src/chunk.c

#define	JEMALLOC_CHUNK_C_
#include "jemalloc/internal/jemalloc_internal.h"

/******************************************************************************/
/* Data. */

const char	*opt_dss = DSS_DEFAULT;
size_t		opt_lg_chunk = 0;

/* Used exclusively for gdump triggering. */
static size_t	curchunks;
static size_t	highchunks;

rtree_t		chunks_rtree;

/* Various chunk-related settings. */
size_t		chunksize;
size_t		chunksize_mask; /* (chunksize - 1). */
size_t		chunk_npages;

static void	*chunk_alloc_default(void *new_addr, size_t size,
    size_t alignment, bool *zero, bool *commit, unsigned arena_ind);
static bool	chunk_dalloc_default(void *chunk, size_t size, bool committed,
    unsigned arena_ind);
static bool	chunk_commit_default(void *chunk, size_t size, size_t offset,
    size_t length, unsigned arena_ind);
static bool	chunk_decommit_default(void *chunk, size_t size, size_t offset,
    size_t length, unsigned arena_ind);
static bool	chunk_purge_default(void *chunk, size_t size, size_t offset,
    size_t length, unsigned arena_ind);
static bool	chunk_split_default(void *chunk, size_t size, size_t size_a,
    size_t size_b, bool committed, unsigned arena_ind);
static bool	chunk_merge_default(void *chunk_a, size_t size_a, void *chunk_b,
    size_t size_b, bool committed, unsigned arena_ind);

const chunk_hooks_t	chunk_hooks_default = {
	chunk_alloc_default,
	chunk_dalloc_default,
	chunk_commit_default,
	chunk_decommit_default,
	chunk_purge_default,
	chunk_split_default,
	chunk_merge_default
};

/******************************************************************************/
/*
 * Function prototypes for static functions that are referenced prior to
 * definition.
 */

static void	chunk_record(tsdn_t *tsdn, arena_t *arena,
    chunk_hooks_t *chunk_hooks, extent_tree_t *chunks_szsnad,
    extent_tree_t *chunks_ad, bool cache, void *chunk, size_t size, size_t sn,
    bool zeroed, bool committed);

/******************************************************************************/

static chunk_hooks_t
chunk_hooks_get_locked(arena_t *arena)
{

	return (arena->chunk_hooks);
}

chunk_hooks_t
chunk_hooks_get(tsdn_t *tsdn, arena_t *arena)
{
	chunk_hooks_t chunk_hooks;

	malloc_mutex_lock(tsdn, &arena->chunks_mtx);
	chunk_hooks = chunk_hooks_get_locked(arena);
	malloc_mutex_unlock(tsdn, &arena->chunks_mtx);

	return (chunk_hooks);
}

chunk_hooks_t
chunk_hooks_set(tsdn_t *tsdn, arena_t *arena, const chunk_hooks_t *chunk_hooks)
{
	chunk_hooks_t old_chunk_hooks;

	malloc_mutex_lock(tsdn, &arena->chunks_mtx);
	old_chunk_hooks = arena->chunk_hooks;
	/*
	 * Copy each field atomically so that it is impossible for readers to
	 * see partially updated pointers.  There are places where readers only
	 * need one hook function pointer (therefore no need to copy the
	 * entirety of arena->chunk_hooks), and stale reads do not affect
	 * correctness, so they perform unlocked reads.
	 */
#define	ATOMIC_COPY_HOOK(n) do {					\
	union {								\
		chunk_##n##_t	**n;					\
		void		**v;					\
	} u;								\
	u.n = &arena->chunk_hooks.n;					\
	atomic_write_p(u.v, chunk_hooks->n);				\
} while (0)
	ATOMIC_COPY_HOOK(alloc);
	ATOMIC_COPY_HOOK(dalloc);
	ATOMIC_COPY_HOOK(commit);
	ATOMIC_COPY_HOOK(decommit);
	ATOMIC_COPY_HOOK(purge);
	ATOMIC_COPY_HOOK(split);
	ATOMIC_COPY_HOOK(merge);
#undef ATOMIC_COPY_HOOK
	malloc_mutex_unlock(tsdn, &arena->chunks_mtx);

