Jan Kiszka wrote:

Gregory Haskins wrote:
  

quoted

Jan Kiszka wrote:
    

quoted

Hi,

did anyone recently tried current KVM for Intel over some real-time
Linux? I'm seeing more than 500 us latency peaks on the host,
specifically during VM startup. This applies to both 2.6.29.6-rt23 and
Xenomai/I-pipe. For -rt, I both tried the included (patched) KVM modules
as well as kvm.git head with some additionally required -rt fixes.
Xenomai ran over a 2.6.30 kernel with my own KVM-enabler patch.

Early instrumentation actually points to the guest exit itself: I added
markers right before and after the assembly part of vmx_vcpu_run, and
further instrumentation reports that the next host APIC tick should go
off right inside guest mode. But KVM leaves the switching part 500 us
too late in that case - as if guest exit on external IRQs was disabled.

Will debug this further, but I'm also curious to hear other user
experiences.

Jan

  
      

Hi Jan,
  Did you try to run with latency-tracer enabled?  If not, this may
pinpoint the source for you.
    

I did, see above.
  

Ah, sorry.  It wasn't clear what "instrumenation" was or if you felt it
was definitively pinpointed.  :P

Regards,
-Greg