xnu-7195.81.3.tar.gz

[apple/xnu.git] / tests / memorystatus_zone_test.c

#include <stdio.h>
#include <mach/mach_vm.h>
#include <mach/mach_port.h>
#include <mach/mach_host.h>
#include <mach/mach_error.h>
#include <mach-o/dyld.h>
#include <sys/sysctl.h>
#include <sys/kdebug.h>
#include <sys/mman.h>
#include <sys/kern_memorystatus.h>
#include <ktrace/session.h>
#include <dispatch/private.h>

#ifdef T_NAMESPACE
#undef T_NAMESPACE
#endif
#include <darwintest.h>
#include <darwintest_utils.h>

T_GLOBAL_META(
        T_META_NAMESPACE("xnu.vm"),
        T_META_CHECK_LEAKS(false)
        );

#define TIMEOUT_SECS                                    10 * 60 /* abort if test takes > 10 minutes */

#if (TARGET_OS_IPHONE && !TARGET_OS_SIMULATOR)
#define ALLOCATION_SIZE_VM_REGION                       (16*1024)               /* 16 KB */
#define ALLOCATION_SIZE_VM_OBJECT                       ALLOCATION_SIZE_VM_REGION
#else
#define ALLOCATION_SIZE_VM_REGION                       (1024*1024*100) /* 100 MB */
#define ALLOCATION_SIZE_VM_OBJECT                       (16*1024)               /* 16 KB */
#endif
#define MAX_CHILD_PROCS                                 100

#define NUM_GIVE_BACK                                   5
#define NUM_GIVE_BACK_PORTS                             20

/* 60% is too high on bridgeOS to achieve without vm-pageshortage jetsams. Set it to 40%. */
#if TARGET_OS_BRIDGE
#define ZONEMAP_JETSAM_LIMIT_SYSCTL                     "kern.zone_map_jetsam_limit=40"
#else
#define ZONEMAP_JETSAM_LIMIT_SYSCTL                     "kern.zone_map_jetsam_limit=60"
#endif

#define VME_ZONE_TEST_OPT                               "allocate_vm_regions"
#define VM_OBJECTS_ZONE_TEST_OPT                        "allocate_vm_objects"
#define GENERIC_ZONE_TEST_OPT                           "allocate_from_generic_zone"

#define VME_ZONE                                        "VM map entries"
#define VMOBJECTS_ZONE                                  "vm objects"
#define VMENTRY_TO_VMOBJECT_COMPARISON_RATIO            98

#define VM_TAG1                                         100
#define VM_TAG2                                         101

#define LARGE_MEM_GB                                    32
#define LARGE_MEM_JETSAM_LIMIT                          40
#define JETSAM_LIMIT_LOWEST                             10

enum {
        VME_ZONE_TEST = 0,
        VM_OBJECTS_ZONE_TEST,
        GENERIC_ZONE_TEST,
};

typedef struct test_config_struct {
        int test_index;
        int num_zones;
        const char *helper_func;
        mach_zone_name_array_t zone_names;
} test_config_struct;

static test_config_struct current_test;
static dispatch_source_t ds_signal = NULL;
static dispatch_source_t ds_timer = NULL;
static dispatch_queue_t dq_spawn = NULL;
static ktrace_session_t session = NULL;

static mach_zone_info_array_t zone_info_array = NULL;
static mach_zone_name_t largest_zone_name;
static mach_zone_info_t largest_zone_info;

static pthread_mutex_t test_mtx = PTHREAD_MUTEX_INITIALIZER;   /* protects the next 3 things */
static bool test_ending = false;
static int num_children = 0;
static pid_t child_pids[MAX_CHILD_PROCS];

static char testpath[PATH_MAX];
static void allocate_vm_stuff(int);
static void allocate_from_generic_zone(void);
static void begin_test_teardown(void);
static void cleanup_and_end_test(void);
static void setup_ktrace_session(void);
static void spawn_child_process(void);
static void run_test(void);
static bool verify_generic_jetsam_criteria(void);
static bool vme_zone_compares_to_vm_objects(void);
static int query_zone_map_size(void);
static void query_zone_info(void);
static void print_zone_info(mach_zone_name_t *zn, mach_zone_info_t *zi);

extern void mach_zone_force_gc(host_t host);
extern kern_return_t mach_zone_info_for_largest_zone(
        host_priv_t host,
        mach_zone_name_t *name,
        mach_zone_info_t *info
        );

static bool
check_time(time_t start, int timeout)
{
        return start + timeout < time(NULL);
}

