[dpdk-dev] [PATCH] hash: update jhash function with the latest available

Pablo de Lara pablo.de.lara.guarch at intel.com
Thu Apr 16 15:26:59 CEST 2015


Jenkins hash function was developed originally in 1996,
and was integrated in first versions of DPDK.
The function has been improved in 2006,
achieving up to 60% better performance, compared to the original one.

Check out: http://burtleburtle.net/bob/c/lookup3.c

This patch integrates that code in the rte_jhash library,
adding also a new function rte_jhash_word2,
that returns two different hash values, for a single key.

Signed-off-by: Pablo de Lara <pablo.de.lara.guarch at intel.com>
---
 lib/librte_hash/rte_jhash.h |  407 ++++++++++++++++++++++++++++++++++++-------
 1 files changed, 347 insertions(+), 60 deletions(-)

diff --git a/lib/librte_hash/rte_jhash.h b/lib/librte_hash/rte_jhash.h
index a4bf5a1..3de006d 100644
--- a/lib/librte_hash/rte_jhash.h
+++ b/lib/librte_hash/rte_jhash.h
@@ -1,7 +1,7 @@
 /*-
  *   BSD LICENSE
  *
- *   Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
+ *   Copyright(c) 2010-2015 Intel Corporation. All rights reserved.
  *   All rights reserved.
  *
  *   Redistribution and use in source and binary forms, with or without
@@ -45,38 +45,51 @@ extern "C" {
 #endif
 
 #include <stdint.h>
+#include <rte_byteorder.h>
 
 /* jhash.h: Jenkins hash support.
  *
- * Copyright (C) 1996 Bob Jenkins (bob_jenkins at burtleburtle.net)
+ * Copyright (C) 2006 Bob Jenkins (bob_jenkins at burtleburtle.net)
  *
  * 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.
+ *
+ * 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.
  *
  * $FreeBSD$
  */
 
+#define rot(x, k) (((x)<<(k)) | ((x)>>(32-(k))))
+
 /** @internal Internal function. NOTE: Arguments are modified. */
 #define __rte_jhash_mix(a, b, c) do { \
-	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); \
+	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; \
+} while (0)
+
+#define __rte_jhash_final(a, b, c) do { \
+	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); \
 } while (0)
 
 /** The golden ratio: an arbitrary value. */
-#define RTE_JHASH_GOLDEN_RATIO      0x9e3779b9
+#define RTE_JHASH_GOLDEN_RATIO      0xdeadbeef
 
 /**
  * The most generic version, hashes an arbitrary sequence
@@ -95,42 +108,256 @@ extern "C" {
 static inline uint32_t
 rte_jhash(const void *key, uint32_t length, uint32_t initval)
 {
-	uint32_t a, b, c, len;
-	const uint8_t *k = (const uint8_t *)key;
-	const uint32_t *k32 = (const uint32_t *)key;
+	uint32_t a, b, c;
+	union {
+		const void *ptr;
+		size_t i;
+	} u;
 
-	len = length;
-	a = b = RTE_JHASH_GOLDEN_RATIO;
-	c = initval;
+	/* Set up the internal state */
+	a = b = c = RTE_JHASH_GOLDEN_RATIO + ((uint32_t)length) + initval;
 
-	while (len >= 12) {
-		a += k32[0];
-		b += k32[1];
-		c += k32[2];
+	u.ptr = key;
 
-		__rte_jhash_mix(a,b,c);
+	if ((u.i & 0x3) == 0) {
+		const uint32_t *k = (const uint32_t *)key;
 
-		k += (3 * sizeof(uint32_t)), k32 += 3;
-		len -= (3 * sizeof(uint32_t));
-	}
+		while (length > 12) {
+			a += k[0];
+			b += k[1];
+			c += k[2];
 
