Kconfig 40 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 drivers that have been replaced by something else, and/or are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 CROSS_COMPILE
  67. string "Cross-compiler tool prefix"
  68. help
  69. Same as running 'make CROSS_COMPILE=prefix-' but stored for
  70. default make runs in this kernel build directory. You don't
  71. need to set this unless you want the configured kernel build
  72. directory to select the cross-compiler automatically.
  73. config LOCALVERSION
  74. string "Local version - append to kernel release"
  75. help
  76. Append an extra string to the end of your kernel version.
  77. This will show up when you type uname, for example.
  78. The string you set here will be appended after the contents of
  79. any files with a filename matching localversion* in your
  80. object and source tree, in that order. Your total string can
  81. be a maximum of 64 characters.
  82. config LOCALVERSION_AUTO
  83. bool "Automatically append version information to the version string"
  84. default y
  85. help
  86. This will try to automatically determine if the current tree is a
  87. release tree by looking for git tags that belong to the current
  88. top of tree revision.
  89. A string of the format -gxxxxxxxx will be added to the localversion
  90. if a git-based tree is found. The string generated by this will be
  91. appended after any matching localversion* files, and after the value
  92. set in CONFIG_LOCALVERSION.
  93. (The actual string used here is the first eight characters produced
  94. by running the command:
  95. $ git rev-parse --verify HEAD
  96. which is done within the script "scripts/setlocalversion".)
  97. config HAVE_KERNEL_GZIP
  98. bool
  99. config HAVE_KERNEL_BZIP2
  100. bool
  101. config HAVE_KERNEL_LZMA
  102. bool
  103. config HAVE_KERNEL_LZO
  104. bool
  105. choice
  106. prompt "Kernel compression mode"
  107. default KERNEL_GZIP
  108. depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
  109. help
  110. The linux kernel is a kind of self-extracting executable.
  111. Several compression algorithms are available, which differ
  112. in efficiency, compression and decompression speed.
  113. Compression speed is only relevant when building a kernel.
  114. Decompression speed is relevant at each boot.
  115. If you have any problems with bzip2 or lzma compressed
  116. kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
  117. version of this functionality (bzip2 only), for 2.4, was
  118. supplied by Christian Ludwig)
  119. High compression options are mostly useful for users, who
  120. are low on disk space (embedded systems), but for whom ram
  121. size matters less.
  122. If in doubt, select 'gzip'
  123. config KERNEL_GZIP
  124. bool "Gzip"
  125. depends on HAVE_KERNEL_GZIP
  126. help
  127. The old and tried gzip compression. It provides a good balance
  128. between compression ratio and decompression speed.
  129. config KERNEL_BZIP2
  130. bool "Bzip2"
  131. depends on HAVE_KERNEL_BZIP2
  132. help
  133. Its compression ratio and speed is intermediate.
  134. Decompression speed is slowest among the three. The kernel
  135. size is about 10% smaller with bzip2, in comparison to gzip.
  136. Bzip2 uses a large amount of memory. For modern kernels you
  137. will need at least 8MB RAM or more for booting.
  138. config KERNEL_LZMA
  139. bool "LZMA"
  140. depends on HAVE_KERNEL_LZMA
  141. help
  142. The most recent compression algorithm.
  143. Its ratio is best, decompression speed is between the other
  144. two. Compression is slowest. The kernel size is about 33%
  145. smaller with LZMA in comparison to gzip.
  146. config KERNEL_LZO
  147. bool "LZO"
  148. depends on HAVE_KERNEL_LZO
  149. help
  150. Its compression ratio is the poorest among the 4. The kernel
  151. size is about about 10% bigger than gzip; however its speed
  152. (both compression and decompression) is the fastest.
  153. endchoice
  154. config SWAP
  155. bool "Support for paging of anonymous memory (swap)"
  156. depends on MMU && BLOCK
  157. default y
  158. help
  159. This option allows you to choose whether you want to have support
  160. for so called swap devices or swap files in your kernel that are
  161. used to provide more virtual memory than the actual RAM present
  162. in your computer. If unsure say Y.
  163. config SYSVIPC
  164. bool "System V IPC"
  165. ---help---
  166. Inter Process Communication is a suite of library functions and
  167. system calls which let processes (running programs) synchronize and
  168. exchange information. It is generally considered to be a good thing,
  169. and some programs won't run unless you say Y here. In particular, if
  170. you want to run the DOS emulator dosemu under Linux (read the
  171. DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
  172. you'll need to say Y here.
  173. You can find documentation about IPC with "info ipc" and also in
  174. section 6.4 of the Linux Programmer's Guide, available from
  175. <http://www.tldp.org/guides.html>.
  176. config SYSVIPC_SYSCTL
  177. bool
  178. depends on SYSVIPC
  179. depends on SYSCTL
  180. default y
  181. config POSIX_MQUEUE
  182. bool "POSIX Message Queues"
  183. depends on NET && EXPERIMENTAL
  184. ---help---
  185. POSIX variant of message queues is a part of IPC. In POSIX message
  186. queues every message has a priority which decides about succession
  187. of receiving it by a process. If you want to compile and run
  188. programs written e.g. for Solaris with use of its POSIX message
  189. queues (functions mq_*) say Y here.
