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SubjectRe: [RFC PATCH 1/3] Unified trace buffer
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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