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    SubjectRe: [patch] memcg: skip scanning active lists based on individual size
    On Wed, Aug 31, 2011 at 07:13:34PM +0900, Minchan Kim wrote:
    > 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>

    Thank you.

    > 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.

    Good catch.

    ---
    Subject: [patch] memcg: skip scanning active lists based on individual fix

    Also ditch the documentation note for the removed stats value.

    Signed-off-by: Johannes Weiner <jweiner@redhat.com>
    ---

    diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
    index 06eb6d9..cc0ebc5 100644
    --- a/Documentation/cgroups/memory.txt
    +++ b/Documentation/cgroups/memory.txt
    @@ -418,7 +418,6 @@ total_unevictable - sum of all children's "unevictable"

    # The following additional stats are dependent on CONFIG_DEBUG_VM.

    -inactive_ratio - VM internal parameter. (see mm/page_alloc.c)
    recent_rotated_anon - VM internal parameter. (see mm/vmscan.c)
    recent_rotated_file - VM internal parameter. (see mm/vmscan.c)
    recent_scanned_anon - VM internal parameter. (see mm/vmscan.c)

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