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* pg_buffercache description
@ 2012-11-24 02:57 Satoshi Nagayasu <[email protected]>
0 siblings, 1 reply; 4+ messages in thread
From: Satoshi Nagayasu @ 2012-11-24 02:57 UTC (permalink / raw)
To: pgsql-docs
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?
Regards,
--
Satoshi Nagayasu <[email protected]>
Uptime Technologies, LLC. http://www.uptime.jp
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: pg_buffercache description
@ 2013-07-03 18:23 Bruce Momjian <[email protected]>
parent: Satoshi Nagayasu <[email protected]>
0 siblings, 1 reply; 4+ messages in thread
From: Bruce Momjian @ 2013-07-03 18:23 UTC (permalink / raw)
To: Satoshi Nagayasu <[email protected]>; +Cc: 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 <[email protected]> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
--
Sent via pgsql-docs mailing list ([email protected])
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Attachments:
[text/x-diff] buffer.diff (1.2K, 2-buffer.diff)
download | inline diff:
diff --git a/doc/src/sgml/pgbuffercache.sgml b/doc/src/sgml/pgbuffercache.sgml
new file mode 100644
index 1d7d95f..685351f
*** a/doc/src/sgml/pgbuffercache.sgml
--- b/doc/src/sgml/pgbuffercache.sgml
***************
*** 84,90 ****
<entry><structfield>relforknumber</structfield></entry>
<entry><type>smallint</type></entry>
<entry></entry>
! <entry>Fork number within the relation</entry>
</row>
<row>
--- 84,91 ----
<entry><structfield>relforknumber</structfield></entry>
<entry><type>smallint</type></entry>
<entry></entry>
! <entry>Fork number within the relation; see
! <filename>include/storage/relfilenode.h</></entry>
</row>
<row>
***************
*** 98,104 ****
<entry><structfield>usagecount</structfield></entry>
<entry><type>smallint</type></entry>
<entry></entry>
! <entry>Page LRU count</entry>
</row>
</tbody>
--- 99,105 ----
<entry><structfield>usagecount</structfield></entry>
<entry><type>smallint</type></entry>
<entry></entry>
! <entry>Clock-sweep access count</entry>
</row>
</tbody>
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: pg_buffercache description
@ 2013-07-03 18:26 Bruce Momjian <[email protected]>
parent: Bruce Momjian <[email protected]>
0 siblings, 1 reply; 4+ messages in thread
From: Bruce Momjian @ 2013-07-03 18:26 UTC (permalink / raw)
To: Satoshi Nagayasu <[email protected]>; +Cc: pgsql-docs
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.
--
Bruce Momjian <[email protected]> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
--
Sent via pgsql-docs mailing list ([email protected])
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-docs
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: pg_buffercache description
@ 2013-07-04 16:16 Satoshi Nagayasu <[email protected]>
parent: Bruce Momjian <[email protected]>
0 siblings, 0 replies; 4+ messages in thread
From: Satoshi Nagayasu @ 2013-07-04 16:16 UTC (permalink / raw)
To: Bruce Momjian <[email protected]>; +Cc: pgsql-docs
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 <[email protected]>
Uptime Technologies, LLC. http://www.uptime.jp
--
Sent via pgsql-docs mailing list ([email protected])
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-docs
^ permalink raw reply [nested|flat] 4+ messages in thread
end of thread, other threads:[~2013-07-04 16:16 UTC | newest]
Thread overview: 4+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2012-11-24 02:57 pg_buffercache description Satoshi Nagayasu <[email protected]>
2013-07-03 18:23 ` Bruce Momjian <[email protected]>
2013-07-03 18:26 ` Bruce Momjian <[email protected]>
2013-07-04 16:16 ` Satoshi Nagayasu <[email protected]>
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