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Dave Hansene1785e82005-06-23 00:07:49 -07001config SELECT_MEMORY_MODEL
2 def_bool y
Kees Cooka8826ee2013-01-16 18:54:17 -08003 depends on ARCH_SELECT_MEMORY_MODEL
Dave Hansene1785e82005-06-23 00:07:49 -07004
Dave Hansen3a9da762005-06-23 00:07:42 -07005choice
6 prompt "Memory model"
Dave Hansene1785e82005-06-23 00:07:49 -07007 depends on SELECT_MEMORY_MODEL
8 default DISCONTIGMEM_MANUAL if ARCH_DISCONTIGMEM_DEFAULT
Andy Whitcroftd41dee32005-06-23 00:07:54 -07009 default SPARSEMEM_MANUAL if ARCH_SPARSEMEM_DEFAULT
Dave Hansene1785e82005-06-23 00:07:49 -070010 default FLATMEM_MANUAL
Dave Hansen3a9da762005-06-23 00:07:42 -070011
Dave Hansene1785e82005-06-23 00:07:49 -070012config FLATMEM_MANUAL
Dave Hansen3a9da762005-06-23 00:07:42 -070013 bool "Flat Memory"
Anton Blanchardc898ec12006-01-06 00:12:07 -080014 depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
Dave Hansen3a9da762005-06-23 00:07:42 -070015 help
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
19 and a correct option.
20
Andy Whitcroftd41dee32005-06-23 00:07:54 -070021 Some users of more advanced features like NUMA and
22 memory hotplug may have different options here.
Geert Uytterhoeven18f65332013-09-15 12:01:33 +020023 DISCONTIGMEM is a more mature, better tested system,
Andy Whitcroftd41dee32005-06-23 00:07:54 -070024 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".
28
29 If unsure, choose this option (Flat Memory) over any other.
Dave Hansen3a9da762005-06-23 00:07:42 -070030
Dave Hansene1785e82005-06-23 00:07:49 -070031config DISCONTIGMEM_MANUAL
Dave Hansenf3519f92005-09-16 19:27:54 -070032 bool "Discontiguous Memory"
Dave Hansen3a9da762005-06-23 00:07:42 -070033 depends on ARCH_DISCONTIGMEM_ENABLE
34 help
Dave Hansen785dcd42005-06-23 00:07:50 -070035 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
Philipp Marekad3d0a32007-10-20 02:46:58 +020040 can have degraded performance from the extra overhead that
Dave Hansen785dcd42005-06-23 00:07:50 -070041 this option imposes.
42
43 Many NUMA configurations will have this as the only option.
44
Dave Hansen3a9da762005-06-23 00:07:42 -070045 If unsure, choose "Flat Memory" over this option.
46
Andy Whitcroftd41dee32005-06-23 00:07:54 -070047config SPARSEMEM_MANUAL
48 bool "Sparse Memory"
49 depends on ARCH_SPARSEMEM_ENABLE
50 help
51 This will be the only option for some systems, including
52 memory hotplug systems. This is normal.
53
54 For many other systems, this will be an alternative to
Dave Hansenf3519f92005-09-16 19:27:54 -070055 "Discontiguous Memory". This option provides some potential
Andy Whitcroftd41dee32005-06-23 00:07:54 -070056 performance benefits, along with decreased code complexity,
57 but it is newer, and more experimental.
58
59 If unsure, choose "Discontiguous Memory" or "Flat Memory"
60 over this option.
61
Dave Hansen3a9da762005-06-23 00:07:42 -070062endchoice
63
Dave Hansene1785e82005-06-23 00:07:49 -070064config DISCONTIGMEM
65 def_bool y
66 depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
67
Andy Whitcroftd41dee32005-06-23 00:07:54 -070068config SPARSEMEM
69 def_bool y
Russell King1a83e172009-10-26 16:50:12 -070070 depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
Andy Whitcroftd41dee32005-06-23 00:07:54 -070071
Dave Hansene1785e82005-06-23 00:07:49 -070072config FLATMEM
73 def_bool y
Andy Whitcroftd41dee32005-06-23 00:07:54 -070074 depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
75
76config FLAT_NODE_MEM_MAP
77 def_bool y
78 depends on !SPARSEMEM
Dave Hansene1785e82005-06-23 00:07:49 -070079
Dave Hansen93b75042005-06-23 00:07:47 -070080#
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.
