MDEV-6150 Speed up connection speed by moving creation of THD to new thread

Creating a CONNECT object on client connect and pass this to the working thread which creates the THD.
Split LOCK_thread_count to different mutexes
Added LOCK_thread_start to syncronize threads
Moved most usage of LOCK_thread_count to dedicated functions
Use next_thread_id() instead of thread_id++

Other things:
- Thread id now starts from 1 instead of 2
- Added cast for thread_id as thread id is now of type my_thread_id
- Made THD->host const (To ensure it's not changed)
- Removed some DBUG_PRINT() about entering/exiting mutex as these was already logged by mutex code
- Fixed that aborted_connects and connection_errors_internal are counted in all cases
- Don't take locks for current_linfo when we set it (not needed as it was 0 before)

1 files changed, 44 insertions, 30 deletions

diff --git a/sql/threadpool_unix.cc b/sql/threadpool_unix.cc
index 89a2036cb10..684b074f9f0 100644
--- a/sql/threadpool_unix.cc
+++ b/sql/threadpool_unix.cc
@@ -809,7 +809,7 @@ static int create_worker(thread_group_t *thread_group)
   if (!err)
   {
     thread_group->last_thread_creation_time=microsecond_interval_timer();
-    thread_created++;
+    statistic_increment(thread_created,&LOCK_status);
     add_thread_count(thread_group, 1);
   }
   else
@@ -1203,14 +1203,14 @@ void wait_end(thread_group_t *thread_group)
   Allocate/initialize a new connection structure.
 */
 
-connection_t *alloc_connection(THD *thd)
+connection_t *alloc_connection()
 {
+  connection_t* connection;
   DBUG_ENTER("alloc_connection");
+  DBUG_EXECUTE_IF("simulate_failed_connection_1", DBUG_RETURN(0); );
   
-  connection_t* connection = (connection_t *)my_malloc(sizeof(connection_t),0);
-  if (connection)
+  if ((connection = (connection_t *)my_malloc(sizeof(connection_t),0)))
   {
-    connection->thd = thd;
     connection->waiting= false;
     connection->logged_in= false;
     connection->bound_to_poll_descriptor= false;
@@ -1225,38 +1225,40 @@ connection_t *alloc_connection(THD *thd)
   Add a new connection to thread pool..
 */
 
-void tp_add_connection(THD *thd)
+void tp_add_connection(CONNECT *connect)
 {
+  connection_t *connection;
+  THD *thd;
   DBUG_ENTER("tp_add_connection");
-  
-  threads.append(thd);
-  mysql_mutex_unlock(&LOCK_thread_count);
-  connection_t *connection= alloc_connection(thd);
-  if (connection)
+
+  if (!(connection= alloc_connection()) || !(thd= connect->create_thd()))
   {
-    thd->event_scheduler.data= connection;
+    my_free(connection);
+    connect->close_and_delete();
+    DBUG_VOID_RETURN;
+  }
+  connection->thd= thd;
+  delete connect;
+
+  add_to_active_threads(thd);
+
+  thd->event_scheduler.data= connection;
       
-    /* Assign connection to a group. */
-    thread_group_t *group= 
-      &all_groups[thd->thread_id%group_count];
+  /* Assign connection to a group. */
+  thread_group_t *group= 
+    &all_groups[thd->thread_id%group_count];
     
-    connection->thread_group=group;
+  connection->thread_group=group;
       
-    mysql_mutex_lock(&group->mutex);
-    group->connection_count++;
-    mysql_mutex_unlock(&group->mutex);
+  mysql_mutex_lock(&group->mutex);
+  group->connection_count++;
+  mysql_mutex_unlock(&group->mutex);
     
-    /*
-       Add connection to the work queue.Actual logon 
-       will be done by a worker thread.
-    */
-    queue_put(group, connection);
-  }
-  else
-  {
-    /* Allocation failed */
-    threadpool_cleanup_connection(thd);
-  } 
+  /*
+    Add connection to the work queue.Actual logon 
+    will be done by a worker thread.
+  */
+  queue_put(group, connection);
   DBUG_VOID_RETURN;
 }
 
@@ -1549,6 +1551,18 @@ bool tp_init()
 }
 
 
+/* Dummy functions, do nothing */
+
+bool tp_init_new_connection_thread()
+{
+  return 0;
+}
+
+bool tp_end_thread(THD *thd, bool cache_thread)
+{
+  return 0;
+}
+
 void tp_end()
 {
   DBUG_ENTER("tp_end");