Comment 18 for bug 1152736

The issue is intermittent, and I don't know what causes it aside from firefox getting handsy with the system memory. There seems to be *some* arbitrary threshold beyond which the behavior becomes nonlinear, but it's not anywhere I would expect it to be: after filing the bug I used SysRq to kill off the session without a full reboot, and
 at this point I still have the following in 'free':

$ free
             total used free shared buffers cached
Mem: 3842476 3371792 470684 0 63260 1176384
-/+ buffers/cache: 2132148 1710328
Swap: 6291452 289828 6001624
$

This is with vm.swappiness=0 - and I still can't swapoff. So I don't know what my kernel is doing, but it's up to no good.

I haven't yet tested whether rebooting to a previous kernel helps; I'll do that shortly.