Kconfig 39 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 drivers that have been replaced by something else, and/or are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. config TINY_RCU
  283. bool "UP-only small-memory-footprint RCU"
  284. depends on !SMP
  285. help
  286. This option selects the RCU implementation that is
  287. designed for UP systems from which real-time response
  288. is not required. This option greatly reduces the
  289. memory footprint of RCU.
  290. endchoice
  291. config RCU_TRACE
  292. bool "Enable tracing for RCU"
  293. depends on TREE_RCU || TREE_PREEMPT_RCU
  294. help
  295. This option provides tracing in RCU which presents stats
  296. in debugfs for debugging RCU implementation.
  297. Say Y here if you want to enable RCU tracing
  298. Say N if you are unsure.
  299. config RCU_FANOUT
  300. int "Tree-based hierarchical RCU fanout value"
  301. range 2 64 if 64BIT
  302. range 2 32 if !64BIT
  303. depends on TREE_RCU || TREE_PREEMPT_RCU
  304. default 64 if 64BIT
  305. default 32 if !64BIT
  306. help
  307. This option controls the fanout of hierarchical implementations
  308. of RCU, allowing RCU to work efficiently on machines with
  309. large numbers of CPUs. This value must be at least the cube
  310. root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
  311. systems and up to 262,144 for 64-bit systems.
  312. Select a specific number if testing RCU itself.
  313. Take the default if unsure.
  314. config RCU_FANOUT_EXACT
  315. bool "Disable tree-based hierarchical RCU auto-balancing"
  316. depends on TREE_RCU || TREE_PREEMPT_RCU
  317. default n
  318. help
  319. This option forces use of the exact RCU_FANOUT value specified,
  320. regardless of imbalances in the hierarchy. This is useful for
  321. testing RCU itself, and might one day be useful on systems with
  322. strong NUMA behavior.
  323. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  324. Say N if unsure.
  325. config TREE_RCU_TRACE
  326. def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
  327. select DEBUG_FS
  328. help
  329. This option provides tracing for the TREE_RCU and
  330. TREE_PREEMPT_RCU implementations, permitting Makefile to
  331. trivially select kernel/rcutree_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. menuconfig CGROUPS
  369. boolean "Control Group support"
  370. help
  371. This option adds support for grouping sets of processes together, for
  372. use with process control subsystems such as Cpusets, CFS, memory
  373. controls or device isolation.
  374. See
  375. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  376. - Documentation/cgroups/ (features for grouping, isolation
  377. and resource control)
  378. Say N if unsure.
  379. if CGROUPS
  380. config CGROUP_DEBUG
  381. bool "Example debug cgroup subsystem"
  382. depends on CGROUPS
  383. default n
  384. help
  385. This option enables a simple cgroup subsystem that
  386. exports useful debugging information about the cgroups
  387. framework.
  388. Say N if unsure.
  389. config CGROUP_NS
  390. bool "Namespace cgroup subsystem"
  391. depends on CGROUPS
  392. help
  393. Provides a simple namespace cgroup subsystem to
  394. provide hierarchical naming of sets of namespaces,
  395. for instance virtual servers and checkpoint/restart
  396. jobs.
  397. config CGROUP_FREEZER
  398. bool "Freezer cgroup subsystem"
  399. depends on CGROUPS
  400. help
  401. Provides a way to freeze and unfreeze all tasks in a
  402. cgroup.
  403. config CGROUP_DEVICE
  404. bool "Device controller for cgroups"
  405. depends on CGROUPS && EXPERIMENTAL
  406. help
  407. Provides a cgroup implementing whitelists for devices which
  408. a process in the cgroup can mknod or open.
  409. config CPUSETS
  410. bool "Cpuset support"
  411. depends on CGROUPS
  412. help
  413. This option will let you create and manage CPUSETs which
  414. allow dynamically partitioning a system into sets of CPUs and
  415. Memory Nodes and assigning tasks to run only within those sets.
  416. This is primarily useful on large SMP or NUMA systems.
  417. Say N if unsure.
  418. config PROC_PID_CPUSET
  419. bool "Include legacy /proc/<pid>/cpuset file"
  420. depends on CPUSETS
  421. default y
  422. config CGROUP_CPUACCT
  423. bool "Simple CPU accounting cgroup subsystem"
  424. depends on CGROUPS
  425. help
  426. Provides a simple Resource Controller for monitoring the
  427. total CPU consumed by the tasks in a cgroup.
