[PATCHv2 0/4] thp: simplify freeze_page() and unfreeze_page()

["Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>]

This patchset rewrites freeze_page() and unfreeze_page() using try_to_unmap()
and remove_migration_ptes(). Result is much simpler, but somewhat slower.

Comparing to v1, I've recovered most of performance for PMD-mapped THPs
with few shortcuts.

Migration 8GiB worth of PMD-mapped THP:

Baseline	20.21 A+- 0.393
Patched		20.73 A+- 0.082
Slowdown	1.03x

It's 3% slower, comparing to 14% in v1. I don't it should be a stopper.

Splitting of PTE-mapped pages slowed more. But this is not that often
case.

Migration 8GiB worth of PMD-mapped THP:

Baseline	20.39 A+- 0.225
Patched		22.43 A+- 0.496
Slowdown	1.10x

Please, consider applying.

Kirill A. Shutemov (4):
  rmap: introduce rmap_walk_locked()
  rmap: extend try_to_unmap() to be usable by split_huge_page()
  mm: make remove_migration_ptes() beyond mm/migration.c
  thp: rewrite freeze_page()/unfreeze_page() with generic rmap walkers

 include/linux/huge_mm.h |  13 ++-
 include/linux/rmap.h    |   6 ++
 mm/huge_memory.c        | 204 +++++++-----------------------------------------
 mm/migrate.c            |  15 ++--
 mm/rmap.c               |  70 +++++++++++++----
 5 files changed, 106 insertions(+), 202 deletions(-)

-- 
2.7.0

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