstall)
878 clear |= TSK_MEMSTALL_RUNNING;
879 if (prev->in_iowait)
880 set |= TSK_IOWAIT;
881
882 /*
883 * Periodic aggregation shuts off if there is a period of no
884 * task changes, so we wake it back up if necessary. However,
885 * don't do this if the task change is the aggregation worker
886 * itself going to sleep, or we'll ping-pong forever.
887 */
888 if (unlikely((prev->flags & PF_WQ_WORKER) &&
889 wq_worker_last_func(prev) == psi_avgs_work))
890 wake_clock = false;
891 }
892
893 psi_flags_change(prev, clear, set);
894
895 group = task_psi_group(prev);
896 do {
897 if (group == common)
898 break;
899 psi_group_change(group, cpu, clear, set, now, wake_clock);
900 } while ((group = group->parent));
901
902 /*
903 * TSK_ONCPU is handled up to the common ancestor. If there are
904 * any other differences between the two tasks (e.g. prev goes
905 * to sleep, or only one task is memstall), finish propagating
906 * those differences all the way up to the root.
907 */
908 if ((prev->psi_flags ^ next->psi_flags) & ~TSK_ONCPU) {
909 clear &= ~TSK_ONCPU;
910 for (; group; group = group->parent)
911 psi_group_change(group, cpu, clear, set, now, wake_clock);
912 }
913 }
914 }
915
916 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
psi_account_irqtime(struct task_struct * task,u32 delta)917 void psi_account_irqtime(struct task_struct *task, u32 delta)
918 {
919 int cpu = task_cpu(task);
920 struct psi_group *group;
921 struct psi_group_cpu *groupc;
922 u64 now;
923
924 if (!task->pid)
925 return;
926
927 now = cpu_clock(cpu);
928
929 group = task_psi_group(task);
930 do {
931 if (!group->enabled)
932 continue;
933
934 groupc = per_cpu_ptr(group->pcpu, cpu);
935
936 write_seqcount_begin(&groupc->seq);
937
938 record_times(groupc, now);
939 groupc->times[PSI_IRQ_FULL] += delta;
940
941 write_seqcount_end(&groupc->seq);
942
943 if (group->poll_states & (1 << PSI_IRQ_FULL))
944 psi_schedule_poll_work(group, 1);
945 } while ((group = group->parent));
946 }
947 #endif
948
949 /**
950 * psi_memstall_enter - mark the beginning of a memory stall section
951 * @flags: flags to handle nested sections
952 *
953 * Marks the calling task as being stalled due to a lack of memory,
954 * such as waiting for a refault or performing reclaim.
955 */
psi_memstall_enter(unsigned long * flags)956 void psi_memstall_enter(unsigned long *flags)
957 {
958 struct rq_flags rf;
959 struct rq *rq;
960
961 if (static_branch_likely(&psi_disabled))
962 return;
963
964 *flags = current->in_memstall;
965 if (*flags)
966 return;
967 /*
968 * in_memstall setting & accounting needs to be atomic wrt
969 * changes to the task's scheduling state, otherwise we can
970 * race with CPU migration.
971 */
972 rq = this_rq_lock_irq(&rf);
973
974 current->in_memstall = 1;
975 psi_task_change(current, 0, TSK_MEMSTALL | TSK_MEMSTALL_RUNNING);
976
977 rq_unlock_irq(rq, &rf);
978 }
979 EXPORT_SYMBOL_GPL(psi_memstall_enter);
980
981 /**
982 * psi_memstall_leave - mark the end of an memory stall section
983 * @flags: flags to handle nested memdelay sections
984 *
985 * Marks the calling task as no longer stalled due to lack of memory.
986 */
psi_memstall_leave(unsigned long * flags)987 void psi_memstall_leave(unsigned long *flags)
988 {
989 struct rq_flags rf;
990 struct rq *rq;
991
992 if (static_branch_likely(&psi_disabled))
993 return;
994
995 if (*flags)
996 return;
997 /*
998 * in_memstall clearing & accounting needs to be atomic wrt
999 * changes to the task's scheduling state, otherwise we could
1000 * race with CPU migration.
