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 HAVE_MEMBLOCK_NODE_MAP
 135         boolean
 136
 137 config ARCH_DISCARD_MEMBLOCK
 138         boolean
 139
 140 config NO_BOOTMEM
 141         boolean
 142
 143 config MEMORY_ISOLATION
 144         boolean
 145
 146 config MOVABLE_NODE
 147         boolean "Enable to assign a node which has only movable memory"
 148         depends on HAVE_MEMBLOCK
 149         depends on NO_BOOTMEM
 150         depends on X86_64
 151         depends on NUMA
 152         depends on BROKEN
 153
 154 # eventually, we can have this option just 'select SPARSEMEM'
 155 config MEMORY_HOTPLUG
 156         bool "Allow for memory hot-add"
 157         select MEMORY_ISOLATION
 158         depends on SPARSEMEM || X86_64_ACPI_NUMA
 159         depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG
 160         depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
 161
 162 config MEMORY_HOTPLUG_SPARSE
 163         def_bool y
 164         depends on SPARSEMEM && MEMORY_HOTPLUG
 165
 166 config MEMORY_HOTREMOVE
 167         bool "Allow for memory hot remove"
 168         depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
 169         depends on MIGRATION
 170
 171 #
 172 # If we have space for more page flags then we can enable additional
 173 # optimizations and functionality.
 174 #
 175 # Regular Sparsemem takes page flag bits for the sectionid if it does not
 176 # use a virtual memmap. Disable extended page flags for 32 bit platforms
 177 # that require the use of a sectionid in the page flags.
 178 #
 179 config PAGEFLAGS_EXTENDED
 180         def_bool y
 181         depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
 182
 183 # Heavily threaded applications may benefit from splitting the mm-wide
 184 # page_table_lock, so that faults on different parts of the user address
 185 # space can be handled with less contention: split it at this NR_CPUS.
 186 # Default to 4 for wider testing, though 8 might be more appropriate.
 187 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
 188 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
 189 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
 190 #
 191 config SPLIT_PTLOCK_CPUS
 192         int
 193         default "999999" if ARM && !CPU_CACHE_VIPT
 194         default "999999" if PARISC && !PA20
 195         default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
 196         default "4"
 197
 198 #
 199 # support for memory balloon compaction
 200 config BALLOON_COMPACTION
 201         bool "Allow for balloon memory compaction/migration"
 202         def_bool y
 203         depends on COMPACTION && VIRTIO_BALLOON
 204         help
 205           Memory fragmentation introduced by ballooning might reduce
 206           significantly the number of 2MB contiguous memory blocks that can be
 207           used within a guest, thus imposing performance penalties associated
 208           with the reduced number of transparent huge pages that could be used
 209           by the guest workload. Allowing the compaction & migration for memory
 210           pages enlisted as being part of memory balloon devices avoids the
 211           scenario aforementioned and helps improving memory defragmentation.
 212
 213 #
 214 # support for memory compaction
 215 config COMPACTION
 216         bool "Allow for memory compaction"
 217         def_bool y
 218         select MIGRATION
 219         depends on MMU
 220         help
 221           Allows the compaction of memory for the allocation of huge pages.
 222
 223 #
 224 # support for page migration
 225 #
 226 config MIGRATION
 227         bool "Page migration"
 228         def_bool y
 229         depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA
 230         help
 231           Allows the migration of the physical location of pages of processes
 232           while the virtual addresses are not changed. This is useful in
 233           two situations. The first is on NUMA systems to put pages nearer
 234           to the processors accessing. The second is when allocating huge
 235           pages as migration can relocate pages to satisfy a huge page
 236           allocation instead of reclaiming.
 237
 238 config PHYS_ADDR_T_64BIT
 239         def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
 240
 241 config ZONE_DMA_FLAG
 242         int
 243         default "0" if !ZONE_DMA
 244         default "1"
 245
 246 config BOUNCE
 247         def_bool y
 248         depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
 249
 250 config NR_QUICK
 251         int
 252         depends on QUICKLIST
 253         default "2" if AVR32
 254         default "1"
 255
 256 config VIRT_TO_BUS
 257         def_bool y
 258         depends on !ARCH_NO_VIRT_TO_BUS
 259
 260 config MMU_NOTIFIER
 261         bool
 262
 263 config KSM
 264         bool "Enable KSM for page merging"
 265         depends on MMU
 266         help
 267           Enable Kernel Samepage Merging: KSM periodically scans those areas
 268           of an application's address space that an app has advised may be
 269           mergeable.  When it finds pages of identical content, it replaces
 270           the many instances by a single page with that content, so
 271           saving memory until one or another app needs to modify the content.
 272           Recommended for use with KVM, or with other duplicative applications.
 273           See Documentation/vm/ksm.txt for more information: KSM is inactive
 274           until a program has madvised that an area is MADV_MERGEABLE, and
 275           root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
 276
 277 config DEFAULT_MMAP_MIN_ADDR
 278         int "Low address space to protect from user allocation"
 279         depends on MMU
 280         default 4096
 281         help
 282           This is the portion of low virtual memory which should be protected
 283           from userspace allocation.  Keeping a user from writing to low pages
 284           can help reduce the impact of kernel NULL pointer bugs.
 285
 286           For most ia64, ppc64 and x86 users with lots of address space
 287           a value of 65536 is reasonable and should cause no problems.
 288           On arm and other archs it should not be higher than 32768.
 289           Programs which use vm86 functionality or have some need to map
 290           this low address space will need CAP_SYS_RAWIO or disable this
 291           protection by setting the value to 0.
 292
 293           This value can be changed after boot using the
 294           /proc/sys/vm/mmap_min_addr tunable.