/*
 * flag values for allocate_vm_stuff()
 */
#define REGIONS 1
#define OBJECTS 2

static void
allocate_vm_stuff(int flags)
{
        uint64_t alloc_size, i;
        time_t start = time(NULL);
        mach_vm_address_t give_back[NUM_GIVE_BACK];
        char *msg;

        if (flags == REGIONS) {
                alloc_size = ALLOCATION_SIZE_VM_REGION;
                msg = "";
        } else {
                alloc_size = ALLOCATION_SIZE_VM_OBJECT;
                msg = " each region backed by a VM object";
        }

        printf("[%d] Allocating VM regions, each of size %lld KB%s\n", getpid(), (alloc_size >> 10), msg);

        for (i = 0;; i++) {
                mach_vm_address_t addr = (mach_vm_address_t)NULL;

                /* Alternate VM tags between consecutive regions to prevent coalescing */
                int vmflags = VM_MAKE_TAG((i % 2)? VM_TAG1: VM_TAG2) | VM_FLAGS_ANYWHERE;

                if ((mach_vm_allocate(mach_task_self(), &addr, (mach_vm_size_t)alloc_size, vmflags)) != KERN_SUCCESS) {
                        break;
                }

                /*
                 * If interested in objects, touch the region so the VM object is created,
                 * then free this page. Keeps us from holding a lot of dirty pages.
                 */
                if (flags == OBJECTS) {
                        *((int *)addr) = 0;
                        madvise((void *)addr, (size_t)alloc_size, MADV_FREE);
                }

                if (check_time(start, TIMEOUT_SECS)) {
                        printf("[%d] child timeout during allocations\n", getpid());
                        exit(0);
                }

                if (i < NUM_GIVE_BACK) {
                        give_back[i] = addr;
                }
        }

        /* return some of the resource to avoid O-O-M problems */
        for (uint64_t j = 0; j < NUM_GIVE_BACK && j < i; ++j) {
                mach_vm_deallocate(mach_task_self(), give_back[j], (mach_vm_size_t)alloc_size);
        }

        printf("[%d] Number of allocations: %lld\n", getpid(), i);

        /* Signal to the parent that we're done allocating */
        kill(getppid(), SIGUSR1);

        while (1) {
                sleep(2);
                /* Exit if parent has exited. Ensures child processes don't linger around after the test exits */
                if (getppid() == 1) {
                        exit(0);
                }

                if (check_time(start, TIMEOUT_SECS)) {
                        printf("[%d] child timeout while waiting\n", getpid());
                        exit(0);
                }
        }
}


static void
allocate_from_generic_zone(void)
{
        uint64_t i = 0;
        time_t start = time(NULL);
        mach_port_t give_back[NUM_GIVE_BACK_PORTS];

        printf("[%d] Allocating mach_ports\n", getpid());
        for (i = 0;; i++) {
                mach_port_t port;

                if ((mach_port_allocate(mach_task_self(), MACH_PORT_RIGHT_RECEIVE, &port)) != KERN_SUCCESS) {
                        break;
                }

                if (check_time(start, TIMEOUT_SECS)) {
                        printf("[%d] child timeout during allocations\n", getpid());
                        exit(0);
                }

                if (i < NUM_GIVE_BACK_PORTS) {
                        give_back[i] = port;
                }
        }

        /* return some of the resource to avoid O-O-M problems */
        for (uint64_t j = 0; j < NUM_GIVE_BACK_PORTS && j < i; ++j) {
                int ret;
                ret = mach_port_mod_refs(mach_task_self(), give_back[j], MACH_PORT_RIGHT_RECEIVE, -1);
                T_ASSERT_MACH_SUCCESS(ret, "mach_port_mod_refs(RECV_RIGHT, -1)");
        }
        printf("[%d] Number of allocations: %lld\n", getpid(), i);

