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    SubjectRe: [BUG] 2.6.37-rc3 massive interactivity regression on ARM
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    On Wed, 2010-12-08 at 15:44 +0100, Peter Zijlstra wrote:
    > On Wed, 2010-12-08 at 14:28 +0000, Russell King - ARM Linux wrote:
    > > So, what I'm saying is that if wrapping in 4 seconds is a problem,
    > > then maybe we shouldn't be providing sched_clock() at all.
    >
    > 4 seconds should be perfectly fine, we call it at least every scheduler
    > tick (HZ) and NO_HZ will either have to limit the max sleep period or
    > provide its own sleep duration (using a more expensive clock) so we can
    > recover (much like GTOD already requires).
    >
    > > Also, if wrapping below 64-bits is also a problem, again, maybe we
    > > shouldn't be providing it there either. Eg:
    >
    > That's mostly due to hysterical raisins and we should just fix that, the
    > simplest way is to use something like kernel/sched_clock.c to use
    > sched_clock() deltas to make a running u64 value.
    >
    > Like said, John Stultz was already looking at doing something like that
    > because there's a number of architectures suffering this same problem
    > and they're all already using part of the clocksource infrastructure to
    > implement the sched_clock() interface simply because they only have a
    > single hardware resource.

    I'm not actively working on it right now, but trying to rework the
    sched_clock code so its more like the generic timekeeping code is on my
    list (I'm Looking to see if I can bump it up to the front in the near
    future).

    thanks
    -john




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