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 340endmenu # SLAB allocator options 341 342config SHUFFLE_PAGE_ALLOCATOR 343 bool "Page allocator randomization" 344 default SLAB_FREELIST_RANDOM && ACPI_NUMA 345 help 346 Randomization of the page allocator improves the average 347 utilization of a direct-mapped memory-side-cache. See section 348 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 349 6.2a specification for an example of how a platform advertises 350 the presence of a memory-side-cache. There are also incidental 351 security benefits as it reduces the predictability of page 352 allocations to compliment SLAB_FREELIST_RANDOM, but the 353 default granularity of shuffling on the MAX_ORDER i.e, 10th 354 order of pages is selected based on cache utilization benefits 355 on x86. 356 357 While the randomization improves cache utilization it may 358 negatively impact workloads on platforms without a cache. For 359 this reason, by default, the randomization is enabled only 360 after runtime detection of a direct-mapped memory-side-cache. 361 Otherwise, the randomization may be force enabled with the 362 'page_alloc.shuffle' kernel command line parameter. 363 364 Say Y if unsure. 365 366config COMPAT_BRK 367 bool "Disable heap randomization" 368 default y 369 help 370 Randomizing heap placement makes heap exploits harder, but it 371 also breaks ancient binaries (including anything libc5 based). 372 This option changes the bootup default to heap randomization 373 disabled, and can be overridden at runtime by setting 374 /proc/sys/kernel/randomize_va_space to 2. 375 376 On non-ancient distros (post-2000 ones) N is usually a safe choice. 377 378config MMAP_ALLOW_UNINITIALIZED 379 bool "Allow mmapped anonymous memory to be uninitialized" 380 depends on EXPERT && !MMU 381 default n 382 help 383 Normally, and according to the Linux spec, anonymous memory obtained 384 from mmap() has its contents cleared before it is passed to 385 userspace. Enabling this config option allows you to request that 386 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 387 providing a huge performance boost. If this option is not enabled, 388 then the flag will be ignored. 389 390 This is taken advantage of by uClibc's malloc(), and also by 391 ELF-FDPIC binfmt's brk and stack allocator. 392 393 Because of the obvious security issues, this option should only be 394 enabled on embedded devices where you control what is run in 395 userspace. Since that isn't generally a problem on no-MMU systems, 396 it is normally safe to say Y here. 397 398 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 399 400config SELECT_MEMORY_MODEL 401 def_bool y 402 depends on ARCH_SELECT_MEMORY_MODEL 403 404choice 405 prompt "Memory model" 406 depends on SELECT_MEMORY_MODEL 407 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT 408 default FLATMEM_MANUAL 409 help 410 This option allows you to change some of the ways that 411 Linux manages its memory internally. Most users will 412 only have one option here selected by the architecture 413 configuration. This is normal. 414 415config FLATMEM_MANUAL 416 bool "Flat Memory" 417 depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE 418 help 419 This option is best suited for non-NUMA systems with 420 flat address space. The FLATMEM is the most efficient 421 system in terms of performance and resource consumption 422 and it is the best option for smaller systems. 423 424 For systems that have holes in their physical address 425 spaces and for features like NUMA and memory hotplug, 426 choose "Sparse Memory". 427 428 If unsure, choose this option (Flat Memory) over any other. 429 430config SPARSEMEM_MANUAL 431 bool "Sparse Memory" 432 depends on ARCH_SPARSEMEM_ENABLE 433 help 434 This will be the only option for some systems, including 435 memory hot-plug systems. This is normal. 