Tested with kernel - Linux 3.15.0-031500rc7-generic
After 24 hours there's no sign of the problem.
After watching numastat for a while I noticed that with the 3.13.0 kernel the allocated memory for qemu does a really sudden drop from 6GB down to 2GB. QEMU then freezes with 100% CPU until the allocation goes back up to 6GB again. On 3.15 the memory stays almost constant and is migrated towards one numa node as you'd expect. Just speculating but there must be some kind of page invalidation bug in the numa balancer.
Tested with kernel - Linux 3.15.0- 031500rc7- generic
After 24 hours there's no sign of the problem.
After watching numastat for a while I noticed that with the 3.13.0 kernel the allocated memory for qemu does a really sudden drop from 6GB down to 2GB. QEMU then freezes with 100% CPU until the allocation goes back up to 6GB again. On 3.15 the memory stays almost constant and is migrated towards one numa node as you'd expect. Just speculating but there must be some kind of page invalidation bug in the numa balancer.