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SubjectRe: Can't sleep less than 20 ms
Matti Aarnio wrote:
> > x86 also takes 10 or more microseconds to service an interrupt (it is
> > said because of motherboards not the CPU itself).
>
> How long IRQ processing takes *does* depend upon used chips.
> When the IRQ-controller is in modern core-logic chipsets, it
> does not need to behave like its ancient ISA-bus-bound
> precursors.

I would like this to be so, but I've heard that current motherboard
designs prevent the core-logic chipsets and the processor from servicing
interrupts at full speed.

I don't have figures though so I can't argue this point.

> > I'd rather see:
> >
> > - slow HZ -- low interrupt load
> > - accurate timers on demand
> > - *precise* timing with accuracy of hardware
>
> RTC based interrupts ? Highly accurate periodic interrupts,
> not re-sceduling based "regular by luck"...

I'd like "regular by design".

Note that RTC interrupts are just as inaccurate for user space apps
than 8253-based accurate timers -- the scheduling overhead and lack of
guarantee is still present.

-- Jamie


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