5.3 Garbage collection

5.3.1 The Dynamic Garbage Collector

The Dynamic Garbage Collector is enabled by default. New Lisp objects are created in only one of the dynamic area's semi-spaces; that semi-space is called the current semi-space. When the current semi-space is full, the Dynamic Garbage Collector is automatically invoked and performs the following procedure:

It locates objects that are still in use by searching the static area, the stack, and the registers for pointers into dynamic space.
It copies valid objects from the current semi-space into the other semi-space, which then becomes the current semi-space.
When garbage collection is completed, the Dynamic Garbage Collector terminates. New objects are now created in the new current semi-space.

When garbage collection begins, the following message is displayed on the screen:

;;; GC:

When garbage collection is finished, information about the available storage is displayed, and computation continues:

;;; GC: 566 words [2264 bytes] of dynamic storage in use.
;;; 458184 words [1832736 bytes] of free storage available 
;;; before a GC. 916934 words [3667736 bytes] of free 
;;; storage available if GC is disabled.
2384
1831592
3665568

5.3.1.1 - Disabling dynamic garbage collection

The User's Guide - 9 SEP 1996

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