pg.ddx.io  pgsql-performance@postgresql.org mailing list archive  

help / color / mirror / Atom feed

From: Jeff Davis <pgsql@j-davis.com>
To: Francisco Reyes <lists@stringsutils.com>
Cc: Michael Stone <mstone+postgres@mathom.us>
Cc: pgsql-performance@postgresql.org
Subject: Re: Vacuums on large busy databases
Date: Thu, 14 Sep 2006 17:52:02 -0700
Message-ID: <1158281522.29889.200.camel@dogma.v10.wvs> (raw)
In-Reply-To: <cone.1158278679.769031.75607.5001@35st-server.simplicato.com>
References: <cone.1158247381.60704.30981.1000@zoraida.natserv.net>
	<56FA8838-6DEA-4505-990D-85D5EDA26243@fastcrypt.com>
	<cone.1158255415.91768.31944.1000@zoraida.natserv.net>
	<470FED70-B3BA-4B6C-A6B1-DFD8882746B2@fastcrypt.com>
	<cone.1158265846.124028.75607.5001@35st-server.simplicato.com>
	<20060914204220.GL6030@mathom.us>
	<cone.1158278679.769031.75607.5001@35st-server.simplicato.com>

On Thu, 2006-09-14 at 20:04 -0400, Francisco Reyes wrote:
> Michael Stone writes:
> 
> > On Thu, Sep 14, 2006 at 04:30:46PM -0400, Francisco Reyes wrote:
> >>Right now adding up from ps the memory I have about 2GB.
> > 
> > That's not how you find out how much memory you have. Try "free" or 
> > somesuch.
> 
> Wasn't trying to get an accurate value, just a ballpark figure.
> 
> When you say "free" are you refering to the free value from top? or some 
> program called free?
> 

Any long-running system will have very little "free" memory. Free memory
is wasted memory, so the OS finds some use for it.

The VM subsystem of an OS uses many tricks, including the sharing of
memory among processes and the disk buffer cache (which is shared also).
It's hard to put a number on the memory demands of a given process, and
it's also hard to put a number on the ability of a system to accommodate
a new process with new memory demands.

You have 8GB total, which sounds like plenty to me. Keep in mind that if
you have the shared_memory all allocated on physical memory (i.e.
"kern.ipc.shm_use_phys: 1" on FreeBSD), then that amount of physical
memory will never be available to processes other than postgres. At 2GB,
that still leaves 6GB for the other process, so you should be fine.

Regards,
	Jeff Davis

view thread (23+ messages)  latest in thread

Message-ID: <1158281522.29889.200.camel@dogma.v10.wvs>
Permalink:  ../1158281522.29889.200.camel@dogma.v10.wvs/
Also on:    postgresql.org/message-id/1158281522.29889.200.camel@dogma.v10.wvs

copy link · copy postgr.es

reply

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: pgsql-performance@postgresql.org
  Cc: pgsql@j-davis.com, lists@stringsutils.com, mstone+postgres@mathom.us
  Subject: Re: Vacuums on large busy databases
  In-Reply-To: <1158281522.29889.200.camel@dogma.v10.wvs>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox