Date: Tue, 27 Feb 1996 09:11:30 -0500 From: Jerry Kendall <jerry@border.com> To: Luigi Rizzo <luigi@labinfo.iet.unipi.it> Cc: hackers@FreeBSD.ORG Subject: Re: RAM compression again Message-ID: <96Feb27.091859est.20483-1@janus.border.com> In-Reply-To: <199602262024.VAA01280@labinfo.iet.unipi.it>
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Luigi, you are an inspiration to all of us... Taking an idea and running to the lab with it... On Mon, 26 Feb 1996, Luigi Rizzo wrote: > > I have been thinking a little bit on the subject. I have come out > with a relatively simple zero-removal algorithm which compresses > (and decompressed) a 4KB page in about 100us (yes, that's 40MB/s) > on a Pentium 100. > > While the compression ratio is not as high as with gzip, I consistently > get a 2.5 reduction on FreeBSD 2.1R and 1.1.5 (maybe this is an > artifact of the inefficient malloc) and on Alpha/OSF (64-bit > architecture, known not to make a very efficient use of memory). > > More interesting is that some 15-20% of the pages compress to > 64-bytes or less. Thus a very effective RAM-swap area could be > implemented with little cost and additional complexity (with > fixed-size, 64-bytes blocks). > > A description of the compression/decompression algorithm and > its implementation are available from the following URL: > > http://www.iet.unipi.it/~luigi/research.html > > I'd be interested if someone could try it on a more recent system > than 2.1R and report the results. > > Thanks > Luigi > ==================================================================== > Luigi Rizzo Dip. di Ingegneria dell'Informazione > email: luigi@iet.unipi.it Universita' di Pisa > tel: +39-50-568533 via Diotisalvi 2, 56126 PISA (Italy) > fax: +39-50-568522 http://www.iet.unipi.it/~luigi/ > ==================================================================== > -------------------------------------------------------------------------------- Any comments or opinions in this message are my own and may or may not reflect the comments or opinions of my present or previous employers. Jerry Kendall Border Network Technologies Inc. System Software Engineer Tel +1-416-368-7157 ext 303 jerry@border.com Fax +1-416-368-7178
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