linux-ext4 - Re: [PATCH] ext2 statfs speed up

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Date:	Thu, 05 Jul 2007 19:08:56 -0700
From:	Badari Pulavarty <pbadari@...ibm.com>
To:	Andreas Dilger <adilger@...sterfs.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	ext4 <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext2 statfs speed up

On Thu, 2007-07-05 at 15:06 -0600, Andreas Dilger wrote:
> On Jul 05, 2007  11:11 -0700, Badari Pulavarty wrote:
> > @@ -1131,17 +1134,22 @@ static int ext2_statfs (struct dentry * 
> >  	buf->f_bfree = ext2_count_free_blocks(sb);
> > +	es->s_free_blocks_count = cpu_to_le32(buf->f_bfree);
> >  	buf->f_ffree = ext2_count_free_inodes(sb);
> > +	es->s_free_inodes_count = cpu_to_le32(buf->f_ffree);
> 
> Hmm, this is still sub-optimal.  For ext3 and ext4 it just uses
> percpu_counter_sum() instead of the slow ext*_count_free_blocks(), which
> walks all of the groups.  Not that this is a reason to hold this patch,
> because at least we are removing 1/2 of the overhead for ext2.

Andrea,

I am wondering why we are not currently using percpu_counter_sum()
for ext2 ? I see that ext2 already has all the stuff it needs. 
Can't I just do following ?

Thanks,
Badari

 fs/ext2/super.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux-2.6.22-rc7/fs/ext2/super.c
===================================================================
--- linux-2.6.22-rc7.orig/fs/ext2/super.c	2007-07-05 12:35:15.000000000 -0700
+++ linux-2.6.22-rc7/fs/ext2/super.c	2007-07-05 20:37:32.000000000 -0700
@@ -1142,13 +1142,13 @@ static int ext2_statfs (struct dentry * 
 	buf->f_type = EXT2_SUPER_MAGIC;
 	buf->f_bsize = sb->s_blocksize;
 	buf->f_blocks = le32_to_cpu(es->s_blocks_count) - sbi->s_overhead_last;
-	buf->f_bfree = ext2_count_free_blocks(sb);
+	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 - le32_to_cpu(es->s_r_blocks_count);
 	if (buf->f_bfree < le32_to_cpu(es->s_r_blocks_count))
 		buf->f_bavail = 0;
 	buf->f_files = le32_to_cpu(es->s_inodes_count);
-	buf->f_ffree = ext2_count_free_inodes(sb);
+	buf->f_ffree = percpu_counter_sum(&sbi->s_freeinodes_counter);
 	es->s_free_inodes_count = cpu_to_le32(buf->f_ffree);
 	buf->f_namelen = EXT2_NAME_LEN;
 	fsid = le64_to_cpup((void *)es->s_uuid) ^


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