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 12menuconfig SWAP 13 bool "Support for paging of anonymous memory (swap)" 14 depends on MMU && BLOCK && !ARCH_NO_SWAP 15 default y 16 help 17 This option allows you to choose whether you want to have support 18 for so called swap devices or swap files in your kernel that are 19 used to provide more virtual memory than the actual RAM present 20 in your computer. If unsure say Y. 21 22config ZSWAP 23 bool "Compressed cache for swap pages" 24 depends on SWAP 25 select CRYPTO 26 select ZSMALLOC 27 help 28 A lightweight compressed cache for swap pages. It takes 29 pages that are in the process of being swapped out and attempts to 30 compress them into a dynamically allocated RAM-based memory pool. 31 This can result in a significant I/O reduction on swap device and, 32 in the case where decompressing from RAM is faster than swap device 33 reads, can also improve workload performance. 34 35config ZSWAP_DEFAULT_ON 36 bool "Enable the compressed cache for swap pages by default" 37 depends on ZSWAP 38 help 39 If selected, the compressed cache for swap pages will be enabled 40 at boot, otherwise it will be disabled. 41 42 The selection made here can be overridden by using the kernel 43 command line 'zswap.enabled=' option. 44 45config ZSWAP_SHRINKER_DEFAULT_ON 46 bool "Shrink the zswap pool on memory pressure" 47 depends on ZSWAP 48 default n 49 help 50 If selected, the zswap shrinker will be enabled, and the pages 51 stored in the zswap pool will become available for reclaim (i.e 52 written back to the backing swap device) on memory pressure. 53 54 This means that zswap writeback could happen even if the pool is 55 not yet full, or the cgroup zswap limit has not been reached, 56 reducing the chance that cold pages will reside in the zswap pool 57 and consume memory indefinitely. 58 59choice 60 prompt "Default compressor" 61 depends on ZSWAP 62 default ZSWAP_COMPRESSOR_DEFAULT_LZO 63 help 64 Selects the default compression algorithm for the compressed cache 65 for swap pages. 66 67 For an overview what kind of performance can be expected from 68 a particular compression algorithm please refer to the benchmarks 69 available at the following LWN page: 70 https://lwn.net/Articles/751795/ 71 72 If in doubt, select 'LZO'. 73 74 The selection made here can be overridden by using the kernel 75 command line 'zswap.compressor=' option. 76 77config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE 78 bool "Deflate" 79 select CRYPTO_DEFLATE 80 help 81 Use the Deflate algorithm as the default compression algorithm. 82 83config ZSWAP_COMPRESSOR_DEFAULT_LZO 84 bool "LZO" 85 select CRYPTO_LZO 86 help 87 Use the LZO algorithm as the default compression algorithm. 88 89config ZSWAP_COMPRESSOR_DEFAULT_842 90 bool "842" 91 select CRYPTO_842 92 help 93 Use the 842 algorithm as the default compression algorithm. 94 95config ZSWAP_COMPRESSOR_DEFAULT_LZ4 96 bool "LZ4" 97 select CRYPTO_LZ4 98 help 99 Use the LZ4 algorithm as the default compression algorithm. 100 101config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC 102 bool "LZ4HC" 103 select CRYPTO_LZ4HC 104 help 105 Use the LZ4HC algorithm as the default compression algorithm. 106 107config ZSWAP_COMPRESSOR_DEFAULT_ZSTD 108 bool "zstd" 109 select CRYPTO_ZSTD 110 help 111 Use the zstd algorithm as the default compression algorithm. 112endchoice 113 114config ZSWAP_COMPRESSOR_DEFAULT 115 string 116 depends on ZSWAP 117 default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE 118 default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO 119 default "842" if ZSWAP_COMPRESSOR_DEFAULT_842 120 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4 121 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC 122 default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD 123 default "" 124 125config ZSMALLOC 126 tristate 127 128if ZSMALLOC 129 130menu "Zsmalloc allocator options" 131 depends on ZSMALLOC 132 133comment "Zsmalloc is a common backend allocator for zswap & zram" 134 135config ZSMALLOC_STAT 136 bool "Export zsmalloc statistics" 137 select DEBUG_FS 138 help 139 This option enables code in the zsmalloc to collect various 140 statistics about what's happening in zsmalloc and exports that 141 information to userspace via debugfs. 142 If unsure, say N. 143 144config ZSMALLOC_CHAIN_SIZE 145 int "Maximum number of physical pages per-zspage" 146 default 8 147 range 4 16 148 help 149 This option sets the upper limit on the number of physical pages 150 that a zmalloc page (zspage) can consist of. The optimal zspage 151 chain size is calculated for each size class during the 152 initialization of the pool. 153 154 Changing this option can alter the characteristics of size classes, 155 such as the number of pages per zspage and the number of objects 156 per zspage. This can also result in different configurations of 157 the pool, as zsmalloc merges size classes with similar 158 characteristics. 159 160 For more information, see zsmalloc documentation. 161 162endmenu 163 164endif 165 166menu "Slab allocator options" 167 168config SLUB 169 def_bool y 170 171config KVFREE_RCU_BATCHED 172 def_bool y 173 depends on !SLUB_TINY && !TINY_RCU 174 175config SLUB_TINY 176 bool "Configure for minimal memory footprint" 177 depends on EXPERT && !COMPILE_TEST 178 select SLAB_MERGE_DEFAULT 179 help 180 Configures the slab allocator in a way to achieve minimal memory 181 footprint, sacrificing scalability, debugging and other features. 