Root/mm/Kconfig

Source at commit b386be689295730688885552666ea40b2e639b14 created 11 years 11 months ago.
By Maarten ter Huurne, Revert "MIPS: JZ4740: reset: Initialize hibernate wakeup counters."
1config SELECT_MEMORY_MODEL
2    def_bool y
3    depends on EXPERIMENTAL || ARCH_SELECT_MEMORY_MODEL
4
5choice
6    prompt "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
11
12config FLATMEM_MANUAL
13    bool "Flat Memory"
14    depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
15    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
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".
28
29      If unsure, choose this option (Flat Memory) over any other.
30
31config DISCONTIGMEM_MANUAL
32    bool "Discontiguous Memory"
33    depends on ARCH_DISCONTIGMEM_ENABLE
34    help
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
41      this option imposes.
42
43      Many NUMA configurations will have this as the only option.
44
45      If unsure, choose "Flat Memory" over this option.
46
47config 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
55      "Discontiguous Memory". This option provides some potential
56      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
62endchoice
63
64config DISCONTIGMEM
65    def_bool y
66    depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
67
68config SPARSEMEM
69    def_bool y
70    depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL
71
72config FLATMEM
73    def_bool y
74    depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
75
76config FLAT_NODE_MEM_MAP
77    def_bool y
78    depends on !SPARSEMEM
79
80#
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
88
89config HAVE_MEMORY_PRESENT
90    def_bool y
91    depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM
92
93#
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.
99#
100# This option will also potentially produce smaller runtime code
101# with gcc 3.4 and later.
102#
103config SPARSEMEM_STATIC
104    bool
105
106#
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.
110#
111config SPARSEMEM_EXTREME
112    def_bool y
113    depends on SPARSEMEM && !SPARSEMEM_STATIC
114
115config SPARSEMEM_VMEMMAP_ENABLE
116    bool
117
118config SPARSEMEM_ALLOC_MEM_MAP_TOGETHER
119    def_bool y
120    depends on SPARSEMEM && X86_64
121
122config SPARSEMEM_VMEMMAP
123    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.
130
131config HAVE_MEMBLOCK
132    boolean
133
134config HAVE_MEMBLOCK_NODE_MAP
135    boolean
136
137config ARCH_DISCARD_MEMBLOCK
138    boolean
139
140config NO_BOOTMEM
141    boolean
142
143# eventually, we can have this option just 'select SPARSEMEM'
144config MEMORY_HOTPLUG
145    bool "Allow for memory hot-add"
146    depends on SPARSEMEM || X86_64_ACPI_NUMA
147    depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG
148    depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390)
149
150config MEMORY_HOTPLUG_SPARSE
151    def_bool y
152    depends on SPARSEMEM && MEMORY_HOTPLUG
153
154config MEMORY_HOTREMOVE
155    bool "Allow for memory hot remove"
156    depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE
157    depends on MIGRATION
158
159#
160# If we have space for more page flags then we can enable additional
161# optimizations and functionality.
162#
163# Regular Sparsemem takes page flag bits for the sectionid if it does not
164# use a virtual memmap. Disable extended page flags for 32 bit platforms
165# that require the use of a sectionid in the page flags.
166#
167config PAGEFLAGS_EXTENDED
168    def_bool y
169    depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM
170
171# Heavily threaded applications may benefit from splitting the mm-wide
172# page_table_lock, so that faults on different parts of the user address
173# space can be handled with less contention: split it at this NR_CPUS.
174# Default to 4 for wider testing, though 8 might be more appropriate.
175# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock.
176# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes.
177# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page.
178#
179config SPLIT_PTLOCK_CPUS
180    int
181    default "999999" if ARM && !CPU_CACHE_VIPT
182    default "999999" if PARISC && !PA20
183    default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC
184    default "4"
185
186#
187# support for memory compaction
188config COMPACTION
189    bool "Allow for memory compaction"
190    select MIGRATION
191    depends on MMU
192    help
193      Allows the compaction of memory for the allocation of huge pages.
194
195#
196# support for page migration
197#
198config MIGRATION
199    bool "Page migration"
200    def_bool y
201    depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION
202    help
203      Allows the migration of the physical location of pages of processes
204      while the virtual addresses are not changed. This is useful in
205      two situations. The first is on NUMA systems to put pages nearer
206      to the processors accessing. The second is when allocating huge
207      pages as migration can relocate pages to satisfy a huge page
208      allocation instead of reclaiming.
209
210config PHYS_ADDR_T_64BIT
211    def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT
212
213config ZONE_DMA_FLAG
214    int
215    default "0" if !ZONE_DMA
216    default "1"
217
218config BOUNCE
219    def_bool y
220    depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)
221
222config NR_QUICK
223    int
224    depends on QUICKLIST
225    default "2" if AVR32
226    default "1"
227
228config VIRT_TO_BUS
229    def_bool y
230    depends on !ARCH_NO_VIRT_TO_BUS
231
232config MMU_NOTIFIER
233    bool
234
235config KSM
236    bool "Enable KSM for page merging"
237    depends on MMU
238    help
239      Enable Kernel Samepage Merging: KSM periodically scans those areas
240      of an application's address space that an app has advised may be
241      mergeable. When it finds pages of identical content, it replaces
242      the many instances by a single page with that content, so
243      saving memory until one or another app needs to modify the content.
