[ntp:questions] Performance of NTP under Windows Vista?

David J Taylor david-taylor at blueyonder.not-this-bit.nor-this-bit.co.uk
Tue Nov 20 14:51:37 UTC 2007

Ryan Malayter wrote:
> On Nov 19, 12:15 pm, "David J Taylor" <david-tay... at blueyonder.not-
> this-bit.nor-this-bit.co.uk> wrote:
>> I don't currently understand the behaviour, as it seemed to take
>> several days to reduce the offset by a hundred milliseconds
>> (averaged), whilst showing a lot of intermediate noise, followed by
>> sudden cessation of the noise when the offset was near zero.
>> I'd love to hear from anyone who has made comparative performance
>> measurements, or who has suggestions as to how to proceed.
> My previous reading indicates that Vista and Server 2008 have had
> significant changes to their internal timing architecutre, mostly to
> better support multi-media and near-real-time applications, as well as
> enhanced power management. So I think, perhaps, ntpd might be making
> assumptions that no longer apply in the Vista world. I am unsure of
> the complete changes, however.
> There is also this bug in the Vista driver for the High Precision
> Event Timer, which is available on newer hardware:
> http://support.microsoft.com/kb/933272. I would test with that patch.
> We only have Vista on laptops at the moment, with variable
> connectivity and lots of sleep/wake cycles. So we just use the built-
> in Windows Time Service, which handles those conditions well enough to
> keep things within 100ms or so. Ntpd did not behave well in my
> previous tests with various network interfaces coming on and off
> (Wired Etherenet, WiFi, and EVDO connections are used intermittently
> throughout the day on all of our laptops). Plus power modes changing
> all the time.
> I will check into deploying ntpd on Vista desktops as soon as we get
> one deployed, but we only seem to be deploying laptops these days.

Thanks, Ryan.  You may well be correct about the changes, but I had read 
here some time ago about the performance being "satisfactory" under Vista 
from (IIRC) Heiko who is usually quite thorough.

Noted on the pointer to the patch, but that doesn't seem to relevant in 
that this PC is permanently on, and not rebooted.  Of course, the patch 
may do more than just fix the restart issue......

Interesting about the desktops - out of fashion!


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