Message-ID: <45E313F3.9070605@commandprompt.com>
Date: Mon, 26 Feb 2007 09:08:03 -0800
From: "Joshua D. Drake" <jd@commandprompt.com>
Organization: Command Prompt, Inc.
User-Agent: Thunderbird 1.5.0.9 (X11/20070103)
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To: Mark Stosberg <mark@summersault.com>
CC: pgsql-performance@postgresql.org
Subject: Re: low memory usage reported by 'top' indicates poor tuning?
References: <erv38o$1su3$1@news.hub.org>
In-Reply-To: <erv38o$1su3$1@news.hub.org>
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Mark Stosberg wrote:
> Hello,
> 
> I'm trying to make sense of the memory usage reported by 'top', compared
> to what "pg_database_size" shows.   Here's one result:'


You are missing the most important parts of the equation:

1. What version of PostgreSQL.
2. What operating system -- scratch , I see freebsd
3. How big is your pg_dump in comparison to the pg_database_size()
4. What type of raid do you have?
5. What is your work_mem set to?
6. What about effective_cache_size?
7. Do you analyze? How often?

> 
> select pg_size_pretty(pg_database_size('production'));
>  pg_size_pretty
> ----------------
>  6573 MB
> 
> Now, looking at memory use with "top", there is a lot memory that isn't
> being used on the system:
> 
>  Mem: 470M Active, 2064M Inact
> 
> ( 3 Gigs RAM, total ).
> 
> Overall performance is decent, so maybe there's no
> problem. However, I wonder if we've under-allocated memory to
> PostgreSQL. (This is a dedicated FreeBSD DB server).
> 
> Some memory settings include:
> 
> shared_buffers = 8192 (we have 450 connections)
> max_fsm_pages = 1250000 (we kept getting HINTs to bump it, so we did)
> 
> Maybe we should be bumping up the "sort_mem" and "vacuum_mem" as well?
> 
> I do sometimes see sorting and vacuuming as showing up as things I'd
> like to run faster.
> 
> This list has been a great resource for performance tuning help, and I
> continue to appreciate your help. We've used PostgreSQL on every project
> we've had a choice on for the last 10 years. (Has it been that long?!)
> We've never regretted it once.
> 
>    Mark
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 2: Don't 'kill -9' the postmaster
> 


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