In the last episode (Sep 13), Brett Glass said:
> Thank you! Since it's tunable at runtime I just tested it, and -- sure
> enough -- no negative ping times.
>
> Ironically, it was the kernel that selected the ACPI timer, scoring it
> higher than the timestamp counter as a clock source. Perhaps code should
> be added to ensure that the timer is not chosen if it rolls over in less
> than a second, since this clearly leads to imprecision and missed
> rollovers.
>
> kern.timecounter.tc.ACPI-safe.mask: 16777215
>
> kern.timecounter.tc.ACPI-safe.counter: 7967112
>
> kern.timecounter.tc.ACPI-safe.frequency: 3579545
>
> kern.timecounter.tc.ACPI-safe.quality: 850
It doesn't roll over in less than a second; it rolls over in 16777215 /
3579545 = 4.6 seconds. Your negative time delta problem isn't due to
rollover.
--
Dan Nelson
dnel...@allantgroup.com
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