1 config SELECT_MEMORY_MODEL
3 depends on ARCH_SELECT_MEMORY_MODEL
7 depends on SELECT_MEMORY_MODEL
8 default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
9 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
10 default FLATMEM_MANUAL
14 depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
16 This option allows you to change some of the ways that
17 Linux manages its memory internally. Most users will
18 only have one option here: FLATMEM. This is normal
21 Some users of more advanced features like NUMA and
22 memory hotplug may have different options here.
23 DISCONTIGMEM is a more mature, better tested system,
24 but is incompatible with memory hotplug and may suffer
25 decreased performance over SPARSEMEM. If unsure between
26 "Sparse Memory" and "Discontiguous Memory", choose
27 "Discontiguous Memory".
29 If unsure, choose this option (Flat Memory) over any other.
31 config DISCONTIGMEM_MANUAL
32 bool "Discontiguous Memory"
33 depends on ARCH_DISCONTIGMEM_ENABLE
35 This option provides enhanced support for discontiguous
36 memory systems, over FLATMEM. These systems have holes
37 in their physical address spaces, and this option provides
38 more efficient handling of these holes. However, the vast
39 majority of hardware has quite flat address spaces, and
40 can have degraded performance from the extra overhead that
43 Many NUMA configurations will have this as the only option.
45 If unsure, choose "Flat Memory" over this option.
47 config SPARSEMEM_MANUAL
49 depends on ARCH_SPARSEMEM_ENABLE
51 This will be the only option for some systems, including
52 memory hotplug systems. This is normal.
54 For many other systems, this will be an alternative to
55 "Discontiguous Memory". This option provides some potential
56 performance benefits, along with decreased code complexity,
57 but it is newer, and more experimental.
59 If unsure, choose "Discontiguous Memory" or "Flat Memory"
66 depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
70 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
74 depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
76 config FLAT_NODE_MEM_MAP
81 # Both the NUMA code and DISCONTIGMEM use arrays of pg_data_t's
82 # to represent different areas of memory. This variable allows
83 # those dependencies to exist individually.
85 config NEED_MULTIPLE_NODES
87 depends on DISCONTIGMEM || NUMA
89 config HAVE_MEMORY_PRESENT
91 depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
94 # SPARSEMEM_EXTREME (which is the default) does some bootmem
95 # allocations when memory_present() is called. If this cannot
96 # be done on your architecture, select this option. However,
97 # statically allocating the mem_section[] array can potentially
98 # consume vast quantities of .bss, so be careful.
100 # This option will also potentially produce smaller runtime code
101 # with gcc 3.4 and later.
103 config SPARSEMEM_STATIC
107 # Architecture platforms which require a two level mem_section in SPARSEMEM
108 # must select this option. This is usually for architecture platforms with
109 # an extremely sparse physical address space.
111 config SPARSEMEM_EXTREME
113 depends on SPARSEMEM && !SPARSEMEM_STATIC
115 config SPARSEMEM_VMEMMAP_ENABLE
118 config SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
120 depends on SPARSEMEM && X86_64
122 config SPARSEMEM_VMEMMAP
123 bool "Sparse Memory virtual memmap"
124 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
127 SPARSEMEM_VMEMMAP uses a virtually mapped memmap to optimise
128 pfn_to_page and page_to_pfn operations. This is the most
129 efficient option when sufficient kernel resources are available.
134 config HAVE_MEMBLOCK_NODE_MAP
137 config HAVE_MEMBLOCK_PHYS_MAP
140 config HAVE_GENERIC_RCU_GUP
143 config ARCH_DISCARD_MEMBLOCK
149 config MEMORY_ISOLATION
153 bool "Enable to assign a node which has only movable memory"
154 depends on HAVE_MEMBLOCK
155 depends on NO_BOOTMEM
160 Allow a node to have only movable memory. Pages used by the kernel,
161 such as direct mapping pages cannot be migrated. So the corresponding
162 memory device cannot be hotplugged. This option allows the following
164 - When the system is booting, node full of hotpluggable memory can
165 be arranged to have only movable memory so that the whole node can
166 be hot-removed. (need movable_node boot option specified).
