Kconfig 38 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. config CONSTRUCTORS
  17. bool
  18. depends on !UML
  19. default y
  20. menu "General setup"
  21. config EXPERIMENTAL
  22. bool "Prompt for development and/or incomplete code/drivers"
  23. ---help---
  24. Some of the various things that Linux supports (such as network
  25. drivers, file systems, network protocols, etc.) can be in a state
  26. of development where the functionality, stability, or the level of
  27. testing is not yet high enough for general use. This is usually
  28. known as the "alpha-test" phase among developers. If a feature is
  29. currently in alpha-test, then the developers usually discourage
  30. uninformed widespread use of this feature by the general public to
  31. avoid "Why doesn't this work?" type mail messages. However, active
  32. testing and use of these systems is welcomed. Just be aware that it
  33. may not meet the normal level of reliability or it may fail to work
  34. in some special cases. Detailed bug reports from people familiar
  35. with the kernel internals are usually welcomed by the developers
  36. (before submitting bug reports, please read the documents
  37. <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  38. <file:Documentation/BUG-HUNTING>, and
  39. <file:Documentation/oops-tracing.txt> in the kernel source).
  40. This option will also make obsoleted drivers available. These are
  41. drivers that have been replaced by something else, and/or are
  42. scheduled to be removed in a future kernel release.
  43. Unless you intend to help test and develop a feature or driver that
  44. falls into this category, or you have a situation that requires
  45. using these features, you should probably say N here, which will
  46. cause the configurator to present you with fewer choices. If
  47. you say Y here, you will be offered the choice of using features or
  48. drivers that are currently considered to be in the alpha-test phase.
  49. config BROKEN
  50. bool
  51. config BROKEN_ON_SMP
  52. bool
  53. depends on BROKEN || !SMP
  54. default y
  55. config LOCK_KERNEL
  56. bool
  57. depends on SMP || PREEMPT
  58. default y
  59. config INIT_ENV_ARG_LIMIT
  60. int
  61. default 32 if !UML
  62. default 128 if UML
  63. help
  64. Maximum of each of the number of arguments and environment
  65. variables passed to init from the kernel command line.
  66. config LOCALVERSION
  67. string "Local version - append to kernel release"
  68. help
  69. Append an extra string to the end of your kernel version.
  70. This will show up when you type uname, for example.
  71. The string you set here will be appended after the contents of
  72. any files with a filename matching localversion* in your
  73. object and source tree, in that order. Your total string can
  74. be a maximum of 64 characters.
  75. config LOCALVERSION_AUTO
  76. bool "Automatically append version information to the version string"
  77. default y
  78. help
  79. This will try to automatically determine if the current tree is a
  80. release tree by looking for git tags that belong to the current
  81. top of tree revision.
  82. A string of the format -gxxxxxxxx will be added to the localversion
  83. if a git-based tree is found. The string generated by this will be
  84. appended after any matching localversion* files, and after the value
  85. set in CONFIG_LOCALVERSION.
  86. (The actual string used here is the first eight characters produced
  87. by running the command:
  88. $ git rev-parse --verify HEAD
  89. which is done within the script "scripts/setlocalversion".)
  90. config HAVE_KERNEL_GZIP
  91. bool
  92. config HAVE_KERNEL_BZIP2
  93. bool
  94. config HAVE_KERNEL_LZMA
  95. bool
  96. choice
  97. prompt "Kernel compression mode"
  98. default KERNEL_GZIP
  99. depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
  100. help
  101. The linux kernel is a kind of self-extracting executable.
  102. Several compression algorithms are available, which differ
  103. in efficiency, compression and decompression speed.
  104. Compression speed is only relevant when building a kernel.
  105. Decompression speed is relevant at each boot.
  106. If you have any problems with bzip2 or lzma compressed
  107. kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
  108. version of this functionality (bzip2 only), for 2.4, was
  109. supplied by Christian Ludwig)
  110. High compression options are mostly useful for users, who
  111. are low on disk space (embedded systems), but for whom ram
  112. size matters less.
  113. If in doubt, select 'gzip'
  114. config KERNEL_GZIP
  115. bool "Gzip"
  116. depends on HAVE_KERNEL_GZIP
  117. help
  118. The old and tried gzip compression. Its compression ratio is
  119. the poorest among the 3 choices; however its speed (both
  120. compression and decompression) is the fastest.
  121. config KERNEL_BZIP2
  122. bool "Bzip2"
  123. depends on HAVE_KERNEL_BZIP2
  124. help
  125. Its compression ratio and speed is intermediate.
  126. Decompression speed is slowest among the three. The kernel
  127. size is about 10% smaller with bzip2, in comparison to gzip.
  128. Bzip2 uses a large amount of memory. For modern kernels you
  129. will need at least 8MB RAM or more for booting.
  130. config KERNEL_LZMA
  131. bool "LZMA"
  132. depends on HAVE_KERNEL_LZMA
  133. help
  134. The most recent compression algorithm.
  135. Its ratio is best, decompression speed is between the other
  136. two. Compression is slowest. The kernel size is about 33%
  137. smaller with LZMA in comparison to gzip.