        /* Signal to the parent that we're done allocating */
        kill(getppid(), SIGUSR1);

        while (1) {
                sleep(2);
                /* Exit if parent has exited. Ensures child processes don't linger around after the test exits */
                if (getppid() == 1) {
                        exit(0);
                }

                if (check_time(start, TIMEOUT_SECS)) {
                        printf("[%d] child timeout while waiting\n", getpid());
                        exit(0);
                }
        }
}

static void
print_zone_info(mach_zone_name_t *zn, mach_zone_info_t *zi)
{
        T_LOG("ZONE NAME: %-35sSIZE: %-25lluELEMENTS: %llu",
            zn->mzn_name, zi->mzi_cur_size, zi->mzi_count);
}

static time_t main_start;

static void
query_zone_info(void)
{
        int i;
        kern_return_t kr;
        static uint64_t num_calls = 0;

        if (check_time(main_start, TIMEOUT_SECS)) {
                T_ASSERT_FAIL("Global timeout expired");
        }
        for (i = 0; i < current_test.num_zones; i++) {
                kr = mach_zone_info_for_zone(mach_host_self(), current_test.zone_names[i], &(zone_info_array[i]));
                T_QUIET; T_ASSERT_MACH_SUCCESS(kr, "mach_zone_info_for_zone(%s) returned %d [%s]", current_test.zone_names[i].mzn_name, kr, mach_error_string(kr));
        }
        kr = mach_zone_info_for_largest_zone(mach_host_self(), &largest_zone_name, &largest_zone_info);
        T_QUIET; T_ASSERT_MACH_SUCCESS(kr, "mach_zone_info_for_largest_zone returned %d [%s]", kr, mach_error_string(kr));

        num_calls++;
        if (num_calls % 5 != 0) {
                return;
        }

        /* Print out size and element count for zones relevant to the test */
        for (i = 0; i < current_test.num_zones; i++) {
                print_zone_info(&(current_test.zone_names[i]), &(zone_info_array[i]));
        }
}

static bool
vme_zone_compares_to_vm_objects(void)
{
        int i;
        uint64_t vm_object_element_count = 0, vm_map_entry_element_count = 0;

        T_LOG("Comparing element counts of \"VM map entries\" and \"vm objects\" zones");
        for (i = 0; i < current_test.num_zones; i++) {
                if (!strcmp(current_test.zone_names[i].mzn_name, VME_ZONE)) {
                        vm_map_entry_element_count = zone_info_array[i].mzi_count;
                } else if (!strcmp(current_test.zone_names[i].mzn_name, VMOBJECTS_ZONE)) {
                        vm_object_element_count = zone_info_array[i].mzi_count;
                }
                print_zone_info(&(current_test.zone_names[i]), &(zone_info_array[i]));
        }

        T_LOG("# VM map entries as percentage of # vm objects = %llu", (vm_map_entry_element_count * 100) / vm_object_element_count);
        if (vm_map_entry_element_count >= ((vm_object_element_count * VMENTRY_TO_VMOBJECT_COMPARISON_RATIO) / 100)) {
                T_LOG("Number of VM map entries is comparable to vm objects\n\n");
                return true;
        }
        T_LOG("Number of VM map entries is NOT comparable to vm objects\n\n");
        return false;
}

static bool
verify_generic_jetsam_criteria(void)
{
        T_LOG("Largest zone info");
        print_zone_info(&largest_zone_name, &largest_zone_info);

        /* If VM map entries is not the largest zone */
        if (strcmp(largest_zone_name.mzn_name, VME_ZONE)) {
                /* If vm objects is the largest zone and the VM map entries zone had comparable # of elements, return false */
                if (!strcmp(largest_zone_name.mzn_name, VMOBJECTS_ZONE) && vme_zone_compares_to_vm_objects()) {
                        return false;
                }
                return true;
        }
        return false;
}

static void
begin_test_teardown(void)
{
        int ret, old_limit = 95;