167 - After the system is up, the option allows users to online all the
168 memory of a node as movable memory so that the whole node can be
171 Users who don't use the memory hotplug feature are fine with this
172 option on since they don't specify movable_node boot option or they
173 don't online memory as movable.
175 Say Y here if you want to hotplug a whole node.
176 Say N here if you want kernel to use memory on all nodes evenly.
179 # Only be set on architectures that have completely implemented memory hotplug
180 # feature. If you are not sure, don't touch it.
182 config HAVE_BOOTMEM_INFO_NODE
185 # eventually, we can have this option just 'select SPARSEMEM'
186 config MEMORY_HOTPLUG
187 bool "Allow for memory hot-add"
188 depends on SPARSEMEM || X86_64_ACPI_NUMA
189 depends on ARCH_ENABLE_MEMORY_HOTPLUG
190 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
192 config MEMORY_HOTPLUG_SPARSE
194 depends on SPARSEMEM && MEMORY_HOTPLUG
196 config MEMORY_HOTREMOVE
197 bool "Allow for memory hot remove"
198 select MEMORY_ISOLATION
199 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
200 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
204 # If we have space for more page flags then we can enable additional
205 # optimizations and functionality.
207 # Regular Sparsemem takes page flag bits for the sectionid if it does not
208 # use a virtual memmap. Disable extended page flags for 32 bit platforms
209 # that require the use of a sectionid in the page flags.
211 config PAGEFLAGS_EXTENDED
213 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
215 # Heavily threaded applications may benefit from splitting the mm-wide
216 # page_table_lock, so that faults on different parts of the user address
217 # space can be handled with less contention: split it at this NR_CPUS.
218 # Default to 4 for wider testing, though 8 might be more appropriate.
219 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
220 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
221 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
223 config SPLIT_PTLOCK_CPUS
225 default "999999" if !MMU
226 default "999999" if ARM && !CPU_CACHE_VIPT
227 default "999999" if PARISC && !PA20
230 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
234 # support for memory balloon
235 config MEMORY_BALLOON
239 # support for memory balloon compaction
240 config BALLOON_COMPACTION
241 bool "Allow for balloon memory compaction/migration"
243 depends on COMPACTION && MEMORY_BALLOON
245 Memory fragmentation introduced by ballooning might reduce
246 significantly the number of 2MB contiguous memory blocks that can be
247 used within a guest, thus imposing performance penalties associated
248 with the reduced number of transparent huge pages that could be used
249 by the guest workload. Allowing the compaction & migration for memory
250 pages enlisted as being part of memory balloon devices avoids the
251 scenario aforementioned and helps improving memory defragmentation.
254 # support for memory compaction
256 bool "Allow for memory compaction"
261 Allows the compaction of memory for the allocation of huge pages.
264 # support for page migration
267 bool "Page migration"
269 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
271 Allows the migration of the physical location of pages of processes
272 while the virtual addresses are not changed. This is useful in
273 two situations. The first is on NUMA systems to put pages nearer
274 to the processors accessing. The second is when allocating huge
275 pages as migration can relocate pages to satisfy a huge page
276 allocation instead of reclaiming.
278 config ARCH_ENABLE_HUGEPAGE_MIGRATION
281 config PHYS_ADDR_T_64BIT
282 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
286 default "0" if !ZONE_DMA
290 bool "Enable bounce buffers"
292 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
294 Enable bounce buffers for devices that cannot access
295 the full range of memory available to the CPU. Enabled
296 by default when ZONE_DMA or HIGHMEM is selected, but you
297 may say n to override this.
299 # On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
300 # have more than 4GB of memory, but we don't currently use the IOTLB to present
301 # a 32-bit address to OHCI. So we need to use a bounce pool instead.
