2008-11-19 05:29:06

by Andrew Morton

[permalink] [raw]
Subject: + ext2-allocate-s_blockgroup_lock-separately.patch added to -mm tree

The patch titled
ext2: allocate ->s_blockgroup_lock separately
has been added to the -mm tree. Its filename is

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The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/

Subject: ext2: allocate ->s_blockgroup_lock separately
From: Pekka J Enberg <[email protected]>

As spotted by kmemtrace, struct ext2_sb_info is 17024 bytes on 64-bit
which makes it a very bad fit for SLAB allocators. The culprit of the
wasted memory is ->s_blockgroup_lock which can be as big as 16 KB when
NR_CPUS >= 32.

To fix that, allocate ->s_blockgroup_lock, which fits nicely in a order 2
page in the worst case, separately. This shinks down struct ext2_sb_info
enough to fit a 1 KB slab cache so now we allocate 16 KB + 1 KB instead of
32 KB saving 15 KB of memory.

Cc: Andreas Dilger <[email protected]>
Signed-off-by: Pekka Enberg <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

fs/ext2/super.c | 10 +++++++++-
include/linux/ext2_fs_sb.h | 4 ++--
2 files changed, 11 insertions(+), 3 deletions(-)

diff -puN fs/ext2/super.c~ext2-allocate-s_blockgroup_lock-separately fs/ext2/super.c
--- a/fs/ext2/super.c~ext2-allocate-s_blockgroup_lock-separately
+++ a/fs/ext2/super.c
@@ -132,6 +132,7 @@ static void ext2_put_super (struct super
brelse (sbi->s_sbh);
sb->s_fs_info = NULL;
+ kfree(sbi->s_blockgroup_lock);

@@ -765,6 +766,13 @@ static int ext2_fill_super(struct super_
sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
if (!sbi)
return -ENOMEM;
+ sbi->s_blockgroup_lock =
+ kzalloc(sizeof(struct blockgroup_lock), GFP_KERNEL);
+ if (!sbi->s_blockgroup_lock) {
+ kfree(sbi);
+ return -ENOMEM;
+ }
sb->s_fs_info = sbi;
sbi->s_sb_block = sb_block;

@@ -992,7 +1000,7 @@ static int ext2_fill_super(struct super_
printk ("EXT2-fs: not enough memory\n");
goto failed_mount;
- bgl_lock_init(&sbi->s_blockgroup_lock);
+ bgl_lock_init(sbi->s_blockgroup_lock);
sbi->s_debts = kcalloc(sbi->s_groups_count, sizeof(*sbi->s_debts), GFP_KERNEL);
if (!sbi->s_debts) {
printk ("EXT2-fs: not enough memory\n");
diff -puN include/linux/ext2_fs_sb.h~ext2-allocate-s_blockgroup_lock-separately include/linux/ext2_fs_sb.h
--- a/include/linux/ext2_fs_sb.h~ext2-allocate-s_blockgroup_lock-separately
+++ a/include/linux/ext2_fs_sb.h
@@ -101,7 +101,7 @@ struct ext2_sb_info {
struct percpu_counter s_freeblocks_counter;
struct percpu_counter s_freeinodes_counter;
struct percpu_counter s_dirs_counter;
- struct blockgroup_lock s_blockgroup_lock;
+ struct blockgroup_lock *s_blockgroup_lock;
/* root of the per fs reservation window tree */
spinlock_t s_rsv_window_lock;
struct rb_root s_rsv_window_root;
@@ -111,7 +111,7 @@ struct ext2_sb_info {
static inline spinlock_t *
sb_bgl_lock(struct ext2_sb_info *sbi, unsigned int block_group)
- return bgl_lock_ptr(&sbi->s_blockgroup_lock, block_group);
+ return bgl_lock_ptr(sbi->s_blockgroup_lock, block_group);

#endif /* _LINUX_EXT2_FS_SB */

Patches currently in -mm which might be from [email protected] are