1# SPDX-License-Identifier: GPL-2.0-only 2 3menu "Memory Management options" 4 5config SELECT_MEMORY_MODEL 6 def_bool y 7 depends on ARCH_SELECT_MEMORY_MODEL 8 9choice 10 prompt "Memory model" 11 depends on SELECT_MEMORY_MODEL 12 default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT 13 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT 14 default FLATMEM_MANUAL 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 selected by the architecture 19 configuration. This is normal. 20 21config FLATMEM_MANUAL 22 bool "Flat Memory" 23 depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE 24 help 25 This option is best suited for non-NUMA systems with 26 flat address space. The FLATMEM is the most efficient 27 system in terms of performance and resource consumption 28 and it is the best option for smaller systems. 29 30 For systems that have holes in their physical address 31 spaces and for features like NUMA and memory hotplug, 32 choose "Sparse Memory". 33 34 If unsure, choose this option (Flat Memory) over any other. 35 36config DISCONTIGMEM_MANUAL 37 bool "Discontiguous Memory" 38 depends on ARCH_DISCONTIGMEM_ENABLE 39 help 40 This option provides enhanced support for discontiguous 41 memory systems, over FLATMEM. These systems have holes 42 in their physical address spaces, and this option provides 43 more efficient handling of these holes. 44 45 Although "Discontiguous Memory" is still used by several 46 architectures, it is considered deprecated in favor of 47 "Sparse Memory". 48 49 If unsure, choose "Sparse Memory" over this option. 50 51config SPARSEMEM_MANUAL 52 bool "Sparse Memory" 53 depends on ARCH_SPARSEMEM_ENABLE 54 help 55 This will be the only option for some systems, including 56 memory hot-plug systems. This is normal. 57 58 This option provides efficient support for systems with 59 holes is their physical address space and allows memory 60 hot-plug and hot-remove. 61 62 If unsure, choose "Flat Memory" over this option. 63 64endchoice 65 66config DISCONTIGMEM 67 def_bool y 68 depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL 69 70config SPARSEMEM 71 def_bool y 72 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL 73 74config FLATMEM 75 def_bool y 76 depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL 77 78config FLAT_NODE_MEM_MAP 79 def_bool y 80 depends on !SPARSEMEM 81 82# 83# Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's 84# to represent different areas of memory. This variable allows 85# those dependencies to exist individually. 86# 87config NEED_MULTIPLE_NODES 88 def_bool y 89 depends on DISCONTIGMEM || NUMA 90 91config HAVE_MEMORY_PRESENT 92 def_bool y 93 depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM 94 95# 96# SPARSEMEM_EXTREME (which is the default) does some bootmem 97# allocations when memory_present() is called. If this cannot 98# be done on your architecture, select this option. However, 99# statically allocating the mem_section[] array can potentially 100# consume vast quantities of .bss, so be careful. 101# 102# This option will also potentially produce smaller runtime code 103# with gcc 3.4 and later. 104# 105config SPARSEMEM_STATIC 106 bool 107 108# 109# Architecture platforms which require a two level mem_section in SPARSEMEM 110# must select this option. This is usually for architecture platforms with 111# an extremely sparse physical address space. 112# 113config SPARSEMEM_EXTREME 114 def_bool y 115 depends on SPARSEMEM && !SPARSEMEM_STATIC 116 117config SPARSEMEM_VMEMMAP_ENABLE 118 bool 119 120config SPARSEMEM_VMEMMAP 121 bool "Sparse Memory virtual memmap" 122 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE 123 default y 124 help 125 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise 126 pfn_to_page and page_to_pfn operations. This is the most 127 efficient option when sufficient kernel resources are available. 