1# SPDX-License-Identifier: GPL-2.0-only 2 3menu "Memory Management options" 4 5# 6# For some reason microblaze and nios2 hard code SWAP=n. Hopefully we can 7# add proper SWAP support to them, in which case this can be remove. 8# 9config ARCH_NO_SWAP 10 bool 11 12menuconfig SWAP 13 bool "Support for paging of anonymous memory (swap)" 14 depends on MMU && BLOCK && !ARCH_NO_SWAP 15 default y 16 help 17 This option allows you to choose whether you want to have support 18 for so called swap devices or swap files in your kernel that are 19 used to provide more virtual memory than the actual RAM present 20 in your computer. If unsure say Y. 21 22config ZSWAP 23 bool "Compressed cache for swap pages" 24 depends on SWAP 25 select CRYPTO 26 select ZSMALLOC 27 help 28 A lightweight compressed cache for swap pages. It takes 29 pages that are in the process of being swapped out and attempts to 30 compress them into a dynamically allocated RAM-based memory pool. 31 This can result in a significant I/O reduction on swap device and, 32 in the case where decompressing from RAM is faster than swap device 33 reads, can also improve workload performance. 34 35config ZSWAP_DEFAULT_ON 36 bool "Enable the compressed cache for swap pages by default" 37 depends on ZSWAP 38 help 39 If selected, the compressed cache for swap pages will be enabled 40 at boot, otherwise it will be disabled. 41 42 The selection made here can be overridden by using the kernel 43 command line 'zswap.enabled=' option. 44 45config ZSWAP_SHRINKER_DEFAULT_ON 46 bool "Shrink the zswap pool on memory pressure" 47 depends on ZSWAP 48 default n 49 help 50 If selected, the zswap shrinker will be enabled, and the pages 51 stored in the zswap pool will become available for reclaim (i.e 52 written back to the backing swap device) on memory pressure. 53 54 This means that zswap writeback could happen even if the pool is 55 not yet full, or the cgroup zswap limit has not been reached, 56 reducing the chance that cold pages will reside in the zswap pool 57 and consume memory indefinitely. 58 59choice 60 prompt "Default compressor" 61 depends on ZSWAP 62 default ZSWAP_COMPRESSOR_DEFAULT_LZO 63 help 64 Selects the default compression algorithm for the compressed cache 65 for swap pages. 66 67 For an overview what kind of performance can be expected from 68 a particular compression algorithm please refer to the benchmarks 69 available at the following LWN page: 70 https://lwn.net/Articles/751795/ 71 72 If in doubt, select 'LZO'. 73 74 The selection made here can be overridden by using the kernel 75 command line 'zswap.compressor=' option. 76 77config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE 78 bool "Deflate" 79 select CRYPTO_DEFLATE 80 help 81 Use the Deflate algorithm as the default compression algorithm. 82 83config ZSWAP_COMPRESSOR_DEFAULT_LZO 84 bool "LZO" 85 select CRYPTO_LZO 86 help 87 Use the LZO algorithm as the default compression algorithm. 88 89config ZSWAP_COMPRESSOR_DEFAULT_842 90 bool "842" 91 select CRYPTO_842 92 help 93 Use the 842 algorithm as the default compression algorithm. 94 95config ZSWAP_COMPRESSOR_DEFAULT_LZ4 96 bool "LZ4" 97 select CRYPTO_LZ4 98 help 99 Use the LZ4 algorithm as the default compression algorithm. 100 101config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC 102 bool "LZ4HC" 103 select CRYPTO_LZ4HC 104 help 105 Use the LZ4HC algorithm as the default compression algorithm. 106 107config ZSWAP_COMPRESSOR_DEFAULT_ZSTD 108 bool "zstd" 109 select CRYPTO_ZSTD 110 help 111 Use the zstd algorithm as the default compression algorithm. 112endchoice 113 114config ZSWAP_COMPRESSOR_DEFAULT 115 string 116 depends on ZSWAP 117 default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE 118 default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO 119 default "842" if ZSWAP_COMPRESSOR_DEFAULT_842 120 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4 121 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC 122 default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD 123 default "" 124 125config ZSMALLOC 126 tristate 127 128if ZSMALLOC 129 130menu "Zsmalloc allocator options" 131 depends on ZSMALLOC 132 133comment "Zsmalloc is a common backend allocator for zswap & zram" 134 135config ZSMALLOC_STAT 136 bool "Export zsmalloc statistics" 137 select DEBUG_FS 138 help 139 This option enables code in the zsmalloc to collect various 140 statistics about what's happening in zsmalloc and exports that 141 information to userspace via debugfs. 142 If unsure, say N. 143 144config ZSMALLOC_CHAIN_SIZE 145 int "Maximum number of physical pages per-zspage" 146 default 8 147 range 4 16 148 help 149 This option sets the upper limit on the number of physical pages 150 that a zmalloc page (zspage) can consist of. The optimal zspage 151 chain size is calculated for each size class during the 152 initialization of the pool. 153 154 Changing this option can alter the characteristics of size classes, 155 such as the number of pages per zspage and the number of objects 156 per zspage. This can also result in different configurations of 157 the pool, as zsmalloc merges size classes with similar 158 characteristics. 159 160 For more information, see zsmalloc documentation. 161 162endmenu 163 164endif 165 166menu "Slab allocator options" 167 168config SLUB 169 def_bool y 170 select IRQ_WORK 171 172config KVFREE_RCU_BATCHED 173 def_bool y 174 depends on !SLUB_TINY && !TINY_RCU 175 176config SLUB_TINY 177 bool "Configure for minimal memory footprint" 178 depends on EXPERT && !COMPILE_TEST 179 select SLAB_MERGE_DEFAULT 180 help 181 Configures the slab allocator in a way to achieve minimal memory 182 footprint, sacrificing scalability, debugging and other features. 183 This is intended only for the smallest system that had used the 184 SLOB allocator and is not recommended for systems with more than 185 16MB RAM. 186 187 If unsure, say N. 188 189config SLAB_MERGE_DEFAULT 190 bool "Allow slab caches to be merged" 191 default y 192 help 193 For reduced kernel memory fragmentation, slab caches can be 194 merged when they share the same size and other characteristics. 