/*
* Copyright (c) 2006-2021 Apple Inc. All rights reserved.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_START@
*
* This file contains Original Code and/or Modifications of Original Code
* as defined in and that are subject to the Apple Public Source License
* Version 2.0 (the 'License'). You may not use this file except in
* compliance with the License. The rights granted to you under the License
* may not be used to create, or enable the creation or redistribution of,
* unlawful or unlicensed copies of an Apple operating system, or to
* circumvent, violate, or enable the circumvention or violation of, any
* terms of an Apple operating system software license agreement.
*
* Please obtain a copy of the License at
* http://www.opensource.apple.com/apsl/ and read it before using this file.
*
* The Original Code and all software distributed under the License are
* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
* Please see the License for the specific language governing rights and
* limitations under the License.
*
* @APPLE_OSREFERENCE_LICENSE_HEADER_END@
*
*/
#include <kern/task.h>
#include <libkern/libkern.h>
#include <machine/atomic.h>
#include <mach/coalition.h>
#include <os/log.h>
#include <sys/coalition.h>
#include <sys/proc.h>
#include <sys/proc_internal.h>
#include <sys/sysctl.h>
#include <sys/kdebug.h>
#include <sys/kern_memorystatus.h>
#include <vm/vm_protos.h>
#include <vm/vm_compressor_xnu.h>
#include <kern/kern_memorystatus_internal.h>
/*
* All memory pressure policy decisions should live here, and there should be
* as little mechanism as possible. This file prioritizes readability.
*/
#pragma mark Policy Function Declarations
#if CONFIG_JETSAM
static bool memorystatus_check_aggressive_jetsam_needed(int *jld_idle_kills);
#endif /* CONFIG_JETSAM */
#pragma mark Memorystatus Health Check
/*
* Each subsystem that relies on the memorystatus thread
* for resource exhaustion should put a health check in this section.
* The memorystatus thread runs all of the health checks
* to determine if the system is healthy. If the system is unhealthy
* it picks an action based on the system health status. See the
* Memorystatus Thread Actions section below.
*/
#if XNU_TARGET_OS_WATCH
#define FREEZE_PREVENT_REFREEZE_OF_LAST_THAWED true
#define FREEZE_PREVENT_REFREEZE_OF_LAST_THAWED_TIMEOUT_SECONDS (60 * 15)
#else
#define FREEZE_PREVENT_REFREEZE_OF_LAST_THAWED false
#endif
extern pid_t memorystatus_freeze_last_pid_thawed;
extern uint64_t memorystatus_freeze_last_pid_thawed_ts;
static void
memorystatus_health_check(memorystatus_system_health_t *status)
{
memset(status, 0, sizeof(memorystatus_system_health_t));
#if CONFIG_JETSAM
status->msh_available_pages_below_pressure = memorystatus_avail_pages_below_pressure();
status->msh_available_pages_below_critical = memorystatus_avail_pages_below_critical();
status->msh_compressor_is_low_on_space = (vm_compressor_low_on_space() == TRUE);
status->msh_compressed_pages_nearing_limit = vm_compressor_compressed_pages_nearing_limit();
status->msh_compressor_is_thrashing = !memorystatus_swap_all_apps && vm_compressor_is_thrashing();
#if CONFIG_PHANTOM_CACHE
status->msh_phantom_cache_pressure = os_atomic_load(&memorystatus_phantom_cache_pressure, acquire);
#else
status->msh_phantom_cache_pressure = false;
#endif /* CONFIG_PHANTOM_CACHE */
if (!memorystatus_swap_all_apps &&
status->msh_phantom_cache_pressure &&
!(status->msh_compressor_is_thrashing && status->msh_compressor_is_low_on_space)) {
status->msh_filecache_is_thrashing = true;
}
status->msh_compressor_is_low_on_space = os_atomic_load(&memorystatus_compressor_space_shortage, acquire);
status->msh_pageout_starved = os_atomic_load(&memorystatus_pageout_starved, acquire);
status->msh_swappable_compressor_segments_over_limit = memorystatus_swap_over_trigger(100);
status->msh_swapin_queue_over_limit = memorystatus_swapin_over_trigger();
status->msh_swap_low_on_space = vm_swap_low_on_space();
status->msh_swap_out_of_space = vm_swap_out_of_space();
#endif /* CONFIG_JETSAM */
status->msh_zone_map_is_exhausted = os_atomic_load(&memorystatus_zone_map_is_exhausted, relaxed);
}
bool
memorystatus_is_system_healthy(const memorystatus_system_health_t *status)
{
#if CONFIG_JETSAM
return !(status->msh_available_pages_below_critical ||
status->msh_compressor_is_low_on_space ||
status->msh_compressor_is_thrashing ||
status->msh_filecache_is_thrashing ||
status->msh_zone_map_is_exhausted ||
status->msh_pageout_starved);
#else /* CONFIG_JETSAM */
return !status->msh_zone_map_is_exhausted;
#endif /* CONFIG_JETSAM */
}
#pragma mark Memorystatus Thread Actions
/*
* This section picks the appropriate memorystatus_action & deploys it.
