We lately mved to MySQL V5.5 on CentOS release 6.7 with master and 2 slaves. Since then the replication process lags a lot behind the master with the line in the process list of: invalidating query cache entries (table).
the global query_cache_type & size were set to=0.
I have checked around and i can see its a known old bug in MySQL https://bugs.mysql.com/bug.php?id=60696 but could not find a workaround for this issue. Any advice? Thanks,