5.2 Storage allocation

5.2.2 Storage areas

• read-only

The two read-only areas are the readonly-non-pointer area and the readonly-pointer area. These areas contain data structures whose contents cannot be altered and cannot contain pointers. Compiled code, symbol names, and various constant structures are put into read-only areas. Storage in these areas cannot be reclaimed by garbage collection.

• read-write

This area contains data structures whose contents can be altered but cannot contain pointers. Certain permanent data structures are put into the read-write area. Storage in this area cannot be reclaimed by garbage collection.

• static

This area contains data structures whose contents can be altered and can contain pointers to objects in dynamic space or ephemeral space. The static area contains permanent data structures, such as symbols, and various tables and buffers that are internal to the system. Storage in this area cannot be reclaimed by garbage collection.

• reserved

This area contains space that can be allocated to the read-only, read-write, and static areas when those areas are full. Space from the reserved area is also allocated to the ephemeral area when ephemeral garbage collection is enabled. When the reserved area is depleted, space is reallocated to it from the dynamic areas.

• ephemeral

This area contains user-defined data structures. Ephemeral storage is normally organized into three ephemeral levels that are created from the reserved area only when ephemeral garbage collection is enabled. Storage in this area is reclaimed by garbage collection when any of the levels is full.

• dynamic

This area contains user-defined data structures. Dynamic storage is normally organized into two semi-spaces, only one of which is in use at any time. Storage in this area is reclaimed by garbage collection when one of the semi-spaces is full. Storage is allocated to this area from the operating system pool.

• discardable

The two discardable areas are the discardable-read-write-area and the discardable-static-area. These areas contain data structures that are not saved in an image saved bydisksave. Storage in this area cannot be reclaimed by garbage collection.

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