84#
85config NEED_MULTIPLE_NODES
86 def_bool y
87 depends on DISCONTIGMEM || NUMA
Andy Whitcroftaf705362005-06-23 00:07:53 -070088
89config HAVE_MEMORY_PRESENT
90 def_bool y
Andy Whitcroftd41dee32005-06-23 00:07:54 -070091 depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
Bob Picco802f1922005-09-03 15:54:26 -070092
93#
Bob Picco3e347262005-09-03 15:54:28 -070094# SPARSEMEM_EXTREME (which is the default) does some bootmem
Matt LaPlante84eb8d02006-10-03 22:53:09 +020095# allocations when memory_present() is called. If this cannot
Bob Picco3e347262005-09-03 15:54:28 -070096# 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.
99#
100# This option will also potentially produce smaller runtime code
101# with gcc 3.4 and later.
102#
103config SPARSEMEM_STATIC
Jan Beulich9ba16082008-10-15 22:01:38 -0700104 bool
Bob Picco3e347262005-09-03 15:54:28 -0700105
106#
Matt LaPlante44c09202006-10-03 22:34:14 +0200107# Architecture platforms which require a two level mem_section in SPARSEMEM
Bob Picco802f1922005-09-03 15:54:26 -0700108# must select this option. This is usually for architecture platforms with
109# an extremely sparse physical address space.
110#
Bob Picco3e347262005-09-03 15:54:28 -0700111config SPARSEMEM_EXTREME
112 def_bool y
113 depends on SPARSEMEM && !SPARSEMEM_STATIC
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700114
Andy Whitcroft29c71112007-10-16 01:24:14 -0700115config SPARSEMEM_VMEMMAP_ENABLE
Jan Beulich9ba16082008-10-15 22:01:38 -0700116 bool
Andy Whitcroft29c71112007-10-16 01:24:14 -0700117
Yinghai Lu9bdac912010-02-10 01:20:22 -0800118config SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
119 def_bool y
120 depends on SPARSEMEM && X86_64
121
Andy Whitcroft29c71112007-10-16 01:24:14 -0700122config SPARSEMEM_VMEMMAP
Geoff Levanda5ee6da2007-12-17 16:19:53 -0800123 bool "Sparse Memory virtual memmap"
124 depends on SPARSEMEM && SPARSEMEM_VMEMMAP_ENABLE
125 default y
126 help
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.
Andy Whitcroft29c71112007-10-16 01:24:14 -0700130
Yinghai Lu95f72d12010-07-12 14:36:09 +1000131config HAVE_MEMBLOCK
132 boolean
133
Tejun Heo7c0caeb2011-07-14 11:43:42 +0200134config HAVE_MEMBLOCK_NODE_MAP
135 boolean
136
Philipp Hachtmann70210ed2014-01-29 18:16:01 +0100137config HAVE_MEMBLOCK_PHYS_MAP
138 boolean
139
Steve Capper2667f502014-10-09 15:29:14 -0700140config HAVE_GENERIC_RCU_GUP
141 boolean
142
Tejun Heoc378ddd2011-07-14 11:46:03 +0200143config ARCH_DISCARD_MEMBLOCK
144 boolean
145
Sam Ravnborg66616722011-10-31 17:08:20 -0700146config NO_BOOTMEM
147 boolean
148
Minchan Kimee6f5092012-07-31 16:43:50 -0700149config MEMORY_ISOLATION
150 boolean
151
Lai Jiangshan20b2f522012-12-12 13:52:00 -0800152config MOVABLE_NODE
153 boolean "Enable to assign a node which has only movable memory"
154 depends on HAVE_MEMBLOCK
155 depends on NO_BOOTMEM
156 depends on X86_64
157 depends on NUMA
Tang Chenc2974052012-12-18 14:21:33 -0800158 default n
159 help
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
Tang Chenc5320922013-11-12 15:08:10 -0800162 memory device cannot be hotplugged. This option allows the following
163 two things:
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
169 hot-removed.
170
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.
Tang Chenc2974052012-12-18 14:21:33 -0800174
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.
Lai Jiangshan20b2f522012-12-12 13:52:00 -0800177
Yasuaki Ishimatsu46723bf2013-02-22 16:33:00 -0800178#
179# Only be set on architectures that have completely implemented memory hotplug
180# feature. If you are not sure, don't touch it.
