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 select IRQ_WORK 171 172config KVFREE_RCU_BATCHED 173 def_bool y 174 depends on !SLUB_TINY && !TINY_RCU 175 176config SLUB_TINY 177 bool "Configure for minimal memory footprint" 178 depends on EXPERT && !COMPILE_TEST 179 select SLAB_MERGE_DEFAULT 180 help 181 Configures the slab allocator in a way to achieve minimal memory 182 footprint, sacrificing scalability, debugging and other features. 183 This is intended only for the smallest system that had used the 184 SLOB allocator and is not recommended for systems with more than 185 16MB RAM. 186 187 If unsure, say N. 188 189config SLAB_MERGE_DEFAULT 190 bool "Allow slab caches to be merged" 191 default y 192 help 193 For reduced kernel memory fragmentation, slab caches can be 194 merged when they share the same size and other characteristics. 195 This carries a risk of kernel heap overflows being able to 196 overwrite objects from merged caches (and more easily control 197 cache layout), which makes such heap attacks easier to exploit 198 by attackers. By keeping caches unmerged, these kinds of exploits 199 can usually only damage objects in the same cache. To disable 200 merging at runtime, "slab_nomerge" can be passed on the kernel 201 command line. 202 203config SLAB_FREELIST_RANDOM 204 bool "Randomize slab freelist" 205 depends on !SLUB_TINY 206 help 207 Randomizes the freelist order used on creating new pages. This 208 security feature reduces the predictability of the kernel slab 209 allocator against heap overflows. 210 211config SLAB_FREELIST_HARDENED 212 bool "Harden slab freelist metadata" 213 depends on !SLUB_TINY 214 help 215 Many kernel heap attacks try to target slab cache metadata and 216 other infrastructure. This options makes minor performance 217 sacrifices to harden the kernel slab allocator against common 218 freelist exploit methods. 219 220config SLAB_BUCKETS 221 bool "Support allocation from separate kmalloc buckets" 222 depends on !SLUB_TINY 223 default SLAB_FREELIST_HARDENED 224 help 225 Kernel heap attacks frequently depend on being able to create 226 specifically-sized allocations with user-controlled contents 227 that will be allocated into the same kmalloc bucket as a 228 target object. To avoid sharing these allocation buckets, 229 provide an explicitly separated set of buckets to be used for 230 user-controlled allocations. This may very slightly increase 231 memory fragmentation, though in practice it's only a handful 232 of extra pages since the bulk of user-controlled allocations 233 are relatively long-lived. 234 235 If unsure, say Y. 236 237config SLUB_STATS 238 default n 239 bool "Enable performance statistics" 240 depends on SYSFS && !SLUB_TINY 241 help 242 The statistics are useful to debug slab allocation behavior in 243 order find ways to optimize the allocator. This should never be 244 enabled for production use since keeping statistics slows down 245 the allocator by a few percentage points. The slabinfo command 246 supports the determination of the most active slabs to figure 247 out which slabs are relevant to a particular load. 248 Try running: slabinfo -DA 249 250config SLUB_CPU_PARTIAL 251 default y 252 depends on SMP && !SLUB_TINY 253 bool "Enable per cpu partial caches" 254 help 255 Per cpu partial caches accelerate objects allocation and freeing 256 that is local to a processor at the price of more indeterminism 257 in the latency of the free. On overflow these caches will be cleared 258 which requires the taking of locks that may cause latency spikes. 259 Typically one would choose no for a realtime system. 