From: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
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 <adilger@xxxxxxx>
Signed-off-by: Pekka Enberg <penberg@xxxxxxxxxxxxxx>
---
fs/ext2/super.c | 10 +++++++++-
include/linux/ext2_fs_sb.h | 4 ++--
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/fs/ext2/super.c b/fs/ext2/super.c
index 647cd88..da8bdea 100644
--- a/fs/ext2/super.c
+++ b/fs/ext2/super.c
@@ -132,6 +132,7 @@ static void ext2_put_super (struct super_block * sb)
percpu_counter_destroy(&sbi->s_dirs_counter);
brelse (sbi->s_sbh);
sb->s_fs_info = NULL;
+ kfree(sbi->s_blockgroup_lock);
kfree(sbi);
return;
@@ -756,6 +757,13 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
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;
@@ -983,7 +991,7 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent)
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 --git a/include/linux/ext2_fs_sb.h b/include/linux/ext2_fs_sb.h
index dc541f3..1cdb663 100644
--- a/include/linux/ext2_fs_sb.h
+++ b/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 */
--
1.5.4.3
--
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