Johan, If I am not very wrong, you should have plenty experiences with VxWorks (Maintainer of VxWorks FAQ ?). So if you have the correct timing measurements for Xenomai, could you make similar tests on your board with VxWorks, just to have a comparision ? I understand that this comparision is not fair, but I think people can better see, where Xenomai is currently standing.
Philip: Also for our MPC5200B based board we get bogus latency measurements. How can we find out the right value of /proc/xenomai/latency ? Wouldn't an auto calibration be more useful when starting up (similar to the Linux Bogo Mips value), because actually one can configure the boards to have different bus speed settings, so the CPU detection alone will not be sufficient ? Best regards, Daniel Schnell. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Johan Borkhuis Sent: 3. maí 2007 12:36 To: [email protected] Subject: [Xenomai-help] Latency calculation and test I am quite new to Xenomai, but not to realtime and embedded development. I am trying to run Xenomai on a MVME3100 board (PPC8540 processor, kernel version 2.6.14, Xenomai 2.3.1). I am trying to do latency measurements on my target, and I have some questions. As far as I understand it, the value in /proc/xenomai/latency is the time needed to start a timer, and this value is subtracted from the value provided to the timer. The value calculated by Xenomai on my platform is 9489. All latencies reported with the latency tool are negative when this value is used. When I write 0 to this setting (to get the real values without offset) and run the latency test program I see different values for the different modes: user space = 3.6 usec, kernel space = 1.8 usec and IRQ = 0.9 usec. What is the relation between the value calculated by Xenomai and the values measured by the latency program, and what is the correct way to calculate the latency setting? I also did a port of the cyclictest program to Xenomai. Instead of the pthreads I used the RT-tasks, like the latency program. The cyclictest program uses signals to trigger the task, but as I found out this does not work in userspace: the applications returns to secondary mode at the moment the thread waits for a signal. Is there another way to do this (next to moving the whole program to kernel space)? One option of the cyclictest program is that you can have several threads running. I modified the output of the cyclictest tool somewhat, to have min, max and average like the latency program. When running multiple threads within this program (without load) the values range from -5 usec to +5 usec, with an average of around 0 usec. But with more RT tasks I see a very high latency once in a while (over 400 usec). Below is the example of such a test run with 10 threads/tasks: T: 0 ( 1305) P:80 I:1000 O: 0 Min: -2.404 Avg: -0.001 Max: 1.873 T: 1 ( 1306) P:79 I:1000 O: 0 Min: -3.052 Avg: -0.001 Max: 1.584 T: 2 ( 1307) P:78 I:1000 O: 0 Min: -5.694 Avg: 0.000 Max: 18.282 T: 3 ( 1308) P:77 I:1000 O: 0 Min: -5.166 Avg: 0.046 Max: 479.782 T: 4 ( 1309) P:76 I:1000 O: 0 Min: -2.595 Avg: 0.036 Max: 368.310 T: 5 ( 1310) P:75 I:1000 O: 0 Min: -1.731 Avg: -0.001 Max: 1.633 T: 6 ( 1311) P:74 I:1000 O: 0 Min: -481.273 Avg: -0.001 Max: 490.352 T: 7 ( 1312) P:73 I:1000 O: 0 Min: -273.947 Avg: -0.001 Max: 277.717 T: 8 ( 1313) P:72 I:1000 O: 0 Min: -47.016 Avg: -0.001 Max: 45.789 T: 9 ( 1314) P:71 I:1000 O: 0 Min: -22.968 Avg: -0.001 Max: 29.572 (P=Priority, I=interval, O=overruns) When looking at the detailed information, I see that the latencies occur when a higher priority task is ending. Is there some specific reason for this, or is there some kind of configuration problem with my setup? Kind regards, Johan Borkhuis _______________________________________________ Xenomai-help mailing list [email protected] https://mail.gna.org/listinfo/xenomai-help _______________________________________________ Xenomai-help mailing list [email protected] https://mail.gna.org/listinfo/xenomai-help
