MySQL InnoDB page_cleaner settings might not be optimal
The innodb_page_cleaners default value was changed from 1 to 4 in MySQL 5.7.8. If the number of page cleaner threads exceeds the number of buffer pool instances, innodb_page_cleaners is automatically set to the same value as innodb_buffer_pool_instances


Check innodb_buffer_pool_instances with:

mysql&gt; SHOW GLOBAL VARIABLES LIKE 'innodb_buffer_pool_instances'


You can only set innodb_page_cleaners as high as innodb_buffer_pool_instances. If you want innodb_page_cleaners=4 then you also need innodb_buffer_pool_instances=4.