  428. config RESOURCE_COUNTERS
  429. bool "Resource counters"
  430. help
  431. This option enables controller independent resource accounting
  432. infrastructure that works with cgroups.
  433. depends on CGROUPS
  434. config CGROUP_MEM_RES_CTLR
  435. bool "Memory Resource Controller for Control Groups"
  436. depends on CGROUPS && RESOURCE_COUNTERS
  437. select MM_OWNER
  438. help
  439. Provides a memory resource controller that manages both anonymous
  440. memory and page cache. (See Documentation/cgroups/memory.txt)
  441. Note that setting this option increases fixed memory overhead
  442. associated with each page of memory in the system. By this,
  443. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  444. usage tracking struct at boot. Total amount of this is printed out
  445. at boot.
  446. Only enable when you're ok with these trade offs and really
  447. sure you need the memory resource controller. Even when you enable
  448. this, you can set "cgroup_disable=memory" at your boot option to
  449. disable memory resource controller and you can avoid overheads.
  450. (and lose benefits of memory resource controller)
  451. This config option also selects MM_OWNER config option, which
  452. could in turn add some fork/exit overhead.
  453. config CGROUP_MEM_RES_CTLR_SWAP
  454. bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
  455. depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
  456. help
  457. Add swap management feature to memory resource controller. When you
  458. enable this, you can limit mem+swap usage per cgroup. In other words,
  459. when you disable this, memory resource controller has no cares to
  460. usage of swap...a process can exhaust all of the swap. This extension
  461. is useful when you want to avoid exhaustion swap but this itself
  462. adds more overheads and consumes memory for remembering information.
  463. Especially if you use 32bit system or small memory system, please
  464. be careful about enabling this. When memory resource controller
  465. is disabled by boot option, this will be automatically disabled and
  466. there will be no overhead from this. Even when you set this config=y,
  467. if boot option "noswapaccount" is set, swap will not be accounted.
  468. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  469. size is 4096bytes, 512k per 1Gbytes of swap.
  470. menuconfig CGROUP_SCHED
  471. bool "Group CPU scheduler"
  472. depends on EXPERIMENTAL && CGROUPS
  473. default n
  474. help
  475. This feature lets CPU scheduler recognize task groups and control CPU
  476. bandwidth allocation to such task groups. It uses cgroups to group
  477. tasks.
  478. if CGROUP_SCHED
  479. config FAIR_GROUP_SCHED
  480. bool "Group scheduling for SCHED_OTHER"
  481. depends on CGROUP_SCHED
  482. default CGROUP_SCHED
  483. config RT_GROUP_SCHED
  484. bool "Group scheduling for SCHED_RR/FIFO"
  485. depends on EXPERIMENTAL
  486. depends on CGROUP_SCHED
  487. default n
  488. help
  489. This feature lets you explicitly allocate real CPU bandwidth
  490. to users or control groups (depending on the "Basis for grouping tasks"
  491. setting below. If enabled, it will also make it impossible to
  492. schedule realtime tasks for non-root users until you allocate
  493. realtime bandwidth for them.
  494. See Documentation/scheduler/sched-rt-group.txt for more information.
  495. endif #CGROUP_SCHED
  496. endif # CGROUPS
  497. config MM_OWNER
  498. bool
  499. config SYSFS_DEPRECATED
  500. bool
  501. config SYSFS_DEPRECATED_V2
  502. bool "enable deprecated sysfs features to support old userspace tools"
  503. depends on SYSFS
  504. default n
  505. select SYSFS_DEPRECATED
  506. help
  507. This option switches the layout of sysfs to the deprecated
  508. version. Do not use it on recent distributions.
  509. The current sysfs layout features a unified device tree at
  510. /sys/devices/, which is able to express a hierarchy between
  511. class devices. If the deprecated option is set to Y, the
  512. unified device tree is split into a bus device tree at
  513. /sys/devices/ and several individual class device trees at
  514. /sys/class/. The class and bus devices will be connected by
  515. "<subsystem>:<name>" and the "device" links. The "block"
  516. class devices, will not show up in /sys/class/block/. Some
  517. subsystems will suppress the creation of some devices which
  518. depend on the unified device tree.
