Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ncar!asuvax!mcdphx!udc!chant!aglew From: aglew@urbana.mcd.mot.com (Andy-Krazy-Glew) Newsgroups: comp.arch Subject: Re: Memory utilization & inter-process contention Message-ID: Date: 29 Aug 89 14:48:41 GMT References: <3332@blake.acs.washington.edu> <261500008@S34.Prime.COM> <249@gp.govt.nz> <2389@auspex.auspex.com> Sender: aglew@urbana.mcd.mot.com Organization: Work: Motorola MCD, Urbana Design Center; School: University of Illinois at Urbana-Champaign Lines: 30 In-reply-to: guy@auspex.auspex.com's message of 28 Aug 89 18:58:14 GMT >OK, so which of the OSes that support working set scheduling do so >without having to be told by some external agent what the working set of >a process at some given time is? (Do the VMS calls even tell the OS >that, or do they just tell it how big the working set is?) It may have gotten lost: Gould NP1 UNIX. The NP1 hardware supports reference bits. >Jerry Leichter claimed that the VMS software people showed that a >reference bit is not necessary, given the appropriate algorithms; does >VMS how have appropriate algorithms to determine the contents of the >working set without requiring a reference bit, or did the designers >decide that the appropriate algorithm is to believe what the user or the >application tells you and not try to figure it out for yourself? (Not a >rhetorical question - I'm willing to accept that the latter is the >appropriate algorithm, given sufficient evidence to demonstrate that >claim.) Simulate reference bits by making the page non-RW, and faulting when you try to read - voila, a reference, and then you just make the page readable. Similarly, simulate modify bits by making the page non-W... I posted a reference to a SPUR paper that discusses the HW/SW tradeoffs involved, yesterday. -- Andy "Krazy" Glew, Motorola MCD, aglew@urbana.mcd.mot.com 1101 E. University, Urbana, IL 61801, USA. {uunet!,}uiucuxc!udc!aglew My opinions are my own; I indicate my company only so that the reader may account for any possible bias I may have towards our products.