*/
/*
* Inspects the state of various resources in the system to see if
* the system is healthy. If the system is not healthy, picks a
* memorystatus_action_t to recover the system.
*
* Every time the memorystatus thread wakes up it calls into here
* to pick an action. It will continue performing memorystatus actions until this
* function returns MEMORYSTATUS_KILL_NONE. At that point the thread will block.
*/
memorystatus_action_t
memorystatus_pick_action(jetsam_state_t state,
uint32_t *kill_cause,
bool highwater_remaining,
bool suspended_swappable_apps_remaining,
bool swappable_apps_remaining,
int *jld_idle_kills)
{
memorystatus_system_health_t status;
memorystatus_health_check(&status);
memorystatus_log_system_health(&status);
bool is_system_healthy = memorystatus_is_system_healthy(&status);
#if CONFIG_JETSAM
if (status.msh_available_pages_below_pressure || !is_system_healthy) {
/*
* If swap is enabled, first check if we're running low or are out of swap space.
*/
if (memorystatus_swap_all_apps && jetsam_kill_on_low_swap) {
if (swappable_apps_remaining && status.msh_swap_out_of_space) {
*kill_cause = kMemorystatusKilledLowSwap;
return MEMORYSTATUS_KILL_SWAPPABLE;
} else if (suspended_swappable_apps_remaining && status.msh_swap_low_on_space) {
*kill_cause = kMemorystatusKilledLowSwap;
return MEMORYSTATUS_KILL_SUSPENDED_SWAPPABLE;
}
}
/*
* We're below the pressure level or the system is unhealthy,
* regardless of the system health let's check if we should be swapping
* and if there are high watermark kills left to do.
*/
if (memorystatus_swap_all_apps) {
if (status.msh_swappable_compressor_segments_over_limit && !vm_swapout_thread_running && !os_atomic_load(&vm_swapout_wake_pending, relaxed)) {
/*
* TODO: The swapper will keep running until it has drained the entire early swapout queue.
* That might be overly aggressive & we should look into tuning it.
* See rdar://84102304.
*/
return MEMORYSTATUS_WAKE_SWAPPER;
} else if (status.msh_swapin_queue_over_limit) {
return MEMORYSTATUS_PROCESS_SWAPIN_QUEUE;
} else if (status.msh_swappable_compressor_segments_over_limit) {
memorystatus_log_info(
"memorystatus: Skipping swap wakeup because the swap thread is already running. vm_swapout_thread_running=%d, vm_swapout_wake_pending=%d\n",
vm_swapout_thread_running, os_atomic_load(&vm_swapout_wake_pending, relaxed));
}
}
if (highwater_remaining) {
*kill_cause = kMemorystatusKilledHiwat;
memorystatus_log("memorystatus: Looking for highwatermark kills.\n");
return MEMORYSTATUS_KILL_HIWATER;
}
}
if (is_system_healthy) {
*kill_cause = 0;
return MEMORYSTATUS_KILL_NONE;
}
/*
* At this point the system is unhealthy and there are no
* more highwatermark processes to kill.