302 config NEED_BOUNCE_POOL
304 default y if TILE && USB_OHCI_HCD
315 An architecture should select this if it implements the
316 deprecated interface virt_to_bus(). All new architectures
317 should probably not select this.
325 bool "Enable KSM for page merging"
328 Enable Kernel Samepage Merging: KSM periodically scans those areas
329 of an application's address space that an app has advised may be
330 mergeable. When it finds pages of identical content, it replaces
331 the many instances by a single page with that content, so
332 saving memory until one or another app needs to modify the content.
333 Recommended for use with KVM, or with other duplicative applications.
334 See Documentation/vm/ksm.txt for more information: KSM is inactive
335 until a program has madvised that an area is MADV_MERGEABLE, and
336 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
338 config DEFAULT_MMAP_MIN_ADDR
339 int "Low address space to protect from user allocation"
343 This is the portion of low virtual memory which should be protected
344 from userspace allocation. Keeping a user from writing to low pages
345 can help reduce the impact of kernel NULL pointer bugs.
347 For most ia64, ppc64 and x86 users with lots of address space
348 a value of 65536 is reasonable and should cause no problems.
349 On arm and other archs it should not be higher than 32768.
350 Programs which use vm86 functionality or have some need to map
351 this low address space will need CAP_SYS_RAWIO or disable this
352 protection by setting the value to 0.
354 This value can be changed after boot using the
355 /proc/sys/vm/mmap_min_addr tunable.
357 config ARCH_SUPPORTS_MEMORY_FAILURE
360 config MEMORY_FAILURE
362 depends on ARCH_SUPPORTS_MEMORY_FAILURE
363 bool "Enable recovery from hardware memory errors"
364 select MEMORY_ISOLATION
367 Enables code to recover from some memory failures on systems
368 with MCA recovery. This allows a system to continue running
369 even when some of its memory has uncorrected errors. This requires
370 special hardware support and typically ECC memory.
372 config HWPOISON_INJECT
373 tristate "HWPoison pages injector"
374 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
375 select PROC_PAGE_MONITOR
377 config NOMMU_INITIAL_TRIM_EXCESS
378 int "Turn on mmap() excess space trimming before booting"
382 The NOMMU mmap() frequently needs to allocate large contiguous chunks
383 of memory on which to store mappings, but it can only ask the system
384 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
385 more than it requires. To deal with this, mmap() is able to trim off
386 the excess and return it to the allocator.
388 If trimming is enabled, the excess is trimmed off and returned to the
389 system allocator, which can cause extra fragmentation, particularly
390 if there are a lot of transient processes.
392 If trimming is disabled, the excess is kept, but not used, which for
393 long-term mappings means that the space is wasted.
395 Trimming can be dynamically controlled through a sysctl option
396 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
397 excess pages there must be before trimming should occur, or zero if
398 no trimming is to occur.
400 This option specifies the initial value of this option. The default
401 of 1 says that all excess pages should be trimmed.
403 See Documentation/nommu-mmap.txt for more information.
405 config TRANSPARENT_HUGEPAGE
406 bool "Transparent Hugepage Support"
407 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
410 Transparent Hugepages allows the kernel to use huge pages and
411 huge tlb transparently to the applications whenever possible.
412 This feature can improve computing performance to certain
413 applications by speeding up page faults during memory
414 allocation, by reducing the number of tlb misses and by speeding
415 up the pagetable walking.
417 If memory constrained on embedded, you may want to say N.
420 prompt "Transparent Hugepage Support sysfs defaults"
421 depends on TRANSPARENT_HUGEPAGE
422 default TRANSPARENT_HUGEPAGE_ALWAYS
424 Selects the sysfs defaults for Transparent Hugepage Support.
426 config TRANSPARENT_HUGEPAGE_ALWAYS
429 Enabling Transparent Hugepage always, can increase the
430 memory footprint of applications without a guaranteed
431 benefit but it will work automatically for all applications.
