On 2012/10/31 19:23, Wen Congyang wrote:
> NR_FREE_PAGES will be wrong after offlining pages. We add/dec
> NR_FREE_PAGES like this now:
>
> 1. move all pages in buddy system to MIGRATE_ISOLATE, and dec NR_FREE_PAGES
>
> 2. don't add NR_FREE_PAGES when it is freed and the migratetype is
> MIGRATE_ISOLATE
>
> 3. dec NR_FREE_PAGES when offlining isolated pages.
>
> 4. add NR_FREE_PAGES when undoing isolate pages.
>
> When we come to step 3, all pages are in MIGRATE_ISOLATE list, and
> NR_FREE_PAGES are right. When we come to step4, all pages are not in
> buddy system, so we don't change NR_FREE_PAGES in this step, but we change
> NR_FREE_PAGES in step3. So NR_FREE_PAGES is wrong after offlining pages.
> So there is no need to change NR_FREE_PAGES in step3.
>
> This patch also fixs a problem in step2: if the migratetype is
> MIGRATE_ISOLATE, we should not add NR_FRR_PAGES when we remove pages from
> pcppages.
>
> Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
> Cc: David Rientjes <rientjes@xxxxxxxxxx>
> Cc: Jiang Liu <liuj97@xxxxxxxxx>
> Cc: Len Brown <len.brown@xxxxxxxxx>
> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
> Cc: Paul Mackerras <paulus@xxxxxxxxx>
> Cc: Christoph Lameter <cl@xxxxxxxxx>
> Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
> Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
> Cc: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
> Cc: Mel Gorman <mel@xxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> ---
> mm/page_alloc.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 5b74de6..a7cd2d1 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -667,11 +667,13 @@ static void free_pcppages_bulk(struct zone *zone, int count,
> /* MIGRATE_MOVABLE list may include MIGRATE_RESERVEs */
> __free_one_page(page, zone, 0, mt);
> trace_mm_page_pcpu_drain(page, 0, mt);
> - if (is_migrate_cma(mt))
> - __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, 1);
> + if (likely(mt != MIGRATE_ISOLATE)) {
Hi Congyang,
I think mt != MIGRATE_ISOLATE is always true here,
page from PCP's migratetype < MIGRATE_PCPTYPES.
When isolate page, we change pageblock's migratetype to MIGRATE_ISOLATE,
but set_freepage_migratetype() isn't called.
Maybe we can use mt = get_pageblock_migratetype() here ?
Thanks,
Jianguo Wu.
> + __mod_zone_page_state(zone, NR_FREE_PAGES, 1);
> + if (is_migrate_cma(mt))
> + __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, 1);
> + }
> } while (--to_free && --batch_free && !list_empty(list));
> }
> - __mod_zone_page_state(zone, NR_FREE_PAGES, count);
> spin_unlock(&zone->lock);
> }
>
> @@ -5987,8 +5989,6 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
> list_del(&page->lru);
> rmv_page_order(page);
> zone->free_area[order].nr_free--;
> - __mod_zone_page_state(zone, NR_FREE_PAGES,
> - - (1UL << order));
> for (i = 0; i < (1 << order); i++)
> SetPageReserved((page+i));
> pfn += (1 << order);
>
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