1 /*
2 * Copyright (c) 2006-2021 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 */
29
30 #include <kern/task.h>
31 #include <libkern/libkern.h>
32 #include <machine/atomic.h>
33 #include <mach/coalition.h>
34 #include <os/log.h>
35 #include <sys/coalition.h>
36 #include <sys/proc.h>
37 #include <sys/proc_internal.h>
38 #include <sys/kdebug.h>
39 #include <sys/kern_memorystatus.h>
40 #include <vm/vm_protos.h>
41
42 #include <kern/kern_memorystatus_internal.h>
43
44 /*
45 * All memory pressure policy decisions should live here, and there should be
46 * as little mechanism as possible. This file prioritizes readability.
47 */
48
49 #pragma mark Policy Function Declarations
50
51 #if CONFIG_JETSAM
52 static bool memorystatus_check_aggressive_jetsam_needed(int *jld_idle_kills);
53 #endif /* CONFIG_JETSAM */
54
55 #pragma mark Memorystatus Health Check
56
57 /*
58 * Each subsystem that relies on the memorystatus thread
59 * for resource exhaustion should put a health check in this section.
60 * The memorystatus thread runs all of the health checks
61 * to determine if the system is healthy. If the system is unhealthy
62 * it picks an action based on the system health status. See the
63 * Memorystatus Thread Actions section below.
64 */
65
66 extern bool vm_compressor_needs_to_swap(bool wake_memorystatus_thread);
67 extern boolean_t vm_compressor_low_on_space(void);
68 extern bool vm_compressor_compressed_pages_nearing_limit(void);
69 extern bool vm_compressor_is_thrashing(void);
70 extern bool vm_compressor_swapout_is_ripe(void);
71
72 #if XNU_TARGET_OS_WATCH
73 #define FREEZE_PREVENT_REFREEZE_OF_LAST_THAWED true
74 #define FREEZE_PREVENT_REFREEZE_OF_LAST_THAWED_TIMEOUT_SECONDS (60 * 15)
75 #else
76 #define FREEZE_PREVENT_REFREEZE_OF_LAST_THAWED false
77 #endif
78 extern pid_t memorystatus_freeze_last_pid_thawed;
79 extern uint64_t memorystatus_freeze_last_pid_thawed_ts;
80
81 static void
memorystatus_health_check(memorystatus_system_health_t * status)82 memorystatus_health_check(memorystatus_system_health_t *status)
83 {
84 memset(status, 0, sizeof(memorystatus_system_health_t));
85 #if CONFIG_JETSAM
86 status->msh_available_pages_below_pressure = memorystatus_avail_pages_below_pressure();
87 status->msh_available_pages_below_critical = memorystatus_avail_pages_below_critical();
88 status->msh_compressor_is_low_on_space = (vm_compressor_low_on_space() == TRUE);
89 status->msh_compressed_pages_nearing_limit = vm_compressor_compressed_pages_nearing_limit();
90 status->msh_compressor_is_thrashing = !memorystatus_swap_all_apps && vm_compressor_is_thrashing();
91 #if CONFIG_PHANTOM_CACHE
92 status->msh_phantom_cache_pressure = os_atomic_load(&memorystatus_phantom_cache_pressure, acquire);
93 #else
94 status->msh_phantom_cache_pressure = false;
95 #endif /* CONFIG_PHANTOM_CACHE */
96 if (!memorystatus_swap_all_apps &&
97 status->msh_phantom_cache_pressure &&
98 !(status->msh_compressor_is_thrashing && status->msh_compressor_is_low_on_space)) {
99 status->msh_filecache_is_thrashing = true;
100 }
101 status->msh_compressor_is_low_on_space = os_atomic_load(&memorystatus_compressor_space_shortage, acquire);
102 status->msh_pageout_starved = os_atomic_load(&memorystatus_pageout_starved, acquire);
103 status->msh_swappable_compressor_segments_over_limit = memorystatus_swap_over_trigger(100);
