[Bridge] Bridge performance problem

Joubert Berger joubert at berger-family.org
Wed Aug 25 20:20:32 PDT 2004


I need some help understanding a strange bridge performance problem I am
seeing.  Maybe I am making more out of this than I need to.  I need your
opinions.

The setup:

The first configuration is two machines connected via a cross over
cable:

Machine A <====> Machine B

The second configuration is two machines with a Linux bridge between
them:

Machine A  <===> Linux Bridge <===> Machine B

I am using netperf to do some performance measuring.  

I am running two tests.  One is the "streaming" test (the default test
for netperf) and the other is the "Connect Request/Response" (TCP_CRR)
test.

When I run the stream test against the top two setups, I get near line
speed.  I am happy with these numbers.

When I run the TCP_CRR test, for the first setup I get around 2200
connections per second, but in the second configuration I are getting
around 700-800 connections per second.  Why am I getting this big of a
difference?

I am running Redhat kernel 2.4.20-30.9 (RH9).  I also changed the
txqueuelen on the two bridge interfaces to 50000.

Anyone have any idea why I am seeing such a big difference in the
TCP_CRR test?  The introduction of the Linux bridge cause me some real
performance problems.

--joubert




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