Kconfig 36 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 drivers that have been replaced by something else, and/or are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 HAVE_KERNEL_GZIP
  87. bool
  88. config HAVE_KERNEL_BZIP2
  89. bool
  90. config HAVE_KERNEL_LZMA
  91. bool
  92. choice
  93. prompt "Kernel compression mode"
  94. default KERNEL_GZIP
  95. depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
  96. help
  97. The linux kernel is a kind of self-extracting executable.
  98. Several compression algorithms are available, which differ
  99. in efficiency, compression and decompression speed.
  100. Compression speed is only relevant when building a kernel.
  101. Decompression speed is relevant at each boot.
  102. If you have any problems with bzip2 or lzma compressed
  103. kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
  104. version of this functionality (bzip2 only), for 2.4, was
  105. supplied by Christian Ludwig)
  106. High compression options are mostly useful for users, who
  107. are low on disk space (embedded systems), but for whom ram
  108. size matters less.
  109. If in doubt, select 'gzip'
  110. config KERNEL_GZIP
  111. bool "Gzip"
  112. depends on HAVE_KERNEL_GZIP
  113. help
  114. The old and tried gzip compression. Its compression ratio is
  115. the poorest among the 3 choices; however its speed (both
  116. compression and decompression) is the fastest.
  117. config KERNEL_BZIP2
  118. bool "Bzip2"
  119. depends on HAVE_KERNEL_BZIP2
  120. help
  121. Its compression ratio and speed is intermediate.
  122. Decompression speed is slowest among the three. The kernel
  123. size is about 10% smaller with bzip2, in comparison to gzip.
  124. Bzip2 uses a large amount of memory. For modern kernels you
  125. will need at least 8MB RAM or more for booting.
  126. config KERNEL_LZMA
  127. bool "LZMA"
  128. depends on HAVE_KERNEL_LZMA
  129. help
  130. The most recent compression algorithm.
  131. Its ratio is best, decompression speed is between the other
  132. two. Compression is slowest. The kernel size is about 33%
  133. smaller with LZMA in comparison to gzip.
  134. endchoice
  135. config SWAP
  136. bool "Support for paging of anonymous memory (swap)"
  137. depends on MMU && BLOCK
  138. default y
  139. help
  140. This option allows you to choose whether you want to have support
  141. for so called swap devices or swap files in your kernel that are
  142. used to provide more virtual memory than the actual RAM present
  143. in your computer. If unsure say Y.
  144. config SYSVIPC
  145. bool "System V IPC"
  146. ---help---
  147. Inter Process Communication is a suite of library functions and
  148. system calls which let processes (running programs) synchronize and
  149. exchange information. It is generally considered to be a good thing,
  150. and some programs won't run unless you say Y here. In particular, if
  151. you want to run the DOS emulator dosemu under Linux (read the
  152. DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
  153. you'll need to say Y here.
  154. You can find documentation about IPC with "info ipc" and also in
  155. section 6.4 of the Linux Programmer's Guide, available from
  156. <http://www.tldp.org/guides.html>.
  157. config SYSVIPC_SYSCTL
  158. bool
  159. depends on SYSVIPC
  160. depends on SYSCTL
  161. default y
  162. config POSIX_MQUEUE
  163. bool "POSIX Message Queues"
  164. depends on NET && EXPERIMENTAL
  165. ---help---
  166. POSIX variant of message queues is a part of IPC. In POSIX message
  167. queues every message has a priority which decides about succession
  168. of receiving it by a process. If you want to compile and run
  169. programs written e.g. for Solaris with use of its POSIX message
  170. queues (functions mq_*) say Y here.
  171. POSIX message queues are visible as a filesystem called 'mqueue'
  172. and can be mounted somewhere if you want to do filesystem
  173. operations on message queues.
  174. If unsure, say Y.
  175. config POSIX_MQUEUE_SYSCTL
  176. bool
  177. depends on POSIX_MQUEUE
  178. depends on SYSCTL
  179. default y
  180. config BSD_PROCESS_ACCT
  181. bool "BSD Process Accounting"
  182. help
  183. If you say Y here, a user level program will be able to instruct the
  184. kernel (via a special system call) to write process accounting
  185. information to a file: whenever a process exits, information about
  186. that process will be appended to the file by the kernel. The
  187. information includes things such as creation time, owning user,
  188. command name, memory usage, controlling terminal etc. (the complete
  189. list is in the struct acct in <file:include/linux/acct.h>). It is
  190. up to the user level program to do useful things with this
  191. information. This is generally a good idea, so say Y.
