* Rik van Riel <r...@redhat.com> wrote:
> > I can understand people running hard-RT workloads not wanting to
> > see the overhead of a timer tick or a scheduler tick with variable
> > (and occasionally heavy) work done in IRQ context, but the jitter
> > caused by a single trivial IPI with constant work should be very,
> > very low and constant.
>
> Not if the realtime workload is running inside a KVM guest.
I don't buy this:
> At that point an IPI, either on the host or in the guest, involves a
> full VMEXIT & VMENTER cycle.
So a full VMEXIT/VMENTER costs how much, 2000 cycles? That's around 1
usec on recent hardware, and I bet it will get better with time.
I'm not aware of any hard-RT workload that cannot take 1 usec
latencies.
Thanks,
Ingo
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