104 status->msh_swapin_queue_over_limit = memorystatus_swapin_over_trigger();
105 status->msh_swap_low_on_space = vm_swap_low_on_space();
106 status->msh_swap_out_of_space = vm_swap_out_of_space();
107 #endif /* CONFIG_JETSAM */
108 status->msh_zone_map_is_exhausted = os_atomic_load(&memorystatus_zone_map_is_exhausted, relaxed);
109 }
110
111 bool
memorystatus_is_system_healthy(const memorystatus_system_health_t * status)112 memorystatus_is_system_healthy(const memorystatus_system_health_t *status)
113 {
114 #if CONFIG_JETSAM
115 return !(status->msh_available_pages_below_critical ||
116 status->msh_compressor_is_low_on_space ||
117 status->msh_compressor_is_thrashing ||
118 status->msh_filecache_is_thrashing ||
119 status->msh_zone_map_is_exhausted ||
120 status->msh_pageout_starved);
121 #else /* CONFIG_JETSAM */
122 return !status->msh_zone_map_is_exhausted;
123 #endif /* CONFIG_JETSAM */
124 }
125
126
127 #pragma mark Memorystatus Thread Actions
128
129 /*
130 * This section picks the appropriate memorystatus_action & deploys it.
131 */
132
133 /*
134 * Inspects the state of various resources in the system to see if
135 * the system is healthy. If the system is not healthy, picks a
136 * memorystatus_action_t to recover the system.
137 *
138 * Every time the memorystatus thread wakes up it calls into here
139 * to pick an action. It will continue performing memorystatus actions until this
140 * function returns MEMORYSTATUS_KILL_NONE. At that point the thread will block.
141 */
142 memorystatus_action_t
memorystatus_pick_action(struct jetsam_thread_state * jetsam_thread,uint32_t * kill_cause,bool highwater_remaining,bool suspended_swappable_apps_remaining,bool swappable_apps_remaining,int * jld_idle_kills)143 memorystatus_pick_action(struct jetsam_thread_state *jetsam_thread,
144 uint32_t *kill_cause,
145 bool highwater_remaining,
146 bool suspended_swappable_apps_remaining,
147 bool swappable_apps_remaining,
148 int *jld_idle_kills)
149 {
150 memorystatus_system_health_t status;
151 memorystatus_health_check(&status);
152 memorystatus_log_system_health(&status);
153 bool is_system_healthy = memorystatus_is_system_healthy(&status);
154
155 #if CONFIG_JETSAM
156 if (status.msh_available_pages_below_pressure || !is_system_healthy) {
157 /*
158 * If swap is enabled, first check if we're running low or are out of swap space.
159 */
160 if (memorystatus_swap_all_apps && jetsam_kill_on_low_swap) {
161 if (swappable_apps_remaining && status.msh_swap_out_of_space) {
162 *kill_cause = kMemorystatusKilledLowSwap;
163 return MEMORYSTATUS_KILL_SWAPPABLE;
164 } else if (suspended_swappable_apps_remaining && status.msh_swap_low_on_space) {
165 *kill_cause = kMemorystatusKilledLowSwap;
166 return MEMORYSTATUS_KILL_SUSPENDED_SWAPPABLE;
167 }
168 }
169
170 /*
171 * We're below the pressure level or the system is unhealthy,
172 * regardless of the system health let's check if we should be swapping
173 * and if there are high watermark kills left to do.
174 */
175 if (memorystatus_swap_all_apps) {
176 if (status.msh_swappable_compressor_segments_over_limit && !vm_swapout_thread_running && !os_atomic_load(&vm_swapout_wake_pending, relaxed)) {
177 /*
178 * TODO: The swapper will keep running until it has drained the entire early swapout queue.
179 * That might be overly aggressive & we should look into tuning it.
180 * See rdar://84102304.
