Date: Tue, 13 Feb 2001 20:31:33 -0500 (EST) From: "Richard A. Steenbergen" <ras@e-gerbil.net> To: Luigi Rizzo <rizzo@aciri.org> Cc: net@freebsd.org Subject: Re: fxp performance ? Message-ID: <Pine.BSF.4.21.0102132026190.38591-100000@overlord.e-gerbil.net> In-Reply-To: <200102140053.f1E0rET55388@iguana.aciri.org>
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On Tue, 13 Feb 2001, Luigi Rizzo wrote: > Hi, > don't know how many of you have ever tried this... > > I am trying to generate (send only) packets at maximum rate on a > 100Mbit ethernet, which means using 64-byte packets and, once you > do the math (counting preamble, packet and inter-packet gap), > results in some 148.000 packets-per-second (and just to get the > idea, this also means that a new packet is transmitted every 6.72us). > > Note, the above is not trivial as you need a fast CPU, and probably > some tricks in order to avoid parf of the overhead of ip_output(). > > In any case, on botu a P3-650 and an Athlon-750, I managed to > achieve this speed using the "dc" driver. When i tried the same > with the 'fxp' driver, there was no way i managed to go above > 105-110.000 packets per second (meaning an average of 9.1us/packet). > > Any idea on what is going on ? I have spent quite some time in > the fxp driver and cannot really tell where the problem is. > Unfortunately my diagnostic tools do not let me see what is going > on on the wire, whether the spacing is larger than it should be, > etc. etc. I have had no problem doing line rate w/fxp and a p3 500 (well not to say no problem, but it is achievable). In my experience the biggest overheads are ip_output() and routing lookups. If you can't push past a certain amount and you're not CPU bound, check the device you're connected to because often times its inability to transmit the packet. Were both cards connected to the same device outputting to the same destination under the same lan conditions? -- Richard A Steenbergen <ras@e-gerbil.net> http://www.e-gerbil.net/ras PGP Key ID: 0x138EA177 (67 29 D7 BC E8 18 3E DA B2 46 B3 D8 14 36 FE B6) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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