From 6cdbb0effc2f511ced23e46f2117e4b31d3d4a50 Mon Sep 17 00:00:00 2001
From: Theodore Ts'o <tytso@mit.edu>
Date: Sat, 29 Oct 2011 08:24:18 -0400
Subject: [PATCH] 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>
---
include/linux/fs.h | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 178cdb4f1d4af..fbda9a662f579 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -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 */
};
--
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