Kconfig 34 KB

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  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. menu "General setup"
  17. config EXPERIMENTAL
  18. bool "Prompt for development and/or incomplete code/drivers"
  19. ---help---
  20. Some of the various things that Linux supports (such as network
  21. drivers, file systems, network protocols, etc.) can be in a state
  22. of development where the functionality, stability, or the level of
  23. testing is not yet high enough for general use. This is usually
  24. known as the "alpha-test" phase among developers. If a feature is
  25. currently in alpha-test, then the developers usually discourage
  26. uninformed widespread use of this feature by the general public to
  27. avoid "Why doesn't this work?" type mail messages. However, active
  28. testing and use of these systems is welcomed. Just be aware that it
  29. may not meet the normal level of reliability or it may fail to work
  30. in some special cases. Detailed bug reports from people familiar
  31. with the kernel internals are usually welcomed by the developers
  32. (before submitting bug reports, please read the documents
  33. <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  34. <file:Documentation/BUG-HUNTING>, and
  35. <file:Documentation/oops-tracing.txt> in the kernel source).
  36. This option will also make obsoleted drivers available. These are
  37. drivers that have been replaced by something else, and/or are
  38. scheduled to be removed in a future kernel release.
  39. Unless you intend to help test and develop a feature or driver that
  40. falls into this category, or you have a situation that requires
  41. using these features, you should probably say N here, which will
  42. cause the configurator to present you with fewer choices. If
  43. you say Y here, you will be offered the choice of using features or
  44. drivers that are currently considered to be in the alpha-test phase.
  45. config BROKEN
  46. bool
  47. config BROKEN_ON_SMP
  48. bool
  49. depends on BROKEN || !SMP
  50. default y
  51. config LOCK_KERNEL
  52. bool
  53. depends on SMP || PREEMPT
  54. default y
  55. config INIT_ENV_ARG_LIMIT
  56. int
  57. default 32 if !UML
  58. default 128 if UML
  59. help
  60. Maximum of each of the number of arguments and environment
  61. variables passed to init from the kernel command line.
  62. config LOCALVERSION
  63. string "Local version - append to kernel release"
  64. help
  65. Append an extra string to the end of your kernel version.
  66. This will show up when you type uname, for example.
  67. The string you set here will be appended after the contents of
  68. any files with a filename matching localversion* in your
  69. object and source tree, in that order. Your total string can
  70. be a maximum of 64 characters.
  71. config LOCALVERSION_AUTO
  72. bool "Automatically append version information to the version string"
  73. default y
  74. help
  75. This will try to automatically determine if the current tree is a
  76. release tree by looking for git tags that belong to the current
  77. top of tree revision.
  78. A string of the format -gxxxxxxxx will be added to the localversion
  79. if a git-based tree is found. The string generated by this will be
  80. appended after any matching localversion* files, and after the value
  81. set in CONFIG_LOCALVERSION.
  82. (The actual string used here is the first eight characters produced
  83. by running the command:
  84. $ git rev-parse --verify HEAD
  85. which is done within the script "scripts/setlocalversion".)
  86. config SWAP
  87. bool "Support for paging of anonymous memory (swap)"
  88. depends on MMU && BLOCK
  89. default y
  90. help
  91. This option allows you to choose whether you want to have support
  92. for so called swap devices or swap files in your kernel that are
  93. used to provide more virtual memory than the actual RAM present
  94. in your computer. If unsure say Y.
  95. config SYSVIPC
  96. bool "System V IPC"
  97. ---help---
  98. Inter Process Communication is a suite of library functions and
  99. system calls which let processes (running programs) synchronize and
  100. exchange information. It is generally considered to be a good thing,
  101. and some programs won't run unless you say Y here. In particular, if
  102. you want to run the DOS emulator dosemu under Linux (read the
  103. DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
  104. you'll need to say Y here.
  105. You can find documentation about IPC with "info ipc" and also in
  106. section 6.4 of the Linux Programmer's Guide, available from
  107. <http://www.tldp.org/guides.html>.
  108. config SYSVIPC_SYSCTL
  109. bool
  110. depends on SYSVIPC
  111. depends on SYSCTL
  112. default y
  113. config POSIX_MQUEUE
  114. bool "POSIX Message Queues"
  115. depends on NET && EXPERIMENTAL
  116. ---help---
  117. POSIX variant of message queues is a part of IPC. In POSIX message
  118. queues every message has a priority which decides about succession
  119. of receiving it by a process. If you want to compile and run
  120. programs written e.g. for Solaris with use of its POSIX message
  121. queues (functions mq_*) say Y here.