*/
if (!state->limit_to_low_bands) {
if (memorystatus_check_aggressive_jetsam_needed(jld_idle_kills)) {
memorystatus_log("memorystatus: Starting aggressive jetsam.\n");
*kill_cause = kMemorystatusKilledProcThrashing;
return MEMORYSTATUS_KILL_AGGRESSIVE;
}
}
/*
* The system is unhealthy and we either don't need aggressive jetsam
* or are not allowed to deploy it.
* Kill in priority order. We'll use LRU within every band except the
* FG (which will be sorted by coalition role).
*/
*kill_cause = memorystatus_pick_kill_cause(&status);
return MEMORYSTATUS_KILL_TOP_PROCESS;
#else /* CONFIG_JETSAM */
(void) state;
(void) jld_idle_kills;
(void) suspended_swappable_apps_remaining;
(void) swappable_apps_remaining;
/*
* Without CONFIG_JETSAM, we only kill if the system is unhealthy.
* There is no aggressive jetsam and no
* early highwatermark killing.
*/
if (is_system_healthy) {
*kill_cause = 0;
return MEMORYSTATUS_KILL_NONE;
}
if (highwater_remaining) {
*kill_cause = kMemorystatusKilledHiwat;
return MEMORYSTATUS_KILL_HIWATER;
} else {
*kill_cause = memorystatus_pick_kill_cause(&status);
return MEMORYSTATUS_KILL_TOP_PROCESS;
}
#endif /* CONFIG_JETSAM */
}
#pragma mark Aggressive Jetsam
/*
* This section defines when we deploy aggressive jetsam.
* Aggressive jetsam kills everything up to the jld_priority_band_max band.
*/
#if CONFIG_JETSAM
static bool
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);
/*
* kJetsamHighRelaunchCandidatesThreshold defines the percentage of candidates
* in the idle & deferred bands that need to be bad candidates in order to trigger
* aggressive jetsam.
*/
TUNABLE_DEV_WRITEABLE(unsigned int, kJetsamHighRelaunchCandidatesThreshold, "jetsam_high_relaunch_candidates_threshold_percent", 100);
#if DEVELOPMENT || DEBUG
SYSCTL_UINT(_kern, OID_AUTO, jetsam_high_relaunch_candidates_threshold_percent, CTLFLAG_RW | CTLFLAG_LOCKED, &kJetsamHighRelaunchCandidatesThreshold, 100, "");
#endif /* DEVELOPMENT || DEBUG */
/* kJetsamMinCandidatesThreshold defines the minimum number of candidates in the
* idle/deferred bands to trigger aggressive jetsam. This value basically decides
* how much memory the system is ready to hold in the lower bands without triggering
* aggressive jetsam. This number should ideally be tuned based on the memory config
* of the device.
*/
TUNABLE_DT_DEV_WRITEABLE(unsigned int, kJetsamMinCandidatesThreshold, "/defaults", "kern.jetsam_min_candidates_threshold", "jetsam_min_candidates_threshold", 5, TUNABLE_DT_CHECK_CHOSEN);
#if DEVELOPMENT || DEBUG
SYSCTL_UINT(_kern, OID_AUTO, jetsam_min_candidates_threshold, CTLFLAG_RW | CTLFLAG_LOCKED, &kJetsamMinCandidatesThreshold, 5, "");
#endif /* DEVELOPMENT || DEBUG */
static bool
memorystatus_check_aggressive_jetsam_needed(int *jld_idle_kills)
{
bool aggressive_jetsam_needed = false;
int total_candidates = 0;
/*
* The aggressive jetsam logic looks at the number of times it has been in the
* aggressive loop to determine the max priority band it should kill upto. The
* static variables below are used to track that property.
*
* To reset those values, the implementation checks if it has been
* memorystatus_jld_eval_period_msecs since the parameters were reset.
*/
if (memorystatus_jld_enabled == FALSE) {
/* If aggressive jetsam is disabled, nothing to do here */
return false;
}
/* Get current timestamp (msecs only) */
struct timeval jld_now_tstamp = {0, 0};
uint64_t jld_now_msecs = 0;
microuptime(&jld_now_tstamp);
jld_now_msecs = (jld_now_tstamp.tv_sec * 1000);
/*
* Look at the number of candidates in the idle and deferred band and
* how many out of them are marked as high relaunch probability.
