Kconfig 56 KB

12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576777879808182838485868788899091929394959697989910010110210310410510610710810911011111211311411511611711811912012112212312412512612712812913013113213313413513613713813914014114214314414514614714814915015115215315415515615715815916016116216316416516616716816917017117217317417517617717817918018118218318418518618718818919019119219319419519619719819920020120220320420520620720820921021121221321421521621721821922022122222322422522622722822923023123223323423523623723823924024124224324424524624724824925025125225325425525625725825926026126226326426526626726826927027127227327427527627727827928028128228328428528628728828929029129229329429529629729829930030130230330430530630730830931031131231331431531631731831932032132232332432532632732832933033133233333433533633733833934034134234334434534634734834935035135235335435535635735835936036136236336436536636736836937037137237337437537637737837938038138238338438538638738838939039139239339439539639739839940040140240340440540640740840941041141241341441541641741841942042142242342442542642742842943043143243343443543643743843944044144244344444544644744844945045145245345445545645745845946046146246346446546646746846947047147247347447547647747847948048148248348448548648748848949049149249349449549649749849950050150250350450550650750850951051151251351451551651751851952052152252352452552652752852953053153253353453553653753853954054154254354454554654754854955055155255355455555655755855956056156256356456556656756856957057157257357457557657757857958058158258358458558658758858959059159259359459559659759859960060160260360460560660760860961061161261361461561661761861962062162262362462562662762862963063163263363463563663763863964064164264364464564664764864965065165265365465565665765865966066166266366466566666766866967067167267367467567667767867968068168268368468568668768868969069169269369469569669769869970070170270370470570670770870971071171271371471571671771871972072172272372472572672772872973073173273373473573673773873974074174274374474574674774874975075175275375475575675775875976076176276376476576676776876977077177277377477577677777877978078178278378478578678778878979079179279379479579679779879980080180280380480580680780880981081181281381481581681781881982082182282382482582682782882983083183283383483583683783883984084184284384484584684784884985085185285385485585685785885986086186286386486586686786886987087187287387487587687787887988088188288388488588688788888989089189289389489589689789889990090190290390490590690790890991091191291391491591691791891992092192292392492592692792892993093193293393493593693793893994094194294394494594694794894995095195295395495595695795895996096196296396496596696796896997097197297397497597697797897998098198298398498598698798898999099199299399499599699799899910001001100210031004100510061007100810091010101110121013101410151016101710181019102010211022102310241025102610271028102910301031103210331034103510361037103810391040104110421043104410451046104710481049105010511052105310541055105610571058105910601061106210631064106510661067106810691070107110721073107410751076107710781079108010811082108310841085108610871088108910901091109210931094109510961097109810991100110111021103110411051106110711081109111011111112111311141115111611171118111911201121112211231124112511261127112811291130113111321133113411351136113711381139114011411142114311441145114611471148114911501151115211531154115511561157115811591160116111621163116411651166116711681169117011711172117311741175117611771178117911801181118211831184118511861187118811891190119111921193119411951196119711981199120012011202120312041205120612071208120912101211121212131214121512161217121812191220122112221223122412251226122712281229123012311232123312341235123612371238123912401241124212431244124512461247124812491250125112521253125412551256125712581259126012611262126312641265126612671268126912701271127212731274127512761277127812791280128112821283128412851286128712881289129012911292129312941295129612971298129913001301130213031304130513061307130813091310131113121313131413151316131713181319132013211322132313241325132613271328132913301331133213331334133513361337133813391340134113421343134413451346134713481349135013511352135313541355135613571358135913601361136213631364136513661367136813691370137113721373137413751376137713781379138013811382138313841385138613871388138913901391139213931394139513961397139813991400140114021403140414051406140714081409141014111412141314141415141614171418141914201421142214231424142514261427142814291430143114321433143414351436143714381439144014411442144314441445144614471448144914501451145214531454145514561457145814591460146114621463146414651466146714681469147014711472147314741475147614771478147914801481148214831484148514861487148814891490149114921493149414951496149714981499150015011502150315041505150615071508150915101511151215131514151515161517151815191520152115221523152415251526152715281529153015311532153315341535153615371538153915401541154215431544154515461547154815491550155115521553155415551556155715581559156015611562156315641565156615671568156915701571157215731574157515761577157815791580158115821583158415851586158715881589159015911592159315941595159615971598159916001601160216031604160516061607160816091610161116121613161416151616161716181619162016211622162316241625162616271628162916301631163216331634163516361637163816391640164116421643164416451646164716481649165016511652165316541655165616571658165916601661166216631664166516661667166816691670167116721673167416751676167716781679168016811682168316841685168616871688168916901691169216931694169516961697169816991700170117021703170417051706170717081709171017111712171317141715171617171718171917201721172217231724172517261727172817291730173117321733173417351736173717381739174017411742174317441745174617471748174917501751175217531754175517561757175817591760176117621763176417651766176717681769
  1. config ARCH
  2. string
  3. option env="ARCH"
  4. config KERNELVERSION
  5. string
  6. option env="KERNELVERSION"
  7. config DEFCONFIG_LIST
  8. string
  9. depends on !UML
  10. option defconfig_list
  11. default "/lib/modules/$UNAME_RELEASE/.config"
  12. default "/etc/kernel-config"
  13. default "/boot/config-$UNAME_RELEASE"
  14. default "$ARCH_DEFCONFIG"
  15. default "arch/$ARCH/defconfig"
  16. config CONSTRUCTORS
  17. bool
  18. depends on !UML
  19. config IRQ_WORK
  20. bool
  21. config BUILDTIME_EXTABLE_SORT
  22. bool
  23. menu "General setup"
  24. config EXPERIMENTAL
  25. bool "Prompt for development and/or incomplete code/drivers"
  26. ---help---
  27. Some of the various things that Linux supports (such as network
  28. drivers, file systems, network protocols, etc.) can be in a state
  29. of development where the functionality, stability, or the level of
  30. testing is not yet high enough for general use. This is usually
  31. known as the "alpha-test" phase among developers. If a feature is
  32. currently in alpha-test, then the developers usually discourage
  33. uninformed widespread use of this feature by the general public to
  34. avoid "Why doesn't this work?" type mail messages. However, active
  35. testing and use of these systems is welcomed. Just be aware that it
  36. may not meet the normal level of reliability or it may fail to work
  37. in some special cases. Detailed bug reports from people familiar
  38. with the kernel internals are usually welcomed by the developers
  39. (before submitting bug reports, please read the documents
  40. <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  41. <file:Documentation/BUG-HUNTING>, and
  42. <file:Documentation/oops-tracing.txt> in the kernel source).
  43. This option will also make obsoleted drivers available. These are
  44. drivers that have been replaced by something else, and/or are
  45. scheduled to be removed in a future kernel release.
  46. Unless you intend to help test and develop a feature or driver that
  47. falls into this category, or you have a situation that requires
  48. using these features, you should probably say N here, which will
  49. cause the configurator to present you with fewer choices. If
  50. you say Y here, you will be offered the choice of using features or
  51. drivers that are currently considered to be in the alpha-test phase.
  52. config BROKEN
  53. bool
  54. config BROKEN_ON_SMP
  55. bool
  56. depends on BROKEN || !SMP
  57. default y
  58. config INIT_ENV_ARG_LIMIT
  59. int
  60. default 32 if !UML
  61. default 128 if UML
  62. help
  63. Maximum of each of the number of arguments and environment
  64. variables passed to init from the kernel command line.
  65. config CROSS_COMPILE
  66. string "Cross-compiler tool prefix"
  67. help
  68. Same as running 'make CROSS_COMPILE=prefix-' but stored for
  69. default make runs in this kernel build directory. You don't
  70. need to set this unless you want the configured kernel build
  71. directory to select the cross-compiler automatically.
  72. config LOCALVERSION
  73. string "Local version - append to kernel release"
  74. help
  75. Append an extra string to the end of your kernel version.
  76. This will show up when you type uname, for example.
  77. The string you set here will be appended after the contents of
  78. any files with a filename matching localversion* in your
  79. object and source tree, in that order. Your total string can
  80. be a maximum of 64 characters.
  81. config LOCALVERSION_AUTO
  82. bool "Automatically append version information to the version string"
  83. default y
  84. help
  85. This will try to automatically determine if the current tree is a
  86. release tree by looking for git tags that belong to the current
  87. top of tree revision.
