Kconfig 32 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 drivers that have been replaced by something else, and/or are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. config CGROUPS
  234. bool "Control Group support"
  235. help
  236. This option will let you use process cgroup subsystems
  237. such as Cpusets
  238. Say N if unsure.
  239. config CGROUP_DEBUG
  240. bool "Example debug cgroup subsystem"
  241. depends on CGROUPS
  242. default n
  243. help
  244. This option enables a simple cgroup subsystem that
  245. exports useful debugging information about the cgroups
  246. framework
  247. Say N if unsure
  248. config CGROUP_NS
  249. bool "Namespace cgroup subsystem"
  250. depends on CGROUPS
  251. help
  252. Provides a simple namespace cgroup subsystem to
  253. provide hierarchical naming of sets of namespaces,
  254. for instance virtual servers and checkpoint/restart
  255. jobs.
  256. config CGROUP_FREEZER
  257. bool "control group freezer subsystem"
  258. depends on CGROUPS
  259. help
  260. Provides a way to freeze and unfreeze all tasks in a
  261. cgroup.
  262. config CGROUP_DEVICE
  263. bool "Device controller for cgroups"
  264. depends on CGROUPS && EXPERIMENTAL
  265. help
  266. Provides a cgroup implementing whitelists for devices which
  267. a process in the cgroup can mknod or open.
  268. config CPUSETS
  269. bool "Cpuset support"
  270. depends on SMP && CGROUPS
  271. help
  272. This option will let you create and manage CPUSETs which
  273. allow dynamically partitioning a system into sets of CPUs and
  274. Memory Nodes and assigning tasks to run only within those sets.
  275. This is primarily useful on large SMP or NUMA systems.
  276. Say N if unsure.
  277. #
  278. # Architectures with an unreliable sched_clock() should select this:
  279. #
  280. config HAVE_UNSTABLE_SCHED_CLOCK
  281. bool
  282. config GROUP_SCHED
  283. bool "Group CPU scheduler"
  284. depends on EXPERIMENTAL
  285. default n
  286. help
  287. This feature lets CPU scheduler recognize task groups and control CPU
  288. bandwidth allocation to such task groups.
  289. config FAIR_GROUP_SCHED
  290. bool "Group scheduling for SCHED_OTHER"
  291. depends on GROUP_SCHED
  292. default GROUP_SCHED
  293. config RT_GROUP_SCHED
  294. bool "Group scheduling for SCHED_RR/FIFO"
  295. depends on EXPERIMENTAL
  296. depends on GROUP_SCHED
  297. default n
  298. help
  299. This feature lets you explicitly allocate real CPU bandwidth
  300. to users or control groups (depending on the "Basis for grouping tasks"
  301. setting below. If enabled, it will also make it impossible to
  302. schedule realtime tasks for non-root users until you allocate
  303. realtime bandwidth for them.
  304. See Documentation/scheduler/sched-rt-group.txt for more information.
  305. choice
  306. depends on GROUP_SCHED
  307. prompt "Basis for grouping tasks"
  308. default USER_SCHED
  309. config USER_SCHED
  310. bool "user id"
  311. help
  312. This option will choose userid as the basis for grouping
  313. tasks, thus providing equal CPU bandwidth to each user.
  314. config CGROUP_SCHED
  315. bool "Control groups"
  316. depends on CGROUPS
  317. help
  318. This option allows you to create arbitrary task groups
  319. using the "cgroup" pseudo filesystem and control
  320. the cpu bandwidth allocated to each such task group.
  321. Refer to Documentation/cgroups.txt for more information
  322. on "cgroup" pseudo filesystem.
  323. endchoice
  324. config CGROUP_CPUACCT
  325. bool "Simple CPU accounting cgroup subsystem"
  326. depends on CGROUPS
  327. help
  328. Provides a simple Resource Controller for monitoring the
  329. total CPU consumed by the tasks in a cgroup
  330. config RESOURCE_COUNTERS
  331. bool "Resource counters"
  332. help
  333. This option enables controller independent resource accounting
  334. infrastructure that works with cgroups
  335. depends on CGROUPS
  336. config MM_OWNER
  337. bool
  338. config CGROUP_MEM_RES_CTLR
  339. bool "Memory Resource Controller for Control Groups"
  340. depends on CGROUPS && RESOURCE_COUNTERS
  341. select MM_OWNER
  342. help
  343. Provides a memory resource controller that manages both anonymous
  344. memory and page cache. (See Documentation/controllers/memory.txt)
  345. Note that setting this option increases fixed memory overhead
  346. associated with each page of memory in the system. By this,
  347. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  348. usage tracking struct at boot. Total amount of this is printed out
  349. at boot.