	return (old_chunk_hooks);
}

static void
chunk_hooks_assure_initialized_impl(tsdn_t *tsdn, arena_t *arena,
    chunk_hooks_t *chunk_hooks, bool locked)
{
	static const chunk_hooks_t uninitialized_hooks =
	    CHUNK_HOOKS_INITIALIZER;

	if (memcmp(chunk_hooks, &uninitialized_hooks, sizeof(chunk_hooks_t)) ==
	    0) {
		*chunk_hooks = locked ? chunk_hooks_get_locked(arena) :
		    chunk_hooks_get(tsdn, arena);
	}
}

static void
chunk_hooks_assure_initialized_locked(tsdn_t *tsdn, arena_t *arena,
    chunk_hooks_t *chunk_hooks)
{

	chunk_hooks_assure_initialized_impl(tsdn, arena, chunk_hooks, true);
}

static void
chunk_hooks_assure_initialized(tsdn_t *tsdn, arena_t *arena,
    chunk_hooks_t *chunk_hooks)
{

	chunk_hooks_assure_initialized_impl(tsdn, arena, chunk_hooks, false);
}

bool
chunk_register(tsdn_t *tsdn, const void *chunk, const extent_node_t *node)
{

	assert(extent_node_addr_get(node) == chunk);

	if (rtree_set(&chunks_rtree, (uintptr_t)chunk, node))
		return (true);
	if (config_prof && opt_prof) {
		size_t size = extent_node_size_get(node);
		size_t nadd = (size == 0) ? 1 : size / chunksize;
		size_t cur = atomic_add_z(&curchunks, nadd);
		size_t high = atomic_read_z(&highchunks);
		while (cur > high && atomic_cas_z(&highchunks, high, cur)) {
			/*
			 * Don't refresh cur, because it may have decreased
			 * since this thread lost the highchunks update race.
			 */
			high = atomic_read_z(&highchunks);
		}
		if (cur > high && prof_gdump_get_unlocked())
			prof_gdump(tsdn);
	}

	return (false);
}

void
chunk_deregister(const void *chunk, const extent_node_t *node)
{
	bool err;

	err = rtree_set(&chunks_rtree, (uintptr_t)chunk, NULL);
	assert(!err);
	if (config_prof && opt_prof) {
		size_t size = extent_node_size_get(node);
		size_t nsub = (size == 0) ? 1 : size / chunksize;
		assert(atomic_read_z(&curchunks) >= nsub);
		atomic_sub_z(&curchunks, nsub);
	}
}

/*
 * Do first-best-fit chunk selection, i.e. select the oldest/lowest chunk that
 * best fits.
 */
static extent_node_t *
chunk_first_best_fit(arena_t *arena, extent_tree_t *chunks_szsnad, size_t size)
{
	extent_node_t *node;
	size_t qsize;
	extent_node_t key;

	assert(size == CHUNK_CEILING(size));

	qsize = extent_size_quantize_ceil(size);
	extent_node_init(&key, arena, NULL, qsize, 0, false, false);
	node = extent_tree_szsnad_nsearch(chunks_szsnad, &key);
	assert(node == NULL || extent_node_size_get(node) >= size);
	return node;
}

static void *
chunk_recycle(tsdn_t *tsdn, arena_t *arena, chunk_hooks_t *chunk_hooks,
    extent_tree_t *chunks_szsnad, extent_tree_t *chunks_ad, bool cache,
    void *new_addr, size_t size, size_t alignment, size_t *sn, bool *zero,
    bool *commit, bool dalloc_node)
{
	void *ret;
	extent_node_t *node;
	size_t alloc_size, leadsize, trailsize;
	bool zeroed, committed;

	assert(CHUNK_CEILING(size) == size);
	assert(alignment > 0);
	assert(new_addr == NULL || alignment == chunksize);
	assert(CHUNK_ADDR2BASE(new_addr) == new_addr);
	/*
	 * Cached chunks use the node linkage embedded in their headers, in
	 * which case dalloc_node is true, and new_addr is non-NULL because
	 * we're operating on a specific chunk.
	 */
	assert(dalloc_node || new_addr != NULL);

