Re: Possible performance improvement: buffer replacement policy

On Fri, Jan 19, 2001 at 12:03:58PM -0500, Bruce Momjian wrote:
> 
> Tom, did we ever test this?  I think we did and found that it was the
> same or worse, right?

(Funnily enough, I just read that message:)

To: Bruce Momjian <pgman@candle.pha.pa.us>
cc: pgsql-hackers@postgreSQL.org
Subject: Re: [HACKERS] Possible performance improvement: buffer replacement policy 
In-reply-to: <200010161541.LAA06653@candle.pha.pa.us> 
References: <200010161541.LAA06653@candle.pha.pa.us>
Comments: In-reply-to Bruce Momjian <pgman@candle.pha.pa.us>message dated "Mon, 16 Oct 2000 11:41:41 -0400"
Date: Mon, 16 Oct 2000 11:49:52 -0400
Message-ID: <26100.971711392@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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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