[rabbitmq-discuss] RabbitMQ / Erlang not running on all cores?

Matthias Radestock matthias at rabbitmq.com
Wed Oct 23 08:08:22 BST 2013


On 22/10/13 23:44, Matt Pietrek wrote:
> The load on our box (it's in production) has dropped a little bit, but
> core 0 is still running nearly flat out.

If you are seeing *less* than 100% utilisation of one core then your 
system is *not* CPU bound.

Check that RabbitMQ is actually a bottlneck here, rather than, say, your 
producers or consumers.

> Are there other useful "eval" commands that I could use to ferret out
> what's happening? This is a box in production and we have an upcoming
> release that's only going to add more load on this box.

We could come up with some eval code to identify the top running 
processes. Or perhaps find a way to get etop to run (Erlang's equivalent 
of 'top'). But...

> Also, we are running this in a cluster with another box, with all queues
> in HA mode.

There have been tons of improvements *and bug fixes* to mirrored queues. 
Some relating to performance. So I strongly recommend you upgrade 
RabbitMQ to the lastest version. And Erlang too, due to the SMP 
scheduler improvements I mentioned in my earlier email.

If you still see performance anomalies after the upgrade then we can 
investigate further.



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