  138. endchoice
  139. config SWAP
  140. bool "Support for paging of anonymous memory (swap)"
  141. depends on MMU && BLOCK
  142. default y
  143. help
  144. This option allows you to choose whether you want to have support
  145. for so called swap devices or swap files in your kernel that are
  146. used to provide more virtual memory than the actual RAM present
  147. in your computer. If unsure say Y.
  148. config SYSVIPC
  149. bool "System V IPC"
  150. ---help---
  151. Inter Process Communication is a suite of library functions and
  152. system calls which let processes (running programs) synchronize and
  153. exchange information. It is generally considered to be a good thing,
  154. and some programs won't run unless you say Y here. In particular, if
  155. you want to run the DOS emulator dosemu under Linux (read the
  156. DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
  157. you'll need to say Y here.
  158. You can find documentation about IPC with "info ipc" and also in
  159. section 6.4 of the Linux Programmer's Guide, available from
  160. <http://www.tldp.org/guides.html>.
  161. config SYSVIPC_SYSCTL
  162. bool
  163. depends on SYSVIPC
  164. depends on SYSCTL
  165. default y
  166. config POSIX_MQUEUE
  167. bool "POSIX Message Queues"
  168. depends on NET && EXPERIMENTAL
  169. ---help---
  170. POSIX variant of message queues is a part of IPC. In POSIX message
  171. queues every message has a priority which decides about succession
  172. of receiving it by a process. If you want to compile and run
  173. programs written e.g. for Solaris with use of its POSIX message
  174. queues (functions mq_*) say Y here.
  175. POSIX message queues are visible as a filesystem called 'mqueue'
  176. and can be mounted somewhere if you want to do filesystem
  177. operations on message queues.
  178. If unsure, say Y.
  179. config POSIX_MQUEUE_SYSCTL
  180. bool
  181. depends on POSIX_MQUEUE
  182. depends on SYSCTL
  183. default y
  184. config BSD_PROCESS_ACCT
  185. bool "BSD Process Accounting"
  186. help
  187. If you say Y here, a user level program will be able to instruct the
  188. kernel (via a special system call) to write process accounting
  189. information to a file: whenever a process exits, information about
  190. that process will be appended to the file by the kernel. The
  191. information includes things such as creation time, owning user,
  192. command name, memory usage, controlling terminal etc. (the complete
  193. list is in the struct acct in <file:include/linux/acct.h>). It is
  194. up to the user level program to do useful things with this
  195. information. This is generally a good idea, so say Y.
  196. config BSD_PROCESS_ACCT_V3
  197. bool "BSD Process Accounting version 3 file format"
  198. depends on BSD_PROCESS_ACCT
  199. default n
  200. help
  201. If you say Y here, the process accounting information is written
  202. in a new file format that also logs the process IDs of each
  203. process and it's parent. Note that this file format is incompatible
  204. with previous v0/v1/v2 file formats, so you will need updated tools
  205. for processing it. A preliminary version of these tools is available
  206. at <http://www.gnu.org/software/acct/>.
  207. config TASKSTATS
  208. bool "Export task/process statistics through netlink (EXPERIMENTAL)"
  209. depends on NET
  210. default n
  211. help
  212. Export selected statistics for tasks/processes through the
  213. generic netlink interface. Unlike BSD process accounting, the
  214. statistics are available during the lifetime of tasks/processes as
  215. responses to commands. Like BSD accounting, they are sent to user
  216. space on task exit.
  217. Say N if unsure.
  218. config TASK_DELAY_ACCT
  219. bool "Enable per-task delay accounting (EXPERIMENTAL)"
  220. depends on TASKSTATS
  221. help
  222. Collect information on time spent by a task waiting for system
  223. resources like cpu, synchronous block I/O completion and swapping
  224. in pages. Such statistics can help in setting a task's priorities
  225. relative to other tasks for cpu, io, rss limits etc.
  226. Say N if unsure.
  227. config TASK_XACCT
  228. bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
  229. depends on TASKSTATS
  230. help
  231. Collect extended task accounting data and send the data
  232. to userland for processing over the taskstats interface.
  233. Say N if unsure.
  234. config TASK_IO_ACCOUNTING
  235. bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
  236. depends on TASK_XACCT
  237. help
  238. Collect information on the number of bytes of storage I/O which this
  239. task has caused.
  240. Say N if unsure.
  241. config AUDIT
  242. bool "Auditing support"
  243. depends on NET
  244. help
  245. Enable auditing infrastructure that can be used with another
  246. kernel subsystem, such as SELinux (which requires this for
  247. logging of avc messages output). Does not do system-call
  248. auditing without CONFIG_AUDITSYSCALL.
  249. config AUDITSYSCALL
  250. bool "Enable system-call auditing support"
  251. depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
  252. default y if SECURITY_SELINUX
  253. help
  254. Enable low-overhead system-call auditing infrastructure that
  255. can be used independently or with another kernel subsystem,
  256. such as SELinux. To use audit's filesystem watch feature, please
  257. ensure that INOTIFY is configured.
