Kconfig 54 KB

1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071727374757677787980818283848586878889909192939495969798991001011021031041051061071081091101111121131141151161171181191201211221231241251261271281291301311321331341351361371381391401411421431441451461471481491501511521531541551561571581591601611621631641651661671681691701711721731741751761771781791801811821831841851861871881891901911921931941951961971981992002012022032042052062072082092102112122132142152162172182192202212222232242252262272282292302312322332342352362372382392402412422432442452462472482492502512522532542552562572582592602612622632642652662672682692702712722732742752762772782792802812822832842852862872882892902912922932942952962972982993003013023033043053063073083093103113123133143153163173183193203213223233243253263273283293303313323333343353363373383393403413423433443453463473483493503513523533543553563573583593603613623633643653663673683693703713723733743753763773783793803813823833843853863873883893903913923933943953963973983994004014024034044054064074084094104114124134144154164174184194204214224234244254264274284294304314324334344354364374384394404414424434444454464474484494504514524534544554564574584594604614624634644654664674684694704714724734744754764774784794804814824834844854864874884894904914924934944954964974984995005015025035045055065075085095105115125135145155165175185195205215225235245255265275285295305315325335345355365375385395405415425435445455465475485495505515525535545555565575585595605615625635645655665675685695705715725735745755765775785795805815825835845855865875885895905915925935945955965975985996006016026036046056066076086096106116126136146156166176186196206216226236246256266276286296306316326336346356366376386396406416426436446456466476486496506516526536546556566576586596606616626636646656666676686696706716726736746756766776786796806816826836846856866876886896906916926936946956966976986997007017027037047057067077087097107117127137147157167177187197207217227237247257267277287297307317327337347357367377387397407417427437447457467477487497507517527537547557567577587597607617627637647657667677687697707717727737747757767777787797807817827837847857867877887897907917927937947957967977987998008018028038048058068078088098108118128138148158168178188198208218228238248258268278288298308318328338348358368378388398408418428438448458468478488498508518528538548558568578588598608618628638648658668678688698708718728738748758768778788798808818828838848858868878888898908918928938948958968978988999009019029039049059069079089099109119129139149159169179189199209219229239249259269279289299309319329339349359369379389399409419429439449459469479489499509519529539549559569579589599609619629639649659669679689699709719729739749759769779789799809819829839849859869879889899909919929939949959969979989991000100110021003100410051006100710081009101010111012101310141015101610171018101910201021102210231024102510261027102810291030103110321033103410351036103710381039104010411042104310441045104610471048104910501051105210531054105510561057105810591060106110621063106410651066106710681069107010711072107310741075107610771078107910801081108210831084108510861087108810891090109110921093109410951096109710981099110011011102110311041105110611071108110911101111111211131114111511161117111811191120112111221123112411251126112711281129113011311132113311341135113611371138113911401141114211431144114511461147114811491150115111521153115411551156115711581159116011611162116311641165116611671168116911701171117211731174117511761177117811791180118111821183118411851186118711881189119011911192119311941195119611971198119912001201120212031204120512061207120812091210121112121213121412151216121712181219122012211222122312241225122612271228122912301231123212331234123512361237123812391240124112421243124412451246124712481249125012511252125312541255125612571258125912601261126212631264126512661267126812691270127112721273127412751276127712781279128012811282128312841285128612871288128912901291129212931294129512961297129812991300130113021303130413051306130713081309131013111312131313141315131613171318131913201321132213231324132513261327132813291330133113321333133413351336133713381339134013411342134313441345134613471348134913501351135213531354135513561357135813591360136113621363136413651366136713681369137013711372137313741375137613771378137913801381138213831384138513861387138813891390139113921393139413951396139713981399140014011402140314041405140614071408140914101411141214131414141514161417141814191420142114221423142414251426142714281429143014311432143314341435143614371438143914401441144214431444144514461447144814491450145114521453145414551456145714581459146014611462146314641465146614671468146914701471147214731474147514761477147814791480148114821483148414851486148714881489149014911492149314941495149614971498149915001501150215031504150515061507150815091510151115121513151415151516151715181519152015211522152315241525152615271528152915301531153215331534153515361537153815391540154115421543154415451546154715481549155015511552155315541555155615571558155915601561156215631564156515661567156815691570157115721573157415751576157715781579158015811582158315841585158615871588158915901591159215931594159515961597159815991600160116021603160416051606160716081609161016111612161316141615161616171618161916201621162216231624162516261627162816291630163116321633163416351636163716381639164016411642164316441645164616471648164916501651165216531654165516561657165816591660166116621663166416651666166716681669167016711672167316741675167616771678167916801681168216831684168516861687168816891690169116921693169416951696169716981699
  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 HAVE_IRQ_WORK
  20. bool
  21. config IRQ_WORK
  22. bool
  23. depends on HAVE_IRQ_WORK
  24. config BUILDTIME_EXTABLE_SORT
  25. bool
  26. menu "General setup"
  27. config EXPERIMENTAL
  28. bool "Prompt for development and/or incomplete code/drivers"
  29. ---help---
  30. Some of the various things that Linux supports (such as network
  31. drivers, file systems, network protocols, etc.) can be in a state
  32. of development where the functionality, stability, or the level of
  33. testing is not yet high enough for general use. This is usually
  34. known as the "alpha-test" phase among developers. If a feature is
  35. currently in alpha-test, then the developers usually discourage
  36. uninformed widespread use of this feature by the general public to
  37. avoid "Why doesn't this work?" type mail messages. However, active
  38. testing and use of these systems is welcomed. Just be aware that it
  39. may not meet the normal level of reliability or it may fail to work
  40. in some special cases. Detailed bug reports from people familiar
  41. with the kernel internals are usually welcomed by the developers
  42. (before submitting bug reports, please read the documents
  43. <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  44. <file:Documentation/BUG-HUNTING>, and
  45. <file:Documentation/oops-tracing.txt> in the kernel source).
  46. This option will also make obsoleted drivers available. These are
  47. drivers that have been replaced by something else, and/or are
  48. scheduled to be removed in a future kernel release.
  49. Unless you intend to help test and develop a feature or driver that
  50. falls into this category, or you have a situation that requires
  51. using these features, you should probably say N here, which will
  52. cause the configurator to present you with fewer choices. If
  53. you say Y here, you will be offered the choice of using features or
  54. drivers that are currently considered to be in the alpha-test phase.
  55. config BROKEN
  56. bool
  57. config BROKEN_ON_SMP
  58. bool
  59. depends on BROKEN || !SMP
  60. default y
  61. config INIT_ENV_ARG_LIMIT
  62. int
  63. default 32 if !UML
  64. default 128 if UML
  65. help
  66. Maximum of each of the number of arguments and environment
  67. variables passed to init from the kernel command line.
  68. config CROSS_COMPILE
  69. string "Cross-compiler tool prefix"
  70. help
  71. Same as running 'make CROSS_COMPILE=prefix-' but stored for
  72. default make runs in this kernel build directory. You don't
  73. need to set this unless you want the configured kernel build
  74. directory to select the cross-compiler automatically.
  75. config LOCALVERSION
  76. string "Local version - append to kernel release"
  77. help
  78. Append an extra string to the end of your kernel version.
  79. This will show up when you type uname, for example.
  80. The string you set here will be appended after the contents of
  81. any files with a filename matching localversion* in your
  82. object and source tree, in that order. Your total string can
  83. be a maximum of 64 characters.
  84. config LOCALVERSION_AUTO
  85. bool "Automatically append version information to the version string"
  86. default y
  87. help
  88. This will try to automatically determine if the current tree is a
  89. release tree by looking for git tags that belong to the current
  90. top of tree revision.
  91. A string of the format -gxxxxxxxx will be added to the localversion
  92. if a git-based tree is found. The string generated by this will be
  93. appended after any matching localversion* files, and after the value
  94. set in CONFIG_LOCALVERSION.