260 261config RANDOM_KMALLOC_CACHES 262 default n 263 depends on !SLUB_TINY 264 bool "Randomize slab caches for normal kmalloc" 265 help 266 A hardening feature that creates multiple copies of slab caches for 267 normal kmalloc allocation and makes kmalloc randomly pick one based 268 on code address, which makes the attackers more difficult to spray 269 vulnerable memory objects on the heap for the purpose of exploiting 270 memory vulnerabilities. 271 272 Currently the number of copies is set to 16, a reasonably large value 273 that effectively diverges the memory objects allocated for different 274 subsystems or modules into different caches, at the expense of a 275 limited degree of memory and CPU overhead that relates to hardware and 276 system workload. 277 278endmenu # Slab allocator options 279 280config SHUFFLE_PAGE_ALLOCATOR 281 bool "Page allocator randomization" 282 default SLAB_FREELIST_RANDOM && ACPI_NUMA 283 help 284 Randomization of the page allocator improves the average 285 utilization of a direct-mapped memory-side-cache. See section 286 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI 287 6.2a specification for an example of how a platform advertises 288 the presence of a memory-side-cache. There are also incidental 289 security benefits as it reduces the predictability of page 290 allocations to compliment SLAB_FREELIST_RANDOM, but the 291 default granularity of shuffling on the MAX_PAGE_ORDER i.e, 10th 292 order of pages is selected based on cache utilization benefits 293 on x86. 294 295 While the randomization improves cache utilization it may 296 negatively impact workloads on platforms without a cache. For 297 this reason, by default, the randomization is not enabled even 298 if SHUFFLE_PAGE_ALLOCATOR=y. The randomization may be force enabled 299 with the 'page_alloc.shuffle' kernel command line parameter. 300 301 Say Y if unsure. 302 303config COMPAT_BRK 304 bool "Disable heap randomization" 305 default y 306 help 307 Randomizing heap placement makes heap exploits harder, but it 308 also breaks ancient binaries (including anything libc5 based). 309 This option changes the bootup default to heap randomization 310 disabled, and can be overridden at runtime by setting 311 /proc/sys/kernel/randomize_va_space to 2. 312 313 On non-ancient distros (post-2000 ones) N is usually a safe choice. 314 315config MMAP_ALLOW_UNINITIALIZED 316 bool "Allow mmapped anonymous memory to be uninitialized" 317 depends on EXPERT && !MMU 318 default n 319 help 320 Normally, and according to the Linux spec, anonymous memory obtained 321 from mmap() has its contents cleared before it is passed to 322 userspace. Enabling this config option allows you to request that 323 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus 324 providing a huge performance boost. If this option is not enabled, 325 then the flag will be ignored. 326 327 This is taken advantage of by uClibc's malloc(), and also by 328 ELF-FDPIC binfmt's brk and stack allocator. 329 330 Because of the obvious security issues, this option should only be 331 enabled on embedded devices where you control what is run in 332 userspace. Since that isn't generally a problem on no-MMU systems, 333 it is normally safe to say Y here. 334 335 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 336 337config SELECT_MEMORY_MODEL 338 def_bool y 339 depends on ARCH_SELECT_MEMORY_MODEL 340 341choice 342 prompt "Memory model" 343 depends on SELECT_MEMORY_MODEL 344 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT 345 default FLATMEM_MANUAL 346 help 347 This option allows you to change some of the ways that 348 Linux manages its memory internally. Most users will 349 only have one option here selected by the architecture 350 configuration. This is normal. 351 352config FLATMEM_MANUAL 353 bool "Flat Memory" 354 depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE 355 help 356 This option is best suited for non-NUMA systems with 357 flat address space. The FLATMEM is the most efficient 358 system in terms of performance and resource consumption 359 and it is the best option for smaller systems. 