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Commit b7ccc7f8 authored by Matthew Wilcox's avatar Matthew Wilcox Committed by Linus Torvalds
Browse files

mm: move lru union within struct page 

Since the LRU is two words, this does not affect the double-word alignment
of SLUB's freelist.

Link: http://lkml.kernel.org/r/20180518194519.3820-10-willy@infradead.org


Signed-off-by: default avatarMatthew Wilcox <mawilcox@microsoft.com>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarKirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fa3015b7

include/linux/mm_types.h

+51 −51
Original line number Diff line number Diff line
@@ -72,6 +72,57 @@ struct hmm; 
struct page {

	unsigned long flags;		/* Atomic flags, some possibly

					 * updated asynchronously */

	/*

	 * WARNING: bit 0 of the first word encode PageTail(). That means

	 * the rest users of the storage space MUST NOT use the bit to

	 * avoid collision and false-positive PageTail().

	 */

	union {

		struct list_head lru;	/* Pageout list, eg. active_list

					 * protected by zone_lru_lock !

					 * Can be used as a generic list

					 * by the page owner.

					 */

		struct dev_pagemap *pgmap; /* ZONE_DEVICE pages are never on an

					    * lru or handled by a slab

					    * allocator, this points to the

					    * hosting device page map.

					    */

		struct {		/* slub per cpu partial pages */

			struct page *next;	/* Next partial slab */

#ifdef CONFIG_64BIT

			int pages;	/* Nr of partial slabs left */

			int pobjects;	/* Approximate # of objects */

#else

			short int pages;

			short int pobjects;

#endif

		};



		struct rcu_head rcu_head;	/* Used by SLAB

						 * when destroying via RCU

						 */

		/* Tail pages of compound page */

		struct {

			unsigned long compound_head; /* If bit zero is set */



			/* First tail page only */

			unsigned char compound_dtor;

			unsigned char compound_order;

			/* two/six bytes available here */

		};



#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && USE_SPLIT_PMD_PTLOCKS

		struct {

			unsigned long __pad;	/* do not overlay pmd_huge_pte

						 * with compound_head to avoid

						 * possible bit 0 collision.

						 */

			pgtable_t pmd_huge_pte; /* protected by page->ptl */

		};

#endif

	};



	/* Three words (12/24 bytes) are available in this union. */

	union {

		struct {	/* Page cache and anonymous pages */
@@ -135,57 +186,6 @@ struct page { 
	/* Usage count. *DO NOT USE DIRECTLY*. See page_ref.h */

	atomic_t _refcount;



	/*

	 * WARNING: bit 0 of the first word encode PageTail(). That means

	 * the rest users of the storage space MUST NOT use the bit to

	 * avoid collision and false-positive PageTail().

	 */

	union {

		struct list_head lru;	/* Pageout list, eg. active_list

					 * protected by zone_lru_lock !

					 * Can be used as a generic list

					 * by the page owner.

					 */

		struct dev_pagemap *pgmap; /* ZONE_DEVICE pages are never on an

					    * lru or handled by a slab

					    * allocator, this points to the

					    * hosting device page map.

					    */

		struct {		/* slub per cpu partial pages */

			struct page *next;	/* Next partial slab */

#ifdef CONFIG_64BIT

			int pages;	/* Nr of partial slabs left */

			int pobjects;	/* Approximate # of objects */

#else

			short int pages;

			short int pobjects;

#endif

		};



		struct rcu_head rcu_head;	/* Used by SLAB

						 * when destroying via RCU

						 */

		/* Tail pages of compound page */

		struct {

			unsigned long compound_head; /* If bit zero is set */



			/* First tail page only */

			unsigned char compound_dtor;

			unsigned char compound_order;

			/* two/six bytes available here */

		};



#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && USE_SPLIT_PMD_PTLOCKS

		struct {

			unsigned long __pad;	/* do not overlay pmd_huge_pte

						 * with compound_head to avoid

						 * possible bit 0 collision.

						 */

			pgtable_t pmd_huge_pte; /* protected by page->ptl */

		};

#endif

	};



#ifdef CONFIG_MEMCG

	struct mem_cgroup *mem_cgroup;

#endif

mm/slub.c

+4 −4
Original line number Diff line number Diff line
@@ -52,11 +52,11 @@ 
 *   and to synchronize major metadata changes to slab cache structures.

 *

 *   The slab_lock is only used for debugging and on arches that do not

 *   have the ability to do a cmpxchg_double. It only protects the second

 *   double word in the page struct. Meaning

 *   have the ability to do a cmpxchg_double. It only protects:

 *	A. page->freelist	-> List of object free in a page

 *	B. page->counters	-> Counters of objects

 *	C. page->frozen		-> frozen state

 *	B. page->inuse		-> Number of objects in use

 *	C. page->objects	-> Number of objects in page

 *	D. page->frozen		-> frozen state

 *

 *   If a slab is frozen then it is exempt from list management. It is not

 *   on any list. The processor that froze the slab is the one who can