From 689110098c7df10fab8800d3bf8e727c21f426fb Mon Sep 17 00:00:00 2001 From: Lukas Czerner Date: Wed, 3 Apr 2013 22:12:52 -0400 Subject: 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 Signed-off-by: "Theodore Ts'o" --- fs/ext4/balloc.c | 22 ++++++++++++++++------ 1 file changed, 16 insertions(+), 6 deletions(-) (limited to 'fs/ext4/balloc.c') diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c index 92e68b33fffd..d6babf94907e 100644 --- a/fs/ext4/balloc.c +++ b/fs/ext4/balloc.c @@ -49,14 +49,24 @@ void ext4_get_group_no_and_offset(struct super_block *sb, ext4_fsblk_t blocknr, } -static int ext4_block_in_group(struct super_block *sb, ext4_fsblk_t block, - ext4_group_t block_group) +/* + * Check whether the 'block' lives within the 'block_group'. Returns 1 if so + * and 0 otherwise. + */ +static inline int ext4_block_in_group(struct super_block *sb, + ext4_fsblk_t block, + ext4_group_t block_group) { ext4_group_t actual_group; - ext4_get_group_no_and_offset(sb, block, &actual_group, NULL); - if (actual_group == block_group) - return 1; - return 0; + + if (test_opt2(sb, STD_GROUP_SIZE)) + actual_group = + (le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block) + + block) >> + (EXT4_BLOCK_SIZE_BITS(sb) + EXT4_CLUSTER_BITS(sb) + 3); + else + ext4_get_group_no_and_offset(sb, block, &actual_group, NULL); + return (actual_group == block_group) ? 1 : 0; } /* Return the number of clusters used for file system metadata; this -- cgit v1.2.1