Re: [PATCH] ext2 statfs improvement for block and inode free count

[Badari]

Andrew Morton wrote:
> On Fri, 13 Jul 2007 18:36:54 -0700
> Badari Pulavarty <pbadari@xxxxxxxxxx> wrote:
>
>   
> > More statfs() improvements for ext2. ext2 already maintains
> > percpu counters for free blocks and inodes. Derive free
> > block count and inode count by summing up percpu counters,
> > instead of counting up all the groups in the filesystem
> > each time.
> >
> >
> > Signed-off-by: Badari Pulavarty <pbadari@xxxxxxxxxx>
> > Acked-by: Andreas Dilger <adilger@xxxxxxxxxxxxx>
> >
> >  fs/ext2/super.c |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > Index: linux-2.6.22/fs/ext2/super.c
> > ===================================================================
> > --- linux-2.6.22.orig/fs/ext2/super.c	2007-07-13 20:06:38.000000000 -0700
> > +++ linux-2.6.22/fs/ext2/super.c	2007-07-13 20:06:51.000000000 -0700
> > @@ -1136,12 +1136,12 @@ 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) - overhead;
> > -	buf->f_bfree = ext2_count_free_blocks(sb);
> > + 	buf->f_bfree = percpu_counter_sum(&sbi->s_freeblocks_counter);
> >  	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);
> >  	buf->f_namelen = EXT2_NAME_LEN;
> >  	fsid = le64_to_cpup((void *)es->s_uuid) ^
> >  	       le64_to_cpup((void *)es->s_uuid + sizeof(u64));
> >
> >     
>
> Guys, I have this patch in a stalled state pending some convincing
> demonstration/argument that it's actually a worthwhile change.
>
> How much hurt will it cause on large-numa, and how much benefit do we get
> for that hurt? 
>   
Unfortunately, I couldn't find any noticeable significant improvements 
with or without this patch.
May be none of my filesystems are large enough on a large enough NUMA 
box to verify.
Lets drop it for now and re-visit it if needed.

Thanks,
Badari

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