I was researching on cache replacement strategy as well. 2Q has one
disadvantage see this exellent paper:
http://www.almaden.ibm.com/cs/people/dmodha/#ARC see the paper
"ARC: A Self-Tuning, Low Overhead Replacement Cache" for theory and "One
Up on LRU" for implementation details. ARC requires no tuning and can
switch fast between chaging patterns. Best of all is it is resistant to a
"sequential scan" pattern. and i think it's even easier to implement then
2q :)
does pgbench test with relatively large sequential scans?