[ntp:questions] Re: Post processing of NTP data...

John Pettitt jpp at cloudview.com
Thu Sep 29 19:55:11 UTC 2005


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Brad Knowles wrote:

>> At 4:53 PM +0000 2005-09-29, John Pettitt wrote:
>>
>
>>>>  I don't agree with Brad that 10ms is as good as it gets,
>
>>
>>
>>     If your HZ= setting is 100, then 10ms is, by definition, as good
>> as it gets.  At least, when it comes to measuring short-term single
>> event clock timing matters.
>>
>>

No HZ is not the gating factor because the system returns a time based
on the processor cycle count (*)    On my FreeBSD Celeron box a tight
loop calling gettimeofday() shows an average increment of 1.4
microseconds per loop and yes the values change on every call.

John
(*) on machines with APM enabled all bets are off because the CPU
frequency is not stable.


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