[rabbitmq-discuss] Fwd: Performance bottleneck on inter-node connection

Matthias Radestock matthias at rabbitmq.com
Thu Apr 17 14:56:32 BST 2014

On 15/04/14 14:20, joseph rouphael wrote:
> On Mon, Apr 14, 2014 at 12:00 PM, Matthias Radestock
> <matthias at rabbitmq.com <mailto:matthias at rabbitmq.com>> wrote:
>     What happens when you run the above test with both nodes on the same
>     machine?
> The result is almost the same: Fluctuating between 10 and 23KHZ

Thanks for running all these tests. I've reproduced your observations.

What we are seeing here is, at least partially, an issue with the Erlang 

I noticed that when running the test with PerfTest, single producer, 
single consumer, two nodes, the consuming node was using 100% CPU, i.e. 
the equivalent of a single core. That is usually an indication of an 
Erlang scheduler issue since there is an appreciable degree of 
parallelism that should be exploitable.

For this particular test I managed to double performance by supplying 
the "+swt very_low" or "+sfwi 1" flags to Erlang via 

So these flags, plus the other +s... flags of the Erlang VM, are worth 
playing with.


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