Re: Possible performance improvement: buffer replacement policy

Bruce Momjian <pgman@candle.pha.pa.us> writes:
>> It looks like it wouldn't take too much work to replace shared buffers
>> on the basis of LRU-2 instead of LRU, so I'm thinking about trying it.
>> 
>> Has anyone looked into this area?  Is there a better method to try?

> Sounds like a perfect idea.  Good luck.  :-)

Actually, the idea went down in flames :-(, but I neglected to report
back to pghackers about it.  I did do some code to manage buffers as
LRU-2.  I didn't have any good performance test cases to try it with,
but Richard Brosnahan was kind enough to re-run the TPC tests previously
published by Great Bridge with that code in place.  Wasn't any faster,
in fact possibly a little slower, likely due to the extra CPU time spent
on buffer freelist management.  It's possible that other scenarios might
show a better result, but right now I feel pretty discouraged about the
LRU-2 idea and am not pursuing it.
        regards, tom lane