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 a 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 the following 157 two things: 158 - When the system is booting, node full of hotpluggable memory can 159 be arranged to have only movable memory so that the whole node can 160 be hot-removed. (need movable_node boot option specified). 161 - After the system is up, the option allows users to online all the 162 memory of a node as movable memory so that the whole node can be 163 hot-removed. 164 165 Users who don't use the memory hotplug feature are fine with this 166 option on since they don't specify movable_node boot option or they 167 don't online memory as movable. 168 169 Say Y here if you want to hotplug a whole node. 170 Say N here if you want kernel to use memory on all nodes evenly. 171 172# 173# Only be set on architectures that have completely implemented memory hotplug 174# feature. If you are not sure, don't touch it. 175# 176config HAVE_BOOTMEM_INFO_NODE 177 def_bool n 178 179# eventually, we can have this option just 'select SPARSEMEM' 180config MEMORY_HOTPLUG 181 bool "Allow for memory hot-add" 182 depends on SPARSEMEM || X86_64_ACPI_NUMA 183 depends on ARCH_ENABLE_MEMORY_HOTPLUG 184 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390) 185 186config MEMORY_HOTPLUG_SPARSE 187 def_bool y 188 depends on SPARSEMEM && MEMORY_HOTPLUG 189 190config MEMORY_HOTREMOVE 191 bool "Allow for memory hot remove" 192 select MEMORY_ISOLATION 193 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64) 194 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 195 depends on MIGRATION 196 197# 198# If we have space for more page flags then we can enable additional 199# optimizations and functionality. 200# 201# Regular Sparsemem takes page flag bits for the sectionid if it does not 202# use a virtual memmap. Disable extended page flags for 32 bit platforms 203# that require the use of a sectionid in the page flags. 204# 205config PAGEFLAGS_EXTENDED 206 def_bool y 207 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM 208 209# Heavily threaded applications may benefit from splitting the mm-wide 210# page_table_lock, so that faults on different parts of the user address 211# space can be handled with less contention: split it at this NR_CPUS. 212# Default to 4 for wider testing, though 8 might be more appropriate. 213# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 214# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 215# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 216# 217config SPLIT_PTLOCK_CPUS 218 int 219 default "999999" if ARM && !CPU_CACHE_VIPT 220 default "999999" if PARISC && !PA20 221 default "4" 222 223config ARCH_ENABLE_SPLIT_PMD_PTLOCK 224 boolean 225 226# 227# support for memory balloon compaction 228config BALLOON_COMPACTION 229 bool "Allow for balloon memory compaction/migration" 230 def_bool y 231 depends on COMPACTION && VIRTIO_BALLOON 232 help 233 Memory fragmentation introduced by ballooning might reduce 234 significantly the number of 2MB contiguous memory blocks that can be 235 used within a guest, thus imposing performance penalties associated 236 with the reduced number of transparent huge pages that could be used 237 by the guest workload. Allowing the compaction & migration for memory 238 pages enlisted as being part of memory balloon devices avoids the 239 scenario aforementioned and helps improving memory defragmentation. 240 241# 242# support for memory compaction 243config COMPACTION 244 bool "Allow for memory compaction" 245 def_bool y 246 select MIGRATION 247 depends on MMU 248 help 249 Allows the compaction of memory for the allocation of huge pages. 250 251# 252# support for page migration 253# 254config MIGRATION 255 bool "Page migration" 256 def_bool y 257 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU 258 help 259 Allows the migration of the physical location of pages of processes 260 while the virtual addresses are not changed. This is useful in 261 two situations. The first is on NUMA systems to put pages nearer 262 to the processors accessing. The second is when allocating huge 263 pages as migration can relocate pages to satisfy a huge page 264 allocation instead of reclaiming. 265 266config PHYS_ADDR_T_64BIT 267 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 268 269config ZONE_DMA_FLAG 270 int 271 default "0" if !ZONE_DMA 272 default "1" 273 274config BOUNCE 275 bool "Enable bounce buffers" 276 default y 277 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 278 help 279 Enable bounce buffers for devices that cannot access 280 the full range of memory available to the CPU. Enabled 281 by default when ZONE_DMA or HIGHMEM is selected, but you 282 may say n to override this. 283 284# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often 285# have more than 4GB of memory, but we don't currently use the IOTLB to present 286# a 32-bit address to OHCI. So we need to use a bounce pool instead. 287# 288# We also use the bounce pool to provide stable page writes for jbd. jbd 289# initiates buffer writeback without locking the page or setting PG_writeback, 290# and fixing that behavior (a second time; jbd2 doesn't have this problem) is 291# a major rework effort. Instead, use the bounce buffer to snapshot pages 292# (until jbd goes away). The only jbd user is ext3. 