xref: /xnu-12377.41.6/bsd/kern/kern_memorystatus_internal.h (revision bbb1b6f9e71b8cdde6e5cd6f4841f207dee3d828)

/*
 * Copyright (c) 2006-2019 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,
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 * Please obtain a copy of the License at
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#ifndef _KERN_MEMORYSTATUS_INTERNAL_H_
#define _KERN_MEMORYSTATUS_INTERNAL_H_

/*
 * Contains memorystatus subsystem definitions that are not
 * exported outside of the memorystatus subsystem.
 *
 * For example, all of the mechanisms used by kern_memorystatus_policy.c
 * should be defined in this header.
 */

#if BSD_KERNEL_PRIVATE

#include <mach/boolean.h>
#include <stdbool.h>
#include <os/atomic_private.h>
#include <os/base.h>
#include <os/log.h>
#include <os/overflow.h>
#include <kern/locks.h>
#include <kern/sched_prim.h>
#include <sys/kern_memorystatus.h>
#include <sys/kernel_types.h>
#include <sys/proc.h>
#include <sys/proc_internal.h>

#if CONFIG_FREEZE
#include <sys/kern_memorystatus_freeze.h>
#endif /* CONFIG_FREEZE */

/*
 * memorystatus subsystem globals
 */
extern uint32_t memorystatus_available_pages;
#if CONFIG_JETSAM
extern bool jetsam_kill_on_low_swap;
#endif /* CONFIG_JETSAM */
extern bool kill_on_no_paging_space;
extern int block_corpses; /* counter to block new corpses if jetsam purges them */
extern int system_procs_aging_band;
extern int applications_aging_band;
/* the jetsam band which will contain P_MEMSTAT_FROZEN processes */
extern int memorystatus_freeze_jetsam_band;
#if CONFIG_FREEZE
extern unsigned int memorystatus_suspended_count;
#endif /* CONFIG_FREEZE */
extern uint64_t memorystatus_sysprocs_idle_delay_time;
extern uint64_t memorystatus_apps_idle_delay_time;

/*
 * TODO(jason): This should really be calculated dynamically by the zalloc
 * subsystem before we do a zone map exhaustion kill. But the zone_gc
 * logic is non-trivial, so for now it just sets this global.
 */
extern _Atomic bool memorystatus_zone_map_is_exhausted;
/*
 * TODO(jason): We should get rid of this global
 * and have the memorystatus thread check for compressor space shortages
 * itself. However, there are 3 async call sites remaining that require more work to get us there:
 * 2 of them are in vm_swap_defragment. When it's about to swap in a segment, it checks if that
 * will cause a compressor space shortage & pre-emptively triggers jetsam. vm_compressor_backing_store
 * needs to keep track of in-flight swapins due to defrag so we can perform those checks
 * in the memorystatus thread.
 * The other is in no_paging_space_action. This is only on macOS right now, but will
 * be needed on iPad when we run out of swap space. This should be a new kill
 * reason and we need to add a new health check for it.
 * We need to maintain the macOS behavior though that we kill no more than 1 process
 * every 5 seconds.
 */
extern _Atomic bool memorystatus_compressor_space_shortage;
/*
 * TODO(jason): We should also get rid of this global
 * and check for phantom cache pressure from the memorystatus
 * thread. But first we need to fix the syncronization in
 * vm_phantom_cache_check_pressure
 */
extern _Atomic bool memorystatus_phantom_cache_pressure;

extern _Atomic bool memorystatus_pageout_starved;
/*
 * The actions that the memorystatus thread can perform
 * when we're low on memory.
 * See memorystatus_pick_action to see when each action is deployed.
 */
OS_CLOSED_ENUM(memorystatus_action, uint32_t,
    MEMORYSTATUS_KILL_HIWATER,     // Kill 1 highwatermark process
    MEMORYSTATUS_KILL_AGGRESSIVE,     // Do aggressive jetsam
    MEMORYSTATUS_KILL_TOP_PROCESS,     // Kill based on jetsam priority
    MEMORYSTATUS_WAKE_SWAPPER,  // Wake up the swap thread
    MEMORYSTATUS_PROCESS_SWAPIN_QUEUE, // Compact the swapin queue and move segments to the swapout queue
    MEMORYSTATUS_KILL_SUSPENDED_SWAPPABLE, // Kill a suspended swap-eligible processes based on jetsam priority
    MEMORYSTATUS_KILL_SWAPPABLE, // Kill a swap-eligible process (even if it's running)  based on jetsam priority
    MEMORYSTATUS_KILL_IDLE, // Kill an idle process
    MEMORYSTATUS_KILL_LONG_IDLE, // Kill a long-idle process (reaper)
    MEMORYSTATUS_NO_PAGING_SPACE, // Perform a no-paging-space-action
    MEMORYSTATUS_PURGE_CACHES, // Purge system memory caches (e.g. corpses, deferred reclaim memory)
    MEMORYSTATUS_KILL_NONE,     // Do nothing
    );

