kernel: replace jhash2 with the faster jhash3 algorithm

SVN-Revision: 15128

target/linux/generic-2.6/patches-2.6.28/201-jhash3.patch

@@ -0,0 +1,227 @@
+--- a/include/linux/jhash.h
++++ b/include/linux/jhash.h
+@@ -3,80 +3,95 @@
+ 
+ /* jhash.h: Jenkins hash support.
+  *
+- * Copyright (C) 1996 Bob Jenkins ([email protected])
++ * Copyright (C) 2006. Bob Jenkins ([email protected])
+  *
+  * http://burtleburtle.net/bob/hash/
+  *
+  * These are the credits from Bob's sources:
+  *
+- * lookup2.c, by Bob Jenkins, December 1996, Public Domain.
+- * hash(), hash2(), hash3, and mix() are externally useful functions.
+- * Routines to test the hash are included if SELF_TEST is defined.
+- * You can use this free for any purpose.  It has no warranty.
++ * lookup3.c, by Bob Jenkins, May 2006, Public Domain.
+  *
+- * Copyright (C) 2003 David S. Miller ([email protected])
++ * These are functions for producing 32-bit hashes for hash table lookup.
++ * hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final() 
++ * are externally useful functions.  Routines to test the hash are included 
++ * if SELF_TEST is defined.  You can use this free for any purpose.  It's in
++ * the public domain.  It has no warranty.
++ *
++ * Copyright (C) 2009 Jozsef Kadlecsik ([email protected])
+  *
+  * I've modified Bob's hash to be useful in the Linux kernel, and
+- * any bugs present are surely my fault.  -DaveM
++ * any bugs present are my fault.  Jozsef
+  */
+ 
+-/* NOTE: Arguments are modified. */
+-#define __jhash_mix(a, b, c) \
++#define __rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
++
++/* __jhash_mix - mix 3 32-bit values reversibly. */
++#define __jhash_mix(a,b,c) \
++{ \
++  a -= c;  a ^= __rot(c, 4);  c += b; \
++  b -= a;  b ^= __rot(a, 6);  a += c; \
++  c -= b;  c ^= __rot(b, 8);  b += a; \
++  a -= c;  a ^= __rot(c,16);  c += b; \
++  b -= a;  b ^= __rot(a,19);  a += c; \
++  c -= b;  c ^= __rot(b, 4);  b += a; \
++}
++
++/* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */
++#define __jhash_final(a,b,c) \
+ { \
+-  a -= b; a -= c; a ^= (c>>13); \
+-  b -= c; b -= a; b ^= (a<<8); \
+-  c -= a; c -= b; c ^= (b>>13); \
+-  a -= b; a -= c; a ^= (c>>12);  \
+-  b -= c; b -= a; b ^= (a<<16); \
+-  c -= a; c -= b; c ^= (b>>5); \
+-  a -= b; a -= c; a ^= (c>>3);  \
+-  b -= c; b -= a; b ^= (a<<10); \
+-  c -= a; c -= b; c ^= (b>>15); \
++  c ^= b; c -= __rot(b,14); \
++  a ^= c; a -= __rot(c,11); \
++  b ^= a; b -= __rot(a,25); \
++  c ^= b; c -= __rot(b,16); \
++  a ^= c; a -= __rot(c,4);  \
++  b ^= a; b -= __rot(a,14); \
++  c ^= b; c -= __rot(b,24); \
+ }
+ 
+-/* The golden ration: an arbitrary value */
+-#define JHASH_GOLDEN_RATIO	0x9e3779b9
++/* An arbitrary initial parameter */
++#define JHASH_INIT_PARAM	0xdeadbeef
+ 
+ /* The most generic version, hashes an arbitrary sequence
+  * of bytes.  No alignment or length assumptions are made about
+- * the input key.
++ * the input key. The result depends on endianness.
+  */
+ static inline u32 jhash(const void *key, u32 length, u32 initval)
+ {
+-	u32 a, b, c, len;
++	u32 a,b,c;
+ 	const u8 *k = key;
+ 
+-	len = length;
+-	a = b = JHASH_GOLDEN_RATIO;
+-	c = initval;
+-
+-	while (len >= 12) {
+-		a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24));
+-		b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24));
