Hi Brain, 
I think Gabriel talked about memory leak in query cache + xtradb (or innodb)
Elena put this comment in JIRA:

The fix should be in 5.5.32 release. The bug was fixed in XtraDB 5.5.32 (at least it is marked as such inhttps://bugs.launchpad.net/percona-server/+bug/1170103), and MariaDB 5.5.32 includes XtraDB 5.5.32. 
We didn't have a reproducible test case to verify it, so please re-open the issue (or comment on it to get it re-opened) if you still have the problem with MariaDB 5.5.32,

and reporter (Gabriel), send this comment:
Gabriel Sosa added a comment - Today 14:01
excellent! perfect. Thanks for your time

Gabriel, i made this:
try a small database with 5.5.32 and check if bug persist, if not, upgrade production servers without problems 
i updated 3 production servers and they are working normally without the bug and query cache enabled, i'm using xtradb (not innodb plugin)