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    SubjectRe: [PATCH v4.15-rc9] sched, cgroup: Don't reject lower cpu.max on ancestors
    Hello,

    On Tue, Jan 30, 2018 at 11:21:56AM +0100, Peter Zijlstra wrote:
    > afaiu the existing code does exactly the opposite, it forces the
    > descendants to configure less than the parent allows.
    >
    > You're taking out an error condition and silently allowing descentant
    > misconfiguration. How does that make sense?

    Well, they're upper limits, not strict allocations. The current
    behavior implemented by cpu isn't either a strict allocation or upper
    limits. It disallows a child from having a value higher than the
    parent (allocation-ish) but the sum of the children is allowed to
    exceed the parent's (limit-ish).

    The combination is rather arbitrary and makes it impossible to
    delegate safely (a delegatee can block the delegator from reducing the
    amount resource allocated to the delegatee) while not really
    protecting against overcommit from descendants either.

    We had this sort of input validations in different controllers all in
    their own ways. In most cases, these aren't well thought out and we
    can't support things like delegation without aligning controller
    behaviors.

    Thanks.

    --
    tejun

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