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 CRYPTO 29 select ZPOOL 30 help 31 A lightweight compressed cache for swap pages. It takes 32 pages that are in the process of being swapped out and attempts to 33 compress them into a dynamically allocated RAM-based memory pool. 34 This can result in a significant I/O reduction on swap device and, 35 in the case where decompressing from RAM is faster than swap device 36 reads, can also improve workload performance. 37 38config ZSWAP_DEFAULT_ON 39 bool "Enable the compressed cache for swap pages by default" 40 depends on ZSWAP 41 help 42 If selected, the compressed cache for swap pages will be enabled 43 at boot, otherwise it will be disabled. 44 45 The selection made here can be overridden by using the kernel 46 command line 'zswap.enabled=' option. 47 48config ZSWAP_EXCLUSIVE_LOADS_DEFAULT_ON 49 bool "Invalidate zswap entries when pages are loaded" 50 depends on ZSWAP 51 help 52 If selected, exclusive loads for zswap will be enabled at boot, 53 otherwise it will be disabled. 54 55 If exclusive loads are enabled, when a page is loaded from zswap, 56 the zswap entry is invalidated at once, as opposed to leaving it 57 in zswap until the swap entry is freed. 58 59 This avoids having two copies of the same page in memory 60 (compressed and uncompressed) after faulting in a page from zswap. 61 The cost is that if the page was never dirtied and needs to be 62 swapped out again, it will be re-compressed. 63 64choice 65 prompt "Default compressor" 66 depends on ZSWAP 67 default ZSWAP_COMPRESSOR_DEFAULT_LZO 68 help 69 Selects the default compression algorithm for the compressed cache 70 for swap pages. 71 72 For an overview what kind of performance can be expected from 73 a particular compression algorithm please refer to the benchmarks 74 available at the following LWN page: 75 https://lwn.net/Articles/751795/ 76 77 If in doubt, select 'LZO'. 78 79 The selection made here can be overridden by using the kernel 80 command line 'zswap.compressor=' option. 81 82config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE 83 bool "Deflate" 84 select CRYPTO_DEFLATE 85 help 86 Use the Deflate algorithm as the default compression algorithm. 87 88config ZSWAP_COMPRESSOR_DEFAULT_LZO 89 bool "LZO" 90 select CRYPTO_LZO 91 help 92 Use the LZO algorithm as the default compression algorithm. 93 94config ZSWAP_COMPRESSOR_DEFAULT_842 95 bool "842" 96 select CRYPTO_842 97 help 98 Use the 842 algorithm as the default compression algorithm. 99 100config ZSWAP_COMPRESSOR_DEFAULT_LZ4 101 bool "LZ4" 102 select CRYPTO_LZ4 103 help 104 Use the LZ4 algorithm as the default compression algorithm. 105 106config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC 107 bool "LZ4HC" 108 select CRYPTO_LZ4HC 109 help 110 Use the LZ4HC algorithm as the default compression algorithm. 111 112config ZSWAP_COMPRESSOR_DEFAULT_ZSTD 113 bool "zstd" 114 select CRYPTO_ZSTD 115 help 116 Use the zstd algorithm as the default compression algorithm. 117endchoice 118 119config ZSWAP_COMPRESSOR_DEFAULT 120 string 121 depends on ZSWAP 122 default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE 123 default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO 124 default "842" if ZSWAP_COMPRESSOR_DEFAULT_842 125 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4 126 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC 127 default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD 128 default "" 129 130choice 131 prompt "Default allocator" 132 depends on ZSWAP 133 default ZSWAP_ZPOOL_DEFAULT_ZBUD 134 help 135 Selects the default allocator for the compressed cache for 136 swap pages. 137 The default is 'zbud' for compatibility, however please do 138 read the description of each of the allocators below before 139 making a right choice. 140 141 The selection made here can be overridden by using the kernel 142 command line 'zswap.zpool=' option. 143 144config ZSWAP_ZPOOL_DEFAULT_ZBUD 145 bool "zbud" 146 select ZBUD 147 help 148 Use the zbud allocator as the default allocator. 149 150config ZSWAP_ZPOOL_DEFAULT_Z3FOLD 151 bool "z3fold" 152 select Z3FOLD 153 help 154 Use the z3fold allocator as the default allocator. 155 156config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC 157 bool "zsmalloc" 158 select ZSMALLOC 159 help 160 Use the zsmalloc allocator as the default allocator. 161endchoice 162 163config ZSWAP_ZPOOL_DEFAULT 164 string 165 depends on ZSWAP 166 default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD 167 default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD 168 default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC 169 default "" 170 171config ZBUD 172 tristate "2:1 compression allocator (zbud)" 173 depends on ZSWAP 174 help 175 A special purpose allocator for storing compressed pages. 176 It is designed to store up to two compressed pages per physical 177 page. While this design limits storage density, it has simple and 178 deterministic reclaim properties that make it preferable to a higher 179 density approach when reclaim will be used. 180 181config Z3FOLD 182 tristate "3:1 compression allocator (z3fold)" 183 depends on ZSWAP 184 help 185 A special purpose allocator for storing compressed pages. 