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 bool 133 134config HAVE_MEMBLOCK_NODE_MAP 135 bool 136 137config HAVE_MEMBLOCK_PHYS_MAP 138 bool 139 140config HAVE_GENERIC_RCU_GUP 141 bool 142 143config ARCH_DISCARD_MEMBLOCK 144 bool 145 146config NO_BOOTMEM 147 bool 148 149config MEMORY_ISOLATION 150 bool 151 152config MOVABLE_NODE 153 bool "Enable to assign a node which has only movable memory" 154 depends on HAVE_MEMBLOCK 155 depends on NO_BOOTMEM 156 depends on X86_64 || OF_EARLY_FLATTREE || MEMORY_HOTPLUG 157 depends on NUMA 158 default n 159 help 160 Allow a node to have only movable memory. Pages used by the kernel, 161 such as direct mapping pages cannot be migrated. So the corresponding 162 memory device cannot be hotplugged. This option allows the following 163 two things: 164 - When the system is booting, node full of hotpluggable memory can 165 be arranged to have only movable memory so that the whole node can 166 be hot-removed. (need movable_node boot option specified). 167 - After the system is up, the option allows users to online all the 168 memory of a node as movable memory so that the whole node can be 169 hot-removed. 170 171 Users who don't use the memory hotplug feature are fine with this 172 option on since they don't specify movable_node boot option or they 173 don't online memory as movable. 174 175 Say Y here if you want to hotplug a whole node. 176 Say N here if you want kernel to use memory on all nodes evenly. 177 178# 179# Only be set on architectures that have completely implemented memory hotplug 180# feature. If you are not sure, don't touch it. 181# 182config HAVE_BOOTMEM_INFO_NODE 183 def_bool n 184 185# eventually, we can have this option just 'select SPARSEMEM' 186config MEMORY_HOTPLUG 187 bool "Allow for memory hot-add" 188 depends on SPARSEMEM || X86_64_ACPI_NUMA 189 depends on ARCH_ENABLE_MEMORY_HOTPLUG 190 depends on COMPILE_TEST || !KASAN 191 192config MEMORY_HOTPLUG_SPARSE 193 def_bool y 194 depends on SPARSEMEM && MEMORY_HOTPLUG 195 196config MEMORY_HOTPLUG_DEFAULT_ONLINE 197 bool "Online the newly added memory blocks by default" 198 default n 199 depends on MEMORY_HOTPLUG 200 help 201 This option sets the default policy setting for memory hotplug 202 onlining policy (/sys/devices/system/memory/auto_online_blocks) which 203 determines what happens to newly added memory regions. Policy setting 204 can always be changed at runtime. 205 See Documentation/memory-hotplug.txt for more information. 206 207 Say Y here if you want all hot-plugged memory blocks to appear in 208 'online' state by default. 209 Say N here if you want the default policy to keep all hot-plugged 210 memory blocks in 'offline' state. 211 212config MEMORY_HOTREMOVE 213 bool "Allow for memory hot remove" 214 select MEMORY_ISOLATION 215 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64) 216 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 217 depends on MIGRATION 218 219# Heavily threaded applications may benefit from splitting the mm-wide 220# page_table_lock, so that faults on different parts of the user address 221# space can be handled with less contention: split it at this NR_CPUS. 222# Default to 4 for wider testing, though 8 might be more appropriate. 223# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 224# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 225# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 226# 227config SPLIT_PTLOCK_CPUS 228 int 229 default "999999" if !MMU 230 default "999999" if ARM && !CPU_CACHE_VIPT 231 default "999999" if PARISC && !PA20 232 default "4" 233 234config ARCH_ENABLE_SPLIT_PMD_PTLOCK 235 bool 236 237# 238# support for memory balloon 239config MEMORY_BALLOON 240 bool 241 242# 243# support for memory balloon compaction 244config BALLOON_COMPACTION 245 bool "Allow for balloon memory compaction/migration" 246 def_bool y 247 depends on COMPACTION && MEMORY_BALLOON 248 help 249 Memory fragmentation introduced by ballooning might reduce 250 significantly the number of 2MB contiguous memory blocks that can be 251 used within a guest, thus imposing performance penalties associated 252 with the reduced number of transparent huge pages that could be used 253 by the guest workload. Allowing the compaction & migration for memory 254 pages enlisted as being part of memory balloon devices avoids the 255 scenario aforementioned and helps improving memory defragmentation. 