linux-6.8/mm/Kconfig

1 # SPDX-License-Identifier: GPL-2.0-only
17 	depends on MMU && BLOCK && !ARCH_NO_SWAP
18 	default y
27 	depends on SWAP
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,
39 	bool "Enable the compressed cache for swap pages by default"
40 	depends on ZSWAP
50 	depends on ZSWAP
62 	  swapped out again, it will be re-compressed.
65 	bool "Shrink the zswap pool on memory pressure"
66 	depends on ZSWAP
67 	default n
71 	  written back to the backing swap device) on memory pressure.
79 	prompt "Default compressor"
80 	depends on ZSWAP
81 	default ZSWAP_COMPRESSOR_DEFAULT_LZO
83 	  Selects the default compression algorithm for the compressed cache
100 	  Use the Deflate algorithm as the default compression algorithm.
106 	  Use the LZO algorithm as the default compression algorithm.
112 	  Use the 842 algorithm as the default compression algorithm.
118 	  Use the LZ4 algorithm as the default compression algorithm.
124 	  Use the LZ4HC algorithm as the default compression algorithm.
130 	  Use the zstd algorithm as the default compression algorithm.
135        depends on ZSWAP
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
142        default ""
145 	prompt "Default allocator"
146 	depends on ZSWAP
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
163 	  Use the zbud allocator as the default allocator.
169 	  Use the z3fold allocator as the default allocator.
175 	  Use the zsmalloc allocator as the default allocator.
180        depends on ZSWAP
181        default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
182        default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD
183        default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
184        default ""
188 	depends on ZSWAP
198 	depends on ZSWAP
208 	depends on MMU
210 	  zsmalloc is a slab-based memory allocator designed to store
216 	depends on ZSMALLOC
225 	int "Maximum number of physical pages per-zspage"
226 	default 8
228 	depends on ZSMALLOC
230 	  This option sets the upper limit on the number of physical pages
250 	depends on EXPERT
263 	default y
272 	  merging at runtime, "slab_nomerge" can be passed on the kernel
277 	depends on !SLUB_TINY
279 	  Randomizes the freelist order used on creating new pages. This
285 	depends on !SLUB_TINY
293 	default n
295 	depends on SYSFS && !SLUB_TINY
303 	  Try running: slabinfo -DA
306 	default y
307 	depends on SMP && !SLUB_TINY
312 	  in the latency of the free. On overflow these caches will be cleared
317 	default n
318 	depends on !SLUB_TINY
323 	  on code address, which makes the attackers more difficult to spray
324 	  vulnerable memory objects on the heap for the purpose of exploiting
337 	default SLAB_FREELIST_RANDOM && ACPI_NUMA
340 	  utilization of a direct-mapped memory-side-cache. See section
343 	  the presence of a memory-side-cache. There are also incidental
346 	  default granularity of shuffling on the MAX_PAGE_ORDER i.e, 10th
347 	  order of pages is selected based on cache utilization benefits
348 	  on x86.
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.
361 	default y
365 	  This option changes the bootup default to heap randomization
369 	  On non-ancient distros (post-2000 ones) N is usually a safe choice.
373 	depends on EXPERT && !MMU
374 	default n
384 	  ELF-FDPIC binfmt's brk and stack allocator.
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,
391 	  See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
395 	depends on ARCH_SELECT_MEMORY_MODEL
399 	depends on SELECT_MEMORY_MODEL
400 	default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
401 	default FLATMEM_MANUAL
410 	depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE
412 	  This option is best suited for non-NUMA systems with
425 	depends on ARCH_SPARSEMEM_ENABLE
428 	  memory hot-plug systems.  This is normal.
432 	  hot-plug and hot-remove.
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
449 # be done on your architecture, select this option.  However,
466 	depends on SPARSEMEM && !SPARSEMEM_STATIC
473 	depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
474 	default y
493 	depends on MMU
502 # Keep arch NUMA mapping infrastructure post-init.
514 	depends on !DEVMEM || STRICT_DEVMEM
517 # Only be set on architectures that have completely implemented memory hotplug
533 	depends on SPARSEMEM
534 	depends on ARCH_ENABLE_MEMORY_HOTPLUG
535 	depends on 64BIT
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
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
558 	depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
559 	depends on MIGRATION
563 	depends on MEMORY_HOTPLUG && SPARSEMEM_VMEMMAP
564 	depends on 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
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.
578 # a per-page lock leads to problems when multiple tables need to be locked
584 	default "999999" if !MMU
585 	default "999999" if ARM && !CPU_CACHE_VIPT
586 	default "999999" if PARISC && !PA20
587 	default "999999" if SPARC32
588 	default "4"
603 	depends on COMPACTION && MEMORY_BALLOON
619 	depends on MMU
623 	  reliably. The page allocator relies on compaction heavily and
628 	  linux-mm@kvack.org.
632 	depends on COMPACTION
633 	default 0 if PREEMPT_RT
634 	default 1
653 	depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
657 	  two situations. The first is on NUMA systems to put pages nearer
676 	  on a platform.
