Possible memory leak in percona server

[Steffen Boehme]

A few days ago we updated some of our database servers to the current latest version 5.5.30-30.2.
The days after we found the server consumed more memory then allowed over the time.
Our server runs with exactly the same configuration weeks before and the memory consumption was fine all the time, but after the upgrade I noticed a permanent incrementation of the memory consumption of the server process until all memory was in use and the server starts swapping and we had to restart the instance.

I downgraded the server to version 5.5.30-30.1, since we had also running instances with the same load on this versions and those servers did not show this behavior.

And voila, after downgrading all was fine again ,-).

So I assume there is some kind of memory leak in the latest version.
It may be this comes only up with enough load on the servers.
In our case we have 3 db slaves acting as read only notes for our web application.
Each server has 2 percona instances running with avg 4000 (5000 max) queries/sec on the one and avg 2500 (3300 max) queries/sec on the other instance.
The instances data are ~110GB and ~50GB.

As example I would give you this numbers for the moment:
Thats the stats for the second instance with ~2500 q/sec

root@dbslave:~# ps -p 7471 -o pid,cmd,rss,vsz,size
  PID CMD RSS VSZ SIZE
 7471 /usr/sbin/mysqld --defaults 16504096 23791408 23744528

The server runs with 6GB inno db buffer pool size, 2,5GB Key buffer and 224MB query cache.
The other buffers are also moderate (the global and the per connection buffers).
The underlying hardware has 64G Ram.
The memory consumption persists even if no (or nearly no) connections are on the server ...

The Global Variables and Status numbers are attached ...

[Alexey Kopytov (akopytov)]

Thanks. 5.5.30-30.2 indeed introduced a memory leak which has already been reported as bug #1170103. It will be fixed in the next Percona Server 5.5 release. The workaround is to disable the query cache (query_cache_type=0).