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| author | OGAWA Hirofumi <hirofumi@mail.parknet.co.jp> | 2008-11-06 12:53:49 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-11-06 15:41:20 -0800 |
| commit | d3dfa8228f87ab9960ab8b4718013d68e3c25a43 (patch) | |
| tree | 236784875a5c735688e644fe8412649e5fdbfcd7 /fs/fat | |
| parent | 52e9d9f4b32a3bec91feb76c84e37b7dcffe5040 (diff) | |
| download | linux-3.10-d3dfa8228f87ab9960ab8b4718013d68e3c25a43.tar.gz linux-3.10-d3dfa8228f87ab9960ab8b4718013d68e3c25a43.tar.bz2 linux-3.10-d3dfa8228f87ab9960ab8b4718013d68e3c25a43.zip | |
fat: improve fat_hash()
fat_hash() is using the algorithm known as bad. Instead of it, this
uses hash_32(). The following is the summary of test.
old hash:
hash func (1000 times): 33489 cycles
total inodes in hash table: 70926
largest bucket contains: 696
smallest bucket contains: 54
new hash:
hash func (1000 times): 33129 cycles
total inodes in hash table: 70926
largest bucket contains: 315
smallest bucket contains: 236
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/fat')
| -rw-r--r-- | fs/fat/fat.h | 1 | ||||
| -rw-r--r-- | fs/fat/inode.c | 18 |
2 files changed, 7 insertions, 12 deletions
diff --git a/fs/fat/fat.h b/fs/fat/fat.h index a2a570f8171..2b8e94c3eef 100644 --- a/fs/fat/fat.h +++ b/fs/fat/fat.h @@ -43,7 +43,6 @@ struct fat_mount_options { #define FAT_HASH_BITS 8 #define FAT_HASH_SIZE (1UL << FAT_HASH_BITS) -#define FAT_HASH_MASK (FAT_HASH_SIZE-1) /* * MS-DOS file system in-core superblock data diff --git a/fs/fat/inode.c b/fs/fat/inode.c index 079d9d5e0d3..f58cd48d98b 100644 --- a/fs/fat/inode.c +++ b/fs/fat/inode.c @@ -26,6 +26,7 @@ #include <linux/uio.h> #include <linux/writeback.h> #include <linux/log2.h> +#include <linux/hash.h> #include <asm/unaligned.h> #include "fat.h" @@ -247,25 +248,21 @@ static void fat_hash_init(struct super_block *sb) INIT_HLIST_HEAD(&sbi->inode_hashtable[i]); } -static inline unsigned long fat_hash(struct super_block *sb, loff_t i_pos) +static inline unsigned long fat_hash(loff_t i_pos) { - unsigned long tmp = (unsigned long)i_pos | (unsigned long) sb; - tmp = tmp + (tmp >> FAT_HASH_BITS) + (tmp >> FAT_HASH_BITS * 2); - return tmp & FAT_HASH_MASK; + return hash_32(i_pos, FAT_HASH_BITS); } void fat_attach(struct inode *inode, loff_t i_pos) { - struct super_block *sb = inode->i_sb; - struct msdos_sb_info *sbi = MSDOS_SB(sb); + struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb); + struct hlist_head *head = sbi->inode_hashtable + fat_hash(i_pos); spin_lock(&sbi->inode_hash_lock); MSDOS_I(inode)->i_pos = i_pos; - hlist_add_head(&MSDOS_I(inode)->i_fat_hash, - sbi->inode_hashtable + fat_hash(sb, i_pos)); + hlist_add_head(&MSDOS_I(inode)->i_fat_hash, head); spin_unlock(&sbi->inode_hash_lock); } - EXPORT_SYMBOL_GPL(fat_attach); void fat_detach(struct inode *inode) @@ -276,13 +273,12 @@ void fat_detach(struct inode *inode) hlist_del_init(&MSDOS_I(inode)->i_fat_hash); spin_unlock(&sbi->inode_hash_lock); } - EXPORT_SYMBOL_GPL(fat_detach); struct inode *fat_iget(struct super_block *sb, loff_t i_pos) { struct msdos_sb_info *sbi = MSDOS_SB(sb); - struct hlist_head *head = sbi->inode_hashtable + fat_hash(sb, i_pos); + struct hlist_head *head = sbi->inode_hashtable + fat_hash(i_pos); struct hlist_node *_p; struct msdos_inode_info *i; struct inode *inode = NULL; |