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 drivers that have been replaced by something else, and/or are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. menu "RCU Subsystem"
  204. choice
  205. prompt "RCU Implementation"
  206. default CLASSIC_RCU
  207. config CLASSIC_RCU
  208. bool "Classic RCU"
  209. help
  210. This option selects the classic RCU implementation that is
  211. designed for best read-side performance on non-realtime
  212. systems.
  213. Select this option if you are unsure.
  214. config TREE_RCU
  215. bool "Tree-based hierarchical RCU"
  216. help
  217. This option selects the RCU implementation that is
  218. designed for very large SMP system with hundreds or
  219. thousands of CPUs.
  220. config PREEMPT_RCU
  221. bool "Preemptible RCU"
  222. depends on PREEMPT
  223. help
  224. This option reduces the latency of the kernel by making certain
  225. RCU sections preemptible. Normally RCU code is non-preemptible, if
  226. this option is selected then read-only RCU sections become
  227. preemptible. This helps latency, but may expose bugs due to
  228. now-naive assumptions about each RCU read-side critical section
  229. remaining on a given CPU through its execution.
  230. endchoice
  231. config RCU_TRACE
  232. bool "Enable tracing for RCU"
  233. depends on TREE_RCU || PREEMPT_RCU
  234. help
  235. This option provides tracing in RCU which presents stats
  236. in debugfs for debugging RCU implementation.
  237. Say Y here if you want to enable RCU tracing
  238. Say N if you are unsure.
  239. config RCU_FANOUT
  240. int "Tree-based hierarchical RCU fanout value"
  241. range 2 64 if 64BIT
  242. range 2 32 if !64BIT
  243. depends on TREE_RCU
  244. default 64 if 64BIT
  245. default 32 if !64BIT
  246. help
  247. This option controls the fanout of hierarchical implementations
  248. of RCU, allowing RCU to work efficiently on machines with
  249. large numbers of CPUs. This value must be at least the cube
  250. root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
  251. systems and up to 262,144 for 64-bit systems.
  252. Select a specific number if testing RCU itself.
  253. Take the default if unsure.
  254. config RCU_FANOUT_EXACT
  255. bool "Disable tree-based hierarchical RCU auto-balancing"
  256. depends on TREE_RCU
  257. default n
  258. help
  259. This option forces use of the exact RCU_FANOUT value specified,
  260. regardless of imbalances in the hierarchy. This is useful for
  261. testing RCU itself, and might one day be useful on systems with
  262. strong NUMA behavior.
  263. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  264. Say N if unsure.
  265. config TREE_RCU_TRACE
  266. def_bool RCU_TRACE && TREE_RCU
  267. select DEBUG_FS
  268. help
  269. This option provides tracing for the TREE_RCU implementation,
  270. permitting Makefile to trivially select kernel/rcutree_trace.c.
  271. config PREEMPT_RCU_TRACE
  272. def_bool RCU_TRACE && PREEMPT_RCU
  273. select DEBUG_FS
  274. help
  275. This option provides tracing for the PREEMPT_RCU implementation,
  276. permitting Makefile to trivially select kernel/rcupreempt_trace.c.
  277. endmenu # "RCU Subsystem"
  278. config IKCONFIG
  279. tristate "Kernel .config support"
  280. ---help---
  281. This option enables the complete Linux kernel ".config" file
  282. contents to be saved in the kernel. It provides documentation
  283. of which kernel options are used in a running kernel or in an
  284. on-disk kernel. This information can be extracted from the kernel
  285. image file with the script scripts/extract-ikconfig and used as
  286. input to rebuild the current kernel or to build another kernel.
  287. It can also be extracted from a running kernel by reading
  288. /proc/config.gz if enabled (below).
  289. config IKCONFIG_PROC
  290. bool "Enable access to .config through /proc/config.gz"
  291. depends on IKCONFIG && PROC_FS
  292. ---help---
  293. This option enables access to the kernel configuration file
  294. through /proc/config.gz.
