[ntp:questions] how to change the runtime priority of NTPD on Windows

Dave Hart davehart at gmail.com
Thu Feb 9 13:13:04 UTC 2012

On Wed, Feb 8, 2012 at 19:55, Ron Frazier (NTP)
<timekeepingntplist at c3energy.com> wrote:
> It doesn't appear to me that -M is related to process priority, but to
> internal scheduler timing.  I tinkered around with the -P parameter a
> little, but couldn't detect any changes.

-P is a no-op for the Windows port.  Windows doesn't use a simple
numeric priority scheme.  The NT microkernel underneath does, but
Windows exposes priority class, which is process-wide, and thread
priority deltas (above normal, below normal, etc).  The ntpd Windows
port has always ignored -P, changing that would be a
backwards-incompatible change for little to no benefit.  As previously
described, ntpd on Windows always raises the priority class as much as
possible, and sets different threads' relative priorities
appropriately (unlike POSIX ntpd, Windows ntpd has also long used
threads, one for I/O completions, and if interpolating a
higher-resolution clock using the performance counter, another to
gather correlations between the two oscillators involved, and
transiently for DNS lookups).  More recently, POSIX ntpd moved to
using threads where available instead of a forked child for
otherwise-blocking DNS queries.

Dave Hart

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