"A number of changes in Linux 3.3 are intended to take care of
various problems that can, in certain situations, cause systems to
temporarily stall when the kernel is writing large amounts of data
to a slow disk (such as a USB flash drive). Linux 3.2 already fixed
some of these types of issues where the writeback code was to blame
? now the changes are targeting the memory compaction code and
fixing problems related to transparent hugepages (THP).