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 config HAVE_MEMBLOCK
 132         boolean
 133
 134 config NO_BOOTMEM
 135         boolean
 136
 137 # eventually, we can have this option just 'select SPARSEMEM'
 138 config MEMORY_HOTPLUG
 139         bool "Allow for memory hot-add"
 140         depends on SPARSEMEM || X86_64_ACPI_NUMA
 141         depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG
 142         depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
 143
 144 config MEMORY_HOTPLUG_SPARSE
 145         def_bool y
 146         depends on SPARSEMEM && MEMORY_HOTPLUG
 147
 148 config MEMORY_HOTREMOVE
 149         bool "Allow for memory hot remove"
 150         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 151         depends on MIGRATION
 152
 153 #
 154 # If we have space for more page flags then we can enable additional
 155 # optimizations and functionality.
 156 #
 157 # Regular Sparsemem takes page flag bits for the sectionid if it does not
 158 # use a virtual memmap. Disable extended page flags for 32 bit platforms
 159 # that require the use of a sectionid in the page flags.
 160 #
 161 config PAGEFLAGS_EXTENDED
 162         def_bool y
 163         depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
 164
 165 # Heavily threaded applications may benefit from splitting the mm-wide
 166 # page_table_lock, so that faults on different parts of the user address
 167 # space can be handled with less contention: split it at this NR_CPUS.
 168 # Default to 4 for wider testing, though 8 might be more appropriate.
 169 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 170 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 171 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
 172 #
 173 config SPLIT_PTLOCK_CPUS
 174         int
 175         default "999999" if ARM && !CPU_CACHE_VIPT
 176         default "999999" if PARISC && !PA20
 177         default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
 178         default "4"
 179
 180 #
 181 # support for memory compaction
 182 config COMPACTION
 183         bool "Allow for memory compaction"
 184         select MIGRATION
 185         depends on MMU
 186         help
 187           Allows the compaction of memory for the allocation of huge pages.
 188
 189 #
 190 # support for page migration
 191 #
 192 config MIGRATION
 193         bool "Page migration"
 194         def_bool y
 195         depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION
 196         help
 197           Allows the migration of the physical location of pages of processes
 198           while the virtual addresses are not changed. This is useful in
 199           two situations. The first is on NUMA systems to put pages nearer
 200           to the processors accessing. The second is when allocating huge
 201           pages as migration can relocate pages to satisfy a huge page
 202           allocation instead of reclaiming.
 203
 204 config PHYS_ADDR_T_64BIT
 205         def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
 206
 207 config ZONE_DMA_FLAG
 208         int
 209         default "0" if !ZONE_DMA
 210         default "1"
 211
 212 config BOUNCE
 213         def_bool y
 214         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 215
 216 config NR_QUICK
 217         int
 218         depends on QUICKLIST
 219         default "2" if AVR32
 220         default "1"
 221
 222 config VIRT_TO_BUS
 223         def_bool y
 224         depends on !ARCH_NO_VIRT_TO_BUS
 225
 226 config MMU_NOTIFIER
 227         bool
 228
 229 config KSM
 230         bool "Enable KSM for page merging"
 231         depends on MMU
 232         help
 233           Enable Kernel Samepage Merging: KSM periodically scans those areas
 234           of an application's address space that an app has advised may be
 235           mergeable.  When it finds pages of identical content, it replaces
 236           the many instances by a single page with that content, so
 237           saving memory until one or another app needs to modify the content.
 238           Recommended for use with KVM, or with other duplicative applications.
 239           See Documentation/vm/ksm.txt for more information: KSM is inactive
 240           until a program has madvised that an area is MADV_MERGEABLE, and
 241           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 242
 243 config DEFAULT_MMAP_MIN_ADDR
 244         int "Low address space to protect from user allocation"
 245         depends on MMU
 246         default 4096
 247         help
 248           This is the portion of low virtual memory which should be protected
 249           from userspace allocation.  Keeping a user from writing to low pages
 250           can help reduce the impact of kernel NULL pointer bugs.
 251
 252           For most ia64, ppc64 and x86 users with lots of address space
 253           a value of 65536 is reasonable and should cause no problems.
 254           On arm and other archs it should not be higher than 32768.
 255           Programs which use vm86 functionality or have some need to map
 256           this low address space will need CAP_SYS_RAWIO or disable this
 257           protection by setting the value to 0.
 258
 259           This value can be changed after boot using the
 260           /proc/sys/vm/mmap_min_addr tunable.