436 437 This option provides efficient support for systems with 438 holes is their physical address space and allows memory 439 hot-plug and hot-remove. 440 441 If unsure, choose "Flat Memory" over this option. 442 443endchoice 444 445config SPARSEMEM 446 def_bool y 447 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL 448 449config FLATMEM 450 def_bool y 451 depends on !SPARSEMEM || FLATMEM_MANUAL 452 453# 454# SPARSEMEM_EXTREME (which is the default) does some bootmem 455# allocations when sparse_init() is called. If this cannot 456# be done on your architecture, select this option. However, 457# statically allocating the mem_section[] array can potentially 458# consume vast quantities of .bss, so be careful. 459# 460# This option will also potentially produce smaller runtime code 461# with gcc 3.4 and later. 462# 463config SPARSEMEM_STATIC 464 bool 465 466# 467# Architecture platforms which require a two level mem_section in SPARSEMEM 468# must select this option. This is usually for architecture platforms with 469# an extremely sparse physical address space. 470# 471config SPARSEMEM_EXTREME 472 def_bool y 473 depends on SPARSEMEM && !SPARSEMEM_STATIC 474 475config SPARSEMEM_VMEMMAP_ENABLE 476 bool 477 478config SPARSEMEM_VMEMMAP 479 bool "Sparse Memory virtual memmap" 480 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE 481 default y 482 help 483 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise 484 pfn_to_page and page_to_pfn operations. This is the most 485 efficient option when sufficient kernel resources are available. 486# 487# Select this config option from the architecture Kconfig, if it is preferred 488# to enable the feature of HugeTLB/dev_dax vmemmap optimization. 489# 490config ARCH_WANT_OPTIMIZE_VMEMMAP 491 bool 492 493config HAVE_MEMBLOCK_PHYS_MAP 494 bool 495 496config HAVE_FAST_GUP 497 depends on MMU 498 bool 499 500# Don't discard allocated memory used to track "memory" and "reserved" memblocks 501# after early boot, so it can still be used to test for validity of memory. 502# Also, memblocks are updated with memory hot(un)plug. 503config ARCH_KEEP_MEMBLOCK 504 bool 505 506# Keep arch NUMA mapping infrastructure post-init. 507config NUMA_KEEP_MEMINFO 508 bool 509 510config MEMORY_ISOLATION 511 bool 512 513# IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked 514# IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via 515# /dev/mem. 516config EXCLUSIVE_SYSTEM_RAM 517 def_bool y 518 depends on !DEVMEM || STRICT_DEVMEM 519 520# 521# Only be set on architectures that have completely implemented memory hotplug 522# feature. If you are not sure, don't touch it. 523# 524config HAVE_BOOTMEM_INFO_NODE 525 def_bool n 526 527config ARCH_ENABLE_MEMORY_HOTPLUG 528 bool 529 530config ARCH_ENABLE_MEMORY_HOTREMOVE 531 bool 532 533# eventually, we can have this option just 'select SPARSEMEM' 534menuconfig MEMORY_HOTPLUG 535 bool "Memory hotplug" 536 select MEMORY_ISOLATION 537 depends on SPARSEMEM 538 depends on ARCH_ENABLE_MEMORY_HOTPLUG 539 depends on 64BIT 540 select NUMA_KEEP_MEMINFO if NUMA 541 542if MEMORY_HOTPLUG 543 544config MEMORY_HOTPLUG_DEFAULT_ONLINE 545 bool "Online the newly added memory blocks by default" 546 depends on MEMORY_HOTPLUG 547 help 548 This option sets the default policy setting for memory hotplug 549 onlining policy (/sys/devices/system/memory/auto_online_blocks) which 550 determines what happens to newly added memory regions. Policy setting 551 can always be changed at runtime. 552 See Documentation/admin-guide/mm/memory-hotplug.rst for more information. 553 554 Say Y here if you want all hot-plugged memory blocks to appear in 555 'online' state by default. 556 Say N here if you want the default policy to keep all hot-plugged 557 memory blocks in 'offline' state. 