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Commit 705895b6 authored by Pekka Enberg's avatar Pekka Enberg Committed by Theodore Ts'o
Browse files

ext4: allocate ->s_blockgroup_lock separately 



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: default avatarAndreas Dilger <adilger@sun.com>
Signed-off-by: default avatarPekka Enberg <penberg@cs.helsinki.fi>
Cc: <linux-ext4@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 3d0518f4

fs/ext4/ext4_sb.h

+2 −2
Original line number Diff line number Diff line
@@ -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 */

fs/ext4/super.c

+9 −1
Original line number Diff line number Diff line
@@ -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);