  295. config LOG_BUF_SHIFT
  296. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  297. range 12 21
  298. default 17
  299. help
  300. Select kernel log buffer size as a power of 2.
  301. Examples:
  302. 17 => 128 KB
  303. 16 => 64 KB
  304. 15 => 32 KB
  305. 14 => 16 KB
  306. 13 => 8 KB
  307. 12 => 4 KB
  308. #
  309. # Architectures with an unreliable sched_clock() should select this:
  310. #
  311. config HAVE_UNSTABLE_SCHED_CLOCK
  312. bool
  313. config GROUP_SCHED
  314. bool "Group CPU scheduler"
  315. depends on EXPERIMENTAL
  316. default n
  317. help
  318. This feature lets CPU scheduler recognize task groups and control CPU
  319. bandwidth allocation to such task groups.
  320. In order to create a group from arbitrary set of processes, use
  321. CONFIG_CGROUPS. (See Control Group support.)
  322. config FAIR_GROUP_SCHED
  323. bool "Group scheduling for SCHED_OTHER"
  324. depends on GROUP_SCHED
  325. default GROUP_SCHED
  326. config RT_GROUP_SCHED
  327. bool "Group scheduling for SCHED_RR/FIFO"
  328. depends on EXPERIMENTAL
  329. depends on GROUP_SCHED
  330. default n
  331. help
  332. This feature lets you explicitly allocate real CPU bandwidth
  333. to users or control groups (depending on the "Basis for grouping tasks"
  334. setting below. If enabled, it will also make it impossible to
  335. schedule realtime tasks for non-root users until you allocate
  336. realtime bandwidth for them.
  337. See Documentation/scheduler/sched-rt-group.txt for more information.
  338. choice
  339. depends on GROUP_SCHED
  340. prompt "Basis for grouping tasks"
  341. default USER_SCHED
  342. config USER_SCHED
  343. bool "user id"
  344. help
  345. This option will choose userid as the basis for grouping
  346. tasks, thus providing equal CPU bandwidth to each user.
  347. config CGROUP_SCHED
  348. bool "Control groups"
  349. depends on CGROUPS
  350. help
  351. This option allows you to create arbitrary task groups
  352. using the "cgroup" pseudo filesystem and control
  353. the cpu bandwidth allocated to each such task group.
  354. Refer to Documentation/cgroups/cgroups.txt for more
  355. information on "cgroup" pseudo filesystem.
  356. endchoice
  357. menuconfig CGROUPS
  358. boolean "Control Group support"
  359. help
  360. This option adds support for grouping sets of processes together, for
  361. use with process control subsystems such as Cpusets, CFS, memory
  362. controls or device isolation.
  363. See
  364. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  365. - Documentation/cgroups/ (features for grouping, isolation
  366. and resource control)
  367. Say N if unsure.
  368. if CGROUPS
  369. config CGROUP_DEBUG
  370. bool "Example debug cgroup subsystem"
  371. depends on CGROUPS
  372. default n
  373. help
  374. This option enables a simple cgroup subsystem that
  375. exports useful debugging information about the cgroups
  376. framework.
  377. Say N if unsure.
  378. config CGROUP_NS
  379. bool "Namespace cgroup subsystem"
  380. depends on CGROUPS
  381. help
  382. Provides a simple namespace cgroup subsystem to
  383. provide hierarchical naming of sets of namespaces,
  384. for instance virtual servers and checkpoint/restart
  385. jobs.
  386. config CGROUP_FREEZER
  387. bool "Freezer cgroup subsystem"
  388. depends on CGROUPS
  389. help
  390. Provides a way to freeze and unfreeze all tasks in a
  391. cgroup.
  392. config CGROUP_DEVICE
  393. bool "Device controller for cgroups"
  394. depends on CGROUPS && EXPERIMENTAL
  395. help
  396. Provides a cgroup implementing whitelists for devices which
  397. a process in the cgroup can mknod or open.
