PROBLEM: oom killer and swap weirdness on 2.6.3* kernels

[dave b]

In 2.6.3* kernels (test case was performed on the 2.6.33.3 kernel)
when physical memory runs out and there is a large swap partition -
the system completely stalls.

I noticed that when running debian lenny using dm-crypt  with
encrypted / and swap with a  2.6.33.3 kernel (and all of the 2.6.3*
series iirc) when all physical memory is used (swapiness was left at
the default 60) the system hangs and does not respond. It can resume
normal operation some time later - however it seems to take a *very*
long time for the oom killer to come in. Obviously with swapoff this
doesn't happen - the oom killer comes in and does its job.


free -m
             total       used       free     shared    buffers     cached
Mem:          1980       1101        879          0         58        201
-/+ buffers/cache:        840       1139
Swap:        24943          0      24943


My simple test case is

dd if=/dev/zero of=/tmp/stall
and wait till /tmp fills...
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