1 # SPDX-License-Identifier: GPL-2.0-only
3 menu "Memory Management options"
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.
16 bool "Support for paging of anonymous memory (swap)"
17 depends on MMU && BLOCK && !ARCH_NO_SWAP
20 This option allows you to choose whether you want to have support
21 for so called swap devices or swap files in your kernel that are
22 used to provide more virtual memory than the actual RAM present
23 in your computer. If unsure say Y.
26 bool "Compressed cache for swap pages"
31 A lightweight compressed cache for swap pages. It takes
32 pages that are in the process of being swapped out and attempts to
33 compress them into a dynamically allocated RAM-based memory pool.
34 This can result in a significant I/O reduction on swap device and,
35 in the case where decompressing from RAM is faster than swap device
36 reads, can also improve workload performance.
38 config ZSWAP_DEFAULT_ON
39 bool "Enable the compressed cache for swap pages by default"
42 If selected, the compressed cache for swap pages will be enabled
43 at boot, otherwise it will be disabled.
45 The selection made here can be overridden by using the kernel
46 command line 'zswap.enabled=' option.
48 config ZSWAP_EXCLUSIVE_LOADS_DEFAULT_ON
49 bool "Invalidate zswap entries when pages are loaded"
52 If selected, exclusive loads for zswap will be enabled at boot,
53 otherwise it will be disabled.
55 If exclusive loads are enabled, when a page is loaded from zswap,
56 the zswap entry is invalidated at once, as opposed to leaving it
57 in zswap until the swap entry is freed.
59 This avoids having two copies of the same page in memory
60 (compressed and uncompressed) after faulting in a page from zswap.
61 The cost is that if the page was never dirtied and needs to be
62 swapped out again, it will be re-compressed.
64 config ZSWAP_SHRINKER_DEFAULT_ON
65 bool "Shrink the zswap pool on memory pressure"
69 If selected, the zswap shrinker will be enabled, and the pages
70 stored in the zswap pool will become available for reclaim (i.e
71 written back to the backing swap device) on memory pressure.
73 This means that zswap writeback could happen even if the pool is
74 not yet full, or the cgroup zswap limit has not been reached,
75 reducing the chance that cold pages will reside in the zswap pool
76 and consume memory indefinitely.
79 prompt "Default compressor"
81 default ZSWAP_COMPRESSOR_DEFAULT_LZO
83 Selects the default compression algorithm for the compressed cache
86 For an overview what kind of performance can be expected from
87 a particular compression algorithm please refer to the benchmarks
88 available at the following LWN page:
89 https://lwn.net/Articles/751795/
91 If in doubt, select 'LZO'.
93 The selection made here can be overridden by using the kernel
94 command line 'zswap.compressor=' option.
96 config ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
100 Use the Deflate algorithm as the default compression algorithm.
102 config ZSWAP_COMPRESSOR_DEFAULT_LZO
106 Use the LZO algorithm as the default compression algorithm.
108 config ZSWAP_COMPRESSOR_DEFAULT_842
112 Use the 842 algorithm as the default compression algorithm.
114 config ZSWAP_COMPRESSOR_DEFAULT_LZ4
118 Use the LZ4 algorithm as the default compression algorithm.
120 config ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
124 Use the LZ4HC algorithm as the default compression algorithm.
126 config ZSWAP_COMPRESSOR_DEFAULT_ZSTD
130 Use the zstd algorithm as the default compression algorithm.
133 config ZSWAP_COMPRESSOR_DEFAULT
136 default "deflate" if ZSWAP_COMPRESSOR_DEFAULT_DEFLATE
137 default "lzo" if ZSWAP_COMPRESSOR_DEFAULT_LZO
138 default "842" if ZSWAP_COMPRESSOR_DEFAULT_842
139 default "lz4" if ZSWAP_COMPRESSOR_DEFAULT_LZ4
140 default "lz4hc" if ZSWAP_COMPRESSOR_DEFAULT_LZ4HC
141 default "zstd" if ZSWAP_COMPRESSOR_DEFAULT_ZSTD
145 prompt "Default allocator"
147 default ZSWAP_ZPOOL_DEFAULT_ZSMALLOC if MMU
148 default ZSWAP_ZPOOL_DEFAULT_ZBUD
150 Selects the default allocator for the compressed cache for
152 The default is 'zbud' for compatibility, however please do
153 read the description of each of the allocators below before
154 making a right choice.