  192. config BSD_PROCESS_ACCT_V3
  193. bool "BSD Process Accounting version 3 file format"
  194. depends on BSD_PROCESS_ACCT
  195. default n
  196. help
  197. If you say Y here, the process accounting information is written
  198. in a new file format that also logs the process IDs of each
  199. process and it's parent. Note that this file format is incompatible
  200. with previous v0/v1/v2 file formats, so you will need updated tools
  201. for processing it. A preliminary version of these tools is available
  202. at <http://www.gnu.org/software/acct/>.
  203. config TASKSTATS
  204. bool "Export task/process statistics through netlink (EXPERIMENTAL)"
  205. depends on NET
  206. default n
  207. help
  208. Export selected statistics for tasks/processes through the
  209. generic netlink interface. Unlike BSD process accounting, the
  210. statistics are available during the lifetime of tasks/processes as
  211. responses to commands. Like BSD accounting, they are sent to user
  212. space on task exit.
  213. Say N if unsure.
  214. config TASK_DELAY_ACCT
  215. bool "Enable per-task delay accounting (EXPERIMENTAL)"
  216. depends on TASKSTATS
  217. help
  218. Collect information on time spent by a task waiting for system
  219. resources like cpu, synchronous block I/O completion and swapping
  220. in pages. Such statistics can help in setting a task's priorities
  221. relative to other tasks for cpu, io, rss limits etc.
  222. Say N if unsure.
  223. config TASK_XACCT
  224. bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
  225. depends on TASKSTATS
  226. help
  227. Collect extended task accounting data and send the data
  228. to userland for processing over the taskstats interface.
  229. Say N if unsure.
  230. config TASK_IO_ACCOUNTING
  231. bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
  232. depends on TASK_XACCT
  233. help
  234. Collect information on the number of bytes of storage I/O which this
  235. task has caused.
  236. Say N if unsure.
  237. config AUDIT
  238. bool "Auditing support"
  239. depends on NET
  240. help
  241. Enable auditing infrastructure that can be used with another
  242. kernel subsystem, such as SELinux (which requires this for
  243. logging of avc messages output). Does not do system-call
  244. auditing without CONFIG_AUDITSYSCALL.
  245. config AUDITSYSCALL
  246. bool "Enable system-call auditing support"
  247. depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
  248. default y if SECURITY_SELINUX
  249. help
  250. Enable low-overhead system-call auditing infrastructure that
  251. can be used independently or with another kernel subsystem,
  252. such as SELinux. To use audit's filesystem watch feature, please
  253. ensure that INOTIFY is configured.
  254. config AUDIT_TREE
  255. def_bool y
  256. depends on AUDITSYSCALL && INOTIFY
  257. menu "RCU Subsystem"
  258. choice
  259. prompt "RCU Implementation"
  260. default CLASSIC_RCU
  261. config CLASSIC_RCU
  262. bool "Classic RCU"
  263. help
  264. This option selects the classic RCU implementation that is
  265. designed for best read-side performance on non-realtime
  266. systems.
  267. Select this option if you are unsure.
  268. config TREE_RCU
  269. bool "Tree-based hierarchical RCU"
  270. help
  271. This option selects the RCU implementation that is
  272. designed for very large SMP system with hundreds or
  273. thousands of CPUs.
  274. config PREEMPT_RCU
  275. bool "Preemptible RCU"
  276. depends on PREEMPT
  277. help
  278. This option reduces the latency of the kernel by making certain
  279. RCU sections preemptible. Normally RCU code is non-preemptible, if
  280. this option is selected then read-only RCU sections become
  281. preemptible. This helps latency, but may expose bugs due to
  282. now-naive assumptions about each RCU read-side critical section
  283. remaining on a given CPU through its execution.
  284. endchoice
  285. config RCU_TRACE
  286. bool "Enable tracing for RCU"
  287. depends on TREE_RCU || PREEMPT_RCU
  288. help
  289. This option provides tracing in RCU which presents stats
  290. in debugfs for debugging RCU implementation.
  291. Say Y here if you want to enable RCU tracing
  292. Say N if you are unsure.
  293. config RCU_FANOUT
  294. int "Tree-based hierarchical RCU fanout value"
  295. range 2 64 if 64BIT
  296. range 2 32 if !64BIT
  297. depends on TREE_RCU
  298. default 64 if 64BIT
  299. default 32 if !64BIT
  300. help
  301. This option controls the fanout of hierarchical implementations
  302. of RCU, allowing RCU to work efficiently on machines with
  303. large numbers of CPUs. This value must be at least the cube
  304. root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
  305. systems and up to 262,144 for 64-bit systems.