195 This carries a risk of kernel heap overflows being able to 196 overwrite objects from merged caches (and more easily control 197 cache layout), which makes such heap attacks easier to exploit 198 by attackers. By keeping caches unmerged, these kinds of exploits 199 can usually only damage objects in the same cache. To disable 200 merging at runtime, "slab_nomerge" can be passed on the kernel 201 command line. 202 203config SLAB_FREELIST_RANDOM 204 bool "Randomize slab freelist" 205 depends on !SLUB_TINY 206 help 207 Randomizes the freelist order used on creating new pages. This 208 security feature reduces the predictability of the kernel slab 209 allocator against heap overflows. 210 211config SLAB_FREELIST_HARDENED 212 bool "Harden slab freelist metadata" 213 depends on !SLUB_TINY 214 help 215 Many kernel heap attacks try to target slab cache metadata and 216 other infrastructure. This options makes minor performance 217 sacrifices to harden the kernel slab allocator against common 218 freelist exploit methods. 219 220config SLAB_BUCKETS 221 bool "Support allocation from separate kmalloc buckets" 222 depends on !SLUB_TINY 223 default SLAB_FREELIST_HARDENED 224 help 225 Kernel heap attacks frequently depend on being able to create 226 specifically-sized allocations with user-controlled contents 227 that will be allocated into the same kmalloc bucket as a 228 target object. To avoid sharing these allocation buckets, 229 provide an explicitly separated set of buckets to be used for 230 user-controlled allocations. This may very slightly increase 231 memory fragmentation, though in practice it's only a handful 232 of extra pages since the bulk of user-controlled allocations 233 are relatively long-lived. 234 235 If unsure, say Y. 236 237config SLUB_STATS 238 default n 239 bool "Enable performance statistics" 240 depends on SYSFS && !SLUB_TINY 241 help 242 The statistics are useful to debug slab allocation behavior in 243 order find ways to optimize the allocator. This should never be 244 enabled for production use since keeping statistics slows down 245 the allocator by a few percentage points. The slabinfo command 246 supports the determination of the most active slabs to figure 247 out which slabs are relevant to a particular load. 248 Try running: slabinfo -DA 249 250config SLUB_CPU_PARTIAL 251 default y 252 depends on SMP && !SLUB_TINY 253 bool "Enable per cpu partial caches" 254 help 255 Per cpu partial caches accelerate objects allocation and freeing 256 that is local to a processor at the price of more indeterminism 257 in the latency of the free. On overflow these caches will be cleared 258 which requires the taking of locks that may cause latency spikes. 259 Typically one would choose no for a realtime system. 260 261config RANDOM_KMALLOC_CACHES 262 default n 263 depends on !SLUB_TINY 264 bool "Randomize slab caches for normal kmalloc" 265 help 266 A hardening feature that creates multiple copies of slab caches for 267 normal kmalloc allocation and makes kmalloc randomly pick one based 268 on code address, which makes the attackers more difficult to spray 269 vulnerable memory objects on the heap for the purpose of exploiting 270 memory vulnerabilities. 271 272 Currently the number of copies is set to 16, a reasonably large value 273 that effectively diverges the memory objects allocated for different 274 subsystems or modules into different caches, at the expense of a 275 limited degree of memory and CPU overhead that relates to hardware and 276 system workload. 277 278endmenu # Slab allocator options 279 280config SHUFFLE_PAGE_ALLOCATOR 281 bool "Page allocator randomization" 282 default SLAB_FREELIST_RANDOM && ACPI_NUMA 283 help 284 Randomization of the page allocator improves the average 285 utilization of a direct-mapped memory-side-cache. See section 286 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 287 6.2a specification for an example of how a platform advertises 288 the presence of a memory-side-cache. There are also incidental 289 security benefits as it reduces the predictability of page 290 allocations to compliment SLAB_FREELIST_RANDOM, but the 291 default granularity of shuffling on the MAX_PAGE_ORDER i.e, 10th 292 order of pages is selected based on cache utilization benefits 293 on x86. 294 295 While the randomization improves cache utilization it may 296 negatively impact workloads on platforms without a cache. For 297 this reason, by default, the randomization is not enabled even 298 if SHUFFLE_PAGE_ALLOCATOR=y. The randomization may be force enabled 299 with the 'page_alloc.shuffle' kernel command line parameter. 300 301 Say Y if unsure. 302 303config COMPAT_BRK 304 bool "Disable heap randomization" 305 default y 306 help 307 Randomizing heap placement makes heap exploits harder, but it 308 also breaks ancient binaries (including anything libc5 based). 309 This option changes the bootup default to heap randomization 310 disabled, and can be overridden at runtime by setting 311 /proc/sys/kernel/randomize_va_space to 2. 312 313 On non-ancient distros (post-2000 ones) N is usually a safe choice. 314 315config MMAP_ALLOW_UNINITIALIZED 316 bool "Allow mmapped anonymous memory to be uninitialized" 317 depends on EXPERT && !MMU 318 default n 319 help 320 Normally, and according to the Linux spec, anonymous memory obtained 321 from mmap() has its contents cleared before it is passed to 322 userspace. Enabling this config option allows you to request that 323 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 324 providing a huge performance boost. If this option is not enabled, 325 then the flag will be ignored. 326 327 This is taken advantage of by uClibc's malloc(), and also by 328 ELF-FDPIC binfmt's brk and stack allocator. 329 330 Because of the obvious security issues, this option should only be 331 enabled on embedded devices where you control what is run in 332 userspace. Since that isn't generally a problem on no-MMU systems, 333 it is normally safe to say Y here. 334 335 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 336 337config SELECT_MEMORY_MODEL 338 def_bool y 339 depends on ARCH_SELECT_MEMORY_MODEL 340 341choice 342 prompt "Memory model" 343 depends on SELECT_MEMORY_MODEL 344 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT 345 default FLATMEM_MANUAL 346 help 347 This option allows you to change some of the ways that 348 Linux manages its memory internally. Most users will 349 only have one option here selected by the architecture 350 configuration. This is normal. 