182 This is intended only for the smallest system that had used the 183 SLOB allocator and is not recommended for systems with more than 184 16MB RAM. 185 186 If unsure, say N. 187 188config SLAB_MERGE_DEFAULT 189 bool "Allow slab caches to be merged" 190 default y 191 help 192 For reduced kernel memory fragmentation, slab caches can be 193 merged when they share the same size and other characteristics. 194 This carries a risk of kernel heap overflows being able to 195 overwrite objects from merged caches (and more easily control 196 cache layout), which makes such heap attacks easier to exploit 197 by attackers. By keeping caches unmerged, these kinds of exploits 198 can usually only damage objects in the same cache. To disable 199 merging at runtime, "slab_nomerge" can be passed on the kernel 200 command line. 201 202config SLAB_FREELIST_RANDOM 203 bool "Randomize slab freelist" 204 depends on !SLUB_TINY 205 help 206 Randomizes the freelist order used on creating new pages. This 207 security feature reduces the predictability of the kernel slab 208 allocator against heap overflows. 209 210config SLAB_FREELIST_HARDENED 211 bool "Harden slab freelist metadata" 212 depends on !SLUB_TINY 213 help 214 Many kernel heap attacks try to target slab cache metadata and 215 other infrastructure. This options makes minor performance 216 sacrifices to harden the kernel slab allocator against common 217 freelist exploit methods. 218 219config SLAB_BUCKETS 220 bool "Support allocation from separate kmalloc buckets" 221 depends on !SLUB_TINY 222 default SLAB_FREELIST_HARDENED 223 help 224 Kernel heap attacks frequently depend on being able to create 225 specifically-sized allocations with user-controlled contents 226 that will be allocated into the same kmalloc bucket as a 227 target object. To avoid sharing these allocation buckets, 228 provide an explicitly separated set of buckets to be used for 229 user-controlled allocations. This may very slightly increase 230 memory fragmentation, though in practice it's only a handful 231 of extra pages since the bulk of user-controlled allocations 232 are relatively long-lived. 233 234 If unsure, say Y. 235 236config SLUB_STATS 237 default n 238 bool "Enable performance statistics" 239 depends on SYSFS && !SLUB_TINY 240 help 241 The statistics are useful to debug slab allocation behavior in 242 order find ways to optimize the allocator. This should never be 243 enabled for production use since keeping statistics slows down 244 the allocator by a few percentage points. The slabinfo command 245 supports the determination of the most active slabs to figure 246 out which slabs are relevant to a particular load. 247 Try running: slabinfo -DA 248 249config SLUB_CPU_PARTIAL 250 default y 251 depends on SMP && !SLUB_TINY 252 bool "Enable per cpu partial caches" 253 help 254 Per cpu partial caches accelerate objects allocation and freeing 255 that is local to a processor at the price of more indeterminism 256 in the latency of the free. On overflow these caches will be cleared 257 which requires the taking of locks that may cause latency spikes. 258 Typically one would choose no for a realtime system. 259 260config RANDOM_KMALLOC_CACHES 261 default n 262 depends on !SLUB_TINY 263 bool "Randomize slab caches for normal kmalloc" 264 help 265 A hardening feature that creates multiple copies of slab caches for 266 normal kmalloc allocation and makes kmalloc randomly pick one based 267 on code address, which makes the attackers more difficult to spray 268 vulnerable memory objects on the heap for the purpose of exploiting 269 memory vulnerabilities. 270 271 Currently the number of copies is set to 16, a reasonably large value 272 that effectively diverges the memory objects allocated for different 273 subsystems or modules into different caches, at the expense of a 274 limited degree of memory and CPU overhead that relates to hardware and 275 system workload. 276 277endmenu # Slab allocator options 278 279config SHUFFLE_PAGE_ALLOCATOR 280 bool "Page allocator randomization" 281 default SLAB_FREELIST_RANDOM && ACPI_NUMA 282 help 283 Randomization of the page allocator improves the average 284 utilization of a direct-mapped memory-side-cache. See section 285 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 286 6.2a specification for an example of how a platform advertises 287 the presence of a memory-side-cache. There are also incidental 288 security benefits as it reduces the predictability of page 289 allocations to compliment SLAB_FREELIST_RANDOM, but the 290 default granularity of shuffling on the MAX_PAGE_ORDER i.e, 10th 291 order of pages is selected based on cache utilization benefits 292 on x86. 293 294 While the randomization improves cache utilization it may 295 negatively impact workloads on platforms without a cache. For 296 this reason, by default, the randomization is not enabled even 297 if SHUFFLE_PAGE_ALLOCATOR=y. The randomization may be force enabled 298 with the 'page_alloc.shuffle' kernel command line parameter. 299 300 Say Y if unsure. 301 302config COMPAT_BRK 303 bool "Disable heap randomization" 304 default y 305 help 306 Randomizing heap placement makes heap exploits harder, but it 307 also breaks ancient binaries (including anything libc5 based). 308 This option changes the bootup default to heap randomization 309 disabled, and can be overridden at runtime by setting 310 /proc/sys/kernel/randomize_va_space to 2. 311 312 On non-ancient distros (post-2000 ones) N is usually a safe choice. 