433 config TRANSPARENT_HUGEPAGE_MADVISE
436 Enabling Transparent Hugepage madvise, will only provide a
437 performance improvement benefit to the applications using
438 madvise(MADV_HUGEPAGE) but it won't risk to increase the
439 memory footprint of applications without a guaranteed
444 # UP and nommu archs use km based percpu allocator
446 config NEED_PER_CPU_KM
452 bool "Enable cleancache driver to cache clean pages if tmem is present"
455 Cleancache can be thought of as a page-granularity victim cache
456 for clean pages that the kernel's pageframe replacement algorithm
457 (PFRA) would like to keep around, but can't since there isn't enough
458 memory. So when the PFRA "evicts" a page, it first attempts to use
459 cleancache code to put the data contained in that page into
460 "transcendent memory", memory that is not directly accessible or
461 addressable by the kernel and is of unknown and possibly
462 time-varying size. And when a cleancache-enabled
463 filesystem wishes to access a page in a file on disk, it first
464 checks cleancache to see if it already contains it; if it does,
465 the page is copied into the kernel and a disk access is avoided.
466 When a transcendent memory driver is available (such as zcache or
467 Xen transcendent memory), a significant I/O reduction
468 may be achieved. When none is available, all cleancache calls
469 are reduced to a single pointer-compare-against-NULL resulting
470 in a negligible performance hit.
472 If unsure, say Y to enable cleancache
475 bool "Enable frontswap to cache swap pages if tmem is present"
479 Frontswap is so named because it can be thought of as the opposite
480 of a "backing" store for a swap device. The data is stored into
481 "transcendent memory", memory that is not directly accessible or
482 addressable by the kernel and is of unknown and possibly
483 time-varying size. When space in transcendent memory is available,
484 a significant swap I/O reduction may be achieved. When none is
485 available, all frontswap calls are reduced to a single pointer-
486 compare-against-NULL resulting in a negligible performance hit
487 and swap data is stored as normal on the matching swap device.
489 If unsure, say Y to enable frontswap.
492 bool "Contiguous Memory Allocator"
493 depends on HAVE_MEMBLOCK && MMU
495 select MEMORY_ISOLATION
497 This enables the Contiguous Memory Allocator which allows other
498 subsystems to allocate big physically-contiguous blocks of memory.
499 CMA reserves a region of memory and allows only movable pages to
500 be allocated from it. This way, the kernel can use the memory for
501 pagecache and when a subsystem requests for contiguous area, the
502 allocated pages are migrated away to serve the contiguous request.
507 bool "CMA debug messages (DEVELOPMENT)"
508 depends on DEBUG_KERNEL && CMA
510 Turns on debug messages in CMA. This produces KERN_DEBUG
511 messages for every CMA call as well as various messages while
512 processing calls such as dma_alloc_from_contiguous().
513 This option does not affect warning and error messages.
516 bool "CMA debugfs interface"
517 depends on CMA && DEBUG_FS
519 Turns on the DebugFS interface for CMA.
522 int "Maximum count of the CMA areas"
526 CMA allows to create CMA areas for particular purpose, mainly,
527 used as device private area. This parameter sets the maximum
528 number of CMA area in the system.
530 If unsure, leave the default value "7".
532 config MEM_SOFT_DIRTY
533 bool "Track memory changes"
534 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
535 select PROC_PAGE_MONITOR
537 This option enables memory changes tracking by introducing a
538 soft-dirty bit on pte-s. This bit it set when someone writes
539 into a page just as regular dirty bit, but unlike the latter
540 it can be cleared by hands.
542 See Documentation/vm/soft-dirty.txt for more details.
545 bool "Compressed cache for swap pages (EXPERIMENTAL)"
546 depends on FRONTSWAP && CRYPTO=y
551 A lightweight compressed cache for swap pages. It takes
552 pages that are in the process of being swapped out and attempts to
553 compress them into a dynamically allocated RAM-based memory pool.
554 This can result in a significant I/O reduction on swap device and,
555 in the case where decompressing from RAM is faster that swap device
556 reads, can also improve workload performance.