558 559config MEMORY_HOTREMOVE 560 bool "Allow for memory hot remove" 561 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64) 562 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 563 depends on MIGRATION 564 565config MHP_MEMMAP_ON_MEMORY 566 def_bool y 567 depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP 568 depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE 569 570endif # MEMORY_HOTPLUG 571 572# Heavily threaded applications may benefit from splitting the mm-wide 573# page_table_lock, so that faults on different parts of the user address 574# space can be handled with less contention: split it at this NR_CPUS. 575# Default to 4 for wider testing, though 8 might be more appropriate. 576# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 577# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 578# SPARC32 allocates multiple pte tables within a single page, and therefore 579# a per-page lock leads to problems when multiple tables need to be locked 580# at the same time (e.g. copy_page_range()). 581# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 582# 583config SPLIT_PTLOCK_CPUS 584 int 585 default "999999" if !MMU 586 default "999999" if ARM && !CPU_CACHE_VIPT 587 default "999999" if PARISC && !PA20 588 default "999999" if SPARC32 589 default "4" 590 591config ARCH_ENABLE_SPLIT_PMD_PTLOCK 592 bool 593 594# 595# support for memory balloon 596config MEMORY_BALLOON 597 bool 598 599# 600# support for memory balloon compaction 601config BALLOON_COMPACTION 602 bool "Allow for balloon memory compaction/migration" 603 def_bool y 604 depends on COMPACTION && MEMORY_BALLOON 605 help 606 Memory fragmentation introduced by ballooning might reduce 607 significantly the number of 2MB contiguous memory blocks that can be 608 used within a guest, thus imposing performance penalties associated 609 with the reduced number of transparent huge pages that could be used 610 by the guest workload. Allowing the compaction & migration for memory 611 pages enlisted as being part of memory balloon devices avoids the 612 scenario aforementioned and helps improving memory defragmentation. 613 614# 615# support for memory compaction 616config COMPACTION 617 bool "Allow for memory compaction" 618 def_bool y 619 select MIGRATION 620 depends on MMU 621 help 622 Compaction is the only memory management component to form 623 high order (larger physically contiguous) memory blocks 624 reliably. The page allocator relies on compaction heavily and 625 the lack of the feature can lead to unexpected OOM killer 626 invocations for high order memory requests. You shouldn't 627 disable this option unless there really is a strong reason for 628 it and then we would be really interested to hear about that at 629 linux-mm@kvack.org. 630 631config COMPACT_UNEVICTABLE_DEFAULT 632 int 633 depends on COMPACTION 634 default 0 if PREEMPT_RT 635 default 1 636 637# 638# support for free page reporting 639config PAGE_REPORTING 640 bool "Free page reporting" 641 def_bool n 642 help 643 Free page reporting allows for the incremental acquisition of 644 free pages from the buddy allocator for the purpose of reporting 645 those pages to another entity, such as a hypervisor, so that the 646 memory can be freed within the host for other uses. 647 648# 649# support for page migration 650# 651config MIGRATION 652 bool "Page migration" 653 def_bool y 654 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU 655 help 656 Allows the migration of the physical location of pages of processes 657 while the virtual addresses are not changed. This is useful in 658 two situations. The first is on NUMA systems to put pages nearer 659 to the processors accessing. The second is when allocating huge 660 pages as migration can relocate pages to satisfy a huge page 661 allocation instead of reclaiming. 