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    SubjectRe: sched_clock() uses are broken
    On Tue, 2 May 2006, Andi Kleen wrote:

    > On Tuesday 02 May 2006 18:50, Russell King wrote:
    >
    > > You're right assuming you have a 64-bit TSC, but ARM has at best a
    > > 32-bit cycle counter which rolls over about every 179 seconds - with
    > > gives a range of values from sched_clock from 0 to 178956970625 or
    > > 0x29AAAAAA81.
    > >
    > > That's rather more of a problem than having it happen every 208 days.
    >
    > Ok but you know it's always 32bit right? You can fix it up then
    > with your proposal of a sched_diff()
    >
    > The problem would be fixing it up with a unknown number of bits.

    Just shift it left so you know you always have the most significant bits
    valid. The sched_diff() would take care of scaling it back to nanosecs.


    Nicolas
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