186 It is designed to store up to three compressed pages per physical 187 page. It is a ZBUD derivative so the simplicity and determinism are 188 still there. 189 190config ZSMALLOC 191 tristate 192 prompt "N:1 compression allocator (zsmalloc)" if ZSWAP 193 depends on MMU 194 help 195 zsmalloc is a slab-based memory allocator designed to store 196 pages of various compression levels efficiently. It achieves 197 the highest storage density with the least amount of fragmentation. 198 199config ZSMALLOC_STAT 200 bool "Export zsmalloc statistics" 201 depends on ZSMALLOC 202 select DEBUG_FS 203 help 204 This option enables code in the zsmalloc to collect various 205 statistics about what's happening in zsmalloc and exports that 206 information to userspace via debugfs. 207 If unsure, say N. 208 209config ZSMALLOC_CHAIN_SIZE 210 int "Maximum number of physical pages per-zspage" 211 default 8 212 range 4 16 213 depends on ZSMALLOC 214 help 215 This option sets the upper limit on the number of physical pages 216 that a zmalloc page (zspage) can consist of. The optimal zspage 217 chain size is calculated for each size class during the 218 initialization of the pool. 219 220 Changing this option can alter the characteristics of size classes, 221 such as the number of pages per zspage and the number of objects 222 per zspage. This can also result in different configurations of 223 the pool, as zsmalloc merges size classes with similar 224 characteristics. 225 226 For more information, see zsmalloc documentation. 227 228menu "SLAB allocator options" 229 230choice 231 prompt "Choose SLAB allocator" 232 default SLUB 233 help 234 This option allows to select a slab allocator. 235 236config SLAB_DEPRECATED 237 bool "SLAB (DEPRECATED)" 238 depends on !PREEMPT_RT 239 help 240 Deprecated and scheduled for removal in a few cycles. Replaced by 241 SLUB. 242 243 If you cannot migrate to SLUB, please contact linux-mm@kvack.org 244 and the people listed in the SLAB ALLOCATOR section of MAINTAINERS 245 file, explaining why. 246 247 The regular slab allocator that is established and known to work 248 well in all environments. It organizes cache hot objects in 249 per cpu and per node queues. 250 251config SLUB 252 bool "SLUB (Unqueued Allocator)" 253 help 254 SLUB is a slab allocator that minimizes cache line usage 255 instead of managing queues of cached objects (SLAB approach). 256 Per cpu caching is realized using slabs of objects instead 257 of queues of objects. SLUB can use memory efficiently 258 and has enhanced diagnostics. SLUB is the default choice for 259 a slab allocator. 260 261endchoice 262 263config SLAB 264 bool 265 default y 266 depends on SLAB_DEPRECATED 267 268config SLUB_TINY 269 bool "Configure SLUB for minimal memory footprint" 270 depends on SLUB && EXPERT 271 select SLAB_MERGE_DEFAULT 272 help 273 Configures the SLUB allocator in a way to achieve minimal memory 274 footprint, sacrificing scalability, debugging and other features. 275 This is intended only for the smallest system that had used the 276 SLOB allocator and is not recommended for systems with more than 277 16MB RAM. 278 279 If unsure, say N. 280 281config SLAB_MERGE_DEFAULT 282 bool "Allow slab caches to be merged" 283 default y 284 depends on SLAB || SLUB 285 help 286 For reduced kernel memory fragmentation, slab caches can be 287 merged when they share the same size and other characteristics. 288 This carries a risk of kernel heap overflows being able to 289 overwrite objects from merged caches (and more easily control 290 cache layout), which makes such heap attacks easier to exploit 291 by attackers. By keeping caches unmerged, these kinds of exploits 292 can usually only damage objects in the same cache. To disable 293 merging at runtime, "slab_nomerge" can be passed on the kernel 294 command line. 295 296config SLAB_FREELIST_RANDOM 297 bool "Randomize slab freelist" 298 depends on SLAB || (SLUB && !SLUB_TINY) 299 help 300 Randomizes the freelist order used on creating new pages. This 301 security feature reduces the predictability of the kernel slab 302 allocator against heap overflows. 303 304config SLAB_FREELIST_HARDENED 305 bool "Harden slab freelist metadata" 306 depends on SLAB || (SLUB && !SLUB_TINY) 307 help 308 Many kernel heap attacks try to target slab cache metadata and 309 other infrastructure. This options makes minor performance 310 sacrifices to harden the kernel slab allocator against common 311 freelist exploit methods. Some slab implementations have more 312 sanity-checking than others. This option is most effective with 313 CONFIG_SLUB. 314 315config SLUB_STATS 316 default n 317 bool "Enable SLUB performance statistics" 318 depends on SLUB && SYSFS && !SLUB_TINY 319 help 320 SLUB statistics are useful to debug SLUBs allocation behavior in 321 order find ways to optimize the allocator. This should never be 322 enabled for production use since keeping statistics slows down 323 the allocator by a few percentage points. The slabinfo command 324 supports the determination of the most active slabs to figure 325 out which slabs are relevant to a particular load. 326 Try running: slabinfo -DA 327 328config SLUB_CPU_PARTIAL 329 default y 330 depends on SLUB && SMP && !SLUB_TINY 331 bool "SLUB per cpu partial cache" 332 help 333 Per cpu partial caches accelerate objects allocation and freeing 334 that is local to a processor at the price of more indeterminism 335 in the latency of the free. On overflow these caches will be cleared 336 which requires the taking of locks that may cause latency spikes. 