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Subject[PATCH v2 0/3] fixes for large mm_populate() and munlock() operations
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These 3 changes are to improve the handling of large mm_populate and
munlock operations. They apply on top of mmotm (in particular, they
depend on both my prior mm_populate work and Kirill's "thp: avoid
dumping huge zero page" change).

- Patch 1 fixes an integer overflow issue when populating 2^32 pages.
The nr_pages argument to get_user_pages would overflow, resulting in 0
pages being processed per iteration. I am proposing to simply convert
the nr_pages argument to a long.

- Patch 2 accelerates populating regions with THP pages. get_user_pages()
can increment the address by a huge page size in this case instead of
a small page size, and avoid repeated mm->page_table_lock acquisitions.
This fixes an issue reported by Roman Dubtsov where populating regions
via mmap MAP_POPULATE was significantly slower than doing so by
touching pages from userspace.

- Patch 3 is a similar acceleration for the munlock case. I would actually
like to get Andrea's attention on this one, as I can't explain how
munlock_vma_page() is safe against racing with split_huge_page().

Note that patches 1-2 are logically independent of patch 3, so if the
discussion of patch 3 takes too long I would ask Andrew to consider
merging patches 1-2 first.

Changes since v1:

- Andrew accepted patch 1 into his -mm tree but suggested the nr_pages
argument type should actually be unsigned long; I am sending this as
a "fix" for the previous patch 1 to be collapsed over the previous one.

- In patch 2, I am adding a separate follow_page_mask() function so that
the callers to the original follow_page() don't have to be modified to
ignore the returned page_mask (following another suggestion from Andrew).
Also the page_mask argument type was changed to unsigned int.

- In patch 3, I similarly changed the page_mask values to unsigned int.

Michel Lespinasse (3):
fix mm: use long type for page counts in mm_populate() and get_user_pages()
mm: accelerate mm_populate() treatment of THP pages
mm: accelerate munlock() treatment of THP pages

include/linux/hugetlb.h | 2 +-
include/linux/mm.h | 24 +++++++++++++++++-------
mm/hugetlb.c | 8 ++++----
mm/internal.h | 2 +-
mm/memory.c | 43 +++++++++++++++++++++++++++++--------------
mm/mlock.c | 34 ++++++++++++++++++++++------------
mm/nommu.c | 6 ++++--
7 files changed, 78 insertions(+), 41 deletions(-)

--
1.8.1


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