* container_try_to_free_pages() walks containers
  page list and tries to shrink pages. This is based
  on try_to_free_pages() and Co code.
  Called from core code when no resource left at the
  moment of page touching.

* container_out_of_memory() selects a process to be
  killed which mm_struct belongs to container in question.
  Called from core code when no resources left and no
  pages were reclaimed.