1
2
3
4
5
6
7
8
9
10
11
12
13
14#include <linux/cpu.h>
15#include <linux/err.h>
16#include <linux/hrtimer.h>
17#include <linux/interrupt.h>
18#include <linux/kernel_stat.h>
19#include <linux/percpu.h>
20#include <linux/profile.h>
21#include <linux/sched.h>
22#include <linux/tick.h>
23#include <linux/module.h>
24
25#include <asm/irq_regs.h>
26
27#include "tick-internal.h"
28
29
30
31
32static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
33
34
35
36
37static ktime_t last_jiffies_update;
38
39struct tick_sched *tick_get_tick_sched(int cpu)
40{
41 return &per_cpu(tick_cpu_sched, cpu);
42}
43
44
45
46
47static void tick_do_update_jiffies64(ktime_t now)
48{
49 unsigned long ticks = 0;
50 ktime_t delta;
51
52
53
54
55 delta = ktime_sub(now, last_jiffies_update);
56 if (delta.tv64 < tick_period.tv64)
57 return;
58
59
60 write_seqlock(&xtime_lock);
61
62 delta = ktime_sub(now, last_jiffies_update);
63 if (delta.tv64 >= tick_period.tv64) {
64
65 delta = ktime_sub(delta, tick_period);
66 last_jiffies_update = ktime_add(last_jiffies_update,
67 tick_period);
68
69
70 if (unlikely(delta.tv64 >= tick_period.tv64)) {
71 s64 incr = ktime_to_ns(tick_period);
72
73 ticks = ktime_divns(delta, incr);
74
75 last_jiffies_update = ktime_add_ns(last_jiffies_update,
76 incr * ticks);
77 }
78 do_timer(++ticks);
79
80
81 tick_next_period = ktime_add(last_jiffies_update, tick_period);
82 }
83 write_sequnlock(&xtime_lock);
84}
85
86
87
88
89static ktime_t tick_init_jiffy_update(void)
90{
91 ktime_t period;
92
93 write_seqlock(&xtime_lock);
94
95 if (last_jiffies_update.tv64 == 0)
96 last_jiffies_update = tick_next_period;
97 period = last_jiffies_update;
98 write_sequnlock(&xtime_lock);
99 return period;
100}
101
102
103
104
105#ifdef CONFIG_NO_HZ
106
107
108
109static int tick_nohz_enabled __read_mostly = 1;
110
111
112
113
114static int __init setup_tick_nohz(char *str)
115{
116 if (!strcmp(str, "off"))
117 tick_nohz_enabled = 0;
118 else if (!strcmp(str, "on"))
119 tick_nohz_enabled = 1;
120 else
121 return 0;
122 return 1;
123}
124
125__setup("nohz=", setup_tick_nohz);
126
127
128
129
130
131
132
133
134
135
136
137static void tick_nohz_update_jiffies(void)
138{
139 int cpu = smp_processor_id();
140 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
141 unsigned long flags;
142 ktime_t now;
143
144 if (!ts->tick_stopped)
145 return;
146
147 cpumask_clear_cpu(cpu, nohz_cpu_mask);
148 now = ktime_get();
149 ts->idle_waketime = now;
150
151 local_irq_save(flags);
152 tick_do_update_jiffies64(now);
153 local_irq_restore(flags);
154
155 touch_softlockup_watchdog();
156}
157
158static void tick_nohz_stop_idle(int cpu)
159{
160 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
161
162 if (ts->idle_active) {
163 ktime_t now, delta;
164 now = ktime_get();
165 delta = ktime_sub(now, ts->idle_entrytime);
166 ts->idle_lastupdate = now;
167 ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
168 ts->idle_active = 0;
169
170 sched_clock_idle_wakeup_event(0);
171 }
172}
173
174static ktime_t tick_nohz_start_idle(struct tick_sched *ts)
175{
176 ktime_t now, delta;
177
178 now = ktime_get();
179 if (ts->idle_active) {
180 delta = ktime_sub(now, ts->idle_entrytime);
181 ts->idle_lastupdate = now;
182 ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
183 }
184 ts->idle_entrytime = now;
185 ts->idle_active = 1;
186 sched_clock_idle_sleep_event();
187 return now;
188}
189
190u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
191{
192 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
193
194 if (!tick_nohz_enabled)
