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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!news.bhp.com.au!mel.dit.csiro.au!actcsiro!news.nsw.CSIRO.AU!metro!metro!inferno.mpx.com.au!news.mel.aone.net.au!imci4!newsfeed.internetmci.com!news.kei.com!nntp.coast.net!news00.sunet.se!sunic!news99.sunet.se!nntp-trd.UNINETT.no!due.unit.no!sthaug From: sthaug@nethelp.no (Steinar Haug) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: Glaring anomaly in lmbench results: socket bandwidth using localhost = 0.21 MB/s Date: 11 Feb 1996 23:34:46 GMT Organization: Nethelp Consulting, Trondheim, Norway Lines: 19 Message-ID: <4fluem$rps@stork.runit.sintef.no> References: <4fkus7$kab@stork.runit.sintef.no> <4fl75p$rlv@nntp5.u.washington.edu> <4fkuq0$1ev@dyson.iquest.net> NNTP-Posting-Host: trane.uninett.no In-reply-to: root@dyson.iquest.net's message of Sun, 11 Feb 1996 14:34:40 GMT [John S. Dyson] | 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. OK, I tried 4K, and got consistently 11.80 MByte/s. Much nicer, thanks! I also tried 32K, which is the default in NetBSD-1.1, and that gave me an even better loopback performance of 15.50 MByte/s. Now tell me - why shouldn't I leave the loopback MTU at 32K? Steinar Haug, Nethelp consulting, sthaug@nethelp.no