        /*
         * Restore kern.zone_map_jetsam_limit to the default high value, to prevent further jetsams.
         * We should change the value of old_limit if ZONE_MAP_JETSAM_LIMIT_DEFAULT changes in the kernel.
         * We don't have a way to capture what the original value was before the test, because the
         * T_META_SYSCTL_INT macro will have changed the value before the test starts running.
         */
        ret = sysctlbyname("kern.zone_map_jetsam_limit", NULL, NULL, &old_limit, sizeof(old_limit));
        T_QUIET; T_ASSERT_POSIX_SUCCESS(ret, "sysctl kern.zone_map_jetsam_limit failed");
        T_LOG("kern.zone_map_jetsam_limit set to %d%%", old_limit);


        /* End ktrace session */
        if (session != NULL) {
                T_LOG("Ending ktrace session...");
                ktrace_end(session, 1);
        }

        dispatch_sync(dq_spawn, ^{
                T_LOG("Cancelling dispatch sources...");

                /* Disable the timer that queries and prints zone info periodically */
                if (ds_timer != NULL) {
                        dispatch_source_cancel(ds_timer);
                }

                /* Disable signal handler that spawns child processes */
                if (ds_signal != NULL) {
                        /*
                         * No need for a dispatch_source_cancel_and_wait here.
                         * We're queueing this on the spawn queue, so no further
                         * processes will be spawned after the source is cancelled.
                         */
                        dispatch_source_cancel(ds_signal);
                }
        });
}

static void
cleanup_and_end_test(void)
{
        int i;

        /*
         * The atend handler executes on a different dispatch queue.
         * We want to do the cleanup only once.
         */
        pthread_mutex_lock(&test_mtx);
        if (test_ending) {
                pthread_mutex_unlock(&test_mtx);
                return;
        }
        test_ending = TRUE;
        pthread_mutex_unlock(&test_mtx);

        dispatch_async(dq_spawn, ^{
                /*
                 * If the test succeeds, we will call dispatch_source_cancel twice, which is fine since
                 * the operation is idempotent. Just make sure to not drop all references to the dispatch sources
                 * (in this case we're not, we have globals holding references to them), or we can end up with
                 * use-after-frees which would be a problem.
                 */
                /* Disable the timer that queries and prints zone info periodically */
                if (ds_timer != NULL) {
                        dispatch_source_cancel(ds_timer);
                }

                /* Disable signal handler that spawns child processes */
                if (ds_signal != NULL) {
                        dispatch_source_cancel(ds_signal);
                }
        });

        pthread_mutex_lock(&test_mtx);
        T_LOG("Number of processes spawned: %d", num_children);
        T_LOG("Killing child processes...");

        /* Kill all the child processes that were spawned */
        for (i = 0; i < num_children; i++) {
                pid_t pid = child_pids[i];
                int status = 0;

                /*
                 * Kill and wait for each child to exit
                 * Without this we were seeing hw_lock_bit timeouts in BATS.
                 */
                kill(pid, SIGKILL);
                pthread_mutex_unlock(&test_mtx);
                if (waitpid(pid, &status, 0) < 0) {
                        T_LOG("waitpid returned status %d", status);
                }
                pthread_mutex_lock(&test_mtx);
        }
        sleep(1);

        /* Force zone_gc before starting test for another zone or exiting */
        mach_zone_force_gc(mach_host_self());

        /* End ktrace session */
        if (session != NULL) {
                ktrace_end(session, 1);
        }

        if (current_test.num_zones > 0) {
                T_LOG("Relevant zone info at the end of the test:");
                for (i = 0; i < current_test.num_zones; i++) {
                        print_zone_info(&(current_test.zone_names[i]), &(zone_info_array[i]));
                }
        }
}

static void
setup_ktrace_session(void)
{
        int ret = 0;

        T_LOG("Setting up ktrace session...");
        session = ktrace_session_create();
        T_QUIET; T_ASSERT_NOTNULL(session, "ktrace_session_create");

        ktrace_set_interactive(session);

        ktrace_set_dropped_events_handler(session, ^{
                T_FAIL("Dropped ktrace events; might have missed an expected jetsam event. Terminating early.");
        });

        ktrace_set_completion_handler(session, ^{
                ktrace_session_destroy(session);
                T_END;
        });

