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_64 157 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 (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390) 191 192config MEMORY_HOTPLUG_SPARSE 193 def_bool y 194 depends on SPARSEMEM && MEMORY_HOTPLUG 195 196config MEMORY_HOTREMOVE 197 bool "Allow for memory hot remove" 198 select MEMORY_ISOLATION 199 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64) 200 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 201 depends on MIGRATION 202 203# 204# If we have space for more page flags then we can enable additional 205# optimizations and functionality. 206# 207# Regular Sparsemem takes page flag bits for the sectionid if it does not 208# use a virtual memmap. Disable extended page flags for 32 bit platforms 209# that require the use of a sectionid in the page flags. 210# 211config PAGEFLAGS_EXTENDED 212 def_bool y 213 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM 214 215# Heavily threaded applications may benefit from splitting the mm-wide 216# page_table_lock, so that faults on different parts of the user address 217# space can be handled with less contention: split it at this NR_CPUS. 218# Default to 4 for wider testing, though 8 might be more appropriate. 219# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 220# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 221# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 222# 223config SPLIT_PTLOCK_CPUS 224 int 225 default "999999" if !MMU 226 default "999999" if ARM && !CPU_CACHE_VIPT 227 default "999999" if PARISC && !PA20 228 default "4" 229 230config ARCH_ENABLE_SPLIT_PMD_PTLOCK 231 bool 232 233# 234# support for memory balloon 235config MEMORY_BALLOON 236 bool 237 238# 239# support for memory balloon compaction 240config BALLOON_COMPACTION 241 bool "Allow for balloon memory compaction/migration" 242 def_bool y 243 depends on COMPACTION && MEMORY_BALLOON 244 help 245 Memory fragmentation introduced by ballooning might reduce 246 significantly the number of 2MB contiguous memory blocks that can be 247 used within a guest, thus imposing performance penalties associated 248 with the reduced number of transparent huge pages that could be used 249 by the guest workload. Allowing the compaction & migration for memory 250 pages enlisted as being part of memory balloon devices avoids the 251 scenario aforementioned and helps improving memory defragmentation. 252 253# 254# support for memory compaction 255config COMPACTION 256 bool "Allow for memory compaction" 257 def_bool y 258 select MIGRATION 259 depends on MMU 260 help 261 Allows the compaction of memory for the allocation of huge pages. 262 263# 264# support for page migration 265# 266config MIGRATION 267 bool "Page migration" 268 def_bool y 269 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU 270 help 271 Allows the migration of the physical location of pages of processes 272 while the virtual addresses are not changed. This is useful in 273 two situations. The first is on NUMA systems to put pages nearer 274 to the processors accessing. The second is when allocating huge 275 pages as migration can relocate pages to satisfy a huge page 276 allocation instead of reclaiming. 277 278config ARCH_ENABLE_HUGEPAGE_MIGRATION 279 bool 280 281config PHYS_ADDR_T_64BIT 282 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 283 284config ZONE_DMA_FLAG 285 int 286 default "0" if !ZONE_DMA 287 default "1" 288 289config BOUNCE 290 bool "Enable bounce buffers" 291 default y 292 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 293 help 294 Enable bounce buffers for devices that cannot access 295 the full range of memory available to the CPU. Enabled 296 by default when ZONE_DMA or HIGHMEM is selected, but you 297 may say n to override this. 298 299# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often 300# have more than 4GB of memory, but we don't currently use the IOTLB to present 301# a 32-bit address to OHCI. So we need to use a bounce pool instead. 302config NEED_BOUNCE_POOL 303 bool 304 default y if TILE && USB_OHCI_HCD 305 306config NR_QUICK 307 int 308 depends on QUICKLIST 309 default "2" if AVR32 310 default "1" 311 312config VIRT_TO_BUS 313 bool 314 help 315 An architecture should select this if it implements the 316 deprecated interface virt_to_bus(). All new architectures 317 should probably not select this. 318 319 320config MMU_NOTIFIER 321 bool 322 select SRCU 323 324config KSM 325 bool "Enable KSM for page merging" 326 depends on MMU 327 help 328 Enable Kernel Samepage Merging: KSM periodically scans those areas 329 of an application's address space that an app has advised may be 330 mergeable. When it finds pages of identical content, it replaces 331 the many instances by a single page with that content, so 332 saving memory until one or another app needs to modify the content. 