181 */
182 return MEMORYSTATUS_WAKE_SWAPPER;
183 } else if (status.msh_swapin_queue_over_limit) {
184 return MEMORYSTATUS_PROCESS_SWAPIN_QUEUE;
185 } else if (status.msh_swappable_compressor_segments_over_limit) {
186 memorystatus_log_info(
187 "memorystatus: Skipping swap wakeup because the swap thread is already running. vm_swapout_thread_running=%d, vm_swapout_wake_pending=%d\n",
188 vm_swapout_thread_running, os_atomic_load(&vm_swapout_wake_pending, relaxed));
189 }
190 }
191
192 if (highwater_remaining) {
193 *kill_cause = kMemorystatusKilledHiwat;
194 memorystatus_log("memorystatus: Looking for highwatermark kills.\n");
195 return MEMORYSTATUS_KILL_HIWATER;
196 }
197 }
198
199 if (is_system_healthy) {
200 *kill_cause = 0;
201 return MEMORYSTATUS_KILL_NONE;
202 }
203
204 /*
205 * At this point the system is unhealthy and there are no
206 * more highwatermark processes to kill.
207 */
208
209 if (!jetsam_thread->limit_to_low_bands) {
210 if (memorystatus_check_aggressive_jetsam_needed(jld_idle_kills)) {
211 memorystatus_log("memorystatus: Starting aggressive jetsam.\n");
212 *kill_cause = kMemorystatusKilledProcThrashing;
213 return MEMORYSTATUS_KILL_AGGRESSIVE;
214 }
215 }
216 /*
217 * The system is unhealthy and we either don't need aggressive jetsam
218 * or are not allowed to deploy it.
219 * Kill in priority order. We'll use LRU within every band except the
220 * FG (which will be sorted by coalition role).
221 */
222 *kill_cause = memorystatus_pick_kill_cause(&status);
223 return MEMORYSTATUS_KILL_TOP_PROCESS;
224 #else /* CONFIG_JETSAM */
225 (void) jetsam_thread;
226 (void) jld_idle_kills;
227 (void) suspended_swappable_apps_remaining;
228 (void) swappable_apps_remaining;
229 /*
230 * Without CONFIG_JETSAM, we only kill if the system is unhealthy.
231 * There is no aggressive jetsam and no
232 * early highwatermark killing.
233 */
234 if (is_system_healthy) {
235 *kill_cause = 0;
236 return MEMORYSTATUS_KILL_NONE;
237 }
238 if (highwater_remaining) {
239 *kill_cause = kMemorystatusKilledHiwat;
240 return MEMORYSTATUS_KILL_HIWATER;
241 } else {
242 *kill_cause = memorystatus_pick_kill_cause(&status);
243 return MEMORYSTATUS_KILL_TOP_PROCESS;
244 }
245 #endif /* CONFIG_JETSAM */
246 }
247
248 #pragma mark Aggressive Jetsam
249 /*
250 * This section defines when we deploy aggressive jetsam.
251 * Aggressive jetsam kills everything up to the jld_priority_band_max band.
252 */
253
254 #if CONFIG_JETSAM
255
256 static bool
257 memorystatus_aggressive_jetsam_needed_sysproc_aging(__unused int jld_eval_aggressive_count, __unused int *jld_idle_kills, __unused int jld_idle_kill_candidates, int *total_candidates);
258
259 /*
260 * kJetsamHighRelaunchCandidatesThreshold defines the percentage of candidates
261 * in the idle & deferred bands that need to be bad candidates in order to trigger
262 * aggressive jetsam.
263 */
264 #define kJetsamHighRelaunchCandidatesThreshold (100)
265
266 /* kJetsamMinCandidatesThreshold defines the minimum number of candidates in the
267 * idle/deferred bands to trigger aggressive jetsam. This value basically decides
268 * how much memory the system is ready to hold in the lower bands without triggering
269 * aggressive jetsam. This number should ideally be tuned based on the memory config
270 * of the device.
