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>
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d3dfa8228f
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@ -43,7 +43,6 @@ struct fat_mount_options {
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#define FAT_HASH_BITS 8
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#define FAT_HASH_BITS 8
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#define FAT_HASH_SIZE (1UL << FAT_HASH_BITS)
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#define FAT_HASH_SIZE (1UL << FAT_HASH_BITS)
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#define FAT_HASH_MASK (FAT_HASH_SIZE-1)
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/*
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/*
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* MS-DOS file system in-core superblock data
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* MS-DOS file system in-core superblock data
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@ -26,6 +26,7 @@
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#include <linux/uio.h>
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#include <linux/uio.h>
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#include <linux/writeback.h>
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#include <linux/writeback.h>
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#include <linux/log2.h>
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#include <linux/log2.h>
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#include <linux/hash.h>
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#include <asm/unaligned.h>
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#include <asm/unaligned.h>
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#include "fat.h"
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#include "fat.h"
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@ -247,25 +248,21 @@ static void fat_hash_init(struct super_block *sb)
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INIT_HLIST_HEAD(&sbi->inode_hashtable[i]);
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INIT_HLIST_HEAD(&sbi->inode_hashtable[i]);
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}
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}
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static inline unsigned long fat_hash(struct super_block *sb, loff_t i_pos)
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static inline unsigned long fat_hash(loff_t i_pos)
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{
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{
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unsigned long tmp = (unsigned long)i_pos | (unsigned long) sb;
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return hash_32(i_pos, FAT_HASH_BITS);
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tmp = tmp + (tmp >> FAT_HASH_BITS) + (tmp >> FAT_HASH_BITS * 2);
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return tmp & FAT_HASH_MASK;
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}
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}
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void fat_attach(struct inode *inode, loff_t i_pos)
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void fat_attach(struct inode *inode, loff_t i_pos)
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{
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{
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struct super_block *sb = inode->i_sb;
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struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
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struct msdos_sb_info *sbi = MSDOS_SB(sb);
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struct hlist_head *head = sbi->inode_hashtable + fat_hash(i_pos);
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spin_lock(&sbi->inode_hash_lock);
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spin_lock(&sbi->inode_hash_lock);
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MSDOS_I(inode)->i_pos = i_pos;
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MSDOS_I(inode)->i_pos = i_pos;
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hlist_add_head(&MSDOS_I(inode)->i_fat_hash,
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hlist_add_head(&MSDOS_I(inode)->i_fat_hash, head);
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sbi->inode_hashtable + fat_hash(sb, i_pos));
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spin_unlock(&sbi->inode_hash_lock);
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spin_unlock(&sbi->inode_hash_lock);
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}
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}
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EXPORT_SYMBOL_GPL(fat_attach);
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EXPORT_SYMBOL_GPL(fat_attach);
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void fat_detach(struct inode *inode)
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void fat_detach(struct inode *inode)
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@ -276,13 +273,12 @@ void fat_detach(struct inode *inode)
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hlist_del_init(&MSDOS_I(inode)->i_fat_hash);
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hlist_del_init(&MSDOS_I(inode)->i_fat_hash);
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spin_unlock(&sbi->inode_hash_lock);
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spin_unlock(&sbi->inode_hash_lock);
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}
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}
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EXPORT_SYMBOL_GPL(fat_detach);
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EXPORT_SYMBOL_GPL(fat_detach);
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struct inode *fat_iget(struct super_block *sb, loff_t i_pos)
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struct inode *fat_iget(struct super_block *sb, loff_t i_pos)
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{
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{
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struct msdos_sb_info *sbi = MSDOS_SB(sb);
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struct msdos_sb_info *sbi = MSDOS_SB(sb);
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struct hlist_head *head = sbi->inode_hashtable + fat_hash(sb, i_pos);
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struct hlist_head *head = sbi->inode_hashtable + fat_hash(i_pos);
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struct hlist_node *_p;
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struct hlist_node *_p;
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struct msdos_inode_info *i;
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struct msdos_inode_info *i;
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struct inode *inode = NULL;
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struct inode *inode = NULL;
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