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Message-ID: <51D59FD6.3080901@uptime.jp>
Date: Fri, 05 Jul 2013 01:16:22 +0900
From: Satoshi Nagayasu <snaga@uptime.jp>
Organization: Uptime Technologies, LLC
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To: Bruce Momjian <bruce@momjian.us>
CC: pgsql-docs@postgresql.org
Subject: Re: pg_buffercache description
References: <50B037AF.4040900@uptime.jp> <20130703182311.GC6521@momjian.us>
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Thanks, Bruce!

2013/07/04 3:26, Bruce Momjian wrote:
> On Wed, Jul  3, 2013 at 02:23:11PM -0400, Bruce Momjian wrote:
>> On Sat, Nov 24, 2012 at 11:57:51AM +0900, Satoshi Nagayasu wrote:
>>> Hi,
>>>
>>> I found that the manual page for pg_buffercache module explains
>>> "usagecount" as "Page LRU count".
>>>
>>> http://www.postgresql.org/docs/devel/static/pgbuffercache.html
>>>
>>> However, AFAIK, "usagecount" is not a LRU count nowadays, because
>>> LRU is no longer used for the buffer management algorithm.
>>>
>>> I think it should be described as "Clock-sweep count" or something
>>> like that.
>>>
>>> And I'd like to add some additional explanation for the "forknumber"
>>> as below:
>>>
>>> "0 for heap file, 1 for FreeSpaceMap, and 2 for VisibilityMap".
>>>
>>> Any comments?
>>
>> Good suggestion.  I ended up referencing the C file that contains the
>> "forknumber" definitions, rather than recreating the list in the docs.
>> I applied the attached patch to head and 9.3.
>
> I ended up applying it to 9.2 as well.
>


-- 
Satoshi Nagayasu <snaga@uptime.jp>
Uptime Technologies, LLC. http://www.uptime.jp


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