  190. POSIX message queues are visible as a filesystem called 'mqueue'
  191. and can be mounted somewhere if you want to do filesystem
  192. operations on message queues.
  193. If unsure, say Y.
  194. config POSIX_MQUEUE_SYSCTL
  195. bool
  196. depends on POSIX_MQUEUE
  197. depends on SYSCTL
  198. default y
  199. config BSD_PROCESS_ACCT
  200. bool "BSD Process Accounting"
  201. help
  202. If you say Y here, a user level program will be able to instruct the
  203. kernel (via a special system call) to write process accounting
  204. information to a file: whenever a process exits, information about
  205. that process will be appended to the file by the kernel. The
  206. information includes things such as creation time, owning user,
  207. command name, memory usage, controlling terminal etc. (the complete
  208. list is in the struct acct in <file:include/linux/acct.h>). It is
  209. up to the user level program to do useful things with this
  210. information. This is generally a good idea, so say Y.
  211. config BSD_PROCESS_ACCT_V3
  212. bool "BSD Process Accounting version 3 file format"
  213. depends on BSD_PROCESS_ACCT
  214. default n
  215. help
  216. If you say Y here, the process accounting information is written
  217. in a new file format that also logs the process IDs of each
  218. process and it's parent. Note that this file format is incompatible
  219. with previous v0/v1/v2 file formats, so you will need updated tools
  220. for processing it. A preliminary version of these tools is available
  221. at <http://www.gnu.org/software/acct/>.
  222. config TASKSTATS
  223. bool "Export task/process statistics through netlink (EXPERIMENTAL)"
  224. depends on NET
  225. default n
  226. help
  227. Export selected statistics for tasks/processes through the
  228. generic netlink interface. Unlike BSD process accounting, the
  229. statistics are available during the lifetime of tasks/processes as
  230. responses to commands. Like BSD accounting, they are sent to user
  231. space on task exit.
  232. Say N if unsure.
  233. config TASK_DELAY_ACCT
  234. bool "Enable per-task delay accounting (EXPERIMENTAL)"
  235. depends on TASKSTATS
  236. help
  237. Collect information on time spent by a task waiting for system
  238. resources like cpu, synchronous block I/O completion and swapping
  239. in pages. Such statistics can help in setting a task's priorities
  240. relative to other tasks for cpu, io, rss limits etc.
  241. Say N if unsure.
  242. config TASK_XACCT
  243. bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
  244. depends on TASKSTATS
  245. help
  246. Collect extended task accounting data and send the data
  247. to userland for processing over the taskstats interface.
  248. Say N if unsure.
  249. config TASK_IO_ACCOUNTING
  250. bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
  251. depends on TASK_XACCT
  252. help
  253. Collect information on the number of bytes of storage I/O which this
  254. task has caused.
  255. Say N if unsure.
  256. config AUDIT
  257. bool "Auditing support"
  258. depends on NET
  259. help
  260. Enable auditing infrastructure that can be used with another
  261. kernel subsystem, such as SELinux (which requires this for
  262. logging of avc messages output). Does not do system-call
  263. auditing without CONFIG_AUDITSYSCALL.
  264. config AUDITSYSCALL
  265. bool "Enable system-call auditing support"
  266. depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
  267. default y if SECURITY_SELINUX
  268. help
  269. Enable low-overhead system-call auditing infrastructure that
  270. can be used independently or with another kernel subsystem,
  271. such as SELinux.
  272. config AUDIT_WATCH
  273. def_bool y
  274. depends on AUDITSYSCALL
  275. select FSNOTIFY
  276. config AUDIT_TREE
  277. def_bool y
  278. depends on AUDITSYSCALL
  279. select FSNOTIFY
  280. menu "RCU Subsystem"
  281. choice
  282. prompt "RCU Implementation"
  283. default TREE_RCU
  284. config TREE_RCU
  285. bool "Tree-based hierarchical RCU"
  286. depends on !PREEMPT && SMP
  287. help
  288. This option selects the RCU implementation that is
  289. designed for very large SMP system with hundreds or
  290. thousands of CPUs. It also scales down nicely to
  291. smaller systems.
  292. config TREE_PREEMPT_RCU
  293. bool "Preemptible tree-based hierarchical RCU"
  294. depends on PREEMPT
  295. help
  296. This option selects the RCU implementation that is
  297. designed for very large SMP systems with hundreds or
  298. thousands of CPUs, but for which real-time response
  299. is also required. It also scales down nicely to
  300. smaller systems.
  301. config TINY_RCU
  302. bool "UP-only small-memory-footprint RCU"
  303. depends on !SMP
  304. help
  305. This option selects the RCU implementation that is
  306. designed for UP systems from which real-time response
  307. is not required. This option greatly reduces the
  308. memory footprint of RCU.
