On Mon, Mar 22, 2010 at 10:55:18AM +0100, Alexander Graf wrote: > > On 22.03.2010, at 10:15, Dor Laor wrote: > > > On 03/21/2010 01:29 PM, Thomas Løcke wrote: > >> Hey, > >> > >> What is considered "best practice" when running a KVM host with a > >> mixture of Linux and Windows guests? > >> > >> Currently I have ntpd running on the host, and I start my guests using > >> "-rtc base=localhost,clock=host", with an extra "-tdf" added for > >> Windows guests, just to keep their clock from drifting madly during > >> load. > >> > >> But with this setup, all my guests are constantly 1-2 seconds behind > >> the host. I can live with that for the Windows guests, as they are not > > > > Is it just during boot time? If you run ntpdate after the boot inside the guest, does the time is 100% in sync with the host from that moment on? > > > > Glauber once analyzed it and blames hwclock call in rc.sysinit > > In fact, my kvm-clock based guests lag about 1 second behind as well. I suppose there's some compensation code that doesn't work correctly. The problem I found, is that we read wallclock information from kvm host, but later on boot, we call the hwclock binary, which adjusts things as it sees fit. So in this scenario, kvmclock wallclock time is just not being used at all. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