1001 */
1002 rq = this_rq_lock_irq(&rf);
1003
1004 current->in_memstall = 0;
1005 psi_task_change(current, TSK_MEMSTALL | TSK_MEMSTALL_RUNNING, 0);
1006
1007 rq_unlock_irq(rq, &rf);
1008 }
1009 EXPORT_SYMBOL_GPL(psi_memstall_leave);
1010
1011 #ifdef CONFIG_CGROUPS
psi_cgroup_alloc(struct cgroup * cgroup)1012 int psi_cgroup_alloc(struct cgroup *cgroup)
1013 {
1014 if (!static_branch_likely(&psi_cgroups_enabled))
1015 return 0;
1016
1017 cgroup->psi = kzalloc(sizeof(struct psi_group), GFP_KERNEL);
1018 if (!cgroup->psi)
1019 return -ENOMEM;
1020
1021 cgroup->psi->pcpu = alloc_percpu(struct psi_group_cpu);
1022 if (!cgroup->psi->pcpu) {
1023 kfree(cgroup->psi);
1024 return -ENOMEM;
1025 }
1026 group_init(cgroup->psi);
1027 cgroup->psi->parent = cgroup_psi(cgroup_parent(cgroup));
1028 return 0;
1029 }
1030
psi_cgroup_free(struct cgroup * cgroup)1031 void psi_cgroup_free(struct cgroup *cgroup)
1032 {
1033 if (!static_branch_likely(&psi_cgroups_enabled))
1034 return;
1035
1036 cancel_delayed_work_sync(&cgroup->psi->avgs_work);
1037 free_percpu(cgroup->psi->pcpu);
1038 /* All triggers must be removed by now */
1039 WARN_ONCE(cgroup->psi->poll_states, "psi: trigger leak\n");
1040 kfree(cgroup->psi);
1041 }
1042
1043 /**
1044 * cgroup_move_task - move task to a different cgroup
1045 * @task: the task
1046 * @to: the target css_set
1047 *
1048 * Move task to a new cgroup and safely migrate its associated stall
1049 * state between the different groups.
1050 *
1051 * This function acquires the task's rq lock to lock out concurrent
1052 * changes to the task's scheduling state and - in case the task is
1053 * running - concurrent changes to its stall state.
1054 */
cgroup_move_task(struct task_struct * task,struct css_set * to)1055 void cgroup_move_task(struct task_struct *task, struct css_set *to)
1056 {
1057 unsigned int task_flags;
1058 struct rq_flags rf;
1059 struct rq *rq;
1060
1061 if (!static_branch_likely(&psi_cgroups_enabled)) {
1062 /*
1063 * Lame to do this here, but the scheduler cannot be locked
1064 * from the outside, so we move cgroups from inside sched/.
1065 */
1066 rcu_assign_pointer(task->cgroups, to);
1067 return;
1068 }
1069
1070 rq = task_rq_lock(task, &rf);
1071
1072 /*
1073 * We may race with schedule() dropping the rq lock between
1074 * deactivating prev and switching to next. Because the psi
1075 * updates from the deactivation are deferred to the switch
1076 * callback to save cgroup tree updates, the task's scheduling
1077 * state here is not coherent with its psi state:
1078 *
1079 * schedule() cgroup_move_task()
1080 * rq_lock()
1081 * deactivate_task()
1082 * p->on_rq = 0
1083 * psi_dequeue() // defers TSK_RUNNING & TSK_IOWAIT updates
1084 * pick_next_task()
1085 * rq_unlock()
1086 * rq_lock()
1087 * psi_task_change() // old cgroup
1088 * task->cgroups = to
1089 * psi_task_change() // new cgroup
1090 * rq_unlock()
1091 * rq_lock()
1092 * psi_sched_switch() // does deferred updates in new cgroup
1093 *
1094 * Don't rely on the scheduling state. Use psi_flags instead.
1095 */
1096 task_flags = task->psi_flags;
1097
1098 if (task_flags)
1099 psi_task_change(task, task_flags, 0);
1100
1101 /* See comment above */
1102 rcu_assign_pointer(task->cgroups, to);
1103
1104 if (task_flags)
1105 psi_task_change(task, 0, task_flags);
1106
1107 task_rq_unlock(rq, task, &rf);
1108 }
1109
psi_cgroup_restart(struct psi_group * group)1110 void psi_cgroup_restart(struct psi_group *group)
1111 {
1112 int cpu;
1113
1114 /*
1115 * After we disable psi_group->enabled, we don't actually
1116 * stop percpu tasks accounting in each psi_group_cpu,
1117 * instead only stop test_state() loop, record_times()
1118 * and averaging worker, see psi_group_change() for details.