  95. (The actual string used here is the first eight characters produced
  96. by running the command:
  97. $ git rev-parse --verify HEAD
  98. which is done within the script "scripts/setlocalversion".)
  99. config HAVE_KERNEL_GZIP
  100. bool
  101. config HAVE_KERNEL_BZIP2
  102. bool
  103. config HAVE_KERNEL_LZMA
  104. bool
  105. config HAVE_KERNEL_XZ
  106. bool
  107. config HAVE_KERNEL_LZO
  108. bool
  109. choice
  110. prompt "Kernel compression mode"
  111. default KERNEL_GZIP
  112. depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
  113. help
  114. The linux kernel is a kind of self-extracting executable.
  115. Several compression algorithms are available, which differ
  116. in efficiency, compression and decompression speed.
  117. Compression speed is only relevant when building a kernel.
  118. Decompression speed is relevant at each boot.
  119. If you have any problems with bzip2 or lzma compressed
  120. kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
  121. version of this functionality (bzip2 only), for 2.4, was
  122. supplied by Christian Ludwig)
  123. High compression options are mostly useful for users, who
  124. are low on disk space (embedded systems), but for whom ram
  125. size matters less.
  126. If in doubt, select 'gzip'
  127. config KERNEL_GZIP
  128. bool "Gzip"
  129. depends on HAVE_KERNEL_GZIP
  130. help
  131. The old and tried gzip compression. It provides a good balance
  132. between compression ratio and decompression speed.
  133. config KERNEL_BZIP2
  134. bool "Bzip2"
  135. depends on HAVE_KERNEL_BZIP2
  136. help
  137. Its compression ratio and speed is intermediate.
  138. Decompression speed is slowest among the choices. The kernel
  139. size is about 10% smaller with bzip2, in comparison to gzip.
  140. Bzip2 uses a large amount of memory. For modern kernels you
  141. will need at least 8MB RAM or more for booting.
  142. config KERNEL_LZMA
  143. bool "LZMA"
  144. depends on HAVE_KERNEL_LZMA
  145. help
  146. This compression algorithm's ratio is best. Decompression speed
  147. is between gzip and bzip2. Compression is slowest.
  148. The kernel size is about 33% smaller with LZMA in comparison to gzip.
  149. config KERNEL_XZ
  150. bool "XZ"
  151. depends on HAVE_KERNEL_XZ
  152. help
  153. XZ uses the LZMA2 algorithm and instruction set specific
  154. BCJ filters which can improve compression ratio of executable
  155. code. The size of the kernel is about 30% smaller with XZ in
  156. comparison to gzip. On architectures for which there is a BCJ
  157. filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
  158. will create a few percent smaller kernel than plain LZMA.
  159. The speed is about the same as with LZMA: The decompression
  160. speed of XZ is better than that of bzip2 but worse than gzip
  161. and LZO. Compression is slow.
  162. config KERNEL_LZO
  163. bool "LZO"
  164. depends on HAVE_KERNEL_LZO
  165. help
  166. Its compression ratio is the poorest among the choices. The kernel
  167. size is about 10% bigger than gzip; however its speed
  168. (both compression and decompression) is the fastest.
  169. endchoice
  170. config DEFAULT_HOSTNAME
  171. string "Default hostname"
  172. default "(none)"
  173. help
  174. This option determines the default system hostname before userspace
  175. calls sethostname(2). The kernel traditionally uses "(none)" here,
  176. but you may wish to use a different default here to make a minimal
  177. system more usable with less configuration.
  178. config SWAP
  179. bool "Support for paging of anonymous memory (swap)"
  180. depends on MMU && BLOCK
  181. default y
  182. help
  183. This option allows you to choose whether you want to have support
  184. for so called swap devices or swap files in your kernel that are
  185. used to provide more virtual memory than the actual RAM present
  186. in your computer. If unsure say Y.
  187. config SYSVIPC
  188. bool "System V IPC"
  189. ---help---
  190. Inter Process Communication is a suite of library functions and
  191. system calls which let processes (running programs) synchronize and
  192. exchange information. It is generally considered to be a good thing,
  193. and some programs won't run unless you say Y here. In particular, if
  194. you want to run the DOS emulator dosemu under Linux (read the
  195. DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
  196. you'll need to say Y here.
  197. You can find documentation about IPC with "info ipc" and also in
  198. section 6.4 of the Linux Programmer's Guide, available from
  199. <http://www.tldp.org/guides.html>.
  200. config SYSVIPC_SYSCTL
  201. bool
  202. depends on SYSVIPC
  203. depends on SYSCTL
  204. default y
  205. config POSIX_MQUEUE
  206. bool "POSIX Message Queues"
  207. depends on NET && EXPERIMENTAL
  208. ---help---
  209. POSIX variant of message queues is a part of IPC. In POSIX message
  210. queues every message has a priority which decides about succession
  211. of receiving it by a process. If you want to compile and run
  212. programs written e.g. for Solaris with use of its POSIX message
  213. queues (functions mq_*) say Y here.
  214. POSIX message queues are visible as a filesystem called 'mqueue'
  215. and can be mounted somewhere if you want to do filesystem
  216. operations on message queues.
  217. If unsure, say Y.
  218. config POSIX_MQUEUE_SYSCTL
  219. bool
  220. depends on POSIX_MQUEUE
  221. depends on SYSCTL
  222. default y
  223. config FHANDLE
  224. bool "open by fhandle syscalls"
  225. select EXPORTFS
  226. help
  227. If you say Y here, a user level program will be able to map
  228. file names to handle and then later use the handle for
  229. different file system operations. This is useful in implementing
  230. userspace file servers, which now track files using handles instead
  231. of names. The handle would remain the same even if file names
  232. get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
  233. syscalls.
  234. config AUDIT
  235. bool "Auditing support"
  236. depends on NET
  237. help
  238. Enable auditing infrastructure that can be used with another
  239. kernel subsystem, such as SELinux (which requires this for
  240. logging of avc messages output). Does not do system-call
  241. auditing without CONFIG_AUDITSYSCALL.
  242. config AUDITSYSCALL
  243. bool "Enable system-call auditing support"
  244. depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
  245. default y if SECURITY_SELINUX
  246. help
  247. Enable low-overhead system-call auditing infrastructure that
  248. can be used independently or with another kernel subsystem,
  249. such as SELinux.
  250. config AUDIT_WATCH
  251. def_bool y
  252. depends on AUDITSYSCALL
  253. select FSNOTIFY
  254. config AUDIT_TREE
  255. def_bool y
  256. depends on AUDITSYSCALL
  257. select FSNOTIFY
  258. config AUDIT_LOGINUID_IMMUTABLE
  259. bool "Make audit loginuid immutable"
  260. depends on AUDIT
  261. help
  262. The config option toggles if a task setting its loginuid requires
  263. CAP_SYS_AUDITCONTROL or if that task should require no special permissions
  264. but should instead only allow setting its loginuid if it was never
  265. previously set. On systems which use systemd or a similar central
  266. process to restart login services this should be set to true. On older
  267. systems in which an admin would typically have to directly stop and
  268. start processes this should be set to false. Setting this to true allows
  269. one to drop potentially dangerous capabilites from the login tasks,
  270. but may not be backwards compatible with older init systems.
  271. source "kernel/irq/Kconfig"
  272. source "kernel/time/Kconfig"
  273. menu "CPU/Task time and stats accounting"
  274. choice
  275. prompt "Cputime accounting"
  276. default TICK_CPU_ACCOUNTING if !PPC64
  277. default VIRT_CPU_ACCOUNTING if PPC64
  278. # Kind of a stub config for the pure tick based cputime accounting
  279. config TICK_CPU_ACCOUNTING
  280. bool "Simple tick based cputime accounting"
  281. depends on !S390
  282. help
  283. This is the basic tick based cputime accounting that maintains
  284. statistics about user, system and idle time spent on per jiffies
  285. granularity.
