Asymtopic Behavior in IP Hashing Performance All Kernels and above

From: Jeffrey Merkey
Date: Fri Jul 30 2010 - 13:26:38 EST

With the cwgen.ko packet generator set to the following range of
settings on a Compaw Presario 2200 laptop, I see the following
performance behavior on system throughput:



Interface: lo
Mode: continuous
IP Mode: Random Source/IP/Ports
pktsize: 1500
Interpacket Gap Time: 0 ns

runs at 89 megabytes per second throughput

Interface: lo
Mode: Continuous
IP Mode: Static IP/Static Ports
Range: 16 addresses
pktsize: 1500
Interpacket Gap Time: 0 ns

runs at 217 megabytes per second throughput

There is a significant performance drop (to roughly 1/3) when large
numbers of random IP addresses are routed through the IP stack.
Utilization does not seem to vary much, but the routing throughput
drops drastically.

Jeff Merkey
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