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 12config ZPOOL 13 bool 14 15menuconfig SWAP 16 bool "Support for paging of anonymous memory (swap)" 17 depends on MMU && BLOCK && !ARCH_NO_SWAP 18 default y 19 help 20 This option allows you to choose whether you want to have support 21 for so called swap devices or swap files in your kernel that are 22 used to provide more virtual memory than the actual RAM present 23 in your computer. If unsure say Y. 24 25config ZSWAP 26 bool "Compressed cache for swap pages" 27 depends on SWAP 28 select FRONTSWAP 29 select CRYPTO 30 select ZPOOL 31 help 32 A lightweight compressed cache for swap pages. It takes 33 pages that are in the process of being swapped out and attempts to 34 compress them into a dynamically allocated RAM-based memory pool. 35 This can result in a significant I/O reduction on swap device and, 36 in the case where decompressing from RAM is faster than swap device 37 reads, can also improve workload performance. 38 39config ZSWAP_DEFAULT_ON 40 bool "Enable the compressed cache for swap pages by default" 41 depends on ZSWAP 42 help 43 If selected, the compressed cache for swap pages will be enabled 44 at boot, otherwise it will be disabled. 45 46 The selection made here can be overridden by using the kernel 47 command line 'zswap.enabled=' option. 48 49config ZSWAP_EXCLUSIVE_LOADS_DEFAULT_ON 50 bool "Invalidate zswap entries when pages are loaded" 51 depends on ZSWAP 52 help 53 If selected, exclusive loads for zswap will be enabled at boot, 54 otherwise it will be disabled. 55 56 If exclusive loads are enabled, when a page is loaded from zswap, 57 the zswap entry is invalidated at once, as opposed to leaving it 58 in zswap until the swap entry is freed. 59 60 This avoids having two copies of the same page in memory 61 (compressed and uncompressed) after faulting in a page from zswap. 62 The cost is that if the page was never dirtied and needs to be 63 swapped out again, it will be re-compressed. 64 65choice 66 prompt "Default compressor" 67 depends on ZSWAP 68 default ZSWAP_COMPRESSOR_DEFAULT_LZO 69 help 70 Selects the default compression algorithm for the compressed cache 71 for swap pages. 72 73 For an overview what kind of performance can be expected from 74 a particular compression algorithm please refer to the benchmarks 75 available at the following LWN page: 76 https://lwn.net/Articles/751795/ 77 78 If in doubt, select 'LZO'. 79 80 The selection made here can be overridden by using the kernel 81 command line 'zswap.compressor=' option. 82 83config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE 84 bool "Deflate" 85 select CRYPTO_DEFLATE 86 help 87 Use the Deflate algorithm as the default compression algorithm. 88 89config ZSWAP_COMPRESSOR_DEFAULT_LZO 90 bool "LZO" 91 select CRYPTO_LZO 92 help 93 Use the LZO algorithm as the default compression algorithm. 94 95config ZSWAP_COMPRESSOR_DEFAULT_842 96 bool "842" 97 select CRYPTO_842 98 help 99 Use the 842 algorithm as the default compression algorithm. 100 101config ZSWAP_COMPRESSOR_DEFAULT_LZ4 102 bool "LZ4" 103 select CRYPTO_LZ4 104 help 105 Use the LZ4 algorithm as the default compression algorithm. 106 107config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC 108 bool "LZ4HC" 109 select CRYPTO_LZ4HC 110 help 111 Use the LZ4HC algorithm as the default compression algorithm. 112 113config ZSWAP_COMPRESSOR_DEFAULT_ZSTD 114 bool "zstd" 115 select CRYPTO_ZSTD 116 help 117 Use the zstd algorithm as the default compression algorithm. 118endchoice 119 120config ZSWAP_COMPRESSOR_DEFAULT 121 string 122 depends on ZSWAP 123 default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE 124 default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO 125 default "842" if ZSWAP_COMPRESSOR_DEFAULT_842 126 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4 127 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC 128 default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD 129 default "" 130 131choice 132 prompt "Default allocator" 133 depends on ZSWAP 134 default ZSWAP_ZPOOL_DEFAULT_ZBUD 135 help 136 Selects the default allocator for the compressed cache for 137 swap pages. 138 The default is 'zbud' for compatibility, however please do 139 read the description of each of the allocators below before 140 making a right choice. 141 142 The selection made here can be overridden by using the kernel 143 command line 'zswap.zpool=' option. 144 145config ZSWAP_ZPOOL_DEFAULT_ZBUD 146 bool "zbud" 147 select ZBUD 148 help 149 Use the zbud allocator as the default allocator. 150 151config ZSWAP_ZPOOL_DEFAULT_Z3FOLD 152 bool "z3fold" 153 select Z3FOLD 154 help 155 Use the z3fold allocator as the default allocator. 156 157config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC 158 bool "zsmalloc" 159 select ZSMALLOC 160 help 161 Use the zsmalloc allocator as the default allocator. 162endchoice 163 164config ZSWAP_ZPOOL_DEFAULT 165 string 166 depends on ZSWAP 167 default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD 168 default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD 169 default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC 170 default "" 171 172config ZBUD 173 tristate "2:1 compression allocator (zbud)" 174 depends on ZSWAP 175 help 176 A special purpose allocator for storing compressed pages. 