Request for information - timers, hz, interrupts

[Ivan Voras]

2009/12/4 John Baldwin <jhb at freebsd.org>:
> On Friday 04 December 2009 9:52:39 am Ivan Voras wrote:
>> For a long time, at least in the 6-stable timeframe, I was used to
>> seeing timer interrupts going at the frequency of 2*HZ, e.g. this is
>> from 6.4-RELEASE:
>>
>> kern.clockrate: { hz = 250, tick = 4000, profhz = 1000, stathz = 142 }
>> kern.hz: 250

> It actually was changed to provide saner behavior when you use low hz values
> like 'hz=100'.  Note that your stathz is now 142 instead of 33.  The scheduler
> is likely far happier with that stathz.  There is more detail in the commit
> log I believe (just look at the logs for local_apic.c in either svn or
> cvsweb).

Ok. Some more questions:

What does "ticks" do in the above sysctl output?

So 4000 interrupts/s per CPU in the default configuration isn't
considered excessive? :)

I see stathz isn't a divisor of any number in kern.clockrate, which
probably means it's not triggered from one of them firing; can't it be
a separately configurable value?