Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!nstn.ns.ca!wrdis01!gatech!ncar!elroy.jpl.nasa.gov!sdd.hp.com!samsung!uunet!mcsun!ukc!dcl-cs!aber-cs!athene!pcg From: pcg@cs.aber.ac.uk (Piercarlo Grandi) Newsgroups: comp.arch Subject: Re: Be Prepared... Message-ID: Date: 27 Feb 91 17:11:41 GMT References: <7517@uceng.UC.EDU> <12064@pt.cs.cmu.edu> Sender: aro@aber-cs.UUCP Organization: Coleg Prifysgol Cymru Lines: 34 Nntp-Posting-Host: odin In-reply-to: glew@pdx007.intel.com's message of 23 Feb 91 04:17:10 GMT On 23 Feb 91 04:17:10 GMT, glew@pdx007.intel.com (Andy Glew) said: lindsay> One of perennial topics in the OS world is the latest idea for Lindsay> using memory. No, no, it is the perennial race to *waste* memory. It is *wasting* memory that increases sales, not putting it to good use :-). glew> Anecdote: Gould NP1 was supposed to be a massive memory system. It glew> was not supposed to be shipped with less than 256 megabytes of glew> memory. [ ... ] Cutting the kernel down so that a 16 megabyte system glew> was useable was a thorny project. Pure billjoysm. I cannot imagine properly designed mechanisms that take advantage of big memory but that perform poorly with smaller memories. Save for trace scheduling maybe, but that is definitely not general purpose. glew> The NP1 UNIX team used a lot of those ideas for using cheap glew> memory. Like 32KB pages that are a win only if you do numerical calculations in the same memory order as the matrix is stored, so that you have less TLB reloads, for a speed up of maybe 5%, and in all other cases *waste* 50-80% of memory? :-). Let's distinguish between ideas for *using* cheap memory and ideas for *productively using* cheap memory. And let's distinguish between programs with hardwired assumptions and flexible programs. -- Piercarlo Grandi | ARPA: pcg%uk.ac.aber.cs@nsfnet-relay.ac.uk Dept of CS, UCW Aberystwyth | UUCP: ...!mcsun!ukc!aber-cs!pcg Penglais, Aberystwyth SY23 3BZ, UK | INET: pcg@cs.aber.ac.uk