linux-kernel - [PATCH v2 1/2] xxHash: create arch dependent 32/64-bit xxhash()

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Message-Id: <20170922095225.343-2-nefelim4ag@gmail.com>
Date:   Fri, 22 Sep 2017 12:52:24 +0300
From:   Timofey Titovets <nefelim4ag@...il.com>
To:     linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, borntraeger@...ibm.com,
        kvm@...r.kernel.org, Timofey Titovets <nefelim4ag@...il.com>
Subject: [PATCH v2 1/2] xxHash: create arch dependent 32/64-bit xxhash()

xxh32() - fast on both 32/64-bit platforms
xxh64() - fast only on 64-bit platform

Create xxhash() which will pickup fastest version
on compile time.

Add type xxhash_t to map correct hash size.

As result depends on cpu word size,
the main proporse of that - in memory hashing.

Signed-off-by: Timofey Titovets <nefelim4ag@...il.com>
Acked-by: Andi Kleen <ak@...ux.intel.com>
Cc: Linux-kernel <linux-kernel@...r.kernel.org>
---
 include/linux/xxhash.h | 24 ++++++++++++++++++++++++
 lib/xxhash.c           | 10 ++++++++++
 2 files changed, 34 insertions(+)

diff --git a/include/linux/xxhash.h b/include/linux/xxhash.h
index 9e1f42cb57e9..195a0ae10e9b 100644
--- a/include/linux/xxhash.h
+++ b/include/linux/xxhash.h
@@ -76,6 +76,7 @@
 #define XXHASH_H

 #include <linux/types.h>
+#include <linux/bitops.h> /* BITS_PER_LONG */

 /*-****************************
  * Simple Hash Functions
@@ -107,6 +108,29 @@ uint32_t xxh32(const void *input, size_t length, uint32_t seed);
  */
 uint64_t xxh64(const void *input, size_t length, uint64_t seed);

+#if BITS_PER_LONG == 64
+typedef	u64	xxhash_t;
+#else
+typedef	u32	xxhash_t;
+#endif
+
+/**
+ * xxhash() - calculate 32/64-bit hash based on cpu word size
+ *
+ * @input:  The data to hash.
+ * @length: The length of the data to hash.
+ * @seed:   The seed can be used to alter the result predictably.
+ *
+ * This function always work as xxh32() for 32-bit systems
+ * and as xxh64() for 64-bit systems.
+ * Because result depends on cpu work size,
+ * the main proporse of that function is for  in memory hashing.
+ *
+ * Return:  32/64-bit hash of the data.
+ */
+
+xxhash_t xxhash(const void *input, size_t length, uint64_t seed);
+
 /*-****************************
  * Streaming Hash Functions
  *****************************/
diff --git a/lib/xxhash.c b/lib/xxhash.c
index aa61e2a3802f..7dd1105fcc30 100644
--- a/lib/xxhash.c
+++ b/lib/xxhash.c
@@ -236,6 +236,16 @@ uint64_t xxh64(const void *input, const size_t len, const uint64_t seed)
 }
 EXPORT_SYMBOL(xxh64);

+xxhash_t xxhash(const void *input, size_t length, uint64_t seed)
+{
+#if BITS_PER_LONG == 64
+	return xxh64(input, length, seed);
+#else
+	return xxh32(input, length, seed);
+#endif
+}
+EXPORT_SYMBOL(xxhash);
+
 /*-**************************************************
  * Advanced Hash Functions
  ***************************************************/
--
2.14.1