linux-kernel - [PATCH v3 1/2] xxHash: create arch dependent 32/64-bit xxhash()

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Date:   Mon, 25 Sep 2017 22:33:19 +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 v3 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.

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>
Acked-by: Christian Borntraeger <borntraeger@...ibm.com>
Cc: Linux-kernel <linux-kernel@...r.kernel.org>
Cc: Linux-kvm <kvm@...r.kernel.org>
---
 include/linux/xxhash.h | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/include/linux/xxhash.h b/include/linux/xxhash.h
index 9e1f42cb57e9..2a04ee5c5219 100644
--- a/include/linux/xxhash.h
+++ b/include/linux/xxhash.h
@@ -107,6 +107,29 @@ uint32_t xxh32(const void *input, size_t length, uint32_t seed);
  */
 uint64_t xxh64(const void *input, size_t length, uint64_t seed);

+/**
+ * xxhash() - calculate wordsize hash of the input with a given seed
+ * @input:  The data to hash.
+ * @length: The length of the data to hash.
+ * @seed:   The seed can be used to alter the result predictably.
+ *
+ * If the hash does not need to be comparable between machines with
+ * different word sizes, this function will call whichever of xxh32()
+ * or xxh64() is faster.
+ *
+ * Return:  wordsize hash of the data.
+ */
+
+static inline unsigned long 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
+}
+
 /*-****************************
  * Streaming Hash Functions
  *****************************/
--
2.14.1