Commit | Line | Data |
---|---|---|
79bf2bb3 TG |
1 | /* |
2 | * linux/kernel/time/tick-sched.c | |
3 | * | |
4 | * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de> | |
5 | * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar | |
6 | * Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner | |
7 | * | |
8 | * No idle tick implementation for low and high resolution timers | |
9 | * | |
10 | * Started by: Thomas Gleixner and Ingo Molnar | |
11 | * | |
b10db7f0 | 12 | * Distribute under GPLv2. |
79bf2bb3 TG |
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> | |
8083e4ad | 22 | #include <linux/module.h> |
00b42959 | 23 | #include <linux/irq_work.h> |
9014c45d FW |
24 | #include <linux/posix-timers.h> |
25 | #include <linux/perf_event.h> | |
2e709338 | 26 | #include <linux/context_tracking.h> |
79bf2bb3 | 27 | |
9e203bcc DM |
28 | #include <asm/irq_regs.h> |
29 | ||
79bf2bb3 TG |
30 | #include "tick-internal.h" |
31 | ||
cb41a290 FW |
32 | #include <trace/events/timer.h> |
33 | ||
79bf2bb3 TG |
34 | /* |
35 | * Per cpu nohz control structure | |
36 | */ | |
c1797baf | 37 | static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched); |
79bf2bb3 TG |
38 | |
39 | /* | |
d6ad4187 | 40 | * The time, when the last jiffy update happened. Protected by jiffies_lock. |
79bf2bb3 TG |
41 | */ |
42 | static ktime_t last_jiffies_update; | |
43 | ||
289f480a IM |
44 | struct tick_sched *tick_get_tick_sched(int cpu) |
45 | { | |
46 | return &per_cpu(tick_cpu_sched, cpu); | |
47 | } | |
48 | ||
79bf2bb3 TG |
49 | /* |
50 | * Must be called with interrupts disabled ! | |
51 | */ | |
52 | static void tick_do_update_jiffies64(ktime_t now) | |
53 | { | |
54 | unsigned long ticks = 0; | |
55 | ktime_t delta; | |
56 | ||
7a14ce1d | 57 | /* |
d6ad4187 | 58 | * Do a quick check without holding jiffies_lock: |
7a14ce1d IM |
59 | */ |
60 | delta = ktime_sub(now, last_jiffies_update); | |
61 | if (delta.tv64 < tick_period.tv64) | |
62 | return; | |
63 | ||
d6ad4187 JS |
64 | /* Reevalute with jiffies_lock held */ |
65 | write_seqlock(&jiffies_lock); | |
79bf2bb3 TG |
66 | |
67 | delta = ktime_sub(now, last_jiffies_update); | |
68 | if (delta.tv64 >= tick_period.tv64) { | |
69 | ||
70 | delta = ktime_sub(delta, tick_period); | |
71 | last_jiffies_update = ktime_add(last_jiffies_update, | |
72 | tick_period); | |
73 | ||
74 | /* Slow path for long timeouts */ | |
75 | if (unlikely(delta.tv64 >= tick_period.tv64)) { | |
76 | s64 incr = ktime_to_ns(tick_period); | |
77 | ||
78 | ticks = ktime_divns(delta, incr); | |
79 | ||
80 | last_jiffies_update = ktime_add_ns(last_jiffies_update, | |
81 | incr * ticks); | |
82 | } | |
83 | do_timer(++ticks); | |
49d670fb TG |
84 | |
85 | /* Keep the tick_next_period variable up to date */ | |
86 | tick_next_period = ktime_add(last_jiffies_update, tick_period); | |
03e6bdc5 VK |
87 | } else { |
88 | write_sequnlock(&jiffies_lock); | |
89 | return; | |
79bf2bb3 | 90 | } |
d6ad4187 | 91 | write_sequnlock(&jiffies_lock); |
47a1b796 | 92 | update_wall_time(); |
79bf2bb3 TG |
93 | } |
94 | ||
95 | /* | |
96 | * Initialize and return retrieve the jiffies update. | |
97 | */ | |
98 | static ktime_t tick_init_jiffy_update(void) | |
99 | { | |
100 | ktime_t period; | |
101 | ||
d6ad4187 | 102 | write_seqlock(&jiffies_lock); |
79bf2bb3 TG |
103 | /* Did we start the jiffies update yet ? */ |
104 | if (last_jiffies_update.tv64 == 0) | |
105 | last_jiffies_update = tick_next_period; | |
106 | period = last_jiffies_update; | |
d6ad4187 | 107 | write_sequnlock(&jiffies_lock); |
79bf2bb3 TG |
108 | return period; |
109 | } | |
110 | ||
5bb96226 FW |
111 | |
112 | static void tick_sched_do_timer(ktime_t now) | |
113 | { | |
114 | int cpu = smp_processor_id(); | |
115 | ||
3451d024 | 116 | #ifdef CONFIG_NO_HZ_COMMON |
5bb96226 FW |
117 | /* |
118 | * Check if the do_timer duty was dropped. We don't care about | |
119 | * concurrency: This happens only when the cpu in charge went | |
120 | * into a long sleep. If two cpus happen to assign themself to | |
121 | * this duty, then the jiffies update is still serialized by | |
9c3f9e28 | 122 | * jiffies_lock. |
5bb96226 | 123 | */ |
a382bf93 | 124 | if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE) |
c5bfece2 | 125 | && !tick_nohz_full_cpu(cpu)) |
5bb96226 FW |
126 | tick_do_timer_cpu = cpu; |
127 | #endif | |
128 | ||
129 | /* Check, if the jiffies need an update */ | |
130 | if (tick_do_timer_cpu == cpu) | |
131 | tick_do_update_jiffies64(now); | |
132 | } | |
133 | ||
9e8f559b FW |
134 | static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs) |
135 | { | |
3451d024 | 136 | #ifdef CONFIG_NO_HZ_COMMON |
9e8f559b FW |
137 | /* |
138 | * When we are idle and the tick is stopped, we have to touch | |
139 | * the watchdog as we might not schedule for a really long | |
140 | * time. This happens on complete idle SMP systems while | |
141 | * waiting on the login prompt. We also increment the "start of | |
142 | * idle" jiffy stamp so the idle accounting adjustment we do | |
143 | * when we go busy again does not account too much ticks. | |
144 | */ | |
145 | if (ts->tick_stopped) { | |
146 | touch_softlockup_watchdog(); | |
147 | if (is_idle_task(current)) | |
148 | ts->idle_jiffies++; | |
149 | } | |
94a57140 | 150 | #endif |
9e8f559b FW |
151 | update_process_times(user_mode(regs)); |
152 | profile_tick(CPU_PROFILING); | |
153 | } | |
154 | ||
c5bfece2 | 155 | #ifdef CONFIG_NO_HZ_FULL |
460775df | 156 | cpumask_var_t tick_nohz_full_mask; |
c0f489d2 | 157 | cpumask_var_t housekeeping_mask; |
73867dcd | 158 | bool tick_nohz_full_running; |
a831881b | 159 | |
9014c45d FW |
160 | static bool can_stop_full_tick(void) |
161 | { | |
162 | WARN_ON_ONCE(!irqs_disabled()); | |
163 | ||
cb41a290 FW |
164 | if (!sched_can_stop_tick()) { |
165 | trace_tick_stop(0, "more than 1 task in runqueue\n"); | |
