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Date:	Tue, 18 Nov 2008 21:28:59 -0800
From:	akpm@...ux-foundation.org
To:	mm-commits@...r.kernel.org
Cc:	penberg@...helsinki.fi, adilger@....com, linux-ext4@...r.kernel.org
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
     ext2-allocate-s_blockgroup_lock-separately.patch

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   a) Consider who else should be cc'ed
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*** Remember to use Documentation/SubmitChecklist when testing your code ***

See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this

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 <penberg@...helsinki.fi>

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@....com>
Signed-off-by: Pekka Enberg <penberg@...helsinki.fi>
Cc: <linux-ext4@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 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
 	percpu_counter_destroy(&sbi->s_dirs_counter);
 	brelse (sbi->s_sbh);
 	sb->s_fs_info = NULL;
+	kfree(sbi->s_blockgroup_lock);
 	kfree(sbi);
 
 	return;
@@ -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 penberg@...helsinki.fi are

fs-introduce-bgl_lock_ptr.patch
repeatable-slab-corruption-with-ltp-msgctl08.patch
linux-next.patch
ext4-allocate-s_blockgroup_lock-separately.patch
ext2-allocate-s_blockgroup_lock-separately.patch
ext3-allocate-s_blockgroup_lock-separately.patch
slab-leaks3-default-y.patch

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