  258. config AUDIT_TREE
  259. def_bool y
  260. depends on AUDITSYSCALL
  261. select INOTIFY
  262. menu "RCU Subsystem"
  263. choice
  264. prompt "RCU Implementation"
  265. default TREE_RCU
  266. config TREE_RCU
  267. bool "Tree-based hierarchical RCU"
  268. help
  269. This option selects the RCU implementation that is
  270. designed for very large SMP system with hundreds or
  271. thousands of CPUs. It also scales down nicely to
  272. smaller systems.
  273. config TREE_PREEMPT_RCU
  274. bool "Preemptable tree-based hierarchical RCU"
  275. depends on PREEMPT
  276. help
  277. This option selects the RCU implementation that is
  278. designed for very large SMP systems with hundreds or
  279. thousands of CPUs, but for which real-time response
  280. is also required. It also scales down nicely to
  281. smaller systems.
  282. endchoice
  283. config RCU_TRACE
  284. bool "Enable tracing for RCU"
  285. depends on TREE_RCU || TREE_PREEMPT_RCU
  286. help
  287. This option provides tracing in RCU which presents stats
  288. in debugfs for debugging RCU implementation.
  289. Say Y here if you want to enable RCU tracing
  290. Say N if you are unsure.
  291. config RCU_FANOUT
  292. int "Tree-based hierarchical RCU fanout value"
  293. range 2 64 if 64BIT
  294. range 2 32 if !64BIT
  295. depends on TREE_RCU || TREE_PREEMPT_RCU
  296. default 64 if 64BIT
  297. default 32 if !64BIT
  298. help
  299. This option controls the fanout of hierarchical implementations
  300. of RCU, allowing RCU to work efficiently on machines with
  301. large numbers of CPUs. This value must be at least the cube
  302. root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
  303. systems and up to 262,144 for 64-bit systems.
  304. Select a specific number if testing RCU itself.
  305. Take the default if unsure.
  306. config RCU_FANOUT_EXACT
  307. bool "Disable tree-based hierarchical RCU auto-balancing"
  308. depends on TREE_RCU || TREE_PREEMPT_RCU
  309. default n
  310. help
  311. This option forces use of the exact RCU_FANOUT value specified,
  312. regardless of imbalances in the hierarchy. This is useful for
  313. testing RCU itself, and might one day be useful on systems with
  314. strong NUMA behavior.
  315. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  316. Say N if unsure.
  317. config TREE_RCU_TRACE
  318. def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
  319. select DEBUG_FS
  320. help
  321. This option provides tracing for the TREE_RCU and
  322. TREE_PREEMPT_RCU implementations, permitting Makefile to
  323. trivially select kernel/rcutree_trace.c.
  324. endmenu # "RCU Subsystem"
  325. config IKCONFIG
  326. tristate "Kernel .config support"
  327. ---help---
  328. This option enables the complete Linux kernel ".config" file
  329. contents to be saved in the kernel. It provides documentation
  330. of which kernel options are used in a running kernel or in an
  331. on-disk kernel. This information can be extracted from the kernel
  332. image file with the script scripts/extract-ikconfig and used as
  333. input to rebuild the current kernel or to build another kernel.
  334. It can also be extracted from a running kernel by reading
  335. /proc/config.gz if enabled (below).
  336. config IKCONFIG_PROC
  337. bool "Enable access to .config through /proc/config.gz"
  338. depends on IKCONFIG && PROC_FS
  339. ---help---
  340. This option enables access to the kernel configuration file
  341. through /proc/config.gz.
  342. config LOG_BUF_SHIFT
  343. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  344. range 12 21
  345. default 17
  346. help
  347. Select kernel log buffer size as a power of 2.
  348. Examples:
  349. 17 => 128 KB
  350. 16 => 64 KB
  351. 15 => 32 KB
  352. 14 => 16 KB
  353. 13 => 8 KB
  354. 12 => 4 KB
  355. #
  356. # Architectures with an unreliable sched_clock() should select this:
  357. #
  358. config HAVE_UNSTABLE_SCHED_CLOCK
  359. bool
  360. config GROUP_SCHED
  361. bool "Group CPU scheduler"
  362. depends on EXPERIMENTAL
  363. default n
  364. help
  365. This feature lets CPU scheduler recognize task groups and control CPU
  366. bandwidth allocation to such task groups.
  367. In order to create a group from arbitrary set of processes, use
  368. CONFIG_CGROUPS. (See Control Group support.)
  369. config FAIR_GROUP_SCHED
  370. bool "Group scheduling for SCHED_OTHER"
  371. depends on GROUP_SCHED
  372. default GROUP_SCHED
  373. config RT_GROUP_SCHED
  374. bool "Group scheduling for SCHED_RR/FIFO"
  375. depends on EXPERIMENTAL
  376. depends on GROUP_SCHED
  377. default n
  378. help
  379. This feature lets you explicitly allocate real CPU bandwidth
  380. to users or control groups (depending on the "Basis for grouping tasks"
  381. setting below. If enabled, it will also make it impossible to
  382. schedule realtime tasks for non-root users until you allocate
  383. realtime bandwidth for them.
