Return to BSD News archive
Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!nntp.coast.net!newsfeed.direct.ca!news.emf.net!overload.lbl.gov!agate!howland.erols.net!vixen.cso.uiuc.edu!sdd.hp.com!hp-pcd!hpbs2500.boi.hp.com!hpax!cupnews2.cup.hp.com!raj From: raj@cup.hp.com (Rick Jones) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: 100BaseT tuning considerations? Date: 29 Aug 1996 22:29:37 GMT Organization: Hewlett-Packard's Network Computing Division Lines: 23 Message-ID: <5055kh$bkc@hpindda.cup.hp.com> References: <4vin1s$4um@server.cs.vt.edu> <4vsr44$iom@hpindda.cup.hp.com> <4vv36e$dqo@shellx.best.com> Reply-To: raj@cup.hp.com NNTP-Posting-Host: hpindio.cup.hp.com X-Newsreader: TIN [version 1.2 PL2.2] Russell Carter (rcarter@best.com) wrote: : In article <4vsr44$iom@hpindda.cup.hp.com>, Rick Jones <raj@cup.hp.com> wrote: : >So, if you needed 25% of your CPU to go 10 Mbit/s, 40 Mbit/s with : >100BT seems quite reasonable to expect. : Actually, the maximum network bandwidth is much more strongly : correlated to main memory bandwidth, not CPU. In order to peak out Is the strength of that correlation related to the number of data copies made by the stack on the way in or out? If the stack is really inefficient and copies once from user to transport, checksums in transport, copes between transport and driver, and then DMA's I can see that being the main thing. If the stack is say a one or two pass stack instead I have a slightly harder time, depending on the link MTU. : The 'stream' benchmark from McCalpin is an excellent measure of main : memory bandwidth. Is there a particular correction factor one can apply to the output of the stream benchmark to predict the performance of something like ttcp or netperf on the same box? rick jones