[LSF/MM/BPF TOPIC] HGM for hugetlbfs

[Mike Kravetz <mike.kravetz@oracle.com>]

This is past the deadline, so feel free to ignore.  However, ...

James Houghton has been working on the concept of HugeTLB High Granularity
Mapping (HGM) as discussed here:
https://lore.kernel.org/linux-mm/20230218002819.1486479-1-jthoughton@google.com/

The primary motivation for this work is post-copy live migration of VMs backed
by hugetlb pages via userfaultfd.  A followup use case is more gracefully
handling memory errors/poison on hugetlb pages.

As can be seen by the size of James's patch set, the required changes for
HGM are a bit complex and involved.  This is also complicated the need
choosing a 'mapcount strategy' as the previous scheme used by hugetlb
will no longer work.

A HGM for hugetlbfs session would present the current approach and challenges.  
While much of the work is confined to hugetlb, there is a bit spill over to
other mm areas: specifically page table walking.  A discussion on ways to
move forward with this effort would be appreciated.
-- 
Mike Kravetz