Re: [PATCH] i386: Selectable Frequency of the Timer Interrupt

Maciej W. Rozycki
2005-07-14T10:05:29Z

On Wed, 13 Jul 2005, Benjamin LaHaise wrote:

> That's one thing I truely dislike about the current timer code. If we
> could program the RTC interrupt to come into the system as an NMI (iirc
> oprofile already has code to do this), we could get much better TSC
> interpolation since we would be sampling the TSC at a much smaller, less
> variable offset, which can only be a good thing.

And we'd get a lot more crashes on broken systems that do not handle NMIs
in the SMM -- this is the very reason the NMI watchdog is disabled these
days by default. A whole lot of systems simply cannot handle NMIs
happening randomly.

Programming an I/O APIC to deliver the RTC interrupt (or any other that's
edge-triggered) as an NMI is itself trivial (we can do this for the PIT
for the NMI watchdog already).

Maciej