diff options
Diffstat (limited to 'mm/Kconfig')
| -rw-r--r-- | mm/Kconfig | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/mm/Kconfig b/mm/Kconfig index b53427ad30a..c2b57d81e15 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -213,6 +213,8 @@ config UNEVICTABLE_LRU will use one page flag and increase the code size a little, say Y unless you know what you are doing. + See Documentation/vm/unevictable-lru.txt for more information. + config HAVE_MLOCK bool default y if MMU=y @@ -223,3 +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. |