Re: [PATCH v3 2/5] cma: fix counting of isolated pages

[Minchan Kim <minchan@kernel.org>]

On Tue, Sep 04, 2012 at 03:26:22PM +0200, Bartlomiej Zolnierkiewicz wrote:
> Isolated free pages shouldn't be accounted to NR_FREE_PAGES counter.
> Fix it by properly decreasing/increasing NR_FREE_PAGES counter in
> set_migratetype_isolate()/unset_migratetype_isolate() and removing
> counter adjustment for isolated pages from free_one_page() and
> split_free_page().
> 
> Cc: Marek Szyprowski <m.szyprowski@samsung.com>
> Cc: Michal Nazarewicz <mina86@mina86.com>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Mel Gorman <mgorman@suse.de>
> Cc: Hugh Dickins <hughd@google.com>
> Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
> ---
>  mm/page_alloc.c     |  7 +++++--
>  mm/page_isolation.c | 13 ++++++++++---
>  2 files changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index e9da55c..3acdf0f 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -691,7 +691,8 @@ static void free_one_page(struct zone *zone, struct page *page, int order,
>  	zone->pages_scanned = 0;
>  
>  	__free_one_page(page, zone, order, migratetype);
> -	__mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order);
> +	if (migratetype != MIGRATE_ISOLATE)

We can add unlikely.

> +		__mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order);
>  	spin_unlock(&zone->lock);
>  }
>  
> @@ -1414,7 +1415,9 @@ int split_free_page(struct page *page, bool check_wmark)
>  	list_del(&page->lru);
>  	zone->free_area[order].nr_free--;
>  	rmv_page_order(page);
> -	__mod_zone_page_state(zone, NR_FREE_PAGES, -(1UL << order));
> +
> +	if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)

The get_pageblock_migratetype isn't cheap.
You can use get_freepage_migratetype.

-- 
Kind regards,
Minchan Kim

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