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 an 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 ARCH_DISCARD_MEMBLOCK
143 config MEMORY_ISOLATION
147 boolean "Enable to assign a node which has only movable memory"
148 depends on HAVE_MEMBLOCK
149 depends on NO_BOOTMEM
154 Allow a node to have only movable memory. Pages used by the kernel,
155 such as direct mapping pages cannot be migrated. So the corresponding
156 memory device cannot be hotplugged. This option allows the following
158 - When the system is booting, node full of hotpluggable memory can
159 be arranged to have only movable memory so that the whole node can
160 be hot-removed. (need movable_node boot option specified).
161 - After the system is up, the option allows users to online all the
162 memory of a node as movable memory so that the whole node can be
165 Users who don't use the memory hotplug feature are fine with this
166 option on since they don't specify movable_node boot option or they
167 don't online memory as movable.
169 Say Y here if you want to hotplug a whole node.
170 Say N here if you want kernel to use memory on all nodes evenly.
173 # Only be set on architectures that have completely implemented memory hotplug
174 # feature. If you are not sure, don't touch it.
176 config HAVE_BOOTMEM_INFO_NODE
179 # eventually, we can have this option just 'select SPARSEMEM'
180 config MEMORY_HOTPLUG
181 bool "Allow for memory hot-add"
182 depends on SPARSEMEM || X86_64_ACPI_NUMA
183 depends on ARCH_ENABLE_MEMORY_HOTPLUG
184 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
186 config MEMORY_HOTPLUG_SPARSE
188 depends on SPARSEMEM && MEMORY_HOTPLUG
190 config MEMORY_HOTREMOVE
191 bool "Allow for memory hot remove"
192 select MEMORY_ISOLATION
193 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
194 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
198 # If we have space for more page flags then we can enable additional
199 # optimizations and functionality.
201 # Regular Sparsemem takes page flag bits for the sectionid if it does not
202 # use a virtual memmap. Disable extended page flags for 32 bit platforms
203 # that require the use of a sectionid in the page flags.
205 config PAGEFLAGS_EXTENDED
207 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
209 # Heavily threaded applications may benefit from splitting the mm-wide
210 # page_table_lock, so that faults on different parts of the user address
211 # space can be handled with less contention: split it at this NR_CPUS.
212 # Default to 4 for wider testing, though 8 might be more appropriate.
213 # ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
214 # PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
215 # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
217 config SPLIT_PTLOCK_CPUS
219 default "999999" if ARM && !CPU_CACHE_VIPT
220 default "999999" if PARISC && !PA20
221 default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
222 default "999999" if !64BIT && GENERIC_LOCKBREAK
225 config ARCH_ENABLE_SPLIT_PMD_PTLOCK
229 # support for memory balloon compaction
230 config BALLOON_COMPACTION
231 bool "Allow for balloon memory compaction/migration"
233 depends on COMPACTION && VIRTIO_BALLOON
235 Memory fragmentation introduced by ballooning might reduce
236 significantly the number of 2MB contiguous memory blocks that can be
237 used within a guest, thus imposing performance penalties associated
238 with the reduced number of transparent huge pages that could be used
239 by the guest workload. Allowing the compaction & migration for memory
240 pages enlisted as being part of memory balloon devices avoids the
241 scenario aforementioned and helps improving memory defragmentation.
244 # support for memory compaction
246 bool "Allow for memory compaction"
251 Allows the compaction of memory for the allocation of huge pages.
254 # support for page migration
257 bool "Page migration"
259 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
261 Allows the migration of the physical location of pages of processes
262 while the virtual addresses are not changed. This is useful in
263 two situations. The first is on NUMA systems to put pages nearer
264 to the processors accessing. The second is when allocating huge
265 pages as migration can relocate pages to satisfy a huge page
266 allocation instead of reclaiming.
268 config PHYS_ADDR_T_64BIT
269 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
273 default "0" if !ZONE_DMA
277 bool "Enable bounce buffers"
279 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
281 Enable bounce buffers for devices that cannot access
282 the full range of memory available to the CPU. Enabled
283 by default when ZONE_DMA or HIGHMEM is selected, but you
284 may say n to override this.
286 # On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
287 # have more than 4GB of memory, but we don't currently use the IOTLB to present
288 # a 32-bit address to OHCI. So we need to use a bounce pool instead.
