Why does MySQL uses only 0.5% Memory for every query?

Why does MySQL uses only 0.5% Memory of 4 available GBs for every query on a huge ta开发者_开发问答ble containing many joins and millions of rows? Is this an indicator for a false configured MySQL-Server?

Silly me. There were two indices missing. The performance is good now. It still uses only 0.5% of memory in average and that's fine with me! =)