337 Typically one would choose no for a realtime system. 338 339endmenu # SLAB allocator options 340 341config SHUFFLE_PAGE_ALLOCATOR 342 bool "Page allocator randomization" 343 default SLAB_FREELIST_RANDOM && ACPI_NUMA 344 help 345 Randomization of the page allocator improves the average 346 utilization of a direct-mapped memory-side-cache. See section 347 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 348 6.2a specification for an example of how a platform advertises 349 the presence of a memory-side-cache. There are also incidental 350 security benefits as it reduces the predictability of page 351 allocations to compliment SLAB_FREELIST_RANDOM, but the 352 default granularity of shuffling on the MAX_ORDER i.e, 10th 353 order of pages is selected based on cache utilization benefits 354 on x86. 355 356 While the randomization improves cache utilization it may 357 negatively impact workloads on platforms without a cache. For 358 this reason, by default, the randomization is enabled only 359 after runtime detection of a direct-mapped memory-side-cache. 360 Otherwise, the randomization may be force enabled with the 361 'page_alloc.shuffle' kernel command line parameter. 362 363 Say Y if unsure. 364 365config COMPAT_BRK 366 bool "Disable heap randomization" 367 default y 368 help 369 Randomizing heap placement makes heap exploits harder, but it 370 also breaks ancient binaries (including anything libc5 based). 371 This option changes the bootup default to heap randomization 372 disabled, and can be overridden at runtime by setting 373 /proc/sys/kernel/randomize_va_space to 2. 374 375 On non-ancient distros (post-2000 ones) N is usually a safe choice. 376 377config MMAP_ALLOW_UNINITIALIZED 378 bool "Allow mmapped anonymous memory to be uninitialized" 379 depends on EXPERT && !MMU 380 default n 381 help 382 Normally, and according to the Linux spec, anonymous memory obtained 383 from mmap() has its contents cleared before it is passed to 384 userspace. Enabling this config option allows you to request that 385 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 386 providing a huge performance boost. If this option is not enabled, 387 then the flag will be ignored. 388 389 This is taken advantage of by uClibc's malloc(), and also by 390 ELF-FDPIC binfmt's brk and stack allocator. 391 392 Because of the obvious security issues, this option should only be 393 enabled on embedded devices where you control what is run in 394 userspace. Since that isn't generally a problem on no-MMU systems, 395 it is normally safe to say Y here. 396 397 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 398 399config SELECT_MEMORY_MODEL 400 def_bool y 401 depends on ARCH_SELECT_MEMORY_MODEL 402 403choice 404 prompt "Memory model" 405 depends on SELECT_MEMORY_MODEL 406 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT 407 default FLATMEM_MANUAL 408 help 409 This option allows you to change some of the ways that 410 Linux manages its memory internally. Most users will 411 only have one option here selected by the architecture 412 configuration. This is normal. 413 414config FLATMEM_MANUAL 415 bool "Flat Memory" 416 depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE 417 help 418 This option is best suited for non-NUMA systems with 419 flat address space. The FLATMEM is the most efficient 420 system in terms of performance and resource consumption 421 and it is the best option for smaller systems. 422 423 For systems that have holes in their physical address 424 spaces and for features like NUMA and memory hotplug, 425 choose "Sparse Memory". 426 427 If unsure, choose this option (Flat Memory) over any other. 428 429config SPARSEMEM_MANUAL 430 bool "Sparse Memory" 431 depends on ARCH_SPARSEMEM_ENABLE 432 help 433 This will be the only option for some systems, including 434 memory hot-plug systems. This is normal. 435 436 This option provides efficient support for systems with 437 holes is their physical address space and allows memory 438 hot-plug and hot-remove. 439 440 If unsure, choose "Flat Memory" over this option. 441 442endchoice 443 444config SPARSEMEM 445 def_bool y 446 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL 447 448config FLATMEM 449 def_bool y 450 depends on !SPARSEMEM || FLATMEM_MANUAL 451 452# 453# SPARSEMEM_EXTREME (which is the default) does some bootmem 454# allocations when sparse_init() is called. If this cannot 455# be done on your architecture, select this option. However, 456# statically allocating the mem_section[] array can potentially 457# consume vast quantities of .bss, so be careful. 458# 459# This option will also potentially produce smaller runtime code 460# with gcc 3.4 and later. 