To provide for memory acquisition during system operation without incurring the high overhead associated with the GETMAIN/FREEMAIN memory services, TDP acquires units of main memory, or cells, from its own, more efficient memory manager.
During startup, the memory manager pre-allocates a number of cells in sizes that are convenient for use by TDP. The sizes of the cells are internal constants. The initial number of cells is an internal default.
WHEN a . . . | THEN the . . . |
---|---|
TDP subtask requests a cell from the memory manager, but all available cells are being used by other TDP subtasks | memory manager does one of the
following:
|
requester is placed into a wait | wait ends when another TDP subtask
releases a cell. The decision to use GETMAIN or wait is based on the cell size and the identity of the requesting subtask. |