[rabbitmq-discuss] 3.2.2 triple mem

Simon MacMullen simon at rabbitmq.com
Wed Feb 19 10:30:19 GMT 2014

On 19/02/14 09:25, der.hans wrote:
> Is there a known reason for 3.2.2 to use 3x the memory used by 3.1.5 for
> the same load?

Possibly. 3.1.x and earlier would page messages to disk if memory use 
went above 20% of the vm_memory_high_watermark (i.e. if > 8% memory was 
used with the default watermark).

3.2.x made this setting configurable (as 
vm_memory_high_watermark_paging_ratio) and also changed the default 
value for it from 20% to 50%, so it will start paging once > 20% memory 
is used.

See http://www.rabbitmq.com/memory.html#memsup-paging for information on 
this setting.

In general the default values for vm_memory_high_watermark and 
vm_memory_high_watermark_paging_ratio are set on the assumption that 
RabbitMQ is the only significant thing running on the machine, and thus 
that it's reasonable for it to use all available memory if it will make 
things go faster.

Cheers, Simon

Simon MacMullen
RabbitMQ, Pivotal

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