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    SubjectRe: [PATCH] CFS: Fix missing digit off in wmult table

    * James Bruce <bruce@andrew.cmu.edu> wrote:

    > While we're at it, isn't the comment above the wmult table incorrect?
    > The multiplier is 1.25, meaning a 25% change per nice level, not 10%.

    yes, the weight multiplier 1.25, but the actual difference in CPU
    utilization, when running two CPU intense tasks, is ~10%:

    PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
    8246 mingo 20 0 1576 244 196 R 55 0.0 0:11.96 loop
    8247 mingo 21 1 1576 244 196 R 45 0.0 0:10.52 loop

    so the first task 'wins' +10% CPU utilization (relative to the 50% it
    had before), the second task 'loses' -10% CPU utilization (relative to
    the 50% it had before).

    so what the comment says is true:

    * The "10% effect" is relative and cumulative: from _any_ nice level,
    * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
    * it's +10% CPU usage.

    for there to be a ~+10% change in CPU utilization for a task that races
    against another CPU-intense task there needs to be a ~25% change in the
    weight.

    Ingo
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