1 /*
2 * Copyright (c) 2013 Apple Inc. All rights reserved.
3 *
4 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
5 *
6 * This file contains Original Code and/or Modifications of Original Code
7 * as defined in and that are subject to the Apple Public Source License
8 * Version 2.0 (the 'License'). You may not use this file except in
9 * compliance with the License. The rights granted to you under the License
10 * may not be used to create, or enable the creation or redistribution of,
11 * unlawful or unlicensed copies of an Apple operating system, or to
12 * circumvent, violate, or enable the circumvention or violation of, any
13 * terms of an Apple operating system software license agreement.
14 *
15 * Please obtain a copy of the License at
16 * http://www.opensource.apple.com/apsl/ and read it before using this file.
17 *
18 * The Original Code and all software distributed under the License are
19 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
20 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
21 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
22 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
23 * Please see the License for the specific language governing rights and
24 * limitations under the License.
25 *
26 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
27 */
28 #include <mach/mach_types.h>
29 #include <kern/assert.h>
30 #include <kern/clock.h>
31 #include <kern/coalition.h>
32 #include <kern/debug.h>
33 #include <kern/startup.h>
34 #include <kern/host.h>
35 #include <kern/kern_types.h>
36 #include <kern/machine.h>
37 #include <kern/simple_lock.h>
38 #include <kern/misc_protos.h>
39 #include <kern/sched.h>
40 #include <kern/sched_prim.h>
41 #include <kern/sfi.h>
42 #include <kern/timer_call.h>
43 #include <kern/waitq.h>
44 #include <kern/ledger.h>
45 #include <kern/policy_internal.h>
46
47 #include <machine/atomic.h>
48
49 #include <pexpert/pexpert.h>
50
51 #include <libkern/kernel_mach_header.h>
52
53 #include <sys/kdebug.h>
54
55 #if CONFIG_SCHED_SFI
56
57 #define SFI_DEBUG 0
58
59 #if SFI_DEBUG
60 #define dprintf(...) kprintf(__VA_ARGS__)
61 #else
62 #define dprintf(...) do { } while(0)
63 #endif
64
65 /*
66 * SFI (Selective Forced Idle) operates by enabling a global
67 * timer on the SFI window interval. When it fires, all processors
68 * running a thread that should be SFI-ed are sent an AST.
69 * As threads become runnable while in their "off phase", they
70 * are placed on a deferred ready queue. When a per-class
71 * "on timer" fires, the ready threads for that class are
72 * re-enqueued for running. As an optimization to avoid spurious
73 * wakeups, the timer may be lazily programmed.
74 */
75
76 /*
77 * The "sfi_lock" simple lock guards access to static configuration
78 * parameters (as specified by userspace), dynamic state changes
79 * (as updated by the timer event routine), and timer data structures.
80 * Since it can be taken with interrupts disabled in some cases, all
81 * uses should be taken with interrupts disabled at splsched(). The
82 * "sfi_lock" also guards the "sfi_wait_class" field of thread_t, and
83 * must only be accessed with it held.
84 *
85 * When an "on timer" fires, we must deterministically be able to drain
86 * the wait queue, since if any threads are added to the queue afterwards,
87 * they may never get woken out of SFI wait. So sfi_lock must be
88 * taken before the wait queue's own spinlock.
89 *
90 * The wait queue will take the thread's scheduling lock. We may also take
91 * the thread_lock directly to update the "sfi_class" field and determine
92 * if the thread should block in the wait queue, but the lock will be
93 * released before doing so.
94 *
95 * The pset lock may also be taken, but not while any other locks are held.
96 *
97 * The task and thread mutex may also be held while reevaluating sfi state.
98 *
99 * splsched ---> sfi_lock ---> waitq ---> thread_lock
100 * \ \ \__ thread_lock (*)
101 * \ \__ pset_lock
102 * \
103 * \__ thread_lock
104 */
105
106 decl_simple_lock_data(static, sfi_lock);
107 static timer_call_data_t sfi_timer_call_entry;
108 volatile boolean_t sfi_is_enabled;
109
110 boolean_t sfi_window_is_set;
111 uint64_t sfi_window_usecs;
112 uint64_t sfi_window_interval;
113 uint64_t sfi_next_off_deadline;
114
115 typedef struct {
116 sfi_class_id_t class_id;
117 thread_continue_t class_continuation;
118 const char * class_name;
119 const char * class_ledger_name;
120 } sfi_class_registration_t;
121
122 /*
123 * To add a new SFI class:
124 *
125 * 1) Raise MAX_SFI_CLASS_ID in mach/sfi_class.h
126 * 2) Add a #define for it to mach/sfi_class.h. It need not be inserted in order of restrictiveness.
127 * 3) Add a call to SFI_CLASS_REGISTER below
128 * 4) Augment sfi_thread_classify to categorize threads as early as possible for as restrictive as possible.