  350. Only enable when you're ok with these trade offs and really
  351. sure you need the memory resource controller. Even when you enable
  352. this, you can set "cgroup_disable=memory" at your boot option to
  353. disable memory resource controller and you can avoid overheads.
  354. (and lose benefits of memory resource contoller)
  355. This config option also selects MM_OWNER config option, which
  356. could in turn add some fork/exit overhead.
  357. config SYSFS_DEPRECATED
  358. bool
  359. config SYSFS_DEPRECATED_V2
  360. bool "Create deprecated sysfs files"
  361. depends on SYSFS
  362. default y
  363. select SYSFS_DEPRECATED
  364. help
  365. This option creates deprecated symlinks such as the
  366. "device"-link, the <subsystem>:<name>-link, and the
  367. "bus"-link. It may also add deprecated key in the
  368. uevent environment.
  369. None of these features or values should be used today, as
  370. they export driver core implementation details to userspace
  371. or export properties which can't be kept stable across kernel
  372. releases.
  373. If enabled, this option will also move any device structures
  374. that belong to a class, back into the /sys/class hierarchy, in
  375. order to support older versions of udev and some userspace
  376. programs.
  377. If you are using a distro with the most recent userspace
  378. packages, it should be safe to say N here.
  379. config PROC_PID_CPUSET
  380. bool "Include legacy /proc/<pid>/cpuset file"
  381. depends on CPUSETS
  382. default y
  383. config RELAY
  384. bool "Kernel->user space relay support (formerly relayfs)"
  385. help
  386. This option enables support for relay interface support in
  387. certain file systems (such as debugfs).
  388. It is designed to provide an efficient mechanism for tools and
  389. facilities to relay large amounts of data from kernel space to
  390. user space.
  391. If unsure, say N.
  392. config NAMESPACES
  393. bool "Namespaces support" if EMBEDDED
  394. default !EMBEDDED
  395. help
  396. Provides the way to make tasks work with different objects using
  397. the same id. For example same IPC id may refer to different objects
  398. or same user id or pid may refer to different tasks when used in
  399. different namespaces.
  400. config UTS_NS
  401. bool "UTS namespace"
  402. depends on NAMESPACES
  403. help
  404. In this namespace tasks see different info provided with the
  405. uname() system call
  406. config IPC_NS
  407. bool "IPC namespace"
  408. depends on NAMESPACES && SYSVIPC
  409. help
  410. In this namespace tasks work with IPC ids which correspond to
  411. different IPC objects in different namespaces
  412. config USER_NS
  413. bool "User namespace (EXPERIMENTAL)"
  414. depends on NAMESPACES && EXPERIMENTAL
  415. help
  416. This allows containers, i.e. vservers, to use user namespaces
  417. to provide different user info for different servers.
  418. If unsure, say N.
  419. config PID_NS
  420. bool "PID Namespaces (EXPERIMENTAL)"
  421. default n
  422. depends on NAMESPACES && EXPERIMENTAL
  423. help
  424. Support process id namespaces. This allows having multiple
  425. process with the same pid as long as they are in different
  426. pid namespaces. This is a building block of containers.
  427. Unless you want to work with an experimental feature
  428. say N here.
  429. config BLK_DEV_INITRD
  430. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  431. depends on BROKEN || !FRV
  432. help
  433. The initial RAM filesystem is a ramfs which is loaded by the
  434. boot loader (loadlin or lilo) and that is mounted as root
  435. before the normal boot procedure. It is typically used to
  436. load modules needed to mount the "real" root file system,
  437. etc. See <file:Documentation/initrd.txt> for details.
  438. If RAM disk support (BLK_DEV_RAM) is also included, this
  439. also enables initial RAM disk (initrd) support and adds
  440. 15 Kbytes (more on some other architectures) to the kernel size.
