Xenomai with isolcpus and workqueue task

Alexander Frolov frolov at nicevt.ru
Sat Jul 11 16:25:48 CEST 2020


Hi all!

I am using Xenomai 3.1 with 4.19.124 I-pipe patchon a smp motherboard.  
For my RT task I allocate few CPU cores
with isolcpus option. However, large latency spikes are noticed due to 
igb watchdog activities (I am using common
igb driver, not rt_igb).

Looking into igb sources, it was understood that workqueue is used for 
some tasks (afaiu, it is used to link status
monitoring)

from igb_main.c
...
   INIT_WORK(&adapter->reset_task, igb_reset_task);
   INIT_WORK(&adapter->watchdog_task, igb_watchdog_task);
...

The Linux kernel scheduler runs this igb activities on isolated CPUs 
disregarding isolcpus option, ruining real-time
system behavior.

So the question, is it a correct way to use normal igb on Xenomai at all 
or it is not recommended? What can be done
to prohibit Linux scheduler to allocate those tasks on isolated cores?

Thank you!

Best,
    Alex



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