  286. If unsure, say Y.
  287. config VIRT_CPU_ACCOUNTING
  288. bool "Deterministic task and CPU time accounting"
  289. depends on HAVE_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 IRQ_TIME_ACCOUNTING
  299. bool "Fine granularity task level IRQ time accounting"
  300. depends on HAVE_IRQ_TIME_ACCOUNTING
  301. help
  302. Select this option to enable fine granularity task irq time
  303. accounting. This is done by reading a timestamp on each
  304. transitions between softirq and hardirq state, so there can be a
  305. small performance impact.
  306. If in doubt, say N here.
  307. endchoice
  308. config BSD_PROCESS_ACCT
  309. bool "BSD Process Accounting"
  310. help
  311. If you say Y here, a user level program will be able to instruct the
  312. kernel (via a special system call) to write process accounting
  313. information to a file: whenever a process exits, information about
  314. that process will be appended to the file by the kernel. The
  315. information includes things such as creation time, owning user,
  316. command name, memory usage, controlling terminal etc. (the complete
  317. list is in the struct acct in <file:include/linux/acct.h>). It is
  318. up to the user level program to do useful things with this
  319. information. This is generally a good idea, so say Y.
  320. config BSD_PROCESS_ACCT_V3
  321. bool "BSD Process Accounting version 3 file format"
  322. depends on BSD_PROCESS_ACCT
  323. default n
  324. help
  325. If you say Y here, the process accounting information is written
  326. in a new file format that also logs the process IDs of each
  327. process and it's parent. Note that this file format is incompatible
  328. with previous v0/v1/v2 file formats, so you will need updated tools
  329. for processing it. A preliminary version of these tools is available
  330. at <http://www.gnu.org/software/acct/>.
  331. config TASKSTATS
  332. bool "Export task/process statistics through netlink (EXPERIMENTAL)"
  333. depends on NET
  334. default n
  335. help
  336. Export selected statistics for tasks/processes through the
  337. generic netlink interface. Unlike BSD process accounting, the
  338. statistics are available during the lifetime of tasks/processes as
  339. responses to commands. Like BSD accounting, they are sent to user
  340. space on task exit.
  341. Say N if unsure.
  342. config TASK_DELAY_ACCT
  343. bool "Enable per-task delay accounting (EXPERIMENTAL)"
  344. depends on TASKSTATS
  345. help
  346. Collect information on time spent by a task waiting for system
  347. resources like cpu, synchronous block I/O completion and swapping
  348. in pages. Such statistics can help in setting a task's priorities
  349. relative to other tasks for cpu, io, rss limits etc.
  350. Say N if unsure.
  351. config TASK_XACCT
  352. bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
  353. depends on TASKSTATS
  354. help
  355. Collect extended task accounting data and send the data
  356. to userland for processing over the taskstats interface.
  357. Say N if unsure.
  358. config TASK_IO_ACCOUNTING
  359. bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
  360. depends on TASK_XACCT
  361. help
  362. Collect information on the number of bytes of storage I/O which this
  363. task has caused.
  364. Say N if unsure.
  365. endmenu # "CPU/Task time and stats accounting"
  366. menu "RCU Subsystem"
  367. choice
  368. prompt "RCU Implementation"
  369. default TREE_RCU
  370. config TREE_RCU
  371. bool "Tree-based hierarchical RCU"
  372. depends on !PREEMPT && SMP
  373. help
  374. This option selects the RCU implementation that is
  375. designed for very large SMP system with hundreds or
  376. thousands of CPUs. It also scales down nicely to
  377. smaller systems.
  378. config TREE_PREEMPT_RCU
  379. bool "Preemptible tree-based hierarchical RCU"
  380. depends on PREEMPT && SMP
  381. help
  382. This option selects the RCU implementation that is
  383. designed for very large SMP systems with hundreds or
  384. thousands of CPUs, but for which real-time response
  385. is also required. It also scales down nicely to
  386. smaller systems.
  387. config TINY_RCU
  388. bool "UP-only small-memory-footprint RCU"
  389. depends on !PREEMPT && !SMP
  390. help
  391. This option selects the RCU implementation that is
  392. designed for UP systems from which real-time response
  393. is not required. This option greatly reduces the
  394. memory footprint of RCU.
  395. config TINY_PREEMPT_RCU
  396. bool "Preemptible UP-only small-memory-footprint RCU"
  397. depends on PREEMPT && !SMP
  398. help
  399. This option selects the RCU implementation that is designed
  400. for real-time UP systems. This option greatly reduces the
  401. memory footprint of RCU.
  402. endchoice
  403. config PREEMPT_RCU
  404. def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
  405. help
  406. This option enables preemptible-RCU code that is common between
  407. the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
  408. config CONTEXT_TRACKING
  409. bool
  410. config RCU_USER_QS
  411. bool "Consider userspace as in RCU extended quiescent state"
  412. depends on HAVE_CONTEXT_TRACKING && SMP
  413. select CONTEXT_TRACKING
  414. help
  415. This option sets hooks on kernel / userspace boundaries and
  416. puts RCU in extended quiescent state when the CPU runs in
  417. userspace. It means that when a CPU runs in userspace, it is
  418. excluded from the global RCU state machine and thus doesn't
  419. try to keep the timer tick on for RCU.
  420. Unless you want to hack and help the development of the full
  421. dynticks mode, you shouldn't enable this option. It also
  422. adds unnecessary overhead.
  423. If unsure say N
  424. config CONTEXT_TRACKING_FORCE
  425. bool "Force context tracking"
  426. depends on CONTEXT_TRACKING
  427. help
  428. Probe on user/kernel boundaries by default in order to
  429. test the features that rely on it such as userspace RCU extended
  430. quiescent states.
  431. This test is there for debugging until we have a real user like the
  432. full dynticks mode.
  433. config RCU_FANOUT
  434. int "Tree-based hierarchical RCU fanout value"
  435. range 2 64 if 64BIT
  436. range 2 32 if !64BIT
  437. depends on TREE_RCU || TREE_PREEMPT_RCU
  438. default 64 if 64BIT
  439. default 32 if !64BIT
  440. help
  441. This option controls the fanout of hierarchical implementations
  442. of RCU, allowing RCU to work efficiently on machines with
  443. large numbers of CPUs. This value must be at least the fourth
  444. root of NR_CPUS, which allows NR_CPUS to be insanely large.
  445. The default value of RCU_FANOUT should be used for production
  446. systems, but if you are stress-testing the RCU implementation
  447. itself, small RCU_FANOUT values allow you to test large-system
  448. code paths on small(er) systems.
  449. Select a specific number if testing RCU itself.
  450. Take the default if unsure.
  451. config RCU_FANOUT_LEAF
  452. int "Tree-based hierarchical RCU leaf-level fanout value"
  453. range 2 RCU_FANOUT if 64BIT
  454. range 2 RCU_FANOUT if !64BIT
  455. depends on TREE_RCU || TREE_PREEMPT_RCU
  456. default 16
  457. help
  458. This option controls the leaf-level fanout of hierarchical
  459. implementations of RCU, and allows trading off cache misses
  460. against lock contention. Systems that synchronize their
  461. scheduling-clock interrupts for energy-efficiency reasons will
  462. want the default because the smaller leaf-level fanout keeps
  463. lock contention levels acceptably low. Very large systems
  464. (hundreds or thousands of CPUs) will instead want to set this
  465. value to the maximum value possible in order to reduce the
  466. number of cache misses incurred during RCU's grace-period
  467. initialization. These systems tend to run CPU-bound, and thus
  468. are not helped by synchronized interrupts, and thus tend to
  469. skew them, which reduces lock contention enough that large
  470. leaf-level fanouts work well.
  471. Select a specific number if testing RCU itself.
  472. Select the maximum permissible value for large systems.
  473. Take the default if unsure.
  474. config RCU_FANOUT_EXACT
  475. bool "Disable tree-based hierarchical RCU auto-balancing"
  476. depends on TREE_RCU || TREE_PREEMPT_RCU
  477. default n
  478. help
  479. This option forces use of the exact RCU_FANOUT value specified,
  480. regardless of imbalances in the hierarchy. This is useful for
  481. testing RCU itself, and might one day be useful on systems with
  482. strong NUMA behavior.
