diff options
author | Jens Axboe <jens.axboe@oracle.com> | 2009-05-22 20:25:34 +0200 |
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committer | Jens Axboe <jens.axboe@oracle.com> | 2009-05-22 20:25:34 +0200 |
commit | e4b636366c00738b9609cda307014d71b1225b7f (patch) | |
tree | 760b67b3624eda62e943e48ce93635c30a5b47bf /mm/Kconfig | |
parent | b9ed7252d219c1c663944bf03846eabb515dbe75 (diff) | |
parent | 279e677faa775ad16e75c32e1bf4a37f8158bc61 (diff) |
Merge branch 'master' into for-2.6.31
Conflicts:
drivers/block/hd.c
drivers/block/mg_disk.c
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'mm/Kconfig')
-rw-r--r-- | mm/Kconfig | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/mm/Kconfig b/mm/Kconfig index 57971d2ab848..c2b57d81e153 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -225,3 +225,31 @@ config HAVE_MLOCKED_PAGE_BIT config MMU_NOTIFIER bool + +config NOMMU_INITIAL_TRIM_EXCESS + int "Turn on mmap() excess space trimming before booting" + depends on !MMU + default 1 + help + The NOMMU mmap() frequently needs to allocate large contiguous chunks + of memory on which to store mappings, but it can only ask the system + allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently + more than it requires. To deal with this, mmap() is able to trim off + the excess and return it to the allocator. + + If trimming is enabled, the excess is trimmed off and returned to the + system allocator, which can cause extra fragmentation, particularly + if there are a lot of transient processes. + + If trimming is disabled, the excess is kept, but not used, which for + long-term mappings means that the space is wasted. + + Trimming can be dynamically controlled through a sysctl option + (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of + excess pages there must be before trimming should occur, or zero if + no trimming is to occur. + + This option specifies the initial value of this option. The default + of 1 says that all excess pages should be trimmed. + + See Documentation/nommu-mmap.txt for more information. |