360 361 For systems that have holes in their physical address 362 spaces and for features like NUMA and memory hotplug, 363 choose "Sparse Memory". 364 365 If unsure, choose this option (Flat Memory) over any other. 366 367config SPARSEMEM_MANUAL 368 bool "Sparse Memory" 369 depends on ARCH_SPARSEMEM_ENABLE 370 help 371 This will be the only option for some systems, including 372 memory hot-plug systems. This is normal. 373 374 This option provides efficient support for systems with 375 holes is their physical address space and allows memory 376 hot-plug and hot-remove. 377 378 If unsure, choose "Flat Memory" over this option. 379 380endchoice 381 382config SPARSEMEM 383 def_bool y 384 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL 385 386config FLATMEM 387 def_bool y 388 depends on !SPARSEMEM || FLATMEM_MANUAL 389 390# 391# SPARSEMEM_EXTREME (which is the default) does some bootmem 392# allocations when sparse_init() is called. If this cannot 393# be done on your architecture, select this option. However, 394# statically allocating the mem_section[] array can potentially 395# consume vast quantities of .bss, so be careful. 396# 397# This option will also potentially produce smaller runtime code 398# with gcc 3.4 and later. 399# 400config SPARSEMEM_STATIC 401 bool 402 403# 404# Architecture platforms which require a two level mem_section in SPARSEMEM 405# must select this option. This is usually for architecture platforms with 406# an extremely sparse physical address space. 407# 408config SPARSEMEM_EXTREME 409 def_bool y 410 depends on SPARSEMEM && !SPARSEMEM_STATIC 411 412config SPARSEMEM_VMEMMAP_ENABLE 413 bool 414 415config SPARSEMEM_VMEMMAP 416 def_bool y 417 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE 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 RAS 753 help 754 Enables code to recover from some memory failures on systems 755 with MCA recovery. This allows a system to continue running 756 even when some of its memory has uncorrected errors. This requires 757 special hardware support and typically ECC memory. 758 759config HWPOISON_INJECT 760 tristate "HWPoison pages injector" 761 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 762 select PROC_PAGE_MONITOR 763 764config NOMMU_INITIAL_TRIM_EXCESS 765 int "Turn on mmap() excess space trimming before booting" 766 depends on !MMU 767 default 1 768 help 769 The NOMMU mmap() frequently needs to allocate large contiguous chunks 770 of memory on which to store mappings, but it can only ask the system 771 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 772 more than it requires. To deal with this, mmap() is able to trim off 773 the excess and return it to the allocator. 774 775 If trimming is enabled, the excess is trimmed off and returned to the 776 system allocator, which can cause extra fragmentation, particularly 777 if there are a lot of transient processes. 778 779 If trimming is disabled, the excess is kept, but not used, which for 780 long-term mappings means that the space is wasted. 781 782 Trimming can be dynamically controlled through a sysctl option 783 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 784 excess pages there must be before trimming should occur, or zero if 785 no trimming is to occur. 786 787 This option specifies the initial value of this option. The default 788 of 1 says that all excess pages should be trimmed. 789 790 See Documentation/admin-guide/mm/nommu-mmap.rst for more information. 