313 314config MMAP_ALLOW_UNINITIALIZED 315 bool "Allow mmapped anonymous memory to be uninitialized" 316 depends on EXPERT && !MMU 317 default n 318 help 319 Normally, and according to the Linux spec, anonymous memory obtained 320 from mmap() has its contents cleared before it is passed to 321 userspace. Enabling this config option allows you to request that 322 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 323 providing a huge performance boost. If this option is not enabled, 324 then the flag will be ignored. 325 326 This is taken advantage of by uClibc's malloc(), and also by 327 ELF-FDPIC binfmt's brk and stack allocator. 328 329 Because of the obvious security issues, this option should only be 330 enabled on embedded devices where you control what is run in 331 userspace. Since that isn't generally a problem on no-MMU systems, 332 it is normally safe to say Y here. 333 334 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 335 336config SELECT_MEMORY_MODEL 337 def_bool y 338 depends on ARCH_SELECT_MEMORY_MODEL 339 340choice 341 prompt "Memory model" 342 depends on SELECT_MEMORY_MODEL 343 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT 344 default FLATMEM_MANUAL 345 help 346 This option allows you to change some of the ways that 347 Linux manages its memory internally. Most users will 348 only have one option here selected by the architecture 349 configuration. This is normal. 350 351config FLATMEM_MANUAL 352 bool "Flat Memory" 353 depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE 354 help 355 This option is best suited for non-NUMA systems with 356 flat address space. The FLATMEM is the most efficient 357 system in terms of performance and resource consumption 358 and it is the best option for smaller systems. 359 360 For systems that have holes in their physical address 361 spaces and for features like NUMA and memory hotplug, 362 choose "Sparse Memory". 363 364 If unsure, choose this option (Flat Memory) over any other. 365 366config SPARSEMEM_MANUAL 367 bool "Sparse Memory" 368 depends on ARCH_SPARSEMEM_ENABLE 369 help 370 This will be the only option for some systems, including 371 memory hot-plug systems. This is normal. 372 373 This option provides efficient support for systems with 374 holes is their physical address space and allows memory 375 hot-plug and hot-remove. 376 377 If unsure, choose "Flat Memory" over this option. 378 379endchoice 380 381config SPARSEMEM 382 def_bool y 383 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL 384 385config FLATMEM 386 def_bool y 387 depends on !SPARSEMEM || FLATMEM_MANUAL 388 389# 390# SPARSEMEM_EXTREME (which is the default) does some bootmem 391# allocations when sparse_init() is called. If this cannot 392# be done on your architecture, select this option. However, 393# statically allocating the mem_section[] array can potentially 394# consume vast quantities of .bss, so be careful. 395# 396# This option will also potentially produce smaller runtime code 397# with gcc 3.4 and later. 398# 399config SPARSEMEM_STATIC 400 bool 401 402# 403# Architecture platforms which require a two level mem_section in SPARSEMEM 404# must select this option. This is usually for architecture platforms with 405# an extremely sparse physical address space. 406# 407config SPARSEMEM_EXTREME 408 def_bool y 409 depends on SPARSEMEM && !SPARSEMEM_STATIC 410 411config SPARSEMEM_VMEMMAP_ENABLE 412 bool 413 414config SPARSEMEM_VMEMMAP 415 bool "Sparse Memory virtual memmap" 416 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE 417 default y 418 help 419 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise 420 pfn_to_page and page_to_pfn operations. This is the most 421 efficient option when sufficient kernel resources are available. 422 423config SPARSEMEM_VMEMMAP_PREINIT 424 bool 425# 426# Select this config option from the architecture Kconfig, if it is preferred 427# to enable the feature of HugeTLB/dev_dax vmemmap optimization. 428# 429config ARCH_WANT_OPTIMIZE_DAX_VMEMMAP 430 bool 431 432config ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP 433 bool 434 435config ARCH_WANT_HUGETLB_VMEMMAP_PREINIT 436 bool 437 438config HAVE_MEMBLOCK_PHYS_MAP 439 bool 440 441config HAVE_GUP_FAST 442 depends on MMU 443 bool 444 445# Enable memblock support for scratch memory which is needed for kexec handover 446config MEMBLOCK_KHO_SCRATCH 447 bool 448 449# Don't discard allocated memory used to track "memory" and "reserved" memblocks 450# after early boot, so it can still be used to test for validity of memory. 451# Also, memblocks are updated with memory hot(un)plug. 452config ARCH_KEEP_MEMBLOCK 453 bool 454 455# Keep arch NUMA mapping infrastructure post-init. 456config NUMA_KEEP_MEMINFO 457 bool 458 459config MEMORY_ISOLATION 460 bool 461 462# IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked 463# IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via 464# /dev/mem. 465config EXCLUSIVE_SYSTEM_RAM 466 def_bool y 467 depends on !DEVMEM || STRICT_DEVMEM 468 469# 470# Only be set on architectures that have completely implemented memory hotplug 471# feature. If you are not sure, don't touch it. 472# 473config HAVE_BOOTMEM_INFO_NODE 474 def_bool n 475 476config ARCH_ENABLE_MEMORY_HOTPLUG 477 bool 478 479config ARCH_ENABLE_MEMORY_HOTREMOVE 480 bool 481 482# eventually, we can have this option just 'select SPARSEMEM' 483menuconfig MEMORY_HOTPLUG 484 bool "Memory hotplug" 485 select MEMORY_ISOLATION 486 depends on SPARSEMEM 487 depends on ARCH_ENABLE_MEMORY_HOTPLUG 488 depends on 64BIT 489 select NUMA_KEEP_MEMINFO if NUMA 490 491if MEMORY_HOTPLUG 492 493choice 494 prompt "Memory Hotplug Default Online Type" 495 default MHP_DEFAULT_ONLINE_TYPE_OFFLINE 496 help 497 Default memory type for hotplugged memory. 