linux-kernel - [PATCH 0/3] fixes for large mm_populate() and munlock() operations

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Message-Id: <1359591980-29542-1-git-send-email-walken@google.com>
Date:	Wed, 30 Jan 2013 16:26:17 -0800
From:	Michel Lespinasse <walken@...gle.com>
To:	Andrea Arcangeli <aarcange@...hat.com>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Hugh Dickins <hughd@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH 0/3] fixes for large mm_populate() and munlock() operations

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.

Michel Lespinasse (3):
  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

 arch/ia64/xen/xencomm.c    |  3 ++-
 arch/powerpc/kernel/vdso.c |  9 +++++----
 arch/s390/mm/pgtable.c     |  3 ++-
 include/linux/hugetlb.h    |  6 +++---
 include/linux/mm.h         | 16 ++++++++--------
 mm/hugetlb.c               | 10 +++++-----
 mm/internal.h              |  2 +-
 mm/ksm.c                   | 10 +++++++---
 mm/memory.c                | 39 ++++++++++++++++++++++++++-------------
 mm/migrate.c               |  7 +++++--
 mm/mlock.c                 | 37 ++++++++++++++++++++++++-------------
 11 files changed, 88 insertions(+), 54 deletions(-)

-- 
1.8.1

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