MDEV-10296 - Multi-instance table cache

Improve scalability by implementing multi-instance table cache.

mysql-test/r/mysqld--help.result

@@ -1091,6 +1091,8 @@ The following options may be given as the first argument:
  The number of cached table definitions
  --table-open-cache=# 
  The number of cached open tables
+ --table-open-cache-instances=# 
+ The number of table cache instances
  --tc-heuristic-recover=name 
  Decision to use in heuristic recover process. One of: OFF,
  COMMIT, ROLLBACK
@@ -1457,6 +1459,7 @@ sysdate-is-now FALSE
 table-cache 431
 table-definition-cache 400
 table-open-cache 431
+table-open-cache-instances 1
 tc-heuristic-recover OFF
 thread-cache-size 151
 thread-pool-idle-timeout 60

mysql-test/suite/sys_vars/r/sysvars_server_embedded.result

@@ -3887,6 +3887,20 @@ NUMERIC_BLOCK_SIZE	1
 ENUM_VALUE_LIST	NULL
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
+VARIABLE_NAME	TABLE_OPEN_CACHE_INSTANCES
+SESSION_VALUE	NULL
+GLOBAL_VALUE	1
+GLOBAL_VALUE_ORIGIN	COMPILE-TIME
+DEFAULT_VALUE	1
+VARIABLE_SCOPE	GLOBAL
+VARIABLE_TYPE	BIGINT UNSIGNED
+VARIABLE_COMMENT	The number of table cache instances
+NUMERIC_MIN_VALUE	1
+NUMERIC_MAX_VALUE	64
+NUMERIC_BLOCK_SIZE	1
+ENUM_VALUE_LIST	NULL
+READ_ONLY	YES
+COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	THREAD_CACHE_SIZE
 SESSION_VALUE	NULL
 GLOBAL_VALUE	151

mysql-test/suite/sys_vars/r/sysvars_server_notembedded.result

@@ -4657,6 +4657,20 @@ NUMERIC_BLOCK_SIZE	1
 ENUM_VALUE_LIST	NULL
 READ_ONLY	NO
 COMMAND_LINE_ARGUMENT	REQUIRED
+VARIABLE_NAME	TABLE_OPEN_CACHE_INSTANCES
+SESSION_VALUE	NULL
+GLOBAL_VALUE	1
+GLOBAL_VALUE_ORIGIN	COMPILE-TIME
+DEFAULT_VALUE	1
+VARIABLE_SCOPE	GLOBAL
+VARIABLE_TYPE	BIGINT UNSIGNED
+VARIABLE_COMMENT	The number of table cache instances
+NUMERIC_MIN_VALUE	1
+NUMERIC_MAX_VALUE	64
+NUMERIC_BLOCK_SIZE	1
+ENUM_VALUE_LIST	NULL
+READ_ONLY	YES
+COMMAND_LINE_ARGUMENT	REQUIRED
 VARIABLE_NAME	THREAD_CACHE_SIZE
 SESSION_VALUE	NULL
 GLOBAL_VALUE	151

sql/mysqld.cc

@@ -4974,8 +4974,7 @@ static int init_server_components()
     all things are initialized so that unireg_abort() doesn't fail
   */
   mdl_init();
-  tdc_init();
+  if (tdc_init() || hostname_cache_init())
-  if (hostname_cache_init())
     unireg_abort(1);
 
   query_cache_set_min_res_unit(query_cache_min_res_unit);
@@ -7643,7 +7642,6 @@ struct my_option my_long_options[]=
   MYSQL_TO_BE_IMPLEMENTED_OPTION("eq-range-index-dive-limit"),
   MYSQL_COMPATIBILITY_OPTION("server-id-bits"),
   MYSQL_TO_BE_IMPLEMENTED_OPTION("slave-rows-search-algorithms"), // HAVE_REPLICATION
-  MYSQL_COMPATIBILITY_OPTION("table-open-cache-instances"),
   MYSQL_TO_BE_IMPLEMENTED_OPTION("slave-allow-batching"),         // HAVE_REPLICATION
   MYSQL_COMPATIBILITY_OPTION("slave-checkpoint-period"),      // HAVE_REPLICATION
   MYSQL_COMPATIBILITY_OPTION("slave-checkpoint-group"),       // HAVE_REPLICATION

