[Xenomai] real-time guarantee issues on xenomai 2.6.2.1

Ludovic Righetti ludovic.righetti at tuebingen.mpg.de
Thu Aug 7 21:16:20 CEST 2014


> This is more likely a I-pipe issue (3.4.6/x86 is outdated, although 1 ms
> is really above usual issues), a kernel configuration issue (e.g.
> CONFIG_CPU_FREQ, or other latency killer), or maybe a SMI problem. Or
> maybe an issue induced by a graphic card driver if you happen to run
> with a GUI.
>
we have the same issue (same machine Alexander described - xeno 2.6.3 /
kernel 3.8.13 ipipe patch from the xenomai tar)
below the xeno latency output when I run with a watch -n .1 cat
/proc/xenomai/stat and no X-windows server. I do not have the problem
without the watch command and with running a x-window (ubuntu 12.04
desktop) although I get latency spikes when opening open gl windows
(which I know is normal).

CONFIG_CPU_FREQ, CPU_IDLE, ACPI_PROCESSOR, INPUT_PCSPKR are disabled in
my kernel config. Not sure if there could be other latency killers I
should disable.

RTH|----lat min|----lat avg|----lat max|-overrun|---msw|---lat
best|--lat worst
RTD|     -2.413|     -0.799|    141.488|       1|     0|     -2.413|   
141.488
RTD|     -2.423|     -0.494|    477.758|      15|     0|     -2.423|   
477.758
RTD|     -2.440|     -0.564|    286.563|      23|     0|     -2.440|   
477.758
RTD|     -2.389|     -0.858|    118.116|      24|     0|     -2.440|   
477.758
RTD|     -2.376|     -0.980|     71.960|      24|     0|     -2.440|   
477.758
RTD|     -2.375|     -0.671|    100.248|      24|     0|     -2.440|   
477.758
RTD|     -2.382|     -0.872|    184.203|      26|     0|     -2.440|   
477.758
RTD|     -2.383|     -0.739|    260.341|      33|     0|     -2.440|   
477.758
RTD|     -2.380|     -0.760|    711.203|      41|     0|     -2.440|   
711.203
RTD|     -2.314|     -0.658|   1664.493|      63|     0|     -2.440|  
1664.493
RTD|     -2.413|     -0.838|    134.240|      65|     0|     -2.440|  
1664.493
RTD|     -2.435|     -0.661|    381.385|      68|     0|     -2.440|  
1664.493
RTD|     -2.317|     -0.872|     93.973|      68|     0|     -2.440|  
1664.493
RTD|     -2.316|     -0.568|   2756.048|     100|     0|     -2.440|  
2756.048
RTD|     -2.387|     -0.870|    117.891|     102|     0|     -2.440|  
2756.048
RTD|     -2.319|     -0.950|     66.645|     102|     0|     -2.440|  
2756.048
RTD|     -2.384|     -0.864|     86.956|     102|     0|     -2.440|  
2756.048
RTD|     -2.385|     -0.878|     73.840|     102|     0|     -2.440|  
2756.048
RTD|     -2.380|     -1.000|     42.325|     102|     0|     -2.440|  
2756.048

best wishes
ludovic



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