129 * 5) Modify thermald to use the SFI class
130 */
131
132 static inline void _sfi_wait_cleanup(void);
133
134 static void sfi_class_register(sfi_class_registration_t *);
135
136 #define SFI_CLASS_REGISTER(clsid, ledger_name) \
137 \
138 static void __attribute__((noinline, noreturn)) \
139 SFI_ ## clsid ## _THREAD_IS_WAITING(void *arg __unused, wait_result_t wret __unused) \
140 { \
141 _sfi_wait_cleanup(); \
142 thread_exception_return(); \
143 } \
144 \
145 static_assert(SFI_CLASS_ ## clsid < MAX_SFI_CLASS_ID, "Invalid ID"); \
146 \
147 static __startup_data sfi_class_registration_t \
148 SFI_ ## clsid ## _registration = { \
149 .class_id = SFI_CLASS_ ## clsid, \
150 .class_continuation = SFI_ ## clsid ## _THREAD_IS_WAITING, \
151 .class_name = "SFI_CLASS_" # clsid, \
152 .class_ledger_name = "SFI_CLASS_" # ledger_name, \
153 }; \
154 STARTUP_ARG(TUNABLES, STARTUP_RANK_MIDDLE, \
155 sfi_class_register, &SFI_ ## clsid ## _registration)
156
157 /* SFI_CLASS_UNSPECIFIED not included here */
158 SFI_CLASS_REGISTER(MAINTENANCE, MAINTENANCE);
159 SFI_CLASS_REGISTER(DARWIN_BG, DARWIN_BG);
160 SFI_CLASS_REGISTER(APP_NAP, APP_NAP);
161 SFI_CLASS_REGISTER(MANAGED_FOCAL, MANAGED);
162 SFI_CLASS_REGISTER(MANAGED_NONFOCAL, MANAGED);
163 SFI_CLASS_REGISTER(UTILITY, UTILITY);
164 SFI_CLASS_REGISTER(DEFAULT_FOCAL, DEFAULT);
165 SFI_CLASS_REGISTER(DEFAULT_NONFOCAL, DEFAULT);
166 SFI_CLASS_REGISTER(LEGACY_FOCAL, LEGACY);
167 SFI_CLASS_REGISTER(LEGACY_NONFOCAL, LEGACY);
168 SFI_CLASS_REGISTER(USER_INITIATED_FOCAL, USER_INITIATED);
169 SFI_CLASS_REGISTER(USER_INITIATED_NONFOCAL, USER_INITIATED);
170 SFI_CLASS_REGISTER(USER_INTERACTIVE_FOCAL, USER_INTERACTIVE);
171 SFI_CLASS_REGISTER(USER_INTERACTIVE_NONFOCAL, USER_INTERACTIVE);
172 SFI_CLASS_REGISTER(KERNEL, OPTED_OUT);
173 SFI_CLASS_REGISTER(OPTED_OUT, OPTED_OUT);
174
175 struct sfi_class_state {
176 uint64_t off_time_usecs;
177 uint64_t off_time_interval;
178
179 thread_call_t on_timer;
180 uint64_t on_timer_deadline;
181 boolean_t on_timer_programmed;
182
183 boolean_t class_sfi_is_enabled;
184 volatile boolean_t class_in_on_phase;
185
186 struct waitq waitq; /* threads in ready state */
187 thread_continue_t continuation;
188
189 const char * class_name;
190 const char * class_ledger_name;
191 };
192
193 /* Static configuration performed in sfi_early_init() */
194 struct sfi_class_state sfi_classes[MAX_SFI_CLASS_ID];
195
196 int sfi_enabled_class_count; // protected by sfi_lock and used atomically
197
198 static void sfi_timer_global_off(
199 timer_call_param_t param0,
200 timer_call_param_t param1);
201
202 static void sfi_timer_per_class_on(
203 timer_call_param_t param0,
204 timer_call_param_t param1);
205
206 /* Called early in boot, when kernel is single-threaded */
207 __startup_func
208 static void
sfi_class_register(sfi_class_registration_t * reg)209 sfi_class_register(sfi_class_registration_t *reg)
210 {
211 sfi_class_id_t class_id = reg->class_id;
212
213 if (class_id >= MAX_SFI_CLASS_ID) {
214 panic("Invalid SFI class 0x%x", class_id);
215 }
216 if (sfi_classes[class_id].continuation != NULL) {
217 panic("Duplicate SFI registration for class 0x%x", class_id);
218 }
219 sfi_classes[class_id].class_sfi_is_enabled = FALSE;
220 sfi_classes[class_id].class_in_on_phase = TRUE;
221 sfi_classes[class_id].continuation = reg->class_continuation;
222 sfi_classes[class_id].class_name = reg->class_name;
223 sfi_classes[class_id].class_ledger_name = reg->class_ledger_name;
224 }
225
226 void
sfi_init(void)227 sfi_init(void)
228 {
229 sfi_class_id_t i;
230
231 simple_lock_init(&sfi_lock, 0);
232 timer_call_setup(&sfi_timer_call_entry, sfi_timer_global_off, NULL);
233 sfi_window_is_set = FALSE;
234 os_atomic_init(&sfi_enabled_class_count, 0);
235 sfi_is_enabled = FALSE;
236
237 for (i = 0; i < MAX_SFI_CLASS_ID; i++) {
238 /* If the class was set up in sfi_early_init(), initialize remaining fields */
239 if (sfi_classes[i].continuation) {
240 sfi_classes[i].on_timer = thread_call_allocate_with_options(
241 sfi_timer_per_class_on, (void *)(uintptr_t)i, THREAD_CALL_PRIORITY_HIGH,
242 THREAD_CALL_OPTIONS_ONCE);
243 sfi_classes[i].on_timer_programmed = FALSE;
244
245 waitq_init(&sfi_classes[i].waitq, WQT_QUEUE, SYNC_POLICY_FIFO);
246 } else {
247 /* The only allowed gap is for SFI_CLASS_UNSPECIFIED */
248 if (i != SFI_CLASS_UNSPECIFIED) {
249 panic("Gap in registered SFI classes");
250 }
251 }
252 }
253 }
254
255 /* Can be called before sfi_init() by task initialization, but after sfi_early_init() */
256 sfi_class_id_t
sfi_get_ledger_alias_for_class(sfi_class_id_t class_id)257 sfi_get_ledger_alias_for_class(sfi_class_id_t class_id)
258 {
259 sfi_class_id_t i;
260 const char *ledger_name = NULL;
261
262 ledger_name = sfi_classes[class_id].class_ledger_name;
263
264 /* Find the first class in the registration table with this ledger name */
265 if (ledger_name) {
266 for (i = SFI_CLASS_UNSPECIFIED + 1; i < class_id; i++) {
267 if (0 == strcmp(sfi_classes[i].class_ledger_name, ledger_name)) {