sql/sql_base.cc

@@ -878,7 +878,6 @@ void close_thread_table(THD *thd, TABLE **table_ptr)
     Do this *before* entering the TABLE_SHARE::tdc.LOCK_table_share
     critical section.
   */
-  if (table->file != NULL)
   MYSQL_UNBIND_TABLE(table->file);
 
   tc_release_table(table);

sql/sys_vars.cc

@@ -3227,6 +3227,11 @@ static Sys_var_ulong Sys_table_cache_size(
        BLOCK_SIZE(1), NO_MUTEX_GUARD, NOT_IN_BINLOG, ON_CHECK(0),
        ON_UPDATE(fix_table_open_cache));
 
+static Sys_var_ulong Sys_table_cache_instances(
+       "table_open_cache_instances", "The number of table cache instances",
+       READ_ONLY GLOBAL_VAR(tc_instances), CMD_LINE(REQUIRED_ARG),
+       VALID_RANGE(1, 64), DEFAULT(1), BLOCK_SIZE(1));
+
 static Sys_var_ulong Sys_thread_cache_size(
        "thread_cache_size",
        "How many threads we should keep in a cache for reuse. These are freed after 5 minutes of idle time",

sql/table.h

@@ -1021,13 +1021,13 @@ private:
      One should use methods of I_P_List template instead.
   */
   TABLE *share_all_next, **share_all_prev;
+  TABLE *global_free_next, **global_free_prev;
   friend struct All_share_tables;
+  friend class Table_cache_instance;
 
 public:
 
   THD	*in_use;                        /* Which thread uses this */
-  /* Time when table was released to table cache. Valid for unused tables. */
-  ulonglong tc_time;
   Field **field;			/* Pointer to fields */
 
   uchar *record[2];			/* Pointer to records */

sql/table_cache.cc

@@ -55,10 +55,12 @@
 /** Configuration. */
 ulong tdc_size; /**< Table definition cache threshold for LRU eviction. */
 ulong tc_size; /**< Table cache threshold for LRU eviction. */
+ulong tc_instances;
 
 /** Data collections. */
 static LF_HASH tdc_hash; /**< Collection of TABLE_SHARE objects. */
 /** Collection of unused TABLE_SHARE objects. */
+static
 I_P_List <TDC_element,
           I_P_List_adapter<TDC_element, &TDC_element::next, &TDC_element::prev>,
           I_P_List_null_counter,
@@ -67,8 +69,6 @@ I_P_List <TDC_element,
 static int64 tdc_version;  /* Increments on each reload */
 static bool tdc_inited;
 
-static int32 tc_count; /**< Number of TABLE objects in table cache. */
-
 
 /**
   Protects unused shares list.
@@ -81,11 +81,13 @@ static int32 tc_count; /**< Number of TABLE objects in table cache. */
 static mysql_mutex_t LOCK_unused_shares;
 
 #ifdef HAVE_PSI_INTERFACE
-static PSI_mutex_key key_LOCK_unused_shares, key_TABLE_SHARE_LOCK_table_share;
+static PSI_mutex_key key_LOCK_unused_shares, key_TABLE_SHARE_LOCK_table_share,
+                     key_LOCK_table_cache;
 static PSI_mutex_info all_tc_mutexes[]=
 {
   { &key_LOCK_unused_shares, "LOCK_unused_shares", PSI_FLAG_GLOBAL },
-  { &key_TABLE_SHARE_LOCK_table_share, "TABLE_SHARE::tdc.LOCK_table_share", 0 }
+  { &key_TABLE_SHARE_LOCK_table_share, "TABLE_SHARE::tdc.LOCK_table_share", 0 },
+  { &key_LOCK_table_cache, "LOCK_table_cache", 0 }
 };
 