351 352config FLATMEM_MANUAL 353 bool "Flat Memory" 354 depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE 355 help 356 This option is best suited for non-NUMA systems with 357 flat address space. The FLATMEM is the most efficient 358 system in terms of performance and resource consumption 359 and it is the best option for smaller systems. 360 361 For systems that have holes in their physical address 362 spaces and for features like NUMA and memory hotplug, 363 choose "Sparse Memory". 364 365 If unsure, choose this option (Flat Memory) over any other. 366 367config SPARSEMEM_MANUAL 368 bool "Sparse Memory" 369 depends on ARCH_SPARSEMEM_ENABLE 370 help 371 This will be the only option for some systems, including 372 memory hot-plug systems. This is normal. 373 374 This option provides efficient support for systems with 375 holes is their physical address space and allows memory 376 hot-plug and hot-remove. 377 378 If unsure, choose "Flat Memory" over this option. 379 380endchoice 381 382config SPARSEMEM 383 def_bool y 384 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL 385 386config FLATMEM 387 def_bool y 388 depends on !SPARSEMEM || FLATMEM_MANUAL 389 390# 391# SPARSEMEM_EXTREME (which is the default) does some bootmem 392# allocations when sparse_init() is called. If this cannot 393# be done on your architecture, select this option. However, 394# statically allocating the mem_section[] array can potentially 395# consume vast quantities of .bss, so be careful. 396# 397# This option will also potentially produce smaller runtime code 398# with gcc 3.4 and later. 399# 400config SPARSEMEM_STATIC 401 bool 402 403# 404# Architecture platforms which require a two level mem_section in SPARSEMEM 405# must select this option. This is usually for architecture platforms with 406# an extremely sparse physical address space. 407# 408config SPARSEMEM_EXTREME 409 def_bool y 410 depends on SPARSEMEM && !SPARSEMEM_STATIC 411 412config SPARSEMEM_VMEMMAP_ENABLE 413 bool 414 415config SPARSEMEM_VMEMMAP 416 def_bool y 417 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE 418 help 419 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise 420 pfn_to_page and page_to_pfn operations. This is the most 421 efficient option when sufficient kernel resources are available. 422 423config SPARSEMEM_VMEMMAP_PREINIT 424 bool 425# 426# Select this config option from the architecture Kconfig, if it is preferred 427# to enable the feature of HugeTLB/dev_dax vmemmap optimization. 428# 429config ARCH_WANT_OPTIMIZE_DAX_VMEMMAP 430 bool 431 432config ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP 433 bool 434 435config ARCH_WANT_HUGETLB_VMEMMAP_PREINIT 436 bool 437 438config HAVE_MEMBLOCK_PHYS_MAP 439 bool 440 441config HAVE_GUP_FAST 442 depends on MMU 443 bool 444 445# Enable memblock support for scratch memory which is needed for kexec handover 446config MEMBLOCK_KHO_SCRATCH 447 bool 448 449# Don't discard allocated memory used to track "memory" and "reserved" memblocks 450# after early boot, so it can still be used to test for validity of memory. 451# Also, memblocks are updated with memory hot(un)plug. 452config ARCH_KEEP_MEMBLOCK 453 bool 454 455# Keep arch NUMA mapping infrastructure post-init. 456config NUMA_KEEP_MEMINFO 457 bool 458 459config MEMORY_ISOLATION 460 bool 461 462# IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked 463# IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via 464# /dev/mem. 465config EXCLUSIVE_SYSTEM_RAM 466 def_bool y 467 depends on !DEVMEM || STRICT_DEVMEM 468 469# 470# Only be set on architectures that have completely implemented memory hotplug 471# feature. If you are not sure, don't touch it. 472# 473config HAVE_BOOTMEM_INFO_NODE 474 def_bool n 475 476config ARCH_ENABLE_MEMORY_HOTPLUG 477 bool 478 479config ARCH_ENABLE_MEMORY_HOTREMOVE 480 bool 481 482# eventually, we can have this option just 'select SPARSEMEM' 483menuconfig MEMORY_HOTPLUG 484 bool "Memory hotplug" 485 select MEMORY_ISOLATION 486 depends on SPARSEMEM 487 depends on ARCH_ENABLE_MEMORY_HOTPLUG 488 depends on 64BIT 489 select NUMA_KEEP_MEMINFO if NUMA 490 491if MEMORY_HOTPLUG 492 493choice 494 prompt "Memory Hotplug Default Online Type" 495 default MHP_DEFAULT_ONLINE_TYPE_OFFLINE 496 help 497 Default memory type for hotplugged memory. 498 499 This option sets the default policy setting for memory hotplug 500 onlining policy (/sys/devices/system/memory/auto_online_blocks) which 501 determines what happens to newly added memory regions. Policy setting 502 can always be changed at runtime. 503 504 The default is 'offline'. 505 506 Select offline to defer onlining to drivers and user policy. 507 Select auto to let the kernel choose what zones to utilize. 508 Select online_kernel to generally allow kernel usage of this memory. 509 Select online_movable to generally disallow kernel usage of this memory. 510 511 Example kernel usage would be page structs and page tables. 512 513 See Documentation/admin-guide/mm/memory-hotplug.rst for more information. 514 515config MHP_DEFAULT_ONLINE_TYPE_OFFLINE 516 bool "offline" 517 help 518 Hotplugged memory will not be onlined by default. 519 Choose this for systems with drivers and user policy that 520 handle onlining of hotplug memory policy. 521 522config MHP_DEFAULT_ONLINE_TYPE_ONLINE_AUTO 523 bool "auto" 524 help 525 Select this if you want the kernel to automatically online 526 hotplugged memory into the zone it thinks is reasonable. 527 This memory may be utilized for kernel data. 528 529config MHP_DEFAULT_ONLINE_TYPE_ONLINE_KERNEL 530 bool "kernel" 531 help 532 Select this if you want the kernel to automatically online 533 hotplugged memory into a zone capable of being used for kernel 534 data. This typically means ZONE_NORMAL. 535 536config MHP_DEFAULT_ONLINE_TYPE_ONLINE_MOVABLE 537 bool "movable" 538 help 539 Select this if you want the kernel to automatically online 540 hotplug memory into ZONE_MOVABLE. This memory will generally 541 not be utilized for kernel data. 542 543 This should only be used when the admin knows sufficient 544 ZONE_NORMAL memory is available to describe hotplug memory, 545 otherwise hotplug memory may fail to online. For example, 546 sufficient kernel-capable memory (ZONE_NORMAL) must be 547 available to allocate page structs to describe ZONE_MOVABLE. 