Re: 2.6.9-ck1: swap mayhem under UT2004

[Con Kolivas <kernel@kolivas.org>]

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Alastair Stevens wrote:
> Con and others: I've been running 2.6.9-ck1 for a couple of days, and seem 
> to have hit on a major swapping issue....
> 
> My machine is a UP Athlon 2500+ with 512MB, and everything hums along 
> nicely under normal desktop usage.  But when launching UT2004, it just 
> crawls and jerks like hell.  At one point, it appeared to have frozen 
> completely, but I managed to switch to a text console to see what was 
> happening, and basically I'd hit a swap frenzy: kswapd was sucking 50% of 
> the CPU, fighting with the UT2004 process.
> 
> My RAM appeared to be almost "full", with no cache/buffers, but only a few 
> hundred K of swap was actually being used, and this wasn't changing.   
> The kswapd frenzy carried on for at least a couple of minutes; then 
> suddenly everything went smooth again and the game played perfectly from 
> then on.
> 
> This is definitely new behaviour; I've run every recent 2.6 kernel, with 
> and without the staircase scheduler patch (but not the full -ck), and 
> never had any problems before.  Yes, I'm running the dratted Nvidia 
> driver, but that's not the issue as it's been loaded with every other 
> kernel.  Switching back to 2.6.9-rc3 makes everything behave perfectly 
> again....
> 
> Any ideas?  Any more info required?

I've seen reports of this happening since 2.6.9 _even on mainline_. 
Something seems very sick with kswapd where it consumes massive amounts 
of cpu. Can you reproduce without any -ck patches? Others have already 
done so, but it seems to happen earlier with -ck.

Con

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