From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Andrea Arcangeli <aarcange@redhat.com>,
Avi Kivity <avi@redhat.com>, Thomas Gleixner <tglx@linutronix.de>,
Rik van Riel <riel@redhat.com>, Ingo Molnar <mingo@elte.hu>,
akpm@linux-foundation.org,
Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
David Miller <davem@davemloft.net>,
Hugh Dickins <hugh.dickins@tiscali.co.uk>,
Mel Gorman <mel@csn.ul.ie>, Nick Piggin <npiggin@suse.de>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: [PATCH 10/28] mm: Make use of the anon_vma ref count
Date: Mon, 07 Jun 2010 13:07:04 +0200 [thread overview]
Message-ID: <20100607111407.309924253@chello.nl> (raw)
In-Reply-To: 20100607110654.606530953@chello.nl
[-- Attachment #1: mm-use-anon_vma-ref.patch --]
[-- Type: text/plain, Size: 6872 bytes --]
This patch changes the anon_vma refcount to be 0 when the object is
free. It does this by adding 1 ref to being in use in the anon_vma
structure (iow. the anon_vma->head list is not empty).
This allows a simpler release scheme without having to check both the
refcount and the list as well as avoids taking a ref for each entry
on the list.
We then convert page_lock_anon_vma() over to use refcounts. This is
done for each of convertion of anon_vma from spinlock to mutex.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
include/linux/rmap.h | 11 ++++-
mm/ksm.c | 4 --
mm/rmap.c | 94 ++++++++++++++++++++++-----------------------------
3 files changed, 52 insertions(+), 57 deletions(-)
Index: linux-2.6/include/linux/rmap.h
===================================================================
--- linux-2.6.orig/include/linux/rmap.h
+++ linux-2.6/include/linux/rmap.h
@@ -73,7 +73,13 @@ static inline void get_anon_vma(struct a
atomic_inc(&anon_vma->refcount);
}
-void put_anon_vma(struct anon_vma *);
+void __put_anon_vma(struct anon_vma *anon_vma);
+
+static inline void put_anon_vma(struct anon_vma *anon_vma)
+{
+ if (atomic_dec_and_test(&anon_vma->refcount))
+ __put_anon_vma(anon_vma);
+}
static inline struct anon_vma *page_anon_vma(struct page *page)
{
@@ -116,7 +122,6 @@ void unlink_anon_vmas(struct vm_area_str
int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);
void __anon_vma_link(struct vm_area_struct *);
-void anon_vma_free(struct anon_vma *);
static inline void anon_vma_merge(struct vm_area_struct *vma,
struct vm_area_struct *next)
@@ -125,6 +130,8 @@ static inline void anon_vma_merge(struct
unlink_anon_vmas(next);
}
+struct anon_vma *page_get_anon_vma(struct page *page);
+
/*
* rmap interfaces called when adding or removing pte of page
*/
Index: linux-2.6/mm/ksm.c
===================================================================
--- linux-2.6.orig/mm/ksm.c
+++ linux-2.6/mm/ksm.c
@@ -323,9 +323,7 @@ static void hold_anon_vma(struct rmap_it
static void ksm_put_anon_vma(struct rmap_item *rmap_item)
{
- struct anon_vma *anon_vma = rmap_item->anon_vma;
-
- put_anon_vma(anon_vma);
+ put_anon_vma(rmap_item->anon_vma);
}
/*
Index: linux-2.6/mm/rmap.c
===================================================================
--- linux-2.6.orig/mm/rmap.c
+++ linux-2.6/mm/rmap.c
@@ -66,11 +66,24 @@ static struct kmem_cache *anon_vma_chain
static inline struct anon_vma *anon_vma_alloc(void)
{
- return kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
+ struct anon_vma *anon_vma;
+
+ anon_vma = kmem_cache_alloc(anon_vma_cachep, GFP_KERNEL);
+ if (anon_vma) {
+ atomic_set(&anon_vma->refcount, 1);
+ /*
+ * This VMA had no anon_vma yet. This anon_vma is
+ * the root of any anon_vma tree that might form.
+ */
+ anon_vma->root = anon_vma;
+ }
+
+ return anon_vma;
}
-void anon_vma_free(struct anon_vma *anon_vma)
+static inline void anon_vma_free(struct anon_vma *anon_vma)
{
+ VM_BUG_ON(atomic_read(&anon_vma->refcount));
kmem_cache_free(anon_vma_cachep, anon_vma);
}
@@ -132,11 +145,6 @@ int anon_vma_prepare(struct vm_area_stru
if (unlikely(!anon_vma))
goto out_enomem_free_avc;
allocated = anon_vma;
- /*
- * This VMA had no anon_vma yet. This anon_vma is
- * the root of any anon_vma tree that might form.
