jemalloc/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 = LG_CHUNK_DEFAULT;

/* 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;

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

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

	assert(node->addr == chunk);

	if (rtree_set(&chunks_rtree, (uintptr_t)chunk, node))
		return (true);
	if (config_prof && opt_prof) {
		size_t nadd = (node->size == 0) ? 1 : node->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();
	}

	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 nsub = (node->size == 0) ? 1 : node->size / chunksize;
		assert(atomic_read_z(&curchunks) >= nsub);
		atomic_sub_z(&curchunks, nsub);
	}
}

static void *
chunk_recycle(arena_t *arena, extent_tree_t *chunks_szad,
    extent_tree_t *chunks_ad, void *new_addr, size_t size, size_t alignment,
    bool *zero)
{
	void *ret;
	extent_node_t *node;
	extent_node_t key;
	size_t alloc_size, leadsize, trailsize;
	bool zeroed;

	assert(new_addr == NULL || alignment == chunksize);

	alloc_size = size + alignment - chunksize;
	/* Beware size_t wrap-around. */
	if (alloc_size < size)
		return (NULL);
	key.addr = new_addr;
	key.size = alloc_size;
	malloc_mutex_lock(&arena->chunks_mtx);
	node = (new_addr != NULL) ? extent_tree_ad_search(chunks_ad, &key) :
	    extent_tree_szad_nsearch(chunks_szad, &key);
	if (node == NULL || (new_addr != NULL && node->size < size)) {
		malloc_mutex_unlock(&arena->chunks_mtx);
		return (NULL);
	}
	leadsize = ALIGNMENT_CEILING((uintptr_t)node->addr, alignment) -
	    (uintptr_t)node->addr;
	assert(new_addr == NULL || leadsize == 0);
	assert(node->size >= leadsize + size);
	trailsize = node->size - leadsize - size;
	ret = (void *)((uintptr_t)node->addr + leadsize);
	zeroed = node->zeroed;
	if (zeroed)
	    *zero = true;
	/* Remove node from the tree. */
	extent_tree_szad_remove(chunks_szad, node);
	extent_tree_ad_remove(chunks_ad, node);
	if (leadsize != 0) {
		/* Insert the leading space as a smaller chunk. */
		node->size = leadsize;
		extent_tree_szad_insert(chunks_szad, node);
		extent_tree_ad_insert(chunks_ad, node);
		node = NULL;
	}
	if (trailsize != 0) {
		/* Insert the trailing space as a smaller chunk. */
		if (node == NULL) {
			node = arena_node_alloc(arena);
			if (node == NULL) {
				malloc_mutex_unlock(&arena->chunks_mtx);
				chunk_unmap(arena, ret, size);
				return (NULL);
			}
		}
		node->addr = (void *)((uintptr_t)(ret) + size);
		node->size = trailsize;
		node->zeroed = zeroed;
		extent_tree_szad_insert(chunks_szad, node);
		extent_tree_ad_insert(chunks_ad, node);
		node = NULL;
	}
	malloc_mutex_unlock(&arena->chunks_mtx);

	if (node != NULL)
		arena_node_dalloc(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;

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

static void *
chunk_alloc_core_dss(arena_t *arena, void *new_addr, size_t size,
    size_t alignment, bool *zero)
{
	void *ret;

	if ((ret = chunk_recycle(arena, &arena->chunks_szad_dss,
	    &arena->chunks_ad_dss, new_addr, size, alignment, zero)) != NULL)
		return (ret);
	ret = chunk_alloc_dss(arena, new_addr, size, alignment, zero);
	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(arena_t *arena, void *new_addr, size_t size, size_t alignment,
    bool *zero, 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_core_dss(arena, new_addr, size, alignment, zero)) !=
	    NULL)
		return (ret);
	/* mmap. */
	if (!config_munmap && (ret = chunk_recycle(arena,
	    &arena->chunks_szad_mmap, &arena->chunks_ad_mmap, new_addr, size,
	    alignment, zero)) != NULL)
		return (ret);
	/*
	 * Requesting an address is not implemented for chunk_alloc_mmap(), so
	 * only call it if (new_addr == NULL).
	 */
	if (new_addr == NULL && (ret = chunk_alloc_mmap(size, alignment, zero))
	    != NULL)
		return (ret);
	/* "secondary" dss. */
	if (have_dss && dss_prec == dss_prec_secondary && (ret =
	    chunk_alloc_core_dss(arena, new_addr, size, alignment, zero)) !=
	    NULL)
		return (ret);

