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Re: clock constantly out of sync

To: "LinuxVirtualServer.org users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: clock constantly out of sync
From: Claudio Di Martino <claudio@xxxxxxxxxxxxxxxxxxxxxx>
Date: Thu, 17 Nov 2005 12:03:48 +0100 (CET)
On Thu, 17 Nov 2005, Leon Keijser wrote:

AFAIK if the guest clock is too slow you may fix it reducing the 
interrupt frequency as suggested here:

> > - On the  VMWare Server management console webinterface, go 
> > to Options , 
> > Advanced Settings, and search fro the option  Misc.TimerHardPeriod. 
> > Default value is 1000 , adjust it to 333.

You could reduce it even more, setting it at 100 (which was the default
with 2.4 kernels).

However, if I remember correctly, your clock runs too fast.
This is due to lost ticks. The kernel tries to compensate for lost ticks
but different timers handle this too aggressively and over compensate.
This happened to me with two GSX guests running gentoo and 2.6 kernels.
The clock went so fast that it gained more than an hour a day!
I'm using ntpd (ntpdate makes the clock jump at a discrete point in time 
while ntpd tries to slowly adapt the clock over a period) but the clock
went so fast that ntpd refused to compensate it. 
I finally solved the problem changing the timer used by the kernel to 
clock=pit. With this option addet to my lilo.conf the ntpd daemon works
flawlessy now on my gentoo guests...

Ciao!!!

Claudio


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