Commit 18a82eb9 authored by Pekka J Enberg's avatar Pekka J Enberg Committed by Linus Torvalds
Browse files

ext2: allocate ->s_blockgroup_lock separately 



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.

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 avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 22d613d1

fs/ext2/super.c

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

include/linux/ext2_fs_sb.h

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

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