293config NEED_BOUNCE_POOL 294 bool 295 default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD) 296 297config NR_QUICK 298 int 299 depends on QUICKLIST 300 default "2" if AVR32 301 default "1" 302 303config VIRT_TO_BUS 304 bool 305 help 306 An architecture should select this if it implements the 307 deprecated interface virt_to_bus(). All new architectures 308 should probably not select this. 309 310 311config MMU_NOTIFIER 312 bool 313 314config KSM 315 bool "Enable KSM for page merging" 316 depends on MMU 317 help 318 Enable Kernel Samepage Merging: KSM periodically scans those areas 319 of an application's address space that an app has advised may be 320 mergeable. When it finds pages of identical content, it replaces 321 the many instances by a single page with that content, so 322 saving memory until one or another app needs to modify the content. 323 Recommended for use with KVM, or with other duplicative applications. 324 See Documentation/vm/ksm.txt for more information: KSM is inactive 325 until a program has madvised that an area is MADV_MERGEABLE, and 326 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 327 328config DEFAULT_MMAP_MIN_ADDR 329 int "Low address space to protect from user allocation" 330 depends on MMU 331 default 4096 332 help 333 This is the portion of low virtual memory which should be protected 334 from userspace allocation. Keeping a user from writing to low pages 335 can help reduce the impact of kernel NULL pointer bugs. 336 337 For most ia64, ppc64 and x86 users with lots of address space 338 a value of 65536 is reasonable and should cause no problems. 339 On arm and other archs it should not be higher than 32768. 340 Programs which use vm86 functionality or have some need to map 341 this low address space will need CAP_SYS_RAWIO or disable this 342 protection by setting the value to 0. 343 344 This value can be changed after boot using the 345 /proc/sys/vm/mmap_min_addr tunable. 346 347config ARCH_SUPPORTS_MEMORY_FAILURE 348 bool 349 350config MEMORY_FAILURE 351 depends on MMU 352 depends on ARCH_SUPPORTS_MEMORY_FAILURE 353 bool "Enable recovery from hardware memory errors" 354 select MEMORY_ISOLATION 355 help 356 Enables code to recover from some memory failures on systems 357 with MCA recovery. This allows a system to continue running 358 even when some of its memory has uncorrected errors. This requires 359 special hardware support and typically ECC memory. 360 361config HWPOISON_INJECT 362 tristate "HWPoison pages injector" 363 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 364 select PROC_PAGE_MONITOR 365 366config NOMMU_INITIAL_TRIM_EXCESS 367 int "Turn on mmap() excess space trimming before booting" 368 depends on !MMU 369 default 1 370 help 371 The NOMMU mmap() frequently needs to allocate large contiguous chunks 372 of memory on which to store mappings, but it can only ask the system 373 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 374 more than it requires. To deal with this, mmap() is able to trim off 375 the excess and return it to the allocator. 376 377 If trimming is enabled, the excess is trimmed off and returned to the 378 system allocator, which can cause extra fragmentation, particularly 379 if there are a lot of transient processes. 380 381 If trimming is disabled, the excess is kept, but not used, which for 382 long-term mappings means that the space is wasted. 383 384 Trimming can be dynamically controlled through a sysctl option 385 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 386 excess pages there must be before trimming should occur, or zero if 387 no trimming is to occur. 388 389 This option specifies the initial value of this option. The default 390 of 1 says that all excess pages should be trimmed. 391 392 See Documentation/nommu-mmap.txt for more information. 393 394config TRANSPARENT_HUGEPAGE 395 bool "Transparent Hugepage Support" 396 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 397 select COMPACTION 398 help 399 Transparent Hugepages allows the kernel to use huge pages and 400 huge tlb transparently to the applications whenever possible. 401 This feature can improve computing performance to certain 402 applications by speeding up page faults during memory 403 allocation, by reducing the number of tlb misses and by speeding 404 up the pagetable walking. 405 406 If memory constrained on embedded, you may want to say N. 407 408choice 409 prompt "Transparent Hugepage Support sysfs defaults" 410 depends on TRANSPARENT_HUGEPAGE 411 default TRANSPARENT_HUGEPAGE_ALWAYS 412 help 413 Selects the sysfs defaults for Transparent Hugepage Support. 414 415 config TRANSPARENT_HUGEPAGE_ALWAYS 416 bool "always" 417 help 418 Enabling Transparent Hugepage always, can increase the 419 memory footprint of applications without a guaranteed 420 benefit but it will work automatically for all applications. 421 422 config TRANSPARENT_HUGEPAGE_MADVISE 423 bool "madvise" 424 help 425 Enabling Transparent Hugepage madvise, will only provide a 426 performance improvement benefit to the applications using 427 madvise(MADV_HUGEPAGE) but it won't risk to increase the 428 memory footprint of applications without a guaranteed 429 benefit. 