*/
aggressive_jetsam_needed = memorystatus_aggressive_jetsam_needed_sysproc_aging(jld_eval_aggressive_count,
jld_idle_kills, jld_idle_kill_candidates, &total_candidates);
/*
* It is also possible that the system is down to a very small number of processes in the candidate
* bands. In that case, the decisions made by the memorystatus_aggressive_jetsam_needed_* routines
* would not be useful. In that case, do not trigger aggressive jetsam.
*/
if (total_candidates < kJetsamMinCandidatesThreshold) {
memorystatus_log_debug(
"memorystatus: aggressive: [FAILED] Low Candidate "
"Count (current: %d, threshold: %d)\n",
total_candidates, kJetsamMinCandidatesThreshold);
aggressive_jetsam_needed = false;
}
/*
* Check if its been really long since the aggressive jetsam evaluation
* parameters have been refreshed. This logic also resets the jld_eval_aggressive_count
* counter to make sure we reset the aggressive jetsam severity.
*/
if ((total_candidates == 0) ||
(jld_now_msecs > (jld_timestamp_msecs + memorystatus_jld_eval_period_msecs))) {
jld_timestamp_msecs = jld_now_msecs;
jld_idle_kill_candidates = total_candidates;
*jld_idle_kills = 0;
jld_eval_aggressive_count = 0;
}
return aggressive_jetsam_needed;
}
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)
{
bool aggressive_jetsam_needed = false;
/*
* For the kJetsamAgingPolicySysProcsReclaimedFirst aging policy, we maintain the jetsam
* relaunch behavior for all daemons. Also, daemons and apps are aged in deferred bands on
* every dirty->clean transition. For this aging policy, the best way to determine if
* aggressive jetsam is needed, is to see if the kill candidates are mostly bad candidates.
* If yes, then we need to go to higher bands to reclaim memory.
*/
proc_list_lock();
/* Get total candidate counts for idle and idle deferred bands */
*total_candidates = memstat_bucket[JETSAM_PRIORITY_IDLE].count + memstat_bucket[system_procs_aging_band].count;
/* Get counts of bad kill candidates in idle and idle deferred bands */
int bad_candidates = memstat_bucket[JETSAM_PRIORITY_IDLE].relaunch_high_count + memstat_bucket[system_procs_aging_band].relaunch_high_count;
proc_list_unlock();
/* Check if the number of bad candidates is greater than kJetsamHighRelaunchCandidatesThreshold % */
aggressive_jetsam_needed = (((bad_candidates * 100) / *total_candidates) >= kJetsamHighRelaunchCandidatesThreshold);
/*
* Since the new aging policy bases the aggressive jetsam trigger on percentage of
* bad candidates, it is prone to being overly aggressive. In order to mitigate that,
* make sure the system is really under memory pressure before triggering aggressive
* jetsam.
*/
if (memorystatus_available_pages > memorystatus_sysproc_aging_aggr_pages) {
aggressive_jetsam_needed = false;
}
#if DEVELOPMENT || DEBUG
memorystatus_log_info(
"memorystatus: aggressive%d: [%s] Bad Candidate Threshold Check (total: %d, bad: %d, threshold: %d %%); Memory Pressure Check (available_pgs: %llu, threshold_pgs: %llu)\n",
eval_aggressive_count, aggressive_jetsam_needed ? "PASSED" : "FAILED", *total_candidates, bad_candidates,
kJetsamHighRelaunchCandidatesThreshold, (uint64_t)MEMORYSTATUS_LOG_AVAILABLE_PAGES, (uint64_t)memorystatus_sysproc_aging_aggr_pages);
#endif /* DEVELOPMENT || DEBUG */
return aggressive_jetsam_needed;
}
#endif /* CONFIG_JETSAM */
#pragma mark Freezer
#if CONFIG_FREEZE
/*
* Freezer policies
*/
/*
* These functions determine what is eligible for the freezer
* and the order that we consider freezing them
*/
/*
* Checks if the given process is eligible for the freezer.
