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    SubjectRe: [PATCH] memcg: change behavior of moving charges at task move
    On Fri, 23 Mar 2012 09:18:46 +0900 KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:

    > >> +#ifdef CONFIG_SWAP
    > >> + /*
    > >> + * Avoid lookup_swap_cache() not to update statistics.
    > >> + */
    > >
    > > I don't understand this comment - what is it trying to tell us?
    > >
    >
    >
    > High Dickins advised me to use find_get_page() rather than lookup_swap_cache()
    > because lookup_swap_cache() has some statistics with swap.

    ah.

    --- a/mm/memcontrol.c~memcg-change-behavior-of-moving-charges-at-task-move-fix
    +++ a/mm/memcontrol.c
    @@ -5137,7 +5137,8 @@ static struct page *mc_handle_swap_pte(s
    return NULL;
    #ifdef CONFIG_SWAP
    /*
    - * Avoid lookup_swap_cache() not to update statistics.
    + * Use find_get_page() rather than lookup_swap_cache() because the
    + * latter alters statistics.
    */
    page = find_get_page(&swapper_space, ent.val);
    #endif
    > >> + page = find_get_page(&swapper_space, ent.val);
    > >
    > > The code won't even compile if CONFIG_SWAP=n?
    > >
    >
    > mm/built-in.o: In function `mc_handle_swap_pte':
    > /home/kamezawa/Kernel/next/linux/mm/memcontrol.c:5172: undefined reference to `swapper_space'
    > make: *** [.tmp_vmlinux1] Error 1
    >
    > Ah...but I think this function (mc_handle_swap_pte) itself should be under CONFIG_SWAP.
    > I'll post v2.

    Confused. The new reference to swapper_space is already inside #ifdef
    CONFIG_SWAP.


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