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    SubjectRe: 50 Watt idle power regression bisected to Linux-3.10
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    On Wed, 2013-12-11 at 13:43 +0100, Peter Zijlstra wrote: 
    > On Wed, Dec 11, 2013 at 01:29:15PM +0100, Mike Galbraith wrote:
    > > On Wed, 2013-12-11 at 12:52 +0100, Peter Zijlstra wrote:
    > > > On Wed, Dec 11, 2013 at 12:38:39PM +0100, Borislav Petkov wrote:
    > > > > Right, if it turns out that this is really the case and that this
    > > > > erratum hasn't been fixed for models later than 29 - we'd need the
    > > > > additional model numbers to set X86_FEATURE_CLFLUSH_MONITOR correctly.
    > > >
    > > > You also need: https://lkml.org/lkml/2013/11/19/143
    > > >
    > > > Because obviously not all mwait idle loops check that cpu bit.
    > >
    > > I had tried that patch, to see if it would magically make the thing
    > > start working, nope. I had also tried...
    >
    > > + if (this_cpu_has(X86_FEATURE_CLFLUSH_MONITOR))
    > > + clflush((void *)&current_thread_info()->flags);
    >
    > Yeah, you need a bit extra to enable that feature bit for your CPU as
    > bpetkov said.

    Works for me, one more for the stable bucket.

    So as soon as Len resurrects mwait_idle for Q6600 (and other core2 when
    booted max_cstates=1 so tsc clocksource is used instead of pos hpet),
    all the (known) idle regressions should be history.

    -Mike



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