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Newsgroups: comp.unix.bsd.freebsd.misc Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!news.mel.connect.com.au!munnari.OZ.AU!news.ecn.uoknor.edu!paladin.american.edu!zombie.ncsc.mil!news.mathworks.com!newsfeed.internetmci.com!news.sprintlink.net!news1!not-for-mail From: root@dyson.iquest.net (John S. Dyson) Subject: Re: Glaring anomaly in lmbench results: socket bandwidth using localhost = 0.21 MB/s X-Nntp-Posting-Host: dyson.iquest.net Message-ID: <4fkuq0$1ev@dyson.iquest.net> Sender: news@iquest.net (News Admin) Organization: John S. Dyson's home machine References: <4fkus7$kab@stork.runit.sintef.no> <4fl75p$rlv@nntp5.u.washington.edu> Date: Sun, 11 Feb 1996 14:34:40 GMT Lines: 21 In article <4fl75p$rlv@nntp5.u.washington.edu>, Craig Johnston <caj@tower.stc.housing.washington.edu> wrote: >Yes. I got about the same result. I actually got as low as .17 MB/s on >486 dx4-100 testing socket bandwidth using localhost. > >Machine is otherwise a good performer. What gives? > Actually, it is a good performer. The effect that you are seeing is due to an unfortunate clash between the size of the loopback mtu, some new tcp code and an option set in the lmbench code. The problem is that it hasn't been clearly determined what to do about it. Larry McVoy has authorized a very minor mod to lmbench. I think that is okay, but to get an actual idea of the loopback performance without changing the benchmark (loopback is what is being measured -- not TCP performance with a network adapter), you might want to change the def for LOMTU in /sys/net/if_loop.c from 16K to 4K. You'll see nicer (and more accurate reflection of the perf) numbers. John Dyson dyson@freebsd.org