128 129config HAVE_MEMBLOCK_NODE_MAP 130 bool 131 132config HAVE_MEMBLOCK_PHYS_MAP 133 bool 134 135config HAVE_FAST_GUP 136 depends on MMU 137 bool 138 139config ARCH_KEEP_MEMBLOCK 140 bool 141 142config MEMORY_ISOLATION 143 bool 144 145# 146# Only be set on architectures that have completely implemented memory hotplug 147# feature. If you are not sure, don't touch it. 148# 149config HAVE_BOOTMEM_INFO_NODE 150 def_bool n 151 152# eventually, we can have this option just 'select SPARSEMEM' 153config MEMORY_HOTPLUG 154 bool "Allow for memory hot-add" 155 depends on SPARSEMEM || X86_64_ACPI_NUMA 156 depends on ARCH_ENABLE_MEMORY_HOTPLUG 157 158config MEMORY_HOTPLUG_SPARSE 159 def_bool y 160 depends on SPARSEMEM && MEMORY_HOTPLUG 161 162config MEMORY_HOTPLUG_DEFAULT_ONLINE 163 bool "Online the newly added memory blocks by default" 164 depends on MEMORY_HOTPLUG 165 help 166 This option sets the default policy setting for memory hotplug 167 onlining policy (/sys/devices/system/memory/auto_online_blocks) which 168 determines what happens to newly added memory regions. Policy setting 169 can always be changed at runtime. 170 See Documentation/admin-guide/mm/memory-hotplug.rst for more information. 171 172 Say Y here if you want all hot-plugged memory blocks to appear in 173 'online' state by default. 174 Say N here if you want the default policy to keep all hot-plugged 175 memory blocks in 'offline' state. 176 177config MEMORY_HOTREMOVE 178 bool "Allow for memory hot remove" 179 select MEMORY_ISOLATION 180 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64) 181 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 182 depends on MIGRATION 183 184# Heavily threaded applications may benefit from splitting the mm-wide 185# page_table_lock, so that faults on different parts of the user address 186# space can be handled with less contention: split it at this NR_CPUS. 187# Default to 4 for wider testing, though 8 might be more appropriate. 188# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 189# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 190# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 191# 192config SPLIT_PTLOCK_CPUS 193 int 194 default "999999" if !MMU 195 default "999999" if ARM && !CPU_CACHE_VIPT 196 default "999999" if PARISC && !PA20 197 default "4" 198 199config ARCH_ENABLE_SPLIT_PMD_PTLOCK 200 bool 201 202# 203# support for memory balloon 204config MEMORY_BALLOON 205 bool 206 207# 208# support for memory balloon compaction 209config BALLOON_COMPACTION 210 bool "Allow for balloon memory compaction/migration" 211 def_bool y 212 depends on COMPACTION && MEMORY_BALLOON 213 help 214 Memory fragmentation introduced by ballooning might reduce 215 significantly the number of 2MB contiguous memory blocks that can be 216 used within a guest, thus imposing performance penalties associated 217 with the reduced number of transparent huge pages that could be used 218 by the guest workload. Allowing the compaction & migration for memory 219 pages enlisted as being part of memory balloon devices avoids the 220 scenario aforementioned and helps improving memory defragmentation. 221 222# 223# support for memory compaction 224config COMPACTION 225 bool "Allow for memory compaction" 226 def_bool y 227 select MIGRATION 228 depends on MMU 229 help 230 Compaction is the only memory management component to form 231 high order (larger physically contiguous) memory blocks 232 reliably. The page allocator relies on compaction heavily and 233 the lack of the feature can lead to unexpected OOM killer 234 invocations for high order memory requests. You shouldn't 235 disable this option unless there really is a strong reason for 236 it and then we would be really interested to hear about that at 237 linux-mm@kvack.org. 238 239# 240# support for page migration 241# 242config MIGRATION 243 bool "Page migration" 244 def_bool y 245 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU 246 help 247 Allows the migration of the physical location of pages of processes 248 while the virtual addresses are not changed. This is useful in 249 two situations. The first is on NUMA systems to put pages nearer 250 to the processors accessing. The second is when allocating huge 251 pages as migration can relocate pages to satisfy a huge page 252 allocation instead of reclaiming. 