  309. config TINY_PREEMPT_RCU
  310. bool "Preemptible UP-only small-memory-footprint RCU"
  311. depends on !SMP && PREEMPT
  312. help
  313. This option selects the RCU implementation that is designed
  314. for real-time UP systems. This option greatly reduces the
  315. memory footprint of RCU.
  316. endchoice
  317. config PREEMPT_RCU
  318. def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
  319. help
  320. This option enables preemptible-RCU code that is common between
  321. the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
  322. config RCU_TRACE
  323. bool "Enable tracing for RCU"
  324. depends on TREE_RCU || TREE_PREEMPT_RCU
  325. help
  326. This option provides tracing in RCU which presents stats
  327. in debugfs for debugging RCU implementation.
  328. Say Y here if you want to enable RCU tracing
  329. Say N if you are unsure.
  330. config RCU_FANOUT
  331. int "Tree-based hierarchical RCU fanout value"
  332. range 2 64 if 64BIT
  333. range 2 32 if !64BIT
  334. depends on TREE_RCU || TREE_PREEMPT_RCU
  335. default 64 if 64BIT
  336. default 32 if !64BIT
  337. help
  338. This option controls the fanout of hierarchical implementations
  339. of RCU, allowing RCU to work efficiently on machines with
  340. large numbers of CPUs. This value must be at least the fourth
  341. root of NR_CPUS, which allows NR_CPUS to be insanely large.
  342. The default value of RCU_FANOUT should be used for production
  343. systems, but if you are stress-testing the RCU implementation
  344. itself, small RCU_FANOUT values allow you to test large-system
  345. code paths on small(er) systems.
  346. Select a specific number if testing RCU itself.
  347. Take the default if unsure.
  348. config RCU_FANOUT_EXACT
  349. bool "Disable tree-based hierarchical RCU auto-balancing"
  350. depends on TREE_RCU || TREE_PREEMPT_RCU
  351. default n
  352. help
  353. This option forces use of the exact RCU_FANOUT value specified,
  354. regardless of imbalances in the hierarchy. This is useful for
  355. testing RCU itself, and might one day be useful on systems with
  356. strong NUMA behavior.
  357. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  358. Say N if unsure.
  359. config RCU_FAST_NO_HZ
  360. bool "Accelerate last non-dyntick-idle CPU's grace periods"
  361. depends on TREE_RCU && NO_HZ && SMP
  362. default n
  363. help
  364. This option causes RCU to attempt to accelerate grace periods
  365. in order to allow the final CPU to enter dynticks-idle state
  366. more quickly. On the other hand, this option increases the
  367. overhead of the dynticks-idle checking, particularly on systems
  368. with large numbers of CPUs.
  369. Say Y if energy efficiency is critically important, particularly
  370. if you have relatively few CPUs.
  371. Say N if you are unsure.
  372. config TREE_RCU_TRACE
  373. def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
  374. select DEBUG_FS
  375. help
  376. This option provides tracing for the TREE_RCU and
  377. TREE_PREEMPT_RCU implementations, permitting Makefile to
  378. trivially select kernel/rcutree_trace.c.
  379. endmenu # "RCU Subsystem"
  380. config IKCONFIG
  381. tristate "Kernel .config support"
  382. ---help---
  383. This option enables the complete Linux kernel ".config" file
  384. contents to be saved in the kernel. It provides documentation
  385. of which kernel options are used in a running kernel or in an
  386. on-disk kernel. This information can be extracted from the kernel
  387. image file with the script scripts/extract-ikconfig and used as
  388. input to rebuild the current kernel or to build another kernel.
  389. It can also be extracted from a running kernel by reading
  390. /proc/config.gz if enabled (below).
  391. config IKCONFIG_PROC
  392. bool "Enable access to .config through /proc/config.gz"
  393. depends on IKCONFIG && PROC_FS
  394. ---help---
  395. This option enables access to the kernel configuration file
  396. through /proc/config.gz.
  397. config LOG_BUF_SHIFT
  398. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  399. range 12 21
  400. default 17
  401. help
  402. Select kernel log buffer size as a power of 2.
  403. Examples:
  404. 17 => 128 KB
  405. 16 => 64 KB
  406. 15 => 32 KB
  407. 14 => 16 KB
  408. 13 => 8 KB
  409. 12 => 4 KB
  410. #
  411. # Architectures with an unreliable sched_clock() should select this:
  412. #
  413. config HAVE_UNSTABLE_SCHED_CLOCK
  414. bool
  415. menuconfig CGROUPS
  416. boolean "Control Group support"
  417. depends on EVENTFD
  418. help
  419. This option adds support for grouping sets of processes together, for
  420. use with process control subsystems such as Cpusets, CFS, memory
  421. controls or device isolation.
  422. See
  423. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  424. - Documentation/cgroups/ (features for grouping, isolation
  425. and resource control)
  426. Say N if unsure.
  427. if CGROUPS
  428. config CGROUP_DEBUG
  429. bool "Example debug cgroup subsystem"
  430. depends on CGROUPS
  431. default n
  432. help
  433. This option enables a simple cgroup subsystem that
  434. exports useful debugging information about the cgroups
  435. framework.
