memory leak with "in memory" storage?

[Eneko Ibarzabal]

I am using a 64 bit linux machine with 64Gb RAM and mysql 5.1.31.

The idea is that in my company we store data in a database engine, using regular disk storage, and everyday we move that data using CSV files into mysql in memory tables, for high performance reporting.

I created the db schema and tables and after importing data into mysql, which uses approximately 35 Gb, everything works fine. The problem comes when I perform delete operations. If I delete from or drop tables, memory usage does not decrease to the same extent as when I populated the tables. As a matter of fact, if I drop all the in memory tables, the mysqld process is still using far more memory than before populating the tables. Even if I restart mysql, it uses much more memory than after restarting the linux server.

Has anyone experienced similar problems? Thanks in advance!