177 It is designed to store up to two compressed pages per physical 178 page. While this design limits storage density, it has simple and 179 deterministic reclaim properties that make it preferable to a higher 180 density approach when reclaim will be used. 181 182config Z3FOLD 183 tristate "3:1 compression allocator (z3fold)" 184 depends on ZSWAP 185 help 186 A special purpose allocator for storing compressed pages. 187 It is designed to store up to three compressed pages per physical 188 page. It is a ZBUD derivative so the simplicity and determinism are 189 still there. 190 191config ZSMALLOC 192 tristate 193 prompt "N:1 compression allocator (zsmalloc)" if ZSWAP 194 depends on MMU 195 help 196 zsmalloc is a slab-based memory allocator designed to store 197 pages of various compression levels efficiently. It achieves 198 the highest storage density with the least amount of fragmentation. 199 200config ZSMALLOC_STAT 201 bool "Export zsmalloc statistics" 202 depends on ZSMALLOC 203 select DEBUG_FS 204 help 205 This option enables code in the zsmalloc to collect various 206 statistics about what's happening in zsmalloc and exports that 207 information to userspace via debugfs. 208 If unsure, say N. 209 210config ZSMALLOC_CHAIN_SIZE 211 int "Maximum number of physical pages per-zspage" 212 default 8 213 range 4 16 214 depends on ZSMALLOC 215 help 216 This option sets the upper limit on the number of physical pages 217 that a zmalloc page (zspage) can consist of. The optimal zspage 218 chain size is calculated for each size class during the 219 initialization of the pool. 220 221 Changing this option can alter the characteristics of size classes, 222 such as the number of pages per zspage and the number of objects 223 per zspage. This can also result in different configurations of 224 the pool, as zsmalloc merges size classes with similar 225 characteristics. 226 227 For more information, see zsmalloc documentation. 228 229menu "SLAB allocator options" 230 231choice 232 prompt "Choose SLAB allocator" 233 default SLUB 234 help 235 This option allows to select a slab allocator. 236 237config SLAB_DEPRECATED 238 bool "SLAB (DEPRECATED)" 239 depends on !PREEMPT_RT 240 help 241 Deprecated and scheduled for removal in a few cycles. Replaced by 242 SLUB. 243 244 If you cannot migrate to SLUB, please contact linux-mm@kvack.org 245 and the people listed in the SLAB ALLOCATOR section of MAINTAINERS 246 file, explaining why. 247 248 The regular slab allocator that is established and known to work 249 well in all environments. It organizes cache hot objects in 250 per cpu and per node queues. 251 252config SLUB 253 bool "SLUB (Unqueued Allocator)" 254 help 255 SLUB is a slab allocator that minimizes cache line usage 256 instead of managing queues of cached objects (SLAB approach). 257 Per cpu caching is realized using slabs of objects instead 258 of queues of objects. SLUB can use memory efficiently 259 and has enhanced diagnostics. SLUB is the default choice for 260 a slab allocator. 261 262endchoice 263 264config SLAB 265 bool 266 default y 267 depends on SLAB_DEPRECATED 268 269config SLUB_TINY 270 bool "Configure SLUB for minimal memory footprint" 271 depends on SLUB && EXPERT 272 select SLAB_MERGE_DEFAULT 273 help 274 Configures the SLUB allocator in a way to achieve minimal memory 275 footprint, sacrificing scalability, debugging and other features. 276 This is intended only for the smallest system that had used the 277 SLOB allocator and is not recommended for systems with more than 278 16MB RAM. 279 280 If unsure, say N. 281 282config SLAB_MERGE_DEFAULT 283 bool "Allow slab caches to be merged" 284 default y 285 depends on SLAB || SLUB 286 help 287 For reduced kernel memory fragmentation, slab caches can be 288 merged when they share the same size and other characteristics. 289 This carries a risk of kernel heap overflows being able to 290 overwrite objects from merged caches (and more easily control 291 cache layout), which makes such heap attacks easier to exploit 292 by attackers. By keeping caches unmerged, these kinds of exploits 293 can usually only damage objects in the same cache. To disable 294 merging at runtime, "slab_nomerge" can be passed on the kernel 295 command line. 296 297config SLAB_FREELIST_RANDOM 298 bool "Randomize slab freelist" 299 depends on SLAB || (SLUB && !SLUB_TINY) 300 help 301 Randomizes the freelist order used on creating new pages. This 302 security feature reduces the predictability of the kernel slab 303 allocator against heap overflows. 