David,
I beg to differ. All the machines I used are PCs or similar
workstations. They really and truly behave according to an exponential
distribution with a small mean of a few to a few tens of microseconds. I
have done a tedious histogram from which I can pick out the cache
replacement, context-switch and timer interrupts. I've used both uniform
and exponential noise models with substantially the same results. Since
I was looking for the best performers, most of the data was collected on
lightly loaded machines; the characteristics with a heavily loaded
campus server are much worse.
Dave
David Woolley wrote:
Miroslav Lichvar wrote:
A very useful statistics is the Allan deviation. It can be used to
compare performance of oscillators, to make a guess of the optimal
Surely that is based on a particular model of the phase noise and the
big argument about ntpd is that PC's don't follow that model.
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