  122. POSIX message queues are visible as a filesystem called 'mqueue'
  123. and can be mounted somewhere if you want to do filesystem
  124. operations on message queues.
  125. If unsure, say Y.
  126. config BSD_PROCESS_ACCT
  127. bool "BSD Process Accounting"
  128. help
  129. If you say Y here, a user level program will be able to instruct the
  130. kernel (via a special system call) to write process accounting
  131. information to a file: whenever a process exits, information about
  132. that process will be appended to the file by the kernel. The
  133. information includes things such as creation time, owning user,
  134. command name, memory usage, controlling terminal etc. (the complete
  135. list is in the struct acct in <file:include/linux/acct.h>). It is
  136. up to the user level program to do useful things with this
  137. information. This is generally a good idea, so say Y.
  138. config BSD_PROCESS_ACCT_V3
  139. bool "BSD Process Accounting version 3 file format"
  140. depends on BSD_PROCESS_ACCT
  141. default n
  142. help
  143. If you say Y here, the process accounting information is written
  144. in a new file format that also logs the process IDs of each
  145. process and it's parent. Note that this file format is incompatible
  146. with previous v0/v1/v2 file formats, so you will need updated tools
  147. for processing it. A preliminary version of these tools is available
  148. at <http://www.gnu.org/software/acct/>.
  149. config TASKSTATS
  150. bool "Export task/process statistics through netlink (EXPERIMENTAL)"
  151. depends on NET
  152. default n
  153. help
  154. Export selected statistics for tasks/processes through the
  155. generic netlink interface. Unlike BSD process accounting, the
  156. statistics are available during the lifetime of tasks/processes as
  157. responses to commands. Like BSD accounting, they are sent to user
  158. space on task exit.
  159. Say N if unsure.
  160. config TASK_DELAY_ACCT
  161. bool "Enable per-task delay accounting (EXPERIMENTAL)"
  162. depends on TASKSTATS
  163. help
  164. Collect information on time spent by a task waiting for system
  165. resources like cpu, synchronous block I/O completion and swapping
  166. in pages. Such statistics can help in setting a task's priorities
  167. relative to other tasks for cpu, io, rss limits etc.
  168. Say N if unsure.
  169. config TASK_XACCT
  170. bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
  171. depends on TASKSTATS
  172. help
  173. Collect extended task accounting data and send the data
  174. to userland for processing over the taskstats interface.
  175. Say N if unsure.
  176. config TASK_IO_ACCOUNTING
  177. bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
  178. depends on TASK_XACCT
  179. help
  180. Collect information on the number of bytes of storage I/O which this
  181. task has caused.
  182. Say N if unsure.
  183. config AUDIT
  184. bool "Auditing support"
  185. depends on NET
  186. help
  187. Enable auditing infrastructure that can be used with another
  188. kernel subsystem, such as SELinux (which requires this for
  189. logging of avc messages output). Does not do system-call
  190. auditing without CONFIG_AUDITSYSCALL.
  191. config AUDITSYSCALL
  192. bool "Enable system-call auditing support"
  193. depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
  194. default y if SECURITY_SELINUX
  195. help
  196. Enable low-overhead system-call auditing infrastructure that
  197. can be used independently or with another kernel subsystem,
  198. such as SELinux. To use audit's filesystem watch feature, please
  199. ensure that INOTIFY is configured.
  200. config AUDIT_TREE
  201. def_bool y
  202. depends on AUDITSYSCALL && INOTIFY
  203. config IKCONFIG
  204. tristate "Kernel .config support"
  205. ---help---
  206. This option enables the complete Linux kernel ".config" file
  207. contents to be saved in the kernel. It provides documentation
  208. of which kernel options are used in a running kernel or in an
  209. on-disk kernel. This information can be extracted from the kernel
  210. image file with the script scripts/extract-ikconfig and used as
  211. input to rebuild the current kernel or to build another kernel.
  212. It can also be extracted from a running kernel by reading
  213. /proc/config.gz if enabled (below).
  214. config IKCONFIG_PROC
  215. bool "Enable access to .config through /proc/config.gz"
  216. depends on IKCONFIG && PROC_FS
  217. ---help---
  218. This option enables access to the kernel configuration file
  219. through /proc/config.gz.
