pg.ddx.io pgsql-admin@postgresql.org mailing list archive help / color / mirror / Atom feed From: Bruce Momjian <bruce@momjian.us>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Alvaro Herrera <alvherre@commandprompt.com>
Cc: valiouk@yahoo.co.uk, pgsql-docs@postgresql.org, dx k9 <bitsandbytes88@hotmail.com>
Subject: Re: [ADMIN] shared_buffers and shmmax
Date: Tue, 16 Dec 2008 20:33:36 -0500 (EST)
Message-ID: <200812170133.mBH1Xac23918@momjian.us> (raw )
In-Reply-To: <17528.1229470697@sss.pgh.pa.us >
Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > OK, updated patch. I added item descriptions and removed Alvaro's
> > paragraph; I worked with Alvaro on this patch.
>
> This still seems pretty misleading, as for example
>
> > <tbody>
> > <row>
> > <entry><xref linkend="guc-max-connections"></>
> > ! <entry>1800 + 270 * <xref
> > ! linkend="guc-max-locks-per-transaction"> bytes per connection</entry>
> > </row>
>
> sounds like it might mean bytes per *active* connection, when of course
> the correct way to figure it is by multiplying by max_connections.
> If you're going to give a formula, why not just give a formula, eg
>
> (1800 + 270 * max_locks_per_transaction) * (max_connections + autovacuum_max_workers)
>
> regards, tom lane
You mean like this:
http://momjian.us/tmp/pgsql/kernel-resources.html
--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
Attachments:
/pgpatches/shared_mem_table (text/plain, 3.4K) download
Index: doc/src/sgml/runtime.sgml
===================================================================
RCS file: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v
retrieving revision 1.423
diff -c -c -r1.423 runtime.sgml
*** doc/src/sgml/runtime.sgml 16 Dec 2008 19:30:43 -0000 1.423
--- doc/src/sgml/runtime.sgml 17 Dec 2008 01:30:21 -0000
***************
*** 1087,1141 ****
<thead>
<row>
<entry>Name</>
! <entry>Approximate multiplier (bytes per increment) as of 8.3</>
</row>
</thead>
<tbody>
<row>
! <entry><xref linkend="guc-max-connections"></>
! <entry>1800 + 270 * <xref linkend="guc-max-locks-per-transaction"></entry>
! </row>
!
! <row>
! <entry><xref linkend="guc-autovacuum-max-workers"></>
! <entry>1800 + 270 * <xref linkend="guc-max-locks-per-transaction"></entry>
</row>
<row>
<entry><xref linkend="guc-max-prepared-transactions"></>
! <entry>770 + 270 * <xref linkend="guc-max-locks-per-transaction"></entry>
</row>
<row>
<entry><xref linkend="guc-shared-buffers"></>
! <entry>8400 (assuming 8 kB <symbol>BLCKSZ</>)</entry>
</row>
<row>
<entry><xref linkend="guc-wal-buffers"></>
! <entry>8200 (assuming 8 kB <symbol>XLOG_BLCKSZ</>)</entry>
</row>
<row>
<entry>Fixed space requirements</>
! <entry>770 kB</entry>
</row>
</tbody>
</tgroup>
</table>
! <note>
! <para>
! The multipliers for <varname>shared_buffers</> and
! <varname>wal_buffers</> should be the number of buffers, not the
! amount in bytes. To find out the number of shared or wal buffers, divide
! the amount in bytes by <xref linkend="guc-block-size"> and
! <xref linkend="guc-wal-block-size">, respectively.
! </para>
! </note>
! </sect2>
!
<sect2>
<title>Resource Limits</title>
--- 1087,1132 ----
<thead>
<row>
<entry>Name</>
! <entry>Shared memory bytes required, as of 8.3</>
</row>
</thead>
<tbody>
<row>
! <entry><xref linkend="guc-max-connections">, <xref linkend="guc-autovacuum-max-workers"></>
! <entry>(1800 + 270 * <xref
! linkend="guc-max-locks-per-transaction">) * (<xref
! linkend="guc-max-connections"> + <xref linkend="guc-autovacuum-max-workers">)</entry>
</row>
<row>
<entry><xref linkend="guc-max-prepared-transactions"></>
! <entry>(770 + 270 * <xref
! linkend="guc-max-locks-per-transaction">) * <xref linkend="guc-max-prepared-transactions"></entry>
</row>
<row>
<entry><xref linkend="guc-shared-buffers"></>
! <entry>(<xref linkend="guc-block-size"> + 208) * <xref linkend="guc-shared-buffers"></entry>
</row>
<row>
<entry><xref linkend="guc-wal-buffers"></>
! <entry>(<xref linkend="guc-wal-block-size"> + 8) * <xref linkend="guc-wal-buffers"></entry>
</row>
<row>
<entry>Fixed space requirements</>
! <entry>770k bytes</entry>
</row>
</tbody>
</tgroup>
</table>
! <para>
! These shared memory allocations are reserved at database server
! start and remain static.
! </para>
<sect2>
<title>Resource Limits</title>
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To: pgsql-admin@postgresql.org
Cc: bruce@momjian.us, tgl@sss.pgh.pa.us, alvherre@commandprompt.com, bitsandbytes88@hotmail.com
Subject: Re: [ADMIN] shared_buffers and shmmax
In-Reply-To: <200812170133.mBH1Xac23918@momjian.us>
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