  384. See Documentation/scheduler/sched-rt-group.txt for more information.
  385. choice
  386. depends on GROUP_SCHED
  387. prompt "Basis for grouping tasks"
  388. default USER_SCHED
  389. config USER_SCHED
  390. bool "user id"
  391. help
  392. This option will choose userid as the basis for grouping
  393. tasks, thus providing equal CPU bandwidth to each user.
  394. config CGROUP_SCHED
  395. bool "Control groups"
  396. depends on CGROUPS
  397. help
  398. This option allows you to create arbitrary task groups
  399. using the "cgroup" pseudo filesystem and control
  400. the cpu bandwidth allocated to each such task group.
  401. Refer to Documentation/cgroups/cgroups.txt for more
  402. information on "cgroup" pseudo filesystem.
  403. endchoice
  404. menuconfig CGROUPS
  405. boolean "Control Group support"
  406. help
  407. This option adds support for grouping sets of processes together, for
  408. use with process control subsystems such as Cpusets, CFS, memory
  409. controls or device isolation.
  410. See
  411. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  412. - Documentation/cgroups/ (features for grouping, isolation
  413. and resource control)
  414. Say N if unsure.
  415. if CGROUPS
  416. config CGROUP_DEBUG
  417. bool "Example debug cgroup subsystem"
  418. depends on CGROUPS
  419. default n
  420. help
  421. This option enables a simple cgroup subsystem that
  422. exports useful debugging information about the cgroups
  423. framework.
  424. Say N if unsure.
  425. config CGROUP_NS
  426. bool "Namespace cgroup subsystem"
  427. depends on CGROUPS
  428. help
  429. Provides a simple namespace cgroup subsystem to
  430. provide hierarchical naming of sets of namespaces,
  431. for instance virtual servers and checkpoint/restart
  432. jobs.
  433. config CGROUP_FREEZER
  434. bool "Freezer cgroup subsystem"
  435. depends on CGROUPS
  436. help
  437. Provides a way to freeze and unfreeze all tasks in a
  438. cgroup.
  439. config CGROUP_DEVICE
  440. bool "Device controller for cgroups"
  441. depends on CGROUPS && EXPERIMENTAL
  442. help
  443. Provides a cgroup implementing whitelists for devices which
  444. a process in the cgroup can mknod or open.
  445. config CPUSETS
  446. bool "Cpuset support"
  447. depends on CGROUPS
  448. help
  449. This option will let you create and manage CPUSETs which
  450. allow dynamically partitioning a system into sets of CPUs and
  451. Memory Nodes and assigning tasks to run only within those sets.
  452. This is primarily useful on large SMP or NUMA systems.
  453. Say N if unsure.
  454. config PROC_PID_CPUSET
  455. bool "Include legacy /proc/<pid>/cpuset file"
  456. depends on CPUSETS
  457. default y
  458. config CGROUP_CPUACCT
  459. bool "Simple CPU accounting cgroup subsystem"
  460. depends on CGROUPS
  461. help
  462. Provides a simple Resource Controller for monitoring the
  463. total CPU consumed by the tasks in a cgroup.
  464. config RESOURCE_COUNTERS
  465. bool "Resource counters"
  466. help
  467. This option enables controller independent resource accounting
  468. infrastructure that works with cgroups.
  469. depends on CGROUPS
  470. config CGROUP_MEM_RES_CTLR
  471. bool "Memory Resource Controller for Control Groups"
  472. depends on CGROUPS && RESOURCE_COUNTERS
  473. select MM_OWNER
  474. help
  475. Provides a memory resource controller that manages both anonymous
  476. memory and page cache. (See Documentation/cgroups/memory.txt)
  477. Note that setting this option increases fixed memory overhead
  478. associated with each page of memory in the system. By this,
  479. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  480. usage tracking struct at boot. Total amount of this is printed out
  481. at boot.
  482. Only enable when you're ok with these trade offs and really
  483. sure you need the memory resource controller. Even when you enable
  484. this, you can set "cgroup_disable=memory" at your boot option to
  485. disable memory resource controller and you can avoid overheads.
  486. (and lose benefits of memory resource controller)
  487. This config option also selects MM_OWNER config option, which
  488. could in turn add some fork/exit overhead.
  489. config CGROUP_MEM_RES_CTLR_SWAP
  490. bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
  491. depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
  492. help
  493. Add swap management feature to memory resource controller. When you
  494. enable this, you can limit mem+swap usage per cgroup. In other words,
  495. when you disable this, memory resource controller has no cares to
  496. usage of swap...a process can exhaust all of the swap. This extension
  497. is useful when you want to avoid exhaustion swap but this itself
  498. adds more overheads and consumes memory for remembering information.
  499. Especially if you use 32bit system or small memory system, please
  500. be careful about enabling this. When memory resource controller
  501. is disabled by boot option, this will be automatically disabled and
  502. there will be no overhead from this. Even when you set this config=y,
  503. if boot option "noswapaccount" is set, swap will not be accounted.
  504. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  505. size is 4096bytes, 512k per 1Gbytes of swap.