  436. Say N if unsure.
  437. config CGROUP_NS
  438. bool "Namespace cgroup subsystem"
  439. depends on CGROUPS
  440. help
  441. Provides a simple namespace cgroup subsystem to
  442. provide hierarchical naming of sets of namespaces,
  443. for instance virtual servers and checkpoint/restart
  444. jobs.
  445. config CGROUP_FREEZER
  446. bool "Freezer cgroup subsystem"
  447. depends on CGROUPS
  448. help
  449. Provides a way to freeze and unfreeze all tasks in a
  450. cgroup.
  451. config CGROUP_DEVICE
  452. bool "Device controller for cgroups"
  453. depends on CGROUPS && EXPERIMENTAL
  454. help
  455. Provides a cgroup implementing whitelists for devices which
  456. a process in the cgroup can mknod or open.
  457. config CPUSETS
  458. bool "Cpuset support"
  459. depends on CGROUPS
  460. help
  461. This option will let you create and manage CPUSETs which
  462. allow dynamically partitioning a system into sets of CPUs and
  463. Memory Nodes and assigning tasks to run only within those sets.
  464. This is primarily useful on large SMP or NUMA systems.
  465. Say N if unsure.
  466. config PROC_PID_CPUSET
  467. bool "Include legacy /proc/<pid>/cpuset file"
  468. depends on CPUSETS
  469. default y
  470. config CGROUP_CPUACCT
  471. bool "Simple CPU accounting cgroup subsystem"
  472. depends on CGROUPS
  473. help
  474. Provides a simple Resource Controller for monitoring the
  475. total CPU consumed by the tasks in a cgroup.
  476. config RESOURCE_COUNTERS
  477. bool "Resource counters"
  478. help
  479. This option enables controller independent resource accounting
  480. infrastructure that works with cgroups.
  481. depends on CGROUPS
  482. config CGROUP_MEM_RES_CTLR
  483. bool "Memory Resource Controller for Control Groups"
  484. depends on CGROUPS && RESOURCE_COUNTERS
  485. select MM_OWNER
  486. help
  487. Provides a memory resource controller that manages both anonymous
  488. memory and page cache. (See Documentation/cgroups/memory.txt)
  489. Note that setting this option increases fixed memory overhead
  490. associated with each page of memory in the system. By this,
  491. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  492. usage tracking struct at boot. Total amount of this is printed out
  493. at boot.
  494. Only enable when you're ok with these trade offs and really
  495. sure you need the memory resource controller. Even when you enable
  496. this, you can set "cgroup_disable=memory" at your boot option to
  497. disable memory resource controller and you can avoid overheads.
  498. (and lose benefits of memory resource controller)
  499. This config option also selects MM_OWNER config option, which
  500. could in turn add some fork/exit overhead.
  501. config CGROUP_MEM_RES_CTLR_SWAP
  502. bool "Memory Resource Controller Swap Extension"
  503. depends on CGROUP_MEM_RES_CTLR && SWAP
  504. help
  505. Add swap management feature to memory resource controller. When you
  506. enable this, you can limit mem+swap usage per cgroup. In other words,
  507. when you disable this, memory resource controller has no cares to
  508. usage of swap...a process can exhaust all of the swap. This extension
  509. is useful when you want to avoid exhaustion swap but this itself
  510. adds more overheads and consumes memory for remembering information.
  511. Especially if you use 32bit system or small memory system, please
  512. be careful about enabling this. When memory resource controller
  513. is disabled by boot option, this will be automatically disabled and
  514. there will be no overhead from this. Even when you set this config=y,
  515. if boot option "noswapaccount" is set, swap will not be accounted.
  516. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  517. size is 4096bytes, 512k per 1Gbytes of swap.
  518. menuconfig CGROUP_SCHED
  519. bool "Group CPU scheduler"
  520. depends on EXPERIMENTAL && CGROUPS
  521. default n
  522. help
  523. This feature lets CPU scheduler recognize task groups and control CPU
  524. bandwidth allocation to such task groups. It uses cgroups to group
  525. tasks.
  526. if CGROUP_SCHED
  527. config FAIR_GROUP_SCHED
  528. bool "Group scheduling for SCHED_OTHER"
  529. depends on CGROUP_SCHED
  530. default CGROUP_SCHED
  531. config RT_GROUP_SCHED
  532. bool "Group scheduling for SCHED_RR/FIFO"
  533. depends on EXPERIMENTAL
  534. depends on CGROUP_SCHED
  535. default n
  536. help
  537. This feature lets you explicitly allocate real CPU bandwidth
  538. to task groups. If enabled, it will also make it impossible to
  539. schedule realtime tasks for non-root users until you allocate
  540. realtime bandwidth for them.
  541. See Documentation/scheduler/sched-rt-group.txt for more information.
  542. endif #CGROUP_SCHED
  543. config BLK_CGROUP
  544. tristate "Block IO controller"
  545. depends on CGROUPS && BLOCK
  546. default n
  547. ---help---
  548. Generic block IO controller cgroup interface. This is the common
  549. cgroup interface which should be used by various IO controlling
  550. policies.
