[rabbitmq-discuss] 3.2.2 triple mem

[der.hans]

Am 19. Feb, 2014 schwätzte Simon MacMullen so:

moin moin,

> 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.

Cool. Sounds like a good feature to me. I'll propose adjusting the setting
to prove that's the difference and allay any worries.

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

Would you add a comment to that page that the default was 20% prior to
3.2.x?

> 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.

A very good presumption in our case :). These machines are dedicated
brokers, so I'm in favor of exclusive use configurations.

ciao,

der.hans
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