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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