Transferring Memory to Other Tasks

The previous section explained how to use ControlMem() to grant and revoke write access to memory pages. You can also use ControlMem() to transfer ownership of memory pages to other tasks:

Err ControlMem( void *p, int32 size, int32 cmd, Item task )

If the value of the cmd argument is MEMC_GIVE, the call gives the memory pages to the task specified by the task argument. In this case, the p argument, a pointer to a memory location, and the size argument, the amount of the contiguous memory, in bytes, beginning at the memory location specified by the p argument, together specify the memory to give away. If these two arguments specify any part of a page, the entire page is given away.

You can also give memory pages back to the kernel-and thereby return them to the system-wide free memory pool-by calling ControlMem() as described here, but with 0 as the value of the task argument. Memory pages can be returned to the kernel automatically when a task calls the ScavengeMem() function described in Reclaiming Memory for Other Tasks.