253 254config ARCH_ENABLE_HUGEPAGE_MIGRATION 255 bool 256 257config ARCH_ENABLE_THP_MIGRATION 258 bool 259 260config CONTIG_ALLOC 261 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA 262 263config PHYS_ADDR_T_64BIT 264 def_bool 64BIT 265 266config BOUNCE 267 bool "Enable bounce buffers" 268 default y 269 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 270 help 271 Enable bounce buffers for devices that cannot access 272 the full range of memory available to the CPU. Enabled 273 by default when ZONE_DMA or HIGHMEM is selected, but you 274 may say n to override this. 275 276config VIRT_TO_BUS 277 bool 278 help 279 An architecture should select this if it implements the 280 deprecated interface virt_to_bus(). All new architectures 281 should probably not select this. 282 283 284config MMU_NOTIFIER 285 bool 286 select SRCU 287 select INTERVAL_TREE 288 289config KSM 290 bool "Enable KSM for page merging" 291 depends on MMU 292 select XXHASH 293 help 294 Enable Kernel Samepage Merging: KSM periodically scans those areas 295 of an application's address space that an app has advised may be 296 mergeable. When it finds pages of identical content, it replaces 297 the many instances by a single page with that content, so 298 saving memory until one or another app needs to modify the content. 299 Recommended for use with KVM, or with other duplicative applications. 300 See Documentation/vm/ksm.rst for more information: KSM is inactive 301 until a program has madvised that an area is MADV_MERGEABLE, and 302 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 303 304config DEFAULT_MMAP_MIN_ADDR 305 int "Low address space to protect from user allocation" 306 depends on MMU 307 default 4096 308 help 309 This is the portion of low virtual memory which should be protected 310 from userspace allocation. Keeping a user from writing to low pages 311 can help reduce the impact of kernel NULL pointer bugs. 312 313 For most ia64, ppc64 and x86 users with lots of address space 314 a value of 65536 is reasonable and should cause no problems. 315 On arm and other archs it should not be higher than 32768. 316 Programs which use vm86 functionality or have some need to map 317 this low address space will need CAP_SYS_RAWIO or disable this 318 protection by setting the value to 0. 319 320 This value can be changed after boot using the 321 /proc/sys/vm/mmap_min_addr tunable. 322 323config ARCH_SUPPORTS_MEMORY_FAILURE 324 bool 325 326config MEMORY_FAILURE 327 depends on MMU 328 depends on ARCH_SUPPORTS_MEMORY_FAILURE 329 bool "Enable recovery from hardware memory errors" 330 select MEMORY_ISOLATION 331 select RAS 332 help 333 Enables code to recover from some memory failures on systems 334 with MCA recovery. This allows a system to continue running 335 even when some of its memory has uncorrected errors. This requires 336 special hardware support and typically ECC memory. 337 338config HWPOISON_INJECT 339 tristate "HWPoison pages injector" 340 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 341 select PROC_PAGE_MONITOR 342 343config NOMMU_INITIAL_TRIM_EXCESS 344 int "Turn on mmap() excess space trimming before booting" 345 depends on !MMU 346 default 1 347 help 348 The NOMMU mmap() frequently needs to allocate large contiguous chunks 349 of memory on which to store mappings, but it can only ask the system 350 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 351 more than it requires. To deal with this, mmap() is able to trim off 352 the excess and return it to the allocator. 353 354 If trimming is enabled, the excess is trimmed off and returned to the 355 system allocator, which can cause extra fragmentation, particularly 356 if there are a lot of transient processes. 357 358 If trimming is disabled, the excess is kept, but not used, which for 359 long-term mappings means that the space is wasted. 360 361 Trimming can be dynamically controlled through a sysctl option 362 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 363 excess pages there must be before trimming should occur, or zero if 364 no trimming is to occur. 365 366 This option specifies the initial value of this option. The default 367 of 1 says that all excess pages should be trimmed. 368 369 See Documentation/nommu-mmap.txt for more information. 370 371config TRANSPARENT_HUGEPAGE 372 bool "Transparent Hugepage Support" 373 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 374 select COMPACTION 375 select XARRAY_MULTI 376 help 377 Transparent Hugepages allows the kernel to use huge pages and 378 huge tlb transparently to the applications whenever possible. 379 This feature can improve computing performance to certain 380 applications by speeding up page faults during memory 381 allocation, by reducing the number of tlb misses and by speeding 382 up the pagetable walking. 