Function malloc_elem_alloc

dpdk/lib/eal/common/malloc_elem.c:427–488

* reserve a block of data in an existing malloc_elem. If the malloc_elem * is much larger than the data block requested, we split the element in two. * This function is only called from malloc_heap_alloc so parameter checking * is not done here, as it's done there previously. */

 * is not done here, as it's done there previously.
 */
struct malloc_elem *
malloc_elem_alloc(struct malloc_elem *elem, size_t size, unsigned align,
		size_t bound, bool contig)
{
	struct malloc_elem *new_elem = elem_start_pt(elem, size, align, bound,
			contig);
	const size_t old_elem_size = (uintptr_t)new_elem - (uintptr_t)elem;
	const size_t trailer_size = elem->size - old_elem_size - size -
		MALLOC_ELEM_OVERHEAD;

	malloc_elem_free_list_remove(elem);

	if (trailer_size > MALLOC_ELEM_OVERHEAD + MIN_DATA_SIZE) {
		/* split it, too much free space after elem */
		struct malloc_elem *new_free_elem =
				RTE_PTR_ADD(new_elem, size + MALLOC_ELEM_OVERHEAD);

		asan_clear_split_alloczone(new_free_elem);

		split_elem(elem, new_free_elem);
		malloc_elem_free_list_insert(new_free_elem);

		if (elem == elem->heap->last)
			elem->heap->last = new_free_elem;
	}

	if (old_elem_size < MALLOC_ELEM_OVERHEAD + MIN_DATA_SIZE) {
		/* don't split it, pad the element instead */
		elem->state = ELEM_BUSY;
		elem->pad = old_elem_size;

		asan_clear_alloczone(elem);

		/* put a dummy header in padding, to point to real element header */
		if (elem->pad > 0) { /* pad will be at least 64-bytes, as everything
		                     * is cache-line aligned */
			new_elem->pad = elem->pad;
			new_elem->state = ELEM_PAD;
			new_elem->size = elem->size - elem->pad;
			set_header(new_elem);
		}

		return new_elem;
	}

	asan_clear_split_alloczone(new_elem);

	/* we are going to split the element in two. The original element
	 * remains free, and the new element is the one allocated.
	 * Re-insert original element, in case its new size makes it
	 * belong on a different list.
	 */

	split_elem(elem, new_elem);

	asan_clear_alloczone(new_elem);

	new_elem->state = ELEM_BUSY;