Re: extremly low memory usage

From: Ron <rjpeace(at)earthlink(dot)net>
To: Jeremiah Jahn <jeremiah(at)cs(dot)earlham(dot)edu>
Cc: postgres performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: extremly low memory usage
Date: 2005-08-20 21:23:25
Message-ID: 6.2.3.4.0.20050820171521.05bd0a38@pop.earthlink.net
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At 02:16 PM 8/20/2005, Jeremiah Jahn wrote:
>I'm just watching gnome-system-monoitor. Which after careful
>consideration.....and looking at dstat means I'm on CRACK....GSM isn't
>showing cached memory usage....I asume that the cache memory usage
>is where data off of the disks would be cached...?
>
>memory output from dstat is this for a few seconds:
>
>---procs--- ------memory-usage----- ---paging--
>--disk/sda----disk/sdb- ----swap--- ----total-cpu-usage----
>run blk new|_used _buff _cach _free|__in_ _out_|_read write:_read
>write|_used _free|usr sys idl wai hiq siq
> 0 0 0|1336M 10M 4603M 17M| 490B 833B|3823B 3503k:1607k
> 4285k| 160k 2048M| 4 1 89 7 0 0
> 1 0 0|1337M 10M 4600M 18M| 0 0 | 0 0
> : 0 464k| 160k 2048M| 25 0 75 0 0 0
><snip>
> 1 0 0|1334M 10M 4596M 25M| 0 0 | 0 0
> : 0 56k| 160k 2048M| 21 4 75 0 0 0

Then the "low memory usage" was a chimera. Excellent!

Given the evidence in this thread, IMO you should upgrade your box to
16GB of RAM ASAP. That should be enough to cache most, if not all,
of the 10GB of the "hot" part of your DB; thereby dedicating your HD
subsystem as much as possible to writes (which is unavoidable HD
IO). As I've posted before, at $75-$150/GB, it's well worth the
investment whenever you can prove it will help as we have here.

Hope this helps,
Ron Peacetree

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