181#
182config HAVE_BOOTMEM_INFO_NODE
183 def_bool n
184
Dave Hansen3947be12005-10-29 18:16:54 -0700185# eventually, we can have this option just 'select SPARSEMEM'
186config MEMORY_HOTPLUG
187 bool "Allow for memory hot-add"
Keith Manntheyec69acb2006-09-30 23:27:05 -0700188 depends on SPARSEMEM || X86_64_ACPI_NUMA
Stephen Rothwell40b31362013-05-21 13:49:35 +1000189 depends on ARCH_ENABLE_MEMORY_HOTPLUG
Kumar Galaed84a072009-10-16 07:21:36 +0000190 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
Dave Hansen3947be12005-10-29 18:16:54 -0700191
Keith Manntheyec69acb2006-09-30 23:27:05 -0700192config MEMORY_HOTPLUG_SPARSE
193 def_bool y
194 depends on SPARSEMEM && MEMORY_HOTPLUG
195
KAMEZAWA Hiroyuki0c0e6192007-10-16 01:26:12 -0700196config MEMORY_HOTREMOVE
197 bool "Allow for memory hot remove"
Yasuaki Ishimatsu46723bf2013-02-22 16:33:00 -0800198 select MEMORY_ISOLATION
Nathan Fontenotf7e33342013-09-27 10:18:09 -0500199 select HAVE_BOOTMEM_INFO_NODE if (X86_64 || PPC64)
KAMEZAWA Hiroyuki0c0e6192007-10-16 01:26:12 -0700200 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
201 depends on MIGRATION
202
Christoph Lametere20b8cc2008-04-28 02:12:55 -0700203#
204# If we have space for more page flags then we can enable additional
205# optimizations and functionality.
206#
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.
210#
211config PAGEFLAGS_EXTENDED
212 def_bool y
H. Peter Anvina269cca2009-08-31 11:17:44 -0700213 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
Christoph Lametere20b8cc2008-04-28 02:12:55 -0700214
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700215# 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.
Hugh Dickins7b6ac9d2005-11-23 13:37:37 -0800220# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
Hugh Dickinsa70caa82009-12-14 17:59:02 -0800221# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700222#
223config SPLIT_PTLOCK_CPUS
224 int
Kirill A. Shutemov91645502014-04-07 15:37:14 -0700225 default "999999" if !MMU
Hugh Dickinsa70caa82009-12-14 17:59:02 -0800226 default "999999" if ARM && !CPU_CACHE_VIPT
227 default "999999" if PARISC && !PA20
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700228 default "4"
Christoph Lameter7cbe34c2006-01-08 01:00:49 -0800229
Kirill A. Shutemove009bb32013-11-14 14:31:07 -0800230config ARCH_ENABLE_SPLIT_PMD_PTLOCK
231 boolean
232
Christoph Lameter7cbe34c2006-01-08 01:00:49 -0800233#
Konstantin Khlebnikov09316c02014-10-09 15:29:32 -0700234# support for memory balloon
235config MEMORY_BALLOON
236 boolean
237
238#
Rafael Aquini18468d92012-12-11 16:02:38 -0800239# support for memory balloon compaction
240config BALLOON_COMPACTION
241 bool "Allow for balloon memory compaction/migration"
242 def_bool y
Konstantin Khlebnikov09316c02014-10-09 15:29:32 -0700243 depends on COMPACTION && MEMORY_BALLOON
Rafael Aquini18468d92012-12-11 16:02:38 -0800244 help
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.
252
253#
Mel Gormane9e96b32010-05-24 14:32:21 -0700254# support for memory compaction
255config COMPACTION
256 bool "Allow for memory compaction"
Rik van Riel05106e62012-10-08 16:33:03 -0700257 def_bool y
Mel Gormane9e96b32010-05-24 14:32:21 -0700258 select MIGRATION
Andrea Arcangeli33a93872011-01-25 15:07:25 -0800259 depends on MMU
Mel Gormane9e96b32010-05-24 14:32:21 -0700260 help
261 Allows the compaction of memory for the allocation of huge pages.
262
263#
Christoph Lameter7cbe34c2006-01-08 01:00:49 -0800264# support for page migration
265#
266config MIGRATION
Christoph Lameterb20a3502006-03-22 00:09:12 -0800267 bool "Page migration"
Christoph Lameter6c5240a2006-06-23 02:03:37 -0700268 def_bool y
Chen Gangde32a812013-09-12 15:14:08 -0700269 depends on (NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA) && MMU
Christoph Lameterb20a3502006-03-22 00:09:12 -0800270 help
271 Allows the migration of the physical location of pages of processes
Mel Gormane9e96b32010-05-24 14:32:21 -0700272 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.
