linux-kernel - [PATCH 0/6] mlock: do not hold mmap

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Date:	Thu,  2 Dec 2010 16:16:46 -0800
From:	Michel Lespinasse <walken@...gle.com>
To:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Nick Piggin <npiggin@...nel.dk>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 0/6] mlock: do not hold mmap_sem for extended periods of time

Currently mlock() holds mmap_sem in exclusive mode while the pages get
faulted in. In the case of a large mlock, this can potentially take a
very long time, during which various commands such as 'ps auxw' will
block. This makes sysadmins unhappy:

real    14m36.232s
user    0m0.003s
sys     0m0.015s
(output from 'time ps auxw' while a 20GB file was being mlocked without
being previously preloaded into page cache)

I propose that mlock() could release mmap_sem after the VM_LOCKED bits
have been set in all appropriate VMAs. Then a second pass could be done
to actually mlock the pages, in small batches, releasing mmap_sem when
we block on disk access or when we detect some contention.

Patches are against v2.6.37-rc4 plus my patches to avoid mlock dirtying
(presently queued in -mm).

Michel Lespinasse (6):
  mlock: only hold mmap_sem in shared mode when faulting in pages
  mm: add FOLL_MLOCK follow_page flag.
  mm: move VM_LOCKED check to __mlock_vma_pages_range()
  rwsem: implement rwsem_is_contended()
  mlock: do not hold mmap_sem for extended periods of time
  x86 rwsem: more precise rwsem_is_contended() implementation

 arch/alpha/include/asm/rwsem.h   |    5 +
 arch/ia64/include/asm/rwsem.h    |    5 +
 arch/powerpc/include/asm/rwsem.h |    5 +
 arch/s390/include/asm/rwsem.h    |    5 +
 arch/sh/include/asm/rwsem.h      |    5 +
 arch/sparc/include/asm/rwsem.h   |    5 +
 arch/x86/include/asm/rwsem.h     |   35 ++++++---
 arch/x86/lib/rwsem_64.S          |    4 +-
 arch/x86/lib/semaphore_32.S      |    4 +-
 arch/xtensa/include/asm/rwsem.h  |    5 +
 include/linux/mm.h               |    1 +
 include/linux/rwsem-spinlock.h   |    1 +
 lib/rwsem-spinlock.c             |   12 +++
 mm/internal.h                    |    3 +-
 mm/memory.c                      |   54 ++++++++++++--
 mm/mlock.c                       |  150 ++++++++++++++++++--------------------
 mm/nommu.c                       |    6 +-
 17 files changed, 201 insertions(+), 104 deletions(-)

-- 
1.7.3.1

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