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SubjectRe: 2.6.20-rc6-mm3

* Daniel Walker <dwalker@mvista.com> wrote:

> > it's quite easy to explain: because of the new dynticks feature.
> > Both 'timer' and 'LOC' counts go way down.
>
> I don't have that enabled tho .. This is with HRT/dynamic tick both
> off..

your kernel utilizes the kernelin a more optimal way: the new
clockevents code now utilizes the local APIC timer irq (represented by
the LOC field) for periodic interrupts. The local APIC timer irq has a
cost of ~2 usecs per IRQ, while the PIT irq is ~10 usecs per irq. With
HZ=1000 this means savings of ~8000 usecs per second - i.e. 8 msecs per
second, which is 0.8% more raw CPU power available - which isnt that
bad.

we could make this clearer by renaming 'LOC' (which stands for 'LOCal
timer interupts' and was added [and misnamed] by yours truly many moons
ago) to 'apic-timer' and 'timer' to 'PIT-timer' but /that/ would be more
of a userspace visible change than the change in the counter rates.

Ingo
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