271 */
272 #define kJetsamMinCandidatesThreshold (5)
273
274 static bool
memorystatus_check_aggressive_jetsam_needed(int * jld_idle_kills)275 memorystatus_check_aggressive_jetsam_needed(int *jld_idle_kills)
276 {
277 bool aggressive_jetsam_needed = false;
278 int total_candidates = 0;
279 /*
280 * The aggressive jetsam logic looks at the number of times it has been in the
281 * aggressive loop to determine the max priority band it should kill upto. The
282 * static variables below are used to track that property.
283 *
284 * To reset those values, the implementation checks if it has been
285 * memorystatus_jld_eval_period_msecs since the parameters were reset.
286 */
287
288 if (memorystatus_jld_enabled == FALSE) {
289 /* If aggressive jetsam is disabled, nothing to do here */
290 return FALSE;
291 }
292
293 /* Get current timestamp (msecs only) */
294 struct timeval jld_now_tstamp = {0, 0};
295 uint64_t jld_now_msecs = 0;
296 microuptime(&jld_now_tstamp);
297 jld_now_msecs = (jld_now_tstamp.tv_sec * 1000);
298
299 /*
300 * Look at the number of candidates in the idle and deferred band and
301 * how many out of them are marked as high relaunch probability.
302 */
303 aggressive_jetsam_needed = memorystatus_aggressive_jetsam_needed_sysproc_aging(jld_eval_aggressive_count,
304 jld_idle_kills, jld_idle_kill_candidates, &total_candidates);
305
306 /*
307 * Check if its been really long since the aggressive jetsam evaluation
308 * parameters have been refreshed. This logic also resets the jld_eval_aggressive_count
309 * counter to make sure we reset the aggressive jetsam severity.
310 */
311 boolean_t param_reval = false;
312
313 if ((total_candidates == 0) ||
314 (jld_now_msecs > (jld_timestamp_msecs + memorystatus_jld_eval_period_msecs))) {
315 jld_timestamp_msecs = jld_now_msecs;
316 jld_idle_kill_candidates = total_candidates;
317 *jld_idle_kills = 0;
318 jld_eval_aggressive_count = 0;
319 jld_priority_band_max = JETSAM_PRIORITY_UI_SUPPORT;
320 param_reval = true;
321 }
322
323 /*
324 * It is also possible that the system is down to a very small number of processes in the candidate
325 * bands. In that case, the decisions made by the memorystatus_aggressive_jetsam_needed_* routines
326 * would not be useful. In that case, do not trigger aggressive jetsam.
327 */
328 if (total_candidates < kJetsamMinCandidatesThreshold) {
329 #if DEVELOPMENT || DEBUG
330 memorystatus_log_info(
331 "memorystatus: aggressive: [FAILED] Low Candidate Count (current: %d, threshold: %d)\n", total_candidates, kJetsamMinCandidatesThreshold);
332 #endif /* DEVELOPMENT || DEBUG */
333 aggressive_jetsam_needed = false;
334 }
335 return aggressive_jetsam_needed;
336 }
337
338 static bool
memorystatus_aggressive_jetsam_needed_sysproc_aging(__unused int eval_aggressive_count,__unused int * idle_kills,__unused int idle_kill_candidates,int * total_candidates)339 memorystatus_aggressive_jetsam_needed_sysproc_aging(__unused int eval_aggressive_count, __unused int *idle_kills, __unused int idle_kill_candidates, int *total_candidates)
340 {
341 bool aggressive_jetsam_needed = false;
342
343 /*
344 * For the kJetsamAgingPolicySysProcsReclaimedFirst aging policy, we maintain the jetsam
345 * relaunch behavior for all daemons. Also, daemons and apps are aged in deferred bands on
346 * every dirty->clean transition. For this aging policy, the best way to determine if
347 * aggressive jetsam is needed, is to see if the kill candidates are mostly bad candidates.
348 * If yes, then we need to go to higher bands to reclaim memory.