  88. A string of the format -gxxxxxxxx will be added to the localversion
  89. if a git-based tree is found. The string generated by this will be
  90. appended after any matching localversion* files, and after the value
  91. set in CONFIG_LOCALVERSION.
  92. (The actual string used here is the first eight characters produced
  93. by running the command:
  94. $ git rev-parse --verify HEAD
  95. which is done within the script "scripts/setlocalversion".)
  96. config HAVE_KERNEL_GZIP
  97. bool
  98. config HAVE_KERNEL_BZIP2
  99. bool
  100. config HAVE_KERNEL_LZMA
  101. bool
  102. config HAVE_KERNEL_XZ
  103. bool
  104. config HAVE_KERNEL_LZO
  105. bool
  106. choice
  107. prompt "Kernel compression mode"
  108. default KERNEL_GZIP
  109. depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
  110. help
  111. The linux kernel is a kind of self-extracting executable.
  112. Several compression algorithms are available, which differ
  113. in efficiency, compression and decompression speed.
  114. Compression speed is only relevant when building a kernel.
  115. Decompression speed is relevant at each boot.
  116. If you have any problems with bzip2 or lzma compressed
  117. kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
  118. version of this functionality (bzip2 only), for 2.4, was
  119. supplied by Christian Ludwig)
  120. High compression options are mostly useful for users, who
  121. are low on disk space (embedded systems), but for whom ram
  122. size matters less.
  123. If in doubt, select 'gzip'
  124. config KERNEL_GZIP
  125. bool "Gzip"
  126. depends on HAVE_KERNEL_GZIP
  127. help
  128. The old and tried gzip compression. It provides a good balance
  129. between compression ratio and decompression speed.
  130. config KERNEL_BZIP2
  131. bool "Bzip2"
  132. depends on HAVE_KERNEL_BZIP2
  133. help
  134. Its compression ratio and speed is intermediate.
  135. Decompression speed is slowest among the choices. The kernel
  136. size is about 10% smaller with bzip2, in comparison to gzip.
  137. Bzip2 uses a large amount of memory. For modern kernels you
  138. will need at least 8MB RAM or more for booting.
  139. config KERNEL_LZMA
  140. bool "LZMA"
  141. depends on HAVE_KERNEL_LZMA
  142. help
  143. This compression algorithm's ratio is best. Decompression speed
  144. is between gzip and bzip2. Compression is slowest.
  145. The kernel size is about 33% smaller with LZMA in comparison to gzip.
  146. config KERNEL_XZ
  147. bool "XZ"
  148. depends on HAVE_KERNEL_XZ
  149. help
  150. XZ uses the LZMA2 algorithm and instruction set specific
  151. BCJ filters which can improve compression ratio of executable
  152. code. The size of the kernel is about 30% smaller with XZ in
  153. comparison to gzip. On architectures for which there is a BCJ
  154. filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
  155. will create a few percent smaller kernel than plain LZMA.
  156. The speed is about the same as with LZMA: The decompression
  157. speed of XZ is better than that of bzip2 but worse than gzip
  158. and LZO. Compression is slow.
  159. config KERNEL_LZO
  160. bool "LZO"
  161. depends on HAVE_KERNEL_LZO
  162. help
  163. Its compression ratio is the poorest among the choices. The kernel
  164. size is about 10% bigger than gzip; however its speed
  165. (both compression and decompression) is the fastest.
  166. endchoice
  167. config DEFAULT_HOSTNAME
  168. string "Default hostname"
  169. default "(none)"
  170. help
  171. This option determines the default system hostname before userspace
  172. calls sethostname(2). The kernel traditionally uses "(none)" here,
  173. but you may wish to use a different default here to make a minimal
  174. system more usable with less configuration.
  175. config SWAP
  176. bool "Support for paging of anonymous memory (swap)"
  177. depends on MMU && BLOCK
  178. default y
  179. help
  180. This option allows you to choose whether you want to have support
  181. for so called swap devices or swap files in your kernel that are
  182. used to provide more virtual memory than the actual RAM present
  183. in your computer. If unsure say Y.
  184. config SYSVIPC
  185. bool "System V IPC"
  186. ---help---
  187. Inter Process Communication is a suite of library functions and
  188. system calls which let processes (running programs) synchronize and
  189. exchange information. It is generally considered to be a good thing,
  190. and some programs won't run unless you say Y here. In particular, if
  191. you want to run the DOS emulator dosemu under Linux (read the
  192. DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
  193. you'll need to say Y here.
  194. You can find documentation about IPC with "info ipc" and also in
  195. section 6.4 of the Linux Programmer's Guide, available from
  196. <http://www.tldp.org/guides.html>.
  197. config SYSVIPC_SYSCTL
  198. bool
  199. depends on SYSVIPC
  200. depends on SYSCTL
  201. default y
  202. config POSIX_MQUEUE
  203. bool "POSIX Message Queues"
  204. depends on NET && EXPERIMENTAL
  205. ---help---
  206. POSIX variant of message queues is a part of IPC. In POSIX message
  207. queues every message has a priority which decides about succession
  208. of receiving it by a process. If you want to compile and run
  209. programs written e.g. for Solaris with use of its POSIX message
  210. queues (functions mq_*) say Y here.
  211. POSIX message queues are visible as a filesystem called 'mqueue'
  212. and can be mounted somewhere if you want to do filesystem
  213. operations on message queues.
  214. If unsure, say Y.
  215. config POSIX_MQUEUE_SYSCTL
  216. bool
  217. depends on POSIX_MQUEUE
  218. depends on SYSCTL
  219. default y
  220. config FHANDLE
  221. bool "open by fhandle syscalls"
  222. select EXPORTFS
  223. help
  224. If you say Y here, a user level program will be able to map
  225. file names to handle and then later use the handle for
  226. different file system operations. This is useful in implementing
  227. userspace file servers, which now track files using handles instead
  228. of names. The handle would remain the same even if file names
  229. get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
  230. syscalls.
  231. config AUDIT
  232. bool "Auditing support"
  233. depends on NET
  234. help
  235. Enable auditing infrastructure that can be used with another
  236. kernel subsystem, such as SELinux (which requires this for
  237. logging of avc messages output). Does not do system-call
  238. auditing without CONFIG_AUDITSYSCALL.
  239. config AUDITSYSCALL
  240. bool "Enable system-call auditing support"
  241. depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
  242. default y if SECURITY_SELINUX
  243. help
  244. Enable low-overhead system-call auditing infrastructure that
  245. can be used independently or with another kernel subsystem,
  246. such as SELinux.
  247. config AUDIT_WATCH
  248. def_bool y
  249. depends on AUDITSYSCALL
  250. select FSNOTIFY
  251. config AUDIT_TREE
  252. def_bool y
  253. depends on AUDITSYSCALL
  254. select FSNOTIFY
  255. config AUDIT_LOGINUID_IMMUTABLE
  256. bool "Make audit loginuid immutable"
  257. depends on AUDIT
  258. help
  259. The config option toggles if a task setting its loginuid requires
  260. CAP_SYS_AUDITCONTROL or if that task should require no special permissions
  261. but should instead only allow setting its loginuid if it was never
  262. previously set. On systems which use systemd or a similar central
  263. process to restart login services this should be set to true. On older
  264. systems in which an admin would typically have to directly stop and
  265. start processes this should be set to false. Setting this to true allows
  266. one to drop potentially dangerous capabilites from the login tasks,
  267. but may not be backwards compatible with older init systems.
  268. source "kernel/irq/Kconfig"
  269. source "kernel/time/Kconfig"
  270. menu "CPU/Task time and stats accounting"
  271. config VIRT_CPU_ACCOUNTING
  272. bool
  273. choice
  274. prompt "Cputime accounting"
  275. default TICK_CPU_ACCOUNTING if !PPC64
  276. default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
  277. # Kind of a stub config for the pure tick based cputime accounting
  278. config TICK_CPU_ACCOUNTING
  279. bool "Simple tick based cputime accounting"
  280. depends on !S390
  281. help
  282. This is the basic tick based cputime accounting that maintains
  283. statistics about user, system and idle time spent on per jiffies
  284. granularity.
  285. If unsure, say Y.
  286. config VIRT_CPU_ACCOUNTING_NATIVE
  287. bool "Deterministic task and CPU time accounting"
  288. depends on HAVE_VIRT_CPU_ACCOUNTING
  289. select VIRT_CPU_ACCOUNTING
  290. help
  291. Select this option to enable more accurate task and CPU time
  292. accounting. This is done by reading a CPU counter on each
  293. kernel entry and exit and on transitions within the kernel
  294. between system, softirq and hardirq state, so there is a
  295. small performance impact. In the case of s390 or IBM POWER > 5,
  296. this also enables accounting of stolen time on logically-partitioned
  297. systems.