791 792config ARCH_WANT_GENERAL_HUGETLB 793 bool 794 795config ARCH_WANTS_THP_SWAP 796 def_bool n 797 798config PERSISTENT_HUGE_ZERO_FOLIO 799 bool "Allocate a PMD sized folio for zeroing" 800 depends on TRANSPARENT_HUGEPAGE 801 help 802 Enable this option to reduce the runtime refcounting overhead 803 of the huge zero folio and expand the places in the kernel 804 that can use huge zero folios. For instance, block I/O benefits 805 from access to large folios for zeroing memory. 806 807 With this option enabled, the huge zero folio is allocated 808 once and never freed. One full huge page's worth of memory shall 809 be used. 810 811 Say Y if your system has lots of memory. Say N if you are 812 memory constrained. 813 814config MM_ID 815 def_bool n 816 817menuconfig TRANSPARENT_HUGEPAGE 818 bool "Transparent Hugepage Support" 819 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT 820 select COMPACTION 821 select XARRAY_MULTI 822 select MM_ID 823 help 824 Transparent Hugepages allows the kernel to use huge pages and 825 huge tlb transparently to the applications whenever possible. 826 This feature can improve computing performance to certain 827 applications by speeding up page faults during memory 828 allocation, by reducing the number of tlb misses and by speeding 829 up the pagetable walking. 830 831 If memory constrained on embedded, you may want to say N. 832 833if TRANSPARENT_HUGEPAGE 834 835choice 836 prompt "Transparent Hugepage Support sysfs defaults" 837 depends on TRANSPARENT_HUGEPAGE 838 default TRANSPARENT_HUGEPAGE_ALWAYS 839 help 840 Selects the sysfs defaults for Transparent Hugepage Support. 841 842 config TRANSPARENT_HUGEPAGE_ALWAYS 843 bool "always" 844 help 845 Enabling Transparent Hugepage always, can increase the 846 memory footprint of applications without a guaranteed 847 benefit but it will work automatically for all applications. 848 849 config TRANSPARENT_HUGEPAGE_MADVISE 850 bool "madvise" 851 help 852 Enabling Transparent Hugepage madvise, will only provide a 853 performance improvement benefit to the applications using 854 madvise(MADV_HUGEPAGE) but it won't risk to increase the 855 memory footprint of applications without a guaranteed 856 benefit. 857 858 config TRANSPARENT_HUGEPAGE_NEVER 859 bool "never" 860 help 861 Disable Transparent Hugepage by default. It can still be 862 enabled at runtime via sysfs. 863endchoice 864 865config THP_SWAP 866 def_bool y 867 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT 868 help 869 Swap transparent huge pages in one piece, without splitting. 870 XXX: For now, swap cluster backing transparent huge page 871 will be split after swapout. 872 873 For selection by architectures with reasonable THP sizes. 874 875config READ_ONLY_THP_FOR_FS 876 bool "Read-only THP for filesystems (EXPERIMENTAL)" 877 depends on TRANSPARENT_HUGEPAGE 878 879 help 880 Allow khugepaged to put read-only file-backed pages in THP. 881 882 This is marked experimental because it is a new feature. Write 883 support of file THPs will be developed in the next few release 884 cycles. 885 886config NO_PAGE_MAPCOUNT 887 bool "No per-page mapcount (EXPERIMENTAL)" 888 help 889 Do not maintain per-page mapcounts for pages part of larger 890 allocations, such as transparent huge pages. 891 892 When this config option is enabled, some interfaces that relied on 893 this information will rely on less-precise per-allocation information 894 instead: for example, using the average per-page mapcount in such 895 a large allocation instead of the per-page mapcount. 896 897 EXPERIMENTAL because the impact of some changes is still unclear. 898 899endif # TRANSPARENT_HUGEPAGE 900 901# simple helper to make the code a bit easier to read 902config PAGE_MAPCOUNT 903 def_bool !NO_PAGE_MAPCOUNT 904 905# 906# The architecture supports pgtable leaves that is larger than PAGE_SIZE 907# 908config PGTABLE_HAS_HUGE_LEAVES 909 def_bool TRANSPARENT_HUGEPAGE || HUGETLB_PAGE 910 911# 912# We can end up creating gigantic folio. 