498 499 This option sets the default policy setting for memory hotplug 500 onlining policy (/sys/devices/system/memory/auto_online_blocks) which 501 determines what happens to newly added memory regions. Policy setting 502 can always be changed at runtime. 503 504 The default is 'offline'. 505 506 Select offline to defer onlining to drivers and user policy. 507 Select auto to let the kernel choose what zones to utilize. 508 Select online_kernel to generally allow kernel usage of this memory. 509 Select online_movable to generally disallow kernel usage of this memory. 510 511 Example kernel usage would be page structs and page tables. 512 513 See Documentation/admin-guide/mm/memory-hotplug.rst for more information. 514 515config MHP_DEFAULT_ONLINE_TYPE_OFFLINE 516 bool "offline" 517 help 518 Hotplugged memory will not be onlined by default. 519 Choose this for systems with drivers and user policy that 520 handle onlining of hotplug memory policy. 521 522config MHP_DEFAULT_ONLINE_TYPE_ONLINE_AUTO 523 bool "auto" 524 help 525 Select this if you want the kernel to automatically online 526 hotplugged memory into the zone it thinks is reasonable. 527 This memory may be utilized for kernel data. 528 529config MHP_DEFAULT_ONLINE_TYPE_ONLINE_KERNEL 530 bool "kernel" 531 help 532 Select this if you want the kernel to automatically online 533 hotplugged memory into a zone capable of being used for kernel 534 data. This typically means ZONE_NORMAL. 535 536config MHP_DEFAULT_ONLINE_TYPE_ONLINE_MOVABLE 537 bool "movable" 538 help 539 Select this if you want the kernel to automatically online 540 hotplug memory into ZONE_MOVABLE. This memory will generally 541 not be utilized for kernel data. 542 543 This should only be used when the admin knows sufficient 544 ZONE_NORMAL memory is available to describe hotplug memory, 545 otherwise hotplug memory may fail to online. For example, 546 sufficient kernel-capable memory (ZONE_NORMAL) must be 547 available to allocate page structs to describe ZONE_MOVABLE. 548 549endchoice 550 551config MEMORY_HOTREMOVE 552 bool "Allow for memory hot remove" 553 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64) 554 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 555 depends on MIGRATION 556 557config MHP_MEMMAP_ON_MEMORY 558 def_bool y 559 depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP 560 depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE 561 562endif # MEMORY_HOTPLUG 563 564config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE 565 bool 566 567# Heavily threaded applications may benefit from splitting the mm-wide 568# page_table_lock, so that faults on different parts of the user address 569# space can be handled with less contention: split it at this NR_CPUS. 570# Default to 4 for wider testing, though 8 might be more appropriate. 571# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 572# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 573# SPARC32 allocates multiple pte tables within a single page, and therefore 574# a per-page lock leads to problems when multiple tables need to be locked 575# at the same time (e.g. copy_page_range()). 576# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 577# 578config SPLIT_PTE_PTLOCKS 579 def_bool y 580 depends on MMU 581 depends on SMP 582 depends on NR_CPUS >= 4 583 depends on !ARM || CPU_CACHE_VIPT 584 depends on !PARISC || PA20 585 depends on !SPARC32 586 587config ARCH_ENABLE_SPLIT_PMD_PTLOCK 588 bool 589 590config SPLIT_PMD_PTLOCKS 591 def_bool y 592 depends on SPLIT_PTE_PTLOCKS && ARCH_ENABLE_SPLIT_PMD_PTLOCK 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 default 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 default 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 help 642 Free page reporting allows for the incremental acquisition of 643 free pages from the buddy allocator for the purpose of reporting 644 those pages to another entity, such as a hypervisor, so that the 645 memory can be freed within the host for other uses. 646 647# 648# support for page migration 649# 650config MIGRATION 651 bool "Page migration" 652 default y 653 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU 654 help 655 Allows the migration of the physical location of pages of processes 656 while the virtual addresses are not changed. This is useful in 657 two situations. The first is on NUMA systems to put pages nearer 658 to the processors accessing. The second is when allocating huge 659 pages as migration can relocate pages to satisfy a huge page 660 allocation instead of reclaiming. 661 662config DEVICE_MIGRATION 663 def_bool MIGRATION && ZONE_DEVICE 664 665config ARCH_ENABLE_HUGEPAGE_MIGRATION 666 bool 667 668config ARCH_ENABLE_THP_MIGRATION 669 bool 670 671config HUGETLB_PAGE_SIZE_VARIABLE 672 def_bool n 673 help 674 Allows the pageblock_order value to be dynamic instead of just standard 675 HUGETLB_PAGE_ORDER when there are multiple HugeTLB page sizes available 676 on a platform. 677 678 Note that the pageblock_order cannot exceed MAX_PAGE_ORDER and will be 679 clamped down to MAX_PAGE_ORDER. 680 681config CONTIG_ALLOC 682 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA 683 684config PCP_BATCH_SCALE_MAX 685 int "Maximum scale factor of PCP (Per-CPU pageset) batch allocate/free" 686 default 5 687 range 0 6 688 help 689 In page allocator, PCP (Per-CPU pageset) is refilled and drained in 690 batches. The batch number is scaled automatically to improve page 691 allocation/free throughput. But too large scale factor may hurt 692 latency. This option sets the upper limit of scale factor to limit 693 the maximum latency. 