  519. This option is not a pure compatibility option that can
  520. be safely enabled on newer distributions. It will change the
  521. layout of sysfs to the non-extensible deprecated version,
  522. and disable some features, which can not be exported without
  523. confusing older userspace tools. Since 2007/2008 all major
  524. distributions do not enable this option, and ship no tools which
  525. depend on the deprecated layout or this option.
  526. If you are using a new kernel on an older distribution, or use
  527. older userspace tools, you might need to say Y here. Do not say Y,
  528. if the original kernel, that came with your distribution, has
  529. this option set to N.
  530. config RELAY
  531. bool "Kernel->user space relay support (formerly relayfs)"
  532. help
  533. This option enables support for relay interface support in
  534. certain file systems (such as debugfs).
  535. It is designed to provide an efficient mechanism for tools and
  536. facilities to relay large amounts of data from kernel space to
  537. user space.
  538. If unsure, say N.
  539. config NAMESPACES
  540. bool "Namespaces support" if EMBEDDED
  541. default !EMBEDDED
  542. help
  543. Provides the way to make tasks work with different objects using
  544. the same id. For example same IPC id may refer to different objects
  545. or same user id or pid may refer to different tasks when used in
  546. different namespaces.
  547. config UTS_NS
  548. bool "UTS namespace"
  549. depends on NAMESPACES
  550. help
  551. In this namespace tasks see different info provided with the
  552. uname() system call
  553. config IPC_NS
  554. bool "IPC namespace"
  555. depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
  556. help
  557. In this namespace tasks work with IPC ids which correspond to
  558. different IPC objects in different namespaces.
  559. config USER_NS
  560. bool "User namespace (EXPERIMENTAL)"
  561. depends on NAMESPACES && EXPERIMENTAL
  562. help
  563. This allows containers, i.e. vservers, to use user namespaces
  564. to provide different user info for different servers.
  565. If unsure, say N.
  566. config PID_NS
  567. bool "PID Namespaces (EXPERIMENTAL)"
  568. default n
  569. depends on NAMESPACES && EXPERIMENTAL
  570. help
  571. Support process id namespaces. This allows having multiple
  572. processes with the same pid as long as they are in different
  573. pid namespaces. This is a building block of containers.
  574. Unless you want to work with an experimental feature
  575. say N here.
  576. config NET_NS
  577. bool "Network namespace"
  578. default n
  579. depends on NAMESPACES && EXPERIMENTAL && NET
  580. help
  581. Allow user space to create what appear to be multiple instances
  582. of the network stack.
  583. config BLK_DEV_INITRD
  584. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  585. depends on BROKEN || !FRV
  586. help
  587. The initial RAM filesystem is a ramfs which is loaded by the
  588. boot loader (loadlin or lilo) and that is mounted as root
  589. before the normal boot procedure. It is typically used to
  590. load modules needed to mount the "real" root file system,
  591. etc. See <file:Documentation/initrd.txt> for details.
  592. If RAM disk support (BLK_DEV_RAM) is also included, this
  593. also enables initial RAM disk (initrd) support and adds
  594. 15 Kbytes (more on some other architectures) to the kernel size.
  595. If unsure say Y.
  596. if BLK_DEV_INITRD
  597. source "usr/Kconfig"
  598. endif
  599. config CC_OPTIMIZE_FOR_SIZE
  600. bool "Optimize for size"
  601. default y
  602. help
  603. Enabling this option will pass "-Os" instead of "-O2" to gcc
  604. resulting in a smaller kernel.
  605. If unsure, say Y.
  606. config SYSCTL
  607. bool
  608. config ANON_INODES
  609. bool
  610. menuconfig EMBEDDED
  611. bool "Configure standard kernel features (for small systems)"
  612. help
  613. This option allows certain base kernel options and settings
  614. to be disabled or tweaked. This is for specialized
  615. environments which can tolerate a "non-standard" kernel.
