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 49choice 50 prompt "Default compressor" 51 depends on ZSWAP 52 default ZSWAP_COMPRESSOR_DEFAULT_LZO 53 help 54 Selects the default compression algorithm for the compressed cache 55 for swap pages. 56 57 For an overview what kind of performance can be expected from 58 a particular compression algorithm please refer to the benchmarks 59 available at the following LWN page: 60 https://lwn.net/Articles/751795/ 61 62 If in doubt, select 'LZO'. 63 64 The selection made here can be overridden by using the kernel 65 command line 'zswap.compressor=' option. 66 67config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE 68 bool "Deflate" 69 select CRYPTO_DEFLATE 70 help 71 Use the Deflate algorithm as the default compression algorithm. 72 73config ZSWAP_COMPRESSOR_DEFAULT_LZO 74 bool "LZO" 75 select CRYPTO_LZO 76 help 77 Use the LZO algorithm as the default compression algorithm. 78 79config ZSWAP_COMPRESSOR_DEFAULT_842 80 bool "842" 81 select CRYPTO_842 82 help 83 Use the 842 algorithm as the default compression algorithm. 84 85config ZSWAP_COMPRESSOR_DEFAULT_LZ4 86 bool "LZ4" 87 select CRYPTO_LZ4 88 help 89 Use the LZ4 algorithm as the default compression algorithm. 90 91config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC 92 bool "LZ4HC" 93 select CRYPTO_LZ4HC 94 help 95 Use the LZ4HC algorithm as the default compression algorithm. 96 97config ZSWAP_COMPRESSOR_DEFAULT_ZSTD 98 bool "zstd" 99 select CRYPTO_ZSTD 100 help 101 Use the zstd algorithm as the default compression algorithm. 102endchoice 103 104config ZSWAP_COMPRESSOR_DEFAULT 105 string 106 depends on ZSWAP 107 default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE 108 default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO 109 default "842" if ZSWAP_COMPRESSOR_DEFAULT_842 110 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4 111 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC 112 default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD 113 default "" 114 115choice 116 prompt "Default allocator" 117 depends on ZSWAP 118 default ZSWAP_ZPOOL_DEFAULT_ZBUD 119 help 120 Selects the default allocator for the compressed cache for 121 swap pages. 122 The default is 'zbud' for compatibility, however please do 123 read the description of each of the allocators below before 124 making a right choice. 125 126 The selection made here can be overridden by using the kernel 127 command line 'zswap.zpool=' option. 128 129config ZSWAP_ZPOOL_DEFAULT_ZBUD 130 bool "zbud" 131 select ZBUD 132 help 133 Use the zbud allocator as the default allocator. 134 135config ZSWAP_ZPOOL_DEFAULT_Z3FOLD 136 bool "z3fold" 137 select Z3FOLD 138 help 139 Use the z3fold allocator as the default allocator. 140 141config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC 142 bool "zsmalloc" 143 select ZSMALLOC 144 help 145 Use the zsmalloc allocator as the default allocator. 146endchoice 147 148config ZSWAP_ZPOOL_DEFAULT 149 string 150 depends on ZSWAP 151 default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD 152 default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD 153 default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC 154 default "" 155 156config ZBUD 157 tristate "2:1 compression allocator (zbud)" 158 depends on ZSWAP 159 help 160 A special purpose allocator for storing compressed pages. 161 It is designed to store up to two compressed pages per physical 162 page. While this design limits storage density, it has simple and 163 deterministic reclaim properties that make it preferable to a higher 164 density approach when reclaim will be used. 165 166config Z3FOLD 167 tristate "3:1 compression allocator (z3fold)" 168 depends on ZSWAP 169 help 170 A special purpose allocator for storing compressed pages. 171 It is designed to store up to three compressed pages per physical 172 page. It is a ZBUD derivative so the simplicity and determinism are 173 still there. 174 175config ZSMALLOC 176 tristate 177 prompt "N:1 compression allocator (zsmalloc)" if ZSWAP 178 depends on MMU 179 help 180 zsmalloc is a slab-based memory allocator designed to store 181 pages of various compression levels efficiently. It achieves 182 the highest storage density with the least amount of fragmentation. 183 184config ZSMALLOC_STAT 185 bool "Export zsmalloc statistics" 186 depends on ZSMALLOC 187 select DEBUG_FS 188 help 189 This option enables code in the zsmalloc to collect various 190 statistics about what's happening in zsmalloc and exports that 191 information to userspace via debugfs. 192 If unsure, say N. 193 194menu "SLAB allocator options" 195 196choice 197 prompt "Choose SLAB allocator" 198 default SLUB 199 help 200 This option allows to select a slab allocator. 