662 663config DEVICE_MIGRATION 664 def_bool MIGRATION && ZONE_DEVICE 665 666config ARCH_ENABLE_HUGEPAGE_MIGRATION 667 bool 668 669config ARCH_ENABLE_THP_MIGRATION 670 bool 671 672config HUGETLB_PAGE_SIZE_VARIABLE 673 def_bool n 674 help 675 Allows the pageblock_order value to be dynamic instead of just standard 676 HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available 677 on a platform. 678 679 Note that the pageblock_order cannot exceed MAX_ORDER and will be 680 clamped down to MAX_ORDER. 681 682config CONTIG_ALLOC 683 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA 684 685config PHYS_ADDR_T_64BIT 686 def_bool 64BIT 687 688config BOUNCE 689 bool "Enable bounce buffers" 690 default y 691 depends on BLOCK && MMU && HIGHMEM 692 help 693 Enable bounce buffers for devices that cannot access the full range of 694 memory available to the CPU. Enabled by default when HIGHMEM is 695 selected, but you may say n to override this. 696 697config MMU_NOTIFIER 698 bool 699 select INTERVAL_TREE 700 701config KSM 702 bool "Enable KSM for page merging" 703 depends on MMU 704 select XXHASH 705 help 706 Enable Kernel Samepage Merging: KSM periodically scans those areas 707 of an application's address space that an app has advised may be 708 mergeable. When it finds pages of identical content, it replaces 709 the many instances by a single page with that content, so 710 saving memory until one or another app needs to modify the content. 711 Recommended for use with KVM, or with other duplicative applications. 712 See Documentation/mm/ksm.rst for more information: KSM is inactive 713 until a program has madvised that an area is MADV_MERGEABLE, and 714 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 715 716config DEFAULT_MMAP_MIN_ADDR 717 int "Low address space to protect from user allocation" 718 depends on MMU 719 default 4096 720 help 721 This is the portion of low virtual memory which should be protected 722 from userspace allocation. Keeping a user from writing to low pages 723 can help reduce the impact of kernel NULL pointer bugs. 724 725 For most ia64, ppc64 and x86 users with lots of address space 726 a value of 65536 is reasonable and should cause no problems. 727 On arm and other archs it should not be higher than 32768. 728 Programs which use vm86 functionality or have some need to map 729 this low address space will need CAP_SYS_RAWIO or disable this 730 protection by setting the value to 0. 731 732 This value can be changed after boot using the 733 /proc/sys/vm/mmap_min_addr tunable. 734 735config ARCH_SUPPORTS_MEMORY_FAILURE 736 bool 737 738config MEMORY_FAILURE 739 depends on MMU 740 depends on ARCH_SUPPORTS_MEMORY_FAILURE 741 bool "Enable recovery from hardware memory errors" 742 select MEMORY_ISOLATION 743 select RAS 744 help 745 Enables code to recover from some memory failures on systems 746 with MCA recovery. This allows a system to continue running 747 even when some of its memory has uncorrected errors. This requires 748 special hardware support and typically ECC memory. 749 750config HWPOISON_INJECT 751 tristate "HWPoison pages injector" 752 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 753 select PROC_PAGE_MONITOR 754 755config NOMMU_INITIAL_TRIM_EXCESS 756 int "Turn on mmap() excess space trimming before booting" 757 depends on !MMU 758 default 1 759 help 760 The NOMMU mmap() frequently needs to allocate large contiguous chunks 761 of memory on which to store mappings, but it can only ask the system 762 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 763 more than it requires. To deal with this, mmap() is able to trim off 764 the excess and return it to the allocator. 765 766 If trimming is enabled, the excess is trimmed off and returned to the 767 system allocator, which can cause extra fragmentation, particularly 768 if there are a lot of transient processes. 