9014c45d | 166 | return false; |
cb41a290 | 167 | } |
9014c45d | 168 | |
cb41a290 FW |
169 | if (!posix_cpu_timers_can_stop_tick(current)) { |
170 | trace_tick_stop(0, "posix timers running\n"); | |
9014c45d | 171 | return false; |
cb41a290 | 172 | } |
9014c45d | 173 | |
cb41a290 FW |
174 | if (!perf_event_can_stop_tick()) { |
175 | trace_tick_stop(0, "perf events running\n"); | |
9014c45d | 176 | return false; |
cb41a290 | 177 | } |
9014c45d FW |
178 | |
179 | /* sched_clock_tick() needs us? */ | |
180 | #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK | |
181 | /* | |
182 | * TODO: kick full dynticks CPUs when | |
183 | * sched_clock_stable is set. | |
184 | */ | |
35af99e6 | 185 | if (!sched_clock_stable()) { |
cb41a290 | 186 | trace_tick_stop(0, "unstable sched clock\n"); |
e12d0271 SR |
187 | /* |
188 | * Don't allow the user to think they can get | |
189 | * full NO_HZ with this machine. | |
190 | */ | |
73867dcd | 191 | WARN_ONCE(tick_nohz_full_running, |
543487c7 | 192 | "NO_HZ FULL will not work with unstable sched clock"); |
9014c45d | 193 | return false; |
cb41a290 | 194 | } |
9014c45d FW |
195 | #endif |
196 | ||
197 | return true; | |
198 | } | |
199 | ||
200 | static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now); | |
201 | ||
76c24fb0 FW |
202 | /* |
203 | * Re-evaluate the need for the tick on the current CPU | |
204 | * and restart it if necessary. | |
205 | */ | |
d13508f9 | 206 | void __tick_nohz_full_check(void) |
76c24fb0 | 207 | { |
22127e93 | 208 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
9014c45d FW |
209 | |
210 | if (tick_nohz_full_cpu(smp_processor_id())) { | |
211 | if (ts->tick_stopped && !is_idle_task(current)) { | |
212 | if (!can_stop_full_tick()) | |
213 | tick_nohz_restart_sched_tick(ts, ktime_get()); | |
214 | } | |
215 | } | |
76c24fb0 FW |
216 | } |
217 | ||
218 | static void nohz_full_kick_work_func(struct irq_work *work) | |
219 | { | |
d13508f9 | 220 | __tick_nohz_full_check(); |
76c24fb0 FW |
221 | } |
222 | ||
223 | static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = { | |
224 | .func = nohz_full_kick_work_func, | |
225 | }; | |
226 | ||
40bea039 FW |
227 | /* |
228 | * Kick this CPU if it's full dynticks in order to force it to | |
229 | * re-evaluate its dependency on the tick and restart it if necessary. | |
230 | * This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(), | |
231 | * is NMI safe. | |
232 | */ | |
233 | void tick_nohz_full_kick(void) | |
234 | { | |
235 | if (!tick_nohz_full_cpu(smp_processor_id())) | |
236 | return; | |
237 | ||
56e4dea8 | 238 | irq_work_queue(this_cpu_ptr(&nohz_full_kick_work)); |
40bea039 FW |
239 | } |
240 | ||
76c24fb0 | 241 | /* |
3d36aebc | 242 | * Kick the CPU if it's full dynticks in order to force it to |
76c24fb0 FW |
243 | * re-evaluate its dependency on the tick and restart it if necessary. |
244 | */ | |
3d36aebc | 245 | void tick_nohz_full_kick_cpu(int cpu) |
76c24fb0 | 246 | { |
3d36aebc FW |
247 | if (!tick_nohz_full_cpu(cpu)) |
248 | return; | |
249 | ||
250 | irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu); | |
76c24fb0 FW |
251 | } |
252 | ||
253 | static void nohz_full_kick_ipi(void *info) | |
254 | { | |
d13508f9 | 255 | __tick_nohz_full_check(); |
76c24fb0 FW |
256 | } |
257 | ||
258 | /* | |
259 | * Kick all full dynticks CPUs in order to force these to re-evaluate | |
260 | * their dependency on the tick and restart it if necessary. | |
261 | */ | |
262 | void tick_nohz_full_kick_all(void) | |
263 | { | |
73867dcd | 264 | if (!tick_nohz_full_running) |
76c24fb0 FW |
265 | return; |
266 | ||
267 | preempt_disable(); | |
73867dcd | 268 | smp_call_function_many(tick_nohz_full_mask, |
76c24fb0 | 269 | nohz_full_kick_ipi, NULL, false); |
c2e7fcf5 | 270 | tick_nohz_full_kick(); |
76c24fb0 FW |
271 | preempt_enable(); |
272 | } | |
273 | ||
99e5ada9 FW |
274 | /* |
275 | * Re-evaluate the need for the tick as we switch the current task. | |
276 | * It might need the tick due to per task/process properties: | |
277 | * perf events, posix cpu timers, ... | |
278 | */ | |
d13508f9 | 279 | void __tick_nohz_task_switch(struct task_struct *tsk) |
99e5ada9 FW |
280 | { |
281 | unsigned long flags; | |
282 | ||
99e5ada9 FW |
283 | local_irq_save(flags); |
284 | ||
6296ace4 LZ |
285 | if (!tick_nohz_full_cpu(smp_processor_id())) |
286 | goto out; | |
287 | ||
99e5ada9 FW |
288 | if (tick_nohz_tick_stopped() && !can_stop_full_tick()) |
289 | tick_nohz_full_kick(); | |
290 | ||
6296ace4 | 291 | out: |
99e5ada9 FW |
292 | local_irq_restore(flags); |
293 | } | |
294 | ||
a831881b | 295 | /* Parse the boot-time nohz CPU list from the kernel parameters. */ |
c5bfece2 | 296 | static int __init tick_nohz_full_setup(char *str) |
a831881b | 297 | { |
73867dcd FW |
298 | alloc_bootmem_cpumask_var(&tick_nohz_full_mask); |
299 | if (cpulist_parse(str, tick_nohz_full_mask) < 0) { | |
c5bfece2 | 300 | pr_warning("NOHZ: Incorrect nohz_full cpumask\n"); |
4327b15f | 301 | free_bootmem_cpumask_var(tick_nohz_full_mask); |
0453b435 FW |
302 | return 1; |
303 | } | |
73867dcd | 304 | tick_nohz_full_running = true; |
0453b435 | 305 | |
a831881b FW |
306 | return 1; |
307 | } | |
c5bfece2 | 308 | __setup("nohz_full=", tick_nohz_full_setup); |
a831881b | 309 | |
0db0628d | 310 | static int tick_nohz_cpu_down_callback(struct notifier_block *nfb, |
a382bf93 FW |
311 | unsigned long action, |
312 | void *hcpu) | |
313 | { | |
314 | unsigned int cpu = (unsigned long)hcpu; | |
315 | ||
316 | switch (action & ~CPU_TASKS_FROZEN) { | |
317 | case CPU_DOWN_PREPARE: | |
318 | /* | |
319 | * If we handle the timekeeping duty for full dynticks CPUs, | |
320 | * we can't safely shutdown that CPU. | |
321 | */ | |
73867dcd | 322 | if (tick_nohz_full_running && tick_do_timer_cpu == cpu) |
1a7f829f | 323 | return NOTIFY_BAD; |
