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From: Cesar Eduardo Barros <cesarb@cesarb.net>
To: linux-mm@kvack.org
Cc: Minchan Kim <minchan.kim@gmail.com>,
	Jan Beulich <JBeulich@novell.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andreas Dilger <adilger@sun.com>,
	Dan Magenheimer <dan.magenheimer@oracle.com>,
	Jeremy Fitzhardinge <jeremy@goop.org>,
	linux-kernel@vger.kernel.org,
	Cesar Eduardo Barros <cesarb@cesarb.net>
Subject: [PATCH] cleancache: use __read_mostly for cleancache_enabled
Date: Sun, 29 May 2011 17:38:18 -0300	[thread overview]
Message-ID: <1306701498-10846-1-git-send-email-cesarb@cesarb.net> (raw)

The global variable cleancache_enabled is read often but written to
rarely. Use __read_mostly to prevent it being on the same cacheline as
another variable which is written to often, which would cause cacheline
bouncing.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 include/linux/cleancache.h |    2 +-
 mm/cleancache.c            |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/cleancache.h b/include/linux/cleancache.h
index 04ffb2e..83fffe8 100644
--- a/include/linux/cleancache.h
+++ b/include/linux/cleancache.h
@@ -42,7 +42,7 @@ extern void __cleancache_put_page(struct page *);
 extern void __cleancache_flush_page(struct address_space *, struct page *);
 extern void __cleancache_flush_inode(struct address_space *);
 extern void __cleancache_flush_fs(struct super_block *);
-extern int cleancache_enabled;
+extern int cleancache_enabled __read_mostly;
 
 #ifdef CONFIG_CLEANCACHE
 static inline bool cleancache_fs_enabled(struct page *page)
diff --git a/mm/cleancache.c b/mm/cleancache.c
index bcaae4c..a3d7a22 100644
--- a/mm/cleancache.c
+++ b/mm/cleancache.c
@@ -24,7 +24,7 @@
  * disabled), so is preferred to the slower alternative: a function
  * call that checks a non-global.
  */
-int cleancache_enabled;
+int cleancache_enabled __read_mostly;
 EXPORT_SYMBOL(cleancache_enabled);
 
 /*
-- 
1.7.4.4


WARNING: multiple messages have this Message-ID (diff)
From: Cesar Eduardo Barros <cesarb@cesarb.net>
To: linux-mm@kvack.org
Cc: Minchan Kim <minchan.kim@gmail.com>,
	Jan Beulich <JBeulich@novell.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Andreas Dilger <adilger@sun.com>,
	Dan Magenheimer <dan.magenheimer@oracle.com>,
	Jeremy Fitzhardinge <jeremy@goop.org>,
	linux-kernel@vger.kernel.org,
	Cesar Eduardo Barros <cesarb@cesarb.net>
Subject: [PATCH] cleancache: use __read_mostly for cleancache_enabled
Date: Sun, 29 May 2011 17:38:18 -0300	[thread overview]
Message-ID: <1306701498-10846-1-git-send-email-cesarb@cesarb.net> (raw)

The global variable cleancache_enabled is read often but written to
rarely. Use __read_mostly to prevent it being on the same cacheline as
another variable which is written to often, which would cause cacheline
bouncing.

Signed-off-by: Cesar Eduardo Barros <cesarb@cesarb.net>
---
 include/linux/cleancache.h |    2 +-
 mm/cleancache.c            |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/cleancache.h b/include/linux/cleancache.h
index 04ffb2e..83fffe8 100644
--- a/include/linux/cleancache.h
+++ b/include/linux/cleancache.h
@@ -42,7 +42,7 @@ extern void __cleancache_put_page(struct page *);
 extern void __cleancache_flush_page(struct address_space *, struct page *);
 extern void __cleancache_flush_inode(struct address_space *);
 extern void __cleancache_flush_fs(struct super_block *);
-extern int cleancache_enabled;
+extern int cleancache_enabled __read_mostly;
 
 #ifdef CONFIG_CLEANCACHE
 static inline bool cleancache_fs_enabled(struct page *page)
diff --git a/mm/cleancache.c b/mm/cleancache.c
index bcaae4c..a3d7a22 100644
--- a/mm/cleancache.c
+++ b/mm/cleancache.c
@@ -24,7 +24,7 @@
  * disabled), so is preferred to the slower alternative: a function
  * call that checks a non-global.
  */
-int cleancache_enabled;
+int cleancache_enabled __read_mostly;
 EXPORT_SYMBOL(cleancache_enabled);
 
 /*
-- 
1.7.4.4

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             reply	other threads:[~2011-05-29 20:46 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-05-29 20:38 Cesar Eduardo Barros [this message]
2011-05-29 20:38 ` [PATCH] cleancache: use __read_mostly for cleancache_enabled Cesar Eduardo Barros
2011-05-30  0:35 ` Minchan Kim
2011-05-30  0:35   ` Minchan Kim

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