769 770 If trimming is disabled, the excess is kept, but not used, which for 771 long-term mappings means that the space is wasted. 772 773 Trimming can be dynamically controlled through a sysctl option 774 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 775 excess pages there must be before trimming should occur, or zero if 776 no trimming is to occur. 777 778 This option specifies the initial value of this option. The default 779 of 1 says that all excess pages should be trimmed. 780 781 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 782 783config ARCH_WANT_GENERAL_HUGETLB 784 bool 785 786config ARCH_WANTS_THP_SWAP 787 def_bool n 788 789menuconfig TRANSPARENT_HUGEPAGE 790 bool "Transparent Hugepage Support" 791 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT 792 select COMPACTION 793 select XARRAY_MULTI 794 help 795 Transparent Hugepages allows the kernel to use huge pages and 796 huge tlb transparently to the applications whenever possible. 797 This feature can improve computing performance to certain 798 applications by speeding up page faults during memory 799 allocation, by reducing the number of tlb misses and by speeding 800 up the pagetable walking. 801 802 If memory constrained on embedded, you may want to say N. 803 804if TRANSPARENT_HUGEPAGE 805 806choice 807 prompt "Transparent Hugepage Support sysfs defaults" 808 depends on TRANSPARENT_HUGEPAGE 809 default TRANSPARENT_HUGEPAGE_ALWAYS 810 help 811 Selects the sysfs defaults for Transparent Hugepage Support. 812 813 config TRANSPARENT_HUGEPAGE_ALWAYS 814 bool "always" 815 help 816 Enabling Transparent Hugepage always, can increase the 817 memory footprint of applications without a guaranteed 818 benefit but it will work automatically for all applications. 819 820 config TRANSPARENT_HUGEPAGE_MADVISE 821 bool "madvise" 822 help 823 Enabling Transparent Hugepage madvise, will only provide a 824 performance improvement benefit to the applications using 825 madvise(MADV_HUGEPAGE) but it won't risk to increase the 826 memory footprint of applications without a guaranteed 827 benefit. 828endchoice 829 830config THP_SWAP 831 def_bool y 832 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT 833 help 834 Swap transparent huge pages in one piece, without splitting. 835 XXX: For now, swap cluster backing transparent huge page 836 will be split after swapout. 837 838 For selection by architectures with reasonable THP sizes. 839 840config READ_ONLY_THP_FOR_FS 841 bool "Read-only THP for filesystems (EXPERIMENTAL)" 842 depends on TRANSPARENT_HUGEPAGE && SHMEM 843 844 help 845 Allow khugepaged to put read-only file-backed pages in THP. 846 847 This is marked experimental because it is a new feature. Write 848 support of file THPs will be developed in the next few release 849 cycles. 850 851endif # TRANSPARENT_HUGEPAGE 852 853# 854# UP and nommu archs use km based percpu allocator 855# 856config NEED_PER_CPU_KM 857 depends on !SMP || !MMU 858 bool 859 default y 860 861config NEED_PER_CPU_EMBED_FIRST_CHUNK 862 bool 863 864config NEED_PER_CPU_PAGE_FIRST_CHUNK 865 bool 866 867config USE_PERCPU_NUMA_NODE_ID 868 bool 869 870config HAVE_SETUP_PER_CPU_AREA 871 bool 872 873config FRONTSWAP 874 bool 875 876config CMA 877 bool "Contiguous Memory Allocator" 878 depends on MMU 879 select MIGRATION 880 select MEMORY_ISOLATION 881 help 882 This enables the Contiguous Memory Allocator which allows other 883 subsystems to allocate big physically-contiguous blocks of memory. 884 CMA reserves a region of memory and allows only movable pages to 885 be allocated from it. This way, the kernel can use the memory for 886 pagecache and when a subsystem requests for contiguous area, the 887 allocated pages are migrated away to serve the contiguous request. 888 889 If unsure, say "n". 