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 boolean "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 compaction
235 config BALLOON_COMPACTION
236 bool "Allow for balloon memory compaction/migration"
238 depends on COMPACTION && VIRTIO_BALLOON
240 Memory fragmentation introduced by ballooning might reduce
241 significantly the number of 2MB contiguous memory blocks that can be
242 used within a guest, thus imposing performance penalties associated
243 with the reduced number of transparent huge pages that could be used
244 by the guest workload. Allowing the compaction & migration for memory
245 pages enlisted as being part of memory balloon devices avoids the
246 scenario aforementioned and helps improving memory defragmentation.
249 # support for memory compaction
251 bool "Allow for memory compaction"
256 Allows the compaction of memory for the allocation of huge pages.
259 # support for page migration
262 bool "Page migration"
264 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
266 Allows the migration of the physical location of pages of processes
267 while the virtual addresses are not changed. This is useful in
268 two situations. The first is on NUMA systems to put pages nearer
269 to the processors accessing. The second is when allocating huge
270 pages as migration can relocate pages to satisfy a huge page
271 allocation instead of reclaiming.
273 config ARCH_ENABLE_HUGEPAGE_MIGRATION
276 config PHYS_ADDR_T_64BIT
277 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
281 default "0" if !ZONE_DMA
285 bool "Enable bounce buffers"
287 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
289 Enable bounce buffers for devices that cannot access
290 the full range of memory available to the CPU. Enabled
291 by default when ZONE_DMA or HIGHMEM is selected, but you
292 may say n to override this.
294 # On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
295 # have more than 4GB of memory, but we don't currently use the IOTLB to present
296 # a 32-bit address to OHCI. So we need to use a bounce pool instead.
298 # We also use the bounce pool to provide stable page writes for jbd. jbd
299 # initiates buffer writeback without locking the page or setting PG_writeback,
300 # and fixing that behavior (a second time; jbd2 doesn't have this problem) is
301 # a major rework effort. Instead, use the bounce buffer to snapshot pages
302 # (until jbd goes away). The only jbd user is ext3.
303 config NEED_BOUNCE_POOL
305 default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD)
316 An architecture should select this if it implements the
317 deprecated interface virt_to_bus(). All new architectures
318 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
366 Enables code to recover from some memory failures on systems
367 with MCA recovery. This allows a system to continue running
368 even when some of its memory has uncorrected errors. This requires
369 special hardware support and typically ECC memory.
371 config HWPOISON_INJECT
372 tristate "HWPoison pages injector"
373 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
374 select PROC_PAGE_MONITOR
376 config NOMMU_INITIAL_TRIM_EXCESS
377 int "Turn on mmap() excess space trimming before booting"
381 The NOMMU mmap() frequently needs to allocate large contiguous chunks
382 of memory on which to store mappings, but it can only ask the system
383 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
384 more than it requires. To deal with this, mmap() is able to trim off
385 the excess and return it to the allocator.
387 If trimming is enabled, the excess is trimmed off and returned to the
388 system allocator, which can cause extra fragmentation, particularly
389 if there are a lot of transient processes.
391 If trimming is disabled, the excess is kept, but not used, which for
392 long-term mappings means that the space is wasted.
394 Trimming can be dynamically controlled through a sysctl option
395 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
396 excess pages there must be before trimming should occur, or zero if
397 no trimming is to occur.
399 This option specifies the initial value of this option. The default
400 of 1 says that all excess pages should be trimmed.
402 See Documentation/nommu-mmap.txt for more information.
404 config TRANSPARENT_HUGEPAGE
405 bool "Transparent Hugepage Support"
406 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
409 Transparent Hugepages allows the kernel to use huge pages and
410 huge tlb transparently to the applications whenever possible.
411 This feature can improve computing performance to certain
412 applications by speeding up page faults during memory
413 allocation, by reducing the number of tlb misses and by speeding
414 up the pagetable walking.
416 If memory constrained on embedded, you may want to say N.
419 prompt "Transparent Hugepage Support sysfs defaults"
420 depends on TRANSPARENT_HUGEPAGE
421 default TRANSPARENT_HUGEPAGE_ALWAYS
423 Selects the sysfs defaults for Transparent Hugepage Support.
425 config TRANSPARENT_HUGEPAGE_ALWAYS
428 Enabling Transparent Hugepage always, can increase the
429 memory footprint of applications without a guaranteed
430 benefit but it will work automatically for all applications.
432 config TRANSPARENT_HUGEPAGE_MADVISE
435 Enabling Transparent Hugepage madvise, will only provide a
436 performance improvement benefit to the applications using
437 madvise(MADV_HUGEPAGE) but it won't risk to increase the
438 memory footprint of applications without a guaranteed
443 # UP and nommu archs use km based percpu allocator
445 config NEED_PER_CPU_KM
451 bool "Enable cleancache driver to cache clean pages if tmem is present"
454 Cleancache can be thought of as a page-granularity victim cache
455 for clean pages that the kernel's pageframe replacement algorithm
456 (PFRA) would like to keep around, but can't since there isn't enough
457 memory. So when the PFRA "evicts" a page, it first attempts to use
458 cleancache code to put the data contained in that page into
459 "transcendent memory", memory that is not directly accessible or
460 addressable by the kernel and is of unknown and possibly
461 time-varying size. And when a cleancache-enabled
462 filesystem wishes to access a page in a file on disk, it first
463 checks cleancache to see if it already contains it; if it does,
464 the page is copied into the kernel and a disk access is avoided.
