[ros-users] Arm Core Performance

[Daniel Stonier]

On 6 August 2010 00:22, Ken Conley <kwc at willowgarage.com> wrote:

> Does the RPC latency include the time going to the master to lookup
> the service, or is it just measuring the service throughput (i.e. with
> persistent enabled)?
>
> I would expect relatively high latency is this was establishing new
> connections for each service call.
>
>  - Ken
>
>
It's looking for the master - about 98ms for the client to initiate and
reach the server, then ~4ms for the return trip. Still, I'm thinking 98ms is
quite relatively high.



>
> On Wed, Aug 4, 2010 at 11:27 PM, Daniel Stonier <d.stonier at gmail.com>
> 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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> >
> >
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