Reply-To: <gnanam@zoniac.com>
From: "Gnanakumar" <gnanam@zoniac.com>
To: <pgsql-admin@postgresql.org>
Subject: Advice/guideline on increasing shared_buffers and kernel parameters
Date: Tue, 8 May 2012 12:22:58 +0530
Organization: Zoniac Software Private Limited
Message-ID: <00da01cd2ce7$35d17780$a1746680$@com>
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Hi,

Our Production server has got 35 GB physical RAM size.   Since the server
has lots of RAM, we want to really make use of it.  We've already configured
"max_connections" to 1000 and "shared_buffers" to 1536 MB, but when we tried
to increase only "shared_buffers" to 3072MB (keeping "max_connections" as it
is), PostgreSQL failed to start with the following error:

	EDTFATAL:  could not create shared memory segment: Invalid argument
	EDTDETAIL:  Failed system call was shmget(key=5432001,
size=3307192320, 03600).

Keeping max connection property to 1000, how do I "best" tune/set up its
memory related parameters (including Linux Kernel parameters -- SHMMAX and
SHMALL)?

Experts insights/pointers on this are really appreciated.

Given below current settings available in our server:
-- SHMMAX & SHMALL --
# cat /proc/sys/kernel/shmall
2097152
# cat /proc/sys/kernel/shmmax
2147483648

-- OS & Kernel --
OS: CentOS release 5.2
Arch: 64-bit
Kernel: 2.6.18

-- PostgreSQL conf --
shared_buffers = 1536MB
max_connections = 1000

We're currently running PostgreSQL v8.2.22.

Regards,
Gnanam