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    SubjectRe: [PATCH] memory-hotplug: fix zone stat mismatch
    At 09/20/2012 04:17 AM, Minchan Kim Wrote:
    > Hi KOSAKI,
    >
    > On Wed, Sep 19, 2012 at 02:05:20PM -0400, KOSAKI Motohiro wrote:
    >> On Wed, Sep 19, 2012 at 3:29 AM, Minchan Kim <minchan@kernel.org> wrote:
    >>> During memory-hotplug stress test, I found NR_ISOLATED_[ANON|FILE]
    >>> are increasing so that kernel are hang out.
    >>>
    >>> The cause is that when we do memory-hotadd after memory-remove,
    >>> __zone_pcp_update clear out zone's ZONE_STAT_ITEMS in setup_pageset
    >>> without draining vm_stat_diff of all CPU.
    >>>
    >>> This patch fixes it.
    >>
    >> zone_pcp_update() is called from online pages path. but IMHO,
    >> the statistics should be drained offline path. isn't it?
    >
    > It isn't necessary because statistics is right until we reset it to zero
    > in online path.
    > Do you have something on your mind that we have to drain it in offline path?

    When a node is offlined and onlined again. We create node_data[i] in the
    function hotadd_new_pgdat(), and we will lost the statistics stored in
    zone->pageset. So we should drain it in offline path.

    Thanks
    Wen Congyang

    >
    >>
    >> thanks.
    >



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