694 695config PHYS_ADDR_T_64BIT 696 def_bool 64BIT 697 698config BOUNCE 699 bool "Enable bounce buffers" 700 default y 701 depends on BLOCK && MMU && HIGHMEM 702 help 703 Enable bounce buffers for devices that cannot access the full range of 704 memory available to the CPU. Enabled by default when HIGHMEM is 705 selected, but you may say n to override this. 706 707config MMU_NOTIFIER 708 bool 709 select INTERVAL_TREE 710 711config KSM 712 bool "Enable KSM for page merging" 713 depends on MMU 714 select XXHASH 715 help 716 Enable Kernel Samepage Merging: KSM periodically scans those areas 717 of an application's address space that an app has advised may be 718 mergeable. When it finds pages of identical content, it replaces 719 the many instances by a single page with that content, so 720 saving memory until one or another app needs to modify the content. 721 Recommended for use with KVM, or with other duplicative applications. 722 See Documentation/mm/ksm.rst for more information: KSM is inactive 723 until a program has madvised that an area is MADV_MERGEABLE, and 724 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 725 726config DEFAULT_MMAP_MIN_ADDR 727 int "Low address space to protect from user allocation" 728 depends on MMU 729 default 4096 730 help 731 This is the portion of low virtual memory which should be protected 732 from userspace allocation. Keeping a user from writing to low pages 733 can help reduce the impact of kernel NULL pointer bugs. 734 735 For most arm64, ppc64 and x86 users with lots of address space 736 a value of 65536 is reasonable and should cause no problems. 737 On arm and other archs it should not be higher than 32768. 738 Programs which use vm86 functionality or have some need to map 739 this low address space will need CAP_SYS_RAWIO or disable this 740 protection by setting the value to 0. 741 742 This value can be changed after boot using the 743 /proc/sys/vm/mmap_min_addr tunable. 744 745config ARCH_SUPPORTS_MEMORY_FAILURE 746 bool 747 748config MEMORY_FAILURE 749 depends on MMU 750 depends on ARCH_SUPPORTS_MEMORY_FAILURE 751 bool "Enable recovery from hardware memory errors" 752 select MEMORY_ISOLATION 753 select RAS 754 help 755 Enables code to recover from some memory failures on systems 756 with MCA recovery. This allows a system to continue running 757 even when some of its memory has uncorrected errors. This requires 758 special hardware support and typically ECC memory. 759 760config HWPOISON_INJECT 761 tristate "HWPoison pages injector" 762 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 763 select PROC_PAGE_MONITOR 764 765config NOMMU_INITIAL_TRIM_EXCESS 766 int "Turn on mmap() excess space trimming before booting" 767 depends on !MMU 768 default 1 769 help 770 The NOMMU mmap() frequently needs to allocate large contiguous chunks 771 of memory on which to store mappings, but it can only ask the system 772 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 773 more than it requires. To deal with this, mmap() is able to trim off 774 the excess and return it to the allocator. 775 776 If trimming is enabled, the excess is trimmed off and returned to the 777 system allocator, which can cause extra fragmentation, particularly 778 if there are a lot of transient processes. 779 780 If trimming is disabled, the excess is kept, but not used, which for 781 long-term mappings means that the space is wasted. 782 783 Trimming can be dynamically controlled through a sysctl option 784 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 785 excess pages there must be before trimming should occur, or zero if 786 no trimming is to occur. 787 788 This option specifies the initial value of this option. The default 789 of 1 says that all excess pages should be trimmed. 790 791 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 792 793config ARCH_WANT_GENERAL_HUGETLB 794 bool 795 796config ARCH_WANTS_THP_SWAP 797 def_bool n 798 799config PERSISTENT_HUGE_ZERO_FOLIO 800 bool "Allocate a PMD sized folio for zeroing" 801 depends on TRANSPARENT_HUGEPAGE 802 help 803 Enable this option to reduce the runtime refcounting overhead 804 of the huge zero folio and expand the places in the kernel 805 that can use huge zero folios. For instance, block I/O benefits 806 from access to large folios for zeroing memory. 807 808 With this option enabled, the huge zero folio is allocated 809 once and never freed. One full huge page's worth of memory shall 810 be used. 811 812 Say Y if your system has lots of memory. Say N if you are 813 memory constrained. 814 815config MM_ID 816 def_bool n 817 818menuconfig TRANSPARENT_HUGEPAGE 819 bool "Transparent Hugepage Support" 820 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT 821 select COMPACTION 822 select XARRAY_MULTI 823 select MM_ID 824 help 825 Transparent Hugepages allows the kernel to use huge pages and 826 huge tlb transparently to the applications whenever possible. 827 This feature can improve computing performance to certain 828 applications by speeding up page faults during memory 829 allocation, by reducing the number of tlb misses and by speeding 830 up the pagetable walking. 831 832 If memory constrained on embedded, you may want to say N. 833 834if TRANSPARENT_HUGEPAGE 835 836choice 837 prompt "Transparent Hugepage Support sysfs defaults" 838 depends on TRANSPARENT_HUGEPAGE 839 default TRANSPARENT_HUGEPAGE_ALWAYS 840 help 841 Selects the sysfs defaults for Transparent Hugepage Support. 842 843 config TRANSPARENT_HUGEPAGE_ALWAYS 844 bool "always" 845 help 846 Enabling Transparent Hugepage always, can increase the 847 memory footprint of applications without a guaranteed 848 benefit but it will work automatically for all applications. 