Kconfig 37 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 drivers that have been replaced by something else, and/or are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
  257. select INOTIFY
  258. menu "RCU Subsystem"
  259. choice
  260. prompt "RCU Implementation"
  261. default TREE_RCU
  262. config CLASSIC_RCU
  263. bool "Classic RCU"
  264. help
  265. This option selects the classic RCU implementation that is
  266. designed for best read-side performance on non-realtime
  267. systems.
  268. Select this option if you are unsure.
  269. config TREE_RCU
  270. bool "Tree-based hierarchical RCU"
  271. help
  272. This option selects the RCU implementation that is
  273. designed for very large SMP system with hundreds or
  274. thousands of CPUs.
  275. config PREEMPT_RCU
  276. bool "Preemptible RCU"
  277. depends on PREEMPT
  278. help
  279. This option reduces the latency of the kernel by making certain
  280. RCU sections preemptible. Normally RCU code is non-preemptible, if
  281. this option is selected then read-only RCU sections become
  282. preemptible. This helps latency, but may expose bugs due to
  283. now-naive assumptions about each RCU read-side critical section
  284. remaining on a given CPU through its execution.
  285. endchoice
  286. config RCU_TRACE
  287. bool "Enable tracing for RCU"
  288. depends on TREE_RCU || PREEMPT_RCU
  289. help
  290. This option provides tracing in RCU which presents stats
  291. in debugfs for debugging RCU implementation.
  292. Say Y here if you want to enable RCU tracing
  293. Say N if you are unsure.
  294. config RCU_FANOUT
  295. int "Tree-based hierarchical RCU fanout value"
  296. range 2 64 if 64BIT
  297. range 2 32 if !64BIT
  298. depends on TREE_RCU
  299. default 64 if 64BIT
  300. default 32 if !64BIT
  301. help
  302. This option controls the fanout of hierarchical implementations
  303. of RCU, allowing RCU to work efficiently on machines with
  304. large numbers of CPUs. This value must be at least the cube
  305. root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
  306. systems and up to 262,144 for 64-bit systems.
  307. Select a specific number if testing RCU itself.
  308. Take the default if unsure.
  309. config RCU_FANOUT_EXACT
  310. bool "Disable tree-based hierarchical RCU auto-balancing"
  311. depends on TREE_RCU
  312. default n
  313. help
  314. This option forces use of the exact RCU_FANOUT value specified,
  315. regardless of imbalances in the hierarchy. This is useful for
  316. testing RCU itself, and might one day be useful on systems with
  317. strong NUMA behavior.
  318. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  319. Say N if unsure.
  320. config TREE_RCU_TRACE
  321. def_bool RCU_TRACE && TREE_RCU
  322. select DEBUG_FS
  323. help
  324. This option provides tracing for the TREE_RCU implementation,
  325. permitting Makefile to trivially select kernel/rcutree_trace.c.
  326. config PREEMPT_RCU_TRACE
  327. def_bool RCU_TRACE && PREEMPT_RCU
  328. select DEBUG_FS
  329. help
  330. This option provides tracing for the PREEMPT_RCU implementation,
  331. permitting Makefile to trivially select kernel/rcupreempt_trace.c.
  332. endmenu # "RCU Subsystem"
  333. config IKCONFIG
  334. tristate "Kernel .config support"
  335. ---help---
  336. This option enables the complete Linux kernel ".config" file
  337. contents to be saved in the kernel. It provides documentation
  338. of which kernel options are used in a running kernel or in an
  339. on-disk kernel. This information can be extracted from the kernel
  340. image file with the script scripts/extract-ikconfig and used as
  341. input to rebuild the current kernel or to build another kernel.
  342. It can also be extracted from a running kernel by reading
  343. /proc/config.gz if enabled (below).
  344. config IKCONFIG_PROC
  345. bool "Enable access to .config through /proc/config.gz"
  346. depends on IKCONFIG && PROC_FS
  347. ---help---
  348. This option enables access to the kernel configuration file
  349. through /proc/config.gz.
