Good day.
  I have come across the occasional issue of clock drift when running

(earlier) kernels inside a virtual machine. The reason for drift is

simple enough - host may be under heavy load, guest may not get enough

resources to run all the ticks (HZ) it is supposed to. At least to put

it simply.
  Now, I have been wondering how the introduction of CFS and CONFIG_NOHZ

(dynticks) change this, or if they do at all. If I have understood

correctly, only the host's scheduler is really involved so it enters the

picture when host is running a recent kernel. In a pure hypervisor-only

virtualization, that point should be moot.
  And then we have dynticks. Try as I might, I haven't been able to wrap

my head around the combination. What happens to the kernel and

timekeeping when guest has NOHZ enabled?
  My google-fu is not good enough to find the relevant documentation if

such even exists on this subject. To top it off, I'm not certain whether

my question is trivial, non-issue or just plain weird.
  Any pointers on where I should look for more information will be

appreciated.
--

 Mika Boström      +358-40-525-7347  -=-  The flogging will continue

 Bostik@iki.fi    www.iki.fi/bostik  -=-  until morale improves

 GPG: 0x039F188E; EC67 5B3A E6E3 6A84 9CB2  94D3 BFCD BD57 039F 188E

--