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SubjectRe: Few interrupts with NO_HZ
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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