890 891config CMA_DEBUG 892 bool "CMA debug messages (DEVELOPMENT)" 893 depends on DEBUG_KERNEL && CMA 894 help 895 Turns on debug messages in CMA. This produces KERN_DEBUG 896 messages for every CMA call as well as various messages while 897 processing calls such as dma_alloc_from_contiguous(). 898 This option does not affect warning and error messages. 899 900config CMA_DEBUGFS 901 bool "CMA debugfs interface" 902 depends on CMA && DEBUG_FS 903 help 904 Turns on the DebugFS interface for CMA. 905 906config CMA_SYSFS 907 bool "CMA information through sysfs interface" 908 depends on CMA && SYSFS 909 help 910 This option exposes some sysfs attributes to get information 911 from CMA. 912 913config CMA_AREAS 914 int "Maximum count of the CMA areas" 915 depends on CMA 916 default 19 if NUMA 917 default 7 918 help 919 CMA allows to create CMA areas for particular purpose, mainly, 920 used as device private area. This parameter sets the maximum 921 number of CMA area in the system. 922 923 If unsure, leave the default value "7" in UMA and "19" in NUMA. 924 925config MEM_SOFT_DIRTY 926 bool "Track memory changes" 927 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 928 select PROC_PAGE_MONITOR 929 help 930 This option enables memory changes tracking by introducing a 931 soft-dirty bit on pte-s. This bit it set when someone writes 932 into a page just as regular dirty bit, but unlike the latter 933 it can be cleared by hands. 934 935 See Documentation/admin-guide/mm/soft-dirty.rst for more details. 936 937config GENERIC_EARLY_IOREMAP 938 bool 939 940config STACK_MAX_DEFAULT_SIZE_MB 941 int "Default maximum user stack size for 32-bit processes (MB)" 942 default 100 943 range 8 2048 944 depends on STACK_GROWSUP && (!64BIT || COMPAT) 945 help 946 This is the maximum stack size in Megabytes in the VM layout of 32-bit 947 user processes when the stack grows upwards (currently only on parisc 948 arch) when the RLIMIT_STACK hard limit is unlimited. 949 950 A sane initial value is 100 MB. 951 952config DEFERRED_STRUCT_PAGE_INIT 953 bool "Defer initialisation of struct pages to kthreads" 954 depends on SPARSEMEM 955 depends on !NEED_PER_CPU_KM 956 depends on 64BIT 957 select PADATA 958 help 959 Ordinarily all struct pages are initialised during early boot in a 960 single thread. On very large machines this can take a considerable 961 amount of time. If this option is set, large machines will bring up 962 a subset of memmap at boot and then initialise the rest in parallel. 963 This has a potential performance impact on tasks running early in the 964 lifetime of the system until these kthreads finish the 965 initialisation. 966 967config PAGE_IDLE_FLAG 968 bool 969 select PAGE_EXTENSION if !64BIT 970 help 971 This adds PG_idle and PG_young flags to 'struct page'. PTE Accessed 972 bit writers can set the state of the bit in the flags so that PTE 973 Accessed bit readers may avoid disturbance. 974 975config IDLE_PAGE_TRACKING 976 bool "Enable idle page tracking" 977 depends on SYSFS && MMU 978 select PAGE_IDLE_FLAG 979 help 980 This feature allows to estimate the amount of user pages that have 981 not been touched during a given period of time. This information can 982 be useful to tune memory cgroup limits and/or for job placement 983 within a compute cluster. 984 985 See Documentation/admin-guide/mm/idle_page_tracking.rst for 986 more details. 987 988config ARCH_HAS_CACHE_LINE_SIZE 989 bool 990 991config ARCH_HAS_CURRENT_STACK_POINTER 992 bool 993 help 994 In support of HARDENED_USERCOPY performing stack variable lifetime 995 checking, an architecture-agnostic way to find the stack pointer 996 is needed. Once an architecture defines an unsigned long global 997 register alias named "current_stack_pointer", this config can be 998 selected. 