-	c += length;
-	switch (len) {
-		case 11: c += ((uint32_t)k[10] << 24);
-		case 10: c += ((uint32_t)k[9] << 16);
-		case 9 : c += ((uint32_t)k[8] << 8);
-		case 8 : b += ((uint32_t)k[7] << 24);
-		case 7 : b += ((uint32_t)k[6] << 16);
-		case 6 : b += ((uint32_t)k[5] << 8);
-		case 5 : b += k[4];
-		case 4 : a += ((uint32_t)k[3] << 24);
-		case 3 : a += ((uint32_t)k[2] << 16);
-		case 2 : a += ((uint32_t)k[1] << 8);
-		case 1 : a += k[0];
-		default: break;
-	};
+			__rte_jhash_mix(a, b, c);
+
+			k += 3;
+			length -= 12;
+		}
+
+		switch (length) {
+#if RTE_BYTE_ORDER == RTE_LITTLE_ENDIAN
+		case 12:
+			c += k[2]; b += k[1]; a += k[0]; break;
+		case 11:
+			c += k[2]&0xffffff; b += k[1]; a += k[0]; break;
+		case 10:
+			c += k[2]&0xffff; b += k[1]; a += k[0]; break;
+		case 9:
+			c += k[2]&0xff; b += k[1]; a += k[0]; break;
+		case 8:
+			b += k[1]; a += k[0]; break;
+		case 7:
+			b += k[1]&0xffffff; a += k[0]; break;
+		case 6:
+			b += k[1]&0xffff; a += k[0]; break;
+		case 5:
+			b += k[1]&0xff; a += k[0]; break;
+		case 4:
+			a += k[0]; break;
+		case 3:
+			a += k[0]&0xffffff; break;
+		case 2:
+			a += k[0]&0xffff; break;
+		case 1:
+			a += k[0]&0xff; break;
+#else
+		case 12:
+			c += k[2]; b += k[1]; a += k[0]; break;
+		case 11:
+			c += k[2]&0xffffff00; b += k[1]; a += k[0]; break;
+		case 10:
+			c += k[2]&0xffff0000; b += k[1]; a += k[0]; break;
+		case 9:
+			c += k[2]&0xff000000; b += k[1]; a += k[0]; break;
+		case 8:
+			b += k[1]; a += k[0]; break;
+		case 7:
+			b += k[1]&0xffffff00; a += k[0]; break;
+		case 6:
+			b += k[1]&0xffff0000; a += k[0]; break;
+		case 5:
+			b += k[1]&0xff000000; a += k[0]; break;
+		case 4:
+			a += k[0]; break;
+		case 3:
+			a += k[0]&0xffffff00; break;
+		case 2:
+			a += k[0]&0xffff0000; break;
+		case 1:
+			a += k[0]&0xff000000; break;
+#endif
+		/* zero length strings require no mixing */
+		case 0:
+			return c;
+		};
+#if RTE_BYTE_ORDER == RTE_LITTLE_ENDIAN
+	} else if ((u.i & 0x1) == 0) {
+		/* read 16-bit chunks */
+		const uint16_t *k = (const uint16_t *)key;
+		const uint8_t  *k8;
+
+		/* all but last block: aligned reads and different mixing */
+		while (length > 12) {
+			a += k[0] + (((uint32_t)k[1])<<16);
+			b += k[2] + (((uint32_t)k[3])<<16);
+			c += k[4] + (((uint32_t)k[5])<<16);
+
+			__rte_jhash_mix(a, b, c);
+
+			k += 6;
+			length -= 12;
+		}
+
+		/* handle the last (probably partial) block */
+		k8 = (const uint8_t *)k;
+		switch (length) {
+		case 12:
+			c += k[4]+(((uint32_t)k[5])<<16);
+			b += k[2]+(((uint32_t)k[3])<<16);
+			a += k[0]+(((uint32_t)k[1])<<16);
+			break;
+		case 11:
+			/* fall through */
+			c += ((uint32_t)k8[10])<<16;
+		case 10:
+			c += k[4];
+			b += k[2]+(((uint32_t)k[3])<<16);
+			a += k[0]+(((uint32_t)k[1])<<16);
+			break;
+		case 9:
+			/* fall through */
+			c += k8[8];
+		case 8:
+			b += k[2]+(((uint32_t)k[3])<<16);
+			a += k[0]+(((uint32_t)k[1])<<16);
+			break;
+		case 7:
+			/* fall through */
+			b += ((uint32_t)k8[6])<<16;
+		case 6:
+			b += k[2];
+			a += k[0]+(((uint32_t)k[1])<<16);
+			break;
+		case 5:
+			/* fall through */
+			b += k8[4];
+		case 4:
+			a += k[0]+(((uint32_t)k[1])<<16);
+			break;
+		case 3:
+			/* fall through */
+			a += ((uint32_t)k8[2])<<16;
+		case 2:
+			a += k[0];
+			break;
+		case 1:
+			a += k8[0];
+			break;
+		case 0:
+			/* zero length requires no mixing */
+			return c;
+		}
+#endif
+	} else {
+		const uint8_t *k = (const uint8_t *)key;
+
+		/* all but the last block: affect some 32 bits of (a, b, c) */
+		while (length > 12) {
+#if RTE_BYTE_ORDER == RTE_LITTLE_ENDIAN
+			a += k[0];
+			a += ((uint32_t)k[1])<<8;
+			a += ((uint32_t)k[2])<<16;
+			a += ((uint32_t)k[3])<<24;
+			b += k[4];
+			b += ((uint32_t)k[5])<<8;
+			b += ((uint32_t)k[6])<<16;
+			b += ((uint32_t)k[7])<<24;
+			c += k[8];
+			c += ((uint32_t)k[9])<<8;
+			c += ((uint32_t)k[10])<<16;
+			c += ((uint32_t)k[11])<<24;
+#else
+			a += ((uint32_t)k[0])<<24;
+			a += ((uint32_t)k[1])<<16;
+			a += ((uint32_t)k[2])<<8;
+			a += ((uint32_t)k[3]);
+			b += ((uint32_t)k[4])<<24;
+			b += ((uint32_t)k[5])<<16;
+			b += ((uint32_t)k[6])<<8;
+			b += ((uint32_t)k[7]);
+			c += ((uint32_t)k[8])<<32;
+			c += ((uint32_t)k[9])<<16;
+			c += ((uint32_t)k[10])<<8;
+			c += ((uint32_t)k[11]);
+#endif
+
+			__rte_jhash_mix(a, b, c);
 
