Percona Server has had a buffer pool pages I_S table for a while, based on an earlier patch by Jeremy Cole or Eric Bergen, I think. However, I suspect that the Oracle implementation is likely to be safer. Some of the Percona I_S tables dealing with InnoDB internal information have had bugs, and I have become reluctant to use them on production systems. I am glad to see InnoDB providing their own implementation. Here is a link to the list of additional I_S tables provided in Percona Server: http://www.percona.com/docs/wiki/percona-server:features:indexes:index_info_schema_tables
I believe that we documented the query cache’s behavior, and the actual mechanism for it, in High Performance MySQL 2nd Edition. The blog post looks like FromDual has found an additional bug, though.
Percona Server has an option to limit amount of memory consumed by dictionary entries. This might be similar to what is in 5.6 from Oracle; I have not looked at the 5.6 code yet. We created this feature specifically for hosting providers :-)