  298. config VIRT_CPU_ACCOUNTING_GEN
  299. bool "Full dynticks CPU time accounting"
  300. depends on HAVE_CONTEXT_TRACKING && 64BIT
  301. select VIRT_CPU_ACCOUNTING
  302. select CONTEXT_TRACKING
  303. help
  304. Select this option to enable task and CPU time accounting on full
  305. dynticks systems. This accounting is implemented by watching every
  306. kernel-user boundaries using the context tracking subsystem.
  307. The accounting is thus performed at the expense of some significant
  308. overhead.
  309. For now this is only useful if you are working on the full
  310. dynticks subsystem development.
  311. If unsure, say N.
  312. config IRQ_TIME_ACCOUNTING
  313. bool "Fine granularity task level IRQ time accounting"
  314. depends on HAVE_IRQ_TIME_ACCOUNTING
  315. help
  316. Select this option to enable fine granularity task irq time
  317. accounting. This is done by reading a timestamp on each
  318. transitions between softirq and hardirq state, so there can be a
  319. small performance impact.
  320. If in doubt, say N here.
  321. endchoice
  322. config BSD_PROCESS_ACCT
  323. bool "BSD Process Accounting"
  324. help
  325. If you say Y here, a user level program will be able to instruct the
  326. kernel (via a special system call) to write process accounting
  327. information to a file: whenever a process exits, information about
  328. that process will be appended to the file by the kernel. The
  329. information includes things such as creation time, owning user,
  330. command name, memory usage, controlling terminal etc. (the complete
  331. list is in the struct acct in <file:include/linux/acct.h>). It is
  332. up to the user level program to do useful things with this
  333. information. This is generally a good idea, so say Y.
  334. config BSD_PROCESS_ACCT_V3
  335. bool "BSD Process Accounting version 3 file format"
  336. depends on BSD_PROCESS_ACCT
  337. default n
  338. help
  339. If you say Y here, the process accounting information is written
  340. in a new file format that also logs the process IDs of each
  341. process and it's parent. Note that this file format is incompatible
  342. with previous v0/v1/v2 file formats, so you will need updated tools
  343. for processing it. A preliminary version of these tools is available
  344. at <http://www.gnu.org/software/acct/>.
  345. config TASKSTATS
  346. bool "Export task/process statistics through netlink (EXPERIMENTAL)"
  347. depends on NET
  348. default n
  349. help
  350. Export selected statistics for tasks/processes through the
  351. generic netlink interface. Unlike BSD process accounting, the
  352. statistics are available during the lifetime of tasks/processes as
  353. responses to commands. Like BSD accounting, they are sent to user
  354. space on task exit.
  355. Say N if unsure.
  356. config TASK_DELAY_ACCT
  357. bool "Enable per-task delay accounting (EXPERIMENTAL)"
  358. depends on TASKSTATS
  359. help
  360. Collect information on time spent by a task waiting for system
  361. resources like cpu, synchronous block I/O completion and swapping
  362. in pages. Such statistics can help in setting a task's priorities
  363. relative to other tasks for cpu, io, rss limits etc.
  364. Say N if unsure.
  365. config TASK_XACCT
  366. bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
  367. depends on TASKSTATS
  368. help
  369. Collect extended task accounting data and send the data
  370. to userland for processing over the taskstats interface.
  371. Say N if unsure.
  372. config TASK_IO_ACCOUNTING
  373. bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
  374. depends on TASK_XACCT
  375. help
  376. Collect information on the number of bytes of storage I/O which this
  377. task has caused.
  378. Say N if unsure.
  379. endmenu # "CPU/Task time and stats accounting"
  380. menu "RCU Subsystem"
  381. choice
  382. prompt "RCU Implementation"
  383. default TREE_RCU
  384. config TREE_RCU
  385. bool "Tree-based hierarchical RCU"
  386. depends on !PREEMPT && SMP
  387. help
  388. This option selects the RCU implementation that is
  389. designed for very large SMP system with hundreds or
  390. thousands of CPUs. It also scales down nicely to
  391. smaller systems.
  392. config TREE_PREEMPT_RCU
  393. bool "Preemptible tree-based hierarchical RCU"
  394. depends on PREEMPT
  395. help
  396. This option selects the RCU implementation that is
  397. designed for very large SMP systems with hundreds or
  398. thousands of CPUs, but for which real-time response
  399. is also required. It also scales down nicely to
  400. smaller systems.
  401. Select this option if you are unsure.
  402. config TINY_RCU
  403. bool "UP-only small-memory-footprint RCU"
  404. depends on !PREEMPT && !SMP
  405. help
  406. This option selects the RCU implementation that is
  407. designed for UP systems from which real-time response
  408. is not required. This option greatly reduces the
  409. memory footprint of RCU.
  410. config TINY_PREEMPT_RCU
  411. bool "Preemptible UP-only small-memory-footprint RCU"
  412. depends on PREEMPT && !SMP
  413. help
  414. This option selects the RCU implementation that is designed
  415. for real-time UP systems. This option greatly reduces the
  416. memory footprint of RCU.
  417. endchoice
  418. config PREEMPT_RCU
  419. def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
  420. help
  421. This option enables preemptible-RCU code that is common between
  422. the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
  423. config RCU_STALL_COMMON
  424. def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
  425. help
  426. This option enables RCU CPU stall code that is common between
  427. the TINY and TREE variants of RCU. The purpose is to allow
  428. the tiny variants to disable RCU CPU stall warnings, while
  429. making these warnings mandatory for the tree variants.
  430. config CONTEXT_TRACKING
  431. bool
  432. config RCU_USER_QS
  433. bool "Consider userspace as in RCU extended quiescent state"
  434. depends on HAVE_CONTEXT_TRACKING && SMP
  435. select CONTEXT_TRACKING
  436. help
  437. This option sets hooks on kernel / userspace boundaries and
  438. puts RCU in extended quiescent state when the CPU runs in
  439. userspace. It means that when a CPU runs in userspace, it is
  440. excluded from the global RCU state machine and thus doesn't
  441. try to keep the timer tick on for RCU.
  442. Unless you want to hack and help the development of the full
  443. dynticks mode, you shouldn't enable this option. It also
  444. adds unnecessary overhead.
  445. If unsure say N
  446. config CONTEXT_TRACKING_FORCE
  447. bool "Force context tracking"
  448. depends on CONTEXT_TRACKING
  449. help
  450. Probe on user/kernel boundaries by default in order to
  451. test the features that rely on it such as userspace RCU extended
  452. quiescent states.
  453. This test is there for debugging until we have a real user like the
  454. full dynticks mode.
  455. config RCU_FANOUT
  456. int "Tree-based hierarchical RCU fanout value"
  457. range 2 64 if 64BIT
  458. range 2 32 if !64BIT
  459. depends on TREE_RCU || TREE_PREEMPT_RCU
  460. default 64 if 64BIT
  461. default 32 if !64BIT
  462. help
  463. This option controls the fanout of hierarchical implementations
  464. of RCU, allowing RCU to work efficiently on machines with
  465. large numbers of CPUs. This value must be at least the fourth
  466. root of NR_CPUS, which allows NR_CPUS to be insanely large.
  467. The default value of RCU_FANOUT should be used for production
  468. systems, but if you are stress-testing the RCU implementation
  469. itself, small RCU_FANOUT values allow you to test large-system
  470. code paths on small(er) systems.
  471. Select a specific number if testing RCU itself.
  472. Take the default if unsure.
  473. config RCU_FANOUT_LEAF
  474. int "Tree-based hierarchical RCU leaf-level fanout value"
  475. range 2 RCU_FANOUT if 64BIT
  476. range 2 RCU_FANOUT if !64BIT
  477. depends on TREE_RCU || TREE_PREEMPT_RCU
  478. default 16
  479. help
  480. This option controls the leaf-level fanout of hierarchical
  481. implementations of RCU, and allows trading off cache misses
  482. against lock contention. Systems that synchronize their
  483. scheduling-clock interrupts for energy-efficiency reasons will
  484. want the default because the smaller leaf-level fanout keeps
  485. lock contention levels acceptably low. Very large systems
  486. (hundreds or thousands of CPUs) will instead want to set this
  487. value to the maximum value possible in order to reduce the
  488. number of cache misses incurred during RCU's grace-period
  489. initialization. These systems tend to run CPU-bound, and thus
  490. are not helped by synchronized interrupts, and thus tend to
  491. skew them, which reduces lock contention enough that large
  492. leaf-level fanouts work well.
