[rabbitmq-discuss] MTU

Sat May 8 18:04:30 BST 2010

On Sat, 08 May 2010 13:05:39 +0100, David Wragg wrote:

> Gustavo Aquino <aquino.gustavo at gmail.com>
> writes:
>> I want to know if I post a message with 213 Bytes whats your MTU? whats
>> the oversize ? And what MTU for high throughput ? if I change my network
>> interface to 2000 MTU Rabbit will follow it ?
> 
> The MTU is decided by the operating system's network stack.  As Emile
> said, RabbitMQ has no way to observe or control the MTU.

It is certainly possible and not at all unusual for network software to
observe the MTU of a given interface (via an ioctl) and use it
accordingly. The most obvious use case for Rabbit would be batching of
small messages, where every payload is just a few bytes. This would
significantly reduce kernel context switches and NIC interrupts, at the
obvious expense of per-batch latency.
The throughput increase in scenarios with many small messages can be quite
dramatic, especially when the entire network is using jumbo frames.

-h