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SubjectRe: [PATCH 13/39] NLKD/x86-64 - time adjustment
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@mvista.com
HRT (High-res-timers): http://sourceforge.net/projects/high-res-timers/
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