__options_closed_decl(memstat_kill_options_t, uint8_t, {
	MEMSTAT_ONLY_SWAPPABBLE = 0x01,
	MEMSTAT_ONLY_LONG_IDLE  = 0x02,
	MEMSTAT_SORT_BUCKET     = 0x04,
});

/*
 * Structure to hold state for a jetsam thread.
 * Typically there should be a single jetsam thread
 * unless parallel jetsam is enabled.
 */
typedef struct jetsam_state_s {
	bool                            inited; /* if the thread is initialized */
	bool                            limit_to_low_bands; /* limit kills to < JETSAM_PRIORITY_ELEVATED_INACTIVE */
	int                             index; /* jetsam thread index */
	thread_t                        thread; /* jetsam thread pointer */
	int                             jld_idle_kills; /*  idle jetsam kill counter for this session */
	uint32_t                        errors; /* Error accumulator */
	bool                            errors_cleared; /* Have we tried clearing all errors this iteration? */
	bool                            sort_flag; /* Sort the fg band (idle on macOS) before killing? */
	bool                            corpse_list_purged; /* Has the corpse list been purged? */
	bool                            bg_approached; /* Has the BG band been approached? */
	bool                            fg_approached; /* Has the FG band been approached? */
	bool                            post_snapshot; /* Do we need to post a jetsam snapshot after this session? */
	uint64_t                        memory_reclaimed; /* Amount of memory that was just reclaimed */
	uint32_t                        hwm_kills; /* hwm kill counter for this session */
	sched_cond_atomic_t             jt_wakeup_cond; /* condition var used to synchronize wake/sleep operations for this jetsam thread */
} *jetsam_state_t;

/*
 * The memorystatus thread monitors these conditions
 * and will continue to act until the system is considered
 * healthy.
 */
typedef struct memorystatus_system_health_s {
#if CONFIG_JETSAM
	bool msh_available_pages_below_soft;
	bool msh_available_pages_below_idle;
	bool msh_available_pages_below_critical;
	bool msh_available_pages_below_reaper;
	bool msh_compressor_needs_to_swap;
	bool msh_compressor_is_thrashing;
	bool msh_filecache_is_thrashing;
	bool msh_phantom_cache_pressure;
	bool msh_swappable_compressor_segments_over_limit;
	bool msh_swapin_queue_over_limit;
	bool msh_pageout_starved;
#endif /* CONFIG_JETSAM */
	bool msh_vm_pressure_warning;
	bool msh_vm_pressure_critical;
	bool msh_compressor_low_on_space;
	bool msh_compressor_exhausted;
	bool msh_swap_exhausted;
	bool msh_swap_low_on_space;
	bool msh_zone_map_is_exhausted;
} *memorystatus_system_health_t;

/*
 * @func memstat_check_system_health
 *
 * @brief Evaluate system memory conditions and return if the system is healthy.
 *
 * @discussion
 * Evaluates various system memory conditions, including compressor size and
 * available page quantities. If conditions indicate a kill should be
 * performed, the system is considered "unhealthy".
 *
 * @returns @c true if the system is healthy, @c false otherwise.
 */
extern bool memstat_check_system_health(memorystatus_system_health_t status);

#pragma mark Locks

extern lck_mtx_t memorystatus_jetsam_broadcast_lock;