  350. config LOG_BUF_SHIFT
  351. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  352. range 12 21
  353. default 17
  354. help
  355. Select kernel log buffer size as a power of 2.
  356. Examples:
  357. 17 => 128 KB
  358. 16 => 64 KB
  359. 15 => 32 KB
  360. 14 => 16 KB
  361. 13 => 8 KB
  362. 12 => 4 KB
  363. #
  364. # Architectures with an unreliable sched_clock() should select this:
  365. #
  366. config HAVE_UNSTABLE_SCHED_CLOCK
  367. bool
  368. config GROUP_SCHED
  369. bool "Group CPU scheduler"
  370. depends on EXPERIMENTAL
  371. default n
  372. help
  373. This feature lets CPU scheduler recognize task groups and control CPU
  374. bandwidth allocation to such task groups.
  375. In order to create a group from arbitrary set of processes, use
  376. CONFIG_CGROUPS. (See Control Group support.)
  377. config FAIR_GROUP_SCHED
  378. bool "Group scheduling for SCHED_OTHER"
  379. depends on GROUP_SCHED
  380. default GROUP_SCHED
  381. config RT_GROUP_SCHED
  382. bool "Group scheduling for SCHED_RR/FIFO"
  383. depends on EXPERIMENTAL
  384. depends on GROUP_SCHED
  385. default n
  386. help
  387. This feature lets you explicitly allocate real CPU bandwidth
  388. to users or control groups (depending on the "Basis for grouping tasks"
  389. setting below. If enabled, it will also make it impossible to
  390. schedule realtime tasks for non-root users until you allocate
  391. realtime bandwidth for them.
  392. See Documentation/scheduler/sched-rt-group.txt for more information.
  393. choice
  394. depends on GROUP_SCHED
  395. prompt "Basis for grouping tasks"
  396. default USER_SCHED
  397. config USER_SCHED
  398. bool "user id"
  399. help
  400. This option will choose userid as the basis for grouping
  401. tasks, thus providing equal CPU bandwidth to each user.
  402. config CGROUP_SCHED
  403. bool "Control groups"
  404. depends on CGROUPS
  405. help
  406. This option allows you to create arbitrary task groups
  407. using the "cgroup" pseudo filesystem and control
  408. the cpu bandwidth allocated to each such task group.
  409. Refer to Documentation/cgroups/cgroups.txt for more
  410. information on "cgroup" pseudo filesystem.
  411. endchoice
  412. menuconfig CGROUPS
  413. boolean "Control Group support"
  414. help
  415. This option adds support for grouping sets of processes together, for
  416. use with process control subsystems such as Cpusets, CFS, memory
  417. controls or device isolation.
  418. See
  419. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  420. - Documentation/cgroups/ (features for grouping, isolation
  421. and resource control)
  422. Say N if unsure.
  423. if CGROUPS
  424. config CGROUP_DEBUG
  425. bool "Example debug cgroup subsystem"
  426. depends on CGROUPS
  427. default n
  428. help
  429. This option enables a simple cgroup subsystem that
  430. exports useful debugging information about the cgroups
  431. framework.
  432. Say N if unsure.
  433. config CGROUP_NS
  434. bool "Namespace cgroup subsystem"
  435. depends on CGROUPS
  436. help
  437. Provides a simple namespace cgroup subsystem to
  438. provide hierarchical naming of sets of namespaces,
  439. for instance virtual servers and checkpoint/restart
  440. jobs.
  441. config CGROUP_FREEZER
  442. bool "Freezer cgroup subsystem"
  443. depends on CGROUPS
  444. help
  445. Provides a way to freeze and unfreeze all tasks in a
  446. cgroup.
  447. config CGROUP_DEVICE
  448. bool "Device controller for cgroups"
  449. depends on CGROUPS && EXPERIMENTAL
  450. help
  451. Provides a cgroup implementing whitelists for devices which
  452. a process in the cgroup can mknod or open.
  453. config CPUSETS
  454. bool "Cpuset support"
  455. depends on CGROUPS
  456. help
  457. This option will let you create and manage CPUSETs which
  458. allow dynamically partitioning a system into sets of CPUs and
  459. Memory Nodes and assigning tasks to run only within those sets.
  460. This is primarily useful on large SMP or NUMA systems.
  461. Say N if unsure.
  462. config PROC_PID_CPUSET
  463. bool "Include legacy /proc/<pid>/cpuset file"
  464. depends on CPUSETS
  465. default y
  466. config CGROUP_CPUACCT
  467. bool "Simple CPU accounting cgroup subsystem"
  468. depends on CGROUPS
  469. help
  470. Provides a simple Resource Controller for monitoring the
  471. total CPU consumed by the tasks in a cgroup.
