The patch titled
mm: share the anon_vma ref counts between KSM and page migration
has been added to the -mm tree. Its filename is
mm-share-the-anon_vma-ref-counts-between-ksm-and-page-migration.patch
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------------------------------------------------------
Subject: mm: share the anon_vma ref counts between KSM and page migration
From: Mel Gorman <mel@xxxxxxxxx>
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@xxxxxxxxx>
Reviewed-by: Minchan Kim <minchan.kim@xxxxxxxxx>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Reviewed-by: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/rmap.h | 50 ++++++++++++++---------------------------
mm/ksm.c | 4 +--
mm/migrate.c | 4 +--
mm/rmap.c | 6 +---
4 files changed, 24 insertions(+), 40 deletions(-)
diff -puN include/linux/rmap.h~mm-share-the-anon_vma-ref-counts-between-ksm-and-page-migration include/linux/rmap.h
--- a/include/linux/rmap.h~mm-share-the-anon_vma-ref-counts-between-ksm-and-page-migration
+++ a/include/linux/rmap.h
@@ -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)
{
diff -puN mm/ksm.c~mm-share-the-anon_vma-ref-counts-between-ksm-and-page-migration mm/ksm.c
--- a/mm/ksm.c~mm-share-the-anon_vma-ref-counts-between-ksm-and-page-migration
+++ a/mm/ksm.c
@@ -318,14 +318,14 @@ static void hold_anon_vma(struct rmap_it
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)
diff -puN mm/migrate.c~mm-share-the-anon_vma-ref-counts-between-ksm-and-page-migration mm/migrate.c
--- a/mm/migrate.c~mm-share-the-anon_vma-ref-counts-between-ksm-and-page-migration
+++ a/mm/migrate.c
@@ -612,7 +612,7 @@ static int unmap_and_move(new_page_t get
goto rcu_unlock;
anon_vma = page_anon_vma(page);
- atomic_inc(&anon_vma->migrate_refcount);
+ atomic_inc(&anon_vma->external_refcount);
}
/*
@@ -654,7 +654,7 @@ 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)
diff -puN mm/rmap.c~mm-share-the-anon_vma-ref-counts-between-ksm-and-page-migration mm/rmap.c
--- a/mm/rmap.c~mm-share-the-anon_vma-ref-counts-between-ksm-and-page-migration
+++ a/mm/rmap.c
@@ -249,8 +249,7 @@ static void anon_vma_unlink(struct anon_
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)
@@ -274,8 +273,7 @@ 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);
}
_
Patches currently in -mm which might be from mel@xxxxxxxxx are
page-allocator-reduce-fragmentation-in-buddy-allocator-by-adding-buddies-that-are-merging-to-the-tail-of-the-free-lists.patch
mempolicy-remove-redundant-code.patch
mm-default-to-node-zonelist-ordering-when-nodes-have-only-lowmem.patch
mm-migration-take-a-reference-to-the-anon_vma-before-migrating.patch
mm-migration-do-not-try-to-migrate-unmapped-anonymous-pages.patch
mm-share-the-anon_vma-ref-counts-between-ksm-and-page-migration.patch
mm-allow-config_migration-to-be-set-without-config_numa-or-memory-hot-remove.patch
mm-export-unusable-free-space-index-via-proc-unusable_index.patch
mm-export-fragmentation-index-via-proc-extfrag_index.patch
mm-move-definition-for-lru-isolation-modes-to-a-header.patch
mm-compaction-memory-compaction-core.patch
mm-compaction-add-proc-trigger-for-memory-compaction.patch
mm-compaction-add-sys-trigger-for-per-node-memory-compaction.patch
mm-compaction-direct-compact-when-a-high-order-allocation-fails.patch
mm-compaction-add-a-tunable-that-decides-when-memory-should-be-compacted-and-when-it-should-be-reclaimed.patch
mm-compaction-do-not-compact-within-a-preferred-zone-after-a-compaction-failure.patch
mm-migration-allow-the-migration-of-pageswapcache-pages.patch
delay-accounting-re-implement-c-for-getdelaysc-to-report-information-on-a-target-command.patch
delay-accounting-re-implement-c-for-getdelaysc-to-report-information-on-a-target-command-checkpatch-fixes.patch
add-debugging-aid-for-memory-initialisation-problems.patch
--
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