913# 914config HAVE_GIGANTIC_FOLIOS 915 def_bool (HUGETLB_PAGE && ARCH_HAS_GIGANTIC_PAGE) || \ 916 (ZONE_DEVICE && HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) 917 918# TODO: Allow to be enabled without THP 919config ARCH_SUPPORTS_HUGE_PFNMAP 920 def_bool n 921 depends on TRANSPARENT_HUGEPAGE 922 923config ARCH_SUPPORTS_PMD_PFNMAP 924 def_bool y 925 depends on ARCH_SUPPORTS_HUGE_PFNMAP && HAVE_ARCH_TRANSPARENT_HUGEPAGE 926 927config ARCH_SUPPORTS_PUD_PFNMAP 928 def_bool y 929 depends on ARCH_SUPPORTS_HUGE_PFNMAP && HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD 930 931# 932# Architectures that always use weak definitions for percpu 933# variables in modules should set this. 934# 935config ARCH_MODULE_NEEDS_WEAK_PER_CPU 936 bool 937 938# 939# UP and nommu archs use km based percpu allocator 940# 941config NEED_PER_CPU_KM 942 depends on !SMP || !MMU 943 bool 944 default y 945 946config NEED_PER_CPU_EMBED_FIRST_CHUNK 947 bool 948 949config NEED_PER_CPU_PAGE_FIRST_CHUNK 950 bool 951 952config USE_PERCPU_NUMA_NODE_ID 953 bool 954 955config HAVE_SETUP_PER_CPU_AREA 956 bool 957 958config CMA 959 bool "Contiguous Memory Allocator" 960 depends on MMU 961 select MIGRATION 962 select MEMORY_ISOLATION 963 help 964 This enables the Contiguous Memory Allocator which allows other 965 subsystems to allocate big physically-contiguous blocks of memory. 966 CMA reserves a region of memory and allows only movable pages to 967 be allocated from it. This way, the kernel can use the memory for 968 pagecache and when a subsystem requests for contiguous area, the 969 allocated pages are migrated away to serve the contiguous request. 970 971 If unsure, say "n". 972 973config CMA_DEBUGFS 974 bool "CMA debugfs interface" 975 depends on CMA && DEBUG_FS 976 help 977 Turns on the DebugFS interface for CMA. 978 979config CMA_SYSFS 980 bool "CMA information through sysfs interface" 981 depends on CMA && SYSFS 982 help 983 This option exposes some sysfs attributes to get information 984 from CMA. 985 986config CMA_AREAS 987 int "Maximum count of the CMA areas" 988 depends on CMA 989 default 20 if NUMA 990 default 8 991 help 992 CMA allows to create CMA areas for particular purpose, mainly, 993 used as device private area. This parameter sets the maximum 994 number of CMA area in the system. 995 996 If unsure, leave the default value "8" in UMA and "20" in NUMA. 997 998# 999# Select this config option from the architecture Kconfig, if available, to set 1000# the max page order for physically contiguous allocations. 1001# 1002config ARCH_FORCE_MAX_ORDER 1003 int 1004 1005# 1006# When ARCH_FORCE_MAX_ORDER is not defined, 1007# the default page block order is MAX_PAGE_ORDER (10) as per 1008# include/linux/mmzone.h. 1009# 1010config PAGE_BLOCK_MAX_ORDER 1011 int "Page Block Order Upper Limit" 1012 range 1 10 if ARCH_FORCE_MAX_ORDER = 0 1013 default 10 if ARCH_FORCE_MAX_ORDER = 0 1014 range 1 ARCH_FORCE_MAX_ORDER if ARCH_FORCE_MAX_ORDER != 0 1015 default ARCH_FORCE_MAX_ORDER if ARCH_FORCE_MAX_ORDER != 0 1016 help 1017 The page block order refers to the power of two number of pages that 1018 are physically contiguous and can have a migrate type associated to 1019 them. The maximum size of the page block order is at least limited by 1020 ARCH_FORCE_MAX_ORDER/MAX_PAGE_ORDER. 1021 1022 This config adds a new upper limit of default page block 1023 order when the page block order is required to be smaller than 1024 ARCH_FORCE_MAX_ORDER/MAX_PAGE_ORDER or other limits 1025 (see include/linux/pageblock-flags.h for details). 1026 1027 Reducing pageblock order can negatively impact THP generation 1028 success rate. If your workloads use THP heavily, please use this 1029 option with caution. 