While compiling Tagsistant you can choose to enable some experimental features by editing tagsistant.h in the src/ directory. The flags are those reported by the stats/configuration file in the compile flags section.
The only four flags you are supposed to tweak are:
Their purpose is to enable some caching layers to dramatically reduce the volume of SQL queries done. While the second and the third are stable and don't cause too much memory consumption, so being safely enabled on production, the first (the querytree cache) is quite experimental and can cause Tagsistant to exhaust memory during huge data loading.
The suggested configuration is:
Change it at your own risk.