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Commit 7f60c214 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

mm: migration: share the anon_vma ref counts between KSM and page migration 



For clarity of review, KSM and page migration have separate refcounts on
the anon_vma.  While clear, this is a waste of memory.  This patch gets
KSM and page migration to share their toys in a spirit of harmony.

Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
Reviewed-by: default avatarMinchan Kim <minchan.kim@gmail.com>
Reviewed-by: default avatarKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: default avatarChristoph Lameter <cl@linux-foundation.org>
Reviewed-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3f6c8272

include/linux/rmap.h

+18 −32
Original line number Diff line number Diff line
@@ -26,11 +26,17 @@ 
 */

struct anon_vma {

	spinlock_t lock;	/* Serialize access to vma list */

#ifdef CONFIG_KSM

	atomic_t ksm_refcount;

#endif

#ifdef CONFIG_MIGRATION

	atomic_t migrate_refcount;

#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)



	/*

	 * The external_refcount is taken by either KSM or page migration

	 * to take a reference to an anon_vma when there is no

	 * guarantee that the vma of page tables will exist for

	 * the duration of the operation. A caller that takes

	 * the reference is responsible for clearing up the

	 * anon_vma if they are the last user on release

	 */

	atomic_t external_refcount;

#endif

	/*

	 * NOTE: the LSB of the head.next is set by
@@ -64,46 +70,26 @@ struct anon_vma_chain { 
};



#ifdef CONFIG_MMU

#ifdef CONFIG_KSM

static inline void ksm_refcount_init(struct anon_vma *anon_vma)

#if defined(CONFIG_KSM) || defined(CONFIG_MIGRATION)

static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma)

{

	atomic_set(&anon_vma->ksm_refcount, 0);

	atomic_set(&anon_vma->external_refcount, 0);

}



static inline int ksm_refcount(struct anon_vma *anon_vma)

static inline int anonvma_external_refcount(struct anon_vma *anon_vma)

{

	return atomic_read(&anon_vma->ksm_refcount);

	return atomic_read(&anon_vma->external_refcount);

}

#else

static inline void ksm_refcount_init(struct anon_vma *anon_vma)

static inline void anonvma_external_refcount_init(struct anon_vma *anon_vma)

{

}



static inline int ksm_refcount(struct anon_vma *anon_vma)

static inline int anonvma_external_refcount(struct anon_vma *anon_vma)

{

	return 0;

}

#endif /* CONFIG_KSM */

#ifdef CONFIG_MIGRATION

static inline void migrate_refcount_init(struct anon_vma *anon_vma)

{

	atomic_set(&anon_vma->migrate_refcount, 0);

}



static inline int migrate_refcount(struct anon_vma *anon_vma)

{

	return atomic_read(&anon_vma->migrate_refcount);

}

#else

static inline void migrate_refcount_init(struct anon_vma *anon_vma)

{

}



static inline int migrate_refcount(struct anon_vma *anon_vma)

{

	return 0;

}

#endif /* CONFIG_MIGRATE */



static inline struct anon_vma *page_anon_vma(struct page *page)

{

mm/ksm.c

+2 −2
Original line number Diff line number Diff line
@@ -318,14 +318,14 @@ static void hold_anon_vma(struct rmap_item *rmap_item, 
			  struct anon_vma *anon_vma)

{

	rmap_item->anon_vma = anon_vma;

	atomic_inc(&anon_vma->ksm_refcount);

	atomic_inc(&anon_vma->external_refcount);

}



static void drop_anon_vma(struct rmap_item *rmap_item)

{

	struct anon_vma *anon_vma = rmap_item->anon_vma;



	if (atomic_dec_and_lock(&anon_vma->ksm_refcount, &anon_vma->lock)) {

	if (atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->lock)) {

		int empty = list_empty(&anon_vma->head);

		spin_unlock(&anon_vma->lock);

		if (empty)

mm/migrate.c

+2 −2
Original line number Diff line number Diff line
@@ -601,7 +601,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, 
		rcu_read_lock();

		rcu_locked = 1;

		anon_vma = page_anon_vma(page);

		atomic_inc(&anon_vma->migrate_refcount);

		atomic_inc(&anon_vma->external_refcount);

	}



	/*
@@ -643,7 +643,7 @@ static int unmap_and_move(new_page_t get_new_page, unsigned long private, 
rcu_unlock:



	/* Drop an anon_vma reference if we took one */

	if (anon_vma && atomic_dec_and_lock(&anon_vma->migrate_refcount, &anon_vma->lock)) {

	if (anon_vma && atomic_dec_and_lock(&anon_vma->external_refcount, &anon_vma->lock)) {

		int empty = list_empty(&anon_vma->head);

		spin_unlock(&anon_vma->lock);

		if (empty)

mm/rmap.c

+2 −4
Original line number Diff line number Diff line
@@ -250,8 +250,7 @@ static void anon_vma_unlink(struct anon_vma_chain *anon_vma_chain) 
	list_del(&anon_vma_chain->same_anon_vma);



	/* We must garbage collect the anon_vma if it's empty */

	empty = list_empty(&anon_vma->head) && !ksm_refcount(anon_vma) &&

					!migrate_refcount(anon_vma);

	empty = list_empty(&anon_vma->head) && !anonvma_external_refcount(anon_vma);

	spin_unlock(&anon_vma->lock);



	if (empty)
@@ -275,8 +274,7 @@ static void anon_vma_ctor(void *data) 
	struct anon_vma *anon_vma = data;



	spin_lock_init(&anon_vma->lock);

	ksm_refcount_init(anon_vma);

	migrate_refcount_init(anon_vma);

	anonvma_external_refcount_init(anon_vma);

	INIT_LIST_HEAD(&anon_vma->head);

}