On Mon, Nov 22, 2021 at 04:01:02PM -0800, Mina Almasry wrote:

Add PM_THP_MAPPED MAPPING to allow userspace to detect whether a given virt
address is currently mapped by a transparent huge page or not.  Example
use case is a process requesting THPs from the kernel (via a huge tmpfs
mount for example), for a performance critical region of memory.  The
userspace may want to query whether the kernel is actually backing this
memory by hugepages or not.

But what is userspace going to _do_ differently if the kernel hasn't
backed the memory with huge pages?