  483. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  484. Say N if unsure.
  485. config RCU_FAST_NO_HZ
  486. bool "Accelerate last non-dyntick-idle CPU's grace periods"
  487. depends on NO_HZ && SMP
  488. default n
  489. help
  490. This option causes RCU to attempt to accelerate grace periods in
  491. order to allow CPUs to enter dynticks-idle state more quickly.
  492. On the other hand, this option increases the overhead of the
  493. dynticks-idle checking, thus degrading scheduling latency.
  494. Say Y if energy efficiency is critically important, and you don't
  495. care about real-time response.
  496. Say N if you are unsure.
  497. config TREE_RCU_TRACE
  498. def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
  499. select DEBUG_FS
  500. help
  501. This option provides tracing for the TREE_RCU and
  502. TREE_PREEMPT_RCU implementations, permitting Makefile to
  503. trivially select kernel/rcutree_trace.c.
  504. config RCU_BOOST
  505. bool "Enable RCU priority boosting"
  506. depends on RT_MUTEXES && PREEMPT_RCU
  507. default n
  508. help
  509. This option boosts the priority of preempted RCU readers that
  510. block the current preemptible RCU grace period for too long.
  511. This option also prevents heavy loads from blocking RCU
  512. callback invocation for all flavors of RCU.
  513. Say Y here if you are working with real-time apps or heavy loads
  514. Say N here if you are unsure.
  515. config RCU_BOOST_PRIO
  516. int "Real-time priority to boost RCU readers to"
  517. range 1 99
  518. depends on RCU_BOOST
  519. default 1
  520. help
  521. This option specifies the real-time priority to which long-term
  522. preempted RCU readers are to be boosted. If you are working
  523. with a real-time application that has one or more CPU-bound
  524. threads running at a real-time priority level, you should set
  525. RCU_BOOST_PRIO to a priority higher then the highest-priority
  526. real-time CPU-bound thread. The default RCU_BOOST_PRIO value
  527. of 1 is appropriate in the common case, which is real-time
  528. applications that do not have any CPU-bound threads.
  529. Some real-time applications might not have a single real-time
  530. thread that saturates a given CPU, but instead might have
  531. multiple real-time threads that, taken together, fully utilize
  532. that CPU. In this case, you should set RCU_BOOST_PRIO to
  533. a priority higher than the lowest-priority thread that is
  534. conspiring to prevent the CPU from running any non-real-time
  535. tasks. For example, if one thread at priority 10 and another
  536. thread at priority 5 are between themselves fully consuming
  537. the CPU time on a given CPU, then RCU_BOOST_PRIO should be
  538. set to priority 6 or higher.
  539. Specify the real-time priority, or take the default if unsure.
  540. config RCU_BOOST_DELAY
  541. int "Milliseconds to delay boosting after RCU grace-period start"
  542. range 0 3000
  543. depends on RCU_BOOST
  544. default 500
  545. help
  546. This option specifies the time to wait after the beginning of
  547. a given grace period before priority-boosting preempted RCU
  548. readers blocking that grace period. Note that any RCU reader
  549. blocking an expedited RCU grace period is boosted immediately.
  550. Accept the default if unsure.
  551. config RCU_NOCB_CPU
  552. bool "Offload RCU callback processing from boot-selected CPUs"
  553. depends on TREE_RCU || TREE_PREEMPT_RCU
  554. default n
  555. help
  556. Use this option to reduce OS jitter for aggressive HPC or
  557. real-time workloads. It can also be used to offload RCU
  558. callback invocation to energy-efficient CPUs in battery-powered
  559. asymmetric multiprocessors.
  560. This option offloads callback invocation from the set of
  561. CPUs specified at boot time by the rcu_nocbs parameter.
  562. For each such CPU, a kthread ("rcuoN") will be created to
  563. invoke callbacks, where the "N" is the CPU being offloaded.
  564. Nothing prevents this kthread from running on the specified
  565. CPUs, but (1) the kthreads may be preempted between each
  566. callback, and (2) affinity or cgroups can be used to force
  567. the kthreads to run on whatever set of CPUs is desired.
  568. Say Y here if you want reduced OS jitter on selected CPUs.
  569. Say N here if you are unsure.
  570. endmenu # "RCU Subsystem"
  571. config IKCONFIG
  572. tristate "Kernel .config support"
  573. ---help---
  574. This option enables the complete Linux kernel ".config" file
  575. contents to be saved in the kernel. It provides documentation
  576. of which kernel options are used in a running kernel or in an
  577. on-disk kernel. This information can be extracted from the kernel
  578. image file with the script scripts/extract-ikconfig and used as
  579. input to rebuild the current kernel or to build another kernel.
  580. It can also be extracted from a running kernel by reading
  581. /proc/config.gz if enabled (below).
  582. config IKCONFIG_PROC
  583. bool "Enable access to .config through /proc/config.gz"
  584. depends on IKCONFIG && PROC_FS
  585. ---help---
  586. This option enables access to the kernel configuration file
  587. through /proc/config.gz.
  588. config LOG_BUF_SHIFT
  589. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  590. range 12 21
  591. default 17
  592. help
  593. Select kernel log buffer size as a power of 2.
  594. Examples:
  595. 17 => 128 KB
  596. 16 => 64 KB
  597. 15 => 32 KB
  598. 14 => 16 KB
  599. 13 => 8 KB
  600. 12 => 4 KB
  601. #
  602. # Architectures with an unreliable sched_clock() should select this:
  603. #
  604. config HAVE_UNSTABLE_SCHED_CLOCK
  605. bool
  606. menuconfig CGROUPS
  607. boolean "Control Group support"
  608. depends on EVENTFD
  609. help
  610. This option adds support for grouping sets of processes together, for
  611. use with process control subsystems such as Cpusets, CFS, memory
  612. controls or device isolation.
  613. See
  614. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  615. - Documentation/cgroups/ (features for grouping, isolation
  616. and resource control)
  617. Say N if unsure.
  618. if CGROUPS
  619. config CGROUP_DEBUG
  620. bool "Example debug cgroup subsystem"
  621. default n
  622. help
  623. This option enables a simple cgroup subsystem that
  624. exports useful debugging information about the cgroups
  625. framework.
  626. Say N if unsure.
  627. config CGROUP_FREEZER
  628. bool "Freezer cgroup subsystem"
  629. help
  630. Provides a way to freeze and unfreeze all tasks in a
  631. cgroup.
  632. config CGROUP_DEVICE
  633. bool "Device controller for cgroups"
  634. help
  635. Provides a cgroup implementing whitelists for devices which
  636. a process in the cgroup can mknod or open.
  637. config CPUSETS
  638. bool "Cpuset support"
  639. help
  640. This option will let you create and manage CPUSETs which
  641. allow dynamically partitioning a system into sets of CPUs and
  642. Memory Nodes and assigning tasks to run only within those sets.
  643. This is primarily useful on large SMP or NUMA systems.
  644. Say N if unsure.
  645. config PROC_PID_CPUSET
  646. bool "Include legacy /proc/<pid>/cpuset file"
  647. depends on CPUSETS
  648. default y
  649. config CGROUP_CPUACCT
  650. bool "Simple CPU accounting cgroup subsystem"
  651. help
  652. Provides a simple Resource Controller for monitoring the
  653. total CPU consumed by the tasks in a cgroup.
  654. config RESOURCE_COUNTERS
  655. bool "Resource counters"
  656. help
  657. This option enables controller independent resource accounting
  658. infrastructure that works with cgroups.
  659. config MEMCG
  660. bool "Memory Resource Controller for Control Groups"
  661. depends on RESOURCE_COUNTERS
  662. select MM_OWNER
  663. help
  664. Provides a memory resource controller that manages both anonymous
  665. memory and page cache. (See Documentation/cgroups/memory.txt)
  666. Note that setting this option increases fixed memory overhead
  667. associated with each page of memory in the system. By this,
  668. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  669. usage tracking struct at boot. Total amount of this is printed out
  670. at boot.