156 The selection made here can be overridden by using the kernel
157 command line 'zswap.zpool=' option.
159 config ZSWAP_ZPOOL_DEFAULT_ZBUD
163 Use the zbud allocator as the default allocator.
165 config ZSWAP_ZPOOL_DEFAULT_Z3FOLD
169 Use the z3fold allocator as the default allocator.
171 config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
175 Use the zsmalloc allocator as the default allocator.
178 config ZSWAP_ZPOOL_DEFAULT
181 default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
182 default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
183 default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
187 tristate "2:1 compression allocator (zbud)"
190 A special purpose allocator for storing compressed pages.
191 It is designed to store up to two compressed pages per physical
192 page. While this design limits storage density, it has simple and
193 deterministic reclaim properties that make it preferable to a higher
194 density approach when reclaim will be used.
197 tristate "3:1 compression allocator (z3fold)"
200 A special purpose allocator for storing compressed pages.
201 It is designed to store up to three compressed pages per physical
202 page. It is a ZBUD derivative so the simplicity and determinism are
207 prompt "N:1 compression allocator (zsmalloc)" if ZSWAP
210 zsmalloc is a slab-based memory allocator designed to store
211 pages of various compression levels efficiently. It achieves
212 the highest storage density with the least amount of fragmentation.
215 bool "Export zsmalloc statistics"
219 This option enables code in the zsmalloc to collect various
220 statistics about what's happening in zsmalloc and exports that
221 information to userspace via debugfs.
224 config ZSMALLOC_CHAIN_SIZE
225 int "Maximum number of physical pages per-zspage"
230 This option sets the upper limit on the number of physical pages
231 that a zmalloc page (zspage) can consist of. The optimal zspage
232 chain size is calculated for each size class during the
233 initialization of the pool.
235 Changing this option can alter the characteristics of size classes,
236 such as the number of pages per zspage and the number of objects
237 per zspage. This can also result in different configurations of
238 the pool, as zsmalloc merges size classes with similar
241 For more information, see zsmalloc documentation.
243 menu "Slab allocator options"
249 bool "Configure for minimal memory footprint"
251 select SLAB_MERGE_DEFAULT
253 Configures the slab allocator in a way to achieve minimal memory
254 footprint, sacrificing scalability, debugging and other features.
255 This is intended only for the smallest system that had used the
256 SLOB allocator and is not recommended for systems with more than
261 config SLAB_MERGE_DEFAULT
262 bool "Allow slab caches to be merged"
265 For reduced kernel memory fragmentation, slab caches can be
266 merged when they share the same size and other characteristics.
267 This carries a risk of kernel heap overflows being able to
268 overwrite objects from merged caches (and more easily control
269 cache layout), which makes such heap attacks easier to exploit
270 by attackers. By keeping caches unmerged, these kinds of exploits
271 can usually only damage objects in the same cache. To disable
272 merging at runtime, "slab_nomerge" can be passed on the kernel
275 config SLAB_FREELIST_RANDOM
276 bool "Randomize slab freelist"
277 depends on !SLUB_TINY
279 Randomizes the freelist order used on creating new pages. This
280 security feature reduces the predictability of the kernel slab
281 allocator against heap overflows.
283 config SLAB_FREELIST_HARDENED
284 bool "Harden slab freelist metadata"
285 depends on !SLUB_TINY
287 Many kernel heap attacks try to target slab cache metadata and
288 other infrastructure. This options makes minor performance
289 sacrifices to harden the kernel slab allocator against common
290 freelist exploit methods.
294 bool "Enable performance statistics"
295 depends on SYSFS && !SLUB_TINY
297 The statistics are useful to debug slab allocation behavior in
298 order find ways to optimize the allocator. This should never be
299 enabled for production use since keeping statistics slows down
300 the allocator by a few percentage points. The slabinfo command
301 supports the determination of the most active slabs to figure
302 out which slabs are relevant to a particular load.
303 Try running: slabinfo -DA
305 config SLUB_CPU_PARTIAL
307 depends on SMP && !SLUB_TINY
308 bool "Enable per cpu partial caches"
310 Per cpu partial caches accelerate objects allocation and freeing
311 that is local to a processor at the price of more indeterminism
312 in the latency of the free. On overflow these caches will be cleared
313 which requires the taking of locks that may cause latency spikes.