1030 1031 Don't change if unsure. 1032 1033config MEM_SOFT_DIRTY 1034 bool "Track memory changes" 1035 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS 1036 select PROC_PAGE_MONITOR 1037 help 1038 This option enables memory changes tracking by introducing a 1039 soft-dirty bit on pte-s. This bit it set when someone writes 1040 into a page just as regular dirty bit, but unlike the latter 1041 it can be cleared by hands. 1042 1043 See Documentation/admin-guide/mm/soft-dirty.rst for more details. 1044 1045config GENERIC_EARLY_IOREMAP 1046 bool 1047 1048config STACK_MAX_DEFAULT_SIZE_MB 1049 int "Default maximum user stack size for 32-bit processes (MB)" 1050 default 100 1051 range 8 2048 1052 depends on STACK_GROWSUP && (!64BIT || COMPAT) 1053 help 1054 This is the maximum stack size in Megabytes in the VM layout of 32-bit 1055 user processes when the stack grows upwards (currently only on parisc 1056 arch) when the RLIMIT_STACK hard limit is unlimited. 1057 1058 A sane initial value is 100 MB. 1059 1060config DEFERRED_STRUCT_PAGE_INIT 1061 bool "Defer initialisation of struct pages to kthreads" 1062 depends on SPARSEMEM 1063 depends on !NEED_PER_CPU_KM 1064 depends on 64BIT 1065 depends on !KMSAN 1066 select PADATA 1067 help 1068 Ordinarily all struct pages are initialised during early boot in a 1069 single thread. On very large machines this can take a considerable 1070 amount of time. If this option is set, large machines will bring up 1071 a subset of memmap at boot and then initialise the rest in parallel. 1072 This has a potential performance impact on tasks running early in the 1073 lifetime of the system until these kthreads finish the 1074 initialisation. 1075 1076config PAGE_IDLE_FLAG 1077 bool 1078 select PAGE_EXTENSION if !64BIT 1079 help 1080 This adds PG_idle and PG_young flags to 'struct page'. PTE Accessed 1081 bit writers can set the state of the bit in the flags so that PTE 1082 Accessed bit readers may avoid disturbance. 1083 1084config IDLE_PAGE_TRACKING 1085 bool "Enable idle page tracking" 1086 depends on SYSFS && MMU 1087 select PAGE_IDLE_FLAG 1088 help 1089 This feature allows to estimate the amount of user pages that have 1090 not been touched during a given period of time. This information can 1091 be useful to tune memory cgroup limits and/or for job placement 1092 within a compute cluster. 1093 1094 See Documentation/admin-guide/mm/idle_page_tracking.rst for 1095 more details. 1096 1097# Architectures which implement cpu_dcache_is_aliasing() to query 1098# whether the data caches are aliased (VIVT or VIPT with dcache 1099# aliasing) need to select this. 1100config ARCH_HAS_CPU_CACHE_ALIASING 1101 bool 1102 1103config ARCH_HAS_CACHE_LINE_SIZE 1104 bool 1105 1106config ARCH_HAS_CURRENT_STACK_POINTER 1107 bool 1108 help 1109 In support of HARDENED_USERCOPY performing stack variable lifetime 1110 checking, an architecture-agnostic way to find the stack pointer 1111 is needed. Once an architecture defines an unsigned long global 1112 register alias named "current_stack_pointer", this config can be 1113 selected. 1114 1115config ARCH_HAS_ZONE_DMA_SET 1116 bool 1117 1118config ZONE_DMA 1119 bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET 1120 default y if ARM64 || X86 1121 1122config ZONE_DMA32 1123 bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET 1124 depends on !X86_32 1125 default y if ARM64 1126 1127config ZONE_DEVICE 1128 bool "Device memory (pmem, HMM, etc...) hotplug support" 1129 depends on MEMORY_HOTPLUG 1130 depends on MEMORY_HOTREMOVE 1131 depends on SPARSEMEM_VMEMMAP 1132 select XARRAY_MULTI 1133 1134 help 1135 Device memory hotplug support allows for establishing pmem, 1136 or other device driver discovered memory regions, in the 1137 memmap. This allows pfn_to_page() lookups of otherwise 1138 "device-physical" addresses which is needed for using a DAX 1139 mapping in an O_DIRECT operation, among other things. 