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    SubjectRe: [PATCH v2 09/11] memcg: propagate kmem limiting information to children
    On 08/17/2012 02:35 PM, Michal Hocko wrote:
    > On Fri 17-08-12 14:07:00, Glauber Costa wrote:
    >> On 08/17/2012 01:35 PM, Michal Hocko wrote:
    >>>>> Above you said "Once enabled, can't be disabled." and now you can
    >>>>>>> disable it? Say you are a leaf group with non accounted parents. This
    >>>>>>> will clear the flag and so no further accounting is done. Shouldn't
    >>>>>>> unlimited mean that we will never reach the limit? Or am I missing
    >>>>>>> something?
    >>>>>>>
    >>>>>
    >>>>> You are missing something, and maybe I should be more clear about that.
    >>>>> The static branches can't be disabled (it is only safe to disable them
    >>>>> from disarm_static_branches(), when all references are gone). Note that
    >>>>> when unlimited, we flip bits, do a transversal, but there is no mention
    >>>>> to the static branch.
    >>> My little brain still doesn't get this. I wasn't concerned about static
    >>> branches. I was worried about memcg_can_account_kmem which will return
    >>> false now, doesn't it.
    >>>
    >>
    >> Yes, it will. If I got you right, you are concerned because I said that
    >> can't happen. But it will.
    >>
    >> But I never said that can't happen. I said (ok, I meant) the static
    >> branches can't be disabled.
    >
    > Ok, then I misunderstood that because the comment was there even before
    > static branches were introduced and it made sense to me. This is
    > inconsistent with what we do for user accounting because even if we set
    > limit to unlimitted we still account. Why should we differ here?
    >
    There is another thing as well. Mel was right in his comment: I am
    actually abusing this bit (because it is flippable), and it seems the
    static branch can be updated more than once...

    I'll merge your comments, and fix this.


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