[time-nuts] ``direct'' RS-232 vs. RS-232 via USB vs. PPS decoding cards
michael.cook at sfr.fr
Thu Feb 16 17:17:07 EST 2017
> Le 16 févr. 2017 à 13:05, Mike Cook <michael.cook at sfr.fr> a écrit :
>> Le 16 févr. 2017 à 04:09, MLewis <mlewis000 at rogers.com> a écrit :
>> On 15/02/2017 1:17 PM, Chris Albertson wrote:
>>> Why set up a dedicated NTP server if you only have two computers that will use it? ... You could save some money and just run NTP on the two computers. ... NTP is almost zero load on the CPU and the best thing is the NTP accuracy is not effected by CPU load…
> This is not strictly true in all scenarios as the NTP thread has to be able to get to a cpu to be able to do its thing. Higher priority, or CPU intensive threads can starve it.
> The test is not supposed to be an all inclusive and YMMV.
> There are probably methods, such a configuring detected cores for NTP , increasing its priority, and maybe increasing the poll interval that can mitigate the effect.
detected should have been dedicated of course - damned spell checker
> I’ll try that to see what I get.
As I thought the issue can be worked around by tweaking scheduling and cpu affinity.
When I fixed ntpd on cpu 0 and put it in the fifo real time scheduling class there was no change in reported clock offsets when running the same test load.
"The power of accurate observation is commonly called cynicism by those who have not got it. »
George Bernard Shaw
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