1config SELECT_MEMORY_MODEL 2 def_bool y 3 depends on ARCH_SELECT_MEMORY_MODEL 4 5choice 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 12config 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 31config 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 47config 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 62endchoice 63 64config DISCONTIGMEM 65 def_bool y 66 depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL 67 68config SPARSEMEM 69 def_bool y 70 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL 71 72config FLATMEM 73 def_bool y 74 depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL 75 76config 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# 85config NEED_MULTIPLE_NODES 86 def_bool y 87 depends on DISCONTIGMEM || NUMA 88 89config 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# 103config 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# 111config SPARSEMEM_EXTREME 112 def_bool y 113 depends on SPARSEMEM && !SPARSEMEM_STATIC 114 115config SPARSEMEM_VMEMMAP_ENABLE 116 bool 117 118config SPARSEMEM_ALLOC_MEM_MAP_TOGETHER 119 def_bool y 120 depends on SPARSEMEM && X86_64 121 122config 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 131config HAVE_MEMBLOCK 132 boolean 133 134config HAVE_MEMBLOCK_NODE_MAP 135 boolean 136 137config ARCH_DISCARD_MEMBLOCK 138 boolean 139 140config NO_BOOTMEM 141 boolean 142 143config MEMORY_ISOLATION 144 boolean 145 146config 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 default n 153 help 154 Allow a node to have only movable memory. Pages used by the kernel, 155 such as direct mapping pages cannot be migrated. So the corresponding 156 memory device cannot be hotplugged. This option allows users to 157 online all the memory of a node as movable memory so that the whole 158 node can be hotplugged. Users who don't use the memory hotplug 159 feature are fine with this option on since they don't online memory 160 as movable. 161 162 Say Y here if you want to hotplug a whole node. 163 Say N here if you want kernel to use memory on all nodes evenly. 164 165# 166# Only be set on architectures that have completely implemented memory hotplug 167# feature. If you are not sure, don't touch it. 168# 169config HAVE_BOOTMEM_INFO_NODE 170 def_bool n 171 172# eventually, we can have this option just 'select SPARSEMEM' 173config MEMORY_HOTPLUG 174 bool "Allow for memory hot-add" 175 depends on SPARSEMEM || X86_64_ACPI_NUMA 176 depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG 177 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390) 178 179config MEMORY_HOTPLUG_SPARSE 180 def_bool y 181 depends on SPARSEMEM && MEMORY_HOTPLUG 182 183config MEMORY_HOTREMOVE 184 bool "Allow for memory hot remove" 185 select MEMORY_ISOLATION 186 select HAVE_BOOTMEM_INFO_NODE if X86_64 187 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 188 depends on MIGRATION 189 190# 191# If we have space for more page flags then we can enable additional 192# optimizations and functionality. 193# 194# Regular Sparsemem takes page flag bits for the sectionid if it does not 195# use a virtual memmap. Disable extended page flags for 32 bit platforms 196# that require the use of a sectionid in the page flags. 197# 198config PAGEFLAGS_EXTENDED 199 def_bool y 200 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM 201 202# Heavily threaded applications may benefit from splitting the mm-wide 203# page_table_lock, so that faults on different parts of the user address 204# space can be handled with less contention: split it at this NR_CPUS. 205# Default to 4 for wider testing, though 8 might be more appropriate. 206# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 207# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 208# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 209# 210config SPLIT_PTLOCK_CPUS 211 int 212 default "999999" if ARM && !CPU_CACHE_VIPT 213 default "999999" if PARISC && !PA20 214 default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC 215 default "4" 216 217# 218# support for memory balloon compaction 219config BALLOON_COMPACTION 220 bool "Allow for balloon memory compaction/migration" 221 def_bool y 222 depends on COMPACTION && VIRTIO_BALLOON 223 help 224 Memory fragmentation introduced by ballooning might reduce 225 significantly the number of 2MB contiguous memory blocks that can be 226 used within a guest, thus imposing performance penalties associated 227 with the reduced number of transparent huge pages that could be used 228 by the guest workload. Allowing the compaction & migration for memory 229 pages enlisted as being part of memory balloon devices avoids the 230 scenario aforementioned and helps improving memory defragmentation. 