  306. Select a specific number if testing RCU itself.
  307. Take the default if unsure.
  308. config RCU_FANOUT_EXACT
  309. bool "Disable tree-based hierarchical RCU auto-balancing"
  310. depends on TREE_RCU
  311. default n
  312. help
  313. This option forces use of the exact RCU_FANOUT value specified,
  314. regardless of imbalances in the hierarchy. This is useful for
  315. testing RCU itself, and might one day be useful on systems with
  316. strong NUMA behavior.
  317. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  318. Say N if unsure.
  319. config TREE_RCU_TRACE
  320. def_bool RCU_TRACE && TREE_RCU
  321. select DEBUG_FS
  322. help
  323. This option provides tracing for the TREE_RCU implementation,
  324. permitting Makefile to trivially select kernel/rcutree_trace.c.
  325. config PREEMPT_RCU_TRACE
  326. def_bool RCU_TRACE && PREEMPT_RCU
  327. select DEBUG_FS
  328. help
  329. This option provides tracing for the PREEMPT_RCU implementation,
  330. permitting Makefile to trivially select kernel/rcupreempt_trace.c.
  331. endmenu # "RCU Subsystem"
  332. config IKCONFIG
  333. tristate "Kernel .config support"
  334. ---help---
  335. This option enables the complete Linux kernel ".config" file
  336. contents to be saved in the kernel. It provides documentation
  337. of which kernel options are used in a running kernel or in an
  338. on-disk kernel. This information can be extracted from the kernel
  339. image file with the script scripts/extract-ikconfig and used as
  340. input to rebuild the current kernel or to build another kernel.
  341. It can also be extracted from a running kernel by reading
  342. /proc/config.gz if enabled (below).
  343. config IKCONFIG_PROC
  344. bool "Enable access to .config through /proc/config.gz"
  345. depends on IKCONFIG && PROC_FS
  346. ---help---
  347. This option enables access to the kernel configuration file
  348. through /proc/config.gz.
  349. config LOG_BUF_SHIFT
  350. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  351. range 12 21
  352. default 17
  353. help
  354. Select kernel log buffer size as a power of 2.
  355. Examples:
  356. 17 => 128 KB
  357. 16 => 64 KB
  358. 15 => 32 KB
  359. 14 => 16 KB
  360. 13 => 8 KB
  361. 12 => 4 KB
  362. #
  363. # Architectures with an unreliable sched_clock() should select this:
  364. #
  365. config HAVE_UNSTABLE_SCHED_CLOCK
  366. bool
  367. config GROUP_SCHED
  368. bool "Group CPU scheduler"
  369. depends on EXPERIMENTAL
  370. default n
  371. help
  372. This feature lets CPU scheduler recognize task groups and control CPU
  373. bandwidth allocation to such task groups.
  374. In order to create a group from arbitrary set of processes, use
  375. CONFIG_CGROUPS. (See Control Group support.)
  376. config FAIR_GROUP_SCHED
  377. bool "Group scheduling for SCHED_OTHER"
  378. depends on GROUP_SCHED
  379. default GROUP_SCHED
  380. config RT_GROUP_SCHED
  381. bool "Group scheduling for SCHED_RR/FIFO"
  382. depends on EXPERIMENTAL
  383. depends on GROUP_SCHED
  384. default n
  385. help
  386. This feature lets you explicitly allocate real CPU bandwidth
  387. to users or control groups (depending on the "Basis for grouping tasks"
  388. setting below. If enabled, it will also make it impossible to
  389. schedule realtime tasks for non-root users until you allocate
  390. realtime bandwidth for them.
  391. See Documentation/scheduler/sched-rt-group.txt for more information.
  392. choice
  393. depends on GROUP_SCHED
  394. prompt "Basis for grouping tasks"
  395. default USER_SCHED
  396. config USER_SCHED
  397. bool "user id"
  398. help
  399. This option will choose userid as the basis for grouping
  400. tasks, thus providing equal CPU bandwidth to each user.
  401. config CGROUP_SCHED
  402. bool "Control groups"
  403. depends on CGROUPS
  404. help
  405. This option allows you to create arbitrary task groups
  406. using the "cgroup" pseudo filesystem and control
  407. the cpu bandwidth allocated to each such task group.
  408. Refer to Documentation/cgroups/cgroups.txt for more
  409. information on "cgroup" pseudo filesystem.
