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From: barmar@think.com (Barry Margolin)
Newsgroups: comp.object
Subject: Re: Stash Collection
Message-ID: <1990Nov27.074534.17744@Think.COM>
Date: 27 Nov 90 07:45:34 GMT
References: <2849@esquire.dpw.com>
Sender: news@Think.COM
Organization: Thinking Machines Corporation, Cambridge MA, USA
Lines: 24

In article <2849@esquire.dpw.com> yost@DPW.COM (David A. Yost) writes:
>The idea is that when GC can't make enough room to satisfy
>a request, it invokes SC, which looks around for objects
>that will volunteer to give up some memory they don't really
>need, such as cached data or multiple reperesentations of
>the same data.

Symbolics Lisp Machines provide "before-GC initializations", an extensible
list of functions to be called before GC, presumably to allow applications
to clear or consolidate their data structures.  There is also a second set
of "GC Cleanups", which the user may invoke manually and selectively prior
to GC, and which applications may extend.  The before-GC initializations
are generally used for internal data structures; some applications clear
caches, while others reorganize to improve paging and/or to cdr-code lists.
GC Cleanups are generally used for user-visible data, which is why it must
be invoked manually; for instance, window histories can be cleared (this
can be quite significant, because windows remember the objects that were
printed to them, not just the text), and top-level variables such as *, **,
and *** can be cleared.
--
Barry Margolin, Thinking Machines Corp.

barmar@think.com
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