MDEV-22696 TP_pool_generic::set_pool_size logic so that it marks each...

MDEV-22696 TP_pool_generic::set_pool_size logic so that it marks each connection to change group before the next socket read.

sql/threadpool_generic.cc

@@ -1375,6 +1375,12 @@ static void set_next_timeout_check(ulonglong abstime)
   DBUG_VOID_RETURN;
 }
 
+static size_t get_group_id(my_thread_id tid)
+{
+  return size_t(tid % group_count);
+}
+
+
 TP_connection_generic::TP_connection_generic(CONNECT *c):
   TP_connection(c),
   thread_group(0),
@@ -1382,10 +1388,14 @@ TP_connection_generic::TP_connection_generic(CONNECT *c):
   prev_in_queue(0),
   abs_wait_timeout(ULONGLONG_MAX),
   bound_to_poll_descriptor(false),
-  waiting(false)
+  waiting(false),
+  fix_group(false)
 #ifdef HAVE_IOCP
 , overlapped()
 #endif
+#ifdef _WIN32
+, vio_type(c->vio_type)
+#endif
 {
   DBUG_ASSERT(c->vio_type != VIO_CLOSED);
 
@@ -1398,8 +1408,7 @@ TP_connection_generic::TP_connection_generic(CONNECT *c):
 
   /* Assign connection to a group. */
   thread_group_t *group=
-    &all_groups[c->thread_id%group_count];
-
+    &all_groups[get_group_id(c->thread_id)];
   thread_group=group;
 
   mysql_mutex_lock(&group->mutex);
@@ -1473,6 +1482,7 @@ static int change_group(TP_connection_generic *c,
   return ret;
 }
 
+
 int TP_connection_generic::start_io()
 {
   /*
@@ -1485,14 +1495,17 @@ int TP_connection_generic::start_io()
     So we recalculate in which group the connection should be, based
     on thread_id and current group count, and migrate if necessary.
   */
-  thread_group_t *group = 
-    &all_groups[thd->thread_id%group_count];
+  if (fix_group)
+  {
+    fix_group = false;
+    thread_group_t *new_group= &all_groups[get_group_id(thd->thread_id)];
 
-  if (group != thread_group)
+    if (new_group != thread_group)
     {
-    if (change_group(this, thread_group, group))
+      if (change_group(this, thread_group, new_group))
         return -1;
     }
+  }
 
   /* 
     Bind to poll descriptor if not yet done. 
@@ -1615,6 +1628,14 @@ TP_pool_generic::~TP_pool_generic()
 }
 
 
+static my_bool thd_reset_group(THD* thd, void*)
+{
+  auto c= (TP_connection_generic*)thd->event_scheduler.data;
+  if(c)
+    c->fix_group= true;
+  return FALSE;
+}
+
 /** Ensure that poll descriptors are created when threadpool_size changes */
 int TP_pool_generic::set_pool_size(uint size)
 {
@@ -1641,6 +1662,7 @@ int TP_pool_generic::set_pool_size(uint size)
     }
   }
   group_count= size;
+  server_threads.iterate(thd_reset_group);
   return 0;
 }
 

sql/threadpool_generic.h

@@ -89,6 +89,7 @@ struct TP_connection_generic :public TP_connection
   TP_file_handle fd;
   bool bound_to_poll_descriptor;
   int waiting;
+  bool fix_group;
 #ifdef HAVE_IOCP
   OVERLAPPED overlapped;
 #endif