1140 1141 If FS_DAX is enabled, then say Y. 1142 1143# 1144# Helpers to mirror range of the CPU page tables of a process into device page 1145# tables. 1146# 1147config HMM_MIRROR 1148 bool 1149 depends on MMU 1150 1151config GET_FREE_REGION 1152 bool 1153 1154config DEVICE_PRIVATE 1155 bool "Unaddressable device memory (GPU memory, ...)" 1156 depends on ZONE_DEVICE 1157 select GET_FREE_REGION 1158 1159 help 1160 Allows creation of struct pages to represent unaddressable device 1161 memory; i.e., memory that is only accessible from the device (or 1162 group of devices). You likely also want to select HMM_MIRROR. 1163 1164config VMAP_PFN 1165 bool 1166 1167config ARCH_USES_HIGH_VMA_FLAGS 1168 bool 1169config ARCH_HAS_PKEYS 1170 bool 1171 1172config ARCH_USES_PG_ARCH_2 1173 bool 1174config ARCH_USES_PG_ARCH_3 1175 bool 1176 1177config VM_EVENT_COUNTERS 1178 default y 1179 bool "Enable VM event counters for /proc/vmstat" if EXPERT 1180 help 1181 VM event counters are needed for event counts to be shown. 1182 This option allows the disabling of the VM event counters 1183 on EXPERT systems. /proc/vmstat will only show page counts 1184 if VM event counters are disabled. 1185 1186config PERCPU_STATS 1187 bool "Collect percpu memory statistics" 1188 help 1189 This feature collects and exposes statistics via debugfs. The 1190 information includes global and per chunk statistics, which can 1191 be used to help understand percpu memory usage. 1192 1193config GUP_TEST 1194 bool "Enable infrastructure for get_user_pages()-related unit tests" 1195 depends on DEBUG_FS 1196 help 1197 Provides /sys/kernel/debug/gup_test, which in turn provides a way 1198 to make ioctl calls that can launch kernel-based unit tests for 1199 the get_user_pages*() and pin_user_pages*() family of API calls. 1200 1201 These tests include benchmark testing of the _fast variants of 1202 get_user_pages*() and pin_user_pages*(), as well as smoke tests of 1203 the non-_fast variants. 1204 1205 There is also a sub-test that allows running dump_page() on any 1206 of up to eight pages (selected by command line args) within the 1207 range of user-space addresses. These pages are either pinned via 1208 pin_user_pages*(), or pinned via get_user_pages*(), as specified 1209 by other command line arguments. 1210 1211 See tools/testing/selftests/mm/gup_test.c 1212 1213comment "GUP_TEST needs to have DEBUG_FS enabled" 1214 depends on !GUP_TEST && !DEBUG_FS 1215 1216config GUP_GET_PXX_LOW_HIGH 1217 bool 1218 1219config DMAPOOL_TEST 1220 tristate "Enable a module to run time tests on dma_pool" 1221 depends on HAS_DMA 1222 help 1223 Provides a test module that will allocate and free many blocks of 1224 various sizes and report how long it takes. This is intended to 1225 provide a consistent way to measure how changes to the 1226 dma_pool_alloc/free routines affect performance. 1227 1228config ARCH_HAS_PTE_SPECIAL 1229 bool 1230 1231config MAPPING_DIRTY_HELPERS 1232 bool 1233 1234config KMAP_LOCAL 1235 bool 1236 1237config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY 1238 bool 1239 1240config MEMFD_CREATE 1241 bool "Enable memfd_create() system call" if EXPERT 1242 1243config SECRETMEM 1244 default y 1245 bool "Enable memfd_secret() system call" if EXPERT 1246 depends on ARCH_HAS_SET_DIRECT_MAP 1247 help 1248 Enable the memfd_secret() system call with the ability to create 1249 memory areas visible only in the context of the owning process and 1250 not mapped to other processes and other kernel page tables. 1251 1252config ANON_VMA_NAME 1253 bool "Anonymous VMA name support" 1254 depends on PROC_FS && ADVISE_SYSCALLS && MMU 1255 1256 help 1257 Allow naming anonymous virtual memory areas. 