a382bf93 FW |
324 | break; |
325 | } | |
326 | return NOTIFY_OK; | |
327 | } | |
328 | ||
f98823ac FW |
329 | static int tick_nohz_init_all(void) |
330 | { | |
331 | int err = -1; | |
332 | ||
333 | #ifdef CONFIG_NO_HZ_FULL_ALL | |
73867dcd | 334 | if (!alloc_cpumask_var(&tick_nohz_full_mask, GFP_KERNEL)) { |
4327b15f | 335 | WARN(1, "NO_HZ: Can't allocate full dynticks cpumask\n"); |
c0f489d2 PM |
336 | return err; |
337 | } | |
f98823ac | 338 | err = 0; |
73867dcd | 339 | cpumask_setall(tick_nohz_full_mask); |
73867dcd | 340 | tick_nohz_full_running = true; |
f98823ac FW |
341 | #endif |
342 | return err; | |
343 | } | |
344 | ||
d1e43fa5 | 345 | void __init tick_nohz_init(void) |
a831881b | 346 | { |
d1e43fa5 FW |
347 | int cpu; |
348 | ||
73867dcd | 349 | if (!tick_nohz_full_running) { |
f98823ac FW |
350 | if (tick_nohz_init_all() < 0) |
351 | return; | |
352 | } | |
d1e43fa5 | 353 | |
4327b15f FW |
354 | if (!alloc_cpumask_var(&housekeeping_mask, GFP_KERNEL)) { |
355 | WARN(1, "NO_HZ: Can't allocate not-full dynticks cpumask\n"); | |
356 | cpumask_clear(tick_nohz_full_mask); | |
357 | tick_nohz_full_running = false; | |
358 | return; | |
359 | } | |
360 | ||
9b01f5bf FW |
361 | /* |
362 | * Full dynticks uses irq work to drive the tick rescheduling on safe | |
363 | * locking contexts. But then we need irq work to raise its own | |
364 | * interrupts to avoid circular dependency on the tick | |
365 | */ | |
366 | if (!arch_irq_work_has_interrupt()) { | |
367 | pr_warning("NO_HZ: Can't run full dynticks because arch doesn't " | |
368 | "support irq work self-IPIs\n"); | |
369 | cpumask_clear(tick_nohz_full_mask); | |
370 | cpumask_copy(housekeeping_mask, cpu_possible_mask); | |
371 | tick_nohz_full_running = false; | |
372 | return; | |
373 | } | |
374 | ||
4327b15f FW |
375 | cpu = smp_processor_id(); |
376 | ||
377 | if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) { | |
378 | pr_warning("NO_HZ: Clearing %d from nohz_full range for timekeeping\n", cpu); | |
379 | cpumask_clear_cpu(cpu, tick_nohz_full_mask); | |
380 | } | |
381 | ||
382 | cpumask_andnot(housekeeping_mask, | |
383 | cpu_possible_mask, tick_nohz_full_mask); | |
384 | ||
73867dcd | 385 | for_each_cpu(cpu, tick_nohz_full_mask) |
2e709338 FW |
386 | context_tracking_cpu_set(cpu); |
387 | ||
d1e43fa5 | 388 | cpu_notifier(tick_nohz_cpu_down_callback, 0); |
ffda22c1 TH |
389 | pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n", |
390 | cpumask_pr_args(tick_nohz_full_mask)); | |
a831881b | 391 | } |
a831881b FW |
392 | #endif |
393 | ||
79bf2bb3 TG |
394 | /* |
395 | * NOHZ - aka dynamic tick functionality | |
396 | */ | |
3451d024 | 397 | #ifdef CONFIG_NO_HZ_COMMON |
79bf2bb3 TG |
398 | /* |
399 | * NO HZ enabled ? | |
400 | */ | |
d689fe22 TG |
401 | static int tick_nohz_enabled __read_mostly = 1; |
402 | int tick_nohz_active __read_mostly; | |
79bf2bb3 TG |
403 | /* |
404 | * Enable / Disable tickless mode | |
405 | */ | |
406 | static int __init setup_tick_nohz(char *str) | |
407 | { | |
408 | if (!strcmp(str, "off")) | |
409 | tick_nohz_enabled = 0; | |
410 | else if (!strcmp(str, "on")) | |
411 | tick_nohz_enabled = 1; | |
412 | else | |
413 | return 0; | |
414 | return 1; | |
415 | } | |
416 | ||
417 | __setup("nohz=", setup_tick_nohz); | |
418 | ||
c1797baf TG |
419 | int tick_nohz_tick_stopped(void) |
420 | { | |
421 | return __this_cpu_read(tick_cpu_sched.tick_stopped); | |
422 | } | |
423 | ||
79bf2bb3 TG |
424 | /** |
425 | * tick_nohz_update_jiffies - update jiffies when idle was interrupted | |
426 | * | |
427 | * Called from interrupt entry when the CPU was idle | |
428 | * | |
429 | * In case the sched_tick was stopped on this CPU, we have to check if jiffies | |
430 | * must be updated. Otherwise an interrupt handler could use a stale jiffy | |
431 | * value. We do this unconditionally on any cpu, as we don't know whether the | |
432 | * cpu, which has the update task assigned is in a long sleep. | |
433 | */ | |
eed3b9cf | 434 | static void tick_nohz_update_jiffies(ktime_t now) |
79bf2bb3 | 435 | { |
79bf2bb3 | 436 | unsigned long flags; |
79bf2bb3 | 437 | |
e8fcaa5c | 438 | __this_cpu_write(tick_cpu_sched.idle_waketime, now); |
79bf2bb3 TG |
439 | |
440 | local_irq_save(flags); | |
441 | tick_do_update_jiffies64(now); | |
442 | local_irq_restore(flags); | |
02ff3755 IM |
443 | |
444 | touch_softlockup_watchdog(); | |
79bf2bb3 TG |
445 | } |
446 | ||
595aac48 AV |
447 | /* |
448 | * Updates the per cpu time idle statistics counters | |
449 | */ | |
8d63bf94 | 450 | static void |
8c215bd3 | 451 | update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_update_time) |
6378ddb5 | 452 | { |
eed3b9cf | 453 | ktime_t delta; |
6378ddb5 | 454 | |
595aac48 AV |
455 | if (ts->idle_active) { |
456 | delta = ktime_sub(now, ts->idle_entrytime); | |
8c215bd3 | 457 | if (nr_iowait_cpu(cpu) > 0) |
0224cf4c | 458 | ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta); |
6beea0cd MH |
459 | else |
460 | ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta); | |
8c7b09f4 | 461 | ts->idle_entrytime = now; |
595aac48 | 462 | } |
8d63bf94 | 463 | |
e0e37c20 | 464 | if (last_update_time) |
8d63bf94 AV |
465 | *last_update_time = ktime_to_us(now); |
466 | ||
595aac48 AV |
467 | } |
468 | ||
e8fcaa5c | 469 | static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now) |
595aac48 | 470 | { |
e8fcaa5c | 471 | update_ts_time_stats(smp_processor_id(), ts, now, NULL); |
eed3b9cf | 472 | ts->idle_active = 0; |
56c7426b | 473 | |
eed3b9cf | 474 | sched_clock_idle_wakeup_event(0); |
6378ddb5 VP |
475 | } |
476 | ||
e8fcaa5c | 477 | static ktime_t tick_nohz_start_idle(struct tick_sched *ts) |
6378ddb5 | 478 | { |
430ee881 | 479 | ktime_t now = ktime_get(); |
595aac48 | 480 | |
6378ddb5 VP |
481 | ts->idle_entrytime = now; |
482 | ts->idle_active = 1; | |
