static void *
mmap_checked(size_t size, size_t align, int flags)
{
/* The size must be a power of two. */
assert((size & (size - 1)) == 0);
assert((align & (align - 1)) == 0);
/*
* mmap twice the requested amount to be able to align
* the mapped address.
* @todo all mappings except the first are likely to
* be aligned already. Find out if trying to map
* optimistically exactly the requested amount and fall
* back to double-size mapping is a viable strategy.
*/
void *map = mmap(NULL, size + align, PROT_READ | PROT_WRITE,
flags | MAP_ANONYMOUS, -1, 0);
if (map == MAP_FAILED)
return NULL;
/* Align the mapped address around slab size. */
size_t offset = (intptr_t) map & (align - 1);
if (offset != 0) {
/* Unmap unaligned prefix and postfix. */
munmap_checked(map, align - offset);
map += align - offset;
munmap_checked(map + size, offset);
} else {
/* The address is returned aligned. */
munmap_checked(map + size, align);
}
return map;
}
void
slab_arena_destroy(struct slab_arena *arena)
{
void *ptr;
size_t total = 0;
while ((ptr = lf_lifo_pop(&arena->cache))) {
if (arena->arena == NULL || ptr < arena->arena ||
ptr >= arena->arena + arena->prealloc) {
munmap_checked(ptr, arena->slab_size);
}
total += arena->slab_size;
}
if (arena->arena)
munmap_checked(arena->arena, arena->prealloc);
assert(total == arena->used);
}
static void *
mmap_checked(size_t size, size_t align, int flags)
{
/* The alignment must be a power of two. */
assert((align & (align - 1)) == 0);
/* The size must be a multiple of alignment */
assert((size & (align - 1)) == 0);
/*
* All mappings except the first are likely to
* be aligned already. Be optimistic by trying
* to map exactly the requested amount.
*/
void *map = mmap(NULL, size, PROT_READ | PROT_WRITE,
flags | MAP_ANONYMOUS, -1, 0);
if (map == MAP_FAILED)
return NULL;
if (((intptr_t) map & (align - 1)) == 0)
return map;
munmap_checked(map, size);
/*
* mmap enough amount to be able to align
* the mapped address. This can lead to virtual memory
* fragmentation depending on the kernels allocation
* strategy.
*/
map = mmap(NULL, size + align, PROT_READ | PROT_WRITE,
flags | MAP_ANONYMOUS, -1, 0);
if (map == MAP_FAILED)
return NULL;
/* Align the mapped address around slab size. */
size_t offset = (intptr_t) map & (align - 1);
if (offset != 0) {
/* Unmap unaligned prefix and postfix. */
munmap_checked(map, align - offset);
map += align - offset;
munmap_checked(map + size, offset);
} else {
/* The address is returned aligned. */
munmap_checked(map + size, align);
}
return map;
}
