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    SubjectRe: Bootup time regression from 2.6.27 to 2.6.28-rc3+
    On Sat, 15 Nov 2008 18:16:31 +0100
    Frans Pop <elendil@planet.nl> wrote:

    > On Friday 14 November 2008, Frans Pop wrote:
    > > > Find below the lineup of the timers-fixes-for-linus branch of the
    > > > tip tree (the same as Arjan posted minus the irq fixes)
    > >
    > > Could either of you maybe give a status update on this patch set and
    > > the remaining issues with it that were reported (especially the
    > > high C0 reported by powertop)?
    >
    > I guess part of the answer is:
    > commit ae99286b4f1be7788f2d6947c66a91dbd6351eec
    > Author: Thomas Gleixner <tglx@linutronix.de>
    > Date: Mon Nov 10 13:20:23 2008 +0100
    > nohz: disable tick_nohz_kick_tick() for now
    >
    > I've just done some testing using v2.6.28-rc4-322-g58e20d8 which
    > includes this patch.
    >
    > CPU usage reported by powertop is now normal again (close to 100% in
    > lowest C state), but I'm still getting high counts for:
    > - <kernel IPI> : Rescheduling interrupts
    > Typically 3-5 on .26/.27; 15-17 on .28.

    these are caused by the scheduler, not by the timer code.
    (And sometimes they're caused by the scheduler on behalf of something
    else even)

    > - <interrupt> : extra timer interrupt
    > Consistently more prominent for .28 (though not with high values)

    if it's less than 5 total, don't worry about it, some of that can well
    be rounding/measurement effects
    (powertop has to make a few approximations around the edges of the
    measurement interval because things don't always line up perfectly)

    > than for .27, but way better than for .26.
    >
    >
    > powertop questions
    > ------------------
    > - What's with this change from "polling" to "C0" for the 2nd C state?

    that sounds like an interesting bug...

    > After boot I always (both when booted on mains and on battery) get
    > "polling", but after inserting or removing mains it will continue to
    > show "C0" independent of any further power state changes.
    > - After switching to battery the first time I get something like:
    > C1 0.0ms (614891469122.
    > This is reproducible. I guess a rounding error due to the change in
    > the number of C states. Later updates clear this.

    yeah it's annoying but it is only for one display period

    > - Looks like someone could not make up his mind between comma and
    > slash here: "(long term: 26.2W,/1.6h)"

    that sounds easy to fix ;-)

    Thanks for the bugreports; either me or Auke will take a look at these
    shortly.

    --
    Arjan van de Ven Intel Open Source Technology Centre
    For development, discussion and tips for power savings,
    visit http://www.lesswatts.org


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