548 549endchoice 550 551config MEMORY_HOTREMOVE 552 bool "Allow for memory hot remove" 553 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64) 554 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 555 depends on MIGRATION 556 557config MHP_MEMMAP_ON_MEMORY 558 def_bool y 559 depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP 560 depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE 561 562endif # MEMORY_HOTPLUG 563 564config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE 565 bool 566 567# Heavily threaded applications may benefit from splitting the mm-wide 568# page_table_lock, so that faults on different parts of the user address 569# space can be handled with less contention: split it at this NR_CPUS. 570# Default to 4 for wider testing, though 8 might be more appropriate. 571# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 572# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 573# SPARC32 allocates multiple pte tables within a single page, and therefore 574# a per-page lock leads to problems when multiple tables need to be locked 575# at the same time (e.g. copy_page_range()). 576# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 577# 578config SPLIT_PTE_PTLOCKS 579 def_bool y 580 depends on MMU 581 depends on SMP 582 depends on NR_CPUS >= 4 583 depends on !ARM || CPU_CACHE_VIPT 584 depends on !PARISC || PA20 585 depends on !SPARC32 586 587config ARCH_ENABLE_SPLIT_PMD_PTLOCK 588 bool 589 590config SPLIT_PMD_PTLOCKS 591 def_bool y 592 depends on SPLIT_PTE_PTLOCKS && ARCH_ENABLE_SPLIT_PMD_PTLOCK 593 594# 595# support for memory balloon 596config BALLOON 597 bool 598 599# 600# support for memory balloon page migration 601config BALLOON_MIGRATION 602 bool "Allow for balloon memory migration" 603 default y 604 depends on MIGRATION && BALLOON 605 help 606 Allow for migration of pages inflated in a memory balloon such that 607 they can be allocated from memory areas only available for movable 608 allocations (e.g., ZONE_MOVABLE, CMA) and such that they can be 609 migrated for memory defragmentation purposes by memory compaction. 610 611# 612# support for memory compaction 613config COMPACTION 614 bool "Allow for memory compaction" 615 default y 616 select MIGRATION 617 depends on MMU 618 help 619 Compaction is the only memory management component to form 620 high order (larger physically contiguous) memory blocks 621 reliably. The page allocator relies on compaction heavily and 622 the lack of the feature can lead to unexpected OOM killer 623 invocations for high order memory requests. You shouldn't 624 disable this option unless there really is a strong reason for 625 it and then we would be really interested to hear about that at 626 linux-mm@kvack.org. 627 628config COMPACT_UNEVICTABLE_DEFAULT 629 int 630 depends on COMPACTION 631 default 0 if PREEMPT_RT 632 default 1 633 634# 635# support for free page reporting 636config PAGE_REPORTING 637 bool "Free page reporting" 638 help 639 Free page reporting allows for the incremental acquisition of 640 free pages from the buddy allocator for the purpose of reporting 641 those pages to another entity, such as a hypervisor, so that the 642 memory can be freed within the host for other uses. 643 644# 645# support for page migration 646# 647config MIGRATION 648 bool "Page migration" 649 default y 650 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU 651 help 652 Allows the migration of the physical location of pages of processes 653 while the virtual addresses are not changed. This is useful in 654 two situations. The first is on NUMA systems to put pages nearer 655 to the processors accessing. The second is when allocating huge 656 pages as migration can relocate pages to satisfy a huge page 657 allocation instead of reclaiming. 658 659config DEVICE_MIGRATION 660 def_bool MIGRATION && ZONE_DEVICE 661 662config ARCH_ENABLE_HUGEPAGE_MIGRATION 663 bool 664 665config ARCH_ENABLE_THP_MIGRATION 666 bool 667 668config HUGETLB_PAGE_SIZE_VARIABLE 669 def_bool n 670 help 671 Allows the pageblock_order value to be dynamic instead of just standard 672 HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available 673 on a platform. 674 675 Note that the pageblock_order cannot exceed MAX_PAGE_ORDER and will be 676 clamped down to MAX_PAGE_ORDER. 677 678config CONTIG_ALLOC 679 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA 680 681config PCP_BATCH_SCALE_MAX 682 int "Maximum scale factor of PCP (Per-CPU pageset) batch allocate/free" 683 default 5 684 range 0 6 685 help 686 In page allocator, PCP (Per-CPU pageset) is refilled and drained in 687 batches. The batch number is scaled automatically to improve page 688 allocation/free throughput. But too large scale factor may hurt 689 latency. This option sets the upper limit of scale factor to limit 690 the maximum latency. 691 692config PHYS_ADDR_T_64BIT 693 def_bool 64BIT 694 695config MMU_NOTIFIER 696 bool 697 select INTERVAL_TREE 698 699config KSM 700 bool "Enable KSM for page merging" 701 depends on MMU 702 select XXHASH 703 help 704 Enable Kernel Samepage Merging: KSM periodically scans those areas 705 of an application's address space that an app has advised may be 706 mergeable. When it finds pages of identical content, it replaces 707 the many instances by a single page with that content, so 708 saving memory until one or another app needs to modify the content. 709 Recommended for use with KVM, or with other duplicative applications. 710 See Documentation/mm/ksm.rst for more information: KSM is inactive 711 until a program has madvised that an area is MADV_MERGEABLE, and 712 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 713 714config DEFAULT_MMAP_MIN_ADDR 715 int "Low address space to protect from user allocation" 716 depends on MMU 717 default 4096 718 help 719 This is the portion of low virtual memory which should be protected 720 from userspace allocation. Keeping a user from writing to low pages 721 can help reduce the impact of kernel NULL pointer bugs. 722 723 For most arm64, ppc64 and x86 users with lots of address space 724 a value of 65536 is reasonable and should cause no problems. 725 On arm and other archs it should not be higher than 32768. 726 Programs which use vm86 functionality or have some need to map 727 this low address space will need CAP_SYS_RAWIO or disable this 728 protection by setting the value to 0. 