	alloc_size = size + CHUNK_CEILING(alignment) - chunksize;
	/* Beware size_t wrap-around. */
	if (alloc_size < size)
		return (NULL);
	malloc_mutex_lock(tsdn, &arena->chunks_mtx);
	chunk_hooks_assure_initialized_locked(tsdn, arena, chunk_hooks);
	if (new_addr != NULL) {
		extent_node_t key;
		extent_node_init(&key, arena, new_addr, alloc_size, 0, false,
		    false);
		node = extent_tree_ad_search(chunks_ad, &key);
	} else {
		node = chunk_first_best_fit(arena, chunks_szsnad, alloc_size);
	}
	if (node == NULL || (new_addr != NULL && extent_node_size_get(node) <
	    size)) {
		malloc_mutex_unlock(tsdn, &arena->chunks_mtx);
		return (NULL);
	}
	leadsize = ALIGNMENT_CEILING((uintptr_t)extent_node_addr_get(node),
	    alignment) - (uintptr_t)extent_node_addr_get(node);
	assert(new_addr == NULL || leadsize == 0);
	assert(extent_node_size_get(node) >= leadsize + size);
	trailsize = extent_node_size_get(node) - leadsize - size;
	ret = (void *)((uintptr_t)extent_node_addr_get(node) + leadsize);
	*sn = extent_node_sn_get(node);
	zeroed = extent_node_zeroed_get(node);
	if (zeroed)
		*zero = true;
	committed = extent_node_committed_get(node);
	if (committed)
		*commit = true;
	/* Split the lead. */
	if (leadsize != 0 &&
	    chunk_hooks->split(extent_node_addr_get(node),
	    extent_node_size_get(node), leadsize, size, false, arena->ind)) {
		malloc_mutex_unlock(tsdn, &arena->chunks_mtx);
		return (NULL);
	}
	/* Remove node from the tree. */
	extent_tree_szsnad_remove(chunks_szsnad, node);
	extent_tree_ad_remove(chunks_ad, node);
	arena_chunk_cache_maybe_remove(arena, node, cache);
	if (leadsize != 0) {
		/* Insert the leading space as a smaller chunk. */
		extent_node_size_set(node, leadsize);
		extent_tree_szsnad_insert(chunks_szsnad, node);
		extent_tree_ad_insert(chunks_ad, node);
		arena_chunk_cache_maybe_insert(arena, node, cache);
		node = NULL;
	}
	if (trailsize != 0) {
		/* Split the trail. */
		if (chunk_hooks->split(ret, size + trailsize, size,
		    trailsize, false, arena->ind)) {
			if (dalloc_node && node != NULL)
				arena_node_dalloc(tsdn, arena, node);
			malloc_mutex_unlock(tsdn, &arena->chunks_mtx);
			chunk_record(tsdn, arena, chunk_hooks, chunks_szsnad,
			    chunks_ad, cache, ret, size + trailsize, *sn,
			    zeroed, committed);
			return (NULL);
		}
		/* Insert the trailing space as a smaller chunk. */
		if (node == NULL) {
			node = arena_node_alloc(tsdn, arena);
			if (node == NULL) {
				malloc_mutex_unlock(tsdn, &arena->chunks_mtx);
				chunk_record(tsdn, arena, chunk_hooks,
				    chunks_szsnad, chunks_ad, cache, ret, size
				    + trailsize, *sn, zeroed, committed);
				return (NULL);
			}
		}
		extent_node_init(node, arena, (void *)((uintptr_t)(ret) + size),
		    trailsize, *sn, zeroed, committed);
		extent_tree_szsnad_insert(chunks_szsnad, node);
		extent_tree_ad_insert(chunks_ad, node);
		arena_chunk_cache_maybe_insert(arena, node, cache);
		node = NULL;
	}
	if (!committed && chunk_hooks->commit(ret, size, 0, size, arena->ind)) {
		malloc_mutex_unlock(tsdn, &arena->chunks_mtx);
		chunk_record(tsdn, arena, chunk_hooks, chunks_szsnad, chunks_ad,
		    cache, ret, size, *sn, zeroed, committed);
		return (NULL);
	}
	malloc_mutex_unlock(tsdn, &arena->chunks_mtx);

	assert(dalloc_node || node != NULL);
	if (dalloc_node && node != NULL)
		arena_node_dalloc(tsdn, arena, node);
	if (*zero) {
		if (!zeroed)
			memset(ret, 0, size);
		else if (config_debug) {
			size_t i;
			size_t *p = (size_t *)(uintptr_t)ret;

			for (i = 0; i < size / sizeof(size_t); i++)
				assert(p[i] == 0);
		}
		if (config_valgrind)
			JEMALLOC_VALGRIND_MAKE_MEM_DEFINED(ret, size);
	}
	return (ret);
}

