Date: Sat, 01 Mar 2008 00:33:32 +0100 From: Willem Jan Withagen <wjw@digiware.nl> To: Ingo Flaschberger <if@xip.at> Cc: =?ISO-8859-1?Q?alves?= <daniel@dgnetwork.com.br>, =?ISO-8859-1?Q?Daniel_Dias_Gon=E7?=, freebsd-net@freebsd.org, freebsd-performance@freebsd.org, Kevin Oberman <oberman@es.net> Subject: Re: FBSD 1GBit router? Message-ID: <47C8964C.9080309@digiware.nl> In-Reply-To: <alpine.LFD.1.00.0802260132240.9719@filebunker.xip.at> References: <20080226003107.54CD94500E@ptavv.es.net> <alpine.LFD.1.00.0802260132240.9719@filebunker.xip.at>
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> I have a 1.2Ghz Pentium-M appliance, with 4x 32bit, 33MHz pci intel > e1000 cards. > With maximum tuning I can "route" ~400mbps with big packets and ~80mbps > with 64byte packets. > around 100kpps, whats not bad for a pci architecture. > > To reach higher bandwiths, better busses are needed. > pci-express cards are currently the best choice. > one dedicated pci-express lane (1.25gbps) has more bandwith than a whole > 32bit, 33mhz pci-bus. Like you say routing 400 Mb/s is close to the max of the PCI bus, which has a theoretical max of 33*4*8 ~ 1Gbps. Now routing is 500Mb/s in, 500Mb/s out. So you are within 80% of the bus-max, not counting memory-access and others. PCI express will give you a bus per PCI-E device into a central hub, thus upping the limit to the speed of the FrontSideBus in Intel architectures. Which at the moment is a lot higher than what a single PCI bus does. What it does not explain is why you can only get 80Mb/s with 64byte packets, which would suggest other bottlenecks than just the bus. --WjW
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