By reordering the elements in the xfs_inode structure, we can
reduce the padding needed on an x86_64 system by 8 bytes.
Furthermore, it also enables denser packing of xfs_inode
structures within slab pages. In the Debian 6.8.12-amd64,
before applying the patch, the size of xfs_inode is 1000 bytes,
allowing 32 xfs_inode structures to be allocated from an
order-3 slab. After applying the patch, the size of
xfs_inode is reduced to 992 bytes, allowing 33 xfs_inode
structures to be allocated from an order-3 slab.
This improvement is also observed in the mainline kernel
with the same config.
Signed-off-by: Junchao Sun <sunjunchao2870@xxxxxxxxx>
---
fs/xfs/xfs_inode.h | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 292b90b5f2ac..fedac2792a38 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -37,12 +37,6 @@ typedef struct xfs_inode {
struct xfs_ifork i_df; /* data fork */
struct xfs_ifork i_af; /* attribute fork */
- /* Transaction and locking information. */
- struct xfs_inode_log_item *i_itemp; /* logging information */
- struct rw_semaphore i_lock; /* inode lock */
- atomic_t i_pincount; /* inode pin count */
- struct llist_node i_gclist; /* deferred inactivation list */
-
/*
* Bitsets of inode metadata that have been checked and/or are sick.
* Callers must hold i_flags_lock before accessing this field.
@@ -88,6 +82,12 @@ typedef struct xfs_inode {
/* VFS inode */
struct inode i_vnode; /* embedded VFS inode */
+ /* Transaction and locking information. */
+ struct xfs_inode_log_item *i_itemp; /* logging information */
+ struct rw_semaphore i_lock; /* inode lock */
+ struct llist_node i_gclist; /* deferred inactivation list */
+ atomic_t i_pincount; /* inode pin count */
+
/* pending io completions */
spinlock_t i_ioend_lock;
struct work_struct i_ioend_work;
--
2.39.2
