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_ALLOC_MEM_MAP_TOGETHER
 119         def_bool y
 120         depends on SPARSEMEM && X86_64
 121
 122 config SPARSEMEM_VMEMMAP
 123         bool "Sparse Memory virtual memmap"
 124         depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
 125         default y
 126         help
 127          SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
 128          pfn_to_page and page_to_pfn operations.  This is the most
 129          efficient option when sufficient kernel resources are available.
 130
 131 # eventually, we can have this option just 'select SPARSEMEM'
 132 config MEMORY_HOTPLUG
 133         bool "Allow for memory hot-add"
 134         depends on SPARSEMEM || X86_64_ACPI_NUMA
 135         depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG
 136         depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
 137
 138 config MEMORY_HOTPLUG_SPARSE
 139         def_bool y
 140         depends on SPARSEMEM && MEMORY_HOTPLUG
 141
 142 config MEMORY_HOTREMOVE
 143         bool "Allow for memory hot remove"
 144         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 145         depends on MIGRATION
 146
 147 #
 148 # If we have space for more page flags then we can enable additional
 149 # optimizations and functionality.
 150 #
 151 # Regular Sparsemem takes page flag bits for the sectionid if it does not
 152 # use a virtual memmap. Disable extended page flags for 32 bit platforms
 153 # that require the use of a sectionid in the page flags.
 154 #
 155 config PAGEFLAGS_EXTENDED
 156         def_bool y
 157         depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
 158
 159 # Heavily threaded applications may benefit from splitting the mm-wide
 160 # page_table_lock, so that faults on different parts of the user address
 161 # space can be handled with less contention: split it at this NR_CPUS.
 162 # Default to 4 for wider testing, though 8 might be more appropriate.
 163 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 164 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 165 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
 166 #
 167 config SPLIT_PTLOCK_CPUS
 168         int
 169         default "999999" if ARM && !CPU_CACHE_VIPT
 170         default "999999" if PARISC && !PA20
 171         default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
 172         default "4"
 173
 174 #
 175 # support for memory compaction
 176 config COMPACTION
 177         bool "Allow for memory compaction"
 178         select MIGRATION
 179         depends on EXPERIMENTAL && HUGETLB_PAGE && MMU
 180         help
 181           Allows the compaction of memory for the allocation of huge pages.
 182
 183 #
 184 # support for page migration
 185 #
 186 config MIGRATION
 187         bool "Page migration"
 188         def_bool y
 189         depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE
 190         help
 191           Allows the migration of the physical location of pages of processes
 192           while the virtual addresses are not changed. This is useful in
 193           two situations. The first is on NUMA systems to put pages nearer
 194           to the processors accessing. The second is when allocating huge
 195           pages as migration can relocate pages to satisfy a huge page
 196           allocation instead of reclaiming.
 197
 198 config PHYS_ADDR_T_64BIT
 199         def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
 200
 201 config ZONE_DMA_FLAG
 202         int
 203         default "0" if !ZONE_DMA
 204         default "1"
 205
 206 config BOUNCE
 207         def_bool y
 208         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 209
 210 config NR_QUICK
 211         int
 212         depends on QUICKLIST
 213         default "2" if AVR32
 214         default "1"
 215
 216 config VIRT_TO_BUS
 217         def_bool y
 218         depends on !ARCH_NO_VIRT_TO_BUS
 219
 220 config MMU_NOTIFIER
 221         bool
 222
 223 config KSM
 224         bool "Enable KSM for page merging"
 225         depends on MMU
 226         help
 227           Enable Kernel Samepage Merging: KSM periodically scans those areas
 228           of an application's address space that an app has advised may be
 229           mergeable.  When it finds pages of identical content, it replaces
 230           the many instances by a single page with that content, so
 231           saving memory until one or another app needs to modify the content.
 232           Recommended for use with KVM, or with other duplicative applications.
 233           See Documentation/vm/ksm.txt for more information: KSM is inactive
 234           until a program has madvised that an area is MADV_MERGEABLE, and
 235           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 236
 237 config DEFAULT_MMAP_MIN_ADDR
 238         int "Low address space to protect from user allocation"
 239         depends on MMU
 240         default 4096
 241         help
 242           This is the portion of low virtual memory which should be protected
 243           from userspace allocation.  Keeping a user from writing to low pages
 244           can help reduce the impact of kernel NULL pointer bugs.
 245
 246           For most ia64, ppc64 and x86 users with lots of address space
 247           a value of 65536 is reasonable and should cause no problems.
 248           On arm and other archs it should not be higher than 32768.
 249           Programs which use vm86 functionality or have some need to map
 250           this low address space will need CAP_SYS_RAWIO or disable this
 251           protection by setting the value to 0.
 252
 253           This value can be changed after boot using the
 254           /proc/sys/vm/mmap_min_addr tunable.
 255
 256 config ARCH_SUPPORTS_MEMORY_FAILURE
 257         bool
 258
 259 config MEMORY_FAILURE
 260         depends on MMU
 261         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 262         bool "Enable recovery from hardware memory errors"
 263         help
 264           Enables code to recover from some memory failures on systems
 265           with MCA recovery. This allows a system to continue running
 266           even when some of its memory has uncorrected errors. This requires
 267           special hardware support and typically ECC memory.
 268
 269 config HWPOISON_INJECT
 270         tristate "HWPoison pages injector"
 271         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 272         select PROC_PAGE_MONITOR
 273
 274 config NOMMU_INITIAL_TRIM_EXCESS
 275         int "Turn on mmap() excess space trimming before booting"
 276         depends on !MMU
 277         default 1
 278         help
 279           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 280           of memory on which to store mappings, but it can only ask the system
 281           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 282           more than it requires.  To deal with this, mmap() is able to trim off
 283           the excess and return it to the allocator.
 284
 285           If trimming is enabled, the excess is trimmed off and returned to the
 286           system allocator, which can cause extra fragmentation, particularly
 287           if there are a lot of transient processes.
 288
 289           If trimming is disabled, the excess is kept, but not used, which for
 290           long-term mappings means that the space is wasted.
 291
 292           Trimming can be dynamically controlled through a sysctl option
 293           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 294           excess pages there must be before trimming should occur, or zero if
 295           no trimming is to occur.
 296
 297           This option specifies the initial value of this option.  The default
 298           of 1 says that all excess pages should be trimmed.
 299
 300           See Documentation/nommu-mmap.txt for more information.