333 Recommended for use with KVM, or with other duplicative applications. 334 See Documentation/vm/ksm.txt for more information: KSM is inactive 335 until a program has madvised that an area is MADV_MERGEABLE, and 336 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 337 338config DEFAULT_MMAP_MIN_ADDR 339 int "Low address space to protect from user allocation" 340 depends on MMU 341 default 4096 342 help 343 This is the portion of low virtual memory which should be protected 344 from userspace allocation. Keeping a user from writing to low pages 345 can help reduce the impact of kernel NULL pointer bugs. 346 347 For most ia64, ppc64 and x86 users with lots of address space 348 a value of 65536 is reasonable and should cause no problems. 349 On arm and other archs it should not be higher than 32768. 350 Programs which use vm86 functionality or have some need to map 351 this low address space will need CAP_SYS_RAWIO or disable this 352 protection by setting the value to 0. 353 354 This value can be changed after boot using the 355 /proc/sys/vm/mmap_min_addr tunable. 356 357config ARCH_SUPPORTS_MEMORY_FAILURE 358 bool 359 360config MEMORY_FAILURE 361 depends on MMU 362 depends on ARCH_SUPPORTS_MEMORY_FAILURE 363 bool "Enable recovery from hardware memory errors" 364 select MEMORY_ISOLATION 365 select RAS 366 help 367 Enables code to recover from some memory failures on systems 368 with MCA recovery. This allows a system to continue running 369 even when some of its memory has uncorrected errors. This requires 370 special hardware support and typically ECC memory. 371 372config HWPOISON_INJECT 373 tristate "HWPoison pages injector" 374 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 375 select PROC_PAGE_MONITOR 376 377config NOMMU_INITIAL_TRIM_EXCESS 378 int "Turn on mmap() excess space trimming before booting" 379 depends on !MMU 380 default 1 381 help 382 The NOMMU mmap() frequently needs to allocate large contiguous chunks 383 of memory on which to store mappings, but it can only ask the system 384 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 385 more than it requires. To deal with this, mmap() is able to trim off 386 the excess and return it to the allocator. 387 388 If trimming is enabled, the excess is trimmed off and returned to the 389 system allocator, which can cause extra fragmentation, particularly 390 if there are a lot of transient processes. 391 392 If trimming is disabled, the excess is kept, but not used, which for 393 long-term mappings means that the space is wasted. 394 395 Trimming can be dynamically controlled through a sysctl option 396 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 397 excess pages there must be before trimming should occur, or zero if 398 no trimming is to occur. 399 400 This option specifies the initial value of this option. The default 401 of 1 says that all excess pages should be trimmed. 402 403 See Documentation/nommu-mmap.txt for more information. 404 405config TRANSPARENT_HUGEPAGE 406 bool "Transparent Hugepage Support" 407 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 408 select COMPACTION 409 help 410 Transparent Hugepages allows the kernel to use huge pages and 411 huge tlb transparently to the applications whenever possible. 412 This feature can improve computing performance to certain 413 applications by speeding up page faults during memory 414 allocation, by reducing the number of tlb misses and by speeding 415 up the pagetable walking. 416 417 If memory constrained on embedded, you may want to say N. 418 419choice 420 prompt "Transparent Hugepage Support sysfs defaults" 421 depends on TRANSPARENT_HUGEPAGE 422 default TRANSPARENT_HUGEPAGE_ALWAYS 423 help 424 Selects the sysfs defaults for Transparent Hugepage Support. 425 426 config TRANSPARENT_HUGEPAGE_ALWAYS 427 bool "always" 428 help 429 Enabling Transparent Hugepage always, can increase the 430 memory footprint of applications without a guaranteed 431 benefit but it will work automatically for all applications. 432 433 config TRANSPARENT_HUGEPAGE_MADVISE 434 bool "madvise" 435 help 436 Enabling Transparent Hugepage madvise, will only provide a 437 performance improvement benefit to the applications using 438 madvise(MADV_HUGEPAGE) but it won't risk to increase the 439 memory footprint of applications without a guaranteed 440 benefit. 