ZRAM if you have no HDD/SSD swap partition.
ZSWAP if you do have a HDD/SSD swap partition.
ZCACHE: It does what ZSWAP does and ALSO compresses and speeds the filesystem page cache. (It is internally much more complicated and is not in the mainline kernel as it is still under development).
B. Plank, and G. van Noord. Proceedings of the 2010 Workshop on NLP and Linguistics: Finding the Common Ground, page 25--33. Stroudsburg, PA, USA, Association for Computational Linguistics, (2010)
C. Christodoulopoulos, S. Goldwater, and M. Steedman. Proceedings of the 2010 Conference on Empirical Methods in Natural Language Processing, page 575--584. Stroudsburg, PA, USA, Association for Computational Linguistics, (2010)