383 384 If memory constrained on embedded, you may want to say N. 385 386choice 387 prompt "Transparent Hugepage Support sysfs defaults" 388 depends on TRANSPARENT_HUGEPAGE 389 default TRANSPARENT_HUGEPAGE_ALWAYS 390 help 391 Selects the sysfs defaults for Transparent Hugepage Support. 392 393 config TRANSPARENT_HUGEPAGE_ALWAYS 394 bool "always" 395 help 396 Enabling Transparent Hugepage always, can increase the 397 memory footprint of applications without a guaranteed 398 benefit but it will work automatically for all applications. 399 400 config TRANSPARENT_HUGEPAGE_MADVISE 401 bool "madvise" 402 help 403 Enabling Transparent Hugepage madvise, will only provide a 404 performance improvement benefit to the applications using 405 madvise(MADV_HUGEPAGE) but it won't risk to increase the 406 memory footprint of applications without a guaranteed 407 benefit. 408endchoice 409 410config ARCH_WANTS_THP_SWAP 411 def_bool n 412 413config THP_SWAP 414 def_bool y 415 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP 416 help 417 Swap transparent huge pages in one piece, without splitting. 418 XXX: For now, swap cluster backing transparent huge page 419 will be split after swapout. 420 421 For selection by architectures with reasonable THP sizes. 422 423config TRANSPARENT_HUGE_PAGECACHE 424 def_bool y 425 depends on TRANSPARENT_HUGEPAGE 426 427# 428# UP and nommu archs use km based percpu allocator 429# 430config NEED_PER_CPU_KM 431 depends on !SMP 432 bool 433 default y 434 435config CLEANCACHE 436 bool "Enable cleancache driver to cache clean pages if tmem is present" 437 help 438 Cleancache can be thought of as a page-granularity victim cache 439 for clean pages that the kernel's pageframe replacement algorithm 440 (PFRA) would like to keep around, but can't since there isn't enough 441 memory. So when the PFRA "evicts" a page, it first attempts to use 442 cleancache code to put the data contained in that page into 443 "transcendent memory", memory that is not directly accessible or 444 addressable by the kernel and is of unknown and possibly 445 time-varying size. And when a cleancache-enabled 446 filesystem wishes to access a page in a file on disk, it first 447 checks cleancache to see if it already contains it; if it does, 448 the page is copied into the kernel and a disk access is avoided. 449 When a transcendent memory driver is available (such as zcache or 450 Xen transcendent memory), a significant I/O reduction 451 may be achieved. When none is available, all cleancache calls 452 are reduced to a single pointer-compare-against-NULL resulting 453 in a negligible performance hit. 454 455 If unsure, say Y to enable cleancache 456 457config FRONTSWAP 458 bool "Enable frontswap to cache swap pages if tmem is present" 459 depends on SWAP 460 help 461 Frontswap is so named because it can be thought of as the opposite 462 of a "backing" store for a swap device. The data is stored into 463 "transcendent memory", memory that is not directly accessible or 464 addressable by the kernel and is of unknown and possibly 465 time-varying size. When space in transcendent memory is available, 466 a significant swap I/O reduction may be achieved. When none is 467 available, all frontswap calls are reduced to a single pointer- 468 compare-against-NULL resulting in a negligible performance hit 469 and swap data is stored as normal on the matching swap device. 470 471 If unsure, say Y to enable frontswap. 472 473config CMA 474 bool "Contiguous Memory Allocator" 475 depends on MMU 476 select MIGRATION 477 select MEMORY_ISOLATION 478 help 479 This enables the Contiguous Memory Allocator which allows other 480 subsystems to allocate big physically-contiguous blocks of memory. 481 CMA reserves a region of memory and allows only movable pages to 482 be allocated from it. This way, the kernel can use the memory for 483 pagecache and when a subsystem requests for contiguous area, the 484 allocated pages are migrated away to serve the contiguous request. 485 486 If unsure, say "n". 487 488config CMA_DEBUG 489 bool "CMA debug messages (DEVELOPMENT)" 490 depends on DEBUG_KERNEL && CMA 491 help 492 Turns on debug messages in CMA. This produces KERN_DEBUG 493 messages for every CMA call as well as various messages while 494 processing calls such as dma_alloc_from_contiguous(). 