201 202config SLAB 203 bool "SLAB" 204 depends on !PREEMPT_RT 205 select HAVE_HARDENED_USERCOPY_ALLOCATOR 206 help 207 The regular slab allocator that is established and known to work 208 well in all environments. It organizes cache hot objects in 209 per cpu and per node queues. 210 211config SLUB 212 bool "SLUB (Unqueued Allocator)" 213 select HAVE_HARDENED_USERCOPY_ALLOCATOR 214 help 215 SLUB is a slab allocator that minimizes cache line usage 216 instead of managing queues of cached objects (SLAB approach). 217 Per cpu caching is realized using slabs of objects instead 218 of queues of objects. SLUB can use memory efficiently 219 and has enhanced diagnostics. SLUB is the default choice for 220 a slab allocator. 221 222config SLOB_DEPRECATED 223 depends on EXPERT 224 bool "SLOB (Simple Allocator - DEPRECATED)" 225 depends on !PREEMPT_RT 226 help 227 Deprecated and scheduled for removal in a few cycles. SLUB 228 recommended as replacement. CONFIG_SLUB_TINY can be considered 229 on systems with 16MB or less RAM. 230 231 If you need SLOB to stay, please contact linux-mm@kvack.org and 232 people listed in the SLAB ALLOCATOR section of MAINTAINERS file, 233 with your use case. 234 235 SLOB replaces the stock allocator with a drastically simpler 236 allocator. SLOB is generally more space efficient but 237 does not perform as well on large systems. 238 239endchoice 240 241config SLOB 242 bool 243 default y 244 depends on SLOB_DEPRECATED 245 246config SLUB_TINY 247 bool "Configure SLUB for minimal memory footprint" 248 depends on SLUB && EXPERT 249 select SLAB_MERGE_DEFAULT 250 help 251 Configures the SLUB allocator in a way to achieve minimal memory 252 footprint, sacrificing scalability, debugging and other features. 253 This is intended only for the smallest system that had used the 254 SLOB allocator and is not recommended for systems with more than 255 16MB RAM. 256 257 If unsure, say N. 258 259config SLAB_MERGE_DEFAULT 260 bool "Allow slab caches to be merged" 261 default y 262 depends on SLAB || SLUB 263 help 264 For reduced kernel memory fragmentation, slab caches can be 265 merged when they share the same size and other characteristics. 266 This carries a risk of kernel heap overflows being able to 267 overwrite objects from merged caches (and more easily control 268 cache layout), which makes such heap attacks easier to exploit 269 by attackers. By keeping caches unmerged, these kinds of exploits 270 can usually only damage objects in the same cache. To disable 271 merging at runtime, "slab_nomerge" can be passed on the kernel 272 command line. 273 274config SLAB_FREELIST_RANDOM 275 bool "Randomize slab freelist" 276 depends on SLAB || (SLUB && !SLUB_TINY) 277 help 278 Randomizes the freelist order used on creating new pages. This 279 security feature reduces the predictability of the kernel slab 280 allocator against heap overflows. 281 282config SLAB_FREELIST_HARDENED 283 bool "Harden slab freelist metadata" 284 depends on SLAB || (SLUB && !SLUB_TINY) 285 help 286 Many kernel heap attacks try to target slab cache metadata and 287 other infrastructure. This options makes minor performance 288 sacrifices to harden the kernel slab allocator against common 289 freelist exploit methods. Some slab implementations have more 290 sanity-checking than others. This option is most effective with 291 CONFIG_SLUB. 292 293config SLUB_STATS 294 default n 295 bool "Enable SLUB performance statistics" 296 depends on SLUB && SYSFS && !SLUB_TINY 297 help 298 SLUB statistics are useful to debug SLUBs allocation behavior in 299 order find ways to optimize the allocator. This should never be 300 enabled for production use since keeping statistics slows down 301 the allocator by a few percentage points. The slabinfo command 302 supports the determination of the most active slabs to figure 303 out which slabs are relevant to a particular load. 304 Try running: slabinfo -DA 305 306config SLUB_CPU_PARTIAL 307 default y 308 depends on SLUB && SMP && !SLUB_TINY 309 bool "SLUB per cpu partial cache" 310 help 311 Per cpu partial caches accelerate objects allocation and freeing 312 that is local to a processor at the price of more indeterminism 313 in the latency of the free. On overflow these caches will be cleared 314 which requires the taking of locks that may cause latency spikes. 315 Typically one would choose no for a realtime system. 316 317endmenu # SLAB allocator options 318 319config SHUFFLE_PAGE_ALLOCATOR 320 bool "Page allocator randomization" 321 default SLAB_FREELIST_RANDOM && ACPI_NUMA 322 help 323 Randomization of the page allocator improves the average 324 utilization of a direct-mapped memory-side-cache. See section 325 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 326 6.2a specification for an example of how a platform advertises 327 the presence of a memory-side-cache. There are also incidental 328 security benefits as it reduces the predictability of page 329 allocations to compliment SLAB_FREELIST_RANDOM, but the 330 default granularity of shuffling on the "MAX_ORDER - 1" i.e, 331 10th order of pages is selected based on cache utilization 332 benefits on x86. 