244      Recommended for use with KVM, or with other duplicative applications.
245      See Documentation/vm/ksm.txt for more information: KSM is inactive
246      until a program has madvised that an area is MADV_MERGEABLE, and
247      root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set).
248
249config DEFAULT_MMAP_MIN_ADDR
250        int "Low address space to protect from user allocation"
251    depends on MMU
252        default 4096
253        help
254      This is the portion of low virtual memory which should be protected
255      from userspace allocation. Keeping a user from writing to low pages
256      can help reduce the impact of kernel NULL pointer bugs.
257
258      For most ia64, ppc64 and x86 users with lots of address space
259      a value of 65536 is reasonable and should cause no problems.
260      On arm and other archs it should not be higher than 32768.
261      Programs which use vm86 functionality or have some need to map
262      this low address space will need CAP_SYS_RAWIO or disable this
263      protection by setting the value to 0.
264
265      This value can be changed after boot using the
266      /proc/sys/vm/mmap_min_addr tunable.
267
268config ARCH_SUPPORTS_MEMORY_FAILURE
269    bool
270
271config MEMORY_FAILURE
272    depends on MMU
273    depends on ARCH_SUPPORTS_MEMORY_FAILURE
274    bool "Enable recovery from hardware memory errors"
275    help
276      Enables code to recover from some memory failures on systems
277      with MCA recovery. This allows a system to continue running
278      even when some of its memory has uncorrected errors. This requires
279      special hardware support and typically ECC memory.
280
281config HWPOISON_INJECT
282    tristate "HWPoison pages injector"
283    depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS
284    select PROC_PAGE_MONITOR
285
286config NOMMU_INITIAL_TRIM_EXCESS
287    int "Turn on mmap() excess space trimming before booting"
288    depends on !MMU
289    default 1
290    help
291      The NOMMU mmap() frequently needs to allocate large contiguous chunks
292      of memory on which to store mappings, but it can only ask the system
293      allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently
294      more than it requires. To deal with this, mmap() is able to trim off
295      the excess and return it to the allocator.
296
297      If trimming is enabled, the excess is trimmed off and returned to the
298      system allocator, which can cause extra fragmentation, particularly
299      if there are a lot of transient processes.
300
301      If trimming is disabled, the excess is kept, but not used, which for
302      long-term mappings means that the space is wasted.
303
304      Trimming can be dynamically controlled through a sysctl option
305      (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of
306      excess pages there must be before trimming should occur, or zero if
307      no trimming is to occur.
308
309      This option specifies the initial value of this option. The default
310      of 1 says that all excess pages should be trimmed.
311
312      See Documentation/nommu-mmap.txt for more information.
313
314config TRANSPARENT_HUGEPAGE
315    bool "Transparent Hugepage Support"
316    depends on X86 && MMU
317    select COMPACTION
318    help
319      Transparent Hugepages allows the kernel to use huge pages and
320      huge tlb transparently to the applications whenever possible.
321      This feature can improve computing performance to certain
322      applications by speeding up page faults during memory
323      allocation, by reducing the number of tlb misses and by speeding
324      up the pagetable walking.
325
326      If memory constrained on embedded, you may want to say N.
327
328choice
329    prompt "Transparent Hugepage Support sysfs defaults"
330    depends on TRANSPARENT_HUGEPAGE
331    default TRANSPARENT_HUGEPAGE_ALWAYS
332    help
333      Selects the sysfs defaults for Transparent Hugepage Support.
334
335    config TRANSPARENT_HUGEPAGE_ALWAYS
336        bool "always"
337    help
338      Enabling Transparent Hugepage always, can increase the
339      memory footprint of applications without a guaranteed
340      benefit but it will work automatically for all applications.
341
342    config TRANSPARENT_HUGEPAGE_MADVISE
343        bool "madvise"
344    help
345      Enabling Transparent Hugepage madvise, will only provide a
346      performance improvement benefit to the applications using
347      madvise(MADV_HUGEPAGE) but it won't risk to increase the
348      memory footprint of applications without a guaranteed
349      benefit.
350endchoice
351
352#
353# UP and nommu archs use km based percpu allocator
354#
355config NEED_PER_CPU_KM
356    depends on !SMP
357    bool
358    default y
359
360config CLEANCACHE
361    bool "Enable cleancache driver to cache clean pages if tmem is present"
362    default n
363    help
364      Cleancache can be thought of as a page-granularity victim cache
365      for clean pages that the kernel's pageframe replacement algorithm
366      (PFRA) would like to keep around, but can't since there isn't enough
367      memory. So when the PFRA "evicts" a page, it first attempts to use
368      cleancache code to put the data contained in that page into
369      "transcendent memory", memory that is not directly accessible or
370      addressable by the kernel and is of unknown and possibly
371      time-varying size. And when a cleancache-enabled
372      filesystem wishes to access a page in a file on disk, it first
373      checks cleancache to see if it already contains it; if it does,
374      the page is copied into the kernel and a disk access is avoided.
375      When a transcendent memory driver is available (such as zcache or
376      Xen transcendent memory), a significant I/O reduction
377      may be achieved. When none is available, all cleancache calls
378      are reduced to a single pointer-compare-against-NULL resulting
379      in a negligible performance hit.
380
381      If unsure, say Y to enable cleancache
382

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