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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!munnari.OZ.AU!news.ecn.uoknor.edu!news.wildstar.net!news.sdsmt.edu!news.mid.net!newsfeeder.gi.net!newsfeed.internetmci.com!news.sgi.com!news1.best.com!nntp1.best.com!shellx.best.com!not-for-mail From: rcarter@best.com (Russell Carter) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: 100BaseT tuning considerations? Date: 27 Aug 1996 08:11:10 -0700 Organization: BEST Internet Communications Lines: 37 Message-ID: <4vv36e$dqo@shellx.best.com> References: <4vin1s$4um@server.cs.vt.edu> <4vsr44$iom@hpindda.cup.hp.com> NNTP-Posting-Host: shellx.best.com In article <4vsr44$iom@hpindda.cup.hp.com>, Rick Jones <raj@cup.hp.com> wrote: >Carl Harris (ceharris@mal.com) wrote: >: Has anyone experimented with tuning the kernel to get the most out >: of 100BaseT? Seems like it could do better than the ~40 mbit/s I >: can get with a stock kernel config. I'm experimenting with >: transfers that involve no with no disk I/O on a not-so-loaded >: system, equipped with a Pentium 120 and 32 megs EDO... > >How much CPU does it take for the system to drive 10 Mbit Ethernet to >saturation? Since the MTU does not increase between 10BT and 100BT >(nor 1000BT?), the host does not become any more "efficient" at >sending bulk data. > >So, if you needed 25% of your CPU to go 10 Mbit/s, 40 Mbit/s with >100BT seems quite reasonable to expect. > >However, you should also look at the window sizes you are using and >see if there are any TCP retransmissions. > >rick jones >http://www.cup.hp.com/netperf/NetperfPage.html Actually, the maximum network bandwidth is much more strongly correlated to main memory bandwidth, not CPU. In order to peak out at almost 90 Mb/s TCP you need 1. a 66 MHz bus clock and pipelined burst SRAM, or 2. an unbroken P6 (and not because of CPU, either) A properly built P5-100 will sustain over 85Mb/s. A P5-100 with asynchronous SRAM will get maybe 60% of that. The 'stream' benchmark from McCalpin is an excellent measure of main memory bandwidth. Russell