[PATCHv4 0/8] thp/khugepaged improvements and CoW semantics

[Kirill A. Shutemov]

The patchset adds khugepaged selftest (anon-THP only for now), expands
cases khugepaged can handle and switches anon-THP copy-on-write handling
to 4k.

Please review and consider applying.

v4:
 - Rebase to v5.7-rc1;
 - Minor adjustments based on feedback: comments/messages/whitespace
 - Apply Reviewed/Acked/Tested-by;
v3:
 - Fix handling compound pages in swap cache;
 - Rework swaped vs. referenced check;
 - Fix refcounting for compound pages;
 - Drop Reviewed-by/Acked-by as patchset changed non-trivially;
 - Typos;
v2:
 - Fix race in compound page handling;
 - Add one more test-case for compound page case;
 - Rework LRU add cache draining;
 - Typos;

Kirill A. Shutemov (8):
  khugepaged: Add self test
  khugepaged: Do not stop collapse if less than half PTEs are referenced
  khugepaged: Drain all LRU caches before scanning pages
  khugepaged: Drain LRU add pagevec after swapin
  khugepaged: Allow to collapse a page shared across fork
  khugepaged: Allow to collapse PTE-mapped compound pages
  thp: Change CoW semantics for anon-THP
  khugepaged: Introduce 'max_ptes_shared' tunable

 Documentation/admin-guide/mm/transhuge.rst |   7 +
 include/trace/events/huge_memory.h         |   3 +-
 mm/huge_memory.c                           | 250 +-----
 mm/khugepaged.c                            | 220 +++--
 tools/testing/selftests/vm/Makefile        |   1 +
 tools/testing/selftests/vm/khugepaged.c    | 982 +++++++++++++++++++++
 6 files changed, 1175 insertions(+), 288 deletions(-)
 create mode 100644 tools/testing/selftests/vm/khugepaged.c

-- 
2.26.1