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    SubjectRe: vmevent: question?
    On Mon, 30 Apr 2012, Minchan Kim wrote:
    > > What kind of consistency guarantees do you mean? The data sent to
    > > userspace is always a snapshot of the state and therefore can be stale
    > > by the time it reaches userspace.
    >
    > Consistency between component of snapshot.
    > let's assume following as
    >
    > 1. User expect some events's value would be minus when event he expect happen.
    > A : -3, B : -4, C : -5, D : -6
    > 2. Logically, it's not possible to mix plus and minus values for the events.
    > A : -3, B : -4, C : -5, D : -6 ( O )
    > A : -3, B : -4, C : 1, D : 2 ( X )
    >
    > But in current implementation, some of those could be minus and some of those could be plus.
    > Which event could user believe?
    > At least, we need a _captured_ value when event triggered so that user can ignore other values.

    Sorry, I still don't quite understand the problem.

    The current implementation provides the same kind of snapshot consistency
    as reading from /proc/vmstat does (modulo the fact that we read them
    twice) for the values we support.

    Pekka


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