314 Typically one would choose no for a realtime system.
316 config RANDOM_KMALLOC_CACHES
318 depends on !SLUB_TINY
319 bool "Randomize slab caches for normal kmalloc"
321 A hardening feature that creates multiple copies of slab caches for
322 normal kmalloc allocation and makes kmalloc randomly pick one based
323 on code address, which makes the attackers more difficult to spray
324 vulnerable memory objects on the heap for the purpose of exploiting
325 memory vulnerabilities.
327 Currently the number of copies is set to 16, a reasonably large value
328 that effectively diverges the memory objects allocated for different
329 subsystems or modules into different caches, at the expense of a
330 limited degree of memory and CPU overhead that relates to hardware and
333 endmenu # Slab allocator options
335 config SHUFFLE_PAGE_ALLOCATOR
336 bool "Page allocator randomization"
337 default SLAB_FREELIST_RANDOM && ACPI_NUMA
339 Randomization of the page allocator improves the average
340 utilization of a direct-mapped memory-side-cache. See section
341 5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
342 6.2a specification for an example of how a platform advertises
343 the presence of a memory-side-cache. There are also incidental
344 security benefits as it reduces the predictability of page
345 allocations to compliment SLAB_FREELIST_RANDOM, but the
346 default granularity of shuffling on the MAX_PAGE_ORDER i.e, 10th
347 order of pages is selected based on cache utilization benefits
350 While the randomization improves cache utilization it may
351 negatively impact workloads on platforms without a cache. For
352 this reason, by default, the randomization is enabled only
353 after runtime detection of a direct-mapped memory-side-cache.
354 Otherwise, the randomization may be force enabled with the
355 'page_alloc.shuffle' kernel command line parameter.
360 bool "Disable heap randomization"
363 Randomizing heap placement makes heap exploits harder, but it
364 also breaks ancient binaries (including anything libc5 based).
365 This option changes the bootup default to heap randomization
366 disabled, and can be overridden at runtime by setting
367 /proc/sys/kernel/randomize_va_space to 2.
369 On non-ancient distros (post-2000 ones) N is usually a safe choice.
371 config MMAP_ALLOW_UNINITIALIZED
372 bool "Allow mmapped anonymous memory to be uninitialized"
373 depends on EXPERT && !MMU
376 Normally, and according to the Linux spec, anonymous memory obtained
377 from mmap() has its contents cleared before it is passed to
378 userspace. Enabling this config option allows you to request that
379 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
380 providing a huge performance boost. If this option is not enabled,
381 then the flag will be ignored.
383 This is taken advantage of by uClibc's malloc(), and also by
384 ELF-FDPIC binfmt's brk and stack allocator.
386 Because of the obvious security issues, this option should only be
387 enabled on embedded devices where you control what is run in
388 userspace. Since that isn't generally a problem on no-MMU systems,
389 it is normally safe to say Y here.
391 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
393 config SELECT_MEMORY_MODEL
395 depends on ARCH_SELECT_MEMORY_MODEL
398 prompt "Memory model"
399 depends on SELECT_MEMORY_MODEL
400 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
401 default FLATMEM_MANUAL
403 This option allows you to change some of the ways that
404 Linux manages its memory internally. Most users will
405 only have one option here selected by the architecture
406 configuration. This is normal.
408 config FLATMEM_MANUAL
410 depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE
412 This option is best suited for non-NUMA systems with
413 flat address space. The FLATMEM is the most efficient
414 system in terms of performance and resource consumption
415 and it is the best option for smaller systems.
417 For systems that have holes in their physical address
418 spaces and for features like NUMA and memory hotplug,
419 choose "Sparse Memory".
421 If unsure, choose this option (Flat Memory) over any other.
423 config SPARSEMEM_MANUAL
425 depends on ARCH_SPARSEMEM_ENABLE
427 This will be the only option for some systems, including
428 memory hot-plug systems. This is normal.
430 This option provides efficient support for systems with
431 holes is their physical address space and allows memory
432 hot-plug and hot-remove.