  398. config CPUSETS
  399. bool "Cpuset support"
  400. depends on SMP && CGROUPS
  401. help
  402. This option will let you create and manage CPUSETs which
  403. allow dynamically partitioning a system into sets of CPUs and
  404. Memory Nodes and assigning tasks to run only within those sets.
  405. This is primarily useful on large SMP or NUMA systems.
  406. Say N if unsure.
  407. config PROC_PID_CPUSET
  408. bool "Include legacy /proc/<pid>/cpuset file"
  409. depends on CPUSETS
  410. default y
  411. config CGROUP_CPUACCT
  412. bool "Simple CPU accounting cgroup subsystem"
  413. depends on CGROUPS
  414. help
  415. Provides a simple Resource Controller for monitoring the
  416. total CPU consumed by the tasks in a cgroup.
  417. config RESOURCE_COUNTERS
  418. bool "Resource counters"
  419. help
  420. This option enables controller independent resource accounting
  421. infrastructure that works with cgroups.
  422. depends on CGROUPS
  423. config CGROUP_MEM_RES_CTLR
  424. bool "Memory Resource Controller for Control Groups"
  425. depends on CGROUPS && RESOURCE_COUNTERS
  426. select MM_OWNER
  427. help
  428. Provides a memory resource controller that manages both anonymous
  429. memory and page cache. (See Documentation/controllers/memory.txt)
  430. Note that setting this option increases fixed memory overhead
  431. associated with each page of memory in the system. By this,
  432. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  433. usage tracking struct at boot. Total amount of this is printed out
  434. at boot.
  435. Only enable when you're ok with these trade offs and really
  436. sure you need the memory resource controller. Even when you enable
  437. this, you can set "cgroup_disable=memory" at your boot option to
  438. disable memory resource controller and you can avoid overheads.
  439. (and lose benefits of memory resource controller)
  440. This config option also selects MM_OWNER config option, which
  441. could in turn add some fork/exit overhead.
  442. config CGROUP_MEM_RES_CTLR_SWAP
  443. bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
  444. depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
  445. help
  446. Add swap management feature to memory resource controller. When you
  447. enable this, you can limit mem+swap usage per cgroup. In other words,
  448. when you disable this, memory resource controller has no cares to
  449. usage of swap...a process can exhaust all of the swap. This extension
  450. is useful when you want to avoid exhaustion swap but this itself
  451. adds more overheads and consumes memory for remembering information.
  452. Especially if you use 32bit system or small memory system, please
  453. be careful about enabling this. When memory resource controller
  454. is disabled by boot option, this will be automatically disabled and
  455. there will be no overhead from this. Even when you set this config=y,
  456. if boot option "noswapaccount" is set, swap will not be accounted.
  457. endif # CGROUPS
  458. config MM_OWNER
  459. bool
  460. config SYSFS_DEPRECATED
  461. bool
  462. config SYSFS_DEPRECATED_V2
  463. bool "Create deprecated sysfs layout for older userspace tools"
  464. depends on SYSFS
  465. default y
  466. select SYSFS_DEPRECATED
  467. help
  468. This option switches the layout of sysfs to the deprecated
  469. version.
  470. The current sysfs layout features a unified device tree at
  471. /sys/devices/, which is able to express a hierarchy between
  472. class devices. If the deprecated option is set to Y, the
  473. unified device tree is split into a bus device tree at
  474. /sys/devices/ and several individual class device trees at
  475. /sys/class/. The class and bus devices will be connected by
  476. "<subsystem>:<name>" and the "device" links. The "block"
  477. class devices, will not show up in /sys/class/block/. Some
  478. subsystems will suppress the creation of some devices which
  479. depend on the unified device tree.
  480. This option is not a pure compatibility option that can
  481. be safely enabled on newer distributions. It will change the
  482. layout of sysfs to the non-extensible deprecated version,
  483. and disable some features, which can not be exported without
  484. confusing older userspace tools. Since 2007/2008 all major
  485. distributions do not enable this option, and ship no tools which
  486. depend on the deprecated layout or this option.
  487. If you are using a new kernel on an older distribution, or use
  488. older userspace tools, you might need to say Y here. Do not say Y,
  489. if the original kernel, that came with your distribution, has
  490. this option set to N.
