[ntp:questions] VM host not snyching time

Ryan Malayter malayter at gmail.com
Thu Mar 25 01:07:25 UTC 2010


On Wed, Mar 24, 2010 at 7:49 AM, Rob <nomail at example.com> wrote:
> Maarten Wiltink <maarten at kittensandcats.net> wrote:
>> Do VMs still have problems responding to timer ticks when there are
>> enough cores to go around?
>
> If anything, the problems tend to get worse when you have many cores.

Multi-core VMs present a significant challenge in a virtualized
environment, as the cores themselves can actually run at slightly
different times rates, and may be de-scheduled by the hypervisor at
different times.

And this "disparity between cores" has actually become even greater in
the most recent VMware 4:
http://www.vmware.com/files/pdf/perf-vsphere-cpu_scheduler.pdf

Great for aggregate application throughput, but not so good for NTP. I
wonder if setting affinity for NTP to a single virtual core would
help.

-- 
RPM




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