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    DateMon, 1 May 2006 22:04:32 -0700
    From"Randy.Dunlap" <>
    SubjectRe: OOM kills if swappiness set to 0, swap storms otherwise
    On Tue, 2 May 2006 00:21:08 -0400 Charles Shannon Hendrix wrote:
    
    > 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.
    
    It's hidden^w embedded in Documentation/block/ioprio.txt ...
    
    ---
    ~Randy
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