434 If unsure, choose "Flat Memory" over this option.
440 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
444 depends on !SPARSEMEM || FLATMEM_MANUAL
447 # SPARSEMEM_EXTREME (which is the default) does some bootmem
448 # allocations when sparse_init() is called. If this cannot
449 # be done on your architecture, select this option. However,
450 # statically allocating the mem_section[] array can potentially
451 # consume vast quantities of .bss, so be careful.
453 # This option will also potentially produce smaller runtime code
454 # with gcc 3.4 and later.
456 config SPARSEMEM_STATIC
460 # Architecture platforms which require a two level mem_section in SPARSEMEM
461 # must select this option. This is usually for architecture platforms with
462 # an extremely sparse physical address space.
464 config SPARSEMEM_EXTREME
466 depends on SPARSEMEM && !SPARSEMEM_STATIC
468 config SPARSEMEM_VMEMMAP_ENABLE
471 config SPARSEMEM_VMEMMAP
472 bool "Sparse Memory virtual memmap"
473 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
476 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
477 pfn_to_page and page_to_pfn operations. This is the most
478 efficient option when sufficient kernel resources are available.
480 # Select this config option from the architecture Kconfig, if it is preferred
481 # to enable the feature of HugeTLB/dev_dax vmemmap optimization.
483 config ARCH_WANT_OPTIMIZE_DAX_VMEMMAP
486 config ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP
489 config HAVE_MEMBLOCK_PHYS_MAP
496 # Don't discard allocated memory used to track "memory" and "reserved" memblocks
497 # after early boot, so it can still be used to test for validity of memory.
498 # Also, memblocks are updated with memory hot(un)plug.
499 config ARCH_KEEP_MEMBLOCK
502 # Keep arch NUMA mapping infrastructure post-init.
503 config NUMA_KEEP_MEMINFO
506 config MEMORY_ISOLATION
509 # IORESOURCE_SYSTEM_RAM regions in the kernel resource tree that are marked
510 # IORESOURCE_EXCLUSIVE cannot be mapped to user space, for example, via
512 config EXCLUSIVE_SYSTEM_RAM
514 depends on !DEVMEM || STRICT_DEVMEM
517 # Only be set on architectures that have completely implemented memory hotplug
518 # feature. If you are not sure, don't touch it.
520 config HAVE_BOOTMEM_INFO_NODE
523 config ARCH_ENABLE_MEMORY_HOTPLUG
526 config ARCH_ENABLE_MEMORY_HOTREMOVE
529 # eventually, we can have this option just 'select SPARSEMEM'
530 menuconfig MEMORY_HOTPLUG
531 bool "Memory hotplug"
532 select MEMORY_ISOLATION
534 depends on ARCH_ENABLE_MEMORY_HOTPLUG
536 select NUMA_KEEP_MEMINFO if NUMA
540 config MEMORY_HOTPLUG_DEFAULT_ONLINE
541 bool "Online the newly added memory blocks by default"
542 depends on MEMORY_HOTPLUG
544 This option sets the default policy setting for memory hotplug
545 onlining policy (/sys/devices/system/memory/auto_online_blocks) which
546 determines what happens to newly added memory regions. Policy setting
547 can always be changed at runtime.
548 See Documentation/admin-guide/mm/memory-hotplug.rst for more information.
550 Say Y here if you want all hot-plugged memory blocks to appear in
551 'online' state by default.
552 Say N here if you want the default policy to keep all hot-plugged
553 memory blocks in 'offline' state.
555 config MEMORY_HOTREMOVE
556 bool "Allow for memory hot remove"
557 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
558 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
561 config MHP_MEMMAP_ON_MEMORY
563 depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
564 depends on ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
566 endif # MEMORY_HOTPLUG
568 config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE
571 # Heavily threaded applications may benefit from splitting the mm-wide
572 # page_table_lock, so that faults on different parts of the user address
573 # space can be handled with less contention: split it at this NR_CPUS.
574 # Default to 4 for wider testing, though 8 might be more appropriate.
575 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
576 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
577 # SPARC32 allocates multiple pte tables within a single page, and therefore
578 # a per-page lock leads to problems when multiple tables need to be locked
579 # at the same time (e.g. copy_page_range()).
