From: | Patrick Welche <prlw1(at)newn(dot)cam(dot)ac(dot)uk> |
---|---|
To: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: Possible performance improvement: buffer replacement policy |
Date: | 2001-01-19 17:53:28 |
Message-ID: | 20010119175328.A6223@quartz.newn.cam.ac.uk |
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Lists: | pgsql-hackers |
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
In-reply-to: <200010161541(dot)LAA06653(at)candle(dot)pha(dot)pa(dot)us>
References: <200010161541(dot)LAA06653(at)candle(dot)pha(dot)pa(dot)us>
Comments: In-reply-to Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
message dated "Mon, 16 Oct 2000 11:41:41 -0400"
Date: Mon, 16 Oct 2000 11:49:52 -0400
Message-ID: <26100(dot)971711392(at)sss(dot)pgh(dot)pa(dot)us>
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
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