1119 *
1120 * When disable cgroup PSI, this function has nothing to sync
1121 * since cgroup pressure files are hidden and percpu psi_group_cpu
1122 * would see !psi_group->enabled and only do task accounting.
1123 *
1124 * When re-enable cgroup PSI, this function use psi_group_change()
1125 * to get correct state mask from test_state() loop on tasks[],
1126 * and restart groupc->state_start from now, use .clear = .set = 0
1127 * here since no task status really changed.
1128 */
1129 if (!group->enabled)
1130 return;
1131
1132 for_each_possible_cpu(cpu) {
1133 struct rq *rq = cpu_rq(cpu);
1134 struct rq_flags rf;
1135 u64 now;
1136
1137 rq_lock_irq(rq, &rf);
1138 now = cpu_clock(cpu);
1139 psi_group_change(group, cpu, 0, 0, now, true);
1140 rq_unlock_irq(rq, &rf);
1141 }
1142 }
1143 #endif /* CONFIG_CGROUPS */
1144
psi_show(struct seq_file * m,struct psi_group * group,enum psi_res res)1145 int psi_show(struct seq_file *m, struct psi_group *group, enum psi_res res)
1146 {
1147 bool only_full = false;
1148 int full;
1149 u64 now;
1150
1151 if (static_branch_likely(&psi_disabled))
1152 return -EOPNOTSUPP;
1153
1154 /* Update averages before reporting them */
1155 mutex_lock(&group->avgs_lock);
1156 now = sched_clock();
1157 collect_percpu_times(group, PSI_AVGS, NULL);
1158 if (now >= group->avg_next_update)
1159 group->avg_next_update = update_averages(group, now);
1160 mutex_unlock(&group->avgs_lock);
1161
1162 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
1163 only_full = res == PSI_IRQ;
1164 #endif
1165
1166 for (full = 0; full < 2 - only_full; full++) {
1167 unsigned long avg[3] = { 0, };
1168 u64 total = 0;
1169 int w;
1170
1171 /* CPU FULL is undefined at the system level */
1172 if (!(group == &psi_system && res == PSI_CPU && full)) {
1173 for (w = 0; w < 3; w++)
1174 avg[w] = group->avg[res * 2 + full][w];
1175 total = div_u64(group->total[PSI_AVGS][res * 2 + full],
1176 NSEC_PER_USEC);
1177 }
1178
1179 seq_printf(m, "%s avg10=%lu.%02lu avg60=%lu.%02lu avg300=%lu.%02lu total=%llu\n",
1180 full || only_full ? "full" : "some",
1181 LOAD_INT(avg[0]), LOAD_FRAC(avg[0]),
1182 LOAD_INT(avg[1]), LOAD_FRAC(avg[1]),
1183 LOAD_INT(avg[2]), LOAD_FRAC(avg[2]),
1184 total);
1185 }
1186
1187 return 0;
1188 }
1189
psi_trigger_create(struct psi_group * group,char * buf,enum psi_res res)1190 struct psi_trigger *psi_trigger_create(struct psi_group *group,
1191 char *buf, enum psi_res res)
1192 {
1193 struct psi_trigger *t;
1194 enum psi_states state;
1195 u32 threshold_us;
1196 u32 window_us;
1197
1198 if (static_branch_likely(&psi_disabled))
1199 return ERR_PTR(-EOPNOTSUPP);
1200
1201 if (sscanf(buf, "some %u %u", &threshold_us, &window_us) == 2)
1202 state = PSI_IO_SOME + res * 2;
1203 else if (sscanf(buf, "full %u %u", &threshold_us, &window_us) == 2)
1204 state = PSI_IO_FULL + res * 2;
1205 else
1206 return ERR_PTR(-EINVAL);
1207
1208 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
1209 if (res == PSI_IRQ && --state != PSI_IRQ_FULL)
1210 return ERR_PTR(-EINVAL);
1211 #endif
1212
1213 if (state >= PSI_NONIDLE)
1214 return ERR_PTR(-EINVAL);
1215
1216 if (window_us < WINDOW_MIN_US ||
1217 window_us > WINDOW_MAX_US)
1218 return ERR_PTR(-EINVAL);
1219
1220 /* Check threshold */
