Re: [PATCH 13/39] NLKD/x86-64 - time adjustment

[George Anzinger]

Vojtech Pavlik wrote:
> On Sat, Nov 12, 2005 at 06:21:11PM +0100, Andi Kleen wrote:
>
> > On Saturday 12 November 2005 10:22, Vojtech Pavlik wrote:
> >
> >
> > > Is there any advantage to using 64-bit HPET? 
> >
> > Yes - it can tolerate long delays between ticks, e.g. caused by noidletick / 
> > debuggers / target probes / smm etc. At least the first case will be fairly
> > important soon.
>
>
> A 32-bit 14 MHz HPET counter will overflow in approximately 5 minutes. I
> don't think going 64-bit makes sense for noidletick, but for debuggers,
> etc, it could make a good sense indeed.
>
>
> > > It's read is even slower 
> >
> > Why? The read should be on cache line granuality and there shouldn't
> > be any difference in theory.
>
>  
> I'll try to measure this. Indeed, in theory there shouldn't be a
> significant difference.
Doesn't this depend on the atomic nature of the 64-bit read?  If it is really two 32-bit reads one 
would need to do extra work to make sure the two parts belong together.

--
George Anzinger   george@xxxxxxxxxx
HRT (High-res-timers):  http://sourceforge.net/projects/high-res-timers/
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