580 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
582 config SPLIT_PTLOCK_CPUS
584 default "999999" if !MMU
585 default "999999" if ARM && !CPU_CACHE_VIPT
586 default "999999" if PARISC && !PA20
587 default "999999" if SPARC32
590 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
594 # support for memory balloon
595 config MEMORY_BALLOON
599 # support for memory balloon compaction
600 config BALLOON_COMPACTION
601 bool "Allow for balloon memory compaction/migration"
603 depends on COMPACTION && MEMORY_BALLOON
605 Memory fragmentation introduced by ballooning might reduce
606 significantly the number of 2MB contiguous memory blocks that can be
607 used within a guest, thus imposing performance penalties associated
608 with the reduced number of transparent huge pages that could be used
609 by the guest workload. Allowing the compaction & migration for memory
610 pages enlisted as being part of memory balloon devices avoids the
611 scenario aforementioned and helps improving memory defragmentation.
614 # support for memory compaction
616 bool "Allow for memory compaction"
621 Compaction is the only memory management component to form
622 high order (larger physically contiguous) memory blocks
623 reliably. The page allocator relies on compaction heavily and
624 the lack of the feature can lead to unexpected OOM killer
625 invocations for high order memory requests. You shouldn't
626 disable this option unless there really is a strong reason for
627 it and then we would be really interested to hear about that at
630 config COMPACT_UNEVICTABLE_DEFAULT
632 depends on COMPACTION
633 default 0 if PREEMPT_RT
637 # support for free page reporting
638 config PAGE_REPORTING
639 bool "Free page reporting"
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.
648 # support for page migration
651 bool "Page migration"
653 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
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.
662 config DEVICE_MIGRATION
663 def_bool MIGRATION && ZONE_DEVICE
665 config ARCH_ENABLE_HUGEPAGE_MIGRATION
668 config ARCH_ENABLE_THP_MIGRATION
671 config HUGETLB_PAGE_SIZE_VARIABLE
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
678 Note that the pageblock_order cannot exceed MAX_PAGE_ORDER and will be
679 clamped down to MAX_PAGE_ORDER.
682 def_bool (MEMORY_ISOLATION && COMPACTION) || CMA
684 config PCP_BATCH_SCALE_MAX
685 int "Maximum scale factor of PCP (Per-CPU pageset) batch allocate/free"
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
695 config PHYS_ADDR_T_64BIT
699 bool "Enable bounce buffers"
701 depends on BLOCK && MMU && HIGHMEM
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.
712 bool "Enable KSM for page merging"
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).
726 config DEFAULT_MMAP_MIN_ADDR
727 int "Low address space to protect from user allocation"
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.
735 For most 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.
742 This value can be changed after boot using the
743 /proc/sys/vm/mmap_min_addr tunable.
745 config ARCH_SUPPORTS_MEMORY_FAILURE
748 config MEMORY_FAILURE
750 depends on ARCH_SUPPORTS_MEMORY_FAILURE
751 bool "Enable recovery from hardware memory errors"
752 select MEMORY_ISOLATION
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.
760 config HWPOISON_INJECT
761 tristate "HWPoison pages injector"
762 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
763 select PROC_PAGE_MONITOR
765 config NOMMU_INITIAL_TRIM_EXCESS
766 int "Turn on mmap() excess space trimming before booting"
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.
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.
780 If trimming is disabled, the excess is kept, but not used, which for
781 long-term mappings means that the space is wasted.
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.
788 This option specifies the initial value of this option. The default
789 of 1 says that all excess pages should be trimmed.
791 See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
793 config ARCH_WANT_GENERAL_HUGETLB
796 config ARCH_WANTS_THP_SWAP
799 menuconfig TRANSPARENT_HUGEPAGE
800 bool "Transparent Hugepage Support"
801 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT
805 Transparent Hugepages allows the kernel to use huge pages and
806 huge tlb transparently to the applications whenever possible.
807 This feature can improve computing performance to certain
808 applications by speeding up page faults during memory
809 allocation, by reducing the number of tlb misses and by speeding
810 up the pagetable walking.