  493. Select a specific number if testing RCU itself.
  494. Select the maximum permissible value for large systems.
  495. Take the default if unsure.
  496. config RCU_FANOUT_EXACT
  497. bool "Disable tree-based hierarchical RCU auto-balancing"
  498. depends on TREE_RCU || TREE_PREEMPT_RCU
  499. default n
  500. help
  501. This option forces use of the exact RCU_FANOUT value specified,
  502. regardless of imbalances in the hierarchy. This is useful for
  503. testing RCU itself, and might one day be useful on systems with
  504. strong NUMA behavior.
  505. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  506. Say N if unsure.
  507. config RCU_FAST_NO_HZ
  508. bool "Accelerate last non-dyntick-idle CPU's grace periods"
  509. depends on NO_HZ && SMP
  510. default n
  511. help
  512. This option causes RCU to attempt to accelerate grace periods in
  513. order to allow CPUs to enter dynticks-idle state more quickly.
  514. On the other hand, this option increases the overhead of the
  515. dynticks-idle checking, thus degrading scheduling latency.
  516. Say Y if energy efficiency is critically important, and you don't
  517. care about real-time response.
  518. Say N if you are unsure.
  519. config TREE_RCU_TRACE
  520. def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
  521. select DEBUG_FS
  522. help
  523. This option provides tracing for the TREE_RCU and
  524. TREE_PREEMPT_RCU implementations, permitting Makefile to
  525. trivially select kernel/rcutree_trace.c.
  526. config RCU_BOOST
  527. bool "Enable RCU priority boosting"
  528. depends on RT_MUTEXES && PREEMPT_RCU
  529. default n
  530. help
  531. This option boosts the priority of preempted RCU readers that
  532. block the current preemptible RCU grace period for too long.
  533. This option also prevents heavy loads from blocking RCU
  534. callback invocation for all flavors of RCU.
  535. Say Y here if you are working with real-time apps or heavy loads
  536. Say N here if you are unsure.
  537. config RCU_BOOST_PRIO
  538. int "Real-time priority to boost RCU readers to"
  539. range 1 99
  540. depends on RCU_BOOST
  541. default 1
  542. help
  543. This option specifies the real-time priority to which long-term
  544. preempted RCU readers are to be boosted. If you are working
  545. with a real-time application that has one or more CPU-bound
  546. threads running at a real-time priority level, you should set
  547. RCU_BOOST_PRIO to a priority higher then the highest-priority
  548. real-time CPU-bound thread. The default RCU_BOOST_PRIO value
  549. of 1 is appropriate in the common case, which is real-time
  550. applications that do not have any CPU-bound threads.
  551. Some real-time applications might not have a single real-time
  552. thread that saturates a given CPU, but instead might have
  553. multiple real-time threads that, taken together, fully utilize
  554. that CPU. In this case, you should set RCU_BOOST_PRIO to
  555. a priority higher than the lowest-priority thread that is
  556. conspiring to prevent the CPU from running any non-real-time
  557. tasks. For example, if one thread at priority 10 and another
  558. thread at priority 5 are between themselves fully consuming
  559. the CPU time on a given CPU, then RCU_BOOST_PRIO should be
  560. set to priority 6 or higher.
  561. Specify the real-time priority, or take the default if unsure.
  562. config RCU_BOOST_DELAY
  563. int "Milliseconds to delay boosting after RCU grace-period start"
  564. range 0 3000
  565. depends on RCU_BOOST
  566. default 500
  567. help
  568. This option specifies the time to wait after the beginning of
  569. a given grace period before priority-boosting preempted RCU
  570. readers blocking that grace period. Note that any RCU reader
  571. blocking an expedited RCU grace period is boosted immediately.
  572. Accept the default if unsure.
  573. config RCU_NOCB_CPU
  574. bool "Offload RCU callback processing from boot-selected CPUs"
  575. depends on TREE_RCU || TREE_PREEMPT_RCU
  576. default n
  577. help
  578. Use this option to reduce OS jitter for aggressive HPC or
  579. real-time workloads. It can also be used to offload RCU
  580. callback invocation to energy-efficient CPUs in battery-powered
  581. asymmetric multiprocessors.
  582. This option offloads callback invocation from the set of
  583. CPUs specified at boot time by the rcu_nocbs parameter.
  584. For each such CPU, a kthread ("rcuoN") will be created to
  585. invoke callbacks, where the "N" is the CPU being offloaded.
  586. Nothing prevents this kthread from running on the specified
  587. CPUs, but (1) the kthreads may be preempted between each
  588. callback, and (2) affinity or cgroups can be used to force
  589. the kthreads to run on whatever set of CPUs is desired.
  590. Say Y here if you want reduced OS jitter on selected CPUs.
  591. Say N here if you are unsure.
  592. endmenu # "RCU Subsystem"
  593. config IKCONFIG
  594. tristate "Kernel .config support"
  595. ---help---
  596. This option enables the complete Linux kernel ".config" file
  597. contents to be saved in the kernel. It provides documentation
  598. of which kernel options are used in a running kernel or in an
  599. on-disk kernel. This information can be extracted from the kernel
  600. image file with the script scripts/extract-ikconfig and used as
  601. input to rebuild the current kernel or to build another kernel.
  602. It can also be extracted from a running kernel by reading
  603. /proc/config.gz if enabled (below).
  604. config IKCONFIG_PROC
  605. bool "Enable access to .config through /proc/config.gz"
  606. depends on IKCONFIG && PROC_FS
  607. ---help---
  608. This option enables access to the kernel configuration file
  609. through /proc/config.gz.
  610. config LOG_BUF_SHIFT
  611. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  612. range 12 21
  613. default 17
  614. help
  615. Select kernel log buffer size as a power of 2.
  616. Examples:
  617. 17 => 128 KB
  618. 16 => 64 KB
  619. 15 => 32 KB
  620. 14 => 16 KB
  621. 13 => 8 KB
  622. 12 => 4 KB
  623. #
  624. # Architectures with an unreliable sched_clock() should select this:
  625. #
  626. config HAVE_UNSTABLE_SCHED_CLOCK
  627. bool
  628. #
  629. # For architectures that want to enable the support for NUMA-affine scheduler
  630. # balancing logic:
  631. #
  632. config ARCH_SUPPORTS_NUMA_BALANCING
  633. bool
  634. # For architectures that (ab)use NUMA to represent different memory regions
  635. # all cpu-local but of different latencies, such as SuperH.
  636. #
  637. config ARCH_WANT_NUMA_VARIABLE_LOCALITY
  638. bool
  639. #
  640. # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
  641. config ARCH_WANTS_PROT_NUMA_PROT_NONE
  642. bool
  643. config ARCH_USES_NUMA_PROT_NONE
  644. bool
  645. default y
  646. depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
  647. depends on NUMA_BALANCING
  648. config NUMA_BALANCING_DEFAULT_ENABLED
  649. bool "Automatically enable NUMA aware memory/task placement"
  650. default y
  651. depends on NUMA_BALANCING
  652. help
  653. If set, autonumic NUMA balancing will be enabled if running on a NUMA
  654. machine.
  655. config NUMA_BALANCING
  656. bool "Memory placement aware NUMA scheduler"
  657. depends on ARCH_SUPPORTS_NUMA_BALANCING
  658. depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
  659. depends on SMP && NUMA && MIGRATION
  660. help
  661. This option adds support for automatic NUMA aware memory/task placement.
  662. The mechanism is quite primitive and is based on migrating memory when
  663. it is references to the node the task is running on.
  664. This system will be inactive on UMA systems.
  665. menuconfig CGROUPS
  666. boolean "Control Group support"
  667. depends on EVENTFD
  668. help
  669. This option adds support for grouping sets of processes together, for
  670. use with process control subsystems such as Cpusets, CFS, memory
  671. controls or device isolation.
  672. See
  673. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  674. - Documentation/cgroups/ (features for grouping, isolation
  675. and resource control)
  676. Say N if unsure.
  677. if CGROUPS
  678. config CGROUP_DEBUG
  679. bool "Example debug cgroup subsystem"
  680. default n
  681. help
  682. This option enables a simple cgroup subsystem that
  683. exports useful debugging information about the cgroups
  684. framework.