56c7426b | 483 | sched_clock_idle_sleep_event(); |
6378ddb5 VP |
484 | return now; |
485 | } | |
486 | ||
b1f724c3 AV |
487 | /** |
488 | * get_cpu_idle_time_us - get the total idle time of a cpu | |
489 | * @cpu: CPU number to query | |
09a1d34f MH |
490 | * @last_update_time: variable to store update time in. Do not update |
491 | * counters if NULL. | |
b1f724c3 AV |
492 | * |
493 | * Return the cummulative idle time (since boot) for a given | |
6beea0cd | 494 | * CPU, in microseconds. |
b1f724c3 AV |
495 | * |
496 | * This time is measured via accounting rather than sampling, | |
497 | * and is as accurate as ktime_get() is. | |
498 | * | |
499 | * This function returns -1 if NOHZ is not enabled. | |
500 | */ | |
6378ddb5 VP |
501 | u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time) |
502 | { | |
503 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
09a1d34f | 504 | ktime_t now, idle; |
6378ddb5 | 505 | |
d689fe22 | 506 | if (!tick_nohz_active) |
8083e4ad | 507 | return -1; |
508 | ||
09a1d34f MH |
509 | now = ktime_get(); |
510 | if (last_update_time) { | |
511 | update_ts_time_stats(cpu, ts, now, last_update_time); | |
512 | idle = ts->idle_sleeptime; | |
513 | } else { | |
514 | if (ts->idle_active && !nr_iowait_cpu(cpu)) { | |
515 | ktime_t delta = ktime_sub(now, ts->idle_entrytime); | |
516 | ||
517 | idle = ktime_add(ts->idle_sleeptime, delta); | |
518 | } else { | |
519 | idle = ts->idle_sleeptime; | |
520 | } | |
521 | } | |
522 | ||
523 | return ktime_to_us(idle); | |
8083e4ad | 524 | |
6378ddb5 | 525 | } |
8083e4ad | 526 | EXPORT_SYMBOL_GPL(get_cpu_idle_time_us); |
6378ddb5 | 527 | |
6beea0cd | 528 | /** |
0224cf4c AV |
529 | * get_cpu_iowait_time_us - get the total iowait time of a cpu |
530 | * @cpu: CPU number to query | |
09a1d34f MH |
531 | * @last_update_time: variable to store update time in. Do not update |
532 | * counters if NULL. | |
0224cf4c AV |
533 | * |
534 | * Return the cummulative iowait time (since boot) for a given | |
535 | * CPU, in microseconds. | |
536 | * | |
537 | * This time is measured via accounting rather than sampling, | |
538 | * and is as accurate as ktime_get() is. | |
539 | * | |
540 | * This function returns -1 if NOHZ is not enabled. | |
541 | */ | |
542 | u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time) | |
543 | { | |
544 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
09a1d34f | 545 | ktime_t now, iowait; |
0224cf4c | 546 | |
d689fe22 | 547 | if (!tick_nohz_active) |
0224cf4c AV |
548 | return -1; |
549 | ||
09a1d34f MH |
550 | now = ktime_get(); |
551 | if (last_update_time) { | |
552 | update_ts_time_stats(cpu, ts, now, last_update_time); | |
553 | iowait = ts->iowait_sleeptime; | |
554 | } else { | |
555 | if (ts->idle_active && nr_iowait_cpu(cpu) > 0) { | |
556 | ktime_t delta = ktime_sub(now, ts->idle_entrytime); | |
0224cf4c | 557 | |
09a1d34f MH |
558 | iowait = ktime_add(ts->iowait_sleeptime, delta); |
559 | } else { | |
560 | iowait = ts->iowait_sleeptime; | |
561 | } | |
562 | } | |
0224cf4c | 563 | |
09a1d34f | 564 | return ktime_to_us(iowait); |
0224cf4c AV |
565 | } |
566 | EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us); | |
567 | ||
84bf1bcc FW |
568 | static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts, |
569 | ktime_t now, int cpu) | |
79bf2bb3 | 570 | { |
280f0677 | 571 | unsigned long seq, last_jiffies, next_jiffies, delta_jiffies; |
84bf1bcc | 572 | ktime_t last_update, expires, ret = { .tv64 = 0 }; |
aa9b1630 | 573 | unsigned long rcu_delta_jiffies; |
22127e93 | 574 | struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev); |
98962465 | 575 | u64 time_delta; |
79bf2bb3 | 576 | |
855a0fc3 FW |
577 | time_delta = timekeeping_max_deferment(); |
578 | ||
79bf2bb3 TG |
579 | /* Read jiffies and the time when jiffies were updated last */ |
580 | do { | |
d6ad4187 | 581 | seq = read_seqbegin(&jiffies_lock); |
79bf2bb3 TG |
582 | last_update = last_jiffies_update; |
583 | last_jiffies = jiffies; | |
d6ad4187 | 584 | } while (read_seqretry(&jiffies_lock, seq)); |
79bf2bb3 | 585 | |
aa6da514 | 586 | if (rcu_needs_cpu(&rcu_delta_jiffies) || |
fe0f4976 | 587 | arch_needs_cpu() || irq_work_needs_cpu()) { |
3c5d92a0 | 588 | next_jiffies = last_jiffies + 1; |
6ba9b346 | 589 | delta_jiffies = 1; |
3c5d92a0 MS |
590 | } else { |
591 | /* Get the next timer wheel timer */ | |
592 | next_jiffies = get_next_timer_interrupt(last_jiffies); | |
593 | delta_jiffies = next_jiffies - last_jiffies; | |
aa9b1630 PM |
594 | if (rcu_delta_jiffies < delta_jiffies) { |
595 | next_jiffies = last_jiffies + rcu_delta_jiffies; | |
596 | delta_jiffies = rcu_delta_jiffies; | |
597 | } | |
3c5d92a0 | 598 | } |
47aa8b6c | 599 | |
79bf2bb3 | 600 | /* |
47aa8b6c IM |
601 | * Do not stop the tick, if we are only one off (or less) |
602 | * or if the cpu is required for RCU: | |
79bf2bb3 | 603 | */ |
47aa8b6c | 604 | if (!ts->tick_stopped && delta_jiffies <= 1) |
79bf2bb3 TG |
605 | goto out; |
606 | ||
607 | /* Schedule the tick, if we are at least one jiffie off */ | |
608 | if ((long)delta_jiffies >= 1) { | |
609 | ||
00147449 WR |
610 | /* |
611 | * If this cpu is the one which updates jiffies, then | |
612 | * give up the assignment and let it be taken by the | |
613 | * cpu which runs the tick timer next, which might be | |
614 | * this cpu as well. If we don't drop this here the | |
615 | * jiffies might be stale and do_timer() never | |
27185016 TG |
616 | * invoked. Keep track of the fact that it was the one |
617 | * which had the do_timer() duty last. If this cpu is | |
618 | * the one which had the do_timer() duty last, we | |
619 | * limit the sleep time to the timekeeping | |
620 | * max_deferement value which we retrieved | |
621 | * above. Otherwise we can sleep as long as we want. | |
00147449 | 622 | */ |