  491. config RELAY
  492. bool "Kernel->user space relay support (formerly relayfs)"
  493. help
  494. This option enables support for relay interface support in
  495. certain file systems (such as debugfs).
  496. It is designed to provide an efficient mechanism for tools and
  497. facilities to relay large amounts of data from kernel space to
  498. user space.
  499. If unsure, say N.
  500. config NAMESPACES
  501. bool "Namespaces support" if EMBEDDED
  502. default !EMBEDDED
  503. help
  504. Provides the way to make tasks work with different objects using
  505. the same id. For example same IPC id may refer to different objects
  506. or same user id or pid may refer to different tasks when used in
  507. different namespaces.
  508. config UTS_NS
  509. bool "UTS namespace"
  510. depends on NAMESPACES
  511. help
  512. In this namespace tasks see different info provided with the
  513. uname() system call
  514. config IPC_NS
  515. bool "IPC namespace"
  516. depends on NAMESPACES && SYSVIPC
  517. help
  518. In this namespace tasks work with IPC ids which correspond to
  519. different IPC objects in different namespaces
  520. config USER_NS
  521. bool "User namespace (EXPERIMENTAL)"
  522. depends on NAMESPACES && EXPERIMENTAL
  523. help
  524. This allows containers, i.e. vservers, to use user namespaces
  525. to provide different user info for different servers.
  526. If unsure, say N.
  527. config PID_NS
  528. bool "PID Namespaces (EXPERIMENTAL)"
  529. default n
  530. depends on NAMESPACES && EXPERIMENTAL
  531. help
  532. Support process id namespaces. This allows having multiple
  533. process with the same pid as long as they are in different
  534. pid namespaces. This is a building block of containers.
  535. Unless you want to work with an experimental feature
  536. say N here.
  537. config NET_NS
  538. bool "Network namespace"
  539. default n
  540. depends on NAMESPACES && EXPERIMENTAL && NET
  541. help
  542. Allow user space to create what appear to be multiple instances
  543. of the network stack.
  544. config BLK_DEV_INITRD
  545. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  546. depends on BROKEN || !FRV
  547. help
  548. The initial RAM filesystem is a ramfs which is loaded by the
  549. boot loader (loadlin or lilo) and that is mounted as root
  550. before the normal boot procedure. It is typically used to
  551. load modules needed to mount the "real" root file system,
  552. etc. See <file:Documentation/initrd.txt> for details.
  553. If RAM disk support (BLK_DEV_RAM) is also included, this
  554. also enables initial RAM disk (initrd) support and adds
  555. 15 Kbytes (more on some other architectures) to the kernel size.
  556. If unsure say Y.
  557. if BLK_DEV_INITRD
  558. source "usr/Kconfig"
  559. endif
  560. config CC_OPTIMIZE_FOR_SIZE
  561. bool "Optimize for size"
  562. default y
  563. help
  564. Enabling this option will pass "-Os" instead of "-O2" to gcc
  565. resulting in a smaller kernel.
  566. If unsure, say Y.
  567. config SYSCTL
  568. bool
  569. menuconfig EMBEDDED
  570. bool "Configure standard kernel features (for small systems)"
  571. help
  572. This option allows certain base kernel options and settings
  573. to be disabled or tweaked. This is for specialized
  574. environments which can tolerate a "non-standard" kernel.
  575. Only use this if you really know what you are doing.
  576. if EMBEDDED
  577. config UID16
  578. bool "Enable 16-bit UID system calls" if EMBEDDED
  579. depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
  580. default y
  581. help
  582. This enables the legacy 16-bit UID syscall wrappers.
  583. config SYSCTL_SYSCALL
  584. bool "Sysctl syscall support" if EMBEDDED
  585. default y
  586. select SYSCTL
  587. ---help---
  588. sys_sysctl uses binary paths that have been found challenging
  589. to properly maintain and use. The interface in /proc/sys
  590. using paths with ascii names is now the primary path to this
  591. information.
  592. Almost nothing using the binary sysctl interface so if you are
  593. trying to save some space it is probably safe to disable this,
  594. making your kernel marginally smaller.
