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    SubjectRe: [patch, 2.6.11-rc2] sched: RLIMIT_RT_CPU_RATIO feature
    Ingo Molnar wrote:
    > pretty much the only criticism of the RT-CPU patch was that the global
    > sysctl is too rigid and that it doesnt allow privileged tasks to ignore
    > the limit. I've uploaded a new RT-CPU-limit patch that solves this
    > problem:
    > i've removed the global sysctl and implemented a new rlimit,
    > RT_CPU_RATIO: the maximum amount of CPU time RT tasks may use, in
    > percent. For testing purposes it defaults to 80%.
    > the RT-limit being an rlimit makes it much more configurable: root tasks
    > can have unlimited CPU time limit, while users could have a more
    > conservative setting of say 30%. This also makes it per-process and
    > runtime configurable as well. The scheduler will instantly act upon any
    > new RT_CPU_RATIO rlimit.
    > (this approach is fundamentally different from the previous patch that
    > made the "maximum RT-priority available to an unprivileged task" value
    > an rlimit - with priorities being an rlimit we still havent made RT
    > priorities safe against deadlocks.)
    > multiple tasks can have different rlimits as well, and the scheduler
    > interprets it the following way: it maintains a per-CPU "RT CPU use"
    > load-average value and compares it against the per-task rlimit. If e.g.
    > the task says "i'm in the 60% range" and the current average is 70%,
    > then the scheduler delays this RT task - if the next task has an 80%
    > rlimit then it will be allowed to run. This logic is straightforward and
    > can be used as a further control mechanism against runaway highprio RT
    > tasks.

    Very nice. I like the way this approach is evolving.

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