Adding upstream version 5:7.0.15.upstream/5%7.0.15upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 939 insertions, 0 deletions

diff --git a/deps/jemalloc/src/background_thread.c b/deps/jemalloc/src/background_thread.c
new file mode 100644
index 0000000..57b9b25
--- /dev/null
+++ b/deps/jemalloc/src/background_thread.c
@@ -0,0 +1,939 @@
+#define JEMALLOC_BACKGROUND_THREAD_C_
+#include "jemalloc/internal/jemalloc_preamble.h"
+#include "jemalloc/internal/jemalloc_internal_includes.h"
+
+#include "jemalloc/internal/assert.h"
+
+JEMALLOC_DIAGNOSTIC_DISABLE_SPURIOUS
+
+/******************************************************************************/
+/* Data. */
+
+/* This option should be opt-in only. */
+#define BACKGROUND_THREAD_DEFAULT false
+/* Read-only after initialization. */
+bool opt_background_thread = BACKGROUND_THREAD_DEFAULT;
+size_t opt_max_background_threads = MAX_BACKGROUND_THREAD_LIMIT + 1;
+
+/* Used for thread creation, termination and stats. */
+malloc_mutex_t background_thread_lock;
+/* Indicates global state.  Atomic because decay reads this w/o locking. */
+atomic_b_t background_thread_enabled_state;
+size_t n_background_threads;
+size_t max_background_threads;
+/* Thread info per-index. */
+background_thread_info_t *background_thread_info;
+
+/******************************************************************************/
+
+#ifdef JEMALLOC_PTHREAD_CREATE_WRAPPER
+
+static int (*pthread_create_fptr)(pthread_t *__restrict, const pthread_attr_t *,
+    void *(*)(void *), void *__restrict);
+
+static void
+pthread_create_wrapper_init(void) {
+#ifdef JEMALLOC_LAZY_LOCK
+	if (!isthreaded) {
+		isthreaded = true;
+	}
+#endif
+}
+
+int
+pthread_create_wrapper(pthread_t *__restrict thread, const pthread_attr_t *attr,
+    void *(*start_routine)(void *), void *__restrict arg) {
+	pthread_create_wrapper_init();
+
+	return pthread_create_fptr(thread, attr, start_routine, arg);
+}
+#endif /* JEMALLOC_PTHREAD_CREATE_WRAPPER */
+
+#ifndef JEMALLOC_BACKGROUND_THREAD
+#define NOT_REACHED { not_reached(); }
+bool background_thread_create(tsd_t *tsd, unsigned arena_ind) NOT_REACHED
+bool background_threads_enable(tsd_t *tsd) NOT_REACHED
+bool background_threads_disable(tsd_t *tsd) NOT_REACHED
+void background_thread_interval_check(tsdn_t *tsdn, arena_t *arena,
+    arena_decay_t *decay, size_t npages_new) NOT_REACHED
+void background_thread_prefork0(tsdn_t *tsdn) NOT_REACHED
+void background_thread_prefork1(tsdn_t *tsdn) NOT_REACHED
+void background_thread_postfork_parent(tsdn_t *tsdn) NOT_REACHED
+void background_thread_postfork_child(tsdn_t *tsdn) NOT_REACHED
+bool background_thread_stats_read(tsdn_t *tsdn,
+    background_thread_stats_t *stats) NOT_REACHED
+void background_thread_ctl_init(tsdn_t *tsdn) NOT_REACHED
+#undef NOT_REACHED
+#else
+
+static bool background_thread_enabled_at_fork;
+
+static void
+background_thread_info_init(tsdn_t *tsdn, background_thread_info_t *info) {
+	background_thread_wakeup_time_set(tsdn, info, 0);
+	info->npages_to_purge_new = 0;
+	if (config_stats) {
+		info->tot_n_runs = 0;
+		nstime_init(&info->tot_sleep_time, 0);
+	}
+}
+
+static inline bool
+set_current_thread_affinity(int cpu) {
+#if defined(JEMALLOC_HAVE_SCHED_SETAFFINITY)
+	cpu_set_t cpuset;