  220. config LOG_BUF_SHIFT
  221. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  222. range 12 21
  223. default 17
  224. help
  225. Select kernel log buffer size as a power of 2.
  226. Examples:
  227. 17 => 128 KB
  228. 16 => 64 KB
  229. 15 => 32 KB
  230. 14 => 16 KB
  231. 13 => 8 KB
  232. 12 => 4 KB
  233. #
  234. # Architectures with an unreliable sched_clock() should select this:
  235. #
  236. config HAVE_UNSTABLE_SCHED_CLOCK
  237. bool
  238. config GROUP_SCHED
  239. bool "Group CPU scheduler"
  240. depends on EXPERIMENTAL
  241. default n
  242. help
  243. This feature lets CPU scheduler recognize task groups and control CPU
  244. bandwidth allocation to such task groups.
  245. In order to create a group from arbitrary set of processes, use
  246. CONFIG_CGROUPS. (See Control Group support.)
  247. config FAIR_GROUP_SCHED
  248. bool "Group scheduling for SCHED_OTHER"
  249. depends on GROUP_SCHED
  250. default GROUP_SCHED
  251. config RT_GROUP_SCHED
  252. bool "Group scheduling for SCHED_RR/FIFO"
  253. depends on EXPERIMENTAL
  254. depends on GROUP_SCHED
  255. default n
  256. help
  257. This feature lets you explicitly allocate real CPU bandwidth
  258. to users or control groups (depending on the "Basis for grouping tasks"
  259. setting below. If enabled, it will also make it impossible to
  260. schedule realtime tasks for non-root users until you allocate
  261. realtime bandwidth for them.
  262. See Documentation/scheduler/sched-rt-group.txt for more information.
  263. choice
  264. depends on GROUP_SCHED
  265. prompt "Basis for grouping tasks"
  266. default USER_SCHED
  267. config USER_SCHED
  268. bool "user id"
  269. help
  270. This option will choose userid as the basis for grouping
  271. tasks, thus providing equal CPU bandwidth to each user.
  272. config CGROUP_SCHED
  273. bool "Control groups"
  274. depends on CGROUPS
  275. help
  276. This option allows you to create arbitrary task groups
  277. using the "cgroup" pseudo filesystem and control
  278. the cpu bandwidth allocated to each such task group.
  279. Refer to Documentation/cgroups.txt for more information
  280. on "cgroup" pseudo filesystem.
  281. endchoice
  282. menu "Control Group support"
  283. config CGROUPS
  284. bool "Control Group support"
  285. help
  286. This option add support for grouping sets of processes together, for
  287. use with process control subsystems such as Cpusets, CFS, memory
  288. controls or device isolation.
  289. See
  290. - Documentation/cpusets.txt (Cpusets)
  291. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  292. - Documentation/cgroups/ (features for grouping, isolation)
  293. - Documentation/controllers/ (features for resource control)
  294. Say N if unsure.
  295. config CGROUP_DEBUG
  296. bool "Example debug cgroup subsystem"
  297. depends on CGROUPS
  298. default n
  299. help
  300. This option enables a simple cgroup subsystem that
  301. exports useful debugging information about the cgroups
  302. framework
  303. Say N if unsure
  304. config CGROUP_NS
  305. bool "Namespace cgroup subsystem"
  306. depends on CGROUPS
  307. help
  308. Provides a simple namespace cgroup subsystem to
  309. provide hierarchical naming of sets of namespaces,
  310. for instance virtual servers and checkpoint/restart
  311. jobs.
  312. config CGROUP_FREEZER
  313. bool "control group freezer subsystem"
  314. depends on CGROUPS
  315. help
  316. Provides a way to freeze and unfreeze all tasks in a
  317. cgroup.
  318. config CGROUP_DEVICE
  319. bool "Device controller for cgroups"
  320. depends on CGROUPS && EXPERIMENTAL
  321. help
  322. Provides a cgroup implementing whitelists for devices which
  323. a process in the cgroup can mknod or open.
  324. config CPUSETS
  325. bool "Cpuset support"
  326. depends on SMP && CGROUPS
  327. help
  328. This option will let you create and manage CPUSETs which
  329. allow dynamically partitioning a system into sets of CPUs and
  330. Memory Nodes and assigning tasks to run only within those sets.
  331. This is primarily useful on large SMP or NUMA systems.
  332. Say N if unsure.
  333. config CGROUP_CPUACCT
  334. bool "Simple CPU accounting cgroup subsystem"
  335. depends on CGROUPS
  336. help
  337. Provides a simple Resource Controller for monitoring the
  338. total CPU consumed by the tasks in a cgroup
  339. config RESOURCE_COUNTERS
  340. bool "Resource counters"
  341. help
  342. This option enables controller independent resource accounting
  343. infrastructure that works with cgroups
  344. depends on CGROUPS
  345. config CGROUP_MEM_RES_CTLR
  346. bool "Memory Resource Controller for Control Groups"
  347. depends on CGROUPS && RESOURCE_COUNTERS
  348. select MM_OWNER
  349. help
  350. Provides a memory resource controller that manages both anonymous
  351. memory and page cache. (See Documentation/controllers/memory.txt)
  352. Note that setting this option increases fixed memory overhead
  353. associated with each page of memory in the system. By this,
  354. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  355. usage tracking struct at boot. Total amount of this is printed out
  356. at boot.
