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 > wrote: > > On 14 July 2010 03:52, Josh Faust > 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. > > > _______________________________________________ > ros-users mailing list > ros-users@code.ros.org > https://code.ros.org/mailman/listinfo/ros-users > -- Dr. Cedric Pradalier http://www.asl.ethz.ch/people/cedricp