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From Oleg Kalnichevski <>
Subject Re: HTTP Core Performance and Reactor Buffer Size
Date Sun, 24 Nov 2013 12:20:32 GMT
On Thu, 2013-11-21 at 12:08 -0800, Hiranya Jayathilaka wrote:
> Hi Devs,
> I just found out that the performance of the Synapse Pass Through transport is highly
sensitive to the RcvBufferSize of the IO reactors (especially when mediating very large messages).
Here are some test results. In this case, I'm simply passing through a 1M message through
Synapse to a backend server, which simply echoes it back to the client. Notice how the execution
time of the scenario varies with the RcvBufferSize of the IO reactors.
> RcvBufferSize (in bytes)                  Scenario Execution Time (in seconds)
> ========================================================
> 8192 (Synapse default)                    25.9
> 16384                                                   0.4
> 32768                                                   0.2


After experimenting extensively with RCV/SND buffer settings (with mixed
results) my personal conclusion was that those settings were better left
alone (set to their system default values). 

I am however not a TCP/IP specialist by any stretch of imagination, so I
may be missing something important.


> Is this behavior normal? If so does it make sense to change the Synapse default buffer
size to something larger (e.g. 16k)?
> Interestingly I see this difference in behavior on Linux only. I cannot see a significant
change in behavior on Mac. 
> Appreciate your thoughts on this.
> Thanks,
> Hiranya
> --
> Hiranya Jayathilaka
> Mayhem Lab/RACE Lab;
> Dept. of Computer Science, UCSB;
> E-mail:;  Mobile: +1 (805) 895-7443
> Blog:

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