304 305config SLAB_FREELIST_HARDENED 306 bool "Harden slab freelist metadata" 307 depends on SLAB || (SLUB && !SLUB_TINY) 308 help 309 Many kernel heap attacks try to target slab cache metadata and 310 other infrastructure. This options makes minor performance 311 sacrifices to harden the kernel slab allocator against common 312 freelist exploit methods. Some slab implementations have more 313 sanity-checking than others. This option is most effective with 314 CONFIG_SLUB. 315 316config SLUB_STATS 317 default n 318 bool "Enable SLUB performance statistics" 319 depends on SLUB && SYSFS && !SLUB_TINY 320 help 321 SLUB statistics are useful to debug SLUBs allocation behavior in 322 order find ways to optimize the allocator. This should never be 323 enabled for production use since keeping statistics slows down 324 the allocator by a few percentage points. The slabinfo command 325 supports the determination of the most active slabs to figure 326 out which slabs are relevant to a particular load. 327 Try running: slabinfo -DA 328 329config SLUB_CPU_PARTIAL 330 default y 331 depends on SLUB && SMP && !SLUB_TINY 332 bool "SLUB per cpu partial cache" 333 help 334 Per cpu partial caches accelerate objects allocation and freeing 335 that is local to a processor at the price of more indeterminism 336 in the latency of the free. On overflow these caches will be cleared 337 which requires the taking of locks that may cause latency spikes. 338 Typically one would choose no for a realtime system. 339 340config RANDOM_KMALLOC_CACHES 341 default n 342 depends on SLUB && !SLUB_TINY 343 bool "Randomize slab caches for normal kmalloc" 344 help 345 A hardening feature that creates multiple copies of slab caches for 346 normal kmalloc allocation and makes kmalloc randomly pick one based 347 on code address, which makes the attackers more difficult to spray 348 vulnerable memory objects on the heap for the purpose of exploiting 349 memory vulnerabilities. 350 351 Currently the number of copies is set to 16, a reasonably large value 352 that effectively diverges the memory objects allocated for different 353 subsystems or modules into different caches, at the expense of a 354 limited degree of memory and CPU overhead that relates to hardware and 355 system workload. 356 357endmenu # SLAB allocator options 358 359config SHUFFLE_PAGE_ALLOCATOR 360 bool "Page allocator randomization" 361 default SLAB_FREELIST_RANDOM && ACPI_NUMA 362 help 363 Randomization of the page allocator improves the average 364 utilization of a direct-mapped memory-side-cache. See section 365 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 366 6.2a specification for an example of how a platform advertises 367 the presence of a memory-side-cache. There are also incidental 368 security benefits as it reduces the predictability of page 369 allocations to compliment SLAB_FREELIST_RANDOM, but the 370 default granularity of shuffling on the MAX_ORDER i.e, 10th 371 order of pages is selected based on cache utilization benefits 372 on x86. 373 374 While the randomization improves cache utilization it may 375 negatively impact workloads on platforms without a cache. For 376 this reason, by default, the randomization is enabled only 377 after runtime detection of a direct-mapped memory-side-cache. 378 Otherwise, the randomization may be force enabled with the 379 'page_alloc.shuffle' kernel command line parameter. 380 381 Say Y if unsure. 382 383config COMPAT_BRK 384 bool "Disable heap randomization" 385 default y 386 help 387 Randomizing heap placement makes heap exploits harder, but it 388 also breaks ancient binaries (including anything libc5 based). 389 This option changes the bootup default to heap randomization 390 disabled, and can be overridden at runtime by setting 391 /proc/sys/kernel/randomize_va_space to 2. 392 393 On non-ancient distros (post-2000 ones) N is usually a safe choice. 394 395config MMAP_ALLOW_UNINITIALIZED 396 bool "Allow mmapped anonymous memory to be uninitialized" 397 depends on EXPERT && !MMU 398 default n 399 help 400 Normally, and according to the Linux spec, anonymous memory obtained 401 from mmap() has its contents cleared before it is passed to 402 userspace. Enabling this config option allows you to request that 403 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 404 providing a huge performance boost. If this option is not enabled, 405 then the flag will be ignored. 406 407 This is taken advantage of by uClibc's malloc(), and also by 408 ELF-FDPIC binfmt's brk and stack allocator. 409 410 Because of the obvious security issues, this option should only be 411 enabled on embedded devices where you control what is run in 412 userspace. Since that isn't generally a problem on no-MMU systems, 413 it is normally safe to say Y here. 414 415 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 416 417config SELECT_MEMORY_MODEL 418 def_bool y 419 depends on ARCH_SELECT_MEMORY_MODEL 420 421choice 422 prompt "Memory model" 423 depends on SELECT_MEMORY_MODEL 424 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT 425 default FLATMEM_MANUAL 426 help 427 This option allows you to change some of the ways that 428 Linux manages its memory internally. Most users will 429 only have one option here selected by the architecture 430 configuration. This is normal. 431 432config FLATMEM_MANUAL 433 bool "Flat Memory" 434 depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE 435 help 436 This option is best suited for non-NUMA systems with 437 flat address space. The FLATMEM is the most efficient 438 system in terms of performance and resource consumption 439 and it is the best option for smaller systems. 