+	CPU_ZERO(&cpuset);
+	CPU_SET(cpu, &cpuset);
+	int ret = sched_setaffinity(0, sizeof(cpu_set_t), &cpuset);
+
+	return (ret != 0);
+#else
+	return false;
+#endif
+}
+
+/* Threshold for determining when to wake up the background thread. */
+#define BACKGROUND_THREAD_NPAGES_THRESHOLD UINT64_C(1024)
+#define BILLION UINT64_C(1000000000)
+/* Minimal sleep interval 100 ms. */
+#define BACKGROUND_THREAD_MIN_INTERVAL_NS (BILLION / 10)
+
+static inline size_t
+decay_npurge_after_interval(arena_decay_t *decay, size_t interval) {
+	size_t i;
+	uint64_t sum = 0;
+	for (i = 0; i < interval; i++) {
+		sum += decay->backlog[i] * h_steps[i];
+	}
+	for (; i < SMOOTHSTEP_NSTEPS; i++) {
+		sum += decay->backlog[i] * (h_steps[i] - h_steps[i - interval]);
+	}
+
+	return (size_t)(sum >> SMOOTHSTEP_BFP);
+}
+
+static uint64_t
+arena_decay_compute_purge_interval_impl(tsdn_t *tsdn, arena_decay_t *decay,
+    extents_t *extents) {
+	if (malloc_mutex_trylock(tsdn, &decay->mtx)) {
+		/* Use minimal interval if decay is contended. */
+		return BACKGROUND_THREAD_MIN_INTERVAL_NS;
+	}
+
+	uint64_t interval;
+	ssize_t decay_time = atomic_load_zd(&decay->time_ms, ATOMIC_RELAXED);
+	if (decay_time <= 0) {
+		/* Purging is eagerly done or disabled currently. */
+		interval = BACKGROUND_THREAD_INDEFINITE_SLEEP;
+		goto label_done;
+	}
+
+	uint64_t decay_interval_ns = nstime_ns(&decay->interval);
+	assert(decay_interval_ns > 0);
+	size_t npages = extents_npages_get(extents);
+	if (npages == 0) {
+		unsigned i;
+		for (i = 0; i < SMOOTHSTEP_NSTEPS; i++) {
+			if (decay->backlog[i] > 0) {
+				break;
+			}
+		}
+		if (i == SMOOTHSTEP_NSTEPS) {
+			/* No dirty pages recorded.  Sleep indefinitely. */
+			interval = BACKGROUND_THREAD_INDEFINITE_SLEEP;
+			goto label_done;
+		}
+	}
+	if (npages <= BACKGROUND_THREAD_NPAGES_THRESHOLD) {
+		/* Use max interval. */
+		interval = decay_interval_ns * SMOOTHSTEP_NSTEPS;
+		goto label_done;
+	}
+
+	size_t lb = BACKGROUND_THREAD_MIN_INTERVAL_NS / decay_interval_ns;
+	size_t ub = SMOOTHSTEP_NSTEPS;
+	/* Minimal 2 intervals to ensure reaching next epoch deadline. */
+	lb = (lb < 2) ? 2 : lb;
+	if ((decay_interval_ns * ub <= BACKGROUND_THREAD_MIN_INTERVAL_NS) ||
+	    (lb + 2 > ub)) {
+		interval = BACKGROUND_THREAD_MIN_INTERVAL_NS;
+		goto label_done;
+	}
+
+	assert(lb + 2 <= ub);
+	size_t npurge_lb, npurge_ub;
+	npurge_lb = decay_npurge_after_interval(decay, lb);
+	if (npurge_lb > BACKGROUND_THREAD_NPAGES_THRESHOLD) {
+		interval = decay_interval_ns * lb;
+		goto label_done;
+	}
+	npurge_ub = decay_npurge_after_interval(decay, ub);
+	if (npurge_ub < BACKGROUND_THREAD_NPAGES_THRESHOLD) {
+		interval = decay_interval_ns * ub;
+		goto label_done;
+	}
+
+	unsigned n_search = 0;
+	size_t target, npurge;
+	while ((npurge_lb + BACKGROUND_THREAD_NPAGES_THRESHOLD < npurge_ub)
+	    && (lb + 2 < ub)) {
+		target = (lb + ub) / 2;
+		npurge = decay_npurge_after_interval(decay, target);
+		if (npurge > BACKGROUND_THREAD_NPAGES_THRESHOLD) {
+			ub = target;
+			npurge_ub = npurge;
+		} else {
+			lb = target;
+			npurge_lb = npurge;
+		}
+		assert(n_search++ < lg_floor(SMOOTHSTEP_NSTEPS) + 1);
+	}
+	interval = decay_interval_ns * (ub + lb) / 2;
+label_done:
+	interval = (interval < BACKGROUND_THREAD_MIN_INTERVAL_NS) ?