#pragma mark Agressive jetsam tunables

extern boolean_t memorystatus_jld_enabled;              /* Enable jetsam loop detection */
extern uint32_t memorystatus_jld_eval_period_msecs;         /* Init pass sets this based on device memory size */
extern int      memorystatus_jld_max_kill_loops;            /* How many times should we try and kill up to the target band */
extern unsigned int memorystatus_sysproc_aging_aggr_pages; /* Aggressive jetsam pages threshold for sysproc aging policy */
extern unsigned int jld_eval_aggressive_count;
extern uint64_t  jld_timestamp_msecs;
extern int       jld_idle_kill_candidates;

#pragma mark No Paging Space Globals

extern _Atomic uint64_t last_no_space_action_ts;
extern uint64_t no_paging_space_action_throttle_delay_ns;

#pragma mark Pressure Response Globals
extern uint64_t memstat_last_cache_purge_ts;
extern uint64_t memstat_cache_purge_backoff_ns;

__options_decl(memstat_pressure_options_t, uint32_t, {
	/* Kill long idle processes at kVMPressureWarning */
	MEMSTAT_WARNING_KILL_LONG_IDLE = 0x01,
	/* Kill idle processes from the notify thread at kVMPressureWarning */
	MEMSTAT_WARNING_KILL_IDLE_THROTTLED = 0x02,
	/* Purge memory caches (e.g. corpses, deferred reclaim rings) at kVMPressureCritical */
	MEMSTAT_CRITICAL_PURGE_CACHES = 0x04,
	/* Kill all idle processes at kVMPressureCritical */
	MEMSTAT_CRITICAL_KILL_IDLE = 0x08,
	/* Kill when at kVMPressureWarning for a prolonged period */
	MEMSTAT_WARNING_KILL_SUSTAINED = 0x10,
});
/* Maximum value for sysctl handler */
#define MEMSTAT_PRESSURE_CONFIG_MAX (0x18U)

extern memstat_pressure_options_t memstat_pressure_config;

#pragma mark Config Globals
extern boolean_t memstat_reaper_enabled;

#pragma mark VM globals read by the memorystatus subsystem

extern unsigned int    vm_page_free_count;
extern unsigned int    vm_page_active_count;
extern unsigned int    vm_page_inactive_count;
extern unsigned int    vm_page_throttled_count;
extern unsigned int    vm_page_purgeable_count;
extern unsigned int    vm_page_wire_count;
extern unsigned int    vm_page_speculative_count;
extern uint32_t        c_late_swapout_count, c_late_swappedin_count;
extern uint32_t        c_seg_allocsize;
extern bool            vm_swapout_thread_running;
extern _Atomic bool    vm_swapout_wake_pending;
#define VM_PAGE_DONATE_DISABLED     0
#define VM_PAGE_DONATE_ENABLED      1
extern uint32_t vm_page_donate_mode;

#if CONFIG_JETSAM
#define MEMORYSTATUS_LOG_AVAILABLE_PAGES os_atomic_load(&memorystatus_available_pages, relaxed)
#else /* CONFIG_JETSAM */
#define MEMORYSTATUS_LOG_AVAILABLE_PAGES (vm_page_active_count + vm_page_inactive_count + vm_page_free_count + vm_page_speculative_count)
#endif /* CONFIG_JETSAM */

bool memorystatus_avail_pages_below_pressure(void);
bool memorystatus_avail_pages_below_critical(void);
#if CONFIG_JETSAM
bool memorystatus_swap_over_trigger(uint64_t adjustment_factor);
bool memorystatus_swapin_over_trigger(void);
#endif /* CONFIG_JETSAM */

/* Does cause indicate vm or fc thrashing? */
bool is_reason_thrashing(unsigned cause);
/* Is the zone map almost full? */
bool is_reason_zone_map_exhaustion(unsigned cause);

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);

#define MEMSTAT_PERCENT_TOTAL_PAGES(p) ((uint32_t)(p * atop_64(max_mem) / 100))

/*
 * Take a (redacted) zprint snapshot along with the jetsam snapshot.
 */
#define JETSAM_ZPRINT_SNAPSHOT (CONFIG_MEMORYSTATUS && (DEBUG || DEVELOPMENT))

#pragma mark Logging Utilities

__enum_decl(memorystatus_log_level_t, unsigned int, {
	MEMORYSTATUS_LOG_LEVEL_DEFAULT = 0,
	MEMORYSTATUS_LOG_LEVEL_INFO = 1,
	MEMORYSTATUS_LOG_LEVEL_DEBUG = 2,
});

extern os_log_t memorystatus_log_handle;
extern memorystatus_log_level_t memorystatus_log_level;