465 When a transcendent memory driver is available (such as zcache or
466 Xen transcendent memory), a significant I/O reduction
467 may be achieved. When none is available, all cleancache calls
468 are reduced to a single pointer-compare-against-NULL resulting
469 in a negligible performance hit.
471 If unsure, say Y to enable cleancache
474 bool "Enable frontswap to cache swap pages if tmem is present"
478 Frontswap is so named because it can be thought of as the opposite
479 of a "backing" store for a swap device. The data is stored into
480 "transcendent memory", memory that is not directly accessible or
481 addressable by the kernel and is of unknown and possibly
482 time-varying size. When space in transcendent memory is available,
483 a significant swap I/O reduction may be achieved. When none is
484 available, all frontswap calls are reduced to a single pointer-
485 compare-against-NULL resulting in a negligible performance hit
486 and swap data is stored as normal on the matching swap device.
488 If unsure, say Y to enable frontswap.
491 bool "Contiguous Memory Allocator"
492 depends on HAVE_MEMBLOCK && MMU
494 select MEMORY_ISOLATION
496 This enables the Contiguous Memory Allocator which allows other
497 subsystems to allocate big physically-contiguous blocks of memory.
498 CMA reserves a region of memory and allows only movable pages to
499 be allocated from it. This way, the kernel can use the memory for
500 pagecache and when a subsystem requests for contiguous area, the
501 allocated pages are migrated away to serve the contiguous request.
506 bool "CMA debug messages (DEVELOPMENT)"
507 depends on DEBUG_KERNEL && CMA
509 Turns on debug messages in CMA. This produces KERN_DEBUG
510 messages for every CMA call as well as various messages while
511 processing calls such as dma_alloc_from_contiguous().
512 This option does not affect warning and error messages.
515 int "Maximum count of the CMA areas"
519 CMA allows to create CMA areas for particular purpose, mainly,
520 used as device private area. This parameter sets the maximum
521 number of CMA area in the system.
523 If unsure, leave the default value "7".
525 config MEM_SOFT_DIRTY
526 bool "Track memory changes"
527 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
528 select PROC_PAGE_MONITOR
530 This option enables memory changes tracking by introducing a
531 soft-dirty bit on pte-s. This bit it set when someone writes
532 into a page just as regular dirty bit, but unlike the latter
533 it can be cleared by hands.
535 See Documentation/vm/soft-dirty.txt for more details.
538 bool "Compressed cache for swap pages (EXPERIMENTAL)"
539 depends on FRONTSWAP && CRYPTO=y
544 A lightweight compressed cache for swap pages. It takes
545 pages that are in the process of being swapped out and attempts to
546 compress them into a dynamically allocated RAM-based memory pool.
547 This can result in a significant I/O reduction on swap device and,
548 in the case where decompressing from RAM is faster that swap device
549 reads, can also improve workload performance.
551 This is marked experimental because it is a new feature (as of
552 v3.11) that interacts heavily with memory reclaim. While these
553 interactions don't cause any known issues on simple memory setups,
554 they have not be fully explored on the large set of potential
555 configurations and workloads that exist.
558 tristate "Common API for compressed memory storage"
561 Compressed memory storage API. This allows using either zbud or
565 tristate "Low density storage for compressed pages"
568 A special purpose allocator for storing compressed pages.
569 It is designed to store up to two compressed pages per physical
570 page. While this design limits storage density, it has simple and
571 deterministic reclaim properties that make it preferable to a higher
572 density approach when reclaim will be used.
575 tristate "Memory allocator for compressed pages"
579 zsmalloc is a slab-based memory allocator designed to store
580 compressed RAM pages. zsmalloc uses virtual memory mapping
581 in order to reduce fragmentation. However, this results in a
582 non-standard allocator interface where a handle, not a pointer, is
583 returned by an alloc(). This handle must be mapped in order to
584 access the allocated space.
586 config PGTABLE_MAPPING
587 bool "Use page table mapping to access object in zsmalloc"
590 By default, zsmalloc uses a copy-based object mapping method to
591 access allocations that span two pages. However, if a particular
592 architecture (ex, ARM) performs VM mapping faster than copying,
593 then you should select this. This causes zsmalloc to use page table
594 mapping rather than copying for object mapping.
596 You can check speed with zsmalloc benchmark:
597 https://github.com/spartacus06/zsmapbench
599 config GENERIC_EARLY_IOREMAP
602 config MAX_STACK_SIZE_MB
603 int "Maximum user stack size for 32-bit processes (MB)"
607 depends on STACK_GROWSUP && (!64BIT || COMPAT)
609 This is the maximum stack size in Megabytes in the VM layout of 32-bit
610 user processes when the stack grows upwards (currently only on parisc
611 and metag arch). The stack will be located at the highest memory
612 address minus the given value, unless the RLIMIT_STACK hard limit is
613 changed to a smaller value in which case that is used.
615 A sane initial value is 80 MB.