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FromMichel Lespinasse <>
Subject[PATCH 0/6] mlock: do not hold mmap_sem for extended periods of time
DateThu, 2 Dec 2010 16:16:46 -0800
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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