  616. Only use this if you really know what you are doing.
  617. config UID16
  618. bool "Enable 16-bit UID system calls" if EMBEDDED
  619. depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
  620. default y
  621. help
  622. This enables the legacy 16-bit UID syscall wrappers.
  623. config SYSCTL_SYSCALL
  624. bool "Sysctl syscall support" if EMBEDDED
  625. depends on PROC_SYSCTL
  626. default y
  627. select SYSCTL
  628. ---help---
  629. sys_sysctl uses binary paths that have been found challenging
  630. to properly maintain and use. The interface in /proc/sys
  631. using paths with ascii names is now the primary path to this
  632. information.
  633. Almost nothing using the binary sysctl interface so if you are
  634. trying to save some space it is probably safe to disable this,
  635. making your kernel marginally smaller.
  636. If unsure say Y here.
  637. config KALLSYMS
  638. bool "Load all symbols for debugging/ksymoops" if EMBEDDED
  639. default y
  640. help
  641. Say Y here to let the kernel print out symbolic crash information and
  642. symbolic stack backtraces. This increases the size of the kernel
  643. somewhat, as all symbols have to be loaded into the kernel image.
  644. config KALLSYMS_ALL
  645. bool "Include all symbols in kallsyms"
  646. depends on DEBUG_KERNEL && KALLSYMS
  647. help
  648. Normally kallsyms only contains the symbols of functions, for nicer
  649. OOPS messages. Some debuggers can use kallsyms for other
  650. symbols too: say Y here to include all symbols, if you need them
  651. and you don't care about adding 300k to the size of your kernel.
  652. Say N.
  653. config KALLSYMS_EXTRA_PASS
  654. bool "Do an extra kallsyms pass"
  655. depends on KALLSYMS
  656. help
  657. If kallsyms is not working correctly, the build will fail with
  658. inconsistent kallsyms data. If that occurs, log a bug report and
  659. turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
  660. Always say N here unless you find a bug in kallsyms, which must be
  661. reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
  662. you wait for kallsyms to be fixed.
  663. config HOTPLUG
  664. bool "Support for hot-pluggable devices" if EMBEDDED
  665. default y
  666. help
  667. This option is provided for the case where no hotplug or uevent
  668. capabilities is wanted by the kernel. You should only consider
  669. disabling this option for embedded systems that do not use modules, a
  670. dynamic /dev tree, or dynamic device discovery. Just say Y.
  671. config PRINTK
  672. default y
  673. bool "Enable support for printk" if EMBEDDED
  674. help
  675. This option enables normal printk support. Removing it
  676. eliminates most of the message strings from the kernel image
  677. and makes the kernel more or less silent. As this makes it
  678. very difficult to diagnose system problems, saying N here is
  679. strongly discouraged.
  680. config BUG
  681. bool "BUG() support" if EMBEDDED
  682. default y
  683. help
  684. Disabling this option eliminates support for BUG and WARN, reducing
  685. the size of your kernel image and potentially quietly ignoring
  686. numerous fatal conditions. You should only consider disabling this
  687. option for embedded systems with no facilities for reporting errors.
  688. Just say Y.
  689. config ELF_CORE
  690. default y
  691. bool "Enable ELF core dumps" if EMBEDDED
  692. help
  693. Enable support for generating core dumps. Disabling saves about 4k.
  694. config PCSPKR_PLATFORM
  695. bool "Enable PC-Speaker support" if EMBEDDED
  696. depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
  697. default y
  698. help
  699. This option allows to disable the internal PC-Speaker
  700. support, saving some memory.
  701. config BASE_FULL
  702. default y
  703. bool "Enable full-sized data structures for core" if EMBEDDED
  704. help
  705. Disabling this option reduces the size of miscellaneous core
  706. kernel data structures. This saves memory on small machines,
  707. but may reduce performance.
  708. config FUTEX
  709. bool "Enable futex support" if EMBEDDED
  710. default y
  711. select RT_MUTEXES
  712. help
  713. Disabling this option will cause the kernel to be built without
  714. support for "fast userspace mutexes". The resulting kernel may not
  715. run glibc-based applications correctly.
  716. config EPOLL
  717. bool "Enable eventpoll support" if EMBEDDED
  718. default y
  719. select ANON_INODES
  720. help
  721. Disabling this option will cause the kernel to be built without
  722. support for epoll family of system calls.
