xnu-6153.121.1.tar.gz

[apple/xnu.git] / bsd / kern / kern_memorystatus_freeze.c

/*
 * Copyright (c) 2006-2018 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/sched_prim.h>
#include <kern/kalloc.h>
#include <kern/assert.h>
#include <kern/debug.h>
#include <kern/locks.h>
#include <kern/task.h>
#include <kern/thread.h>
#include <kern/host.h>
#include <kern/policy_internal.h>
#include <kern/thread_group.h>

#include <IOKit/IOBSD.h>

#include <libkern/libkern.h>
#include <mach/coalition.h>
#include <mach/mach_time.h>
#include <mach/task.h>
#include <mach/host_priv.h>
#include <mach/mach_host.h>
#include <os/log.h>
#include <pexpert/pexpert.h>
#include <sys/coalition.h>
#include <sys/kern_event.h>
#include <sys/proc.h>
#include <sys/proc_info.h>
#include <sys/reason.h>
#include <sys/signal.h>
#include <sys/signalvar.h>
#include <sys/sysctl.h>
#include <sys/sysproto.h>
#include <sys/wait.h>
#include <sys/tree.h>
#include <sys/priv.h>
#include <vm/vm_pageout.h>
#include <vm/vm_protos.h>
#include <mach/machine/sdt.h>
#include <libkern/section_keywords.h>
#include <stdatomic.h>

#if CONFIG_FREEZE
#include <vm/vm_map.h>
#endif /* CONFIG_FREEZE */

#include <sys/kern_memorystatus.h>
#include <sys/kern_memorystatus_freeze.h>
#include <sys/kern_memorystatus_notify.h>

#if CONFIG_JETSAM

extern unsigned int memorystatus_available_pages;
extern unsigned int memorystatus_available_pages_pressure;
extern unsigned int memorystatus_available_pages_critical;
extern unsigned int memorystatus_available_pages_critical_base;
extern unsigned int memorystatus_available_pages_critical_idle_offset;

#else /* CONFIG_JETSAM */

extern uint64_t memorystatus_available_pages;
extern uint64_t memorystatus_available_pages_pressure;
extern uint64_t memorystatus_available_pages_critical;

#endif /* CONFIG_JETSAM */

unsigned int memorystatus_frozen_count = 0;
unsigned int memorystatus_suspended_count = 0;
unsigned long freeze_threshold_percentage = 50;

#if CONFIG_FREEZE

lck_grp_attr_t *freezer_lck_grp_attr;
lck_grp_t *freezer_lck_grp;
static lck_mtx_t freezer_mutex;

/* Thresholds */
unsigned int memorystatus_freeze_threshold = 0;
unsigned int memorystatus_freeze_pages_min = 0;
unsigned int memorystatus_freeze_pages_max = 0;
unsigned int memorystatus_freeze_suspended_threshold = FREEZE_SUSPENDED_THRESHOLD_DEFAULT;
unsigned int memorystatus_freeze_daily_mb_max = FREEZE_DAILY_MB_MAX_DEFAULT;
uint64_t     memorystatus_freeze_budget_pages_remaining = 0; //remaining # of pages that can be frozen to disk
boolean_t memorystatus_freeze_degradation = FALSE; //protected by the freezer mutex. Signals we are in a degraded freeze mode.

unsigned int memorystatus_max_frozen_demotions_daily = 0;
unsigned int memorystatus_thaw_count_demotion_threshold = 0;

boolean_t memorystatus_freeze_enabled = FALSE;
int memorystatus_freeze_wakeup = 0;
int memorystatus_freeze_jetsam_band = 0; /* the jetsam band which will contain P_MEMSTAT_FROZEN processes */

#define MAX_XPC_SERVICE_PIDS 10 /* Max. # of XPC services per coalition we'll consider freezing. */

#ifdef XNU_KERNEL_PRIVATE

unsigned int memorystatus_frozen_processes_max = 0;
unsigned int memorystatus_frozen_shared_mb = 0;
unsigned int memorystatus_frozen_shared_mb_max = 0;
unsigned int memorystatus_freeze_shared_mb_per_process_max = 0; /* Max. MB allowed per process to be freezer-eligible. */
unsigned int memorystatus_freeze_private_shared_pages_ratio = 2; /* Ratio of private:shared pages for a process to be freezer-eligible. */
unsigned int memorystatus_thaw_count = 0;
unsigned int memorystatus_refreeze_eligible_count = 0; /* # of processes currently thawed i.e. have state on disk & in-memory */

/* Freezer counters collected for telemtry */
static struct memorystatus_freezer_stats_t {
        /*
         * # of processes that we've considered freezing.
         * Used to normalize the error reasons below.
         */
        uint64_t mfs_process_considered_count;

        /*
         * The following counters track how many times we've failed to freeze
         * a process because of a specific FREEZER_ERROR.
         */
        /* EXCESS_SHARED_MEMORY */
        uint64_t mfs_error_excess_shared_memory_count;
        /* LOW_PRIVATE_SHARED_RATIO */
        uint64_t mfs_error_low_private_shared_ratio_count;
        /* NO_COMPRESSOR_SPACE */
        uint64_t mfs_error_no_compressor_space_count;
        /* NO_SWAP_SPACE */
        uint64_t mfs_error_no_swap_space_count;
        /* pages < memorystatus_freeze_pages_min */
        uint64_t mfs_error_below_min_pages_count;
        /* dasd determined it was unlikely to be relaunched. */
        uint64_t mfs_error_low_probability_of_use_count;
        /* transient reasons (like inability to acquire a lock). */
        uint64_t mfs_error_other_count;

        /*
         * # of times that we saw memorystatus_available_pages <= memorystatus_freeze_threshold.
         * Used to normalize skipped_full_count and shared_mb_high_count.
         */
        uint64_t mfs_below_threshold_count;

        /* Skipped running the freezer because we were out of slots */
        uint64_t mfs_skipped_full_count;

        /* Skipped running the freezer because we were over the shared mb limit*/
        uint64_t mfs_skipped_shared_mb_high_count;

        /*
         * How many pages have not been sent to swap because they were in a shared object?
         * This is being used to gather telemtry so we can understand the impact we'd have
         * on our NAND budget if we did swap out these pages.
         */
        uint64_t mfs_shared_pages_skipped;
} memorystatus_freezer_stats = {0};

#endif /* XNU_KERNEL_PRIVATE */

static inline boolean_t memorystatus_can_freeze_processes(void);
static boolean_t memorystatus_can_freeze(boolean_t *memorystatus_freeze_swap_low);
static boolean_t memorystatus_is_process_eligible_for_freeze(proc_t p);
static void memorystatus_freeze_thread(void *param __unused, wait_result_t wr __unused);

void memorystatus_disable_freeze(void);

/* Stats */
static uint64_t memorystatus_freeze_pageouts = 0;

/* Throttling */
#define DEGRADED_WINDOW_MINS    (30)
#define NORMAL_WINDOW_MINS      (24 * 60)

/* Protected by the freezer_mutex */
static throttle_interval_t throttle_intervals[] = {
        { DEGRADED_WINDOW_MINS, 1, 0, 0, { 0, 0 }},
        { NORMAL_WINDOW_MINS, 1, 0, 0, { 0, 0 }},
};
throttle_interval_t *degraded_throttle_window = &throttle_intervals[0];
throttle_interval_t *normal_throttle_window = &throttle_intervals[1];

extern uint64_t vm_swap_get_free_space(void);
extern boolean_t vm_swap_max_budget(uint64_t *);
extern int i_coal_jetsam_get_taskrole(coalition_t coal, task_t task);

static void memorystatus_freeze_update_throttle(uint64_t *budget_pages_allowed);
static void memorystatus_demote_frozen_processes(boolean_t force_one);

static uint64_t memorystatus_freezer_thread_next_run_ts = 0;

/* Sysctls needed for aggd stats */

SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_count, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_frozen_count, 0, "");
SYSCTL_UINT(_kern, OID_AUTO, memorystatus_thaw_count, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_thaw_count, 0, "");
SYSCTL_QUAD(_kern, OID_AUTO, memorystatus_freeze_pageouts, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freeze_pageouts, "");
SYSCTL_QUAD(_kern, OID_AUTO, memorystatus_freeze_budget_pages_remaining, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freeze_budget_pages_remaining, "");
SYSCTL_QUAD(_kern, OID_AUTO, memorystatus_freezer_error_excess_shared_memory_count, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freezer_stats.mfs_error_excess_shared_memory_count, "");
SYSCTL_QUAD(_kern, OID_AUTO, memorystatus_freezer_error_low_private_shared_ratio_count, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freezer_stats.mfs_error_low_private_shared_ratio_count, "");
SYSCTL_QUAD(_kern, OID_AUTO, memorystatus_freezer_error_no_compressor_space_count, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freezer_stats.mfs_error_no_compressor_space_count, "");
SYSCTL_QUAD(_kern, OID_AUTO, memorystatus_freezer_error_no_swap_space_count, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freezer_stats.mfs_error_no_swap_space_count, "");
SYSCTL_QUAD(_kern, OID_AUTO, memorystatus_freezer_error_below_min_pages_count, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freezer_stats.mfs_error_below_min_pages_count, "");
SYSCTL_QUAD(_kern, OID_AUTO, memorystatus_freezer_error_low_probability_of_use_count, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freezer_stats.mfs_error_low_probability_of_use_count, "");
SYSCTL_QUAD(_kern, OID_AUTO, memorystatus_freezer_error_other_count, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freezer_stats.mfs_error_other_count, "");
SYSCTL_QUAD(_kern, OID_AUTO, memorystatus_freezer_process_considered_count, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freezer_stats.mfs_process_considered_count, "");
SYSCTL_QUAD(_kern, OID_AUTO, memorystatus_freezer_below_threshold_count, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freezer_stats.mfs_below_threshold_count, "");
SYSCTL_QUAD(_kern, OID_AUTO, memorystatus_freezer_skipped_full_count, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freezer_stats.mfs_skipped_full_count, "");
SYSCTL_QUAD(_kern, OID_AUTO, memorystatus_freezer_skipped_shared_mb_high_count, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freezer_stats.mfs_skipped_shared_mb_high_count, "");
SYSCTL_QUAD(_kern, OID_AUTO, memorystatus_freezer_shared_pages_skipped, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freezer_stats.mfs_shared_pages_skipped, "");

/*
 * Calculates the hit rate for the freezer.
 * The hit rate is defined as the percentage of procs that are currently in the
 * freezer which we have thawed.
 * A low hit rate means we're freezing bad candidates since they're not re-used.
 */
static int sysctl_memorystatus_freezer_thaw_percentage SYSCTL_HANDLER_ARGS
{
#pragma unused(arg1, arg2)
        size_t thaw_count = 0, frozen_count = 0;
        int thaw_percentage = 100;
        unsigned int band = (unsigned int) memorystatus_freeze_jetsam_band;
        proc_t p = PROC_NULL;
        proc_list_lock();

        p = memorystatus_get_first_proc_locked(&band, FALSE);

        while (p) {
                if (p->p_memstat_state & P_MEMSTAT_FROZEN) {
                        if (p->p_memstat_thaw_count > 0) {
                                thaw_count++;
                        }
                        frozen_count++;
                }
                p = memorystatus_get_next_proc_locked(&band, p, FALSE);
        }
        proc_list_unlock();
        if (frozen_count > 0) {
                thaw_percentage = 100 * thaw_count / frozen_count;
        }
        return sysctl_handle_int(oidp, &thaw_percentage, 0, req);
}
SYSCTL_PROC(_kern, OID_AUTO, memorystatus_freezer_thaw_percentage, CTLTYPE_INT | CTLFLAG_RD | CTLFLAG_LOCKED, 0, 0, &sysctl_memorystatus_freezer_thaw_percentage, "I", "");


