Commit d435edca authored by Vlastimil Babka's avatar Vlastimil Babka Committed by Linus Torvalds
Browse files

mm, page_owner: copy page owner info during migration 



The page_owner mechanism stores gfp_flags of an allocation and stack
trace that lead to it.  During page migration, the original information
is practically replaced by the allocation of free page as the migration
target.  Arguably this is less useful and might lead to all the
page_owner info for migratable pages gradually converge towards
compaction or numa balancing migrations.  It has also lead to
inaccuracies such as one fixed by commit e2cfc911 ("mm/page_owner:
set correct gfp_mask on page_owner").

This patch thus introduces copying the page_owner info during migration.
However, since the fact that the page has been migrated from its
original place might be useful for debugging, the next patch will
introduce a way to track that information as well.

Signed-off-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7dd80b8a

include/linux/page_owner.h

+9 −1
Original line number Diff line number Diff line
@@ -11,6 +11,7 @@ extern void __reset_page_owner(struct page *page, unsigned int order); 
extern void __set_page_owner(struct page *page,

			unsigned int order, gfp_t gfp_mask);

extern gfp_t __get_page_owner_gfp(struct page *page);

extern void __copy_page_owner(struct page *oldpage, struct page *newpage);



static inline void reset_page_owner(struct page *page, unsigned int order)

{
@@ -32,6 +33,11 @@ static inline gfp_t get_page_owner_gfp(struct page *page) 
	else

		return 0;

}

static inline void copy_page_owner(struct page *oldpage, struct page *newpage)

{

	if (static_branch_unlikely(&page_owner_inited))

		__copy_page_owner(oldpage, newpage);

}

#else

static inline void reset_page_owner(struct page *page, unsigned int order)

{
@@ -44,6 +50,8 @@ static inline gfp_t get_page_owner_gfp(struct page *page) 
{

	return 0;

}



static inline void copy_page_owner(struct page *oldpage, struct page *newpage)

{

}

#endif /* CONFIG_PAGE_OWNER */

#endif /* __LINUX_PAGE_OWNER_H */

mm/migrate.c

+3 −0
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ 
#include <linux/balloon_compaction.h>

#include <linux/mmu_notifier.h>

#include <linux/page_idle.h>

#include <linux/page_owner.h>



#include <asm/tlbflush.h>
@@ -578,6 +579,8 @@ void migrate_page_copy(struct page *newpage, struct page *page) 
	 */

	if (PageWriteback(newpage))

		end_page_writeback(newpage);



	copy_page_owner(page, newpage);

}



/************************************************************

mm/page_owner.c

+25 −0
Original line number Diff line number Diff line
@@ -84,6 +84,31 @@ gfp_t __get_page_owner_gfp(struct page *page) 
	return page_ext->gfp_mask;

}



void __copy_page_owner(struct page *oldpage, struct page *newpage)

{

	struct page_ext *old_ext = lookup_page_ext(oldpage);

	struct page_ext *new_ext = lookup_page_ext(newpage);

	int i;



	new_ext->order = old_ext->order;

	new_ext->gfp_mask = old_ext->gfp_mask;

	new_ext->nr_entries = old_ext->nr_entries;



	for (i = 0; i < ARRAY_SIZE(new_ext->trace_entries); i++)

		new_ext->trace_entries[i] = old_ext->trace_entries[i];



	/*

	 * We don't clear the bit on the oldpage as it's going to be freed

	 * after migration. Until then, the info can be useful in case of

	 * a bug, and the overal stats will be off a bit only temporarily.

	 * Also, migrate_misplaced_transhuge_page() can still fail the

	 * migration and then we want the oldpage to retain the info. But

	 * in that case we also don't need to explicitly clear the info from

	 * the new page, which will be freed.

	 */

	__set_bit(PAGE_EXT_OWNER, &new_ext->flags);

}



static ssize_t

print_page_owner(char __user *buf, size_t count, unsigned long pfn,

		struct page *page, struct page_ext *page_ext)

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