From: | Bruce Momjian <bruce(at)momjian(dot)us> |
---|---|
To: | Satoshi Nagayasu <snaga(at)uptime(dot)jp> |
Cc: | pgsql-docs(at)postgresql(dot)org |
Subject: | Re: pg_buffercache description |
Date: | 2013-07-03 18:23:11 |
Message-ID: | 20130703182311.GC6521@momjian.us |
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Thread: | |
Lists: | pgsql-docs |
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.
--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
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