+	    BACKGROUND_THREAD_MIN_INTERVAL_NS : interval;
+	malloc_mutex_unlock(tsdn, &decay->mtx);
+
+	return interval;
+}
+
+/* Compute purge interval for background threads. */
+static uint64_t
+arena_decay_compute_purge_interval(tsdn_t *tsdn, arena_t *arena) {
+	uint64_t i1, i2;
+	i1 = arena_decay_compute_purge_interval_impl(tsdn, &arena->decay_dirty,
+	    &arena->extents_dirty);
+	if (i1 == BACKGROUND_THREAD_MIN_INTERVAL_NS) {
+		return i1;
+	}
+	i2 = arena_decay_compute_purge_interval_impl(tsdn, &arena->decay_muzzy,
+	    &arena->extents_muzzy);
+
+	return i1 < i2 ? i1 : i2;
+}
+
+static void
+background_thread_sleep(tsdn_t *tsdn, background_thread_info_t *info,
+    uint64_t interval) {
+	if (config_stats) {
+		info->tot_n_runs++;
+	}
+	info->npages_to_purge_new = 0;
+
+	struct timeval tv;
+	/* Specific clock required by timedwait. */
+	gettimeofday(&tv, NULL);
+	nstime_t before_sleep;
+	nstime_init2(&before_sleep, tv.tv_sec, tv.tv_usec * 1000);
+
+	int ret;
+	if (interval == BACKGROUND_THREAD_INDEFINITE_SLEEP) {
+		assert(background_thread_indefinite_sleep(info));
+		ret = pthread_cond_wait(&info->cond, &info->mtx.lock);
+		assert(ret == 0);
+	} else {
+		assert(interval >= BACKGROUND_THREAD_MIN_INTERVAL_NS &&
+		    interval <= BACKGROUND_THREAD_INDEFINITE_SLEEP);
+		/* We need malloc clock (can be different from tv). */
+		nstime_t next_wakeup;
+		nstime_init(&next_wakeup, 0);
+		nstime_update(&next_wakeup);
+		nstime_iadd(&next_wakeup, interval);
+		assert(nstime_ns(&next_wakeup) <
+		    BACKGROUND_THREAD_INDEFINITE_SLEEP);
+		background_thread_wakeup_time_set(tsdn, info,
+		    nstime_ns(&next_wakeup));
+
+		nstime_t ts_wakeup;
+		nstime_copy(&ts_wakeup, &before_sleep);
+		nstime_iadd(&ts_wakeup, interval);
+		struct timespec ts;
+		ts.tv_sec = (size_t)nstime_sec(&ts_wakeup);
+		ts.tv_nsec = (size_t)nstime_nsec(&ts_wakeup);
+
+		assert(!background_thread_indefinite_sleep(info));
+		ret = pthread_cond_timedwait(&info->cond, &info->mtx.lock, &ts);
+		assert(ret == ETIMEDOUT || ret == 0);
+		background_thread_wakeup_time_set(tsdn, info,
+		    BACKGROUND_THREAD_INDEFINITE_SLEEP);
+	}
+	if (config_stats) {
+		gettimeofday(&tv, NULL);
+		nstime_t after_sleep;
+		nstime_init2(&after_sleep, tv.tv_sec, tv.tv_usec * 1000);
+		if (nstime_compare(&after_sleep, &before_sleep) > 0) {
+			nstime_subtract(&after_sleep, &before_sleep);
+			nstime_add(&info->tot_sleep_time, &after_sleep);
+		}
+	}
+}
+
+static bool
+background_thread_pause_check(tsdn_t *tsdn, background_thread_info_t *info) {
+	if (unlikely(info->state == background_thread_paused)) {
+		malloc_mutex_unlock(tsdn, &info->mtx);
+		/* Wait on global lock to update status. */
+		malloc_mutex_lock(tsdn, &background_thread_lock);
+		malloc_mutex_unlock(tsdn, &background_thread_lock);
+		malloc_mutex_lock(tsdn, &info->mtx);
+		return true;
+	}
+
+	return false;
+}
+
+static inline void
+background_work_sleep_once(tsdn_t *tsdn, background_thread_info_t *info, unsigned ind) {
+	uint64_t min_interval = BACKGROUND_THREAD_INDEFINITE_SLEEP;
+	unsigned narenas = narenas_total_get();
+
+	for (unsigned i = ind; i < narenas; i += max_background_threads) {
+		arena_t *arena = arena_get(tsdn, i, false);
+		if (!arena) {
+			continue;
+		}
+		arena_decay(tsdn, arena, true, false);
+		if (min_interval == BACKGROUND_THREAD_MIN_INTERVAL_NS) {
+			/* Min interval will be used. */
+			continue;
+		}
+		uint64_t interval = arena_decay_compute_purge_interval(tsdn,
+		    arena);
+		assert(interval >= BACKGROUND_THREAD_MIN_INTERVAL_NS);
+		if (min_interval > interval) {
+			min_interval = interval;
+		}
+	}
+	background_thread_sleep(tsdn, info, min_interval);
+}
+
+static bool
+background_threads_disable_single(tsd_t *tsd, background_thread_info_t *info) {
+	if (info == &background_thread_info[0]) {
+		malloc_mutex_assert_owner(tsd_tsdn(tsd),
+		    &background_thread_lock);
+	} else {
+		malloc_mutex_assert_not_owner(tsd_tsdn(tsd),
+		    &background_thread_lock);
+	}
+
+	pre_reentrancy(tsd, NULL);
+	malloc_mutex_lock(tsd_tsdn(tsd), &info->mtx);
+	bool has_thread;
+	assert(info->state != background_thread_paused);
+	if (info->state == background_thread_started) {
+		has_thread = true;
+		info->state = background_thread_stopped;
+		pthread_cond_signal(&info->cond);
+	} else {
+		has_thread = false;
+	}
+	malloc_mutex_unlock(tsd_tsdn(tsd), &info->mtx);
+
+	if (!has_thread) {
+		post_reentrancy(tsd);
+		return false;
+	}
+	void *ret;
+	if (pthread_join(info->thread, &ret)) {
+		post_reentrancy(tsd);
+		return true;
+	}
+	assert(ret == NULL);
+	n_background_threads--;
+	post_reentrancy(tsd);
+
+	return false;
+}
+
+static void *background_thread_entry(void *ind_arg);
+
+static int
+background_thread_create_signals_masked(pthread_t *thread,
+    const pthread_attr_t *attr, void *(*start_routine)(void *), void *arg) {
+	/*
+	 * Mask signals during thread creation so that the thread inherits
+	 * an empty signal set.