461# 462config SPARSEMEM_STATIC 463 bool 464 465# 466# Architecture platforms which require a two level mem_section in SPARSEMEM 467# must select this option. This is usually for architecture platforms with 468# an extremely sparse physical address space. 469# 470config SPARSEMEM_EXTREME 471 def_bool y 472 depends on SPARSEMEM && !SPARSEMEM_STATIC 473 474config SPARSEMEM_VMEMMAP_ENABLE 475 bool 476 477config SPARSEMEM_VMEMMAP 478 bool "Sparse Memory virtual memmap" 479 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE 480 default y 481 help 482 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise 483 pfn_to_page and page_to_pfn operations. This is the most 484 efficient option when sufficient kernel resources are available. 485# 486# Select this config option from the architecture Kconfig, if it is preferred 487# to enable the feature of HugeTLB/dev_dax vmemmap optimization. 488# 489config ARCH_WANT_OPTIMIZE_DAX_VMEMMAP 490 bool 491 492config ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP 493 bool 494 495config HAVE_MEMBLOCK_PHYS_MAP 496 bool 497 498config HAVE_FAST_GUP 499 depends on MMU 500 bool 501 502# Don't discard allocated memory used to track "memory" and "reserved" memblocks 503# after early boot, so it can still be used to test for validity of memory. 504# Also, memblocks are updated with memory hot(un)plug. 505config ARCH_KEEP_MEMBLOCK 506 bool 507 508# Keep arch NUMA mapping infrastructure post-init. 509config NUMA_KEEP_MEMINFO 510 bool 511 512config MEMORY_ISOLATION 513 bool 514 515# IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked 516# IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via 517# /dev/mem. 518config EXCLUSIVE_SYSTEM_RAM 519 def_bool y 520 depends on !DEVMEM || STRICT_DEVMEM 521 522# 523# Only be set on architectures that have completely implemented memory hotplug 524# feature. If you are not sure, don't touch it. 525# 526config HAVE_BOOTMEM_INFO_NODE 527 def_bool n 528 529config ARCH_ENABLE_MEMORY_HOTPLUG 530 bool 531 532config ARCH_ENABLE_MEMORY_HOTREMOVE 533 bool 534 535# eventually, we can have this option just 'select SPARSEMEM' 536menuconfig MEMORY_HOTPLUG 537 bool "Memory hotplug" 538 select MEMORY_ISOLATION 539 depends on SPARSEMEM 540 depends on ARCH_ENABLE_MEMORY_HOTPLUG 541 depends on 64BIT 542 select NUMA_KEEP_MEMINFO if NUMA 543 544if MEMORY_HOTPLUG 545 546config MEMORY_HOTPLUG_DEFAULT_ONLINE 547 bool "Online the newly added memory blocks by default" 548 depends on MEMORY_HOTPLUG 549 help 550 This option sets the default policy setting for memory hotplug 551 onlining policy (/sys/devices/system/memory/auto_online_blocks) which 552 determines what happens to newly added memory regions. Policy setting 553 can always be changed at runtime. 554 See Documentation/admin-guide/mm/memory-hotplug.rst for more information. 555 556 Say Y here if you want all hot-plugged memory blocks to appear in 557 'online' state by default. 558 Say N here if you want the default policy to keep all hot-plugged 559 memory blocks in 'offline' state. 560 561config MEMORY_HOTREMOVE 562 bool "Allow for memory hot remove" 563 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64) 564 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 565 depends on MIGRATION 566 567config MHP_MEMMAP_ON_MEMORY 568 def_bool y 569 depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP 570 depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE 571 572endif # MEMORY_HOTPLUG 573 574# Heavily threaded applications may benefit from splitting the mm-wide 575# page_table_lock, so that faults on different parts of the user address 576# space can be handled with less contention: split it at this NR_CPUS. 577# Default to 4 for wider testing, though 8 might be more appropriate. 578# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 579# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 580# SPARC32 allocates multiple pte tables within a single page, and therefore 581# a per-page lock leads to problems when multiple tables need to be locked 582# at the same time (e.g. copy_page_range()). 583# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 584# 585config SPLIT_PTLOCK_CPUS 586 int 587 default "999999" if !MMU 588 default "999999" if ARM && !CPU_CACHE_VIPT 589 default "999999" if PARISC && !PA20 590 default "999999" if SPARC32 591 default "4" 592 593config ARCH_ENABLE_SPLIT_PMD_PTLOCK 594 bool 595 596# 597# support for memory balloon 598config MEMORY_BALLOON 599 bool 600 601# 602# support for memory balloon compaction 603config BALLOON_COMPACTION 604 bool "Allow for balloon memory compaction/migration" 605 def_bool y 606 depends on COMPACTION && MEMORY_BALLOON 607 help 608 Memory fragmentation introduced by ballooning might reduce 609 significantly the number of 2MB contiguous memory blocks that can be 610 used within a guest, thus imposing performance penalties associated 611 with the reduced number of transparent huge pages that could be used 612 by the guest workload. Allowing the compaction & migration for memory 613 pages enlisted as being part of memory balloon devices avoids the 614 scenario aforementioned and helps improving memory defragmentation. 