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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.
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".
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
Tejun Heoc378ddd2011-07-14 11:46:03 +0200137config ARCH_DISCARD_MEMBLOCK
138 boolean
139
Sam Ravnborg66616722011-10-31 17:08:20 -0700140config NO_BOOTMEM
141 boolean
142
Minchan Kimee6f5092012-07-31 16:43:50 -0700143config MEMORY_ISOLATION
144 boolean
145
Lai Jiangshan20b2f522012-12-12 13:52:00 -0800146config MOVABLE_NODE
147 boolean "Enable to assign a node which has only movable memory"
148 depends on HAVE_MEMBLOCK
149 depends on NO_BOOTMEM
150 depends on X86_64
151 depends on NUMA
Tang Chenc2974052012-12-18 14:21:33 -0800152 default n
153 help
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 users to
157 online all the memory of a node as movable memory so that the whole
158 node can be hotplugged. Users who don't use the memory hotplug
159 feature are fine with this option on since they don't online memory
160 as movable.
161
162 Say Y here if you want to hotplug a whole node.
163 Say N here if you want kernel to use memory on all nodes evenly.
Lai Jiangshan20b2f522012-12-12 13:52:00 -0800164
Yasuaki Ishimatsu46723bf2013-02-22 16:33:00 -0800165#
166# Only be set on architectures that have completely implemented memory hotplug
167# feature. If you are not sure, don't touch it.
168#
169config HAVE_BOOTMEM_INFO_NODE
170 def_bool n
171
Dave Hansen3947be12005-10-29 18:16:54 -0700172# eventually, we can have this option just 'select SPARSEMEM'
173config MEMORY_HOTPLUG
174 bool "Allow for memory hot-add"
Keith Manntheyec69acb2006-09-30 23:27:05 -0700175 depends on SPARSEMEM || X86_64_ACPI_NUMA
Andi Kleen6ad696d2009-11-17 14:06:22 -0800176 depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG
Kumar Galaed84a072009-10-16 07:21:36 +0000177 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
Dave Hansen3947be12005-10-29 18:16:54 -0700178
Keith Manntheyec69acb2006-09-30 23:27:05 -0700179config MEMORY_HOTPLUG_SPARSE
180 def_bool y
181 depends on SPARSEMEM && MEMORY_HOTPLUG
182
KAMEZAWA Hiroyuki0c0e6192007-10-16 01:26:12 -0700183config MEMORY_HOTREMOVE
184 bool "Allow for memory hot remove"
Yasuaki Ishimatsu46723bf2013-02-22 16:33:00 -0800185 select MEMORY_ISOLATION
186 select HAVE_BOOTMEM_INFO_NODE if X86_64
KAMEZAWA Hiroyuki0c0e6192007-10-16 01:26:12 -0700187 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
188 depends on MIGRATION
189
Christoph Lametere20b8cc2008-04-28 02:12:55 -0700190#
191# If we have space for more page flags then we can enable additional
192# optimizations and functionality.
193#
194# Regular Sparsemem takes page flag bits for the sectionid if it does not
195# use a virtual memmap. Disable extended page flags for 32 bit platforms
196# that require the use of a sectionid in the page flags.
197#
198config PAGEFLAGS_EXTENDED
199 def_bool y
H. Peter Anvina269cca2009-08-31 11:17:44 -0700200 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
Christoph Lametere20b8cc2008-04-28 02:12:55 -0700201
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700202# Heavily threaded applications may benefit from splitting the mm-wide
203# page_table_lock, so that faults on different parts of the user address
204# space can be handled with less contention: split it at this NR_CPUS.
205# Default to 4 for wider testing, though 8 might be more appropriate.
206# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
Hugh Dickins7b6ac9d2005-11-23 13:37:37 -0800207# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
Hugh Dickinsa70caa82009-12-14 17:59:02 -0800208# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700209#
210config SPLIT_PTLOCK_CPUS
211 int
Hugh Dickinsa70caa82009-12-14 17:59:02 -0800212 default "999999" if ARM && !CPU_CACHE_VIPT
213 default "999999" if PARISC && !PA20
214 default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700215 default "4"
Christoph Lameter7cbe34c2006-01-08 01:00:49 -0800216
217#
Rafael Aquini18468d92012-12-11 16:02:38 -0800218# support for memory balloon compaction
219config BALLOON_COMPACTION
220 bool "Allow for balloon memory compaction/migration"
221 def_bool y
222 depends on COMPACTION && VIRTIO_BALLOON
223 help
224 Memory fragmentation introduced by ballooning might reduce
225 significantly the number of 2MB contiguous memory blocks that can be
226 used within a guest, thus imposing performance penalties associated
227 with the reduced number of transparent huge pages that could be used
228 by the guest workload. Allowing the compaction & migration for memory
229 pages enlisted as being part of memory balloon devices avoids the
230 scenario aforementioned and helps improving memory defragmentation.
