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ext4: allocate ->s_blockgroup_lock separately

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As spotted by kmemtrace, struct ext4_sb_info is 17664 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 ext4_sb_info
enough to fit a 2 KB slab cache so now we allocate 16 KB + 2 KB instead of
32 KB saving 14 KB of memory.

Acked-by: Andreas Dilger <adilger@sun.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Pekka Enberg 2009-02-15 18:07:52 -05:00 committed by Theodore Ts'o
parent 3d0518f475
commit 705895b611
2 changed files with 11 additions and 3 deletions
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4
fs/ext4/ext4_sb.h
View file

@ -62,7 +62,7 @@ struct ext4_sb_info {
struct percpu_counter s_freeinodes_counter;
struct percpu_counter s_dirs_counter;
struct percpu_counter s_dirtyblocks_counter;
struct blockgroup_lock s_blockgroup_lock;
struct blockgroup_lock *s_blockgroup_lock;
struct proc_dir_entry *s_proc;
/* Journaling */
@ -149,7 +149,7 @@ struct ext4_sb_info {
static inline spinlock_t *
sb_bgl_lock(struct ext4_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 /* _EXT4_SB */

10
fs/ext4/super.c
View file

@ -615,6 +615,7 @@ static void ext4_put_super(struct super_block *sb)
ext4_blkdev_remove(sbi);
}
sb->s_fs_info = NULL;
kfree(sbi->s_blockgroup_lock);
kfree(sbi);
return;
}
@ -2021,6 +2022,13 @@ static int ext4_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_mount_opt = 0;
sbi->s_resuid = EXT4_DEF_RESUID;
@ -2332,7 +2340,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
&sbi->s_inode_readahead_blks);
#endif
bgl_lock_init(&sbi->s_blockgroup_lock);
bgl_lock_init(sbi->s_blockgroup_lock);
for (i = 0; i < db_count; i++) {
block = descriptor_loc(sb, logical_sb_block, i);