615 616# 617# support for memory compaction 618config COMPACTION 619 bool "Allow for memory compaction" 620 def_bool y 621 select MIGRATION 622 depends on MMU 623 help 624 Compaction is the only memory management component to form 625 high order (larger physically contiguous) memory blocks 626 reliably. The page allocator relies on compaction heavily and 627 the lack of the feature can lead to unexpected OOM killer 628 invocations for high order memory requests. You shouldn't 629 disable this option unless there really is a strong reason for 630 it and then we would be really interested to hear about that at 631 linux-mm@kvack.org. 632 633config COMPACT_UNEVICTABLE_DEFAULT 634 int 635 depends on COMPACTION 636 default 0 if PREEMPT_RT 637 default 1 638 639# 640# support for free page reporting 641config PAGE_REPORTING 642 bool "Free page reporting" 643 def_bool n 644 help 645 Free page reporting allows for the incremental acquisition of 646 free pages from the buddy allocator for the purpose of reporting 647 those pages to another entity, such as a hypervisor, so that the 648 memory can be freed within the host for other uses. 649 650# 651# support for page migration 652# 653config MIGRATION 654 bool "Page migration" 655 def_bool y 656 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU 657 help 658 Allows the migration of the physical location of pages of processes 659 while the virtual addresses are not changed. This is useful in 660 two situations. The first is on NUMA systems to put pages nearer 661 to the processors accessing. The second is when allocating huge 662 pages as migration can relocate pages to satisfy a huge page 663 allocation instead of reclaiming. 664 665config DEVICE_MIGRATION 666 def_bool MIGRATION && ZONE_DEVICE 667 668config ARCH_ENABLE_HUGEPAGE_MIGRATION 669 bool 670 671config ARCH_ENABLE_THP_MIGRATION 672 bool 673 674config HUGETLB_PAGE_SIZE_VARIABLE 675 def_bool n 676 help 677 Allows the pageblock_order value to be dynamic instead of just standard 678 HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available 679 on a platform. 680 681 Note that the pageblock_order cannot exceed MAX_ORDER and will be 682 clamped down to MAX_ORDER. 683 684config CONTIG_ALLOC 685 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA 686 687config PHYS_ADDR_T_64BIT 688 def_bool 64BIT 689 690config BOUNCE 691 bool "Enable bounce buffers" 692 default y 693 depends on BLOCK && MMU && HIGHMEM 694 help 695 Enable bounce buffers for devices that cannot access the full range of 696 memory available to the CPU. Enabled by default when HIGHMEM is 697 selected, but you may say n to override this. 698 699config MMU_NOTIFIER 700 bool 701 select INTERVAL_TREE 702 703config KSM 704 bool "Enable KSM for page merging" 705 depends on MMU 706 select XXHASH 707 help 708 Enable Kernel Samepage Merging: KSM periodically scans those areas 709 of an application's address space that an app has advised may be 710 mergeable. When it finds pages of identical content, it replaces 711 the many instances by a single page with that content, so 712 saving memory until one or another app needs to modify the content. 713 Recommended for use with KVM, or with other duplicative applications. 714 See Documentation/mm/ksm.rst for more information: KSM is inactive 715 until a program has madvised that an area is MADV_MERGEABLE, and 716 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 717 718config DEFAULT_MMAP_MIN_ADDR 719 int "Low address space to protect from user allocation" 720 depends on MMU 721 default 4096 722 help 723 This is the portion of low virtual memory which should be protected 724 from userspace allocation. Keeping a user from writing to low pages 725 can help reduce the impact of kernel NULL pointer bugs. 726 727 For most ia64, ppc64 and x86 users with lots of address space 728 a value of 65536 is reasonable and should cause no problems. 729 On arm and other archs it should not be higher than 32768. 730 Programs which use vm86 functionality or have some need to map 731 this low address space will need CAP_SYS_RAWIO or disable this 732 protection by setting the value to 0. 733 734 This value can be changed after boot using the 735 /proc/sys/vm/mmap_min_addr tunable. 736 737config ARCH_SUPPORTS_MEMORY_FAILURE 738 bool 739 740config MEMORY_FAILURE 741 depends on MMU 742 depends on ARCH_SUPPORTS_MEMORY_FAILURE 743 bool "Enable recovery from hardware memory errors" 744 select MEMORY_ISOLATION 745 select RAS 746 help 747 Enables code to recover from some memory failures on systems 748 with MCA recovery. This allows a system to continue running 749 even when some of its memory has uncorrected errors. This requires 750 special hardware support and typically ECC memory. 751 752config HWPOISON_INJECT 753 tristate "HWPoison pages injector" 754 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 755 select PROC_PAGE_MONITOR 756 757config NOMMU_INITIAL_TRIM_EXCESS 758 int "Turn on mmap() excess space trimming before booting" 759 depends on !MMU 760 default 1 761 help 762 The NOMMU mmap() frequently needs to allocate large contiguous chunks 763 of memory on which to store mappings, but it can only ask the system 764 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 765 more than it requires. To deal with this, mmap() is able to trim off 766 the excess and return it to the allocator. 