[ntp:questions] PPS jitter in Linux

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Tue Apr 3 02:17:49 UTC 2012

Mike S wrote:
> Chris Albertson wrote:
>> Mike S<mikes at flatsurface.com>  wrote:
> I've played around with different cpufreq setting, thinking
>>  it might be related to the processor speed during an IRQ,
>>  but that seems to have minimal impact
>> (performance vs. conservative vs. ondemand).
>> I think your CPU goes into some power saving mode when
>>  there is no load and takes some number of micro seconds
>>  to wake up after an interrupt.
>> Keeping a load on it prevents the sleep or power save
>>  mode and hence the need to "wake up."
> Then explain why setting the cpufreq governor to "performance"
>  (which locks it to the highest frequency (
> http://www.mjmwired.net/kernel/Documentation/cpu-freq/governors.txt )
>  has no significant effect.

_Exactly_ which CPU are you using?

FYI, There are some modern CPUs that ignore OS, BIOS, ...
 under certain conditions, and will power and/or frequency
 manage the cores for thermal management.

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