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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: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2011-10-29 08:24:18 -04:00
parent 80e675f906
commit 6cdbb0effc
1 changed files with 5 additions and 5 deletions
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10
include/linux/fs.h
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@ -771,12 +771,13 @@ struct inode {
unsigned long i_ino; unsigned long i_ino;
unsigned int i_nlink; unsigned int i_nlink;
dev_t i_rdev; dev_t i_rdev;
loff_t i_size;
struct timespec i_atime; struct timespec i_atime;
struct timespec i_mtime; struct timespec i_mtime;
struct timespec i_ctime; 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; blkcnt_t i_blocks;
loff_t i_size;
#ifdef __NEED_I_SIZE_ORDERED #ifdef __NEED_I_SIZE_ORDERED
seqcount_t i_size_seqcount; seqcount_t i_size_seqcount;
@ -784,7 +785,6 @@ struct inode {
/* Misc */ /* Misc */
unsigned long i_state; unsigned long i_state;
spinlock_t i_lock; /* i_blocks, i_bytes, maybe i_size */
struct mutex i_mutex; struct mutex i_mutex;
unsigned long dirtied_when; /* jiffies of first dirtying */ unsigned long dirtied_when; /* jiffies of first dirtying */
@ -798,9 +798,10 @@ struct inode {
struct rcu_head i_rcu; struct rcu_head i_rcu;
}; };
atomic_t i_count; atomic_t i_count;
unsigned int i_blkbits;
u64 i_version; u64 i_version;
unsigned short i_bytes;
atomic_t i_dio_count; atomic_t i_dio_count;
atomic_t i_writecount;
const struct file_operations *i_fop; /* former ->i_op->default_file_ops */ const struct file_operations *i_fop; /* former ->i_op->default_file_ops */
struct file_lock *i_flock; struct file_lock *i_flock;
struct address_space i_data; struct address_space i_data;
@ -824,7 +825,6 @@ struct inode {
#ifdef CONFIG_IMA #ifdef CONFIG_IMA
atomic_t i_readcount; /* struct files open RO */ atomic_t i_readcount; /* struct files open RO */
#endif #endif
atomic_t i_writecount;
void *i_private; /* fs or device private pointer */ void *i_private; /* fs or device private pointer */
}; };