Fedora 13 networking performs extremely well

[Uwe Zimmermann]

Hello,

our product "MIMIC Simulator" has been running on Fedora for a long time
(eg. see

http://www.gambitcomm.com/site/support/support_platforms.shtml

).  But, we have seen a steady decline in performance over successive
versions of Fedora (eg. see

http://gambitcomm.blogspot.com/2010/06/mimic-1030-performance-test-report-high.html

Our application is somewhat unique in that it can create many (10s of
thousands) IP aliases, opens sockets to multiple ports on each.

Only with Fedora 13 (kernel version 2.6.33.6-147.fc13.x86_64) have we
seen a surprising performance improvement, where running 20,000 simulated
agents is the same as running 10, in terms of networking performance. At
first we could not believe it, but subsequent tests have confirmed that
we indeed are seeing the improved performance. The specific improvement
seems to be that the kernel seems to be efficiently demultiplexing among
all open sockets to deliver received messages from the network card.

Can some expert point me at a specific fix (spec, kernel module, source
code revision) that could account for this? It would be in the networking
code, possibly the socket demultiplexer. I have looked for this for a
while and just cannot find it. This change would be after Fedora 12.
Any hint would be appreciated.

Thank you in advance.

Uwe Zimmermann
Gambit Communications