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From: hbaker@netcom.com (Henry Baker)
Subject: Re: Garbage collection cost (was Re: Parenthesized syntax challenge)
Message-ID: <hbaker-2710952309000001@10.0.2.15>
Sender: hbaker@netcom7.netcom.com
Organization: nil organization
References: <44aa9a$j5h@miso.cs.uq.edu.au> <LUDEMANN.95Oct6140930@expernet26.expernet.com> <DGApp8.J41@undergrad.math.uwaterloo.ca> <MAD.95Oct13123618@tanzanite.math.keio.ac.jp> <45ksdk$7gr@jive.cs.utexas.edu> <DGJp8o.7nF@Cadence.COM> <MAD.95Oct18040436@tanzanite.math.keio.ac.jp> <hbaker-1710952127200001@10.0.2.15> <46jb8v$sm8@news.parc.xerox.com> <hbaker-2510951016220001@10.0.2.15> <DH25zB.7D@kroete2.freinet.de>
Date: Sat, 28 Oct 1995 07:09:00 GMT
Lines: 26
Xref: glinda.oz.cs.cmu.edu comp.lang.dylan:5678 comp.lang.lisp:19756 comp.lang.java:3046

In article <DH25zB.7D@kroete2.freinet.de>, ehcorry@inet.uni-c.dk (Erik
Corry) wrote:

> Henry Baker (hbaker@netcom.com) wrote:
> 
> : I would advise using .-relative addressing for all pointers (perhaps some
> : C compiler vendor/GNU is listening), and start using VM compression. 
Once you
> : have encoded pointers as _relative_ addresses instead of _absolute_
> : addresses, then VM compression will work better.
> 
> Could you explain how using .-relative addressing improves compression?
> The way I understood it VM compression (a la Mac RamDoubler) only works
> really well if the pages to be compressed consist mostly of zeros.

If you allocate a list in sequence, and they are allocated contiguously,
then one of the fields will point to a location .+n bytes subsequent.
If these are relative pointers, then they will all be 'n', so a reasonable
compression scheme -- e.g., gzip -- should be able to compress such a
sequence.

I don't know how sophisticated RamDoubler's compression scheme is.

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