        /* Listen for memorystatus_do_kill trace events */
        ret = ktrace_events_single(session, (BSDDBG_CODE(DBG_BSD_MEMSTAT, BSD_MEMSTAT_DO_KILL)), ^(ktrace_event_t event) {
                int i;
                bool received_jetsam_event = false;

                /*
                 * libktrace does not support DBG_FUNC_START/END in the event filter. It simply ignores it.
                 * So we need to explicitly check for the end event (a successful jetsam kill) here,
                 * instead of passing in ((BSDDBG_CODE(DBG_BSD_MEMSTAT, BSD_MEMSTAT_DO_KILL)) | DBG_FUNC_START).
                 */
                if (!(event->debugid & DBG_FUNC_START)) {
                        return;
                }

                /* Check for zone-map-exhaustion jetsam. */
                if (event->arg2 == kMemorystatusKilledZoneMapExhaustion) {
                        begin_test_teardown();
                        T_LOG("[memorystatus_do_kill] jetsam reason: zone-map-exhaustion, pid: %d\n\n", (int)event->arg1);
                        if (current_test.test_index == VME_ZONE_TEST || current_test.test_index == VM_OBJECTS_ZONE_TEST) {
                                /*
                                 * For the VM map entries zone we try to kill the leaking process.
                                 * Verify that we jetsammed one of the processes we spawned.
                                 *
                                 * For the vm objects zone we pick the leaking process via the VM map entries
                                 * zone, if the number of vm objects and VM map entries are comparable.
                                 * The test simulates this scenario, we should see a targeted jetsam for the
                                 * vm objects zone too.
                                 */
                                pthread_mutex_lock(&test_mtx);
                                for (i = 0; i < num_children; i++) {
                                        if (child_pids[i] == (pid_t)event->arg1) {
                                                received_jetsam_event = true;
                                                T_LOG("Received jetsam event for a child");
                                                break;
                                        }
                                }
                                pthread_mutex_unlock(&test_mtx);
                                /*
                                 * If we didn't see a targeted jetsam, verify that the largest zone actually
                                 * fulfilled the criteria for generic jetsams.
                                 */
                                if (!received_jetsam_event && verify_generic_jetsam_criteria()) {
                                        received_jetsam_event = true;
                                        T_LOG("Did not receive jetsam event for a child, but generic jetsam criteria holds");
                                }
                        } else {
                                received_jetsam_event = true;
                                T_LOG("Received generic jetsam event");
                        }

                        T_QUIET; T_ASSERT_TRUE(received_jetsam_event, "Jetsam event not as expected");
                } else {
                        /*
                         * The test relies on the children being able to send a signal to the parent, to continue spawning new processes
                         * that leak more zone memory. If a child is jetsammed for some other reason, the parent can get stuck waiting for
                         * a signal from the child, never being able to make progress (We spawn only a single process at a time to rate-limit
                         * the zone memory bloat.). If this happens, the test eventually times out. So if a child is jetsammed for some
                         * reason other than zone-map-exhaustion, end the test early.
                         *
                         * This typically happens when we end up triggering vm-pageshortage jetsams before zone-map-exhaustion jetsams.
                         * Lowering the zone_map_jetsam_limit if the zone map size was initially low should help with this too.
                         * See sysctlbyname("kern.zone_map_jetsam_limit"...) in run_test() below.
                         */
                        pthread_mutex_lock(&test_mtx);
                        for (i = 0; i < num_children; i++) {
                                if (child_pids[i] == (pid_t)event->arg1) {
                                        begin_test_teardown();
                                        T_PASS("Child pid %d was jetsammed due to reason %d. Terminating early.",
                                        (int)event->arg1, (int)event->arg2);
                                }
                        }
                        pthread_mutex_unlock(&test_mtx);
                }
        });
        T_QUIET; T_ASSERT_POSIX_ZERO(ret, "ktrace_events_single");

        ret = ktrace_start(session, dispatch_get_main_queue());
        T_QUIET; T_ASSERT_POSIX_ZERO(ret, "ktrace_start");
}

static int
query_zone_map_size(void)
{
        int ret;
        uint64_t zstats[2];
        size_t zstats_size = sizeof(zstats);

        ret = sysctlbyname("kern.zone_map_size_and_capacity", &zstats, &zstats_size, NULL, 0);
        T_QUIET; T_ASSERT_POSIX_SUCCESS(ret, "sysctl kern.zone_map_size_and_capacity failed");