231
232#
Mel Gormane9e96b32010-05-24 14:32:21 -0700233# support for memory compaction
234config COMPACTION
235 bool "Allow for memory compaction"
Rik van Riel05106e62012-10-08 16:33:03 -0700236 def_bool y
Mel Gormane9e96b32010-05-24 14:32:21 -0700237 select MIGRATION
Andrea Arcangeli33a93872011-01-25 15:07:25 -0800238 depends on MMU
Mel Gormane9e96b32010-05-24 14:32:21 -0700239 help
240 Allows the compaction of memory for the allocation of huge pages.
241
242#
Christoph Lameter7cbe34c2006-01-08 01:00:49 -0800243# support for page migration
244#
245config MIGRATION
Christoph Lameterb20a3502006-03-22 00:09:12 -0800246 bool "Page migration"
Christoph Lameter6c5240a2006-06-23 02:03:37 -0700247 def_bool y
Michal Nazarewicz47118af2011-12-29 13:09:50 +0100248 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA
Christoph Lameterb20a3502006-03-22 00:09:12 -0800249 help
250 Allows the migration of the physical location of pages of processes
Mel Gormane9e96b32010-05-24 14:32:21 -0700251 while the virtual addresses are not changed. This is useful in
252 two situations. The first is on NUMA systems to put pages nearer
253 to the processors accessing. The second is when allocating huge
254 pages as migration can relocate pages to satisfy a huge page
255 allocation instead of reclaiming.
Greg Kroah-Hartman6550e072006-06-12 17:11:31 -0700256
Jeremy Fitzhardinge600715d2008-09-11 01:31:45 -0700257config PHYS_ADDR_T_64BIT
258 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
259
Christoph Lameter4b51d662007-02-10 01:43:10 -0800260config ZONE_DMA_FLAG
261 int
262 default "0" if !ZONE_DMA
263 default "1"
264
Christoph Lameter2a7326b2007-07-17 04:03:37 -0700265config BOUNCE
266 def_bool y
267 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
268
Darrick J. Wongffecfd12013-02-21 16:42:55 -0800269# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often
270# have more than 4GB of memory, but we don't currently use the IOTLB to present
271# a 32-bit address to OHCI. So we need to use a bounce pool instead.
272#
273# We also use the bounce pool to provide stable page writes for jbd. jbd
274# initiates buffer writeback without locking the page or setting PG_writeback,
275# and fixing that behavior (a second time; jbd2 doesn't have this problem) is
276# a major rework effort. Instead, use the bounce buffer to snapshot pages
277# (until jbd goes away). The only jbd user is ext3.
278config NEED_BOUNCE_POOL
279 bool
280 default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD)
281
Christoph Lameter6225e932007-05-06 14:49:50 -0700282config NR_QUICK
283 int
284 depends on QUICKLIST
Paul Mundt0176bd32010-01-05 12:35:00 +0900285 default "2" if AVR32
Christoph Lameter6225e932007-05-06 14:49:50 -0700286 default "1"
Stephen Rothwellf057eac2007-07-15 23:40:05 -0700287
288config VIRT_TO_BUS
289 def_bool y
Stephen Rothwell887cbce02013-02-27 17:05:48 -0800290 depends on HAVE_VIRT_TO_BUS
Andrea Arcangelicddb8a52008-07-28 15:46:29 -0700291
292config MMU_NOTIFIER
293 bool
David Howellsfc4d5c22009-05-06 16:03:05 -0700294
Hugh Dickinsf8af4da2009-09-21 17:01:57 -0700295config KSM
296 bool "Enable KSM for page merging"
297 depends on MMU
298 help
299 Enable Kernel Samepage Merging: KSM periodically scans those areas
300 of an application's address space that an app has advised may be
301 mergeable. When it finds pages of identical content, it replaces
Hugh Dickinsd0f209f2009-12-14 17:59:34 -0800302 the many instances by a single page with that content, so
Hugh Dickinsf8af4da2009-09-21 17:01:57 -0700303 saving memory until one or another app needs to modify the content.
