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Re: Memory question

From: "Arjen van der Meijden" <acm(at)tweakers(dot)net>
To: "'Matthew Hixson'" <hixson(at)poindextrose(dot)org>,<pgsql-performance(at)postgresql(dot)org>
Subject: Re: Memory question
Date: 2003-06-27 20:55:40
Message-ID: 004b01c33cee$7e6b2560$3ac15e91@acm (view raw or flat)
Thread:
Lists: pgsql-performance
> I've heard that too, but it doesn't seem to make much sense 
> to me.  If 
> you get to the point where your machine is _needing_ 2GB of swap then 
> something has gone horribly wrong (or you just need more RAM in the 
> machine) and it will just crawl until the kernel kills off whatever 
> process causes the swap space to be exceeded.  Seems to me that you 
> should only have that much swap if you can't afford more RAM 
> or you've 
> tapped out your machine's capacity, and your application needs that 
> much memory.
>    -M@
I've heard the same, the reason behind it was that there needs to be
one-to-one copy of the memory to be able to swap out everything and to
have a gain in the total "memory", you'd need twice as much swap as
memory to have a doubling of your memory.

But afaik this behaviour has been adjusted since the 2.4.5 kernel and
isn't a real issue anymore.

Please keep in mind that I'm no expert at all on linux, so if you want
to be sure, you'd better mail to the kernel-mailinglist orso :)

Anyway, I manage a few machines with 1GB++ memory and none of them has
more than 1G of swap and none of them uses that swap for more than a few
MB unless something was terribly wrong, so the actual 'risk' probably
doesn't have a high chance to occur.

Arjen




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