  551. Currently, CFQ IO scheduler uses it to recognize task groups and
  552. control disk bandwidth allocation (proportional time slice allocation)
  553. to such task groups.
  554. This option only enables generic Block IO controller infrastructure.
  555. One needs to also enable actual IO controlling logic in CFQ for it
  556. to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
  557. See Documentation/cgroups/blkio-controller.txt for more information.
  558. config DEBUG_BLK_CGROUP
  559. bool "Enable Block IO controller debugging"
  560. depends on BLK_CGROUP
  561. default n
  562. ---help---
  563. Enable some debugging help. Currently it exports additional stat
  564. files in a cgroup which can be useful for debugging.
  565. endif # CGROUPS
  566. config MM_OWNER
  567. bool
  568. config SYSFS_DEPRECATED
  569. bool
  570. config SYSFS_DEPRECATED_V2
  571. bool "enable deprecated sysfs features to support old userspace tools"
  572. depends on SYSFS
  573. default n
  574. select SYSFS_DEPRECATED
  575. help
  576. This option switches the layout of sysfs to the deprecated
  577. version. Do not use it on recent distributions.
  578. The current sysfs layout features a unified device tree at
  579. /sys/devices/, which is able to express a hierarchy between
  580. class devices. If the deprecated option is set to Y, the
  581. unified device tree is split into a bus device tree at
  582. /sys/devices/ and several individual class device trees at
  583. /sys/class/. The class and bus devices will be connected by
  584. "<subsystem>:<name>" and the "device" links. The "block"
  585. class devices, will not show up in /sys/class/block/. Some
  586. subsystems will suppress the creation of some devices which
  587. depend on the unified device tree.
  588. This option is not a pure compatibility option that can
  589. be safely enabled on newer distributions. It will change the
  590. layout of sysfs to the non-extensible deprecated version,
  591. and disable some features, which can not be exported without
  592. confusing older userspace tools. Since 2007/2008 all major
  593. distributions do not enable this option, and ship no tools which
  594. depend on the deprecated layout or this option.
  595. If you are using a new kernel on an older distribution, or use
  596. older userspace tools, you might need to say Y here. Do not say Y,
  597. if the original kernel, that came with your distribution, has
  598. this option set to N.
  599. config RELAY
  600. bool "Kernel->user space relay support (formerly relayfs)"
  601. help
  602. This option enables support for relay interface support in
  603. certain file systems (such as debugfs).
  604. It is designed to provide an efficient mechanism for tools and
  605. facilities to relay large amounts of data from kernel space to
  606. user space.
  607. If unsure, say N.
  608. config NAMESPACES
  609. bool "Namespaces support" if EMBEDDED
  610. default !EMBEDDED
  611. help
  612. Provides the way to make tasks work with different objects using
  613. the same id. For example same IPC id may refer to different objects
  614. or same user id or pid may refer to different tasks when used in
  615. different namespaces.
  616. config UTS_NS
  617. bool "UTS namespace"
  618. depends on NAMESPACES
  619. help
  620. In this namespace tasks see different info provided with the
  621. uname() system call
  622. config IPC_NS
  623. bool "IPC namespace"
  624. depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
  625. help
  626. In this namespace tasks work with IPC ids which correspond to
  627. different IPC objects in different namespaces.
  628. config USER_NS
  629. bool "User namespace (EXPERIMENTAL)"
  630. depends on NAMESPACES && EXPERIMENTAL
  631. help
  632. This allows containers, i.e. vservers, to use user namespaces
  633. to provide different user info for different servers.
  634. If unsure, say N.
  635. config PID_NS
  636. bool "PID Namespaces (EXPERIMENTAL)"
  637. default n
  638. depends on NAMESPACES && EXPERIMENTAL
  639. help
  640. Support process id namespaces. This allows having multiple
  641. processes with the same pid as long as they are in different
  642. pid namespaces. This is a building block of containers.
  643. Unless you want to work with an experimental feature
  644. say N here.
  645. config NET_NS
  646. bool "Network namespace"
  647. default n
  648. depends on NAMESPACES && EXPERIMENTAL && NET
  649. help
  650. Allow user space to create what appear to be multiple instances
  651. of the network stack.
  652. config BLK_DEV_INITRD
  653. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  654. depends on BROKEN || !FRV
  655. help
  656. The initial RAM filesystem is a ramfs which is loaded by the
  657. boot loader (loadlin or lilo) and that is mounted as root
  658. before the normal boot procedure. It is typically used to
  659. load modules needed to mount the "real" root file system,
  660. etc. See <file:Documentation/initrd.txt> for details.
  661. If RAM disk support (BLK_DEV_RAM) is also included, this
  662. also enables initial RAM disk (initrd) support and adds
  663. 15 Kbytes (more on some other architectures) to the kernel size.