999 1000config ARCH_HAS_PTE_DEVMAP 1001 bool 1002 1003config ARCH_HAS_ZONE_DMA_SET 1004 bool 1005 1006config ZONE_DMA 1007 bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET 1008 default y if ARM64 || X86 1009 1010config ZONE_DMA32 1011 bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET 1012 depends on !X86_32 1013 default y if ARM64 1014 1015config ZONE_DEVICE 1016 bool "Device memory (pmem, HMM, etc...) hotplug support" 1017 depends on MEMORY_HOTPLUG 1018 depends on MEMORY_HOTREMOVE 1019 depends on SPARSEMEM_VMEMMAP 1020 depends on ARCH_HAS_PTE_DEVMAP 1021 select XARRAY_MULTI 1022 1023 help 1024 Device memory hotplug support allows for establishing pmem, 1025 or other device driver discovered memory regions, in the 1026 memmap. This allows pfn_to_page() lookups of otherwise 1027 "device-physical" addresses which is needed for using a DAX 1028 mapping in an O_DIRECT operation, among other things. 1029 1030 If FS_DAX is enabled, then say Y. 1031 1032# 1033# Helpers to mirror range of the CPU page tables of a process into device page 1034# tables. 1035# 1036config HMM_MIRROR 1037 bool 1038 depends on MMU 1039 1040config GET_FREE_REGION 1041 depends on SPARSEMEM 1042 bool 1043 1044config DEVICE_PRIVATE 1045 bool "Unaddressable device memory (GPU memory, ...)" 1046 depends on ZONE_DEVICE 1047 select GET_FREE_REGION 1048 1049 help 1050 Allows creation of struct pages to represent unaddressable device 1051 memory; i.e., memory that is only accessible from the device (or 1052 group of devices). You likely also want to select HMM_MIRROR. 1053 1054config VMAP_PFN 1055 bool 1056 1057config ARCH_USES_HIGH_VMA_FLAGS 1058 bool 1059config ARCH_HAS_PKEYS 1060 bool 1061 1062config ARCH_USES_PG_ARCH_X 1063 bool 1064 help 1065 Enable the definition of PG_arch_x page flags with x > 1. Only 1066 suitable for 64-bit architectures with CONFIG_FLATMEM or 1067 CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be 1068 enough room for additional bits in page->flags. 1069 1070config VM_EVENT_COUNTERS 1071 default y 1072 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1073 help 1074 VM event counters are needed for event counts to be shown. 1075 This option allows the disabling of the VM event counters 1076 on EXPERT systems. /proc/vmstat will only show page counts 1077 if VM event counters are disabled. 1078 1079config PERCPU_STATS 1080 bool "Collect percpu memory statistics" 1081 help 1082 This feature collects and exposes statistics via debugfs. The 1083 information includes global and per chunk statistics, which can 1084 be used to help understand percpu memory usage. 1085 1086config GUP_TEST 1087 bool "Enable infrastructure for get_user_pages()-related unit tests" 1088 depends on DEBUG_FS 1089 help 1090 Provides /sys/kernel/debug/gup_test, which in turn provides a way 1091 to make ioctl calls that can launch kernel-based unit tests for 1092 the get_user_pages*() and pin_user_pages*() family of API calls. 1093 1094 These tests include benchmark testing of the _fast variants of 1095 get_user_pages*() and pin_user_pages*(), as well as smoke tests of 1096 the non-_fast variants. 1097 1098 There is also a sub-test that allows running dump_page() on any 1099 of up to eight pages (selected by command line args) within the 1100 range of user-space addresses. These pages are either pinned via 1101 pin_user_pages*(), or pinned via get_user_pages*(), as specified 1102 by other command line arguments. 1103 1104 See tools/testing/selftests/mm/gup_test.c 1105 1106comment "GUP_TEST needs to have DEBUG_FS enabled" 1107 depends on !GUP_TEST && !DEBUG_FS 1108 1109config GUP_GET_PXX_LOW_HIGH 1110 bool 1111 1112config DMAPOOL_TEST 1113 tristate "Enable a module to run time tests on dma_pool" 1114 depends on HAS_DMA 1115 help 1116 Provides a test module that will allocate and free many blocks of 1117 various sizes and report how long it takes. This is intended to 1118 provide a consistent way to measure how changes to the 1119 dma_pool_alloc/free routines affect performance. 