231 232# 233# support for memory compaction 234config COMPACTION 235 bool "Allow for memory compaction" 236 def_bool y 237 select MIGRATION 238 depends on MMU 239 help 240 Allows the compaction of memory for the allocation of huge pages. 241 242# 243# support for page migration 244# 245config MIGRATION 246 bool "Page migration" 247 def_bool y 248 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA 249 help 250 Allows the migration of the physical location of pages of processes 251 while the virtual addresses are not changed. This is useful in 252 two situations. The first is on NUMA systems to put pages nearer 253 to the processors accessing. The second is when allocating huge 254 pages as migration can relocate pages to satisfy a huge page 255 allocation instead of reclaiming. 256 257config PHYS_ADDR_T_64BIT 258 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 259 260config ZONE_DMA_FLAG 261 int 262 default "0" if !ZONE_DMA 263 default "1" 264 265config BOUNCE 266 bool "Enable bounce buffers" 267 default y 268 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 269 help 270 Enable bounce buffers for devices that cannot access 271 the full range of memory available to the CPU. Enabled 272 by default when ZONE_DMA or HIGHMEM is selected, but you 273 may say n to override this. 274 275# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often 276# have more than 4GB of memory, but we don't currently use the IOTLB to present 277# a 32-bit address to OHCI. So we need to use a bounce pool instead. 278# 279# We also use the bounce pool to provide stable page writes for jbd. jbd 280# initiates buffer writeback without locking the page or setting PG_writeback, 281# and fixing that behavior (a second time; jbd2 doesn't have this problem) is 282# a major rework effort. Instead, use the bounce buffer to snapshot pages 283# (until jbd goes away). The only jbd user is ext3. 284config NEED_BOUNCE_POOL 285 bool 286 default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD) 287 288config NR_QUICK 289 int 290 depends on QUICKLIST 291 default "2" if AVR32 292 default "1" 293 294config VIRT_TO_BUS 295 bool 296 help 297 An architecture should select this if it implements the 298 deprecated interface virt_to_bus(). All new architectures 299 should probably not select this. 300 301 302config MMU_NOTIFIER 303 bool 304 305config KSM 306 bool "Enable KSM for page merging" 307 depends on MMU 308 help 309 Enable Kernel Samepage Merging: KSM periodically scans those areas 310 of an application's address space that an app has advised may be 311 mergeable. When it finds pages of identical content, it replaces 312 the many instances by a single page with that content, so 313 saving memory until one or another app needs to modify the content. 314 Recommended for use with KVM, or with other duplicative applications. 315 See Documentation/vm/ksm.txt for more information: KSM is inactive 316 until a program has madvised that an area is MADV_MERGEABLE, and 317 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 318 319config DEFAULT_MMAP_MIN_ADDR 320 int "Low address space to protect from user allocation" 321 depends on MMU 322 default 4096 323 help 324 This is the portion of low virtual memory which should be protected 325 from userspace allocation. Keeping a user from writing to low pages 326 can help reduce the impact of kernel NULL pointer bugs. 327 328 For most ia64, ppc64 and x86 users with lots of address space 329 a value of 65536 is reasonable and should cause no problems. 330 On arm and other archs it should not be higher than 32768. 331 Programs which use vm86 functionality or have some need to map 332 this low address space will need CAP_SYS_RAWIO or disable this 333 protection by setting the value to 0. 334 335 This value can be changed after boot using the 336 /proc/sys/vm/mmap_min_addr tunable. 337 338config ARCH_SUPPORTS_MEMORY_FAILURE 339 bool 340 341config MEMORY_FAILURE 342 depends on MMU 343 depends on ARCH_SUPPORTS_MEMORY_FAILURE 344 bool "Enable recovery from hardware memory errors" 345 select MEMORY_ISOLATION 346 help 347 Enables code to recover from some memory failures on systems 348 with MCA recovery. This allows a system to continue running 349 even when some of its memory has uncorrected errors. This requires 350 special hardware support and typically ECC memory. 351 352config HWPOISON_INJECT 353 tristate "HWPoison pages injector" 354 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 355 select PROC_PAGE_MONITOR 356 357config NOMMU_INITIAL_TRIM_EXCESS 358 int "Turn on mmap() excess space trimming before booting" 359 depends on !MMU 360 default 1 361 help 362 The NOMMU mmap() frequently needs to allocate large contiguous chunks 363 of memory on which to store mappings, but it can only ask the system 364 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 365 more than it requires. To deal with this, mmap() is able to trim off 366 the excess and return it to the allocator. 