New event timers for 8-STABLE

[Alexander Motin]

Hi.

I've created a patch, merging all kernel event timers related stuff from
HEAD to 8-STABLE. The only thing I have skipped at this moment was mips
architecture, because of too big code difference there between HEAD and
8-STABLE. Patch appeared to be quite large and includes more then 60 SVN
revisions from HEAD. I hope I haven't missed anything important. I would
like to ask interested people to test it. Patched code successfully
builds on all platforms and successfully runs on my amd64 test machine.

In HEAD code seems to be working enough stable, There only two known
open issues at the moment:
 - kernel freeze on XEN HVM when using LAPIC timer in one-shot mode --
can be workarounded by switching to periodic mode or other timer.
 - if HPET interrupt shared with other device, system load average may
lie (report +1 value) -- not a timer problem and not fatal.
Please report me if you find anything else.

Latest patch can be found here:
http://people.freebsd.org/~mav/timers_merge/timers_merge-20101111.patch

Merge instructions (list of revisions, if somebody want to redo it):
http://people.freebsd.org/~mav/timers_merge/guide-20101111

After patching you need just rebuild/reinstall the kernel. I haven't
merged related manual pages yet, so, if needed, consult with man pages
from HEAD: eventtimers(7), attimer(4), atrtc(4), hpet(4).

-- 
Alexander Motin