  472. config RESOURCE_COUNTERS
  473. bool "Resource counters"
  474. help
  475. This option enables controller independent resource accounting
  476. infrastructure that works with cgroups.
  477. depends on CGROUPS
  478. config CGROUP_MEM_RES_CTLR
  479. bool "Memory Resource Controller for Control Groups"
  480. depends on CGROUPS && RESOURCE_COUNTERS
  481. select MM_OWNER
  482. help
  483. Provides a memory resource controller that manages both anonymous
  484. memory and page cache. (See Documentation/cgroups/memory.txt)
  485. Note that setting this option increases fixed memory overhead
  486. associated with each page of memory in the system. By this,
  487. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  488. usage tracking struct at boot. Total amount of this is printed out
  489. at boot.
  490. Only enable when you're ok with these trade offs and really
  491. sure you need the memory resource controller. Even when you enable
  492. this, you can set "cgroup_disable=memory" at your boot option to
  493. disable memory resource controller and you can avoid overheads.
  494. (and lose benefits of memory resource controller)
  495. This config option also selects MM_OWNER config option, which
  496. could in turn add some fork/exit overhead.
  497. config CGROUP_MEM_RES_CTLR_SWAP
  498. bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
  499. depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
  500. help
  501. Add swap management feature to memory resource controller. When you
  502. enable this, you can limit mem+swap usage per cgroup. In other words,
  503. when you disable this, memory resource controller has no cares to
  504. usage of swap...a process can exhaust all of the swap. This extension
  505. is useful when you want to avoid exhaustion swap but this itself
  506. adds more overheads and consumes memory for remembering information.
  507. Especially if you use 32bit system or small memory system, please
  508. be careful about enabling this. When memory resource controller
  509. is disabled by boot option, this will be automatically disabled and
  510. there will be no overhead from this. Even when you set this config=y,
  511. if boot option "noswapaccount" is set, swap will not be accounted.
  512. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  513. size is 4096bytes, 512k per 1Gbytes of swap.
  514. endif # CGROUPS
  515. config MM_OWNER
  516. bool
  517. config SYSFS_DEPRECATED
  518. bool
  519. config SYSFS_DEPRECATED_V2
  520. bool "Create deprecated sysfs layout for older userspace tools"
  521. depends on SYSFS
  522. default y
  523. select SYSFS_DEPRECATED
  524. help
  525. This option switches the layout of sysfs to the deprecated
  526. version.
  527. The current sysfs layout features a unified device tree at
  528. /sys/devices/, which is able to express a hierarchy between
  529. class devices. If the deprecated option is set to Y, the
  530. unified device tree is split into a bus device tree at
  531. /sys/devices/ and several individual class device trees at
  532. /sys/class/. The class and bus devices will be connected by
  533. "<subsystem>:<name>" and the "device" links. The "block"
  534. class devices, will not show up in /sys/class/block/. Some
  535. subsystems will suppress the creation of some devices which
  536. depend on the unified device tree.
  537. This option is not a pure compatibility option that can
  538. be safely enabled on newer distributions. It will change the
  539. layout of sysfs to the non-extensible deprecated version,
  540. and disable some features, which can not be exported without
  541. confusing older userspace tools. Since 2007/2008 all major
  542. distributions do not enable this option, and ship no tools which
  543. depend on the deprecated layout or this option.
  544. If you are using a new kernel on an older distribution, or use
  545. older userspace tools, you might need to say Y here. Do not say Y,
  546. if the original kernel, that came with your distribution, has
  547. this option set to N.
  548. config RELAY
  549. bool "Kernel->user space relay support (formerly relayfs)"
  550. help
  551. This option enables support for relay interface support in
  552. certain file systems (such as debugfs).
  553. It is designed to provide an efficient mechanism for tools and
  554. facilities to relay large amounts of data from kernel space to
  555. user space.
  556. If unsure, say N.
  557. config NAMESPACES
  558. bool "Namespaces support" if EMBEDDED
  559. default !EMBEDDED
  560. help
  561. Provides the way to make tasks work with different objects using
  562. the same id. For example same IPC id may refer to different objects
  563. or same user id or pid may refer to different tasks when used in
  564. different namespaces.
