Re: [Xenomai] xenomia on virtual box

[Jan Kiszka <jan.kiszka@web.de>]

On 2015-03-25 16:38, Roland wrote:
> Thanks Jan.
> 
> Will try KVM on top of PREEMPT-RT.
> 
> Is there a distribution particulalry suited to patch with PREEMPT-RT?

Any is fine, just replace the kernel.

Regarding tuning of the guest, you should try to study some basics in my
original paper [1]. Details have changed, specifically QEMU has evolved
a lot, but the core problem remains: prio inversion due to device emulation.

Therefore, you won't see improvements in worst case latencies just by
using QEMU/KVM on a PREEMPT-RT kernel. You will also have to isolate
anything that triggers problematic emulations (UART, VGA, disk, ... -
just virtio-net is less problematic) from RT applications in your guest
via SMP, possibly also isolcpus and xenomai.supported_cpus.

Given that, the question is which benefits you will get from such a
setup and if the effort pays off.

Jan

[1] http://lwn.net/images/conf/rtlws11/papers/proc/p18.pdf


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