  410. endchoice
  411. menuconfig CGROUPS
  412. boolean "Control Group support"
  413. help
  414. This option adds support for grouping sets of processes together, for
  415. use with process control subsystems such as Cpusets, CFS, memory
  416. controls or device isolation.
  417. See
  418. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  419. - Documentation/cgroups/ (features for grouping, isolation
  420. and resource control)
  421. Say N if unsure.
  422. if CGROUPS
  423. config CGROUP_DEBUG
  424. bool "Example debug cgroup subsystem"
  425. depends on CGROUPS
  426. default n
  427. help
  428. This option enables a simple cgroup subsystem that
  429. exports useful debugging information about the cgroups
  430. framework.
  431. Say N if unsure.
  432. config CGROUP_NS
  433. bool "Namespace cgroup subsystem"
  434. depends on CGROUPS
  435. help
  436. Provides a simple namespace cgroup subsystem to
  437. provide hierarchical naming of sets of namespaces,
  438. for instance virtual servers and checkpoint/restart
  439. jobs.
  440. config CGROUP_FREEZER
  441. bool "Freezer cgroup subsystem"
  442. depends on CGROUPS
  443. help
  444. Provides a way to freeze and unfreeze all tasks in a
  445. cgroup.
  446. config CGROUP_DEVICE
  447. bool "Device controller for cgroups"
  448. depends on CGROUPS && EXPERIMENTAL
  449. help
  450. Provides a cgroup implementing whitelists for devices which
  451. a process in the cgroup can mknod or open.
  452. config CPUSETS
  453. bool "Cpuset support"
  454. depends on CGROUPS
  455. help
  456. This option will let you create and manage CPUSETs which
  457. allow dynamically partitioning a system into sets of CPUs and
  458. Memory Nodes and assigning tasks to run only within those sets.
  459. This is primarily useful on large SMP or NUMA systems.
  460. Say N if unsure.
  461. config PROC_PID_CPUSET
  462. bool "Include legacy /proc/<pid>/cpuset file"
  463. depends on CPUSETS
  464. default y
  465. config CGROUP_CPUACCT
  466. bool "Simple CPU accounting cgroup subsystem"
  467. depends on CGROUPS
  468. help
  469. Provides a simple Resource Controller for monitoring the
  470. total CPU consumed by the tasks in a cgroup.
  471. config RESOURCE_COUNTERS
  472. bool "Resource counters"
  473. help
  474. This option enables controller independent resource accounting
  475. infrastructure that works with cgroups.
  476. depends on CGROUPS
  477. config CGROUP_MEM_RES_CTLR
  478. bool "Memory Resource Controller for Control Groups"
  479. depends on CGROUPS && RESOURCE_COUNTERS
  480. select MM_OWNER
  481. help
  482. Provides a memory resource controller that manages both anonymous
  483. memory and page cache. (See Documentation/cgroups/memory.txt)
  484. Note that setting this option increases fixed memory overhead
  485. associated with each page of memory in the system. By this,
  486. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  487. usage tracking struct at boot. Total amount of this is printed out
  488. at boot.
  489. Only enable when you're ok with these trade offs and really
  490. sure you need the memory resource controller. Even when you enable
  491. this, you can set "cgroup_disable=memory" at your boot option to
  492. disable memory resource controller and you can avoid overheads.
  493. (and lose benefits of memory resource controller)
  494. This config option also selects MM_OWNER config option, which
  495. could in turn add some fork/exit overhead.
  496. config CGROUP_MEM_RES_CTLR_SWAP
  497. bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
  498. depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
  499. help
  500. Add swap management feature to memory resource controller. When you
  501. enable this, you can limit mem+swap usage per cgroup. In other words,
  502. when you disable this, memory resource controller has no cares to
  503. usage of swap...a process can exhaust all of the swap. This extension
  504. is useful when you want to avoid exhaustion swap but this itself
  505. adds more overheads and consumes memory for remembering information.
  506. Especially if you use 32bit system or small memory system, please
  507. be careful about enabling this. When memory resource controller
  508. is disabled by boot option, this will be automatically disabled and
  509. there will be no overhead from this. Even when you set this config=y,
  510. if boot option "noswapaccount" is set, swap will not be accounted.
  511. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  512. size is 4096bytes, 512k per 1Gbytes of swap.
