1config SELECT_MEMORY_MODEL 2 def_bool y 3 depends on 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# 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 171 172# eventually, we can have this option just 'select SPARSEMEM' 173config MEMORY_HOTPLUG 174 bool "Allow for memory hot-add" 175 depends on SPARSEMEM || X86_64_ACPI_NUMA 176 depends on HOTPLUG && ARCH_ENABLE_MEMORY_HOTPLUG 177 depends on (IA64 || X86 || PPC_BOOK3S_64 || SUPERH || S390) 178 179config MEMORY_HOTPLUG_SPARSE 180 def_bool y 181 depends on SPARSEMEM && MEMORY_HOTPLUG 182 183config MEMORY_HOTREMOVE 184 bool "Allow for memory hot remove" 185 select MEMORY_ISOLATION 186 select HAVE_BOOTMEM_INFO_NODE if X86_64 187 depends on MEMORY_HOTPLUG && ARCH_ENABLE_MEMORY_HOTREMOVE 188 depends on MIGRATION 189 190# 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 200 depends on 64BIT || SPARSEMEM_VMEMMAP || !SPARSEMEM 201 202# 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. 207# PA-RISC 7xxx's spinlock_t would enlarge struct page from 32 to 44 bytes. 208# DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. 209# 210config SPLIT_PTLOCK_CPUS 211 int 212 default "999999" if ARM && !CPU_CACHE_VIPT 213 default "999999" if PARISC && !PA20 214 default "999999" if DEBUG_SPINLOCK || DEBUG_LOCK_ALLOC 215 default "4" 216 217# 218# 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# 233# support for memory compaction 234config COMPACTION 235 bool "Allow for memory compaction" 236 def_bool y 237 select MIGRATION 238 depends on MMU 239 help 240 Allows the compaction of memory for the allocation of huge pages. 241 242# 243# support for page migration 244# 245config MIGRATION 246 bool "Page migration" 247 def_bool y 248 depends on NUMA || ARCH_ENABLE_MEMORY_HOTREMOVE || COMPACTION || CMA 249 help 250 Allows the migration of the physical location of pages of processes 251 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. 256 257config PHYS_ADDR_T_64BIT 258 def_bool 64BIT || ARCH_PHYS_ADDR_T_64BIT 259 260config ZONE_DMA_FLAG 261 int 262 default "0" if !ZONE_DMA 263 default "1" 264 265config BOUNCE 266 def_bool y 267 depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM) 268 269# 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 282config NR_QUICK 283 int 284 depends on QUICKLIST 285 default "2" if AVR32 286 default "1" 287 288config VIRT_TO_BUS 289 def_bool y 290 depends on HAVE_VIRT_TO_BUS 291 292config MMU_NOTIFIER 293 bool 294 295config 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 302 the many instances by a single page with that content, so 303 saving memory until one or another app needs to modify the content. 304 Recommended for use with KVM, or with other duplicative applications. 305 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). 308 309config DEFAULT_MMAP_MIN_ADDR 310 int "Low address space to protect from user allocation" 311 depends on MMU 312 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. 321 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. 324 325 This value can be changed after boot using the 326 /proc/sys/vm/mmap_min_addr tunable. 327 328config ARCH_SUPPORTS_MEMORY_FAILURE 329 bool 330 331config MEMORY_FAILURE 332 depends on MMU 333 depends on ARCH_SUPPORTS_MEMORY_FAILURE 334 bool "Enable recovery from hardware memory errors" 335 select MEMORY_ISOLATION 336 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 342config HWPOISON_INJECT 343 tristate "HWPoison pages injector" 344 depends on MEMORY_FAILURE && DEBUG_KERNEL && PROC_FS 345 select PROC_PAGE_MONITOR 346 347config 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. 374 375config TRANSPARENT_HUGEPAGE 376 bool "Transparent Hugepage Support" 377 depends on HAVE_ARCH_TRANSPARENT_HUGEPAGE 378 select COMPACTION 379 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 389choice 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 413config 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. 422 423# 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 430 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 439 cleancache code to put the data contained in that page into 440 "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 453 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. 470