812 If memory constrained on embedded, you may want to say N.
814 if TRANSPARENT_HUGEPAGE
817 prompt "Transparent Hugepage Support sysfs defaults"
818 depends on TRANSPARENT_HUGEPAGE
819 default TRANSPARENT_HUGEPAGE_ALWAYS
821 Selects the sysfs defaults for Transparent Hugepage Support.
823 config TRANSPARENT_HUGEPAGE_ALWAYS
826 Enabling Transparent Hugepage always, can increase the
827 memory footprint of applications without a guaranteed
828 benefit but it will work automatically for all applications.
830 config TRANSPARENT_HUGEPAGE_MADVISE
833 Enabling Transparent Hugepage madvise, will only provide a
834 performance improvement benefit to the applications using
835 madvise(MADV_HUGEPAGE) but it won't risk to increase the
836 memory footprint of applications without a guaranteed
839 config TRANSPARENT_HUGEPAGE_NEVER
842 Disable Transparent Hugepage by default. It can still be
843 enabled at runtime via sysfs.
848 depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT
850 Swap transparent huge pages in one piece, without splitting.
851 XXX: For now, swap cluster backing transparent huge page
852 will be split after swapout.
854 For selection by architectures with reasonable THP sizes.
856 config READ_ONLY_THP_FOR_FS
857 bool "Read-only THP for filesystems (EXPERIMENTAL)"
858 depends on TRANSPARENT_HUGEPAGE && SHMEM
861 Allow khugepaged to put read-only file-backed pages in THP.
863 This is marked experimental because it is a new feature. Write
864 support of file THPs will be developed in the next few release
867 endif # TRANSPARENT_HUGEPAGE
870 # UP and nommu archs use km based percpu allocator
872 config NEED_PER_CPU_KM
873 depends on !SMP || !MMU
877 config NEED_PER_CPU_EMBED_FIRST_CHUNK
880 config NEED_PER_CPU_PAGE_FIRST_CHUNK
883 config USE_PERCPU_NUMA_NODE_ID
886 config HAVE_SETUP_PER_CPU_AREA
890 bool "Contiguous Memory Allocator"
893 select MEMORY_ISOLATION
895 This enables the Contiguous Memory Allocator which allows other
896 subsystems to allocate big physically-contiguous blocks of memory.
897 CMA reserves a region of memory and allows only movable pages to
898 be allocated from it. This way, the kernel can use the memory for
899 pagecache and when a subsystem requests for contiguous area, the
900 allocated pages are migrated away to serve the contiguous request.
905 bool "CMA debug messages (DEVELOPMENT)"
906 depends on DEBUG_KERNEL && CMA
908 Turns on debug messages in CMA. This produces KERN_DEBUG
909 messages for every CMA call as well as various messages while
910 processing calls such as dma_alloc_from_contiguous().
911 This option does not affect warning and error messages.
914 bool "CMA debugfs interface"
915 depends on CMA && DEBUG_FS
917 Turns on the DebugFS interface for CMA.
920 bool "CMA information through sysfs interface"
921 depends on CMA && SYSFS
923 This option exposes some sysfs attributes to get information
927 int "Maximum count of the CMA areas"
932 CMA allows to create CMA areas for particular purpose, mainly,
933 used as device private area. This parameter sets the maximum
934 number of CMA area in the system.
936 If unsure, leave the default value "7" in UMA and "19" in NUMA.
938 config MEM_SOFT_DIRTY
939 bool "Track memory changes"
940 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
941 select PROC_PAGE_MONITOR
943 This option enables memory changes tracking by introducing a
944 soft-dirty bit on pte-s. This bit it set when someone writes
945 into a page just as regular dirty bit, but unlike the latter
946 it can be cleared by hands.
948 See Documentation/admin-guide/mm/soft-dirty.rst for more details.
950 config GENERIC_EARLY_IOREMAP
953 config STACK_MAX_DEFAULT_SIZE_MB
954 int "Default maximum user stack size for 32-bit processes (MB)"
957 depends on STACK_GROWSUP && (!64BIT || COMPAT)
959 This is the maximum stack size in Megabytes in the VM layout of 32-bit
960 user processes when the stack grows upwards (currently only on parisc
961 arch) when the RLIMIT_STACK hard limit is unlimited.
963 A sane initial value is 100 MB.
965 config DEFERRED_STRUCT_PAGE_INIT
966 bool "Defer initialisation of struct pages to kthreads"
968 depends on !NEED_PER_CPU_KM
972 Ordinarily all struct pages are initialised during early boot in a
973 single thread. On very large machines this can take a considerable
974 amount of time. If this option is set, large machines will bring up
975 a subset of memmap at boot and then initialise the rest in parallel.
