[ntp:hackers] Of Linux and jitter

David L. Mills mills at udel.edu
Tue Oct 19 13:00:16 PDT 2004


Brian,

We have a lot of Ultra 10s around here and are about to upgrade pogo. 
The staff saays we will upgrade to 10 when it is officially announced; 
however, I'll see if it can happen quicker for at least one of my 
Solariba. Thanks for the tip.

Dave

Brian Utterback wrote:

> I would suggest that you upgrade or at least dual boot the Blade to use
> Solaris 10. The Dtrace facility makes debugging this kind of problem
> pretty simple. Unfortunately, the Ultra-1 will not run Solaris 10, much
> to my chagrin.
>
> David L. Mills wrote:
>
>> Guys,
>>
>> 1. All the backroom and campus machines are now running ntp-dev and 
>> all seem to work except Linux albert on the campus wire. It segfaults 
>> after a few minutes. I am dumb with Linux debugging tools, so I'll 
>> leave the carcass on the hope some Linux jockey can look at it.
>>
>> 2. I'm very suspicious about the Solaris jitter using a serial port 
>> and any of several radios. The jitter can be over one second(!) and 
>> varies in intensity with time. I can't believe the port interrupt 
>> routine can have jitter that high. The jitter does not occur with a 
>> SunOS SPARC IPC running ntp-dev, which is now the best timekeeper we 
>> have. The jitter first showed up on Ultra-1 pogo running Solaris 8/9 
>> and Blade 1500 running Solaris 9. Could there be something in the 
>> ntpd I/O code causing this? It's only in the serial port code; there 
>> is no such jitter in the packet I/O code.
>>
>> Dave
>>
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>
>




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