[Beowulf] ...Re: Benchmark results

Andrew Piskorski atp at piskorski.com
Thu Jan 8 16:48:35 EST 2004


On Thu, Jan 08, 2004 at 11:34:26AM -0500, Robert G. Brown wrote:
> On Thu, 8 Jan 2004, Josip Loncaric wrote:

> > I love NTP, but in its current state it does not deliver microsecond 
> > level synchronization.

> > NTP may need to be streamlined and tuned for clusters...
> 
> I'm not sure that the problem is NTP itself -- from what I recall
> reading in its documentation it is CAPABLE of achieving 1 usec
> synchronization, over time.  However, in order to do that it needs
> better tools than the current gettimeofday (and other time calls) which
> seem to deliver no better than perhaps millisecond resolution.  It also
> very likely needs to be done not by a userspace daemon but by the
> kernel, as only the kernel can decide to do something in a true "single

Would DJB's clockspeed, taiclock, etc. stuff be any better than ntp
for that?  His website mentions using CPU hardware tick or nanosecond
counters, but doesn't define "precise" when it says that taiclock is
"... suitable for precise time synchronization over a local area
network ...":

  http://cr.yp.to/clockspeed.html
  http://cr.yp.to/libtai.html

-- 
Andrew Piskorski <atp at piskorski.com>
http://www.piskorski.com/
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