  506. endif # CGROUPS
  507. config MM_OWNER
  508. bool
  509. config SYSFS_DEPRECATED
  510. bool
  511. config SYSFS_DEPRECATED_V2
  512. bool "remove sysfs features which may confuse old userspace tools"
  513. depends on SYSFS
  514. default n
  515. select SYSFS_DEPRECATED
  516. help
  517. This option switches the layout of sysfs to the deprecated
  518. version. Do not use it on recent distributions.
  519. The current sysfs layout features a unified device tree at
  520. /sys/devices/, which is able to express a hierarchy between
  521. class devices. If the deprecated option is set to Y, the
  522. unified device tree is split into a bus device tree at
  523. /sys/devices/ and several individual class device trees at
  524. /sys/class/. The class and bus devices will be connected by
  525. "<subsystem>:<name>" and the "device" links. The "block"
  526. class devices, will not show up in /sys/class/block/. Some
  527. subsystems will suppress the creation of some devices which
  528. depend on the unified device tree.
  529. This option is not a pure compatibility option that can
  530. be safely enabled on newer distributions. It will change the
  531. layout of sysfs to the non-extensible deprecated version,
  532. and disable some features, which can not be exported without
  533. confusing older userspace tools. Since 2007/2008 all major
  534. distributions do not enable this option, and ship no tools which
  535. depend on the deprecated layout or this option.
  536. If you are using a new kernel on an older distribution, or use
  537. older userspace tools, you might need to say Y here. Do not say Y,
  538. if the original kernel, that came with your distribution, has
  539. this option set to N.
  540. config RELAY
  541. bool "Kernel->user space relay support (formerly relayfs)"
  542. help
  543. This option enables support for relay interface support in
  544. certain file systems (such as debugfs).
  545. It is designed to provide an efficient mechanism for tools and
  546. facilities to relay large amounts of data from kernel space to
  547. user space.
  548. If unsure, say N.
  549. config NAMESPACES
  550. bool "Namespaces support" if EMBEDDED
  551. default !EMBEDDED
  552. help
  553. Provides the way to make tasks work with different objects using
  554. the same id. For example same IPC id may refer to different objects
  555. or same user id or pid may refer to different tasks when used in
  556. different namespaces.
  557. config UTS_NS
  558. bool "UTS namespace"
  559. depends on NAMESPACES
  560. help
  561. In this namespace tasks see different info provided with the
  562. uname() system call
  563. config IPC_NS
  564. bool "IPC namespace"
  565. depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
  566. help
  567. In this namespace tasks work with IPC ids which correspond to
  568. different IPC objects in different namespaces.
  569. config USER_NS
  570. bool "User namespace (EXPERIMENTAL)"
  571. depends on NAMESPACES && EXPERIMENTAL
  572. help
  573. This allows containers, i.e. vservers, to use user namespaces
  574. to provide different user info for different servers.
  575. If unsure, say N.
  576. config PID_NS
  577. bool "PID Namespaces (EXPERIMENTAL)"
  578. default n
  579. depends on NAMESPACES && EXPERIMENTAL
  580. help
  581. Support process id namespaces. This allows having multiple
  582. processes with the same pid as long as they are in different
  583. pid namespaces. This is a building block of containers.
  584. Unless you want to work with an experimental feature
  585. say N here.
  586. config NET_NS
  587. bool "Network namespace"
  588. default n
  589. depends on NAMESPACES && EXPERIMENTAL && NET
  590. help
  591. Allow user space to create what appear to be multiple instances
  592. of the network stack.
  593. config BLK_DEV_INITRD
  594. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  595. depends on BROKEN || !FRV
  596. help
  597. The initial RAM filesystem is a ramfs which is loaded by the
  598. boot loader (loadlin or lilo) and that is mounted as root
  599. before the normal boot procedure. It is typically used to
  600. load modules needed to mount the "real" root file system,
  601. etc. See <file:Documentation/initrd.txt> for details.
  602. If RAM disk support (BLK_DEV_RAM) is also included, this
  603. also enables initial RAM disk (initrd) support and adds
  604. 15 Kbytes (more on some other architectures) to the kernel size.
  605. If unsure say Y.
  606. if BLK_DEV_INITRD
  607. source "usr/Kconfig"
  608. endif
  609. config CC_OPTIMIZE_FOR_SIZE
  610. bool "Optimize for size"
  611. default y
  612. help
  613. Enabling this option will pass "-Os" instead of "-O2" to gcc
  614. resulting in a smaller kernel.
  615. If unsure, say Y.
  616. config SYSCTL
  617. bool
  618. config ANON_INODES
  619. bool
  620. menuconfig EMBEDDED
  621. bool "Configure standard kernel features (for small systems)"
  622. help
  623. This option allows certain base kernel options and settings
  624. to be disabled or tweaked. This is for specialized
  625. environments which can tolerate a "non-standard" kernel.
