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    SubjectRe: [PATCH v3 3/7] sched: throttle cfs_rq entities which exceed their local quota
    On Thu, 14 Oct 2010 11:12:22 +0200
    Peter Zijlstra <peterz@infradead.org> wrote:

    > On Wed, 2010-10-13 at 15:34 +0900, KAMEZAWA Hiroyuki wrote:
    > > cpu.share and bandwidth control can't be used simultaneously or...
    > > is this fair ? I'm not familiar with scheduler but this allows boost this tg.
    > > Could you add a brief documentaion of a spec/feature. in the next post ?
    >
    > Like explained, shares control the proportional distribution of time
    > between groups, bandwidth puts a limit on how much time a group can
    > take. It can cause a group to receive less than its fair share, but
    > never more.
    >
    > There is, however, a problem with all this, and that is that all this
    > explicit idling of tasks can lead to a form of priority inversion.
    > Regular preemptive scheduling already suffers from this, but explicitly
    > idling tasks exacerbates the situation.
    >
    > You basically get to add the longest induced idle time to all your lock
    > hold times.
    >

    What is the user-visible difference of the problem between
    1) limit share to be very small.
    2) use throttole.

    If share is used, lock-hodler's priority is boosted ?

    Thanks,
    -Kame



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