333 334 While the randomization improves cache utilization it may 335 negatively impact workloads on platforms without a cache. For 336 this reason, by default, the randomization is enabled only 337 after runtime detection of a direct-mapped memory-side-cache. 338 Otherwise, the randomization may be force enabled with the 339 'page_alloc.shuffle' kernel command line parameter. 340 341 Say Y if unsure. 342 343config COMPAT_BRK 344 bool "Disable heap randomization" 345 default y 346 help 347 Randomizing heap placement makes heap exploits harder, but it 348 also breaks ancient binaries (including anything libc5 based). 349 This option changes the bootup default to heap randomization 350 disabled, and can be overridden at runtime by setting 351 /proc/sys/kernel/randomize_va_space to 2. 352 353 On non-ancient distros (post-2000 ones) N is usually a safe choice. 354 355config MMAP_ALLOW_UNINITIALIZED 356 bool "Allow mmapped anonymous memory to be uninitialized" 357 depends on EXPERT && !MMU 358 default n 359 help 360 Normally, and according to the Linux spec, anonymous memory obtained 361 from mmap() has its contents cleared before it is passed to 362 userspace. Enabling this config option allows you to request that 363 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 364 providing a huge performance boost. If this option is not enabled, 365 then the flag will be ignored. 366 367 This is taken advantage of by uClibc's malloc(), and also by 368 ELF-FDPIC binfmt's brk and stack allocator. 369 370 Because of the obvious security issues, this option should only be 371 enabled on embedded devices where you control what is run in 372 userspace. Since that isn't generally a problem on no-MMU systems, 373 it is normally safe to say Y here. 374 375 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 376 377config SELECT_MEMORY_MODEL 378 def_bool y 379 depends on ARCH_SELECT_MEMORY_MODEL 380 381choice 382 prompt "Memory model" 383 depends on SELECT_MEMORY_MODEL 384 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT 385 default FLATMEM_MANUAL 386 help 387 This option allows you to change some of the ways that 388 Linux manages its memory internally. Most users will 389 only have one option here selected by the architecture 390 configuration. This is normal. 391 392config FLATMEM_MANUAL 393 bool "Flat Memory" 394 depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE 395 help 396 This option is best suited for non-NUMA systems with 397 flat address space. The FLATMEM is the most efficient 398 system in terms of performance and resource consumption 399 and it is the best option for smaller systems. 400 401 For systems that have holes in their physical address 402 spaces and for features like NUMA and memory hotplug, 403 choose "Sparse Memory". 404 405 If unsure, choose this option (Flat Memory) over any other. 406 407config SPARSEMEM_MANUAL 408 bool "Sparse Memory" 409 depends on ARCH_SPARSEMEM_ENABLE 410 help 411 This will be the only option for some systems, including 412 memory hot-plug systems. This is normal. 413 414 This option provides efficient support for systems with 415 holes is their physical address space and allows memory 416 hot-plug and hot-remove. 417 418 If unsure, choose "Flat Memory" over this option. 419 420endchoice 421 422config SPARSEMEM 423 def_bool y 424 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL 425 426config FLATMEM 427 def_bool y 428 depends on !SPARSEMEM || FLATMEM_MANUAL 429 430# 431# SPARSEMEM_EXTREME (which is the default) does some bootmem 432# allocations when sparse_init() is called. If this cannot 433# be done on your architecture, select this option. However, 434# statically allocating the mem_section[] array can potentially 435# consume vast quantities of .bss, so be careful. 436# 437# This option will also potentially produce smaller runtime code 438# with gcc 3.4 and later. 439# 440config SPARSEMEM_STATIC 441 bool 442 443# 444# Architecture platforms which require a two level mem_section in SPARSEMEM 445# must select this option. This is usually for architecture platforms with 446# an extremely sparse physical address space. 447# 448config SPARSEMEM_EXTREME 449 def_bool y 450 depends on SPARSEMEM && !SPARSEMEM_STATIC 451 452config SPARSEMEM_VMEMMAP_ENABLE 453 bool 454 455config SPARSEMEM_VMEMMAP 456 bool "Sparse Memory virtual memmap" 457 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE 458 default y 459 help 460 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise 461 pfn_to_page and page_to_pfn operations. This is the most 462 efficient option when sufficient kernel resources are available. 