256 257# 258# support for memory compaction 259config COMPACTION 260 bool "Allow for memory compaction" 261 def_bool y 262 select MIGRATION 263 depends on MMU 264 help 265 Compaction is the only memory management component to form 266 high order (larger physically contiguous) memory blocks 267 reliably. The page allocator relies on compaction heavily and 268 the lack of the feature can lead to unexpected OOM killer 269 invocations for high order memory requests. You shouldn't 270 disable this option unless there really is a strong reason for 271 it and then we would be really interested to hear about that at 272 linux-mm@kvack.org. 273 274# 275# support for page migration 276# 277config MIGRATION 278 bool "Page migration" 279 def_bool y 280 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU 281 help 282 Allows the migration of the physical location of pages of processes 283 while the virtual addresses are not changed. This is useful in 284 two situations. The first is on NUMA systems to put pages nearer 285 to the processors accessing. The second is when allocating huge 286 pages as migration can relocate pages to satisfy a huge page 287 allocation instead of reclaiming. 288 289config ARCH_ENABLE_HUGEPAGE_MIGRATION 290 bool 291 292config PHYS_ADDR_T_64BIT 293 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 294 295config BOUNCE 296 bool "Enable bounce buffers" 297 default y 298 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 299 help 300 Enable bounce buffers for devices that cannot access 301 the full range of memory available to the CPU. Enabled 302 by default when ZONE_DMA or HIGHMEM is selected, but you 303 may say n to override this. 304 305# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often 306# have more than 4GB of memory, but we don't currently use the IOTLB to present 307# a 32-bit address to OHCI. So we need to use a bounce pool instead. 308config NEED_BOUNCE_POOL 309 bool 310 default y if TILE && USB_OHCI_HCD 311 312config NR_QUICK 313 int 314 depends on QUICKLIST 315 default "2" if AVR32 316 default "1" 317 318config VIRT_TO_BUS 319 bool 320 help 321 An architecture should select this if it implements the 322 deprecated interface virt_to_bus(). All new architectures 323 should probably not select this. 324 325 326config MMU_NOTIFIER 327 bool 328 select SRCU 329 330config KSM 331 bool "Enable KSM for page merging" 332 depends on MMU 333 help 334 Enable Kernel Samepage Merging: KSM periodically scans those areas 335 of an application's address space that an app has advised may be 336 mergeable. When it finds pages of identical content, it replaces 337 the many instances by a single page with that content, so 338 saving memory until one or another app needs to modify the content. 339 Recommended for use with KVM, or with other duplicative applications. 340 See Documentation/vm/ksm.txt for more information: KSM is inactive 341 until a program has madvised that an area is MADV_MERGEABLE, and 342 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 343 344config DEFAULT_MMAP_MIN_ADDR 345 int "Low address space to protect from user allocation" 346 depends on MMU 347 default 4096 348 help 349 This is the portion of low virtual memory which should be protected 350 from userspace allocation. Keeping a user from writing to low pages 351 can help reduce the impact of kernel NULL pointer bugs. 352 353 For most ia64, ppc64 and x86 users with lots of address space 354 a value of 65536 is reasonable and should cause no problems. 355 On arm and other archs it should not be higher than 32768. 356 Programs which use vm86 functionality or have some need to map 357 this low address space will need CAP_SYS_RAWIO or disable this 358 protection by setting the value to 0. 359 360 This value can be changed after boot using the 361 /proc/sys/vm/mmap_min_addr tunable. 362 363config ARCH_SUPPORTS_MEMORY_FAILURE 364 bool 365 366config MEMORY_FAILURE 367 depends on MMU 368 depends on ARCH_SUPPORTS_MEMORY_FAILURE 369 bool "Enable recovery from hardware memory errors" 370 select MEMORY_ISOLATION 371 select RAS 372 help 373 Enables code to recover from some memory failures on systems 374 with MCA recovery. This allows a system to continue running 375 even when some of its memory has uncorrected errors. This requires 376 special hardware support and typically ECC memory. 