 static PSI_cond_key key_TABLE_SHARE_COND_release;
@@ -93,19 +95,6 @@ static PSI_cond_info all_tc_conds[]=
 {
   { &key_TABLE_SHARE_COND_release, "TABLE_SHARE::tdc.COND_release", 0 }
 };
-
-
-static void init_tc_psi_keys(void)
-{
-  const char *category= "sql";
-  int count;
-
-  count= array_elements(all_tc_mutexes);
-  mysql_mutex_register(category, all_tc_mutexes, count);
-
-  count= array_elements(all_tc_conds);
-  mysql_cond_register(category, all_tc_conds, count);
-}
 #endif
 
 
@@ -125,23 +114,47 @@ static int fix_thd_pins(THD *thd)
   part of table definition cache.
 */
 
+struct Table_cache_instance
+{
+  /**
+    Protects free_tables (TABLE::global_free_next and TABLE::global_free_prev),
+    records, Share_free_tables::List (TABLE::prev and TABLE::next),
+    TABLE::in_use.
+  */
+  mysql_mutex_t LOCK_table_cache;
+  I_P_List <TABLE, I_P_List_adapter<TABLE, &TABLE::global_free_next,
+                                    &TABLE::global_free_prev>,
+            I_P_List_null_counter, I_P_List_fast_push_back<TABLE> >
+    free_tables;
+  ulong records;
+  /** Avoid false sharing between instances */
+  char pad[CPU_LEVEL1_DCACHE_LINESIZE];
+
+  Table_cache_instance(): records(0)
+  {
+    mysql_mutex_init(key_LOCK_table_cache, &LOCK_table_cache,
+                     MY_MUTEX_INIT_FAST);
+  }
+
+  ~Table_cache_instance()
+  {
+    mysql_mutex_destroy(&LOCK_table_cache);
+    DBUG_ASSERT(free_tables.is_empty());
+    DBUG_ASSERT(records == 0);
+  }
+};
+
+
+static Table_cache_instance *tc;
+
+
 static void intern_close_table(TABLE *table)
 {
-  DBUG_ENTER("intern_close_table");
-  DBUG_PRINT("tcache", ("table: '%s'.'%s' 0x%lx",
-                        table->s ? table->s->db.str : "?",
-                        table->s ? table->s->table_name.str : "?",
-                        (long) table));
-
   delete table->triggers;
-  if (table->file)                              // Not true if placeholder
+  DBUG_ASSERT(table->file);
-  {
+  closefrm(table);
-    (void) closefrm(table);
   tdc_release_share(table->s);
-  }
-  table->alias.free();
   my_free(table);
-  DBUG_VOID_RETURN;
 }
 
 
@@ -151,41 +164,38 @@ static void intern_close_table(TABLE *table)
 
 uint tc_records(void)
 {
-  return my_atomic_load32_explicit(&tc_count, MY_MEMORY_ORDER_RELAXED);
+  ulong total= 0;
-}
+  for (ulong i= 0; i < tc_instances; i++)
-
+  {
-
+    mysql_mutex_lock(&tc[i].LOCK_table_cache);
-/**
+    total+= tc[i].records;
-  Wait for MDL deadlock detector to complete traversing tdc.all_tables.
+    mysql_mutex_unlock(&tc[i].LOCK_table_cache);
-
+  }
-  Must be called before updating TABLE_SHARE::tdc.all_tables.
+  return total;
-*/
-
-static void tc_wait_for_mdl_deadlock_detector(TDC_element *element)
-{
-  while (element->all_tables_refs)
-    mysql_cond_wait(&element->COND_release, &element->LOCK_table_share);
 }
 