463 464config HAVE_MEMBLOCK_PHYS_MAP 465 bool 466 467config HAVE_FAST_GUP 468 depends on MMU 469 bool 470 471# Don't discard allocated memory used to track "memory" and "reserved" memblocks 472# after early boot, so it can still be used to test for validity of memory. 473# Also, memblocks are updated with memory hot(un)plug. 474config ARCH_KEEP_MEMBLOCK 475 bool 476 477# Keep arch NUMA mapping infrastructure post-init. 478config NUMA_KEEP_MEMINFO 479 bool 480 481config MEMORY_ISOLATION 482 bool 483 484# IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked 485# IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via 486# /dev/mem. 487config EXCLUSIVE_SYSTEM_RAM 488 def_bool y 489 depends on !DEVMEM || STRICT_DEVMEM 490 491# 492# Only be set on architectures that have completely implemented memory hotplug 493# feature. If you are not sure, don't touch it. 494# 495config HAVE_BOOTMEM_INFO_NODE 496 def_bool n 497 498config ARCH_ENABLE_MEMORY_HOTPLUG 499 bool 500 501config ARCH_ENABLE_MEMORY_HOTREMOVE 502 bool 503 504# eventually, we can have this option just 'select SPARSEMEM' 505menuconfig MEMORY_HOTPLUG 506 bool "Memory hotplug" 507 select MEMORY_ISOLATION 508 depends on SPARSEMEM 509 depends on ARCH_ENABLE_MEMORY_HOTPLUG 510 depends on 64BIT 511 select NUMA_KEEP_MEMINFO if NUMA 512 513if MEMORY_HOTPLUG 514 515config MEMORY_HOTPLUG_DEFAULT_ONLINE 516 bool "Online the newly added memory blocks by default" 517 depends on MEMORY_HOTPLUG 518 help 519 This option sets the default policy setting for memory hotplug 520 onlining policy (/sys/devices/system/memory/auto_online_blocks) which 521 determines what happens to newly added memory regions. Policy setting 522 can always be changed at runtime. 523 See Documentation/admin-guide/mm/memory-hotplug.rst for more information. 524 525 Say Y here if you want all hot-plugged memory blocks to appear in 526 'online' state by default. 527 Say N here if you want the default policy to keep all hot-plugged 528 memory blocks in 'offline' state. 529 530config MEMORY_HOTREMOVE 531 bool "Allow for memory hot remove" 532 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64) 533 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 534 depends on MIGRATION 535 536config MHP_MEMMAP_ON_MEMORY 537 def_bool y 538 depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP 539 depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE 540 541endif # MEMORY_HOTPLUG 542 543# Heavily threaded applications may benefit from splitting the mm-wide 544# page_table_lock, so that faults on different parts of the user address 545# space can be handled with less contention: split it at this NR_CPUS. 546# Default to 4 for wider testing, though 8 might be more appropriate. 547# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 548# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 549# SPARC32 allocates multiple pte tables within a single page, and therefore 550# a per-page lock leads to problems when multiple tables need to be locked 551# at the same time (e.g. copy_page_range()). 552# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 553# 554config SPLIT_PTLOCK_CPUS 555 int 556 default "999999" if !MMU 557 default "999999" if ARM && !CPU_CACHE_VIPT 558 default "999999" if PARISC && !PA20 559 default "999999" if SPARC32 560 default "4" 561 562config ARCH_ENABLE_SPLIT_PMD_PTLOCK 563 bool 564 565# 566# support for memory balloon 567config MEMORY_BALLOON 568 bool 569 570# 571# support for memory balloon compaction 572config BALLOON_COMPACTION 573 bool "Allow for balloon memory compaction/migration" 574 def_bool y 575 depends on COMPACTION && MEMORY_BALLOON 576 help 577 Memory fragmentation introduced by ballooning might reduce 578 significantly the number of 2MB contiguous memory blocks that can be 579 used within a guest, thus imposing performance penalties associated 580 with the reduced number of transparent huge pages that could be used 581 by the guest workload. Allowing the compaction & migration for memory 582 pages enlisted as being part of memory balloon devices avoids the 583 scenario aforementioned and helps improving memory defragmentation. 