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

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

	/*
	 * 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;
	ret = chunk_alloc_mmap(size, chunksize, &zero);
	if (ret == NULL)
		return (NULL);
	if (config_valgrind)
		JEMALLOC_VALGRIND_MAKE_MEM_UNDEFINED(ret, size);

	return (ret);
}

void *
chunk_alloc_arena(chunk_alloc_t *chunk_alloc, chunk_dalloc_t *chunk_dalloc,
    unsigned arena_ind, void *new_addr, size_t size, size_t alignment,
    bool *zero)
{
	void *ret;

	ret = chunk_alloc(new_addr, size, alignment, zero, arena_ind);
	if (ret == NULL)
		return (NULL);
	if (config_valgrind)
		JEMALLOC_VALGRIND_MAKE_MEM_UNDEFINED(ret, size);

	return (ret);
}

static arena_t *
chunk_arena_get(unsigned arena_ind)
{
	arena_t *arena;

	/* Dodge tsd for a0 in order to avoid bootstrapping issues. */
	arena = (arena_ind == 0) ? a0get() : arena_get(tsd_fetch(), arena_ind,
	     false, true);
	/*
	 * The arena we're allocating on behalf of must have been initialized
	 * already.
	 */
	assert(arena != NULL);
	return (arena);
}

/* Default arena chunk allocation routine in the absence of user override. */
void *
chunk_alloc_default(void *new_addr, size_t size, size_t alignment, bool *zero,
    unsigned arena_ind)
{
	arena_t *arena;

	arena = chunk_arena_get(arena_ind);
	return (chunk_alloc_core(arena, new_addr, size, alignment, zero,
	    arena->dss_prec));
}

static void
chunk_record(arena_t *arena, extent_tree_t *chunks_szad,
    extent_tree_t *chunks_ad, void *chunk, size_t size)
{
	bool unzeroed;
	extent_node_t *node, *prev, key;

	unzeroed = pages_purge(chunk, size);
	JEMALLOC_VALGRIND_MAKE_MEM_NOACCESS(chunk, size);

	malloc_mutex_lock(&arena->chunks_mtx);
	key.addr = (void *)((uintptr_t)chunk + size);
	node = extent_tree_ad_nsearch(chunks_ad, &key);
	/* Try to coalesce forward. */
	if (node != NULL && node->addr == key.addr) {
		/*
		 * Coalesce chunk with the following address range.  This does
		 * not change the position within chunks_ad, so only
		 * remove/insert from/into chunks_szad.
		 */
		extent_tree_szad_remove(chunks_szad, node);
		node->addr = chunk;
		node->size += size;
		node->zeroed = (node->zeroed && !unzeroed);
		extent_tree_szad_insert(chunks_szad, node);
	} else {
		/* Coalescing forward failed, so insert a new node. */
		node = arena_node_alloc(arena);
		if (node == NULL) {
			/*
			 * Node allocation failed, which is an exceedingly
			 * unlikely failure.  Leak chunk; its pages have
			 * already been purged, so this is only a virtual
			 * memory leak.
			 */
			goto label_return;
		}
		node->addr = chunk;
		node->size = size;
		node->zeroed = !unzeroed;
		extent_tree_ad_insert(chunks_ad, node);
		extent_tree_szad_insert(chunks_szad, node);
	}

	/* Try to coalesce backward. */
	prev = extent_tree_ad_prev(chunks_ad, node);
	if (prev != NULL && (void *)((uintptr_t)prev->addr + prev->size) ==
	    chunk) {
		/*
		 * Coalesce chunk with the previous address range.  This does
		 * not change the position within chunks_ad, so only
		 * remove/insert node from/into chunks_szad.
		 */
		extent_tree_szad_remove(chunks_szad, prev);
		extent_tree_ad_remove(chunks_ad, prev);

		extent_tree_szad_remove(chunks_szad, node);
		node->addr = prev->addr;
		node->size += prev->size;
		node->zeroed = (node->zeroed && prev->zeroed);
		extent_tree_szad_insert(chunks_szad, node);

		arena_node_dalloc(arena, prev);
	}

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

void
chunk_unmap(arena_t *arena, void *chunk, size_t size)
{

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

	if (have_dss && chunk_in_dss(chunk)) {
		chunk_record(arena, &arena->chunks_szad_dss,
		    &arena->chunks_ad_dss, chunk, size);
	} else if (chunk_dalloc_mmap(chunk, size)) {
		chunk_record(arena, &arena->chunks_szad_mmap,
		    &arena->chunks_ad_mmap, chunk, size);
	}
}

/* Default arena chunk deallocation routine in the absence of user override. */
bool
chunk_dalloc_default(void *chunk, size_t size, unsigned arena_ind)
{

	chunk_unmap(chunk_arena_get(arena_ind), chunk, size);
	return (false);
}

static rtree_node_elm_t *
chunks_rtree_node_alloc(size_t nelms)
{

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

bool
chunk_boot(void)
{

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

	return (false);
}

void
chunk_prefork(void)
{

	chunk_dss_prefork();
}

void
chunk_postfork_parent(void)
{

	chunk_dss_postfork_parent();
}

void
chunk_postfork_child(void)
{

	chunk_dss_postfork_child();
}