  626. Only use this if you really know what you are doing.
  627. config UID16
  628. bool "Enable 16-bit UID system calls" if EMBEDDED
  629. depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
  630. default y
  631. help
  632. This enables the legacy 16-bit UID syscall wrappers.
  633. config SYSCTL_SYSCALL
  634. bool "Sysctl syscall support" if EMBEDDED
  635. depends on PROC_SYSCTL
  636. default y
  637. select SYSCTL
  638. ---help---
  639. sys_sysctl uses binary paths that have been found challenging
  640. to properly maintain and use. The interface in /proc/sys
  641. using paths with ascii names is now the primary path to this
  642. information.
  643. Almost nothing using the binary sysctl interface so if you are
  644. trying to save some space it is probably safe to disable this,
  645. making your kernel marginally smaller.
  646. If unsure say Y here.
  647. config KALLSYMS
  648. bool "Load all symbols for debugging/ksymoops" if EMBEDDED
  649. default y
  650. help
  651. Say Y here to let the kernel print out symbolic crash information and
  652. symbolic stack backtraces. This increases the size of the kernel
  653. somewhat, as all symbols have to be loaded into the kernel image.
  654. config KALLSYMS_ALL
  655. bool "Include all symbols in kallsyms"
  656. depends on DEBUG_KERNEL && KALLSYMS
  657. help
  658. Normally kallsyms only contains the symbols of functions, for nicer
  659. OOPS messages. Some debuggers can use kallsyms for other
  660. symbols too: say Y here to include all symbols, if you need them
  661. and you don't care about adding 300k to the size of your kernel.
  662. Say N.
  663. config KALLSYMS_EXTRA_PASS
  664. bool "Do an extra kallsyms pass"
  665. depends on KALLSYMS
  666. help
  667. If kallsyms is not working correctly, the build will fail with
  668. inconsistent kallsyms data. If that occurs, log a bug report and
  669. turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
  670. Always say N here unless you find a bug in kallsyms, which must be
  671. reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
  672. you wait for kallsyms to be fixed.
  673. config HOTPLUG
  674. bool "Support for hot-pluggable devices" if EMBEDDED
  675. default y
  676. help
  677. This option is provided for the case where no hotplug or uevent
  678. capabilities is wanted by the kernel. You should only consider
  679. disabling this option for embedded systems that do not use modules, a
  680. dynamic /dev tree, or dynamic device discovery. Just say Y.
  681. config PRINTK
  682. default y
  683. bool "Enable support for printk" if EMBEDDED
  684. help
  685. This option enables normal printk support. Removing it
  686. eliminates most of the message strings from the kernel image
  687. and makes the kernel more or less silent. As this makes it
  688. very difficult to diagnose system problems, saying N here is
  689. strongly discouraged.
  690. config BUG
  691. bool "BUG() support" if EMBEDDED
  692. default y
  693. help
  694. Disabling this option eliminates support for BUG and WARN, reducing
  695. the size of your kernel image and potentially quietly ignoring
  696. numerous fatal conditions. You should only consider disabling this
  697. option for embedded systems with no facilities for reporting errors.
  698. Just say Y.
  699. config ELF_CORE
  700. default y
  701. bool "Enable ELF core dumps" if EMBEDDED
  702. help
  703. Enable support for generating core dumps. Disabling saves about 4k.
  704. config PCSPKR_PLATFORM
  705. bool "Enable PC-Speaker support" if EMBEDDED
  706. depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
  707. default y
  708. help
  709. This option allows to disable the internal PC-Speaker
  710. support, saving some memory.
  711. config BASE_FULL
  712. default y
  713. bool "Enable full-sized data structures for core" if EMBEDDED
  714. help
  715. Disabling this option reduces the size of miscellaneous core
  716. kernel data structures. This saves memory on small machines,
  717. but may reduce performance.
  718. config FUTEX
  719. bool "Enable futex support" if EMBEDDED
  720. default y
  721. select RT_MUTEXES
  722. help
  723. Disabling this option will cause the kernel to be built without
  724. support for "fast userspace mutexes". The resulting kernel may not
  725. run glibc-based applications correctly.
  726. config EPOLL
  727. bool "Enable eventpoll support" if EMBEDDED
  728. default y
  729. select ANON_INODES
  730. help
  731. Disabling this option will cause the kernel to be built without
  732. support for epoll family of system calls.
  733. config SIGNALFD
  734. bool "Enable signalfd() system call" if EMBEDDED
  735. select ANON_INODES
  736. default y
  737. help
  738. Enable the signalfd() system call that allows to receive signals
  739. on a file descriptor.
  740. If unsure, say Y.
  741. config TIMERFD
  742. bool "Enable timerfd() system call" if EMBEDDED
  743. select ANON_INODES
  744. default y
  745. help
  746. Enable the timerfd() system call that allows to receive timer
  747. events on a file descriptor.
  748. If unsure, say Y.
  749. config EVENTFD
  750. bool "Enable eventfd() system call" if EMBEDDED
  751. select ANON_INODES
  752. default y
  753. help
  754. Enable the eventfd() system call that allows to receive both
  755. kernel notification (ie. KAIO) or userspace notifications.
  756. If unsure, say Y.
  757. config SHMEM
  758. bool "Use full shmem filesystem" if EMBEDDED
  759. default y
  760. depends on MMU
  761. help
  762. The shmem is an internal filesystem used to manage shared memory.
  763. It is backed by swap and manages resource limits. It is also exported
  764. to userspace as tmpfs if TMPFS is enabled. Disabling this
  765. option replaces shmem and tmpfs with the much simpler ramfs code,
  766. which may be appropriate on small systems without swap.