584 585# 586# support for memory compaction 587config COMPACTION 588 bool "Allow for memory compaction" 589 def_bool y 590 select MIGRATION 591 depends on MMU 592 help 593 Compaction is the only memory management component to form 594 high order (larger physically contiguous) memory blocks 595 reliably. The page allocator relies on compaction heavily and 596 the lack of the feature can lead to unexpected OOM killer 597 invocations for high order memory requests. You shouldn't 598 disable this option unless there really is a strong reason for 599 it and then we would be really interested to hear about that at 600 linux-mm@kvack.org. 601 602config COMPACT_UNEVICTABLE_DEFAULT 603 int 604 depends on COMPACTION 605 default 0 if PREEMPT_RT 606 default 1 607 608# 609# support for free page reporting 610config PAGE_REPORTING 611 bool "Free page reporting" 612 def_bool n 613 help 614 Free page reporting allows for the incremental acquisition of 615 free pages from the buddy allocator for the purpose of reporting 616 those pages to another entity, such as a hypervisor, so that the 617 memory can be freed within the host for other uses. 618 619# 620# support for page migration 621# 622config MIGRATION 623 bool "Page migration" 624 def_bool y 625 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU 626 help 627 Allows the migration of the physical location of pages of processes 628 while the virtual addresses are not changed. This is useful in 629 two situations. The first is on NUMA systems to put pages nearer 630 to the processors accessing. The second is when allocating huge 631 pages as migration can relocate pages to satisfy a huge page 632 allocation instead of reclaiming. 633 634config DEVICE_MIGRATION 635 def_bool MIGRATION && ZONE_DEVICE 636 637config ARCH_ENABLE_HUGEPAGE_MIGRATION 638 bool 639 640config ARCH_ENABLE_THP_MIGRATION 641 bool 642 643config HUGETLB_PAGE_SIZE_VARIABLE 644 def_bool n 645 help 646 Allows the pageblock_order value to be dynamic instead of just standard 647 HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available 648 on a platform. 649 650 Note that the pageblock_order cannot exceed MAX_ORDER - 1 and will be 651 clamped down to MAX_ORDER - 1. 652 653config CONTIG_ALLOC 654 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA 655 656config PHYS_ADDR_T_64BIT 657 def_bool 64BIT 658 659config BOUNCE 660 bool "Enable bounce buffers" 661 default y 662 depends on BLOCK && MMU && HIGHMEM 663 help 664 Enable bounce buffers for devices that cannot access the full range of 665 memory available to the CPU. Enabled by default when HIGHMEM is 666 selected, but you may say n to override this. 667 668config MMU_NOTIFIER 669 bool 670 select SRCU 671 select INTERVAL_TREE 672 673config KSM 674 bool "Enable KSM for page merging" 675 depends on MMU 676 select XXHASH 677 help 678 Enable Kernel Samepage Merging: KSM periodically scans those areas 679 of an application's address space that an app has advised may be 680 mergeable. When it finds pages of identical content, it replaces 681 the many instances by a single page with that content, so 682 saving memory until one or another app needs to modify the content. 683 Recommended for use with KVM, or with other duplicative applications. 684 See Documentation/mm/ksm.rst for more information: KSM is inactive 685 until a program has madvised that an area is MADV_MERGEABLE, and 686 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 687 688config DEFAULT_MMAP_MIN_ADDR 689 int "Low address space to protect from user allocation" 690 depends on MMU 691 default 4096 692 help 693 This is the portion of low virtual memory which should be protected 694 from userspace allocation. Keeping a user from writing to low pages 695 can help reduce the impact of kernel NULL pointer bugs. 696 697 For most ia64, ppc64 and x86 users with lots of address space 698 a value of 65536 is reasonable and should cause no problems. 699 On arm and other archs it should not be higher than 32768. 700 Programs which use vm86 functionality or have some need to map 701 this low address space will need CAP_SYS_RAWIO or disable this 702 protection by setting the value to 0. 703 704 This value can be changed after boot using the 705 /proc/sys/vm/mmap_min_addr tunable. 706 707config ARCH_SUPPORTS_MEMORY_FAILURE 708 bool 709 710config MEMORY_FAILURE 711 depends on MMU 712 depends on ARCH_SUPPORTS_MEMORY_FAILURE 713 bool "Enable recovery from hardware memory errors" 714 select MEMORY_ISOLATION 715 select RAS 716 help 717 Enables code to recover from some memory failures on systems 718 with MCA recovery. This allows a system to continue running 719 even when some of its memory has uncorrected errors. This requires 720 special hardware support and typically ECC memory. 721 722config HWPOISON_INJECT 723 tristate "HWPoison pages injector" 724 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 725 select PROC_PAGE_MONITOR 726 727config NOMMU_INITIAL_TRIM_EXCESS 728 int "Turn on mmap() excess space trimming before booting" 729 depends on !MMU 730 default 1 731 help 732 The NOMMU mmap() frequently needs to allocate large contiguous chunks 733 of memory on which to store mappings, but it can only ask the system 734 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 735 more than it requires. To deal with this, mmap() is able to trim off 736 the excess and return it to the allocator. 737 738 If trimming is enabled, the excess is trimmed off and returned to the 739 system allocator, which can cause extra fragmentation, particularly 740 if there are a lot of transient processes. 