195 return -1;
196
197 if (ts->idle_active)
198 *last_update_time = ktime_to_us(ts->idle_lastupdate);
199 else
200 *last_update_time = ktime_to_us(ktime_get());
201
202 return ktime_to_us(ts->idle_sleeptime);
203}
204EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
205
206
207
208
209
210
211
212
213void tick_nohz_stop_sched_tick(int inidle)
214{
215 unsigned long seq, last_jiffies, next_jiffies, delta_jiffies, flags;
216 struct tick_sched *ts;
217 ktime_t last_update, expires, now;
218 struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
219 int cpu;
220
221 local_irq_save(flags);
222
223 cpu = smp_processor_id();
224 ts = &per_cpu(tick_cpu_sched, cpu);
225
226
227
228
229
230
231 if (!inidle && !ts->inidle)
232 goto end;
233
234
235
236
237
238
239 ts->inidle = 1;
240
241 now = tick_nohz_start_idle(ts);
242
243
244
245
246
247
248
249
250 if (unlikely(!cpu_online(cpu))) {
251 if (cpu == tick_do_timer_cpu)
252 tick_do_timer_cpu = TICK_DO_TIMER_NONE;
253 }
254
255 if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
256 goto end;
257
258 if (need_resched())
259 goto end;
260
261 if (unlikely(local_softirq_pending() && cpu_online(cpu))) {
262 static int ratelimit;
263
264 if (ratelimit < 10) {
265 printk(KERN_ERR "NOHZ: local_softirq_pending %02x\n",
266 local_softirq_pending());
267 ratelimit++;
268 }
269 goto end;
270 }
271
272 ts->idle_calls++;
273
274 do {
275 seq = read_seqbegin(&xtime_lock);
276 last_update = last_jiffies_update;
277 last_jiffies = jiffies;
278 } while (read_seqretry(&xtime_lock, seq));
279
280
281 next_jiffies = get_next_timer_interrupt(last_jiffies);
282 delta_jiffies = next_jiffies - last_jiffies;
283
284 if (rcu_needs_cpu(cpu) || printk_needs_cpu(cpu))
285 delta_jiffies = 1;
286
287
288
289
290 if (!ts->tick_stopped && delta_jiffies == 1)
291 goto out;
292
293
294 if ((long)delta_jiffies >= 1) {
295
296
297
298
299
300 expires = ktime_add_ns(last_update, tick_period.tv64 *
301 delta_jiffies);
302
303
304
305
306
307
308
309
310
311 if (cpu == tick_do_timer_cpu)
312 tick_do_timer_cpu = TICK_DO_TIMER_NONE;
313
314 if (delta_jiffies > 1)
315 cpumask_set_cpu(cpu, nohz_cpu_mask);
316
317
318 if (ts->tick_stopped && ktime_equal(expires, dev->next_event))
319 goto out;
320
321
322
323
324
325
326
327
328 if (!ts->tick_stopped) {
329 if (select_nohz_load_balancer(1)) {
330
331
332
333 cpumask_clear_cpu(cpu, nohz_cpu_mask);
334 goto out;
335 }
336
337 ts->idle_tick = hrtimer_get_expires(&ts->sched_timer);
338 ts->tick_stopped = 1;
339 ts->idle_jiffies = last_jiffies;
340 rcu_enter_nohz();
341 }
342
343 ts->idle_sleeps++;
344
345
346
347
348
349
350
351 if (unlikely(delta_jiffies >= NEXT_TIMER_MAX_DELTA)) {
352 ts->idle_expires.tv64 = KTIME_MAX;
353 if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
354 hrtimer_cancel(&ts->sched_timer);
355 goto out;
356 }
357
358
359 ts->idle_expires = expires;
360
361 if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
362 hrtimer_start(&ts->sched_timer, expires,
363 HRTIMER_MODE_ABS_PINNED);
364
365 if (hrtimer_active(&ts->sched_timer))
366 goto out;
367 } else if (!tick_program_event(expires, 0))
368 goto out;
369
370
371
372
373
374 tick_do_update_jiffies64(ktime_get());
375 cpumask_clear_cpu(cpu, nohz_cpu_mask);
376 }
377 raise_softirq_irqoff(TIMER_SOFTIRQ);
378out:
379 ts->next_jiffies = next_jiffies;
380 ts->last_jiffies = last_jiffies;
381 ts->sleep_length = ktime_sub(dev->next_event, now);
382end:
383 local_irq_restore(flags);
384}
385
386
387
388
389
390
391ktime_t tick_nohz_get_sleep_length(void)
392{