 
 /**
   Remove TABLE object from table cache.
-
-  - decrement tc_count
-  - remove object from TABLE_SHARE::tdc.all_tables
 */
 
 static void tc_remove_table(TABLE *table)
 {
-  mysql_mutex_assert_owner(&table->s->tdc->LOCK_table_share);
+  TDC_element *element= table->s->tdc;
-  tc_wait_for_mdl_deadlock_detector(table->s->tdc);
+
-  my_atomic_add32_explicit(&tc_count, -1, MY_MEMORY_ORDER_RELAXED);
+  mysql_mutex_lock(&element->LOCK_table_share);
-  table->s->tdc->all_tables.remove(table);
+  /* Wait for MDL deadlock detector to complete traversing tdc.all_tables. */
+  while (element->all_tables_refs)
+    mysql_cond_wait(&element->COND_release, &element->LOCK_table_share);
+  element->all_tables.remove(table);
+  mysql_mutex_unlock(&element->LOCK_table_share);
+
+  intern_close_table(table);
 }
 
 
 static void tc_remove_all_unused_tables(TDC_element *element,
-                                        TDC_element::TABLE_list *purge_tables,
+                                        Share_free_tables::List *purge_tables,
                                         bool mark_flushed)
 {
   TABLE *table;
@@ -200,11 +210,19 @@ static void tc_remove_all_unused_tables(TDC_element *element,
   */
   if (mark_flushed)
     element->flushed= true;
-  while ((table= element->free_tables.pop_front()))
+  for (ulong i= 0; i < tc_instances; i++)
   {
-    tc_remove_table(table);
+    mysql_mutex_lock(&tc[i].LOCK_table_cache);
+    while ((table= element->free_tables[i].list.pop_front()))
+    {
+      tc[i].records--;
+      tc[i].free_tables.remove(table);
+      DBUG_ASSERT(element->all_tables_refs == 0);
+      element->all_tables.remove(table);
       purge_tables->push_front(table);
     }
+    mysql_mutex_unlock(&tc[i].LOCK_table_cache);
+  }
 }
 
 
@@ -225,7 +243,7 @@ static void tc_remove_all_unused_tables(TDC_element *element,
 
 struct tc_purge_arg
 {
-  TDC_element::TABLE_list purge_tables;
+  Share_free_tables::List purge_tables;
   bool mark_flushed;
 };
 
@@ -251,20 +269,6 @@ void tc_purge(bool mark_flushed)
 }
 
 
-/**
-  Get last element of free_tables.
-*/
-
-static TABLE *tc_free_tables_back(TDC_element *element)
-{
-  TDC_element::TABLE_list::Iterator it(element->free_tables);
-  TABLE *entry, *last= 0;
-   while ((entry= it++))
-     last= entry;
-  return last;
-}
-
-
 /**
   Add new TABLE object to table cache.
 
@@ -281,79 +285,33 @@ static TABLE *tc_free_tables_back(TDC_element *element)
   - free evicted object
 */
 