377 378config HWPOISON_INJECT 379 tristate "HWPoison pages injector" 380 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 381 select PROC_PAGE_MONITOR 382 383config NOMMU_INITIAL_TRIM_EXCESS 384 int "Turn on mmap() excess space trimming before booting" 385 depends on !MMU 386 default 1 387 help 388 The NOMMU mmap() frequently needs to allocate large contiguous chunks 389 of memory on which to store mappings, but it can only ask the system 390 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 391 more than it requires. To deal with this, mmap() is able to trim off 392 the excess and return it to the allocator. 393 394 If trimming is enabled, the excess is trimmed off and returned to the 395 system allocator, which can cause extra fragmentation, particularly 396 if there are a lot of transient processes. 397 398 If trimming is disabled, the excess is kept, but not used, which for 399 long-term mappings means that the space is wasted. 400 401 Trimming can be dynamically controlled through a sysctl option 402 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 403 excess pages there must be before trimming should occur, or zero if 404 no trimming is to occur. 405 406 This option specifies the initial value of this option. The default 407 of 1 says that all excess pages should be trimmed. 408 409 See Documentation/nommu-mmap.txt for more information. 410 411config TRANSPARENT_HUGEPAGE 412 bool "Transparent Hugepage Support" 413 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 414 select COMPACTION 415 select RADIX_TREE_MULTIORDER 416 help 417 Transparent Hugepages allows the kernel to use huge pages and 418 huge tlb transparently to the applications whenever possible. 419 This feature can improve computing performance to certain 420 applications by speeding up page faults during memory 421 allocation, by reducing the number of tlb misses and by speeding 422 up the pagetable walking. 423 424 If memory constrained on embedded, you may want to say N. 425 426choice 427 prompt "Transparent Hugepage Support sysfs defaults" 428 depends on TRANSPARENT_HUGEPAGE 429 default TRANSPARENT_HUGEPAGE_ALWAYS 430 help 431 Selects the sysfs defaults for Transparent Hugepage Support. 432 433 config TRANSPARENT_HUGEPAGE_ALWAYS 434 bool "always" 435 help 436 Enabling Transparent Hugepage always, can increase the 437 memory footprint of applications without a guaranteed 438 benefit but it will work automatically for all applications. 439 440 config TRANSPARENT_HUGEPAGE_MADVISE 441 bool "madvise" 442 help 443 Enabling Transparent Hugepage madvise, will only provide a 444 performance improvement benefit to the applications using 445 madvise(MADV_HUGEPAGE) but it won't risk to increase the 446 memory footprint of applications without a guaranteed 447 benefit. 448endchoice 449 450config TRANSPARENT_HUGE_PAGECACHE 451 def_bool y 452 depends on TRANSPARENT_HUGEPAGE 453 454# 455# UP and nommu archs use km based percpu allocator 456# 457config NEED_PER_CPU_KM 458 depends on !SMP 459 bool 460 default y 461 462config CLEANCACHE 463 bool "Enable cleancache driver to cache clean pages if tmem is present" 464 default n 465 help 466 Cleancache can be thought of as a page-granularity victim cache 467 for clean pages that the kernel's pageframe replacement algorithm 468 (PFRA) would like to keep around, but can't since there isn't enough 469 memory. So when the PFRA "evicts" a page, it first attempts to use 470 cleancache code to put the data contained in that page 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. And when a cleancache-enabled 474 filesystem wishes to access a page in a file on disk, it first 475 checks cleancache to see if it already contains it; if it does, 476 the page is copied into the kernel and a disk access is avoided. 