From: Jan Kara <jack@suse.cz>
Remove unnecessary division and modulo from ext3 code in often used paths.
Without the patch an oprofile of dbench load shows ext3_get_group_desc()
uses 0.84% and ext3_group_sparse() 1.51%, with the patch the numbers are
0.33% and 0.27% respectively.
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andreas Dilger <adilger@clusterfs.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
---
25-akpm/fs/ext3/balloc.c | 20 +++++++++-----------
1 files changed, 9 insertions(+), 11 deletions(-)
diff -puN fs/ext3/balloc.c~minor-ext3-speedup fs/ext3/balloc.c
--- 25/fs/ext3/balloc.c~minor-ext3-speedup Thu Jan 13 15:42:06 2005
+++ 25-akpm/fs/ext3/balloc.c Thu Jan 13 15:42:06 2005
@@ -56,8 +56,8 @@ struct ext3_group_desc * ext3_get_group_
}
smp_rmb();
- group_desc = block_group / EXT3_DESC_PER_BLOCK(sb);
- desc = block_group % EXT3_DESC_PER_BLOCK(sb);
+ group_desc = block_group >> EXT3_DESC_PER_BLOCK_BITS(sb);
+ desc = block_group & (EXT3_DESC_PER_BLOCK(sb) - 1);
if (!EXT3_SB(sb)->s_group_desc[group_desc]) {
ext3_error (sb, "ext3_get_group_desc",
"Group descriptor not loaded - "
@@ -1440,19 +1440,17 @@ static inline int block_in_use(unsigned
static inline int test_root(int a, int b)
{
- if (a == 0)
- return 1;
- while (1) {
- if (a == 1)
- return 1;
- if (a % b)
- return 0;
- a = a / b;
- }
+ int num = b;
+
+ while (a > num)
+ num *= b;
+ return num == a;
}
static int ext3_group_sparse(int group)
{
+ if (group <= 1)
+ return 1;
return (test_root(group, 3) || test_root(group, 5) ||
test_root(group, 7));
}
_