/*
 * If the caller specifies (!*zero), it is still possible to receive zeroed
 * memory, in which case *zero is toggled to true.  arena_chunk_alloc() takes
 * advantage of this to avoid demanding zeroed chunks, but taking advantage of
 * them if they are returned.
 */
static void *
chunk_alloc_core(tsdn_t *tsdn, arena_t *arena, void *new_addr, size_t size,
    size_t alignment, bool *zero, bool *commit, dss_prec_t dss_prec)
{
	void *ret;

	assert(size != 0);
	assert((size & chunksize_mask) == 0);
	assert(alignment != 0);
	assert((alignment & chunksize_mask) == 0);

	/* "primary" dss. */
	if (have_dss && dss_prec == dss_prec_primary && (ret =
	    chunk_alloc_dss(tsdn, arena, new_addr, size, alignment, zero,
	    commit)) != NULL)
		return (ret);
	/* mmap. */
	if ((ret = chunk_alloc_mmap(new_addr, size, alignment, zero, commit)) !=
	    NULL)
		return (ret);
	/* "secondary" dss. */
	if (have_dss && dss_prec == dss_prec_secondary && (ret =
	    chunk_alloc_dss(tsdn, arena, new_addr, size, alignment, zero,
	    commit)) != NULL)
		return (ret);

	/* All strategies for allocation failed. */
	return (NULL);
}

void *
chunk_alloc_base(size_t size)
{
	void *ret;
	bool zero, commit;

	/*
	 * Directly call chunk_alloc_mmap() rather than chunk_alloc_core()
	 * because it's critical that chunk_alloc_base() return untouched
	 * demand-zeroed virtual memory.
	 */
	zero = true;
	commit = true;
	ret = chunk_alloc_mmap(NULL, size, chunksize, &zero, &commit);
	if (ret == NULL)
		return (NULL);
	if (config_valgrind)
		JEMALLOC_VALGRIND_MAKE_MEM_UNDEFINED(ret, size);

	return (ret);
}

void *
chunk_alloc_cache(tsdn_t *tsdn, arena_t *arena, chunk_hooks_t *chunk_hooks,
    void *new_addr, size_t size, size_t alignment, size_t *sn, bool *zero,
    bool *commit, bool dalloc_node)
{
	void *ret;

	assert(size != 0);
	assert((size & chunksize_mask) == 0);
	assert(alignment != 0);
	assert((alignment & chunksize_mask) == 0);

	ret = chunk_recycle(tsdn, arena, chunk_hooks,
	    &arena->chunks_szsnad_cached, &arena->chunks_ad_cached, true,
	    new_addr, size, alignment, sn, zero, commit, dalloc_node);
	if (ret == NULL)
		return (NULL);
	if (config_valgrind)
		JEMALLOC_VALGRIND_MAKE_MEM_UNDEFINED(ret, size);
	return (ret);
}

static arena_t *
chunk_arena_get(tsdn_t *tsdn, unsigned arena_ind)
{
	arena_t *arena;

	arena = arena_get(tsdn, arena_ind, false);
	/*
	 * The arena we're allocating on behalf of must have been initialized
	 * already.
	 */
	assert(arena != NULL);
	return (arena);
}

static void *
chunk_alloc_default_impl(tsdn_t *tsdn, arena_t *arena, void *new_addr,
    size_t size, size_t alignment, bool *zero, bool *commit)
{
	void *ret;

	ret = chunk_alloc_core(tsdn, arena, new_addr, size, alignment, zero,
	    commit, arena->dss_prec);
	if (ret == NULL)
		return (NULL);
	if (config_valgrind)
		JEMALLOC_VALGRIND_MAKE_MEM_UNDEFINED(ret, size);

	return (ret);
}

static void *
chunk_alloc_default(void *new_addr, size_t size, size_t alignment, bool *zero,
    bool *commit, unsigned arena_ind)
{
	tsdn_t *tsdn;
	arena_t *arena;