#if DEVELOPMENT || DEBUG

SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_jetsam_band, CTLFLAG_RW | CTLFLAG_LOCKED, &memorystatus_freeze_jetsam_band, 0, "");
SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_daily_mb_max, CTLFLAG_RW | CTLFLAG_LOCKED, &memorystatus_freeze_daily_mb_max, 0, "");
SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_degraded_mode, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_freeze_degradation, 0, "");
SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_threshold, CTLFLAG_RW | CTLFLAG_LOCKED, &memorystatus_freeze_threshold, 0, "");
SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_pages_min, CTLFLAG_RW | CTLFLAG_LOCKED, &memorystatus_freeze_pages_min, 0, "");
SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_pages_max, CTLFLAG_RW | CTLFLAG_LOCKED, &memorystatus_freeze_pages_max, 0, "");
SYSCTL_UINT(_kern, OID_AUTO, memorystatus_refreeze_eligible_count, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_refreeze_eligible_count, 0, "");
SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_processes_max, CTLFLAG_RW | CTLFLAG_LOCKED, &memorystatus_frozen_processes_max, 0, "");

/*
 * Max. shared-anonymous memory in MB that can be held by frozen processes in the high jetsam band.
 * "0" means no limit.
 * Default is 10% of system-wide task limit.
 */

SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_shared_mb_max, CTLFLAG_RW | CTLFLAG_LOCKED, &memorystatus_frozen_shared_mb_max, 0, "");
SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_shared_mb, CTLFLAG_RD | CTLFLAG_LOCKED, &memorystatus_frozen_shared_mb, 0, "");

SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_shared_mb_per_process_max, CTLFLAG_RW | CTLFLAG_LOCKED, &memorystatus_freeze_shared_mb_per_process_max, 0, "");
SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_private_shared_pages_ratio, CTLFLAG_RW | CTLFLAG_LOCKED, &memorystatus_freeze_private_shared_pages_ratio, 0, "");

SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_min_processes, CTLFLAG_RW | CTLFLAG_LOCKED, &memorystatus_freeze_suspended_threshold, 0, "");

/*
 * max. # of frozen process demotions we will allow in our daily cycle.
 */
SYSCTL_UINT(_kern, OID_AUTO, memorystatus_max_freeze_demotions_daily, CTLFLAG_RW | CTLFLAG_LOCKED, &memorystatus_max_frozen_demotions_daily, 0, "");
/*
 * min # of thaws needed by a process to protect it from getting demoted into the IDLE band.
 */
SYSCTL_UINT(_kern, OID_AUTO, memorystatus_thaw_count_demotion_threshold, CTLFLAG_RW | CTLFLAG_LOCKED, &memorystatus_thaw_count_demotion_threshold, 0, "");

boolean_t memorystatus_freeze_throttle_enabled = TRUE;
SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_throttle_enabled, CTLFLAG_RW | CTLFLAG_LOCKED, &memorystatus_freeze_throttle_enabled, 0, "");

/*
 * When set to true, this keeps frozen processes in the compressor pool in memory, instead of swapping them out to disk.
 * Exposed via the sysctl kern.memorystatus_freeze_to_memory.
 */
boolean_t memorystatus_freeze_to_memory = FALSE;
SYSCTL_UINT(_kern, OID_AUTO, memorystatus_freeze_to_memory, CTLFLAG_RW | CTLFLAG_LOCKED, &memorystatus_freeze_to_memory, 0, "");

#define VM_PAGES_FOR_ALL_PROCS    (2)
/*
 * Manual trigger of freeze and thaw for dev / debug kernels only.
 */
static int
sysctl_memorystatus_freeze SYSCTL_HANDLER_ARGS
{
#pragma unused(arg1, arg2)
        int error, pid = 0;
        proc_t p;
        int freezer_error_code = 0;
        pid_t pid_list[MAX_XPC_SERVICE_PIDS];
        int ntasks = 0;
        coalition_t coal = COALITION_NULL;

        if (memorystatus_freeze_enabled == FALSE) {
                printf("sysctl_freeze: Freeze is DISABLED\n");
                return ENOTSUP;
        }

        error = sysctl_handle_int(oidp, &pid, 0, req);
        if (error || !req->newptr) {
                return error;
        }

        if (pid == VM_PAGES_FOR_ALL_PROCS) {
                vm_pageout_anonymous_pages();

                return 0;
        }

        lck_mtx_lock(&freezer_mutex);

again:
        p = proc_find(pid);
        if (p != NULL) {
                memorystatus_freezer_stats.mfs_process_considered_count++;
                uint32_t purgeable, wired, clean, dirty, shared;
                uint32_t max_pages = 0, state = 0;

                if (VM_CONFIG_FREEZER_SWAP_IS_ACTIVE) {
                        /*
                         * Freezer backed by the compressor and swap file(s)
                         * will hold compressed data.
                         *
                         * Set the sysctl kern.memorystatus_freeze_to_memory to true to keep compressed data from
                         * being swapped out to disk. Note that this disables freezer swap support globally,
                         * not just for the process being frozen.
                         *
                         *
                         * We don't care about the global freezer budget or the process's (min/max) budget here.
                         * The freeze sysctl is meant to force-freeze a process.
                         *
                         * We also don't update any global or process stats on this path, so that the jetsam/ freeze
                         * logic remains unaffected. The tasks we're performing here are: freeze the process, set the
                         * P_MEMSTAT_FROZEN bit, and elevate the process to a higher band (if the freezer is active).
                         */
                        max_pages = memorystatus_freeze_pages_max;
                } else {
                        /*
                         * We only have the compressor without any swap.
                         */
                        max_pages = UINT32_MAX - 1;
                }

                proc_list_lock();
                state = p->p_memstat_state;
                proc_list_unlock();

                /*
                 * The jetsam path also verifies that the process is a suspended App. We don't care about that here.
                 * We simply ensure that jetsam is not already working on the process and that the process has not
                 * explicitly disabled freezing.
                 */
                if (state & (P_MEMSTAT_TERMINATED | P_MEMSTAT_LOCKED | P_MEMSTAT_FREEZE_DISABLED)) {
                        printf("sysctl_freeze: p_memstat_state check failed, process is%s%s%s\n",
                            (state & P_MEMSTAT_TERMINATED) ? " terminated" : "",
                            (state & P_MEMSTAT_LOCKED) ? " locked" : "",
                            (state & P_MEMSTAT_FREEZE_DISABLED) ? " unfreezable" : "");

                        proc_rele(p);
                        lck_mtx_unlock(&freezer_mutex);
                        return EPERM;
                }

                error = task_freeze(p->task, &purgeable, &wired, &clean, &dirty, max_pages, &shared, &freezer_error_code, FALSE /* eval only */);
                if (!error || freezer_error_code == FREEZER_ERROR_LOW_PRIVATE_SHARED_RATIO) {
                        memorystatus_freezer_stats.mfs_shared_pages_skipped += shared;
                }

                if (error) {
                        char reason[128];
                        if (freezer_error_code == FREEZER_ERROR_EXCESS_SHARED_MEMORY) {
                                memorystatus_freezer_stats.mfs_error_excess_shared_memory_count++;
                                strlcpy(reason, "too much shared memory", 128);
                        }

                        if (freezer_error_code == FREEZER_ERROR_LOW_PRIVATE_SHARED_RATIO) {
                                memorystatus_freezer_stats.mfs_error_low_private_shared_ratio_count++;
                                strlcpy(reason, "low private-shared pages ratio", 128);
                        }

                        if (freezer_error_code == FREEZER_ERROR_NO_COMPRESSOR_SPACE) {
                                memorystatus_freezer_stats.mfs_error_no_compressor_space_count++;
                                strlcpy(reason, "no compressor space", 128);
                        }

                        if (freezer_error_code == FREEZER_ERROR_NO_SWAP_SPACE) {
                                strlcpy(reason, "no swap space", 128);
                        }

                        printf("sysctl_freeze: task_freeze failed: %s\n", reason);

                        if (error == KERN_NO_SPACE) {
                                /* Make it easy to distinguish between failures due to low compressor/ swap space and other failures. */
                                error = ENOSPC;
                        } else {
                                error = EIO;
                        }
                } else {
                        proc_list_lock();
                        if ((p->p_memstat_state & P_MEMSTAT_FROZEN) == 0) {
                                p->p_memstat_state |= P_MEMSTAT_FROZEN;
                                memorystatus_frozen_count++;
                        }
                        p->p_memstat_frozen_count++;


                        proc_list_unlock();

                        if (VM_CONFIG_FREEZER_SWAP_IS_ACTIVE) {
                                /*
                                 * We elevate only if we are going to swap out the data.
                                 */
                                error = memorystatus_update_inactive_jetsam_priority_band(pid, MEMORYSTATUS_CMD_ELEVATED_INACTIVEJETSAMPRIORITY_ENABLE,
                                    memorystatus_freeze_jetsam_band, TRUE);

                                if (error) {
                                        printf("sysctl_freeze: Elevating frozen process to higher jetsam band failed with %d\n", error);
                                }
                        }
                }

                if ((error == 0) && (coal == NULL)) {
                        /*
                         * We froze a process and so we check to see if it was
                         * a coalition leader and if it has XPC services that
                         * might need freezing.
                         * Only one leader can be frozen at a time and so we shouldn't
                         * enter this block more than once per call. Hence the
                         * check that 'coal' has to be NULL. We should make this an
                         * assert() or panic() once we have a much more concrete way
                         * to detect an app vs a daemon.
                         */

                        task_t          curr_task = NULL;

                        curr_task = proc_task(p);
                        coal = task_get_coalition(curr_task, COALITION_TYPE_JETSAM);
                        if (coalition_is_leader(curr_task, coal)) {
                                ntasks = coalition_get_pid_list(coal, COALITION_ROLEMASK_XPC,
                                    COALITION_SORT_DEFAULT, pid_list, MAX_XPC_SERVICE_PIDS);

                                if (ntasks > MAX_XPC_SERVICE_PIDS) {
                                        ntasks = MAX_XPC_SERVICE_PIDS;
                                }
                        }
                }

                proc_rele(p);

                while (ntasks) {
                        pid = pid_list[--ntasks];
                        goto again;
                }

                lck_mtx_unlock(&freezer_mutex);
                return error;
        } else {
                printf("sysctl_freeze: Invalid process\n");
        }


        lck_mtx_unlock(&freezer_mutex);
        return EINVAL;
}

SYSCTL_PROC(_kern, OID_AUTO, memorystatus_freeze, CTLTYPE_INT | CTLFLAG_WR | CTLFLAG_LOCKED | CTLFLAG_MASKED,
    0, 0, &sysctl_memorystatus_freeze, "I", "");

/*
 * Manual trigger of agressive frozen demotion for dev / debug kernels only.
 */
static int
sysctl_memorystatus_demote_frozen_process SYSCTL_HANDLER_ARGS
{
#pragma unused(arg1, arg2, oidp, req)
        int error, val;
        /*
         * Only demote on write to prevent demoting during `sysctl -a`.
         * The actual value written doesn't matter.
         */
        error = sysctl_handle_int(oidp, &val, 0, req);
        if (error || !req->newptr) {
                return error;
        }
        memorystatus_demote_frozen_processes(false);
        return 0;
}

