zcache: a compressed page cache

zlib was shown many years ago to be suboptimal w.r.t memory compression. There are a few new papers (2-4 years old I think) that pit zlib vs. lzo vs. a solution specific to 'normal' operating system memory usage patterns with the latter coming in around 1.3x better and 4x faster. The author should really look into these papers if he/she hasn't already.