Merged fix for bug #16396598 "MDL HASH CAN STILL BE

CONCURRENCY BOTTLENECK" into mysql-trunk.

Author: Dmitry Lenev

include/hash.h

@@ -1,4 +1,4 @@
-/* Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
 
    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -45,9 +45,19 @@ extern "C" {
 /* flags for hash_init */
 #define HASH_UNIQUE     1       /* hash_insert fails on duplicate key */
 
+struct st_hash;
 typedef uint my_hash_value_type;
 typedef uchar *(*my_hash_get_key)(const uchar *,size_t*,my_bool);
 typedef void (*my_hash_free_key)(void *);
+/**
+  Function type representing a hash function to be used with the HASH
+  container.
+  Should accept pointer to HASH, pointer to key buffer and key length
+  as parameters.
+*/
+typedef my_hash_value_type (*my_hash_function)(const struct st_hash *,
+                                               const uchar *,
+                                               size_t);
 
 typedef struct st_hash {
   size_t key_offset,key_length;		/* Length of key if const length */
@@ -58,16 +68,20 @@ typedef struct st_hash {
   my_hash_get_key get_key;
   void (*free)(void *);
   CHARSET_INFO *charset;
+  my_hash_function hash_function;
 } HASH;
 
 /* A search iterator state */
 typedef uint HASH_SEARCH_STATE;
 
 #define my_hash_init(A,B,C,D,E,F,G,H) \
-          _my_hash_init(A,0,B,C,D,E,F,G,H)
+          _my_hash_init(A,0,B,NULL,C,D,E,F,G,H)
 #define my_hash_init2(A,B,C,D,E,F,G,H,I) \
-          _my_hash_init(A,B,C,D,E,F,G,H,I)
+          _my_hash_init(A,B,C,NULL,D,E,F,G,H,I)
+#define my_hash_init3(A,B,C,D,E,F,G,H,I,J) \
+          _my_hash_init(A,B,C,D,E,F,G,H,I,J)
 my_bool _my_hash_init(HASH *hash, uint growth_size, CHARSET_INFO *charset,
+                      my_hash_function hash_function,
                       ulong default_array_elements, size_t key_offset,
                       size_t key_length, my_hash_get_key get_key,
                       void (*free_element)(void*),
@@ -100,7 +114,7 @@ my_bool my_hash_check(HASH *hash); /* Only in debug library */
 #define my_hash_clear(H) memset((H), 0, sizeof(*(H)))
 #define my_hash_inited(H) ((H)->blength != 0)
 #define my_hash_init_opt(A,B,C,D,E,F,G,H) \
-          (!my_hash_inited(A) && _my_hash_init(A,0,B,C,D,E,F,G,H))
+          (!my_hash_inited(A) && _my_hash_init(A,0,B,NULL,C,D,E,F,G,H))
 
 #ifdef	__cplusplus
 }

include/my_murmur3.h

@@ -0,0 +1,27 @@
+#ifndef MY_MURMUR3_INCLUDED
+#define MY_MURMUR3_INCLUDED
+
+/* Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */
+
+#include <my_global.h>
+
+C_MODE_START
+
+uint32 murmur3_32(const uchar * key, size_t len, uint32 seed);
+
+C_MODE_END
+
+#endif /* MY_MURMUR3_INCLUDED */