  595. If unsure say Y here.
  596. config KALLSYMS
  597. bool "Load all symbols for debugging/ksymoops" if EMBEDDED
  598. default y
  599. help
  600. Say Y here to let the kernel print out symbolic crash information and
  601. symbolic stack backtraces. This increases the size of the kernel
  602. somewhat, as all symbols have to be loaded into the kernel image.
  603. config KALLSYMS_ALL
  604. bool "Include all symbols in kallsyms"
  605. depends on DEBUG_KERNEL && KALLSYMS
  606. help
  607. Normally kallsyms only contains the symbols of functions, for nicer
  608. OOPS messages. Some debuggers can use kallsyms for other
  609. symbols too: say Y here to include all symbols, if you need them
  610. and you don't care about adding 300k to the size of your kernel.
  611. Say N.
  612. config KALLSYMS_EXTRA_PASS
  613. bool "Do an extra kallsyms pass"
  614. depends on KALLSYMS
  615. help
  616. If kallsyms is not working correctly, the build will fail with
  617. inconsistent kallsyms data. If that occurs, log a bug report and
  618. turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
  619. Always say N here unless you find a bug in kallsyms, which must be
  620. reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
  621. you wait for kallsyms to be fixed.
  622. config HOTPLUG
  623. bool "Support for hot-pluggable devices" if EMBEDDED
  624. default y
  625. help
  626. This option is provided for the case where no hotplug or uevent
  627. capabilities is wanted by the kernel. You should only consider
  628. disabling this option for embedded systems that do not use modules, a
  629. dynamic /dev tree, or dynamic device discovery. Just say Y.
  630. config PRINTK
  631. default y
  632. bool "Enable support for printk" if EMBEDDED
  633. help
  634. This option enables normal printk support. Removing it
  635. eliminates most of the message strings from the kernel image
  636. and makes the kernel more or less silent. As this makes it
  637. very difficult to diagnose system problems, saying N here is
  638. strongly discouraged.
  639. config BUG
  640. bool "BUG() support" if EMBEDDED
  641. default y
  642. help
  643. Disabling this option eliminates support for BUG and WARN, reducing
  644. the size of your kernel image and potentially quietly ignoring
  645. numerous fatal conditions. You should only consider disabling this
  646. option for embedded systems with no facilities for reporting errors.
  647. Just say Y.
  648. config ELF_CORE
  649. default y
  650. bool "Enable ELF core dumps" if EMBEDDED
  651. help
  652. Enable support for generating core dumps. Disabling saves about 4k.
  653. config PCSPKR_PLATFORM
  654. bool "Enable PC-Speaker support" if EMBEDDED
  655. depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
  656. default y
  657. help
  658. This option allows to disable the internal PC-Speaker
  659. support, saving some memory.
  660. config BASE_FULL
  661. default y
  662. bool "Enable full-sized data structures for core" if EMBEDDED
  663. help
  664. Disabling this option reduces the size of miscellaneous core
  665. kernel data structures. This saves memory on small machines,
  666. but may reduce performance.
  667. config FUTEX
  668. bool "Enable futex support" if EMBEDDED
  669. default y
  670. select RT_MUTEXES
  671. help
  672. Disabling this option will cause the kernel to be built without
  673. support for "fast userspace mutexes". The resulting kernel may not
  674. run glibc-based applications correctly.
  675. config ANON_INODES
  676. bool
  677. config EPOLL
  678. bool "Enable eventpoll support" if EMBEDDED
  679. default y
  680. select ANON_INODES
  681. help
  682. Disabling this option will cause the kernel to be built without
  683. support for epoll family of system calls.
  684. config SIGNALFD
  685. bool "Enable signalfd() system call" if EMBEDDED
  686. select ANON_INODES
  687. default y
  688. help
  689. Enable the signalfd() system call that allows to receive signals
  690. on a file descriptor.
