[ntp:questions] What should the poll be for the shared memory driver (type 28)?

David Taylor david-taylor at blueyonder.co.uk.invalid
Mon Jun 17 18:02:09 UTC 2013

On 17/06/2013 17:36, Steve Kostecke wrote:
> grepping the source tree is very informative...
> According to ./ntpd/ntp_peer.c:
> /*
>   * It is an error to set minpoll less than NTP_MINPOLL or to
>   * set maxpoll greater than NTP_MAXPOLL. However, minpoll is
>   * clamped not greater than NTP_MAXPOLL and maxpoll is clamped
>   * not less than NTP_MINPOLL without complaint. Finally,
>   * minpoll is clamped not greater than maxpoll.
>   */
> And in ./include/ntp.h we find:
> :#define NTP_MINPOLL     3       /* log2 min poll interval (8 s) */

Thanks, Steve.  My knowledge of the source tree is even more limited 
than my knowledge of "C"!  In refclock_shm.c, it does say that the 
"peek" routine is called every second, so if the type 28 driver has an 
internal poll of one second, does it matter what min/max poll is set in 
the ntp.conf file?  Does it even need to be set at all?

I'll try setting it to 4, as a test, and see whether anything changes.

Sorry if I'm asking very basic questions, but if I'm going to write a 
small Web page about this I would rather the contents be accurate and, 
if possible, best practice.
Web: http://www.satsignal.eu

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