  767. config AIO
  768. bool "Enable AIO support" if EMBEDDED
  769. default y
  770. help
  771. This option enables POSIX asynchronous I/O which may by used
  772. by some high performance threaded applications. Disabling
  773. this option saves about 7k.
  774. config HAVE_PERF_EVENTS
  775. bool
  776. help
  777. See tools/perf/design.txt for details.
  778. config PERF_USE_VMALLOC
  779. bool
  780. help
  781. See tools/perf/design.txt for details
  782. menu "Kernel Performance Events And Counters"
  783. config PERF_EVENTS
  784. bool "Kernel performance events and counters"
  785. default y if (PROFILING || PERF_COUNTERS)
  786. depends on HAVE_PERF_EVENTS
  787. select ANON_INODES
  788. help
  789. Enable kernel support for various performance events provided
  790. by software and hardware.
  791. Software events are supported either build-in or via the
  792. use of generic tracepoints.
  793. Most modern CPUs support performance events via performance
  794. counter registers. These registers count the number of certain
  795. types of hw events: such as instructions executed, cachemisses
  796. suffered, or branches mis-predicted - without slowing down the
  797. kernel or applications. These registers can also trigger interrupts
  798. when a threshold number of events have passed - and can thus be
  799. used to profile the code that runs on that CPU.
  800. The Linux Performance Event subsystem provides an abstraction of
  801. these software and hardware cevent apabilities, available via a
  802. system call and used by the "perf" utility in tools/perf/. It
  803. provides per task and per CPU counters, and it provides event
  804. capabilities on top of those.
  805. Say Y if unsure.
  806. config EVENT_PROFILE
  807. bool "Tracepoint profiling sources"
  808. depends on PERF_EVENTS && EVENT_TRACING
  809. default y
  810. help
  811. Allow the use of tracepoints as software performance events.
  812. When this is enabled, you can create perf events based on
  813. tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID
  814. found in debugfs://tracing/events/*/*/id. (The -e/--events
  815. option to the perf tool can parse and interpret symbolic
  816. tracepoints, in the subsystem:tracepoint_name format.)
  817. config PERF_COUNTERS
  818. bool "Kernel performance counters (old config option)"
  819. depends on HAVE_PERF_EVENTS
  820. help
  821. This config has been obsoleted by the PERF_EVENTS
  822. config option - please see that one for details.
  823. It has no effect on the kernel whether you enable
  824. it or not, it is a compatibility placeholder.
  825. Say N if unsure.
  826. config DEBUG_PERF_USE_VMALLOC
  827. default n
  828. bool "Debug: use vmalloc to back perf mmap() buffers"
  829. depends on PERF_EVENTS && DEBUG_KERNEL
  830. select PERF_USE_VMALLOC
  831. help
  832. Use vmalloc memory to back perf mmap() buffers.
  833. Mostly useful for debugging the vmalloc code on platforms
  834. that don't require it.
  835. Say N if unsure.
  836. endmenu
  837. config VM_EVENT_COUNTERS
  838. default y
  839. bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
  840. help
  841. VM event counters are needed for event counts to be shown.
  842. This option allows the disabling of the VM event counters
  843. on EMBEDDED systems. /proc/vmstat will only show page counts
  844. if VM event counters are disabled.
  845. config PCI_QUIRKS
  846. default y
  847. bool "Enable PCI quirk workarounds" if EMBEDDED
  848. depends on PCI
  849. help
  850. This enables workarounds for various PCI chipset
  851. bugs/quirks. Disable this only if your target machine is
  852. unaffected by PCI quirks.
  853. config SLUB_DEBUG
  854. default y
  855. bool "Enable SLUB debugging support" if EMBEDDED
  856. depends on SLUB && SYSFS
  857. help
  858. SLUB has extensive debug support features. Disabling these can
  859. result in significant savings in code size. This also disables
  860. SLUB sysfs support. /sys/slab will not exist and there will be
  861. no support for cache validation etc.
  862. config COMPAT_BRK
  863. bool "Disable heap randomization"
  864. default y
  865. help
  866. Randomizing heap placement makes heap exploits harder, but it
  867. also breaks ancient binaries (including anything libc5 based).
  868. This option changes the bootup default to heap randomization
  869. disabled, and can be overridden at runtime by setting
  870. /proc/sys/kernel/randomize_va_space to 2.
  871. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  872. choice
  873. prompt "Choose SLAB allocator"
  874. default SLUB
  875. help
  876. This option allows to select a slab allocator.
  877. config SLAB
  878. bool "SLAB"
  879. help
  880. The regular slab allocator that is established and known to work
  881. well in all environments. It organizes cache hot objects in
  882. per cpu and per node queues.
  883. config SLUB
  884. bool "SLUB (Unqueued Allocator)"
  885. help
  886. SLUB is a slab allocator that minimizes cache line usage
  887. instead of managing queues of cached objects (SLAB approach).
