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