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:
|The mapping will only succeed if there is a free region of the requested length at the given address *addr.
|The mapping will succeed as long as there is a free region.
|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.
|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.
|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.
|September 12, 2013
|This philosophy, in the hands of amateurs, leads to inexplicably mind-numbing botches like the existence of two programs, “head” and “tail,” which print the first part or the last part of a file, depending. Even though their operations are duals of one another, “head” and “tail” are different programs, written by different authors, and take different options!
|— The Unix Haters' handbook