976 This has a potential performance impact on tasks running early in the
977 lifetime of the system until these kthreads finish the
980 config PAGE_IDLE_FLAG
982 select PAGE_EXTENSION if !64BIT
984 This adds PG_idle and PG_young flags to 'struct page'. PTE Accessed
985 bit writers can set the state of the bit in the flags so that PTE
986 Accessed bit readers may avoid disturbance.
988 config IDLE_PAGE_TRACKING
989 bool "Enable idle page tracking"
990 depends on SYSFS && MMU
991 select PAGE_IDLE_FLAG
993 This feature allows to estimate the amount of user pages that have
994 not been touched during a given period of time. This information can
995 be useful to tune memory cgroup limits and/or for job placement
996 within a compute cluster.
998 See Documentation/admin-guide/mm/idle_page_tracking.rst for
1001 config ARCH_HAS_CACHE_LINE_SIZE
1004 config ARCH_HAS_CURRENT_STACK_POINTER
1007 In support of HARDENED_USERCOPY performing stack variable lifetime
1008 checking, an architecture-agnostic way to find the stack pointer
1009 is needed. Once an architecture defines an unsigned long global
1010 register alias named "current_stack_pointer", this config can be
1013 config ARCH_HAS_PTE_DEVMAP
1016 config ARCH_HAS_ZONE_DMA_SET
1020 bool "Support DMA zone" if ARCH_HAS_ZONE_DMA_SET
1021 default y if ARM64 || X86
1024 bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET
1029 bool "Device memory (pmem, HMM, etc...) hotplug support"
1030 depends on MEMORY_HOTPLUG
1031 depends on MEMORY_HOTREMOVE
1032 depends on SPARSEMEM_VMEMMAP
1033 depends on ARCH_HAS_PTE_DEVMAP
1037 Device memory hotplug support allows for establishing pmem,
1038 or other device driver discovered memory regions, in the
1039 memmap. This allows pfn_to_page() lookups of otherwise
1040 "device-physical" addresses which is needed for using a DAX
1041 mapping in an O_DIRECT operation, among other things.
1043 If FS_DAX is enabled, then say Y.
1046 # Helpers to mirror range of the CPU page tables of a process into device page
1053 config GET_FREE_REGION
1054 depends on SPARSEMEM
1057 config DEVICE_PRIVATE
1058 bool "Unaddressable device memory (GPU memory, ...)"
1059 depends on ZONE_DEVICE
1060 select GET_FREE_REGION
1063 Allows creation of struct pages to represent unaddressable device
1064 memory; i.e., memory that is only accessible from the device (or
1065 group of devices). You likely also want to select HMM_MIRROR.
1070 config ARCH_USES_HIGH_VMA_FLAGS
1072 config ARCH_HAS_PKEYS
1075 config ARCH_USES_PG_ARCH_X
1078 Enable the definition of PG_arch_x page flags with x > 1. Only
1079 suitable for 64-bit architectures with CONFIG_FLATMEM or
1080 CONFIG_SPARSEMEM_VMEMMAP enabled, otherwise there may not be
1081 enough room for additional bits in page->flags.
1083 config VM_EVENT_COUNTERS
1085 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1087 VM event counters are needed for event counts to be shown.
1088 This option allows the disabling of the VM event counters
1089 on EXPERT systems. /proc/vmstat will only show page counts
1090 if VM event counters are disabled.
1093 bool "Collect percpu memory statistics"
1095 This feature collects and exposes statistics via debugfs. The
1096 information includes global and per chunk statistics, which can
1097 be used to help understand percpu memory usage.
1100 bool "Enable infrastructure for get_user_pages()-related unit tests"
1103 Provides /sys/kernel/debug/gup_test, which in turn provides a way
1104 to make ioctl calls that can launch kernel-based unit tests for
1105 the get_user_pages*() and pin_user_pages*() family of API calls.
1107 These tests include benchmark testing of the _fast variants of
1108 get_user_pages*() and pin_user_pages*(), as well as smoke tests of
1109 the non-_fast variants.