767 768 If trimming is enabled, the excess is trimmed off and returned to the 769 system allocator, which can cause extra fragmentation, particularly 770 if there are a lot of transient processes. 771 772 If trimming is disabled, the excess is kept, but not used, which for 773 long-term mappings means that the space is wasted. 774 775 Trimming can be dynamically controlled through a sysctl option 776 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 777 excess pages there must be before trimming should occur, or zero if 778 no trimming is to occur. 779 780 This option specifies the initial value of this option. The default 781 of 1 says that all excess pages should be trimmed. 782 783 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 784 785config ARCH_WANT_GENERAL_HUGETLB 786 bool 787 788config ARCH_WANTS_THP_SWAP 789 def_bool n 790 791menuconfig TRANSPARENT_HUGEPAGE 792 bool "Transparent Hugepage Support" 793 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT 794 select COMPACTION 795 select XARRAY_MULTI 796 help 797 Transparent Hugepages allows the kernel to use huge pages and 798 huge tlb transparently to the applications whenever possible. 799 This feature can improve computing performance to certain 800 applications by speeding up page faults during memory 801 allocation, by reducing the number of tlb misses and by speeding 802 up the pagetable walking. 803 804 If memory constrained on embedded, you may want to say N. 805 806if TRANSPARENT_HUGEPAGE 807 808choice 809 prompt "Transparent Hugepage Support sysfs defaults" 810 depends on TRANSPARENT_HUGEPAGE 811 default TRANSPARENT_HUGEPAGE_ALWAYS 812 help 813 Selects the sysfs defaults for Transparent Hugepage Support. 814 815 config TRANSPARENT_HUGEPAGE_ALWAYS 816 bool "always" 817 help 818 Enabling Transparent Hugepage always, can increase the 819 memory footprint of applications without a guaranteed 820 benefit but it will work automatically for all applications. 821 822 config TRANSPARENT_HUGEPAGE_MADVISE 823 bool "madvise" 824 help 825 Enabling Transparent Hugepage madvise, will only provide a 826 performance improvement benefit to the applications using 827 madvise(MADV_HUGEPAGE) but it won't risk to increase the 828 memory footprint of applications without a guaranteed 829 benefit. 830endchoice 831 832config THP_SWAP 833 def_bool y 834 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT 835 help 836 Swap transparent huge pages in one piece, without splitting. 837 XXX: For now, swap cluster backing transparent huge page 838 will be split after swapout. 839 840 For selection by architectures with reasonable THP sizes. 841 842config READ_ONLY_THP_FOR_FS 843 bool "Read-only THP for filesystems (EXPERIMENTAL)" 844 depends on TRANSPARENT_HUGEPAGE && SHMEM 845 846 help 847 Allow khugepaged to put read-only file-backed pages in THP. 848 849 This is marked experimental because it is a new feature. Write 850 support of file THPs will be developed in the next few release 851 cycles. 852 853endif # TRANSPARENT_HUGEPAGE 854 855# 856# UP and nommu archs use km based percpu allocator 857# 858config NEED_PER_CPU_KM 859 depends on !SMP || !MMU 860 bool 861 default y 862 863config NEED_PER_CPU_EMBED_FIRST_CHUNK 864 bool 865 866config NEED_PER_CPU_PAGE_FIRST_CHUNK 867 bool 868 869config USE_PERCPU_NUMA_NODE_ID 870 bool 871 872config HAVE_SETUP_PER_CPU_AREA 873 bool 874 875config CMA 876 bool "Contiguous Memory Allocator" 877 depends on MMU 878 select MIGRATION 879 select MEMORY_ISOLATION 880 help 881 This enables the Contiguous Memory Allocator which allows other 882 subsystems to allocate big physically-contiguous blocks of memory. 883 CMA reserves a region of memory and allows only movable pages to 884 be allocated from it. This way, the kernel can use the memory for 885 pagecache and when a subsystem requests for contiguous area, the 886 allocated pages are migrated away to serve the contiguous request. 887 888 If unsure, say "n". 889 890config CMA_DEBUG 891 bool "CMA debug messages (DEVELOPMENT)" 892 depends on DEBUG_KERNEL && CMA 893 help 894 Turns on debug messages in CMA. This produces KERN_DEBUG 895 messages for every CMA call as well as various messages while 896 processing calls such as dma_alloc_from_contiguous(). 897 This option does not affect warning and error messages. 898 899config CMA_DEBUGFS 900 bool "CMA debugfs interface" 901 depends on CMA && DEBUG_FS 902 help 903 Turns on the DebugFS interface for CMA. 904 905config CMA_SYSFS 906 bool "CMA information through sysfs interface" 907 depends on CMA && SYSFS 908 help 909 This option exposes some sysfs attributes to get information 910 from CMA. 911 912config CMA_AREAS 913 int "Maximum count of the CMA areas" 914 depends on CMA 915 default 19 if NUMA 916 default 7 917 help 918 CMA allows to create CMA areas for particular purpose, mainly, 919 used as device private area. This parameter sets the maximum 920 number of CMA area in the system. 921 922 If unsure, leave the default value "7" in UMA and "19" in NUMA. 923 924config MEM_SOFT_DIRTY 925 bool "Track memory changes" 926 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 927 select PROC_PAGE_MONITOR 928 help 929 This option enables memory changes tracking by introducing a 930 soft-dirty bit on pte-s. This bit it set when someone writes 931 into a page just as regular dirty bit, but unlike the latter 932 it can be cleared by hands. 