mm/Kconfig

   1 config SELECT_MEMORY_MODEL
   2         def_bool y
   3         depends on EXPERIMENTAL || ARCH_SELECT_MEMORY_MODEL
   4
   5 choice
   6         prompt "Memory model"
   7         depends on SELECT_MEMORY_MODEL
   8         default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
   9         default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
  10         default FLATMEM_MANUAL
  11
  12 config FLATMEM_MANUAL
  13         bool "Flat Memory"
  14         depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
  15         help
  16           This option allows you to change some of the ways that
  17           Linux manages its memory internally.  Most users will
  18           only have one option here: FLATMEM.  This is normal
  19           and a correct option.
  20
  21           Some users of more advanced features like NUMA and
  22           memory hotplug may have different options here.
  23           DISCONTIGMEM is an more mature, better tested system,
  24           but is incompatible with memory hotplug and may suffer
  25           decreased performance over SPARSEMEM.  If unsure between
  26           "Sparse Memory" and "Discontiguous Memory", choose
  27           "Discontiguous Memory".
  28
  29           If unsure, choose this option (Flat Memory) over any other.
  30
  31 config DISCONTIGMEM_MANUAL
  32         bool "Discontiguous Memory"
  33         depends on ARCH_DISCONTIGMEM_ENABLE
  34         help
  35           This option provides enhanced support for discontiguous
  36           memory systems, over FLATMEM.  These systems have holes
  37           in their physical address spaces, and this option provides
  38           more efficient handling of these holes.  However, the vast
  39           majority of hardware has quite flat address spaces, and
  40           can have degraded performance from the extra overhead that
  41           this option imposes.
  42
  43           Many NUMA configurations will have this as the only option.
  44
  45           If unsure, choose "Flat Memory" over this option.
  46
  47 config SPARSEMEM_MANUAL
  48         bool "Sparse Memory"
  49         depends on ARCH_SPARSEMEM_ENABLE
  50         help
  51           This will be the only option for some systems, including
  52           memory hotplug systems.  This is normal.
  53
  54           For many other systems, this will be an alternative to
  55           "Discontiguous Memory".  This option provides some potential
  56           performance benefits, along with decreased code complexity,
  57           but it is newer, and more experimental.
  58
  59           If unsure, choose "Discontiguous Memory" or "Flat Memory"
  60           over this option.
  61
  62 endchoice
  63
  64 config DISCONTIGMEM
  65         def_bool y
  66         depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
  67
  68 config SPARSEMEM
  69         def_bool y
  70         depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
  71
  72 config FLATMEM
  73         def_bool y
  74         depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
  75
  76 config FLAT_NODE_MEM_MAP
  77         def_bool y
  78         depends on !SPARSEMEM
  79
  80 #
  81 # Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
  82 # to represent different areas of memory.  This variable allows
  83 # those dependencies to exist individually.
  84 #
  85 config NEED_MULTIPLE_NODES
  86         def_bool y
  87         depends on DISCONTIGMEM || NUMA
  88
  89 config HAVE_MEMORY_PRESENT
  90         def_bool y
  91         depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
  92
  93 #
  94 # SPARSEMEM_EXTREME (which is the default) does some bootmem
  95 # allocations when memory_present() is called.  If this cannot
  96 # be done on your architecture, select this option.  However,
  97 # statically allocating the mem_section[] array can potentially
  98 # consume vast quantities of .bss, so be careful.
  99 #
 100 # This option will also potentially produce smaller runtime code
 101 # with gcc 3.4 and later.
 102 #
 103 config SPARSEMEM_STATIC
 104         bool
 105
 106 #
 107 # Architecture platforms which require a two level mem_section in SPARSEMEM
 108 # must select this option. This is usually for architecture platforms with
 109 # an extremely sparse physical address space.
 110 #
 111 config SPARSEMEM_EXTREME
 112         def_bool y
 113         depends on SPARSEMEM && !SPARSEMEM_STATIC
 114
 115 config SPARSEMEM_VMEMMAP_ENABLE
 116         bool
 117
 118 config SPARSEMEM_VMEMMAP
 119         bool "Sparse Memory virtual memmap"
 120         depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
 121         default y
 122         help
 123          SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
 124          pfn_to_page and page_to_pfn operations.  This is the most
 125          efficient option when sufficient kernel resources are available.
 126
 127 # eventually, we can have this option just 'select SPARSEMEM'
 128 config MEMORY_HOTPLUG
 129         bool "Allow for memory hot-add"
 130         depends on SPARSEMEM || X86_64_ACPI_NUMA
 131         depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG
 132         depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
 133
 134 config MEMORY_HOTPLUG_SPARSE
 135         def_bool y
 136         depends on SPARSEMEM && MEMORY_HOTPLUG
 137
 138 config MEMORY_HOTREMOVE
 139         bool "Allow for memory hot remove"
 140         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 141         depends on MIGRATION
 142
 143 #
 144 # If we have space for more page flags then we can enable additional
 145 # optimizations and functionality.