  441. If unsure say Y.
  442. if BLK_DEV_INITRD
  443. source "usr/Kconfig"
  444. endif
  445. config CC_OPTIMIZE_FOR_SIZE
  446. bool "Optimize for size"
  447. default y
  448. help
  449. Enabling this option will pass "-Os" instead of "-O2" to gcc
  450. resulting in a smaller kernel.
  451. If unsure, say Y.
  452. config SYSCTL
  453. bool
  454. menuconfig EMBEDDED
  455. bool "Configure standard kernel features (for small systems)"
  456. help
  457. This option allows certain base kernel options and settings
  458. to be disabled or tweaked. This is for specialized
  459. environments which can tolerate a "non-standard" kernel.
  460. Only use this if you really know what you are doing.
  461. config UID16
  462. bool "Enable 16-bit UID system calls" if EMBEDDED
  463. depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
  464. default y
  465. help
  466. This enables the legacy 16-bit UID syscall wrappers.
  467. config SYSCTL_SYSCALL
  468. bool "Sysctl syscall support" if EMBEDDED
  469. default y
  470. select SYSCTL
  471. ---help---
  472. sys_sysctl uses binary paths that have been found challenging
  473. to properly maintain and use. The interface in /proc/sys
  474. using paths with ascii names is now the primary path to this
  475. information.
  476. Almost nothing using the binary sysctl interface so if you are
  477. trying to save some space it is probably safe to disable this,
  478. making your kernel marginally smaller.
  479. If unsure say Y here.
  480. config KALLSYMS
  481. bool "Load all symbols for debugging/ksymoops" if EMBEDDED
  482. default y
  483. help
  484. Say Y here to let the kernel print out symbolic crash information and
  485. symbolic stack backtraces. This increases the size of the kernel
  486. somewhat, as all symbols have to be loaded into the kernel image.
  487. config KALLSYMS_ALL
  488. bool "Include all symbols in kallsyms"
  489. depends on DEBUG_KERNEL && KALLSYMS
  490. help
  491. Normally kallsyms only contains the symbols of functions, for nicer
  492. OOPS messages. Some debuggers can use kallsyms for other
  493. symbols too: say Y here to include all symbols, if you need them
  494. and you don't care about adding 300k to the size of your kernel.
  495. Say N.
  496. config KALLSYMS_STRIP_GENERATED
  497. bool "Strip machine generated symbols from kallsyms"
  498. depends on KALLSYMS_ALL
  499. default y
  500. help
  501. Say N if you want kallsyms to retain even machine generated symbols.
  502. config KALLSYMS_EXTRA_PASS
  503. bool "Do an extra kallsyms pass"
  504. depends on KALLSYMS
  505. help
  506. If kallsyms is not working correctly, the build will fail with
  507. inconsistent kallsyms data. If that occurs, log a bug report and
  508. turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
  509. Always say N here unless you find a bug in kallsyms, which must be
  510. reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
  511. you wait for kallsyms to be fixed.
  512. config HOTPLUG
  513. bool "Support for hot-pluggable devices" if EMBEDDED
  514. default y
  515. help
  516. This option is provided for the case where no hotplug or uevent
  517. capabilities is wanted by the kernel. You should only consider
  518. disabling this option for embedded systems that do not use modules, a
  519. dynamic /dev tree, or dynamic device discovery. Just say Y.
  520. config PRINTK
  521. default y
  522. bool "Enable support for printk" if EMBEDDED
  523. help
  524. This option enables normal printk support. Removing it
  525. eliminates most of the message strings from the kernel image
  526. and makes the kernel more or less silent. As this makes it
  527. very difficult to diagnose system problems, saying N here is
  528. strongly discouraged.
  529. config BUG
  530. bool "BUG() support" if EMBEDDED
  531. default y
  532. help
  533. Disabling this option eliminates support for BUG and WARN, reducing
  534. the size of your kernel image and potentially quietly ignoring
  535. numerous fatal conditions. You should only consider disabling this
  536. option for embedded systems with no facilities for reporting errors.
  537. Just say Y.
  538. config ELF_CORE
  539. default y
  540. bool "Enable ELF core dumps" if EMBEDDED
  541. help
  542. Enable support for generating core dumps. Disabling saves about 4k.
  543. config PCSPKR_PLATFORM
  544. bool "Enable PC-Speaker support" if EMBEDDED
  545. depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
  546. default y
  547. help
  548. This option allows to disable the internal PC-Speaker
  549. support, saving some memory.