1221 if (threshold_us == 0 || threshold_us > window_us)
1222 return ERR_PTR(-EINVAL);
1223
1224 t = kmalloc(sizeof(*t), GFP_KERNEL);
1225 if (!t)
1226 return ERR_PTR(-ENOMEM);
1227
1228 t->group = group;
1229 t->state = state;
1230 t->threshold = threshold_us * NSEC_PER_USEC;
1231 t->win.size = window_us * NSEC_PER_USEC;
1232 window_reset(&t->win, sched_clock(),
1233 group->total[PSI_POLL][t->state], 0);
1234
1235 t->event = 0;
1236 t->last_event_time = 0;
1237 init_waitqueue_head(&t->event_wait);
1238 t->pending_event = false;
1239
1240 mutex_lock(&group->trigger_lock);
1241
1242 if (!rcu_access_pointer(group->poll_task)) {
1243 struct task_struct *task;
1244
1245 task = kthread_create(psi_poll_worker, group, "psimon");
1246 if (IS_ERR(task)) {
1247 kfree(t);
1248 mutex_unlock(&group->trigger_lock);
1249 return ERR_CAST(task);
1250 }
1251 atomic_set(&group->poll_wakeup, 0);
1252 wake_up_process(task);
1253 rcu_assign_pointer(group->poll_task, task);
1254 }
1255
1256 list_add(&t->node, &group->triggers);
1257 group->poll_min_period = min(group->poll_min_period,
1258 div_u64(t->win.size, UPDATES_PER_WINDOW));
1259 group->nr_triggers[t->state]++;
1260 group->poll_states |= (1 << t->state);
1261
1262 mutex_unlock(&group->trigger_lock);
1263
1264 return t;
1265 }
1266
psi_trigger_destroy(struct psi_trigger * t)1267 void psi_trigger_destroy(struct psi_trigger *t)
1268 {
1269 struct psi_group *group;
1270 struct task_struct *task_to_destroy = NULL;
1271
1272 /*
1273 * We do not check psi_disabled since it might have been disabled after
1274 * the trigger got created.
1275 */
1276 if (!t)
1277 return;
1278
1279 group = t->group;
1280 /*
1281 * Wakeup waiters to stop polling. Can happen if cgroup is deleted
1282 * from under a polling process.
1283 */
1284 wake_up_interruptible(&t->event_wait);
1285
1286 mutex_lock(&group->trigger_lock);
1287
1288 if (!list_empty(&t->node)) {
1289 struct psi_trigger *tmp;
1290 u64 period = ULLONG_MAX;
1291
1292 list_del(&t->node);
1293 group->nr_triggers[t->state]--;
1294 if (!group->nr_triggers[t->state])
1295 group->poll_states &= ~(1 << t->state);
1296 /* reset min update period for the remaining triggers */
1297 list_for_each_entry(tmp, &group->triggers, node)
1298 period = min(period, div_u64(tmp->win.size,
1299 UPDATES_PER_WINDOW));
1300 group->poll_min_period = period;
1301 /* Destroy poll_task when the last trigger is destroyed */
1302 if (group->poll_states == 0) {
1303 group->polling_until = 0;
1304 task_to_destroy = rcu_dereference_protected(
1305 group->poll_task,
1306 lockdep_is_held(&group->trigger_lock));
1307 rcu_assign_pointer(group->poll_task, NULL);
1308 del_timer(&group->poll_timer);
1309 }
1310 }
1311
1312 mutex_unlock(&group->trigger_lock);
1313
1314 /*
1315 * Wait for psi_schedule_poll_work RCU to complete its read-side
1316 * critical section before destroying the trigger and optionally the
1317 * poll_task.
1318 */
1319 synchronize_rcu();
1320 /*
1321 * Stop kthread 'psimon' after releasing trigger_lock to prevent a
1322 * deadlock while waiting for psi_poll_work to acquire trigger_lock
1323 */
1324 if (task_to_destroy) {
1325 /*
1326 * After the RCU grace period has expired, the worker
1327 * can no longer be found through group->poll_task.