+	 */
+	sigset_t set;
+	sigfillset(&set);
+	sigset_t oldset;
+	int mask_err = pthread_sigmask(SIG_SETMASK, &set, &oldset);
+	if (mask_err != 0) {
+		return mask_err;
+	}
+	int create_err = pthread_create_wrapper(thread, attr, start_routine,
+	    arg);
+	/*
+	 * Restore the signal mask.  Failure to restore the signal mask here
+	 * changes program behavior.
+	 */
+	int restore_err = pthread_sigmask(SIG_SETMASK, &oldset, NULL);
+	if (restore_err != 0) {
+		malloc_printf("<jemalloc>: background thread creation "
+		    "failed (%d), and signal mask restoration failed "
+		    "(%d)\n", create_err, restore_err);
+		if (opt_abort) {
+			abort();
+		}
+	}
+	return create_err;
+}
+
+static bool
+check_background_thread_creation(tsd_t *tsd, unsigned *n_created,
+    bool *created_threads) {
+	bool ret = false;
+	if (likely(*n_created == n_background_threads)) {
+		return ret;
+	}
+
+	tsdn_t *tsdn = tsd_tsdn(tsd);
+	malloc_mutex_unlock(tsdn, &background_thread_info[0].mtx);
+	for (unsigned i = 1; i < max_background_threads; i++) {
+		if (created_threads[i]) {
+			continue;
+		}
+		background_thread_info_t *info = &background_thread_info[i];
+		malloc_mutex_lock(tsdn, &info->mtx);
+		/*
+		 * In case of the background_thread_paused state because of
+		 * arena reset, delay the creation.
+		 */
+		bool create = (info->state == background_thread_started);
+		malloc_mutex_unlock(tsdn, &info->mtx);
+		if (!create) {
+			continue;
+		}
+
+		pre_reentrancy(tsd, NULL);
+		int err = background_thread_create_signals_masked(&info->thread,
+		    NULL, background_thread_entry, (void *)(uintptr_t)i);
+		post_reentrancy(tsd);
+
+		if (err == 0) {
+			(*n_created)++;
+			created_threads[i] = true;
+		} else {
+			malloc_printf("<jemalloc>: background thread "
+			    "creation failed (%d)\n", err);
+			if (opt_abort) {
+				abort();
+			}
+		}
+		/* Return to restart the loop since we unlocked. */
+		ret = true;
+		break;
+	}
+	malloc_mutex_lock(tsdn, &background_thread_info[0].mtx);
+
+	return ret;
+}
+
+static void
+background_thread0_work(tsd_t *tsd) {
+	/* Thread0 is also responsible for launching / terminating threads. */
+	VARIABLE_ARRAY(bool, created_threads, max_background_threads);
+	unsigned i;
+	for (i = 1; i < max_background_threads; i++) {
+		created_threads[i] = false;
+	}
+	/* Start working, and create more threads when asked. */
+	unsigned n_created = 1;
+	while (background_thread_info[0].state != background_thread_stopped) {
+		if (background_thread_pause_check(tsd_tsdn(tsd),
+		    &background_thread_info[0])) {
+			continue;
+		}
+		if (check_background_thread_creation(tsd, &n_created,
+		    (bool *)&created_threads)) {
+			continue;
+		}
+		background_work_sleep_once(tsd_tsdn(tsd),
+		    &background_thread_info[0], 0);
+	}
+
+	/*
+	 * Shut down other threads at exit.  Note that the ctl thread is holding
+	 * the global background_thread mutex (and is waiting) for us.