Greg Kroah-Hartman6550e072006-06-12 17:11:31 -0700277
Naoya Horiguchic177c812014-06-04 16:05:35 -0700278config ARCH_ENABLE_HUGEPAGE_MIGRATION
279 boolean
280
Jeremy Fitzhardinge600715d2008-09-11 01:31:45 -0700281config PHYS_ADDR_T_64BIT
282 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
283
Christoph Lameter4b51d662007-02-10 01:43:10 -0800284config ZONE_DMA_FLAG
285 int
286 default "0" if !ZONE_DMA
287 default "1"
288
Christoph Lameter2a7326b2007-07-17 04:03:37 -0700289config BOUNCE
Vinayak Menon9ca24e22013-04-29 15:08:55 -0700290 bool "Enable bounce buffers"
291 default y
Christoph Lameter2a7326b2007-07-17 04:03:37 -0700292 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
Vinayak Menon9ca24e22013-04-29 15:08:55 -0700293 help
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.
Christoph Lameter2a7326b2007-07-17 04:03:37 -0700298
Darrick J. Wongffecfd12013-02-21 16:42:55 -0800299# 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#
303# We also use the bounce pool to provide stable page writes for jbd. jbd
304# initiates buffer writeback without locking the page or setting PG_writeback,
305# and fixing that behavior (a second time; jbd2 doesn't have this problem) is
306# a major rework effort. Instead, use the bounce buffer to snapshot pages
307# (until jbd goes away). The only jbd user is ext3.
308config NEED_BOUNCE_POOL
309 bool
310 default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD)
311
Christoph Lameter6225e932007-05-06 14:49:50 -0700312config NR_QUICK
313 int
314 depends on QUICKLIST
Paul Mundt0176bd32010-01-05 12:35:00 +0900315 default "2" if AVR32
Christoph Lameter6225e932007-05-06 14:49:50 -0700316 default "1"
Stephen Rothwellf057eac2007-07-15 23:40:05 -0700317
318config VIRT_TO_BUS
Stephen Rothwell4febd952013-03-07 15:48:16 +1100319 bool
320 help
321 An architecture should select this if it implements the
322 deprecated interface virt_to_bus(). All new architectures
323 should probably not select this.
324
Andrea Arcangelicddb8a52008-07-28 15:46:29 -0700325
326config MMU_NOTIFIER
327 bool
Pranith Kumar83fe27e2014-12-05 11:24:45 -0500328 select SRCU
David Howellsfc4d5c22009-05-06 16:03:05 -0700329
Hugh Dickinsf8af4da2009-09-21 17:01:57 -0700330config KSM
331 bool "Enable KSM for page merging"
332 depends on MMU
333 help
334 Enable Kernel Samepage Merging: KSM periodically scans those areas
335 of an application's address space that an app has advised may be
336 mergeable. When it finds pages of identical content, it replaces
Hugh Dickinsd0f209f2009-12-14 17:59:34 -0800337 the many instances by a single page with that content, so
Hugh Dickinsf8af4da2009-09-21 17:01:57 -0700338 saving memory until one or another app needs to modify the content.
339 Recommended for use with KVM, or with other duplicative applications.
Hugh Dickinsc73602a2009-10-07 16:32:22 -0700340 See Documentation/vm/ksm.txt for more information: KSM is inactive
341 until a program has madvised that an area is MADV_MERGEABLE, and
342 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
Hugh Dickinsf8af4da2009-09-21 17:01:57 -0700343
Christoph Lametere0a94c22009-06-03 16:04:31 -0400344config DEFAULT_MMAP_MIN_ADDR
345 int "Low address space to protect from user allocation"
David Howells6e141542009-12-15 19:27:45 +0000346 depends on MMU
Christoph Lametere0a94c22009-06-03 16:04:31 -0400347 default 4096
348 help
349 This is the portion of low virtual memory which should be protected
350 from userspace allocation. Keeping a user from writing to low pages
351 can help reduce the impact of kernel NULL pointer bugs.
352
353 For most ia64, ppc64 and x86 users with lots of address space
354 a value of 65536 is reasonable and should cause no problems.
355 On arm and other archs it should not be higher than 32768.
Eric Paris788084a2009-07-31 12:54:11 -0400356 Programs which use vm86 functionality or have some need to map
357 this low address space will need CAP_SYS_RAWIO or disable this
358 protection by setting the value to 0.