 295
 296 config ARCH_SUPPORTS_MEMORY_FAILURE
 297         bool
 298
 299 config MEMORY_FAILURE
 300         depends on MMU
 301         depends on ARCH_SUPPORTS_MEMORY_FAILURE
 302         bool "Enable recovery from hardware memory errors"
 303         select MEMORY_ISOLATION
 304         help
 305           Enables code to recover from some memory failures on systems
 306           with MCA recovery. This allows a system to continue running
 307           even when some of its memory has uncorrected errors. This requires
 308           special hardware support and typically ECC memory.
 309
 310 config HWPOISON_INJECT
 311         tristate "HWPoison pages injector"
 312         depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
 313         select PROC_PAGE_MONITOR
 314
 315 config NOMMU_INITIAL_TRIM_EXCESS
 316         int "Turn on mmap() excess space trimming before booting"
 317         depends on !MMU
 318         default 1
 319         help
 320           The NOMMU mmap() frequently needs to allocate large contiguous chunks
 321           of memory on which to store mappings, but it can only ask the system
 322           allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
 323           more than it requires.  To deal with this, mmap() is able to trim off
 324           the excess and return it to the allocator.
 325
 326           If trimming is enabled, the excess is trimmed off and returned to the
 327           system allocator, which can cause extra fragmentation, particularly
 328           if there are a lot of transient processes.
 329
 330           If trimming is disabled, the excess is kept, but not used, which for
 331           long-term mappings means that the space is wasted.
 332
 333           Trimming can be dynamically controlled through a sysctl option
 334           (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
 335           excess pages there must be before trimming should occur, or zero if
 336           no trimming is to occur.
 337
 338           This option specifies the initial value of this option.  The default
 339           of 1 says that all excess pages should be trimmed.
 340
 341           See Documentation/nommu-mmap.txt for more information.
 342
 343 config TRANSPARENT_HUGEPAGE
 344         bool "Transparent Hugepage Support"
 345         depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
 346         select COMPACTION
 347         help
 348           Transparent Hugepages allows the kernel to use huge pages and
 349           huge tlb transparently to the applications whenever possible.
 350           This feature can improve computing performance to certain
 351           applications by speeding up page faults during memory
 352           allocation, by reducing the number of tlb misses and by speeding
 353           up the pagetable walking.
 354
 355           If memory constrained on embedded, you may want to say N.
 356
 357 choice
 358         prompt "Transparent Hugepage Support sysfs defaults"
 359         depends on TRANSPARENT_HUGEPAGE
 360         default TRANSPARENT_HUGEPAGE_ALWAYS
 361         help
 362           Selects the sysfs defaults for Transparent Hugepage Support.
 363
 364         config TRANSPARENT_HUGEPAGE_ALWAYS
 365                 bool "always"
 366         help
 367           Enabling Transparent Hugepage always, can increase the
 368           memory footprint of applications without a guaranteed
 369           benefit but it will work automatically for all applications.
 370
 371         config TRANSPARENT_HUGEPAGE_MADVISE
 372                 bool "madvise"
 373         help
 374           Enabling Transparent Hugepage madvise, will only provide a
 375           performance improvement benefit to the applications using
 376           madvise(MADV_HUGEPAGE) but it won't risk to increase the
 377           memory footprint of applications without a guaranteed
 378           benefit.
 379 endchoice
 380
 381 config CROSS_MEMORY_ATTACH
 382         bool "Cross Memory Support"
 383         depends on MMU
 384         default y
 385         help
 386           Enabling this option adds the system calls process_vm_readv and
 387           process_vm_writev which allow a process with the correct privileges
 388           to directly read from or write to to another process's address space.
 389           See the man page for more details.
 390
 391 #
 392 # UP and nommu archs use km based percpu allocator
 393 #
 394 config NEED_PER_CPU_KM
 395         depends on !SMP
 396         bool
 397         default y
 398
 399 config CLEANCACHE
 400         bool "Enable cleancache driver to cache clean pages if tmem is present"
 401         default n
 402         help
 403           Cleancache can be thought of as a page-granularity victim cache
 404           for clean pages that the kernel's pageframe replacement algorithm
 405           (PFRA) would like to keep around, but can't since there isn't enough
 406           memory.  So when the PFRA "evicts" a page, it first attempts to use
 407           cleancache code to put the data contained in that page into
 408           "transcendent memory", memory that is not directly accessible or
 409           addressable by the kernel and is of unknown and possibly
 410           time-varying size.  And when a cleancache-enabled
 411           filesystem wishes to access a page in a file on disk, it first
 412           checks cleancache to see if it already contains it; if it does,
 413           the page is copied into the kernel and a disk access is avoided.
 414           When a transcendent memory driver is available (such as zcache or
 415           Xen transcendent memory), a significant I/O reduction
 416           may be achieved.  When none is available, all cleancache calls
 417           are reduced to a single pointer-compare-against-NULL resulting
 418           in a negligible performance hit.
 419
 420           If unsure, say Y to enable cleancache
 421
 422 config FRONTSWAP
 423         bool "Enable frontswap to cache swap pages if tmem is present"
 424         depends on SWAP
 425         default n
 426         help
 427           Frontswap is so named because it can be thought of as the opposite
 428           of a "backing" store for a swap device.  The data is stored into
 429           "transcendent memory", memory that is not directly accessible or
 430           addressable by the kernel and is of unknown and possibly
 431           time-varying size.  When space in transcendent memory is available,
 432           a significant swap I/O reduction may be achieved.  When none is
 433           available, all frontswap calls are reduced to a single pointer-
 434           compare-against-NULL resulting in a negligible performance hit
 435           and swap data is stored as normal on the matching swap device.
 436
 437           If unsure, say Y to enable frontswap.