/*
 * NB: Critical memorystatus logs (e.g. jetsam kills) are load-bearing for OS
 * performance testing infrastructure. Be careful when modifying the log-level for
 * important system events.
 *
 * Memorystatus logs are interpreted by a wide audience. To avoid logging information
 * that could lead to false diagnoses, INFO and DEBUG messages are only logged if the
 * system has been configured to do so via `kern.memorystatus_log_level` (sysctl) or
 * `memorystatus_log_level` (boot-arg).
 *
 * os_log supports a mechanism for configuring these properties dynamically; however,
 * this mechanism is currently unsupported in XNU.
 *
 * TODO (JC) Deprecate sysctl/boot-arg and move to subsystem preferences pending:
 *  - rdar://27006343 (Custom kernel log handles)
 *  - rdar://80958044 (Kernel Logging Configuration)
 */
#define _memorystatus_log_with_type(type, format, ...) os_log_with_startup_serial_and_type(memorystatus_log_handle, type, format, ##__VA_ARGS__)
#define memorystatus_log(format, ...) _memorystatus_log_with_type(OS_LOG_TYPE_DEFAULT, format, ##__VA_ARGS__)
#define memorystatus_log_info(format, ...) if (memorystatus_log_level >= MEMORYSTATUS_LOG_LEVEL_INFO) { _memorystatus_log_with_type(OS_LOG_TYPE_INFO, format, ##__VA_ARGS__); }
#define memorystatus_log_debug(format, ...) if (memorystatus_log_level >= MEMORYSTATUS_LOG_LEVEL_DEBUG) { _memorystatus_log_with_type(OS_LOG_TYPE_DEBUG, format, ##__VA_ARGS__); }
#define memorystatus_log_error(format, ...) _memorystatus_log_with_type(OS_LOG_TYPE_ERROR, format, ##__VA_ARGS__)
#define memorystatus_log_fault(format, ...) _memorystatus_log_with_type(OS_LOG_TYPE_FAULT, format, ##__VA_ARGS__)

#pragma mark Jetsam Priority Management

/*
 * Cancel a process' idle aging
 * Returns whether a reschedule of the idle demotion thread is needed.
 */
void memstat_update_priority_locked(proc_t p, int priority,
    memstat_priority_options_t options);

static inline bool
_memstat_proc_is_aging(proc_t p)
{
	return p->p_memstat_dirty & P_DIRTY_AGING_IN_PROGRESS;
}

static inline bool
_memstat_proc_is_tracked(proc_t p)
{
	return p->p_memstat_dirty & P_DIRTY_TRACK;
}

static inline bool
_memstat_proc_is_dirty(proc_t p)
{
	return p->p_memstat_dirty & P_DIRTY_IS_DIRTY;
}

/*
 * Return true if this process is self-terminating via ActivityTracking.
 */
static inline bool
_memstat_proc_is_terminating(proc_t p)
{
	return p->p_memstat_dirty & P_DIRTY_TERMINATED;
}

/*
 * Return true if this process has been killed and is in the process of exiting.
 */
static inline bool
_memstat_proc_was_killed(proc_t p)
{
	return p->p_memstat_state & P_MEMSTAT_TERMINATED;
}

static inline bool
_memstat_proc_is_internal(proc_t p)
{
	return p->p_memstat_state & P_MEMSTAT_INTERNAL;
}

static inline bool
_memstat_proc_can_idle_exit(proc_t p)
{
	return _memstat_proc_is_tracked(p) &&
	       (p->p_memstat_dirty & P_DIRTY_ALLOW_IDLE_EXIT);
}

static inline bool
_memstat_proc_shutdown_on_clean(proc_t p)
{
	return _memstat_proc_is_tracked(p) &&
	       (p->p_memstat_dirty & P_DIRTY_SHUTDOWN_ON_CLEAN);
}

static inline bool
_memstat_proc_has_priority_assertion(proc_t p)
{
	return p->p_memstat_state & P_MEMSTAT_PRIORITY_ASSERTION;
}

static inline bool
_memstat_proc_is_managed(proc_t p)
{
	return p->p_memstat_state & P_MEMSTAT_MANAGED;
}