+	 */
+	assert(!background_thread_enabled());
+	for (i = 1; i < max_background_threads; i++) {
+		background_thread_info_t *info = &background_thread_info[i];
+		assert(info->state != background_thread_paused);
+		if (created_threads[i]) {
+			background_threads_disable_single(tsd, info);
+		} else {
+			malloc_mutex_lock(tsd_tsdn(tsd), &info->mtx);
+			if (info->state != background_thread_stopped) {
+				/* The thread was not created. */
+				assert(info->state ==
+				    background_thread_started);
+				n_background_threads--;
+				info->state = background_thread_stopped;
+			}
+			malloc_mutex_unlock(tsd_tsdn(tsd), &info->mtx);
+		}
+	}
+	background_thread_info[0].state = background_thread_stopped;
+	assert(n_background_threads == 1);
+}
+
+static void
+background_work(tsd_t *tsd, unsigned ind) {
+	background_thread_info_t *info = &background_thread_info[ind];
+
+	malloc_mutex_lock(tsd_tsdn(tsd), &info->mtx);
+	background_thread_wakeup_time_set(tsd_tsdn(tsd), info,
+	    BACKGROUND_THREAD_INDEFINITE_SLEEP);
+	if (ind == 0) {
+		background_thread0_work(tsd);
+	} else {
+		while (info->state != background_thread_stopped) {
+			if (background_thread_pause_check(tsd_tsdn(tsd),
+			    info)) {
+				continue;
+			}
+			background_work_sleep_once(tsd_tsdn(tsd), info, ind);
+		}
+	}
+	assert(info->state == background_thread_stopped);
+	background_thread_wakeup_time_set(tsd_tsdn(tsd), info, 0);
+	malloc_mutex_unlock(tsd_tsdn(tsd), &info->mtx);
+}
+
+static void *
+background_thread_entry(void *ind_arg) {
+	unsigned thread_ind = (unsigned)(uintptr_t)ind_arg;
+	assert(thread_ind < max_background_threads);
+#ifdef JEMALLOC_HAVE_PTHREAD_SETNAME_NP
+	pthread_setname_np(pthread_self(), "jemalloc_bg_thd");
+#elif defined(__FreeBSD__)
+	pthread_set_name_np(pthread_self(), "jemalloc_bg_thd");
+#endif
+	if (opt_percpu_arena != percpu_arena_disabled) {
+		set_current_thread_affinity((int)thread_ind);
+	}
+	/*
+	 * Start periodic background work.  We use internal tsd which avoids
+	 * side effects, for example triggering new arena creation (which in
+	 * turn triggers another background thread creation).
+	 */
+	background_work(tsd_internal_fetch(), thread_ind);
+	assert(pthread_equal(pthread_self(),
+	    background_thread_info[thread_ind].thread));
+
+	return NULL;
+}
+
+static void
+background_thread_init(tsd_t *tsd, background_thread_info_t *info) {
+	malloc_mutex_assert_owner(tsd_tsdn(tsd), &background_thread_lock);
+	info->state = background_thread_started;
+	background_thread_info_init(tsd_tsdn(tsd), info);
+	n_background_threads++;
+}
+
+static bool
+background_thread_create_locked(tsd_t *tsd, unsigned arena_ind) {
+	assert(have_background_thread);
+	malloc_mutex_assert_owner(tsd_tsdn(tsd), &background_thread_lock);
+
+	/* We create at most NCPUs threads. */
+	size_t thread_ind = arena_ind % max_background_threads;
+	background_thread_info_t *info = &background_thread_info[thread_ind];
+
+	bool need_new_thread;
+	malloc_mutex_lock(tsd_tsdn(tsd), &info->mtx);
+	need_new_thread = background_thread_enabled() &&
+	    (info->state == background_thread_stopped);
+	if (need_new_thread) {
+		background_thread_init(tsd, info);
+	}
+	malloc_mutex_unlock(tsd_tsdn(tsd), &info->mtx);
+	if (!need_new_thread) {
+		return false;
+	}
+	if (arena_ind != 0) {
+		/* Threads are created asynchronously by Thread 0. */
+		background_thread_info_t *t0 = &background_thread_info[0];
+		malloc_mutex_lock(tsd_tsdn(tsd), &t0->mtx);
+		assert(t0->state == background_thread_started);
+		pthread_cond_signal(&t0->cond);
+		malloc_mutex_unlock(tsd_tsdn(tsd), &t0->mtx);
+
+		return false;
+	}
+
+	pre_reentrancy(tsd, NULL);
+	/*
+	 * To avoid complications (besides reentrancy), create internal
+	 * background threads with the underlying pthread_create.
