[time-nuts] Cheap jitter measurements
Hal Murray
hmurray at megapathdsl.net
Tue Apr 10 22:41:41 UTC 2018
Gary said:
>> The API for the kernel clock can be read to a ns. I don't see ntpd
>> having much use for finer grain than that. I should look at the
>> source to see what the internal details look like.
> Yeah, but the granularity is much worse.
Do you have code that demonstrates that? (or tell me how and I'll try it)
I think most modern kernels derive time from a cycle-count register. So the
basic clock should be accurate to a cycle. Yes, that's worse than a ns on
slow CPUs.
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