268 dprintf("sfi_get_ledger_alias_for_class(0x%x) -> 0x%x\n", class_id, i);
269 return i;
270 }
271 }
272
273 /* This class is the primary one for the ledger, so there is no alias */
274 dprintf("sfi_get_ledger_alias_for_class(0x%x) -> 0x%x\n", class_id, SFI_CLASS_UNSPECIFIED);
275 return SFI_CLASS_UNSPECIFIED;
276 }
277
278 /* We are permissive on SFI class lookup failures. In sfi_init(), we assert more */
279 return SFI_CLASS_UNSPECIFIED;
280 }
281
282 int
sfi_ledger_entry_add(ledger_template_t template,sfi_class_id_t class_id)283 sfi_ledger_entry_add(ledger_template_t template, sfi_class_id_t class_id)
284 {
285 const char *ledger_name = NULL;
286
287 ledger_name = sfi_classes[class_id].class_ledger_name;
288
289 dprintf("sfi_ledger_entry_add(%p, 0x%x) -> %s\n", template, class_id, ledger_name);
290 return ledger_entry_add(template, ledger_name, "sfi", "MATUs");
291 }
292
293 static void
sfi_timer_global_off(timer_call_param_t param0 __unused,timer_call_param_t param1 __unused)294 sfi_timer_global_off(
295 timer_call_param_t param0 __unused,
296 timer_call_param_t param1 __unused)
297 {
298 uint64_t now = mach_absolute_time();
299 sfi_class_id_t i;
300 processor_set_t pset, nset;
301 processor_t processor;
302 uint32_t needs_cause_ast_mask = 0x0;
303 spl_t s;
304
305 s = splsched();
306
307 simple_lock(&sfi_lock, LCK_GRP_NULL);
308 if (!sfi_is_enabled) {
309 /* If SFI has been disabled, let all "on" timers drain naturally */
310 KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SFI, SFI_OFF_TIMER) | DBG_FUNC_NONE, 1, 0, 0, 0, 0);
311
312 simple_unlock(&sfi_lock);
313 splx(s);
314 return;
315 }
316
317 KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SFI, SFI_OFF_TIMER) | DBG_FUNC_START, 0, 0, 0, 0, 0);
318
319 /* First set all configured classes into the off state, and program their "on" timer */
320 for (i = 0; i < MAX_SFI_CLASS_ID; i++) {
321 if (sfi_classes[i].class_sfi_is_enabled) {
322 uint64_t on_timer_deadline;
323
324 sfi_classes[i].class_in_on_phase = FALSE;
325 sfi_classes[i].on_timer_programmed = TRUE;
326
327 /* Push out on-timer */
328 on_timer_deadline = now + sfi_classes[i].off_time_interval;
329 sfi_classes[i].on_timer_deadline = on_timer_deadline;
330
331 thread_call_enter_delayed_with_leeway(sfi_classes[i].on_timer, NULL, on_timer_deadline, 0, THREAD_CALL_DELAY_SYS_CRITICAL);
332 } else {
333 /* If this class no longer needs SFI, make sure the timer is cancelled */
334 sfi_classes[i].class_in_on_phase = TRUE;
335 if (sfi_classes[i].on_timer_programmed) {
336 sfi_classes[i].on_timer_programmed = FALSE;
337 sfi_classes[i].on_timer_deadline = ~0ULL;
338 thread_call_cancel(sfi_classes[i].on_timer);
339 }
340 }
341 }
342 simple_unlock(&sfi_lock);
343
344 /* Iterate over processors, call cause_ast_check() on ones running a thread that should be in an off phase */
345 processor = processor_list;
346 pset = processor->processor_set;
347
348 pset_lock(pset);
349
350 do {
351 nset = processor->processor_set;
352 if (nset != pset) {
353 pset_unlock(pset);
354 pset = nset;
355 pset_lock(pset);
356 }
357
358 /* "processor" and its pset are locked */
359 if (processor->state == PROCESSOR_RUNNING) {
360 if (AST_NONE != sfi_processor_needs_ast(processor)) {
361 needs_cause_ast_mask |= (1U << processor->cpu_id);
362 }
363 }
364 } while ((processor = processor->processor_list) != NULL);
365
366 pset_unlock(pset);
367
368 for (int cpuid = lsb_first(needs_cause_ast_mask); cpuid >= 0; cpuid = lsb_next(needs_cause_ast_mask, cpuid)) {
369 processor = processor_array[cpuid];
370 if (processor == current_processor()) {
371 ast_on(AST_SFI);
372 } else {
373 cause_ast_check(processor);
374 }
375 }
376
377 /* Re-arm timer if still enabled */
378 simple_lock(&sfi_lock, LCK_GRP_NULL);
379 if (sfi_is_enabled) {
380 clock_deadline_for_periodic_event(sfi_window_interval,
381 now,
382 &sfi_next_off_deadline);
383 timer_call_enter1(&sfi_timer_call_entry,
384 NULL,
385 sfi_next_off_deadline,
386 TIMER_CALL_SYS_CRITICAL);
387 }
388
389 KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SFI, SFI_OFF_TIMER) | DBG_FUNC_END, 0, 0, 0, 0, 0);
390
391 simple_unlock(&sfi_lock);
392
393 splx(s);
394 }
395
396 static void
sfi_timer_per_class_on(timer_call_param_t param0,timer_call_param_t param1 __unused)397 sfi_timer_per_class_on(
398 timer_call_param_t param0,
399 timer_call_param_t param1 __unused)
400 {
401 sfi_class_id_t sfi_class_id = (sfi_class_id_t)(uintptr_t)param0;
402 struct sfi_class_state *sfi_class = &sfi_classes[sfi_class_id];
403
404 spl_t s = splsched();
405
406 simple_lock(&sfi_lock, LCK_GRP_NULL);
407
408 KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SFI, SFI_ON_TIMER) | DBG_FUNC_START, sfi_class_id, 0, 0, 0, 0);
409
410 /*
411 * Any threads that may have accumulated in the ready queue for this class should get re-enqueued.
412 * Since we have the sfi_lock held and have changed "class_in_on_phase", we expect
413 * no new threads to be put on this wait queue until the global "off timer" has fired.