	tsdn = tsdn_fetch();
	arena = chunk_arena_get(tsdn, arena_ind);

	return (chunk_alloc_default_impl(tsdn, arena, new_addr, size, alignment,
	    zero, commit));
}

static void *
chunk_alloc_retained(tsdn_t *tsdn, arena_t *arena, chunk_hooks_t *chunk_hooks,
    void *new_addr, size_t size, size_t alignment, size_t *sn, bool *zero,
    bool *commit)
{
	void *ret;

	assert(size != 0);
	assert((size & chunksize_mask) == 0);
	assert(alignment != 0);
	assert((alignment & chunksize_mask) == 0);

	ret = chunk_recycle(tsdn, arena, chunk_hooks,
	    &arena->chunks_szsnad_retained, &arena->chunks_ad_retained, false,
	    new_addr, size, alignment, sn, zero, commit, true);

	if (config_stats && ret != NULL)
		arena->stats.retained -= size;

	return (ret);
}

void *
chunk_alloc_wrapper(tsdn_t *tsdn, arena_t *arena, chunk_hooks_t *chunk_hooks,
    void *new_addr, size_t size, size_t alignment, size_t *sn, bool *zero,
    bool *commit)
{
	void *ret;

	chunk_hooks_assure_initialized(tsdn, arena, chunk_hooks);

	ret = chunk_alloc_retained(tsdn, arena, chunk_hooks, new_addr, size,
	    alignment, sn, zero, commit);
	if (ret == NULL) {
		if (chunk_hooks->alloc == chunk_alloc_default) {
			/* Call directly to propagate tsdn. */
			ret = chunk_alloc_default_impl(tsdn, arena, new_addr,
			    size, alignment, zero, commit);
		} else {
			ret = chunk_hooks->alloc(new_addr, size, alignment,
			    zero, commit, arena->ind);
		}

		if (ret == NULL)
			return (NULL);

		*sn = arena_extent_sn_next(arena);

		if (config_valgrind && chunk_hooks->alloc !=
		    chunk_alloc_default)
			JEMALLOC_VALGRIND_MAKE_MEM_UNDEFINED(ret, chunksize);
	}

	return (ret);
}

static void
chunk_record(tsdn_t *tsdn, arena_t *arena, chunk_hooks_t *chunk_hooks,
    extent_tree_t *chunks_szsnad, extent_tree_t *chunks_ad, bool cache,
    void *chunk, size_t size, size_t sn, bool zeroed, bool committed)
{
	bool unzeroed;
	extent_node_t *node, *prev;
	extent_node_t key;

	assert(!cache || !zeroed);
	unzeroed = cache || !zeroed;
	JEMALLOC_VALGRIND_MAKE_MEM_NOACCESS(chunk, size);

	malloc_mutex_lock(tsdn, &arena->chunks_mtx);
	chunk_hooks_assure_initialized_locked(tsdn, arena, chunk_hooks);
	extent_node_init(&key, arena, (void *)((uintptr_t)chunk + size), 0, 0,
	    false, false);
	node = extent_tree_ad_nsearch(chunks_ad, &key);
	/* Try to coalesce forward. */
	if (node != NULL && extent_node_addr_get(node) ==
	    extent_node_addr_get(&key) && extent_node_committed_get(node) ==
	    committed && !chunk_hooks->merge(chunk, size,
	    extent_node_addr_get(node), extent_node_size_get(node), false,
	    arena->ind)) {
		/*
		 * Coalesce chunk with the following address range.  This does
		 * not change the position within chunks_ad, so only
		 * remove/insert from/into chunks_szsnad.
		 */
		extent_tree_szsnad_remove(chunks_szsnad, node);
		arena_chunk_cache_maybe_remove(arena, node, cache);
		extent_node_addr_set(node, chunk);
		extent_node_size_set(node, size + extent_node_size_get(node));
		if (sn < extent_node_sn_get(node))
			extent_node_sn_set(node, sn);
		extent_node_zeroed_set(node, extent_node_zeroed_get(node) &&
		    !unzeroed);
		extent_tree_szsnad_insert(chunks_szsnad, node);
		arena_chunk_cache_maybe_insert(arena, node, cache);
	} else {
		/* Coalescing forward failed, so insert a new node. */
		node = arena_node_alloc(tsdn, arena);
		if (node == NULL) {
			/*
			 * Node allocation failed, which is an exceedingly
			 * unlikely failure.  Leak chunk after making sure its
			 * pages have already been purged, so that this is only
			 * a virtual memory leak.
			 */
			if (cache) {
				chunk_purge_wrapper(tsdn, arena, chunk_hooks,
				    chunk, size, 0, size);
			}
			goto label_return;
		}
		extent_node_init(node, arena, chunk, size, sn, !unzeroed,
		    committed);
		extent_tree_ad_insert(chunks_ad, node);
		extent_tree_szsnad_insert(chunks_szsnad, node);
		arena_chunk_cache_maybe_insert(arena, node, cache);
	}