393 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
394
395 return ts->sleep_length;
396}
397
398static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
399{
400 hrtimer_cancel(&ts->sched_timer);
401 hrtimer_set_expires(&ts->sched_timer, ts->idle_tick);
402
403 while (1) {
404
405 hrtimer_forward(&ts->sched_timer, now, tick_period);
406
407 if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
408 hrtimer_start_expires(&ts->sched_timer,
409 HRTIMER_MODE_ABS_PINNED);
410
411 if (hrtimer_active(&ts->sched_timer))
412 break;
413 } else {
414 if (!tick_program_event(
415 hrtimer_get_expires(&ts->sched_timer), 0))
416 break;
417 }
418
419 tick_do_update_jiffies64(now);
420 now = ktime_get();
421 }
422}
423
424
425
426
427
428
429void tick_nohz_restart_sched_tick(void)
430{
431 int cpu = smp_processor_id();
432 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
433#ifndef CONFIG_VIRT_CPU_ACCOUNTING
434 unsigned long ticks;
435#endif
436 ktime_t now;
437
438 local_irq_disable();
439 tick_nohz_stop_idle(cpu);
440
441 if (!ts->inidle || !ts->tick_stopped) {
442 ts->inidle = 0;
443 local_irq_enable();
444 return;
445 }
446
447 ts->inidle = 0;
448
449 rcu_exit_nohz();
450
451
452 select_nohz_load_balancer(0);
453 now = ktime_get();
454 tick_do_update_jiffies64(now);
455 cpumask_clear_cpu(cpu, nohz_cpu_mask);
456
457#ifndef CONFIG_VIRT_CPU_ACCOUNTING
458
459
460
461
462
463 ticks = jiffies - ts->idle_jiffies;
464
465
466
467 if (ticks && ticks < LONG_MAX)
468 account_idle_ticks(ticks);
469#endif
470
471 touch_softlockup_watchdog();
472
473
474
475 ts->tick_stopped = 0;
476 ts->idle_exittime = now;
477
478 tick_nohz_restart(ts, now);
479
480 local_irq_enable();
481}
482
483static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now)
484{
485 hrtimer_forward(&ts->sched_timer, now, tick_period);
486 return tick_program_event(hrtimer_get_expires(&ts->sched_timer), 0);
487}
488
489
490
491
492static void tick_nohz_handler(struct clock_event_device *dev)
493{
494 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
495 struct pt_regs *regs = get_irq_regs();
496 int cpu = smp_processor_id();
497 ktime_t now = ktime_get();
498
499 dev->next_event.tv64 = KTIME_MAX;
500
501
502
503
504
505
506
507
508 if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
509 tick_do_timer_cpu = cpu;
510
511
512 if (tick_do_timer_cpu == cpu)
513 tick_do_update_jiffies64(now);
514
515
516
517
518
519
520
521
522
523 if (ts->tick_stopped) {
524 touch_softlockup_watchdog();
525 ts->idle_jiffies++;
526 }
527
528 update_process_times(user_mode(regs));
529 profile_tick(CPU_PROFILING);
530
531 while (tick_nohz_reprogram(ts, now)) {
532 now = ktime_get();
533 tick_do_update_jiffies64(now);
534 }
535}
536
537
538
539
540static void tick_nohz_switch_to_nohz(void)
541{
542 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
543 ktime_t next;
544
545 if (!tick_nohz_enabled)
546 return;
547
548 local_irq_disable();
549 if (tick_switch_to_oneshot(tick_nohz_handler)) {
550 local_irq_enable();
551 return;
552 }
553
554 ts->nohz_mode = NOHZ_MODE_LOWRES;
555
556
557
558
559
560 hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
561
562 next = tick_init_jiffy_update();
563
564 for (;;) {
565 hrtimer_set_expires(&ts->sched_timer, next);
566 if (!tick_program_event(next, 0))
567 break;
568 next = ktime_add(next, tick_period);
569 }
570 local_irq_enable();
571
572 printk(KERN_INFO "Switched to NOHz mode on CPU #%d\n",
573 smp_processor_id());
574}
575
576
577
578
579
580
581
582
583
584
585
586
587static void tick_nohz_kick_tick(int cpu)
588{
589#if 0