  565. config UTS_NS
  566. bool "UTS namespace"
  567. depends on NAMESPACES
  568. help
  569. In this namespace tasks see different info provided with the
  570. uname() system call
  571. config IPC_NS
  572. bool "IPC namespace"
  573. depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
  574. help
  575. In this namespace tasks work with IPC ids which correspond to
  576. different IPC objects in different namespaces.
  577. config USER_NS
  578. bool "User namespace (EXPERIMENTAL)"
  579. depends on NAMESPACES && EXPERIMENTAL
  580. help
  581. This allows containers, i.e. vservers, to use user namespaces
  582. to provide different user info for different servers.
  583. If unsure, say N.
  584. config PID_NS
  585. bool "PID Namespaces (EXPERIMENTAL)"
  586. default n
  587. depends on NAMESPACES && EXPERIMENTAL
  588. help
  589. Support process id namespaces. This allows having multiple
  590. processes with the same pid as long as they are in different
  591. pid namespaces. This is a building block of containers.
  592. Unless you want to work with an experimental feature
  593. say N here.
  594. config NET_NS
  595. bool "Network namespace"
  596. default n
  597. depends on NAMESPACES && EXPERIMENTAL && NET
  598. help
  599. Allow user space to create what appear to be multiple instances
  600. of the network stack.
  601. config BLK_DEV_INITRD
  602. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  603. depends on BROKEN || !FRV
  604. help
  605. The initial RAM filesystem is a ramfs which is loaded by the
  606. boot loader (loadlin or lilo) and that is mounted as root
  607. before the normal boot procedure. It is typically used to
  608. load modules needed to mount the "real" root file system,
  609. etc. See <file:Documentation/initrd.txt> for details.
  610. If RAM disk support (BLK_DEV_RAM) is also included, this
  611. also enables initial RAM disk (initrd) support and adds
  612. 15 Kbytes (more on some other architectures) to the kernel size.
  613. If unsure say Y.
  614. if BLK_DEV_INITRD
  615. source "usr/Kconfig"
  616. endif
  617. config CC_OPTIMIZE_FOR_SIZE
  618. bool "Optimize for size"
  619. default y
  620. help
  621. Enabling this option will pass "-Os" instead of "-O2" to gcc
  622. resulting in a smaller kernel.
  623. If unsure, say Y.
  624. config SYSCTL
  625. bool
  626. config ANON_INODES
  627. bool
  628. menuconfig EMBEDDED
  629. bool "Configure standard kernel features (for small systems)"
  630. help
  631. This option allows certain base kernel options and settings
  632. to be disabled or tweaked. This is for specialized
  633. environments which can tolerate a "non-standard" kernel.
  634. Only use this if you really know what you are doing.
  635. config UID16
  636. bool "Enable 16-bit UID system calls" if EMBEDDED
  637. depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
  638. default y
  639. help
  640. This enables the legacy 16-bit UID syscall wrappers.
  641. config SYSCTL_SYSCALL
  642. bool "Sysctl syscall support" if EMBEDDED
  643. default y
  644. select SYSCTL
  645. ---help---
  646. sys_sysctl uses binary paths that have been found challenging
  647. to properly maintain and use. The interface in /proc/sys
  648. using paths with ascii names is now the primary path to this
  649. information.
  650. Almost nothing using the binary sysctl interface so if you are
  651. trying to save some space it is probably safe to disable this,
  652. making your kernel marginally smaller.
  653. If unsure say Y here.
  654. config KALLSYMS
  655. bool "Load all symbols for debugging/ksymoops" if EMBEDDED
  656. default y
  657. help
  658. Say Y here to let the kernel print out symbolic crash information and
  659. symbolic stack backtraces. This increases the size of the kernel
  660. somewhat, as all symbols have to be loaded into the kernel image.
  661. config KALLSYMS_ALL
  662. bool "Include all symbols in kallsyms"
  663. depends on DEBUG_KERNEL && KALLSYMS
  664. help
  665. Normally kallsyms only contains the symbols of functions, for nicer
  666. OOPS messages. Some debuggers can use kallsyms for other
  667. symbols too: say Y here to include all symbols, if you need them
  668. and you don't care about adding 300k to the size of your kernel.