349 */
350 proc_list_lock();
351 /* Get total candidate counts for idle and idle deferred bands */
352 *total_candidates = memstat_bucket[JETSAM_PRIORITY_IDLE].count + memstat_bucket[system_procs_aging_band].count;
353 /* Get counts of bad kill candidates in idle and idle deferred bands */
354 int bad_candidates = memstat_bucket[JETSAM_PRIORITY_IDLE].relaunch_high_count + memstat_bucket[system_procs_aging_band].relaunch_high_count;
355
356 proc_list_unlock();
357
358 /* Check if the number of bad candidates is greater than kJetsamHighRelaunchCandidatesThreshold % */
359 aggressive_jetsam_needed = (((bad_candidates * 100) / *total_candidates) >= kJetsamHighRelaunchCandidatesThreshold);
360
361 /*
362 * Since the new aging policy bases the aggressive jetsam trigger on percentage of
363 * bad candidates, it is prone to being overly aggressive. In order to mitigate that,
364 * make sure the system is really under memory pressure before triggering aggressive
365 * jetsam.
366 */
367 if (memorystatus_available_pages > memorystatus_sysproc_aging_aggr_pages) {
368 aggressive_jetsam_needed = false;
369 }
370
371 #if DEVELOPMENT || DEBUG
372 memorystatus_log_info(
373 "memorystatus: aggressive%d: [%s] Bad Candidate Threshold Check (total: %d, bad: %d, threshold: %d %%); Memory Pressure Check (available_pgs: %llu, threshold_pgs: %llu)\n",
374 eval_aggressive_count, aggressive_jetsam_needed ? "PASSED" : "FAILED", *total_candidates, bad_candidates,
375 kJetsamHighRelaunchCandidatesThreshold, (uint64_t)MEMORYSTATUS_LOG_AVAILABLE_PAGES, (uint64_t)memorystatus_sysproc_aging_aggr_pages);
376 #endif /* DEVELOPMENT || DEBUG */
377 return aggressive_jetsam_needed;
378 }
379
380 #endif /* CONFIG_JETSAM */
381
382 #pragma mark Freezer
383 #if CONFIG_FREEZE
384 /*
385 * Freezer policies
386 */
387
388 /*
389 * These functions determine what is eligible for the freezer
390 * and the order that we consider freezing them
391 */
392
393 /*
394 * Checks if the given process is eligible for the freezer.
395 * Processes can only be frozen if this returns true.
396 */
397 bool
memorystatus_is_process_eligible_for_freeze(proc_t p)398 memorystatus_is_process_eligible_for_freeze(proc_t p)
399 {
400 /*
401 * Called with proc_list_lock held.
402 */
403
404 LCK_MTX_ASSERT(&proc_list_mlock, LCK_MTX_ASSERT_OWNED);
405
406 bool should_freeze = false;
407 uint32_t state = 0, pages = 0;
408 bool first_consideration = true;
409 task_t task;
410
411 state = p->p_memstat_state;
412
413 if (state & (P_MEMSTAT_TERMINATED | P_MEMSTAT_LOCKED | P_MEMSTAT_FREEZE_DISABLED | P_MEMSTAT_FREEZE_IGNORE)) {
414 if (state & P_MEMSTAT_FREEZE_DISABLED) {
415 p->p_memstat_freeze_skip_reason = kMemorystatusFreezeSkipReasonDisabled;
416 }
417 goto out;
418 }
419
420 task = proc_task(p);
421
422 if (isSysProc(p)) {
423 /*
424 * Daemon:- We consider freezing it if:
425 * - it belongs to a coalition and the leader is frozen, and,
426 * - its role in the coalition is XPC service.
427 *
428 * We skip memory size requirements in this case.
429 */
430 int task_role_in_coalition = 0;
431 proc_t leader_proc = memorystatus_get_coalition_leader_and_role(p, &task_role_in_coalition);
432 if (leader_proc == PROC_NULL || leader_proc == p) {
433 /*
434 * Jetsam coalition is leaderless or the leader is not an app.
435 * Either way, don't freeze this proc.
