Re: [RFC 1/8] Only isolate page we can handle

[Minchan Kim <minchan.kim@gmail.com>]

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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