Wolfgang Grandegger wrote:
On 10/18/2005 01:44 PM Philippe Gerum wrote:

Philippe Gerum wrote:

Wolfgang Grandegger wrote:


attached you will find the results of Xemonai latency measurements on
various embedded PowerPC boards using MPC 8xx and AMCC 4xx processors,
from low to high end covering a worst case latency range from 25 to 225
us. It also includes a comparison with RTAI 3.0r5 on the slowest CPU.
Here are some remarks and comments:

- On low-end processor code size matters a lot and it's difficult to

Beat no, get closer, yes, probably. The good news is that looking at the figures, we do have a margin of improvement! :o>

Btw, the nucleus can be configured so that the user-space threading engine is compiled out (i.e. CONFIG_XENO_OPT_PERVASIVE from the nucleus menu), which would be the corresponding profile to compare with klatency (i.e. sched_up). Disabling this option reduces the code size for the nucleus from:

  text       data        bss        dec        hex    filename
66740 792 6540 74072 12158 nucleus/xeno_nucleus.ko


 text       data        bss        dec        hex    filename
52596 576 3956 57128 df28 nucleus/xeno_nucleus.ko

Disabling the periodic timer support which is unused for the klatency test brings this down to:

   text    data     bss     dec     hex filename
  51040     544    3956   55540    d8f4 nucleus/xeno_nucleus.ko

OK, here are the new figures with (*)


           |-----lat min|-----lat avg|-----lat max|-overrun|---test-time
RTAI 3.0r5 |       23120|       31838|       70520|       ?|    00:12:26
Xenomai    |       50560|       98976|      199040|       0|    00:09:45
Xenomai (*)|       44160|       96215|      200640|       0|    00:09:53

The min latency decreases as expected.

I just discovered that -00 did not include some recent changes I had in my tree, aimed at prevent high latencies during fork pressure. I've committed -01 which does include them. When time allows, I'd be interested to know if this has some impact on the Ocotea figures. TIA,



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