414 */
415
416 sfi_class->class_in_on_phase = TRUE;
417 sfi_class->on_timer_programmed = FALSE;
418
419 simple_unlock(&sfi_lock);
420
421 /*
422 * Issue the wakeup outside the lock to reduce lock hold time
423 * rdar://problem/96463639
424 */
425 __assert_only kern_return_t kret;
426
427 kret = waitq_wakeup64_all(&sfi_class->waitq,
428 CAST_EVENT64_T(sfi_class_id),
429 THREAD_AWAKENED, waitq_flags_splx(s));
430 assert(kret == KERN_SUCCESS || kret == KERN_NOT_WAITING);
431
432 KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SFI, SFI_ON_TIMER) | DBG_FUNC_END, 0, 0, 0, 0, 0);
433 }
434
435
436 kern_return_t
sfi_set_window(uint64_t window_usecs)437 sfi_set_window(uint64_t window_usecs)
438 {
439 uint64_t interval, deadline;
440 uint64_t now = mach_absolute_time();
441 sfi_class_id_t i;
442 spl_t s;
443 uint64_t largest_class_off_interval = 0;
444
445 if (window_usecs < MIN_SFI_WINDOW_USEC) {
446 window_usecs = MIN_SFI_WINDOW_USEC;
447 }
448
449 if (window_usecs > UINT32_MAX) {
450 return KERN_INVALID_ARGUMENT;
451 }
452
453 KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SFI, SFI_SET_WINDOW), window_usecs, 0, 0, 0, 0);
454
455 clock_interval_to_absolutetime_interval((uint32_t)window_usecs, NSEC_PER_USEC, &interval);
456 deadline = now + interval;
457
458 s = splsched();
459
460 simple_lock(&sfi_lock, LCK_GRP_NULL);
461
462 /* Check that we are not bringing in the SFI window smaller than any class */
463 for (i = 0; i < MAX_SFI_CLASS_ID; i++) {
464 if (sfi_classes[i].class_sfi_is_enabled) {
465 largest_class_off_interval = MAX(largest_class_off_interval, sfi_classes[i].off_time_interval);
466 }
467 }
468
469 /*
470 * Off window must be strictly greater than all enabled classes,
471 * otherwise threads would build up on ready queue and never be able to run.
472 */
473 if (interval <= largest_class_off_interval) {
474 simple_unlock(&sfi_lock);
475 splx(s);
476 return KERN_INVALID_ARGUMENT;
477 }
478
479 /*
480 * If the new "off" deadline is further out than the current programmed timer,
481 * just let the current one expire (and the new cadence will be established thereafter).
482 * If the new "off" deadline is nearer than the current one, bring it in, so we
483 * can start the new behavior sooner. Note that this may cause the "off" timer to
484 * fire before some of the class "on" timers have fired.
485 */
486 sfi_window_usecs = window_usecs;
487 sfi_window_interval = interval;
488 sfi_window_is_set = TRUE;
489
490 if (os_atomic_load(&sfi_enabled_class_count, relaxed) == 0) {
491 /* Can't program timer yet */
492 } else if (!sfi_is_enabled) {
493 sfi_is_enabled = TRUE;
494 sfi_next_off_deadline = deadline;
495 timer_call_enter1(&sfi_timer_call_entry,
496 NULL,
497 sfi_next_off_deadline,
498 TIMER_CALL_SYS_CRITICAL);
499 } else if (deadline >= sfi_next_off_deadline) {
500 sfi_next_off_deadline = deadline;
501 } else {
502 sfi_next_off_deadline = deadline;
503 timer_call_enter1(&sfi_timer_call_entry,
504 NULL,
505 sfi_next_off_deadline,
506 TIMER_CALL_SYS_CRITICAL);
507 }
508
509 simple_unlock(&sfi_lock);
510 splx(s);
511
512 return KERN_SUCCESS;
513 }
514
515 kern_return_t
sfi_window_cancel(void)516 sfi_window_cancel(void)
517 {
518 spl_t s;
519
520 s = splsched();
521
522 KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SFI, SFI_CANCEL_WINDOW), 0, 0, 0, 0, 0);
523
524 /* Disable globals so that global "off-timer" is not re-armed */
525 simple_lock(&sfi_lock, LCK_GRP_NULL);
526 sfi_window_is_set = FALSE;
527 sfi_window_usecs = 0;
528 sfi_window_interval = 0;
529 sfi_next_off_deadline = 0;
530 sfi_is_enabled = FALSE;
531 simple_unlock(&sfi_lock);
532
533 splx(s);
534
535 return KERN_SUCCESS;
536 }
537
538 /* Defers SFI off and per-class on timers (if live) by the specified interval
539 * in Mach Absolute Time Units. Currently invoked to align with the global
540 * forced idle mechanism. Making some simplifying assumptions, the iterative GFI
541 * induced SFI on+off deferrals form a geometric series that converges to yield
542 * an effective SFI duty cycle that is scaled by the GFI duty cycle. Initial phase
543 * alignment and congruency of the SFI/GFI periods can distort this to some extent.