477 When a transcendent memory driver is available (such as zcache or 478 Xen transcendent memory), a significant I/O reduction 479 may be achieved. When none is available, all cleancache calls 480 are reduced to a single pointer-compare-against-NULL resulting 481 in a negligible performance hit. 482 483 If unsure, say Y to enable cleancache 484 485config FRONTSWAP 486 bool "Enable frontswap to cache swap pages if tmem is present" 487 depends on SWAP 488 default n 489 help 490 Frontswap is so named because it can be thought of as the opposite 491 of a "backing" store for a swap device. The data is stored into 492 "transcendent memory", memory that is not directly accessible or 493 addressable by the kernel and is of unknown and possibly 494 time-varying size. When space in transcendent memory is available, 495 a significant swap I/O reduction may be achieved. When none is 496 available, all frontswap calls are reduced to a single pointer- 497 compare-against-NULL resulting in a negligible performance hit 498 and swap data is stored as normal on the matching swap device. 499 500 If unsure, say Y to enable frontswap. 501 502config CMA 503 bool "Contiguous Memory Allocator" 504 depends on HAVE_MEMBLOCK && MMU 505 select MIGRATION 506 select MEMORY_ISOLATION 507 help 508 This enables the Contiguous Memory Allocator which allows other 509 subsystems to allocate big physically-contiguous blocks of memory. 510 CMA reserves a region of memory and allows only movable pages to 511 be allocated from it. This way, the kernel can use the memory for 512 pagecache and when a subsystem requests for contiguous area, the 513 allocated pages are migrated away to serve the contiguous request. 514 515 If unsure, say "n". 516 517config CMA_DEBUG 518 bool "CMA debug messages (DEVELOPMENT)" 519 depends on DEBUG_KERNEL && CMA 520 help 521 Turns on debug messages in CMA. This produces KERN_DEBUG 522 messages for every CMA call as well as various messages while 523 processing calls such as dma_alloc_from_contiguous(). 524 This option does not affect warning and error messages. 525 526config CMA_DEBUGFS 527 bool "CMA debugfs interface" 528 depends on CMA && DEBUG_FS 529 help 530 Turns on the DebugFS interface for CMA. 531 532config CMA_AREAS 533 int "Maximum count of the CMA areas" 534 depends on CMA 535 default 7 536 help 537 CMA allows to create CMA areas for particular purpose, mainly, 538 used as device private area. This parameter sets the maximum 539 number of CMA area in the system. 540 541 If unsure, leave the default value "7". 542 543config MEM_SOFT_DIRTY 544 bool "Track memory changes" 545 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 546 select PROC_PAGE_MONITOR 547 help 548 This option enables memory changes tracking by introducing a 549 soft-dirty bit on pte-s. This bit it set when someone writes 550 into a page just as regular dirty bit, but unlike the latter 551 it can be cleared by hands. 552 553 See Documentation/vm/soft-dirty.txt for more details. 554 555config ZSWAP 556 bool "Compressed cache for swap pages (EXPERIMENTAL)" 557 depends on FRONTSWAP && CRYPTO=y 558 select CRYPTO_LZO 559 select ZPOOL 560 default n 561 help 562 A lightweight compressed cache for swap pages. It takes 563 pages that are in the process of being swapped out and attempts to 564 compress them into a dynamically allocated RAM-based memory pool. 565 This can result in a significant I/O reduction on swap device and, 566 in the case where decompressing from RAM is faster that swap device 567 reads, can also improve workload performance. 568 569 This is marked experimental because it is a new feature (as of 570 v3.11) that interacts heavily with memory reclaim. While these 571 interactions don't cause any known issues on simple memory setups, 572 they have not be fully explored on the large set of potential 573 configurations and workloads that exist. 574 575config ZPOOL 576 tristate "Common API for compressed memory storage" 577 default n 578 help 579 Compressed memory storage API. This allows using either zbud or 580 zsmalloc. 581 582config ZBUD 583 tristate "Low (Up to 2x) density storage for compressed pages" 584 default n 585 help 586 A special purpose allocator for storing compressed pages. 587 It is designed to store up to two compressed pages per physical 588 page. While this design limits storage density, it has simple and 589 deterministic reclaim properties that make it preferable to a higher 590 density approach when reclaim will be used. 591 592config Z3FOLD 593 tristate "Up to 3x density storage for compressed pages" 594 depends on ZPOOL 595 default n 596 help 597 A special purpose allocator for storing compressed pages. 