ksm: add some documentation

[pandora-kernel.git] / mm / Kconfig

diff --git a/mm/Kconfig b/mm/Kconfig
index c948d4c..71eb0b4 100644 (file)
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -153,7 +153,7 @@ config MEMORY_HOTREMOVE
 #
 config PAGEFLAGS_EXTENDED
        def_bool y
-       depends on 64BIT || SPARSEMEM_VMEMMAP || !NUMA || !SPARSEMEM
+       depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
 
 # Heavily threaded applications may benefit from splitting the mm-wide
 # page_table_lock, so that faults on different parts of the user address
@@ -214,6 +214,18 @@ config HAVE_MLOCKED_PAGE_BIT
 config MMU_NOTIFIER
        bool
 
+config KSM
+       bool "Enable KSM for page merging"
+       depends on MMU
+       help
+         Enable Kernel Samepage Merging: KSM periodically scans those areas
+         of an application's address space that an app has advised may be
+         mergeable.  When it finds pages of identical content, it replaces
+         the many instances by a single resident page with that content, so
+         saving memory until one or another app needs to modify the content.
+         Recommended for use with KVM, or with other duplicative applications.
+         See Documentation/vm/ksm.txt for more information.
+
 config DEFAULT_MMAP_MIN_ADDR
         int "Low address space to protect from user allocation"
         default 4096
@@ -225,9 +237,9 @@ config DEFAULT_MMAP_MIN_ADDR
          For most ia64, ppc64 and x86 users with lots of address space
          a value of 65536 is reasonable and should cause no problems.
          On arm and other archs it should not be higher than 32768.
-         Programs which use vm86 functionality would either need additional
-         permissions from either the LSM or the capabilities module or have
-         this protection disabled.
+         Programs which use vm86 functionality or have some need to map
+         this low address space will need CAP_SYS_RAWIO or disable this
+         protection by setting the value to 0.
 
          This value can be changed after boot using the
          /proc/sys/vm/mmap_min_addr tunable.