Tannert Christian wrote:
Hello to all,
is it possible, to run rtnet in soft realtimemode in rtai or is it always necessary to run it in hardrealtime mode ?
Our requirements are not so strict (latency ~15ms) and our application has to use functions that are not allowed to be used in hard realtime. But straight linux is too slow and too unpredictable, so in our case the soft realtime mode in rtai would be the best for us.
I 've done tests with softrealtime mode, but it seems that the rtnet communication doesn't work. The same application works in hardrealtime mode. Do I have to adjust some details or is it impossible to run rtnet in softrealtimemode ?
I use kernel 2.4.18, rtai24.1.11, rtnet 0.7.0.
Generally, I don't advise users to select an older version, but in your case this may help for now. I think, 0.6.2 (+patch) should work with NEWLXRT tasks in soft real-time mode.
0.7.0 does not (yet) work in soft mode because the interface between RTnet and the user-space task has changed. In former versions, RTnet relied on the automatic migration of soft real-time calls to hard real-time (RTnet requires hard real-time internally) by LXRT. Now, the new glueing layer between tasks and RTnet (=>RTDM) allows to let the driver (here: RTnet) to decide if the migration shall be performed or if different contexts shall be handled by different functions. Unfortunately, this is not fully implemented yet in RTDM, so your soft real-time call simply fails (-ENOSYS).
Alternatively, as you don't seem to be very time-constricted, you could set up an additional hard real-time communication task for the RTnet calls which would communicate with your soft real-time task via mailboxes etc. This adds some overhead but would allow you to already use all improvements and fixes of 0.7.0.
Jan
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