[ros-users] Arm Core Performance

[Cedric Pradalier]

Hello Daniel,

Could this be linked with the high-frequency loops I mentioned in my 
posts last week?
Or, could the latency be affected (positively or negatively) by the 
changes I was proposing?

Cheers

On 08/05/10 08:27, Daniel Stonier wrote:
>
>
> On 14 July 2010 15:51, Daniel Stonier <d.stonier at gmail.com 
> <mailto:d.stonier at gmail.com>> wrote:
>
>     On 14 July 2010 03:52, Josh Faust <jfaust at willowgarage.com
>     <mailto:jfaust at willowgarage.com>> wrote:
>     >> == NUM_PTS 1000 ==
>     >>
>     >> board               avg_ser     avg_deser
>     >> intel i5             0.000011    0.000025
>     >> arm1176jzf-s   0.001328    0.003354
>     >
>     > Ok, so serialization is definitely much slower, but with the
>     latency test
>     > you're using it shouldn't affect anything.  Good to know though.
>     >
>     >>
>     >> == Latency Results ==
>     >>
>     >>                          IPC        NoTCP      Bypass
>     >> intel i5           :   0.4ms     0.10ms     0.05ms
>     >> arm1176jzf-s :   25.0ms   4.50ms     3.50ms
>     >>
>     >> ====== Raw Socket Tests ======
>     >>
>     >> Tests the latencies of sending a single char from server to client,
>     >> written using simple posix socket code.
>     >>
>     >> intel i5           : 0.1ms
>     >> arm1176jzf-s : 1.4ms
>     >
>     > Do you have any way of profiling exactly what's taking time,
>     either with
>     > gprof, google perf tools, or something else?
>     > Josh
>
>     Since the slowdowns were across the board I started doubting the
>     platform underneath the ros - ran some test programs I have back on
>     our very simple non-ros platform and noticed a significant difference.
>     So I'll rebuild the platform, check some of the flags used on the old
>     build and make sure I match them on the new one and see how that goes.
>     Will try gprof in parallel too I think, but its going to be a couple
>     of days recompiling. Will let you know how it goes and thanks for the
>     advice.
>
>
> Got waylaid by another project for a while - sorry to drag out old 
> cobwebs!
>
> Optimised everything else, made sure I'm using the correct flags for 
> the platform and the tcp/ip msg latencies have dropped from 25ms -> 
> 9-10ms, which is starting to perhaps seem reasonable. The rpc 
> latencies are still horrendous though - ~100ms for one process to get 
> in contact with another (and about 5ms for the return trip). I managed 
> to get gprof working on it and compared it to the same processes 
> running on the intel i5, but its showing up nothing of considerable 
> note. Just some boost spinlocks contributing an extra 10% worth of cpu 
> time (which probably dont show up on the i5 simply because they 
> trigger on and off so fast). But certainly nothing obvious.
>
> So, I'm guessing that the process (or roscore) is idling/hanging 
> somewhere. I'm going to have to manually hack some of the ros code and 
> pull some timings to figure out just where I think (don't know of a 
> better way).
>
> The results are at http://snorriheim.dnsdojo.com/tmp/rpc_latency if 
> interested.
>
>
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>    


-- 
Dr. Cedric Pradalier
http://www.asl.ethz.ch/people/cedricp

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