According to empirical results (I doubt there is any analytic
demonstration) that you can find in any good OS book, LRU is the
algorithm which is most closed the OPT algorithm (select the page wich
will be used more far away in the future) for page replacement.
LRU is exactly the "opposite" to OPT, it reverts future to past. If you
believes in programs' locality* (in space and time), you should believe
in LRU. Problems arise with your understanding of "least". How do you
measure it? (I am going to take a look to Andrea's code, I can learn a
lot). Do you timestamp the last referece to every page? What's the
resolution? Do you maintain an ordered list of pages according to their
timestamp? If not, you may get closer to CLOCK, which is in fact a
"second chance" FIFO.
Andrea, can you give some pointers to the kernel files where you play
around this?
* I believe this is normally true for no bloating software written in C
or Pascal, but I really doubt it's still true for a C++ program ;-)
-- Ricardo Galli
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