  664. If unsure say Y.
  665. if BLK_DEV_INITRD
  666. source "usr/Kconfig"
  667. endif
  668. config CC_OPTIMIZE_FOR_SIZE
  669. bool "Optimize for size"
  670. default y
  671. help
  672. Enabling this option will pass "-Os" instead of "-O2" to gcc
  673. resulting in a smaller kernel.
  674. If unsure, say Y.
  675. config SYSCTL
  676. bool
  677. config ANON_INODES
  678. bool
  679. menuconfig EMBEDDED
  680. bool "Configure standard kernel features (for small systems)"
  681. help
  682. This option allows certain base kernel options and settings
  683. to be disabled or tweaked. This is for specialized
  684. environments which can tolerate a "non-standard" kernel.
  685. Only use this if you really know what you are doing.
  686. config UID16
  687. bool "Enable 16-bit UID system calls" if EMBEDDED
  688. depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
  689. default y
  690. help
  691. This enables the legacy 16-bit UID syscall wrappers.
  692. config SYSCTL_SYSCALL
  693. bool "Sysctl syscall support" if EMBEDDED
  694. depends on PROC_SYSCTL
  695. default y
  696. select SYSCTL
  697. ---help---
  698. sys_sysctl uses binary paths that have been found challenging
  699. to properly maintain and use. The interface in /proc/sys
  700. using paths with ascii names is now the primary path to this
  701. information.
  702. Almost nothing using the binary sysctl interface so if you are
  703. trying to save some space it is probably safe to disable this,
  704. making your kernel marginally smaller.
  705. If unsure say Y here.
  706. config KALLSYMS
  707. bool "Load all symbols for debugging/ksymoops" if EMBEDDED
  708. default y
  709. help
  710. Say Y here to let the kernel print out symbolic crash information and
  711. symbolic stack backtraces. This increases the size of the kernel
  712. somewhat, as all symbols have to be loaded into the kernel image.
  713. config KALLSYMS_ALL
  714. bool "Include all symbols in kallsyms"
  715. depends on DEBUG_KERNEL && KALLSYMS
  716. help
  717. Normally kallsyms only contains the symbols of functions, for nicer
  718. OOPS messages. Some debuggers can use kallsyms for other
  719. symbols too: say Y here to include all symbols, if you need them
  720. and you don't care about adding 300k to the size of your kernel.
  721. Say N.
  722. config KALLSYMS_EXTRA_PASS
  723. bool "Do an extra kallsyms pass"
  724. depends on KALLSYMS
  725. help
  726. If kallsyms is not working correctly, the build will fail with
  727. inconsistent kallsyms data. If that occurs, log a bug report and
  728. turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
  729. Always say N here unless you find a bug in kallsyms, which must be
  730. reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
  731. you wait for kallsyms to be fixed.
  732. config HOTPLUG
  733. bool "Support for hot-pluggable devices" if EMBEDDED
  734. default y
  735. help
  736. This option is provided for the case where no hotplug or uevent
  737. capabilities is wanted by the kernel. You should only consider
  738. disabling this option for embedded systems that do not use modules, a
  739. dynamic /dev tree, or dynamic device discovery. Just say Y.
  740. config PRINTK
  741. default y
  742. bool "Enable support for printk" if EMBEDDED
  743. help
  744. This option enables normal printk support. Removing it
  745. eliminates most of the message strings from the kernel image
  746. and makes the kernel more or less silent. As this makes it
  747. very difficult to diagnose system problems, saying N here is
  748. strongly discouraged.
  749. config BUG
  750. bool "BUG() support" if EMBEDDED
  751. default y
  752. help
  753. Disabling this option eliminates support for BUG and WARN, reducing
  754. the size of your kernel image and potentially quietly ignoring
  755. numerous fatal conditions. You should only consider disabling this
  756. option for embedded systems with no facilities for reporting errors.
  757. Just say Y.
  758. config ELF_CORE
  759. default y
  760. bool "Enable ELF core dumps" if EMBEDDED
  761. help
  762. Enable support for generating core dumps. Disabling saves about 4k.
  763. config PCSPKR_PLATFORM
  764. bool "Enable PC-Speaker support" if EMBEDDED
  765. depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
  766. default y
  767. help
  768. This option allows to disable the internal PC-Speaker
  769. support, saving some memory.
  770. config BASE_FULL
  771. default y
  772. bool "Enable full-sized data structures for core" if EMBEDDED
  773. help
  774. Disabling this option reduces the size of miscellaneous core
  775. kernel data structures. This saves memory on small machines,
  776. but may reduce performance.
  777. config FUTEX
  778. bool "Enable futex support" if EMBEDDED
  779. default y
  780. select RT_MUTEXES
  781. help
  782. Disabling this option will cause the kernel to be built without
  783. support for "fast userspace mutexes". The resulting kernel may not
  784. run glibc-based applications correctly.
  785. config EPOLL
  786. bool "Enable eventpoll support" if EMBEDDED
  787. default y
  788. select ANON_INODES
  789. help
  790. Disabling this option will cause the kernel to be built without
  791. support for epoll family of system calls.
