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Date: Fri, 09 Jun 2006 21:23:32 +0300
From: Andriy Gapon <avg@icyb.net.ua>
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Subject: in-flight timer(s) recalibration
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In-flight timer(s) recalibration - is it a good idea ? How to do it ?

This question comes from the following: in 6.1 we use LAPIC timer even
on UP systems; in scenarios where FSB frequency can be changed on the
fly (this is not hypothetical) that results in bad time-keeping as LAPIC
timer frequency is derived from FSB frequency. I'd like to be able to do
something like what lapic_setup_clock() does, but through a proper
interface and probably at smaller cost (I mean 2 second DELAY).
I think that my need is pretty much LAPIC-timer centered because TSC
should not be used in my case anyway and i8254 is mutually exclusive
with LAPIC (at present, I think) and it is not affected by FSB frequency
(is it?).

BTW, maybe I will talk utter nonsense now, but is it possible to
self-tune timer interrupt frequency by checking time elapsed between
interrupts using the best available (or currently selected) timecounter ?


-- 
Andriy Gapon