436 */
437 goto out;
438 }
439
440 /* Leader must be frozen */
441 if (!(leader_proc->p_memstat_state & P_MEMSTAT_FROZEN)) {
442 goto out;
443 }
444 /* Only freeze XPC services */
445 if (task_role_in_coalition == COALITION_TASKROLE_XPC) {
446 should_freeze = true;
447 }
448
449 goto out;
450 } else {
451 /*
452 * Application. Only freeze if it's suspended.
453 */
454 if (!(state & P_MEMSTAT_SUSPENDED)) {
455 goto out;
456 }
457 }
458
459 /*
460 * We're interested in tracking what percentage of
461 * eligible apps actually get frozen.
462 * To avoid skewing the metrics towards processes which
463 * are considered more frequently, we only track failures once
464 * per process.
465 */
466 first_consideration = !(state & P_MEMSTAT_FREEZE_CONSIDERED);
467
468 if (first_consideration) {
469 memorystatus_freezer_stats.mfs_process_considered_count++;
470 p->p_memstat_state |= P_MEMSTAT_FREEZE_CONSIDERED;
471 }
472
473 /* Only freeze applications meeting our minimum resident page criteria */
474 memorystatus_get_task_page_counts(proc_task(p), &pages, NULL, NULL);
475 if (pages < memorystatus_freeze_pages_min) {
476 if (first_consideration) {
477 memorystatus_freezer_stats.mfs_error_below_min_pages_count++;
478 }
479 p->p_memstat_freeze_skip_reason = kMemorystatusFreezeSkipReasonBelowMinPages;
480 goto out;
481 }
482
483 /* Don't freeze processes that are already exiting on core. It may have started exiting
484 * after we chose it for freeze, but before we obtained the proc_list_lock.
485 * NB: This is only possible if we're coming in from memorystatus_freeze_process_sync.
486 * memorystatus_freeze_top_process holds the proc_list_lock while it traverses the bands.
487 */
488 if (proc_list_exited(p)) {
489 if (first_consideration) {
490 memorystatus_freezer_stats.mfs_error_other_count++;
491 }
492 p->p_memstat_freeze_skip_reason = kMemorystatusFreezeSkipReasonOther;
493 goto out;
494 }
495
496 if (!memorystatus_freezer_use_ordered_list) {
497 /*
498 * We're not using the ordered list so we need to check
499 * that dasd recommended the process. Note that the ordered list
500 * algorithm only considers processes on the list in the first place
501 * so there's no need to double check here.
502 */
503 if (!memorystatus_freeze_process_is_recommended(p)) {
504 if (first_consideration) {
505 memorystatus_freezer_stats.mfs_error_low_probability_of_use_count++;
506 }
507 p->p_memstat_freeze_skip_reason = kMemorystatusFreezeSkipReasonLowProbOfUse;
508 goto out;
509 }
510 }
511
512 if (!(state & P_MEMSTAT_FROZEN) && p->p_memstat_effectivepriority > memorystatus_freeze_max_candidate_band) {
513 /*
514 * Proc has been elevated by something else.
515 * Don't freeze it.
516 */
517 if (first_consideration) {
518 memorystatus_freezer_stats.mfs_error_elevated_count++;
519 }
520 p->p_memstat_freeze_skip_reason = kMemorystatusFreezeSkipReasonElevated;
521 goto out;
522 }
523
524 should_freeze = true;
525 out:
526 if (should_freeze && !(state & P_MEMSTAT_FROZEN)) {
527 /*
528 * Reset the skip reason. If it's killed before we manage to actually freeze it
529 * we failed to consider it early enough.
530 */
531 p->p_memstat_freeze_skip_reason = kMemorystatusFreezeSkipReasonNone;
532 if (!first_consideration) {
533 /*
534 * We're freezing this for the first time and we previously considered it ineligible.
535 * Bump the considered count so that we track this as 1 failure
536 * and 1 success.