27185016 | 623 | if (cpu == tick_do_timer_cpu) { |
00147449 | 624 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; |
27185016 TG |
625 | ts->do_timer_last = 1; |
626 | } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) { | |
627 | time_delta = KTIME_MAX; | |
628 | ts->do_timer_last = 0; | |
629 | } else if (!ts->do_timer_last) { | |
630 | time_delta = KTIME_MAX; | |
631 | } | |
632 | ||
265f22a9 FW |
633 | #ifdef CONFIG_NO_HZ_FULL |
634 | if (!ts->inidle) { | |
635 | time_delta = min(time_delta, | |
636 | scheduler_tick_max_deferment()); | |
637 | } | |
638 | #endif | |
639 | ||
00147449 | 640 | /* |
98962465 JH |
641 | * calculate the expiry time for the next timer wheel |
642 | * timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals | |
643 | * that there is no timer pending or at least extremely | |
644 | * far into the future (12 days for HZ=1000). In this | |
645 | * case we set the expiry to the end of time. | |
646 | */ | |
647 | if (likely(delta_jiffies < NEXT_TIMER_MAX_DELTA)) { | |
648 | /* | |
649 | * Calculate the time delta for the next timer event. | |
650 | * If the time delta exceeds the maximum time delta | |
651 | * permitted by the current clocksource then adjust | |
652 | * the time delta accordingly to ensure the | |
653 | * clocksource does not wrap. | |
654 | */ | |
655 | time_delta = min_t(u64, time_delta, | |
656 | tick_period.tv64 * delta_jiffies); | |
98962465 | 657 | } |
00147449 | 658 | |
27185016 TG |
659 | if (time_delta < KTIME_MAX) |
660 | expires = ktime_add_ns(last_update, time_delta); | |
661 | else | |
662 | expires.tv64 = KTIME_MAX; | |
00147449 | 663 | |
00147449 WR |
664 | /* Skip reprogram of event if its not changed */ |
665 | if (ts->tick_stopped && ktime_equal(expires, dev->next_event)) | |
666 | goto out; | |
667 | ||
84bf1bcc FW |
668 | ret = expires; |
669 | ||
79bf2bb3 TG |
670 | /* |
671 | * nohz_stop_sched_tick can be called several times before | |
672 | * the nohz_restart_sched_tick is called. This happens when | |
673 | * interrupts arrive which do not cause a reschedule. In the | |
674 | * first call we save the current tick time, so we can restart | |
675 | * the scheduler tick in nohz_restart_sched_tick. | |
676 | */ | |
677 | if (!ts->tick_stopped) { | |
c1cc017c | 678 | nohz_balance_enter_idle(cpu); |
5167e8d5 | 679 | calc_load_enter_idle(); |
46cb4b7c | 680 | |
f5d411c9 | 681 | ts->last_tick = hrtimer_get_expires(&ts->sched_timer); |
79bf2bb3 | 682 | ts->tick_stopped = 1; |
cb41a290 | 683 | trace_tick_stop(1, " "); |
79bf2bb3 | 684 | } |
d3ed7824 | 685 | |
eaad084b | 686 | /* |
98962465 JH |
687 | * If the expiration time == KTIME_MAX, then |
688 | * in this case we simply stop the tick timer. | |
eaad084b | 689 | */ |
98962465 | 690 | if (unlikely(expires.tv64 == KTIME_MAX)) { |
eaad084b TG |
691 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) |
692 | hrtimer_cancel(&ts->sched_timer); | |
693 | goto out; | |
694 | } | |
695 | ||
79bf2bb3 TG |
696 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { |
697 | hrtimer_start(&ts->sched_timer, expires, | |
5c333864 | 698 | HRTIMER_MODE_ABS_PINNED); |
79bf2bb3 TG |
699 | /* Check, if the timer was already in the past */ |
700 | if (hrtimer_active(&ts->sched_timer)) | |
701 | goto out; | |
4c9dc641 | 702 | } else if (!tick_program_event(expires, 0)) |
79bf2bb3 TG |
703 | goto out; |
704 | /* | |
705 | * We are past the event already. So we crossed a | |
706 | * jiffie boundary. Update jiffies and raise the | |
707 | * softirq. | |
708 | */ | |
709 | tick_do_update_jiffies64(ktime_get()); | |
79bf2bb3 TG |
710 | } |
711 | raise_softirq_irqoff(TIMER_SOFTIRQ); | |
712 | out: | |
713 | ts->next_jiffies = next_jiffies; | |
714 | ts->last_jiffies = last_jiffies; | |
4f86d3a8 | 715 | ts->sleep_length = ktime_sub(dev->next_event, now); |
84bf1bcc FW |
716 | |
717 | return ret; | |
280f0677 FW |
718 | } |
719 | ||
5811d996 FW |
720 | static void tick_nohz_full_stop_tick(struct tick_sched *ts) |
721 | { | |
722 | #ifdef CONFIG_NO_HZ_FULL | |
e9a2eb40 | 723 | int cpu = smp_processor_id(); |
5811d996 | 724 | |
e9a2eb40 AS |
725 | if (!tick_nohz_full_cpu(cpu) || is_idle_task(current)) |
726 | return; | |
5811d996 | 727 | |
e9a2eb40 AS |
728 | if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE) |
729 | return; | |
5811d996 | 730 | |
e9a2eb40 AS |
731 | if (!can_stop_full_tick()) |
732 | return; | |
5811d996 | 733 | |
e9a2eb40 | 734 | tick_nohz_stop_sched_tick(ts, ktime_get(), cpu); |
5811d996 FW |
735 | #endif |
736 | } | |
737 | ||
5b39939a FW |
738 | static bool can_stop_idle_tick(int cpu, struct tick_sched *ts) |
739 | { | |
740 | /* | |
741 | * If this cpu is offline and it is the one which updates | |
742 | * jiffies, then give up the assignment and let it be taken by | |
743 | * the cpu which runs the tick timer next. If we don't drop | |
744 | * this here the jiffies might be stale and do_timer() never | |
745 | * invoked. | |
746 | */ | |
747 | if (unlikely(!cpu_online(cpu))) { | |
748 | if (cpu == tick_do_timer_cpu) | |
749 | tick_do_timer_cpu = TICK_DO_TIMER_NONE; | |
f7ea0fd6 | 750 | return false; |
5b39939a FW |
751 | } |
752 | ||
0e576acb TG |
753 | if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE)) { |
754 | ts->sleep_length = (ktime_t) { .tv64 = NSEC_PER_SEC/HZ }; | |
5b39939a | 755 | return false; |
0e576acb | 756 | } |
5b39939a FW |
757 | |
758 | if (need_resched()) | |
759 | return false; | |
760 | ||
761 | if (unlikely(local_softirq_pending() && cpu_online(cpu))) { | |
762 | static int ratelimit; | |
763 | ||
803b0eba PM |
764 | if (ratelimit < 10 && |
765 | (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) { | |
cfea7d7e RV |
766 | pr_warn("NOHZ: local_softirq_pending %02x\n", |
767 | (unsigned int) local_softirq_pending()); | |
5b39939a FW |
768 | ratelimit++; |
769 | } | |
