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Commit 6cdbb0ef authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

fs: optimize out 16 bytes worth of padding in struct inode 



Rearrange the fields in struct inode so that on an x86_64 system,
fields that require 8-byte alignment don't end up causing 4-byte holes
in the structure.  It reduces the size of struct inode from 568 bytes
to 552 bytes.

Also move the fields protected by i_lock (i_blocks, i_bytes, and
i_size) into the same cache line as i_lock.

Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 80e675f9

include/linux/fs.h

+5 −5
Original line number Diff line number Diff line
@@ -771,12 +771,13 @@ struct inode { 
	unsigned long		i_ino;

	unsigned int		i_nlink;

	dev_t			i_rdev;

	loff_t			i_size;

	struct timespec		i_atime;

	struct timespec		i_mtime;

	struct timespec		i_ctime;

	unsigned int		i_blkbits;

	spinlock_t		i_lock;	/* i_blocks, i_bytes, maybe i_size */

	unsigned short          i_bytes;

	blkcnt_t		i_blocks;

	loff_t			i_size;



#ifdef __NEED_I_SIZE_ORDERED

	seqcount_t		i_size_seqcount;
@@ -784,7 +785,6 @@ struct inode { 


	/* Misc */

	unsigned long		i_state;

	spinlock_t		i_lock;	/* i_blocks, i_bytes, maybe i_size */

	struct mutex		i_mutex;



	unsigned long		dirtied_when;	/* jiffies of first dirtying */
@@ -798,9 +798,10 @@ struct inode { 
		struct rcu_head		i_rcu;

	};

	atomic_t		i_count;

	unsigned int		i_blkbits;

	u64			i_version;

	unsigned short          i_bytes;

	atomic_t		i_dio_count;

	atomic_t		i_writecount;

	const struct file_operations	*i_fop;	/* former ->i_op->default_file_ops */

	struct file_lock	*i_flock;

	struct address_space	i_data;
@@ -824,7 +825,6 @@ struct inode { 
#ifdef CONFIG_IMA

	atomic_t		i_readcount; /* struct files open RO */

#endif

	atomic_t		i_writecount;

	void			*i_private; /* fs or device private pointer */

};