static inline bool
_memstat_proc_is_frozen(proc_t p)
{
	return p->p_memstat_state & P_MEMSTAT_FROZEN;
}

static inline bool
_memstat_proc_is_suspended(proc_t p)
{
	return p->p_memstat_state & P_MEMSTAT_SUSPENDED;
}

static inline void
_memstat_proc_set_suspended(proc_t p)
{
	LCK_MTX_ASSERT(&proc_list_mlock, LCK_ASSERT_OWNED);
	if (!_memstat_proc_is_suspended(p)) {
		p->p_memstat_state |= P_MEMSTAT_SUSPENDED;
#if CONFIG_FREEZE
		if (os_inc_overflow(&memorystatus_suspended_count)) {
			panic("Overflowed memorystatus_suspended_count");
		}
#endif /* CONFIG_FREEZE */
	}
}

static inline void
_memstat_proc_set_resumed(proc_t p)
{
	LCK_MTX_ASSERT(&proc_list_mlock, LCK_ASSERT_OWNED);
	if (_memstat_proc_is_suspended(p)) {
		p->p_memstat_state &= ~P_MEMSTAT_SUSPENDED;
#if CONFIG_FREEZE
		if (os_dec_overflow(&memorystatus_suspended_count)) {
			panic("Underflowed memorystatus_suspended_count");
		}
#endif /* CONFIG_FREEZE */
	}
}

/*
 * Return whether the process is to be placed in an elevated band while idle.
 */
static inline bool
_memstat_proc_is_elevated(proc_t p)
{
	return p->p_memstat_state & P_MEMSTAT_USE_ELEVATED_INACTIVE_BAND;
}

/*
 * Return whether p's ledger-enforced memlimit is fatal (as last cached by
 * memorystatus)
 */
static inline bool
_memstat_proc_cached_memlimit_is_fatal(proc_t p)
{
	return p->p_memstat_state & P_MEMSTAT_FATAL_MEMLIMIT;
}

/*
 * Return whether p's inactive/active memlimit is fatal
 */
static inline bool
_memstat_proc_memlimit_is_fatal(proc_t p, bool is_active)
{
	const uint32_t flag = is_active ?
	    P_MEMSTAT_MEMLIMIT_ACTIVE_FATAL : P_MEMSTAT_MEMLIMIT_INACTIVE_FATAL;
	return p->p_memstat_state & flag;
}

static inline bool
_memstat_proc_active_memlimit_is_fatal(proc_t p)
{
	return _memstat_proc_memlimit_is_fatal(p, true);
}

static inline bool
_memstat_proc_inactive_memlimit_is_fatal(proc_t p)
{
	return _memstat_proc_memlimit_is_fatal(p, false);
}

#pragma mark Jetsam

/*
 * @func memstat_evaluate_page_shortage
 *
 * @brief
 * Evaluate page shortage conditions. Returns true if the jetsam thread should be woken up.
 *
 * @param should_enforce_memlimits
 * Set to true if soft memory limits should be enforced
 *
 * @param should_idle_exit
 * Set to true if idle processes should begin exiting
 *
 * @param should_jetsam
 * Set to true if non-idle processes should be jetsammed
 *
 * @param should_reap
 * Set to true if long-idle processes should be jetsammed
 */
bool memstat_evaluate_page_shortage(
	bool *should_enforce_memlimits,
	bool *should_idle_exit,
	bool *should_jetsam,
	bool *should_reap);

/*
 * In nautical applications, ballast tanks are tanks on boats or submarines
 * which can be filled with water. When flooded, they provide stability and
 * reduce buoyancy. When drained (and filled with air), they provide buoyancy.
 *
 * In our analogy, the ballast tanks may be drained of unneeded weight (as
 * occupied by idle processes or processes who have exceeded their memory
 * limit) and filled with air (available memory). Userspace may toggle between
 * these two states (filled/drained) depending on system requirements. For
 * example, drained ballast tanks (i.e. evelated available memory pools) may
 * have benefits to power and latency. However, applications with large
 * working sets may need to flood the ballast tanks (i.e. with
 * anonymous/wired memory) to avoid issues like jetsam loops of daemons that it
 * has IPC relationships with.
 *
 * Mechanically, "draining" the ballast tanks means applying a configurable
 * offset to the idle and soft available page shortage thresholds. This offset
 * is then removed when the policy is disengaged.
 *
 * The ballast mechanism is intended to be used over long time periods and the
 * ballast_offset should be sustainable for general applications. If response to
 * transient spikes in memory demand is desired, the clear-the-decks policy
 * should be used instead.
 *
 * Clients may toggle this behavior via sysctl: kern.memorystatus.ballast_drained
 */
int memorystatus_ballast_control(bool drain);

