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SubjectRe: [PATCH] ext2 statfs improvement for block and inode free count
Andrew Morton wrote:
> On Fri, 13 Jul 2007 18:36:54 -0700
> Badari Pulavarty <pbadari@us.ibm.com> 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@us.ibm.com>
>> Acked-by: Andreas Dilger <adilger@clusterfs.com>
>>
>> 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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