770 | return false; | |
771 | } | |
772 | ||
460775df | 773 | if (tick_nohz_full_enabled()) { |
a382bf93 FW |
774 | /* |
775 | * Keep the tick alive to guarantee timekeeping progression | |
776 | * if there are full dynticks CPUs around | |
777 | */ | |
778 | if (tick_do_timer_cpu == cpu) | |
779 | return false; | |
780 | /* | |
781 | * Boot safety: make sure the timekeeping duty has been | |
782 | * assigned before entering dyntick-idle mode, | |
783 | */ | |
784 | if (tick_do_timer_cpu == TICK_DO_TIMER_NONE) | |
785 | return false; | |
786 | } | |
787 | ||
5b39939a FW |
788 | return true; |
789 | } | |
790 | ||
19f5f736 FW |
791 | static void __tick_nohz_idle_enter(struct tick_sched *ts) |
792 | { | |
84bf1bcc | 793 | ktime_t now, expires; |
5b39939a | 794 | int cpu = smp_processor_id(); |
19f5f736 | 795 | |
e8fcaa5c | 796 | now = tick_nohz_start_idle(ts); |
2ac0d98f | 797 | |
5b39939a FW |
798 | if (can_stop_idle_tick(cpu, ts)) { |
799 | int was_stopped = ts->tick_stopped; | |
800 | ||
801 | ts->idle_calls++; | |
84bf1bcc FW |
802 | |
803 | expires = tick_nohz_stop_sched_tick(ts, now, cpu); | |
804 | if (expires.tv64 > 0LL) { | |
805 | ts->idle_sleeps++; | |
806 | ts->idle_expires = expires; | |
807 | } | |
5b39939a FW |
808 | |
809 | if (!was_stopped && ts->tick_stopped) | |
810 | ts->idle_jiffies = ts->last_jiffies; | |
811 | } | |
280f0677 FW |
812 | } |
813 | ||
814 | /** | |
815 | * tick_nohz_idle_enter - stop the idle tick from the idle task | |
816 | * | |
817 | * When the next event is more than a tick into the future, stop the idle tick | |
818 | * Called when we start the idle loop. | |
2bbb6817 | 819 | * |
1268fbc7 | 820 | * The arch is responsible of calling: |
2bbb6817 FW |
821 | * |
822 | * - rcu_idle_enter() after its last use of RCU before the CPU is put | |
823 | * to sleep. | |
824 | * - rcu_idle_exit() before the first use of RCU after the CPU is woken up. | |
280f0677 | 825 | */ |
1268fbc7 | 826 | void tick_nohz_idle_enter(void) |
280f0677 FW |
827 | { |
828 | struct tick_sched *ts; | |
829 | ||
1268fbc7 FW |
830 | WARN_ON_ONCE(irqs_disabled()); |
831 | ||
0db49b72 LT |
832 | /* |
833 | * Update the idle state in the scheduler domain hierarchy | |
834 | * when tick_nohz_stop_sched_tick() is called from the idle loop. | |
835 | * State will be updated to busy during the first busy tick after | |
836 | * exiting idle. | |
837 | */ | |
838 | set_cpu_sd_state_idle(); | |
839 | ||
1268fbc7 FW |
840 | local_irq_disable(); |
841 | ||
22127e93 | 842 | ts = this_cpu_ptr(&tick_cpu_sched); |
280f0677 | 843 | ts->inidle = 1; |
19f5f736 | 844 | __tick_nohz_idle_enter(ts); |
1268fbc7 FW |
845 | |
846 | local_irq_enable(); | |
280f0677 FW |
847 | } |
848 | ||
849 | /** | |
850 | * tick_nohz_irq_exit - update next tick event from interrupt exit | |
851 | * | |
852 | * When an interrupt fires while we are idle and it doesn't cause | |
853 | * a reschedule, it may still add, modify or delete a timer, enqueue | |
854 | * an RCU callback, etc... | |
855 | * So we need to re-calculate and reprogram the next tick event. | |
856 | */ | |
857 | void tick_nohz_irq_exit(void) | |
858 | { | |
22127e93 | 859 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
280f0677 | 860 | |
14851912 | 861 | if (ts->inidle) |
5811d996 | 862 | __tick_nohz_idle_enter(ts); |
14851912 | 863 | else |
5811d996 | 864 | tick_nohz_full_stop_tick(ts); |
79bf2bb3 TG |
865 | } |
866 | ||
4f86d3a8 LB |
867 | /** |
868 | * tick_nohz_get_sleep_length - return the length of the current sleep | |
869 | * | |
870 | * Called from power state control code with interrupts disabled | |
871 | */ | |
872 | ktime_t tick_nohz_get_sleep_length(void) | |
873 | { | |
22127e93 | 874 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
4f86d3a8 LB |
875 | |
876 | return ts->sleep_length; | |
877 | } | |
878 | ||
c34bec5a TG |
879 | static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) |
880 | { | |
881 | hrtimer_cancel(&ts->sched_timer); | |
f5d411c9 | 882 | hrtimer_set_expires(&ts->sched_timer, ts->last_tick); |
c34bec5a TG |
883 | |
884 | while (1) { | |
885 | /* Forward the time to expire in the future */ | |
886 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
887 | ||
888 | if (ts->nohz_mode == NOHZ_MODE_HIGHRES) { | |
268a3dcf | 889 | hrtimer_start_expires(&ts->sched_timer, |
5c333864 | 890 | HRTIMER_MODE_ABS_PINNED); |
c34bec5a TG |
891 | /* Check, if the timer was already in the past */ |
892 | if (hrtimer_active(&ts->sched_timer)) | |
893 | break; | |
894 | } else { | |
268a3dcf TG |
895 | if (!tick_program_event( |
896 | hrtimer_get_expires(&ts->sched_timer), 0)) | |
c34bec5a TG |
897 | break; |
898 | } | |
6f103929 | 899 | /* Reread time and update jiffies */ |
c34bec5a | 900 | now = ktime_get(); |
6f103929 | 901 | tick_do_update_jiffies64(now); |
c34bec5a TG |
902 | } |
903 | } | |
904 | ||
19f5f736 | 905 | static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now) |
79bf2bb3 | 906 | { |
79bf2bb3 | 907 | /* Update jiffies first */ |
79bf2bb3 | 908 | tick_do_update_jiffies64(now); |
5aaa0b7a | 909 | update_cpu_load_nohz(); |
79bf2bb3 | 910 | |
749c8814 | 911 | calc_load_exit_idle(); |
2ac0d98f FW |
912 | touch_softlockup_watchdog(); |
913 | /* | |
914 | * Cancel the scheduled timer and restore the tick | |
915 | */ | |
916 | ts->tick_stopped = 0; | |
917 | ts->idle_exittime = now; | |
918 | ||
919 | tick_nohz_restart(ts, now); | |
920 | } | |
921 | ||
922 | static void tick_nohz_account_idle_ticks(struct tick_sched *ts) | |
923 | { | |
3f4724ea | 924 | #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE |
2ac0d98f | 925 | unsigned long ticks; |
3f4724ea FW |
926 | |
927 | if (vtime_accounting_enabled()) | |
928 | return; | |
79bf2bb3 TG |
929 | /* |
930 | * We stopped the tick in idle. Update process times would miss the | |
