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authorOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>2008-11-06 15:53:49 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2008-11-06 18:41:20 -0500
commitd3dfa8228f87ab9960ab8b4718013d68e3c25a43 (patch)
tree236784875a5c735688e644fe8412649e5fdbfcd7 /fs/fat
parent52e9d9f4b32a3bec91feb76c84e37b7dcffe5040 (diff)
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.h1
-rw-r--r--fs/fat/inode.c18
2 files changed, 7 insertions, 12 deletions
diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index a2a570f81719..2b8e94c3eef4 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -43,7 +43,6 @@ struct fat_mount_options {
43 43
44#define FAT_HASH_BITS 8 44#define FAT_HASH_BITS 8
45#define FAT_HASH_SIZE (1UL << FAT_HASH_BITS) 45#define FAT_HASH_SIZE (1UL << FAT_HASH_BITS)
46#define FAT_HASH_MASK (FAT_HASH_SIZE-1)
47 46
48/* 47/*
49 * MS-DOS file system in-core superblock data 48 * MS-DOS file system in-core superblock data
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 079d9d5e0d36..f58cd48d98b8 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -26,6 +26,7 @@
26#include <linux/uio.h> 26#include <linux/uio.h>
27#include <linux/writeback.h> 27#include <linux/writeback.h>
28#include <linux/log2.h> 28#include <linux/log2.h>
29#include <linux/hash.h>
29#include <asm/unaligned.h> 30#include <asm/unaligned.h>
30#include "fat.h" 31#include "fat.h"
31 32
@@ -247,25 +248,21 @@ static void fat_hash_init(struct super_block *sb)
247 INIT_HLIST_HEAD(&sbi->inode_hashtable[i]); 248 INIT_HLIST_HEAD(&sbi->inode_hashtable[i]);
248} 249}
249 250
250static inline unsigned long fat_hash(struct super_block *sb, loff_t i_pos) 251static inline unsigned long fat_hash(loff_t i_pos)
251{ 252{
252 unsigned long tmp = (unsigned long)i_pos | (unsigned long) sb; 253 return hash_32(i_pos, FAT_HASH_BITS);
253 tmp = tmp + (tmp >> FAT_HASH_BITS) + (tmp >> FAT_HASH_BITS * 2);
254 return tmp & FAT_HASH_MASK;
255} 254}
256 255
257void fat_attach(struct inode *inode, loff_t i_pos) 256void fat_attach(struct inode *inode, loff_t i_pos)
258{ 257{
259 struct super_block *sb = inode->i_sb; 258 struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
260 struct msdos_sb_info *sbi = MSDOS_SB(sb); 259 struct hlist_head *head = sbi->inode_hashtable + fat_hash(i_pos);
261 260
262 spin_lock(&sbi->inode_hash_lock); 261 spin_lock(&sbi->inode_hash_lock);
263 MSDOS_I(inode)->i_pos = i_pos; 262 MSDOS_I(inode)->i_pos = i_pos;
264 hlist_add_head(&MSDOS_I(inode)->i_fat_hash, 263 hlist_add_head(&MSDOS_I(inode)->i_fat_hash, head);
265 sbi->inode_hashtable + fat_hash(sb, i_pos));
266 spin_unlock(&sbi->inode_hash_lock); 264 spin_unlock(&sbi->inode_hash_lock);
267} 265}
268
269EXPORT_SYMBOL_GPL(fat_attach); 266EXPORT_SYMBOL_GPL(fat_attach);
270 267
271void fat_detach(struct inode *inode) 268void fat_detach(struct inode *inode)
@@ -276,13 +273,12 @@ void fat_detach(struct inode *inode)
276 hlist_del_init(&MSDOS_I(inode)->i_fat_hash); 273 hlist_del_init(&MSDOS_I(inode)->i_fat_hash);
277 spin_unlock(&sbi->inode_hash_lock); 274 spin_unlock(&sbi->inode_hash_lock);
278} 275}
279
280EXPORT_SYMBOL_GPL(fat_detach); 276EXPORT_SYMBOL_GPL(fat_detach);
281 277
282struct inode *fat_iget(struct super_block *sb, loff_t i_pos) 278struct inode *fat_iget(struct super_block *sb, loff_t i_pos)
283{ 279{
284 struct msdos_sb_info *sbi = MSDOS_SB(sb); 280 struct msdos_sb_info *sbi = MSDOS_SB(sb);
285 struct hlist_head *head = sbi->inode_hashtable + fat_hash(sb, i_pos); 281 struct hlist_head *head = sbi->inode_hashtable + fat_hash(i_pos);
286 struct hlist_node *_p; 282 struct hlist_node *_p;
287 struct msdos_inode_info *i; 283 struct msdos_inode_info *i;
288 struct inode *inode = NULL; 284 struct inode *inode = NULL;