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

Tue Apr 22 14:06:37 BST 2014

Thanks for your note regarding the scheduler.

Indeed the performance doubled once I set +sfwi flag to 1. I could achieve
40KHZ inter-node instead of 20KHZ (Expected 100KHZ)
I will try to play with other scheduler flags and see what will happen

Thanks again. I would appreciate updating me if you got the chance to have
more info related to this inter-node bottleneck.

On Thu, Apr 17, 2014 at 4:56 PM, Matthias Radestock
<matthias at rabbitmq.com>wrote:

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