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    SubjectRe: BUG: unable to handle kernel NULL pointer dereference at 00000002
    > > A power saving feature that has a significant trade off between power
    > > and performance.
    >
    > do you have numbers to explain "significant tradeoff" ?

    I don't have numbers, but from the theory it seems pretty clear.
    When you e.g. have two processes with 6MB cache foot print and
    you have two 2C CPUs with 6MB cache they will fit in cache, but
    with power aware scheduler they won't because both processes will run on
    the single 6MB package. With NUMA the effect is even worse because
    also the memory controllers are not used evenly.
    And there's the FSB bandwidth, but that's a secondary issue.
    >
    >
    > > This means performance will go down. Perhaps it would be ok on
    > > battery,
    >
    > the illusion that power only matters on battery got buried a few years
    > ago ;)

    My understanding was always that unless you're on battery power saving
    features that are enabled by default are not supposed to impact performance
    significantly. When the user says impacting performance is ok then
    doing that is fine of course, but not by default. And I don't think
    that's an illusion. In fact if power saving means losing a lot of performance
    people would get discouraged from using it, and surely you don't want that.

    -Andi



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