Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752165Ab0BRSC6 (ORCPT ); Thu, 18 Feb 2010 13:02:58 -0500 Received: from gir.skynet.ie ([193.1.99.77]:44675 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751002Ab0BRSCp (ORCPT ); Thu, 18 Feb 2010 13:02:45 -0500 From: Mel Gorman To: Andrea Arcangeli Cc: Christoph Lameter , Adam Litke , Avi Kivity , David Rientjes , KOSAKI Motohiro , Rik van Riel , Mel Gorman , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH 03/12] mm: Share the anon_vma ref counts between KSM and page migration Date: Thu, 18 Feb 2010 18:02:33 +0000 Message-Id: <1266516162-14154-4-git-send-email-mel@csn.ul.ie> X-Mailer: git-send-email 1.6.5 In-Reply-To: <1266516162-14154-1-git-send-email-mel@csn.ul.ie> References: <1266516162-14154-1-git-send-email-mel@csn.ul.ie> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5133 Lines: 168 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 --- 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 --git a/include/linux/rmap.h b/include/linux/rmap.h index 6b5a1a9..55c0e9e 100644 --- a/include/linux/rmap.h +++ b/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 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 refcount; #endif /* * NOTE: the LSB of the head.next is set by @@ -44,46 +50,26 @@ struct anon_vma { }; #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_refcount_init(struct anon_vma *anon_vma) { - atomic_set(&anon_vma->ksm_refcount, 0); + atomic_set(&anon_vma->refcount, 0); } -static inline int ksm_refcount(struct anon_vma *anon_vma) +static inline int anonvma_refcount(struct anon_vma *anon_vma) { - return atomic_read(&anon_vma->ksm_refcount); + return atomic_read(&anon_vma->refcount); } #else -static inline void ksm_refcount_init(struct anon_vma *anon_vma) +static inline void anonvma_refcount_init(struct anon_vma *anon_vma) { } -static inline int ksm_refcount(struct anon_vma *anon_vma) +static inline int anonvma_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 --git a/mm/ksm.c b/mm/ksm.c index 56a0da1..7decf73 100644 --- a/mm/ksm.c +++ b/mm/ksm.c @@ -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->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->refcount, &anon_vma->lock)) { int empty = list_empty(&anon_vma->head); spin_unlock(&anon_vma->lock); if (empty) diff --git a/mm/migrate.c b/mm/migrate.c index 1ce6a2f..00777b0 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -619,7 +619,7 @@ 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->refcount); } /* @@ -661,7 +661,7 @@ 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->refcount, &anon_vma->lock)) { int empty = list_empty(&anon_vma->head); spin_unlock(&anon_vma->lock); if (empty) diff --git a/mm/rmap.c b/mm/rmap.c index 11ba74a..96b5905 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -172,8 +172,7 @@ void anon_vma_unlink(struct vm_area_struct *vma) list_del(&vma->anon_vma_node); /* 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_refcount(anon_vma); spin_unlock(&anon_vma->lock); if (empty) @@ -185,8 +184,7 @@ 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_refcount_init(anon_vma); INIT_LIST_HEAD(&anon_vma->head); } -- 1.6.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/