  792. config SIGNALFD
  793. bool "Enable signalfd() system call" if EMBEDDED
  794. select ANON_INODES
  795. default y
  796. help
  797. Enable the signalfd() system call that allows to receive signals
  798. on a file descriptor.
  799. If unsure, say Y.
  800. config TIMERFD
  801. bool "Enable timerfd() system call" if EMBEDDED
  802. select ANON_INODES
  803. default y
  804. help
  805. Enable the timerfd() system call that allows to receive timer
  806. events on a file descriptor.
  807. If unsure, say Y.
  808. config EVENTFD
  809. bool "Enable eventfd() system call" if EMBEDDED
  810. select ANON_INODES
  811. default y
  812. help
  813. Enable the eventfd() system call that allows to receive both
  814. kernel notification (ie. KAIO) or userspace notifications.
  815. If unsure, say Y.
  816. config SHMEM
  817. bool "Use full shmem filesystem" if EMBEDDED
  818. default y
  819. depends on MMU
  820. help
  821. The shmem is an internal filesystem used to manage shared memory.
  822. It is backed by swap and manages resource limits. It is also exported
  823. to userspace as tmpfs if TMPFS is enabled. Disabling this
  824. option replaces shmem and tmpfs with the much simpler ramfs code,
  825. which may be appropriate on small systems without swap.
  826. config AIO
  827. bool "Enable AIO support" if EMBEDDED
  828. default y
  829. help
  830. This option enables POSIX asynchronous I/O which may by used
  831. by some high performance threaded applications. Disabling
  832. this option saves about 7k.
  833. config HAVE_PERF_EVENTS
  834. bool
  835. help
  836. See tools/perf/design.txt for details.
  837. config PERF_USE_VMALLOC
  838. bool
  839. help
  840. See tools/perf/design.txt for details
  841. menu "Kernel Performance Events And Counters"
  842. config PERF_EVENTS
  843. bool "Kernel performance events and counters"
  844. default y if (PROFILING || PERF_COUNTERS)
  845. depends on HAVE_PERF_EVENTS
  846. select ANON_INODES
  847. help
  848. Enable kernel support for various performance events provided
  849. by software and hardware.
  850. Software events are supported either built-in or via the
  851. use of generic tracepoints.
  852. Most modern CPUs support performance events via performance
  853. counter registers. These registers count the number of certain
  854. types of hw events: such as instructions executed, cachemisses
  855. suffered, or branches mis-predicted - without slowing down the
  856. kernel or applications. These registers can also trigger interrupts
  857. when a threshold number of events have passed - and can thus be
  858. used to profile the code that runs on that CPU.
  859. The Linux Performance Event subsystem provides an abstraction of
  860. these software and hardware event capabilities, available via a
  861. system call and used by the "perf" utility in tools/perf/. It
  862. provides per task and per CPU counters, and it provides event
  863. capabilities on top of those.
  864. Say Y if unsure.
  865. config PERF_COUNTERS
  866. bool "Kernel performance counters (old config option)"
  867. depends on HAVE_PERF_EVENTS
  868. help
  869. This config has been obsoleted by the PERF_EVENTS
  870. config option - please see that one for details.
  871. It has no effect on the kernel whether you enable
  872. it or not, it is a compatibility placeholder.
  873. Say N if unsure.
  874. config DEBUG_PERF_USE_VMALLOC
  875. default n
  876. bool "Debug: use vmalloc to back perf mmap() buffers"
  877. depends on PERF_EVENTS && DEBUG_KERNEL
  878. select PERF_USE_VMALLOC
  879. help
  880. Use vmalloc memory to back perf mmap() buffers.
  881. Mostly useful for debugging the vmalloc code on platforms
  882. that don't require it.
  883. Say N if unsure.
  884. endmenu
  885. config VM_EVENT_COUNTERS
  886. default y
  887. bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
  888. help
  889. VM event counters are needed for event counts to be shown.
  890. This option allows the disabling of the VM event counters
  891. on EMBEDDED systems. /proc/vmstat will only show page counts
  892. if VM event counters are disabled.
  893. config PCI_QUIRKS
  894. default y
  895. bool "Enable PCI quirk workarounds" if EMBEDDED
  896. depends on PCI
  897. help
  898. This enables workarounds for various PCI chipset
  899. bugs/quirks. Disable this only if your target machine is
  900. unaffected by PCI quirks.
  901. config SLUB_DEBUG
  902. default y
  903. bool "Enable SLUB debugging support" if EMBEDDED
  904. depends on SLUB && SYSFS
  905. help
  906. SLUB has extensive debug support features. Disabling these can
  907. result in significant savings in code size. This also disables
  908. SLUB sysfs support. /sys/slab will not exist and there will be
  909. no support for cache validation etc.
  910. config COMPAT_BRK
  911. bool "Disable heap randomization"
  912. default y
  913. help
  914. Randomizing heap placement makes heap exploits harder, but it
  915. also breaks ancient binaries (including anything libc5 based).
  916. This option changes the bootup default to heap randomization
  917. disabled, and can be overridden at runtime by setting
  918. /proc/sys/kernel/randomize_va_space to 2.