  550. config COMPAT_BRK
  551. bool "Disable heap randomization"
  552. default y
  553. help
  554. Randomizing heap placement makes heap exploits harder, but it
  555. also breaks ancient binaries (including anything libc5 based).
  556. This option changes the bootup default to heap randomization
  557. disabled, and can be overriden runtime by setting
  558. /proc/sys/kernel/randomize_va_space to 2.
  559. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  560. config BASE_FULL
  561. default y
  562. bool "Enable full-sized data structures for core" if EMBEDDED
  563. help
  564. Disabling this option reduces the size of miscellaneous core
  565. kernel data structures. This saves memory on small machines,
  566. but may reduce performance.
  567. config FUTEX
  568. bool "Enable futex support" if EMBEDDED
  569. default y
  570. select RT_MUTEXES
  571. help
  572. Disabling this option will cause the kernel to be built without
  573. support for "fast userspace mutexes". The resulting kernel may not
  574. run glibc-based applications correctly.
  575. config ANON_INODES
  576. bool
  577. config EPOLL
  578. bool "Enable eventpoll support" if EMBEDDED
  579. default y
  580. select ANON_INODES
  581. help
  582. Disabling this option will cause the kernel to be built without
  583. support for epoll family of system calls.
  584. config SIGNALFD
  585. bool "Enable signalfd() system call" if EMBEDDED
  586. select ANON_INODES
  587. default y
  588. help
  589. Enable the signalfd() system call that allows to receive signals
  590. on a file descriptor.
  591. If unsure, say Y.
  592. config TIMERFD
  593. bool "Enable timerfd() system call" if EMBEDDED
  594. select ANON_INODES
  595. default y
  596. help
  597. Enable the timerfd() system call that allows to receive timer
  598. events on a file descriptor.
  599. If unsure, say Y.
  600. config EVENTFD
  601. bool "Enable eventfd() system call" if EMBEDDED
  602. select ANON_INODES
  603. default y
  604. help
  605. Enable the eventfd() system call that allows to receive both
  606. kernel notification (ie. KAIO) or userspace notifications.
  607. If unsure, say Y.
  608. config SHMEM
  609. bool "Use full shmem filesystem" if EMBEDDED
  610. default y
  611. depends on MMU
  612. help
  613. The shmem is an internal filesystem used to manage shared memory.
  614. It is backed by swap and manages resource limits. It is also exported
  615. to userspace as tmpfs if TMPFS is enabled. Disabling this
  616. option replaces shmem and tmpfs with the much simpler ramfs code,
  617. which may be appropriate on small systems without swap.
  618. config AIO
  619. bool "Enable AIO support" if EMBEDDED
  620. default y
  621. help
  622. This option enables POSIX asynchronous I/O which may by used
  623. by some high performance threaded applications. Disabling
  624. this option saves about 7k.
  625. config VM_EVENT_COUNTERS
  626. default y
  627. bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
  628. help
  629. VM event counters are needed for event counts to be shown.
  630. This option allows the disabling of the VM event counters
  631. on EMBEDDED systems. /proc/vmstat will only show page counts
  632. if VM event counters are disabled.
  633. config PCI_QUIRKS
  634. default y
  635. bool "Enable PCI quirk workarounds" if EMBEDDED
  636. depends on PCI
  637. help
  638. This enables workarounds for various PCI chipset
  639. bugs/quirks. Disable this only if your target machine is
  640. unaffected by PCI quirks.
  641. config SLUB_DEBUG
  642. default y
  643. bool "Enable SLUB debugging support" if EMBEDDED
  644. depends on SLUB && SYSFS
  645. help
  646. SLUB has extensive debug support features. Disabling these can
  647. result in significant savings in code size. This also disables
  648. SLUB sysfs support. /sys/slab will not exist and there will be
  649. no support for cache validation etc.
  650. choice
  651. prompt "Choose SLAB allocator"
  652. default SLUB
  653. help
  654. This option allows to select a slab allocator.
  655. config SLAB
  656. bool "SLAB"
  657. help
  658. The regular slab allocator that is established and known to work
  659. well in all environments. It organizes cache hot objects in
  660. per cpu and per node queues.