+-		c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24));
+-
+-		__jhash_mix(a,b,c);
++	/* Set up the internal state */
++	a = b = c = JHASH_INIT_PARAM + length + initval;
+ 
++	/* all but the last block: affect some 32 bits of (a,b,c) */
++	while (length > 12) {
++    		a += (k[0] + ((u32)k[1]<<8) + ((u32)k[2]<<16) + ((u32)k[3]<<24));
++		b += (k[4] + ((u32)k[5]<<8) + ((u32)k[6]<<16) + ((u32)k[7]<<24));
++		c += (k[8] + ((u32)k[9]<<8) + ((u32)k[10]<<16) + ((u32)k[11]<<24));
++		__jhash_mix(a, b, c);
++		length -= 12;
+ 		k += 12;
+-		len -= 12;
+ 	}
+ 
+-	c += length;
+-	switch (len) {
+-	case 11: c += ((u32)k[10]<<24);
+-	case 10: c += ((u32)k[9]<<16);
+-	case 9 : c += ((u32)k[8]<<8);
+-	case 8 : b += ((u32)k[7]<<24);
+-	case 7 : b += ((u32)k[6]<<16);
+-	case 6 : b += ((u32)k[5]<<8);
++	/* last block: affect all 32 bits of (c) */
++	/* all the case statements fall through */
++	switch (length) {
++	case 12: c += (u32)k[11]<<24;
++	case 11: c += (u32)k[10]<<16;
++	case 10: c += (u32)k[9]<<8;
++	case 9 : c += k[8];
++	case 8 : b += (u32)k[7]<<24;
++	case 7 : b += (u32)k[6]<<16;
++	case 6 : b += (u32)k[5]<<8;
+ 	case 5 : b += k[4];
+-	case 4 : a += ((u32)k[3]<<24);
+-	case 3 : a += ((u32)k[2]<<16);
+-	case 2 : a += ((u32)k[1]<<8);
++	case 4 : a += (u32)k[3]<<24;
++	case 3 : a += (u32)k[2]<<16;
++	case 2 : a += (u32)k[1]<<8;
+ 	case 1 : a += k[0];
+-	};
+-
+-	__jhash_mix(a,b,c);
++		__jhash_final(a, b, c);
++	case 0 :
++		break;
++	}
+ 
+ 	return c;
+ }
+@@ -86,58 +101,57 @@ static inline u32 jhash(const void *key,
+  */
+ static inline u32 jhash2(const u32 *k, u32 length, u32 initval)
+ {
+-	u32 a, b, c, len;
++	u32 a, b, c;
+ 
+-	a = b = JHASH_GOLDEN_RATIO;
+-	c = initval;
+-	len = length;
++	/* Set up the internal state */
++	a = b = c = JHASH_INIT_PARAM + (length<<2) + initval;
+ 
+-	while (len >= 3) {
++	/* handle most of the key */
++	while (length > 3) {
+ 		a += k[0];
+ 		b += k[1];
+ 		c += k[2];
+ 		__jhash_mix(a, b, c);
+-		k += 3; len -= 3;
++		length -= 3;
++		k += 3;
+ 	}
+ 
+-	c += length * 4;
+-
+-	switch (len) {
+-	case 2 : b += k[1];
+-	case 1 : a += k[0];
+-	};
+-
+-	__jhash_mix(a,b,c);
++	/* handle the last 3 u32's */
++	/* all the case statements fall through */ 
++	switch (length) {
++	case 3: c += k[2];
++	case 2: b += k[1];
++	case 1: a += k[0];
++		__jhash_final(a, b, c);
++	case 0:     /* case 0: nothing left to add */
++		break;
++	}
+ 
+ 	return c;
+ }
+ 
+-
+ /* A special ultra-optimized versions that knows they are hashing exactly
+  * 3, 2 or 1 word(s).
+- *
+- * NOTE: In partilar the "c += length; __jhash_mix(a,b,c);" normally
+- *       done at the end is not done here.
+  */
+ static inline u32 jhash_3words(u32 a, u32 b, u32 c, u32 initval)
+ {
+-	a += JHASH_GOLDEN_RATIO;
+-	b += JHASH_GOLDEN_RATIO;
+-	c += initval;
++	a += JHASH_INIT_PARAM + initval;
++	b += JHASH_INIT_PARAM + initval;
++	c += JHASH_INIT_PARAM + initval;
+ 
+-	__jhash_mix(a, b, c);
++	__jhash_final(a, b, c);
+ 
+ 	return c;
+ }
+ 
+ static inline u32 jhash_2words(u32 a, u32 b, u32 initval)
+ {
+-	return jhash_3words(a, b, 0, initval);
++	return jhash_3words(0, a, b, initval);
+ }
+ 
+ static inline u32 jhash_1word(u32 a, u32 initval)
+ {
+-	return jhash_3words(a, 0, 0, initval);
++	return jhash_3words(0, 0, a, initval);
+ }
+ 
+ #endif /* _LINUX_JHASH_H */