933 934 See Documentation/admin-guide/mm/soft-dirty.rst for more details. 935 936config GENERIC_EARLY_IOREMAP 937 bool 938 939config STACK_MAX_DEFAULT_SIZE_MB 940 int "Default maximum user stack size for 32-bit processes (MB)" 941 default 100 942 range 8 2048 943 depends on STACK_GROWSUP && (!64BIT || COMPAT) 944 help 945 This is the maximum stack size in Megabytes in the VM layout of 32-bit 946 user processes when the stack grows upwards (currently only on parisc 947 arch) when the RLIMIT_STACK hard limit is unlimited. 948 949 A sane initial value is 100 MB. 950 951config DEFERRED_STRUCT_PAGE_INIT 952 bool "Defer initialisation of struct pages to kthreads" 953 depends on SPARSEMEM 954 depends on !NEED_PER_CPU_KM 955 depends on 64BIT 956 select PADATA 957 help 958 Ordinarily all struct pages are initialised during early boot in a 959 single thread. On very large machines this can take a considerable 960 amount of time. If this option is set, large machines will bring up 961 a subset of memmap at boot and then initialise the rest in parallel. 962 This has a potential performance impact on tasks running early in the 963 lifetime of the system until these kthreads finish the 964 initialisation. 965 966config PAGE_IDLE_FLAG 967 bool 968 select PAGE_EXTENSION if !64BIT 969 help 970 This adds PG_idle and PG_young flags to 'struct page'. PTE Accessed 971 bit writers can set the state of the bit in the flags so that PTE 972 Accessed bit readers may avoid disturbance. 973 974config IDLE_PAGE_TRACKING 975 bool "Enable idle page tracking" 976 depends on SYSFS && MMU 977 select PAGE_IDLE_FLAG 978 help 979 This feature allows to estimate the amount of user pages that have 980 not been touched during a given period of time. This information can 981 be useful to tune memory cgroup limits and/or for job placement 982 within a compute cluster. 983 984 See Documentation/admin-guide/mm/idle_page_tracking.rst for 985 more details. 986 987config ARCH_HAS_CACHE_LINE_SIZE 988 bool 989 990config ARCH_HAS_CURRENT_STACK_POINTER 991 bool 992 help 993 In support of HARDENED_USERCOPY performing stack variable lifetime 994 checking, an architecture-agnostic way to find the stack pointer 995 is needed. Once an architecture defines an unsigned long global 996 register alias named "current_stack_pointer", this config can be 997 selected. 998 999config ARCH_HAS_PTE_DEVMAP 1000 bool 1001 1002config ARCH_HAS_ZONE_DMA_SET 1003 bool 1004 1005config ZONE_DMA 1006 bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET 1007 default y if ARM64 || X86 1008 1009config ZONE_DMA32 1010 bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET 1011 depends on !X86_32 1012 default y if ARM64 1013 1014config ZONE_DEVICE 1015 bool "Device memory (pmem, HMM, etc...) hotplug support" 1016 depends on MEMORY_HOTPLUG 1017 depends on MEMORY_HOTREMOVE 1018 depends on SPARSEMEM_VMEMMAP 1019 depends on ARCH_HAS_PTE_DEVMAP 1020 select XARRAY_MULTI 1021 1022 help 1023 Device memory hotplug support allows for establishing pmem, 1024 or other device driver discovered memory regions, in the 1025 memmap. This allows pfn_to_page() lookups of otherwise 1026 "device-physical" addresses which is needed for using a DAX 1027 mapping in an O_DIRECT operation, among other things. 1028 1029 If FS_DAX is enabled, then say Y. 1030 1031# 1032# Helpers to mirror range of the CPU page tables of a process into device page 1033# tables. 1034# 1035config HMM_MIRROR 1036 bool 1037 depends on MMU 1038 1039config GET_FREE_REGION 1040 depends on SPARSEMEM 1041 bool 1042 1043config DEVICE_PRIVATE 1044 bool "Unaddressable device memory (GPU memory, ...)" 1045 depends on ZONE_DEVICE 1046 select GET_FREE_REGION 1047 1048 help 1049 Allows creation of struct pages to represent unaddressable device 1050 memory; i.e., memory that is only accessible from the device (or 1051 group of devices). You likely also want to select HMM_MIRROR. 1052 1053config VMAP_PFN 1054 bool 1055 1056config ARCH_USES_HIGH_VMA_FLAGS 1057 bool 1058config ARCH_HAS_PKEYS 1059 bool 1060 1061config ARCH_USES_PG_ARCH_X 1062 bool 1063 help 1064 Enable the definition of PG_arch_x page flags with x > 1. Only 1065 suitable for 64-bit architectures with CONFIG_FLATMEM or 1066 CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be 1067 enough room for additional bits in page->flags. 1068 1069config VM_EVENT_COUNTERS 1070 default y 1071 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1072 help 1073 VM event counters are needed for event counts to be shown. 1074 This option allows the disabling of the VM event counters 1075 on EXPERT systems. /proc/vmstat will only show page counts 1076 if VM event counters are disabled. 1077 1078config PERCPU_STATS 1079 bool "Collect percpu memory statistics" 1080 help 1081 This feature collects and exposes statistics via debugfs. The 1082 information includes global and per chunk statistics, which can 1083 be used to help understand percpu memory usage. 