  669. Say N.
  670. config KALLSYMS_EXTRA_PASS
  671. bool "Do an extra kallsyms pass"
  672. depends on KALLSYMS
  673. help
  674. If kallsyms is not working correctly, the build will fail with
  675. inconsistent kallsyms data. If that occurs, log a bug report and
  676. turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
  677. Always say N here unless you find a bug in kallsyms, which must be
  678. reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
  679. you wait for kallsyms to be fixed.
  680. config HOTPLUG
  681. bool "Support for hot-pluggable devices" if EMBEDDED
  682. default y
  683. help
  684. This option is provided for the case where no hotplug or uevent
  685. capabilities is wanted by the kernel. You should only consider
  686. disabling this option for embedded systems that do not use modules, a
  687. dynamic /dev tree, or dynamic device discovery. Just say Y.
  688. config PRINTK
  689. default y
  690. bool "Enable support for printk" if EMBEDDED
  691. help
  692. This option enables normal printk support. Removing it
  693. eliminates most of the message strings from the kernel image
  694. and makes the kernel more or less silent. As this makes it
  695. very difficult to diagnose system problems, saying N here is
  696. strongly discouraged.
  697. config BUG
  698. bool "BUG() support" if EMBEDDED
  699. default y
  700. help
  701. Disabling this option eliminates support for BUG and WARN, reducing
  702. the size of your kernel image and potentially quietly ignoring
  703. numerous fatal conditions. You should only consider disabling this
  704. option for embedded systems with no facilities for reporting errors.
  705. Just say Y.
  706. config ELF_CORE
  707. default y
  708. bool "Enable ELF core dumps" if EMBEDDED
  709. help
  710. Enable support for generating core dumps. Disabling saves about 4k.
  711. config PCSPKR_PLATFORM
  712. bool "Enable PC-Speaker support" if EMBEDDED
  713. depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
  714. default y
  715. help
  716. This option allows to disable the internal PC-Speaker
  717. support, saving some memory.
  718. config BASE_FULL
  719. default y
  720. bool "Enable full-sized data structures for core" if EMBEDDED
  721. help
  722. Disabling this option reduces the size of miscellaneous core
  723. kernel data structures. This saves memory on small machines,
  724. but may reduce performance.
  725. config FUTEX
  726. bool "Enable futex support" if EMBEDDED
  727. default y
  728. select RT_MUTEXES
  729. help
  730. Disabling this option will cause the kernel to be built without
  731. support for "fast userspace mutexes". The resulting kernel may not
  732. run glibc-based applications correctly.
  733. config EPOLL
  734. bool "Enable eventpoll support" if EMBEDDED
  735. default y
  736. select ANON_INODES
  737. help
  738. Disabling this option will cause the kernel to be built without
  739. support for epoll family of system calls.
  740. config SIGNALFD
  741. bool "Enable signalfd() system call" if EMBEDDED
  742. select ANON_INODES
  743. default y
  744. help
  745. Enable the signalfd() system call that allows to receive signals
  746. on a file descriptor.
  747. If unsure, say Y.
  748. config TIMERFD
  749. bool "Enable timerfd() system call" if EMBEDDED
  750. select ANON_INODES
  751. default y
  752. help
  753. Enable the timerfd() system call that allows to receive timer
  754. events on a file descriptor.
  755. If unsure, say Y.
  756. config EVENTFD
  757. bool "Enable eventfd() system call" if EMBEDDED
  758. select ANON_INODES
  759. default y
  760. help
  761. Enable the eventfd() system call that allows to receive both
  762. kernel notification (ie. KAIO) or userspace notifications.
  763. If unsure, say Y.
  764. config SHMEM
  765. bool "Use full shmem filesystem" if EMBEDDED
  766. default y
  767. depends on MMU
  768. help
  769. The shmem is an internal filesystem used to manage shared memory.
  770. It is backed by swap and manages resource limits. It is also exported
  771. to userspace as tmpfs if TMPFS is enabled. Disabling this
  772. option replaces shmem and tmpfs with the much simpler ramfs code,
  773. which may be appropriate on small systems without swap.
  774. config AIO
  775. bool "Enable AIO support" if EMBEDDED
  776. default y
  777. help
  778. This option enables POSIX asynchronous I/O which may by used
  779. by some high performance threaded applications. Disabling
  780. this option saves about 7k.