+	 */
+	int err = background_thread_create_signals_masked(&info->thread, NULL,
+	    background_thread_entry, (void *)thread_ind);
+	post_reentrancy(tsd);
+
+	if (err != 0) {
+		malloc_printf("<jemalloc>: arena 0 background thread creation "
+		    "failed (%d)\n", err);
+		malloc_mutex_lock(tsd_tsdn(tsd), &info->mtx);
+		info->state = background_thread_stopped;
+		n_background_threads--;
+		malloc_mutex_unlock(tsd_tsdn(tsd), &info->mtx);
+
+		return true;
+	}
+
+	return false;
+}
+
+/* Create a new background thread if needed. */
+bool
+background_thread_create(tsd_t *tsd, unsigned arena_ind) {
+	assert(have_background_thread);
+
+	bool ret;
+	malloc_mutex_lock(tsd_tsdn(tsd), &background_thread_lock);
+	ret = background_thread_create_locked(tsd, arena_ind);
+	malloc_mutex_unlock(tsd_tsdn(tsd), &background_thread_lock);
+
+	return ret;
+}
+
+bool
+background_threads_enable(tsd_t *tsd) {
+	assert(n_background_threads == 0);
+	assert(background_thread_enabled());
+	malloc_mutex_assert_owner(tsd_tsdn(tsd), &background_thread_lock);
+
+	VARIABLE_ARRAY(bool, marked, max_background_threads);
+	unsigned i, nmarked;
+	for (i = 0; i < max_background_threads; i++) {
+		marked[i] = false;
+	}
+	nmarked = 0;
+	/* Thread 0 is required and created at the end. */
+	marked[0] = true;
+	/* Mark the threads we need to create for thread 0. */
+	unsigned n = narenas_total_get();
+	for (i = 1; i < n; i++) {
+		if (marked[i % max_background_threads] ||
+		    arena_get(tsd_tsdn(tsd), i, false) == NULL) {
+			continue;
+		}
+		background_thread_info_t *info = &background_thread_info[
+		    i % max_background_threads];
+		malloc_mutex_lock(tsd_tsdn(tsd), &info->mtx);
+		assert(info->state == background_thread_stopped);
+		background_thread_init(tsd, info);
+		malloc_mutex_unlock(tsd_tsdn(tsd), &info->mtx);
+		marked[i % max_background_threads] = true;
+		if (++nmarked == max_background_threads) {
+			break;
+		}
+	}
+
+	return background_thread_create_locked(tsd, 0);
+}
+
+bool
+background_threads_disable(tsd_t *tsd) {
+	assert(!background_thread_enabled());
+	malloc_mutex_assert_owner(tsd_tsdn(tsd), &background_thread_lock);
+
+	/* Thread 0 will be responsible for terminating other threads. */
+	if (background_threads_disable_single(tsd,
+	    &background_thread_info[0])) {
+		return true;
+	}
+	assert(n_background_threads == 0);
+
+	return false;
+}
+
+/* Check if we need to signal the background thread early. */
+void
+background_thread_interval_check(tsdn_t *tsdn, arena_t *arena,
+    arena_decay_t *decay, size_t npages_new) {
+	background_thread_info_t *info = arena_background_thread_info_get(
+	    arena);
+	if (malloc_mutex_trylock(tsdn, &info->mtx)) {
+		/*
+		 * Background thread may hold the mutex for a long period of
+		 * time.  We'd like to avoid the variance on application
+		 * threads.  So keep this non-blocking, and leave the work to a
+		 * future epoch.
+		 */
+		return;
+	}
+
+	if (info->state != background_thread_started) {
+		goto label_done;
+	}
+	if (malloc_mutex_trylock(tsdn, &decay->mtx)) {
+		goto label_done;
+	}
+
+	ssize_t decay_time = atomic_load_zd(&decay->time_ms, ATOMIC_RELAXED);
+	if (decay_time <= 0) {
+		/* Purging is eagerly done or disabled currently. */
+		goto label_done_unlock2;
+	}
+	uint64_t decay_interval_ns = nstime_ns(&decay->interval);
+	assert(decay_interval_ns > 0);
+
+	nstime_t diff;
+	nstime_init(&diff, background_thread_wakeup_time_get(info));
+	if (nstime_compare(&diff, &decay->epoch) <= 0) {
+		goto label_done_unlock2;
+	}
+	nstime_subtract(&diff, &decay->epoch);
+	if (nstime_ns(&diff) < BACKGROUND_THREAD_MIN_INTERVAL_NS) {
+		goto label_done_unlock2;
+	}
+
+	if (npages_new > 0) {
+		size_t n_epoch = (size_t)(nstime_ns(&diff) / decay_interval_ns);
+		/*
+		 * Compute how many new pages we would need to purge by the next
+		 * wakeup, which is used to determine if we should signal the
+		 * background thread.