  671. Only enable when you're ok with these trade offs and really
  672. sure you need the memory resource controller. Even when you enable
  673. this, you can set "cgroup_disable=memory" at your boot option to
  674. disable memory resource controller and you can avoid overheads.
  675. (and lose benefits of memory resource controller)
  676. This config option also selects MM_OWNER config option, which
  677. could in turn add some fork/exit overhead.
  678. config MEMCG_SWAP
  679. bool "Memory Resource Controller Swap Extension"
  680. depends on MEMCG && SWAP
  681. help
  682. Add swap management feature to memory resource controller. When you
  683. enable this, you can limit mem+swap usage per cgroup. In other words,
  684. when you disable this, memory resource controller has no cares to
  685. usage of swap...a process can exhaust all of the swap. This extension
  686. is useful when you want to avoid exhaustion swap but this itself
  687. adds more overheads and consumes memory for remembering information.
  688. Especially if you use 32bit system or small memory system, please
  689. be careful about enabling this. When memory resource controller
  690. is disabled by boot option, this will be automatically disabled and
  691. there will be no overhead from this. Even when you set this config=y,
  692. if boot option "swapaccount=0" is set, swap will not be accounted.
  693. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  694. size is 4096bytes, 512k per 1Gbytes of swap.
  695. config MEMCG_SWAP_ENABLED
  696. bool "Memory Resource Controller Swap Extension enabled by default"
  697. depends on MEMCG_SWAP
  698. default y
  699. help
  700. Memory Resource Controller Swap Extension comes with its price in
  701. a bigger memory consumption. General purpose distribution kernels
  702. which want to enable the feature but keep it disabled by default
  703. and let the user enable it by swapaccount boot command line
  704. parameter should have this option unselected.
  705. For those who want to have the feature enabled by default should
  706. select this option (if, for some reason, they need to disable it
  707. then swapaccount=0 does the trick).
  708. config MEMCG_KMEM
  709. bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
  710. depends on MEMCG && EXPERIMENTAL
  711. default n
  712. help
  713. The Kernel Memory extension for Memory Resource Controller can limit
  714. the amount of memory used by kernel objects in the system. Those are
  715. fundamentally different from the entities handled by the standard
  716. Memory Controller, which are page-based, and can be swapped. Users of
  717. the kmem extension can use it to guarantee that no group of processes
  718. will ever exhaust kernel resources alone.
  719. config CGROUP_HUGETLB
  720. bool "HugeTLB Resource Controller for Control Groups"
  721. depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
  722. default n
  723. help
  724. Provides a cgroup Resource Controller for HugeTLB pages.
  725. When you enable this, you can put a per cgroup limit on HugeTLB usage.
  726. The limit is enforced during page fault. Since HugeTLB doesn't
  727. support page reclaim, enforcing the limit at page fault time implies
  728. that, the application will get SIGBUS signal if it tries to access
  729. HugeTLB pages beyond its limit. This requires the application to know
  730. beforehand how much HugeTLB pages it would require for its use. The
  731. control group is tracked in the third page lru pointer. This means
  732. that we cannot use the controller with huge page less than 3 pages.
  733. config CGROUP_PERF
  734. bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
  735. depends on PERF_EVENTS && CGROUPS
  736. help
  737. This option extends the per-cpu mode to restrict monitoring to
  738. threads which belong to the cgroup specified and run on the
  739. designated cpu.
  740. Say N if unsure.
  741. menuconfig CGROUP_SCHED
  742. bool "Group CPU scheduler"
  743. default n
  744. help
  745. This feature lets CPU scheduler recognize task groups and control CPU
  746. bandwidth allocation to such task groups. It uses cgroups to group
  747. tasks.
  748. if CGROUP_SCHED
  749. config FAIR_GROUP_SCHED
  750. bool "Group scheduling for SCHED_OTHER"
  751. depends on CGROUP_SCHED
  752. default CGROUP_SCHED
  753. config CFS_BANDWIDTH
  754. bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
  755. depends on EXPERIMENTAL
  756. depends on FAIR_GROUP_SCHED
  757. default n
  758. help
  759. This option allows users to define CPU bandwidth rates (limits) for
  760. tasks running within the fair group scheduler. Groups with no limit
  761. set are considered to be unconstrained and will run with no
  762. restriction.
  763. See tip/Documentation/scheduler/sched-bwc.txt for more information.
  764. config RT_GROUP_SCHED
  765. bool "Group scheduling for SCHED_RR/FIFO"
  766. depends on EXPERIMENTAL
  767. depends on CGROUP_SCHED
  768. default n
  769. help
  770. This feature lets you explicitly allocate real CPU bandwidth
  771. to task groups. If enabled, it will also make it impossible to
  772. schedule realtime tasks for non-root users until you allocate
  773. realtime bandwidth for them.
  774. See Documentation/scheduler/sched-rt-group.txt for more information.
  775. endif #CGROUP_SCHED
  776. config BLK_CGROUP
  777. bool "Block IO controller"
  778. depends on BLOCK
  779. default n
  780. ---help---
  781. Generic block IO controller cgroup interface. This is the common
  782. cgroup interface which should be used by various IO controlling
  783. policies.
  784. Currently, CFQ IO scheduler uses it to recognize task groups and
  785. control disk bandwidth allocation (proportional time slice allocation)
  786. to such task groups. It is also used by bio throttling logic in
  787. block layer to implement upper limit in IO rates on a device.
  788. This option only enables generic Block IO controller infrastructure.
  789. One needs to also enable actual IO controlling logic/policy. For
  790. enabling proportional weight division of disk bandwidth in CFQ, set
  791. CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
  792. CONFIG_BLK_DEV_THROTTLING=y.
  793. See Documentation/cgroups/blkio-controller.txt for more information.
  794. config DEBUG_BLK_CGROUP
  795. bool "Enable Block IO controller debugging"
  796. depends on BLK_CGROUP
  797. default n
  798. ---help---
  799. Enable some debugging help. Currently it exports additional stat
  800. files in a cgroup which can be useful for debugging.
  801. endif # CGROUPS
  802. config CHECKPOINT_RESTORE
  803. bool "Checkpoint/restore support" if EXPERT
  804. default n
  805. help
  806. Enables additional kernel features in a sake of checkpoint/restore.
  807. In particular it adds auxiliary prctl codes to setup process text,
  808. data and heap segment sizes, and a few additional /proc filesystem
  809. entries.
  810. If unsure, say N here.
  811. menuconfig NAMESPACES
  812. bool "Namespaces support" if EXPERT
  813. default !EXPERT
  814. help
  815. Provides the way to make tasks work with different objects using
  816. the same id. For example same IPC id may refer to different objects
  817. or same user id or pid may refer to different tasks when used in
  818. different namespaces.
  819. if NAMESPACES
  820. config UTS_NS
  821. bool "UTS namespace"
  822. default y
  823. help
  824. In this namespace tasks see different info provided with the
  825. uname() system call
  826. config IPC_NS
  827. bool "IPC namespace"
  828. depends on (SYSVIPC || POSIX_MQUEUE)
  829. default y
  830. help
  831. In this namespace tasks work with IPC ids which correspond to
  832. different IPC objects in different namespaces.
  833. config USER_NS
  834. bool "User namespace (EXPERIMENTAL)"
  835. depends on EXPERIMENTAL
  836. depends on UIDGID_CONVERTED
  837. select UIDGID_STRICT_TYPE_CHECKS
  838. default n
  839. help
  840. This allows containers, i.e. vservers, to use user namespaces
  841. to provide different user info for different servers.
  842. If unsure, say N.
  843. config PID_NS
  844. bool "PID Namespaces"
  845. default y
  846. help
  847. Support process id namespaces. This allows having multiple
  848. processes with the same pid as long as they are in different
  849. pid namespaces. This is a building block of containers.