  513. endif # CGROUPS
  514. config MM_OWNER
  515. bool
  516. config SYSFS_DEPRECATED
  517. bool
  518. config SYSFS_DEPRECATED_V2
  519. bool "Create deprecated sysfs layout for older userspace tools"
  520. depends on SYSFS
  521. default y
  522. select SYSFS_DEPRECATED
  523. help
  524. This option switches the layout of sysfs to the deprecated
  525. version.
  526. The current sysfs layout features a unified device tree at
  527. /sys/devices/, which is able to express a hierarchy between
  528. class devices. If the deprecated option is set to Y, the
  529. unified device tree is split into a bus device tree at
  530. /sys/devices/ and several individual class device trees at
  531. /sys/class/. The class and bus devices will be connected by
  532. "<subsystem>:<name>" and the "device" links. The "block"
  533. class devices, will not show up in /sys/class/block/. Some
  534. subsystems will suppress the creation of some devices which
  535. depend on the unified device tree.
  536. This option is not a pure compatibility option that can
  537. be safely enabled on newer distributions. It will change the
  538. layout of sysfs to the non-extensible deprecated version,
  539. and disable some features, which can not be exported without
  540. confusing older userspace tools. Since 2007/2008 all major
  541. distributions do not enable this option, and ship no tools which
  542. depend on the deprecated layout or this option.
  543. If you are using a new kernel on an older distribution, or use
  544. older userspace tools, you might need to say Y here. Do not say Y,
  545. if the original kernel, that came with your distribution, has
  546. this option set to N.
  547. config RELAY
  548. bool "Kernel->user space relay support (formerly relayfs)"
  549. help
  550. This option enables support for relay interface support in
  551. certain file systems (such as debugfs).
  552. It is designed to provide an efficient mechanism for tools and
  553. facilities to relay large amounts of data from kernel space to
  554. user space.
  555. If unsure, say N.
  556. config NAMESPACES
  557. bool "Namespaces support" if EMBEDDED
  558. default !EMBEDDED
  559. help
  560. Provides the way to make tasks work with different objects using
  561. the same id. For example same IPC id may refer to different objects
  562. or same user id or pid may refer to different tasks when used in
  563. different namespaces.
  564. config UTS_NS
  565. bool "UTS namespace"
  566. depends on NAMESPACES
  567. help
  568. In this namespace tasks see different info provided with the
  569. uname() system call
  570. config IPC_NS
  571. bool "IPC namespace"
  572. depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
  573. help
  574. In this namespace tasks work with IPC ids which correspond to
  575. different IPC objects in different namespaces.
  576. config USER_NS
  577. bool "User namespace (EXPERIMENTAL)"
  578. depends on NAMESPACES && EXPERIMENTAL
  579. help
  580. This allows containers, i.e. vservers, to use user namespaces
  581. to provide different user info for different servers.
  582. If unsure, say N.
  583. config PID_NS
  584. bool "PID Namespaces (EXPERIMENTAL)"
  585. default n
  586. depends on NAMESPACES && EXPERIMENTAL
  587. help
  588. Support process id namespaces. This allows having multiple
  589. processes with the same pid as long as they are in different
  590. pid namespaces. This is a building block of containers.
  591. Unless you want to work with an experimental feature
  592. say N here.
  593. config NET_NS
  594. bool "Network namespace"
  595. default n
  596. depends on NAMESPACES && EXPERIMENTAL && NET
  597. help
  598. Allow user space to create what appear to be multiple instances
  599. of the network stack.
  600. config BLK_DEV_INITRD
  601. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  602. depends on BROKEN || !FRV
  603. help
  604. The initial RAM filesystem is a ramfs which is loaded by the
  605. boot loader (loadlin or lilo) and that is mounted as root
  606. before the normal boot procedure. It is typically used to
  607. load modules needed to mount the "real" root file system,
  608. etc. See <file:Documentation/initrd.txt> for details.
  609. If RAM disk support (BLK_DEV_RAM) is also included, this
  610. also enables initial RAM disk (initrd) support and adds
  611. 15 Kbytes (more on some other architectures) to the kernel size.
  612. If unsure say Y.
  613. if BLK_DEV_INITRD
  614. source "usr/Kconfig"
  615. endif
  616. config CC_OPTIMIZE_FOR_SIZE
  617. bool "Optimize for size"
  618. default y
  619. help
  620. Enabling this option will pass "-Os" instead of "-O2" to gcc
  621. resulting in a smaller kernel.
  622. If unsure, say Y.
  623. config SYSCTL
  624. bool
  625. config ANON_INODES
  626. bool
  627. menuconfig EMBEDDED
  628. bool "Configure standard kernel features (for small systems)"
  629. help
  630. This option allows certain base kernel options and settings
  631. to be disabled or tweaked. This is for specialized
  632. environments which can tolerate a "non-standard" kernel.
