Messages in this thread | | | Date | Wed, 30 Jan 2008 08:01:46 -0600 (CST) | From | Bruce Allen <> | Subject | Re: e1000 full-duplex TCP performance well below wire speed |
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Hi David,
Thanks for your note.
>> (The performance of a full duplex stream should be close to 1Gb/s in >> both directions.) > > This is not a reasonable expectation. > > ACKs take up space on the link in the opposite direction of the > transfer. > > So the link usage in the opposite direction of the transfer is > very far from zero.
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.
We have run these same tests on older kernels (with Broadcomm NICS) and gotten above 900 Mb/s full duplex.
Cheers, Bruce
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