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Date: Mon, 26 Jul 2004 13:42:58 -0700
From: Andrew Morton <akpm@osdl.org>
To: Joel Becker <Joel.Becker@oracle.com>
Cc: kernel@kolivas.org, linux-kernel@vger.kernel.org
Subject: Re: Autotune swappiness01
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Joel Becker <Joel.Becker@oracle.com> wrote:
>
> On Mon, Jul 26, 2004 at 10:43:01AM +1000, Con Kolivas wrote:
> > Low memory boxes and ones that are heavily laden with applications find 
> > that ends up making things slow down trying to keep all applications in 
> > physical ram.
> 
> 	Lowish memory boxes with plain desktop loads find that the default
> of '60' is a terrible one (I'm speaking of 1GHz-ish machines with 256MB
> (like mine) or 512MB (like a guy next to me)).  Every person I know who
> installs 2.6 complains about how it feels slow and choppy.  I tell them
> "The first thing I do after installing 2.6 is set swappiness to '20'."
> Sure enough, they set swappiness to 20 and their box starts behaving
> like a properly tuned one.
> 	I don't know what workload the default of '60' is for, but for
> the (128MB < x < 1GB) of RAM case, it sucks (and I've seen the same
> behavior on a 300MHz 196MB box).
> 

Yes, I think 60% is about right for a 512-768M box.  Too high for the
smaller machines, too low for the larger ones.

More intelligent selection of the initial value is needed.