729 730 This value can be changed after boot using the 731 /proc/sys/vm/mmap_min_addr tunable. 732 733config ARCH_SUPPORTS_MEMORY_FAILURE 734 bool 735 736config MEMORY_FAILURE 737 depends on MMU 738 depends on ARCH_SUPPORTS_MEMORY_FAILURE 739 bool "Enable recovery from hardware memory errors" 740 select INTERVAL_TREE 741 help 742 Enables code to recover from some memory failures on systems 743 with MCA recovery. This allows a system to continue running 744 even when some of its memory has uncorrected errors. This requires 745 special hardware support and typically ECC memory. 746 747config HWPOISON_INJECT 748 tristate "HWPoison pages injector" 749 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 750 select PROC_PAGE_MONITOR 751 752config NOMMU_INITIAL_TRIM_EXCESS 753 int "Turn on mmap() excess space trimming before booting" 754 depends on !MMU 755 default 1 756 help 757 The NOMMU mmap() frequently needs to allocate large contiguous chunks 758 of memory on which to store mappings, but it can only ask the system 759 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 760 more than it requires. To deal with this, mmap() is able to trim off 761 the excess and return it to the allocator. 762 763 If trimming is enabled, the excess is trimmed off and returned to the 764 system allocator, which can cause extra fragmentation, particularly 765 if there are a lot of transient processes. 766 767 If trimming is disabled, the excess is kept, but not used, which for 768 long-term mappings means that the space is wasted. 769 770 Trimming can be dynamically controlled through a sysctl option 771 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 772 excess pages there must be before trimming should occur, or zero if 773 no trimming is to occur. 774 775 This option specifies the initial value of this option. The default 776 of 1 says that all excess pages should be trimmed. 777 778 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 779 780config ARCH_WANT_GENERAL_HUGETLB 781 bool 782 783config ARCH_WANTS_THP_SWAP 784 def_bool n 785 786config PERSISTENT_HUGE_ZERO_FOLIO 787 bool "Allocate a PMD sized folio for zeroing" 788 depends on TRANSPARENT_HUGEPAGE 789 help 790 Enable this option to reduce the runtime refcounting overhead 791 of the huge zero folio and expand the places in the kernel 792 that can use huge zero folios. For instance, block I/O benefits 793 from access to large folios for zeroing memory. 794 795 With this option enabled, the huge zero folio is allocated 796 once and never freed. One full huge page's worth of memory shall 797 be used. 798 799 Say Y if your system has lots of memory. Say N if you are 800 memory constrained. 801 802config MM_ID 803 def_bool n 804 805menuconfig TRANSPARENT_HUGEPAGE 806 bool "Transparent Hugepage Support" 807 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT 808 select COMPACTION 809 select XARRAY_MULTI 810 select MM_ID 811 help 812 Transparent Hugepages allows the kernel to use huge pages and 813 huge tlb transparently to the applications whenever possible. 814 This feature can improve computing performance to certain 815 applications by speeding up page faults during memory 816 allocation, by reducing the number of tlb misses and by speeding 817 up the pagetable walking. 818 819 If memory constrained on embedded, you may want to say N. 820 821if TRANSPARENT_HUGEPAGE 822 823choice 824 prompt "Transparent Hugepage Support sysfs defaults" 825 depends on TRANSPARENT_HUGEPAGE 826 default TRANSPARENT_HUGEPAGE_ALWAYS 827 help 828 Selects the sysfs defaults for Transparent Hugepage Support. 829 830 config TRANSPARENT_HUGEPAGE_ALWAYS 831 bool "always" 832 help 833 Enabling Transparent Hugepage always, can increase the 834 memory footprint of applications without a guaranteed 835 benefit but it will work automatically for all applications. 836 837 config TRANSPARENT_HUGEPAGE_MADVISE 838 bool "madvise" 839 help 840 Enabling Transparent Hugepage madvise, will only provide a 841 performance improvement benefit to the applications using 842 madvise(MADV_HUGEPAGE) but it won't risk to increase the 843 memory footprint of applications without a guaranteed 844 benefit. 845 846 config TRANSPARENT_HUGEPAGE_NEVER 847 bool "never" 848 help 849 Disable Transparent Hugepage by default. It can still be 850 enabled at runtime via sysfs. 851endchoice 852 853choice 854 prompt "Shmem hugepage allocation defaults" 855 depends on TRANSPARENT_HUGEPAGE 856 default TRANSPARENT_HUGEPAGE_SHMEM_HUGE_NEVER 857 help 858 Selects the hugepage allocation policy defaults for 859 the internal shmem mount. 860 861 The selection made here can be overridden by using the kernel 862 command line 'transparent_hugepage_shmem=' option. 863 864 config TRANSPARENT_HUGEPAGE_SHMEM_HUGE_NEVER 865 bool "never" 866 help 867 Disable hugepage allocation for shmem mount by default. It can 868 still be enabled with the kernel command line 869 'transparent_hugepage_shmem=' option or at runtime via sysfs 870 knob. Note that madvise(MADV_COLLAPSE) can still cause 871 transparent huge pages to be obtained even if this mode is 872 specified. 873 874 config TRANSPARENT_HUGEPAGE_SHMEM_HUGE_ALWAYS 875 bool "always" 876 help 877 Always attempt to allocate hugepage for shmem mount, can 878 increase the memory footprint of applications without a 879 guaranteed benefit but it will work automatically for all 880 applications. 881 882 config TRANSPARENT_HUGEPAGE_SHMEM_HUGE_WITHIN_SIZE 883 bool "within_size" 884 help 885 Enable hugepage allocation for shmem mount if the allocation 886 will be fully within the i_size. This configuration also takes 887 into account any madvise(MADV_HUGEPAGE) hints that may be 888 provided by the applications. 889 890 config TRANSPARENT_HUGEPAGE_SHMEM_HUGE_ADVISE 891 bool "advise" 892 help 893 Enable hugepage allocation for the shmem mount exclusively when 894 applications supply the madvise(MADV_HUGEPAGE) hint. 895 This ensures that hugepages are used only in response to explicit 896 requests from applications. 897endchoice 898 899choice 900 prompt "Tmpfs hugepage allocation defaults" 901 depends on TRANSPARENT_HUGEPAGE 902 default TRANSPARENT_HUGEPAGE_TMPFS_HUGE_NEVER 903 help 904 Selects the hugepage allocation policy defaults for 905 the tmpfs mount. 906 907 The selection made here can be overridden by using the kernel 908 command line 'transparent_hugepage_tmpfs=' option. 