-struct tc_add_table_arg
-{
-  char key[MAX_DBKEY_LENGTH];
-  uint key_length;
-  ulonglong purge_time;
-};
-
-
-static my_bool tc_add_table_callback(TDC_element *element, tc_add_table_arg *arg)
-{
-  TABLE *table;
-
-  mysql_mutex_lock(&element->LOCK_table_share);
-  if ((table= tc_free_tables_back(element)) && table->tc_time < arg->purge_time)
-  {
-    memcpy(arg->key, element->m_key, element->m_key_length);
-    arg->key_length= element->m_key_length;
-    arg->purge_time= table->tc_time;
-  }
-  mysql_mutex_unlock(&element->LOCK_table_share);
-  return FALSE;
-}
-
-
 void tc_add_table(THD *thd, TABLE *table)
 {
-  bool need_purge;
+  ulong i= thd->thread_id % tc_instances;
+  TABLE *LRU_table= 0;
+  TDC_element *element= table->s->tdc;
+
   DBUG_ASSERT(table->in_use == thd);
-  mysql_mutex_lock(&table->s->tdc->LOCK_table_share);
-  tc_wait_for_mdl_deadlock_detector(table->s->tdc);
-  table->s->tdc->all_tables.push_front(table);
-  mysql_mutex_unlock(&table->s->tdc->LOCK_table_share);
-
-  /* If we have too many TABLE instances around, try to get rid of them */
-  need_purge= my_atomic_add32_explicit(&tc_count, 1, MY_MEMORY_ORDER_RELAXED) >=
-              (int32) tc_size;
-
-  if (need_purge)
-  {
-    tc_add_table_arg argument;
-    argument.purge_time= ULONGLONG_MAX;
-    tdc_iterate(thd, (my_hash_walk_action) tc_add_table_callback, &argument);
-
-    if (argument.purge_time != ULONGLONG_MAX)
-    {
-      TDC_element *element= (TDC_element*) lf_hash_search(&tdc_hash,
-                                                          thd->tdc_hash_pins,
-                                                          argument.key,
-                                                          argument.key_length);
-      if (element)
-      {
-        TABLE *entry;
   mysql_mutex_lock(&element->LOCK_table_share);
-        lf_hash_search_unpin(thd->tdc_hash_pins);
+  /* Wait for MDL deadlock detector to complete traversing tdc.all_tables. */
-
+  while (element->all_tables_refs)
-        /*
+    mysql_cond_wait(&element->COND_release, &element->LOCK_table_share);
-          It may happen that oldest table was acquired meanwhile. In this case
+  element->all_tables.push_front(table);
-          just go ahead, number of objects in table cache will normalize
-          eventually.
-        */
-        if ((entry= tc_free_tables_back(element)) &&
-            entry->tc_time == argument.purge_time)
-        {
-          element->free_tables.remove(entry);
-          tc_remove_table(entry);
   mysql_mutex_unlock(&element->LOCK_table_share);
-          intern_close_table(entry);
+
+  mysql_mutex_lock(&tc[i].LOCK_table_cache);
+  if (tc[i].records == tc_size && (LRU_table= tc[i].free_tables.pop_front()))
+  {
+    LRU_table->s->tdc->free_tables[i].list.remove(LRU_table);
+    /* Needed if MDL deadlock detector chimes in before tc_remove_table() */
+    LRU_table->in_use= thd;
   }
   else
-          mysql_mutex_unlock(&element->LOCK_table_share);
+    tc[i].records++;
-      }
+  mysql_mutex_unlock(&tc[i].LOCK_table_cache);
-    }
+
-  }
+  if (LRU_table)
+    tc_remove_table(LRU_table);
 }
 
 
@@ -369,10 +327,11 @@ void tc_add_table(THD *thd, TABLE *table)
 
 static TABLE *tc_acquire_table(THD *thd, TDC_element *element)
 {
+  ulong i= thd->thread_id % tc_instances;
   TABLE *table;
 
-  mysql_mutex_lock(&element->LOCK_table_share);
+  mysql_mutex_lock(&tc[i].LOCK_table_cache);
-  table= element->free_tables.pop_front();
+  table= element->free_tables[i].list.pop_front();
   if (table)
   {
     DBUG_ASSERT(!table->in_use);
@@ -381,8 +340,9 @@ static TABLE *tc_acquire_table(THD *thd, TDC_element *element)
     DBUG_ASSERT(table->db_stat && table->file);
     /* The children must be detached from the table. */
     DBUG_ASSERT(!table->file->extra(HA_EXTRA_IS_ATTACHED_CHILDREN));
+    tc[i].free_tables.remove(table);
   }
-  mysql_mutex_unlock(&element->LOCK_table_share);
+  mysql_mutex_unlock(&tc[i].LOCK_table_cache);
   return table;
 }
 