  781. config HAVE_PERF_COUNTERS
  782. bool
  783. help
  784. See tools/perf/design.txt for details.
  785. menu "Performance Counters"
  786. config PERF_COUNTERS
  787. bool "Kernel Performance Counters"
  788. depends on HAVE_PERF_COUNTERS
  789. select ANON_INODES
  790. help
  791. Enable kernel support for performance counter hardware.
  792. Performance counters are special hardware registers available
  793. on most modern CPUs. These registers count the number of certain
  794. types of hw events: such as instructions executed, cachemisses
  795. suffered, or branches mis-predicted - without slowing down the
  796. kernel or applications. These registers can also trigger interrupts
  797. when a threshold number of events have passed - and can thus be
  798. used to profile the code that runs on that CPU.
  799. The Linux Performance Counter subsystem provides an abstraction of
  800. these hardware capabilities, available via a system call. It
  801. provides per task and per CPU counters, and it provides event
  802. capabilities on top of those.
  803. Say Y if unsure.
  804. config EVENT_PROFILE
  805. bool "Tracepoint profile sources"
  806. depends on PERF_COUNTERS && EVENT_TRACER
  807. default y
  808. endmenu
  809. config VM_EVENT_COUNTERS
  810. default y
  811. bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
  812. help
  813. VM event counters are needed for event counts to be shown.
  814. This option allows the disabling of the VM event counters
  815. on EMBEDDED systems. /proc/vmstat will only show page counts
  816. if VM event counters are disabled.
  817. config PCI_QUIRKS
  818. default y
  819. bool "Enable PCI quirk workarounds" if EMBEDDED
  820. depends on PCI
  821. help
  822. This enables workarounds for various PCI chipset
  823. bugs/quirks. Disable this only if your target machine is
  824. unaffected by PCI quirks.
  825. config SLUB_DEBUG
  826. default y
  827. bool "Enable SLUB debugging support" if EMBEDDED
  828. depends on SLUB && SYSFS
  829. help
  830. SLUB has extensive debug support features. Disabling these can
  831. result in significant savings in code size. This also disables
  832. SLUB sysfs support. /sys/slab will not exist and there will be
  833. no support for cache validation etc.
  834. config STRIP_ASM_SYMS
  835. bool "Strip assembler-generated symbols during link"
  836. default n
  837. help
  838. Strip internal assembler-generated symbols during a link (symbols
  839. that look like '.Lxxx') so they don't pollute the output of
  840. get_wchan() and suchlike.
  841. config COMPAT_BRK
  842. bool "Disable heap randomization"
  843. default y
  844. help
  845. Randomizing heap placement makes heap exploits harder, but it
  846. also breaks ancient binaries (including anything libc5 based).
  847. This option changes the bootup default to heap randomization
  848. disabled, and can be overridden at runtime by setting
  849. /proc/sys/kernel/randomize_va_space to 2.
  850. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  851. choice
  852. prompt "Choose SLAB allocator"
  853. default SLUB
  854. help
  855. This option allows to select a slab allocator.
  856. config SLAB
  857. bool "SLAB"
  858. help
  859. The regular slab allocator that is established and known to work
  860. well in all environments. It organizes cache hot objects in
  861. per cpu and per node queues.
  862. config SLUB
  863. bool "SLUB (Unqueued Allocator)"
  864. help
  865. SLUB is a slab allocator that minimizes cache line usage
  866. instead of managing queues of cached objects (SLAB approach).
  867. Per cpu caching is realized using slabs of objects instead
  868. of queues of objects. SLUB can use memory efficiently
  869. and has enhanced diagnostics. SLUB is the default choice for
  870. a slab allocator.
  871. config SLOB
  872. depends on EMBEDDED
  873. bool "SLOB (Simple Allocator)"
  874. help
  875. SLOB replaces the stock allocator with a drastically simpler
  876. allocator. SLOB is generally more space efficient but
  877. does not perform as well on large systems.
  878. endchoice
  879. config PROFILING
  880. bool "Profiling support (EXPERIMENTAL)"
  881. help
  882. Say Y here to enable the extended profiling support mechanisms used
  883. by profilers such as OProfile.
  884. #
  885. # Place an empty function call at each tracepoint site. Can be
  886. # dynamically changed for a probe function.
  887. #
  888. config TRACEPOINTS
  889. bool
  890. config MARKERS
  891. bool "Activate markers"
  892. select TRACEPOINTS
  893. help
  894. Place an empty function call at each marker site. Can be
  895. dynamically changed for a probe function.
