page migration: Only migrate pages if allocation in the highest zone is possible (906e0be1) · Commits · 戴 / test

Address spaces contain an allocation flag that specifies restriction on the zone for pages placed in the mapping. I.e. some device may require pages to be allocated from a DMA zone. Block devices may not be able to use pages from HIGHMEM. Memory policies and the common use of page migration works only on the highest zone. If the address space does not allow allocation from the highest zone then the pages in the address space are not migratable simply because we can only allocate memory for a specified node if we allow allocation for the highest zone on each node. Acked-by:

Hugh Dickins <hugh@veritas.com> Signed-off-by:

Christoph Lameter <clameter@sgi.com> Signed-off-by:

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

Linus Torvalds <torvalds@linux-foundation.org>

include/linux/migrate.h

+14 −1

Original line number	Diff line number	Diff line
		@@ -2,18 +2,29 @@
		#define _LINUX_MIGRATE_H

		#include <linux/mm.h>
		#include <linux/mempolicy.h>
		#include <linux/pagemap.h>

		typedef struct page new_page_t(struct page , unsigned long private, int **);

		#ifdef CONFIG_MIGRATION
		/* Check if a vma is migratable */
		static inline int vma_migratable(struct vm_area_struct *vma)
		{
		if (vma->vm_flags & (VM_IO\|VM_HUGETLB\|VM_PFNMAP\|VM_RESERVED))
		return 0;
		/*
		* Migration allocates pages in the highest zone. If we cannot
		* do so then migration (at least from node to node) is not
		* possible.
		*/
		if (vma->vm_file &&
		gfp_zone(mapping_gfp_mask(vma->vm_file->f_mapping))
		< policy_zone)
		return 0;
		return 1;
		}

		#ifdef CONFIG_MIGRATION
		extern int isolate_lru_page(struct page p, struct list_head pagelist);
		extern int putback_lru_pages(struct list_head *l);
		extern int migrate_page(struct address_space *,
		@@ -28,6 +39,8 @@ extern int migrate_vmas(struct mm_struct *mm,
		const nodemask_t from, const nodemask_t to,
		unsigned long flags);
		#else
		static inline int vma_migratable(struct vm_area_struct *vma)
		{ return 0; }

		static inline int isolate_lru_page(struct page p, struct list_head list)
		{ return -ENOSYS; }

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