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    SubjectRe: [patch 1/3] sched: init rt_avg stat whenever rq comes online
    On Mon, 2010-08-16 at 00:47 -0700, Peter Zijlstra wrote:
    > On Fri, 2010-08-13 at 12:45 -0700, Suresh Siddha wrote:
    > > plain text document attachment (sched_reset_rt_avg_stat_online.patch)
    > > TSC's get reset after suspend/resume and this leads to a scenario of
    > > rq->clock (sched_clock_cpu()) less than rq->age_stamp. This leads
    > > to a big value returned by scale_rt_power() and the resulting big group
    > > power set by the update_group_power() is causing improper load balancing
    > > between busy and idle cpu's after suspend/resume.
    > ARGH, so i[357] westmere mobile stops TSC on some power state?

    WSM has working TSC with constant rate across P/C/T-states. This issue
    is about suspend/resume (S-states).

    > Why don't we sync it back to the other CPUs instead?

    All the cpu's entered suspend state and during resume it gets reset for
    all the CPU's.

    > Or does it simply mark TSCs unstable and leaves it at that?

    TSCs are stable and in sync after resume aswell. If we want to do SW
    sync, we need to keep track of the time we spent in the suspend state
    and do a SW sync (during resume) that can potentially disturb the HW

    > In any case, this needs to be fixed at the clock level, not like this.

    If we have more such dependencies on TSC then we may need to address the
    issue at clock level aswell. Nevertheless, across cpu online/offline,
    current scheduler code is expecting TSC (sched_clock) to be going
    forward and not sure why we need to carry the rt_avg history across


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