590
591
592 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
593 ktime_t delta, now;
594
595 if (!ts->tick_stopped)
596 return;
597
598
599
600
601
602 now = ktime_get();
603 delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now);
604 if (delta.tv64 <= tick_period.tv64)
605 return;
606
607 tick_nohz_restart(ts, now);
608#endif
609}
610
611#else
612
613static inline void tick_nohz_switch_to_nohz(void) { }
614
615#endif
616
617
618
619
620void tick_check_idle(int cpu)
621{
622 tick_check_oneshot_broadcast(cpu);
623#ifdef CONFIG_NO_HZ
624 tick_nohz_stop_idle(cpu);
625 tick_nohz_update_jiffies();
626 tick_nohz_kick_tick(cpu);
627#endif
628}
629
630
631
632
633#ifdef CONFIG_HIGH_RES_TIMERS
634
635
636
637
638static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
639{
640 struct tick_sched *ts =
641 container_of(timer, struct tick_sched, sched_timer);
642 struct pt_regs *regs = get_irq_regs();
643 ktime_t now = ktime_get();
644 int cpu = smp_processor_id();
645
646#ifdef CONFIG_NO_HZ
647
648
649
650
651
652
653
654 if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
655 tick_do_timer_cpu = cpu;
656#endif
657
658
659 if (tick_do_timer_cpu == cpu)
660 tick_do_update_jiffies64(now);
661
662
663
664
665
666 if (regs) {
667
668
669
670
671
672
673
674
675 if (ts->tick_stopped) {
676 touch_softlockup_watchdog();
677 ts->idle_jiffies++;
678 }
679 update_process_times(user_mode(regs));
680 profile_tick(CPU_PROFILING);
681 }
682
683 hrtimer_forward(timer, now, tick_period);
684
685 return HRTIMER_RESTART;
686}
687
688
689
690
691void tick_setup_sched_timer(void)
692{
693 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
694 ktime_t now = ktime_get();
695 u64 offset;
696
697
698
699
700 hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
701 ts->sched_timer.function = tick_sched_timer;
702
703
704 hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
705 offset = ktime_to_ns(tick_period) >> 1;
706 do_div(offset, num_possible_cpus());
707 offset *= smp_processor_id();
708 hrtimer_add_expires_ns(&ts->sched_timer, offset);
709
710 for (;;) {
711 hrtimer_forward(&ts->sched_timer, now, tick_period);
712 hrtimer_start_expires(&ts->sched_timer,
713 HRTIMER_MODE_ABS_PINNED);
714
715 if (hrtimer_active(&ts->sched_timer))
716 break;
717 now = ktime_get();
718 }
719
720#ifdef CONFIG_NO_HZ
721 if (tick_nohz_enabled)
722 ts->nohz_mode = NOHZ_MODE_HIGHRES;
723#endif
724}
725#endif
726
727#if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS
728void tick_cancel_sched_timer(int cpu)
729{
730 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
731
732# ifdef CONFIG_HIGH_RES_TIMERS
733 if (ts->sched_timer.base)
734 hrtimer_cancel(&ts->sched_timer);
735# endif
736
737 ts->nohz_mode = NOHZ_MODE_INACTIVE;
738}
739#endif
740
741
742
743
744void tick_clock_notify(void)
745{
746 int cpu;
747
748 for_each_possible_cpu(cpu)
749 set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks);
750}
751
752
753
754
755void tick_oneshot_notify(void)
756{
757 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
758
759 set_bit(0, &ts->check_clocks);
760}
761
762
763
764
765
766
767
768
769
770int tick_check_oneshot_change(int allow_nohz)
771{
772 struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
773
774 if (!test_and_clear_bit(0, &ts->check_clocks))
775 return 0;
776
777 if (ts->nohz_mode != NOHZ_MODE_INACTIVE)
778 return 0;
779
780 if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available())
781 return 0;
782
783 if (!allow_nohz)
784 return 1;
785
786 tick_nohz_switch_to_nohz();
787 return 0;
788}
789