+		 */
+		uint64_t npurge_new;
+		if (n_epoch >= SMOOTHSTEP_NSTEPS) {
+			npurge_new = npages_new;
+		} else {
+			uint64_t h_steps_max = h_steps[SMOOTHSTEP_NSTEPS - 1];
+			assert(h_steps_max >=
+			    h_steps[SMOOTHSTEP_NSTEPS - 1 - n_epoch]);
+			npurge_new = npages_new * (h_steps_max -
+			    h_steps[SMOOTHSTEP_NSTEPS - 1 - n_epoch]);
+			npurge_new >>= SMOOTHSTEP_BFP;
+		}
+		info->npages_to_purge_new += npurge_new;
+	}
+
+	bool should_signal;
+	if (info->npages_to_purge_new > BACKGROUND_THREAD_NPAGES_THRESHOLD) {
+		should_signal = true;
+	} else if (unlikely(background_thread_indefinite_sleep(info)) &&
+	    (extents_npages_get(&arena->extents_dirty) > 0 ||
+	    extents_npages_get(&arena->extents_muzzy) > 0 ||
+	    info->npages_to_purge_new > 0)) {
+		should_signal = true;
+	} else {
+		should_signal = false;
+	}
+
+	if (should_signal) {
+		info->npages_to_purge_new = 0;
+		pthread_cond_signal(&info->cond);
+	}
+label_done_unlock2:
+	malloc_mutex_unlock(tsdn, &decay->mtx);
+label_done:
+	malloc_mutex_unlock(tsdn, &info->mtx);
+}
+
+void
+background_thread_prefork0(tsdn_t *tsdn) {
+	malloc_mutex_prefork(tsdn, &background_thread_lock);
+	background_thread_enabled_at_fork = background_thread_enabled();
+}
+
+void
+background_thread_prefork1(tsdn_t *tsdn) {
+	for (unsigned i = 0; i < max_background_threads; i++) {
+		malloc_mutex_prefork(tsdn, &background_thread_info[i].mtx);
+	}
+}
+
+void
+background_thread_postfork_parent(tsdn_t *tsdn) {
+	for (unsigned i = 0; i < max_background_threads; i++) {
+		malloc_mutex_postfork_parent(tsdn,
+		    &background_thread_info[i].mtx);
+	}
+	malloc_mutex_postfork_parent(tsdn, &background_thread_lock);
+}
+
+void
+background_thread_postfork_child(tsdn_t *tsdn) {
+	for (unsigned i = 0; i < max_background_threads; i++) {
+		malloc_mutex_postfork_child(tsdn,
+		    &background_thread_info[i].mtx);
+	}
+	malloc_mutex_postfork_child(tsdn, &background_thread_lock);
+	if (!background_thread_enabled_at_fork) {
+		return;
+	}
+
+	/* Clear background_thread state (reset to disabled for child). */
+	malloc_mutex_lock(tsdn, &background_thread_lock);
+	n_background_threads = 0;
+	background_thread_enabled_set(tsdn, false);
+	for (unsigned i = 0; i < max_background_threads; i++) {
+		background_thread_info_t *info = &background_thread_info[i];
+		malloc_mutex_lock(tsdn, &info->mtx);
+		info->state = background_thread_stopped;
+		int ret = pthread_cond_init(&info->cond, NULL);
+		assert(ret == 0);
+		background_thread_info_init(tsdn, info);
+		malloc_mutex_unlock(tsdn, &info->mtx);
+	}
+	malloc_mutex_unlock(tsdn, &background_thread_lock);
+}
+
+bool
+background_thread_stats_read(tsdn_t *tsdn, background_thread_stats_t *stats) {
+	assert(config_stats);
+	malloc_mutex_lock(tsdn, &background_thread_lock);
+	if (!background_thread_enabled()) {
+		malloc_mutex_unlock(tsdn, &background_thread_lock);
+		return true;
+	}
+
+	stats->num_threads = n_background_threads;
+	uint64_t num_runs = 0;
+	nstime_init(&stats->run_interval, 0);
+	for (unsigned i = 0; i < max_background_threads; i++) {
+		background_thread_info_t *info = &background_thread_info[i];
+		if (malloc_mutex_trylock(tsdn, &info->mtx)) {
+			/*
+			 * Each background thread run may take a long time;
+			 * avoid waiting on the stats if the thread is active.