  357. Only enable when you're ok with these trade offs and really
  358. sure you need the memory resource controller. Even when you enable
  359. this, you can set "cgroup_disable=memory" at your boot option to
  360. disable memory resource controller and you can avoid overheads.
  361. (and lose benefits of memory resource controller)
  362. This config option also selects MM_OWNER config option, which
  363. could in turn add some fork/exit overhead.
  364. config MM_OWNER
  365. bool
  366. config CGROUP_MEM_RES_CTLR_SWAP
  367. bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
  368. depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
  369. help
  370. Add swap management feature to memory resource controller. When you
  371. enable this, you can limit mem+swap usage per cgroup. In other words,
  372. when you disable this, memory resource controller has no cares to
  373. usage of swap...a process can exhaust all of the swap. This extension
  374. is useful when you want to avoid exhaustion swap but this itself
  375. adds more overheads and consumes memory for remembering information.
  376. Especially if you use 32bit system or small memory system, please
  377. be careful about enabling this. When memory resource controller
  378. is disabled by boot option, this will be automatically disabled and
  379. there will be no overhead from this. Even when you set this config=y,
  380. if boot option "noswapaccount" is set, swap will not be accounted.
  381. endmenu
  382. config SYSFS_DEPRECATED
  383. bool
  384. config SYSFS_DEPRECATED_V2
  385. bool "Create deprecated sysfs layout for older userspace tools"
  386. depends on SYSFS
  387. default y
  388. select SYSFS_DEPRECATED
  389. help
  390. This option switches the layout of sysfs to the deprecated
  391. version.
  392. The current sysfs layout features a unified device tree at
  393. /sys/devices/, which is able to express a hierarchy between
  394. class devices. If the deprecated option is set to Y, the
  395. unified device tree is split into a bus device tree at
  396. /sys/devices/ and several individual class device trees at
  397. /sys/class/. The class and bus devices will be connected by
  398. "<subsystem>:<name>" and the "device" links. The "block"
  399. class devices, will not show up in /sys/class/block/. Some
  400. subsystems will suppress the creation of some devices which
  401. depend on the unified device tree.
  402. This option is not a pure compatibility option that can
  403. be safely enabled on newer distributions. It will change the
  404. layout of sysfs to the non-extensible deprecated version,
  405. and disable some features, which can not be exported without
  406. confusing older userspace tools. Since 2007/2008 all major
  407. distributions do not enable this option, and ship no tools which
  408. depend on the deprecated layout or this option.
  409. If you are using a new kernel on an older distribution, or use
  410. older userspace tools, you might need to say Y here. Do not say Y,
  411. if the original kernel, that came with your distribution, has
  412. this option set to N.
  413. config PROC_PID_CPUSET
  414. bool "Include legacy /proc/<pid>/cpuset file"
  415. depends on CPUSETS
  416. default y
  417. config RELAY
  418. bool "Kernel->user space relay support (formerly relayfs)"
  419. help
  420. This option enables support for relay interface support in
  421. certain file systems (such as debugfs).
  422. It is designed to provide an efficient mechanism for tools and
  423. facilities to relay large amounts of data from kernel space to
  424. user space.
  425. If unsure, say N.
  426. config NAMESPACES
  427. bool "Namespaces support" if EMBEDDED
  428. default !EMBEDDED
  429. help
  430. Provides the way to make tasks work with different objects using
  431. the same id. For example same IPC id may refer to different objects
  432. or same user id or pid may refer to different tasks when used in
  433. different namespaces.
  434. config UTS_NS
  435. bool "UTS namespace"
  436. depends on NAMESPACES
  437. help
  438. In this namespace tasks see different info provided with the
  439. uname() system call
  440. config IPC_NS
  441. bool "IPC namespace"
  442. depends on NAMESPACES && SYSVIPC
  443. help
  444. In this namespace tasks work with IPC ids which correspond to
  445. different IPC objects in different namespaces
  446. config USER_NS
  447. bool "User namespace (EXPERIMENTAL)"
  448. depends on NAMESPACES && EXPERIMENTAL
  449. help
  450. This allows containers, i.e. vservers, to use user namespaces
  451. to provide different user info for different servers.
