Date: Tue, 2 May 2006 00:21:08 -0400
From: Charles Shannon Hendrix <shannon@widomaker.com>
To: Linux Kernel <linux-kernel@vger.kernel.org>
Subject: Re: OOM kills if swappiness set to 0, swap storms otherwise
Message-ID: <20060502042108.GD5691@widomaker.com>
References: <1143510828.1792.353.camel@mindpipe> <20060327195905.7f666cb5.akpm@osdl.org> <20060405144716.GA10353@widomaker.com> <443B69BE.6060601@tlinx.org>
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Tue, 11 Apr 2006 @ 01:33 -0700, Linda Walsh said:

>    Hmmm, not to be contrary, but I have a 1GB system that refuses to swap
> during large file i/o operations.  For the first time in a *long* time,
> I read someone's suggestion to increase swappiness -- I did, to 75 or 80,
> (I've booted since then, so it's back to 60 and no swap usage) and some of
> the programs that rarely run actually swapped.  It was great!  I finally had
> more memory for file i/o operations.

It's great if you actually need the file data that gets stored.

>    Maybe you are telling the system to "feel free" to use swap by having a
> large swap file?  

I don't believe that matters, and certainly doesn't seem to affect my
own system.

If I use a smaller swap file, I just run out faster.

Is your experience different?

> I agree.  Try getting rid of your swap file entirely -- your system
> will still run unless you are overloading memory, but you have a Gig.
> How much do you need to keep in memory?  Sure, if/when I get a 4-way
> CPU (I have a 2-cpu setup now), I might go up to 4G, but I might be
> running multiple virtual machines too!

Sure it will run, but I *want* swap to be used to remove unused
programs.

My current problem is that *useful* program code is being swapped out and
being replaced by *useless* cached file data.

>    You might try the "cfq" block i/o algorithm.  Then you can
> ionice down the disk priority of background processes (though you need
> to be root to reduce ionice levels at this point, unlike cpu nice).

I've not seen ionice.


-- 
shannon "AT" widomaker.com -- ["All of us get lost in the darkness,
dreamers turn to look at the stars" -- Rush ]
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