  661. config SLUB
  662. bool "SLUB (Unqueued Allocator)"
  663. help
  664. SLUB is a slab allocator that minimizes cache line usage
  665. instead of managing queues of cached objects (SLAB approach).
  666. Per cpu caching is realized using slabs of objects instead
  667. of queues of objects. SLUB can use memory efficiently
  668. and has enhanced diagnostics. SLUB is the default choice for
  669. a slab allocator.
  670. config SLOB
  671. depends on EMBEDDED
  672. bool "SLOB (Simple Allocator)"
  673. help
  674. SLOB replaces the stock allocator with a drastically simpler
  675. allocator. SLOB is generally more space efficient but
  676. does not perform as well on large systems.
  677. endchoice
  678. config PROFILING
  679. bool "Profiling support (EXPERIMENTAL)"
  680. help
  681. Say Y here to enable the extended profiling support mechanisms used
  682. by profilers such as OProfile.
  683. #
  684. # Place an empty function call at each tracepoint site. Can be
  685. # dynamically changed for a probe function.
  686. #
  687. config TRACEPOINTS
  688. bool
  689. config MARKERS
  690. bool "Activate markers"
  691. depends on TRACEPOINTS
  692. help
  693. Place an empty function call at each marker site. Can be
  694. dynamically changed for a probe function.
  695. source "arch/Kconfig"
  696. endmenu # General setup
  697. config HAVE_GENERIC_DMA_COHERENT
  698. bool
  699. default n
  700. config SLABINFO
  701. bool
  702. depends on PROC_FS
  703. depends on SLAB || SLUB_DEBUG
  704. default y
  705. config RT_MUTEXES
  706. boolean
  707. select PLIST
  708. config TINY_SHMEM
  709. default !SHMEM
  710. bool
  711. config BASE_SMALL
  712. int
  713. default 0 if BASE_FULL
  714. default 1 if !BASE_FULL
  715. menuconfig MODULES
  716. bool "Enable loadable module support"
  717. help
  718. Kernel modules are small pieces of compiled code which can
  719. be inserted in the running kernel, rather than being
  720. permanently built into the kernel. You use the "modprobe"
  721. tool to add (and sometimes remove) them. If you say Y here,
  722. many parts of the kernel can be built as modules (by
  723. answering M instead of Y where indicated): this is most
  724. useful for infrequently used options which are not required
  725. for booting. For more information, see the man pages for
  726. modprobe, lsmod, modinfo, insmod and rmmod.
  727. If you say Y here, you will need to run "make
  728. modules_install" to put the modules under /lib/modules/
  729. where modprobe can find them (you may need to be root to do
  730. this).
  731. If unsure, say Y.
  732. if MODULES
  733. config MODULE_FORCE_LOAD
  734. bool "Forced module loading"
  735. default n
  736. help
  737. Allow loading of modules without version information (ie. modprobe
  738. --force). Forced module loading sets the 'F' (forced) taint flag and
  739. is usually a really bad idea.
  740. config MODULE_UNLOAD
  741. bool "Module unloading"
  742. help
  743. Without this option you will not be able to unload any
  744. modules (note that some modules may not be unloadable
  745. anyway), which makes your kernel smaller, faster
  746. and simpler. If unsure, say Y.
  747. config MODULE_FORCE_UNLOAD
  748. bool "Forced module unloading"
  749. depends on MODULE_UNLOAD && EXPERIMENTAL
  750. help
  751. This option allows you to force a module to unload, even if the
  752. kernel believes it is unsafe: the kernel will remove the module
  753. without waiting for anyone to stop using it (using the -f option to
  754. rmmod). This is mainly for kernel developers and desperate users.
  755. If unsure, say N.
  756. config MODVERSIONS
  757. bool "Module versioning support"
  758. help
  759. Usually, you have to use modules compiled with your kernel.
  760. Saying Y here makes it sometimes possible to use modules
  761. compiled for different kernels, by adding enough information
  762. to the modules to (hopefully) spot any changes which would
  763. make them incompatible with the kernel you are running. If
  764. unsure, say N.
