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    SubjectRe: [revert] mysql+oltp regression
    Ingo Molnar wrote:
    > * Gregory Haskins <ghaskins@novell.com> wrote:
    >
    >
    >>>> Speaking of this: Another patch I submitted to you Ingo (had to do
    >>>> with updating the load_weight inside task_setprio) seems to also
    >>>> have this phenomenon: e.g. its technically correct but further
    >>>> testing has revealed negative repercussions elsewhere. So please
    >>>> ignore that patch (or revert if you already pulled in, but I don't
    >>>> think you have). Ill try to look into this issue as well.
    >>>>
    >>> ok, under which thread/subject is that? Not queued in tip/sched/*
    >>> yet, correct?
    >>>
    >>>
    >> Here is the original thread:
    >>
    >> http://lkml.org/lkml/2008/7/3/416
    >>
    >> I do not believe you have queued it anywhere (public anyway) yet.
    >>
    >> Note I have already invalidated 1/2, and now I am retracting 2/2 as
    >> well. (1/2 is actually a bogus patch, 2/2 is "technically correct"
    >> but causes ripples in the load balancer that need to be sorted out
    >> first.
    >>
    >
    > ok, thanks. I'm curious, what are those ripple effects? Stability or
    > performance?
    >

    Performance. I found it while working on my pi series (which fyi I
    should have a v2 refresh for soon, probably today...i am hoping to get
    some review feedback from you on that as well, time permitting of course ;).

    Basically the behavior I was observing was that kernel builds via distcc
    would cluster all the cc1 jobs on a single core. At first I thought my
    pi-series was screwed up, but then I realized I had applied the patch
    referenced above earlier in my development tree, and removing it allowed
    pi to work fine.

    I found the problem with in once boot cycle with ftrace (thanks
    Steve!). Basically newidle balancing was always returning "no
    imbalance" even though I had 32 cc1 threads on 1 core, and 3 idle
    cores. Clearly not correct! So I think that by adjusting the load up,
    we throw off the hysteresis built into the load averages and cause the
    system to incorrectly think it's balanced. TBD.

    -Greg


    > Ingo
    >


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