  850. config NET_NS
  851. bool "Network namespace"
  852. depends on NET
  853. default y
  854. help
  855. Allow user space to create what appear to be multiple instances
  856. of the network stack.
  857. endif # NAMESPACES
  858. config UIDGID_CONVERTED
  859. # True if all of the selected software conmponents are known
  860. # to have uid_t and gid_t converted to kuid_t and kgid_t
  861. # where appropriate and are otherwise safe to use with
  862. # the user namespace.
  863. bool
  864. default y
  865. # Networking
  866. depends on NET_9P = n
  867. # Filesystems
  868. depends on 9P_FS = n
  869. depends on AFS_FS = n
  870. depends on AUTOFS4_FS = n
  871. depends on CEPH_FS = n
  872. depends on CIFS = n
  873. depends on CODA_FS = n
  874. depends on FUSE_FS = n
  875. depends on GFS2_FS = n
  876. depends on NCP_FS = n
  877. depends on NFSD = n
  878. depends on NFS_FS = n
  879. depends on OCFS2_FS = n
  880. depends on XFS_FS = n
  881. config UIDGID_STRICT_TYPE_CHECKS
  882. bool "Require conversions between uid/gids and their internal representation"
  883. depends on UIDGID_CONVERTED
  884. default n
  885. help
  886. While the nececessary conversions are being added to all subsystems this option allows
  887. the code to continue to build for unconverted subsystems.
  888. Say Y here if you want the strict type checking enabled
  889. config SCHED_AUTOGROUP
  890. bool "Automatic process group scheduling"
  891. select EVENTFD
  892. select CGROUPS
  893. select CGROUP_SCHED
  894. select FAIR_GROUP_SCHED
  895. help
  896. This option optimizes the scheduler for common desktop workloads by
  897. automatically creating and populating task groups. This separation
  898. of workloads isolates aggressive CPU burners (like build jobs) from
  899. desktop applications. Task group autogeneration is currently based
  900. upon task session.
  901. config MM_OWNER
  902. bool
  903. config SYSFS_DEPRECATED
  904. bool "Enable deprecated sysfs features to support old userspace tools"
  905. depends on SYSFS
  906. default n
  907. help
  908. This option adds code that switches the layout of the "block" class
  909. devices, to not show up in /sys/class/block/, but only in
  910. /sys/block/.
  911. This switch is only active when the sysfs.deprecated=1 boot option is
  912. passed or the SYSFS_DEPRECATED_V2 option is set.
  913. This option allows new kernels to run on old distributions and tools,
  914. which might get confused by /sys/class/block/. Since 2007/2008 all
  915. major distributions and tools handle this just fine.
  916. Recent distributions and userspace tools after 2009/2010 depend on
  917. the existence of /sys/class/block/, and will not work with this
  918. option enabled.
  919. Only if you are using a new kernel on an old distribution, you might
  920. need to say Y here.
  921. config SYSFS_DEPRECATED_V2
  922. bool "Enable deprecated sysfs features by default"
  923. default n
  924. depends on SYSFS
  925. depends on SYSFS_DEPRECATED
  926. help
  927. Enable deprecated sysfs by default.
  928. See the CONFIG_SYSFS_DEPRECATED option for more details about this
  929. option.
  930. Only if you are using a new kernel on an old distribution, you might
  931. need to say Y here. Even then, odds are you would not need it
  932. enabled, you can always pass the boot option if absolutely necessary.
  933. config RELAY
  934. bool "Kernel->user space relay support (formerly relayfs)"
  935. help
  936. This option enables support for relay interface support in
  937. certain file systems (such as debugfs).
  938. It is designed to provide an efficient mechanism for tools and
  939. facilities to relay large amounts of data from kernel space to
  940. user space.
  941. If unsure, say N.
  942. config BLK_DEV_INITRD
  943. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  944. depends on BROKEN || !FRV
  945. help
  946. The initial RAM filesystem is a ramfs which is loaded by the
  947. boot loader (loadlin or lilo) and that is mounted as root
  948. before the normal boot procedure. It is typically used to
  949. load modules needed to mount the "real" root file system,
  950. etc. See <file:Documentation/initrd.txt> for details.
  951. If RAM disk support (BLK_DEV_RAM) is also included, this
  952. also enables initial RAM disk (initrd) support and adds
  953. 15 Kbytes (more on some other architectures) to the kernel size.
  954. If unsure say Y.
  955. if BLK_DEV_INITRD
  956. source "usr/Kconfig"
  957. endif
  958. config CC_OPTIMIZE_FOR_SIZE
  959. bool "Optimize for size"
  960. help
  961. Enabling this option will pass "-Os" instead of "-O2" to gcc
  962. resulting in a smaller kernel.
  963. If unsure, say Y.
  964. config SYSCTL
  965. bool
  966. config ANON_INODES
  967. bool
  968. menuconfig EXPERT
  969. bool "Configure standard kernel features (expert users)"
  970. # Unhide debug options, to make the on-by-default options visible
  971. select DEBUG_KERNEL
  972. help
  973. This option allows certain base kernel options and settings
  974. to be disabled or tweaked. This is for specialized
  975. environments which can tolerate a "non-standard" kernel.
  976. Only use this if you really know what you are doing.
  977. config HAVE_UID16
  978. bool
  979. config UID16
  980. bool "Enable 16-bit UID system calls" if EXPERT
  981. depends on HAVE_UID16
  982. default y
  983. help
  984. This enables the legacy 16-bit UID syscall wrappers.
  985. config SYSCTL_SYSCALL
  986. bool "Sysctl syscall support" if EXPERT
  987. depends on PROC_SYSCTL
  988. default n
  989. select SYSCTL
  990. ---help---
  991. sys_sysctl uses binary paths that have been found challenging
  992. to properly maintain and use. The interface in /proc/sys
  993. using paths with ascii names is now the primary path to this
  994. information.
  995. Almost nothing using the binary sysctl interface so if you are
  996. trying to save some space it is probably safe to disable this,
  997. making your kernel marginally smaller.
  998. If unsure say N here.
  999. config SYSCTL_EXCEPTION_TRACE
  1000. bool
  1001. help
  1002. Enable support for /proc/sys/debug/exception-trace.
  1003. config KALLSYMS
  1004. bool "Load all symbols for debugging/ksymoops" if EXPERT
  1005. default y
  1006. help
  1007. Say Y here to let the kernel print out symbolic crash information and
  1008. symbolic stack backtraces. This increases the size of the kernel
  1009. somewhat, as all symbols have to be loaded into the kernel image.
  1010. config KALLSYMS_ALL
  1011. bool "Include all symbols in kallsyms"
  1012. depends on DEBUG_KERNEL && KALLSYMS
  1013. help
  1014. Normally kallsyms only contains the symbols of functions for nicer
  1015. OOPS messages and backtraces (i.e., symbols from the text and inittext
  1016. sections). This is sufficient for most cases. And only in very rare
  1017. cases (e.g., when a debugger is used) all symbols are required (e.g.,
  1018. names of variables from the data sections, etc).
  1019. This option makes sure that all symbols are loaded into the kernel
  1020. image (i.e., symbols from all sections) in cost of increased kernel
  1021. size (depending on the kernel configuration, it may be 300KiB or
  1022. something like this).
  1023. Say N unless you really need all symbols.
  1024. config HOTPLUG
  1025. def_bool y
  1026. config PRINTK
  1027. default y
  1028. bool "Enable support for printk" if EXPERT
  1029. help
  1030. This option enables normal printk support. Removing it
  1031. eliminates most of the message strings from the kernel image
  1032. and makes the kernel more or less silent. As this makes it
  1033. very difficult to diagnose system problems, saying N here is
  1034. strongly discouraged.
  1035. config BUG
  1036. bool "BUG() support" if EXPERT
  1037. default y
  1038. help
  1039. Disabling this option eliminates support for BUG and WARN, reducing
  1040. the size of your kernel image and potentially quietly ignoring
  1041. numerous fatal conditions. You should only consider disabling this
  1042. option for embedded systems with no facilities for reporting errors.