741 742 If trimming is disabled, the excess is kept, but not used, which for 743 long-term mappings means that the space is wasted. 744 745 Trimming can be dynamically controlled through a sysctl option 746 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 747 excess pages there must be before trimming should occur, or zero if 748 no trimming is to occur. 749 750 This option specifies the initial value of this option. The default 751 of 1 says that all excess pages should be trimmed. 752 753 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 754 755config ARCH_WANT_GENERAL_HUGETLB 756 bool 757 758config ARCH_WANTS_THP_SWAP 759 def_bool n 760 761menuconfig TRANSPARENT_HUGEPAGE 762 bool "Transparent Hugepage Support" 763 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT 764 select COMPACTION 765 select XARRAY_MULTI 766 help 767 Transparent Hugepages allows the kernel to use huge pages and 768 huge tlb transparently to the applications whenever possible. 769 This feature can improve computing performance to certain 770 applications by speeding up page faults during memory 771 allocation, by reducing the number of tlb misses and by speeding 772 up the pagetable walking. 773 774 If memory constrained on embedded, you may want to say N. 775 776if TRANSPARENT_HUGEPAGE 777 778choice 779 prompt "Transparent Hugepage Support sysfs defaults" 780 depends on TRANSPARENT_HUGEPAGE 781 default TRANSPARENT_HUGEPAGE_ALWAYS 782 help 783 Selects the sysfs defaults for Transparent Hugepage Support. 784 785 config TRANSPARENT_HUGEPAGE_ALWAYS 786 bool "always" 787 help 788 Enabling Transparent Hugepage always, can increase the 789 memory footprint of applications without a guaranteed 790 benefit but it will work automatically for all applications. 791 792 config TRANSPARENT_HUGEPAGE_MADVISE 793 bool "madvise" 794 help 795 Enabling Transparent Hugepage madvise, will only provide a 796 performance improvement benefit to the applications using 797 madvise(MADV_HUGEPAGE) but it won't risk to increase the 798 memory footprint of applications without a guaranteed 799 benefit. 800endchoice 801 802config THP_SWAP 803 def_bool y 804 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT 805 help 806 Swap transparent huge pages in one piece, without splitting. 807 XXX: For now, swap cluster backing transparent huge page 808 will be split after swapout. 809 810 For selection by architectures with reasonable THP sizes. 811 812config READ_ONLY_THP_FOR_FS 813 bool "Read-only THP for filesystems (EXPERIMENTAL)" 814 depends on TRANSPARENT_HUGEPAGE && SHMEM 815 816 help 817 Allow khugepaged to put read-only file-backed pages in THP. 818 819 This is marked experimental because it is a new feature. Write 820 support of file THPs will be developed in the next few release 821 cycles. 822 823endif # TRANSPARENT_HUGEPAGE 824 825# 826# UP and nommu archs use km based percpu allocator 827# 828config NEED_PER_CPU_KM 829 depends on !SMP || !MMU 830 bool 831 default y 832 833config NEED_PER_CPU_EMBED_FIRST_CHUNK 834 bool 835 836config NEED_PER_CPU_PAGE_FIRST_CHUNK 837 bool 838 839config USE_PERCPU_NUMA_NODE_ID 840 bool 841 842config HAVE_SETUP_PER_CPU_AREA 843 bool 844 845config FRONTSWAP 846 bool 847 848config CMA 849 bool "Contiguous Memory Allocator" 850 depends on MMU 851 select MIGRATION 852 select MEMORY_ISOLATION 853 help 854 This enables the Contiguous Memory Allocator which allows other 855 subsystems to allocate big physically-contiguous blocks of memory. 856 CMA reserves a region of memory and allows only movable pages to 857 be allocated from it. This way, the kernel can use the memory for 858 pagecache and when a subsystem requests for contiguous area, the 859 allocated pages are migrated away to serve the contiguous request. 860 861 If unsure, say "n". 862 863config CMA_DEBUG 864 bool "CMA debug messages (DEVELOPMENT)" 865 depends on DEBUG_KERNEL && CMA 866 help 867 Turns on debug messages in CMA. This produces KERN_DEBUG 868 messages for every CMA call as well as various messages while 869 processing calls such as dma_alloc_from_contiguous(). 870 This option does not affect warning and error messages. 871 872config CMA_DEBUGFS 873 bool "CMA debugfs interface" 874 depends on CMA && DEBUG_FS 875 help 876 Turns on the DebugFS interface for CMA. 877 878config CMA_SYSFS 879 bool "CMA information through sysfs interface" 880 depends on CMA && SYSFS 881 help 882 This option exposes some sysfs attributes to get information 883 from CMA. 884 885config CMA_AREAS 886 int "Maximum count of the CMA areas" 887 depends on CMA 888 default 19 if NUMA 889 default 7 890 help 891 CMA allows to create CMA areas for particular purpose, mainly, 892 used as device private area. This parameter sets the maximum 893 number of CMA area in the system. 