SYSCTL_PROC(_kern, OID_AUTO, memorystatus_demote_frozen_processes, CTLTYPE_INT | CTLFLAG_WR | CTLFLAG_LOCKED | CTLFLAG_MASKED, 0, 0, &sysctl_memorystatus_demote_frozen_process, "I", "");

static int
sysctl_memorystatus_available_pages_thaw SYSCTL_HANDLER_ARGS
{
#pragma unused(arg1, arg2)

        int error, pid = 0;
        proc_t p;

        if (memorystatus_freeze_enabled == FALSE) {
                return ENOTSUP;
        }

        error = sysctl_handle_int(oidp, &pid, 0, req);
        if (error || !req->newptr) {
                return error;
        }

        if (pid == VM_PAGES_FOR_ALL_PROCS) {
                do_fastwake_warmup_all();
                return 0;
        } else {
                p = proc_find(pid);
                if (p != NULL) {
                        error = task_thaw(p->task);

                        if (error) {
                                error = EIO;
                        } else {
                                /*
                                 * task_thaw() succeeded.
                                 *
                                 * We increment memorystatus_frozen_count on the sysctl freeze path.
                                 * And so we need the P_MEMSTAT_FROZEN to decrement the frozen count
                                 * when this process exits.
                                 *
                                 * proc_list_lock();
                                 * p->p_memstat_state &= ~P_MEMSTAT_FROZEN;
                                 * proc_list_unlock();
                                 */
                        }
                        proc_rele(p);
                        return error;
                }
        }

        return EINVAL;
}

SYSCTL_PROC(_kern, OID_AUTO, memorystatus_thaw, CTLTYPE_INT | CTLFLAG_WR | CTLFLAG_LOCKED | CTLFLAG_MASKED,
    0, 0, &sysctl_memorystatus_available_pages_thaw, "I", "");


typedef struct _global_freezable_status {
        boolean_t       freeze_pages_threshold_crossed;
        boolean_t       freeze_eligible_procs_available;
        boolean_t       freeze_scheduled_in_future;
}global_freezable_status_t;

typedef struct _proc_freezable_status {
        boolean_t    freeze_has_memstat_state;
        boolean_t    freeze_has_pages_min;
        int        freeze_has_probability;
        int        freeze_leader_eligible;
        boolean_t    freeze_attempted;
        uint32_t    p_memstat_state;
        uint32_t    p_pages;
        int        p_freeze_error_code;
        int        p_pid;
        int        p_leader_pid;
        char        p_name[MAXCOMLEN + 1];
}proc_freezable_status_t;

#define MAX_FREEZABLE_PROCESSES 200 /* Total # of processes in band 0 that we evaluate for freezability */

/*
 * For coalition based freezing evaluations, we proceed as follows:
 *  - detect that the process is a coalition member and a XPC service
 *  - mark its 'freeze_leader_eligible' field with FREEZE_PROC_LEADER_FREEZABLE_UNKNOWN
 *  - continue its freezability evaluation assuming its leader will be freezable too
 *
 * Once we are done evaluating all processes, we do a quick run thru all
 * processes and for a coalition member XPC service we look up the 'freezable'
 * status of its leader and iff:
 *  - the xpc service is freezable i.e. its individual freeze evaluation worked
 *  - and, its leader is also marked freezable
 * we update its 'freeze_leader_eligible' to FREEZE_PROC_LEADER_FREEZABLE_SUCCESS.
 */

#define FREEZE_PROC_LEADER_FREEZABLE_UNKNOWN   (-1)
#define FREEZE_PROC_LEADER_FREEZABLE_SUCCESS    (1)
#define FREEZE_PROC_LEADER_FREEZABLE_FAILURE    (2)

static int
memorystatus_freezer_get_status(user_addr_t buffer, size_t buffer_size, int32_t *retval)
{
        uint32_t            proc_count = 0, freeze_eligible_proc_considered = 0, band = 0, xpc_index = 0, leader_index = 0;
        global_freezable_status_t    *list_head;
        proc_freezable_status_t     *list_entry, *list_entry_start;
        size_t                list_size = 0;
        proc_t                p, leader_proc;
        memstat_bucket_t        *bucket;
        uint32_t            state = 0, pages = 0, entry_count = 0;
        boolean_t            try_freeze = TRUE, xpc_skip_size_probability_check = FALSE;
        int                error = 0, probability_of_use = 0;
        pid_t              leader_pid = 0;


        if (VM_CONFIG_FREEZER_SWAP_IS_ACTIVE == FALSE) {
                return ENOTSUP;
        }

        list_size = sizeof(global_freezable_status_t) + (sizeof(proc_freezable_status_t) * MAX_FREEZABLE_PROCESSES);

        if (buffer_size < list_size) {
                return EINVAL;
        }

        list_head = (global_freezable_status_t*)kalloc(list_size);
        if (list_head == NULL) {
                return ENOMEM;
        }

        memset(list_head, 0, list_size);

        list_size = sizeof(global_freezable_status_t);

        proc_list_lock();

        uint64_t curr_time = mach_absolute_time();

        list_head->freeze_pages_threshold_crossed = (memorystatus_available_pages < memorystatus_freeze_threshold);
        list_head->freeze_eligible_procs_available = ((memorystatus_suspended_count - memorystatus_frozen_count) > memorystatus_freeze_suspended_threshold);
        list_head->freeze_scheduled_in_future = (curr_time < memorystatus_freezer_thread_next_run_ts);

        list_entry_start = (proc_freezable_status_t*) ((uintptr_t)list_head + sizeof(global_freezable_status_t));
        list_entry = list_entry_start;

        bucket = &memstat_bucket[JETSAM_PRIORITY_IDLE];

        entry_count = (memorystatus_global_probabilities_size / sizeof(memorystatus_internal_probabilities_t));

        p = memorystatus_get_first_proc_locked(&band, FALSE);
        proc_count++;

        while ((proc_count <= MAX_FREEZABLE_PROCESSES) &&
            (p) &&
            (list_size < buffer_size)) {
                if (isSysProc(p)) {
                        /*
                         * Daemon:- We will consider freezing it iff:
                         * - it belongs to a coalition and the leader is freeze-eligible (delayed evaluation)
                         * - its role in the coalition is XPC service.
                         *
                         * We skip memory size requirements in this case.
                         */

                        coalition_t     coal = COALITION_NULL;
                        task_t          leader_task = NULL, curr_task = NULL;
                        int             task_role_in_coalition = 0;

                        curr_task = proc_task(p);
                        coal = task_get_coalition(curr_task, COALITION_TYPE_JETSAM);

                        if (coal == COALITION_NULL || coalition_is_leader(curr_task, coal)) {
                                /*
                                 * By default, XPC services without an app
                                 * will be the leader of their own single-member
                                 * coalition.
                                 */
                                goto skip_ineligible_xpc;
                        }

                        leader_task = coalition_get_leader(coal);
                        if (leader_task == TASK_NULL) {
                                /*
                                 * This jetsam coalition is currently leader-less.
                                 * This could happen if the app died, but XPC services
                                 * have not yet exited.
                                 */
                                goto skip_ineligible_xpc;
                        }

                        leader_proc = (proc_t)get_bsdtask_info(leader_task);
                        task_deallocate(leader_task);

                        if (leader_proc == PROC_NULL) {
                                /* leader task is exiting */
                                goto skip_ineligible_xpc;
                        }

                        task_role_in_coalition = i_coal_jetsam_get_taskrole(coal, curr_task);

                        if (task_role_in_coalition == COALITION_TASKROLE_XPC) {
                                xpc_skip_size_probability_check = TRUE;
                                leader_pid = leader_proc->p_pid;
                                goto continue_eval;
                        }

skip_ineligible_xpc:
                        p = memorystatus_get_next_proc_locked(&band, p, FALSE);
                        proc_count++;
                        continue;
                }

continue_eval:
                strlcpy(list_entry->p_name, p->p_name, MAXCOMLEN + 1);

                list_entry->p_pid = p->p_pid;

                state = p->p_memstat_state;

                if ((state & (P_MEMSTAT_TERMINATED | P_MEMSTAT_LOCKED | P_MEMSTAT_FREEZE_DISABLED | P_MEMSTAT_FREEZE_IGNORE)) ||
                    !(state & P_MEMSTAT_SUSPENDED)) {
                        try_freeze = list_entry->freeze_has_memstat_state = FALSE;
                } else {
                        try_freeze = list_entry->freeze_has_memstat_state = TRUE;
                }

                list_entry->p_memstat_state = state;

                if (xpc_skip_size_probability_check == TRUE) {
                        /*
                         * Assuming the coalition leader is freezable
                         * we don't care re. minimum pages and probability
                         * as long as the process isn't marked P_MEMSTAT_FREEZE_DISABLED.
                         * XPC services have to be explicity opted-out of the disabled
                         * state. And we checked that state above.
                         */
                        list_entry->freeze_has_pages_min = TRUE;
                        list_entry->p_pages = -1;
                        list_entry->freeze_has_probability = -1;

                        list_entry->freeze_leader_eligible = FREEZE_PROC_LEADER_FREEZABLE_UNKNOWN;
                        list_entry->p_leader_pid = leader_pid;

                        xpc_skip_size_probability_check = FALSE;
                } else {
                        list_entry->freeze_leader_eligible = FREEZE_PROC_LEADER_FREEZABLE_SUCCESS; /* Apps are freeze eligible and their own leaders. */
                        list_entry->p_leader_pid = 0; /* Setting this to 0 signifies this isn't a coalition driven freeze. */

                        memorystatus_get_task_page_counts(p->task, &pages, NULL, NULL);
                        if (pages < memorystatus_freeze_pages_min) {
                                try_freeze = list_entry->freeze_has_pages_min = FALSE;
                        } else {
                                list_entry->freeze_has_pages_min = TRUE;
                        }

                        list_entry->p_pages = pages;

                        if (entry_count) {
                                uint32_t j = 0;
                                for (j = 0; j < entry_count; j++) {
                                        if (strncmp(memorystatus_global_probabilities_table[j].proc_name,
                                            p->p_name,
                                            MAXCOMLEN + 1) == 0) {
                                                probability_of_use = memorystatus_global_probabilities_table[j].use_probability;
                                                break;
                                        }
                                }

                                list_entry->freeze_has_probability = probability_of_use;

                                try_freeze = ((probability_of_use > 0) && try_freeze);
                        } else {
                                list_entry->freeze_has_probability = -1;
                        }
                }

                if (try_freeze) {
                        uint32_t purgeable, wired, clean, dirty, shared;
                        uint32_t max_pages = 0;
                        int freezer_error_code = 0;

                        error = task_freeze(p->task, &purgeable, &wired, &clean, &dirty, max_pages, &shared, &freezer_error_code, TRUE /* eval only */);

                        if (error) {
                                list_entry->p_freeze_error_code = freezer_error_code;
                        }

                        list_entry->freeze_attempted = TRUE;
                }

                list_entry++;
                freeze_eligible_proc_considered++;

                list_size += sizeof(proc_freezable_status_t);

                p = memorystatus_get_next_proc_locked(&band, p, FALSE);
                proc_count++;
        }

        proc_list_unlock();

        list_entry = list_entry_start;

        for (xpc_index = 0; xpc_index < freeze_eligible_proc_considered; xpc_index++) {
                if (list_entry[xpc_index].freeze_leader_eligible == FREEZE_PROC_LEADER_FREEZABLE_UNKNOWN) {
                        leader_pid = list_entry[xpc_index].p_leader_pid;

                        leader_proc = proc_find(leader_pid);

                        if (leader_proc) {
                                if (leader_proc->p_memstat_state & P_MEMSTAT_FROZEN) {
                                        /*
                                         * Leader has already been frozen.
                                         */
                                        list_entry[xpc_index].freeze_leader_eligible = FREEZE_PROC_LEADER_FREEZABLE_SUCCESS;
                                        proc_rele(leader_proc);
                                        continue;
                                }
                                proc_rele(leader_proc);
                        }

