For services, I would make sure to enable the 'persistent' mode so
that you are only testing the C++ code and not looping through a
service lookup, but given that services and topics are both showing
slowdowns, perhaps you already did this.

 - Ken

On Thu, Jul 8, 2010 at 7:02 PM, Daniel Stonier <d.stonier@gmail.com> wrote:
> Now that I'm getting some working results, I'm a bit curious about the
> arm performance for ros messaging. I have two test cases running on an
> armv6 core (arm1176jzf-s).
>
> Topics (time taken from publisher sending a message to subscriber
> callback activating)
>  - intel i5: ~200us
>  - armv6: ~ 20ms
>
> Services (time taken on a round trip rpc request response passing
> float64 data values)
>  - intel i5: ~2ms
>  - armv6: ~ 190ms
>
> Can it really be 100x slower? This kernel does not yet have a low
> latency scheduler (kernel premption is not configured, will figure out
> how to do that later) but I thought that would only affect performance
> by a few milliseconds, not tens or hundreds of ms. Is there perhaps
> some critical kernel configuration or something similar I'm missing? I
> guess the next thing to do would be to write a very simple tcp/ip
> client/server pair and test it without ros.
>
> Regards,
> Daniel.
>
> --
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> Home: http://snorriheim.dnsdojo.com/
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