Messages in this thread | | | Date | Tue, 6 Feb 2007 22:09:59 +0100 | From | Ingo Molnar <> | Subject | Re: 2.6.20-rc6-mm3 |
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* 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.
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