Re: intel 82599 multi-port performance

On 09/27/2011 11:14 AM, Alexander Duyck wrote:

This more or less confirms what I was thinking. You are likely hitting
the PCIe limits of the adapters. The overhead for 64 byte packets is too
great and as a result you are exceeding the PCIe bandwidth available to
the adapter. In order to achieve line rate on both ports you would
likely need to increase your packet size to something along the lines of
256 bytes so that the additional PCIe overhead only contributes 50% or
less to the total PCIe traffic across the bus. Then the 2.5Gb/s of
network traffic should consume less than 4.0GT/s of PCIe traffic.

For some further information, according to the information here:

http://shader.kaist.edu/packetshader/io_engine/benchmark/i3.html

a dual-port 82599 controller with an i3 CPU can in fact handle sending *or* receiving (and then dropping) full line rate on both ports for minimum-sized packets.  It can't do both though.  The CPU used in tose tests isn't the greatest however, so it's tough to say where the bottleneck is.


Chris

-- 
Chris Friesen
Software Developer
GENBAND
chris.friesen@genband.com
www.genband.com