685 	int "Maximum scale factor of PCP (Per-CPU pageset) batch allocate/free"
686 	default 5
689 	  In page allocator, PCP (Per-CPU pageset) is refilled and drained in
700 	default y
701 	depends on BLOCK && MMU && HIGHMEM
704 	  memory available to the CPU. Enabled by default when HIGHMEM is
713 	depends on MMU
728 	depends on MMU
729 	default 4096
737 	  On arm and other archs it should not be higher than 32768.
749 	depends on MMU
750 	depends on ARCH_SUPPORTS_MEMORY_FAILURE
755 	  Enables code to recover from some memory failures on systems
762 	depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
766 	int "Turn on mmap() excess space trimming before booting"
767 	depends on !MMU
768 	default 1
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
781 	  long-term mappings means that the space is wasted.
788 	  This option specifies the initial value of this option.  The default
791 	  See Documentation/admin-guide/mm/nommu-mmap.rst for more information.
801 	depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE && !PREEMPT_RT
812 	  If memory constrained on embedded, you may want to say N.
818 	depends on TRANSPARENT_HUGEPAGE
819 	default TRANSPARENT_HUGEPAGE_ALWAYS
842 	  Disable Transparent Hugepage by default. It can still be
848 	depends on TRANSPARENT_HUGEPAGE && ARCH_WANTS_THP_SWAP && SWAP && 64BIT
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.
873 	depends on !SMP || !MMU
875 	default y
891 	depends on MMU
896 	  subsystems to allocate big physically-contiguous blocks of memory.
906 	depends on DEBUG_KERNEL && CMA
908 	  Turns on debug messages in CMA.  This produces KERN_DEBUG
915 	depends on CMA && DEBUG_FS
917 	  Turns on the DebugFS interface for CMA.
921 	depends on CMA && SYSFS
928 	depends on CMA
929 	default 19 if NUMA
930 	default 7
936 	  If unsure, leave the default value "7" in UMA and "19" in NUMA.
940 	depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
944 	  soft-dirty bit on pte-s. This bit it set when someone writes
948 	  See Documentation/admin-guide/mm/soft-dirty.rst for more details.
954 	int "Default maximum user stack size for 32-bit processes (MB)"
955 	default 100
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
967 	depends on SPARSEMEM
968 	depends on !NEED_PER_CPU_KM
969 	depends on 64BIT
973 	  single thread. On very large machines this can take a considerable
976 	  This has a potential performance impact on tasks running early in the
990 	depends on SYSFS && MMU
998 	  See Documentation/admin-guide/mm/idle_page_tracking.rst for
1008 	  checking, an architecture-agnostic way to find the stack pointer
1021 	default y if ARM64 || X86
1025 	depends on !X86_32
1026 	default y if ARM64
1030 	depends on MEMORY_HOTPLUG
1031 	depends on MEMORY_HOTREMOVE
1032 	depends on SPARSEMEM_VMEMMAP
1033 	depends on ARCH_HAS_PTE_DEVMAP
1040 	  "device-physical" addresses which is needed for using a DAX
1051 	depends on MMU
1054 	depends on SPARSEMEM
1059 	depends on ZONE_DEVICE
1079 	  suitable for 64-bit architectures with CONFIG_FLATMEM or
1081 	  enough room for additional bits in page->flags.
1084 	default y
1089 	  on EXPERT systems.  /proc/vmstat will only show page counts
1100 	bool "Enable infrastructure for get_user_pages()-related unit tests"
1101 	depends on DEBUG_FS
1104 	  to make ioctl calls that can launch kernel-based unit tests for
1109 	  the non-_fast variants.
1111 	  There is also a sub-test that allows running dump_page() on any
1113 	  range of user-space addresses. These pages are either pinned via
1120 	depends on !GUP_TEST && !DEBUG_FS
1126 	tristate "Enable a module to run time tests on dma_pool"
1127 	depends on HAS_DMA
1141 # introduced it on powerpc.  This allows for a more flexible hugepage
1164 	default y
1166 	depends on ARCH_HAS_SET_DIRECT_MAP
1174 	depends on PROC_FS && ADVISE_SYSCALLS && MMU
1198 	depends on MMU
1206 	default y
1207 	depends on HAVE_ARCH_USERFAULTFD_WP
1211 	  purposes.  It is required to enable userfaultfd write protection on
1212 	  file-backed memory types like shmem and hugetlbfs.
1215 # multi-gen LRU {
1217 	bool "Multi-Gen LRU"
1218 	depends on MMU
1219 	# make sure folio->flags has enough spare bits
1220 	depends on 64BIT || !SPARSEMEM || SPARSEMEM_VMEMMAP
1223 	  Documentation/admin-guide/mm/multigen_lru.rst for details.
1226 	bool "Enable by default"
1227 	depends on LRU_GEN
1229 	  This option enables the multi-gen LRU by default.
1233 	depends on LRU_GEN
1238 	  This option has a per-memcg and per-node memory overhead.
1242 	depends on LRU_GEN && ARCH_HAS_HW_PTE_YOUNG
1250 	depends on ARCH_SUPPORTS_PER_VMA_LOCK && MMU && SMP
1252 	  Allow per-vma locking during page fault handling.
1259 	depends on !STACK_GROWSUP