  691. If unsure, say Y.
  692. config TIMERFD
  693. bool "Enable timerfd() system call" if EMBEDDED
  694. select ANON_INODES
  695. default y
  696. help
  697. Enable the timerfd() system call that allows to receive timer
  698. events on a file descriptor.
  699. If unsure, say Y.
  700. config EVENTFD
  701. bool "Enable eventfd() system call" if EMBEDDED
  702. select ANON_INODES
  703. default y
  704. help
  705. Enable the eventfd() system call that allows to receive both
  706. kernel notification (ie. KAIO) or userspace notifications.
  707. If unsure, say Y.
  708. config SHMEM
  709. bool "Use full shmem filesystem" if EMBEDDED
  710. default y
  711. depends on MMU
  712. help
  713. The shmem is an internal filesystem used to manage shared memory.
  714. It is backed by swap and manages resource limits. It is also exported
  715. to userspace as tmpfs if TMPFS is enabled. Disabling this
  716. option replaces shmem and tmpfs with the much simpler ramfs code,
  717. which may be appropriate on small systems without swap.
  718. config AIO
  719. bool "Enable AIO support" if EMBEDDED
  720. default y
  721. help
  722. This option enables POSIX asynchronous I/O which may by used
  723. by some high performance threaded applications. Disabling
  724. this option saves about 7k.
  725. config VM_EVENT_COUNTERS
  726. default y
  727. bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
  728. help
  729. VM event counters are needed for event counts to be shown.
  730. This option allows the disabling of the VM event counters
  731. on EMBEDDED systems. /proc/vmstat will only show page counts
  732. if VM event counters are disabled.
  733. config PCI_QUIRKS
  734. default y
  735. bool "Enable PCI quirk workarounds" if EMBEDDED
  736. depends on PCI
  737. help
  738. This enables workarounds for various PCI chipset
  739. bugs/quirks. Disable this only if your target machine is
  740. unaffected by PCI quirks.
  741. config SLUB_DEBUG
  742. default y
  743. bool "Enable SLUB debugging support" if EMBEDDED
  744. depends on SLUB && SYSFS
  745. help
  746. SLUB has extensive debug support features. Disabling these can
  747. result in significant savings in code size. This also disables
  748. SLUB sysfs support. /sys/slab will not exist and there will be
  749. no support for cache validation etc.
  750. endif # EMBEDDED
  751. config COMPAT_BRK
  752. bool "Disable heap randomization"
  753. default y
  754. help
  755. Randomizing heap placement makes heap exploits harder, but it
  756. also breaks ancient binaries (including anything libc5 based).
  757. This option changes the bootup default to heap randomization
  758. disabled, and can be overriden runtime by setting
  759. /proc/sys/kernel/randomize_va_space to 2.
  760. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  761. choice
  762. prompt "Choose SLAB allocator"
  763. default SLUB
  764. help
  765. This option allows to select a slab allocator.
  766. config SLAB
  767. bool "SLAB"
  768. help
  769. The regular slab allocator that is established and known to work
  770. well in all environments. It organizes cache hot objects in
  771. per cpu and per node queues.
  772. config SLUB
  773. bool "SLUB (Unqueued Allocator)"
  774. help
  775. SLUB is a slab allocator that minimizes cache line usage
  776. instead of managing queues of cached objects (SLAB approach).
  777. Per cpu caching is realized using slabs of objects instead
  778. of queues of objects. SLUB can use memory efficiently
  779. and has enhanced diagnostics. SLUB is the default choice for
  780. a slab allocator.
  781. config SLOB
  782. depends on EMBEDDED
  783. bool "SLOB (Simple Allocator)"
  784. help
  785. SLOB replaces the stock allocator with a drastically simpler
  786. allocator. SLOB is generally more space efficient but
  787. does not perform as well on large systems.
  788. endchoice
  789. config PROFILING
  790. bool "Profiling support (EXPERIMENTAL)"
  791. help
  792. Say Y here to enable the extended profiling support mechanisms used
  793. by profilers such as OProfile.
  794. #
  795. # Place an empty function call at each tracepoint site. Can be
  796. # dynamically changed for a probe function.
