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    SubjectRe: [PATCH -mm] memcg: fix handling of shmem migration(v2)
    On Wed, 17 Sep 2008 16:55:44 +0900
    Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

    > Before this patch, if migrating shmem/tmpfs pages, newpage would be
    > charged with PAGE_CGROUP_FLAG_FILE set, while oldpage has been charged
    > without the flag.
    >
    > The problem here is mem_cgroup_move_lists doesn't clear(or set)
    > the PAGE_CGROUP_FLAG_FILE flag, so pc->flags of the newpage
    > remains PAGE_CGROUP_FLAG_FILE set even when the pc is moved to
    > another lru(anon) by mem_cgroup_move_lists. And this leads to
    > incorrect MEM_CGROUP_ZSTAT.
    > (In my test, I see an underflow of MEM_CGROUP_ZSTAT(active_file).
    > As a result, mem_cgroup_calc_reclaim returns very huge number and
    > causes soft lockup on page reclaim.)
    >
    > I'm not sure if mem_cgroup_move_lists should handle PAGE_CGROUP_FLAG_FILE
    > or not(I suppose it should be used to move between active <-> inactive,
    > not anon <-> file), I added MEM_CGROUP_CHARGE_TYPE_SHMEM for precharge
    > at shmem's page migration.
    >
    >
    > ChangeLog: v1->v2
    > - instead of modifying migrate.c, modify memcontrol.c only.
    > - add MEM_CGROUP_CHARGE_TYPE_SHMEM.
    >
    I'll fix mem_cgroup_charge_cache_page() to use TYPE_SHMEM later.
    Thank you.

    Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>




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