module Ancient:sig..end
Mark objects as 'ancient' so they are taken out of the OCaml heap.
type 'a ancient
val mark : 'a -> 'a ancientmark obj copies obj and all objects referenced
by obj out of the OCaml heap. It returns the proxy
for obj.
The copy of obj accessed through the proxy MUST NOT be mutated.
If obj represents a large object, then it is a good
idea to call Gc.compact after marking to recover the
OCaml heap memory.
val follow : 'a ancient -> 'a
val delete : 'a ancient -> unit
val is_ancient : 'a -> boolis_ancient ptr returns true if ptr is an object on the ancient
heap.
val address_of : 'a -> nativeintaddress_of obj returns the address of obj, or 0n if obj
is not a block.
type
Memory descriptor handle.
val attach : Unix.file_descr -> nativeint -> mdattach fd baseaddr attaches to a new or existing file
which may contain shared objects.
Initially fd should be a read/writable, zero-length file
(for example you could create this using Unix.openfile and
passing the flags O_RDWR, O_TRUNC, O_CREAT).
One or more objects can then be shared in this file
using Unix.share.
For new files, baseaddr specifies the virtual address to
map the file. Specifying Nativeint.zero (0n) here lets mmap(2)
choose this, but on some platforms (notably Linux/AMD64)
mmap chooses very unwisely, tending to map the memory
just before libc with hardly any headroom to grow. If
you encounter this sort of problem (usually a segfault or
illegal instruction inside libc), then look at /proc/PID/maps
and choose a more suitable address.
If the file was created previously, then the baseaddr is
ignored. The underlying mmalloc library will map the
file in at the same place as before.
val detach : md -> unitdetach md detaches from an existing file, and closes it.
: md -> int -> 'a -> 'a ancientshare md key obj does the same as Ancient.mark except
that instead of copying the object into local memory, it
writes it into memory which is backed by the attached file.
Shared mappings created this way may be shared between
other OCaml processes which can access the underlying
file. See Ancient.attach, Ancient.detach.
More than one object can be stored in a file. The key
parameter controls which object is written/overwritten by share.
If you do not wish to use this feature, just pass 0
as the key.
Do not call Ancient.delete on a mapping created like this.
Instead, call Ancient.detach and, if necessary, delete the
underlying file.
Caution when sharing files/objects between processes:
The underlying mmalloc library does not do any sort of
locking, so all calls to share must ensure that they have
exclusive access to the underlying file while in progress.
(Other processes should not even call Ancient.get while
this is happening, but it seems safe to be just reading an
ancient object from the file).
val get : md -> int -> 'a ancientget md key returns the object indexed by key in the
attached file.
For details of the key parameter see Ancient.share.
You need to annotate the returned object with the correct
type. As with the Marshal module, there is no type checking,
and setting the wrong type will likely cause a segfault
or undefined behaviour. Note that the returned object has
type sometype ancient, not just sometype.
type
|
i_size : |
(* | Allocated size, bytes. | *) |
Extra information fields. See Ancient.mark_info and
Ancient.share_info.
val mark_info : 'a -> 'a ancient * infoSame as Ancient.mark, but also returns some extra information.
: md -> int -> 'a -> 'a ancient * infoSame as Ancient.share, but also returns some extra information.