441endchoice 442 443# 444# UP and nommu archs use km based percpu allocator 445# 446config NEED_PER_CPU_KM 447 depends on !SMP 448 bool 449 default y 450 451config CLEANCACHE 452 bool "Enable cleancache driver to cache clean pages if tmem is present" 453 default n 454 help 455 Cleancache can be thought of as a page-granularity victim cache 456 for clean pages that the kernel's pageframe replacement algorithm 457 (PFRA) would like to keep around, but can't since there isn't enough 458 memory. So when the PFRA "evicts" a page, it first attempts to use 459 cleancache code to put the data contained in that page into 460 "transcendent memory", memory that is not directly accessible or 461 addressable by the kernel and is of unknown and possibly 462 time-varying size. And when a cleancache-enabled 463 filesystem wishes to access a page in a file on disk, it first 464 checks cleancache to see if it already contains it; if it does, 465 the page is copied into the kernel and a disk access is avoided. 466 When a transcendent memory driver is available (such as zcache or 467 Xen transcendent memory), a significant I/O reduction 468 may be achieved. When none is available, all cleancache calls 469 are reduced to a single pointer-compare-against-NULL resulting 470 in a negligible performance hit. 471 472 If unsure, say Y to enable cleancache 473 474config FRONTSWAP 475 bool "Enable frontswap to cache swap pages if tmem is present" 476 depends on SWAP 477 default n 478 help 479 Frontswap is so named because it can be thought of as the opposite 480 of a "backing" store for a swap device. The data is stored into 481 "transcendent memory", memory that is not directly accessible or 482 addressable by the kernel and is of unknown and possibly 483 time-varying size. When space in transcendent memory is available, 484 a significant swap I/O reduction may be achieved. When none is 485 available, all frontswap calls are reduced to a single pointer- 486 compare-against-NULL resulting in a negligible performance hit 487 and swap data is stored as normal on the matching swap device. 488 489 If unsure, say Y to enable frontswap. 490 491config CMA 492 bool "Contiguous Memory Allocator" 493 depends on HAVE_MEMBLOCK && MMU 494 select MIGRATION 495 select MEMORY_ISOLATION 496 help 497 This enables the Contiguous Memory Allocator which allows other 498 subsystems to allocate big physically-contiguous blocks of memory. 499 CMA reserves a region of memory and allows only movable pages to 500 be allocated from it. This way, the kernel can use the memory for 501 pagecache and when a subsystem requests for contiguous area, the 502 allocated pages are migrated away to serve the contiguous request. 503 504 If unsure, say "n". 505 506config CMA_DEBUG 507 bool "CMA debug messages (DEVELOPMENT)" 508 depends on DEBUG_KERNEL && CMA 509 help 510 Turns on debug messages in CMA. This produces KERN_DEBUG 511 messages for every CMA call as well as various messages while 512 processing calls such as dma_alloc_from_contiguous(). 513 This option does not affect warning and error messages. 514 515config CMA_DEBUGFS 516 bool "CMA debugfs interface" 517 depends on CMA && DEBUG_FS 518 help 519 Turns on the DebugFS interface for CMA. 520 521config CMA_AREAS 522 int "Maximum count of the CMA areas" 523 depends on CMA 524 default 7 525 help 526 CMA allows to create CMA areas for particular purpose, mainly, 527 used as device private area. This parameter sets the maximum 528 number of CMA area in the system. 529 530 If unsure, leave the default value "7". 531 532config MEM_SOFT_DIRTY 533 bool "Track memory changes" 534 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 535 select PROC_PAGE_MONITOR 536 help 537 This option enables memory changes tracking by introducing a 538 soft-dirty bit on pte-s. This bit it set when someone writes 539 into a page just as regular dirty bit, but unlike the latter 540 it can be cleared by hands. 541 542 See Documentation/vm/soft-dirty.txt for more details. 543 544config ZSWAP 545 bool "Compressed cache for swap pages (EXPERIMENTAL)" 546 depends on FRONTSWAP && CRYPTO=y 547 select CRYPTO_LZO 548 select ZPOOL 549 default n 550 help 551 A lightweight compressed cache for swap pages. It takes 552 pages that are in the process of being swapped out and attempts to 553 compress them into a dynamically allocated RAM-based memory pool. 554 This can result in a significant I/O reduction on swap device and, 555 in the case where decompressing from RAM is faster that swap device 556 reads, can also improve workload performance. 557 558 This is marked experimental because it is a new feature (as of 559 v3.11) that interacts heavily with memory reclaim. While these 560 interactions don't cause any known issues on simple memory setups, 561 they have not be fully explored on the large set of potential 562 configurations and workloads that exist. 