bool
chunk_dealloc_dss(void *chunk, size_t size)
{
bool ret;
malloc_mutex_lock(&dss_mtx);
if ((uintptr_t)chunk >= (uintptr_t)dss_base
&& (uintptr_t)chunk < (uintptr_t)dss_max) {
extent_node_t *node;
/* Try to coalesce with other unused chunks. */
node = chunk_dealloc_dss_record(chunk, size);
if (node != NULL) {
chunk = node->addr;
size = node->size;
}
/* Get the current end of the DSS. */
dss_max = sbrk(0);
/*
* Try to shrink the DSS if this chunk is at the end of the
* DSS. The sbrk() call here is subject to a race condition
* with threads that use brk(2) or sbrk(2) directly, but the
* alternative would be to leak memory for the sake of poorly
* designed multi-threaded programs.
*/
if ((void *)((uintptr_t)chunk + size) == dss_max
&& (dss_prev = sbrk(-(intptr_t)size)) == dss_max) {
/* Success. */
dss_max = (void *)((intptr_t)dss_prev - (intptr_t)size);
if (node != NULL) {
extent_tree_szad_remove(&dss_chunks_szad, node);
extent_tree_ad_remove(&dss_chunks_ad, node);
base_node_dealloc(node);
}
} else
madvise(chunk, size, MADV_DONTNEED);
ret = false;
goto RETURN;
}
ret = true;
RETURN:
malloc_mutex_unlock(&dss_mtx);
return (ret);
}
bool
chunk_dealloc_swap(void *chunk, size_t size)
{
bool ret;
assert(swap_enabled);
malloc_mutex_lock(&swap_mtx);
if ((uintptr_t)chunk >= (uintptr_t)swap_base
&& (uintptr_t)chunk < (uintptr_t)swap_max) {
extent_node_t *node;
/* Try to coalesce with other unused chunks. */
node = chunk_dealloc_swap_record(chunk, size);
if (node != NULL) {
chunk = node->addr;
size = node->size;
}
/*
* Try to shrink the in-use memory if this chunk is at the end
* of the in-use memory.
*/
if ((void *)((uintptr_t)chunk + size) == swap_end) {
swap_end = (void *)((uintptr_t)swap_end - size);
if (node != NULL) {
extent_tree_szad_remove(&swap_chunks_szad,
node);
extent_tree_ad_remove(&swap_chunks_ad, node);
base_node_dealloc(node);
}
} else
madvise(chunk, size, MADV_DONTNEED);
#ifdef JEMALLOC_STATS
swap_avail += size;
#endif
ret = false;
goto RETURN;
}
ret = true;
RETURN:
malloc_mutex_unlock(&swap_mtx);
return (ret);
}
static void *
chunk_recycle_swap(size_t size, bool *zero)
{
extent_node_t *node, key;
key.addr = NULL;
key.size = size;
malloc_mutex_lock(&swap_mtx);
node = extent_tree_szad_nsearch(&swap_chunks_szad, &key);
if (node != NULL) {
void *ret = node->addr;
/* Remove node from the tree. */
extent_tree_szad_remove(&swap_chunks_szad, node);
if (node->size == size) {
extent_tree_ad_remove(&swap_chunks_ad, node);
base_node_dealloc(node);
} else {
/*
* Insert the remainder of node's address range as a
* smaller chunk. Its position within swap_chunks_ad
* does not change.
*/
assert(node->size > size);
node->addr = (void *)((uintptr_t)node->addr + size);
node->size -= size;
extent_tree_szad_insert(&swap_chunks_szad, node);
}
#ifdef JEMALLOC_STATS
swap_avail -= size;
#endif
malloc_mutex_unlock(&swap_mtx);
if (*zero)
memset(ret, 0, size);
return (ret);
}
malloc_mutex_unlock(&swap_mtx);
return (NULL);
}
static extent_node_t *
chunk_dealloc_swap_record(void *chunk, size_t size)
{
extent_node_t *xnode, *node, *prev, key;
xnode = NULL;
while (true) {
key.addr = (void *)((uintptr_t)chunk + size);
node = extent_tree_ad_nsearch(&swap_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
* swap_chunks_ad, so only remove/insert from/into
* swap_chunks_szad.
*/
extent_tree_szad_remove(&swap_chunks_szad, node);
node->addr = chunk;
node->size += size;
extent_tree_szad_insert(&swap_chunks_szad, node);
break;
} else if (xnode == NULL) {
/*
* It is possible that base_node_alloc() will cause a
* new base chunk to be allocated, so take care not to
* deadlock on swap_mtx, and recover if another thread
* deallocates an adjacent chunk while this one is busy
* allocating xnode.
*/
malloc_mutex_unlock(&swap_mtx);
xnode = base_node_alloc();
malloc_mutex_lock(&swap_mtx);
if (xnode == NULL)
return (NULL);
} else {
/* Coalescing forward failed, so insert a new node. */
node = xnode;
xnode = NULL;
node->addr = chunk;
node->size = size;
extent_tree_ad_insert(&swap_chunks_ad, node);
extent_tree_szad_insert(&swap_chunks_szad, node);
break;
}
}
/* Discard xnode if it ended up unused do to a race. */
if (xnode != NULL)
base_node_dealloc(xnode);
/* Try to coalesce backward. */
prev = extent_tree_ad_prev(&swap_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 swap_chunks_ad, so only
* remove/insert node from/into swap_chunks_szad.
*/
extent_tree_szad_remove(&swap_chunks_szad, prev);
extent_tree_ad_remove(&swap_chunks_ad, prev);
extent_tree_szad_remove(&swap_chunks_szad, node);
node->addr = prev->addr;
node->size += prev->size;
extent_tree_szad_insert(&swap_chunks_szad, node);
base_node_dealloc(prev);
}
return (node);
}