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    SubjectRe: [RFC 1/8] Only isolate page we can handle
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    On Wed, Apr 27, 2011 at 1:25 AM, Minchan Kim <minchan.kim@gmail.com> wrote:
    > There are some places to isolate lru page and I believe
    > users of isolate_lru_page will be growing.
    > The purpose of them is each different so part of isolated pages
    > should put back to LRU, again.
    >
    > The problem is when we put back the page into LRU,
    > we lose LRU ordering and the page is inserted at head of LRU list.
    > It makes unnecessary LRU churning so that vm can evict working set pages
    > rather than idle pages.
    >
    > This patch adds new filter mask when we isolate page in LRU.
    > So, we don't isolate pages if we can't handle it.
    > It could reduce LRU churning.
    >
    > This patch shouldn't change old behavior.
    > It's just used by next patches.
    >
    > Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    > Cc: Mel Gorman <mgorman@suse.de>
    > Cc: Rik van Riel <riel@redhat.com>
    > Cc: Andrea Arcangeli <aarcange@redhat.com>
    > Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
    > ---
    >  include/linux/swap.h |    3 ++-
    >  mm/compaction.c      |    2 +-
    >  mm/memcontrol.c      |    2 +-
    >  mm/vmscan.c          |   26 ++++++++++++++++++++------
    >  4 files changed, 24 insertions(+), 9 deletions(-)
    >
    > diff --git a/include/linux/swap.h b/include/linux/swap.h
    > index 384eb5f..baef4ad 100644
    > --- a/include/linux/swap.h
    > +++ b/include/linux/swap.h
    > @@ -259,7 +259,8 @@ extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
    >                                                unsigned int swappiness,
    >                                                struct zone *zone,
    >                                                unsigned long *nr_scanned);
    > -extern int __isolate_lru_page(struct page *page, int mode, int file);
    > +extern int __isolate_lru_page(struct page *page, int mode, int file,
    > +                               int not_dirty, int not_mapped);
    >  extern unsigned long shrink_all_memory(unsigned long nr_pages);
    >  extern int vm_swappiness;
    >  extern int remove_mapping(struct address_space *mapping, struct page *page);
    > diff --git a/mm/compaction.c b/mm/compaction.c
    > index 021a296..dea32e3 100644
    > --- a/mm/compaction.c
    > +++ b/mm/compaction.c
    > @@ -335,7 +335,7 @@ static unsigned long isolate_migratepages(struct zone *zone,
    >                }
    >
    >                /* Try isolate the page */
    > -               if (__isolate_lru_page(page, ISOLATE_BOTH, 0) != 0)
    > +               if (__isolate_lru_page(page, ISOLATE_BOTH, 0, 0, 0) != 0)
    >                        continue;
    >
    >                VM_BUG_ON(PageTransCompound(page));
    > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
    > index c2776f1..471e7fd 100644
    > --- a/mm/memcontrol.c
    > +++ b/mm/memcontrol.c
    > @@ -1193,7 +1193,7 @@ unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
    >                        continue;
    >
    >                scan++;
    > -               ret = __isolate_lru_page(page, mode, file);
    > +               ret = __isolate_lru_page(page, mode, file, 0, 0);
    >                switch (ret) {
    >                case 0:
    >                        list_move(&page->lru, dst);
    > diff --git a/mm/vmscan.c b/mm/vmscan.c
    > index b3a569f..71d2da9 100644
    > --- a/mm/vmscan.c
    > +++ b/mm/vmscan.c
    > @@ -954,10 +954,13 @@ keep_lumpy:
    >  *
    >  * page:       page to consider
    >  * mode:       one of the LRU isolation modes defined above
    > - *
    > + * file:       page be on a file LRU
    > + * not_dirty:  page should be not dirty or not writeback
    > + * not_mapped: page should be not mapped
    >  * returns 0 on success, -ve errno on failure.
    >  */
    > -int __isolate_lru_page(struct page *page, int mode, int file)
    > +int __isolate_lru_page(struct page *page, int mode, int file,
    > +                               int not_dirty, int not_mapped)
    >  {
    >        int ret = -EINVAL;
    >
    > @@ -976,6 +979,12 @@ int __isolate_lru_page(struct page *page, int mode, int file)
    >        if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file)
    >                return ret;
    >
    > +       if (not_dirty)
    > +               if (PageDirty(page) || PageWriteback(page))
    > +                       return ret;
    > +       if (not_mapped)
    > +               if (page_mapped(page))
    > +                       return ret;

    I should have fixed this return value.
    Now caller regards -EINVAL with BUG.
    I will fix it in next version.

    --
    Kind regards,
    Minchan Kim
    --
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