  797. #
  798. config TRACEPOINTS
  799. bool
  800. config MARKERS
  801. bool "Activate markers"
  802. depends on TRACEPOINTS
  803. help
  804. Place an empty function call at each marker site. Can be
  805. dynamically changed for a probe function.
  806. source "arch/Kconfig"
  807. endmenu # General setup
  808. config HAVE_GENERIC_DMA_COHERENT
  809. bool
  810. default n
  811. config SLABINFO
  812. bool
  813. depends on PROC_FS
  814. depends on SLAB || SLUB_DEBUG
  815. default y
  816. config RT_MUTEXES
  817. boolean
  818. select PLIST
  819. config BASE_SMALL
  820. int
  821. default 0 if BASE_FULL
  822. default 1 if !BASE_FULL
  823. menuconfig MODULES
  824. bool "Enable loadable module support"
  825. help
  826. Kernel modules are small pieces of compiled code which can
  827. be inserted in the running kernel, rather than being
  828. permanently built into the kernel. You use the "modprobe"
  829. tool to add (and sometimes remove) them. If you say Y here,
  830. many parts of the kernel can be built as modules (by
  831. answering M instead of Y where indicated): this is most
  832. useful for infrequently used options which are not required
  833. for booting. For more information, see the man pages for
  834. modprobe, lsmod, modinfo, insmod and rmmod.
  835. If you say Y here, you will need to run "make
  836. modules_install" to put the modules under /lib/modules/
  837. where modprobe can find them (you may need to be root to do
  838. this).
  839. If unsure, say Y.
  840. if MODULES
  841. config MODULE_FORCE_LOAD
  842. bool "Forced module loading"
  843. default n
  844. help
  845. Allow loading of modules without version information (ie. modprobe
  846. --force). Forced module loading sets the 'F' (forced) taint flag and
  847. is usually a really bad idea.
  848. config MODULE_UNLOAD
  849. bool "Module unloading"
  850. help
  851. Without this option you will not be able to unload any
  852. modules (note that some modules may not be unloadable
  853. anyway), which makes your kernel smaller, faster
  854. and simpler. If unsure, say Y.
  855. config MODULE_FORCE_UNLOAD
  856. bool "Forced module unloading"
  857. depends on MODULE_UNLOAD && EXPERIMENTAL
  858. help
  859. This option allows you to force a module to unload, even if the
  860. kernel believes it is unsafe: the kernel will remove the module
  861. without waiting for anyone to stop using it (using the -f option to
  862. rmmod). This is mainly for kernel developers and desperate users.
  863. If unsure, say N.
  864. config MODVERSIONS
  865. bool "Module versioning support"
  866. help
  867. Usually, you have to use modules compiled with your kernel.
  868. Saying Y here makes it sometimes possible to use modules
  869. compiled for different kernels, by adding enough information
  870. to the modules to (hopefully) spot any changes which would
  871. make them incompatible with the kernel you are running. If
  872. unsure, say N.
  873. config MODULE_SRCVERSION_ALL
  874. bool "Source checksum for all modules"
  875. help
  876. Modules which contain a MODULE_VERSION get an extra "srcversion"
  877. field inserted into their modinfo section, which contains a
  878. sum of the source files which made it. This helps maintainers
  879. see exactly which source was used to build a module (since
  880. others sometimes change the module source without updating
  881. the version). With this option, such a "srcversion" field
  882. will be created for all modules. If unsure, say N.
  883. endif # MODULES
  884. config INIT_ALL_POSSIBLE
  885. bool
  886. help
  887. Back when each arch used to define their own cpu_online_map and
  888. cpu_possible_map, some of them chose to initialize cpu_possible_map
  889. with all 1s, and others with all 0s. When they were centralised,
  890. it was better to provide this option than to break all the archs
  891. and have several arch maintainers persuing me down dark alleys.
  892. config STOP_MACHINE
  893. bool
  894. default y
  895. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  896. help
  897. Need stop_machine() primitive.
  898. source "block/Kconfig"
  899. config PREEMPT_NOTIFIERS
  900. bool