909 910 config TRANSPARENT_HUGEPAGE_TMPFS_HUGE_NEVER 911 bool "never" 912 help 913 Disable hugepage allocation for tmpfs mount by default. It can 914 still be enabled with the kernel command line 915 'transparent_hugepage_tmpfs=' option. Note that 916 madvise(MADV_COLLAPSE) can still cause transparent huge pages 917 to be obtained even if this mode is specified. 918 919 config TRANSPARENT_HUGEPAGE_TMPFS_HUGE_ALWAYS 920 bool "always" 921 help 922 Always attempt to allocate hugepage for tmpfs mount, can 923 increase the memory footprint of applications without a 924 guaranteed benefit but it will work automatically for all 925 applications. 926 927 config TRANSPARENT_HUGEPAGE_TMPFS_HUGE_WITHIN_SIZE 928 bool "within_size" 929 help 930 Enable hugepage allocation for tmpfs mount if the allocation 931 will be fully within the i_size. This configuration also takes 932 into account any madvise(MADV_HUGEPAGE) hints that may be 933 provided by the applications. 934 935 config TRANSPARENT_HUGEPAGE_TMPFS_HUGE_ADVISE 936 bool "advise" 937 help 938 Enable hugepage allocation for the tmpfs mount exclusively when 939 applications supply the madvise(MADV_HUGEPAGE) hint. 940 This ensures that hugepages are used only in response to explicit 941 requests from applications. 942endchoice 943 944config THP_SWAP 945 def_bool y 946 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT 947 help 948 Swap transparent huge pages in one piece, without splitting. 949 XXX: For now, swap cluster backing transparent huge page 950 will be split after swapout. 951 952 For selection by architectures with reasonable THP sizes. 953 954config READ_ONLY_THP_FOR_FS 955 bool "Read-only THP for filesystems (EXPERIMENTAL)" 956 depends on TRANSPARENT_HUGEPAGE 957 958 help 959 Allow khugepaged to put read-only file-backed pages in THP. 960 961 This is marked experimental because it is a new feature. Write 962 support of file THPs will be developed in the next few release 963 cycles. 964 965config NO_PAGE_MAPCOUNT 966 bool "No per-page mapcount (EXPERIMENTAL)" 967 help 968 Do not maintain per-page mapcounts for pages part of larger 969 allocations, such as transparent huge pages. 970 971 When this config option is enabled, some interfaces that relied on 972 this information will rely on less-precise per-allocation information 973 instead: for example, using the average per-page mapcount in such 974 a large allocation instead of the per-page mapcount. 975 976 EXPERIMENTAL because the impact of some changes is still unclear. 977 978endif # TRANSPARENT_HUGEPAGE 979 980# simple helper to make the code a bit easier to read 981config PAGE_MAPCOUNT 982 def_bool !NO_PAGE_MAPCOUNT 983 984# 985# The architecture supports pgtable leaves that is larger than PAGE_SIZE 986# 987config PGTABLE_HAS_HUGE_LEAVES 988 def_bool TRANSPARENT_HUGEPAGE || HUGETLB_PAGE 989 990# 991# We can end up creating gigantic folio. 992# 993config HAVE_GIGANTIC_FOLIOS 994 def_bool (HUGETLB_PAGE && ARCH_HAS_GIGANTIC_PAGE) || \ 995 (ZONE_DEVICE && HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) 996 997config ASYNC_KERNEL_PGTABLE_FREE 998 def_bool n 999 1000# TODO: Allow to be enabled without THP 1001config ARCH_SUPPORTS_HUGE_PFNMAP 1002 def_bool n 1003 depends on TRANSPARENT_HUGEPAGE 1004 1005config ARCH_SUPPORTS_PMD_PFNMAP 1006 def_bool y 1007 depends on ARCH_SUPPORTS_HUGE_PFNMAP && HAVE_ARCH_TRANSPARENT_HUGEPAGE 1008 1009config ARCH_SUPPORTS_PUD_PFNMAP 1010 def_bool y 1011 depends on ARCH_SUPPORTS_HUGE_PFNMAP && HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 1012 1013# 1014# Architectures that always use weak definitions for percpu 1015# variables in modules should set this. 1016# 1017config ARCH_MODULE_NEEDS_WEAK_PER_CPU 1018 bool 1019 1020# 1021# UP and nommu archs use km based percpu allocator 1022# 1023config NEED_PER_CPU_KM 1024 depends on !SMP || !MMU 1025 bool 1026 default y 1027 1028config NEED_PER_CPU_EMBED_FIRST_CHUNK 1029 bool 1030 1031config NEED_PER_CPU_PAGE_FIRST_CHUNK 1032 bool 1033 1034config USE_PERCPU_NUMA_NODE_ID 1035 bool 1036 1037config HAVE_SETUP_PER_CPU_AREA 1038 bool 1039 1040config CMA 1041 bool "Contiguous Memory Allocator" 1042 depends on MMU 1043 select MIGRATION 1044 select MEMORY_ISOLATION 1045 help 1046 This enables the Contiguous Memory Allocator which allows other 1047 subsystems to allocate big physically-contiguous blocks of memory. 1048 CMA reserves a region of memory and allows only movable pages to 1049 be allocated from it. This way, the kernel can use the memory for 1050 pagecache and when a subsystem requests for contiguous area, the 1051 allocated pages are migrated away to serve the contiguous request. 1052 1053 If unsure, say "n". 1054 1055config CMA_DEBUGFS 1056 bool "CMA debugfs interface" 1057 depends on CMA && DEBUG_FS 1058 help 1059 Turns on the DebugFS interface for CMA. 1060 1061config CMA_SYSFS 1062 bool "CMA information through sysfs interface" 1063 depends on CMA && SYSFS 1064 help 1065 This option exposes some sysfs attributes to get information 1066 from CMA. 1067 1068config CMA_AREAS 1069 int "Maximum count of the CMA areas" 1070 depends on CMA 1071 default 20 if NUMA 1072 default 8 1073 help 1074 CMA allows to create CMA areas for particular purpose, mainly, 1075 used as device private area. This parameter sets the maximum 1076 number of CMA area in the system. 1077 1078 If unsure, leave the default value "8" in UMA and "20" in NUMA. 1079 1080# 1081# Select this config option from the architecture Kconfig, if available, to set 1082# the max page order for physically contiguous allocations. 1083# 1084config ARCH_FORCE_MAX_ORDER 1085 int 1086 1087# 1088# When ARCH_FORCE_MAX_ORDER is not defined, 1089# the default page block order is MAX_PAGE_ORDER (10) as per 1090# include/linux/mmzone.h. 1091# 1092config PAGE_BLOCK_MAX_ORDER 1093 int "Page Block Order Upper Limit" 1094 range 1 10 if ARCH_FORCE_MAX_ORDER = 0 1095 default 10 if ARCH_FORCE_MAX_ORDER = 0 1096 range 1 ARCH_FORCE_MAX_ORDER if ARCH_FORCE_MAX_ORDER != 0 1097 default ARCH_FORCE_MAX_ORDER if ARCH_FORCE_MAX_ORDER != 0 1098 help 1099 The page block order refers to the power of two number of pages that 1100 are physically contiguous and can have a migrate type associated to 1101 them. The maximum size of the page block order is at least limited by 1102 ARCH_FORCE_MAX_ORDER/MAX_PAGE_ORDER. 