  723. config SIGNALFD
  724. bool "Enable signalfd() system call" if EMBEDDED
  725. select ANON_INODES
  726. default y
  727. help
  728. Enable the signalfd() system call that allows to receive signals
  729. on a file descriptor.
  730. If unsure, say Y.
  731. config TIMERFD
  732. bool "Enable timerfd() system call" if EMBEDDED
  733. select ANON_INODES
  734. default y
  735. help
  736. Enable the timerfd() system call that allows to receive timer
  737. events on a file descriptor.
  738. If unsure, say Y.
  739. config EVENTFD
  740. bool "Enable eventfd() system call" if EMBEDDED
  741. select ANON_INODES
  742. default y
  743. help
  744. Enable the eventfd() system call that allows to receive both
  745. kernel notification (ie. KAIO) or userspace notifications.
  746. If unsure, say Y.
  747. config SHMEM
  748. bool "Use full shmem filesystem" if EMBEDDED
  749. default y
  750. depends on MMU
  751. help
  752. The shmem is an internal filesystem used to manage shared memory.
  753. It is backed by swap and manages resource limits. It is also exported
  754. to userspace as tmpfs if TMPFS is enabled. Disabling this
  755. option replaces shmem and tmpfs with the much simpler ramfs code,
  756. which may be appropriate on small systems without swap.
  757. config AIO
  758. bool "Enable AIO support" if EMBEDDED
  759. default y
  760. help
  761. This option enables POSIX asynchronous I/O which may by used
  762. by some high performance threaded applications. Disabling
  763. this option saves about 7k.
  764. config HAVE_PERF_EVENTS
  765. bool
  766. help
  767. See tools/perf/design.txt for details.
  768. config PERF_USE_VMALLOC
  769. bool
  770. help
  771. See tools/perf/design.txt for details
  772. menu "Kernel Performance Events And Counters"
  773. config PERF_EVENTS
  774. bool "Kernel performance events and counters"
  775. default y if (PROFILING || PERF_COUNTERS)
  776. depends on HAVE_PERF_EVENTS
  777. select ANON_INODES
  778. help
  779. Enable kernel support for various performance events provided
  780. by software and hardware.
  781. Software events are supported either built-in or via the
  782. use of generic tracepoints.
  783. Most modern CPUs support performance events via performance
  784. counter registers. These registers count the number of certain
  785. types of hw events: such as instructions executed, cachemisses
  786. suffered, or branches mis-predicted - without slowing down the
  787. kernel or applications. These registers can also trigger interrupts
  788. when a threshold number of events have passed - and can thus be
  789. used to profile the code that runs on that CPU.
  790. The Linux Performance Event subsystem provides an abstraction of
  791. these software and hardware event capabilities, available via a
  792. system call and used by the "perf" utility in tools/perf/. It
  793. provides per task and per CPU counters, and it provides event
  794. capabilities on top of those.
  795. Say Y if unsure.
  796. config EVENT_PROFILE
  797. bool "Tracepoint profiling sources"
  798. depends on PERF_EVENTS && EVENT_TRACING
  799. default y
  800. help
  801. Allow the use of tracepoints as software performance events.
  802. When this is enabled, you can create perf events based on
  803. tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID
  804. found in debugfs://tracing/events/*/*/id. (The -e/--events
  805. option to the perf tool can parse and interpret symbolic
  806. tracepoints, in the subsystem:tracepoint_name format.)
  807. config PERF_COUNTERS
  808. bool "Kernel performance counters (old config option)"
  809. depends on HAVE_PERF_EVENTS
  810. help
  811. This config has been obsoleted by the PERF_EVENTS
  812. config option - please see that one for details.
  813. It has no effect on the kernel whether you enable
  814. it or not, it is a compatibility placeholder.
  815. Say N if unsure.
  816. config DEBUG_PERF_USE_VMALLOC
  817. default n
  818. bool "Debug: use vmalloc to back perf mmap() buffers"
  819. depends on PERF_EVENTS && DEBUG_KERNEL
  820. select PERF_USE_VMALLOC
  821. help
  822. Use vmalloc memory to back perf mmap() buffers.
  823. Mostly useful for debugging the vmalloc code on platforms
  824. that don't require it.