                        for (leader_index = 0; leader_index < freeze_eligible_proc_considered; leader_index++) {
                                if (list_entry[leader_index].p_pid == leader_pid) {
                                        if (list_entry[leader_index].freeze_attempted && list_entry[leader_index].p_freeze_error_code == 0) {
                                                list_entry[xpc_index].freeze_leader_eligible = FREEZE_PROC_LEADER_FREEZABLE_SUCCESS;
                                        } else {
                                                list_entry[xpc_index].freeze_leader_eligible = FREEZE_PROC_LEADER_FREEZABLE_FAILURE;
                                                list_entry[xpc_index].p_freeze_error_code = FREEZER_ERROR_GENERIC;
                                        }
                                        break;
                                }
                        }

                        /*
                         * Didn't find the leader entry. This might be likely because
                         * the leader never made it down to band 0.
                         */
                        if (leader_index == freeze_eligible_proc_considered) {
                                list_entry[xpc_index].freeze_leader_eligible = FREEZE_PROC_LEADER_FREEZABLE_FAILURE;
                                list_entry[xpc_index].p_freeze_error_code = FREEZER_ERROR_GENERIC;
                        }
                }
        }

        buffer_size = list_size;

        error = copyout(list_head, buffer, buffer_size);
        if (error == 0) {
                *retval = buffer_size;
        } else {
                *retval = 0;
        }

        list_size = sizeof(global_freezable_status_t) + (sizeof(proc_freezable_status_t) * MAX_FREEZABLE_PROCESSES);
        kfree(list_head, list_size);

        MEMORYSTATUS_DEBUG(1, "memorystatus_freezer_get_status: returning %d (%lu - size)\n", error, (unsigned long)*list_size);

        return error;
}

int
memorystatus_freezer_control(int32_t flags, user_addr_t buffer, size_t buffer_size, int32_t *retval)
{
        int err = ENOTSUP;

        if (flags == FREEZER_CONTROL_GET_STATUS) {
                err = memorystatus_freezer_get_status(buffer, buffer_size, retval);
        }

        return err;
}

#endif /* DEVELOPMENT || DEBUG */

extern void        vm_swap_consider_defragmenting(int);
extern boolean_t memorystatus_kill_elevated_process(uint32_t, os_reason_t, unsigned int, int, uint32_t *, uint64_t *);

/*
 * This routine will _jetsam_ all frozen processes
 * and reclaim the swap space immediately.
 *
 * So freeze has to be DISABLED when we call this routine.
 */

void
memorystatus_disable_freeze(void)
{
        memstat_bucket_t *bucket;
        int bucket_count = 0, retries = 0;
        boolean_t retval = FALSE, killed = FALSE;
        uint32_t errors = 0, errors_over_prev_iteration = 0;
        os_reason_t jetsam_reason = 0;
        unsigned int band = 0;
        proc_t p = PROC_NULL, next_p = PROC_NULL;
        uint64_t memory_reclaimed = 0, footprint = 0;

        KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_MEMSTAT, BSD_MEMSTAT_FREEZE_DISABLE) | DBG_FUNC_START,
            memorystatus_available_pages, 0, 0, 0, 0);

        assert(memorystatus_freeze_enabled == FALSE);

        jetsam_reason = os_reason_create(OS_REASON_JETSAM, JETSAM_REASON_MEMORY_DISK_SPACE_SHORTAGE);
        if (jetsam_reason == OS_REASON_NULL) {
                printf("memorystatus_disable_freeze: failed to allocate jetsam reason\n");
        }

        /*
         * Let's relocate all frozen processes into band 8. Demoted frozen processes
         * are sitting in band 0 currently and it's possible to have a frozen process
         * in the FG band being actively used. We don't reset its frozen state when
         * it is resumed because it has state on disk.
         *
         * We choose to do this relocation rather than implement a new 'kill frozen'
         * process function for these reasons:
         * - duplication of code: too many kill functions exist and we need to rework them better.
         * - disk-space-shortage kills are rare
         * - not having the 'real' jetsam band at time of the this frozen kill won't preclude us
         *   from answering any imp. questions re. jetsam policy/effectiveness.
         *
         * This is essentially what memorystatus_update_inactive_jetsam_priority_band() does while
         * avoiding the application of memory limits.
         */

again:
        proc_list_lock();

        band = JETSAM_PRIORITY_IDLE;
        p = PROC_NULL;
        next_p = PROC_NULL;

        next_p = memorystatus_get_first_proc_locked(&band, TRUE);
        while (next_p) {
                p = next_p;
                next_p = memorystatus_get_next_proc_locked(&band, p, TRUE);

                if (p->p_memstat_effectivepriority > JETSAM_PRIORITY_FOREGROUND) {
                        break;
                }

                if ((p->p_memstat_state & P_MEMSTAT_FROZEN) == FALSE) {
                        continue;
                }

                if (p->p_memstat_state & P_MEMSTAT_ERROR) {
                        p->p_memstat_state &= ~P_MEMSTAT_ERROR;
                }

                if (p->p_memstat_effectivepriority == memorystatus_freeze_jetsam_band) {
                        continue;
                }

                /*
                 * We explicitly add this flag here so the process looks like a normal
                 * frozen process i.e. P_MEMSTAT_FROZEN and P_MEMSTAT_USE_ELEVATED_INACTIVE_BAND.
                 * We don't bother with assigning the 'active' memory
                 * limits at this point because we are going to be killing it soon below.
                 */
                p->p_memstat_state |= P_MEMSTAT_USE_ELEVATED_INACTIVE_BAND;
                memorystatus_invalidate_idle_demotion_locked(p, TRUE);

                memorystatus_update_priority_locked(p, memorystatus_freeze_jetsam_band, FALSE, TRUE);
        }

        bucket = &memstat_bucket[memorystatus_freeze_jetsam_band];
        bucket_count = bucket->count;
        proc_list_unlock();

        /*
         * Bucket count is already stale at this point. But, we don't expect
         * freezing to continue since we have already disabled the freeze functionality.
         * However, an existing freeze might be in progress. So we might miss that process
         * in the first go-around. We hope to catch it in the next.
         */

        errors_over_prev_iteration = 0;
        while (bucket_count) {
                bucket_count--;

                /*
                 * memorystatus_kill_elevated_process() drops a reference,
                 * so take another one so we can continue to use this exit reason
                 * even after it returns.
                 */

                os_reason_ref(jetsam_reason);
                retval = memorystatus_kill_elevated_process(
                        kMemorystatusKilledDiskSpaceShortage,
                        jetsam_reason,
                        memorystatus_freeze_jetsam_band,
                        0,                             /* the iteration of aggressive jetsam..ignored here */
                        &errors,
                        &footprint);

                if (errors > 0) {
                        printf("memorystatus_disable_freeze: memorystatus_kill_elevated_process returned %d error(s)\n", errors);
                        errors_over_prev_iteration += errors;
                        errors = 0;
                }

                if (retval == 0) {
                        /*
                         * No frozen processes left to kill.
                         */
                        break;
                }

                killed = TRUE;
                memory_reclaimed += footprint;
        }

        proc_list_lock();

        if (memorystatus_frozen_count) {
                /*
                 * A frozen process snuck in and so
                 * go back around to kill it. That
                 * process may have been resumed and
                 * put into the FG band too. So we
                 * have to do the relocation again.
                 */
                assert(memorystatus_freeze_enabled == FALSE);

                retries++;
                if (retries < 3) {
                        proc_list_unlock();
                        goto again;
                }
#if DEVELOPMENT || DEBUG
                panic("memorystatus_disable_freeze: Failed to kill all frozen processes, memorystatus_frozen_count = %d, errors = %d",
                    memorystatus_frozen_count, errors_over_prev_iteration);
#endif /* DEVELOPMENT || DEBUG */
        }
        proc_list_unlock();

        os_reason_free(jetsam_reason);

        if (killed) {
                vm_swap_consider_defragmenting(VM_SWAP_FLAGS_FORCE_DEFRAG | VM_SWAP_FLAGS_FORCE_RECLAIM);

                proc_list_lock();
                size_t snapshot_size = sizeof(memorystatus_jetsam_snapshot_t) +
                    sizeof(memorystatus_jetsam_snapshot_entry_t) * (memorystatus_jetsam_snapshot_count);
                uint64_t timestamp_now = mach_absolute_time();
                memorystatus_jetsam_snapshot->notification_time = timestamp_now;
                memorystatus_jetsam_snapshot->js_gencount++;
                if (memorystatus_jetsam_snapshot_count > 0 && (memorystatus_jetsam_snapshot_last_timestamp == 0 ||
                    timestamp_now > memorystatus_jetsam_snapshot_last_timestamp + memorystatus_jetsam_snapshot_timeout)) {
                        proc_list_unlock();
                        int ret = memorystatus_send_note(kMemorystatusSnapshotNote, &snapshot_size, sizeof(snapshot_size));
                        if (!ret) {
                                proc_list_lock();
                                memorystatus_jetsam_snapshot_last_timestamp = timestamp_now;
                                proc_list_unlock();
                        }
                } else {
                        proc_list_unlock();
                }
        }

        KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_MEMSTAT, BSD_MEMSTAT_FREEZE_DISABLE) | DBG_FUNC_END,
            memorystatus_available_pages, memory_reclaimed, 0, 0, 0);

        return;
}

__private_extern__ void
memorystatus_freeze_init(void)
{
        kern_return_t result;
        thread_t thread;

        freezer_lck_grp_attr = lck_grp_attr_alloc_init();
        freezer_lck_grp = lck_grp_alloc_init("freezer", freezer_lck_grp_attr);

        lck_mtx_init(&freezer_mutex, freezer_lck_grp, NULL);

        /*
         * This is just the default value if the underlying
         * storage device doesn't have any specific budget.
         * We check with the storage layer in memorystatus_freeze_update_throttle()
         * before we start our freezing the first time.
         */
        memorystatus_freeze_budget_pages_remaining = (memorystatus_freeze_daily_mb_max * 1024 * 1024) / PAGE_SIZE;

        result = kernel_thread_start(memorystatus_freeze_thread, NULL, &thread);
        if (result == KERN_SUCCESS) {
                proc_set_thread_policy(thread, TASK_POLICY_INTERNAL, TASK_POLICY_IO, THROTTLE_LEVEL_COMPRESSOR_TIER2);
                proc_set_thread_policy(thread, TASK_POLICY_INTERNAL, TASK_POLICY_PASSIVE_IO, TASK_POLICY_ENABLE);
                thread_set_thread_name(thread, "VM_freezer");

                thread_deallocate(thread);
        } else {
                panic("Could not create memorystatus_freeze_thread");
        }
}

static boolean_t
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);

        boolean_t should_freeze = FALSE;
        uint32_t state = 0, entry_count = 0, pages = 0, i = 0;
        int probability_of_use = 0;

        state = p->p_memstat_state;

        if (state & (P_MEMSTAT_TERMINATED | P_MEMSTAT_LOCKED | P_MEMSTAT_FREEZE_DISABLED | P_MEMSTAT_FREEZE_IGNORE)) {
                goto out;
        }