  633. Only use this if you really know what you are doing.
  634. config UID16
  635. bool "Enable 16-bit UID system calls" if EMBEDDED
  636. depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
  637. default y
  638. help
  639. This enables the legacy 16-bit UID syscall wrappers.
  640. config SYSCTL_SYSCALL
  641. bool "Sysctl syscall support" if EMBEDDED
  642. default y
  643. select SYSCTL
  644. ---help---
  645. sys_sysctl uses binary paths that have been found challenging
  646. to properly maintain and use. The interface in /proc/sys
  647. using paths with ascii names is now the primary path to this
  648. information.
  649. Almost nothing using the binary sysctl interface so if you are
  650. trying to save some space it is probably safe to disable this,
  651. making your kernel marginally smaller.
  652. If unsure say Y here.
  653. config KALLSYMS
  654. bool "Load all symbols for debugging/ksymoops" if EMBEDDED
  655. default y
  656. help
  657. Say Y here to let the kernel print out symbolic crash information and
  658. symbolic stack backtraces. This increases the size of the kernel
  659. somewhat, as all symbols have to be loaded into the kernel image.
  660. config KALLSYMS_ALL
  661. bool "Include all symbols in kallsyms"
  662. depends on DEBUG_KERNEL && KALLSYMS
  663. help
  664. Normally kallsyms only contains the symbols of functions, for nicer
  665. OOPS messages. Some debuggers can use kallsyms for other
  666. symbols too: say Y here to include all symbols, if you need them
  667. and you don't care about adding 300k to the size of your kernel.
  668. Say N.
  669. config KALLSYMS_EXTRA_PASS
  670. bool "Do an extra kallsyms pass"
  671. depends on KALLSYMS
  672. help
  673. If kallsyms is not working correctly, the build will fail with
  674. inconsistent kallsyms data. If that occurs, log a bug report and
  675. turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
  676. Always say N here unless you find a bug in kallsyms, which must be
  677. reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
  678. you wait for kallsyms to be fixed.
  679. config STRIP_ASM_SYMS
  680. bool "Strip assembler-generated symbols during link"
  681. default n
  682. help
  683. Strip internal assembler-generated symbols during a link (symbols
  684. that look like '.Lxxx') so they don't pollute the output of
  685. get_wchan() and suchlike.
  686. config HOTPLUG
  687. bool "Support for hot-pluggable devices" if EMBEDDED
  688. default y
  689. help
  690. This option is provided for the case where no hotplug or uevent
  691. capabilities is wanted by the kernel. You should only consider
  692. disabling this option for embedded systems that do not use modules, a
  693. dynamic /dev tree, or dynamic device discovery. Just say Y.
  694. config PRINTK
  695. default y
  696. bool "Enable support for printk" if EMBEDDED
  697. help
  698. This option enables normal printk support. Removing it
  699. eliminates most of the message strings from the kernel image
  700. and makes the kernel more or less silent. As this makes it
  701. very difficult to diagnose system problems, saying N here is
  702. strongly discouraged.
  703. config BUG
  704. bool "BUG() support" if EMBEDDED
  705. default y
  706. help
  707. Disabling this option eliminates support for BUG and WARN, reducing
  708. the size of your kernel image and potentially quietly ignoring
  709. numerous fatal conditions. You should only consider disabling this
  710. option for embedded systems with no facilities for reporting errors.
  711. Just say Y.
  712. config ELF_CORE
  713. default y
  714. bool "Enable ELF core dumps" if EMBEDDED
  715. help
  716. Enable support for generating core dumps. Disabling saves about 4k.
  717. config PCSPKR_PLATFORM
  718. bool "Enable PC-Speaker support" if EMBEDDED
  719. depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
  720. default y
  721. help
  722. This option allows to disable the internal PC-Speaker
  723. support, saving some memory.
  724. config BASE_FULL
  725. default y
  726. bool "Enable full-sized data structures for core" if EMBEDDED
  727. help
  728. Disabling this option reduces the size of miscellaneous core
  729. kernel data structures. This saves memory on small machines,
  730. but may reduce performance.
  731. config FUTEX
  732. bool "Enable futex support" if EMBEDDED
  733. default y
  734. select RT_MUTEXES
  735. help
  736. Disabling this option will cause the kernel to be built without
  737. support for "fast userspace mutexes". The resulting kernel may not
  738. run glibc-based applications correctly.
