There are too many messages in form
"InnoDB: page_cleaner: 1000ms intended loop took 4450ms. The settings might not be optimal".
An example of the flood is here https://jira.mariadb.org/secure/attachmentzip/unzip/64627/44712%5B0%5D/
A message like this is written every 15 seconds.
A better idea is to write only seldomly. If this is something performance related, you can expose the average slowness via status variable or something like that.