931 | * time we slept as update_process_times does only a 1 tick | |
932 | * accounting. Enforce that this is accounted to idle ! | |
933 | */ | |
934 | ticks = jiffies - ts->idle_jiffies; | |
935 | /* | |
936 | * We might be one off. Do not randomly account a huge number of ticks! | |
937 | */ | |
79741dd3 MS |
938 | if (ticks && ticks < LONG_MAX) |
939 | account_idle_ticks(ticks); | |
940 | #endif | |
19f5f736 FW |
941 | } |
942 | ||
79bf2bb3 | 943 | /** |
280f0677 | 944 | * tick_nohz_idle_exit - restart the idle tick from the idle task |
79bf2bb3 TG |
945 | * |
946 | * Restart the idle tick when the CPU is woken up from idle | |
280f0677 FW |
947 | * This also exit the RCU extended quiescent state. The CPU |
948 | * can use RCU again after this function is called. | |
79bf2bb3 | 949 | */ |
280f0677 | 950 | void tick_nohz_idle_exit(void) |
79bf2bb3 | 951 | { |
4a32fea9 | 952 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
6378ddb5 | 953 | ktime_t now; |
79bf2bb3 | 954 | |
6378ddb5 | 955 | local_irq_disable(); |
2bbb6817 | 956 | |
15f827be FW |
957 | WARN_ON_ONCE(!ts->inidle); |
958 | ||
959 | ts->inidle = 0; | |
960 | ||
961 | if (ts->idle_active || ts->tick_stopped) | |
eed3b9cf MS |
962 | now = ktime_get(); |
963 | ||
964 | if (ts->idle_active) | |
e8fcaa5c | 965 | tick_nohz_stop_idle(ts, now); |
6378ddb5 | 966 | |
2ac0d98f | 967 | if (ts->tick_stopped) { |
19f5f736 | 968 | tick_nohz_restart_sched_tick(ts, now); |
2ac0d98f | 969 | tick_nohz_account_idle_ticks(ts); |
6378ddb5 | 970 | } |
79bf2bb3 | 971 | |
79bf2bb3 TG |
972 | local_irq_enable(); |
973 | } | |
974 | ||
975 | static int tick_nohz_reprogram(struct tick_sched *ts, ktime_t now) | |
976 | { | |
977 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
cc584b21 | 978 | return tick_program_event(hrtimer_get_expires(&ts->sched_timer), 0); |
79bf2bb3 TG |
979 | } |
980 | ||
981 | /* | |
982 | * The nohz low res interrupt handler | |
983 | */ | |
984 | static void tick_nohz_handler(struct clock_event_device *dev) | |
985 | { | |
22127e93 | 986 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
79bf2bb3 TG |
987 | struct pt_regs *regs = get_irq_regs(); |
988 | ktime_t now = ktime_get(); | |
989 | ||
990 | dev->next_event.tv64 = KTIME_MAX; | |
991 | ||
5bb96226 | 992 | tick_sched_do_timer(now); |
9e8f559b | 993 | tick_sched_handle(ts, regs); |
79bf2bb3 | 994 | |
b5e995e6 VK |
995 | /* No need to reprogram if we are running tickless */ |
996 | if (unlikely(ts->tick_stopped)) | |
997 | return; | |
998 | ||
79bf2bb3 TG |
999 | while (tick_nohz_reprogram(ts, now)) { |
1000 | now = ktime_get(); | |
1001 | tick_do_update_jiffies64(now); | |
1002 | } | |
1003 | } | |
1004 | ||
1005 | /** | |
1006 | * tick_nohz_switch_to_nohz - switch to nohz mode | |
1007 | */ | |
1008 | static void tick_nohz_switch_to_nohz(void) | |
1009 | { | |
22127e93 | 1010 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
79bf2bb3 TG |
1011 | ktime_t next; |
1012 | ||
27630532 | 1013 | if (!tick_nohz_enabled) |
79bf2bb3 TG |
1014 | return; |
1015 | ||
1016 | local_irq_disable(); | |
1017 | if (tick_switch_to_oneshot(tick_nohz_handler)) { | |
1018 | local_irq_enable(); | |
1019 | return; | |
1020 | } | |
d689fe22 | 1021 | tick_nohz_active = 1; |
79bf2bb3 TG |
1022 | ts->nohz_mode = NOHZ_MODE_LOWRES; |
1023 | ||
1024 | /* | |
1025 | * Recycle the hrtimer in ts, so we can share the | |
1026 | * hrtimer_forward with the highres code. | |
1027 | */ | |
1028 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
1029 | /* Get the next period */ | |
1030 | next = tick_init_jiffy_update(); | |
1031 | ||
1032 | for (;;) { | |
cc584b21 | 1033 | hrtimer_set_expires(&ts->sched_timer, next); |
79bf2bb3 TG |
1034 | if (!tick_program_event(next, 0)) |
1035 | break; | |
1036 | next = ktime_add(next, tick_period); | |
1037 | } | |
1038 | local_irq_enable(); | |
79bf2bb3 TG |
1039 | } |
1040 | ||
fb02fbc1 TG |
1041 | /* |
1042 | * When NOHZ is enabled and the tick is stopped, we need to kick the | |
1043 | * tick timer from irq_enter() so that the jiffies update is kept | |
1044 | * alive during long running softirqs. That's ugly as hell, but | |
1045 | * correctness is key even if we need to fix the offending softirq in | |
1046 | * the first place. | |
1047 | * | |
1048 | * Note, this is different to tick_nohz_restart. We just kick the | |
1049 | * timer and do not touch the other magic bits which need to be done | |
1050 | * when idle is left. | |
1051 | */ | |
e8fcaa5c | 1052 | static void tick_nohz_kick_tick(struct tick_sched *ts, ktime_t now) |
fb02fbc1 | 1053 | { |
ae99286b TG |
1054 | #if 0 |
1055 | /* Switch back to 2.6.27 behaviour */ | |
eed3b9cf | 1056 | ktime_t delta; |
fb02fbc1 | 1057 | |
c4bd822e TG |
1058 | /* |
1059 | * Do not touch the tick device, when the next expiry is either | |
1060 | * already reached or less/equal than the tick period. | |
1061 | */ | |
268a3dcf | 1062 | delta = ktime_sub(hrtimer_get_expires(&ts->sched_timer), now); |
c4bd822e TG |
1063 | if (delta.tv64 <= tick_period.tv64) |
1064 | return; | |
1065 | ||
1066 | tick_nohz_restart(ts, now); | |
ae99286b | 1067 | #endif |
fb02fbc1 TG |
1068 | } |
1069 | ||
5acac1be | 1070 | static inline void tick_nohz_irq_enter(void) |
eed3b9cf | 1071 | { |
4a32fea9 | 1072 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
eed3b9cf MS |
1073 | ktime_t now; |
1074 | ||
1075 | if (!ts->idle_active && !ts->tick_stopped) | |
1076 | return; | |
1077 | now = ktime_get(); | |
1078 | if (ts->idle_active) | |
e8fcaa5c | 1079 | tick_nohz_stop_idle(ts, now); |
eed3b9cf MS |
1080 | if (ts->tick_stopped) { |
1081 | tick_nohz_update_jiffies(now); | |
e8fcaa5c | 1082 | tick_nohz_kick_tick(ts, now); |
eed3b9cf MS |
1083 | } |
1084 | } | |
1085 | ||
79bf2bb3 TG |
1086 | #else |
1087 | ||
1088 | static inline void tick_nohz_switch_to_nohz(void) { } | |