Christoph Lametere0a94c22009-06-03 16:04:31 -0400359
360 This value can be changed after boot using the
361 /proc/sys/vm/mmap_min_addr tunable.
362
Linus Torvaldsd949f362009-09-26 09:35:07 -0700363config ARCH_SUPPORTS_MEMORY_FAILURE
364 bool
Christoph Lametere0a94c22009-06-03 16:04:31 -0400365
Andi Kleen6a460792009-09-16 11:50:15 +0200366config MEMORY_FAILURE
367 depends on MMU
Linus Torvaldsd949f362009-09-26 09:35:07 -0700368 depends on ARCH_SUPPORTS_MEMORY_FAILURE
Andi Kleen6a460792009-09-16 11:50:15 +0200369 bool "Enable recovery from hardware memory errors"
Minchan Kimee6f5092012-07-31 16:43:50 -0700370 select MEMORY_ISOLATION
Andi Kleen6a460792009-09-16 11:50:15 +0200371 help
372 Enables code to recover from some memory failures on systems
373 with MCA recovery. This allows a system to continue running
374 even when some of its memory has uncorrected errors. This requires
375 special hardware support and typically ECC memory.
376
Andi Kleencae681f2009-09-16 11:50:17 +0200377config HWPOISON_INJECT
Andi Kleen413f9ef2009-12-16 12:20:00 +0100378 tristate "HWPoison pages injector"
Andi Kleen27df5062009-12-21 19:56:42 +0100379 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
Wu Fengguang478c5ff2009-12-16 12:19:59 +0100380 select PROC_PAGE_MONITOR
Andi Kleencae681f2009-09-16 11:50:17 +0200381
David Howellsfc4d5c22009-05-06 16:03:05 -0700382config NOMMU_INITIAL_TRIM_EXCESS
383 int "Turn on mmap() excess space trimming before booting"
384 depends on !MMU
385 default 1
386 help
387 The NOMMU mmap() frequently needs to allocate large contiguous chunks
388 of memory on which to store mappings, but it can only ask the system
389 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
390 more than it requires. To deal with this, mmap() is able to trim off
391 the excess and return it to the allocator.
392
393 If trimming is enabled, the excess is trimmed off and returned to the
394 system allocator, which can cause extra fragmentation, particularly
395 if there are a lot of transient processes.
396
397 If trimming is disabled, the excess is kept, but not used, which for
398 long-term mappings means that the space is wasted.
399
400 Trimming can be dynamically controlled through a sysctl option
401 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
402 excess pages there must be before trimming should occur, or zero if
403 no trimming is to occur.
404
405 This option specifies the initial value of this option. The default
406 of 1 says that all excess pages should be trimmed.
407
408 See Documentation/nommu-mmap.txt for more information.
Tejun Heobbddff02010-09-03 18:22:48 +0200409
Andrea Arcangeli4c76d9d2011-01-13 15:46:39 -0800410config TRANSPARENT_HUGEPAGE
Andrea Arcangeli13ece882011-01-13 15:47:07 -0800411 bool "Transparent Hugepage Support"
Gerald Schaefer15626062012-10-08 16:30:04 -0700412 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
Andrea Arcangeli5d689242011-01-13 15:47:07 -0800413 select COMPACTION
Andrea Arcangeli4c76d9d2011-01-13 15:46:39 -0800414 help
415 Transparent Hugepages allows the kernel to use huge pages and
416 huge tlb transparently to the applications whenever possible.
417 This feature can improve computing performance to certain
418 applications by speeding up page faults during memory
419 allocation, by reducing the number of tlb misses and by speeding
420 up the pagetable walking.
421
422 If memory constrained on embedded, you may want to say N.
423
Andrea Arcangeli13ece882011-01-13 15:47:07 -0800424choice
425 prompt "Transparent Hugepage Support sysfs defaults"
426 depends on TRANSPARENT_HUGEPAGE
427 default TRANSPARENT_HUGEPAGE_ALWAYS
428 help
429 Selects the sysfs defaults for Transparent Hugepage Support.
430
431 config TRANSPARENT_HUGEPAGE_ALWAYS
432 bool "always"
433 help
434 Enabling Transparent Hugepage always, can increase the
435 memory footprint of applications without a guaranteed
436 benefit but it will work automatically for all applications.