  896. source "arch/Kconfig"
  897. config SLOW_WORK
  898. default n
  899. bool
  900. help
  901. The slow work thread pool provides a number of dynamically allocated
  902. threads that can be used by the kernel to perform operations that
  903. take a relatively long time.
  904. An example of this would be CacheFiles doing a path lookup followed
  905. by a series of mkdirs and a create call, all of which have to touch
  906. disk.
  907. See Documentation/slow-work.txt.
  908. endmenu # General setup
  909. config HAVE_GENERIC_DMA_COHERENT
  910. bool
  911. default n
  912. config SLABINFO
  913. bool
  914. depends on PROC_FS
  915. depends on SLAB || SLUB_DEBUG
  916. default y
  917. config RT_MUTEXES
  918. boolean
  919. config BASE_SMALL
  920. int
  921. default 0 if BASE_FULL
  922. default 1 if !BASE_FULL
  923. menuconfig MODULES
  924. bool "Enable loadable module support"
  925. help
  926. Kernel modules are small pieces of compiled code which can
  927. be inserted in the running kernel, rather than being
  928. permanently built into the kernel. You use the "modprobe"
  929. tool to add (and sometimes remove) them. If you say Y here,
  930. many parts of the kernel can be built as modules (by
  931. answering M instead of Y where indicated): this is most
  932. useful for infrequently used options which are not required
  933. for booting. For more information, see the man pages for
  934. modprobe, lsmod, modinfo, insmod and rmmod.
  935. If you say Y here, you will need to run "make
  936. modules_install" to put the modules under /lib/modules/
  937. where modprobe can find them (you may need to be root to do
  938. this).
  939. If unsure, say Y.
  940. if MODULES
  941. config MODULE_FORCE_LOAD
  942. bool "Forced module loading"
  943. default n
  944. help
  945. Allow loading of modules without version information (ie. modprobe
  946. --force). Forced module loading sets the 'F' (forced) taint flag and
  947. is usually a really bad idea.
  948. config MODULE_UNLOAD
  949. bool "Module unloading"
  950. help
  951. Without this option you will not be able to unload any
  952. modules (note that some modules may not be unloadable
  953. anyway), which makes your kernel smaller, faster
  954. and simpler. If unsure, say Y.
  955. config MODULE_FORCE_UNLOAD
  956. bool "Forced module unloading"
  957. depends on MODULE_UNLOAD && EXPERIMENTAL
  958. help
  959. This option allows you to force a module to unload, even if the
  960. kernel believes it is unsafe: the kernel will remove the module
  961. without waiting for anyone to stop using it (using the -f option to
  962. rmmod). This is mainly for kernel developers and desperate users.
  963. If unsure, say N.
  964. config MODVERSIONS
  965. bool "Module versioning support"
  966. help
  967. Usually, you have to use modules compiled with your kernel.
  968. Saying Y here makes it sometimes possible to use modules
  969. compiled for different kernels, by adding enough information
  970. to the modules to (hopefully) spot any changes which would
  971. make them incompatible with the kernel you are running. If
  972. unsure, say N.
  973. config MODULE_SRCVERSION_ALL
  974. bool "Source checksum for all modules"
  975. help
  976. Modules which contain a MODULE_VERSION get an extra "srcversion"
  977. field inserted into their modinfo section, which contains a
  978. sum of the source files which made it. This helps maintainers
  979. see exactly which source was used to build a module (since
  980. others sometimes change the module source without updating
  981. the version). With this option, such a "srcversion" field
  982. will be created for all modules. If unsure, say N.
  983. endif # MODULES
  984. config INIT_ALL_POSSIBLE
  985. bool
  986. help
  987. Back when each arch used to define their own cpu_online_map and
  988. cpu_possible_map, some of them chose to initialize cpu_possible_map
  989. with all 1s, and others with all 0s. When they were centralised,
  990. it was better to provide this option than to break all the archs
  991. and have several arch maintainers pursuing me down dark alleys.
  992. config STOP_MACHINE
  993. bool
  994. default y
  995. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  996. help
  997. Need stop_machine() primitive.
  998. source "block/Kconfig"
  999. config PREEMPT_NOTIFIERS
  1000. bool