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 143config MEMORY_ISOLATION 144 boolean 145 146config 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 152 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. 164 165# eventually, we can have this option just 'select SPARSEMEM' 166config MEMORY_HOTPLUG 167 bool "Allow for memory hot-add" 168 select MEMORY_ISOLATION 169 depends on SPARSEMEM || X86_64_ACPI_NUMA 170 depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG 171 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390) 172 173config MEMORY_HOTPLUG_SPARSE 174 def_bool y 175 depends on SPARSEMEM && MEMORY_HOTPLUG 176 177config MEMORY_HOTREMOVE 178 bool "Allow for memory hot remove" 179 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 180 depends on MIGRATION 181 182# 183# If we have space for more page flags then we can enable additional 184# optimizations and functionality. 185# 186# Regular Sparsemem takes page flag bits for the sectionid if it does not 187# use a virtual memmap. Disable extended page flags for 32 bit platforms 188# that require the use of a sectionid in the page flags. 189# 190config PAGEFLAGS_EXTENDED 191 def_bool y 192 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM 193 194# Heavily threaded applications may benefit from splitting the mm-wide 195# page_table_lock, so that faults on different parts of the user address 196# space can be handled with less contention: split it at this NR_CPUS. 197# Default to 4 for wider testing, though 8 might be more appropriate. 198# ARM's adjust_pte (unused if VIPT) depends on mm-wide page_table_lock. 199# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 200# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 201# 202config SPLIT_PTLOCK_CPUS 203 int 204 default "999999" if ARM && !CPU_CACHE_VIPT 205 default "999999" if PARISC && !PA20 206 default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC 207 default "4" 208 209# 210# support for memory balloon compaction 211config BALLOON_COMPACTION 212 bool "Allow for balloon memory compaction/migration" 213 def_bool y 214 depends on COMPACTION && VIRTIO_BALLOON 215 help 216 Memory fragmentation introduced by ballooning might reduce 217 significantly the number of 2MB contiguous memory blocks that can be 218 used within a guest, thus imposing performance penalties associated 219 with the reduced number of transparent huge pages that could be used 220 by the guest workload. Allowing the compaction & migration for memory 221 pages enlisted as being part of memory balloon devices avoids the 222 scenario aforementioned and helps improving memory defragmentation. 223 224# 225# support for memory compaction 226config COMPACTION 227 bool "Allow for memory compaction" 228 def_bool y 229 select MIGRATION 230 depends on MMU 231 help 232 Allows the compaction of memory for the allocation of huge pages. 233 234# 235# support for page migration 236# 237config MIGRATION 238 bool "Page migration" 239 def_bool y 240 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA 241 help 242 Allows the migration of the physical location of pages of processes 243 while the virtual addresses are not changed. This is useful in 244 two situations. The first is on NUMA systems to put pages nearer 245 to the processors accessing. The second is when allocating huge 246 pages as migration can relocate pages to satisfy a huge page 247 allocation instead of reclaiming. 248 249config PHYS_ADDR_T_64BIT 250 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 251 252config ZONE_DMA_FLAG 253 int 254 default "0" if !ZONE_DMA 255 default "1" 256 257config BOUNCE 258 def_bool y 259 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 260 261# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often 262# have more than 4GB of memory, but we don't currently use the IOTLB to present 263# a 32-bit address to OHCI. So we need to use a bounce pool instead. 264# 265# We also use the bounce pool to provide stable page writes for jbd. jbd 266# initiates buffer writeback without locking the page or setting PG_writeback, 267# and fixing that behavior (a second time; jbd2 doesn't have this problem) is 268# a major rework effort. Instead, use the bounce buffer to snapshot pages 269# (until jbd goes away). The only jbd user is ext3. 270config NEED_BOUNCE_POOL 271 bool 272 default y if (TILE && USB_OHCI_HCD) || (BLK_DEV_INTEGRITY && JBD) 273 274config NR_QUICK 275 int 276 depends on QUICKLIST 277 default "2" if AVR32 278 default "1" 279 280config VIRT_TO_BUS 281 def_bool y 282 depends on !ARCH_NO_VIRT_TO_BUS 283 284config MMU_NOTIFIER 285 bool 286 287config KSM 288 bool "Enable KSM for page merging" 289 depends on MMU 290 help 291 Enable Kernel Samepage Merging: KSM periodically scans those areas 292 of an application's address space that an app has advised may be 293 mergeable. When it finds pages of identical content, it replaces 294 the many instances by a single page with that content, so 295 saving memory until one or another app needs to modify the content. 296 Recommended for use with KVM, or with other duplicative applications. 297 See Documentation/vm/ksm.txt for more information: KSM is inactive 298 until a program has madvised that an area is MADV_MERGEABLE, and 299 root has set /sys/kernel/mm/ksm/run to 1 (if CONFIG_SYSFS is set). 300 301config DEFAULT_MMAP_MIN_ADDR 302 int "Low address space to protect from user allocation" 303 depends on MMU 304 default 4096 305 help 306 This is the portion of low virtual memory which should be protected 307 from userspace allocation. Keeping a user from writing to low pages 308 can help reduce the impact of kernel NULL pointer bugs. 309 310 For most ia64, ppc64 and x86 users with lots of address space 311 a value of 65536 is reasonable and should cause no problems. 312 On arm and other archs it should not be higher than 32768. 313 Programs which use vm86 functionality or have some need to map 314 this low address space will need CAP_SYS_RAWIO or disable this 315 protection by setting the value to 0. 