Comment 5 for bug 1342341

It appears to be the kernel bug. Sort of. I've bisected the kernel to commit ab8fabd46f811d5153d8a0cd2fac9a0d41fb593d. There's a discussion of this problem in this thread:
https://groups.google.com/forum/#!topic/linux.kernel/Jc69VRli3k0

This seems basically WONTFIX from linux side. But a workarounds are:

1. "vm.highmem_is_dirtyable=1" sysctl option — although this makes the performance not as high as it was in 3.2.x kernels, it at least allows one to use the disk subsystem
2. "mem=15G" kernel parameter limits the amount of usable memory, preventing the problems discussed in the thread I linked above
3. Use 64 bit kernel. This seems to be not a trivial thing to do with Ubuntu, but I may be wrong. But this is proposed as _the solution_.