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From: Greg Smith <greg@2ndQuadrant.com>
To: pgsql-hackers@postgresql.org
Subject: Re: Page replacement algorithm in buffer cache
Date: Wed, 03 Apr 2013 21:49:20 -0400
Message-ID: <515CDC20.5090005@2ndQuadrant.com> (raw)
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On 4/2/13 11:54 AM, Robert Haas wrote:
> But, having said that, I still think the best idea is what Andres
> proposed, which pretty much matches my own thoughts: the bgwriter
> needs to populate the free list, so that buffer allocations don't have
> to wait for linear scans of the buffer array.

I was hoping this one would make it to a full six years of being on the 
TODO list before it came up again, missed it by a few weeks.  The 
funniest part is that Amit even submitted a patch on this theme a few 
months ago without much feedback: 
http://www.postgresql.org/message-id/6C0B27F7206C9E4CA54AE035729E9C382852FF97@szxeml509-mbs 
  That stalled where a few things have, on a) needing more regression 
test workloads, and b) wondering just what the deal with large 
shared_buffers setting degrading performance was.

I saw refactoring in this area as waiting behind it being easier to 
experiment with adding new processes, but that barrier has fallen now. 
Maybe it needs a new freelist process, maybe it doesn't, today the code 
needed to try both is relatively cheap.

The other thing that always seemed to stop me was never having a typical 
Linux system big enough to hit some of these problems available all the 
time.  What I did this week on that front was just go buy a 24 core 
server with 64GB of RAM that lives in my house.  I just need to keep it 
two floors away if I want to sleep at night.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com


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