290 # We also use the bounce pool to provide stable page writes for jbd. jbd
291 # initiates buffer writeback without locking the page or setting PG_writeback,
292 # and fixing that behavior (a second time; jbd2 doesn't have this problem) is
293 # a major rework effort. Instead, use the bounce buffer to snapshot pages
294 # (until jbd goes away). The only jbd user is ext3.
295 config NEED_BOUNCE_POOL
297 default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD)
308 An architecture should select this if it implements the
309 deprecated interface virt_to_bus(). All new architectures
310 should probably not select this.
317 bool "Enable KSM for page merging"
320 Enable Kernel Samepage Merging: KSM periodically scans those areas
321 of an application's address space that an app has advised may be
322 mergeable. When it finds pages of identical content, it replaces
323 the many instances by a single page with that content, so
324 saving memory until one or another app needs to modify the content.
325 Recommended for use with KVM, or with other duplicative applications.
326 See Documentation/vm/ksm.txt for more information: KSM is inactive
327 until a program has madvised that an area is MADV_MERGEABLE, and
328 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
330 config DEFAULT_MMAP_MIN_ADDR
331 int "Low address space to protect from user allocation"
335 This is the portion of low virtual memory which should be protected
336 from userspace allocation. Keeping a user from writing to low pages
337 can help reduce the impact of kernel NULL pointer bugs.
339 For most ia64, ppc64 and x86 users with lots of address space
340 a value of 65536 is reasonable and should cause no problems.
341 On arm and other archs it should not be higher than 32768.
342 Programs which use vm86 functionality or have some need to map
343 this low address space will need CAP_SYS_RAWIO or disable this
344 protection by setting the value to 0.
346 This value can be changed after boot using the
347 /proc/sys/vm/mmap_min_addr tunable.
349 config ARCH_SUPPORTS_MEMORY_FAILURE
352 config MEMORY_FAILURE
354 depends on ARCH_SUPPORTS_MEMORY_FAILURE
355 bool "Enable recovery from hardware memory errors"
356 select MEMORY_ISOLATION
358 Enables code to recover from some memory failures on systems
359 with MCA recovery. This allows a system to continue running
360 even when some of its memory has uncorrected errors. This requires
361 special hardware support and typically ECC memory.
363 config HWPOISON_INJECT
364 tristate "HWPoison pages injector"
365 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
366 select PROC_PAGE_MONITOR
368 config NOMMU_INITIAL_TRIM_EXCESS
369 int "Turn on mmap() excess space trimming before booting"
373 The NOMMU mmap() frequently needs to allocate large contiguous chunks
374 of memory on which to store mappings, but it can only ask the system
375 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
376 more than it requires. To deal with this, mmap() is able to trim off
377 the excess and return it to the allocator.
379 If trimming is enabled, the excess is trimmed off and returned to the
380 system allocator, which can cause extra fragmentation, particularly
381 if there are a lot of transient processes.
383 If trimming is disabled, the excess is kept, but not used, which for
384 long-term mappings means that the space is wasted.
386 Trimming can be dynamically controlled through a sysctl option
387 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
388 excess pages there must be before trimming should occur, or zero if
389 no trimming is to occur.
391 This option specifies the initial value of this option. The default
392 of 1 says that all excess pages should be trimmed.
394 See Documentation/nommu-mmap.txt for more information.
396 config TRANSPARENT_HUGEPAGE
397 bool "Transparent Hugepage Support"
398 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
401 Transparent Hugepages allows the kernel to use huge pages and
402 huge tlb transparently to the applications whenever possible.
403 This feature can improve computing performance to certain
404 applications by speeding up page faults during memory
405 allocation, by reducing the number of tlb misses and by speeding
406 up the pagetable walking.
408 If memory constrained on embedded, you may want to say N.
411 prompt "Transparent Hugepage Support sysfs defaults"
412 depends on TRANSPARENT_HUGEPAGE
413 default TRANSPARENT_HUGEPAGE_ALWAYS
415 Selects the sysfs defaults for Transparent Hugepage Support.
417 config TRANSPARENT_HUGEPAGE_ALWAYS
420 Enabling Transparent Hugepage always, can increase the
421 memory footprint of applications without a guaranteed
422 benefit but it will work automatically for all applications.