* Processes can only be frozen if this returns true.
*/
bool
memorystatus_is_process_eligible_for_freeze(proc_t p)
{
/*
* Called with proc_list_lock held.
*/
LCK_MTX_ASSERT(&proc_list_mlock, LCK_MTX_ASSERT_OWNED);
bool should_freeze = false;
uint32_t state = 0, pages = 0;
bool first_consideration = true;
task_t task;
state = p->p_memstat_state;
if (state & (P_MEMSTAT_TERMINATED | P_MEMSTAT_LOCKED | P_MEMSTAT_FREEZE_DISABLED | P_MEMSTAT_FREEZE_IGNORE)) {
if (state & P_MEMSTAT_FREEZE_DISABLED) {
p->p_memstat_freeze_skip_reason = kMemorystatusFreezeSkipReasonDisabled;
}
goto out;
}
task = proc_task(p);
if (isSysProc(p)) {
/*
* Daemon:- We consider freezing it if:
* - it belongs to a coalition and the leader is frozen, and,
* - its role in the coalition is XPC service.
*
* We skip memory size requirements in this case.
*/
int task_role_in_coalition = 0;
proc_t leader_proc = memorystatus_get_coalition_leader_and_role(p, &task_role_in_coalition);
if (leader_proc == PROC_NULL || leader_proc == p) {
/*
* Jetsam coalition is leaderless or the leader is not an app.
* Either way, don't freeze this proc.
*/
goto out;
}
/* Leader must be frozen */
if (!(leader_proc->p_memstat_state & P_MEMSTAT_FROZEN)) {
goto out;
}
/* Only freeze XPC services */
if (task_role_in_coalition == COALITION_TASKROLE_XPC) {
should_freeze = true;
}
goto out;
} else {
/*
* Application. Only freeze if it's suspended.
*/
if (!(state & P_MEMSTAT_SUSPENDED)) {
goto out;
}
}
/*
* We're interested in tracking what percentage of
* eligible apps actually get frozen.
* To avoid skewing the metrics towards processes which
* are considered more frequently, we only track failures once
* per process.
*/
first_consideration = !(state & P_MEMSTAT_FREEZE_CONSIDERED);
if (first_consideration) {
memorystatus_freezer_stats.mfs_process_considered_count++;
p->p_memstat_state |= P_MEMSTAT_FREEZE_CONSIDERED;
}
/* Only freeze applications meeting our minimum resident page criteria */
memorystatus_get_task_page_counts(proc_task(p), &pages, NULL, NULL);
if (pages < memorystatus_freeze_pages_min) {
if (first_consideration) {
memorystatus_freezer_stats.mfs_error_below_min_pages_count++;
}
p->p_memstat_freeze_skip_reason = kMemorystatusFreezeSkipReasonBelowMinPages;
goto out;
}
/* Don't freeze processes that are already exiting on core. It may have started exiting
* after we chose it for freeze, but before we obtained the proc_list_lock.
* NB: This is only possible if we're coming in from memorystatus_freeze_process_sync.
* memorystatus_freeze_top_process holds the proc_list_lock while it traverses the bands.
*/
if (proc_list_exited(p)) {
if (first_consideration) {
memorystatus_freezer_stats.mfs_error_other_count++;
}
p->p_memstat_freeze_skip_reason = kMemorystatusFreezeSkipReasonOther;
goto out;
}
if (!memorystatus_freezer_use_ordered_list) {
/*
* We're not using the ordered list so we need to check
* that dasd recommended the process. Note that the ordered list
* algorithm only considers processes on the list in the first place
* so there's no need to double check here.
*/
if (!memorystatus_freeze_process_is_recommended(p)) {
if (first_consideration) {
memorystatus_freezer_stats.mfs_error_low_probability_of_use_count++;
}
p->p_memstat_freeze_skip_reason = kMemorystatusFreezeSkipReasonLowProbOfUse;
goto out;
}
}
if (!(state & P_MEMSTAT_FROZEN) && p->p_memstat_effectivepriority > memorystatus_freeze_max_candidate_band) {
/*
* Proc has been elevated by something else.
