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Re: rfc: high-resolution timer framework
On Wed, Jun 25, 2008 at 03:25:40PM +0000, Andrew Doran wrote:
> +#ifdef LAPIC_HRTIMER
> +lapic_clockintr(void *arg, struct intrframe *frame)
> It breaks if the machine has more than one CPU, because clock interrupts
> will only occur on the boot CPU. Presumably it also prevents the lapic from
> being used as a timecounter source, but that's not a big deal. It's also
> unfortunate that it's optional.
This is actually one of the fundamental issues I have with the current
callout and time handling. It is inherently bound to a single CPU
system, without many good reasons.
> One solution it is to always use the i8254 for the clock interrupt, and
> trigger a broadcast IPI to the other CPUs from the i8254 clock ISR before
> calling the MI hardclock().
I think it is much better to decouple the system time from hardclock and
derive it from time counters. This is also a lot more work though.
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