430endchoice 431 432config CROSS_MEMORY_ATTACH 433 bool "Cross Memory Support" 434 depends on MMU 435 default y 436 help 437 Enabling this option adds the system calls process_vm_readv and 438 process_vm_writev which allow a process with the correct privileges 439 to directly read from or write to to another process's address space. 440 See the man page for more details. 441 442# 443# UP and nommu archs use km based percpu allocator 444# 445config NEED_PER_CPU_KM 446 depends on !SMP 447 bool 448 default y 449 450config CLEANCACHE 451 bool "Enable cleancache driver to cache clean pages if tmem is present" 452 default n 453 help 454 Cleancache can be thought of as a page-granularity victim cache 455 for clean pages that the kernel's pageframe replacement algorithm 456 (PFRA) would like to keep around, but can't since there isn't enough 457 memory. So when the PFRA "evicts" a page, it first attempts to use 458 cleancache code to put the data contained in that page into 459 "transcendent memory", memory that is not directly accessible or 460 addressable by the kernel and is of unknown and possibly 461 time-varying size. And when a cleancache-enabled 462 filesystem wishes to access a page in a file on disk, it first 463 checks cleancache to see if it already contains it; if it does, 464 the page is copied into the kernel and a disk access is avoided. 465 When a transcendent memory driver is available (such as zcache or 466 Xen transcendent memory), a significant I/O reduction 467 may be achieved. When none is available, all cleancache calls 468 are reduced to a single pointer-compare-against-NULL resulting 469 in a negligible performance hit. 470 471 If unsure, say Y to enable cleancache 472 473config FRONTSWAP 474 bool "Enable frontswap to cache swap pages if tmem is present" 475 depends on SWAP 476 default n 477 help 478 Frontswap is so named because it can be thought of as the opposite 479 of a "backing" store for a swap device. The data is stored into 480 "transcendent memory", memory that is not directly accessible or 481 addressable by the kernel and is of unknown and possibly 482 time-varying size. When space in transcendent memory is available, 483 a significant swap I/O reduction may be achieved. When none is 484 available, all frontswap calls are reduced to a single pointer- 485 compare-against-NULL resulting in a negligible performance hit 486 and swap data is stored as normal on the matching swap device. 487 488 If unsure, say Y to enable frontswap. 489 490config CMA 491 bool "Contiguous Memory Allocator" 492 depends on HAVE_MEMBLOCK && MMU 493 select MIGRATION 494 select MEMORY_ISOLATION 495 help 496 This enables the Contiguous Memory Allocator which allows other 497 subsystems to allocate big physically-contiguous blocks of memory. 498 CMA reserves a region of memory and allows only movable pages to 499 be allocated from it. This way, the kernel can use the memory for 500 pagecache and when a subsystem requests for contiguous area, the 501 allocated pages are migrated away to serve the contiguous request. 502 503 If unsure, say "n". 504 505config CMA_DEBUG 506 bool "CMA debug messages (DEVELOPMENT)" 507 depends on DEBUG_KERNEL && CMA 508 help 509 Turns on debug messages in CMA. This produces KERN_DEBUG 510 messages for every CMA call as well as various messages while 511 processing calls such as dma_alloc_from_contiguous(). 512 This option does not affect warning and error messages. 513 514config ZBUD 515 tristate 516 default n 517 help 518 A special purpose allocator for storing compressed pages. 519 It is designed to store up to two compressed pages per physical 520 page. While this design limits storage density, it has simple and 521 deterministic reclaim properties that make it preferable to a higher 522 density approach when reclaim will be used. 523 524config ZSWAP 525 bool "Compressed cache for swap pages (EXPERIMENTAL)" 526 depends on FRONTSWAP && CRYPTO=y 527 select CRYPTO_LZO 528 select ZBUD 529 default n 530 help 531 A lightweight compressed cache for swap pages. It takes 532 pages that are in the process of being swapped out and attempts to 533 compress them into a dynamically allocated RAM-based memory pool. 534 This can result in a significant I/O reduction on swap device and, 535 in the case where decompressing from RAM is faster that swap device 536 reads, can also improve workload performance. 537 538 This is marked experimental because it is a new feature (as of 539 v3.11) that interacts heavily with memory reclaim. While these 540 interactions don't cause any known issues on simple memory setups, 541 they have not be fully explored on the large set of potential 542 configurations and workloads that exist. 543 544config MEM_SOFT_DIRTY 545 bool "Track memory changes" 546 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 547 select PROC_PAGE_MONITOR 548 help 549 This option enables memory changes tracking by introducing a 550 soft-dirty bit on pte-s. This bit it set when someone writes 551 into a page just as regular dirty bit, but unlike the latter 552 it can be cleared by hands. 553 554 See Documentation/vm/soft-dirty.txt for more details. 555