mysql-test/suite/perfschema/r/mdl_func.result

@@ -268,7 +268,7 @@ OPERATION	metadata lock
 execute dump_waits_history_long;
 THREAD_ID	USER2
 EVENT_NAME	wait/lock/metadata/sql/mdl
-SOURCE	mdl.cc:2254
+SOURCE	mdl.cc:2275
 TIMER_START_SET	1
 TIMER_END_SET	1
 OBJECT_TYPE	TABLE
@@ -425,7 +425,7 @@ execute dump_waits_current;
 execute dump_waits_history_long;
 THREAD_ID	USER2
 EVENT_NAME	wait/lock/metadata/sql/mdl
-SOURCE	mdl.cc:2254
+SOURCE	mdl.cc:2275
 TIMER_START_SET	1
 TIMER_END_SET	1
 OBJECT_TYPE	TABLE
@@ -498,7 +498,7 @@ OPERATION	metadata lock
 execute dump_waits_history_long;
 THREAD_ID	USER2
 EVENT_NAME	wait/lock/metadata/sql/mdl
-SOURCE	mdl.cc:2254
+SOURCE	mdl.cc:2275
 TIMER_START_SET	1
 TIMER_END_SET	1
 OBJECT_TYPE	TABLE
@@ -541,7 +541,7 @@ execute dump_waits_current;
 execute dump_waits_history_long;
 THREAD_ID	USER2
 EVENT_NAME	wait/lock/metadata/sql/mdl
-SOURCE	mdl.cc:2254
+SOURCE	mdl.cc:2275
 TIMER_START_SET	1
 TIMER_END_SET	1
 OBJECT_TYPE	TABLE
@@ -551,7 +551,7 @@ INDEX_NAME	NULL
 OPERATION	metadata lock
 THREAD_ID	USER1
 EVENT_NAME	wait/lock/metadata/sql/mdl
-SOURCE	mdl.cc:2254
+SOURCE	mdl.cc:2275
 TIMER_START_SET	1
 TIMER_END_SET	1
 OBJECT_TYPE	TABLE
@@ -594,7 +594,7 @@ execute dump_waits_current;
 execute dump_waits_history_long;
 THREAD_ID	USER2
 EVENT_NAME	wait/lock/metadata/sql/mdl
-SOURCE	mdl.cc:2254
+SOURCE	mdl.cc:2275
 TIMER_START_SET	1
 TIMER_END_SET	1
 OBJECT_TYPE	TABLE
@@ -604,7 +604,7 @@ INDEX_NAME	NULL
 OPERATION	metadata lock
 THREAD_ID	USER1
 EVENT_NAME	wait/lock/metadata/sql/mdl
-SOURCE	mdl.cc:2254
+SOURCE	mdl.cc:2275
 TIMER_START_SET	1
 TIMER_END_SET	1
 OBJECT_TYPE	TABLE

mysys/hash.c

@@ -41,12 +41,26 @@ static int hashcmp(const HASH *hash, HASH_LINK *pos, const uchar *key,
 
 static my_hash_value_type calc_hash(const HASH *hash,
                                     const uchar *key, size_t length)
+{
+  return hash->hash_function(hash, key, length);
+}
+
+
+/**
+  Adaptor function which allows to use hash function from character
+  set with HASH.
+*/
+
+static my_hash_value_type cset_hash_sort_adapter(const HASH *hash,
+                                                 const uchar *key,
+                                                 size_t length)
 {
   ulong nr1=1, nr2=4;
   hash->charset->coll->hash_sort(hash->charset,(uchar*) key,length,&nr1,&nr2);
   return (my_hash_value_type)nr1;
 }
 
+
 /**
   @brief Initialize the hash
   
@@ -60,6 +74,9 @@ static my_hash_value_type calc_hash(const HASH *hash,
 
   @param[in,out] hash         The hash that is initialized
   @param[in]     charset      The charater set information
+  @param[in]     hash_function Hash function to be used. NULL -
+                               use standard hash from character
+                               set.
   @param[in]     size         The hash size
   @param[in]     key_offest   The key offset for the hash
   @param[in]     key_length   The length of the key used in
@@ -74,6 +91,7 @@ static my_hash_value_type calc_hash(const HASH *hash,
 */
 my_bool
 _my_hash_init(HASH *hash, uint growth_size, CHARSET_INFO *charset,
+              my_hash_function hash_function,
               ulong size, size_t key_offset, size_t key_length,
               my_hash_get_key get_key,
               void (*free_element)(void*), uint flags)
@@ -89,6 +107,7 @@ _my_hash_init(HASH *hash, uint growth_size, CHARSET_INFO *charset,
   hash->free=free_element;
   hash->flags=flags;
   hash->charset=charset;
+  hash->hash_function= hash_function ? hash_function : cset_hash_sort_adapter;
   DBUG_RETURN(my_init_dynamic_array_ci(&hash->array, 
                                        sizeof(HASH_LINK), size, growth_size));
 }

mysys_ssl/CMakeLists.txt

@@ -1,4 +1,4 @@
-# Copyright (c) 2012, Oracle and/or its affiliates. All rights reserved.
+# Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
 # 
 # This program is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -43,6 +43,7 @@ SET(MYSYS_SSL_SOURCES
     my_sha2.cc
     my_md5.cc
     my_rnd.cc
+    my_murmur3.cc
    )
 