1258 1259 This feature allows assigning names to virtual memory areas. Assigned 1260 names can be later retrieved from /proc/pid/maps and /proc/pid/smaps 1261 and help identifying individual anonymous memory areas. 1262 Assigning a name to anonymous virtual memory area might prevent that 1263 area from being merged with adjacent virtual memory areas due to the 1264 difference in their name. 1265 1266config HAVE_ARCH_USERFAULTFD_WP 1267 bool 1268 help 1269 Arch has userfaultfd write protection support 1270 1271config HAVE_ARCH_USERFAULTFD_MINOR 1272 bool 1273 help 1274 Arch has userfaultfd minor fault support 1275 1276menuconfig USERFAULTFD 1277 bool "Enable userfaultfd() system call" 1278 depends on MMU 1279 help 1280 Enable the userfaultfd() system call that allows to intercept and 1281 handle page faults in userland. 1282 1283if USERFAULTFD 1284config PTE_MARKER_UFFD_WP 1285 bool "Userfaultfd write protection support for shmem/hugetlbfs" 1286 default y 1287 depends on HAVE_ARCH_USERFAULTFD_WP 1288 1289 help 1290 Allows to create marker PTEs for userfaultfd write protection 1291 purposes. It is required to enable userfaultfd write protection on 1292 file-backed memory types like shmem and hugetlbfs. 1293endif # USERFAULTFD 1294 1295# multi-gen LRU { 1296config LRU_GEN 1297 bool "Multi-Gen LRU" 1298 depends on MMU 1299 # make sure folio->flags has enough spare bits 1300 depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP 1301 help 1302 A high performance LRU implementation to overcommit memory. See 1303 Documentation/admin-guide/mm/multigen_lru.rst for details. 1304 1305config LRU_GEN_ENABLED 1306 bool "Enable by default" 1307 depends on LRU_GEN 1308 help 1309 This option enables the multi-gen LRU by default. 1310 1311config LRU_GEN_STATS 1312 bool "Full stats for debugging" 1313 depends on LRU_GEN 1314 help 1315 Do not enable this option unless you plan to look at historical stats 1316 from evicted generations for debugging purpose. 1317 1318 This option has a per-memcg and per-node memory overhead. 1319 1320config LRU_GEN_WALKS_MMU 1321 def_bool y 1322 depends on LRU_GEN && ARCH_HAS_HW_PTE_YOUNG 1323# } 1324 1325config ARCH_SUPPORTS_PER_VMA_LOCK 1326 def_bool n 1327 1328config PER_VMA_LOCK 1329 def_bool y 1330 depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP 1331 help 1332 Allow per-vma locking during page fault handling. 1333 1334 This feature allows locking each virtual memory area separately when 1335 handling page faults instead of taking mmap_lock. 1336 1337config LOCK_MM_AND_FIND_VMA 1338 bool 1339 depends on !STACK_GROWSUP 1340 1341config IOMMU_MM_DATA 1342 bool 1343 1344config EXECMEM 1345 bool 1346 1347config NUMA_MEMBLKS 1348 bool 1349 1350config NUMA_EMU 1351 bool "NUMA emulation" 1352 depends on NUMA_MEMBLKS 1353 depends on X86 || GENERIC_ARCH_NUMA 1354 help 1355 Enable NUMA emulation. A flat machine will be split 1356 into virtual nodes when booted with "numa=fake=N", where N is the 1357 number of nodes. This is only useful for debugging. 1358 1359config ARCH_HAS_USER_SHADOW_STACK 1360 bool 1361 help 1362 The architecture has hardware support for userspace shadow call 1363 stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss). 1364 1365config ARCH_SUPPORTS_PT_RECLAIM 1366 def_bool n 1367 1368config PT_RECLAIM 1369 bool "reclaim empty user page table pages" 1370 default y 1371 depends on ARCH_SUPPORTS_PT_RECLAIM && MMU && SMP 1372 select MMU_GATHER_RCU_TABLE_FREE 1373 help 1374 Try to reclaim empty user page table pages in paths other than munmap 1375 and exit_mmap path. 1376 1377 Note: now only empty user PTE page table pages will be reclaimed. 1378 1379config FIND_NORMAL_PAGE 1380 def_bool n 1381 1382source "mm/damon/Kconfig" 1383 1384endmenu 1385