440 441 For systems that have holes in their physical address 442 spaces and for features like NUMA and memory hotplug, 443 choose "Sparse Memory". 444 445 If unsure, choose this option (Flat Memory) over any other. 446 447config SPARSEMEM_MANUAL 448 bool "Sparse Memory" 449 depends on ARCH_SPARSEMEM_ENABLE 450 help 451 This will be the only option for some systems, including 452 memory hot-plug systems. This is normal. 453 454 This option provides efficient support for systems with 455 holes is their physical address space and allows memory 456 hot-plug and hot-remove. 457 458 If unsure, choose "Flat Memory" over this option. 459 460endchoice 461 462config SPARSEMEM 463 def_bool y 464 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL 465 466config FLATMEM 467 def_bool y 468 depends on !SPARSEMEM || FLATMEM_MANUAL 469 470# 471# SPARSEMEM_EXTREME (which is the default) does some bootmem 472# allocations when sparse_init() is called. If this cannot 473# be done on your architecture, select this option. However, 474# statically allocating the mem_section[] array can potentially 475# consume vast quantities of .bss, so be careful. 476# 477# This option will also potentially produce smaller runtime code 478# with gcc 3.4 and later. 479# 480config SPARSEMEM_STATIC 481 bool 482 483# 484# Architecture platforms which require a two level mem_section in SPARSEMEM 485# must select this option. This is usually for architecture platforms with 486# an extremely sparse physical address space. 487# 488config SPARSEMEM_EXTREME 489 def_bool y 490 depends on SPARSEMEM && !SPARSEMEM_STATIC 491 492config SPARSEMEM_VMEMMAP_ENABLE 493 bool 494 495config SPARSEMEM_VMEMMAP 496 bool "Sparse Memory virtual memmap" 497 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE 498 default y 499 help 500 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise 501 pfn_to_page and page_to_pfn operations. This is the most 502 efficient option when sufficient kernel resources are available. 503# 504# Select this config option from the architecture Kconfig, if it is preferred 505# to enable the feature of HugeTLB/dev_dax vmemmap optimization. 506# 507config ARCH_WANT_OPTIMIZE_VMEMMAP 508 bool 509 510config HAVE_MEMBLOCK_PHYS_MAP 511 bool 512 513config HAVE_FAST_GUP 514 depends on MMU 515 bool 516 517# Don't discard allocated memory used to track "memory" and "reserved" memblocks 518# after early boot, so it can still be used to test for validity of memory. 519# Also, memblocks are updated with memory hot(un)plug. 520config ARCH_KEEP_MEMBLOCK 521 bool 522 523# Keep arch NUMA mapping infrastructure post-init. 524config NUMA_KEEP_MEMINFO 525 bool 526 527config MEMORY_ISOLATION 528 bool 529 530# IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked 531# IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via 532# /dev/mem. 533config EXCLUSIVE_SYSTEM_RAM 534 def_bool y 535 depends on !DEVMEM || STRICT_DEVMEM 536 537# 538# Only be set on architectures that have completely implemented memory hotplug 539# feature. If you are not sure, don't touch it. 540# 541config HAVE_BOOTMEM_INFO_NODE 542 def_bool n 543 544config ARCH_ENABLE_MEMORY_HOTPLUG 545 bool 546 547config ARCH_ENABLE_MEMORY_HOTREMOVE 548 bool 549 550# eventually, we can have this option just 'select SPARSEMEM' 551menuconfig MEMORY_HOTPLUG 552 bool "Memory hotplug" 553 select MEMORY_ISOLATION 554 depends on SPARSEMEM 555 depends on ARCH_ENABLE_MEMORY_HOTPLUG 556 depends on 64BIT 557 select NUMA_KEEP_MEMINFO if NUMA 558 559if MEMORY_HOTPLUG 560 561config MEMORY_HOTPLUG_DEFAULT_ONLINE 562 bool "Online the newly added memory blocks by default" 563 depends on MEMORY_HOTPLUG 564 help 565 This option sets the default policy setting for memory hotplug 566 onlining policy (/sys/devices/system/memory/auto_online_blocks) which 567 determines what happens to newly added memory regions. Policy setting 568 can always be changed at runtime. 569 See Documentation/admin-guide/mm/memory-hotplug.rst for more information. 570 571 Say Y here if you want all hot-plugged memory blocks to appear in 572 'online' state by default. 573 Say N here if you want the default policy to keep all hot-plugged 574 memory blocks in 'offline' state. 575 576config MEMORY_HOTREMOVE 577 bool "Allow for memory hot remove" 578 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64) 579 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 580 depends on MIGRATION 581 582config MHP_MEMMAP_ON_MEMORY 583 def_bool y 584 depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP 585 depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE 586 587endif # MEMORY_HOTPLUG 588 589# Heavily threaded applications may benefit from splitting the mm-wide 590# page_table_lock, so that faults on different parts of the user address 591# space can be handled with less contention: split it at this NR_CPUS. 592# Default to 4 for wider testing, though 8 might be more appropriate. 593# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 594# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 595# SPARC32 allocates multiple pte tables within a single page, and therefore 596# a per-page lock leads to problems when multiple tables need to be locked 597# at the same time (e.g. copy_page_range()). 598# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 599# 600config SPLIT_PTLOCK_CPUS 601 int 602 default "999999" if !MMU 603 default "999999" if ARM && !CPU_CACHE_VIPT 604 default "999999" if PARISC && !PA20 605 default "999999" if SPARC32 606 default "4" 607 608config ARCH_ENABLE_SPLIT_PMD_PTLOCK 609 bool 610 611# 612# support for memory balloon 613config MEMORY_BALLOON 614 bool 615 616# 617# support for memory balloon compaction 618config BALLOON_COMPACTION 619 bool "Allow for balloon memory compaction/migration" 620 def_bool y 621 depends on COMPACTION && MEMORY_BALLOON 622 help 623 Memory fragmentation introduced by ballooning might reduce 624 significantly the number of 2MB contiguous memory blocks that can be 625 used within a guest, thus imposing performance penalties associated 626 with the reduced number of transparent huge pages that could be used 627 by the guest workload. Allowing the compaction & migration for memory 628 pages enlisted as being part of memory balloon devices avoids the 629 scenario aforementioned and helps improving memory defragmentation. 630 631# 632# support for memory compaction 633config COMPACTION 634 bool "Allow for memory compaction" 635 def_bool y 636 select MIGRATION 637 depends on MMU 638 help 639 Compaction is the only memory management component to form 640 high order (larger physically contiguous) memory blocks 641 reliably. The page allocator relies on compaction heavily and 642 the lack of the feature can lead to unexpected OOM killer 643 invocations for high order memory requests. You shouldn't 644 disable this option unless there really is a strong reason for 645 it and then we would be really interested to hear about that at 646 linux-mm@kvack.org. 647 648config COMPACT_UNEVICTABLE_DEFAULT 649 int 650 depends on COMPACTION 651 default 0 if PREEMPT_RT 652 default 1 653 654# 655# support for free page reporting 656config PAGE_REPORTING 657 bool "Free page reporting" 658 def_bool n 659 help 660 Free page reporting allows for the incremental acquisition of 661 free pages from the buddy allocator for the purpose of reporting 662 those pages to another entity, such as a hypervisor, so that the 663 memory can be freed within the host for other uses. 664 665# 666# support for page migration 667# 668config MIGRATION 669 bool "Page migration" 670 def_bool y 671 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU 672 help 673 Allows the migration of the physical location of pages of processes 674 while the virtual addresses are not changed. This is useful in 675 two situations. The first is on NUMA systems to put pages nearer 676 to the processors accessing. The second is when allocating huge 677 pages as migration can relocate pages to satisfy a huge page 678 allocation instead of reclaiming. 679 680config DEVICE_MIGRATION 681 def_bool MIGRATION && ZONE_DEVICE 682 683config ARCH_ENABLE_HUGEPAGE_MIGRATION 684 bool 685 686config ARCH_ENABLE_THP_MIGRATION 687 bool 688 689config HUGETLB_PAGE_SIZE_VARIABLE 690 def_bool n 691 help 692 Allows the pageblock_order value to be dynamic instead of just standard 693 HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available 694 on a platform. 695 696 Note that the pageblock_order cannot exceed MAX_ORDER and will be 697 clamped down to MAX_ORDER. 698 699config CONTIG_ALLOC 700 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA 701 702config PHYS_ADDR_T_64BIT 703 def_bool 64BIT 704 705config BOUNCE 706 bool "Enable bounce buffers" 707 default y 708 depends on BLOCK && MMU && HIGHMEM 709 help 710 Enable bounce buffers for devices that cannot access the full range of 711 memory available to the CPU. Enabled by default when HIGHMEM is 712 selected, but you may say n to override this. 713 714config MMU_NOTIFIER 715 bool 716 select INTERVAL_TREE 717 718config KSM 719 bool "Enable KSM for page merging" 720 depends on MMU 721 select XXHASH 722 help 723 Enable Kernel Samepage Merging: KSM periodically scans those areas 724 of an application's address space that an app has advised may be 725 mergeable. When it finds pages of identical content, it replaces 726 the many instances by a single page with that content, so 727 saving memory until one or another app needs to modify the content. 728 Recommended for use with KVM, or with other duplicative applications. 729 See Documentation/mm/ksm.rst for more information: KSM is inactive 730 until a program has madvised that an area is MADV_MERGEABLE, and 731 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 732 733config DEFAULT_MMAP_MIN_ADDR 734 int "Low address space to protect from user allocation" 735 depends on MMU 736 default 4096 737 help 738 This is the portion of low virtual memory which should be protected 739 from userspace allocation. Keeping a user from writing to low pages 740 can help reduce the impact of kernel NULL pointer bugs. 741 742 For most ia64, ppc64 and x86 users with lots of address space 743 a value of 65536 is reasonable and should cause no problems. 744 On arm and other archs it should not be higher than 32768. 745 Programs which use vm86 functionality or have some need to map 746 this low address space will need CAP_SYS_RAWIO or disable this 747 protection by setting the value to 0. 