	/* Try to coalesce backward. */
	prev = extent_tree_ad_prev(chunks_ad, node);
	if (prev != NULL && (void *)((uintptr_t)extent_node_addr_get(prev) +
	    extent_node_size_get(prev)) == chunk &&
	    extent_node_committed_get(prev) == committed &&
	    !chunk_hooks->merge(extent_node_addr_get(prev),
	    extent_node_size_get(prev), chunk, size, false, arena->ind)) {
		/*
		 * Coalesce chunk with the previous address range.  This does
		 * not change the position within chunks_ad, so only
		 * remove/insert node from/into chunks_szsnad.
		 */
		extent_tree_szsnad_remove(chunks_szsnad, prev);
		extent_tree_ad_remove(chunks_ad, prev);
		arena_chunk_cache_maybe_remove(arena, prev, cache);
		extent_tree_szsnad_remove(chunks_szsnad, node);
		arena_chunk_cache_maybe_remove(arena, node, cache);
		extent_node_addr_set(node, extent_node_addr_get(prev));
		extent_node_size_set(node, extent_node_size_get(prev) +
		    extent_node_size_get(node));
		if (extent_node_sn_get(prev) < extent_node_sn_get(node))
			extent_node_sn_set(node, extent_node_sn_get(prev));
		extent_node_zeroed_set(node, extent_node_zeroed_get(prev) &&
		    extent_node_zeroed_get(node));
		extent_tree_szsnad_insert(chunks_szsnad, node);
		arena_chunk_cache_maybe_insert(arena, node, cache);

		arena_node_dalloc(tsdn, arena, prev);
	}

label_return:
	malloc_mutex_unlock(tsdn, &arena->chunks_mtx);
}

void
chunk_dalloc_cache(tsdn_t *tsdn, arena_t *arena, chunk_hooks_t *chunk_hooks,
    void *chunk, size_t size, size_t sn, bool committed)
{

	assert(chunk != NULL);
	assert(CHUNK_ADDR2BASE(chunk) == chunk);
	assert(size != 0);
	assert((size & chunksize_mask) == 0);

	chunk_record(tsdn, arena, chunk_hooks, &arena->chunks_szsnad_cached,
	    &arena->chunks_ad_cached, true, chunk, size, sn, false,
	    committed);
	arena_maybe_purge(tsdn, arena);
}

static bool
chunk_dalloc_default_impl(void *chunk, size_t size)
{

	if (!have_dss || !chunk_in_dss(chunk))
		return (chunk_dalloc_mmap(chunk, size));
	return (true);
}

static bool
chunk_dalloc_default(void *chunk, size_t size, bool committed,
    unsigned arena_ind)
{

	return (chunk_dalloc_default_impl(chunk, size));
}

void
chunk_dalloc_wrapper(tsdn_t *tsdn, arena_t *arena, chunk_hooks_t *chunk_hooks,
    void *chunk, size_t size, size_t sn, bool zeroed, bool committed)
{
	bool err;

	assert(chunk != NULL);
	assert(CHUNK_ADDR2BASE(chunk) == chunk);
	assert(size != 0);
	assert((size & chunksize_mask) == 0);

	chunk_hooks_assure_initialized(tsdn, arena, chunk_hooks);
	/* Try to deallocate. */
	if (chunk_hooks->dalloc == chunk_dalloc_default) {
		/* Call directly to propagate tsdn. */
		err = chunk_dalloc_default_impl(chunk, size);
	} else
		err = chunk_hooks->dalloc(chunk, size, committed, arena->ind);

