Messages in this thread Patch in this message | | | From | "Srivatsa S. Bhat" <> | Subject | [RFC PATCH v3 30/35] mm: Provide a mechanism to check if a given page is in the region allocator | Date | Fri, 30 Aug 2013 18:53:31 +0530 |
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With the introduction of the region allocator, a freepage can be either in one of the buddy freelists or in the region allocator. In cases where we want to move freepages to a given migratetype's freelists, we will need to know where they were originally located. So provide a helper to distinguish whether the freepage resides in the region allocator or the buddy freelists.
Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> ---
mm/page_alloc.c | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index a62730b..3f49ca8 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1047,6 +1047,37 @@ static int del_from_region_allocator(struct zone *zone, unsigned int order, } /* + * Return 1 if the page is in the region allocator, else return 0 + * (which usually means that the page is in the buddy freelists). + */ +static int page_in_region_allocator(struct page *page) +{ + struct region_allocator *reg_alloc; + struct free_area_region *reg_area; + int order, region_id; + + /* We keep only MAX_ORDER-1 pages in the region allocator */ + order = page_order(page); + if (order != MAX_ORDER-1) + return 0; + + /* + * It is sufficient to check if (any of) the pages belonging to + * that region are in the region allocator, because a page resides + * in the region allocator if and only if all the pages of that + * region are also in the region allocator. + */ + region_id = page_zone_region_id(page); + reg_alloc = &page_zone(page)->region_allocator; + reg_area = ®_alloc->region[region_id].region_area[order]; + + if (reg_area->nr_free) + return 1; + + return 0; +} + +/* * Freeing function for a buddy system allocator. * * The concept of a buddy system is to maintain direct-mapped table
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