* Don't freeze it.
*/
if (first_consideration) {
memorystatus_freezer_stats.mfs_error_elevated_count++;
}
p->p_memstat_freeze_skip_reason = kMemorystatusFreezeSkipReasonElevated;
goto out;
}
should_freeze = true;
out:
if (should_freeze && !(state & P_MEMSTAT_FROZEN)) {
/*
* Reset the skip reason. If it's killed before we manage to actually freeze it
* we failed to consider it early enough.
*/
p->p_memstat_freeze_skip_reason = kMemorystatusFreezeSkipReasonNone;
if (!first_consideration) {
/*
* We're freezing this for the first time and we previously considered it ineligible.
* Bump the considered count so that we track this as 1 failure
* and 1 success.
*/
memorystatus_freezer_stats.mfs_process_considered_count++;
}
}
return should_freeze;
}
bool
memorystatus_freeze_proc_is_refreeze_eligible(proc_t p)
{
return (p->p_memstat_state & P_MEMSTAT_REFREEZE_ELIGIBLE) != 0;
}
static proc_t
memorystatus_freeze_pick_refreeze_process(proc_t last_p)
{
proc_t p = PROC_NULL, next_p = PROC_NULL;
unsigned int band = (unsigned int) memorystatus_freeze_jetsam_band;
if (last_p == PROC_NULL) {
next_p = memorystatus_get_first_proc_locked(&band, FALSE);
} else {
next_p = memorystatus_get_next_proc_locked(&band, last_p, FALSE);
}
while (next_p) {
p = next_p;
next_p = memorystatus_get_next_proc_locked(&band, p, FALSE);
if ((p->p_memstat_state & P_MEMSTAT_FROZEN) && !memorystatus_freeze_proc_is_refreeze_eligible(p)) {
/* Process is already frozen & hasn't been thawed. */
continue;
}
/*
* Has to have been frozen once before.
*/
if (!(p->p_memstat_state & P_MEMSTAT_FROZEN)) {
continue;
}
/*
* Not currently being looked at for something.
*/
if (p->p_memstat_state & P_MEMSTAT_LOCKED) {
continue;
}
#if FREEZE_PREVENT_REFREEZE_OF_LAST_THAWED
/*
* Don't refreeze the last process we just thawed if still within the timeout window
*/
if (p->p_pid == memorystatus_freeze_last_pid_thawed) {
uint64_t timeout_delta_abs;
nanoseconds_to_absolutetime(FREEZE_PREVENT_REFREEZE_OF_LAST_THAWED_TIMEOUT_SECONDS * NSEC_PER_SEC, &timeout_delta_abs);
if (mach_absolute_time() < (memorystatus_freeze_last_pid_thawed_ts + timeout_delta_abs)) {
continue;
}
}
#endif
/*
* Found it
*/
return p;
}
return PROC_NULL;
}
proc_t
memorystatus_freeze_pick_process(struct memorystatus_freeze_list_iterator *iterator)
{
proc_t p = PROC_NULL, next_p = PROC_NULL;
unsigned int band = JETSAM_PRIORITY_IDLE;
LCK_MTX_ASSERT(&proc_list_mlock, LCK_MTX_ASSERT_OWNED);
/*
* If the freezer is full, only consider refreezes.
*/
if (iterator->refreeze_only || memorystatus_frozen_count >= memorystatus_frozen_processes_max) {
if (!iterator->refreeze_only) {
/*
* The first time the iterator starts to return refreeze
* candidates, we need to reset the last pointer b/c it's pointing into the wrong band.
*/
iterator->last_p = PROC_NULL;
iterator->refreeze_only = true;
}
iterator->last_p = memorystatus_freeze_pick_refreeze_process(iterator->last_p);
return iterator->last_p;
}
/*
* Search for the next freezer candidate.