598 It is designed to store up to three compressed pages per physical 599 page. It is a ZBUD derivative so the simplicity and determinism are 600 still there. 601 602config ZSMALLOC 603 tristate "Memory allocator for compressed pages" 604 depends on MMU 605 default n 606 help 607 zsmalloc is a slab-based memory allocator designed to store 608 compressed RAM pages. zsmalloc uses virtual memory mapping 609 in order to reduce fragmentation. However, this results in a 610 non-standard allocator interface where a handle, not a pointer, is 611 returned by an alloc(). This handle must be mapped in order to 612 access the allocated space. 613 614config PGTABLE_MAPPING 615 bool "Use page table mapping to access object in zsmalloc" 616 depends on ZSMALLOC 617 help 618 By default, zsmalloc uses a copy-based object mapping method to 619 access allocations that span two pages. However, if a particular 620 architecture (ex, ARM) performs VM mapping faster than copying, 621 then you should select this. This causes zsmalloc to use page table 622 mapping rather than copying for object mapping. 623 624 You can check speed with zsmalloc benchmark: 625 https://github.com/spartacus06/zsmapbench 626 627config ZSMALLOC_STAT 628 bool "Export zsmalloc statistics" 629 depends on ZSMALLOC 630 select DEBUG_FS 631 help 632 This option enables code in the zsmalloc to collect various 633 statistics about whats happening in zsmalloc and exports that 634 information to userspace via debugfs. 635 If unsure, say N. 636 637config GENERIC_EARLY_IOREMAP 638 bool 639 640config MAX_STACK_SIZE_MB 641 int "Maximum user stack size for 32-bit processes (MB)" 642 default 80 643 range 8 256 if METAG 644 range 8 2048 645 depends on STACK_GROWSUP && (!64BIT || COMPAT) 646 help 647 This is the maximum stack size in Megabytes in the VM layout of 32-bit 648 user processes when the stack grows upwards (currently only on parisc 649 and metag arch). The stack will be located at the highest memory 650 address minus the given value, unless the RLIMIT_STACK hard limit is 651 changed to a smaller value in which case that is used. 652 653 A sane initial value is 80 MB. 654 655# For architectures that support deferred memory initialisation 656config ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT 657 bool 658 659config DEFERRED_STRUCT_PAGE_INIT 660 bool "Defer initialisation of struct pages to kthreads" 661 default n 662 depends on ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT 663 depends on NO_BOOTMEM && MEMORY_HOTPLUG 664 depends on !FLATMEM 665 help 666 Ordinarily all struct pages are initialised during early boot in a 667 single thread. On very large machines this can take a considerable 668 amount of time. If this option is set, large machines will bring up 669 a subset of memmap at boot and then initialise the rest in parallel 670 by starting one-off "pgdatinitX" kernel thread for each node X. This 671 has a potential performance impact on processes running early in the 672 lifetime of the system until these kthreads finish the 673 initialisation. 674 675config IDLE_PAGE_TRACKING 676 bool "Enable idle page tracking" 677 depends on SYSFS && MMU 678 select PAGE_EXTENSION if !64BIT 679 help 680 This feature allows to estimate the amount of user pages that have 681 not been touched during a given period of time. This information can 682 be useful to tune memory cgroup limits and/or for job placement 683 within a compute cluster. 684 685 See Documentation/vm/idle_page_tracking.txt for more details. 686 687config ZONE_DEVICE 688 bool "Device memory (pmem, etc...) hotplug support" 689 depends on MEMORY_HOTPLUG 690 depends on MEMORY_HOTREMOVE 691 depends on SPARSEMEM_VMEMMAP 692 depends on X86_64 #arch_add_memory() comprehends device memory 693 694 help 695 Device memory hotplug support allows for establishing pmem, 696 or other device driver discovered memory regions, in the 697 memmap. This allows pfn_to_page() lookups of otherwise 698 "device-physical" addresses which is needed for using a DAX 699 mapping in an O_DIRECT operation, among other things. 700 701 If FS_DAX is enabled, then say Y. 702 703config FRAME_VECTOR 704 bool 705 706config ARCH_USES_HIGH_VMA_FLAGS 707 bool 708config ARCH_HAS_PKEYS 709 bool 710