544 */
545
546 kern_return_t
sfi_defer(uint64_t sfi_defer_matus)547 sfi_defer(uint64_t sfi_defer_matus)
548 {
549 kern_return_t kr = KERN_FAILURE;
550 spl_t s = splsched();
551
552 KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SFI, SFI_GLOBAL_DEFER), sfi_defer_matus, 0, 0, 0, 0);
553
554 simple_lock(&sfi_lock, LCK_GRP_NULL);
555 if (!sfi_is_enabled) {
556 goto sfi_defer_done;
557 }
558
559 assert(sfi_next_off_deadline != 0);
560
561 sfi_next_off_deadline += sfi_defer_matus;
562 timer_call_enter1(&sfi_timer_call_entry, NULL, sfi_next_off_deadline, TIMER_CALL_SYS_CRITICAL);
563
564 for (int i = 0; i < MAX_SFI_CLASS_ID; i++) {
565 if (sfi_classes[i].class_sfi_is_enabled) {
566 if (sfi_classes[i].on_timer_programmed) {
567 uint64_t new_on_deadline = sfi_classes[i].on_timer_deadline + sfi_defer_matus;
568 sfi_classes[i].on_timer_deadline = new_on_deadline;
569 thread_call_enter_delayed_with_leeway(sfi_classes[i].on_timer, NULL, new_on_deadline, 0, THREAD_CALL_DELAY_SYS_CRITICAL);
570 }
571 }
572 }
573
574 kr = KERN_SUCCESS;
575 sfi_defer_done:
576 simple_unlock(&sfi_lock);
577
578 splx(s);
579
580 return kr;
581 }
582
583
584 kern_return_t
sfi_get_window(uint64_t * window_usecs)585 sfi_get_window(uint64_t *window_usecs)
586 {
587 spl_t s;
588 uint64_t off_window_us;
589
590 s = splsched();
591 simple_lock(&sfi_lock, LCK_GRP_NULL);
592
593 off_window_us = sfi_window_usecs;
594
595 simple_unlock(&sfi_lock);
596 splx(s);
597
598 *window_usecs = off_window_us;
599
600 return KERN_SUCCESS;
601 }
602
603
604 kern_return_t
sfi_set_class_offtime(sfi_class_id_t class_id,uint64_t offtime_usecs)605 sfi_set_class_offtime(sfi_class_id_t class_id, uint64_t offtime_usecs)
606 {
607 uint64_t interval;
608 spl_t s;
609 uint64_t off_window_interval;
610
611 if (offtime_usecs < MIN_SFI_WINDOW_USEC) {
612 offtime_usecs = MIN_SFI_WINDOW_USEC;
613 }
614
615 if (class_id == SFI_CLASS_UNSPECIFIED || class_id >= MAX_SFI_CLASS_ID) {
616 return KERN_INVALID_ARGUMENT;
617 }
618
619 if (offtime_usecs > UINT32_MAX) {
620 return KERN_INVALID_ARGUMENT;
621 }
622
623 KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SFI, SFI_SET_CLASS_OFFTIME), offtime_usecs, class_id, 0, 0, 0);
624
625 clock_interval_to_absolutetime_interval((uint32_t)offtime_usecs, NSEC_PER_USEC, &interval);
626
627 s = splsched();
628
629 simple_lock(&sfi_lock, LCK_GRP_NULL);
630 off_window_interval = sfi_window_interval;
631
632 /* Check that we are not bringing in class off-time larger than the SFI window */
633 if (off_window_interval && (interval >= off_window_interval)) {
634 simple_unlock(&sfi_lock);
635 splx(s);
636 return KERN_INVALID_ARGUMENT;
637 }
638
639 /* We never re-program the per-class on-timer, but rather just let it expire naturally */
640 if (!sfi_classes[class_id].class_sfi_is_enabled) {
641 os_atomic_inc(&sfi_enabled_class_count, relaxed);
642 }
643 sfi_classes[class_id].off_time_usecs = offtime_usecs;
644 sfi_classes[class_id].off_time_interval = interval;
645 sfi_classes[class_id].class_sfi_is_enabled = TRUE;
646
647 if (sfi_window_is_set && !sfi_is_enabled) {
648 /* start global off timer */
649 sfi_is_enabled = TRUE;
650 sfi_next_off_deadline = mach_absolute_time() + sfi_window_interval;
651 timer_call_enter1(&sfi_timer_call_entry,
652 NULL,
653 sfi_next_off_deadline,
654 TIMER_CALL_SYS_CRITICAL);
655 }
656
657 simple_unlock(&sfi_lock);
658
659 splx(s);
660
661 return KERN_SUCCESS;
662 }
663
664 kern_return_t
sfi_class_offtime_cancel(sfi_class_id_t class_id)665 sfi_class_offtime_cancel(sfi_class_id_t class_id)
666 {
667 spl_t s;
668
669 if (class_id == SFI_CLASS_UNSPECIFIED || class_id >= MAX_SFI_CLASS_ID) {
670 return KERN_INVALID_ARGUMENT;
671 }
672
673 s = splsched();
674
675 KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SFI, SFI_CANCEL_CLASS_OFFTIME), class_id, 0, 0, 0, 0);
676
677 simple_lock(&sfi_lock, LCK_GRP_NULL);
678
679 /* We never re-program the per-class on-timer, but rather just let it expire naturally */
680 if (sfi_classes[class_id].class_sfi_is_enabled) {
681 os_atomic_dec(&sfi_enabled_class_count, relaxed);
682 }
683 sfi_classes[class_id].off_time_usecs = 0;
684 sfi_classes[class_id].off_time_interval = 0;
685 sfi_classes[class_id].class_sfi_is_enabled = FALSE;
686
687 if (os_atomic_load(&sfi_enabled_class_count, relaxed) == 0) {
688 sfi_is_enabled = FALSE;
689 }
690
691 simple_unlock(&sfi_lock);
692
693 splx(s);
694
695 return KERN_SUCCESS;
696 }
697
698 kern_return_t
sfi_get_class_offtime(sfi_class_id_t class_id,uint64_t * offtime_usecs)699 sfi_get_class_offtime(sfi_class_id_t class_id, uint64_t *offtime_usecs)
700 {
701 uint64_t off_time_us;
702 spl_t s;
703
704 if (class_id == SFI_CLASS_UNSPECIFIED || class_id >= MAX_SFI_CLASS_ID) {
705 return 0;
706 }
707
708 s = splsched();
709
710 simple_lock(&sfi_lock, LCK_GRP_NULL);
711 off_time_us = sfi_classes[class_id].off_time_usecs;
712 simple_unlock(&sfi_lock);
713
714 splx(s);
715
716 *offtime_usecs = off_time_us;
717
718 return KERN_SUCCESS;
719 }
720
721 /*
722 * sfi_thread_classify and sfi_processor_active_thread_classify perform the critical
723 * role of quickly categorizing a thread into its SFI class so that an AST_SFI can be
724 * set. As the thread is unwinding to userspace, sfi_ast() performs full locking
725 * and determines whether the thread should enter an SFI wait state. Because of
726 * the inherent races between the time the AST is set and when it is evaluated,
727 * thread classification can be inaccurate (but should always be safe). This is
728 * especially the case for sfi_processor_active_thread_classify, which must
729 * classify the active thread on a remote processor without taking the thread lock.