1328 */
1329 kthread_stop(task_to_destroy);
1330 }
1331 kfree(t);
1332 }
1333
psi_trigger_poll(void ** trigger_ptr,struct file * file,poll_table * wait)1334 __poll_t psi_trigger_poll(void **trigger_ptr,
1335 struct file *file, poll_table *wait)
1336 {
1337 __poll_t ret = DEFAULT_POLLMASK;
1338 struct psi_trigger *t;
1339
1340 if (static_branch_likely(&psi_disabled))
1341 return DEFAULT_POLLMASK | EPOLLERR | EPOLLPRI;
1342
1343 t = smp_load_acquire(trigger_ptr);
1344 if (!t)
1345 return DEFAULT_POLLMASK | EPOLLERR | EPOLLPRI;
1346
1347 poll_wait(file, &t->event_wait, wait);
1348
1349 if (cmpxchg(&t->event, 1, 0) == 1)
1350 ret |= EPOLLPRI;
1351
1352 return ret;
1353 }
1354
1355 #ifdef CONFIG_PROC_FS
psi_io_show(struct seq_file * m,void * v)1356 static int psi_io_show(struct seq_file *m, void *v)
1357 {
1358 return psi_show(m, &psi_system, PSI_IO);
1359 }
1360
psi_memory_show(struct seq_file * m,void * v)1361 static int psi_memory_show(struct seq_file *m, void *v)
1362 {
1363 return psi_show(m, &psi_system, PSI_MEM);
1364 }
1365
psi_cpu_show(struct seq_file * m,void * v)1366 static int psi_cpu_show(struct seq_file *m, void *v)
1367 {
1368 return psi_show(m, &psi_system, PSI_CPU);
1369 }
1370
psi_open(struct file * file,int (* psi_show)(struct seq_file *,void *))1371 static int psi_open(struct file *file, int (*psi_show)(struct seq_file *, void *))
1372 {
1373 if (file->f_mode & FMODE_WRITE && !capable(CAP_SYS_RESOURCE))
1374 return -EPERM;
1375
1376 return single_open(file, psi_show, NULL);
1377 }
1378
psi_io_open(struct inode * inode,struct file * file)1379 static int psi_io_open(struct inode *inode, struct file *file)
1380 {
1381 return psi_open(file, psi_io_show);
1382 }
1383
psi_memory_open(struct inode * inode,struct file * file)1384 static int psi_memory_open(struct inode *inode, struct file *file)
1385 {
1386 return psi_open(file, psi_memory_show);
1387 }
1388
psi_cpu_open(struct inode * inode,struct file * file)1389 static int psi_cpu_open(struct inode *inode, struct file *file)
1390 {
1391 return psi_open(file, psi_cpu_show);
1392 }
1393
psi_write(struct file * file,const char __user * user_buf,size_t nbytes,enum psi_res res)1394 static ssize_t psi_write(struct file *file, const char __user *user_buf,
1395 size_t nbytes, enum psi_res res)
1396 {
1397 char buf[32];
1398 size_t buf_size;
1399 struct seq_file *seq;
1400 struct psi_trigger *new;
1401
1402 if (static_branch_likely(&psi_disabled))
1403 return -EOPNOTSUPP;
1404
1405 if (!nbytes)
1406 return -EINVAL;
1407
1408 buf_size = min(nbytes, sizeof(buf));
1409 if (copy_from_user(buf, user_buf, buf_size))
1410 return -EFAULT;
1411
1412 buf[buf_size - 1] = '\0';
1413
1414 seq = file->private_data;
1415
1416 /* Take seq->lock to protect seq->private from concurrent writes */
1417 mutex_lock(&seq->lock);
1418
1419 /* Allow only one trigger per file descriptor */
1420 if (seq->private) {
1421 mutex_unlock(&seq->lock);
1422 return -EBUSY;
1423 }
1424
1425 new = psi_trigger_create(&psi_system, buf, res);
1426 if (IS_ERR(new)) {
1427 mutex_unlock(&seq->lock);
1428 return PTR_ERR(new);
1429 }
1430
1431 smp_store_release(&seq->private, new);
1432 mutex_unlock(&seq->lock);
1433
1434 return nbytes;
1435 }
1436
psi_io_write(struct file * file,const char __user * user_buf,size_t nbytes,loff_t * ppos)1437 static ssize_t psi_io_write(struct file *file, const char __user *user_buf,
1438 size_t nbytes, loff_t *ppos)
1439 {
1440 return psi_write(file, user_buf, nbytes, PSI_IO);