  685. Say N if unsure.
  686. config CGROUP_FREEZER
  687. bool "Freezer cgroup subsystem"
  688. help
  689. Provides a way to freeze and unfreeze all tasks in a
  690. cgroup.
  691. config CGROUP_DEVICE
  692. bool "Device controller for cgroups"
  693. help
  694. Provides a cgroup implementing whitelists for devices which
  695. a process in the cgroup can mknod or open.
  696. config CPUSETS
  697. bool "Cpuset support"
  698. help
  699. This option will let you create and manage CPUSETs which
  700. allow dynamically partitioning a system into sets of CPUs and
  701. Memory Nodes and assigning tasks to run only within those sets.
  702. This is primarily useful on large SMP or NUMA systems.
  703. Say N if unsure.
  704. config PROC_PID_CPUSET
  705. bool "Include legacy /proc/<pid>/cpuset file"
  706. depends on CPUSETS
  707. default y
  708. config CGROUP_CPUACCT
  709. bool "Simple CPU accounting cgroup subsystem"
  710. help
  711. Provides a simple Resource Controller for monitoring the
  712. total CPU consumed by the tasks in a cgroup.
  713. config RESOURCE_COUNTERS
  714. bool "Resource counters"
  715. help
  716. This option enables controller independent resource accounting
  717. infrastructure that works with cgroups.
  718. config MEMCG
  719. bool "Memory Resource Controller for Control Groups"
  720. depends on RESOURCE_COUNTERS
  721. select MM_OWNER
  722. help
  723. Provides a memory resource controller that manages both anonymous
  724. memory and page cache. (See Documentation/cgroups/memory.txt)
  725. Note that setting this option increases fixed memory overhead
  726. associated with each page of memory in the system. By this,
  727. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  728. usage tracking struct at boot. Total amount of this is printed out
  729. at boot.
  730. Only enable when you're ok with these trade offs and really
  731. sure you need the memory resource controller. Even when you enable
  732. this, you can set "cgroup_disable=memory" at your boot option to
  733. disable memory resource controller and you can avoid overheads.
  734. (and lose benefits of memory resource controller)
  735. This config option also selects MM_OWNER config option, which
  736. could in turn add some fork/exit overhead.
  737. config MEMCG_SWAP
  738. bool "Memory Resource Controller Swap Extension"
  739. depends on MEMCG && SWAP
  740. help
  741. Add swap management feature to memory resource controller. When you
  742. enable this, you can limit mem+swap usage per cgroup. In other words,
  743. when you disable this, memory resource controller has no cares to
  744. usage of swap...a process can exhaust all of the swap. This extension
  745. is useful when you want to avoid exhaustion swap but this itself
  746. adds more overheads and consumes memory for remembering information.
  747. Especially if you use 32bit system or small memory system, please
  748. be careful about enabling this. When memory resource controller
  749. is disabled by boot option, this will be automatically disabled and
  750. there will be no overhead from this. Even when you set this config=y,
  751. if boot option "swapaccount=0" is set, swap will not be accounted.
  752. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  753. size is 4096bytes, 512k per 1Gbytes of swap.
  754. config MEMCG_SWAP_ENABLED
  755. bool "Memory Resource Controller Swap Extension enabled by default"
  756. depends on MEMCG_SWAP
  757. default y
  758. help
  759. Memory Resource Controller Swap Extension comes with its price in
  760. a bigger memory consumption. General purpose distribution kernels
  761. which want to enable the feature but keep it disabled by default
  762. and let the user enable it by swapaccount boot command line
  763. parameter should have this option unselected.
  764. For those who want to have the feature enabled by default should
  765. select this option (if, for some reason, they need to disable it
  766. then swapaccount=0 does the trick).
  767. config MEMCG_KMEM
  768. bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
  769. depends on MEMCG && EXPERIMENTAL
  770. depends on SLUB || SLAB
  771. help
  772. The Kernel Memory extension for Memory Resource Controller can limit
  773. the amount of memory used by kernel objects in the system. Those are
  774. fundamentally different from the entities handled by the standard
  775. Memory Controller, which are page-based, and can be swapped. Users of
  776. the kmem extension can use it to guarantee that no group of processes
  777. will ever exhaust kernel resources alone.
  778. config CGROUP_HUGETLB
  779. bool "HugeTLB Resource Controller for Control Groups"
  780. depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
  781. default n
  782. help
  783. Provides a cgroup Resource Controller for HugeTLB pages.
  784. When you enable this, you can put a per cgroup limit on HugeTLB usage.
  785. The limit is enforced during page fault. Since HugeTLB doesn't
  786. support page reclaim, enforcing the limit at page fault time implies
  787. that, the application will get SIGBUS signal if it tries to access
  788. HugeTLB pages beyond its limit. This requires the application to know
  789. beforehand how much HugeTLB pages it would require for its use. The
  790. control group is tracked in the third page lru pointer. This means
  791. that we cannot use the controller with huge page less than 3 pages.
  792. config CGROUP_PERF
  793. bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
  794. depends on PERF_EVENTS && CGROUPS
  795. help
  796. This option extends the per-cpu mode to restrict monitoring to
  797. threads which belong to the cgroup specified and run on the
  798. designated cpu.
  799. Say N if unsure.
  800. menuconfig CGROUP_SCHED
  801. bool "Group CPU scheduler"
  802. default n
  803. help
  804. This feature lets CPU scheduler recognize task groups and control CPU
  805. bandwidth allocation to such task groups. It uses cgroups to group
  806. tasks.
  807. if CGROUP_SCHED
  808. config FAIR_GROUP_SCHED
  809. bool "Group scheduling for SCHED_OTHER"
  810. depends on CGROUP_SCHED
  811. default CGROUP_SCHED
  812. config CFS_BANDWIDTH
  813. bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
  814. depends on EXPERIMENTAL
  815. depends on FAIR_GROUP_SCHED
  816. default n
  817. help
  818. This option allows users to define CPU bandwidth rates (limits) for
  819. tasks running within the fair group scheduler. Groups with no limit
  820. set are considered to be unconstrained and will run with no
  821. restriction.
  822. See tip/Documentation/scheduler/sched-bwc.txt for more information.
  823. config RT_GROUP_SCHED
  824. bool "Group scheduling for SCHED_RR/FIFO"
  825. depends on EXPERIMENTAL
  826. depends on CGROUP_SCHED
  827. default n
  828. help
  829. This feature lets you explicitly allocate real CPU bandwidth
  830. to task groups. If enabled, it will also make it impossible to
  831. schedule realtime tasks for non-root users until you allocate
  832. realtime bandwidth for them.
  833. See Documentation/scheduler/sched-rt-group.txt for more information.
  834. endif #CGROUP_SCHED
  835. config BLK_CGROUP
  836. bool "Block IO controller"
  837. depends on BLOCK
  838. default n
  839. ---help---
  840. Generic block IO controller cgroup interface. This is the common
  841. cgroup interface which should be used by various IO controlling
  842. policies.
  843. Currently, CFQ IO scheduler uses it to recognize task groups and
  844. control disk bandwidth allocation (proportional time slice allocation)
  845. to such task groups. It is also used by bio throttling logic in
  846. block layer to implement upper limit in IO rates on a device.
  847. This option only enables generic Block IO controller infrastructure.
  848. One needs to also enable actual IO controlling logic/policy. For
  849. enabling proportional weight division of disk bandwidth in CFQ, set
  850. CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
  851. CONFIG_BLK_DEV_THROTTLING=y.
  852. See Documentation/cgroups/blkio-controller.txt for more information.
  853. config DEBUG_BLK_CGROUP
  854. bool "Enable Block IO controller debugging"
  855. depends on BLK_CGROUP
  856. default n
  857. ---help---
  858. Enable some debugging help. Currently it exports additional stat
  859. files in a cgroup which can be useful for debugging.
  860. endif # CGROUPS
  861. config CHECKPOINT_RESTORE
  862. bool "Checkpoint/restore support" if EXPERT
  863. default n
  864. help
  865. Enables additional kernel features in a sake of checkpoint/restore.
  866. In particular it adds auxiliary prctl codes to setup process text,
  867. data and heap segment sizes, and a few additional /proc filesystem
  868. entries.
