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| author | Lukas Czerner <lczerner@redhat.com> | 2013-04-04 06:12:52 +0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2013-04-04 06:12:52 +0400 |
| commit | 689110098c7df10fab8800d3bf8e727c21f426fb (patch) | |
| tree | 4115e575da8b49716e358ebd2459095863ad00e1 /fs/ext4/super.c | |
| parent | a75ae78f087f933ab3432e98bb4dbbf2196cf6d5 (diff) | |
| download | linux-689110098c7df10fab8800d3bf8e727c21f426fb.tar.xz | |
ext4: make ext4_block_in_group() much more efficient
Currently in when getting the block group number for a particular
block in ext4_block_in_group() we're using
ext4_get_group_no_and_offset() which uses do_div() to get the block
group and the remainer which is offset within the group.
We don't need all of that in ext4_block_in_group() as we only need to
figure out the group number.
This commit changes ext4_block_in_group() to calculate group number
directly. This shows as a big improvement with regards to cpu
utilization. Measuring fallocate -l 15T on fresh file system with perf
showed that 23% of cpu time was spend in the
ext4_get_group_no_and_offset(). With this change it completely
disappears from the list only bumping the occurrence of
ext4_init_block_bitmap() which is the biggest user of
ext4_block_in_group() by 4%. As the result of this change on my system
the fallocate call was approx. 10% faster.
However since there is '-g' option in mkfs which allow us setting
different groups size (mostly for developers) I've introduced new per
file system flag whether we have a standard block group size or
not. The flag is used to determine whether we can use the bit shift
optimization or not.
Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Diffstat (limited to 'fs/ext4/super.c')
| -rw-r--r-- | fs/ext4/super.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/fs/ext4/super.c b/fs/ext4/super.c index febbe0e18024..525beb6e3e1e 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -3529,6 +3529,10 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent) sbi->s_addr_per_block_bits = ilog2(EXT4_ADDR_PER_BLOCK(sb)); sbi->s_desc_per_block_bits = ilog2(EXT4_DESC_PER_BLOCK(sb)); + /* Do we have standard group size of blocksize * 8 blocks ? */ + if (sbi->s_blocks_per_group == blocksize << 3) + set_opt2(sb, STD_GROUP_SIZE); + for (i = 0; i < 4; i++) sbi->s_hash_seed[i] = le32_to_cpu(es->s_hash_seed[i]); sbi->s_def_hash_version = es->s_def_hash_version; |