The patch titled
ext3: mostly fix blobk bitmap read performance regression
has been added to the -mm tree. Its filename is
ridiculous-ext3-costs-was-re-page-fault-costs.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: ext3: mostly fix blobk bitmap read performance regression
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
The ext3 block bitmap functions got added validation recently, which caused
a huge performance regression (ie 5x slower) due to very expensive modulus
calculations being done in a loop.
This largely fixes it, by moving the calculations out of the loop. The
sanity checking is still expensive, but no longer totally excessively so.
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Andreas Dilger <adilger@xxxxxxxxxxxxx>
Cc: Mingming Cao <cmm@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: <linux-ext4@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/ext3/balloc.c | 26 ++++++++++++++------------
1 file changed, 14 insertions(+), 12 deletions(-)
diff -puN fs/ext3/balloc.c~ridiculous-ext3-costs-was-re-page-fault-costs fs/ext3/balloc.c
--- a/fs/ext3/balloc.c~ridiculous-ext3-costs-was-re-page-fault-costs
+++ a/fs/ext3/balloc.c
@@ -80,12 +80,12 @@ struct ext3_group_desc * ext3_get_group_
return desc + offset;
}
-static inline int
-block_in_use(ext3_fsblk_t block, struct super_block *sb, unsigned char *map)
+static inline unsigned int
+block_bit_number(__le32 block, struct super_block *sb)
{
- return ext3_test_bit ((block -
- le32_to_cpu(EXT3_SB(sb)->s_es->s_first_data_block)) %
- EXT3_BLOCKS_PER_GROUP(sb), map);
+ __le32 first = EXT3_SB(sb)->s_es->s_first_data_block;
+
+ return (le32_to_cpu(block) - le32_to_cpu(first)) % EXT3_BLOCKS_PER_GROUP(sb);
}
/**
@@ -102,6 +102,7 @@ static struct buffer_head *
read_block_bitmap(struct super_block *sb, unsigned int block_group)
{
int i;
+ unsigned offset;
struct ext3_group_desc * desc;
struct buffer_head * bh = NULL;
ext3_fsblk_t bitmap_blk;
@@ -120,20 +121,21 @@ read_block_bitmap(struct super_block *sb
}
/* check whether block bitmap block number is set */
- if (!block_in_use(bitmap_blk, sb, bh->b_data)) {
+ offset = block_bit_number(desc->bg_block_bitmap, sb);
+ if (!ext3_test_bit(offset, bh->b_data)) {
/* bad block bitmap */
goto error_out;
}
/* check whether the inode bitmap block number is set */
- bitmap_blk = le32_to_cpu(desc->bg_inode_bitmap);
- if (!block_in_use(bitmap_blk, sb, bh->b_data)) {
+ offset = block_bit_number(desc->bg_inode_bitmap, sb);
+ if (!ext3_test_bit(offset, bh->b_data)) {
/* bad block bitmap */
goto error_out;
}
- /* check whether the inode table block number is set */
- bitmap_blk = le32_to_cpu(desc->bg_inode_table);
- for (i = 0; i < EXT3_SB(sb)->s_itb_per_group; i++, bitmap_blk++) {
- if (!block_in_use(bitmap_blk, sb, bh->b_data)) {
+ /* check whether the inode table block numbers are set */
+ offset = block_bit_number(desc->bg_inode_table, sb);
+ for (i = 0; i < EXT3_SB(sb)->s_itb_per_group; i++, offset++) {
+ if (!ext3_test_bit(offset, bh->b_data)) {
/* bad block bitmap */
goto error_out;
}
_
Patches currently in -mm which might be from torvalds@xxxxxxxxxxxxxxxxxxxx are
git-x86.patch
ridiculous-ext3-costs-was-re-page-fault-costs.patch
workaround-for-a-pci-restoring-bug.patch
-
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