-	__rte_jhash_mix(a,b,c);
+			k += 12;
+			length -= 12;
+		}
+
+		/* last block: affect all 32 bits of (c) */
+		/* all the case statements fall through */
+		switch (length) {
+#if RTE_BYTE_ORDER == RTE_LITTLE_ENDIAN
+		case 12:
+			c += ((uint32_t)k[11])<<24;
+		case 11:
+			c += ((uint32_t)k[10])<<16;
+		case 10:
+			c += ((uint32_t)k[9])<<8;
+		case 9:
+			c += k[8];
+		case 8:
+			b += ((uint32_t)k[7])<<24;
+		case 7:
+			b += ((uint32_t)k[6])<<16;
+		case 6:
+			b += ((uint32_t)k[5])<<8;
+		case 5:
+			b += k[4];
+		case 4:
+			a += ((uint32_t)k[3])<<24;
+		case 3:
+			a += ((uint32_t)k[2])<<16;
+		case 2:
+			a += ((uint32_t)k[1])<<8;
+		case 1:
+			a += k[0];
+		break;
+#else
+		case 12:
+			c += k[11];
+		case 11:
+			c += ((uint32_t)k[10])<<8;
+		case 10:
+			c += ((uint32_t)k[9])<<16;
+		case 9:
+			c += ((uint32_t)k[8])<<24;
+		case 8:
+			b += k[7];
+		case 7:
+			b += ((uint32_t)k[6])<<8;
+		case 6:
+			b += ((uint32_t)k[5])<<16;
+		case 5:
+			b += ((uint32_t)k[4])<<24;
+		case 4:
+			a += k[3];
+		case 3:
+			a += ((uint32_t)k[2])<<8;
+		case 2:
+			a += ((uint32_t)k[1])<<16;
+		case 1:
+			a += ((uint32_t)k[0])<<24;
+		break;
+#endif
+		case 0:
+			return c;
+		}
+	}
+
+	__rte_jhash_final(a, b, c);
 
 	return c;
 }
@@ -151,33 +378,93 @@ rte_jhash(const void *key, uint32_t length, uint32_t initval)
 static inline uint32_t
 rte_jhash2(const uint32_t *k, uint32_t length, uint32_t initval)
 {
-	uint32_t a, b, c, len;
+	uint32_t a, b, c;
 
-	a = b = RTE_JHASH_GOLDEN_RATIO;
-	c = initval;
-	len = length;
+	/* Set up the internal state */
+	a = b = c = RTE_JHASH_GOLDEN_RATIO + (((uint32_t)length)<<2) + initval;
 
-	while (len >= 3) {
+	/* Handle most of the key */
+	while (length > 3) {
 		a += k[0];
 		b += k[1];
 		c += k[2];
+
 		__rte_jhash_mix(a, b, c);
-		k += 3; len -= 3;
-	}
 
-	c += length * 4;
+		k += 3;
+		length -= 3;
+	}
 
-	switch (len) {
-		case 2 : b += k[1];
-		case 1 : a += k[0];
-		default: break;
+	/* Handle the last 3 uint32_t's */
+	switch (length) {
+	case 3:
+		c += k[2];
+	case 2:
+		b += k[1];
+	case 1:
+		a += k[0];
+		__rte_jhash_final(a, b, c);
+	/* case 0: nothing left to add */
+	case 0:
+		break;
 	};
 
-	__rte_jhash_mix(a,b,c);
-
 	return c;
 }
 
+/**
+ * Same as rte_jhash2, but take two seeds and return two uint32_ts.
+ * pc and pb must be non-null, and *pc and *pb must both be initialized
+ * with seeds. If you pass in (*pb)=0, the output (*pc) will be
+ * the same as the return value from rte_jhash.
+ *
+ * @param k
+ *   Key to calculate hash of.
+ * @param length
+ *   Length of key in units of 4 bytes.
+ * @param pc
+ *   IN: seed OUT: primary hash value.
+ * @param pc
+ *   IN: second seed OUT: secondary hash value.
+ */
+static inline void
+rte_jhash_word2(const uint32_t *k, uint32_t length, uint32_t *pc, uint32_t *pb)
+{
+	uint32_t a, b, c;
+
+	/* Set up the internal state */
+	a = b = c = RTE_JHASH_GOLDEN_RATIO + (((uint32_t)length)<<2) + *pc;
+	c += *pb;
+
+	/* Handle most of the key */
+	while (length > 3) {
+		a += k[0];
+		b += k[1];
+		c += k[2];
+
+		__rte_jhash_mix(a, b, c);
+
+		k += 3;
+		length -= 3;
+	}
+
+	/* Handle the last 3 uint32_t's */
+	switch (length) {
+	case 3:
+		c += k[2];
+	case 2:
+		b += k[1];
+	case 1:
+		a += k[0];
+		__rte_jhash_final(a, b, c);
+	/* case 0: nothing left to add */
+	case 0:
+		break;
+	};
+
+	*pc = c;
+	*pb = b;
+}
 
 /**
  * A special ultra-optimized versions that knows it is hashing exactly
-- 
1.7.4.1



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