1120 1121config ARCH_HAS_PTE_SPECIAL 1122 bool 1123 1124# 1125# Some architectures require a special hugepage directory format that is 1126# required to support multiple hugepage sizes. For example a4fe3ce76 1127# "powerpc/mm: Allow more flexible layouts for hugepage pagetables" 1128# introduced it on powerpc. This allows for a more flexible hugepage 1129# pagetable layouts. 1130# 1131config ARCH_HAS_HUGEPD 1132 bool 1133 1134config MAPPING_DIRTY_HELPERS 1135 bool 1136 1137config KMAP_LOCAL 1138 bool 1139 1140config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY 1141 bool 1142 1143# struct io_mapping based helper. Selected by drivers that need them 1144config IO_MAPPING 1145 bool 1146 1147config SECRETMEM 1148 default y 1149 bool "Enable memfd_secret() system call" if EXPERT 1150 depends on ARCH_HAS_SET_DIRECT_MAP 1151 help 1152 Enable the memfd_secret() system call with the ability to create 1153 memory areas visible only in the context of the owning process and 1154 not mapped to other processes and other kernel page tables. 1155 1156config ANON_VMA_NAME 1157 bool "Anonymous VMA name support" 1158 depends on PROC_FS && ADVISE_SYSCALLS && MMU 1159 1160 help 1161 Allow naming anonymous virtual memory areas. 1162 1163 This feature allows assigning names to virtual memory areas. Assigned 1164 names can be later retrieved from /proc/pid/maps and /proc/pid/smaps 1165 and help identifying individual anonymous memory areas. 1166 Assigning a name to anonymous virtual memory area might prevent that 1167 area from being merged with adjacent virtual memory areas due to the 1168 difference in their name. 1169 1170config USERFAULTFD 1171 bool "Enable userfaultfd() system call" 1172 depends on MMU 1173 help 1174 Enable the userfaultfd() system call that allows to intercept and 1175 handle page faults in userland. 1176 1177config HAVE_ARCH_USERFAULTFD_WP 1178 bool 1179 help 1180 Arch has userfaultfd write protection support 1181 1182config HAVE_ARCH_USERFAULTFD_MINOR 1183 bool 1184 help 1185 Arch has userfaultfd minor fault support 1186 1187config PTE_MARKER_UFFD_WP 1188 bool "Userfaultfd write protection support for shmem/hugetlbfs" 1189 default y 1190 depends on HAVE_ARCH_USERFAULTFD_WP 1191 1192 help 1193 Allows to create marker PTEs for userfaultfd write protection 1194 purposes. It is required to enable userfaultfd write protection on 1195 file-backed memory types like shmem and hugetlbfs. 1196 1197# multi-gen LRU { 1198config LRU_GEN 1199 bool "Multi-Gen LRU" 1200 depends on MMU 1201 # make sure folio->flags has enough spare bits 1202 depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP 1203 help 1204 A high performance LRU implementation to overcommit memory. See 1205 Documentation/admin-guide/mm/multigen_lru.rst for details. 1206 1207config LRU_GEN_ENABLED 1208 bool "Enable by default" 1209 depends on LRU_GEN 1210 help 1211 This option enables the multi-gen LRU by default. 1212 1213config LRU_GEN_STATS 1214 bool "Full stats for debugging" 1215 depends on LRU_GEN 1216 help 1217 Do not enable this option unless you plan to look at historical stats 1218 from evicted generations for debugging purpose. 1219 1220 This option has a per-memcg and per-node memory overhead. 1221# } 1222 1223config ARCH_SUPPORTS_PER_VMA_LOCK 1224 def_bool n 1225 1226config PER_VMA_LOCK 1227 def_bool y 1228 depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP 1229 help 1230 Allow per-vma locking during page fault handling. 1231 1232 This feature allows locking each virtual memory area separately when 1233 handling page faults instead of taking mmap_lock. 1234 1235config LOCK_MM_AND_FIND_VMA 1236 bool 1237 depends on !STACK_GROWSUP 1238 1239source "mm/damon/Kconfig" 1240 1241endmenu 1242