Re: Few interrupts with NO_HZ

[Chris Snook <csnook@redhat.com>]

Jan Engelhardt wrote:
> On Aug 6 2007 09:47, Chris Snook wrote:
> > > this more of an informational question. So:
> > > kernel version is 2.6.22.1 on i686
> > > /proc/uptime 9917.81 9140.90 (2h45m)
> > > /proc/cpuinfo:
> > >            CPU0
> > >   0:        282   IO-APIC-edge      timer
> > >
> > > this is kinda neat, I expected much more interrupts than just 282
> > > since boot. What kernel code actually uses the irq0 timer?
> > If you don't have an HPET (and most single-processor systems do not)
>
> This is an AMD Athlon with 'Thoroughbred' core; it does not seem to
> have C-states at all (or: exactly one). It clearly is not idle all the
> time, sometimes I run povray. (And 282 has not changed since the
> morning.)
>
>
> 	Jan

In that case, it's probably the early bootstrap code that runs before the TSC is 
calibrated.  PIT sucks, but it sucks very reliably, so it's a good basis for 
calibrating the other timekeeping devices.  Once you have something better set 
up, you don't need it anymore if you're not doing C-state transitions.

	-- Chris
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