  739. config EPOLL
  740. bool "Enable eventpoll support" if EMBEDDED
  741. default y
  742. select ANON_INODES
  743. help
  744. Disabling this option will cause the kernel to be built without
  745. support for epoll family of system calls.
  746. config SIGNALFD
  747. bool "Enable signalfd() system call" if EMBEDDED
  748. select ANON_INODES
  749. default y
  750. help
  751. Enable the signalfd() system call that allows to receive signals
  752. on a file descriptor.
  753. If unsure, say Y.
  754. config TIMERFD
  755. bool "Enable timerfd() system call" if EMBEDDED
  756. select ANON_INODES
  757. default y
  758. help
  759. Enable the timerfd() system call that allows to receive timer
  760. events on a file descriptor.
  761. If unsure, say Y.
  762. config EVENTFD
  763. bool "Enable eventfd() system call" if EMBEDDED
  764. select ANON_INODES
  765. default y
  766. help
  767. Enable the eventfd() system call that allows to receive both
  768. kernel notification (ie. KAIO) or userspace notifications.
  769. If unsure, say Y.
  770. config SHMEM
  771. bool "Use full shmem filesystem" if EMBEDDED
  772. default y
  773. depends on MMU
  774. help
  775. The shmem is an internal filesystem used to manage shared memory.
  776. It is backed by swap and manages resource limits. It is also exported
  777. to userspace as tmpfs if TMPFS is enabled. Disabling this
  778. option replaces shmem and tmpfs with the much simpler ramfs code,
  779. which may be appropriate on small systems without swap.
  780. config AIO
  781. bool "Enable AIO support" if EMBEDDED
  782. default y
  783. help
  784. This option enables POSIX asynchronous I/O which may by used
  785. by some high performance threaded applications. Disabling
  786. this option saves about 7k.
  787. config VM_EVENT_COUNTERS
  788. default y
  789. bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
  790. help
  791. VM event counters are needed for event counts to be shown.
  792. This option allows the disabling of the VM event counters
  793. on EMBEDDED systems. /proc/vmstat will only show page counts
  794. if VM event counters are disabled.
  795. config PCI_QUIRKS
  796. default y
  797. bool "Enable PCI quirk workarounds" if EMBEDDED
  798. depends on PCI
  799. help
  800. This enables workarounds for various PCI chipset
  801. bugs/quirks. Disable this only if your target machine is
  802. unaffected by PCI quirks.
  803. config SLUB_DEBUG
  804. default y
  805. bool "Enable SLUB debugging support" if EMBEDDED
  806. depends on SLUB && SYSFS
  807. help
  808. SLUB has extensive debug support features. Disabling these can
  809. result in significant savings in code size. This also disables
  810. SLUB sysfs support. /sys/slab will not exist and there will be
  811. no support for cache validation etc.
  812. config COMPAT_BRK
  813. bool "Disable heap randomization"
  814. default y
  815. help
  816. Randomizing heap placement makes heap exploits harder, but it
  817. also breaks ancient binaries (including anything libc5 based).
  818. This option changes the bootup default to heap randomization
  819. disabled, and can be overridden at runtime by setting
  820. /proc/sys/kernel/randomize_va_space to 2.
  821. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  822. choice
  823. prompt "Choose SLAB allocator"
  824. default SLUB
  825. help
  826. This option allows to select a slab allocator.
  827. config SLAB
  828. bool "SLAB"
  829. help
  830. The regular slab allocator that is established and known to work
  831. well in all environments. It organizes cache hot objects in
  832. per cpu and per node queues.
  833. config SLUB
  834. bool "SLUB (Unqueued Allocator)"
  835. help
  836. SLUB is a slab allocator that minimizes cache line usage
  837. instead of managing queues of cached objects (SLAB approach).
  838. Per cpu caching is realized using slabs of objects instead
  839. of queues of objects. SLUB can use memory efficiently
  840. and has enhanced diagnostics. SLUB is the default choice for
  841. a slab allocator.
  842. config SLOB
  843. depends on EMBEDDED
  844. bool "SLOB (Simple Allocator)"
  845. help
  846. SLOB replaces the stock allocator with a drastically simpler
  847. allocator. SLOB is generally more space efficient but
  848. does not perform as well on large systems.
  849. endchoice
  850. config PROFILING
  851. bool "Profiling support (EXPERIMENTAL)"
  852. help
  853. Say Y here to enable the extended profiling support mechanisms used
  854. by profilers such as OProfile.