  452. If unsure, say N.
  453. config PID_NS
  454. bool "PID Namespaces (EXPERIMENTAL)"
  455. default n
  456. depends on NAMESPACES && EXPERIMENTAL
  457. help
  458. Support process id namespaces. This allows having multiple
  459. process with the same pid as long as they are in different
  460. pid namespaces. This is a building block of containers.
  461. Unless you want to work with an experimental feature
  462. say N here.
  463. config BLK_DEV_INITRD
  464. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  465. depends on BROKEN || !FRV
  466. help
  467. The initial RAM filesystem is a ramfs which is loaded by the
  468. boot loader (loadlin or lilo) and that is mounted as root
  469. before the normal boot procedure. It is typically used to
  470. load modules needed to mount the "real" root file system,
  471. etc. See <file:Documentation/initrd.txt> for details.
  472. If RAM disk support (BLK_DEV_RAM) is also included, this
  473. also enables initial RAM disk (initrd) support and adds
  474. 15 Kbytes (more on some other architectures) to the kernel size.
  475. If unsure say Y.
  476. if BLK_DEV_INITRD
  477. source "usr/Kconfig"
  478. endif
  479. config CC_OPTIMIZE_FOR_SIZE
  480. bool "Optimize for size"
  481. default y
  482. help
  483. Enabling this option will pass "-Os" instead of "-O2" to gcc
  484. resulting in a smaller kernel.
  485. If unsure, say Y.
  486. config SYSCTL
  487. bool
  488. menuconfig EMBEDDED
  489. bool "Configure standard kernel features (for small systems)"
  490. help
  491. This option allows certain base kernel options and settings
  492. to be disabled or tweaked. This is for specialized
  493. environments which can tolerate a "non-standard" kernel.
  494. Only use this if you really know what you are doing.
  495. config UID16
  496. bool "Enable 16-bit UID system calls" if EMBEDDED
  497. depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
  498. default y
  499. help
  500. This enables the legacy 16-bit UID syscall wrappers.
  501. config SYSCTL_SYSCALL
  502. bool "Sysctl syscall support" if EMBEDDED
  503. default y
  504. select SYSCTL
  505. ---help---
  506. sys_sysctl uses binary paths that have been found challenging
  507. to properly maintain and use. The interface in /proc/sys
  508. using paths with ascii names is now the primary path to this
  509. information.
  510. Almost nothing using the binary sysctl interface so if you are
  511. trying to save some space it is probably safe to disable this,
  512. making your kernel marginally smaller.
  513. If unsure say Y here.
  514. config KALLSYMS
  515. bool "Load all symbols for debugging/ksymoops" if EMBEDDED
  516. default y
  517. help
  518. Say Y here to let the kernel print out symbolic crash information and
  519. symbolic stack backtraces. This increases the size of the kernel
  520. somewhat, as all symbols have to be loaded into the kernel image.
  521. config KALLSYMS_ALL
  522. bool "Include all symbols in kallsyms"
  523. depends on DEBUG_KERNEL && KALLSYMS
  524. help
  525. Normally kallsyms only contains the symbols of functions, for nicer
  526. OOPS messages. Some debuggers can use kallsyms for other
  527. symbols too: say Y here to include all symbols, if you need them
  528. and you don't care about adding 300k to the size of your kernel.
  529. Say N.
  530. config KALLSYMS_STRIP_GENERATED
  531. bool "Strip machine generated symbols from kallsyms"
  532. depends on KALLSYMS_ALL
  533. default y
  534. help
  535. Say N if you want kallsyms to retain even machine generated symbols.
  536. config KALLSYMS_EXTRA_PASS
  537. bool "Do an extra kallsyms pass"
  538. depends on KALLSYMS
  539. help
  540. If kallsyms is not working correctly, the build will fail with
  541. inconsistent kallsyms data. If that occurs, log a bug report and
  542. turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
  543. Always say N here unless you find a bug in kallsyms, which must be
  544. reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
  545. you wait for kallsyms to be fixed.
  546. config HOTPLUG
  547. bool "Support for hot-pluggable devices" if EMBEDDED
  548. default y
  549. help
  550. This option is provided for the case where no hotplug or uevent
  551. capabilities is wanted by the kernel. You should only consider
  552. disabling this option for embedded systems that do not use modules, a
  553. dynamic /dev tree, or dynamic device discovery. Just say Y.
