[$] Automatic mTHP creation in 7.2

The Linux kernel has long tried to use huge pages as a way to improveperformance, sometimes with more success than others. The size of hugepages has traditionally been imposed by the hardware, which typically onlyoffers a couple of relatively large options. In more recent times, though,the use of multi-size transparent huge pages (mTHPs), with more flexiblesizing implemented in software, has been growing. If all goes well, the7.2 development cycle will include the addition of a new feature,contributed by Nico Pache, to make the use of mTHPs even more transparent.