        T_LOG("Zone map capacity: %-30lldZone map size: %lld [%lld%% full]", zstats[1], zstats[0], (zstats[0] * 100) / zstats[1]);

#if (TARGET_OS_IPHONE && !TARGET_OS_SIMULATOR)
        int memstat_level;
        size_t memstat_level_size = sizeof(memstat_level);
        ret = sysctlbyname("kern.memorystatus_level", &memstat_level, &memstat_level_size, NULL, 0);
        T_QUIET; T_ASSERT_POSIX_SUCCESS(ret, "sysctl kern.memorystatus_level failed");

        T_LOG("kern.memorystatus_level = %d%%", memstat_level);
#endif
        return (int)(zstats[0] * 100 / zstats[1]);
}

static void
spawn_child_process(void)
{
        pid_t pid = -1;
        char helper_func[50];
        char *launch_tool_args[4];

        pthread_mutex_lock(&test_mtx);
        if (!test_ending) {
                if (num_children == MAX_CHILD_PROCS) {
                        pthread_mutex_unlock(&test_mtx);
                        T_ASSERT_FAIL("Spawned too many children. Aborting test");
                        /* not reached */
                }

                strlcpy(helper_func, current_test.helper_func, sizeof(helper_func));
                launch_tool_args[0] = testpath;
                launch_tool_args[1] = "-n";
                launch_tool_args[2] = helper_func;
                launch_tool_args[3] = NULL;

                /* Spawn the child process */
                int rc = dt_launch_tool(&pid, launch_tool_args, false, NULL, NULL);
                if (rc != 0) {
                        T_LOG("dt_launch tool returned %d with error code %d", rc, errno);
                }
                T_QUIET; T_ASSERT_POSIX_SUCCESS(pid, "dt_launch_tool");

                child_pids[num_children++] = pid;
        }
        pthread_mutex_unlock(&test_mtx);
}

static void
run_test(void)
{
        uint64_t mem;
        uint32_t testpath_buf_size, pages;
        int ret, dev, pgsz, initial_zone_occupancy, old_limit, new_limit = 0;
        size_t sysctl_size;

        T_ATEND(cleanup_and_end_test);
        T_SETUPBEGIN;

        main_start = time(NULL);
        dev = 0;
        sysctl_size = sizeof(dev);
        ret = sysctlbyname("kern.development", &dev, &sysctl_size, NULL, 0);
        T_QUIET; T_ASSERT_POSIX_SUCCESS(ret, "sysctl kern.development failed");
        if (dev == 0) {
                T_SKIP("Skipping test on release kernel");
        }

        testpath_buf_size = sizeof(testpath);
        ret = _NSGetExecutablePath(testpath, &testpath_buf_size);
        T_QUIET; T_ASSERT_POSIX_ZERO(ret, "_NSGetExecutablePath");
        T_LOG("Executable path: %s", testpath);

        sysctl_size = sizeof(mem);
        ret = sysctlbyname("hw.memsize", &mem, &sysctl_size, NULL, 0);
        T_QUIET; T_ASSERT_POSIX_SUCCESS(ret, "sysctl hw.memsize failed");
        T_LOG("hw.memsize: %llu", mem);

        sysctl_size = sizeof(pgsz);
        ret = sysctlbyname("vm.pagesize", &pgsz, &sysctl_size, NULL, 0);
        T_QUIET; T_ASSERT_POSIX_SUCCESS(ret, "sysctl vm.pagesize failed");
        T_LOG("vm.pagesize: %d", pgsz);

        sysctl_size = sizeof(pages);
        ret = sysctlbyname("vm.pages", &pages, &sysctl_size, NULL, 0);
        T_QUIET; T_ASSERT_POSIX_SUCCESS(ret, "sysctl vm.pages failed");
        T_LOG("vm.pages: %d", pages);

        sysctl_size = sizeof(old_limit);
        ret = sysctlbyname("kern.zone_map_jetsam_limit", &old_limit, &sysctl_size, NULL, 0);
        T_QUIET; T_ASSERT_POSIX_SUCCESS(ret, "sysctl kern.zone_map_jetsam_limit failed");
        T_LOG("kern.zone_map_jetsam_limit: %d", old_limit);

        initial_zone_occupancy = query_zone_map_size();