 146 #
 147 # Regular Sparsemem takes page flag bits for the sectionid if it does not
 148 # use a virtual memmap. Disable extended page flags for 32 bit platforms
 149 # that require the use of a sectionid in the page flags.
 150 #
 151 config PAGEFLAGS_EXTENDED
 152         def_bool y
 153         depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
 154
 155 # Heavily threaded applications may benefit from splitting the mm-wide
 156 # page_table_lock, so that faults on different parts of the user address
 157 # space can be handled with less contention: split it at this NR_CPUS.
 158 # Default to 4 for wider testing, though 8 might be more appropriate.
 159 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 160 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 161 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
 162 #
 163 config SPLIT_PTLOCK_CPUS
 164         int
 165         default "999999" if ARM && !CPU_CACHE_VIPT
 166         default "999999" if PARISC && !PA20
 167         default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
 168         default "4"
 169
 170 #
 171 # support for page migration
 172 #
 173 config MIGRATION
 174         bool "Page migration"
 175         def_bool y
 176         depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
 177         help
 178           Allows the migration of the physical location of pages of processes
 179           while the virtual addresses are not changed. This is useful for
 180           example on NUMA systems to put pages nearer to the processors accessing
 181           the page.
 182
 183 config PHYS_ADDR_T_64BIT
 184         def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
 185
 186 config ZONE_DMA_FLAG
 187         int
 188         default "0" if !ZONE_DMA
 189         default "1"
 190
 191 config BOUNCE
 192         def_bool y
 193         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 194
 195 config NR_QUICK
 196         int
 197         depends on QUICKLIST
 198         default "2" if SUPERH || AVR32
 199         default "1"
 200
 201 config VIRT_TO_BUS
 202         def_bool y
 203         depends on !ARCH_NO_VIRT_TO_BUS
 204
 205 config MMU_NOTIFIER
 206         bool
 207
 208 config KSM
 209         bool "Enable KSM for page merging"
 210         depends on MMU
 211         help
 212           Enable Kernel Samepage Merging: KSM periodically scans those areas
 213           of an application's address space that an app has advised may be
 214           mergeable.  When it finds pages of identical content, it replaces
 215           the many instances by a single page with that content, so
 216           saving memory until one or another app needs to modify the content.
 217           Recommended for use with KVM, or with other duplicative applications.
 218           See Documentation/vm/ksm.txt for more information: KSM is inactive
 219           until a program has madvised that an area is MADV_MERGEABLE, and
 220           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 221
 222 config DEFAULT_MMAP_MIN_ADDR
 223         int "Low address space to protect from user allocation"
 224         depends on MMU
 225         default 4096
 226         help
 227           This is the portion of low virtual memory which should be protected
 228           from userspace allocation.  Keeping a user from writing to low pages
 229           can help reduce the impact of kernel NULL pointer bugs.
 230
 231           For most ia64, ppc64 and x86 users with lots of address space
 232           a value of 65536 is reasonable and should cause no problems.
 233           On arm and other archs it should not be higher than 32768.
 234           Programs which use vm86 functionality or have some need to map
 235           this low address space will need CAP_SYS_RAWIO or disable this
 236           protection by setting the value to 0.
 237
 238           This value can be changed after boot using the
 239           /proc/sys/vm/mmap_min_addr tunable.
 240
 241 config ARCH_SUPPORTS_MEMORY_FAILURE
 242         bool
 243
 244 config MEMORY_FAILURE
 245         depends on MMU
 246         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 247         bool "Enable recovery from hardware memory errors"
 248         help
 249           Enables code to recover from some memory failures on systems
 250           with MCA recovery. This allows a system to continue running
 251           even when some of its memory has uncorrected errors. This requires
 252           special hardware support and typically ECC memory.
 253
 254 config HWPOISON_INJECT
 255         tristate "HWPoison pages injector"
 256         depends on MEMORY_FAILURE && DEBUG_KERNEL
 257         select PROC_PAGE_MONITOR
 258
 259 config NOMMU_INITIAL_TRIM_EXCESS
 260         int "Turn on mmap() excess space trimming before booting"
 261         depends on !MMU
 262         default 1
 263         help
 264           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 265           of memory on which to store mappings, but it can only ask the system
 266           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 267           more than it requires.  To deal with this, mmap() is able to trim off
 268           the excess and return it to the allocator.
 269
 270           If trimming is enabled, the excess is trimmed off and returned to the
 271           system allocator, which can cause extra fragmentation, particularly
 272           if there are a lot of transient processes.
 273
 274           If trimming is disabled, the excess is kept, but not used, which for
 275           long-term mappings means that the space is wasted.
 276
 277           Trimming can be dynamically controlled through a sysctl option
 278           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 279           excess pages there must be before trimming should occur, or zero if
 280           no trimming is to occur.
 281
 282           This option specifies the initial value of this option.  The default
 283           of 1 says that all excess pages should be trimmed.
 284
 285           See Documentation/nommu-mmap.txt for more information.