748 749 This value can be changed after boot using the 750 /proc/sys/vm/mmap_min_addr tunable. 751 752config ARCH_SUPPORTS_MEMORY_FAILURE 753 bool 754 755config MEMORY_FAILURE 756 depends on MMU 757 depends on ARCH_SUPPORTS_MEMORY_FAILURE 758 bool "Enable recovery from hardware memory errors" 759 select MEMORY_ISOLATION 760 select RAS 761 help 762 Enables code to recover from some memory failures on systems 763 with MCA recovery. This allows a system to continue running 764 even when some of its memory has uncorrected errors. This requires 765 special hardware support and typically ECC memory. 766 767config HWPOISON_INJECT 768 tristate "HWPoison pages injector" 769 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 770 select PROC_PAGE_MONITOR 771 772config NOMMU_INITIAL_TRIM_EXCESS 773 int "Turn on mmap() excess space trimming before booting" 774 depends on !MMU 775 default 1 776 help 777 The NOMMU mmap() frequently needs to allocate large contiguous chunks 778 of memory on which to store mappings, but it can only ask the system 779 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 780 more than it requires. To deal with this, mmap() is able to trim off 781 the excess and return it to the allocator. 782 783 If trimming is enabled, the excess is trimmed off and returned to the 784 system allocator, which can cause extra fragmentation, particularly 785 if there are a lot of transient processes. 786 787 If trimming is disabled, the excess is kept, but not used, which for 788 long-term mappings means that the space is wasted. 789 790 Trimming can be dynamically controlled through a sysctl option 791 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 792 excess pages there must be before trimming should occur, or zero if 793 no trimming is to occur. 794 795 This option specifies the initial value of this option. The default 796 of 1 says that all excess pages should be trimmed. 797 798 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 799 800config ARCH_WANT_GENERAL_HUGETLB 801 bool 802 803config ARCH_WANTS_THP_SWAP 804 def_bool n 805 806menuconfig TRANSPARENT_HUGEPAGE 807 bool "Transparent Hugepage Support" 808 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT 809 select COMPACTION 810 select XARRAY_MULTI 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. 845endchoice 846 847config THP_SWAP 848 def_bool y 849 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT 850 help 851 Swap transparent huge pages in one piece, without splitting. 852 XXX: For now, swap cluster backing transparent huge page 853 will be split after swapout. 854 855 For selection by architectures with reasonable THP sizes. 856 857config READ_ONLY_THP_FOR_FS 858 bool "Read-only THP for filesystems (EXPERIMENTAL)" 859 depends on TRANSPARENT_HUGEPAGE && SHMEM 860 861 help 862 Allow khugepaged to put read-only file-backed pages in THP. 863 864 This is marked experimental because it is a new feature. Write 865 support of file THPs will be developed in the next few release 866 cycles. 867 868endif # TRANSPARENT_HUGEPAGE 869 870# 871# UP and nommu archs use km based percpu allocator 872# 873config NEED_PER_CPU_KM 874 depends on !SMP || !MMU 875 bool 876 default y 877 878config NEED_PER_CPU_EMBED_FIRST_CHUNK 879 bool 880 881config NEED_PER_CPU_PAGE_FIRST_CHUNK 882 bool 883 884config USE_PERCPU_NUMA_NODE_ID 885 bool 886 887config HAVE_SETUP_PER_CPU_AREA 888 bool 889 890config FRONTSWAP 891 bool 892 893config CMA 894 bool "Contiguous Memory Allocator" 895 depends on MMU 896 select MIGRATION 897 select MEMORY_ISOLATION 898 help 899 This enables the Contiguous Memory Allocator which allows other 900 subsystems to allocate big physically-contiguous blocks of memory. 901 CMA reserves a region of memory and allows only movable pages to 902 be allocated from it. This way, the kernel can use the memory for 903 pagecache and when a subsystem requests for contiguous area, the 904 allocated pages are migrated away to serve the contiguous request. 905 906 If unsure, say "n". 907 908config CMA_DEBUG 909 bool "CMA debug messages (DEVELOPMENT)" 910 depends on DEBUG_KERNEL && CMA 911 help 912 Turns on debug messages in CMA. This produces KERN_DEBUG 913 messages for every CMA call as well as various messages while 914 processing calls such as dma_alloc_from_contiguous(). 915 This option does not affect warning and error messages. 916 917config CMA_DEBUGFS 918 bool "CMA debugfs interface" 919 depends on CMA && DEBUG_FS 920 help 921 Turns on the DebugFS interface for CMA. 922 923config CMA_SYSFS 924 bool "CMA information through sysfs interface" 925 depends on CMA && SYSFS 926 help 927 This option exposes some sysfs attributes to get information 928 from CMA. 929 930config CMA_AREAS 931 int "Maximum count of the CMA areas" 932 depends on CMA 933 default 19 if NUMA 934 default 7 935 help 936 CMA allows to create CMA areas for particular purpose, mainly, 937 used as device private area. This parameter sets the maximum 938 number of CMA area in the system. 