Re: [PATCH 08/10] vmscan: isolated_lru_pages() stop neighboursearch if neighbour cannot be isolated

[Wu Fengguang]

On Mon, Sep 06, 2010 at 06:47:31PM +0800, Mel Gorman wrote:
> From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxxxx>
> Signed-off-by: Mel Gorman <mel@xxxxxxxxx>
> ---
>  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 &&
> -						page_count(cursor_page))
> -					nr_lumpy_failed++;
> +				/* the page is freed already. */
> +				if (!page_count(cursor_page))
> +					continue;
> +				nr_lumpy_failed++;
> +				break;
>  			}
>  		}

The many nr_lumpy_failed++ can be moved here:

                if (pfn < end_pfn)
                        nr_lumpy_failed++;

Reviewed-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/