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    SubjectRe: [SCHED] wrong priority calc - SIMPLE test case
    Date
    On Friday 13 January 2006 12:13, Con Kolivas wrote:
    > On Saturday 31 December 2005 00:52, 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:
    >
    > Hi Paolo.
    >
    > Can you try the following patch on 2.6.15 please? I'm interested in how
    > adversely this affects interactive performance as well as whether it helps
    > your test case.

    I should make it clear. This patch _will_ adversely affect interactivity
    because your test case desires that I/O bound tasks get higher priority, and
    this patch will do that. This means that I/O bound tasks will be more
    noticeable now. The question is how much do we trade off one for the other.
    We almost certainly are biased a little too much on the interactive side on
    the mainline kernel at the moment.

    Cheers,
    Con
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