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:

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!