894 895 If unsure, leave the default value "7" in UMA and "19" in NUMA. 896 897config MEM_SOFT_DIRTY 898 bool "Track memory changes" 899 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 900 select PROC_PAGE_MONITOR 901 help 902 This option enables memory changes tracking by introducing a 903 soft-dirty bit on pte-s. This bit it set when someone writes 904 into a page just as regular dirty bit, but unlike the latter 905 it can be cleared by hands. 906 907 See Documentation/admin-guide/mm/soft-dirty.rst for more details. 908 909config GENERIC_EARLY_IOREMAP 910 bool 911 912config STACK_MAX_DEFAULT_SIZE_MB 913 int "Default maximum user stack size for 32-bit processes (MB)" 914 default 100 915 range 8 2048 916 depends on STACK_GROWSUP && (!64BIT || COMPAT) 917 help 918 This is the maximum stack size in Megabytes in the VM layout of 32-bit 919 user processes when the stack grows upwards (currently only on parisc 920 arch) when the RLIMIT_STACK hard limit is unlimited. 921 922 A sane initial value is 100 MB. 923 924config DEFERRED_STRUCT_PAGE_INIT 925 bool "Defer initialisation of struct pages to kthreads" 926 depends on SPARSEMEM 927 depends on !NEED_PER_CPU_KM 928 depends on 64BIT 929 select PADATA 930 help 931 Ordinarily all struct pages are initialised during early boot in a 932 single thread. On very large machines this can take a considerable 933 amount of time. If this option is set, large machines will bring up 934 a subset of memmap at boot and then initialise the rest in parallel. 935 This has a potential performance impact on tasks running early in the 936 lifetime of the system until these kthreads finish the 937 initialisation. 938 939config PAGE_IDLE_FLAG 940 bool 941 select PAGE_EXTENSION if !64BIT 942 help 943 This adds PG_idle and PG_young flags to 'struct page'. PTE Accessed 944 bit writers can set the state of the bit in the flags so that PTE 945 Accessed bit readers may avoid disturbance. 946 947config IDLE_PAGE_TRACKING 948 bool "Enable idle page tracking" 949 depends on SYSFS && MMU 950 select PAGE_IDLE_FLAG 951 help 952 This feature allows to estimate the amount of user pages that have 953 not been touched during a given period of time. This information can 954 be useful to tune memory cgroup limits and/or for job placement 955 within a compute cluster. 956 957 See Documentation/admin-guide/mm/idle_page_tracking.rst for 958 more details. 959 960config ARCH_HAS_CACHE_LINE_SIZE 961 bool 962 963config ARCH_HAS_CURRENT_STACK_POINTER 964 bool 965 help 966 In support of HARDENED_USERCOPY performing stack variable lifetime 967 checking, an architecture-agnostic way to find the stack pointer 968 is needed. Once an architecture defines an unsigned long global 969 register alias named "current_stack_pointer", this config can be 970 selected. 971 972config ARCH_HAS_PTE_DEVMAP 973 bool 974 975config ARCH_HAS_ZONE_DMA_SET 976 bool 977 978config ZONE_DMA 979 bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET 980 default y if ARM64 || X86 981 982config ZONE_DMA32 983 bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET 984 depends on !X86_32 985 default y if ARM64 986 987config ZONE_DEVICE 988 bool "Device memory (pmem, HMM, etc...) hotplug support" 989 depends on MEMORY_HOTPLUG 990 depends on MEMORY_HOTREMOVE 991 depends on SPARSEMEM_VMEMMAP 992 depends on ARCH_HAS_PTE_DEVMAP 993 select XARRAY_MULTI 994 995 help 996 Device memory hotplug support allows for establishing pmem, 997 or other device driver discovered memory regions, in the 998 memmap. This allows pfn_to_page() lookups of otherwise 999 "device-physical" addresses which is needed for using a DAX 1000 mapping in an O_DIRECT operation, among other things. 1001 1002 If FS_DAX is enabled, then say Y. 1003 1004# 1005# Helpers to mirror range of the CPU page tables of a process into device page 1006# tables. 1007# 1008config HMM_MIRROR 1009 bool 1010 depends on MMU 1011 1012config GET_FREE_REGION 1013 depends on SPARSEMEM 1014 bool 1015 1016config DEVICE_PRIVATE 1017 bool "Unaddressable device memory (GPU memory, ...)" 1018 depends on ZONE_DEVICE 1019 select GET_FREE_REGION 1020 1021 help 1022 Allows creation of struct pages to represent unaddressable device 1023 memory; i.e., memory that is only accessible from the device (or 1024 group of devices). You likely also want to select HMM_MIRROR. 1025 1026config VMAP_PFN 1027 bool 1028 1029config ARCH_USES_HIGH_VMA_FLAGS 1030 bool 1031config ARCH_HAS_PKEYS 1032 bool 1033 1034config ARCH_USES_PG_ARCH_X 1035 bool 1036 help 1037 Enable the definition of PG_arch_x page flags with x > 1. Only 1038 suitable for 64-bit architectures with CONFIG_FLATMEM or 1039 CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be 1040 enough room for additional bits in page->flags. 1041 1042config VM_EVENT_COUNTERS 1043 default y 1044 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1045 help 1046 VM event counters are needed for event counts to be shown. 