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SubjectRe: [PATCH 08/10] vmscan: isolated_lru_pages() stop neighbour search if neighbour cannot be isolated
On Mon, Sep 06, 2010 at 11:47:31AM +0100, Mel Gorman wrote:
> From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>
> isolate_lru_pages() does not just isolate LRU tail pages, but also isolate
> neighbour pages of the eviction page. The neighbour search does not stop even
> if neighbours cannot be isolated which is excessive as the lumpy reclaim will
> no longer result in a successful higher order allocation. This patch stops
> the PFN neighbour pages if an isolation fails and moves on to the next block.
>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Signed-off-by: Mel Gorman <mel@csn.ul.ie>
> ---
> mm/vmscan.c | 24 ++++++++++++++++--------
> 1 files changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 64f9ca5..ff52b46 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1047,14 +1047,18 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> continue;
>
> /* Avoid holes within the zone. */
> - if (unlikely(!pfn_valid_within(pfn)))
> + if (unlikely(!pfn_valid_within(pfn))) {
> + nr_lumpy_failed++;
> break;
> + }
>
> cursor_page = pfn_to_page(pfn);
>
> /* Check that we have not crossed a zone boundary. */
> - if (unlikely(page_zone_id(cursor_page) != zone_id))
> - continue;
> + if (unlikely(page_zone_id(cursor_page) != zone_id)) {
> + nr_lumpy_failed++;
> + break;
> + }
>
> /*
> * If we don't have enough swap space, reclaiming of
> @@ -1062,8 +1066,10 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> * pointless.
> */
> if (nr_swap_pages <= 0 && PageAnon(cursor_page) &&
> - !PageSwapCache(cursor_page))
> - continue;
> + !PageSwapCache(cursor_page)) {
> + nr_lumpy_failed++;
> + break;
> + }
>
> if (__isolate_lru_page(cursor_page, mode, file) == 0) {
> list_move(&cursor_page->lru, dst);
> @@ -1074,9 +1080,11 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
> nr_lumpy_dirty++;
> scan++;
> } else {
> - if (mode == ISOLATE_BOTH &&

Why can we remove ISOLATION_BOTH check?
Is it a intentionall behavior change?

> - page_count(cursor_page))
> - nr_lumpy_failed++;
> + /* the page is freed already. */
> + if (!page_count(cursor_page))
> + continue;
> + nr_lumpy_failed++;
> + break;
> }
> }
> }
> --
> 1.7.1
>

--
Kind regards,
Minchan Kim


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