	if (!err)
		return;
	/* Try to decommit; purge if that fails. */
	if (committed) {
		committed = chunk_hooks->decommit(chunk, size, 0, size,
		    arena->ind);
	}
	zeroed = !committed || !chunk_hooks->purge(chunk, size, 0, size,
	    arena->ind);
	chunk_record(tsdn, arena, chunk_hooks, &arena->chunks_szsnad_retained,
	    &arena->chunks_ad_retained, false, chunk, size, sn, zeroed,
	    committed);

	if (config_stats)
		arena->stats.retained += size;
}

static bool
chunk_commit_default(void *chunk, size_t size, size_t offset, size_t length,
    unsigned arena_ind)
{

	return (pages_commit((void *)((uintptr_t)chunk + (uintptr_t)offset),
	    length));
}

static bool
chunk_decommit_default(void *chunk, size_t size, size_t offset, size_t length,
    unsigned arena_ind)
{

	return (pages_decommit((void *)((uintptr_t)chunk + (uintptr_t)offset),
	    length));
}

static bool
chunk_purge_default(void *chunk, size_t size, size_t offset, size_t length,
    unsigned arena_ind)
{

	assert(chunk != NULL);
	assert(CHUNK_ADDR2BASE(chunk) == chunk);
	assert((offset & PAGE_MASK) == 0);
	assert(length != 0);
	assert((length & PAGE_MASK) == 0);

	return (pages_purge((void *)((uintptr_t)chunk + (uintptr_t)offset),
	    length));
}

bool
chunk_purge_wrapper(tsdn_t *tsdn, arena_t *arena, chunk_hooks_t *chunk_hooks,
    void *chunk, size_t size, size_t offset, size_t length)
{

	chunk_hooks_assure_initialized(tsdn, arena, chunk_hooks);
	return (chunk_hooks->purge(chunk, size, offset, length, arena->ind));
}

static bool
chunk_split_default(void *chunk, size_t size, size_t size_a, size_t size_b,
    bool committed, unsigned arena_ind)
{

	if (!maps_coalesce)
		return (true);
	return (false);
}

static bool
chunk_merge_default_impl(void *chunk_a, void *chunk_b)
{

	if (!maps_coalesce)
		return (true);
	if (have_dss && !chunk_dss_mergeable(chunk_a, chunk_b))
		return (true);

	return (false);
}

static bool
chunk_merge_default(void *chunk_a, size_t size_a, void *chunk_b, size_t size_b,
    bool committed, unsigned arena_ind)
{

	return (chunk_merge_default_impl(chunk_a, chunk_b));
}

static rtree_node_elm_t *
chunks_rtree_node_alloc(size_t nelms)
{

	return ((rtree_node_elm_t *)base_alloc(TSDN_NULL, nelms *
	    sizeof(rtree_node_elm_t)));
}

bool
chunk_boot(void)
{
#ifdef _WIN32
	SYSTEM_INFO info;
	GetSystemInfo(&info);

	/*
	 * Verify actual page size is equal to or an integral multiple of
	 * configured page size.
	 */
	if (info.dwPageSize & ((1U << LG_PAGE) - 1))
		return (true);

	/*
	 * Configure chunksize (if not set) to match granularity (usually 64K),
	 * so pages_map will always take fast path.
	 */
	if (!opt_lg_chunk) {
		opt_lg_chunk = ffs_u((unsigned)info.dwAllocationGranularity)
		    - 1;
	}
#else
	if (!opt_lg_chunk)
		opt_lg_chunk = LG_CHUNK_DEFAULT;
#endif

	/* Set variables according to the value of opt_lg_chunk. */
	chunksize = (ZU(1) << opt_lg_chunk);
	assert(chunksize >= PAGE);
	chunksize_mask = chunksize - 1;
	chunk_npages = (chunksize >> LG_PAGE);

	if (have_dss)
		chunk_dss_boot();
	if (rtree_new(&chunks_rtree, (unsigned)((ZU(1) << (LG_SIZEOF_PTR+3)) -
	    opt_lg_chunk), chunks_rtree_node_alloc, NULL))
		return (true);

	return (false);
}