537 */
538 memorystatus_freezer_stats.mfs_process_considered_count++;
539 }
540 }
541 return should_freeze;
542 }
543
544 bool
memorystatus_freeze_proc_is_refreeze_eligible(proc_t p)545 memorystatus_freeze_proc_is_refreeze_eligible(proc_t p)
546 {
547 return (p->p_memstat_state & P_MEMSTAT_REFREEZE_ELIGIBLE) != 0;
548 }
549
550
551 static proc_t
memorystatus_freeze_pick_refreeze_process(proc_t last_p)552 memorystatus_freeze_pick_refreeze_process(proc_t last_p)
553 {
554 proc_t p = PROC_NULL, next_p = PROC_NULL;
555 unsigned int band = (unsigned int) memorystatus_freeze_jetsam_band;
556 if (last_p == PROC_NULL) {
557 next_p = memorystatus_get_first_proc_locked(&band, FALSE);
558 } else {
559 next_p = memorystatus_get_next_proc_locked(&band, last_p, FALSE);
560 }
561 while (next_p) {
562 p = next_p;
563 next_p = memorystatus_get_next_proc_locked(&band, p, FALSE);
564 if ((p->p_memstat_state & P_MEMSTAT_FROZEN) && !memorystatus_freeze_proc_is_refreeze_eligible(p)) {
565 /* Process is already frozen & hasn't been thawed. */
566 continue;
567 }
568 /*
569 * Has to have been frozen once before.
570 */
571 if (!(p->p_memstat_state & P_MEMSTAT_FROZEN)) {
572 continue;
573 }
574
575 /*
576 * Not currently being looked at for something.
577 */
578 if (p->p_memstat_state & P_MEMSTAT_LOCKED) {
579 continue;
580 }
581
582 #if FREEZE_PREVENT_REFREEZE_OF_LAST_THAWED
583 /*
584 * Don't refreeze the last process we just thawed if still within the timeout window
585 */
586 if (p->p_pid == memorystatus_freeze_last_pid_thawed) {
587 uint64_t timeout_delta_abs;
588 nanoseconds_to_absolutetime(FREEZE_PREVENT_REFREEZE_OF_LAST_THAWED_TIMEOUT_SECONDS * NSEC_PER_SEC, &timeout_delta_abs);
589 if (mach_absolute_time() < (memorystatus_freeze_last_pid_thawed_ts + timeout_delta_abs)) {
590 continue;
591 }
592 }
593 #endif
594
595 /*
596 * Found it
597 */
598 return p;
599 }
600 return PROC_NULL;
601 }
602
603 proc_t
memorystatus_freeze_pick_process(struct memorystatus_freeze_list_iterator * iterator)604 memorystatus_freeze_pick_process(struct memorystatus_freeze_list_iterator *iterator)
605 {
606 proc_t p = PROC_NULL, next_p = PROC_NULL;
607 unsigned int band = JETSAM_PRIORITY_IDLE;
608
609 LCK_MTX_ASSERT(&proc_list_mlock, LCK_MTX_ASSERT_OWNED);
610 /*
611 * If the freezer is full, only consider refreezes.
612 */
613 if (iterator->refreeze_only || memorystatus_frozen_count >= memorystatus_frozen_processes_max) {
614 if (!iterator->refreeze_only) {
615 /*
616 * The first time the iterator starts to return refreeze
617 * candidates, we need to reset the last pointer b/c it's pointing into the wrong band.
618 */
619 iterator->last_p = PROC_NULL;
620 iterator->refreeze_only = true;
621 }
622 iterator->last_p = memorystatus_freeze_pick_refreeze_process(iterator->last_p);
623 return iterator->last_p;
624 }
625
626 /*
627 * Search for the next freezer candidate.