1047 This option allows the disabling of the VM event counters 1048 on EXPERT systems. /proc/vmstat will only show page counts 1049 if VM event counters are disabled. 1050 1051config PERCPU_STATS 1052 bool "Collect percpu memory statistics" 1053 help 1054 This feature collects and exposes statistics via debugfs. The 1055 information includes global and per chunk statistics, which can 1056 be used to help understand percpu memory usage. 1057 1058config GUP_TEST 1059 bool "Enable infrastructure for get_user_pages()-related unit tests" 1060 depends on DEBUG_FS 1061 help 1062 Provides /sys/kernel/debug/gup_test, which in turn provides a way 1063 to make ioctl calls that can launch kernel-based unit tests for 1064 the get_user_pages*() and pin_user_pages*() family of API calls. 1065 1066 These tests include benchmark testing of the _fast variants of 1067 get_user_pages*() and pin_user_pages*(), as well as smoke tests of 1068 the non-_fast variants. 1069 1070 There is also a sub-test that allows running dump_page() on any 1071 of up to eight pages (selected by command line args) within the 1072 range of user-space addresses. These pages are either pinned via 1073 pin_user_pages*(), or pinned via get_user_pages*(), as specified 1074 by other command line arguments. 1075 1076 See tools/testing/selftests/vm/gup_test.c 1077 1078comment "GUP_TEST needs to have DEBUG_FS enabled" 1079 depends on !GUP_TEST && !DEBUG_FS 1080 1081config GUP_GET_PXX_LOW_HIGH 1082 bool 1083 1084config ARCH_HAS_PTE_SPECIAL 1085 bool 1086 1087# 1088# Some architectures require a special hugepage directory format that is 1089# required to support multiple hugepage sizes. For example a4fe3ce76 1090# "powerpc/mm: Allow more flexible layouts for hugepage pagetables" 1091# introduced it on powerpc. This allows for a more flexible hugepage 1092# pagetable layouts. 1093# 1094config ARCH_HAS_HUGEPD 1095 bool 1096 1097config MAPPING_DIRTY_HELPERS 1098 bool 1099 1100config KMAP_LOCAL 1101 bool 1102 1103config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY 1104 bool 1105 1106# struct io_mapping based helper. Selected by drivers that need them 1107config IO_MAPPING 1108 bool 1109 1110config SECRETMEM 1111 default y 1112 bool "Enable memfd_secret() system call" if EXPERT 1113 depends on ARCH_HAS_SET_DIRECT_MAP 1114 help 1115 Enable the memfd_secret() system call with the ability to create 1116 memory areas visible only in the context of the owning process and 1117 not mapped to other processes and other kernel page tables. 1118 1119config ANON_VMA_NAME 1120 bool "Anonymous VMA name support" 1121 depends on PROC_FS && ADVISE_SYSCALLS && MMU 1122 1123 help 1124 Allow naming anonymous virtual memory areas. 1125 1126 This feature allows assigning names to virtual memory areas. Assigned 1127 names can be later retrieved from /proc/pid/maps and /proc/pid/smaps 1128 and help identifying individual anonymous memory areas. 1129 Assigning a name to anonymous virtual memory area might prevent that 1130 area from being merged with adjacent virtual memory areas due to the 1131 difference in their name. 1132 1133config USERFAULTFD 1134 bool "Enable userfaultfd() system call" 1135 depends on MMU 1136 help 1137 Enable the userfaultfd() system call that allows to intercept and 1138 handle page faults in userland. 1139 1140config HAVE_ARCH_USERFAULTFD_WP 1141 bool 1142 help 1143 Arch has userfaultfd write protection support 1144 1145config HAVE_ARCH_USERFAULTFD_MINOR 1146 bool 1147 help 1148 Arch has userfaultfd minor fault support 1149 1150config PTE_MARKER_UFFD_WP 1151 bool "Userfaultfd write protection support for shmem/hugetlbfs" 1152 default y 1153 depends on HAVE_ARCH_USERFAULTFD_WP 1154 1155 help 1156 Allows to create marker PTEs for userfaultfd write protection 1157 purposes. It is required to enable userfaultfd write protection on 1158 file-backed memory types like shmem and hugetlbfs. 1159 1160# multi-gen LRU { 1161config LRU_GEN 1162 bool "Multi-Gen LRU" 1163 depends on MMU 1164 # make sure folio->flags has enough spare bits 1165 depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP 1166 help 1167 A high performance LRU implementation to overcommit memory. See 1168 Documentation/admin-guide/mm/multigen_lru.rst for details. 1169 1170config LRU_GEN_ENABLED 1171 bool "Enable by default" 1172 depends on LRU_GEN 1173 help 1174 This option enables the multi-gen LRU by default. 1175 1176config LRU_GEN_STATS 1177 bool "Full stats for debugging" 1178 depends on LRU_GEN 1179 help 1180 Do not enable this option unless you plan to look at historical stats 1181 from evicted generations for debugging purpose. 1182 1183 This option has a per-memcg and per-node memory overhead. 1184# } 1185 1186source "mm/damon/Kconfig" 1187 1188endmenu 1189