  869. If unsure, say N here.
  870. menuconfig NAMESPACES
  871. bool "Namespaces support" if EXPERT
  872. default !EXPERT
  873. help
  874. Provides the way to make tasks work with different objects using
  875. the same id. For example same IPC id may refer to different objects
  876. or same user id or pid may refer to different tasks when used in
  877. different namespaces.
  878. if NAMESPACES
  879. config UTS_NS
  880. bool "UTS namespace"
  881. default y
  882. help
  883. In this namespace tasks see different info provided with the
  884. uname() system call
  885. config IPC_NS
  886. bool "IPC namespace"
  887. depends on (SYSVIPC || POSIX_MQUEUE)
  888. default y
  889. help
  890. In this namespace tasks work with IPC ids which correspond to
  891. different IPC objects in different namespaces.
  892. config USER_NS
  893. bool "User namespace (EXPERIMENTAL)"
  894. depends on EXPERIMENTAL
  895. depends on UIDGID_CONVERTED
  896. select UIDGID_STRICT_TYPE_CHECKS
  897. default n
  898. help
  899. This allows containers, i.e. vservers, to use user namespaces
  900. to provide different user info for different servers.
  901. If unsure, say N.
  902. config PID_NS
  903. bool "PID Namespaces"
  904. default y
  905. help
  906. Support process id namespaces. This allows having multiple
  907. processes with the same pid as long as they are in different
  908. pid namespaces. This is a building block of containers.
  909. config NET_NS
  910. bool "Network namespace"
  911. depends on NET
  912. default y
  913. help
  914. Allow user space to create what appear to be multiple instances
  915. of the network stack.
  916. endif # NAMESPACES
  917. config UIDGID_CONVERTED
  918. # True if all of the selected software conmponents are known
  919. # to have uid_t and gid_t converted to kuid_t and kgid_t
  920. # where appropriate and are otherwise safe to use with
  921. # the user namespace.
  922. bool
  923. default y
  924. # Networking
  925. depends on NET_9P = n
  926. # Filesystems
  927. depends on 9P_FS = n
  928. depends on AFS_FS = n
  929. depends on CEPH_FS = n
  930. depends on CIFS = n
  931. depends on CODA_FS = n
  932. depends on GFS2_FS = n
  933. depends on NCP_FS = n
  934. depends on NFSD = n
  935. depends on NFS_FS = n
  936. depends on OCFS2_FS = n
  937. depends on XFS_FS = n
  938. config UIDGID_STRICT_TYPE_CHECKS
  939. bool "Require conversions between uid/gids and their internal representation"
  940. depends on UIDGID_CONVERTED
  941. default n
  942. help
  943. While the nececessary conversions are being added to all subsystems this option allows
  944. the code to continue to build for unconverted subsystems.
  945. Say Y here if you want the strict type checking enabled
  946. config SCHED_AUTOGROUP
  947. bool "Automatic process group scheduling"
  948. select EVENTFD
  949. select CGROUPS
  950. select CGROUP_SCHED
  951. select FAIR_GROUP_SCHED
  952. help
  953. This option optimizes the scheduler for common desktop workloads by
  954. automatically creating and populating task groups. This separation
  955. of workloads isolates aggressive CPU burners (like build jobs) from
  956. desktop applications. Task group autogeneration is currently based
  957. upon task session.
  958. config MM_OWNER
  959. bool
  960. config SYSFS_DEPRECATED
  961. bool "Enable deprecated sysfs features to support old userspace tools"
  962. depends on SYSFS
  963. default n
  964. help
  965. This option adds code that switches the layout of the "block" class
  966. devices, to not show up in /sys/class/block/, but only in
  967. /sys/block/.
  968. This switch is only active when the sysfs.deprecated=1 boot option is
  969. passed or the SYSFS_DEPRECATED_V2 option is set.
  970. This option allows new kernels to run on old distributions and tools,
  971. which might get confused by /sys/class/block/. Since 2007/2008 all
  972. major distributions and tools handle this just fine.
  973. Recent distributions and userspace tools after 2009/2010 depend on
  974. the existence of /sys/class/block/, and will not work with this
  975. option enabled.
  976. Only if you are using a new kernel on an old distribution, you might
  977. need to say Y here.
  978. config SYSFS_DEPRECATED_V2
  979. bool "Enable deprecated sysfs features by default"
  980. default n
  981. depends on SYSFS
  982. depends on SYSFS_DEPRECATED
  983. help
  984. Enable deprecated sysfs by default.
  985. See the CONFIG_SYSFS_DEPRECATED option for more details about this
  986. option.
  987. Only if you are using a new kernel on an old distribution, you might
  988. need to say Y here. Even then, odds are you would not need it
  989. enabled, you can always pass the boot option if absolutely necessary.
  990. config RELAY
  991. bool "Kernel->user space relay support (formerly relayfs)"
  992. help
  993. This option enables support for relay interface support in
  994. certain file systems (such as debugfs).
  995. It is designed to provide an efficient mechanism for tools and
  996. facilities to relay large amounts of data from kernel space to
  997. user space.
  998. If unsure, say N.
  999. config BLK_DEV_INITRD
  1000. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  1001. depends on BROKEN || !FRV
  1002. help
  1003. The initial RAM filesystem is a ramfs which is loaded by the
  1004. boot loader (loadlin or lilo) and that is mounted as root
  1005. before the normal boot procedure. It is typically used to
  1006. load modules needed to mount the "real" root file system,
  1007. etc. See <file:Documentation/initrd.txt> for details.
  1008. If RAM disk support (BLK_DEV_RAM) is also included, this
  1009. also enables initial RAM disk (initrd) support and adds
  1010. 15 Kbytes (more on some other architectures) to the kernel size.
  1011. If unsure say Y.
  1012. if BLK_DEV_INITRD
  1013. source "usr/Kconfig"
  1014. endif
  1015. config CC_OPTIMIZE_FOR_SIZE
  1016. bool "Optimize for size"
  1017. help
  1018. Enabling this option will pass "-Os" instead of "-O2" to gcc
  1019. resulting in a smaller kernel.
  1020. If unsure, say N.
  1021. config SYSCTL
  1022. bool
  1023. config ANON_INODES
  1024. bool
  1025. menuconfig EXPERT
  1026. bool "Configure standard kernel features (expert users)"
  1027. # Unhide debug options, to make the on-by-default options visible
  1028. select DEBUG_KERNEL
  1029. help
  1030. This option allows certain base kernel options and settings
  1031. to be disabled or tweaked. This is for specialized
  1032. environments which can tolerate a "non-standard" kernel.
  1033. Only use this if you really know what you are doing.
  1034. config HAVE_UID16
  1035. bool
  1036. config UID16
  1037. bool "Enable 16-bit UID system calls" if EXPERT
  1038. depends on HAVE_UID16
  1039. default y
  1040. help
  1041. This enables the legacy 16-bit UID syscall wrappers.
  1042. config SYSCTL_SYSCALL
  1043. bool "Sysctl syscall support" if EXPERT
  1044. depends on PROC_SYSCTL
  1045. default n
  1046. select SYSCTL
  1047. ---help---
  1048. sys_sysctl uses binary paths that have been found challenging
  1049. to properly maintain and use. The interface in /proc/sys
  1050. using paths with ascii names is now the primary path to this
  1051. information.
  1052. Almost nothing using the binary sysctl interface so if you are
  1053. trying to save some space it is probably safe to disable this,
  1054. making your kernel marginally smaller.
  1055. If unsure say N here.
  1056. config SYSCTL_EXCEPTION_TRACE
  1057. bool
  1058. help
  1059. Enable support for /proc/sys/debug/exception-trace.
  1060. config KALLSYMS
  1061. bool "Load all symbols for debugging/ksymoops" if EXPERT
  1062. default y
  1063. help
  1064. Say Y here to let the kernel print out symbolic crash information and
  1065. symbolic stack backtraces. This increases the size of the kernel
  1066. somewhat, as all symbols have to be loaded into the kernel image.
  1067. config KALLSYMS_ALL
  1068. bool "Include all symbols in kallsyms"
  1069. depends on DEBUG_KERNEL && KALLSYMS
  1070. help
  1071. Normally kallsyms only contains the symbols of functions for nicer
  1072. OOPS messages and backtraces (i.e., symbols from the text and inittext
  1073. sections). This is sufficient for most cases. And only in very rare
  1074. cases (e.g., when a debugger is used) all symbols are required (e.g.,
  1075. names of variables from the data sections, etc).
