Evandro, With respect, you miss the point. The ntpd does not require a tickle every second just to scan for polls; it requires that tickle in order to discipline the clcok frequency. The additional cycles necessary to link to the next association structure, then increment and test a variable, are way, way down in the noise.
Folks might not appreciate just how many counters are coincident with the one-second interrupt. Every association has both a poll counter and headway counter. Every cryptotraphic key has a lifetime counter. Several drivers, includiing the WWVB and ACTS drivers, have internal counters for protocol purposes. There are seconds counters for interface refresh, autokey protocol cookie refresh, leapsecond countdown and hourly statistics. While some of these functions could be managed by a timer queue facility, most of the counters are routinely preempted. With a timer queue facility, these operations would require overhead to sort queues and manage hash tables. Since a one-second interrupt is necessary anyway, extra complexity is simply not justified. Dave Evandro Menezes wrote: > On May 15, 9:28 pm, "David L. Mills" <[EMAIL PROTECTED]> wrote: > >>A timer interrupt is required each second to update the clock frequency >>no matter what. In addition, a sweep is made through the associations to >>see if a poll is pending. It would be in principle posssible to >>implement a system of queues to avopid sweeping the associations each >>second, but that would save very few cycles, add some more cycles and >>additional complexity. > > > NTP could set a reminder for itself not for the next second, in case > there's a poll pending, but for the minimum period left among all > polled servers. This would be pretty simple and power-friendly. > > Mind you, a CPU uses orders of magnitude less power in a stand-by > state, even a simple halt-instruction, than running. See page 3 of > http://download.intel.com/technology/itj/2006/volume10issue02/vol10_art03.pdf > for more info. > > HTH _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
