threadpool_size can contribute to the wanted_files

sql/mysqld.cc

@@ -4088,6 +4088,10 @@ static int init_common_variables()
     /* MyISAM requires two file handles per table. */
     wanted_files= (10 + max_connections + extra_max_connections +
                    tc_size * 2);
+#if defined(HAVE_POOL_OF_THREADS) && !defined(__WIN__)
+    // add epoll or kevent fd for each threadpool group, in case pool of threads is used
+    wanted_file+= (thread_handling > SCHEDULER_NO_THREADS) ? 0 : threadpool_size;
+#endif
     /*
       We are trying to allocate no less than max_connections*5 file
       handles (i.e. we are trying to set the limit so that they will