Return to BSD News archive
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.ececs.uc.edu!news.kei.com!news.mathworks.com!news.sgi.com!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,comp.unix.bsd.misc Subject: Re: 100Base-TX: where's the bottleneck? Followup-To: comp.unix.bsd.freebsd.misc,comp.unix.bsd.misc Date: 7 Nov 1996 17:35:43 GMT Organization: Hewlett-Packard's Network Computing Division Lines: 28 Message-ID: <55t6lf$9km@hpindda.cup.hp.com> References: <327D4EE8.2D@cplabs.com> <55jkrt$7jc@cynic.portal.ca> <327E37E4.5AD4@cplabs.com> Reply-To: raj@cup.hp.com NNTP-Posting-Host: hpindio.cup.hp.com X-Newsreader: TIN [version 1.2 PL2.10] Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:30779 comp.unix.bsd.misc:1433 Henry Wong (henry@cplabs.com) wrote: : Yes, the driver just uses PIO mode, not Bus Master mode. But I : think even if it works on PIO mode, it shouldn't get so low : performance. I changed hub to 10M hub, I got the performance about : 7Mbs. Maybe that is a litter faster than normal 10M ethernet : adpter's performance. Also I used netperf to test. I got the : same result either on 100M ethernet or 10M ethernet. If the driver is using PIO instead of DMA, then it will be consuming great quantities of CPU time - the CPU is being used to move the data between the host and card. There is nothing "magical" about 100 Mbit Ethernet that makes your system go faster for bulk throughput. The MTU's are no larger, so it takes just as many packets to transmit a MB of data on 10BaseT as it does on 100BT which means it takes just as many CPU cycles to transmit a MB. If the 10BT solution takes say 40% of the CPU to do its thing, then I would not be surprised to see that same card in 100 Mbit mode only being driven at say 20 Mbit/s. Just imagine what fun it will be to try and drive Gigabit Ethernet at link rate. Maybe people will finally recognize the price being paid for keeping that tiny 1500 byte MTU... rick jones