From: Badari Pulavarty Subject: [PATCH] ext4 statfs speed up Date: Thu, 05 Jul 2007 11:11:38 -0700 Message-ID: <1183659098.19473.9.camel@dyn9047017100.beaverton.ibm.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Andreas Dilger , ext4 To: Andrew Morton Return-path: Received: from e31.co.us.ibm.com ([32.97.110.149]:60270 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759745AbXGESKG (ORCPT ); Thu, 5 Jul 2007 14:10:06 -0400 Received: from d03relay02.boulder.ibm.com (d03relay02.boulder.ibm.com [9.17.195.227]) by e31.co.us.ibm.com (8.13.8/8.13.8) with ESMTP id l65IA5qV019766 for ; Thu, 5 Jul 2007 14:10:05 -0400 Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by d03relay02.boulder.ibm.com (8.13.8/8.13.8/NCO v8.3) with ESMTP id l65IA1l1255536 for ; Thu, 5 Jul 2007 12:10:03 -0600 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.12.11.20060308/8.13.3) with ESMTP id l65IA05d013058 for ; Thu, 5 Jul 2007 12:10:01 -0600 Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org This is a patch that speeds up statfs. It is very simple - the "overhead" calculation, which takes a huge amount of time for large filesystems, never changes unless the size of the filesystem itself changes. That means we can store it in memory and only recalculate if the filesystem has been resized (almost never). It also fixes a minor problem that we never update the on-disk superblock free blocks/inodes counts until the filesystem is unmounted. While not fatal, we may as well update that on disk when we have the information, and it makes things like debugfs and dumpe2fs report a bit more accurate info. Signed-off-by: Badari Pulavarty Signed-off-by: Andreas Dilger fs/ext4/super.c | 25 +++++++++++++++---------- include/linux/ext4_fs_sb.h | 2 ++ 2 files changed, 17 insertions(+), 10 deletions(-) Index: linux-2.6.22-rc7/include/linux/ext4_fs_sb.h =================================================================== --- linux-2.6.22-rc7.orig/include/linux/ext4_fs_sb.h 2007-07-01 12:54:24.000000000 -0700 +++ linux-2.6.22-rc7/include/linux/ext4_fs_sb.h 2007-07-04 22:09:59.000000000 -0700 @@ -39,6 +39,8 @@ struct ext4_sb_info { unsigned long s_gdb_count; /* Number of group descriptor blocks */ unsigned long s_desc_per_block; /* Number of group descriptors per block */ unsigned long s_groups_count; /* Number of groups in the fs */ + unsigned long s_overhead_last; /* Last calculated overhead */ + unsigned long s_blocks_last; /* Last seen block count */ struct buffer_head * s_sbh; /* Buffer containing the super block */ struct ext4_super_block * s_es; /* Pointer to the super block in the buffer */ struct buffer_head ** s_group_desc; Index: linux-2.6.22-rc7/fs/ext4/super.c =================================================================== --- linux-2.6.22-rc7.orig/fs/ext4/super.c 2007-07-01 12:54:24.000000000 -0700 +++ linux-2.6.22-rc7/fs/ext4/super.c 2007-07-04 22:12:27.000000000 -0700 @@ -2481,19 +2481,19 @@ static int ext4_statfs (struct dentry * struct super_block *sb = dentry->d_sb; struct ext4_sb_info *sbi = EXT4_SB(sb); struct ext4_super_block *es = sbi->s_es; - ext4_fsblk_t overhead; - int i; u64 fsid; - if (test_opt (sb, MINIX_DF)) - overhead = 0; - else { - unsigned long ngroups; - ngroups = EXT4_SB(sb)->s_groups_count; + if (test_opt(sb, MINIX_DF)) { + sbi->s_overhead_last = 0; + } else if (sbi->s_blocks_last != le32_to_cpu(es->s_blocks_count)) { + unsigned long ngroups = sbi->s_groups_count, i; + ext4_fsblk_t overhead = 0; smp_rmb(); /* - * Compute the overhead (FS structures) + * Compute the overhead (FS structures). This is constant + * for a given filesystem unless the number of block groups + * changes so we cache the previous value until it does. */ /* @@ -2517,18 +2517,23 @@ static int ext4_statfs (struct dentry * * Every block group has an inode bitmap, a block * bitmap, and an inode table. */ - overhead += (ngroups * (2 + EXT4_SB(sb)->s_itb_per_group)); + overhead += ngroups * (2 + sbi->s_itb_per_group); + sbi->s_overhead_last = overhead; + smp_wmb(); + sbi->s_blocks_last = le32_to_cpu(es->s_blocks_count); } buf->f_type = EXT4_SUPER_MAGIC; buf->f_bsize = sb->s_blocksize; - buf->f_blocks = ext4_blocks_count(es) - overhead; + buf->f_blocks = ext4_blocks_count(es) - sbi->s_overhead_last; buf->f_bfree = percpu_counter_sum(&sbi->s_freeblocks_counter); + es->s_free_blocks_count = cpu_to_le32(buf->f_bfree); buf->f_bavail = buf->f_bfree - ext4_r_blocks_count(es); if (buf->f_bfree < ext4_r_blocks_count(es)) buf->f_bavail = 0; buf->f_files = le32_to_cpu(es->s_inodes_count); buf->f_ffree = percpu_counter_sum(&sbi->s_freeinodes_counter); + es->s_free_inodes_count = cpu_to_le32(buf->f_ffree); buf->f_namelen = EXT4_NAME_LEN; fsid = le64_to_cpup((void *)es->s_uuid) ^ le64_to_cpup((void *)es->s_uuid + sizeof(u64));