        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.
                 */

                coalition_t     coal = COALITION_NULL;
                task_t          leader_task = NULL, curr_task = NULL;
                proc_t          leader_proc = NULL;
                int             task_role_in_coalition = 0;

                curr_task = proc_task(p);
                coal = task_get_coalition(curr_task, COALITION_TYPE_JETSAM);

                if (coal == NULL || coalition_is_leader(curr_task, coal)) {
                        /*
                         * By default, XPC services without an app
                         * will be the leader of their own single-member
                         * coalition.
                         */
                        goto out;
                }

                leader_task = coalition_get_leader(coal);
                if (leader_task == TASK_NULL) {
                        /*
                         * This jetsam coalition is currently leader-less.
                         * This could happen if the app died, but XPC services
                         * have not yet exited.
                         */
                        goto out;
                }

                leader_proc = (proc_t)get_bsdtask_info(leader_task);
                task_deallocate(leader_task);

                if (leader_proc == PROC_NULL) {
                        /* leader task is exiting */
                        goto out;
                }

                if (!(leader_proc->p_memstat_state & P_MEMSTAT_FROZEN)) {
                        goto out;
                }

                task_role_in_coalition = i_coal_jetsam_get_taskrole(coal, curr_task);

                if (task_role_in_coalition == COALITION_TASKROLE_XPC) {
                        should_freeze = TRUE;
                }

                goto out;
        } else {
                /*
                 * Application. In addition to the above states we need to make
                 * sure we only consider suspended applications for freezing.
                 */
                if (!(state & P_MEMSTAT_SUSPENDED)) {
                        goto out;
                }
        }

        /*
         * This proc is a suspended application.
         * We're interested in tracking what percentage of these
         * actually get frozen.
         */
        memorystatus_freezer_stats.mfs_process_considered_count++;

        /* Only freeze applications meeting our minimum resident page criteria */
        memorystatus_get_task_page_counts(p->task, &pages, NULL, NULL);
        if (pages < memorystatus_freeze_pages_min) {
                memorystatus_freezer_stats.mfs_error_below_min_pages_count++;
                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 ((p->p_listflag & P_LIST_EXITED) != 0) {
                memorystatus_freezer_stats.mfs_error_other_count++;
                goto out;
        }

        entry_count = (memorystatus_global_probabilities_size / sizeof(memorystatus_internal_probabilities_t));

        if (entry_count) {
                for (i = 0; i < entry_count; i++) {
                        if (strncmp(memorystatus_global_probabilities_table[i].proc_name,
                            p->p_name,
                            MAXCOMLEN + 1) == 0) {
                                probability_of_use = memorystatus_global_probabilities_table[i].use_probability;
                                break;
                        }
                }

                if (probability_of_use == 0) {
                        memorystatus_freezer_stats.mfs_error_low_probability_of_use_count++;
                        goto out;
                }
        }

        should_freeze = TRUE;
out:
        return should_freeze;
}

/*
 * Synchronously freeze the passed proc. Called with a reference to the proc held.
 *
 * Doesn't deal with:
 * - re-freezing because this is called on a specific process and
 *   not by the freezer thread. If that changes, we'll have to teach it about
 *   refreezing a frozen process.
 *
 * - grouped/coalition freezing because we are hoping to deprecate this
 *   interface as it was used by user-space to freeze particular processes. But
 *   we have moved away from that approach to having the kernel choose the optimal
 *   candidates to be frozen.
 *
 * Returns EINVAL or the value returned by task_freeze().
 */
int
memorystatus_freeze_process_sync(proc_t p)
{
        int ret = EINVAL;
        pid_t aPid = 0;
        boolean_t memorystatus_freeze_swap_low = FALSE;
        int    freezer_error_code = 0;

        lck_mtx_lock(&freezer_mutex);

        if (p == NULL) {
                printf("memorystatus_freeze_process_sync: Invalid process\n");
                goto exit;
        }

        if (memorystatus_freeze_enabled == FALSE) {
                printf("memorystatus_freeze_process_sync: Freezing is DISABLED\n");
                goto exit;
        }

        if (!memorystatus_can_freeze(&memorystatus_freeze_swap_low)) {
                printf("memorystatus_freeze_process_sync: Low compressor and/or low swap space...skipping freeze\n");
                goto exit;
        }

        memorystatus_freeze_update_throttle(&memorystatus_freeze_budget_pages_remaining);
        if (!memorystatus_freeze_budget_pages_remaining) {
                printf("memorystatus_freeze_process_sync: exit with NO available budget\n");
                goto exit;
        }

        proc_list_lock();

        if (p != NULL) {
                uint32_t purgeable, wired, clean, dirty, shared;
                uint32_t max_pages, i;

                aPid = p->p_pid;

                /* Ensure the process is eligible for freezing */
                if (memorystatus_is_process_eligible_for_freeze(p) == FALSE) {
                        proc_list_unlock();
                        goto exit;
                }

                if (VM_CONFIG_FREEZER_SWAP_IS_ACTIVE) {
                        max_pages = MIN(memorystatus_freeze_pages_max, memorystatus_freeze_budget_pages_remaining);
                } else {
                        /*
                         * We only have the compressor without any swap.
                         */
                        max_pages = UINT32_MAX - 1;
                }

                /* Mark as locked temporarily to avoid kill */
                p->p_memstat_state |= P_MEMSTAT_LOCKED;
                proc_list_unlock();

                KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_MEMSTAT, BSD_MEMSTAT_FREEZE) | DBG_FUNC_START,
                    memorystatus_available_pages, 0, 0, 0, 0);

                ret = task_freeze(p->task, &purgeable, &wired, &clean, &dirty, max_pages, &shared, &freezer_error_code, FALSE /* eval only */);
                if (ret == KERN_SUCCESS || freezer_error_code == FREEZER_ERROR_LOW_PRIVATE_SHARED_RATIO) {
                        memorystatus_freezer_stats.mfs_shared_pages_skipped += shared;
                }

                KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_MEMSTAT, BSD_MEMSTAT_FREEZE) | DBG_FUNC_END,
                    memorystatus_available_pages, aPid, 0, 0, 0);

                DTRACE_MEMORYSTATUS6(memorystatus_freeze, proc_t, p, unsigned int, memorystatus_available_pages, boolean_t, purgeable, unsigned int, wired, uint32_t, clean, uint32_t, dirty);

                MEMORYSTATUS_DEBUG(1, "memorystatus_freeze_process_sync: task_freeze %s for pid %d [%s] - "
                    "memorystatus_pages: %d, purgeable: %d, wired: %d, clean: %d, dirty: %d, max_pages %d, shared %d\n",
                    (ret == KERN_SUCCESS) ? "SUCCEEDED" : "FAILED", aPid, (*p->p_name ? p->p_name : "(unknown)"),
                    memorystatus_available_pages, purgeable, wired, clean, dirty, max_pages, shared);

                proc_list_lock();

                if (ret == KERN_SUCCESS) {
                        memorystatus_freeze_entry_t data = { aPid, TRUE, dirty };

                        p->p_memstat_freeze_sharedanon_pages += shared;

                        memorystatus_frozen_shared_mb += shared;

                        if ((p->p_memstat_state & P_MEMSTAT_FROZEN) == 0) {
                                p->p_memstat_state |= P_MEMSTAT_FROZEN;
                                memorystatus_frozen_count++;
                        }

                        p->p_memstat_frozen_count++;

                        /*
                         * Still keeping the P_MEMSTAT_LOCKED bit till we are actually done elevating this frozen process
                         * to its higher jetsam band.
                         */
                        proc_list_unlock();

                        memorystatus_send_note(kMemorystatusFreezeNote, &data, sizeof(data));

                        if (VM_CONFIG_FREEZER_SWAP_IS_ACTIVE) {
                                ret = memorystatus_update_inactive_jetsam_priority_band(p->p_pid, MEMORYSTATUS_CMD_ELEVATED_INACTIVEJETSAMPRIORITY_ENABLE,
                                    memorystatus_freeze_jetsam_band, TRUE);

                                if (ret) {
                                        printf("Elevating the frozen process failed with %d\n", ret);
                                        /* not fatal */
                                        ret = 0;
                                }


                                /* Update stats */
                                for (i = 0; i < sizeof(throttle_intervals) / sizeof(struct throttle_interval_t); i++) {
                                        throttle_intervals[i].pageouts += dirty;
                                }
                        }
                        memorystatus_freeze_update_throttle(&memorystatus_freeze_budget_pages_remaining);
                        os_log_with_startup_serial(OS_LOG_DEFAULT, "memorystatus: freezing (specific) pid %d [%s] done memorystatus_freeze_budget_pages_remaining %llu froze %u pages",
                            aPid, ((p && *p->p_name) ? p->p_name : "unknown"), memorystatus_freeze_budget_pages_remaining, dirty);

                        proc_list_lock();

                        memorystatus_freeze_pageouts += dirty;

                        if (memorystatus_frozen_count == (memorystatus_frozen_processes_max - 1)) {
                                /*
                                 * Add some eviction logic here? At some point should we
                                 * jetsam a process to get back its swap space so that we
                                 * can freeze a more eligible process at this moment in time?
                                 */
                        }
                } else {
                        char reason[128];
                        if (freezer_error_code == FREEZER_ERROR_EXCESS_SHARED_MEMORY) {
                                memorystatus_freezer_stats.mfs_error_excess_shared_memory_count++;
                                strlcpy(reason, "too much shared memory", 128);
                        }

                        if (freezer_error_code == FREEZER_ERROR_LOW_PRIVATE_SHARED_RATIO) {
                                memorystatus_freezer_stats.mfs_error_low_private_shared_ratio_count++;
                                strlcpy(reason, "low private-shared pages ratio", 128);
                        }

                        if (freezer_error_code == FREEZER_ERROR_NO_COMPRESSOR_SPACE) {
                                memorystatus_freezer_stats.mfs_error_no_compressor_space_count++;
                                strlcpy(reason, "no compressor space", 128);
                        }

                        if (freezer_error_code == FREEZER_ERROR_NO_SWAP_SPACE) {
                                memorystatus_freezer_stats.mfs_error_no_swap_space_count++;
                                strlcpy(reason, "no swap space", 128);
                        }

                        os_log_with_startup_serial(OS_LOG_DEFAULT, "memorystatus: freezing (specific) pid %d [%s]...skipped (%s)",
                            aPid, ((p && *p->p_name) ? p->p_name : "unknown"), reason);
                        p->p_memstat_state |= P_MEMSTAT_FREEZE_IGNORE;
                }

                p->p_memstat_state &= ~P_MEMSTAT_LOCKED;
                wakeup(&p->p_memstat_state);
                proc_list_unlock();
        }

exit:
        lck_mtx_unlock(&freezer_mutex);

        return ret;
}

/*
 * Caller must hold the freezer_mutex and it will be locked on return.
 */
static int
memorystatus_freeze_top_process(void)
{
        pid_t aPid = 0, coal_xpc_pid = 0;
        int ret = -1;
        proc_t p = PROC_NULL, next_p = PROC_NULL;
        unsigned int i = 0;
        unsigned int band = JETSAM_PRIORITY_IDLE;
        boolean_t refreeze_processes = FALSE;
        task_t curr_task = NULL;
        coalition_t coal = COALITION_NULL;
        pid_t pid_list[MAX_XPC_SERVICE_PIDS];
        unsigned int    ntasks = 0;
        LCK_MTX_ASSERT(&freezer_mutex, LCK_MTX_ASSERT_OWNED);

        KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_MEMSTAT, BSD_MEMSTAT_FREEZE_SCAN) | DBG_FUNC_START, memorystatus_available_pages, 0, 0, 0, 0);

        proc_list_lock();

        if (memorystatus_frozen_count >= memorystatus_frozen_processes_max) {
                /*
                 * Freezer is already full but we are here and so let's
                 * try to refreeze any processes we might have thawed
                 * in the past and push out their compressed state out.
                 */
                refreeze_processes = TRUE;
                band = (unsigned int) memorystatus_freeze_jetsam_band;
        }

freeze_process:

        next_p = memorystatus_get_first_proc_locked(&band, FALSE);
        while (next_p) {
                kern_return_t kr;
                uint32_t purgeable, wired, clean, dirty, shared;
                uint32_t max_pages = 0;
                int    freezer_error_code = 0;

                p = next_p;

                if (coal == NULL) {
                        next_p = memorystatus_get_next_proc_locked(&band, p, FALSE);
                } else {
                        /*
                         * We have frozen a coalition leader and now are
                         * dealing with its XPC services. We get our
                         * next_p for each XPC service from the pid_list
                         * acquired after a successful task_freeze call
                         * on the coalition leader.
                         */

                        if (ntasks > 0) {
                                coal_xpc_pid = pid_list[--ntasks];
                                next_p = proc_findinternal(coal_xpc_pid, 1 /* proc_list_lock held */);
                                /*
                                 * We grab a reference when we are about to freeze the process. So, drop
                                 * the reference that proc_findinternal() grabbed for us.
                                 * We also have the proc_list_lock and so this process is stable.
                                 */
                                if (next_p) {
                                        proc_rele_locked(next_p);
                                }
                        } else {
                                next_p = NULL;
                        }
                }

                aPid = p->p_pid;

                if (p->p_memstat_effectivepriority != (int32_t) band) {
                        /*
                         * We shouldn't be freezing processes outside the
                         * prescribed band.
                         */
                        break;
                }

                /* Ensure the process is eligible for (re-)freezing */
                if (refreeze_processes) {
                        /*
                         * Has to have been frozen once before.
                         */
                        if ((p->p_memstat_state & P_MEMSTAT_FROZEN) == FALSE) {
                                continue;
                        }

                        /*
                         * Has to have been resumed once before.
                         */
                        if ((p->p_memstat_state & P_MEMSTAT_REFREEZE_ELIGIBLE) == FALSE) {
                                continue;
                        }

                        /*
                         * Not currently being looked at for something.
                         */
                        if (p->p_memstat_state & P_MEMSTAT_LOCKED) {
                                continue;
                        }

                        /*
                         * We are going to try and refreeze and so re-evaluate
                         * the process. We don't want to double count the shared
                         * memory. So deduct the old snapshot here.
                         */
                        memorystatus_frozen_shared_mb -= p->p_memstat_freeze_sharedanon_pages;
                        p->p_memstat_freeze_sharedanon_pages = 0;

                        p->p_memstat_state &= ~P_MEMSTAT_REFREEZE_ELIGIBLE;
                        memorystatus_refreeze_eligible_count--;
                } else {
                        if (memorystatus_is_process_eligible_for_freeze(p) == FALSE) {
                                continue; // with lock held
                        }
                }

                if (VM_CONFIG_FREEZER_SWAP_IS_ACTIVE) {
                        /*
                         * Freezer backed by the compressor and swap file(s)
                         * will hold compressed data.
                         */

                        max_pages = MIN(memorystatus_freeze_pages_max, memorystatus_freeze_budget_pages_remaining);
                } else {
                        /*
                         * We only have the compressor pool.
                         */
                        max_pages = UINT32_MAX - 1;
                }

                /* Mark as locked temporarily to avoid kill */
                p->p_memstat_state |= P_MEMSTAT_LOCKED;

                p = proc_ref_locked(p);
                if (!p) {
                        memorystatus_freezer_stats.mfs_error_other_count++;
                        break;
                }

                proc_list_unlock();

                KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_MEMSTAT, BSD_MEMSTAT_FREEZE) | DBG_FUNC_START,
                    memorystatus_available_pages, 0, 0, 0, 0);

                kr = task_freeze(p->task, &purgeable, &wired, &clean, &dirty, max_pages, &shared, &freezer_error_code, FALSE /* eval only */);
                if (kr == KERN_SUCCESS || freezer_error_code == FREEZER_ERROR_LOW_PRIVATE_SHARED_RATIO) {
                        memorystatus_freezer_stats.mfs_shared_pages_skipped += shared;
                }

                KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_MEMSTAT, BSD_MEMSTAT_FREEZE) | DBG_FUNC_END,
                    memorystatus_available_pages, aPid, 0, 0, 0);

                MEMORYSTATUS_DEBUG(1, "memorystatus_freeze_top_process: task_freeze %s for pid %d [%s] - "
                    "memorystatus_pages: %d, purgeable: %d, wired: %d, clean: %d, dirty: %d, max_pages %d, shared %d\n",
                    (kr == KERN_SUCCESS) ? "SUCCEEDED" : "FAILED", aPid, (*p->p_name ? p->p_name : "(unknown)"),
                    memorystatus_available_pages, purgeable, wired, clean, dirty, max_pages, shared);

                proc_list_lock();

                /* Success? */
                if (KERN_SUCCESS == kr) {
                        memorystatus_freeze_entry_t data = { aPid, TRUE, dirty };

                        p->p_memstat_freeze_sharedanon_pages += shared;

                        memorystatus_frozen_shared_mb += shared;

                        if ((p->p_memstat_state & P_MEMSTAT_FROZEN) == 0) {
                                p->p_memstat_state |= P_MEMSTAT_FROZEN;
                                memorystatus_frozen_count++;
                        }

                        p->p_memstat_frozen_count++;

                        /*
                         * Still keeping the P_MEMSTAT_LOCKED bit till we are actually done elevating this frozen process
                         * to its higher jetsam band.
                         */
                        proc_list_unlock();

                        memorystatus_send_note(kMemorystatusFreezeNote, &data, sizeof(data));

                        if (VM_CONFIG_FREEZER_SWAP_IS_ACTIVE) {
                                ret = memorystatus_update_inactive_jetsam_priority_band(p->p_pid, MEMORYSTATUS_CMD_ELEVATED_INACTIVEJETSAMPRIORITY_ENABLE, memorystatus_freeze_jetsam_band, TRUE);

                                if (ret) {
                                        printf("Elevating the frozen process failed with %d\n", ret);
                                        /* not fatal */
                                        ret = 0;
                                }

                                /* Update stats */
                                for (i = 0; i < sizeof(throttle_intervals) / sizeof(struct throttle_interval_t); i++) {
                                        throttle_intervals[i].pageouts += dirty;
                                }
                        }
                        memorystatus_freeze_update_throttle(&memorystatus_freeze_budget_pages_remaining);
                        os_log_with_startup_serial(OS_LOG_DEFAULT, "memorystatus: %sfreezing (%s) pid %d [%s] done, memorystatus_freeze_budget_pages_remaining %llu %sfroze %u pages\n",
                            refreeze_processes? "re" : "", (coal == NULL ? "general" : "coalition-driven"), aPid, ((p && *p->p_name) ? p->p_name : "unknown"), memorystatus_freeze_budget_pages_remaining, refreeze_processes? "Re" : "", dirty);

                        proc_list_lock();

                        memorystatus_freeze_pageouts += dirty;

                        if (memorystatus_frozen_count == (memorystatus_frozen_processes_max - 1)) {
                                /*
                                 * Add some eviction logic here? At some point should we
                                 * jetsam a process to get back its swap space so that we
                                 * can freeze a more eligible process at this moment in time?
                                 */
                        }

                        /* Return KERN_SUCCESS */
                        ret = kr;

                        /*
                         * We froze a process successfully. We can stop now
                         * and see if that helped if this process isn't part
                         * of a coalition.
                         *
                         * Else:
                         * - if it is a leader, get the list of XPC services
                         *   that need to be frozen.
                         * - if it is a XPC service whose leader was frozen
                         *   here, continue on to the next XPC service in the list.
                         */

                        if (coal == NULL) {
                                curr_task = proc_task(p);
                                coal = task_get_coalition(curr_task, COALITION_TYPE_JETSAM);
                                if (coalition_is_leader(curr_task, coal)) {
                                        ntasks = coalition_get_pid_list(coal, COALITION_ROLEMASK_XPC,
                                            COALITION_SORT_DEFAULT, pid_list, MAX_XPC_SERVICE_PIDS);

                                        if (ntasks > MAX_XPC_SERVICE_PIDS) {
                                                ntasks = MAX_XPC_SERVICE_PIDS;
                                        }
                                }

                                next_p = NULL;

                                if (ntasks > 0) {
                                        /*
                                         * Start off with our first next_p in this list.
                                         */
                                        coal_xpc_pid = pid_list[--ntasks];
                                        next_p = proc_findinternal(coal_xpc_pid, 1 /* proc_list_lock held */);

                                        /*
                                         * We grab a reference when we are about to freeze the process. So drop
                                         * the reference that proc_findinternal() grabbed for us.
                                         * We also have the proc_list_lock and so this process is stable.
                                         */
                                        if (next_p) {
                                                proc_rele_locked(next_p);
                                        }
                                }
                        }

                        p->p_memstat_state &= ~P_MEMSTAT_LOCKED;
                        wakeup(&p->p_memstat_state);
                        proc_rele_locked(p);

                        if (coal && next_p) {
                                continue;
                        }

                        /*
                         * No coalition leader was frozen. So we don't
                         * need to evaluate any XPC services.
                         *
                         * OR
                         *
                         * We have frozen all eligible XPC services for
                         * the current coalition leader.
                         *
                         * Either way, we can break here and see if freezing
                         * helped.
                         */

                        break;
                } else {
                        p->p_memstat_state &= ~P_MEMSTAT_LOCKED;
                        wakeup(&p->p_memstat_state);

                        if (refreeze_processes == TRUE) {
                                if ((freezer_error_code == FREEZER_ERROR_EXCESS_SHARED_MEMORY) ||
                                    (freezer_error_code == FREEZER_ERROR_LOW_PRIVATE_SHARED_RATIO)) {
                                        /*
                                         * Keeping this prior-frozen process in this high band when
                                         * we failed to re-freeze it due to bad shared memory usage
                                         * could cause excessive pressure on the lower bands.
                                         * We need to demote it for now. It'll get re-evaluated next
                                         * time because we don't set the P_MEMSTAT_FREEZE_IGNORE
                                         * bit.
                                         */

                                        p->p_memstat_state &= ~P_MEMSTAT_USE_ELEVATED_INACTIVE_BAND;
                                        memorystatus_invalidate_idle_demotion_locked(p, TRUE);
                                        memorystatus_update_priority_locked(p, JETSAM_PRIORITY_IDLE, TRUE, TRUE);
                                }
                        } else {
                                p->p_memstat_state |= P_MEMSTAT_FREEZE_IGNORE;
                        }

                        char reason[128];
                        if (freezer_error_code == FREEZER_ERROR_EXCESS_SHARED_MEMORY) {
                                memorystatus_freezer_stats.mfs_error_excess_shared_memory_count++;
                                strlcpy(reason, "too much shared memory", 128);
                        }

                        if (freezer_error_code == FREEZER_ERROR_LOW_PRIVATE_SHARED_RATIO) {
                                memorystatus_freezer_stats.mfs_error_low_private_shared_ratio_count++;
                                strlcpy(reason, "low private-shared pages ratio", 128);
                        }

                        if (freezer_error_code == FREEZER_ERROR_NO_COMPRESSOR_SPACE) {
                                memorystatus_freezer_stats.mfs_error_no_compressor_space_count++;
                                strlcpy(reason, "no compressor space", 128);
                        }

                        if (freezer_error_code == FREEZER_ERROR_NO_SWAP_SPACE) {
                                memorystatus_freezer_stats.mfs_error_no_swap_space_count++;
                                strlcpy(reason, "no swap space", 128);
                        }