  1076. This option makes sure that all symbols are loaded into the kernel
  1077. image (i.e., symbols from all sections) in cost of increased kernel
  1078. size (depending on the kernel configuration, it may be 300KiB or
  1079. something like this).
  1080. Say N unless you really need all symbols.
  1081. config HOTPLUG
  1082. def_bool y
  1083. config PRINTK
  1084. default y
  1085. bool "Enable support for printk" if EXPERT
  1086. select IRQ_WORK
  1087. help
  1088. This option enables normal printk support. Removing it
  1089. eliminates most of the message strings from the kernel image
  1090. and makes the kernel more or less silent. As this makes it
  1091. very difficult to diagnose system problems, saying N here is
  1092. strongly discouraged.
  1093. config BUG
  1094. bool "BUG() support" if EXPERT
  1095. default y
  1096. help
  1097. Disabling this option eliminates support for BUG and WARN, reducing
  1098. the size of your kernel image and potentially quietly ignoring
  1099. numerous fatal conditions. You should only consider disabling this
  1100. option for embedded systems with no facilities for reporting errors.
  1101. Just say Y.
  1102. config ELF_CORE
  1103. depends on COREDUMP
  1104. default y
  1105. bool "Enable ELF core dumps" if EXPERT
  1106. help
  1107. Enable support for generating core dumps. Disabling saves about 4k.
  1108. config PCSPKR_PLATFORM
  1109. bool "Enable PC-Speaker support" if EXPERT
  1110. depends on HAVE_PCSPKR_PLATFORM
  1111. select I8253_LOCK
  1112. default y
  1113. help
  1114. This option allows to disable the internal PC-Speaker
  1115. support, saving some memory.
  1116. config HAVE_PCSPKR_PLATFORM
  1117. bool
  1118. config BASE_FULL
  1119. default y
  1120. bool "Enable full-sized data structures for core" if EXPERT
  1121. help
  1122. Disabling this option reduces the size of miscellaneous core
  1123. kernel data structures. This saves memory on small machines,
  1124. but may reduce performance.
  1125. config FUTEX
  1126. bool "Enable futex support" if EXPERT
  1127. default y
  1128. select RT_MUTEXES
  1129. help
  1130. Disabling this option will cause the kernel to be built without
  1131. support for "fast userspace mutexes". The resulting kernel may not
  1132. run glibc-based applications correctly.
  1133. config EPOLL
  1134. bool "Enable eventpoll support" if EXPERT
  1135. default y
  1136. select ANON_INODES
  1137. help
  1138. Disabling this option will cause the kernel to be built without
  1139. support for epoll family of system calls.
  1140. config SIGNALFD
  1141. bool "Enable signalfd() system call" if EXPERT
  1142. select ANON_INODES
  1143. default y
  1144. help
  1145. Enable the signalfd() system call that allows to receive signals
  1146. on a file descriptor.
  1147. If unsure, say Y.
  1148. config TIMERFD
  1149. bool "Enable timerfd() system call" if EXPERT
  1150. select ANON_INODES
  1151. default y
  1152. help
  1153. Enable the timerfd() system call that allows to receive timer
  1154. events on a file descriptor.
  1155. If unsure, say Y.
  1156. config EVENTFD
  1157. bool "Enable eventfd() system call" if EXPERT
  1158. select ANON_INODES
  1159. default y
  1160. help
  1161. Enable the eventfd() system call that allows to receive both
  1162. kernel notification (ie. KAIO) or userspace notifications.
  1163. If unsure, say Y.
  1164. config SHMEM
  1165. bool "Use full shmem filesystem" if EXPERT
  1166. default y
  1167. depends on MMU
  1168. help
  1169. The shmem is an internal filesystem used to manage shared memory.
  1170. It is backed by swap and manages resource limits. It is also exported
  1171. to userspace as tmpfs if TMPFS is enabled. Disabling this
  1172. option replaces shmem and tmpfs with the much simpler ramfs code,
  1173. which may be appropriate on small systems without swap.
  1174. config AIO
  1175. bool "Enable AIO support" if EXPERT
  1176. default y
  1177. help
  1178. This option enables POSIX asynchronous I/O which may by used
  1179. by some high performance threaded applications. Disabling
  1180. this option saves about 7k.
  1181. config EMBEDDED
  1182. bool "Embedded system"
  1183. select EXPERT
  1184. help
  1185. This option should be enabled if compiling the kernel for
  1186. an embedded system so certain expert options are available
  1187. for configuration.
  1188. config HAVE_PERF_EVENTS
  1189. bool
  1190. help
  1191. See tools/perf/design.txt for details.
  1192. config PERF_USE_VMALLOC
  1193. bool
  1194. help
  1195. See tools/perf/design.txt for details
  1196. menu "Kernel Performance Events And Counters"
  1197. config PERF_EVENTS
  1198. bool "Kernel performance events and counters"
  1199. default y if PROFILING
  1200. depends on HAVE_PERF_EVENTS
  1201. select ANON_INODES
  1202. select IRQ_WORK
  1203. help
  1204. Enable kernel support for various performance events provided
  1205. by software and hardware.
  1206. Software events are supported either built-in or via the
  1207. use of generic tracepoints.
  1208. Most modern CPUs support performance events via performance
  1209. counter registers. These registers count the number of certain
  1210. types of hw events: such as instructions executed, cachemisses
  1211. suffered, or branches mis-predicted - without slowing down the
  1212. kernel or applications. These registers can also trigger interrupts
  1213. when a threshold number of events have passed - and can thus be
  1214. used to profile the code that runs on that CPU.
  1215. The Linux Performance Event subsystem provides an abstraction of
  1216. these software and hardware event capabilities, available via a
  1217. system call and used by the "perf" utility in tools/perf/. It
  1218. provides per task and per CPU counters, and it provides event
  1219. capabilities on top of those.
  1220. Say Y if unsure.
  1221. config DEBUG_PERF_USE_VMALLOC
  1222. default n
  1223. bool "Debug: use vmalloc to back perf mmap() buffers"
  1224. depends on PERF_EVENTS && DEBUG_KERNEL
  1225. select PERF_USE_VMALLOC
  1226. help
  1227. Use vmalloc memory to back perf mmap() buffers.
  1228. Mostly useful for debugging the vmalloc code on platforms
  1229. that don't require it.
  1230. Say N if unsure.
  1231. endmenu
  1232. config VM_EVENT_COUNTERS
  1233. default y
  1234. bool "Enable VM event counters for /proc/vmstat" if EXPERT
  1235. help
  1236. VM event counters are needed for event counts to be shown.
  1237. This option allows the disabling of the VM event counters
  1238. on EXPERT systems. /proc/vmstat will only show page counts
  1239. if VM event counters are disabled.
  1240. config PCI_QUIRKS
  1241. default y
  1242. bool "Enable PCI quirk workarounds" if EXPERT
  1243. depends on PCI
  1244. help
  1245. This enables workarounds for various PCI chipset
  1246. bugs/quirks. Disable this only if your target machine is
  1247. unaffected by PCI quirks.
  1248. config SLUB_DEBUG
  1249. default y
  1250. bool "Enable SLUB debugging support" if EXPERT
  1251. depends on SLUB && SYSFS
  1252. help
  1253. SLUB has extensive debug support features. Disabling these can
  1254. result in significant savings in code size. This also disables
  1255. SLUB sysfs support. /sys/slab will not exist and there will be
  1256. no support for cache validation etc.
  1257. config COMPAT_BRK
  1258. bool "Disable heap randomization"
  1259. default y
  1260. help
  1261. Randomizing heap placement makes heap exploits harder, but it
  1262. also breaks ancient binaries (including anything libc5 based).
  1263. This option changes the bootup default to heap randomization
  1264. disabled, and can be overridden at runtime by setting
  1265. /proc/sys/kernel/randomize_va_space to 2.
  1266. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  1267. choice
  1268. prompt "Choose SLAB allocator"
  1269. default SLUB
  1270. help
  1271. This option allows to select a slab allocator.
  1272. config SLAB
  1273. bool "SLAB"
  1274. help
  1275. The regular slab allocator that is established and known to work
  1276. well in all environments. It organizes cache hot objects in
  1277. per cpu and per node queues.
  1278. config SLUB
  1279. bool "SLUB (Unqueued Allocator)"
  1280. help
  1281. SLUB is a slab allocator that minimizes cache line usage
  1282. instead of managing queues of cached objects (SLAB approach).