304 Recommended for use with KVM, or with other duplicative applications.
Hugh Dickinsc73602a2009-10-07 16:32:22 -0700305 See Documentation/vm/ksm.txt for more information: KSM is inactive
306 until a program has madvised that an area is MADV_MERGEABLE, and
307 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
Hugh Dickinsf8af4da2009-09-21 17:01:57 -0700308
Christoph Lametere0a94c22009-06-03 16:04:31 -0400309config DEFAULT_MMAP_MIN_ADDR
310 int "Low address space to protect from user allocation"
David Howells6e141542009-12-15 19:27:45 +0000311 depends on MMU
Christoph Lametere0a94c22009-06-03 16:04:31 -0400312 default 4096
313 help
314 This is the portion of low virtual memory which should be protected
315 from userspace allocation. Keeping a user from writing to low pages
316 can help reduce the impact of kernel NULL pointer bugs.
317
318 For most ia64, ppc64 and x86 users with lots of address space
319 a value of 65536 is reasonable and should cause no problems.
320 On arm and other archs it should not be higher than 32768.
Eric Paris788084a2009-07-31 12:54:11 -0400321 Programs which use vm86 functionality or have some need to map
322 this low address space will need CAP_SYS_RAWIO or disable this
323 protection by setting the value to 0.
Christoph Lametere0a94c22009-06-03 16:04:31 -0400324
325 This value can be changed after boot using the
326 /proc/sys/vm/mmap_min_addr tunable.
327
Linus Torvaldsd949f362009-09-26 09:35:07 -0700328config ARCH_SUPPORTS_MEMORY_FAILURE
329 bool
Christoph Lametere0a94c22009-06-03 16:04:31 -0400330
Andi Kleen6a460792009-09-16 11:50:15 +0200331config MEMORY_FAILURE
332 depends on MMU
Linus Torvaldsd949f362009-09-26 09:35:07 -0700333 depends on ARCH_SUPPORTS_MEMORY_FAILURE
Andi Kleen6a460792009-09-16 11:50:15 +0200334 bool "Enable recovery from hardware memory errors"
Minchan Kimee6f5092012-07-31 16:43:50 -0700335 select MEMORY_ISOLATION
Andi Kleen6a460792009-09-16 11:50:15 +0200336 help
337 Enables code to recover from some memory failures on systems
338 with MCA recovery. This allows a system to continue running
339 even when some of its memory has uncorrected errors. This requires
340 special hardware support and typically ECC memory.
341
Andi Kleencae681f2009-09-16 11:50:17 +0200342config HWPOISON_INJECT
Andi Kleen413f9ef2009-12-16 12:20:00 +0100343 tristate "HWPoison pages injector"
Andi Kleen27df5062009-12-21 19:56:42 +0100344 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
Wu Fengguang478c5ff2009-12-16 12:19:59 +0100345 select PROC_PAGE_MONITOR
Andi Kleencae681f2009-09-16 11:50:17 +0200346
David Howellsfc4d5c22009-05-06 16:03:05 -0700347config NOMMU_INITIAL_TRIM_EXCESS
348 int "Turn on mmap() excess space trimming before booting"
349 depends on !MMU
350 default 1
351 help
352 The NOMMU mmap() frequently needs to allocate large contiguous chunks
353 of memory on which to store mappings, but it can only ask the system
354 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
355 more than it requires. To deal with this, mmap() is able to trim off
356 the excess and return it to the allocator.
357
358 If trimming is enabled, the excess is trimmed off and returned to the
359 system allocator, which can cause extra fragmentation, particularly
360 if there are a lot of transient processes.
361
362 If trimming is disabled, the excess is kept, but not used, which for
363 long-term mappings means that the space is wasted.
364
365 Trimming can be dynamically controlled through a sysctl option
366 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
367 excess pages there must be before trimming should occur, or zero if
368 no trimming is to occur.
369
370 This option specifies the initial value of this option. The default
371 of 1 says that all excess pages should be trimmed.