@@ -413,40 +373,27 @@ static TABLE *tc_acquire_table(THD *thd, TDC_element *element)
     @retval false object released
 */
 
-bool tc_release_table(TABLE *table)
+void tc_release_table(TABLE *table)
 {
+  ulong i= table->in_use->thread_id % tc_instances;
   DBUG_ASSERT(table->in_use);
   DBUG_ASSERT(table->file);
 
-  if (table->needs_reopen() || tc_records() > tc_size)
+  mysql_mutex_lock(&tc[i].LOCK_table_cache);
+  if (table->needs_reopen() || table->s->tdc->flushed ||
+      tc[i].records > tc_size)
   {
-    mysql_mutex_lock(&table->s->tdc->LOCK_table_share);
+    tc[i].records--;
-    goto purge;
+    mysql_mutex_unlock(&tc[i].LOCK_table_cache);
-  }
-
-  table->tc_time= my_interval_timer();
-
-  mysql_mutex_lock(&table->s->tdc->LOCK_table_share);
-  if (table->s->tdc->flushed)
-    goto purge;
-  /*
-    in_use doesn't really need mutex protection, but must be reset after
-    checking tdc.flushed and before this table appears in free_tables.
-    Resetting in_use is needed only for print_cached_tables() and
-    list_open_tables().
-  */
-  table->in_use= 0;
-  /* Add table to the list of unused TABLE objects for this share. */
-  table->s->tdc->free_tables.push_front(table);
-  mysql_mutex_unlock(&table->s->tdc->LOCK_table_share);
-  return false;
-
-purge:
     tc_remove_table(table);
-  mysql_mutex_unlock(&table->s->tdc->LOCK_table_share);
+  }
+  else
+  {
     table->in_use= 0;
-  intern_close_table(table);
+    table->s->tdc->free_tables[i].list.push_front(table);
-  return true;
+    tc[i].free_tables.push_back(table);
+    mysql_mutex_unlock(&tc[i].LOCK_table_cache);
+  }
 }
 
 
@@ -456,7 +403,10 @@ static void tdc_assert_clean_share(TDC_element *element)
   DBUG_ASSERT(element->ref_count == 0);
   DBUG_ASSERT(element->m_flush_tickets.is_empty());
   DBUG_ASSERT(element->all_tables.is_empty());
-  DBUG_ASSERT(element->free_tables.is_empty());
+#ifndef DBUG_OFF
+  for (ulong i= 0; i < tc_instances; i++)
+    DBUG_ASSERT(element->free_tables[i].list.is_empty());
+#endif
   DBUG_ASSERT(element->all_tables_refs == 0);
   DBUG_ASSERT(element->next == 0);
   DBUG_ASSERT(element->prev == 0);
@@ -527,7 +477,8 @@ static void lf_alloc_constructor(uchar *arg)
   mysql_cond_init(key_TABLE_SHARE_COND_release, &element->COND_release, 0);
   element->m_flush_tickets.empty();
   element->all_tables.empty();
-  element->free_tables.empty();
+  for (ulong i= 0; i < tc_instances; i++)
+    element->free_tables[i].list.empty();
   element->all_tables_refs= 0;
   element->share= 0;
   element->ref_count= 0;
@@ -573,23 +524,29 @@ static uchar *tdc_hash_key(const TDC_element *element, size_t *length,
   Initialize table definition cache.
 */
 