  888. Per cpu caching is realized using slabs of objects instead
  889. of queues of objects. SLUB can use memory efficiently
  890. and has enhanced diagnostics. SLUB is the default choice for
  891. a slab allocator.
  892. config SLOB
  893. depends on EMBEDDED
  894. bool "SLOB (Simple Allocator)"
  895. help
  896. SLOB replaces the stock allocator with a drastically simpler
  897. allocator. SLOB is generally more space efficient but
  898. does not perform as well on large systems.
  899. endchoice
  900. config PROFILING
  901. bool "Profiling support (EXPERIMENTAL)"
  902. help
  903. Say Y here to enable the extended profiling support mechanisms used
  904. by profilers such as OProfile.
  905. #
  906. # Place an empty function call at each tracepoint site. Can be
  907. # dynamically changed for a probe function.
  908. #
  909. config TRACEPOINTS
  910. bool
  911. source "arch/Kconfig"
  912. config SLOW_WORK
  913. default n
  914. bool
  915. help
  916. The slow work thread pool provides a number of dynamically allocated
  917. threads that can be used by the kernel to perform operations that
  918. take a relatively long time.
  919. An example of this would be CacheFiles doing a path lookup followed
  920. by a series of mkdirs and a create call, all of which have to touch
  921. disk.
  922. See Documentation/slow-work.txt.
  923. endmenu # General setup
  924. config HAVE_GENERIC_DMA_COHERENT
  925. bool
  926. default n
  927. config SLABINFO
  928. bool
  929. depends on PROC_FS
  930. depends on SLAB || SLUB_DEBUG
  931. default y
  932. config RT_MUTEXES
  933. boolean
  934. config BASE_SMALL
  935. int
  936. default 0 if BASE_FULL
  937. default 1 if !BASE_FULL
  938. menuconfig MODULES
  939. bool "Enable loadable module support"
  940. help
  941. Kernel modules are small pieces of compiled code which can
  942. be inserted in the running kernel, rather than being
  943. permanently built into the kernel. You use the "modprobe"
  944. tool to add (and sometimes remove) them. If you say Y here,
  945. many parts of the kernel can be built as modules (by
  946. answering M instead of Y where indicated): this is most
  947. useful for infrequently used options which are not required
  948. for booting. For more information, see the man pages for
  949. modprobe, lsmod, modinfo, insmod and rmmod.
  950. If you say Y here, you will need to run "make
  951. modules_install" to put the modules under /lib/modules/
  952. where modprobe can find them (you may need to be root to do
  953. this).
  954. If unsure, say Y.
  955. if MODULES
  956. config MODULE_FORCE_LOAD
  957. bool "Forced module loading"
  958. default n
  959. help
  960. Allow loading of modules without version information (ie. modprobe
  961. --force). Forced module loading sets the 'F' (forced) taint flag and
  962. is usually a really bad idea.
  963. config MODULE_UNLOAD
  964. bool "Module unloading"
  965. help
  966. Without this option you will not be able to unload any
  967. modules (note that some modules may not be unloadable
  968. anyway), which makes your kernel smaller, faster
  969. and simpler. If unsure, say Y.
  970. config MODULE_FORCE_UNLOAD
  971. bool "Forced module unloading"
  972. depends on MODULE_UNLOAD && EXPERIMENTAL
  973. help
  974. This option allows you to force a module to unload, even if the
  975. kernel believes it is unsafe: the kernel will remove the module
  976. without waiting for anyone to stop using it (using the -f option to
  977. rmmod). This is mainly for kernel developers and desperate users.
  978. If unsure, say N.
  979. config MODVERSIONS
  980. bool "Module versioning support"
  981. help
  982. Usually, you have to use modules compiled with your kernel.
  983. Saying Y here makes it sometimes possible to use modules
  984. compiled for different kernels, by adding enough information
  985. to the modules to (hopefully) spot any changes which would
  986. make them incompatible with the kernel you are running. If
  987. unsure, say N.
  988. config MODULE_SRCVERSION_ALL
  989. bool "Source checksum for all modules"
  990. help
  991. Modules which contain a MODULE_VERSION get an extra "srcversion"
  992. field inserted into their modinfo section, which contains a
  993. sum of the source files which made it. This helps maintainers
  994. see exactly which source was used to build a module (since
  995. others sometimes change the module source without updating
  996. the version). With this option, such a "srcversion" field
  997. will be created for all modules. If unsure, say N.
  998. endif # MODULES
  999. config INIT_ALL_POSSIBLE
  1000. bool
  1001. help
  1002. Back when each arch used to define their own cpu_online_map and
  1003. cpu_possible_map, some of them chose to initialize cpu_possible_map
  1004. with all 1s, and others with all 0s. When they were centralised,
  1005. it was better to provide this option than to break all the archs
  1006. and have several arch maintainers pursuing me down dark alleys.
  1007. config STOP_MACHINE
  1008. bool
  1009. default y
  1010. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1011. help
  1012. Need stop_machine() primitive.
  1013. source "block/Kconfig"
  1014. config PREEMPT_NOTIFIERS
  1015. bool