Date: Sun, 2 Sep 2001 12:06:40 -0700 (PDT) From: John Polstra <jdp@polstra.com> To: hackers@freebsd.org Cc: deepak@ai.net Subject: Re: Routing Performance? Message-ID: <200109021906.f82J6eh02459@vashon.polstra.com> In-Reply-To: <GPEOJKGHAMKFIOMAGMDIIEPJFEAA.deepak@ai.net> References: <GPEOJKGHAMKFIOMAGMDIIEPJFEAA.deepak@ai.net>
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In article <GPEOJKGHAMKFIOMAGMDIIEPJFEAA.deepak@ai.net>, Deepak Jain <deepak@ai.net> wrote: > > The new P4s are shipping with 800mhz RAMBUS memory modules. Wouldn't 2GB of > 800mhz RAM go a long way to evening out the performance between a PC/FreeBSD > box and all but the most specialized, packet-pushing ASICs? I doubt it. My understanding is that RAMBUS memory is faster for long burst transfers, but that its random access latency is actually worse than that of conventional memory. Your routing table lookups (random accesses into a huge data structure) would be slower, not faster. There is very little bulk copying in the IP forwarding path of the kernel, so the higher bandwidth of RAMBUS would not provide much benefit. I suppose it would speed up the DMA transfers between the NICs and RAM. But I still bet overall performance wouldn't be improved by the use of RAMBUS memory. John -- John Polstra jdp@polstra.com John D. Polstra & Co., Inc. Seattle, Washington USA "Disappointment is a good sign of basic intelligence." -- Chögyam Trungpa To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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