 261
 262 config ARCH_SUPPORTS_MEMORY_FAILURE
 263         bool
 264
 265 config MEMORY_FAILURE
 266         depends on MMU
 267         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 268         bool "Enable recovery from hardware memory errors"
 269         help
 270           Enables code to recover from some memory failures on systems
 271           with MCA recovery. This allows a system to continue running
 272           even when some of its memory has uncorrected errors. This requires
 273           special hardware support and typically ECC memory.
 274
 275 config HWPOISON_INJECT
 276         tristate "HWPoison pages injector"
 277         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 278         select PROC_PAGE_MONITOR
 279
 280 config NOMMU_INITIAL_TRIM_EXCESS
 281         int "Turn on mmap() excess space trimming before booting"
 282         depends on !MMU
 283         default 1
 284         help
 285           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 286           of memory on which to store mappings, but it can only ask the system
 287           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 288           more than it requires.  To deal with this, mmap() is able to trim off
 289           the excess and return it to the allocator.
 290
 291           If trimming is enabled, the excess is trimmed off and returned to the
 292           system allocator, which can cause extra fragmentation, particularly
 293           if there are a lot of transient processes.
 294
 295           If trimming is disabled, the excess is kept, but not used, which for
 296           long-term mappings means that the space is wasted.
 297
 298           Trimming can be dynamically controlled through a sysctl option
 299           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 300           excess pages there must be before trimming should occur, or zero if
 301           no trimming is to occur.
 302
 303           This option specifies the initial value of this option.  The default
 304           of 1 says that all excess pages should be trimmed.
 305
 306           See Documentation/nommu-mmap.txt for more information.
 307
 308 config TRANSPARENT_HUGEPAGE
 309         bool "Transparent Hugepage Support"
 310         depends on X86 && MMU
 311         select COMPACTION
 312         help
 313           Transparent Hugepages allows the kernel to use huge pages and
 314           huge tlb transparently to the applications whenever possible.
 315           This feature can improve computing performance to certain
 316           applications by speeding up page faults during memory
 317           allocation, by reducing the number of tlb misses and by speeding
 318           up the pagetable walking.
 319
 320           If memory constrained on embedded, you may want to say N.
 321
 322 choice
 323         prompt "Transparent Hugepage Support sysfs defaults"
 324         depends on TRANSPARENT_HUGEPAGE
 325         default TRANSPARENT_HUGEPAGE_ALWAYS
 326         help
 327           Selects the sysfs defaults for Transparent Hugepage Support.
 328
 329         config TRANSPARENT_HUGEPAGE_ALWAYS
 330                 bool "always"
 331         help
 332           Enabling Transparent Hugepage always, can increase the
 333           memory footprint of applications without a guaranteed
 334           benefit but it will work automatically for all applications.
 335
 336         config TRANSPARENT_HUGEPAGE_MADVISE
 337                 bool "madvise"
 338         help
 339           Enabling Transparent Hugepage madvise, will only provide a
 340           performance improvement benefit to the applications using
 341           madvise(MADV_HUGEPAGE) but it won't risk to increase the
 342           memory footprint of applications without a guaranteed
 343           benefit.
 344 endchoice
 345
 346 #
 347 # UP and nommu archs use km based percpu allocator
 348 #
 349 config NEED_PER_CPU_KM
 350         depends on !SMP
 351         bool
 352         default y
 353
 354 config CLEANCACHE
 355         bool "Enable cleancache driver to cache clean pages if tmem is present"
 356         default n
 357         help
 358           Cleancache can be thought of as a page-granularity victim cache
 359           for clean pages that the kernel's pageframe replacement algorithm
 360           (PFRA) would like to keep around, but can't since there isn't enough
 361           memory.  So when the PFRA "evicts" a page, it first attempts to use
 362           cleancache code to put the data contained in that page into
 363           "transcendent memory", memory that is not directly accessible or
 364           addressable by the kernel and is of unknown and possibly
 365           time-varying size.  And when a cleancache-enabled
 366           filesystem wishes to access a page in a file on disk, it first
 367           checks cleancache to see if it already contains it; if it does,
 368           the page is copied into the kernel and a disk access is avoided.
 369           When a transcendent memory driver is available (such as zcache or
 370           Xen transcendent memory), a significant I/O reduction
 371           may be achieved.  When none is available, all cleancache calls
 372           are reduced to a single pointer-compare-against-NULL resulting
 373           in a negligible performance hit.
 374
 375           If unsure, say Y to enable cleancache