*/
if (memorystatus_freezer_use_ordered_list) {
while (iterator->global_freeze_list_index < memorystatus_global_freeze_list.mfcl_length) {
p = memorystatus_freezer_candidate_list_get_proc(
&memorystatus_global_freeze_list,
(iterator->global_freeze_list_index)++,
&memorystatus_freezer_stats.mfs_freeze_pid_mismatches);
if (p != PROC_NULL && memorystatus_is_process_eligible_for_freeze(p)) {
#if FREEZE_PREVENT_REFREEZE_OF_LAST_THAWED
/*
* Don't refreeze the last process we just thawed if still within the timeout window
*/
if (p->p_pid == memorystatus_freeze_last_pid_thawed) {
uint64_t timeout_delta_abs;
nanoseconds_to_absolutetime(FREEZE_PREVENT_REFREEZE_OF_LAST_THAWED_TIMEOUT_SECONDS * NSEC_PER_SEC, &timeout_delta_abs);
if (mach_absolute_time() < (memorystatus_freeze_last_pid_thawed_ts + timeout_delta_abs)) {
continue;
}
}
#endif
iterator->last_p = p;
return iterator->last_p;
}
}
} else {
if (iterator->last_p == PROC_NULL) {
next_p = memorystatus_get_first_proc_locked(&band, FALSE);
} else {
next_p = memorystatus_get_next_proc_locked(&band, iterator->last_p, FALSE);
}
while (next_p) {
p = next_p;
if (memorystatus_is_process_eligible_for_freeze(p)) {
iterator->last_p = p;
return iterator->last_p;
} else {
next_p = memorystatus_get_next_proc_locked(&band, p, FALSE);
}
}
}
/*
* Failed to find a new freezer candidate.
* Try to re-freeze.
*/
if (memorystatus_refreeze_eligible_count >= memorystatus_min_thaw_refreeze_threshold) {
assert(!iterator->refreeze_only);
iterator->refreeze_only = true;
iterator->last_p = memorystatus_freeze_pick_refreeze_process(PROC_NULL);
return iterator->last_p;
}
return PROC_NULL;
}
/*
* memorystatus_pages_update calls this function whenever the number
* of available pages changes. It wakes the freezer thread iff the function returns
* true. The freezer thread will try to freeze (or refreeze) up to 1 process
* before blocking again.
*
* Note the freezer thread is also woken up by memorystatus_on_inactivity.
*/
bool
memorystatus_freeze_thread_should_run()
{
/*
* No freezer_mutex held here...see why near call-site
* within memorystatus_pages_update().
*/
if (memorystatus_freeze_enabled == false) {
return false;
}
if (memorystatus_available_pages > memorystatus_freeze_threshold) {
return false;
}
memorystatus_freezer_stats.mfs_below_threshold_count++;
if ((memorystatus_frozen_count >= memorystatus_frozen_processes_max)) {
/*
* Consider this as a skip even if we wake up to refreeze because
* we won't freeze any new procs.
*/
memorystatus_freezer_stats.mfs_skipped_full_count++;
if (memorystatus_refreeze_eligible_count < memorystatus_min_thaw_refreeze_threshold) {
return false;
}
}
if (memorystatus_frozen_shared_mb_max && (memorystatus_frozen_shared_mb >= memorystatus_frozen_shared_mb_max)) {
memorystatus_freezer_stats.mfs_skipped_shared_mb_high_count++;
return false;
}
uint64_t curr_time = mach_absolute_time();
if (curr_time < memorystatus_freezer_thread_next_run_ts) {
return false;
}
return true;
}
size_t
memorystatus_pick_freeze_count_for_wakeup()
{
size_t num_to_freeze = 0;
if (!memorystatus_swap_all_apps) {
num_to_freeze = 1;
} else {
/*
* When app swap is enabled, we want the freezer thread to aggressively freeze
* all candidates so we clear out space for the fg working set.
* But we still cap it to the current size of the candidate bands to avoid
* consuming excessive CPU if there's a lot of churn in the candidate band.
*/
proc_list_lock();
for (unsigned int band = JETSAM_PRIORITY_IDLE; band <= memorystatus_freeze_max_candidate_band; band++) {
num_to_freeze += memstat_bucket[band].count;
}
proc_list_unlock();
}
return num_to_freeze;
}
#endif /* CONFIG_FREEZE */