Badari,
How about the performance improvement, is there any benchmark result ?
Coly
在 2007-07-05四的 11:11 -0700，Badari Pulavarty写道：
> 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 <pbadari@xxxxxxxxxx>
> Signed-off-by: Andreas Dilger <adilger@xxxxxxxxxxxxx>
>
> 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));
>
>
> -
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