730 * When in doubt, classification should err on the side of *not* classifying a
731 * thread at all, and wait for the thread itself to either hit a quantum expiration
732 * or block inside the kernel.
733 */
734
735 /*
736 * Thread must be locked. Ultimately, the real decision to enter
737 * SFI wait happens at the AST boundary.
738 */
739 sfi_class_id_t
sfi_thread_classify(thread_t thread)740 sfi_thread_classify(thread_t thread)
741 {
742 task_t task = get_threadtask(thread);
743 boolean_t is_kernel_thread = (task == kernel_task);
744 sched_mode_t thmode = thread->sched_mode;
745 boolean_t focal = FALSE;
746
747 /* kernel threads never reach the user AST boundary, and are in a separate world for SFI */
748 if (is_kernel_thread) {
749 return SFI_CLASS_KERNEL;
750 }
751
752 /* no need to re-classify threads unless there is at least one enabled SFI class */
753 if (os_atomic_load(&sfi_enabled_class_count, relaxed) == 0) {
754 return SFI_CLASS_OPTED_OUT;
755 }
756
757 int task_role = proc_get_effective_task_policy(task, TASK_POLICY_ROLE);
758 int latency_qos = proc_get_effective_task_policy(task, TASK_POLICY_LATENCY_QOS);
759 int managed_task = proc_get_effective_task_policy(task, TASK_POLICY_SFI_MANAGED);
760
761 int thread_qos = proc_get_effective_thread_policy(thread, TASK_POLICY_QOS);
762 int thread_bg = proc_get_effective_thread_policy(thread, TASK_POLICY_DARWIN_BG);
763
764 if (thread_qos == THREAD_QOS_MAINTENANCE) {
765 return SFI_CLASS_MAINTENANCE;
766 }
767
768 if (thread_bg || thread_qos == THREAD_QOS_BACKGROUND) {
769 return SFI_CLASS_DARWIN_BG;
770 }
771
772 if (latency_qos != 0) {
773 int latency_qos_wtf = latency_qos - 1;
774
775 if ((latency_qos_wtf >= 4) && (latency_qos_wtf <= 5)) {
776 return SFI_CLASS_APP_NAP;
777 }
778 }
779
780 /*
781 * Realtime and fixed priority threads express their duty cycle constraints
782 * via other mechanisms, and are opted out of (most) forms of SFI
783 */
784 if (thmode == TH_MODE_REALTIME || thmode == TH_MODE_FIXED || task_role == TASK_GRAPHICS_SERVER) {
785 return SFI_CLASS_OPTED_OUT;
786 }
787
788 /*
789 * Threads with unspecified, legacy, or user-initiated QOS class can be individually managed.
790 */
791 switch (task_role) {
792 case TASK_CONTROL_APPLICATION:
793 case TASK_FOREGROUND_APPLICATION:
794 focal = TRUE;
795 break;
796 case TASK_BACKGROUND_APPLICATION:
797 case TASK_DEFAULT_APPLICATION:
798 case TASK_UNSPECIFIED:
799 /* Focal if the task is in a coalition with a FG/focal app */
800 if (task_coalition_focal_count(task) > 0) {
801 focal = TRUE;
802 }
803 break;
804 case TASK_THROTTLE_APPLICATION:
805 case TASK_DARWINBG_APPLICATION:
806 case TASK_NONUI_APPLICATION:
807 /* Definitely not focal */
808 default:
809 break;
810 }
811
812 if (managed_task) {
813 switch (thread_qos) {
814 case THREAD_QOS_UNSPECIFIED:
815 case THREAD_QOS_LEGACY:
816 case THREAD_QOS_USER_INITIATED:
817 if (focal) {
818 return SFI_CLASS_MANAGED_FOCAL;
819 } else {
820 return SFI_CLASS_MANAGED_NONFOCAL;
821 }
822 default:
823 break;
824 }
825 }
826
827 if (thread_qos == THREAD_QOS_UTILITY) {
828 return SFI_CLASS_UTILITY;
829 }
830
831 /*
832 * Classify threads in non-managed tasks
833 */
834 if (focal) {
835 switch (thread_qos) {
836 case THREAD_QOS_USER_INTERACTIVE:
837 return SFI_CLASS_USER_INTERACTIVE_FOCAL;
838 case THREAD_QOS_USER_INITIATED:
839 return SFI_CLASS_USER_INITIATED_FOCAL;
840 case THREAD_QOS_LEGACY:
841 return SFI_CLASS_LEGACY_FOCAL;
842 default:
843 return SFI_CLASS_DEFAULT_FOCAL;
844 }
845 } else {
846 switch (thread_qos) {
847 case THREAD_QOS_USER_INTERACTIVE:
848 return SFI_CLASS_USER_INTERACTIVE_NONFOCAL;
849 case THREAD_QOS_USER_INITIATED:
850 return SFI_CLASS_USER_INITIATED_NONFOCAL;
851 case THREAD_QOS_LEGACY:
852 return SFI_CLASS_LEGACY_NONFOCAL;
853 default:
854 return SFI_CLASS_DEFAULT_NONFOCAL;
855 }
856 }
857 }
858
859 /*
860 * pset must be locked.