  765. config MODULE_SRCVERSION_ALL
  766. bool "Source checksum for all modules"
  767. help
  768. Modules which contain a MODULE_VERSION get an extra "srcversion"
  769. field inserted into their modinfo section, which contains a
  770. sum of the source files which made it. This helps maintainers
  771. see exactly which source was used to build a module (since
  772. others sometimes change the module source without updating
  773. the version). With this option, such a "srcversion" field
  774. will be created for all modules. If unsure, say N.
  775. config KMOD
  776. def_bool y
  777. help
  778. This is being removed soon. These days, CONFIG_MODULES
  779. implies CONFIG_KMOD, so use that instead.
  780. endif # MODULES
  781. config INIT_ALL_POSSIBLE
  782. bool
  783. help
  784. Back when each arch used to define their own cpu_online_map and
  785. cpu_possible_map, some of them chose to initialize cpu_possible_map
  786. with all 1s, and others with all 0s. When they were centralised,
  787. it was better to provide this option than to break all the archs
  788. and have several arch maintainers persuing me down dark alleys.
  789. config STOP_MACHINE
  790. bool
  791. default y
  792. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  793. help
  794. Need stop_machine() primitive.
  795. source "block/Kconfig"
  796. config PREEMPT_NOTIFIERS
  797. bool
  798. choice
  799. prompt "RCU Implementation"
  800. default CLASSIC_RCU
  801. config CLASSIC_RCU
  802. bool "Classic RCU"
  803. help
  804. This option selects the classic RCU implementation that is
  805. designed for best read-side performance on non-realtime
  806. systems.
  807. Select this option if you are unsure.
  808. config TREE_RCU
  809. bool "Tree-based hierarchical RCU"
  810. help
  811. This option selects the RCU implementation that is
  812. designed for very large SMP system with hundreds or
  813. thousands of CPUs.
  814. config PREEMPT_RCU
  815. bool "Preemptible RCU"
  816. depends on PREEMPT
  817. help
  818. This option reduces the latency of the kernel by making certain
  819. RCU sections preemptible. Normally RCU code is non-preemptible, if
  820. this option is selected then read-only RCU sections become
  821. preemptible. This helps latency, but may expose bugs due to
  822. now-naive assumptions about each RCU read-side critical section
  823. remaining on a given CPU through its execution.
  824. endchoice
  825. config RCU_TRACE
  826. bool "Enable tracing for RCU"
  827. depends on TREE_RCU || PREEMPT_RCU
  828. help
  829. This option provides tracing in RCU which presents stats
  830. in debugfs for debugging RCU implementation.
  831. Say Y here if you want to enable RCU tracing
  832. Say N if you are unsure.
  833. config RCU_FANOUT
  834. int "Tree-based hierarchical RCU fanout value"
  835. range 2 64 if 64BIT
  836. range 2 32 if !64BIT
  837. depends on TREE_RCU
  838. default 64 if 64BIT
  839. default 32 if !64BIT
  840. help
  841. This option controls the fanout of hierarchical implementations
  842. of RCU, allowing RCU to work efficiently on machines with
  843. large numbers of CPUs. This value must be at least the cube
  844. root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
  845. systems and up to 262,144 for 64-bit systems.
  846. Select a specific number if testing RCU itself.
  847. Take the default if unsure.
  848. config RCU_FANOUT_EXACT
  849. bool "Disable tree-based hierarchical RCU auto-balancing"
  850. depends on TREE_RCU
  851. default n
  852. help
  853. This option forces use of the exact RCU_FANOUT value specified,
  854. regardless of imbalances in the hierarchy. This is useful for
  855. testing RCU itself, and might one day be useful on systems with
  856. strong NUMA behavior.
  857. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  858. Say N if unsure.
  859. config TREE_RCU_TRACE
  860. def_bool RCU_TRACE && TREE_RCU
  861. select DEBUG_FS
  862. help
  863. This option provides tracing for the TREE_RCU implementation,
  864. permitting Makefile to trivially select kernel/rcutree_trace.c.
  865. config PREEMPT_RCU_TRACE
  866. def_bool RCU_TRACE && PREEMPT_RCU
  867. select DEBUG_FS
  868. help
  869. This option provides tracing for the PREEMPT_RCU implementation,
  870. permitting Makefile to trivially select kernel/rcupreempt_trace.c.