5acac1be | 1089 | static inline void tick_nohz_irq_enter(void) { } |
79bf2bb3 | 1090 | |
3451d024 | 1091 | #endif /* CONFIG_NO_HZ_COMMON */ |
79bf2bb3 | 1092 | |
719254fa TG |
1093 | /* |
1094 | * Called from irq_enter to notify about the possible interruption of idle() | |
1095 | */ | |
5acac1be | 1096 | void tick_irq_enter(void) |
719254fa | 1097 | { |
e8fcaa5c | 1098 | tick_check_oneshot_broadcast_this_cpu(); |
5acac1be | 1099 | tick_nohz_irq_enter(); |
719254fa TG |
1100 | } |
1101 | ||
79bf2bb3 TG |
1102 | /* |
1103 | * High resolution timer specific code | |
1104 | */ | |
1105 | #ifdef CONFIG_HIGH_RES_TIMERS | |
1106 | /* | |
4c9dc641 | 1107 | * We rearm the timer until we get disabled by the idle code. |
351f181f | 1108 | * Called with interrupts disabled. |
79bf2bb3 TG |
1109 | */ |
1110 | static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer) | |
1111 | { | |
1112 | struct tick_sched *ts = | |
1113 | container_of(timer, struct tick_sched, sched_timer); | |
79bf2bb3 TG |
1114 | struct pt_regs *regs = get_irq_regs(); |
1115 | ktime_t now = ktime_get(); | |
d3ed7824 | 1116 | |
5bb96226 | 1117 | tick_sched_do_timer(now); |
79bf2bb3 TG |
1118 | |
1119 | /* | |
1120 | * Do not call, when we are not in irq context and have | |
1121 | * no valid regs pointer | |
1122 | */ | |
9e8f559b FW |
1123 | if (regs) |
1124 | tick_sched_handle(ts, regs); | |
79bf2bb3 | 1125 | |
2a16fc93 VK |
1126 | /* No need to reprogram if we are in idle or full dynticks mode */ |
1127 | if (unlikely(ts->tick_stopped)) | |
1128 | return HRTIMER_NORESTART; | |
1129 | ||
79bf2bb3 TG |
1130 | hrtimer_forward(timer, now, tick_period); |
1131 | ||
1132 | return HRTIMER_RESTART; | |
1133 | } | |
1134 | ||
5307c955 MG |
1135 | static int sched_skew_tick; |
1136 | ||
62cf20b3 TG |
1137 | static int __init skew_tick(char *str) |
1138 | { | |
1139 | get_option(&str, &sched_skew_tick); | |
1140 | ||
1141 | return 0; | |
1142 | } | |
1143 | early_param("skew_tick", skew_tick); | |
1144 | ||
79bf2bb3 TG |
1145 | /** |
1146 | * tick_setup_sched_timer - setup the tick emulation timer | |
1147 | */ | |
1148 | void tick_setup_sched_timer(void) | |
1149 | { | |
22127e93 | 1150 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
79bf2bb3 TG |
1151 | ktime_t now = ktime_get(); |
1152 | ||
1153 | /* | |
1154 | * Emulate tick processing via per-CPU hrtimers: | |
1155 | */ | |
1156 | hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); | |
1157 | ts->sched_timer.function = tick_sched_timer; | |
79bf2bb3 | 1158 | |
3704540b | 1159 | /* Get the next period (per cpu) */ |
cc584b21 | 1160 | hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update()); |
79bf2bb3 | 1161 | |
9c3f9e28 | 1162 | /* Offset the tick to avert jiffies_lock contention. */ |
5307c955 MG |
1163 | if (sched_skew_tick) { |
1164 | u64 offset = ktime_to_ns(tick_period) >> 1; | |
1165 | do_div(offset, num_possible_cpus()); | |
1166 | offset *= smp_processor_id(); | |
1167 | hrtimer_add_expires_ns(&ts->sched_timer, offset); | |
1168 | } | |
1169 | ||
79bf2bb3 TG |
1170 | for (;;) { |
1171 | hrtimer_forward(&ts->sched_timer, now, tick_period); | |
5c333864 AB |
1172 | hrtimer_start_expires(&ts->sched_timer, |
1173 | HRTIMER_MODE_ABS_PINNED); | |
79bf2bb3 TG |
1174 | /* Check, if the timer was already in the past */ |
1175 | if (hrtimer_active(&ts->sched_timer)) | |
1176 | break; | |
1177 | now = ktime_get(); | |
1178 | } | |
1179 | ||
3451d024 | 1180 | #ifdef CONFIG_NO_HZ_COMMON |
d689fe22 | 1181 | if (tick_nohz_enabled) { |
79bf2bb3 | 1182 | ts->nohz_mode = NOHZ_MODE_HIGHRES; |
d689fe22 TG |
1183 | tick_nohz_active = 1; |
1184 | } | |
79bf2bb3 TG |
1185 | #endif |
1186 | } | |
3c4fbe5e | 1187 | #endif /* HIGH_RES_TIMERS */ |
79bf2bb3 | 1188 | |
3451d024 | 1189 | #if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS |
79bf2bb3 TG |
1190 | void tick_cancel_sched_timer(int cpu) |
1191 | { | |
1192 | struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu); | |
1193 | ||
3c4fbe5e | 1194 | # ifdef CONFIG_HIGH_RES_TIMERS |
79bf2bb3 TG |
1195 | if (ts->sched_timer.base) |
1196 | hrtimer_cancel(&ts->sched_timer); | |
3c4fbe5e | 1197 | # endif |
a7901766 | 1198 | |
4b0c0f29 | 1199 | memset(ts, 0, sizeof(*ts)); |
79bf2bb3 | 1200 | } |
3c4fbe5e | 1201 | #endif |
79bf2bb3 TG |
1202 | |
1203 | /** | |
1204 | * Async notification about clocksource changes | |
1205 | */ | |
1206 | void tick_clock_notify(void) | |
1207 | { | |
1208 | int cpu; | |
1209 | ||
1210 | for_each_possible_cpu(cpu) | |
1211 | set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks); | |
1212 | } | |
1213 | ||
1214 | /* | |
1215 | * Async notification about clock event changes | |
1216 | */ | |
1217 | void tick_oneshot_notify(void) | |
1218 | { | |
22127e93 | 1219 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
79bf2bb3 TG |
1220 | |
1221 | set_bit(0, &ts->check_clocks); | |
1222 | } | |
1223 | ||
1224 | /** | |
1225 | * Check, if a change happened, which makes oneshot possible. | |
1226 | * | |
1227 | * Called cyclic from the hrtimer softirq (driven by the timer | |
1228 | * softirq) allow_nohz signals, that we can switch into low-res nohz | |
1229 | * mode, because high resolution timers are disabled (either compile | |
1230 | * or runtime). | |
1231 | */ | |
1232 | int tick_check_oneshot_change(int allow_nohz) | |
1233 | { | |
22127e93 | 1234 | struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched); |
79bf2bb3 TG |
1235 | |
1236 | if (!test_and_clear_bit(0, &ts->check_clocks)) | |
1237 | return 0; | |
1238 | ||
1239 | if (ts->nohz_mode != NOHZ_MODE_INACTIVE) | |
1240 | return 0; | |
1241 | ||
cf4fc6cb | 1242 | if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available()) |
79bf2bb3 TG |
1243 | return 0; |
1244 | ||
1245 | if (!allow_nohz) | |
1246 | return 1; | |
1247 | ||
1248 | tick_nohz_switch_to_nohz(); | |
1249 | return 0; | |
1250 | } |