-- 一句sql 獲取 mysql 最大內存用量
select (@@key_buffer_size + @@query_cache_size + @@tmp_table_size + @@innodb_buffer_pool_size + @@innodb_additional_mem_pool_size + @@innodb_log_buffer_size + @@max_connections * (@@sort_buffer_size + @@read_buffer_size + @@read_rnd_buffer_size + @@join_buffer_size + @@thread_stack + @@binlog_cache_size))/1024/1024/1024 max_mem_usage