424 config TRANSPARENT_HUGEPAGE_MADVISE
427 Enabling Transparent Hugepage madvise, will only provide a
428 performance improvement benefit to the applications using
429 madvise(MADV_HUGEPAGE) but it won't risk to increase the
430 memory footprint of applications without a guaranteed
434 config CROSS_MEMORY_ATTACH
435 bool "Cross Memory Support"
439 Enabling this option adds the system calls process_vm_readv and
440 process_vm_writev which allow a process with the correct privileges
441 to directly read from or write to to another process's address space.
442 See the man page for more details.
445 # UP and nommu archs use km based percpu allocator
447 config NEED_PER_CPU_KM
453 bool "Enable cleancache driver to cache clean pages if tmem is present"
456 Cleancache can be thought of as a page-granularity victim cache
457 for clean pages that the kernel's pageframe replacement algorithm
458 (PFRA) would like to keep around, but can't since there isn't enough
459 memory. So when the PFRA "evicts" a page, it first attempts to use
460 cleancache code to put the data contained in that page into
461 "transcendent memory", memory that is not directly accessible or
462 addressable by the kernel and is of unknown and possibly
463 time-varying size. And when a cleancache-enabled
464 filesystem wishes to access a page in a file on disk, it first
465 checks cleancache to see if it already contains it; if it does,
466 the page is copied into the kernel and a disk access is avoided.
467 When a transcendent memory driver is available (such as zcache or
468 Xen transcendent memory), a significant I/O reduction
469 may be achieved. When none is available, all cleancache calls
470 are reduced to a single pointer-compare-against-NULL resulting
471 in a negligible performance hit.
473 If unsure, say Y to enable cleancache
476 bool "Enable frontswap to cache swap pages if tmem is present"
480 Frontswap is so named because it can be thought of as the opposite
481 of a "backing" store for a swap device. The data is stored into
482 "transcendent memory", memory that is not directly accessible or
483 addressable by the kernel and is of unknown and possibly
484 time-varying size. When space in transcendent memory is available,
485 a significant swap I/O reduction may be achieved. When none is
486 available, all frontswap calls are reduced to a single pointer-
487 compare-against-NULL resulting in a negligible performance hit
488 and swap data is stored as normal on the matching swap device.
490 If unsure, say Y to enable frontswap.
493 bool "Contiguous Memory Allocator"
494 depends on HAVE_MEMBLOCK && MMU
496 select MEMORY_ISOLATION
498 This enables the Contiguous Memory Allocator which allows other
499 subsystems to allocate big physically-contiguous blocks of memory.
500 CMA reserves a region of memory and allows only movable pages to
501 be allocated from it. This way, the kernel can use the memory for
502 pagecache and when a subsystem requests for contiguous area, the
503 allocated pages are migrated away to serve the contiguous request.
508 bool "CMA debug messages (DEVELOPMENT)"
509 depends on DEBUG_KERNEL && CMA
511 Turns on debug messages in CMA. This produces KERN_DEBUG
512 messages for every CMA call as well as various messages while
513 processing calls such as dma_alloc_from_contiguous().
514 This option does not affect warning and error messages.
520 A special purpose allocator for storing compressed pages.
521 It is designed to store up to two compressed pages per physical
522 page. While this design limits storage density, it has simple and
523 deterministic reclaim properties that make it preferable to a higher
524 density approach when reclaim will be used.
527 bool "Compressed cache for swap pages (EXPERIMENTAL)"
528 depends on FRONTSWAP && CRYPTO=y
533 A lightweight compressed cache for swap pages. It takes
534 pages that are in the process of being swapped out and attempts to
535 compress them into a dynamically allocated RAM-based memory pool.
536 This can result in a significant I/O reduction on swap device and,
537 in the case where decompressing from RAM is faster that swap device
538 reads, can also improve workload performance.
540 This is marked experimental because it is a new feature (as of
541 v3.11) that interacts heavily with memory reclaim. While these
542 interactions don't cause any known issues on simple memory setups,
543 they have not be fully explored on the large set of potential
544 configurations and workloads that exist.
546 config MEM_SOFT_DIRTY
547 bool "Track memory changes"
548 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY
549 select PROC_PAGE_MONITOR
551 This option enables memory changes tracking by introducing a
552 soft-dirty bit on pte-s. This bit it set when someone writes
553 into a page just as regular dirty bit, but unlike the latter
554 it can be cleared by hands.
556 See Documentation/vm/soft-dirty.txt for more details.