Is it normal for MySQL to gradually increase memory usage over time?

Is it normal for MySQL to increase memory usage over time? See image below of my server's memory usage over the last two weeks. After "service mysql restart" it drops to 40%. The database is used by a node.js app. Server has 4GB of RAM with below additions to mysqld.cnf:

language=no-lang
innodb_ft_min_token_size = 1   
ft_min_word_len = 1  
innodb_buffer_pool_size = 3G  
innodb_buffer_pool_instances = 5  
innodb_read_io_threads = 8  
innodb_write_io_threads = 8  
innodb_log_file_size = 128M  
innodb_flush_method = O_DIRECT  
max_connections = 300  
long_query_time = 1  
innodb_ft_enable_stopword = 0

Thank you!