+			 */
+			continue;
+		}
+		if (info->state != background_thread_stopped) {
+			num_runs += info->tot_n_runs;
+			nstime_add(&stats->run_interval, &info->tot_sleep_time);
+		}
+		malloc_mutex_unlock(tsdn, &info->mtx);
+	}
+	stats->num_runs = num_runs;
+	if (num_runs > 0) {
+		nstime_idivide(&stats->run_interval, num_runs);
+	}
+	malloc_mutex_unlock(tsdn, &background_thread_lock);
+
+	return false;
+}
+
+#undef BACKGROUND_THREAD_NPAGES_THRESHOLD
+#undef BILLION
+#undef BACKGROUND_THREAD_MIN_INTERVAL_NS
+
+#ifdef JEMALLOC_HAVE_DLSYM
+#include <dlfcn.h>
+#endif
+
+static bool
+pthread_create_fptr_init(void) {
+	if (pthread_create_fptr != NULL) {
+		return false;
+	}
+	/*
+	 * Try the next symbol first, because 1) when use lazy_lock we have a
+	 * wrapper for pthread_create; and 2) application may define its own
+	 * wrapper as well (and can call malloc within the wrapper).
+	 */
+#ifdef JEMALLOC_HAVE_DLSYM
+	pthread_create_fptr = dlsym(RTLD_NEXT, "pthread_create");
+#else
+	pthread_create_fptr = NULL;
+#endif
+	if (pthread_create_fptr == NULL) {
+		if (config_lazy_lock) {
+			malloc_write("<jemalloc>: Error in dlsym(RTLD_NEXT, "
+			    "\"pthread_create\")\n");
+			abort();
+		} else {
+			/* Fall back to the default symbol. */
+			pthread_create_fptr = pthread_create;
+		}
+	}
+
+	return false;
+}
+
+/*
+ * When lazy lock is enabled, we need to make sure setting isthreaded before
+ * taking any background_thread locks.  This is called early in ctl (instead of
+ * wait for the pthread_create calls to trigger) because the mutex is required
+ * before creating background threads.
+ */
+void
+background_thread_ctl_init(tsdn_t *tsdn) {
+	malloc_mutex_assert_not_owner(tsdn, &background_thread_lock);
+#ifdef JEMALLOC_PTHREAD_CREATE_WRAPPER
+	pthread_create_fptr_init();
+	pthread_create_wrapper_init();
+#endif
+}
+
+#endif /* defined(JEMALLOC_BACKGROUND_THREAD) */
+
+bool
+background_thread_boot0(void) {
+	if (!have_background_thread && opt_background_thread) {
+		malloc_printf("<jemalloc>: option background_thread currently "
+		    "supports pthread only\n");
+		return true;
+	}
+#ifdef JEMALLOC_PTHREAD_CREATE_WRAPPER
+	if ((config_lazy_lock || opt_background_thread) &&
+	    pthread_create_fptr_init()) {
+		return true;
+	}
+#endif
+	return false;
+}
+
+bool
+background_thread_boot1(tsdn_t *tsdn) {
+#ifdef JEMALLOC_BACKGROUND_THREAD
+	assert(have_background_thread);
+	assert(narenas_total_get() > 0);
+
+	if (opt_max_background_threads > MAX_BACKGROUND_THREAD_LIMIT) {
+		opt_max_background_threads = DEFAULT_NUM_BACKGROUND_THREAD;
+	}
+	max_background_threads = opt_max_background_threads;
+
+	background_thread_enabled_set(tsdn, opt_background_thread);
+	if (malloc_mutex_init(&background_thread_lock,
+	    "background_thread_global",
+	    WITNESS_RANK_BACKGROUND_THREAD_GLOBAL,
+	    malloc_mutex_rank_exclusive)) {
+		return true;
+	}
+
+	background_thread_info = (background_thread_info_t *)base_alloc(tsdn,
+	    b0get(), opt_max_background_threads *
+	    sizeof(background_thread_info_t), CACHELINE);
+	if (background_thread_info == NULL) {
+		return true;
+	}
+
+	for (unsigned i = 0; i < max_background_threads; i++) {
+		background_thread_info_t *info = &background_thread_info[i];
+		/* Thread mutex is rank_inclusive because of thread0. */
+		if (malloc_mutex_init(&info->mtx, "background_thread",
+		    WITNESS_RANK_BACKGROUND_THREAD,
+		    malloc_mutex_address_ordered)) {
+			return true;
+		}
+		if (pthread_cond_init(&info->cond, NULL)) {
+			return true;
+		}
+		malloc_mutex_lock(tsdn, &info->mtx);
+		info->state = background_thread_stopped;
+		background_thread_info_init(tsdn, info);
+		malloc_mutex_unlock(tsdn, &info->mtx);
+	}
+#endif
+
+	return false;
+}