WL#8356 "Improve scalability by not acquiring unnecessary locks for internal temp tables".

Follow-up for the patch removing initialization of THR_LOCK and
THR_LOCK_DATA structs for internal temporary Heap tables.

Remove HP_SHARE::intern_lock mutex which was not used for anything.

Author: Dmitry Lenev

include/heap.h

@@ -149,7 +149,6 @@ typedef struct st_heap_share
   char * name;			/* Name of "memory-file" */
   time_t create_time;
   THR_LOCK lock;
-  mysql_mutex_t intern_lock;            /* Locking for use with _locking */
   my_bool delete_on_close;
   LIST open_list;
   uint auto_key;

storage/heap/heapdef.h

@@ -111,7 +111,6 @@ extern PSI_memory_key hp_key_memory_HP_PTRS;
 extern PSI_memory_key hp_key_memory_HP_KEYDEF;
 
 #ifdef HAVE_PSI_INTERFACE
-extern PSI_mutex_key hp_key_mutex_HP_SHARE_intern_lock;
 
 void init_heap_psi_keys();
 #endif /* HAVE_PSI_INTERFACE */

storage/heap/hp_create.c

@@ -195,17 +195,14 @@ int heap_create(const char *name, HP_CREATE_INFO *create_info,
       my_free(share);
       goto err;
     }
-    /*
-      Do not initialize THR_LOCK object for internal temporary tables.
-      It is not needed for such tables. Calling thr_lock_init() can
-      cause scalability issues since it acquires global lock.
-    */
-    if (!create_info->internal_table)
-       thr_lock_init(&share->lock);
-    mysql_mutex_init(hp_key_mutex_HP_SHARE_intern_lock,
-                     &share->intern_lock, MY_MUTEX_INIT_FAST);
     if (!create_info->internal_table)
     {
+      /*
+        Do not initialize THR_LOCK object for internal temporary tables.
+        It is not needed for such tables. Calling thr_lock_init() can
+        cause scalability issues since it acquires global lock.
+      */
+      thr_lock_init(&share->lock);
       share->open_list.data= (void*) share;
       heap_share_list= list_add(heap_share_list,&share->open_list);
     }
@@ -311,7 +308,6 @@ void hp_free(HP_SHARE *share)
   hp_clear(share);			/* Remove blocks from memory */
   if (not_internal_table)
     thr_lock_delete(&share->lock);
-  mysql_mutex_destroy(&share->intern_lock);
   my_free(share->name);
   my_free(share);
   return;

storage/heap/hp_static.c

@@ -1,4 +1,4 @@
-/* Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.
+/* Copyright (c) 2000, 2015, 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
@@ -30,16 +30,6 @@ PSI_memory_key hp_key_memory_HP_PTRS;
 PSI_memory_key hp_key_memory_HP_KEYDEF;
 
 #ifdef HAVE_PSI_INTERFACE
-PSI_mutex_key hp_key_mutex_HP_SHARE_intern_lock;
-
-static PSI_mutex_info all_heap_mutexes[]=
-{
-  { & hp_key_mutex_HP_SHARE_intern_lock, "HP_SHARE::intern_lock", 0}
-  /*
-    Note:
-    THR_LOCK_heap is part of mysys, not storage/heap.
-  */
-};
 
 static PSI_memory_info all_heap_memory[]=
 {
@@ -54,8 +44,7 @@ void init_heap_psi_keys()
   const char* category= "memory";
   int count;
 
-  count= array_elements(all_heap_mutexes);
-  mysql_mutex_register(category, all_heap_mutexes, count);
+  /* Note: THR_LOCK_heap is part of mysys, not storage/heap. */
 
   count= array_elements(all_heap_memory);
   mysql_memory_register(category, all_heap_memory, count);