8. LO (Leaf Object)

LO is an automatically managed pool class for leaf objects (objects that contain no references). It does not move or protect its objects.

This pool class is intended for unstructured data that needs to be accessed by foreign code. It’s ideal for allocating a buffer that needs to be passed to an operating system I/O function.

Note

A thread that reads or writes from blocks allocated in this pool need not be registered with the arena so long as the liveness of the block is independent of that thread.

This means that you can launch a thread to read or write a buffer allocated in this pool, without having to register the thread, so long as you ensure that the buffer remains alive until the thread has finished (for example, by keeping a reference to the buffer in a root or a scanned object).

If LO is used to allocate large numbers of small objects, the garbage collection performance will degrade. For leaf objects that can move and be protected, it is better to use AMCZ (Automatic Mostly-Copying Zero-rank) instead.

8.1. LO properties

8.2. LO interface

#include "mpsclo.h"
mps_class_t mps_class_lo(void)

Return the pool class for an LO (Leaf Object) pool.

When creating an LO pool, mps_pool_create() takes one extra argument:

mps_res_t mps_pool_create(mps_pool_t *pool_o, mps_arena_t arena,
                          mps_class_t mps_class_lo(),
                          mps_fmt_t fmt)

fmt specifies the object format for the objects allocated in the pool. The format must provide a skip method.