939 940 If unsure, leave the default value "7" in UMA and "19" in NUMA. 941 942config MEM_SOFT_DIRTY 943 bool "Track memory changes" 944 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 945 select PROC_PAGE_MONITOR 946 help 947 This option enables memory changes tracking by introducing a 948 soft-dirty bit on pte-s. This bit it set when someone writes 949 into a page just as regular dirty bit, but unlike the latter 950 it can be cleared by hands. 951 952 See Documentation/admin-guide/mm/soft-dirty.rst for more details. 953 954config GENERIC_EARLY_IOREMAP 955 bool 956 957config STACK_MAX_DEFAULT_SIZE_MB 958 int "Default maximum user stack size for 32-bit processes (MB)" 959 default 100 960 range 8 2048 961 depends on STACK_GROWSUP && (!64BIT || COMPAT) 962 help 963 This is the maximum stack size in Megabytes in the VM layout of 32-bit 964 user processes when the stack grows upwards (currently only on parisc 965 arch) when the RLIMIT_STACK hard limit is unlimited. 966 967 A sane initial value is 100 MB. 968 969config DEFERRED_STRUCT_PAGE_INIT 970 bool "Defer initialisation of struct pages to kthreads" 971 depends on SPARSEMEM 972 depends on !NEED_PER_CPU_KM 973 depends on 64BIT 974 select PADATA 975 help 976 Ordinarily all struct pages are initialised during early boot in a 977 single thread. On very large machines this can take a considerable 978 amount of time. If this option is set, large machines will bring up 979 a subset of memmap at boot and then initialise the rest in parallel. 980 This has a potential performance impact on tasks running early in the 981 lifetime of the system until these kthreads finish the 982 initialisation. 983 984config PAGE_IDLE_FLAG 985 bool 986 select PAGE_EXTENSION if !64BIT 987 help 988 This adds PG_idle and PG_young flags to 'struct page'. PTE Accessed 989 bit writers can set the state of the bit in the flags so that PTE 990 Accessed bit readers may avoid disturbance. 991 992config IDLE_PAGE_TRACKING 993 bool "Enable idle page tracking" 994 depends on SYSFS && MMU 995 select PAGE_IDLE_FLAG 996 help 997 This feature allows to estimate the amount of user pages that have 998 not been touched during a given period of time. This information can 999 be useful to tune memory cgroup limits and/or for job placement 1000 within a compute cluster. 1001 1002 See Documentation/admin-guide/mm/idle_page_tracking.rst for 1003 more details. 1004 1005config ARCH_HAS_CACHE_LINE_SIZE 1006 bool 1007 1008config ARCH_HAS_CURRENT_STACK_POINTER 1009 bool 1010 help 1011 In support of HARDENED_USERCOPY performing stack variable lifetime 1012 checking, an architecture-agnostic way to find the stack pointer 1013 is needed. Once an architecture defines an unsigned long global 1014 register alias named "current_stack_pointer", this config can be 1015 selected. 1016 1017config ARCH_HAS_PTE_DEVMAP 1018 bool 1019 1020config ARCH_HAS_ZONE_DMA_SET 1021 bool 1022 1023config ZONE_DMA 1024 bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET 1025 default y if ARM64 || X86 1026 1027config ZONE_DMA32 1028 bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET 1029 depends on !X86_32 1030 default y if ARM64 1031 1032config ZONE_DEVICE 1033 bool "Device memory (pmem, HMM, etc...) hotplug support" 1034 depends on MEMORY_HOTPLUG 1035 depends on MEMORY_HOTREMOVE 1036 depends on SPARSEMEM_VMEMMAP 1037 depends on ARCH_HAS_PTE_DEVMAP 1038 select XARRAY_MULTI 1039 1040 help 1041 Device memory hotplug support allows for establishing pmem, 1042 or other device driver discovered memory regions, in the 1043 memmap. This allows pfn_to_page() lookups of otherwise 1044 "device-physical" addresses which is needed for using a DAX 1045 mapping in an O_DIRECT operation, among other things. 1046 1047 If FS_DAX is enabled, then say Y. 1048 1049# 1050# Helpers to mirror range of the CPU page tables of a process into device page 1051# tables. 1052# 1053config HMM_MIRROR 1054 bool 1055 depends on MMU 1056 1057config GET_FREE_REGION 1058 depends on SPARSEMEM 1059 bool 1060 1061config DEVICE_PRIVATE 1062 bool "Unaddressable device memory (GPU memory, ...)" 1063 depends on ZONE_DEVICE 1064 select GET_FREE_REGION 1065 1066 help 1067 Allows creation of struct pages to represent unaddressable device 1068 memory; i.e., memory that is only accessible from the device (or 1069 group of devices). You likely also want to select HMM_MIRROR. 1070 1071config VMAP_PFN 1072 bool 1073 1074config ARCH_USES_HIGH_VMA_FLAGS 1075 bool 1076config ARCH_HAS_PKEYS 1077 bool 1078 1079config ARCH_USES_PG_ARCH_X 1080 bool 1081 help 1082 Enable the definition of PG_arch_x page flags with x > 1. Only 1083 suitable for 64-bit architectures with CONFIG_FLATMEM or 1084 CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be 1085 enough room for additional bits in page->flags. 1086 1087config VM_EVENT_COUNTERS 1088 default y 1089 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1090 help 1091 VM event counters are needed for event counts to be shown. 1092 This option allows the disabling of the VM event counters 1093 on EXPERT systems. /proc/vmstat will only show page counts 1094 if VM event counters are disabled. 1095 1096config PERCPU_STATS 1097 bool "Collect percpu memory statistics" 1098 help 1099 This feature collects and exposes statistics via debugfs. The 1100 information includes global and per chunk statistics, which can 1101 be used to help understand percpu memory usage. 