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    SubjectRe: [patch 1/3] sched: init rt_avg stat whenever rq comes online
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    On Mon, 2010-08-16 at 21:25 +0200, Peter Zijlstra wrote:
    > You can use something like:
    >
    > suspend:
    > __get_cpu_var(cyc2ns_suspend) = sched_clock();
    >
    > resume:
    > for_each_possible_cpu(i)
    > per_cpu(cyc2ns_offset, i) += per_cpu(cyc2ns_suspend);
    >
    > or something like that to keep sched_clock() stable, which is exactly
    > what most (all?) its users expect when we report the TSC is usable.

    That's actually broken, you only want a single offset, otherwise we
    de-sync the TSC, which is bad.

    So simply store the sched_clock() value at suspend time on the single
    CPU that is still running, then on resume make sure sched_clock()
    continues there by adding that stamp to all CPU offsets.




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