linux-kernel - fs: remove 8 bytes of padding from block

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Date:	Mon, 14 Feb 2011 16:39:26 +0000
From:	Richard Kennedy <richard@....demon.co.uk>
To:	Alexander Viro <viro@...iv.linux.org.uk>
Cc:	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: fs: remove 8 bytes of padding from block_device on 64bit builds

Re-ordering struct block_inode to remove 8 bytes of padding on 64 bit
builds, which also shrinks bdev_inode by 8 bytes (776 -> 768) allowing
it to fit into one fewer cache lines.
    
Signed-off-by: Richard Kennedy <richard@....demon.co.uk>
------
patch against v2.6.38-rc4
compiled & tested on x86_64

regards
Richard



diff --git a/include/linux/fs.h b/include/linux/fs.h
index bd32159..7c65780 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -658,9 +658,9 @@ struct address_space {
 
 struct block_device {
 	dev_t			bd_dev;  /* not a kdev_t - it's a search key */
+	int			bd_openers;
 	struct inode *		bd_inode;	/* will die */
 	struct super_block *	bd_super;
-	int			bd_openers;
 	struct mutex		bd_mutex;	/* open/close mutex */
 	struct list_head	bd_inodes;
 	void *			bd_claiming;


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