  1043. Just say Y.
  1044. config ELF_CORE
  1045. depends on COREDUMP
  1046. default y
  1047. bool "Enable ELF core dumps" if EXPERT
  1048. help
  1049. Enable support for generating core dumps. Disabling saves about 4k.
  1050. config PCSPKR_PLATFORM
  1051. bool "Enable PC-Speaker support" if EXPERT
  1052. depends on HAVE_PCSPKR_PLATFORM
  1053. select I8253_LOCK
  1054. default y
  1055. help
  1056. This option allows to disable the internal PC-Speaker
  1057. support, saving some memory.
  1058. config HAVE_PCSPKR_PLATFORM
  1059. bool
  1060. config BASE_FULL
  1061. default y
  1062. bool "Enable full-sized data structures for core" if EXPERT
  1063. help
  1064. Disabling this option reduces the size of miscellaneous core
  1065. kernel data structures. This saves memory on small machines,
  1066. but may reduce performance.
  1067. config FUTEX
  1068. bool "Enable futex support" if EXPERT
  1069. default y
  1070. select RT_MUTEXES
  1071. help
  1072. Disabling this option will cause the kernel to be built without
  1073. support for "fast userspace mutexes". The resulting kernel may not
  1074. run glibc-based applications correctly.
  1075. config EPOLL
  1076. bool "Enable eventpoll support" if EXPERT
  1077. default y
  1078. select ANON_INODES
  1079. help
  1080. Disabling this option will cause the kernel to be built without
  1081. support for epoll family of system calls.
  1082. config SIGNALFD
  1083. bool "Enable signalfd() system call" if EXPERT
  1084. select ANON_INODES
  1085. default y
  1086. help
  1087. Enable the signalfd() system call that allows to receive signals
  1088. on a file descriptor.
  1089. If unsure, say Y.
  1090. config TIMERFD
  1091. bool "Enable timerfd() system call" if EXPERT
  1092. select ANON_INODES
  1093. default y
  1094. help
  1095. Enable the timerfd() system call that allows to receive timer
  1096. events on a file descriptor.
  1097. If unsure, say Y.
  1098. config EVENTFD
  1099. bool "Enable eventfd() system call" if EXPERT
  1100. select ANON_INODES
  1101. default y
  1102. help
  1103. Enable the eventfd() system call that allows to receive both
  1104. kernel notification (ie. KAIO) or userspace notifications.
  1105. If unsure, say Y.
  1106. config SHMEM
  1107. bool "Use full shmem filesystem" if EXPERT
  1108. default y
  1109. depends on MMU
  1110. help
  1111. The shmem is an internal filesystem used to manage shared memory.
  1112. It is backed by swap and manages resource limits. It is also exported
  1113. to userspace as tmpfs if TMPFS is enabled. Disabling this
  1114. option replaces shmem and tmpfs with the much simpler ramfs code,
  1115. which may be appropriate on small systems without swap.
  1116. config AIO
  1117. bool "Enable AIO support" if EXPERT
  1118. default y
  1119. help
  1120. This option enables POSIX asynchronous I/O which may by used
  1121. by some high performance threaded applications. Disabling
  1122. this option saves about 7k.
  1123. config EMBEDDED
  1124. bool "Embedded system"
  1125. select EXPERT
  1126. help
  1127. This option should be enabled if compiling the kernel for
  1128. an embedded system so certain expert options are available
  1129. for configuration.
  1130. config HAVE_PERF_EVENTS
  1131. bool
  1132. help
  1133. See tools/perf/design.txt for details.
  1134. config PERF_USE_VMALLOC
  1135. bool
  1136. help
  1137. See tools/perf/design.txt for details
  1138. menu "Kernel Performance Events And Counters"
  1139. config PERF_EVENTS
  1140. bool "Kernel performance events and counters"
  1141. default y if PROFILING
  1142. depends on HAVE_PERF_EVENTS
  1143. select ANON_INODES
  1144. select IRQ_WORK
  1145. help
  1146. Enable kernel support for various performance events provided
  1147. by software and hardware.
  1148. Software events are supported either built-in or via the
  1149. use of generic tracepoints.
  1150. Most modern CPUs support performance events via performance
  1151. counter registers. These registers count the number of certain
  1152. types of hw events: such as instructions executed, cachemisses
  1153. suffered, or branches mis-predicted - without slowing down the
  1154. kernel or applications. These registers can also trigger interrupts
  1155. when a threshold number of events have passed - and can thus be
  1156. used to profile the code that runs on that CPU.
  1157. The Linux Performance Event subsystem provides an abstraction of
  1158. these software and hardware event capabilities, available via a
  1159. system call and used by the "perf" utility in tools/perf/. It
  1160. provides per task and per CPU counters, and it provides event
  1161. capabilities on top of those.
  1162. Say Y if unsure.
  1163. config DEBUG_PERF_USE_VMALLOC
  1164. default n
  1165. bool "Debug: use vmalloc to back perf mmap() buffers"
  1166. depends on PERF_EVENTS && DEBUG_KERNEL
  1167. select PERF_USE_VMALLOC
  1168. help
  1169. Use vmalloc memory to back perf mmap() buffers.
  1170. Mostly useful for debugging the vmalloc code on platforms
  1171. that don't require it.
  1172. Say N if unsure.
  1173. endmenu
  1174. config VM_EVENT_COUNTERS
  1175. default y
  1176. bool "Enable VM event counters for /proc/vmstat" if EXPERT
  1177. help
  1178. VM event counters are needed for event counts to be shown.
  1179. This option allows the disabling of the VM event counters
  1180. on EXPERT systems. /proc/vmstat will only show page counts
  1181. if VM event counters are disabled.
  1182. config PCI_QUIRKS
  1183. default y
  1184. bool "Enable PCI quirk workarounds" if EXPERT
  1185. depends on PCI
  1186. help
  1187. This enables workarounds for various PCI chipset
  1188. bugs/quirks. Disable this only if your target machine is
  1189. unaffected by PCI quirks.
  1190. config SLUB_DEBUG
  1191. default y
  1192. bool "Enable SLUB debugging support" if EXPERT
  1193. depends on SLUB && SYSFS
  1194. help
  1195. SLUB has extensive debug support features. Disabling these can
  1196. result in significant savings in code size. This also disables
  1197. SLUB sysfs support. /sys/slab will not exist and there will be
  1198. no support for cache validation etc.
  1199. config COMPAT_BRK
  1200. bool "Disable heap randomization"
  1201. default y
  1202. help
  1203. Randomizing heap placement makes heap exploits harder, but it
  1204. also breaks ancient binaries (including anything libc5 based).
  1205. This option changes the bootup default to heap randomization
  1206. disabled, and can be overridden at runtime by setting
  1207. /proc/sys/kernel/randomize_va_space to 2.
  1208. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  1209. choice
  1210. prompt "Choose SLAB allocator"
  1211. default SLUB
  1212. help
  1213. This option allows to select a slab allocator.
  1214. config SLAB
  1215. bool "SLAB"
  1216. help
  1217. The regular slab allocator that is established and known to work
  1218. well in all environments. It organizes cache hot objects in
  1219. per cpu and per node queues.
  1220. config SLUB
  1221. bool "SLUB (Unqueued Allocator)"
  1222. help
  1223. SLUB is a slab allocator that minimizes cache line usage
  1224. instead of managing queues of cached objects (SLAB approach).
  1225. Per cpu caching is realized using slabs of objects instead
  1226. of queues of objects. SLUB can use memory efficiently
  1227. and has enhanced diagnostics. SLUB is the default choice for
  1228. a slab allocator.
  1229. config SLOB
  1230. depends on EXPERT
  1231. bool "SLOB (Simple Allocator)"
  1232. help
  1233. SLOB replaces the stock allocator with a drastically simpler
  1234. allocator. SLOB is generally more space efficient but
  1235. does not perform as well on large systems.