1441 }
1442
psi_memory_write(struct file * file,const char __user * user_buf,size_t nbytes,loff_t * ppos)1443 static ssize_t psi_memory_write(struct file *file, const char __user *user_buf,
1444 size_t nbytes, loff_t *ppos)
1445 {
1446 return psi_write(file, user_buf, nbytes, PSI_MEM);
1447 }
1448
psi_cpu_write(struct file * file,const char __user * user_buf,size_t nbytes,loff_t * ppos)1449 static ssize_t psi_cpu_write(struct file *file, const char __user *user_buf,
1450 size_t nbytes, loff_t *ppos)
1451 {
1452 return psi_write(file, user_buf, nbytes, PSI_CPU);
1453 }
1454
psi_fop_poll(struct file * file,poll_table * wait)1455 static __poll_t psi_fop_poll(struct file *file, poll_table *wait)
1456 {
1457 struct seq_file *seq = file->private_data;
1458
1459 return psi_trigger_poll(&seq->private, file, wait);
1460 }
1461
psi_fop_release(struct inode * inode,struct file * file)1462 static int psi_fop_release(struct inode *inode, struct file *file)
1463 {
1464 struct seq_file *seq = file->private_data;
1465
1466 psi_trigger_destroy(seq->private);
1467 return single_release(inode, file);
1468 }
1469
1470 static const struct proc_ops psi_io_proc_ops = {
1471 .proc_open = psi_io_open,
1472 .proc_read = seq_read,
1473 .proc_lseek = seq_lseek,
1474 .proc_write = psi_io_write,
1475 .proc_poll = psi_fop_poll,
1476 .proc_release = psi_fop_release,
1477 };
1478
1479 static const struct proc_ops psi_memory_proc_ops = {
1480 .proc_open = psi_memory_open,
1481 .proc_read = seq_read,
1482 .proc_lseek = seq_lseek,
1483 .proc_write = psi_memory_write,
1484 .proc_poll = psi_fop_poll,
1485 .proc_release = psi_fop_release,
1486 };
1487
1488 static const struct proc_ops psi_cpu_proc_ops = {
1489 .proc_open = psi_cpu_open,
1490 .proc_read = seq_read,
1491 .proc_lseek = seq_lseek,
1492 .proc_write = psi_cpu_write,
1493 .proc_poll = psi_fop_poll,
1494 .proc_release = psi_fop_release,
1495 };
1496
1497 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
psi_irq_show(struct seq_file * m,void * v)1498 static int psi_irq_show(struct seq_file *m, void *v)
1499 {
1500 return psi_show(m, &psi_system, PSI_IRQ);
1501 }
1502
psi_irq_open(struct inode * inode,struct file * file)1503 static int psi_irq_open(struct inode *inode, struct file *file)
1504 {
1505 return psi_open(file, psi_irq_show);
1506 }
1507
psi_irq_write(struct file * file,const char __user * user_buf,size_t nbytes,loff_t * ppos)1508 static ssize_t psi_irq_write(struct file *file, const char __user *user_buf,
1509 size_t nbytes, loff_t *ppos)
1510 {
1511 return psi_write(file, user_buf, nbytes, PSI_IRQ);
1512 }
1513
1514 static const struct proc_ops psi_irq_proc_ops = {
1515 .proc_open = psi_irq_open,
1516 .proc_read = seq_read,
1517 .proc_lseek = seq_lseek,
1518 .proc_write = psi_irq_write,
1519 .proc_poll = psi_fop_poll,
1520 .proc_release = psi_fop_release,
1521 };
1522 #endif
1523
psi_proc_init(void)1524 static int __init psi_proc_init(void)
1525 {
1526 if (psi_enable) {
1527 proc_mkdir("pressure", NULL);
1528 proc_create("pressure/io", 0666, NULL, &psi_io_proc_ops);
1529 proc_create("pressure/memory", 0666, NULL, &psi_memory_proc_ops);
1530 proc_create("pressure/cpu", 0666, NULL, &psi_cpu_proc_ops);
1531 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
1532 proc_create("pressure/irq", 0666, NULL, &psi_irq_proc_ops);
1533 #endif
1534 }
1535 return 0;
1536 }
1537 module_init(psi_proc_init);
1538
1539 #endif /* CONFIG_PROC_FS */
1540