[rabbitmq-discuss] Huge latency in Linux, compared with Leopard

[Bogon Choi]

Wow, two guys are great!



Matthias Radestock-2 wrote:
> 
> Holger,
> 
> Holger Hoffstätte wrote:
> 
>> - the fixed penalty for small packets reminded me of good old Mr. Nagle
>> who is not your friend when it comes to latency..and behold! Setting
>> TCP_NODELAY in both the Java client's SocketFrameHandler and the Rabbit
>> startup script (as documented in inet: {nodelay, Boolean}) did the trick,
>> even *with* auto-ack!
> 
> Adding the line
> 
>      -kernel inet_default_listen_options '[{nodelay, true}]' \
> 
> to the options in the rabbitmq-server script does improve the results 
> significantly.
> 
> When running the tests
> 
>    sh runjava.sh com.rabbitmq.examples.MulticastMain -r 100 -s 1024 -a
> 
> rather than getting min/avg/max latencies of 1500/25000/45000 
> microseconds I now get 750/1000/1200 for 2 out of 3 results, though the 
> third result is still off the scale.
> 
> Turning to the Java client and adding the line
> 
>            _socket.setTcpNoDelay(true);
> 
> to the SocketFrameHandler constructor reduced the figures to 450/500/750 
> !! There's the occasional 1200 microsecond max, but that's nothing like 
> the variation we saw before and is perfectly acceptable.
> 
> Thanks Holger for this excellent piece of investigative work.
> 
> So should we make TCP_NODELAY the default?
> 
> 
> Matthias.
> 
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> 
> 

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