  825. Say N if unsure.
  826. endmenu
  827. config VM_EVENT_COUNTERS
  828. default y
  829. bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
  830. help
  831. VM event counters are needed for event counts to be shown.
  832. This option allows the disabling of the VM event counters
  833. on EMBEDDED systems. /proc/vmstat will only show page counts
  834. if VM event counters are disabled.
  835. config PCI_QUIRKS
  836. default y
  837. bool "Enable PCI quirk workarounds" if EMBEDDED
  838. depends on PCI
  839. help
  840. This enables workarounds for various PCI chipset
  841. bugs/quirks. Disable this only if your target machine is
  842. unaffected by PCI quirks.
  843. config SLUB_DEBUG
  844. default y
  845. bool "Enable SLUB debugging support" if EMBEDDED
  846. depends on SLUB && SYSFS
  847. help
  848. SLUB has extensive debug support features. Disabling these can
  849. result in significant savings in code size. This also disables
  850. SLUB sysfs support. /sys/slab will not exist and there will be
  851. no support for cache validation etc.
  852. config COMPAT_BRK
  853. bool "Disable heap randomization"
  854. default y
  855. help
  856. Randomizing heap placement makes heap exploits harder, but it
  857. also breaks ancient binaries (including anything libc5 based).
  858. This option changes the bootup default to heap randomization
  859. disabled, and can be overridden at runtime by setting
  860. /proc/sys/kernel/randomize_va_space to 2.
  861. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  862. choice
  863. prompt "Choose SLAB allocator"
  864. default SLUB
  865. help
  866. This option allows to select a slab allocator.
  867. config SLAB
  868. bool "SLAB"
  869. help
  870. The regular slab allocator that is established and known to work
  871. well in all environments. It organizes cache hot objects in
  872. per cpu and per node queues.
  873. config SLUB
  874. bool "SLUB (Unqueued Allocator)"
  875. help
  876. SLUB is a slab allocator that minimizes cache line usage
  877. instead of managing queues of cached objects (SLAB approach).
  878. Per cpu caching is realized using slabs of objects instead
  879. of queues of objects. SLUB can use memory efficiently
  880. and has enhanced diagnostics. SLUB is the default choice for
  881. a slab allocator.
  882. config SLOB
  883. depends on EMBEDDED
  884. bool "SLOB (Simple Allocator)"
  885. help
  886. SLOB replaces the stock allocator with a drastically simpler
  887. allocator. SLOB is generally more space efficient but
  888. does not perform as well on large systems.
  889. endchoice
  890. config MMAP_ALLOW_UNINITIALIZED
  891. bool "Allow mmapped anonymous memory to be uninitialized"
  892. depends on EMBEDDED && !MMU
  893. default n
  894. help
  895. Normally, and according to the Linux spec, anonymous memory obtained
  896. from mmap() has it's contents cleared before it is passed to
  897. userspace. Enabling this config option allows you to request that
  898. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  899. providing a huge performance boost. If this option is not enabled,
  900. then the flag will be ignored.
  901. This is taken advantage of by uClibc's malloc(), and also by
  902. ELF-FDPIC binfmt's brk and stack allocator.
  903. Because of the obvious security issues, this option should only be
  904. enabled on embedded devices where you control what is run in
  905. userspace. Since that isn't generally a problem on no-MMU systems,
  906. it is normally safe to say Y here.
  907. See Documentation/nommu-mmap.txt for more information.
  908. config PROFILING
  909. bool "Profiling support (EXPERIMENTAL)"
  910. help
  911. Say Y here to enable the extended profiling support mechanisms used
  912. by profilers such as OProfile.
  913. #
  914. # Place an empty function call at each tracepoint site. Can be
  915. # dynamically changed for a probe function.
  916. #
  917. config TRACEPOINTS
  918. bool
  919. source "arch/Kconfig"
  920. config SLOW_WORK
  921. default n
  922. bool
  923. help
  924. The slow work thread pool provides a number of dynamically allocated
  925. threads that can be used by the kernel to perform operations that
  926. take a relatively long time.
  927. An example of this would be CacheFiles doing a path lookup followed
  928. by a series of mkdirs and a create call, all of which have to touch
  929. disk.
