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, 14 insertions, 7 deletions

diff --git a/sql/scheduler.cc b/sql/scheduler.cc
index bc3166210b5..2a0138d06a8 100644
--- a/sql/scheduler.cc
+++ b/sql/scheduler.cc
@@ -22,9 +22,9 @@
 #pragma implementation
 #endif
 
+#include "mysqld.h"
 #include "sql_connect.h"         // init_new_connection_handler_thread
 #include "scheduler.h"
-#include "mysqld.h"
 #include "sql_class.h"
 #include "sql_callback.h"
 #include <violite.h>
@@ -35,7 +35,8 @@
 
 static bool no_threads_end(THD *thd, bool put_in_cache)
 {
-  unlink_thd(thd);
+  if (thd)
+    unlink_thd(thd);
   return 1;                                     // Abort handle_one_connection
 }
 
@@ -81,7 +82,9 @@ static void scheduler_wait_net_end(void) {
   one_thread_scheduler() or one_thread_per_connection_scheduler() in
   mysqld.cc, so this init function will always be called.
  */
-void scheduler_init() {
+
+void scheduler_init()
+{
   thr_set_lock_wait_callback(scheduler_wait_lock_begin,
                              scheduler_wait_lock_end);
   thr_set_sync_wait_callback(scheduler_wait_sync_begin,
@@ -118,7 +121,6 @@ void post_kill_notification(THD *thd)
 
 #ifndef EMBEDDED_LIBRARY
 
-
 void one_thread_per_connection_scheduler(scheduler_functions *func,
     ulong *arg_max_connections,
     uint *arg_connection_count)
@@ -132,6 +134,14 @@ void one_thread_per_connection_scheduler(scheduler_functions *func,
   func->end_thread= one_thread_per_connection_end;
   func->post_kill_notification= post_kill_notification;
 }
+#else
+bool init_new_connection_handler_thread()
+{
+  return 0;
+}
+void handle_connection_in_main_thread(CONNECT *connect)
+{
+}
 #endif
 
 /*
@@ -144,10 +154,7 @@ void one_thread_scheduler(scheduler_functions *func)
   func->max_threads= 1;
   func->max_connections= &max_connections;
   func->connection_count= &connection_count;
-#ifndef EMBEDDED_LIBRARY
   func->init_new_connection_thread= init_new_connection_handler_thread;
   func->add_connection= handle_connection_in_main_thread;
-#endif
   func->end_thread= no_threads_end;
 }
-