Manual Pages  — VM_MAP_FIND

The arguments offset, prot, max, and cow are passed unchanged to vm_map_insert(9) when creating the mapping, if and only if a free region is found.

If object is non- NULL, the reference count on the object must be incremented by the caller before calling this function to account for the new entry.

If max_addr is non-zero, it specifies an upper bound on the mapping. The mapping will only succeed if a free region can be found that resides entirely below max_addr.

The find_space argument specifies the strategy to use when searching for a free region of the requested length. For all values other than VMFS_NO_SPACE, vm_map_findspace(9) is called to locate a free region of the requested length with a starting address at or above *addr. The following strategies are supported:

VMFS_NO_SPACE	The mapping will only succeed if there is a free region of the requested length at the given address *addr.
VMFS_ANY_SPACE	The mapping will succeed as long as there is a free region.
VMFS_SUPER_SPACE	The mapping will succeed as long as there is a free region that begins on a superpage boundary. If object is non- NULL and is already backed by superpages, then the mapping will require a free region that aligns relative to the existing superpages rather than one beginning on a superpage boundary.
VMFS_OPTIMAL_SPACE	The mapping will succeed as long as there is a free region. However, if object is non- NULL and is already backed by superpages, this strategy will attempt to find a free region aligned relative to the existing superpages.
VMFS_ALIGNED_SPACE(n)
	The mapping will succeed as long as there is a free region that aligns on a 2^n boundary.

The search for a free region is defined to be first-fit, from the address addr onwards.