849 850 config TRANSPARENT_HUGEPAGE_MADVISE 851 bool "madvise" 852 help 853 Enabling Transparent Hugepage madvise, will only provide a 854 performance improvement benefit to the applications using 855 madvise(MADV_HUGEPAGE) but it won't risk to increase the 856 memory footprint of applications without a guaranteed 857 benefit. 858 859 config TRANSPARENT_HUGEPAGE_NEVER 860 bool "never" 861 help 862 Disable Transparent Hugepage by default. It can still be 863 enabled at runtime via sysfs. 864endchoice 865 866config THP_SWAP 867 def_bool y 868 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT 869 help 870 Swap transparent huge pages in one piece, without splitting. 871 XXX: For now, swap cluster backing transparent huge page 872 will be split after swapout. 873 874 For selection by architectures with reasonable THP sizes. 875 876config READ_ONLY_THP_FOR_FS 877 bool "Read-only THP for filesystems (EXPERIMENTAL)" 878 depends on TRANSPARENT_HUGEPAGE 879 880 help 881 Allow khugepaged to put read-only file-backed pages in THP. 882 883 This is marked experimental because it is a new feature. Write 884 support of file THPs will be developed in the next few release 885 cycles. 886 887config NO_PAGE_MAPCOUNT 888 bool "No per-page mapcount (EXPERIMENTAL)" 889 help 890 Do not maintain per-page mapcounts for pages part of larger 891 allocations, such as transparent huge pages. 892 893 When this config option is enabled, some interfaces that relied on 894 this information will rely on less-precise per-allocation information 895 instead: for example, using the average per-page mapcount in such 896 a large allocation instead of the per-page mapcount. 897 898 EXPERIMENTAL because the impact of some changes is still unclear. 899 900endif # TRANSPARENT_HUGEPAGE 901 902# simple helper to make the code a bit easier to read 903config PAGE_MAPCOUNT 904 def_bool !NO_PAGE_MAPCOUNT 905 906# 907# The architecture supports pgtable leaves that is larger than PAGE_SIZE 908# 909config PGTABLE_HAS_HUGE_LEAVES 910 def_bool TRANSPARENT_HUGEPAGE || HUGETLB_PAGE 911 912# TODO: Allow to be enabled without THP 913config ARCH_SUPPORTS_HUGE_PFNMAP 914 def_bool n 915 depends on TRANSPARENT_HUGEPAGE 916 917config ARCH_SUPPORTS_PMD_PFNMAP 918 def_bool y 919 depends on ARCH_SUPPORTS_HUGE_PFNMAP && HAVE_ARCH_TRANSPARENT_HUGEPAGE 920 921config ARCH_SUPPORTS_PUD_PFNMAP 922 def_bool y 923 depends on ARCH_SUPPORTS_HUGE_PFNMAP && HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 924 925# 926# Architectures that always use weak definitions for percpu 927# variables in modules should set this. 928# 929config ARCH_MODULE_NEEDS_WEAK_PER_CPU 930 bool 931 932# 933# UP and nommu archs use km based percpu allocator 934# 935config NEED_PER_CPU_KM 936 depends on !SMP || !MMU 937 bool 938 default y 939 940config NEED_PER_CPU_EMBED_FIRST_CHUNK 941 bool 942 943config NEED_PER_CPU_PAGE_FIRST_CHUNK 944 bool 945 946config USE_PERCPU_NUMA_NODE_ID 947 bool 948 949config HAVE_SETUP_PER_CPU_AREA 950 bool 951 952config CMA 953 bool "Contiguous Memory Allocator" 954 depends on MMU 955 select MIGRATION 956 select MEMORY_ISOLATION 957 help 958 This enables the Contiguous Memory Allocator which allows other 959 subsystems to allocate big physically-contiguous blocks of memory. 960 CMA reserves a region of memory and allows only movable pages to 961 be allocated from it. This way, the kernel can use the memory for 962 pagecache and when a subsystem requests for contiguous area, the 963 allocated pages are migrated away to serve the contiguous request. 964 965 If unsure, say "n". 966 967config CMA_DEBUGFS 968 bool "CMA debugfs interface" 969 depends on CMA && DEBUG_FS 970 help 971 Turns on the DebugFS interface for CMA. 972 973config CMA_SYSFS 974 bool "CMA information through sysfs interface" 975 depends on CMA && SYSFS 976 help 977 This option exposes some sysfs attributes to get information 978 from CMA. 979 980config CMA_AREAS 981 int "Maximum count of the CMA areas" 982 depends on CMA 983 default 20 if NUMA 984 default 8 985 help 986 CMA allows to create CMA areas for particular purpose, mainly, 987 used as device private area. This parameter sets the maximum 988 number of CMA area in the system. 989 990 If unsure, leave the default value "8" in UMA and "20" in NUMA. 991 992# 993# Select this config option from the architecture Kconfig, if available, to set 994# the max page order for physically contiguous allocations. 995# 996config ARCH_FORCE_MAX_ORDER 997 int 998 999# 1000# When ARCH_FORCE_MAX_ORDER is not defined, 1001# the default page block order is MAX_PAGE_ORDER (10) as per 1002# include/linux/mmzone.h. 1003# 1004config PAGE_BLOCK_MAX_ORDER 1005 int "Page Block Order Upper Limit" 1006 range 1 10 if ARCH_FORCE_MAX_ORDER = 0 1007 default 10 if ARCH_FORCE_MAX_ORDER = 0 1008 range 1 ARCH_FORCE_MAX_ORDER if ARCH_FORCE_MAX_ORDER != 0 1009 default ARCH_FORCE_MAX_ORDER if ARCH_FORCE_MAX_ORDER != 0 1010 help 1011 The page block order refers to the power of two number of pages that 1012 are physically contiguous and can have a migrate type associated to 1013 them. The maximum size of the page block order is at least limited by 1014 ARCH_FORCE_MAX_ORDER/MAX_PAGE_ORDER. 1015 1016 This config adds a new upper limit of default page block 1017 order when the page block order is required to be smaller than 1018 ARCH_FORCE_MAX_ORDER/MAX_PAGE_ORDER or other limits 1019 (see include/linux/pageblock-flags.h for details). 1020 1021 Reducing pageblock order can negatively impact THP generation 1022 success rate. If your workloads use THP heavily, please use this 1023 option with caution. 1024 1025 Don't change if unsure. 