From: akpm@linux-foundation.org Subject: [patch 010/123] ext3: allocate ->s_blockgroup_lock separately Date: Wed, 07 Jan 2009 18:07:25 -0800 Message-ID: <200901080207.n0827P5J011687@imap1.linux-foundation.org> Cc: akpm@linux-foundation.org, penberg@cs.helsinki.fi, adilger@sun.com, linux-ext4@vger.kernel.org To: torvalds@linux-foundation.org Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:49418 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751707AbZAHCPH (ORCPT ); Wed, 7 Jan 2009 21:15:07 -0500 Sender: linux-ext4-owner@vger.kernel.org List-ID: From: Pekka Enberg As spotted by kmemtrace, struct ext3_sb_info is 17152 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 ext3_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: Andreas Dilger Signed-off-by: Pekka Enberg Cc: Signed-off-by: Andrew Morton --- fs/ext3/super.c | 10 +++++++++- include/linux/ext3_fs_sb.h | 4 ++-- 2 files changed, 11 insertions(+), 3 deletions(-) diff -puN fs/ext3/super.c~ext3-allocate-s_blockgroup_lock-separately fs/ext3/super.c --- a/fs/ext3/super.c~ext3-allocate-s_blockgroup_lock-separately +++ a/fs/ext3/super.c @@ -439,6 +439,7 @@ static void ext3_put_super (struct super ext3_blkdev_remove(sbi); } sb->s_fs_info = NULL; + kfree(sbi->s_blockgroup_lock); kfree(sbi); return; } @@ -1546,6 +1547,13 @@ static int ext3_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_mount_opt = 0; sbi->s_resuid = EXT3_DEF_RESUID; @@ -1786,7 +1794,7 @@ static int ext3_fill_super (struct super goto failed_mount; } - 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, logic_sb_block, i); diff -puN include/linux/ext3_fs_sb.h~ext3-allocate-s_blockgroup_lock-separately include/linux/ext3_fs_sb.h --- a/include/linux/ext3_fs_sb.h~ext3-allocate-s_blockgroup_lock-separately +++ a/include/linux/ext3_fs_sb.h @@ -60,7 +60,7 @@ struct ext3_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; @@ -86,7 +86,7 @@ struct ext3_sb_info { static inline spinlock_t * sb_bgl_lock(struct ext3_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_EXT3_FS_SB */ _