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(at)candle(dot)pha(dot)pa(dot)us>
cc: pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: [HACKERS] Possible performance improvement: buffer replacement policy
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Comments: In-reply-to Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
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Date: Mon, 16 Oct 2000 11:49:52 -0400
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From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
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Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)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