- */
- anon_vma->root = anon_vma;
}
anon_vma_lock(anon_vma);
@@ -155,7 +163,7 @@ int anon_vma_prepare(struct vm_area_stru
anon_vma_unlock(anon_vma);
if (unlikely(allocated))
- anon_vma_free(allocated);
+ put_anon_vma(allocated);
if (unlikely(avc))
anon_vma_chain_free(avc);
}
@@ -248,7 +256,7 @@ int anon_vma_fork(struct vm_area_struct
return 0;
out_error_free_anon_vma:
- anon_vma_free(anon_vma);
+ put_anon_vma(anon_vma);
out_error:
unlink_anon_vmas(vma);
return -ENOMEM;
@@ -265,16 +273,12 @@ static void anon_vma_unlink(struct anon_
anon_vma_lock(anon_vma);
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) && !atomic_read(&anon_vma->refcount);
+ empty = list_empty(&anon_vma->head);
anon_vma_unlock(anon_vma);
- if (empty) {
- /* We no longer need the root anon_vma */
- put_anon_vma(anon_vma->root);
- anon_vma_free(anon_vma);
- }
+ if (empty)
+ put_anon_vma(anon_vma);
}
void unlink_anon_vmas(struct vm_area_struct *vma)
@@ -326,9 +330,9 @@ void __init anon_vma_init(void)
* that the anon_vma pointer from page->mapping is valid if there is a
* mapcount, we can dereference the anon_vma after observing those.
*/
-struct anon_vma *page_lock_anon_vma(struct page *page)
+struct anon_vma *page_get_anon_vma(struct page *page)
{
- struct anon_vma *anon_vma;
+ struct anon_vma *anon_vma = NULL;
unsigned long anon_mapping;
rcu_read_lock();
@@ -339,17 +343,28 @@ struct anon_vma *page_lock_anon_vma(stru
goto out;
anon_vma = (struct anon_vma *) (anon_mapping - PAGE_MAPPING_ANON);
- anon_vma_lock(anon_vma);
- return anon_vma;
+ if (!atomic_inc_not_zero(&anon_vma->refcount))
+ anon_vma = NULL;
out:
rcu_read_unlock();
- return NULL;
+
+ return anon_vma;
+}
+
+struct anon_vma *page_lock_anon_vma(struct page *page)
+{
+ struct anon_vma *anon_vma = page_get_anon_vma(page);
+
+ if (anon_vma)
+ anon_vma_lock(anon_vma);
+
+ return anon_vma;
}
void page_unlock_anon_vma(struct anon_vma *anon_vma)
{
anon_vma_unlock(anon_vma);
- rcu_read_unlock();
+ put_anon_vma(anon_vma);
}
/*
@@ -1405,36 +1420,11 @@ int try_to_munlock(struct page *page)
return try_to_unmap_file(page, TTU_MUNLOCK);
}
-/*
- * Drop an anon_vma refcount, freeing the anon_vma and anon_vma->root
- * if necessary. Be careful to do all the tests under the lock. Once
- * we know we are the last user, nobody else can get a reference and we
- * can do the freeing without the lock.
- */
-void put_anon_vma(struct anon_vma *anon_vma)
-{
- if (atomic_dec_and_lock(&anon_vma->refcount, &anon_vma->root->lock)) {
- struct anon_vma *root = anon_vma->root;
- int empty = list_empty(&anon_vma->head);
- int last_root_user = 0;
- int root_empty = 0;
-
- /*
- * The refcount on a non-root anon_vma got dropped. Drop
- * the refcount on the root and check if we need to free it.
