diff options
| author |   George Spelvin <linux@sciencehorizons.net> | 2016-06-10 00:22:12 -0400 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2016-06-11 14:57:56 -0700 |
| commit | 703b5faf22fbddf984a361e6555f3a03fdba63d9 (patch) | |
| tree | 6bcfde71273dc055ba28abedd8305d6a829639f5 | |
| parent | vfs: make the string hashes salt the hash (diff) | |
| download | linux-dev-703b5faf22fbddf984a361e6555f3a03fdba63d9.tar.xz linux-dev-703b5faf22fbddf984a361e6555f3a03fdba63d9.zip | |
fs/dcache.c: Save one 32-bit multiply in dcache lookup
Noe that we're mixing in the parent pointer earlier, we
don't need to use hash_32() to mix its bits. Instead, we can
just take the msbits of the hash value directly.
For those applications which use the partial_name_hash(),
move the multiply to end_name_hash.
Signed-off-by: George Spelvin <linux@sciencehorizons.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | fs/dcache.c | 2 | ||||
| -rw-r--r-- | include/linux/stringhash.h | 6 |
2 files changed, 5 insertions, 3 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index 9522b8b63871..03f1a332f677 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -106,7 +106,7 @@ static struct hlist_bl_head *dentry_hashtable __read_mostly; static inline struct hlist_bl_head *d_hash(unsigned int hash) { - return dentry_hashtable + hash_32(hash, d_hash_shift); + return dentry_hashtable + (hash >> (32 - d_hash_shift)); } #define IN_LOOKUP_SHIFT 10 diff --git a/include/linux/stringhash.h b/include/linux/stringhash.h index eb7debb280c0..7c2d95170d01 100644 --- a/include/linux/stringhash.h +++ b/include/linux/stringhash.h @@ -3,6 +3,7 @@ #include <linux/compiler.h> /* For __pure */ #include <linux/types.h> /* For u32, u64 */ +#include <linux/hash.h> /* * Routines for hashing strings of bytes to a 32-bit hash value. @@ -45,11 +46,12 @@ partial_name_hash(unsigned long c, unsigned long prevhash) /* * Finally: cut down the number of bits to a int value (and try to avoid - * losing bits) + * losing bits). This also has the property (wanted by the dcache) + * that the msbits make a good hash table index. */ static inline unsigned long end_name_hash(unsigned long hash) { - return (unsigned int)hash; + return __hash_32((unsigned int)hash); } /* |