437
438 config TRANSPARENT_HUGEPAGE_MADVISE
439 bool "madvise"
440 help
441 Enabling Transparent Hugepage madvise, will only provide a
442 performance improvement benefit to the applications using
443 madvise(MADV_HUGEPAGE) but it won't risk to increase the
444 memory footprint of applications without a guaranteed
445 benefit.
446endchoice
447
Tejun Heobbddff02010-09-03 18:22:48 +0200448#
449# UP and nommu archs use km based percpu allocator
450#
451config NEED_PER_CPU_KM
452 depends on !SMP
453 bool
454 default y
Dan Magenheimer077b1f82011-05-26 10:01:36 -0600455
456config CLEANCACHE
457 bool "Enable cleancache driver to cache clean pages if tmem is present"
458 default n
459 help
460 Cleancache can be thought of as a page-granularity victim cache
461 for clean pages that the kernel's pageframe replacement algorithm
462 (PFRA) would like to keep around, but can't since there isn't enough
463 memory. So when the PFRA "evicts" a page, it first attempts to use
Michael Witten140a1ef2011-06-10 03:57:26 +0000464 cleancache code to put the data contained in that page into
Dan Magenheimer077b1f82011-05-26 10:01:36 -0600465 "transcendent memory", memory that is not directly accessible or
466 addressable by the kernel and is of unknown and possibly
467 time-varying size. And when a cleancache-enabled
468 filesystem wishes to access a page in a file on disk, it first
469 checks cleancache to see if it already contains it; if it does,
470 the page is copied into the kernel and a disk access is avoided.
471 When a transcendent memory driver is available (such as zcache or
472 Xen transcendent memory), a significant I/O reduction
473 may be achieved. When none is available, all cleancache calls
474 are reduced to a single pointer-compare-against-NULL resulting
475 in a negligible performance hit.
476
477 If unsure, say Y to enable cleancache
Dan Magenheimer27c6aec2012-04-09 17:10:34 -0600478
479config FRONTSWAP
480 bool "Enable frontswap to cache swap pages if tmem is present"
481 depends on SWAP
482 default n
483 help
484 Frontswap is so named because it can be thought of as the opposite
485 of a "backing" store for a swap device. The data is stored into
486 "transcendent memory", memory that is not directly accessible or
487 addressable by the kernel and is of unknown and possibly
488 time-varying size. When space in transcendent memory is available,
489 a significant swap I/O reduction may be achieved. When none is
490 available, all frontswap calls are reduced to a single pointer-
491 compare-against-NULL resulting in a negligible performance hit
492 and swap data is stored as normal on the matching swap device.
493
494 If unsure, say Y to enable frontswap.
Aneesh Kumar K.Vf825c732013-07-02 11:15:15 +0530495
496config CMA
497 bool "Contiguous Memory Allocator"
Chen Gangde32a812013-09-12 15:14:08 -0700498 depends on HAVE_MEMBLOCK && MMU
Aneesh Kumar K.Vf825c732013-07-02 11:15:15 +0530499 select MIGRATION
500 select MEMORY_ISOLATION
501 help
502 This enables the Contiguous Memory Allocator which allows other
503 subsystems to allocate big physically-contiguous blocks of memory.
504 CMA reserves a region of memory and allows only movable pages to
505 be allocated from it. This way, the kernel can use the memory for
506 pagecache and when a subsystem requests for contiguous area, the
507 allocated pages are migrated away to serve the contiguous request.
508
509 If unsure, say "n".
510
511config CMA_DEBUG
512 bool "CMA debug messages (DEVELOPMENT)"
513 depends on DEBUG_KERNEL && CMA
514 help
515 Turns on debug messages in CMA. This produces KERN_DEBUG
516 messages for every CMA call as well as various messages while
517 processing calls such as dma_alloc_from_contiguous().
518 This option does not affect warning and error messages.
Alexander Grafbf550fc2013-08-29 00:41:59 +0200519
Joonsoo Kima2541292014-08-06 16:05:25 -0700520config CMA_AREAS
521 int "Maximum count of the CMA areas"
522 depends on CMA
523 default 7
524 help
525 CMA allows to create CMA areas for particular purpose, mainly,
526 used as device private area. This parameter sets the maximum
527 number of CMA area in the system.