- */
- if (empty && anon_vma != root) {
- last_root_user = atomic_dec_and_test(&root->refcount);
- root_empty = list_empty(&root->head);
- }
- anon_vma_unlock(anon_vma);
-
- if (empty) {
- anon_vma_free(anon_vma);
- if (root_empty && last_root_user)
- anon_vma_free(root);
- }
- }
+void __put_anon_vma(struct anon_vma *anon_vma)
+{
+ if (anon_vma->root != anon_vma)
+ put_anon_vma(anon_vma->root);
+ anon_vma_free(anon_vma);
}
#ifdef CONFIG_MIGRATION
next prev parent reply other threads:[~2010-06-07 11:26 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-07 11:06 [PATCH 00/28] mm: preemptibility -v3 Peter Zijlstra
2010-06-07 11:06 ` [PATCH 01/28] powerpc: Use call_rcu_sched() for pagetables Peter Zijlstra
2010-06-07 11:06 ` [PATCH 02/28] mm: Improve page_lock_anon_vma() comment Peter Zijlstra
2010-06-09 10:50 ` Mel Gorman
2010-06-07 11:06 ` [PATCH 03/28] rename anon_vma_lock to vma_lock_anon_vma Peter Zijlstra
2010-06-07 15:01 ` Peter Zijlstra
2010-06-09 10:59 ` Mel Gorman
2010-06-07 11:06 ` [PATCH 04/28] change direct call of spin_lock(anon_vma->lock) to inline function Peter Zijlstra
2010-06-07 11:06 ` [PATCH 05/28] track the root (oldest) anon_vma Peter Zijlstra
2010-06-07 11:07 ` [PATCH 06/28] always lock " Peter Zijlstra
2010-06-07 11:07 ` [PATCH 07/28] extend KSM refcounts to the anon_vma root Peter Zijlstra
2010-06-09 10:55 ` Mel Gorman
2010-06-07 11:07 ` [PATCH 08/28] mm: Rename drop_anon_vma to put_anon_vma Peter Zijlstra
2010-06-07 11:07 ` [PATCH 09/28] mm: Move anon_vma ref out from under CONFIG_KSM Peter Zijlstra
2010-06-09 11:05 ` Mel Gorman
2010-06-07 11:07 ` Peter Zijlstra [this message]
2010-06-09 13:22 ` [PATCH 10/28] mm: Make use of the anon_vma ref count Mel Gorman
2010-06-09 13:32 ` Peter Zijlstra
2010-06-07 11:07 ` [PATCH 11/28] mm: Preemptible mmu_gather Peter Zijlstra
2010-06-07 11:07 ` [PATCH 12/28] powerpc: " Peter Zijlstra
2010-06-07 11:07 ` [PATCH 13/28] sparc: " Peter Zijlstra
2010-06-07 11:07 ` [PATCH 14/28] s390: preemptible mmu_gather Peter Zijlstra
2010-06-07 11:07 ` [PATCH 15/28] arm: Preemptible mmu_gather Peter Zijlstra
2010-06-07 11:07 ` [PATCH 16/28] sh: " Peter Zijlstra
2010-06-07 11:38 ` Peter Zijlstra
2010-06-07 11:07 ` [PATCH 17/28] um: " Peter Zijlstra
2010-06-07 11:07 ` [PATCH 18/28] ia64: " Peter Zijlstra
2010-06-07 11:07 ` [PATCH 19/28] mm, powerpc: Move the RCU page-table freeing into generic code Peter Zijlstra
2010-06-07 11:07 ` [PATCH 20/28] sparc64: Kill page table quicklists Peter Zijlstra
2010-06-07 11:07 ` [PATCH 21/28] sparc64: Use RCU page table freeing Peter Zijlstra
2010-06-07 11:07 ` [PATCH 22/28] sparc64: Add support for _PAGE_SPECIAL Peter Zijlstra
2010-06-07 11:07 ` [PATCH 23/28] sparc64: Implement get_user_pages_fast() Peter Zijlstra
2010-06-07 11:07 ` [PATCH 24/28] lockdep, mutex: Provide mutex_lock_nest_lock Peter Zijlstra
2010-06-07 11:07 ` [PATCH 25/28] mutex: Provide mutex_is_contended Peter Zijlstra
2010-06-07 11:07 ` [PATCH 26/28] mm: Convert i_mmap_lock and anon_vma->lock to mutexes Peter Zijlstra
2010-06-07 11:07 ` [PATCH 27/28] mm: Extended batches for generic mmu_gather Peter Zijlstra
2010-06-07 11:07 ` [PATCH 28/28] mm: Optimize page_lock_anon_vma() fast-path Peter Zijlstra
2010-06-07 13:57 ` [PATCH 00/28] mm: preemptibility -v3 Sam Ravnborg
2010-06-07 15:02 ` Peter Zijlstra
2010-06-07 16:36 ` Andi Kleen
2010-06-07 16:39 ` Peter Zijlstra
2010-06-10 1:45 ` Zhang, Yanmin
2010-06-10 6:52 ` Peter Zijlstra
2010-06-10 6:59 ` Zhang, Yanmin
2010-06-21 10:21 ` Peter Zijlstra
2010-06-24 9:55 ` Peter Zijlstra
2010-06-29 7:40 ` Zhang, Yanmin
2010-06-29 7:48 ` Peter Zijlstra
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