495 This option does not affect warning and error messages. 496 497config CMA_DEBUGFS 498 bool "CMA debugfs interface" 499 depends on CMA && DEBUG_FS 500 help 501 Turns on the DebugFS interface for CMA. 502 503config CMA_AREAS 504 int "Maximum count of the CMA areas" 505 depends on CMA 506 default 7 507 help 508 CMA allows to create CMA areas for particular purpose, mainly, 509 used as device private area. This parameter sets the maximum 510 number of CMA area in the system. 511 512 If unsure, leave the default value "7". 513 514config MEM_SOFT_DIRTY 515 bool "Track memory changes" 516 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 517 select PROC_PAGE_MONITOR 518 help 519 This option enables memory changes tracking by introducing a 520 soft-dirty bit on pte-s. This bit it set when someone writes 521 into a page just as regular dirty bit, but unlike the latter 522 it can be cleared by hands. 523 524 See Documentation/admin-guide/mm/soft-dirty.rst for more details. 525 526config ZSWAP 527 bool "Compressed cache for swap pages (EXPERIMENTAL)" 528 depends on FRONTSWAP && CRYPTO=y 529 select CRYPTO_LZO 530 select ZPOOL 531 help 532 A lightweight compressed cache for swap pages. It takes 533 pages that are in the process of being swapped out and attempts to 534 compress them into a dynamically allocated RAM-based memory pool. 535 This can result in a significant I/O reduction on swap device and, 536 in the case where decompressing from RAM is faster that swap device 537 reads, can also improve workload performance. 538 539 This is marked experimental because it is a new feature (as of 540 v3.11) that interacts heavily with memory reclaim. While these 541 interactions don't cause any known issues on simple memory setups, 542 they have not be fully explored on the large set of potential 543 configurations and workloads that exist. 544 545config ZPOOL 546 tristate "Common API for compressed memory storage" 547 help 548 Compressed memory storage API. This allows using either zbud or 549 zsmalloc. 550 551config ZBUD 552 tristate "Low (Up to 2x) density storage for compressed pages" 553 help 554 A special purpose allocator for storing compressed pages. 555 It is designed to store up to two compressed pages per physical 556 page. While this design limits storage density, it has simple and 557 deterministic reclaim properties that make it preferable to a higher 558 density approach when reclaim will be used. 559 560config Z3FOLD 561 tristate "Up to 3x density storage for compressed pages" 562 depends on ZPOOL 563 help 564 A special purpose allocator for storing compressed pages. 565 It is designed to store up to three compressed pages per physical 566 page. It is a ZBUD derivative so the simplicity and determinism are 567 still there. 568 569config ZSMALLOC 570 tristate "Memory allocator for compressed pages" 571 depends on MMU 572 help 573 zsmalloc is a slab-based memory allocator designed to store 574 compressed RAM pages. zsmalloc uses virtual memory mapping 575 in order to reduce fragmentation. However, this results in a 576 non-standard allocator interface where a handle, not a pointer, is 577 returned by an alloc(). This handle must be mapped in order to 578 access the allocated space. 579 580config PGTABLE_MAPPING 581 bool "Use page table mapping to access object in zsmalloc" 582 depends on ZSMALLOC 583 help 584 By default, zsmalloc uses a copy-based object mapping method to 585 access allocations that span two pages. However, if a particular 586 architecture (ex, ARM) performs VM mapping faster than copying, 587 then you should select this. This causes zsmalloc to use page table 588 mapping rather than copying for object mapping. 589 590 You can check speed with zsmalloc benchmark: 591 https://github.com/spartacus06/zsmapbench 592 593config ZSMALLOC_STAT 594 bool "Export zsmalloc statistics" 595 depends on ZSMALLOC 596 select DEBUG_FS 597 help 598 This option enables code in the zsmalloc to collect various 599 statistics about whats happening in zsmalloc and exports that 600 information to userspace via debugfs. 