628 */
629 if (memorystatus_freezer_use_ordered_list) {
630 while (iterator->global_freeze_list_index < memorystatus_global_freeze_list.mfcl_length) {
631 p = memorystatus_freezer_candidate_list_get_proc(
632 &memorystatus_global_freeze_list,
633 (iterator->global_freeze_list_index)++,
634 &memorystatus_freezer_stats.mfs_freeze_pid_mismatches);
635
636 if (p != PROC_NULL && memorystatus_is_process_eligible_for_freeze(p)) {
637 iterator->last_p = p;
638 return iterator->last_p;
639 }
640 }
641 } else {
642 if (iterator->last_p == PROC_NULL) {
643 next_p = memorystatus_get_first_proc_locked(&band, FALSE);
644 } else {
645 next_p = memorystatus_get_next_proc_locked(&band, iterator->last_p, FALSE);
646 }
647 while (next_p) {
648 p = next_p;
649 if (memorystatus_is_process_eligible_for_freeze(p)) {
650 iterator->last_p = p;
651 return iterator->last_p;
652 } else {
653 next_p = memorystatus_get_next_proc_locked(&band, p, FALSE);
654 }
655 }
656 }
657
658 /*
659 * Failed to find a new freezer candidate.
660 * Try to re-freeze.
661 */
662 if (memorystatus_refreeze_eligible_count >= memorystatus_min_thaw_refreeze_threshold) {
663 assert(!iterator->refreeze_only);
664 iterator->refreeze_only = true;
665 iterator->last_p = memorystatus_freeze_pick_refreeze_process(PROC_NULL);
666 return iterator->last_p;
667 }
668 return PROC_NULL;
669 }
670
671 /*
672 * memorystatus_pages_update calls this function whenever the number
673 * of available pages changes. It wakes the freezer thread iff the function returns
674 * true. The freezer thread will try to freeze (or refreeze) up to 1 process
675 * before blocking again.
676 *
677 * Note the freezer thread is also woken up by memorystatus_on_inactivity.
678 */
679
680 bool
memorystatus_freeze_thread_should_run()681 memorystatus_freeze_thread_should_run()
682 {
683 /*
684 * No freezer_mutex held here...see why near call-site
685 * within memorystatus_pages_update().
686 */
687
688 if (memorystatus_freeze_enabled == false) {
689 return false;
690 }
691
692 if (memorystatus_available_pages > memorystatus_freeze_threshold) {
693 return false;
694 }
695
696 memorystatus_freezer_stats.mfs_below_threshold_count++;
697
698 if ((memorystatus_frozen_count >= memorystatus_frozen_processes_max)) {
699 /*
700 * Consider this as a skip even if we wake up to refreeze because
701 * we won't freeze any new procs.
702 */
703 memorystatus_freezer_stats.mfs_skipped_full_count++;
704 if (memorystatus_refreeze_eligible_count < memorystatus_min_thaw_refreeze_threshold) {
705 return false;
706 }
707 }
708
709 if (memorystatus_frozen_shared_mb_max && (memorystatus_frozen_shared_mb >= memorystatus_frozen_shared_mb_max)) {
710 memorystatus_freezer_stats.mfs_skipped_shared_mb_high_count++;
711 return false;
712 }
713
714 uint64_t curr_time = mach_absolute_time();
715
716 if (curr_time < memorystatus_freezer_thread_next_run_ts) {
717 return false;
718 }
719
720 return true;
721 }
722
723 size_t
memorystatus_pick_freeze_count_for_wakeup()724 memorystatus_pick_freeze_count_for_wakeup()
725 {
726 size_t num_to_freeze = 0;
727 if (!memorystatus_swap_all_apps) {
728 num_to_freeze = 1;
729 } else {
730 /*
731 * When app swap is enabled, we want the freezer thread to aggressively freeze
732 * all candidates so we clear out space for the fg working set.
733 * But we still cap it to the current size of the candidate bands to avoid
734 * consuming excessive CPU if there's a lot of churn in the candidate band.
735 */
736 proc_list_lock();
737 for (unsigned int band = JETSAM_PRIORITY_IDLE; band <= memorystatus_freeze_max_candidate_band; band++) {
738 num_to_freeze += memstat_bucket[band].count;
739 }
740 proc_list_unlock();
741 }
742
743 return num_to_freeze;
744 }
745
746 #endif /* CONFIG_FREEZE */
747