1026 1027config MEM_SOFT_DIRTY 1028 bool "Track memory changes" 1029 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 1030 select PROC_PAGE_MONITOR 1031 help 1032 This option enables memory changes tracking by introducing a 1033 soft-dirty bit on pte-s. This bit it set when someone writes 1034 into a page just as regular dirty bit, but unlike the latter 1035 it can be cleared by hands. 1036 1037 See Documentation/admin-guide/mm/soft-dirty.rst for more details. 1038 1039config GENERIC_EARLY_IOREMAP 1040 bool 1041 1042config STACK_MAX_DEFAULT_SIZE_MB 1043 int "Default maximum user stack size for 32-bit processes (MB)" 1044 default 100 1045 range 8 2048 1046 depends on STACK_GROWSUP && (!64BIT || COMPAT) 1047 help 1048 This is the maximum stack size in Megabytes in the VM layout of 32-bit 1049 user processes when the stack grows upwards (currently only on parisc 1050 arch) when the RLIMIT_STACK hard limit is unlimited. 1051 1052 A sane initial value is 100 MB. 1053 1054config DEFERRED_STRUCT_PAGE_INIT 1055 bool "Defer initialisation of struct pages to kthreads" 1056 depends on SPARSEMEM 1057 depends on !NEED_PER_CPU_KM 1058 depends on 64BIT 1059 depends on !KMSAN 1060 select PADATA 1061 help 1062 Ordinarily all struct pages are initialised during early boot in a 1063 single thread. On very large machines this can take a considerable 1064 amount of time. If this option is set, large machines will bring up 1065 a subset of memmap at boot and then initialise the rest in parallel. 1066 This has a potential performance impact on tasks running early in the 1067 lifetime of the system until these kthreads finish the 1068 initialisation. 1069 1070config PAGE_IDLE_FLAG 1071 bool 1072 select PAGE_EXTENSION if !64BIT 1073 help 1074 This adds PG_idle and PG_young flags to 'struct page'. PTE Accessed 1075 bit writers can set the state of the bit in the flags so that PTE 1076 Accessed bit readers may avoid disturbance. 1077 1078config IDLE_PAGE_TRACKING 1079 bool "Enable idle page tracking" 1080 depends on SYSFS && MMU 1081 select PAGE_IDLE_FLAG 1082 help 1083 This feature allows to estimate the amount of user pages that have 1084 not been touched during a given period of time. This information can 1085 be useful to tune memory cgroup limits and/or for job placement 1086 within a compute cluster. 1087 1088 See Documentation/admin-guide/mm/idle_page_tracking.rst for 1089 more details. 1090 1091# Architectures which implement cpu_dcache_is_aliasing() to query 1092# whether the data caches are aliased (VIVT or VIPT with dcache 1093# aliasing) need to select this. 1094config ARCH_HAS_CPU_CACHE_ALIASING 1095 bool 1096 1097config ARCH_HAS_CACHE_LINE_SIZE 1098 bool 1099 1100config ARCH_HAS_CURRENT_STACK_POINTER 1101 bool 1102 help 1103 In support of HARDENED_USERCOPY performing stack variable lifetime 1104 checking, an architecture-agnostic way to find the stack pointer 1105 is needed. Once an architecture defines an unsigned long global 1106 register alias named "current_stack_pointer", this config can be 1107 selected. 1108 1109config ARCH_HAS_ZONE_DMA_SET 1110 bool 1111 1112config ZONE_DMA 1113 bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET 1114 default y if ARM64 || X86 1115 1116config ZONE_DMA32 1117 bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET 1118 depends on !X86_32 1119 default y if ARM64 1120 1121config ZONE_DEVICE 1122 bool "Device memory (pmem, HMM, etc...) hotplug support" 1123 depends on MEMORY_HOTPLUG 1124 depends on MEMORY_HOTREMOVE 1125 depends on SPARSEMEM_VMEMMAP 1126 select XARRAY_MULTI 1127 1128 help 1129 Device memory hotplug support allows for establishing pmem, 1130 or other device driver discovered memory regions, in the 1131 memmap. This allows pfn_to_page() lookups of otherwise 1132 "device-physical" addresses which is needed for using a DAX 1133 mapping in an O_DIRECT operation, among other things. 1134 1135 If FS_DAX is enabled, then say Y. 1136 1137# 1138# Helpers to mirror range of the CPU page tables of a process into device page 1139# tables. 1140# 1141config HMM_MIRROR 1142 bool 1143 depends on MMU 1144 1145config GET_FREE_REGION 1146 bool 1147 1148config DEVICE_PRIVATE 1149 bool "Unaddressable device memory (GPU memory, ...)" 1150 depends on ZONE_DEVICE 1151 select GET_FREE_REGION 1152 1153 help 1154 Allows creation of struct pages to represent unaddressable device 1155 memory; i.e., memory that is only accessible from the device (or 1156 group of devices). You likely also want to select HMM_MIRROR. 1157 1158config VMAP_PFN 1159 bool 1160 1161config ARCH_USES_HIGH_VMA_FLAGS 1162 bool 1163config ARCH_HAS_PKEYS 1164 bool 1165 1166config ARCH_USES_PG_ARCH_2 1167 bool 1168config ARCH_USES_PG_ARCH_3 1169 bool 1170 1171config VM_EVENT_COUNTERS 1172 default y 1173 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1174 help 1175 VM event counters are needed for event counts to be shown. 1176 This option allows the disabling of the VM event counters 1177 on EXPERT systems. /proc/vmstat will only show page counts 1178 if VM event counters are disabled. 1179 1180config PERCPU_STATS 1181 bool "Collect percpu memory statistics" 1182 help 1183 This feature collects and exposes statistics via debugfs. The 1184 information includes global and per chunk statistics, which can 1185 be used to help understand percpu memory usage. 1186 1187config GUP_TEST 1188 bool "Enable infrastructure for get_user_pages()-related unit tests" 1189 depends on DEBUG_FS 1190 help 1191 Provides /sys/kernel/debug/gup_test, which in turn provides a way 1192 to make ioctl calls that can launch kernel-based unit tests for 1193 the get_user_pages*() and pin_user_pages*() family of API calls. 