freebsd stable - Dec 2005 - Kernel clock for 6-STABLE runs at 1/2 speed in VMware 5.0 - UPDATE (and question)

Problem recap:  Under VMWare 5.0 (and 5.5) running on Windows XP Pro sp2, and
FreeBSD 6-STABLE running as the guest OS, the system clock for the guest OS runs
at exactly 1/2 the rate of the host OS's system clock.

This problem could be worked around by setting hint.apic.0.disabled=1 in
/boot/loader.conf

Other attempts at working around the problem, including setting kern.hz to
something lower than the default 1000 (such as the old default, 100), did not
work.


Update --

After an upgrade to VMWare 5.5.1 build-19175 and a fresh build of RELENG_6 last
week, I've found that setting kern.hz to a lower rate is sufficient to
address the problem.  Disabling the APIC device is no longer necessary.  So, in
/boot/loader.conf, I've got:

kern.hz=200

and that seems to do the trick.  Kudos to whoever made the relevant
improvements.

For what it's worth, I've experimented with the setting, and found that
with the appropriate vmware-guestd installed and running in the FreeBSD 6 guest,
the clocks stay properly synched up to kern.hz=596, and from there the
guest:host system clockrate ratio degrades more or less linearly from 1:1 to 1:2
as kern.hz is increased from 596 to 1000 (this on a 2.4Ghz p4, ymmv).

Logs show the occasional expected error "calcru: runtime went backwards
[...] (vmware-guestd)" regardless of kern.hz setting, though they appear to
increase in frequency as the kern.hz rate increases, and increase dramatically
as the rate of 596 is approached and passed.


Anyhoo, my question now is:  Why was kern.hz (which I'm guessing is an
interrupt frequency for a programmable hardware timer) increased from a default
100 to a default 1000 in FreeBSD 6?  And more concretely, should I set this rate
as high as I reasonably can?