kern.timecounter.hardware change on the fly

Ireneusz Pluta ipluta at
Tue Nov 29 19:01:16 UTC 2011

Hi all,

is it safe to change kern.timecounter.hardware on a busy production system on the fly? Or I better 
schedule a downtime to do that?

It seems I got a bad current selection, somehow, probably as an effect of leaving /etc/sysctl.conf 
contents of early experimental setup stage of this machine.

$ sysctl -a | grep timecounter
kern.timecounter.tick: 1
kern.timecounter.choice: TSC(-100) HPET(900) ACPI-fast(1000) i8254(0) dummy(-1000000)
kern.timecounter.hardware: i8254
kern.timecounter.stepwarnings: 0 65535 23813 1193182 0 16777215 4619803 3579545 1000 4294967295 1703441786 14318180 900 4294967295 2720513805 2266656152 -100
kern.timecounter.smp_tsc: 0
kern.timecounter.invariant_tsc: 1

This setting seems to affect what is generally described here: and this is the primary reason I 
want to change.

Should I switch to HPET or ACPI-fast?

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