setitimer() odd timing

Ian FREISLICH ianf at
Sun Nov 4 20:52:41 PST 2007

David Malone wrote:
> On Thu, Nov 01, 2007 at 03:38:11PM +0200, Ian FREISLICH wrote:
> > I'm not sure where to start looking.  If someone points me at what
> > needs instrumenting, I'll see if I can narrow the problem space.
> I'd have a look at the output of "vmstat -i" and compare it to the
> working machines. It might also be worth checking what timecounter
> hardware is in use: "sysctl kern.timecounter.hardware".

Well on other SMP machines that work fine, the cpu? time interrupt
is 2000Hz.  This one is 724 after the most recent boot.  It changes
every boot.

kern.timecounter.choice: TSC(-100) ACPI-fast(1000) HPET(900) i8254(0) dummy(-1000000)
kern.timecounter.hardware: ACPI-fast

dev.acpi_timer.0.%desc: 24-bit timer at 3.579545MHz

Changing the counter to HPET doesn't change things at all.  I suspect
it's got to do with whatever generates the CPU timer interrupts.


Ian Freislich

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