Received: from maia.hub.org (maia-2.hub.org [200.46.204.251])
	by mail.postgresql.org (Postfix) with ESMTP id D14A41337990
	for <pgsql-performance-postgresql.org@mail.postgresql.org>;
	Mon,  2 May 2011 08:01:51 -0300 (ADT)
Received: from mail.postgresql.org ([200.46.204.86])
	by maia.hub.org (mx1.hub.org [200.46.204.251]) (amavisd-maia,
	port 10024) with ESMTP id 91033-05
	for <pgsql-performance-postgresql.org@mail.postgresql.org>;
	Mon,  2 May 2011 11:01:33 +0000 (UTC)
X-Greylist: from auto-whitelisted by SQLgrey-1.7.6
Received: from smtp110.dfw.emailsrvr.com (smtp110.dfw.emailsrvr.com
	[67.192.241.110])
	by mail.postgresql.org (Postfix) with ESMTP id 3227B13364DE
	for <pgsql-performance@postgresql.org>;
	Mon,  2 May 2011 08:01:32 -0300 (ADT)
Received: from localhost (localhost.localdomain [127.0.0.1])
	by smtp21.relay.dfw1a.emailsrvr.com (SMTP Server) with ESMTP id
	0465A24063D; Mon,  2 May 2011 07:01:33 -0400 (EDT)
X-Virus-Scanned: OK
Received: by smtp21.relay.dfw1a.emailsrvr.com (Authenticated sender:
	adarsh.sharma-AT-orkash.com) with ESMTPSA id AB7E8240112;
	Mon,  2 May 2011 07:01:31 -0400 (EDT)
Message-ID: <4DBE8F17.9060204@orkash.com>
Date: Mon, 02 May 2011 16:31:43 +0530
From: Adarsh Sharma <adarsh.sharma@orkash.com>
User-Agent: Thunderbird 2.0.0.22 (X11/20090625)
MIME-Version: 1.0
To: Tomas Vondra <tv@fuzzy.cz>
CC: pgsql-performance@postgresql.org
Subject: Re: The right SHMMAX and FILE_MAX
References: <BANLkTinCr_+Hs_zzHPb+tBdtuLFhrsfKdg@mail.gmail.com>
	<4DBE38BB.7040106@orkash.com> <4DBE8C6B.9070208@fuzzy.cz>
In-Reply-To: <4DBE8C6B.9070208@fuzzy.cz>
Content-Type: multipart/alternative;
	boundary="------------080905050803000208060906"
X-Virus-Scanned: Maia Mailguard 1.0.1
X-Spam-Status: No, hits=-1.899 tagged_above=-10 required=5
	tests=BAYES_00=-1.9, HTML_MESSAGE=0.001
X-Spam-Level: 
X-Archive-Number: 201105/14
X-Sequence-Number: 43523

This is a multi-part message in MIME format.
--------------080905050803000208060906
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit

Tomas Vondra wrote:
> Dne 2.5.2011 06:53, Adarsh Sharma napsal(a):
>   
>> I am also in need of a proper documentation that explains how to set 
>> SHMAX and SHMALL variables in Postgres.
>>
>> What things need to be taken in consideration before doing that ?
>> What is the value of SHMAX & SHMALL if u have 16 GB RAM for Postgres
>> Server ?
>>     
>
> Well, those two values actually define kernel limits for shared memory
> segments (i.e. memory shared by multiple processes, in this case the
> postmaster proces and backends). So it's rather a question of tuning
> shared_buffers (because that's the shared memory segment) and then
> setting those two values.
>   

When I was tuning Postgresql for best Performance, I set my 
shared_buffers= 4096 MB as I set 25% of RAM ( 1/4 )

So Do I need to set my SHMMAX =4096 MB.

What is the SHMALL size now ?

> SHMMAX - max. size of a single shared segment (in bytes)
> SHMALL - total size of shared segments (in pages, page is usually 4kB)
>
> So if you decide you want 1GB shared buffers, you'll need at least this
>
> SHMMAX = 1024 * 1024 * 1024 (i.e. 1GB)
> SHMALL = 1024 * 256 (1GB in 4kB pages)
>
> (althouth the SHMALL should be higher, as there will be other processes
> that need shared memory).
>
> There's a lot of docs about this, e.g. this one (it's mostly for Oracle,
> but it describes the shared memory quite nicely):
>
> http://www.puschitz.com/TuningLinuxForOracle.shtml#SettingSharedMemory
>
> regards
> Tomas
>
>   


--------------080905050803000208060906
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
  <meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type">
</head>
<body bgcolor="#ffffff" text="#000000">
Tomas Vondra wrote:
<blockquote cite="mid:4DBE8C6B.9070208@fuzzy.cz" type="cite">
  <pre wrap="">Dne 2.5.2011 06:53, Adarsh Sharma napsal(a):
  </pre>
  <blockquote type="cite">
    <pre wrap="">I am also in need of a proper documentation that explains how to set 
SHMAX and SHMALL variables in Postgres.

What things need to be taken in consideration before doing that ?
What is the value of SHMAX &amp; SHMALL if u have 16 GB RAM for Postgres
Server ?
    </pre>
  </blockquote>
  <pre wrap=""><!---->
Well, those two values actually define kernel limits for shared memory
segments (i.e. memory shared by multiple processes, in this case the
postmaster proces and backends). So it's rather a question of tuning
shared_buffers (because that's the shared memory segment) and then
setting those two values.
  </pre>
</blockquote>
<br>
When I was tuning Postgresql for best Performance, I set my
shared_buffers= 4096 MB as I set 25% of RAM ( 1/4 )<br>
<br>
So Do I need to set my SHMMAX =4096 MB.<br>
<br>
What is the SHMALL size now ?<br>
<br>
<blockquote cite="mid:4DBE8C6B.9070208@fuzzy.cz" type="cite">
  <pre wrap="">
SHMMAX - max. size of a single shared segment (in bytes)
SHMALL - total size of shared segments (in pages, page is usually 4kB)

So if you decide you want 1GB shared buffers, you'll need at least this

SHMMAX = 1024 * 1024 * 1024 (i.e. 1GB)
SHMALL = 1024 * 256 (1GB in 4kB pages)

(althouth the SHMALL should be higher, as there will be other processes
that need shared memory).

There's a lot of docs about this, e.g. this one (it's mostly for Oracle,
but it describes the shared memory quite nicely):

<a class="moz-txt-link-freetext" href="http://www.puschitz.com/TuningLinuxForOracle.shtml#SettingSharedMemory">http://www.puschitz.com/TuningLinuxForOracle.shtml#SettingSharedMemory</a>

regards
Tomas

  </pre>
</blockquote>
<br>
</body>
</html>

--------------080905050803000208060906--