[RFC PATCH 0/3] add support for free hugepage reporting

[Liang Li]

A typical usage of hugetlbfs it's to reserve amount of memory when
the during kernel booting stage, and the reserved pages are unlikely
to return to the buddy system. When application need hugepages, kernel
will allocate them from the reserved pool. when application terminates,
huge pages will return to the reserved pool and are kept in the free
list for hugetlb, these free pages will not return to buddy freelist
unless the size fo reserved pool is changed. 
Free page reporting only supports buddy pages, it can't report the
free pages reserved for hugetlbfs. On the other hand, hugetlbfs
is a good choice for system with a huge amount of RAM, because it
can help to reduce the memory management overhead and improve system
performance.
This patch add the support for reporting hugepages in the free list
of hugetlb, it can be used by virtio_balloon driver for memory
overcommit and pre zero out free pages for speeding up memory
population and page fault handling.

Most of the code are 'copied' from free page reporting because they
are working in the same way. So the code can be refined to remove
the duplication code. Since this is an RFC, I didn't do that.

For the virtio_balloon driver, changes for the virtio spec are needed.
Before that, I need the feedback of the comunity about this new feature.

Liang Li (3):
  mm: support hugetlb free page reporting
  virtio-balloon: add support for providing free huge page reports to
    host
  mm: support free hugepage pre zero out

 drivers/virtio/virtio_balloon.c     |  61 ++++++
 include/linux/hugetlb.h             |   3 +
 include/linux/page_reporting.h      |   5 +
 include/uapi/linux/virtio_balloon.h |   1 +
 mm/hugetlb.c                        |  29 +++
 mm/page_prezero.c                   |  17 ++
 mm/page_reporting.c                 | 287 ++++++++++++++++++++++++++++
 mm/page_reporting.h                 |  34 ++++
 8 files changed, 437 insertions(+)

Cc: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>  
Cc: Michal Hocko <mhocko@xxxxxxxx> 
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Alex Williamson <alex.williamson@xxxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Liang Li <liliang324@xxxxxxxxx>
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2.18.2