563 564config ZPOOL 565 tristate "Common API for compressed memory storage" 566 default n 567 help 568 Compressed memory storage API. This allows using either zbud or 569 zsmalloc. 570 571config ZBUD 572 tristate "Low density storage for compressed pages" 573 default n 574 help 575 A special purpose allocator for storing compressed pages. 576 It is designed to store up to two compressed pages per physical 577 page. While this design limits storage density, it has simple and 578 deterministic reclaim properties that make it preferable to a higher 579 density approach when reclaim will be used. 580 581config ZSMALLOC 582 tristate "Memory allocator for compressed pages" 583 depends on MMU 584 default n 585 help 586 zsmalloc is a slab-based memory allocator designed to store 587 compressed RAM pages. zsmalloc uses virtual memory mapping 588 in order to reduce fragmentation. However, this results in a 589 non-standard allocator interface where a handle, not a pointer, is 590 returned by an alloc(). This handle must be mapped in order to 591 access the allocated space. 592 593config PGTABLE_MAPPING 594 bool "Use page table mapping to access object in zsmalloc" 595 depends on ZSMALLOC 596 help 597 By default, zsmalloc uses a copy-based object mapping method to 598 access allocations that span two pages. However, if a particular 599 architecture (ex, ARM) performs VM mapping faster than copying, 600 then you should select this. This causes zsmalloc to use page table 601 mapping rather than copying for object mapping. 602 603 You can check speed with zsmalloc benchmark: 604 https://github.com/spartacus06/zsmapbench 605 606config ZSMALLOC_STAT 607 bool "Export zsmalloc statistics" 608 depends on ZSMALLOC 609 select DEBUG_FS 610 help 611 This option enables code in the zsmalloc to collect various 612 statistics about whats happening in zsmalloc and exports that 613 information to userspace via debugfs. 614 If unsure, say N. 615 616config GENERIC_EARLY_IOREMAP 617 bool 618 619config MAX_STACK_SIZE_MB 620 int "Maximum user stack size for 32-bit processes (MB)" 621 default 80 622 range 8 256 if METAG 623 range 8 2048 624 depends on STACK_GROWSUP && (!64BIT || COMPAT) 625 help 626 This is the maximum stack size in Megabytes in the VM layout of 32-bit 627 user processes when the stack grows upwards (currently only on parisc 628 and metag arch). The stack will be located at the highest memory 629 address minus the given value, unless the RLIMIT_STACK hard limit is 630 changed to a smaller value in which case that is used. 631 632 A sane initial value is 80 MB. 633 634# For architectures that support deferred memory initialisation 635config ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT 636 bool 637 638config DEFERRED_STRUCT_PAGE_INIT 639 bool "Defer initialisation of struct pages to kswapd" 640 default n 641 depends on ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT 642 depends on MEMORY_HOTPLUG 643 help 644 Ordinarily all struct pages are initialised during early boot in a 645 single thread. On very large machines this can take a considerable 646 amount of time. If this option is set, large machines will bring up 647 a subset of memmap at boot and then initialise the rest in parallel 648 when kswapd starts. This has a potential performance impact on 649 processes running early in the lifetime of the systemm until kswapd 650 finishes the initialisation. 651 652config IDLE_PAGE_TRACKING 653 bool "Enable idle page tracking" 654 depends on SYSFS && MMU 655 select PAGE_EXTENSION if !64BIT 656 help 657 This feature allows to estimate the amount of user pages that have 658 not been touched during a given period of time. This information can 659 be useful to tune memory cgroup limits and/or for job placement 660 within a compute cluster. 661 662 See Documentation/vm/idle_page_tracking.txt for more details. 663 664config ZONE_DEVICE 665 bool "Device memory (pmem, etc...) hotplug support" if EXPERT 666 default !ZONE_DMA 667 depends on !ZONE_DMA 668 depends on MEMORY_HOTPLUG 669 depends on MEMORY_HOTREMOVE 670 depends on X86_64 #arch_add_memory() comprehends device memory 671 672 help 673 Device memory hotplug support allows for establishing pmem, 674 or other device driver discovered memory regions, in the 675 memmap. This allows pfn_to_page() lookups of otherwise 676 "device-physical" addresses which is needed for using a DAX 677 mapping in an O_DIRECT operation, among other things. 678 679 If FS_DAX is enabled, then say Y. 680 681config FRAME_VECTOR 682 bool 683