1111 There is also a sub-test that allows running dump_page() on any
1112 of up to eight pages (selected by command line args) within the
1113 range of user-space addresses. These pages are either pinned via
1114 pin_user_pages*(), or pinned via get_user_pages*(), as specified
1115 by other command line arguments.
1117 See tools/testing/selftests/mm/gup_test.c
1119 comment "GUP_TEST needs to have DEBUG_FS enabled"
1120 depends on !GUP_TEST && !DEBUG_FS
1122 config GUP_GET_PXX_LOW_HIGH
1126 tristate "Enable a module to run time tests on dma_pool"
1129 Provides a test module that will allocate and free many blocks of
1130 various sizes and report how long it takes. This is intended to
1131 provide a consistent way to measure how changes to the
1132 dma_pool_alloc/free routines affect performance.
1134 config ARCH_HAS_PTE_SPECIAL
1138 # Some architectures require a special hugepage directory format that is
1139 # required to support multiple hugepage sizes. For example a4fe3ce76
1140 # "powerpc/mm: Allow more flexible layouts for hugepage pagetables"
1141 # introduced it on powerpc. This allows for a more flexible hugepage
1142 # pagetable layouts.
1144 config ARCH_HAS_HUGEPD
1147 config MAPPING_DIRTY_HELPERS
1153 config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY
1156 # struct io_mapping based helper. Selected by drivers that need them
1161 bool "Enable memfd_create() system call" if EXPERT
1165 bool "Enable memfd_secret() system call" if EXPERT
1166 depends on ARCH_HAS_SET_DIRECT_MAP
1168 Enable the memfd_secret() system call with the ability to create
1169 memory areas visible only in the context of the owning process and
1170 not mapped to other processes and other kernel page tables.
1172 config ANON_VMA_NAME
1173 bool "Anonymous VMA name support"
1174 depends on PROC_FS && ADVISE_SYSCALLS && MMU
1177 Allow naming anonymous virtual memory areas.
1179 This feature allows assigning names to virtual memory areas. Assigned
1180 names can be later retrieved from /proc/pid/maps and /proc/pid/smaps
1181 and help identifying individual anonymous memory areas.
1182 Assigning a name to anonymous virtual memory area might prevent that
1183 area from being merged with adjacent virtual memory areas due to the
1184 difference in their name.
1186 config HAVE_ARCH_USERFAULTFD_WP
1189 Arch has userfaultfd write protection support
1191 config HAVE_ARCH_USERFAULTFD_MINOR
1194 Arch has userfaultfd minor fault support
1196 menuconfig USERFAULTFD
1197 bool "Enable userfaultfd() system call"
1200 Enable the userfaultfd() system call that allows to intercept and
1201 handle page faults in userland.
1204 config PTE_MARKER_UFFD_WP
1205 bool "Userfaultfd write protection support for shmem/hugetlbfs"
1207 depends on HAVE_ARCH_USERFAULTFD_WP
1210 Allows to create marker PTEs for userfaultfd write protection
1211 purposes. It is required to enable userfaultfd write protection on
1212 file-backed memory types like shmem and hugetlbfs.
1217 bool "Multi-Gen LRU"
1219 # make sure folio->flags has enough spare bits
1220 depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP
1222 A high performance LRU implementation to overcommit memory. See
1223 Documentation/admin-guide/mm/multigen_lru.rst for details.
1225 config LRU_GEN_ENABLED
1226 bool "Enable by default"
1229 This option enables the multi-gen LRU by default.
1231 config LRU_GEN_STATS
1232 bool "Full stats for debugging"
1235 Do not enable this option unless you plan to look at historical stats
1236 from evicted generations for debugging purpose.
1238 This option has a per-memcg and per-node memory overhead.
1240 config LRU_GEN_WALKS_MMU
1242 depends on LRU_GEN && ARCH_HAS_HW_PTE_YOUNG
1245 config ARCH_SUPPORTS_PER_VMA_LOCK
1250 depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP
1252 Allow per-vma locking during page fault handling.
1254 This feature allows locking each virtual memory area separately when
1255 handling page faults instead of taking mmap_lock.
1257 config LOCK_MM_AND_FIND_VMA
1259 depends on !STACK_GROWSUP
1261 config IOMMU_MM_DATA
1264 source "mm/damon/Kconfig"