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@xxxxxxxxxxx>
> Cc: Michal Nazarewicz <mina86@xxxxxxxxxx>
> Cc: Minchan Kim <minchan@xxxxxxxxxx>
> Cc: Mel Gorman <mgorman@xxxxxxx>
> Cc: Hugh Dickins <hughd@xxxxxxxxxx>
> Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx>
> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> ---
> 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)
> + __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)
> + __mod_zone_page_state(zone, NR_FREE_PAGES, -(1UL << order));
>
Are you *sure* about this part? The page is already free so the
NR_FREE_PAGES counters should already be correct. It feels to me that it
should be the caller that fixes up NR_FREE_PAGES if necessary.
Have you tested this with THP? I have a suspicion that the free page
accounting gets broken when page migration is used there.
> /* Split into individual pages */
> set_page_refcounted(page);
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index 247d1f1..d210cc8 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -76,8 +76,12 @@ int set_migratetype_isolate(struct page *page)
>
> out:
> if (!ret) {
> + unsigned long nr_pages;
> +
> set_pageblock_isolate(page);
> - move_freepages_block(zone, page, MIGRATE_ISOLATE);
> + nr_pages = move_freepages_block(zone, page, MIGRATE_ISOLATE);
> +
> + __mod_zone_page_state(zone, NR_FREE_PAGES, -nr_pages);
> }
>
> spin_unlock_irqrestore(&zone->lock, flags);
> @@ -89,12 +93,15 @@ out:
> void unset_migratetype_isolate(struct page *page, unsigned migratetype)
> {
> struct zone *zone;
> - unsigned long flags;
> + unsigned long flags, nr_pages;
> +
> zone = page_zone(page);
> +
unnecessary whitespace change.
> spin_lock_irqsave(&zone->lock, flags);
> if (get_pageblock_migratetype(page) != MIGRATE_ISOLATE)
> goto out;
> - move_freepages_block(zone, page, migratetype);
> + nr_pages = move_freepages_block(zone, page, migratetype);
> + __mod_zone_page_state(zone, NR_FREE_PAGES, nr_pages);
> restore_pageblock_isolate(page, migratetype);
> out:
> spin_unlock_irqrestore(&zone->lock, flags);
> --
> 1.7.11.3
>
--
Mel Gorman
SUSE Labs
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