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4fb72bf2e9
linux/fs/btrfs
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David Sterba 4fb72bf2e9 btrfs: use smaller type for btrfs_path locks 
The values of btrfs_path::locks are 0 to 4, fit into a u8. Let's see:

* overall size of btrfs_path drops down from 136 to 112 (-24 bytes),
* better packing in a slab page +6 objects
* the whole structure now fits to 2 cachelines
* slight decrease in code size:

   text    data     bss     dec     hex filename
 938731   43670   23144 1005545   f57e9 fs/btrfs/btrfs.ko.before
 938203   43670   23144 1005017   f55d9 fs/btrfs/btrfs.ko.after

(and the generated assembly does not change much)

The main purpose is to decrease the size of the structure without
affecting performance. The byte access is usually well behaving accross
arches, the locks are not accessed frequently and sometimes just
compared to zero.

Note for further size reduction attempts: the slots could be made u16
but this might generate worse code on some arches (non-byte and non-int
access). Also the range of operations on slots is wider compared to
locks and the potential performance drop should be evaluated first.

Signed-off-by: David Sterba <dsterba@suse.com>
2016-01-07 15:01:17 +01:00
..
tests btrfs: constify remaining structs with function pointers 2016-01-07 15:01:14 +01:00
acl.c
async-thread.c btrfs: async_thread: Fix workqueue 'max_active' value when initializing 2015-08-31 11:46:40 -07:00
async-thread.h btrfs: async_thread: Fix workqueue 'max_active' value when initializing 2015-08-31 11:46:40 -07:00
backref.c Btrfs: use btrfs_get_fs_root in resolve_indirect_ref 2015-11-25 05:22:08 -08:00
backref.h btrfs: cleanup, remove inode_item_info helper 2015-01-14 19:23:47 +01:00
btrfs_inode.h btrfs: put delayed item hook into inode 2016-01-07 14:26:58 +01:00
check-integrity.c Merge branch 'cleanups/for-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux into for-linus-4.4 2015-10-21 18:21:40 -07:00
check-integrity.h
compression.c Merge branch 'akpm' (patches from Andrew) 2015-11-07 14:32:45 -08:00
compression.h btrfs: constify structs with op functions or static definitions 2015-02-16 18:48:44 +01:00
ctree.c btrfs: cleanup, use enum values for btrfs_path reada 2016-01-07 15:01:15 +01:00
ctree.h btrfs: use smaller type for btrfs_path locks 2016-01-07 15:01:17 +01:00
delayed-inode.c btrfs: comment the rest of implicit barriers before waitqueue_active 2015-10-10 18:42:00 +02:00
delayed-inode.h
delayed-ref.c btrfs: better packing of btrfs_delayed_extent_op 2016-01-07 14:26:58 +01:00
delayed-ref.h btrfs: better packing of btrfs_delayed_extent_op 2016-01-07 14:26:58 +01:00
dev-replace.c Merge branch 'fix/waitqueue-barriers' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux into for-linus-4.4 2015-10-12 16:24:40 -07:00
dev-replace.h
dir-item.c
disk-io.c Btrfs: add missing brelse when superblock checksum fails 2016-01-07 14:26:53 +01:00
disk-io.h Btrfs: add btrfs_read_dev_one_super() to read one specific SB 2015-10-01 17:29:38 +02:00
export.c BTRFS: support NFSv2 export 2015-10-06 06:55:23 -07:00
export.h
extent_io.c Merge branch 'akpm' (patches from Andrew) 2015-11-07 14:32:45 -08:00
extent_io.h btrfs: qgroup: Introduce btrfs_qgroup_reserve_data function 2015-10-21 18:37:45 -07:00
extent_map.c
extent_map.h
extent-tree.c btrfs: cleanup, use enum values for btrfs_path reada 2016-01-07 15:01:15 +01:00
file-item.c btrfs: cleanup, use enum values for btrfs_path reada 2016-01-07 15:01:15 +01:00
