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    SubjectRe: [RFC] respect the referenced bit of KVM guest pages?
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    On Wed, Aug 19, 2009 at 9:10 PM, Wu Fengguang<fengguang.wu@intel.com> wrote:
    > On Wed, Aug 19, 2009 at 08:05:19PM +0800, KOSAKI Motohiro wrote:
    >> >> page_referenced_file?
    >> >> I think we should change page_referenced().
    >> >
    >> > Yeah, good catch.
    >> >
    >> >>
    >> >> Instead, How about this?
    >> >> ==============================================
    >> >>
    >> >> Subject: [PATCH] mm: stop circulating of referenced mlocked pages
    >> >>
    >> >> Currently, mlock() systemcall doesn't gurantee to mark the page PG_Mlocked
    >> >
    >> >                                                    mark PG_mlocked
    >> >
    >> >> because some race prevent page grabbing.
    >> >> In that case, instead vmscan move the page to unevictable lru.
    >> >>
    >> >> However, Recently Wu Fengguang pointed out current vmscan logic isn't so
    >> >> efficient.
    >> >> mlocked page can move circulatly active and inactive list because
    >> >> vmscan check the page is referenced _before_ cull mlocked page.
    >> >>
    >> >> Plus, vmscan should mark PG_Mlocked when cull mlocked page.
    >> >
    >> >                           PG_mlocked
    >> >
    >> >> Otherwise vm stastics show strange number.
    >> >>
    >> >> This patch does that.
    >> >
    >> > Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>
    >>
    >> Thanks.
    >>
    >>
    >>
    >> >> Index: b/mm/rmap.c
    >> >> ===================================================================
    >> >> --- a/mm/rmap.c       2009-08-18 19:48:14.000000000 +0900
    >> >> +++ b/mm/rmap.c       2009-08-18 23:47:34.000000000 +0900
    >> >> @@ -362,7 +362,9 @@ static int page_referenced_one(struct pa
    >> >>        * unevictable list.
    >> >>        */
    >> >>       if (vma->vm_flags & VM_LOCKED) {
    >> >> -             *mapcount = 1;  /* break early from loop */
    >> >> +             *mapcount = 1;          /* break early from loop */
    >> >> +             *vm_flags |= VM_LOCKED; /* for prevent to move active list */
    >> >
    >> >> +             try_set_page_mlocked(vma, page);
    >> >
    >> > That call is not absolutely necessary?
    >>
    >> Why? I haven't catch your point.
    >
    > Because we'll eventually hit another try_set_page_mlocked() when
    > trying to unmap the page. Ie. duplicated with another call you added
    > in this patch.

    Yes. we don't have to call it and we can make patch simple.
    I already sent patch on yesterday.

    http://marc.info/?l=linux-mm&m=125059325722370&w=2

    I think It's more simple than KOSAKI's idea.
    Is any problem in my patch ?


    >
    > Thanks,
    > Fengguang
    >
    > --
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    > see: http://www.linux-mm.org/ .
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    >



    --
    Kind regards,
    Minchan Kim
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