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    SubjectRe: [PATCH] x86,sched: Fix sched_smt_power_savings totally broken
    On 1/10/2012 1:18 AM, Ingo Molnar wrote:
    >
    > * Suresh Siddha <suresh.b.siddha@intel.com> wrote:
    >
    >> On Tue, 2012-01-10 at 00:58 -0500, Youquan Song wrote:
    >>> Thanks Peter! Here is the patch.
    >>
    >> Youquan, As far as I know both the
    >> sched_smt_power_savings/sched_mc_power_savings are broken for atleast an
    >> year.
    >
    > We want a single knob, sched_power_savings - with the mc_ and
    > smt_ ones still kept and aliased to sched_power_savings, for
    > compatibility reasons.
    >
    > As Peter said, the other reasonable option is to have no knob at
    > all and restart this code from scratch.
    >
    > The other thing we should do is to add sane defaults: to turn on
    > sched_power_savings *AUTOMATICALLY* when a system is obviously
    > battery driven and turn it off when the system is obviously AC
    > driven. User-space can still implement policy and override the
    > kernel's default, but there's absolutely no excuse to not offer
    > this default ourselves.

    a very good default would be to keep all tasks on one package until half
    the cores in the package are busy, and then start spreading out.

    I suspect that'll be the 90% case coverage.


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