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Date: Tue, 5 Apr 2011 07:08:07 -0600
Message-ID: <BANLkTi=GhO3SaXgy7SweHHTO2zTGkLO23Q@mail.gmail.com>
Subject: Re: Postgres Performance Tuning
From: Scott Marlowe <scott.marlowe@gmail.com>
To: Adarsh Sharma <adarsh.sharma@orkash.com>
Cc: Raghavendra <raghavendra.rao@enterprisedb.com>,
	pgsql-performance@postgresql.org
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On Tue, Apr 5, 2011 at 1:33 AM, Adarsh Sharma <adarsh.sharma@orkash.com> wr=
ote:
>
> [root@s8-mysd-2 ~]# free -m
> =A0 =A0 =A0 =A0 =A0 =A0total =A0 =A0 =A0 used =A0 =A0 =A0 free =A0 =A0 sh=
ared =A0 =A0buffers =A0 =A0 cached
> Mem: =A0 =A0 =A0 =A0 15917 =A0 =A0 =A015826 =A0 =A0 =A0 =A0 90 =A0 =A0 =
=A0 =A0 =A00 =A0 =A0 =A0 =A0101 =A0 =A0 =A015013
> -/+ buffers/cache: =A0 =A0 =A0 =A0711 =A0 =A0 =A015205
> Swap: =A0 =A0 =A0 =A016394 =A0 =A0 =A0 =A0143 =A0 =A0 =A016250
>
> It means 15 GB memory is cached.

Note that the kernel takes all otherwise unused memory and uses it for
cache.  If, at any time a process needs more memory, the kernel just
dumps some cached data and frees up the memory and hands it over, it's
all automatic.  As long as cache is large, things are OK.  You need to
be looking to see if you're IO bound or CPU bound first.  so, vmstat
(install the sysstat package) is the first thing to use.