InnoDB uses at least two lists to manage pages in the buffer pool. The LRU is used for pages from compressed and uncompressed tables. If a table is uncompressed then it only uses the LRU. If a table is compressed then compressed pages are on the LRU and the unzip_LRU is used for pages that have an uncompressed and compressed version in the buffer pool. When a server is IO bound then InnoDB allows the unzip_LRU to be 10% the size of the LRU. SHOW INNODB STATUS displays the length of the LRU and unzip_LRU (grep it for "unzip_LRU"). Note that I use the word page in some places when frame might be appropriate.
The …[Read more]