Quoting from the forums:
I'm trying to migrate my application from 2.5.6 to 3.0.0. Surprisingly I can see a significant higher memory consumption in 3.0.0. The DefaultListableBeanFactory uses 8.5 mb in spring 2.5.6 and about 90 mb in spring 3.0.0. As far as I can see, a large part of the memory consumption is due to the usage of CachingMetadataReaderFactory.