  1236. endchoice
  1237. config MMAP_ALLOW_UNINITIALIZED
  1238. bool "Allow mmapped anonymous memory to be uninitialized"
  1239. depends on EXPERT && !MMU
  1240. default n
  1241. help
  1242. Normally, and according to the Linux spec, anonymous memory obtained
  1243. from mmap() has it's contents cleared before it is passed to
  1244. userspace. Enabling this config option allows you to request that
  1245. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  1246. providing a huge performance boost. If this option is not enabled,
  1247. then the flag will be ignored.
  1248. This is taken advantage of by uClibc's malloc(), and also by
  1249. ELF-FDPIC binfmt's brk and stack allocator.
  1250. Because of the obvious security issues, this option should only be
  1251. enabled on embedded devices where you control what is run in
  1252. userspace. Since that isn't generally a problem on no-MMU systems,
  1253. it is normally safe to say Y here.
  1254. See Documentation/nommu-mmap.txt for more information.
  1255. config PROFILING
  1256. bool "Profiling support"
  1257. help
  1258. Say Y here to enable the extended profiling support mechanisms used
  1259. by profilers such as OProfile.
  1260. #
  1261. # Place an empty function call at each tracepoint site. Can be
  1262. # dynamically changed for a probe function.
  1263. #
  1264. config TRACEPOINTS
  1265. bool
  1266. source "arch/Kconfig"
  1267. endmenu # General setup
  1268. config HAVE_GENERIC_DMA_COHERENT
  1269. bool
  1270. default n
  1271. config SLABINFO
  1272. bool
  1273. depends on PROC_FS
  1274. depends on SLAB || SLUB_DEBUG
  1275. default y
  1276. config RT_MUTEXES
  1277. boolean
  1278. config BASE_SMALL
  1279. int
  1280. default 0 if BASE_FULL
  1281. default 1 if !BASE_FULL
  1282. menuconfig MODULES
  1283. bool "Enable loadable module support"
  1284. help
  1285. Kernel modules are small pieces of compiled code which can
  1286. be inserted in the running kernel, rather than being
  1287. permanently built into the kernel. You use the "modprobe"
  1288. tool to add (and sometimes remove) them. If you say Y here,
  1289. many parts of the kernel can be built as modules (by
  1290. answering M instead of Y where indicated): this is most
  1291. useful for infrequently used options which are not required
  1292. for booting. For more information, see the man pages for
  1293. modprobe, lsmod, modinfo, insmod and rmmod.
  1294. If you say Y here, you will need to run "make
  1295. modules_install" to put the modules under /lib/modules/
  1296. where modprobe can find them (you may need to be root to do
  1297. this).
  1298. If unsure, say Y.
  1299. if MODULES
  1300. config MODULE_FORCE_LOAD
  1301. bool "Forced module loading"
  1302. default n
  1303. help
  1304. Allow loading of modules without version information (ie. modprobe
  1305. --force). Forced module loading sets the 'F' (forced) taint flag and
  1306. is usually a really bad idea.
  1307. config MODULE_UNLOAD
  1308. bool "Module unloading"
  1309. help
  1310. Without this option you will not be able to unload any
  1311. modules (note that some modules may not be unloadable
  1312. anyway), which makes your kernel smaller, faster
  1313. and simpler. If unsure, say Y.
  1314. config MODULE_FORCE_UNLOAD
  1315. bool "Forced module unloading"
  1316. depends on MODULE_UNLOAD && EXPERIMENTAL
  1317. help
  1318. This option allows you to force a module to unload, even if the
  1319. kernel believes it is unsafe: the kernel will remove the module
  1320. without waiting for anyone to stop using it (using the -f option to
  1321. rmmod). This is mainly for kernel developers and desperate users.
  1322. If unsure, say N.
  1323. config MODVERSIONS
  1324. bool "Module versioning support"
  1325. help
  1326. Usually, you have to use modules compiled with your kernel.
  1327. Saying Y here makes it sometimes possible to use modules
  1328. compiled for different kernels, by adding enough information
  1329. to the modules to (hopefully) spot any changes which would
  1330. make them incompatible with the kernel you are running. If
  1331. unsure, say N.
  1332. config MODULE_SRCVERSION_ALL
  1333. bool "Source checksum for all modules"
  1334. help
  1335. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1336. field inserted into their modinfo section, which contains a
  1337. sum of the source files which made it. This helps maintainers
  1338. see exactly which source was used to build a module (since
  1339. others sometimes change the module source without updating
  1340. the version). With this option, such a "srcversion" field
  1341. will be created for all modules. If unsure, say N.
  1342. config MODULE_SIG
  1343. bool "Module signature verification"
  1344. depends on MODULES
  1345. select KEYS
  1346. select CRYPTO
  1347. select ASYMMETRIC_KEY_TYPE
  1348. select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  1349. select PUBLIC_KEY_ALGO_RSA
  1350. select ASN1
  1351. select OID_REGISTRY
  1352. select X509_CERTIFICATE_PARSER
  1353. help
  1354. Check modules for valid signatures upon load: the signature
  1355. is simply appended to the module. For more information see
  1356. Documentation/module-signing.txt.
  1357. !!!WARNING!!! If you enable this option, you MUST make sure that the
  1358. module DOES NOT get stripped after being signed. This includes the
  1359. debuginfo strip done by some packagers (such as rpmbuild) and
  1360. inclusion into an initramfs that wants the module size reduced.
  1361. config MODULE_SIG_FORCE
  1362. bool "Require modules to be validly signed"
  1363. depends on MODULE_SIG
  1364. help
  1365. Reject unsigned modules or signed modules for which we don't have a
  1366. key. Without this, such modules will simply taint the kernel.
  1367. choice
  1368. prompt "Which hash algorithm should modules be signed with?"
  1369. depends on MODULE_SIG
  1370. help
  1371. This determines which sort of hashing algorithm will be used during
  1372. signature generation. This algorithm _must_ be built into the kernel
  1373. directly so that signature verification can take place. It is not
  1374. possible to load a signed module containing the algorithm to check
  1375. the signature on that module.
  1376. config MODULE_SIG_SHA1
  1377. bool "Sign modules with SHA-1"
  1378. select CRYPTO_SHA1
  1379. config MODULE_SIG_SHA224
  1380. bool "Sign modules with SHA-224"
  1381. select CRYPTO_SHA256
  1382. config MODULE_SIG_SHA256
  1383. bool "Sign modules with SHA-256"
  1384. select CRYPTO_SHA256
  1385. config MODULE_SIG_SHA384
  1386. bool "Sign modules with SHA-384"
  1387. select CRYPTO_SHA512
  1388. config MODULE_SIG_SHA512
  1389. bool "Sign modules with SHA-512"
  1390. select CRYPTO_SHA512
  1391. endchoice
  1392. endif # MODULES
  1393. config INIT_ALL_POSSIBLE
  1394. bool
  1395. help
  1396. Back when each arch used to define their own cpu_online_mask and
  1397. cpu_possible_mask, some of them chose to initialize cpu_possible_mask
  1398. with all 1s, and others with all 0s. When they were centralised,
  1399. it was better to provide this option than to break all the archs
  1400. and have several arch maintainers pursuing me down dark alleys.
  1401. config STOP_MACHINE
  1402. bool
  1403. default y
  1404. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1405. help
  1406. Need stop_machine() primitive.
  1407. source "block/Kconfig"
  1408. config PREEMPT_NOTIFIERS
  1409. bool
  1410. config PADATA
  1411. depends on SMP
  1412. bool
  1413. # Can be selected by architectures with broken toolchains
  1414. # that get confused by correct const<->read_only section
  1415. # mappings
  1416. config BROKEN_RODATA
  1417. bool
  1418. config ASN1
  1419. tristate
  1420. help
  1421. Build a simple ASN.1 grammar compiler that produces a bytecode output
  1422. that can be interpreted by the ASN.1 stream decoder and used to
  1423. inform it as to what tags are to be expected in a stream and what
  1424. functions to call on what tags.
  1425. source "kernel/Kconfig.locks"