                        os_log_with_startup_serial(OS_LOG_DEFAULT, "memorystatus: freezing (%s) pid %d [%s]...skipped (%s)\n",
                            (coal == NULL ? "general" : "coalition-driven"), aPid, ((p && *p->p_name) ? p->p_name : "unknown"), reason);

                        proc_rele_locked(p);

                        if (vm_compressor_low_on_space() || vm_swap_low_on_space()) {
                                break;
                        }
                }
        }

        if ((ret == -1) &&
            (memorystatus_refreeze_eligible_count >= MIN_THAW_REFREEZE_THRESHOLD) &&
            (refreeze_processes == FALSE)) {
                /*
                 * We failed to freeze a process from the IDLE
                 * band AND we have some thawed  processes
                 * AND haven't tried refreezing as yet.
                 * Let's try and re-freeze processes in the
                 * frozen band that have been resumed in the past
                 * and so have brought in state from disk.
                 */

                band = (unsigned int) memorystatus_freeze_jetsam_band;

                refreeze_processes = TRUE;

                goto freeze_process;
        }

        proc_list_unlock();

        KERNEL_DEBUG_CONSTANT(BSDDBG_CODE(DBG_BSD_MEMSTAT, BSD_MEMSTAT_FREEZE_SCAN) | DBG_FUNC_END, memorystatus_available_pages, aPid, 0, 0, 0);

        return ret;
}

static inline boolean_t
memorystatus_can_freeze_processes(void)
{
        boolean_t ret;

        proc_list_lock();

        if (memorystatus_suspended_count) {
                memorystatus_freeze_suspended_threshold = MIN(memorystatus_freeze_suspended_threshold, FREEZE_SUSPENDED_THRESHOLD_DEFAULT);

                if ((memorystatus_suspended_count - memorystatus_frozen_count) > memorystatus_freeze_suspended_threshold) {
                        ret = TRUE;
                } else {
                        ret = FALSE;
                }
        } else {
                ret = FALSE;
        }

        proc_list_unlock();

        return ret;
}

static boolean_t
memorystatus_can_freeze(boolean_t *memorystatus_freeze_swap_low)
{
        boolean_t can_freeze = TRUE;

        /* Only freeze if we're sufficiently low on memory; this holds off freeze right
        *  after boot,  and is generally is a no-op once we've reached steady state. */
        if (memorystatus_available_pages > memorystatus_freeze_threshold) {
                return FALSE;
        }

        /* Check minimum suspended process threshold. */
        if (!memorystatus_can_freeze_processes()) {
                return FALSE;
        }
        assert(VM_CONFIG_COMPRESSOR_IS_PRESENT);

        if (!VM_CONFIG_FREEZER_SWAP_IS_ACTIVE) {
                /*
                 * In-core compressor used for freezing WITHOUT on-disk swap support.
                 */
                if (vm_compressor_low_on_space()) {
                        if (*memorystatus_freeze_swap_low) {
                                *memorystatus_freeze_swap_low = TRUE;
                        }

                        can_freeze = FALSE;
                } else {
                        if (*memorystatus_freeze_swap_low) {
                                *memorystatus_freeze_swap_low = FALSE;
                        }

                        can_freeze = TRUE;
                }
        } else {
                /*
                 * Freezing WITH on-disk swap support.
                 *
                 * In-core compressor fronts the swap.
                 */
                if (vm_swap_low_on_space()) {
                        if (*memorystatus_freeze_swap_low) {
                                *memorystatus_freeze_swap_low = TRUE;
                        }

                        can_freeze = FALSE;
                }
        }

        return can_freeze;
}

/*
 * This function evaluates if the currently frozen processes deserve
 * to stay in the higher jetsam band. There are 2 modes:
 * - 'force one == TRUE': (urgent mode)
 *      We are out of budget and can't refreeze a process. The process's
 * state, if it was resumed, will stay in compressed memory. If we let it
 * remain up in the higher frozen jetsam band, it'll put a lot of pressure on
 * the lower bands. So we force-demote the least-recently-used-and-thawed
 * process.
 *
 * - 'force_one == FALSE': (normal mode)
 *      If the # of thaws of a process is below our threshold, then we
 * will demote that process into the IDLE band.
 * We don't immediately kill the process here because it  already has
 * state on disk and so it might be worth giving it another shot at
 * getting thawed/resumed and used.
 */
static void
memorystatus_demote_frozen_processes(boolean_t force_one)
{
        unsigned int band = (unsigned int) memorystatus_freeze_jetsam_band;
        unsigned int demoted_proc_count = 0;
        proc_t p = PROC_NULL, next_p = PROC_NULL;
        /* We demote to IDLE unless someone has asserted a higher priority on this process. */
        int maxpriority = JETSAM_PRIORITY_IDLE;

        proc_list_lock();

        if (memorystatus_freeze_enabled == FALSE) {
                /*
                 * Freeze has been disabled likely to
                 * reclaim swap space. So don't change
                 * any state on the frozen processes.
                 */
                proc_list_unlock();
                return;
        }

        next_p = memorystatus_get_first_proc_locked(&band, 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) == FALSE) {
                        continue;
                }

                if (p->p_memstat_state & P_MEMSTAT_LOCKED) {
                        continue;
                }

                if (force_one == TRUE) {
                        if ((p->p_memstat_state & P_MEMSTAT_REFREEZE_ELIGIBLE) == 0) {
                                /*
                                 * This process hasn't been thawed recently and so most of
                                 * its state sits on NAND and so we skip it -- jetsamming it
                                 * won't help with memory pressure.
                                 */
                                continue;
                        }
                } else {
                        if (p->p_memstat_thaw_count >= memorystatus_thaw_count_demotion_threshold) {
                                /*
                                 * This process has met / exceeded our thaw count demotion threshold
                                 * and so we let it live in the higher bands.
                                 */
                                continue;
                        }
                }

                p->p_memstat_state &= ~P_MEMSTAT_USE_ELEVATED_INACTIVE_BAND;
                memorystatus_invalidate_idle_demotion_locked(p, TRUE);

                maxpriority = MAX(p->p_memstat_assertionpriority, maxpriority);
                memorystatus_update_priority_locked(p, maxpriority, FALSE, FALSE);
#if DEVELOPMENT || DEBUG
                os_log_with_startup_serial(OS_LOG_DEFAULT, "memorystatus_demote_frozen_process(%s) pid %d [%s]",
                    (force_one ? "urgent" : "normal"), (p ? p->p_pid : -1), ((p && *p->p_name) ? p->p_name : "unknown"));
#endif /* DEVELOPMENT || DEBUG */

                /*
                 * The freezer thread will consider this a normal app to be frozen
                 * because it is in the IDLE band. So we don't need the
                 * P_MEMSTAT_REFREEZE_ELIGIBLE state here. Also, if it gets resumed
                 * we'll correctly count it as eligible for re-freeze again.
                 *
                 * We don't drop the frozen count because this process still has
                 * state on disk. So there's a chance it gets resumed and then it
                 * should land in the higher jetsam band. For that it needs to
                 * remain marked frozen.
                 */
                if (p->p_memstat_state & P_MEMSTAT_REFREEZE_ELIGIBLE) {
                        p->p_memstat_state &= ~P_MEMSTAT_REFREEZE_ELIGIBLE;
                        memorystatus_refreeze_eligible_count--;
                }

                demoted_proc_count++;

                if ((force_one == TRUE) || (demoted_proc_count == memorystatus_max_frozen_demotions_daily)) {
                        break;
                }
        }

        if (force_one == FALSE) {
                /*
                 * We use these counters to track daily hit rates.
                 * So we only reset them to 0 under the normal
                 * mode.
                 */
                memorystatus_thaw_count = 0;
        }

        proc_list_unlock();
}

/*
 * Calculate a new freezer budget.
 * @param time_since_last_interval_expired_sec How long has it been (in seconds) since the previous interval expired.
 * @param burst_multiple The burst_multiple for the new period
 * @param interval_duration_min How many minutes will the new interval be?
 * @param rollover The amount to rollover from the previous budget.
 *
 * @return A budget for the new interval.
 */
static uint32_t
memorystatus_freeze_calculate_new_budget(
        unsigned int time_since_last_interval_expired_sec,
        unsigned int burst_multiple,
        unsigned int interval_duration_min,
        uint32_t rollover)
{
        uint64_t freeze_daily_budget = 0;
        unsigned int daily_budget_pageouts = 0;
        unsigned int freeze_daily_pageouts_max = 0;
        const static unsigned int kNumSecondsInDay = 60 * 60 * 24;
        /* Precision factor for days_missed. 2 decimal points. */
        const static unsigned int kFixedPointFactor = 100;
        unsigned int days_missed, budget_missed;

        /* Get the daily budget from the storage layer */
        if (vm_swap_max_budget(&freeze_daily_budget)) {
                memorystatus_freeze_daily_mb_max = (freeze_daily_budget / (1024 * 1024));
                os_log_with_startup_serial(OS_LOG_DEFAULT, "memorystatus: memorystatus_freeze_daily_mb_max set to %dMB\n", memorystatus_freeze_daily_mb_max);
        }
        /* Calculate the daily pageout budget */
        freeze_daily_pageouts_max = memorystatus_freeze_daily_mb_max * (1024 * 1024 / PAGE_SIZE);

        daily_budget_pageouts = (burst_multiple * (((uint64_t) interval_duration_min * freeze_daily_pageouts_max) / (kNumSecondsInDay / 60)));

        /*
         * Add additional budget for time since the interval expired.
         * For example, if the interval expired n days ago, we should get an additional n days
         * of budget since we didn't use any budget during those n days.
         */
        days_missed = time_since_last_interval_expired_sec * kFixedPointFactor / kNumSecondsInDay;
        budget_missed = days_missed * freeze_daily_pageouts_max / kFixedPointFactor;
        return rollover + daily_budget_pageouts + budget_missed;
}

#if DEVELOPMENT || DEBUG

static int
sysctl_memorystatus_freeze_calculate_new_budget SYSCTL_HANDLER_ARGS
{
#pragma unused(arg1, arg2)
        int error = 0;
        unsigned int time_since_last_interval_expired_sec = 0;
        unsigned int new_budget;

        error = sysctl_handle_int(oidp, &time_since_last_interval_expired_sec, 0, req);
        if (error || !req->newptr) {
                return error;
        }
        new_budget = memorystatus_freeze_calculate_new_budget(time_since_last_interval_expired_sec, 1, NORMAL_WINDOW_MINS, 0);
        return copyout(&new_budget, req->oldptr, MIN(sizeof(req->oldlen), sizeof(new_budget)));
}

SYSCTL_PROC(_vm, OID_AUTO, memorystatus_freeze_calculate_new_budget, CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_MASKED,
    0, 0, &sysctl_memorystatus_freeze_calculate_new_budget, "I", "");

#endif /* DEVELOPMENT || DEBUG */

/*
 * This function will do 4 things:
 *
 * 1) check to see if we are currently in a degraded freezer mode, and if so:
 *    - check to see if our window has expired and we should exit this mode, OR,
 *    - return a budget based on the degraded throttle window's max. pageouts vs current pageouts.
 *
 * 2) check to see if we are in a NEW normal window and update the normal throttle window's params.
 *
 * 3) check what the current normal window allows for a budget.
 *
 * 4) calculate the current rate of pageouts for DEGRADED_WINDOW_MINS duration. If that rate is below
 *    what we would normally expect, then we are running low on our daily budget and need to enter
 *    degraded perf. mode.
 *
 *    Caller must hold the freezer mutex
 *    Caller must not hold the proc_list lock
 */

static void
memorystatus_freeze_update_throttle(uint64_t *budget_pages_allowed)
{
        clock_sec_t sec;
        clock_nsec_t nsec;
        mach_timespec_t now_ts;
        LCK_MTX_ASSERT(&freezer_mutex, LCK_MTX_ASSERT_OWNED);
        LCK_MTX_ASSERT(proc_list_mlock, LCK_MTX_ASSERT_NOTOWNED);

        unsigned int freeze_daily_pageouts_max = 0;