  554. config PRINTK
  555. default y
  556. bool "Enable support for printk" if EMBEDDED
  557. help
  558. This option enables normal printk support. Removing it
  559. eliminates most of the message strings from the kernel image
  560. and makes the kernel more or less silent. As this makes it
  561. very difficult to diagnose system problems, saying N here is
  562. strongly discouraged.
  563. config BUG
  564. bool "BUG() support" if EMBEDDED
  565. default y
  566. help
  567. Disabling this option eliminates support for BUG and WARN, reducing
  568. the size of your kernel image and potentially quietly ignoring
  569. numerous fatal conditions. You should only consider disabling this
  570. option for embedded systems with no facilities for reporting errors.
  571. Just say Y.
  572. config ELF_CORE
  573. default y
  574. bool "Enable ELF core dumps" if EMBEDDED
  575. help
  576. Enable support for generating core dumps. Disabling saves about 4k.
  577. config PCSPKR_PLATFORM
  578. bool "Enable PC-Speaker support" if EMBEDDED
  579. depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
  580. default y
  581. help
  582. This option allows to disable the internal PC-Speaker
  583. support, saving some memory.
  584. config COMPAT_BRK
  585. bool "Disable heap randomization"
  586. default y
  587. help
  588. Randomizing heap placement makes heap exploits harder, but it
  589. also breaks ancient binaries (including anything libc5 based).
  590. This option changes the bootup default to heap randomization
  591. disabled, and can be overriden runtime by setting
  592. /proc/sys/kernel/randomize_va_space to 2.
  593. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  594. config BASE_FULL
  595. default y
  596. bool "Enable full-sized data structures for core" if EMBEDDED
  597. help
  598. Disabling this option reduces the size of miscellaneous core
  599. kernel data structures. This saves memory on small machines,
  600. but may reduce performance.
  601. config FUTEX
  602. bool "Enable futex support" if EMBEDDED
  603. default y
  604. select RT_MUTEXES
  605. help
  606. Disabling this option will cause the kernel to be built without
  607. support for "fast userspace mutexes". The resulting kernel may not
  608. run glibc-based applications correctly.
  609. config ANON_INODES
  610. bool
  611. config EPOLL
  612. bool "Enable eventpoll support" if EMBEDDED
  613. default y
  614. select ANON_INODES
  615. help
  616. Disabling this option will cause the kernel to be built without
  617. support for epoll family of system calls.
  618. config SIGNALFD
  619. bool "Enable signalfd() system call" if EMBEDDED
  620. select ANON_INODES
  621. default y
  622. help
  623. Enable the signalfd() system call that allows to receive signals
  624. on a file descriptor.
  625. If unsure, say Y.
  626. config TIMERFD
  627. bool "Enable timerfd() system call" if EMBEDDED
  628. select ANON_INODES
  629. default y
  630. help
  631. Enable the timerfd() system call that allows to receive timer
  632. events on a file descriptor.
  633. If unsure, say Y.
  634. config EVENTFD
  635. bool "Enable eventfd() system call" if EMBEDDED
  636. select ANON_INODES
  637. default y
  638. help
  639. Enable the eventfd() system call that allows to receive both
  640. kernel notification (ie. KAIO) or userspace notifications.
  641. If unsure, say Y.
  642. config SHMEM
  643. bool "Use full shmem filesystem" if EMBEDDED
  644. default y
  645. depends on MMU
  646. help
  647. The shmem is an internal filesystem used to manage shared memory.
  648. It is backed by swap and manages resource limits. It is also exported
  649. to userspace as tmpfs if TMPFS is enabled. Disabling this
  650. option replaces shmem and tmpfs with the much simpler ramfs code,
  651. which may be appropriate on small systems without swap.
  652. config AIO
  653. bool "Enable AIO support" if EMBEDDED
  654. default y
  655. help
  656. This option enables POSIX asynchronous I/O which may by used
  657. by some high performance threaded applications. Disabling
  658. this option saves about 7k.
  659. config VM_EVENT_COUNTERS
  660. default y
  661. bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
  662. help
  663. VM event counters are needed for event counts to be shown.
  664. This option allows the disabling of the VM event counters
  665. on EMBEDDED systems. /proc/vmstat will only show page counts
  666. if VM event counters are disabled.