file.c Merge branch 'for-linus-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mason/linux-btrfs 2015-12-18 15:35:08 -08:00
free-space-cache.c btrfs: constify remaining structs with function pointers 2016-01-07 15:01:14 +01:00
free-space-cache.h btrfs: constify remaining structs with function pointers 2016-01-07 15:01:14 +01:00
hash.c
hash.h
inode-item.c Btrfs: consolidate btrfs_error() to btrfs_std_error() 2015-09-29 16:30:00 +02:00
inode-map.c btrfs: cleanup, use enum values for btrfs_path reada 2016-01-07 15:01:15 +01:00
inode-map.h
inode.c btrfs: cleanup, use enum values for btrfs_path reada 2016-01-07 15:01:15 +01:00
ioctl.c btrfs: cleanup, use enum values for btrfs_path reada 2016-01-07 15:01:15 +01:00
Kconfig rcu: Make SRCU optional by using CONFIG_SRCU 2015-01-06 11:04:29 -08:00
locking.c btrfs: comment the rest of implicit barriers before waitqueue_active 2015-10-10 18:42:00 +02:00
locking.h
lzo.c btrfs: constify structs with op functions or static definitions 2015-02-16 18:48:44 +01:00
Makefile
math.h btrfs: cleanup 64bit/32bit divs, compile time constants 2015-03-03 17:23:57 +01:00
ordered-data.c Btrfs: change how we wait for pending ordered extents 2015-10-21 18:51:40 -07:00
ordered-data.h Btrfs: change how we wait for pending ordered extents 2015-10-21 18:51:40 -07:00
orphan.c
print-tree.c
print-tree.h
props.c btrfs: cleanup iterating over prop_handlers array 2015-10-21 18:28:48 +02:00
props.h
qgroup.c btrfs: qgroup: account shared subtree during snapshot delete 2015-11-25 05:27:33 -08:00
qgroup.h btrfs: qgroup: Check if qgroup reserved space leaked 2015-10-21 18:41:10 -07:00
raid56.c btrfs: comment waitqueue_active implied by locks 2015-10-10 18:35:10 +02:00
raid56.h Btrfs: add RAID 5/6 BTRFS_RBIO_REBUILD_MISSING operation 2015-08-09 07:34:26 -07:00
rcu-string.h
reada.c btrfs: reada: Fix returned errno code 2015-10-21 18:29:50 +02:00
relocation.c btrfs: cleanup, use enum values for btrfs_path reada 2016-01-07 15:01:15 +01:00
root-tree.c Merge branch 'cleanups/for-4.4' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux into for-linus-4.4 2015-10-21 18:21:40 -07:00
scrub.c btrfs: cleanup, use enum values for btrfs_path reada 2016-01-07 15:01:15 +01:00
send.c btrfs: fix resending received snapshot with parent 2015-10-13 20:04:10 +01:00
send.h
struct-funcs.c
super.c btrfs: constify static arrays 2016-01-07 15:01:15 +01:00
sysfs.c Btrfs: rename super_kobj to fsid_kobj 2015-09-29 16:29:59 +02:00
sysfs.h Btrfs: rename btrfs_kobj_rm_device to btrfs_sysfs_rm_device_link 2015-09-29 16:29:59 +02:00
transaction.c Btrfs: fix unprotected list move from unused_bgs to deleted_bgs list 2015-12-10 11:22:38 +00:00
transaction.h Btrfs: fix unprotected list move from unused_bgs to deleted_bgs list 2015-12-10 11:22:38 +00:00
tree-defrag.c Btrfs: cleanup: remove unnecessary check before btrfs_free_path is called 2015-08-31 11:46:41 -07:00
tree-log.c Btrfs: fix regression running delayed references when using qgroups 2015-10-25 19:53:26 +00:00
tree-log.h Btrfs: fix metadata inconsistencies after directory fsync 2015-03-26 17:56:23 -07:00
ulist.c btrfs: ulist: Add ulist_del() function. 2015-06-10 09:26:17 -07:00
ulist.h btrfs: ulist: Add ulist_del() function. 2015-06-10 09:26:17 -07:00
uuid-tree.c
volumes.c btrfs: cleanup, use enum values for btrfs_path reada 2016-01-07 15:01:15 +01:00
volumes.h btrfs: fix clashing number of the enhanced balance usage filter 2015-11-25 05:19:50 -08:00
xattr.c btrfs: cleanup, use enum values for btrfs_path reada 2016-01-07 15:01:15 +01:00
xattr.h
zlib.c btrfs: constify structs with op functions or static definitions 2015-02-16 18:48:44 +01:00