861 */
862 sfi_class_id_t
sfi_processor_active_thread_classify(processor_t processor)863 sfi_processor_active_thread_classify(processor_t processor)
864 {
865 return processor->current_sfi_class;
866 }
867
868 /*
869 * thread must be locked. This is inherently racy, with the intent that
870 * at the AST boundary, it will be fully evaluated whether we need to
871 * perform an AST wait
872 */
873 ast_t
sfi_thread_needs_ast(thread_t thread,sfi_class_id_t * out_class)874 sfi_thread_needs_ast(thread_t thread, sfi_class_id_t *out_class)
875 {
876 sfi_class_id_t class_id;
877
878 class_id = sfi_thread_classify(thread);
879
880 if (out_class) {
881 *out_class = class_id;
882 }
883
884 /* No lock taken, so a stale value may be used. */
885 if (!sfi_classes[class_id].class_in_on_phase) {
886 return AST_SFI;
887 } else {
888 return AST_NONE;
889 }
890 }
891
892 /*
893 * pset must be locked. We take the SFI class for
894 * the currently running thread which is cached on
895 * the processor_t, and assume it is accurate. In the
896 * worst case, the processor will get an IPI and be asked
897 * to evaluate if the current running thread at that
898 * later point in time should be in an SFI wait.
899 */
900 ast_t
sfi_processor_needs_ast(processor_t processor)901 sfi_processor_needs_ast(processor_t processor)
902 {
903 sfi_class_id_t class_id;
904
905 class_id = sfi_processor_active_thread_classify(processor);
906
907 /* No lock taken, so a stale value may be used. */
908 if (!sfi_classes[class_id].class_in_on_phase) {
909 return AST_SFI;
910 } else {
911 return AST_NONE;
912 }
913 }
914
915 static inline void
_sfi_wait_cleanup(void)916 _sfi_wait_cleanup(void)
917 {
918 thread_t self = current_thread();
919
920 spl_t s = splsched();
921 simple_lock(&sfi_lock, LCK_GRP_NULL);
922
923 sfi_class_id_t current_sfi_wait_class = self->sfi_wait_class;
924
925 assert((SFI_CLASS_UNSPECIFIED < current_sfi_wait_class) &&
926 (current_sfi_wait_class < MAX_SFI_CLASS_ID));
927
928 self->sfi_wait_class = SFI_CLASS_UNSPECIFIED;
929
930 simple_unlock(&sfi_lock);
931 splx(s);
932
933 /*
934 * It's possible for the thread to be woken up due to the SFI period
935 * ending *before* it finishes blocking. In that case,
936 * wait_sfi_begin_time won't be set.
937 *
938 * Derive the time sacrificed to SFI by looking at when this thread was
939 * awoken by the on-timer, to avoid counting the time this thread spent
940 * waiting to get scheduled.
941 *
942 * Note that last_made_runnable_time could be reset if this thread
943 * gets preempted before we read the value. To fix that, we'd need to
944 * track wait time in a thread timer, sample the timer before blocking,
945 * pass the value through thread->parameter, and subtract that.
946 */
947
948 if (self->wait_sfi_begin_time != 0) {
949 uint64_t made_runnable = os_atomic_load(&self->last_made_runnable_time, relaxed);
950 int64_t sfi_wait_time = made_runnable - self->wait_sfi_begin_time;
951 assert(sfi_wait_time >= 0);
952
953 ledger_credit(get_threadtask(self)->ledger,
954 task_ledgers.sfi_wait_times[current_sfi_wait_class],
955 sfi_wait_time);
956
957 self->wait_sfi_begin_time = 0;
958 }
959 }
960
961 /*
962 * Called at AST context to fully evaluate if the current thread
963 * (which is obviously running) should instead block in an SFI wait.
964 * We must take the sfi_lock to check whether we are in the "off" period
965 * for the class, and if so, block.
966 */
967 void
sfi_ast(thread_t thread)968 sfi_ast(thread_t thread)
969 {
970 sfi_class_id_t class_id;
971 spl_t s;
972 struct sfi_class_state *sfi_class;
973 wait_result_t waitret;
974 boolean_t did_wait = FALSE;
975 thread_continue_t continuation;
976
977 s = splsched();
978
979 simple_lock(&sfi_lock, LCK_GRP_NULL);
980
981 if (!sfi_is_enabled) {
982 /*
983 * SFI is not enabled, or has recently been disabled.
984 * There is no point putting this thread on a deferred ready
985 * queue, even if it were classified as needing it, since
986 * SFI will truly be off at the next global off timer
987 */
988 simple_unlock(&sfi_lock);
989 splx(s);
990
991 return;
992 }
993
994 thread_lock(thread);
995 thread->sfi_class = class_id = sfi_thread_classify(thread);
996 thread_unlock(thread);
997
998 /*
999 * Once the sfi_lock is taken and the thread's ->sfi_class field is updated, we
1000 * are committed to transitioning to whatever state is indicated by "->class_in_on_phase".
1001 * If another thread tries to call sfi_reevaluate() after this point, it will take the
1002 * sfi_lock and see the thread in this wait state. If another thread calls
1003 * sfi_reevaluate() before this point, it would see a runnable thread and at most
1004 * attempt to send an AST to this processor, but we would have the most accurate
1005 * classification.
