Messages in this thread | | | Date | Thu, 25 Sep 2008 16:04:09 -0700 | From | Jeremy Fitzhardinge <> | Subject | Re: [RFC PATCH 1/3] Unified trace buffer |
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Steven Rostedt wrote: > On Fri, 26 Sep 2008, Ingo Molnar wrote: > >> Firstly they need a low-frequency (10khz-100khz) shared clock line >> across all CPUs. A single line - and since it's low frequency it could >> be overlaid on some existing data line and filtered out. That works >> across NUMA nodes as well and physics allows it to be nanosec accurate >> up to dozens of meters or so. >> > > Can this possibly be true? I mean, light travels only one foot every > nanosecond. Can it really keep nanosecond accuracy up to dozens of meters > away?
Sure. NTP keeps machines within 1ms (or better) of each other even though the network latency is much higher and jittery.
J
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