Re: [patch 3/3] mm: keep pages from unevictable mappings off the LRU lists

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

Hmm,,

This patch is another thing unlike previous series patches.
Firstly, It looked good to me.

I think add_to_page_cache_lru have to become a fast path.
But, how often would ramfs and shmem function be called ?

I have a concern for this patch to add another burden.
so, we need any numbers for getting pros and cons.

Any thoughts ?

On Mon, Mar 23, 2009 at 5:13 AM, Johannes Weiner <hannes@cmpxchg.org> wrote:
> Check if the mapping is evictable when initially adding page cache
> pages to the LRU lists.  If that is not the case, add them to the
> unevictable list immediately instead of leaving it up to the reclaim
> code to move them there.
>
> This is useful for ramfs and locked shmem which mark whole mappings as
> unevictable and we know at fault time already that it is useless to
> try reclaiming these pages.
>
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
> Cc: David Howells <dhowells@redhat.com>
> Cc: Nick Piggin <npiggin@suse.de>
> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Cc: Rik van Riel <riel@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.com>
> Cc: MinChan Kim <minchan.kim@gmail.com>
> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
> ---
>  mm/filemap.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 23acefe..8574530 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -506,7 +506,9 @@ int add_to_page_cache_lru(struct page *page, struct address_space *mapping,
>
>        ret = add_to_page_cache(page, mapping, offset, gfp_mask);
>        if (ret == 0) {
> -               if (page_is_file_cache(page))
> +               if (mapping_unevictable(mapping))
> +                       add_page_to_unevictable_list(page);
> +               else if (page_is_file_cache(page))
>                        lru_cache_add_file(page);
>                else
>                        lru_cache_add_active_anon(page);
> --
> 1.6.2.1.135.gde769
>
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-- 
Kinds regards,
Minchan Kim

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