Path: news.daimi.aau.dk!jacobse
From: jacobse@daimi.aau.dk (Jacob Seligmann)
Newsgroups: comp.lang.beta
Subject: Re: Mature garbage collection in BETA
Date: 4 Nov 1994 11:00:09 GMT
Organization: DAIMI, Computer Science Dept. at Aarhus University
Lines: 46
Message-ID: <39d47p$dr2@belfort.daimi.aau.dk>
References: <39cmou$88n@belfort.daimi.aau.dk>
NNTP-Posting-Host: quercus.daimi.aau.dk

Jens Skinnerup <xsfx@daimi.aau.dk> wrote: 

> I've just read Jakob Seligmann's M.Sc. thesis 'Incremental Mature
> Garbage Collection', in which he replaced the Mjoelner BETA run-time
> system's mark-and-sweep mature garbage collection with an
> implementation of the train algorithim fo incremental mature garbage
> collection. Have Mjoelner incorperated those changes, or are they
> still using mark-and-sweep. 

We chose to implement the Train Algorithm in a variant of v2.5.1 of the 
Mjolner BETA run-time system, which was the newest frozen release when 
we began our experiments back in January 1993.

Because of limited resources, the Train Algorithm implementation has 
not been carried forward into the current run-time system (v2.6), 
although most of the general run-time system deficiencies identified in 
our thesis have now been rectified. We do plan to incorporate the Train 
Algorithm in the future.

> The conclusion of the thesis was that the
> train algorithim was less disrupting than mark-and-sweep.

*A lot* less disrupting, that is (replacing old generation collection 
pauses of up to several seconds with a series of small ones, each just 
a few dozen milliseconds long)! And - just as importantly - the Train 
Algorithm was shown to introduce virtually no overhead in time 
(typically less than 1%), and only a modest increase in storage 
requirements (typically around 10%).

The full reference for the thesis is

   Steffen Grarup and Jacob Seligmann: "Incremental Mature Garbage 
   Collection", M.Sc. Thesis, University of Aarhus, Denmark, August 
   1993. Also available as Technical Report DAIMI IR-122, University 
   of Aarhus, Denmark, September 1994, ISSN 0106-9969.

The thesis is also obtainable in PostScript form via anonymous ftp to 
ftp.daimi.aau.dk as pub/thesis/gcthesis.ps.{Z,gz}

/Jacob Seligmann
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