[ntp:questions] Re: ntpd server on Linux/Debian with SPARC Sun Blade 100

Richard B. Gilbert rgilbert88 at comcast.net
Thu Oct 19 15:07:56 UTC 2006

Olivier Bornet wrote:

> Hello,
> On Thu, Oct 19, 2006 at 01:23:36PM +0200, Uwe Klein wrote:
>>i had a similar problem the other way round ( clock gaining) while your
>>clock seems to be loosing.
>>when you do not use ntpd does the clock start to lag rather fast?
> I have manually check without ntpd, and after 2 hours, the system has
> loose about 6 seconds. So, about 2 seconds per hour seems to be too much
> for ntpd.
>>While searching for my problem i seem to remenber some issue with loosing
>>timer interrupts ( i.e. This may not be ntpd related )
> Right. I hope that the solution suggested by the other emails to set HZ
> to 100 instead of 250 or 1000, or adjust the drift will correct the
> problem. If not, I will look in the interrupts direction.

If lost interrupts are the problem, you probably should not try to fix 
it by trying to tinker with the "drift".  The reason is that the lost 
interrupts are the result of device drivers, probably disk drivers, 
disabling or masking interrupts for too long a time.  If this is the 
case, the problem should disappear when the machine is not busy.  (If 
you tinker and the problem disappears when the machine is not busy, your 
clock will be off again when the machine is not busy.)

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