  667. config PCI_QUIRKS
  668. default y
  669. bool "Enable PCI quirk workarounds" if EMBEDDED
  670. depends on PCI
  671. help
  672. This enables workarounds for various PCI chipset
  673. bugs/quirks. Disable this only if your target machine is
  674. unaffected by PCI quirks.
  675. config SLUB_DEBUG
  676. default y
  677. bool "Enable SLUB debugging support" if EMBEDDED
  678. depends on SLUB && SYSFS
  679. help
  680. SLUB has extensive debug support features. Disabling these can
  681. result in significant savings in code size. This also disables
  682. SLUB sysfs support. /sys/slab will not exist and there will be
  683. no support for cache validation etc.
  684. choice
  685. prompt "Choose SLAB allocator"
  686. default SLUB
  687. help
  688. This option allows to select a slab allocator.
  689. config SLAB
  690. bool "SLAB"
  691. help
  692. The regular slab allocator that is established and known to work
  693. well in all environments. It organizes cache hot objects in
  694. per cpu and per node queues.
  695. config SLUB
  696. bool "SLUB (Unqueued Allocator)"
  697. help
  698. SLUB is a slab allocator that minimizes cache line usage
  699. instead of managing queues of cached objects (SLAB approach).
  700. Per cpu caching is realized using slabs of objects instead
  701. of queues of objects. SLUB can use memory efficiently
  702. and has enhanced diagnostics. SLUB is the default choice for
  703. a slab allocator.
  704. config SLOB
  705. depends on EMBEDDED
  706. bool "SLOB (Simple Allocator)"
  707. help
  708. SLOB replaces the stock allocator with a drastically simpler
  709. allocator. SLOB is generally more space efficient but
  710. does not perform as well on large systems.
  711. endchoice
  712. config PROFILING
  713. bool "Profiling support (EXPERIMENTAL)"
  714. help
  715. Say Y here to enable the extended profiling support mechanisms used
  716. by profilers such as OProfile.
  717. #
  718. # Place an empty function call at each tracepoint site. Can be
  719. # dynamically changed for a probe function.
  720. #
  721. config TRACEPOINTS
  722. bool
  723. config MARKERS
  724. bool "Activate markers"
  725. depends on TRACEPOINTS
  726. help
  727. Place an empty function call at each marker site. Can be
  728. dynamically changed for a probe function.
  729. source "arch/Kconfig"
  730. endmenu # General setup
  731. config HAVE_GENERIC_DMA_COHERENT
  732. bool
  733. default n
  734. config SLABINFO
  735. bool
  736. depends on PROC_FS
  737. depends on SLAB || SLUB_DEBUG
  738. default y
  739. config RT_MUTEXES
  740. boolean
  741. select PLIST
  742. config BASE_SMALL
  743. int
  744. default 0 if BASE_FULL
  745. default 1 if !BASE_FULL
  746. menuconfig MODULES
  747. bool "Enable loadable module support"
  748. help
  749. Kernel modules are small pieces of compiled code which can
  750. be inserted in the running kernel, rather than being
  751. permanently built into the kernel. You use the "modprobe"
  752. tool to add (and sometimes remove) them. If you say Y here,
  753. many parts of the kernel can be built as modules (by
  754. answering M instead of Y where indicated): this is most
  755. useful for infrequently used options which are not required
  756. for booting. For more information, see the man pages for
  757. modprobe, lsmod, modinfo, insmod and rmmod.
  758. If you say Y here, you will need to run "make
  759. modules_install" to put the modules under /lib/modules/
  760. where modprobe can find them (you may need to be root to do
  761. this).
  762. If unsure, say Y.
  763. if MODULES
  764. config MODULE_FORCE_LOAD
  765. bool "Forced module loading"
  766. default n
  767. help
  768. Allow loading of modules without version information (ie. modprobe
  769. --force). Forced module loading sets the 'F' (forced) taint flag and
  770. is usually a really bad idea.
  771. config MODULE_UNLOAD
  772. bool "Module unloading"
  773. help
  774. Without this option you will not be able to unload any
  775. modules (note that some modules may not be unloadable
  776. anyway), which makes your kernel smaller, faster
  777. and simpler. If unsure, say Y.
  778. config MODULE_FORCE_UNLOAD
  779. bool "Forced module unloading"
  780. depends on MODULE_UNLOAD && EXPERIMENTAL
  781. help
  782. This option allows you to force a module to unload, even if the
  783. kernel believes it is unsafe: the kernel will remove the module
  784. without waiting for anyone to stop using it (using the -f option to
  785. rmmod). This is mainly for kernel developers and desperate users.
