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    SubjectRe: [SCHED] wrong priority calc - SIMPLE test case
    At 02:52 PM 12/30/2005 +0100, Paolo Ornati wrote:
    >WAS: [SCHED] Totally WRONG prority calculation with specific test-case
    >(since 2.6.10-bk12)
    >http://lkml.org/lkml/2005/12/27/114/index.html
    >
    >On Wed, 28 Dec 2005 10:26:58 +1100
    >Con Kolivas <kernel@kolivas.org> wrote:
    >
    > > The issue is that the scheduler interactivity estimator is a state
    > machine and
    > > can be fooled to some degree, and a cpu intensive task that just
    > happens to
    > > sleep a little bit gets significantly better priority than one that is
    > fully
    > > cpu bound all the time. Reverting that change is not a solution because it
    > > can still be fooled by the same process sleeping lots for a few seconds
    > or so
    > > at startup and then changing to the cpu mostly-sleeping slightly
    > behaviour.
    > > This "fluctuating" behaviour is in my opinion worse which is why I removed
    > > it.
    >
    >Trying to find a "as simple as possible" test case for this problem
    >(that I consider a BUG in priority calculation) I've come up with this
    >very simple program:
    >
    >------ sched_fooler.c -------------------------------

    Ingo seems to have done something in 2.6.15-rc7-rt1 which defeats your
    little proggy. Taking a quick peek at the rt scheduler changes, nothing
    poked me in the eye, but by golly, I can't get this kernel to act up,
    whereas 2.6.14-virgin does.

    -Mike (off to stare harder rt patch)

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