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<  Advanced Erlang/OTP  ~  Erlang Nodes and TCP/IP Traffic congestion?
anderst
Posted: Mon Dec 11, 2006 11:33 am Reply with quote
User Joined: 21 Nov 2006 Posts: 37
I've been experimenting with ejabberd and Tsung. The setup consisted of two Erlang nodes on old PCs (Low spec) being bombarded with requests from a stationary machine and a laptop (Both of a good spec). By finetuning the parameters passed to the emulator (IO threads, Kernel Poll, etc), I managed to get a throughput increase of about 30%.

At this point, the CPU usage was about 70% when the errors started occuring, and slowing down the connection rate resulted in a higher number of simultaneously users. The slave node on another machine helped bring up the load, but still hitting a limit before the machine hit 100% CPU usage. It looks like the system resources TCP/IP stack is the bottleneck, as the system resources were maxed out.

I am wondering about the following:

* Is there an easy way to see how much of the network overhead is caused by the distributed Mnesia and how much is caused by the test clients?

* Is there a preferred OS on which I can run clustered Erlang Nodes under heavy TCP/IP traffic, with thousands of socket connections open? If so, what parameters should be finetuned? Free BSD with a kernel poll flag has been suggested, but the person had no first hand experience.

I emailed the ejabberd mailing list, but got no helpful response. As this is not an IM specific domain, hopefully someone on the list can give me some pointers.

Hilsen,
Anders Trondheim
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anderst
Posted: Wed Jun 20, 2007 12:51 pm Reply with quote
User Joined: 21 Nov 2006 Posts: 37
To reply to my own question, Oscar Hellstrom wrote an excellent thesis which covered part of the issues I raised.

The URL is http://www.erlang-consulting.com/thesis/tcp_optimisation/tcp_optimisation.html

Hilsen,
Anders
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