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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: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Mel Gorman 2010-05-24 14:32:18 -07:00 committed by Linus Torvalds
parent 3f6c82728f
commit 7f60c214fd
4 changed files with 24 additions and 40 deletions
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50
include/linux/rmap.h
View File

@ -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)
{

4
mm/ksm.c
View File

@ -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)

4
mm/migrate.c
View File

@ -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 @@ skip_unmap:
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)

6
mm/rmap.c
View File

@ -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);
}