  930. See Documentation/slow-work.txt.
  931. config SLOW_WORK_DEBUG
  932. bool "Slow work debugging through debugfs"
  933. default n
  934. depends on SLOW_WORK && DEBUG_FS
  935. help
  936. Display the contents of the slow work run queue through debugfs,
  937. including items currently executing.
  938. See Documentation/slow-work.txt.
  939. endmenu # General setup
  940. config HAVE_GENERIC_DMA_COHERENT
  941. bool
  942. default n
  943. config SLABINFO
  944. bool
  945. depends on PROC_FS
  946. depends on SLAB || SLUB_DEBUG
  947. default y
  948. config RT_MUTEXES
  949. boolean
  950. config BASE_SMALL
  951. int
  952. default 0 if BASE_FULL
  953. default 1 if !BASE_FULL
  954. menuconfig MODULES
  955. bool "Enable loadable module support"
  956. help
  957. Kernel modules are small pieces of compiled code which can
  958. be inserted in the running kernel, rather than being
  959. permanently built into the kernel. You use the "modprobe"
  960. tool to add (and sometimes remove) them. If you say Y here,
  961. many parts of the kernel can be built as modules (by
  962. answering M instead of Y where indicated): this is most
  963. useful for infrequently used options which are not required
  964. for booting. For more information, see the man pages for
  965. modprobe, lsmod, modinfo, insmod and rmmod.
  966. If you say Y here, you will need to run "make
  967. modules_install" to put the modules under /lib/modules/
  968. where modprobe can find them (you may need to be root to do
  969. this).
  970. If unsure, say Y.
  971. if MODULES
  972. config MODULE_FORCE_LOAD
  973. bool "Forced module loading"
  974. default n
  975. help
  976. Allow loading of modules without version information (ie. modprobe
  977. --force). Forced module loading sets the 'F' (forced) taint flag and
  978. is usually a really bad idea.
  979. config MODULE_UNLOAD
  980. bool "Module unloading"
  981. help
  982. Without this option you will not be able to unload any
  983. modules (note that some modules may not be unloadable
  984. anyway), which makes your kernel smaller, faster
  985. and simpler. If unsure, say Y.
  986. config MODULE_FORCE_UNLOAD
  987. bool "Forced module unloading"
  988. depends on MODULE_UNLOAD && EXPERIMENTAL
  989. help
  990. This option allows you to force a module to unload, even if the
  991. kernel believes it is unsafe: the kernel will remove the module
  992. without waiting for anyone to stop using it (using the -f option to
  993. rmmod). This is mainly for kernel developers and desperate users.
  994. If unsure, say N.
  995. config MODVERSIONS
  996. bool "Module versioning support"
  997. help
  998. Usually, you have to use modules compiled with your kernel.
  999. Saying Y here makes it sometimes possible to use modules
  1000. compiled for different kernels, by adding enough information
  1001. to the modules to (hopefully) spot any changes which would
  1002. make them incompatible with the kernel you are running. If
  1003. unsure, say N.
  1004. config MODULE_SRCVERSION_ALL
  1005. bool "Source checksum for all modules"
  1006. help
  1007. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1008. field inserted into their modinfo section, which contains a
  1009. sum of the source files which made it. This helps maintainers
  1010. see exactly which source was used to build a module (since
  1011. others sometimes change the module source without updating
  1012. the version). With this option, such a "srcversion" field
  1013. will be created for all modules. If unsure, say N.
  1014. endif # MODULES
  1015. config INIT_ALL_POSSIBLE
  1016. bool
  1017. help
  1018. Back when each arch used to define their own cpu_online_map and
  1019. cpu_possible_map, some of them chose to initialize cpu_possible_map
  1020. with all 1s, and others with all 0s. When they were centralised,
  1021. it was better to provide this option than to break all the archs
  1022. and have several arch maintainers pursuing me down dark alleys.
  1023. config STOP_MACHINE
  1024. bool
  1025. default y
  1026. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1027. help
  1028. Need stop_machine() primitive.
  1029. source "block/Kconfig"
  1030. config PREEMPT_NOTIFIERS
  1031. bool
  1032. source "kernel/Kconfig.locks"