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    SubjectRe: [PATCH] x86,sched: Fix sched_smt_power_savings totally broken
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    Hi Peter,

    I'm also using sched_mc level for doing powersaving load balance on
    ARM platform and we have real benefits.

    On 9 January 2012 12:12, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
    > On Mon, 2012-01-09 at 19:14 -0500, Youquan Song wrote:
    >> > Yes it is.. also that knob should die! Like i've been saying for way too
    >> > long. I'm >< close to committing a patch removing all the power_saving
    >> > magic from the scheduler.
    >> Sorry. I do not notice it.
    >
    > I hadn't posted it before, but just about every time people post
    > something related to smt/mc power balancing I say this needs to get
    > cleaned up. Since telling people doesn't seem to have any effect what so
    > ever, stronger measures are needed.
    >
    >> But currently in many real tests, the knob prove to save power in semi-idle system.
    >> They are useful in many user scenarios currently.
    >
    > I'm not saying the stuff is without merit, I'm just saying that a) the
    > interface is utter crap and b) nobody seems to spend enough time on it
    > to 1) understand the load-balancer so that 2) he can integrate the power
    > saving stuff properly.
    >
    > Instead I get one sporadic band-aid after another.
    >

    I can also help to on the topic

    > Also, fundamentally, the split between {smt/mc/numa/book}_power_savings
    > is completely and fundamentally broken, nobody cares about the actual
    > topology.

    We might modify the way we choose between power or performance mode
    because it's not always a matter of gathering or spreading tasks on
    cpus but until we found a best interface it's the way to enable
    powersaving mode

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