 ADD_CONVENIENCE_LIBRARY(mysys_ssl ${MYSYS_SSL_SOURCES})

mysys_ssl/my_murmur3.cc

@@ -0,0 +1,134 @@
+/* Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */
+
+/*
+  Implementation of 32-bit version of MurmurHash3 - fast non-cryptographic
+  hash function with good statistical properties, which is based on public
+  domain code by Austin Appleby.
+*/
+
+#include <my_murmur3.h>
+
+
+/*
+  Platform-specific implementations of ROTL32 helper.
+*/
+
+#if defined(_MSC_VER)
+
+/* Microsoft Visual Studio supports intrinsic for rotate left. */
+
+#include <stdlib.h>
+
+#define ROTL32(x, y)	_rotl(x, y)
+
+/*
+  Force inlining of intrinsic even though /Oi option is turned off
+  in release builds.
+*/
+#pragma intrinsic(_rotl)
+
+#else // !defined(_MSC_VER)
+
+/*
+  Many other compilers should be able to optimize the below
+  function to single instruction.
+*/
+
+inline uint32 rotl32 (uint32 x, char r)
+{
+  return (x << r) | (x >> (32 - r));
+}
+
+#define	ROTL32(x,y)	rotl32(x,y)
+
+#endif // !defined(_MSC_VER)
+
+
+/**
+  Compute 32-bit version of MurmurHash3 hash for the key.
+
+  @param key   Key for which hash value to be computed.
+  @param len   Key length.
+  @param seed  Seed for hash computation.
+
+  @note WARNING! Since MurmurHash3 is known to be susceptible to "hash DoS"
+        attack it should not be used in any situation where attacker has
+        control over key being hashed and thus can cause performance problems
+        due to degradation of hash lookup to linear list search.
+
+  @returns Hash value for the key.
+*/
+
+uint32 murmur3_32(const uchar *key, size_t len, uint32 seed)
+{
+  const uchar *tail= key + (len  - len % 4);
+
+  uint32 h1= seed;
+
+  /* Constants for magic numbers that are used more than once. */
+  const uint32 c1= 0xcc9e2d51;
+  const uint32 c2= 0x1b873593;
+
+  /* Body: process all 32-bit blocks in the key. */
+
+  for (const uchar *data= key; data != tail; data+= 4)
+  {
+    uint32 k1= uint4korr(data);
+
+    k1*= c1;
+    k1= ROTL32(k1, 15);
+    k1*= c2;
+
+    h1^= k1;
+    h1= ROTL32(h1, 13);
+    h1= h1 * 5 + 0xe6546b64;
+  }
+
+  /* Tail: handle remaining len % 4 bytes. */
+
+  uint32 k1= 0;
+
+  switch(len % 4)
+  {
+  case 3:
+    k1^= static_cast<uint32>(tail[2]) << 16;
+    /* Fall through. */
+  case 2:
+    k1^= static_cast<uint32>(tail[1]) << 8;
+    /* Fall through. */
+  case 1:
+    k1^= tail[0];
+    k1*= c1;
+    k1= ROTL32(k1, 15);
+    k1*= c2;
+    h1^= k1;
+  };
+
+  /*
+    Finalization mix:
+    Add length and force all bits of a hash block to avalanche.
+  */
+
+  h1^= len;
+
+  h1^= h1 >> 16;
+  h1*= 0x85ebca6b;
+  h1^= h1 >> 13;
+  h1*= 0xc2b2ae35;
+  h1^= h1 >> 16;
+
+  return h1;
+}

sql/mdl.cc

@@ -25,6 +25,7 @@
 #include <mysql/psi/mysql_mdl.h>
 #include <pfs_stage_provider.h>
 #include <mysql/psi/mysql_stage.h>
+#include <my_murmur3.h>
 
 static PSI_memory_key key_memory_MDL_context_acquire_locks;
 
@@ -730,13 +731,33 @@ void MDL_map::init()
 }
 
 
+/**
+  Adapter function which allows to use murmur3 with our HASH implementation.
+*/
+
+extern "C" my_hash_value_type murmur3_adapter(const HASH*, const uchar *key,
+                                              size_t length)
+{
+  return murmur3_32(key, length, 0);
+}
+
+
 /** Initialize the partition in the container with all MDL locks. */
 
 MDL_map_partition::MDL_map_partition()
 {
   mysql_mutex_init(key_MDL_map_mutex, &m_mutex, NULL);
-  my_hash_init(&m_locks, &my_charset_bin, 16 /* FIXME */, 0, 0,
-               mdl_locks_key, 0, 0);
+  /*
+    Lower bits of values produced by hash function which is used in 'm_locks'
+    HASH container are also to select specific MDL_map_partition instance.
+    This means that this hash function needs to hash key value in such
+    a way that lower bits in result are sufficiently random. Since standard
+    hash function from 'my_charset_bin' doesn't satisfy this criteria we use
+    MurmurHash3 instead.
+  */
+  my_hash_init3(&m_locks, 0, &my_charset_bin, murmur3_adapter,
+                16 /* FIXME */, 0, 0, mdl_locks_key,
+                0, 0);
 };