1006 */
1007
1008 sfi_class = &sfi_classes[class_id];
1009 if (!sfi_class->class_in_on_phase) {
1010 /* Need to block thread in wait queue */
1011 KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SFI, SFI_THREAD_DEFER),
1012 thread_tid(thread), class_id, 0, 0, 0);
1013
1014 waitret = waitq_assert_wait64(&sfi_class->waitq,
1015 CAST_EVENT64_T(class_id),
1016 THREAD_INTERRUPTIBLE | THREAD_WAIT_NOREPORT, 0);
1017 if (waitret == THREAD_WAITING) {
1018 thread->sfi_wait_class = class_id;
1019 did_wait = TRUE;
1020 continuation = sfi_class->continuation;
1021 } else {
1022 /* thread may be exiting already, all other errors are unexpected */
1023 assert(waitret == THREAD_INTERRUPTED);
1024 }
1025 }
1026 simple_unlock(&sfi_lock);
1027
1028 splx(s);
1029
1030 if (did_wait) {
1031 assert(thread->wait_sfi_begin_time == 0);
1032
1033 thread_block_reason(continuation, NULL, AST_SFI);
1034 }
1035 }
1036
1037 /* Thread must be unlocked */
1038 void
sfi_reevaluate(thread_t thread)1039 sfi_reevaluate(thread_t thread)
1040 {
1041 kern_return_t kret;
1042 spl_t s;
1043 sfi_class_id_t class_id, current_class_id;
1044 ast_t sfi_ast;
1045
1046 s = splsched();
1047
1048 simple_lock(&sfi_lock, LCK_GRP_NULL);
1049
1050 thread_lock(thread);
1051 sfi_ast = sfi_thread_needs_ast(thread, &class_id);
1052 thread->sfi_class = class_id;
1053
1054 /*
1055 * This routine chiefly exists to boost threads out of an SFI wait
1056 * if their classification changes before the "on" timer fires.
1057 *
1058 * If we calculate that a thread is in a different ->sfi_wait_class
1059 * than we think it should be (including no-SFI-wait), we need to
1060 * correct that:
1061 *
1062 * If the thread is in SFI wait and should not be (or should be waiting
1063 * on a different class' "on" timer), we wake it up. If needed, the
1064 * thread may immediately block again in the different SFI wait state.
1065 *
1066 * If the thread is not in an SFI wait state and it should be, we need
1067 * to get that thread's attention, possibly by sending an AST to another
1068 * processor.
1069 */
1070
1071 if ((current_class_id = thread->sfi_wait_class) != SFI_CLASS_UNSPECIFIED) {
1072 thread_unlock(thread); /* not needed anymore */
1073
1074 assert(current_class_id < MAX_SFI_CLASS_ID);
1075
1076 if ((sfi_ast == AST_NONE) || (class_id != current_class_id)) {
1077 struct sfi_class_state *sfi_class = &sfi_classes[current_class_id];
1078
1079 KERNEL_DEBUG_CONSTANT(MACHDBG_CODE(DBG_MACH_SFI, SFI_WAIT_CANCELED), thread_tid(thread), current_class_id, class_id, 0, 0);
1080
1081 kret = waitq_wakeup64_thread(&sfi_class->waitq,
1082 CAST_EVENT64_T(current_class_id),
1083 thread,
1084 THREAD_AWAKENED);
1085 assert(kret == KERN_SUCCESS || kret == KERN_NOT_WAITING);
1086 }
1087 } else {
1088 /*
1089 * Thread's current SFI wait class is not set, and because we
1090 * have the sfi_lock, it won't get set.
1091 */
1092
1093 if ((thread->state & (TH_RUN | TH_IDLE)) == TH_RUN) {
1094 if (sfi_ast != AST_NONE) {
1095 if (thread == current_thread()) {
1096 ast_on(sfi_ast);
1097 } else {
1098 processor_t processor = thread->last_processor;
1099
1100 if (processor != PROCESSOR_NULL &&
1101 processor->state == PROCESSOR_RUNNING &&
1102 processor->active_thread == thread) {
1103 cause_ast_check(processor);
1104 } else {
1105 /*
1106 * Runnable thread that's not on a CPU currently. When a processor
1107 * does context switch to it, the AST will get set based on whether
1108 * the thread is in its "off time".
1109 */
1110 }
1111 }
1112 }
1113 }
1114
1115 thread_unlock(thread);
1116 }
1117
1118 simple_unlock(&sfi_lock);
1119 splx(s);
1120 }
1121
1122 #else /* !CONFIG_SCHED_SFI */
1123
1124 kern_return_t
sfi_set_window(uint64_t window_usecs __unused)1125 sfi_set_window(uint64_t window_usecs __unused)
1126 {
1127 return KERN_NOT_SUPPORTED;
1128 }
1129
1130 kern_return_t
sfi_window_cancel(void)1131 sfi_window_cancel(void)
1132 {
1133 return KERN_NOT_SUPPORTED;
1134 }
1135
1136
1137 kern_return_t
sfi_get_window(uint64_t * window_usecs __unused)1138 sfi_get_window(uint64_t *window_usecs __unused)
1139 {
1140 return KERN_NOT_SUPPORTED;
1141 }
1142
1143
1144 kern_return_t
sfi_set_class_offtime(sfi_class_id_t class_id __unused,uint64_t offtime_usecs __unused)1145 sfi_set_class_offtime(sfi_class_id_t class_id __unused, uint64_t offtime_usecs __unused)
1146 {
1147 return KERN_NOT_SUPPORTED;
1148 }
1149
1150 kern_return_t
sfi_class_offtime_cancel(sfi_class_id_t class_id __unused)1151 sfi_class_offtime_cancel(sfi_class_id_t class_id __unused)
1152 {
1153 return KERN_NOT_SUPPORTED;
1154 }
1155
1156 kern_return_t
sfi_get_class_offtime(sfi_class_id_t class_id __unused,uint64_t * offtime_usecs __unused)1157 sfi_get_class_offtime(sfi_class_id_t class_id __unused, uint64_t *offtime_usecs __unused)
1158 {
1159 return KERN_NOT_SUPPORTED;
1160 }
1161
1162 void
sfi_reevaluate(thread_t thread __unused)1163 sfi_reevaluate(thread_t thread __unused)
1164 {
1165 return;
1166 }
1167
1168 sfi_class_id_t
sfi_thread_classify(thread_t thread)1169 sfi_thread_classify(thread_t thread)
1170 {
1171 task_t task = get_threadtask(thread);
1172 boolean_t is_kernel_thread = (task == kernel_task);
1173
1174 if (is_kernel_thread) {
1175 return SFI_CLASS_KERNEL;
1176 }
1177
1178 return SFI_CLASS_OPTED_OUT;
1179 }
1180
1181 #endif /* !CONFIG_SCHED_SFI */
1182