1103 1104 This config adds a new upper limit of default page block 1105 order when the page block order is required to be smaller than 1106 ARCH_FORCE_MAX_ORDER/MAX_PAGE_ORDER or other limits 1107 (see include/linux/pageblock-flags.h for details). 1108 1109 Reducing pageblock order can negatively impact THP generation 1110 success rate. If your workloads use THP heavily, please use this 1111 option with caution. 1112 1113 Don't change if unsure. 1114 1115config MEM_SOFT_DIRTY 1116 bool "Track memory changes" 1117 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 1118 select PROC_PAGE_MONITOR 1119 help 1120 This option enables memory changes tracking by introducing a 1121 soft-dirty bit on pte-s. This bit it set when someone writes 1122 into a page just as regular dirty bit, but unlike the latter 1123 it can be cleared by hands. 1124 1125 See Documentation/admin-guide/mm/soft-dirty.rst for more details. 1126 1127config GENERIC_EARLY_IOREMAP 1128 bool 1129 1130config STACK_MAX_DEFAULT_SIZE_MB 1131 int "Default maximum user stack size for 32-bit processes (MB)" 1132 default 100 1133 range 8 2048 1134 depends on STACK_GROWSUP && (!64BIT || COMPAT) 1135 help 1136 This is the maximum stack size in Megabytes in the VM layout of 32-bit 1137 user processes when the stack grows upwards (currently only on parisc 1138 arch) when the RLIMIT_STACK hard limit is unlimited. 1139 1140 A sane initial value is 100 MB. 1141 1142config DEFERRED_STRUCT_PAGE_INIT 1143 bool "Defer initialisation of struct pages to kthreads" 1144 depends on SPARSEMEM 1145 depends on !NEED_PER_CPU_KM 1146 depends on 64BIT 1147 depends on !KMSAN 1148 select PADATA 1149 help 1150 Ordinarily all struct pages are initialised during early boot in a 1151 single thread. On very large machines this can take a considerable 1152 amount of time. If this option is set, large machines will bring up 1153 a subset of memmap at boot and then initialise the rest in parallel. 1154 This has a potential performance impact on tasks running early in the 1155 lifetime of the system until these kthreads finish the 1156 initialisation. 1157 1158config PAGE_IDLE_FLAG 1159 bool 1160 select PAGE_EXTENSION if !64BIT 1161 help 1162 This adds PG_idle and PG_young flags to 'struct page'. PTE Accessed 1163 bit writers can set the state of the bit in the flags so that PTE 1164 Accessed bit readers may avoid disturbance. 1165 1166config IDLE_PAGE_TRACKING 1167 bool "Enable idle page tracking" 1168 depends on SYSFS && MMU 1169 select PAGE_IDLE_FLAG 1170 help 1171 This feature allows to estimate the amount of user pages that have 1172 not been touched during a given period of time. This information can 1173 be useful to tune memory cgroup limits and/or for job placement 1174 within a compute cluster. 1175 1176 See Documentation/admin-guide/mm/idle_page_tracking.rst for 1177 more details. 1178 1179# Architectures which implement cpu_dcache_is_aliasing() to query 1180# whether the data caches are aliased (VIVT or VIPT with dcache 1181# aliasing) need to select this. 1182config ARCH_HAS_CPU_CACHE_ALIASING 1183 bool 1184 1185config ARCH_HAS_CACHE_LINE_SIZE 1186 bool 1187 1188config ARCH_HAS_CURRENT_STACK_POINTER 1189 bool 1190 help 1191 In support of HARDENED_USERCOPY performing stack variable lifetime 1192 checking, an architecture-agnostic way to find the stack pointer 1193 is needed. Once an architecture defines an unsigned long global 1194 register alias named "current_stack_pointer", this config can be 1195 selected. 1196 1197config ARCH_HAS_ZONE_DMA_SET 1198 bool 1199 1200config ZONE_DMA 1201 bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET 1202 default y if ARM64 || X86 1203 1204config ZONE_DMA32 1205 bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET 1206 depends on !X86_32 1207 default y if ARM64 1208 1209config ZONE_DEVICE 1210 bool "Device memory (pmem, HMM, etc...) hotplug support" 1211 depends on MEMORY_HOTPLUG 1212 depends on MEMORY_HOTREMOVE 1213 depends on SPARSEMEM_VMEMMAP 1214 select XARRAY_MULTI 1215 1216 help 1217 Device memory hotplug support allows for establishing pmem, 1218 or other device driver discovered memory regions, in the 1219 memmap. This allows pfn_to_page() lookups of otherwise 1220 "device-physical" addresses which is needed for DAX, PCI_P2PDMA, and 1221 DEVICE_PRIVATE features among others. 1222 1223 Enabling this option will reduce the entropy of x86 KASLR memory 1224 regions. For example - on a 46 bit system, the entropy goes down 1225 from 16 bits to 15 bits. The actual reduction in entropy depends 1226 on the physical address bits, on processor features, kernel config 1227 (5 level page table) and physical memory present on the system. 1228 1229# 1230# Helpers to mirror range of the CPU page tables of a process into device page 1231# tables. 1232# 1233config HMM_MIRROR 1234 bool 1235 depends on MMU 1236 1237config GET_FREE_REGION 1238 bool 1239 1240config DEVICE_PRIVATE 1241 bool "Unaddressable device memory (GPU memory, ...)" 1242 depends on ZONE_DEVICE 1243 select GET_FREE_REGION 1244 1245 help 1246 Allows creation of struct pages to represent unaddressable device 1247 memory; i.e., memory that is only accessible from the device (or 1248 group of devices). You likely also want to select HMM_MIRROR. 1249 1250config VMAP_PFN 1251 bool 1252 1253config ARCH_USES_HIGH_VMA_FLAGS 1254 bool 1255config ARCH_HAS_PKEYS 1256 bool 1257 1258config ARCH_USES_PG_ARCH_2 1259 bool 1260config ARCH_USES_PG_ARCH_3 1261 bool 1262 1263config VM_EVENT_COUNTERS 1264 default y 1265 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1266 help 1267 VM event counters are needed for event counts to be shown. 1268 This option allows the disabling of the VM event counters 1269 on EXPERT systems. /proc/vmstat will only show page counts 1270 if VM event counters are disabled. 1271 1272config PERCPU_STATS 1273 bool "Collect percpu memory statistics" 1274 help 1275 This feature collects and exposes statistics via debugfs. The 1276 information includes global and per chunk statistics, which can 1277 be used to help understand percpu memory usage. 1278 1279config GUP_TEST 1280 bool "Enable infrastructure for get_user_pages()-related unit tests" 1281 depends on DEBUG_FS 1282 help 1283 Provides /sys/kernel/debug/gup_test, which in turn provides a way 1284 to make ioctl calls that can launch kernel-based unit tests for 1285 the get_user_pages*() and pin_user_pages*() family of API calls. 