Re: Autotune swappiness01

[Con Kolivas <kernel@kolivas.org>]

Andrew Morton writes:

> 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.

Sigh.. 

I have a 1Gb desktop machine that refuses to keep my applications in ram 
overnight if I have a swappiness higher than the default so I think lots of 
desktop users with more ram will be unhappy with higher settings.

> More intelligent selection of the initial value is needed.

Perhaps, but I really doubt desktop users running mainline would be happy 
about it going significantly higher. 

Cheers,
Con