Re: [Bug #14141] order 2 page allocation failures in iwlagn

[Mel Gorman <mel@csn.ul.ie>]

On Mon, Oct 05, 2009 at 08:50:58AM +0200, Frans Pop wrote:
> On Monday 05 October 2009, Frans Pop wrote:
> > I'll dig into this a bit more as it looks like this should be
> > reproducible, probably even without the kernel build. Next step is to
> > see how .30 behaves in the same situation.
> 
> This looks conclusive. I tested .30 and .32-rc3 from clean reboots and
> only starting gitk. I only started music playing in the background
> (amarok) from an NFS share to ensure network activity.
> 
> With .32-rc3 I got 4 SKB allocation errors while starting the *second* gitk
> instance. And the system was completely frozen with music stopped until gitk
> finished loading.
> 
> With .30 I was able to start *three* gitk's (which meant 2 of them got
> (partially) swapped out) without any allocation errors. And with the system
> remaining relatively responsive. There was a short break in the music while
> I started the 2nd instance, but it just continued playing afterwards. There
> was also some mild latency in the mouse cursor, but nothing like the full
> desktop freeze I get with .32-rc3.
> 
> With .30 I looked at /proc/buddyinfo while the 3rd gitk was being started,
> and that looked fairly healthy all the time:
> Node 0, zone      DMA      5      9     22     20     21     11      0      0      0      0      1
> Node 0, zone    DMA32    579     67     25      8      5      1      1      0      1      1      0
> Node 0, zone      DMA      5      9     22     20     21     11      0      0      0      0      1
> Node 0, zone    DMA32    276     54     13     15      8     10      3      1      1      1      0
> Node 0, zone      DMA      4      9     22     20     21     11      0      0      0      0      1
> Node 0, zone    DMA32    119     45     24     18     12      4      5      2      1      1      0
> Node 0, zone      DMA      4      9     22     20     21     11      0      0      0      0      1
> Node 0, zone    DMA32    527     13      9      5      5      3      2      1      1      1      0
> Node 0, zone      DMA      5      9     22     20     21     11      0      0      0      0      1
> Node 0, zone    DMA32   1375     24      7      7      8      5      1      1      0      1      0
> Node 0, zone      DMA      5      9     22     20     21     11      0      0      0      0      1
> Node 0, zone    DMA32    329     21      3      3     17      8      5      1      0      1      0
> 
> With .32 it was obviously impossible to get that info due to the total
> freeze of the desktop. Not sure if the scheduler changes in .32 contribute
> to this. Guess I could find out by doing the same test with .31.
> 
> One thing I should mention: my swap is an LVM volume that's in a VG that's
> on a LUKS encrypted partition.
> 
> Does this give you enough info to go on, or should I try a bisection?
> 

I'll be trying to reproduce it, but it's unlikely I'll manage to
reproduce it reliably as there may be a specific combination of hardware
necessary as well. What I'm going to try is writing a module that
allocates order-5 every second GFP_ATOMIC and see can I reproduce using
scenarios similar to yours but it'll take some time with no guarantee of
success. If you could bisect it, it would be fantastic.

Thanks

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab

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