1194 1195 These tests include benchmark testing of the _fast variants of 1196 get_user_pages*() and pin_user_pages*(), as well as smoke tests of 1197 the non-_fast variants. 1198 1199 There is also a sub-test that allows running dump_page() on any 1200 of up to eight pages (selected by command line args) within the 1201 range of user-space addresses. These pages are either pinned via 1202 pin_user_pages*(), or pinned via get_user_pages*(), as specified 1203 by other command line arguments. 1204 1205 See tools/testing/selftests/mm/gup_test.c 1206 1207comment "GUP_TEST needs to have DEBUG_FS enabled" 1208 depends on !GUP_TEST && !DEBUG_FS 1209 1210config GUP_GET_PXX_LOW_HIGH 1211 bool 1212 1213config DMAPOOL_TEST 1214 tristate "Enable a module to run time tests on dma_pool" 1215 depends on HAS_DMA 1216 help 1217 Provides a test module that will allocate and free many blocks of 1218 various sizes and report how long it takes. This is intended to 1219 provide a consistent way to measure how changes to the 1220 dma_pool_alloc/free routines affect performance. 1221 1222config ARCH_HAS_PTE_SPECIAL 1223 bool 1224 1225config MAPPING_DIRTY_HELPERS 1226 bool 1227 1228config KMAP_LOCAL 1229 bool 1230 1231config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY 1232 bool 1233 1234config MEMFD_CREATE 1235 bool "Enable memfd_create() system call" if EXPERT 1236 1237config SECRETMEM 1238 default y 1239 bool "Enable memfd_secret() system call" if EXPERT 1240 depends on ARCH_HAS_SET_DIRECT_MAP 1241 help 1242 Enable the memfd_secret() system call with the ability to create 1243 memory areas visible only in the context of the owning process and 1244 not mapped to other processes and other kernel page tables. 1245 1246config ANON_VMA_NAME 1247 bool "Anonymous VMA name support" 1248 depends on PROC_FS && ADVISE_SYSCALLS && MMU 1249 1250 help 1251 Allow naming anonymous virtual memory areas. 1252 1253 This feature allows assigning names to virtual memory areas. Assigned 1254 names can be later retrieved from /proc/pid/maps and /proc/pid/smaps 1255 and help identifying individual anonymous memory areas. 1256 Assigning a name to anonymous virtual memory area might prevent that 1257 area from being merged with adjacent virtual memory areas due to the 1258 difference in their name. 1259 1260config HAVE_ARCH_USERFAULTFD_WP 1261 bool 1262 help 1263 Arch has userfaultfd write protection support 1264 1265config HAVE_ARCH_USERFAULTFD_MINOR 1266 bool 1267 help 1268 Arch has userfaultfd minor fault support 1269 1270menuconfig USERFAULTFD 1271 bool "Enable userfaultfd() system call" 1272 depends on MMU 1273 help 1274 Enable the userfaultfd() system call that allows to intercept and 1275 handle page faults in userland. 1276 1277if USERFAULTFD 1278config PTE_MARKER_UFFD_WP 1279 bool "Userfaultfd write protection support for shmem/hugetlbfs" 1280 default y 1281 depends on HAVE_ARCH_USERFAULTFD_WP 1282 1283 help 1284 Allows to create marker PTEs for userfaultfd write protection 1285 purposes. It is required to enable userfaultfd write protection on 1286 file-backed memory types like shmem and hugetlbfs. 1287endif # USERFAULTFD 1288 1289# multi-gen LRU { 1290config LRU_GEN 1291 bool "Multi-Gen LRU" 1292 depends on MMU 1293 # make sure folio->flags has enough spare bits 1294 depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP 1295 help 1296 A high performance LRU implementation to overcommit memory. See 1297 Documentation/admin-guide/mm/multigen_lru.rst for details. 1298 1299config LRU_GEN_ENABLED 1300 bool "Enable by default" 1301 depends on LRU_GEN 1302 help 1303 This option enables the multi-gen LRU by default. 1304 1305config LRU_GEN_STATS 1306 bool "Full stats for debugging" 1307 depends on LRU_GEN 1308 help 1309 Do not enable this option unless you plan to look at historical stats 1310 from evicted generations for debugging purpose. 1311 1312 This option has a per-memcg and per-node memory overhead. 1313 1314config LRU_GEN_WALKS_MMU 1315 def_bool y 1316 depends on LRU_GEN && ARCH_HAS_HW_PTE_YOUNG 1317# } 1318 1319config ARCH_SUPPORTS_PER_VMA_LOCK 1320 def_bool n 1321 1322config PER_VMA_LOCK 1323 def_bool y 1324 depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP 1325 help 1326 Allow per-vma locking during page fault handling. 1327 1328 This feature allows locking each virtual memory area separately when 1329 handling page faults instead of taking mmap_lock. 1330 1331config LOCK_MM_AND_FIND_VMA 1332 bool 1333 depends on !STACK_GROWSUP 1334 1335config IOMMU_MM_DATA 1336 bool 1337 1338config EXECMEM 1339 bool 1340 1341config NUMA_MEMBLKS 1342 bool 1343 1344config NUMA_EMU 1345 bool "NUMA emulation" 1346 depends on NUMA_MEMBLKS 1347 depends on X86 || GENERIC_ARCH_NUMA 1348 help 1349 Enable NUMA emulation. A flat machine will be split 1350 into virtual nodes when booted with "numa=fake=N", where N is the 1351 number of nodes. This is only useful for debugging. 1352 1353config ARCH_HAS_USER_SHADOW_STACK 1354 bool 1355 help 1356 The architecture has hardware support for userspace shadow call 1357 stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss). 1358 1359config ARCH_SUPPORTS_PT_RECLAIM 1360 def_bool n 1361 1362config PT_RECLAIM 1363 bool "reclaim empty user page table pages" 1364 default y 1365 depends on ARCH_SUPPORTS_PT_RECLAIM && MMU && SMP 1366 select MMU_GATHER_RCU_TABLE_FREE 1367 help 1368 Try to reclaim empty user page table pages in paths other than munmap 1369 and exit_mmap path. 1370 1371 Note: now only empty user PTE page table pages will be reclaimed. 1372 1373config FIND_NORMAL_PAGE 1374 def_bool n 1375 1376source "mm/damon/Kconfig" 1377 1378endmenu 1379