        /* On large memory systems, set the zone maps jetsam limit lower so we can hit it without timing out. */
        if (mem > (uint64_t)LARGE_MEM_GB * 1024 * 1024 * 1024) {
                new_limit = LARGE_MEM_JETSAM_LIMIT;
        }

        /*
         * If we start out with the zone map < 5% full, aim for 10% as the limit, so we don't time out.
         * For anything else aim for 2x the initial size, capped by whatever value was set by T_META_SYSCTL_INT,
         * or LARGE_MEM_JETSAM_LIMIT for large memory systems.
         */
        if (initial_zone_occupancy < 5) {
                new_limit = JETSAM_LIMIT_LOWEST;
        } else {
                new_limit = initial_zone_occupancy * 2;
        }

        if (new_limit > 0 && new_limit < old_limit) {
                /*
                 * We should be fine messing with the zone_map_jetsam_limit here, i.e. outside of T_META_SYSCTL_INT.
                 * When the test ends, T_META_SYSCTL_INT will restore the zone_map_jetsam_limit to what it was
                 * before the test anyway.
                 */
                ret = sysctlbyname("kern.zone_map_jetsam_limit", NULL, NULL, &new_limit, sizeof(new_limit));
                T_QUIET; T_ASSERT_POSIX_SUCCESS(ret, "sysctl kern.zone_map_jetsam_limit failed");
                T_LOG("kern.zone_map_jetsam_limit set to %d%%", new_limit);
        }

        zone_info_array = (mach_zone_info_array_t) calloc((unsigned long)current_test.num_zones, sizeof *zone_info_array);

        /*
         * If the timeout specified by T_META_TIMEOUT is hit, the atend handler does not get called.
         * So we're queueing a dispatch block to fire after TIMEOUT_SECS seconds, so we can exit cleanly.
         */
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, TIMEOUT_SECS * NSEC_PER_SEC), dispatch_get_main_queue(), ^{
                T_ASSERT_FAIL("Timed out after %d seconds", TIMEOUT_SECS);
        });

        /*
         * Create a dispatch source for the signal SIGUSR1. When a child is done allocating zone memory, it
         * sends SIGUSR1 to the parent. Only then does the parent spawn another child. This prevents us from
         * spawning many children at once and creating a lot of memory pressure.
         */
        signal(SIGUSR1, SIG_IGN);
        dq_spawn = dispatch_queue_create("spawn_queue", DISPATCH_QUEUE_SERIAL);
        ds_signal = dispatch_source_create(DISPATCH_SOURCE_TYPE_SIGNAL, SIGUSR1, 0, dq_spawn);
        T_QUIET; T_ASSERT_NOTNULL(ds_signal, "dispatch_source_create: signal");

        dispatch_source_set_event_handler(ds_signal, ^{
                (void)query_zone_map_size();

                /* Wait a few seconds before spawning another child. Keeps us from allocating too aggressively */
                sleep(5);
                spawn_child_process();
        });
        dispatch_activate(ds_signal);

        /* Timer to query jetsam-relevant zone info every second. Print it every 5 seconds. */
        ds_timer = dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER, 0, 0, dispatch_queue_create("timer_queue", NULL));
        T_QUIET; T_ASSERT_NOTNULL(ds_timer, "dispatch_source_create: timer");
        dispatch_source_set_timer(ds_timer, dispatch_time(DISPATCH_TIME_NOW, NSEC_PER_SEC), NSEC_PER_SEC, 0);

        dispatch_source_set_event_handler(ds_timer, ^{
                query_zone_info();
        });
        dispatch_activate(ds_timer);

