Is halting of the CPU0 on SMP supposed to slow down time?

[Alexandre "Sunny" Kovalenko]

While trying to understand why setting hw.acpi.cpu.cx_lowest=C3 makes my
laptop (ThinkPad X60 with Intel T2400 @ 1.8GHz) literally crawl, I have
run across the following observation: if dev.cpu.0.cx_lowest is set to
C3 and machdep.cpu_idle_hlt is set to 1 time slows down at about two
orders of magnitude. The same result could be achieved by setting
machdep.hlt_cpus to 1.

Setting dev.cpu.1.cx_lowest to C3 or machdep.hlt_cpus to 2 does not
cause any negative side effects.

Setting machdep.cpu_idle_hlt to 0 and hw.acpi.cpu.cx_lowest to C3 gets
machine warming all the way up to _PSV rather rapidly.

This was observed with the HPET and ACPI-fast timecounters without
discernible difference.

The system is RELENG_7 as of Feb 15, cpufreq is loaded and powerd is
running.

I would like to have C3 working as it gives me much cooler machine in
the idle state, but not at the cost of losing time accounting.

Any suggestions will be greatly appreciated.

-- 
Alexandre "Sunny" Kovalenko (Олександр Коваленко)