367 368 If trimming is enabled, the excess is trimmed off and returned to the 369 system allocator, which can cause extra fragmentation, particularly 370 if there are a lot of transient processes. 371 372 If trimming is disabled, the excess is kept, but not used, which for 373 long-term mappings means that the space is wasted. 374 375 Trimming can be dynamically controlled through a sysctl option 376 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 377 excess pages there must be before trimming should occur, or zero if 378 no trimming is to occur. 379 380 This option specifies the initial value of this option. The default 381 of 1 says that all excess pages should be trimmed. 382 383 See Documentation/nommu-mmap.txt for more information. 384 385config TRANSPARENT_HUGEPAGE 386 bool "Transparent Hugepage Support" 387 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 388 select COMPACTION 389 help 390 Transparent Hugepages allows the kernel to use huge pages and 391 huge tlb transparently to the applications whenever possible. 392 This feature can improve computing performance to certain 393 applications by speeding up page faults during memory 394 allocation, by reducing the number of tlb misses and by speeding 395 up the pagetable walking. 396 397 If memory constrained on embedded, you may want to say N. 398 399choice 400 prompt "Transparent Hugepage Support sysfs defaults" 401 depends on TRANSPARENT_HUGEPAGE 402 default TRANSPARENT_HUGEPAGE_ALWAYS 403 help 404 Selects the sysfs defaults for Transparent Hugepage Support. 405 406 config TRANSPARENT_HUGEPAGE_ALWAYS 407 bool "always" 408 help 409 Enabling Transparent Hugepage always, can increase the 410 memory footprint of applications without a guaranteed 411 benefit but it will work automatically for all applications. 412 413 config TRANSPARENT_HUGEPAGE_MADVISE 414 bool "madvise" 415 help 416 Enabling Transparent Hugepage madvise, will only provide a 417 performance improvement benefit to the applications using 418 madvise(MADV_HUGEPAGE) but it won't risk to increase the 419 memory footprint of applications without a guaranteed 420 benefit. 421endchoice 422 423config CROSS_MEMORY_ATTACH 424 bool "Cross Memory Support" 425 depends on MMU 426 default y 427 help 428 Enabling this option adds the system calls process_vm_readv and 429 process_vm_writev which allow a process with the correct privileges 430 to directly read from or write to to another process's address space. 431 See the man page for more details. 432 433# 434# UP and nommu archs use km based percpu allocator 435# 436config NEED_PER_CPU_KM 437 depends on !SMP 438 bool 439 default y 440 441config CLEANCACHE 442 bool "Enable cleancache driver to cache clean pages if tmem is present" 443 default n 444 help 445 Cleancache can be thought of as a page-granularity victim cache 446 for clean pages that the kernel's pageframe replacement algorithm 447 (PFRA) would like to keep around, but can't since there isn't enough 448 memory. So when the PFRA "evicts" a page, it first attempts to use 449 cleancache code to put the data contained in that page into 450 "transcendent memory", memory that is not directly accessible or 451 addressable by the kernel and is of unknown and possibly 452 time-varying size. And when a cleancache-enabled 453 filesystem wishes to access a page in a file on disk, it first 454 checks cleancache to see if it already contains it; if it does, 455 the page is copied into the kernel and a disk access is avoided. 456 When a transcendent memory driver is available (such as zcache or 457 Xen transcendent memory), a significant I/O reduction 458 may be achieved. When none is available, all cleancache calls 459 are reduced to a single pointer-compare-against-NULL resulting 460 in a negligible performance hit. 461 462 If unsure, say Y to enable cleancache 463 464config FRONTSWAP 465 bool "Enable frontswap to cache swap pages if tmem is present" 466 depends on SWAP 467 default n 468 help 469 Frontswap is so named because it can be thought of as the opposite 470 of a "backing" store for a swap device. The data is stored into 471 "transcendent memory", memory that is not directly accessible or 472 addressable by the kernel and is of unknown and possibly 473 time-varying size. When space in transcendent memory is available, 474 a significant swap I/O reduction may be achieved. When none is 475 available, all frontswap calls are reduced to a single pointer- 476 compare-against-NULL resulting in a negligible performance hit 477 and swap data is stored as normal on the matching swap device. 478 479 If unsure, say Y to enable frontswap. 480