On Wed, Apr 21, 2010 at 2:17 AM, Rob <[email protected]> wrote: > I am running different Linux kernels (older and newer) under VMware ESX > version 4 but the timekeeping is still worse compared to a physical machine. > You should expect the offset and jitter to be in the several-milliseconds > range on a local network. > It seems that each method of providing timing to the virtual machine has > disadvantages.
I think non-paravirtualized VMs will always be at a serious disadvantage for timekeeping because of the way interrupts are coalesced and the VMs get de-sceduled for variable periods of time. The only alternative I can think of would be to patch the time-related functions in kernels of all guest OS with some sort of pass-through to a host-controlled system timer infrastrcuture, and do no synchronization whatsoever inside of guest OS. I am going to run some tests to see if running Windows Time Service or NTP on Windows guests instead of VMware Tools time synchronization is actually better. The article in question only covers Linux. VMware's previous advice was to use VMware tools time synchronization on both Linux and Windows, so I think perhaps they just haven't gotten around to re-testing NTP-based solutions on Windows. -- RPM _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
