The InnoDB Page Cleaner Thread is an InnoDB background thread that flushes dirty pages from the InnoDB Buffer Pool to disk. Prior MySQL 5.6 this action was performed by the InnoDB Master Thread.
When we analyze our customers systems we see typically a high fragmentation of the query cache after a while. This leads to a less optimal use of the Query Cache than possible.
With the following Query you can see the values for your Query Cache:
