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

Matt Pietrek mpietrek at skytap.com
Tue Oct 22 23:44:36 BST 2013

Hi Matthias,

The load on our box (it's in production) has dropped a little bit, but core
0 is still running nearly flat out.

Here's the output you asked for:

22:39 PROD user at host:rabbitmqctl.py eval 'erlang:statistics(run_queue).'

Which per your comment, doesn't look like a promising lead.

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.

Also, we are running this in a cluster with another box, with all queues in
HA mode. I imagine that would have some overall CPU impact, but don't see
why it would concentrate everything on one core. The slave node CPU
utilization is much lower, but also shows most activity on one CPU.



On Tue, Oct 22, 2013 at 2:55 PM, Matthias Radestock
<matthias at rabbitmq.com>wrote:

> Matt,
> On 22/10/13 22:31, Matt Pietrek wrote:
>> Thanks Zhibo. We actually have hundreds of queues. Two of them are
>> processing several hundred messages/second. The remaining queues are
>> processing 1 or 2 messages second.
> Could be an Erlang scheduler thing. Give the latest Erlang release a try,
> since multi-core scheduling is definitely an area that has undergone
> considerable changes in recent releases.
> Also, try running
>  rabbitmqctl eval 'erlang:statistics(run_queue).**'
> if this is >0 then there are runnable processes waiting for execution,
> which would indicate some scheduler anomaly.
> Matthias.
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