1084 1085config GUP_TEST 1086 bool "Enable infrastructure for get_user_pages()-related unit tests" 1087 depends on DEBUG_FS 1088 help 1089 Provides /sys/kernel/debug/gup_test, which in turn provides a way 1090 to make ioctl calls that can launch kernel-based unit tests for 1091 the get_user_pages*() and pin_user_pages*() family of API calls. 1092 1093 These tests include benchmark testing of the _fast variants of 1094 get_user_pages*() and pin_user_pages*(), as well as smoke tests of 1095 the non-_fast variants. 1096 1097 There is also a sub-test that allows running dump_page() on any 1098 of up to eight pages (selected by command line args) within the 1099 range of user-space addresses. These pages are either pinned via 1100 pin_user_pages*(), or pinned via get_user_pages*(), as specified 1101 by other command line arguments. 1102 1103 See tools/testing/selftests/mm/gup_test.c 1104 1105comment "GUP_TEST needs to have DEBUG_FS enabled" 1106 depends on !GUP_TEST && !DEBUG_FS 1107 1108config GUP_GET_PXX_LOW_HIGH 1109 bool 1110 1111config DMAPOOL_TEST 1112 tristate "Enable a module to run time tests on dma_pool" 1113 depends on HAS_DMA 1114 help 1115 Provides a test module that will allocate and free many blocks of 1116 various sizes and report how long it takes. This is intended to 1117 provide a consistent way to measure how changes to the 1118 dma_pool_alloc/free routines affect performance. 1119 1120config ARCH_HAS_PTE_SPECIAL 1121 bool 1122 1123# 1124# Some architectures require a special hugepage directory format that is 1125# required to support multiple hugepage sizes. For example a4fe3ce76 1126# "powerpc/mm: Allow more flexible layouts for hugepage pagetables" 1127# introduced it on powerpc. This allows for a more flexible hugepage 1128# pagetable layouts. 1129# 1130config ARCH_HAS_HUGEPD 1131 bool 1132 1133config MAPPING_DIRTY_HELPERS 1134 bool 1135 1136config KMAP_LOCAL 1137 bool 1138 1139config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY 1140 bool 1141 1142# struct io_mapping based helper. Selected by drivers that need them 1143config IO_MAPPING 1144 bool 1145 1146config MEMFD_CREATE 1147 bool "Enable memfd_create() system call" if EXPERT 1148 1149config SECRETMEM 1150 default y 1151 bool "Enable memfd_secret() system call" if EXPERT 1152 depends on ARCH_HAS_SET_DIRECT_MAP 1153 help 1154 Enable the memfd_secret() system call with the ability to create 1155 memory areas visible only in the context of the owning process and 1156 not mapped to other processes and other kernel page tables. 1157 1158config ANON_VMA_NAME 1159 bool "Anonymous VMA name support" 1160 depends on PROC_FS && ADVISE_SYSCALLS && MMU 1161 1162 help 1163 Allow naming anonymous virtual memory areas. 1164 1165 This feature allows assigning names to virtual memory areas. Assigned 1166 names can be later retrieved from /proc/pid/maps and /proc/pid/smaps 1167 and help identifying individual anonymous memory areas. 1168 Assigning a name to anonymous virtual memory area might prevent that 1169 area from being merged with adjacent virtual memory areas due to the 1170 difference in their name. 1171 1172config USERFAULTFD 1173 bool "Enable userfaultfd() system call" 1174 depends on MMU 1175 help 1176 Enable the userfaultfd() system call that allows to intercept and 1177 handle page faults in userland. 1178 1179config HAVE_ARCH_USERFAULTFD_WP 1180 bool 1181 help 1182 Arch has userfaultfd write protection support 1183 1184config HAVE_ARCH_USERFAULTFD_MINOR 1185 bool 1186 help 1187 Arch has userfaultfd minor fault support 1188 1189config PTE_MARKER_UFFD_WP 1190 bool "Userfaultfd write protection support for shmem/hugetlbfs" 1191 default y 1192 depends on HAVE_ARCH_USERFAULTFD_WP 1193 1194 help 1195 Allows to create marker PTEs for userfaultfd write protection 1196 purposes. It is required to enable userfaultfd write protection on 1197 file-backed memory types like shmem and hugetlbfs. 1198 1199# multi-gen LRU { 1200config LRU_GEN 1201 bool "Multi-Gen LRU" 1202 depends on MMU 1203 # make sure folio->flags has enough spare bits 1204 depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP 1205 help 1206 A high performance LRU implementation to overcommit memory. See 1207 Documentation/admin-guide/mm/multigen_lru.rst for details. 1208 1209config LRU_GEN_ENABLED 1210 bool "Enable by default" 1211 depends on LRU_GEN 1212 help 1213 This option enables the multi-gen LRU by default. 1214 1215config LRU_GEN_STATS 1216 bool "Full stats for debugging" 1217 depends on LRU_GEN 1218 help 1219 Do not enable this option unless you plan to look at historical stats 1220 from evicted generations for debugging purpose. 1221 1222 This option has a per-memcg and per-node memory overhead. 1223# } 1224 1225config ARCH_SUPPORTS_PER_VMA_LOCK 1226 def_bool n 1227 1228config PER_VMA_LOCK 1229 def_bool y 1230 depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP 1231 help 1232 Allow per-vma locking during page fault handling. 1233 1234 This feature allows locking each virtual memory area separately when 1235 handling page faults instead of taking mmap_lock. 1236 1237config LOCK_MM_AND_FIND_VMA 1238 bool 1239 depends on !STACK_GROWSUP 1240 1241source "mm/damon/Kconfig" 1242 1243endmenu 1244