[ros-users] Arm Core Performance

[Daniel Stonier]

On 5 August 2010 15:35, Cedric Pradalier <cedric.pradalier at mavt.ethz.ch>wrote:

>  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
>
>
That one's on my todo list for this morning already!


>
> On 08/05/10 08:27, Daniel Stonier wrote:
>
>
>
> On 14 July 2010 15:51, Daniel Stonier <d.stonier at gmail.com> wrote:
>
>>  On 14 July 2010 03:52, Josh Faust <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 Pradalierhttp://www.asl.ethz.ch/people/cedricp
>
>
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