Re: OOM kills if swappiness set to 0, swap storms otherwise

[Charles Shannon Hendrix <shannon@widomaker.com>]

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 ]