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Date: Thu, 05 Jul 2007 12:35:01 -0700
From: Badari Pulavarty <pbadari@...ibm.com>
To: coly li <colyli@...il.com>, adilger@...sterfs.com
Cc: ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4 statfs speed up
On Fri, 2007-07-06 at 02:44 +0800, coly li wrote:
> Badari,
>
> How about the performance improvement, is there any benchmark result ?
>
> Coly
The original patch came from Andrea Dilger - where they use this patch
in their luster code. Andrea, do you have perf. numbers ?
BTW, I am doing perf. analysis too. I will share the results.
Thanks,
Badari
>
>
> 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@...ibm.com>
> > Signed-off-by: Andreas Dilger <adilger@...sterfs.com>
> >
> > 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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>
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