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SubjectRe: Linux 3.1-rc9

* Ingo Molnar <mingo@elte.hu> wrote:

> If we used a scalar 64-bit form for all kernel internal time
> representations:
>
> s64 nsecs;
>
> then conversions back to timespec/timeval would involve dividing
> this 64-bit value with 1000000000 or 1000000.
>
> Is there no faster approximation for those than bit by bit?
>
> In particular we could try something like:
>
> (high*2^32 + low)/1e9 ~== ( high * (2^64/1e9) ) / 2^32
>
> ... which reduces it all to a 64-bit multiplication (or two 32-bit
> multiplications) with a known constant, at the cost of 1 nsec
> imprecision of the result - but that's an OK approximation in my
> opinion.

Hm, no, the numeric error would be in the *seconds* result, and would
be 0-3 seconds - which is obviously not acceptable.

Thanks,

Ingo


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