From owner-freebsd-hackers Wed Jan 19 11: 2:20 2000 Delivered-To: freebsd-hackers@freebsd.org Received: from info.iet.unipi.it (info.iet.unipi.it [131.114.9.184]) by hub.freebsd.org (Postfix) with ESMTP id 09136152F1 for ; Wed, 19 Jan 2000 11:02:18 -0800 (PST) (envelope-from luigi@info.iet.unipi.it) Received: (from luigi@localhost) by info.iet.unipi.it (8.9.3/8.9.3) id UAA07154; Wed, 19 Jan 2000 20:02:46 +0100 (CET) (envelope-from luigi) From: Luigi Rizzo Message-Id: <200001191902.UAA07154@info.iet.unipi.it> Subject: Re: UVM vs FreeBSD VM system In-Reply-To: <200001191849.KAA39586@apollo.backplane.com> from Matthew Dillon at "Jan 19, 2000 10:49:52 am" To: Matthew Dillon Date: Wed, 19 Jan 2000 20:02:41 +0100 (CET) Cc: Jonas Bulow , FreeBSD Hackers X-Mailer: ELM [version 2.4ME+ PL61 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > :Hi, > : > :How does the UVM system compare to the VM system in FreeBSD? Are there > :any benchmark tests or research results in this area? speaking of virtual memory: a student of mine here finally completed an implementation of a compressed VM system, running on 3.x If anyone is interested in looking at this I can cleanup the code and prepare a patchfile. Pages candididates to pageout are tentatively compressed using a very fast algorithm (basically a zero-removal thing, i have a small paper on this on OSR April'97 issue, see my web page http://www.iet.unipi.it/~luigi/research.html) and if they give good compression the page is not sent to disk but saved to an area of ram set aside for the purpose. It turns out that many programs (netscape etc. but perhaps compilers as well, we haven't played too much with it) tend to leave pages rather empty so the compression succeeds in many cases. Of course we tried to preserve the advantages of clustering etc (so we don't bother going through compression if many adjacent pages go to disk anyways). cheers luigi -----------------------------------+------------------------------------- Luigi RIZZO, luigi@iet.unipi.it . Dip. di Ing. dell'Informazione http://www.iet.unipi.it/~luigi/ . Universita` di Pisa TEL/FAX: +39-050-568.533/522 . via Diotisalvi 2, 56126 PISA (Italy) Mobile +39-347-0373137 -----------------------------------+------------------------------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message