/* Synchronously kill a process due to sustained memory pressure */
bool memorystatus_kill_on_sustained_pressure(void);

/* Synchronously kill an idle process */
bool memstat_kill_idle_process(memorystatus_kill_cause_t cause,
    uint64_t *footprint_out);

/*
 * Attempt to kill the specified pid with the given reason.
 * Consumes a reference on the jetsam_reason.
 */
bool memstat_kill_with_jetsam_reason_sync(pid_t pid, os_reason_t jetsam_reason);

/* Count the number of processes at priority <= max_bucket_index */
uint32_t memstat_get_proccnt_upto_priority(uint32_t max_bucket_index);

/*
 * @func memstat_get_idle_proccnt
 * @brief Return the number of idle processes which may be terminated.
 */
uint32_t memstat_get_idle_proccnt(void);

/*
 * @func memstat_get_reapable_proccnt
 * @brief Return the number of idle, reapable processes which may be terminated.
 */
uint32_t memstat_get_long_idle_proccnt(void);

#pragma mark Freezer
#if CONFIG_FREEZE
/*
 * Freezer data types
 */

/* An ordered list of freeze or demotion candidates */
struct memorystatus_freezer_candidate_list {
	memorystatus_properties_freeze_entry_v1 *mfcl_list;
	size_t mfcl_length;
};

struct memorystatus_freeze_list_iterator {
	bool refreeze_only;
	proc_t last_p;
	size_t global_freeze_list_index;
};

/*
 * Freezer globals
 */
extern struct memorystatus_freezer_stats_t memorystatus_freezer_stats;
extern int memorystatus_freezer_use_ordered_list;
extern struct memorystatus_freezer_candidate_list memorystatus_global_freeze_list;
extern struct memorystatus_freezer_candidate_list memorystatus_global_demote_list;
extern uint64_t memorystatus_freezer_thread_next_run_ts;
bool memorystatus_is_process_eligible_for_freeze(proc_t p);
bool memorystatus_freeze_proc_is_refreeze_eligible(proc_t p);

proc_t memorystatus_freezer_candidate_list_get_proc(
	struct memorystatus_freezer_candidate_list *list,
	size_t index,
	uint64_t *pid_mismatch_counter);
/*
 * Returns the leader of the p's jetsam coalition
 * and the role of p in that coalition.
 */
proc_t memorystatus_get_coalition_leader_and_role(proc_t p, int *role_in_coalition);
bool memorystatus_freeze_process_is_recommended(const proc_t p);

/*
 * Ordered iterator over all freeze candidates.
 * The iterator should initially be zeroed out by the caller and
 * can be zeroed out whenever the caller wishes to start from the beginning
 * of the list again.
 * Returns PROC_NULL when all candidates have been iterated over.
 */
proc_t memorystatus_freeze_pick_process(struct memorystatus_freeze_list_iterator *iterator);

/*
 * Returns the number of processes that the freezer thread should try to freeze
 * on this wakeup.
 */
size_t memorystatus_pick_freeze_count_for_wakeup(void);

/*
 * Configure the freezer for app-based swap mode.
 * Should be called at boot.
 */
void memorystatus_freeze_configure_for_swap(void);
/*
 * Undo memorystatus_freeze_configure_for_swap
 */
void memorystatus_freeze_disable_swap(void);

/*
 * Cache of pids of most-recently thawed processes.
 * Used to reduce excessive rapid thaw/refreeze cycles.
 */
void memorystatus_freeze_record_process_thawed(proc_t p);
bool memorystatus_freeze_was_process_recently_thawed(proc_t p);
extern boolean_t     memorystatus_freeze_prevent_refreeze_of_recently_thawed;

#endif /* CONFIG_FREEZE */

#endif /* BSD_KERNEL_PRIVATE */

#endif /* _KERN_MEMORYSTATUS_INTERNAL_H_ */