#if DEVELOPMENT || DEBUG
        if (!memorystatus_freeze_throttle_enabled) {
                /*
                 * No throttling...we can use the full budget everytime.
                 */
                *budget_pages_allowed = UINT64_MAX;
                return;
        }
#endif

        clock_get_system_nanotime(&sec, &nsec);
        now_ts.tv_sec = sec;
        now_ts.tv_nsec = nsec;

        struct throttle_interval_t *interval = NULL;

        if (memorystatus_freeze_degradation == TRUE) {
                interval = degraded_throttle_window;

                if (CMP_MACH_TIMESPEC(&now_ts, &interval->ts) >= 0) {
                        memorystatus_freeze_degradation = FALSE;
                        interval->pageouts = 0;
                        interval->max_pageouts = 0;
                } else {
                        *budget_pages_allowed = interval->max_pageouts - interval->pageouts;
                }
        }

        interval = normal_throttle_window;

        if (CMP_MACH_TIMESPEC(&now_ts, &interval->ts) >= 0) {
                /* How long has it been since the previous interval expired? */
                mach_timespec_t expiration_period_ts = now_ts;
                SUB_MACH_TIMESPEC(&expiration_period_ts, &interval->ts);

                interval->max_pageouts = memorystatus_freeze_calculate_new_budget(
                        expiration_period_ts.tv_sec, interval->burst_multiple,
                        interval->mins, interval->max_pageouts - interval->pageouts);
                interval->ts.tv_sec = interval->mins * 60;
                interval->ts.tv_nsec = 0;
                ADD_MACH_TIMESPEC(&interval->ts, &now_ts);
                /* Since we update the throttle stats pre-freeze, adjust for overshoot here */
                if (interval->pageouts > interval->max_pageouts) {
                        interval->pageouts -= interval->max_pageouts;
                } else {
                        interval->pageouts = 0;
                }
                *budget_pages_allowed = interval->max_pageouts;
                memorystatus_freezer_stats.mfs_shared_pages_skipped = 0;

                memorystatus_demote_frozen_processes(FALSE); /* normal mode...don't force a demotion */
        } else {
                /*
                 * Current throttle window.
                 * Deny freezing if we have no budget left.
                 * Try graceful degradation if we are within 25% of:
                 * - the daily budget, and
                 * - the current budget left is below our normal budget expectations.
                 */

#if DEVELOPMENT || DEBUG
                /*
                 * This can only happen in the INTERNAL configs because we allow modifying the daily budget for testing.
                 */

                if (freeze_daily_pageouts_max > interval->max_pageouts) {
                        /*
                         * We just bumped the daily budget. Re-evaluate our normal window params.
                         */
                        interval->max_pageouts = (interval->burst_multiple * (((uint64_t)interval->mins * freeze_daily_pageouts_max) / NORMAL_WINDOW_MINS));
                        memorystatus_freeze_degradation = FALSE; //we'll re-evaluate this below...
                }
#endif /* DEVELOPMENT || DEBUG */

                if (memorystatus_freeze_degradation == FALSE) {
                        if (interval->pageouts >= interval->max_pageouts) {
                                *budget_pages_allowed = 0;
                        } else {
                                int budget_left = interval->max_pageouts - interval->pageouts;
                                int budget_threshold = (freeze_daily_pageouts_max * FREEZE_DEGRADATION_BUDGET_THRESHOLD) / 100;

                                mach_timespec_t time_left = {0, 0};

                                time_left.tv_sec = interval->ts.tv_sec;
                                time_left.tv_nsec = 0;

                                SUB_MACH_TIMESPEC(&time_left, &now_ts);

                                if (budget_left <= budget_threshold) {
                                        /*
                                         * For the current normal window, calculate how much we would pageout in a DEGRADED_WINDOW_MINS duration.
                                         * And also calculate what we would pageout for the same DEGRADED_WINDOW_MINS duration if we had the full
                                         * daily pageout budget.
                                         */

                                        unsigned int current_budget_rate_allowed = ((budget_left / time_left.tv_sec) / 60) * DEGRADED_WINDOW_MINS;
                                        unsigned int normal_budget_rate_allowed = (freeze_daily_pageouts_max / NORMAL_WINDOW_MINS) * DEGRADED_WINDOW_MINS;

                                        /*
                                         * The current rate of pageouts is below what we would expect for
                                         * the normal rate i.e. we have below normal budget left and so...
                                         */

                                        if (current_budget_rate_allowed < normal_budget_rate_allowed) {
                                                memorystatus_freeze_degradation = TRUE;
                                                degraded_throttle_window->max_pageouts = current_budget_rate_allowed;
                                                degraded_throttle_window->pageouts = 0;

                                                /*
                                                 * Switch over to the degraded throttle window so the budget
                                                 * doled out is based on that window.
                                                 */
                                                interval = degraded_throttle_window;
                                        }
                                }

                                *budget_pages_allowed = interval->max_pageouts - interval->pageouts;
                        }
                }
        }

        MEMORYSTATUS_DEBUG(1, "memorystatus_freeze_update_throttle_interval: throttle updated - %d frozen (%d max) within %dm; %dm remaining; throttle %s\n",
            interval->pageouts, interval->max_pageouts, interval->mins, (interval->ts.tv_sec - now_ts->tv_sec) / 60,
            interval->throttle ? "on" : "off");
}

static void
memorystatus_freeze_thread(void *param __unused, wait_result_t wr __unused)
{
        static boolean_t memorystatus_freeze_swap_low = FALSE;

        lck_mtx_lock(&freezer_mutex);

        if (memorystatus_freeze_enabled) {
                if ((memorystatus_frozen_count < memorystatus_frozen_processes_max) ||
                    (memorystatus_refreeze_eligible_count >= MIN_THAW_REFREEZE_THRESHOLD)) {
                        if (memorystatus_can_freeze(&memorystatus_freeze_swap_low)) {
                                /* Only freeze if we've not exceeded our pageout budgets.*/
                                memorystatus_freeze_update_throttle(&memorystatus_freeze_budget_pages_remaining);

                                if (memorystatus_freeze_budget_pages_remaining) {
                                        memorystatus_freeze_top_process();
                                } else {
                                        memorystatus_demote_frozen_processes(TRUE); /* urgent mode..force one demotion */
                                }
                        }
                }
        }

        /*
         * We use memorystatus_apps_idle_delay_time because if/when we adopt aging for applications,
         * it'll tie neatly into running the freezer once we age an application.
         *
         * Till then, it serves as a good interval that can be tuned via a sysctl too.
         */
        memorystatus_freezer_thread_next_run_ts = mach_absolute_time() + memorystatus_apps_idle_delay_time;

        assert_wait((event_t) &memorystatus_freeze_wakeup, THREAD_UNINT);
        lck_mtx_unlock(&freezer_mutex);

        thread_block((thread_continue_t) memorystatus_freeze_thread);
}

boolean_t
memorystatus_freeze_thread_should_run(void)
{
        /*
         * No freezer_mutex held here...see why near call-site
         * within memorystatus_pages_update().
         */

        boolean_t should_run = FALSE;

        if (memorystatus_freeze_enabled == FALSE) {
                goto out;
        }

        if (memorystatus_available_pages > memorystatus_freeze_threshold) {
                goto out;
        }

        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 < MIN_THAW_REFREEZE_THRESHOLD) {
                        goto out;
                }
        }

        if (memorystatus_frozen_shared_mb_max && (memorystatus_frozen_shared_mb >= memorystatus_frozen_shared_mb_max)) {
                memorystatus_freezer_stats.mfs_skipped_shared_mb_high_count++;
                goto out;
        }

        uint64_t curr_time = mach_absolute_time();

        if (curr_time < memorystatus_freezer_thread_next_run_ts) {
                goto out;
        }

        should_run = TRUE;

out:
        return should_run;
}

int
memorystatus_get_process_is_freezable(pid_t pid, int *is_freezable)
{
        proc_t p = PROC_NULL;

        if (pid == 0) {
                return EINVAL;
        }

        p = proc_find(pid);
        if (!p) {
                return ESRCH;
        }

        /*
         * Only allow this on the current proc for now.
         * We can check for privileges and allow targeting another process in the future.
         */
        if (p != current_proc()) {
                proc_rele(p);
                return EPERM;
        }

        proc_list_lock();
        *is_freezable = ((p->p_memstat_state & P_MEMSTAT_FREEZE_DISABLED) ? 0 : 1);
        proc_rele_locked(p);
        proc_list_unlock();

        return 0;
}

int
memorystatus_set_process_is_freezable(pid_t pid, boolean_t is_freezable)
{
        proc_t p = PROC_NULL;

        if (pid == 0) {
                return EINVAL;
        }

        /*
         * To enable freezable status, you need to be root or an entitlement.
         */
        if (is_freezable &&
            !kauth_cred_issuser(kauth_cred_get()) &&
            !IOTaskHasEntitlement(current_task(), MEMORYSTATUS_ENTITLEMENT)) {
                return EPERM;
        }

        p = proc_find(pid);
        if (!p) {
                return ESRCH;
        }

        /*
         * A process can change its own status. A coalition leader can
         * change the status of coalition members.
         */
        if (p != current_proc()) {
                coalition_t coal = task_get_coalition(proc_task(p), COALITION_TYPE_JETSAM);
                if (!coalition_is_leader(proc_task(current_proc()), coal)) {
                        proc_rele(p);
                        return EPERM;
                }
        }

        proc_list_lock();
        if (is_freezable == FALSE) {
                /* Freeze preference set to FALSE. Set the P_MEMSTAT_FREEZE_DISABLED bit. */
                p->p_memstat_state |= P_MEMSTAT_FREEZE_DISABLED;
                printf("memorystatus_set_process_is_freezable: disabling freeze for pid %d [%s]\n",
                    p->p_pid, (*p->p_name ? p->p_name : "unknown"));
        } else {
                p->p_memstat_state &= ~P_MEMSTAT_FREEZE_DISABLED;
                printf("memorystatus_set_process_is_freezable: enabling freeze for pid %d [%s]\n",
                    p->p_pid, (*p->p_name ? p->p_name : "unknown"));
        }
        proc_rele_locked(p);
        proc_list_unlock();

        return 0;
}

static int
sysctl_memorystatus_do_fastwake_warmup_all  SYSCTL_HANDLER_ARGS
{
#pragma unused(oidp, arg1, arg2)

        if (!req->newptr) {
                return EINVAL;
        }

        /* Need to be root or have entitlement */
        if (!kauth_cred_issuser(kauth_cred_get()) && !IOTaskHasEntitlement(current_task(), MEMORYSTATUS_ENTITLEMENT)) {
                return EPERM;
        }

        if (memorystatus_freeze_enabled == FALSE) {
                return ENOTSUP;
        }

        do_fastwake_warmup_all();

        return 0;
}

SYSCTL_PROC(_kern, OID_AUTO, memorystatus_do_fastwake_warmup_all, CTLTYPE_INT | CTLFLAG_WR | CTLFLAG_LOCKED | CTLFLAG_MASKED,
    0, 0, &sysctl_memorystatus_do_fastwake_warmup_all, "I", "");

#endif /* CONFIG_FREEZE */