601 If unsure, say N. 602 603config GENERIC_EARLY_IOREMAP 604 bool 605 606config MAX_STACK_SIZE_MB 607 int "Maximum user stack size for 32-bit processes (MB)" 608 default 80 609 range 8 2048 610 depends on STACK_GROWSUP && (!64BIT || COMPAT) 611 help 612 This is the maximum stack size in Megabytes in the VM layout of 32-bit 613 user processes when the stack grows upwards (currently only on parisc 614 arch). The stack will be located at the highest memory address minus 615 the given value, unless the RLIMIT_STACK hard limit is changed to a 616 smaller value in which case that is used. 617 618 A sane initial value is 80 MB. 619 620config DEFERRED_STRUCT_PAGE_INIT 621 bool "Defer initialisation of struct pages to kthreads" 622 depends on SPARSEMEM 623 depends on !NEED_PER_CPU_KM 624 depends on 64BIT 625 help 626 Ordinarily all struct pages are initialised during early boot in a 627 single thread. On very large machines this can take a considerable 628 amount of time. If this option is set, large machines will bring up 629 a subset of memmap at boot and then initialise the rest in parallel 630 by starting one-off "pgdatinitX" kernel thread for each node X. This 631 has a potential performance impact on processes running early in the 632 lifetime of the system until these kthreads finish the 633 initialisation. 634 635config IDLE_PAGE_TRACKING 636 bool "Enable idle page tracking" 637 depends on SYSFS && MMU 638 select PAGE_EXTENSION if !64BIT 639 help 640 This feature allows to estimate the amount of user pages that have 641 not been touched during a given period of time. This information can 642 be useful to tune memory cgroup limits and/or for job placement 643 within a compute cluster. 644 645 See Documentation/admin-guide/mm/idle_page_tracking.rst for 646 more details. 647 648config ARCH_HAS_PTE_DEVMAP 649 bool 650 651config ZONE_DEVICE 652 bool "Device memory (pmem, HMM, etc...) hotplug support" 653 depends on MEMORY_HOTPLUG 654 depends on MEMORY_HOTREMOVE 655 depends on SPARSEMEM_VMEMMAP 656 depends on ARCH_HAS_PTE_DEVMAP 657 select XARRAY_MULTI 658 659 help 660 Device memory hotplug support allows for establishing pmem, 661 or other device driver discovered memory regions, in the 662 memmap. This allows pfn_to_page() lookups of otherwise 663 "device-physical" addresses which is needed for using a DAX 664 mapping in an O_DIRECT operation, among other things. 665 666 If FS_DAX is enabled, then say Y. 667 668config DEV_PAGEMAP_OPS 669 bool 670 671# 672# Helpers to mirror range of the CPU page tables of a process into device page 673# tables. 674# 675config HMM_MIRROR 676 bool 677 depends on MMU 678 679config DEVICE_PRIVATE 680 bool "Unaddressable device memory (GPU memory, ...)" 681 depends on ZONE_DEVICE 682 select DEV_PAGEMAP_OPS 683 684 help 685 Allows creation of struct pages to represent unaddressable device 686 memory; i.e., memory that is only accessible from the device (or 687 group of devices). You likely also want to select HMM_MIRROR. 688 689config FRAME_VECTOR 690 bool 691 692config ARCH_USES_HIGH_VMA_FLAGS 693 bool 694config ARCH_HAS_PKEYS 695 bool 696 697config PERCPU_STATS 698 bool "Collect percpu memory statistics" 699 help 700 This feature collects and exposes statistics via debugfs. The 701 information includes global and per chunk statistics, which can 702 be used to help understand percpu memory usage. 703 704config GUP_BENCHMARK 705 bool "Enable infrastructure for get_user_pages_fast() benchmarking" 706 help 707 Provides /sys/kernel/debug/gup_benchmark that helps with testing 708 performance of get_user_pages_fast(). 709 710 See tools/testing/selftests/vm/gup_benchmark.c 711 712config GUP_GET_PTE_LOW_HIGH 713 bool 714 715config READ_ONLY_THP_FOR_FS 716 bool "Read-only THP for filesystems (EXPERIMENTAL)" 717 depends on TRANSPARENT_HUGE_PAGECACHE && SHMEM 718 719 help 720 Allow khugepaged to put read-only file-backed pages in THP. 721 722 This is marked experimental because it is a new feature. Write 723 support of file THPs will be developed in the next few release 724 cycles. 725 726config ARCH_HAS_PTE_SPECIAL 727 bool 728 729# 730# Some architectures require a special hugepage directory format that is 731# required to support multiple hugepage sizes. For example a4fe3ce76 732# "powerpc/mm: Allow more flexible layouts for hugepage pagetables" 733# introduced it on powerpc. This allows for a more flexible hugepage 734# pagetable layouts. 735# 736config ARCH_HAS_HUGEPD 737 bool 738 739config MAPPING_DIRTY_HELPERS 740 bool 741 742endmenu 743