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