372
373 See Documentation/nommu-mmap.txt for more information.
Tejun Heobbddff02010-09-03 18:22:48 +0200374
Andrea Arcangeli4c76d9d2011-01-13 15:46:39 -0800375config TRANSPARENT_HUGEPAGE
Andrea Arcangeli13ece882011-01-13 15:47:07 -0800376 bool "Transparent Hugepage Support"
Gerald Schaefer15626062012-10-08 16:30:04 -0700377 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE
Andrea Arcangeli5d689242011-01-13 15:47:07 -0800378 select COMPACTION
Andrea Arcangeli4c76d9d2011-01-13 15:46:39 -0800379 help
380 Transparent Hugepages allows the kernel to use huge pages and
381 huge tlb transparently to the applications whenever possible.
382 This feature can improve computing performance to certain
383 applications by speeding up page faults during memory
384 allocation, by reducing the number of tlb misses and by speeding
385 up the pagetable walking.
386
387 If memory constrained on embedded, you may want to say N.
388
Andrea Arcangeli13ece882011-01-13 15:47:07 -0800389choice
390 prompt "Transparent Hugepage Support sysfs defaults"
391 depends on TRANSPARENT_HUGEPAGE
392 default TRANSPARENT_HUGEPAGE_ALWAYS
393 help
394 Selects the sysfs defaults for Transparent Hugepage Support.
395
396 config TRANSPARENT_HUGEPAGE_ALWAYS
397 bool "always"
398 help
399 Enabling Transparent Hugepage always, can increase the
400 memory footprint of applications without a guaranteed
401 benefit but it will work automatically for all applications.
402
403 config TRANSPARENT_HUGEPAGE_MADVISE
404 bool "madvise"
405 help
406 Enabling Transparent Hugepage madvise, will only provide a
407 performance improvement benefit to the applications using
408 madvise(MADV_HUGEPAGE) but it won't risk to increase the
409 memory footprint of applications without a guaranteed
410 benefit.
411endchoice
412
Christopher Yeoh5febcbe2012-05-29 15:06:27 -0700413config CROSS_MEMORY_ATTACH
414 bool "Cross Memory Support"
415 depends on MMU
416 default y
417 help
418 Enabling this option adds the system calls process_vm_readv and
419 process_vm_writev which allow a process with the correct privileges
420 to directly read from or write to to another process's address space.
421 See the man page for more details.
422
Tejun Heobbddff02010-09-03 18:22:48 +0200423#
424# UP and nommu archs use km based percpu allocator
425#
426config NEED_PER_CPU_KM
427 depends on !SMP
428 bool
429 default y
Dan Magenheimer077b1f82011-05-26 10:01:36 -0600430
431config CLEANCACHE
432 bool "Enable cleancache driver to cache clean pages if tmem is present"
433 default n
434 help
435 Cleancache can be thought of as a page-granularity victim cache
436 for clean pages that the kernel's pageframe replacement algorithm
437 (PFRA) would like to keep around, but can't since there isn't enough
438 memory. So when the PFRA "evicts" a page, it first attempts to use
Michael Witten140a1ef2011-06-10 03:57:26 +0000439 cleancache code to put the data contained in that page into
Dan Magenheimer077b1f82011-05-26 10:01:36 -0600440 "transcendent memory", memory that is not directly accessible or
441 addressable by the kernel and is of unknown and possibly
442 time-varying size. And when a cleancache-enabled
443 filesystem wishes to access a page in a file on disk, it first
444 checks cleancache to see if it already contains it; if it does,
445 the page is copied into the kernel and a disk access is avoided.
446 When a transcendent memory driver is available (such as zcache or
447 Xen transcendent memory), a significant I/O reduction
448 may be achieved. When none is available, all cleancache calls
449 are reduced to a single pointer-compare-against-NULL resulting
450 in a negligible performance hit.
451
452 If unsure, say Y to enable cleancache
Dan Magenheimer27c6aec2012-04-09 17:10:34 -0600453
454config FRONTSWAP
455 bool "Enable frontswap to cache swap pages if tmem is present"
456 depends on SWAP
457 default n
458 help
459 Frontswap is so named because it can be thought of as the opposite
460 of a "backing" store for a swap device. The data is stored 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. When space in transcendent memory is available,
464 a significant swap I/O reduction may be achieved. When none is
465 available, all frontswap calls are reduced to a single pointer-
466 compare-against-NULL resulting in a negligible performance hit
467 and swap data is stored as normal on the matching swap device.
468
469 If unsure, say Y to enable frontswap.