558 This is marked experimental because it is a new feature (as of
559 v3.11) that interacts heavily with memory reclaim. While these
560 interactions don't cause any known issues on simple memory setups,
561 they have not be fully explored on the large set of potential
562 configurations and workloads that exist.
565 tristate "Common API for compressed memory storage"
568 Compressed memory storage API. This allows using either zbud or
572 tristate "Low density storage for compressed pages"
575 A special purpose allocator for storing compressed pages.
576 It is designed to store up to two compressed pages per physical
577 page. While this design limits storage density, it has simple and
578 deterministic reclaim properties that make it preferable to a higher
579 density approach when reclaim will be used.
582 tristate "Memory allocator for compressed pages"
586 zsmalloc is a slab-based memory allocator designed to store
587 compressed RAM pages. zsmalloc uses virtual memory mapping
588 in order to reduce fragmentation. However, this results in a
589 non-standard allocator interface where a handle, not a pointer, is
590 returned by an alloc(). This handle must be mapped in order to
591 access the allocated space.
593 config PGTABLE_MAPPING
594 bool "Use page table mapping to access object in zsmalloc"
597 By default, zsmalloc uses a copy-based object mapping method to
598 access allocations that span two pages. However, if a particular
599 architecture (ex, ARM) performs VM mapping faster than copying,
600 then you should select this. This causes zsmalloc to use page table
601 mapping rather than copying for object mapping.
603 You can check speed with zsmalloc benchmark:
604 https://github.com/spartacus06/zsmapbench
607 bool "Export zsmalloc statistics"
611 This option enables code in the zsmalloc to collect various
612 statistics about whats happening in zsmalloc and exports that
613 information to userspace via debugfs.
616 config GENERIC_EARLY_IOREMAP
619 config MAX_STACK_SIZE_MB
620 int "Maximum user stack size for 32-bit processes (MB)"
624 depends on STACK_GROWSUP && (!64BIT || COMPAT)
626 This is the maximum stack size in Megabytes in the VM layout of 32-bit
627 user processes when the stack grows upwards (currently only on parisc
628 and metag arch). The stack will be located at the highest memory
629 address minus the given value, unless the RLIMIT_STACK hard limit is
630 changed to a smaller value in which case that is used.
632 A sane initial value is 80 MB.
634 # For architectures that support deferred memory initialisation
635 config ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
638 config DEFERRED_STRUCT_PAGE_INIT
639 bool "Defer initialisation of struct pages to kswapd"
641 depends on ARCH_SUPPORTS_DEFERRED_STRUCT_PAGE_INIT
642 depends on MEMORY_HOTPLUG
644 Ordinarily all struct pages are initialised during early boot in a
645 single thread. On very large machines this can take a considerable
646 amount of time. If this option is set, large machines will bring up
647 a subset of memmap at boot and then initialise the rest in parallel
648 when kswapd starts. This has a potential performance impact on
649 processes running early in the lifetime of the systemm until kswapd
650 finishes the initialisation.
652 config IDLE_PAGE_TRACKING
653 bool "Enable idle page tracking"
654 depends on SYSFS && MMU
655 select PAGE_EXTENSION if !64BIT
657 This feature allows to estimate the amount of user pages that have
658 not been touched during a given period of time. This information can
659 be useful to tune memory cgroup limits and/or for job placement
660 within a compute cluster.
662 See Documentation/vm/idle_page_tracking.txt for more details.
665 bool "Device memory (pmem, etc...) hotplug support" if EXPERT
668 depends on MEMORY_HOTPLUG
669 depends on MEMORY_HOTREMOVE
670 depends on X86_64 #arch_add_memory() comprehends device memory
673 Device memory hotplug support allows for establishing pmem,
674 or other device driver discovered memory regions, in the
675 memmap. This allows pfn_to_page() lookups of otherwise
676 "device-physical" addresses which is needed for using a DAX
677 mapping in an O_DIRECT operation, among other things.
679 If FS_DAX is enabled, then say Y.
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