Messages in this thread | | | Date | Wed, 30 Jan 2008 17:23:08 -0600 (CST) | From | Bruce Allen <> | Subject | Re: e1000 full-duplex TCP performance well below wire speed |
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Hi Stephen,
>>>> Indeed, we are not asking to see 1000 Mb/s. We'd be happy to see 900 >>>> Mb/s. >>>> >>>> Netperf is trasmitting a large buffer in MTU-sized packets (min 1500 >>>> bytes). Since the acks are only about 60 bytes in size, they should be >>>> around 4% of the total traffic. Hence we would not expect to see more >>>> than 960 Mb/s. >> >>> Don't forget the network overhead: http://sd.wareonearth.com/~phil/net/overhead/ >>> Max TCP Payload data rates over ethernet: >>> (1500-40)/(38+1500) = 94.9285 % IPv4, minimal headers >>> (1500-52)/(38+1500) = 94.1482 % IPv4, TCP timestamps >> >> Yes. If you look further down the page, you will see that with jumbo >> frames (which we have also tried) on Gb/s ethernet the maximum throughput >> is: >> >> (9000-20-20-12)/(9000+14+4+7+1+12)*1000000000/1000000 = 990.042 Mbps >> >> We are very far from this number -- averaging perhaps 600 or 700 Mbps.
> That is the upper bound of performance on a standard PCI bus (32 bit). > To go higher you need PCI-X or PCI-Express. Also make sure you are really > getting 64-bit PCI, because I have seen some e1000 PCI-X boards that > are only 32bit.
The motherboard NIC is in a PCI-e x1 slot. This has a maximum speed of 250 MB/s (2 Gb/s) in each direction. It should be a factor of 2 more interface speed than is needed.
Cheers, Bruce
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