1286 1287 These tests include benchmark testing of the _fast variants of 1288 get_user_pages*() and pin_user_pages*(), as well as smoke tests of 1289 the non-_fast variants. 1290 1291 There is also a sub-test that allows running dump_page() on any 1292 of up to eight pages (selected by command line args) within the 1293 range of user-space addresses. These pages are either pinned via 1294 pin_user_pages*(), or pinned via get_user_pages*(), as specified 1295 by other command line arguments. 1296 1297 See tools/testing/selftests/mm/gup_test.c 1298 1299comment "GUP_TEST needs to have DEBUG_FS enabled" 1300 depends on !GUP_TEST && !DEBUG_FS 1301 1302config GUP_GET_PXX_LOW_HIGH 1303 bool 1304 1305config DMAPOOL_TEST 1306 tristate "Enable a module to run time tests on dma_pool" 1307 depends on HAS_DMA 1308 help 1309 Provides a test module that will allocate and free many blocks of 1310 various sizes and report how long it takes. This is intended to 1311 provide a consistent way to measure how changes to the 1312 dma_pool_alloc/free routines affect performance. 1313 1314config ARCH_HAS_PTE_SPECIAL 1315 bool 1316 1317config MAPPING_DIRTY_HELPERS 1318 bool 1319 1320config KMAP_LOCAL 1321 bool 1322 1323config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY 1324 bool 1325 1326config MEMFD_CREATE 1327 bool "Enable memfd_create() system call" if EXPERT 1328 1329config SECRETMEM 1330 default y 1331 bool "Enable memfd_secret() system call" if EXPERT 1332 depends on ARCH_HAS_SET_DIRECT_MAP 1333 help 1334 Enable the memfd_secret() system call with the ability to create 1335 memory areas visible only in the context of the owning process and 1336 not mapped to other processes and other kernel page tables. 1337 1338config ANON_VMA_NAME 1339 bool "Anonymous VMA name support" 1340 depends on PROC_FS && ADVISE_SYSCALLS && MMU 1341 1342 help 1343 Allow naming anonymous virtual memory areas. 1344 1345 This feature allows assigning names to virtual memory areas. Assigned 1346 names can be later retrieved from /proc/pid/maps and /proc/pid/smaps 1347 and help identifying individual anonymous memory areas. 1348 Assigning a name to anonymous virtual memory area might prevent that 1349 area from being merged with adjacent virtual memory areas due to the 1350 difference in their name. 1351 1352config HAVE_ARCH_USERFAULTFD_WP 1353 bool 1354 help 1355 Arch has userfaultfd write protection support 1356 1357config HAVE_ARCH_USERFAULTFD_MINOR 1358 bool 1359 help 1360 Arch has userfaultfd minor fault support 1361 1362menuconfig USERFAULTFD 1363 bool "Enable userfaultfd() system call" 1364 depends on MMU 1365 help 1366 Enable the userfaultfd() system call that allows to intercept and 1367 handle page faults in userland. 1368 1369if USERFAULTFD 1370config PTE_MARKER_UFFD_WP 1371 bool "Userfaultfd write protection support for shmem/hugetlbfs" 1372 default y 1373 depends on HAVE_ARCH_USERFAULTFD_WP 1374 1375 help 1376 Allows to create marker PTEs for userfaultfd write protection 1377 purposes. It is required to enable userfaultfd write protection on 1378 file-backed memory types like shmem and hugetlbfs. 1379endif # USERFAULTFD 1380 1381# multi-gen LRU { 1382config LRU_GEN 1383 bool "Multi-Gen LRU" 1384 depends on MMU 1385 # make sure folio->flags has enough spare bits 1386 depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP 1387 help 1388 A high performance LRU implementation to overcommit memory. See 1389 Documentation/admin-guide/mm/multigen_lru.rst for details. 1390 1391config LRU_GEN_ENABLED 1392 bool "Enable by default" 1393 depends on LRU_GEN 1394 help 1395 This option enables the multi-gen LRU by default. 1396 1397config LRU_GEN_STATS 1398 bool "Full stats for debugging" 1399 depends on LRU_GEN 1400 help 1401 Do not enable this option unless you plan to look at historical stats 1402 from evicted generations for debugging purpose. 1403 1404 This option has a per-memcg and per-node memory overhead. 1405 1406config LRU_GEN_WALKS_MMU 1407 def_bool y 1408 depends on LRU_GEN && ARCH_HAS_HW_PTE_YOUNG 1409# } 1410 1411config ARCH_SUPPORTS_PER_VMA_LOCK 1412 def_bool n 1413 1414config PER_VMA_LOCK 1415 def_bool y 1416 depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP 1417 help 1418 Allow per-vma locking during page fault handling. 1419 1420 This feature allows locking each virtual memory area separately when 1421 handling page faults instead of taking mmap_lock. 1422 1423config LOCK_MM_AND_FIND_VMA 1424 bool 1425 depends on !STACK_GROWSUP 1426 1427config IOMMU_MM_DATA 1428 bool 1429 1430config EXECMEM 1431 bool 1432 1433config NUMA_MEMBLKS 1434 bool 1435 1436config NUMA_EMU 1437 bool "NUMA emulation" 1438 depends on NUMA_MEMBLKS 1439 depends on X86 || GENERIC_ARCH_NUMA 1440 help 1441 Enable NUMA emulation. A flat machine will be split 1442 into virtual nodes when booted with "numa=fake=N", where N is the 1443 number of nodes. This is only useful for debugging. 1444 1445config ARCH_HAS_USER_SHADOW_STACK 1446 bool 1447 help 1448 The architecture has hardware support for userspace shadow call 1449 stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss). 1450 1451config HAVE_ARCH_TLB_REMOVE_TABLE 1452 def_bool n 1453 1454config PT_RECLAIM 1455 def_bool y 1456 depends on MMU_GATHER_RCU_TABLE_FREE && !HAVE_ARCH_TLB_REMOVE_TABLE 1457 help 1458 Try to reclaim empty user page table pages in paths other than munmap 1459 and exit_mmap path. 1460 1461 Note: now only empty user PTE page table pages will be reclaimed. 1462 1463config FIND_NORMAL_PAGE 1464 def_bool n 1465 1466config ARCH_HAS_LAZY_MMU_MODE 1467 bool 1468 help 1469 The architecture uses the lazy MMU mode. This allows changes to 1470 MMU-related architectural state to be deferred until the mode is 1471 exited. See <linux/pgtable.h> for details. 1472 1473config LAZY_MMU_MODE_KUNIT_TEST 1474 tristate "KUnit tests for the lazy MMU mode" if !KUNIT_ALL_TESTS 1475 depends on ARCH_HAS_LAZY_MMU_MODE 1476 depends on KUNIT 1477 default KUNIT_ALL_TESTS 1478 help 1479 Enable this option to check that the lazy MMU mode interface behaves 1480 as expected. Only tests for the generic interface are included (not 1481 architecture-specific behaviours). 1482 1483 If unsure, say N. 1484 1485source "mm/damon/Kconfig" 1486 1487endmenu 1488