1102 1103config GUP_TEST 1104 bool "Enable infrastructure for get_user_pages()-related unit tests" 1105 depends on DEBUG_FS 1106 help 1107 Provides /sys/kernel/debug/gup_test, which in turn provides a way 1108 to make ioctl calls that can launch kernel-based unit tests for 1109 the get_user_pages*() and pin_user_pages*() family of API calls. 1110 1111 These tests include benchmark testing of the _fast variants of 1112 get_user_pages*() and pin_user_pages*(), as well as smoke tests of 1113 the non-_fast variants. 1114 1115 There is also a sub-test that allows running dump_page() on any 1116 of up to eight pages (selected by command line args) within the 1117 range of user-space addresses. These pages are either pinned via 1118 pin_user_pages*(), or pinned via get_user_pages*(), as specified 1119 by other command line arguments. 1120 1121 See tools/testing/selftests/mm/gup_test.c 1122 1123comment "GUP_TEST needs to have DEBUG_FS enabled" 1124 depends on !GUP_TEST && !DEBUG_FS 1125 1126config GUP_GET_PXX_LOW_HIGH 1127 bool 1128 1129config DMAPOOL_TEST 1130 tristate "Enable a module to run time tests on dma_pool" 1131 depends on HAS_DMA 1132 help 1133 Provides a test module that will allocate and free many blocks of 1134 various sizes and report how long it takes. This is intended to 1135 provide a consistent way to measure how changes to the 1136 dma_pool_alloc/free routines affect performance. 1137 1138config ARCH_HAS_PTE_SPECIAL 1139 bool 1140 1141# 1142# Some architectures require a special hugepage directory format that is 1143# required to support multiple hugepage sizes. For example a4fe3ce76 1144# "powerpc/mm: Allow more flexible layouts for hugepage pagetables" 1145# introduced it on powerpc. This allows for a more flexible hugepage 1146# pagetable layouts. 1147# 1148config ARCH_HAS_HUGEPD 1149 bool 1150 1151config MAPPING_DIRTY_HELPERS 1152 bool 1153 1154config KMAP_LOCAL 1155 bool 1156 1157config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY 1158 bool 1159 1160# struct io_mapping based helper. Selected by drivers that need them 1161config IO_MAPPING 1162 bool 1163 1164config SECRETMEM 1165 default y 1166 bool "Enable memfd_secret() system call" if EXPERT 1167 depends on ARCH_HAS_SET_DIRECT_MAP 1168 help 1169 Enable the memfd_secret() system call with the ability to create 1170 memory areas visible only in the context of the owning process and 1171 not mapped to other processes and other kernel page tables. 1172 1173config ANON_VMA_NAME 1174 bool "Anonymous VMA name support" 1175 depends on PROC_FS && ADVISE_SYSCALLS && MMU 1176 1177 help 1178 Allow naming anonymous virtual memory areas. 1179 1180 This feature allows assigning names to virtual memory areas. Assigned 1181 names can be later retrieved from /proc/pid/maps and /proc/pid/smaps 1182 and help identifying individual anonymous memory areas. 1183 Assigning a name to anonymous virtual memory area might prevent that 1184 area from being merged with adjacent virtual memory areas due to the 1185 difference in their name. 1186 1187config USERFAULTFD 1188 bool "Enable userfaultfd() system call" 1189 depends on MMU 1190 help 1191 Enable the userfaultfd() system call that allows to intercept and 1192 handle page faults in userland. 1193 1194config HAVE_ARCH_USERFAULTFD_WP 1195 bool 1196 help 1197 Arch has userfaultfd write protection support 1198 1199config HAVE_ARCH_USERFAULTFD_MINOR 1200 bool 1201 help 1202 Arch has userfaultfd minor fault support 1203 1204config PTE_MARKER_UFFD_WP 1205 bool "Userfaultfd write protection support for shmem/hugetlbfs" 1206 default y 1207 depends on HAVE_ARCH_USERFAULTFD_WP 1208 1209 help 1210 Allows to create marker PTEs for userfaultfd write protection 1211 purposes. It is required to enable userfaultfd write protection on 1212 file-backed memory types like shmem and hugetlbfs. 1213 1214# multi-gen LRU { 1215config LRU_GEN 1216 bool "Multi-Gen LRU" 1217 depends on MMU 1218 # make sure folio->flags has enough spare bits 1219 depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP 1220 help 1221 A high performance LRU implementation to overcommit memory. See 1222 Documentation/admin-guide/mm/multigen_lru.rst for details. 1223 1224config LRU_GEN_ENABLED 1225 bool "Enable by default" 1226 depends on LRU_GEN 1227 help 1228 This option enables the multi-gen LRU by default. 1229 1230config LRU_GEN_STATS 1231 bool "Full stats for debugging" 1232 depends on LRU_GEN 1233 help 1234 Do not enable this option unless you plan to look at historical stats 1235 from evicted generations for debugging purpose. 1236 1237 This option has a per-memcg and per-node memory overhead. 1238# } 1239 1240config ARCH_SUPPORTS_PER_VMA_LOCK 1241 def_bool n 1242 1243config PER_VMA_LOCK 1244 def_bool y 1245 depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP 1246 help 1247 Allow per-vma locking during page fault handling. 1248 1249 This feature allows locking each virtual memory area separately when 1250 handling page faults instead of taking mmap_lock. 1251 1252config LOCK_MM_AND_FIND_VMA 1253 bool 1254 depends on !STACK_GROWSUP 1255 1256source "mm/damon/Kconfig" 1257 1258endmenu 1259