  855. #
  856. # Place an empty function call at each tracepoint site. Can be
  857. # dynamically changed for a probe function.
  858. #
  859. config TRACEPOINTS
  860. bool
  861. config MARKERS
  862. bool "Activate markers"
  863. select TRACEPOINTS
  864. help
  865. Place an empty function call at each marker site. Can be
  866. dynamically changed for a probe function.
  867. source "arch/Kconfig"
  868. config SLOW_WORK
  869. default n
  870. bool
  871. help
  872. The slow work thread pool provides a number of dynamically allocated
  873. threads that can be used by the kernel to perform operations that
  874. take a relatively long time.
  875. An example of this would be CacheFiles doing a path lookup followed
  876. by a series of mkdirs and a create call, all of which have to touch
  877. disk.
  878. See Documentation/slow-work.txt.
  879. endmenu # General setup
  880. config HAVE_GENERIC_DMA_COHERENT
  881. bool
  882. default n
  883. config SLABINFO
  884. bool
  885. depends on PROC_FS
  886. depends on SLAB || SLUB_DEBUG
  887. default y
  888. config RT_MUTEXES
  889. boolean
  890. config BASE_SMALL
  891. int
  892. default 0 if BASE_FULL
  893. default 1 if !BASE_FULL
  894. menuconfig MODULES
  895. bool "Enable loadable module support"
  896. help
  897. Kernel modules are small pieces of compiled code which can
  898. be inserted in the running kernel, rather than being
  899. permanently built into the kernel. You use the "modprobe"
  900. tool to add (and sometimes remove) them. If you say Y here,
  901. many parts of the kernel can be built as modules (by
  902. answering M instead of Y where indicated): this is most
  903. useful for infrequently used options which are not required
  904. for booting. For more information, see the man pages for
  905. modprobe, lsmod, modinfo, insmod and rmmod.
  906. If you say Y here, you will need to run "make
  907. modules_install" to put the modules under /lib/modules/
  908. where modprobe can find them (you may need to be root to do
  909. this).
  910. If unsure, say Y.
  911. if MODULES
  912. config MODULE_FORCE_LOAD
  913. bool "Forced module loading"
  914. default n
  915. help
  916. Allow loading of modules without version information (ie. modprobe
  917. --force). Forced module loading sets the 'F' (forced) taint flag and
  918. is usually a really bad idea.
  919. config MODULE_UNLOAD
  920. bool "Module unloading"
  921. help
  922. Without this option you will not be able to unload any
  923. modules (note that some modules may not be unloadable
  924. anyway), which makes your kernel smaller, faster
  925. and simpler. If unsure, say Y.
  926. config MODULE_FORCE_UNLOAD
  927. bool "Forced module unloading"
  928. depends on MODULE_UNLOAD && EXPERIMENTAL
  929. help
  930. This option allows you to force a module to unload, even if the
  931. kernel believes it is unsafe: the kernel will remove the module
  932. without waiting for anyone to stop using it (using the -f option to
  933. rmmod). This is mainly for kernel developers and desperate users.
  934. If unsure, say N.
  935. config MODVERSIONS
  936. bool "Module versioning support"
  937. help
  938. Usually, you have to use modules compiled with your kernel.
  939. Saying Y here makes it sometimes possible to use modules
  940. compiled for different kernels, by adding enough information
  941. to the modules to (hopefully) spot any changes which would
  942. make them incompatible with the kernel you are running. If
  943. unsure, say N.
  944. config MODULE_SRCVERSION_ALL
  945. bool "Source checksum for all modules"
  946. help
  947. Modules which contain a MODULE_VERSION get an extra "srcversion"
  948. field inserted into their modinfo section, which contains a
  949. sum of the source files which made it. This helps maintainers
  950. see exactly which source was used to build a module (since
  951. others sometimes change the module source without updating
  952. the version). With this option, such a "srcversion" field
  953. will be created for all modules. If unsure, say N.
  954. endif # MODULES
  955. config INIT_ALL_POSSIBLE
  956. bool
  957. help
  958. Back when each arch used to define their own cpu_online_map and
  959. cpu_possible_map, some of them chose to initialize cpu_possible_map
  960. with all 1s, and others with all 0s. When they were centralised,
  961. it was better to provide this option than to break all the archs
  962. and have several arch maintainers pursuing me down dark alleys.
  963. config STOP_MACHINE
  964. bool
  965. default y
  966. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  967. help
  968. Need stop_machine() primitive.
  969. source "block/Kconfig"
  970. config PREEMPT_NOTIFIERS
  971. bool