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    SubjectRe: [patch] memcg: skip scanning active lists based on individual size
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    On Wed, Aug 31, 2011 at 6:08 PM, Johannes Weiner <jweiner@redhat.com> wrote:
    > Reclaim decides to skip scanning an active list when the corresponding
    > inactive list is above a certain size in comparison to leave the
    > assumed working set alone while there are still enough reclaim
    > candidates around.
    >
    > The memcg implementation of comparing those lists instead reports
    > whether the whole memcg is low on the requested type of inactive
    > pages, considering all nodes and zones.
    >
    > This can lead to an oversized active list not being scanned because of
    > the state of the other lists in the memcg, as well as an active list
    > being scanned while its corresponding inactive list has enough pages.
    >
    > Not only is this wrong, it's also a scalability hazard, because the
    > global memory state over all nodes and zones has to be gathered for
    > each memcg and zone scanned.
    >
    > Make these calculations purely based on the size of the two LRU lists
    > that are actually affected by the outcome of the decision.
    >
    > Signed-off-by: Johannes Weiner <jweiner@redhat.com>
    > Cc: Rik van Riel <riel@redhat.com>
    > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    > Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
    > Cc: Balbir Singh <bsingharora@gmail.com>

    Reviewed-by: Minchan Kim <minchan.kim@gmail.com>

    I can't understand why memcg is designed for considering all nodes and zones.
    Is it a mistake or on purpose?
    Maybe Kame or Balbir can answer it.

    Anyway, this change does make sense to me.

    Nitpick: Please remove inactive_ratio in Documentation/cgroups/memory.txt.
    I think it would be better to separate it into another patch.

    --
    Kind regards,
    Minchan Kim


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