  1283. Per cpu caching is realized using slabs of objects instead
  1284. of queues of objects. SLUB can use memory efficiently
  1285. and has enhanced diagnostics. SLUB is the default choice for
  1286. a slab allocator.
  1287. config SLOB
  1288. depends on EXPERT
  1289. bool "SLOB (Simple Allocator)"
  1290. help
  1291. SLOB replaces the stock allocator with a drastically simpler
  1292. allocator. SLOB is generally more space efficient but
  1293. does not perform as well on large systems.
  1294. endchoice
  1295. config MMAP_ALLOW_UNINITIALIZED
  1296. bool "Allow mmapped anonymous memory to be uninitialized"
  1297. depends on EXPERT && !MMU
  1298. default n
  1299. help
  1300. Normally, and according to the Linux spec, anonymous memory obtained
  1301. from mmap() has it's contents cleared before it is passed to
  1302. userspace. Enabling this config option allows you to request that
  1303. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  1304. providing a huge performance boost. If this option is not enabled,
  1305. then the flag will be ignored.
  1306. This is taken advantage of by uClibc's malloc(), and also by
  1307. ELF-FDPIC binfmt's brk and stack allocator.
  1308. Because of the obvious security issues, this option should only be
  1309. enabled on embedded devices where you control what is run in
  1310. userspace. Since that isn't generally a problem on no-MMU systems,
  1311. it is normally safe to say Y here.
  1312. See Documentation/nommu-mmap.txt for more information.
  1313. config PROFILING
  1314. bool "Profiling support"
  1315. help
  1316. Say Y here to enable the extended profiling support mechanisms used
  1317. by profilers such as OProfile.
  1318. #
  1319. # Place an empty function call at each tracepoint site. Can be
  1320. # dynamically changed for a probe function.
  1321. #
  1322. config TRACEPOINTS
  1323. bool
  1324. source "arch/Kconfig"
  1325. endmenu # General setup
  1326. config HAVE_GENERIC_DMA_COHERENT
  1327. bool
  1328. default n
  1329. config SLABINFO
  1330. bool
  1331. depends on PROC_FS
  1332. depends on SLAB || SLUB_DEBUG
  1333. default y
  1334. config RT_MUTEXES
  1335. boolean
  1336. config BASE_SMALL
  1337. int
  1338. default 0 if BASE_FULL
  1339. default 1 if !BASE_FULL
  1340. menuconfig MODULES
  1341. bool "Enable loadable module support"
  1342. help
  1343. Kernel modules are small pieces of compiled code which can
  1344. be inserted in the running kernel, rather than being
  1345. permanently built into the kernel. You use the "modprobe"
  1346. tool to add (and sometimes remove) them. If you say Y here,
  1347. many parts of the kernel can be built as modules (by
  1348. answering M instead of Y where indicated): this is most
  1349. useful for infrequently used options which are not required
  1350. for booting. For more information, see the man pages for
  1351. modprobe, lsmod, modinfo, insmod and rmmod.
  1352. If you say Y here, you will need to run "make
  1353. modules_install" to put the modules under /lib/modules/
  1354. where modprobe can find them (you may need to be root to do
  1355. this).
  1356. If unsure, say Y.
  1357. if MODULES
  1358. config MODULE_FORCE_LOAD
  1359. bool "Forced module loading"
  1360. default n
  1361. help
  1362. Allow loading of modules without version information (ie. modprobe
  1363. --force). Forced module loading sets the 'F' (forced) taint flag and
  1364. is usually a really bad idea.
  1365. config MODULE_UNLOAD
  1366. bool "Module unloading"
  1367. help
  1368. Without this option you will not be able to unload any
  1369. modules (note that some modules may not be unloadable
  1370. anyway), which makes your kernel smaller, faster
  1371. and simpler. If unsure, say Y.
  1372. config MODULE_FORCE_UNLOAD
  1373. bool "Forced module unloading"
  1374. depends on MODULE_UNLOAD && EXPERIMENTAL
  1375. help
  1376. This option allows you to force a module to unload, even if the
  1377. kernel believes it is unsafe: the kernel will remove the module
  1378. without waiting for anyone to stop using it (using the -f option to
  1379. rmmod). This is mainly for kernel developers and desperate users.
  1380. If unsure, say N.
  1381. config MODVERSIONS
  1382. bool "Module versioning support"
  1383. help
  1384. Usually, you have to use modules compiled with your kernel.
  1385. Saying Y here makes it sometimes possible to use modules
  1386. compiled for different kernels, by adding enough information
  1387. to the modules to (hopefully) spot any changes which would
  1388. make them incompatible with the kernel you are running. If
  1389. unsure, say N.
  1390. config MODULE_SRCVERSION_ALL
  1391. bool "Source checksum for all modules"
  1392. help
  1393. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1394. field inserted into their modinfo section, which contains a
  1395. sum of the source files which made it. This helps maintainers
  1396. see exactly which source was used to build a module (since
  1397. others sometimes change the module source without updating
  1398. the version). With this option, such a "srcversion" field
  1399. will be created for all modules. If unsure, say N.
  1400. config MODULE_SIG
  1401. bool "Module signature verification"
  1402. depends on MODULES
  1403. select KEYS
  1404. select CRYPTO
  1405. select ASYMMETRIC_KEY_TYPE
  1406. select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  1407. select PUBLIC_KEY_ALGO_RSA
  1408. select ASN1
  1409. select OID_REGISTRY
  1410. select X509_CERTIFICATE_PARSER
  1411. help
  1412. Check modules for valid signatures upon load: the signature
  1413. is simply appended to the module. For more information see
  1414. Documentation/module-signing.txt.
  1415. !!!WARNING!!! If you enable this option, you MUST make sure that the
  1416. module DOES NOT get stripped after being signed. This includes the
  1417. debuginfo strip done by some packagers (such as rpmbuild) and
  1418. inclusion into an initramfs that wants the module size reduced.
  1419. config MODULE_SIG_FORCE
  1420. bool "Require modules to be validly signed"
  1421. depends on MODULE_SIG
  1422. help
  1423. Reject unsigned modules or signed modules for which we don't have a
  1424. key. Without this, such modules will simply taint the kernel.
  1425. choice
  1426. prompt "Which hash algorithm should modules be signed with?"
  1427. depends on MODULE_SIG
  1428. help
  1429. This determines which sort of hashing algorithm will be used during
  1430. signature generation. This algorithm _must_ be built into the kernel
  1431. directly so that signature verification can take place. It is not
  1432. possible to load a signed module containing the algorithm to check
  1433. the signature on that module.
  1434. config MODULE_SIG_SHA1
  1435. bool "Sign modules with SHA-1"
  1436. select CRYPTO_SHA1
  1437. config MODULE_SIG_SHA224
  1438. bool "Sign modules with SHA-224"
  1439. select CRYPTO_SHA256
  1440. config MODULE_SIG_SHA256
  1441. bool "Sign modules with SHA-256"
  1442. select CRYPTO_SHA256
  1443. config MODULE_SIG_SHA384
  1444. bool "Sign modules with SHA-384"
  1445. select CRYPTO_SHA512
  1446. config MODULE_SIG_SHA512
  1447. bool "Sign modules with SHA-512"
  1448. select CRYPTO_SHA512
  1449. endchoice
  1450. endif # MODULES
  1451. config INIT_ALL_POSSIBLE
  1452. bool
  1453. help
  1454. Back when each arch used to define their own cpu_online_mask and
  1455. cpu_possible_mask, some of them chose to initialize cpu_possible_mask
  1456. with all 1s, and others with all 0s. When they were centralised,
  1457. it was better to provide this option than to break all the archs
  1458. and have several arch maintainers pursuing me down dark alleys.
  1459. config STOP_MACHINE
  1460. bool
  1461. default y
  1462. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1463. help
  1464. Need stop_machine() primitive.
  1465. source "block/Kconfig"
  1466. config PREEMPT_NOTIFIERS
  1467. bool
  1468. config PADATA
  1469. depends on SMP
  1470. bool
  1471. # Can be selected by architectures with broken toolchains
  1472. # that get confused by correct const<->read_only section
  1473. # mappings
  1474. config BROKEN_RODATA
  1475. bool
  1476. config ASN1
  1477. tristate
  1478. help
  1479. Build a simple ASN.1 grammar compiler that produces a bytecode output
  1480. that can be interpreted by the ASN.1 stream decoder and used to
  1481. inform it as to what tags are to be expected in a stream and what
  1482. functions to call on what tags.
  1483. source "kernel/Kconfig.locks"