  786. If unsure, say N.
  787. config MODVERSIONS
  788. bool "Module versioning support"
  789. help
  790. Usually, you have to use modules compiled with your kernel.
  791. Saying Y here makes it sometimes possible to use modules
  792. compiled for different kernels, by adding enough information
  793. to the modules to (hopefully) spot any changes which would
  794. make them incompatible with the kernel you are running. If
  795. unsure, say N.
  796. config MODULE_SRCVERSION_ALL
  797. bool "Source checksum for all modules"
  798. help
  799. Modules which contain a MODULE_VERSION get an extra "srcversion"
  800. field inserted into their modinfo section, which contains a
  801. sum of the source files which made it. This helps maintainers
  802. see exactly which source was used to build a module (since
  803. others sometimes change the module source without updating
  804. the version). With this option, such a "srcversion" field
  805. will be created for all modules. If unsure, say N.
  806. endif # MODULES
  807. config INIT_ALL_POSSIBLE
  808. bool
  809. help
  810. Back when each arch used to define their own cpu_online_map and
  811. cpu_possible_map, some of them chose to initialize cpu_possible_map
  812. with all 1s, and others with all 0s. When they were centralised,
  813. it was better to provide this option than to break all the archs
  814. and have several arch maintainers persuing me down dark alleys.
  815. config STOP_MACHINE
  816. bool
  817. default y
  818. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  819. help
  820. Need stop_machine() primitive.
  821. source "block/Kconfig"
  822. config PREEMPT_NOTIFIERS
  823. bool
  824. choice
  825. prompt "RCU Implementation"
  826. default CLASSIC_RCU
  827. config CLASSIC_RCU
  828. bool "Classic RCU"
  829. help
  830. This option selects the classic RCU implementation that is
  831. designed for best read-side performance on non-realtime
  832. systems.
  833. Select this option if you are unsure.
  834. config TREE_RCU
  835. bool "Tree-based hierarchical RCU"
  836. help
  837. This option selects the RCU implementation that is
  838. designed for very large SMP system with hundreds or
  839. thousands of CPUs.
  840. config PREEMPT_RCU
  841. bool "Preemptible RCU"
  842. depends on PREEMPT
  843. help
  844. This option reduces the latency of the kernel by making certain
  845. RCU sections preemptible. Normally RCU code is non-preemptible, if
  846. this option is selected then read-only RCU sections become
  847. preemptible. This helps latency, but may expose bugs due to
  848. now-naive assumptions about each RCU read-side critical section
  849. remaining on a given CPU through its execution.
  850. endchoice
  851. config RCU_TRACE
  852. bool "Enable tracing for RCU"
  853. depends on TREE_RCU || PREEMPT_RCU
  854. help
  855. This option provides tracing in RCU which presents stats
  856. in debugfs for debugging RCU implementation.
  857. Say Y here if you want to enable RCU tracing
  858. Say N if you are unsure.
  859. config RCU_FANOUT
  860. int "Tree-based hierarchical RCU fanout value"
  861. range 2 64 if 64BIT
  862. range 2 32 if !64BIT
  863. depends on TREE_RCU
  864. default 64 if 64BIT
  865. default 32 if !64BIT
  866. help
  867. This option controls the fanout of hierarchical implementations
  868. of RCU, allowing RCU to work efficiently on machines with
  869. large numbers of CPUs. This value must be at least the cube
  870. root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
  871. systems and up to 262,144 for 64-bit systems.
  872. Select a specific number if testing RCU itself.
  873. Take the default if unsure.
  874. config RCU_FANOUT_EXACT
  875. bool "Disable tree-based hierarchical RCU auto-balancing"
  876. depends on TREE_RCU
  877. default n
  878. help
  879. This option forces use of the exact RCU_FANOUT value specified,
  880. regardless of imbalances in the hierarchy. This is useful for
  881. testing RCU itself, and might one day be useful on systems with
  882. strong NUMA behavior.
  883. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  884. Say N if unsure.
  885. config TREE_RCU_TRACE
  886. def_bool RCU_TRACE && TREE_RCU
  887. select DEBUG_FS
  888. help
  889. This option provides tracing for the TREE_RCU implementation,
  890. permitting Makefile to trivially select kernel/rcutree_trace.c.
  891. config PREEMPT_RCU_TRACE
  892. def_bool RCU_TRACE && PREEMPT_RCU
  893. select DEBUG_FS
  894. help
  895. This option provides tracing for the PREEMPT_RCU implementation,
  896. permitting Makefile to trivially select kernel/rcupreempt_trace.c.