-void tdc_init(void)
+bool tdc_init(void)
 {
   DBUG_ENTER("tdc_init");
 #ifdef HAVE_PSI_INTERFACE
-  init_tc_psi_keys();
+  mysql_mutex_register("sql", all_tc_mutexes, array_elements(all_tc_mutexes));
+  mysql_cond_register("sql", all_tc_conds, array_elements(all_tc_conds));
 #endif
+  /* Extra instance is allocated to avoid false sharing */
+  if (!(tc= new Table_cache_instance[tc_instances + 1]))
+    DBUG_RETURN(true);
   tdc_inited= true;
   mysql_mutex_init(key_LOCK_unused_shares, &LOCK_unused_shares,
                    MY_MUTEX_INIT_FAST);
   tdc_version= 1L;  /* Increments on each reload */
-  lf_hash_init(&tdc_hash, sizeof(TDC_element), LF_HASH_UNIQUE, 0, 0,
+  lf_hash_init(&tdc_hash, sizeof(TDC_element) +
+                          sizeof(Share_free_tables) * (tc_instances - 1),
+               LF_HASH_UNIQUE, 0, 0,
                (my_hash_get_key) tdc_hash_key,
                &my_charset_bin);
   tdc_hash.alloc.constructor= lf_alloc_constructor;
   tdc_hash.alloc.destructor= lf_alloc_destructor;
   tdc_hash.initializer= (lf_hash_initializer) tdc_hash_initializer;
-  DBUG_VOID_RETURN;
+  DBUG_RETURN(false);
 }
 
 
@@ -631,6 +588,7 @@ void tdc_deinit(void)
     tdc_inited= false;
     lf_hash_destroy(&tdc_hash);
     mysql_mutex_destroy(&LOCK_unused_shares);
+    delete [] tc;
   }
   DBUG_VOID_RETURN;
 }
@@ -1038,7 +996,7 @@ bool tdc_remove_table(THD *thd, enum_tdc_remove_table_type remove_type,
                       const char *db, const char *table_name,
                       bool kill_delayed_threads)
 {
-  TDC_element::TABLE_list purge_tables;
+  Share_free_tables::List purge_tables;
   TABLE *table;
   TDC_element *element;
   uint my_refs= 1;

sql/table_cache.h

@@ -18,6 +18,15 @@
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
 
 
+struct Share_free_tables
+{
+  typedef I_P_List <TABLE, TABLE_share> List;
+  List list;
+  /** Avoid false sharing between instances */
+  char pad[CPU_LEVEL1_DCACHE_LINESIZE];
+};
+
+
 struct TDC_element
 {
   uchar m_key[NAME_LEN + 1 + NAME_LEN + 1];
@@ -26,10 +35,8 @@ struct TDC_element
   bool flushed;
   TABLE_SHARE *share;
 
-  typedef I_P_List <TABLE, TABLE_share> TABLE_list;
   /**
-    Protects ref_count, m_flush_tickets, all_tables, free_tables, flushed,
+    Protects ref_count, m_flush_tickets, all_tables, flushed, all_tables_refs.
-    all_tables_refs.
   */
   mysql_mutex_t LOCK_table_share;
   mysql_cond_t COND_release;
@@ -45,7 +52,9 @@ struct TDC_element
     for this share.
   */
   All_share_tables_list all_tables;
-  TABLE_list free_tables;
+  /** Avoid false sharing between TDC_element and free_tables */
+  char pad[CPU_LEVEL1_DCACHE_LINESIZE];
+  Share_free_tables free_tables[1];
 };
 
 
@@ -59,8 +68,9 @@ enum enum_tdc_remove_table_type
 
 extern ulong tdc_size;
 extern ulong tc_size;
+extern ulong tc_instances;
 
-extern void tdc_init(void);
+extern bool tdc_init(void);
 extern void tdc_start_shutdown(void);
 extern void tdc_deinit(void);
 extern ulong tdc_records(void);
@@ -86,7 +96,7 @@ extern int tdc_iterate(THD *thd, my_hash_walk_action action, void *argument,
 extern uint tc_records(void);
 extern void tc_purge(bool mark_flushed= false);
 extern void tc_add_table(THD *thd, TABLE *table);
-extern bool tc_release_table(TABLE *table);
+extern void tc_release_table(TABLE *table);
 
 /**
   Create a table cache key for non-temporary table.