Negative ping times with FreeBSD 8.1-RELEASE on older Celeron system

Brett Glass brett at
Tue Sep 13 10:21:45 UTC 2011

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.

--Brett Glass

At 11:04 PM 9/12/2011, Adam Vande More wrote:
>it's a runtime tunable so /etc/sysctl.conf

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