add pfn_valid_within helper for sub-MAX_ORDER hole detection (14e07298) · Commits · 戴 / test

Generally we work under the assumption that memory the mem_map array is contigious and valid out to MAX_ORDER_NR_PAGES block of pages, ie. that if we have validated any page within this MAX_ORDER_NR_PAGES block we need not check any other. This is not true when CONFIG_HOLES_IN_ZONE is set and we must check each and every reference we make from a pfn. Add a pfn_valid_within() helper which should be used when scanning pages within a MAX_ORDER_NR_PAGES block when we have already checked the validility of the block normally with pfn_valid(). This can then be optimised away when we do not have holes within a MAX_ORDER_NR_PAGES block of pages. Signed-off-by:

Andy Whitcroft <apw@shadowen.org> Acked-by:

Mel Gorman <mel@csn.ul.ie> Acked-by:

Bob Picco <bob.picco@hp.com> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mmzone.h

+12 −0

Original line number	Diff line number	Diff line
		@@ -784,6 +784,18 @@ void sparse_init(void);
		void memory_present(int nid, unsigned long start, unsigned long end);
		unsigned long __init node_memmap_size_bytes(int, unsigned long, unsigned long);

		/*
		* If it is possible to have holes within a MAX_ORDER_NR_PAGES, then we
		* need to check pfn validility within that MAX_ORDER_NR_PAGES block.
		* pfn_valid_within() should be used in this case; we optimise this away
		* when we have no holes within a MAX_ORDER_NR_PAGES block.
		*/
		#ifdef CONFIG_HOLES_IN_ZONE
		#define pfn_valid_within(pfn) pfn_valid(pfn)
		#else
		#define pfn_valid_within(pfn) (1)
		#endif

		#endif /* !__ASSEMBLY__ */
		#endif /* __KERNEL__ */
		#endif /* _LINUX_MMZONE_H */

mm/page_alloc.c

+2 −6

Original line number	Diff line number	Diff line
		@@ -156,10 +156,8 @@ static int page_outside_zone_boundaries(struct zone zone, struct page page)

		static int page_is_consistent(struct zone zone, struct page page)
		{
		#ifdef CONFIG_HOLES_IN_ZONE
		if (!pfn_valid(page_to_pfn(page)))
		if (!pfn_valid_within(page_to_pfn(page)))
		return 0;
		#endif
		if (zone != page_zone(page))
		return 0;

		@@ -346,10 +344,8 @@ __find_combined_index(unsigned long page_idx, unsigned int order)
		static inline int page_is_buddy(struct page page, struct page buddy,
		int order)
		{
		#ifdef CONFIG_HOLES_IN_ZONE
		if (!pfn_valid(page_to_pfn(buddy)))
		if (!pfn_valid_within(page_to_pfn(buddy)))
		return 0;
		#endif

		if (page_zone_id(page) != page_zone_id(buddy))
		return 0;

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