528
529 If unsure, leave the default value "7".
530
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700531config MEM_SOFT_DIRTY
532 bool "Track memory changes"
533 depends on CHECKPOINT_RESTORE && HAVE_ARCH_SOFT_DIRTY && PROC_FS
534 select PROC_PAGE_MONITOR
Seth Jennings4e2e2772013-07-10 16:04:55 -0700535 help
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700536 This option enables memory changes tracking by introducing a
537 soft-dirty bit on pte-s. This bit it set when someone writes
538 into a page just as regular dirty bit, but unlike the latter
539 it can be cleared by hands.
540
541 See Documentation/vm/soft-dirty.txt for more details.
Seth Jennings4e2e2772013-07-10 16:04:55 -0700542
Seth Jennings2b281112013-07-10 16:05:03 -0700543config ZSWAP
544 bool "Compressed cache for swap pages (EXPERIMENTAL)"
545 depends on FRONTSWAP && CRYPTO=y
546 select CRYPTO_LZO
Dan Streetman12d79d62014-08-06 16:08:40 -0700547 select ZPOOL
Seth Jennings2b281112013-07-10 16:05:03 -0700548 default n
549 help
550 A lightweight compressed cache for swap pages. It takes
551 pages that are in the process of being swapped out and attempts to
552 compress them into a dynamically allocated RAM-based memory pool.
553 This can result in a significant I/O reduction on swap device and,
554 in the case where decompressing from RAM is faster that swap device
555 reads, can also improve workload performance.
556
557 This is marked experimental because it is a new feature (as of
558 v3.11) that interacts heavily with memory reclaim. While these
559 interactions don't cause any known issues on simple memory setups,
560 they have not be fully explored on the large set of potential
561 configurations and workloads that exist.
562
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700563config ZPOOL
564 tristate "Common API for compressed memory storage"
565 default n
Pavel Emelyanov0f8975e2013-07-03 15:01:20 -0700566 help
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700567 Compressed memory storage API. This allows using either zbud or
568 zsmalloc.
Pavel Emelyanov0f8975e2013-07-03 15:01:20 -0700569
Dan Streetmanaf8d4172014-08-06 16:08:36 -0700570config ZBUD
571 tristate "Low density storage for compressed pages"
572 default n
573 help
574 A special purpose allocator for storing compressed pages.
575 It is designed to store up to two compressed pages per physical
576 page. While this design limits storage density, it has simple and
577 deterministic reclaim properties that make it preferable to a higher
578 density approach when reclaim will be used.
Minchan Kimbcf16472014-01-30 15:45:50 -0800579
580config ZSMALLOC
Minchan Kimd867f202014-06-04 16:11:10 -0700581 tristate "Memory allocator for compressed pages"
Minchan Kimbcf16472014-01-30 15:45:50 -0800582 depends on MMU
583 default n
584 help
585 zsmalloc is a slab-based memory allocator designed to store
586 compressed RAM pages. zsmalloc uses virtual memory mapping
587 in order to reduce fragmentation. However, this results in a
588 non-standard allocator interface where a handle, not a pointer, is
589 returned by an alloc(). This handle must be mapped in order to
590 access the allocated space.
591
592config PGTABLE_MAPPING
593 bool "Use page table mapping to access object in zsmalloc"
594 depends on ZSMALLOC
595 help
596 By default, zsmalloc uses a copy-based object mapping method to
597 access allocations that span two pages. However, if a particular
598 architecture (ex, ARM) performs VM mapping faster than copying,
599 then you should select this. This causes zsmalloc to use page table
600 mapping rather than copying for object mapping.
601
Ben Hutchings2216ee82014-03-10 15:49:46 -0700602 You can check speed with zsmalloc benchmark:
603 https://github.com/spartacus06/zsmapbench
Mark Salter9e5c33d2014-04-07 15:39:48 -0700604
605config GENERIC_EARLY_IOREMAP
606 bool
Helge Deller042d27a2014-04-30 23:26:02 +0200607
608config MAX_STACK_SIZE_MB
609 int "Maximum user stack size for 32-bit processes (MB)"
610 default 80
611 range 8 256 if METAG
612 range 8 2048
613 depends on STACK_GROWSUP && (!64BIT || COMPAT)
614 help
615 This is the maximum stack size in Megabytes in the VM layout of 32-bit
616 user processes when the stack grows upwards (currently only on parisc
617 and metag arch). The stack will be located at the highest memory
618 address minus the given value, unless the RLIMIT_STACK hard limit is
619 changed to a smaller value in which case that is used.
620
621 A sane initial value is 80 MB.