316 317 This value can be changed after boot using the 318 /proc/sys/vm/mmap_min_addr tunable. 319 320config ARCH_SUPPORTS_MEMORY_FAILURE 321 bool 322 323config MEMORY_FAILURE 324 depends on MMU 325 depends on ARCH_SUPPORTS_MEMORY_FAILURE 326 bool "Enable recovery from hardware memory errors" 327 select MEMORY_ISOLATION 328 help 329 Enables code to recover from some memory failures on systems 330 with MCA recovery. This allows a system to continue running 331 even when some of its memory has uncorrected errors. This requires 332 special hardware support and typically ECC memory. 333 334config HWPOISON_INJECT 335 tristate "HWPoison pages injector" 336 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 337 select PROC_PAGE_MONITOR 338 339config NOMMU_INITIAL_TRIM_EXCESS 340 int "Turn on mmap() excess space trimming before booting" 341 depends on !MMU 342 default 1 343 help 344 The NOMMU mmap() frequently needs to allocate large contiguous chunks 345 of memory on which to store mappings, but it can only ask the system 346 allocator for chunks in 2^N*PAGE_SIZE amounts - which is frequently 347 more than it requires. To deal with this, mmap() is able to trim off 348 the excess and return it to the allocator. 349 350 If trimming is enabled, the excess is trimmed off and returned to the 351 system allocator, which can cause extra fragmentation, particularly 352 if there are a lot of transient processes. 353 354 If trimming is disabled, the excess is kept, but not used, which for 355 long-term mappings means that the space is wasted. 356 357 Trimming can be dynamically controlled through a sysctl option 358 (/proc/sys/vm/nr_trim_pages) which specifies the minimum number of 359 excess pages there must be before trimming should occur, or zero if 360 no trimming is to occur. 361 362 This option specifies the initial value of this option. The default 363 of 1 says that all excess pages should be trimmed. 364 365 See Documentation/nommu-mmap.txt for more information. 366 367config TRANSPARENT_HUGEPAGE 368 bool "Transparent Hugepage Support" 369 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 370 select COMPACTION 371 help 372 Transparent Hugepages allows the kernel to use huge pages and 373 huge tlb transparently to the applications whenever possible. 374 This feature can improve computing performance to certain 375 applications by speeding up page faults during memory 376 allocation, by reducing the number of tlb misses and by speeding 377 up the pagetable walking. 378 379 If memory constrained on embedded, you may want to say N. 380 381choice 382 prompt "Transparent Hugepage Support sysfs defaults" 383 depends on TRANSPARENT_HUGEPAGE 384 default TRANSPARENT_HUGEPAGE_ALWAYS 385 help 386 Selects the sysfs defaults for Transparent Hugepage Support. 387 388 config TRANSPARENT_HUGEPAGE_ALWAYS 389 bool "always" 390 help 391 Enabling Transparent Hugepage always, can increase the 392 memory footprint of applications without a guaranteed 393 benefit but it will work automatically for all applications. 394 395 config TRANSPARENT_HUGEPAGE_MADVISE 396 bool "madvise" 397 help 398 Enabling Transparent Hugepage madvise, will only provide a 399 performance improvement benefit to the applications using 400 madvise(MADV_HUGEPAGE) but it won't risk to increase the 401 memory footprint of applications without a guaranteed 402 benefit. 403endchoice 404 405config CROSS_MEMORY_ATTACH 406 bool "Cross Memory Support" 407 depends on MMU 408 default y 409 help 410 Enabling this option adds the system calls process_vm_readv and 411 process_vm_writev which allow a process with the correct privileges 412 to directly read from or write to to another process's address space. 413 See the man page for more details. 414 415# 416# UP and nommu archs use km based percpu allocator 417# 418config NEED_PER_CPU_KM 419 depends on !SMP 420 bool 421 default y 422 423config CLEANCACHE 424 bool "Enable cleancache driver to cache clean pages if tmem is present" 425 default n 426 help 427 Cleancache can be thought of as a page-granularity victim cache 428 for clean pages that the kernel's pageframe replacement algorithm 429 (PFRA) would like to keep around, but can't since there isn't enough 430 memory. So when the PFRA "evicts" a page, it first attempts to use 431 cleancache code to put the data contained in that page into 432 "transcendent memory", memory that is not directly accessible or 433 addressable by the kernel and is of unknown and possibly 434 time-varying size. And when a cleancache-enabled 435 filesystem wishes to access a page in a file on disk, it first 436 checks cleancache to see if it already contains it; if it does, 437 the page is copied into the kernel and a disk access is avoided. 438 When a transcendent memory driver is available (such as zcache or 439 Xen transcendent memory), a significant I/O reduction 440 may be achieved. When none is available, all cleancache calls 441 are reduced to a single pointer-compare-against-NULL resulting 442 in a negligible performance hit. 443 444 If unsure, say Y to enable cleancache 445 446config FRONTSWAP 447 bool "Enable frontswap to cache swap pages if tmem is present" 448 depends on SWAP 449 default n 450 help 451 Frontswap is so named because it can be thought of as the opposite 452 of a "backing" store for a swap device. The data is stored into 453 "transcendent memory", memory that is not directly accessible or 454 addressable by the kernel and is of unknown and possibly 455 time-varying size. When space in transcendent memory is available, 456 a significant swap I/O reduction may be achieved. When none is 457 available, all frontswap calls are reduced to a single pointer- 458 compare-against-NULL resulting in a negligible performance hit 459 and swap data is stored as normal on the matching swap device. 460 461 If unsure, say Y to enable frontswap. 462