        /* Set up a ktrace session to listen for jetsam events */
        setup_ktrace_session();

        T_SETUPEND;

        /* Spawn the first child process */
        T_LOG("Spawning child processes to allocate zone memory...\n\n");
        spawn_child_process();

        dispatch_main();
}

static void
move_to_idle_band(void)
{
        memorystatus_priority_properties_t props;

        /*
         * We want to move the processes we spawn into the idle band, so that jetsam can target them first.
         * This prevents other important BATS tasks from getting killed, specially in LTE where we have very few
         * processes running.
         *
         * This is only needed for tests which (are likely to) lead us down the generic jetsam path.
         */
        props.priority = JETSAM_PRIORITY_IDLE;
        props.user_data = 0;

        if (memorystatus_control(MEMORYSTATUS_CMD_SET_PRIORITY_PROPERTIES, getpid(), 0, &props, sizeof(props))) {
                printf("memorystatus call to change jetsam priority failed\n");
                exit(-1);
        }
}

T_HELPER_DECL(allocate_vm_regions, "allocates VM regions")
{
        move_to_idle_band();
        allocate_vm_stuff(REGIONS);
}

T_HELPER_DECL(allocate_vm_objects, "allocates VM objects and VM regions")
{
        move_to_idle_band();
        allocate_vm_stuff(OBJECTS);
}

T_HELPER_DECL(allocate_from_generic_zone, "allocates from a generic zone")
{
        move_to_idle_band();
        allocate_from_generic_zone();
}

/*
 * T_META_SYSCTL_INT(ZONEMAP_JETSAM_LIMIT_SYSCTL) changes the zone_map_jetsam_limit to a
 * lower value, so that the test can complete faster.
 * The test allocates zone memory pretty aggressively which can cause the system to panic
 * if the jetsam limit is quite high; a lower value keeps us from panicking.
 */
T_DECL( memorystatus_vme_zone_test,
    "allocates elements from the VM map entries zone, verifies zone-map-exhaustion jetsams",
    T_META_ASROOT(true),
    T_META_TIMEOUT(1800),
/*              T_META_LTEPHASE(LTE_POSTINIT),
 */
    T_META_SYSCTL_INT(ZONEMAP_JETSAM_LIMIT_SYSCTL))
{
        current_test = (test_config_struct) {
                .test_index = VME_ZONE_TEST,
                .helper_func = VME_ZONE_TEST_OPT,
                .num_zones = 1,
                .zone_names = (mach_zone_name_t[]){
                        { .mzn_name = VME_ZONE }
                }
        };
        run_test();
}

T_DECL( memorystatus_vm_objects_zone_test,
    "allocates elements from the VM objects and the VM map entries zones, verifies zone-map-exhaustion jetsams",
    T_META_ASROOT(true),
    T_META_TIMEOUT(1800),
/*              T_META_LTEPHASE(LTE_POSTINIT),
 */
    T_META_SYSCTL_INT(ZONEMAP_JETSAM_LIMIT_SYSCTL))
{
        current_test = (test_config_struct) {
                .test_index = VM_OBJECTS_ZONE_TEST,
                .helper_func = VM_OBJECTS_ZONE_TEST_OPT,
                .num_zones = 2,
                .zone_names = (mach_zone_name_t[]){
                        { .mzn_name = VME_ZONE },
                        { .mzn_name = VMOBJECTS_ZONE}
                }
        };
        run_test();
}

T_DECL( memorystatus_generic_zone_test,
    "allocates elements from a zone that doesn't have an optimized jetsam path, verifies zone-map-exhaustion jetsams",
    T_META_ASROOT(true),
    T_META_TIMEOUT(1800),
/*              T_META_LTEPHASE(LTE_POSTINIT),
 */
    T_META_SYSCTL_INT(ZONEMAP_JETSAM_LIMIT_SYSCTL))
{
        current_test = (test_config_struct) {
                .test_index = GENERIC_ZONE_TEST,
                .helper_func = GENERIC_ZONE_TEST_OPT,
                .num_zones = 0,
                .zone_names = NULL
        };
        run_test();
}