  919. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  920. choice
  921. prompt "Choose SLAB allocator"
  922. default SLUB
  923. help
  924. This option allows to select a slab allocator.
  925. config SLAB
  926. bool "SLAB"
  927. help
  928. The regular slab allocator that is established and known to work
  929. well in all environments. It organizes cache hot objects in
  930. per cpu and per node queues.
  931. config SLUB
  932. bool "SLUB (Unqueued Allocator)"
  933. help
  934. SLUB is a slab allocator that minimizes cache line usage
  935. instead of managing queues of cached objects (SLAB approach).
  936. Per cpu caching is realized using slabs of objects instead
  937. of queues of objects. SLUB can use memory efficiently
  938. and has enhanced diagnostics. SLUB is the default choice for
  939. a slab allocator.
  940. config SLOB
  941. depends on EMBEDDED
  942. bool "SLOB (Simple Allocator)"
  943. help
  944. SLOB replaces the stock allocator with a drastically simpler
  945. allocator. SLOB is generally more space efficient but
  946. does not perform as well on large systems.
  947. endchoice
  948. config MMAP_ALLOW_UNINITIALIZED
  949. bool "Allow mmapped anonymous memory to be uninitialized"
  950. depends on EMBEDDED && !MMU
  951. default n
  952. help
  953. Normally, and according to the Linux spec, anonymous memory obtained
  954. from mmap() has it's contents cleared before it is passed to
  955. userspace. Enabling this config option allows you to request that
  956. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  957. providing a huge performance boost. If this option is not enabled,
  958. then the flag will be ignored.
  959. This is taken advantage of by uClibc's malloc(), and also by
  960. ELF-FDPIC binfmt's brk and stack allocator.
  961. Because of the obvious security issues, this option should only be
  962. enabled on embedded devices where you control what is run in
  963. userspace. Since that isn't generally a problem on no-MMU systems,
  964. it is normally safe to say Y here.
  965. See Documentation/nommu-mmap.txt for more information.
  966. config PROFILING
  967. bool "Profiling support"
  968. help
  969. Say Y here to enable the extended profiling support mechanisms used
  970. by profilers such as OProfile.
  971. #
  972. # Place an empty function call at each tracepoint site. Can be
  973. # dynamically changed for a probe function.
  974. #
  975. config TRACEPOINTS
  976. bool
  977. source "arch/Kconfig"
  978. endmenu # General setup
  979. config HAVE_GENERIC_DMA_COHERENT
  980. bool
  981. default n
  982. config SLABINFO
  983. bool
  984. depends on PROC_FS
  985. depends on SLAB || SLUB_DEBUG
  986. default y
  987. config RT_MUTEXES
  988. boolean
  989. config BASE_SMALL
  990. int
  991. default 0 if BASE_FULL
  992. default 1 if !BASE_FULL
  993. menuconfig MODULES
  994. bool "Enable loadable module support"
  995. help
  996. Kernel modules are small pieces of compiled code which can
  997. be inserted in the running kernel, rather than being
  998. permanently built into the kernel. You use the "modprobe"
  999. tool to add (and sometimes remove) them. If you say Y here,
  1000. many parts of the kernel can be built as modules (by
  1001. answering M instead of Y where indicated): this is most
  1002. useful for infrequently used options which are not required
  1003. for booting. For more information, see the man pages for
  1004. modprobe, lsmod, modinfo, insmod and rmmod.
  1005. If you say Y here, you will need to run "make
  1006. modules_install" to put the modules under /lib/modules/
  1007. where modprobe can find them (you may need to be root to do
  1008. this).
  1009. If unsure, say Y.
  1010. if MODULES
  1011. config MODULE_FORCE_LOAD
  1012. bool "Forced module loading"
  1013. default n
  1014. help
  1015. Allow loading of modules without version information (ie. modprobe
  1016. --force). Forced module loading sets the 'F' (forced) taint flag and
  1017. is usually a really bad idea.
  1018. config MODULE_UNLOAD
  1019. bool "Module unloading"
  1020. help
  1021. Without this option you will not be able to unload any
  1022. modules (note that some modules may not be unloadable
  1023. anyway), which makes your kernel smaller, faster
  1024. and simpler. If unsure, say Y.
  1025. config MODULE_FORCE_UNLOAD
  1026. bool "Forced module unloading"
  1027. depends on MODULE_UNLOAD && EXPERIMENTAL
  1028. help
  1029. This option allows you to force a module to unload, even if the
  1030. kernel believes it is unsafe: the kernel will remove the module
  1031. without waiting for anyone to stop using it (using the -f option to
  1032. rmmod). This is mainly for kernel developers and desperate users.
  1033. If unsure, say N.
  1034. config MODVERSIONS
  1035. bool "Module versioning support"
  1036. help
  1037. Usually, you have to use modules compiled with your kernel.
  1038. Saying Y here makes it sometimes possible to use modules
  1039. compiled for different kernels, by adding enough information
  1040. to the modules to (hopefully) spot any changes which would
  1041. make them incompatible with the kernel you are running. If
  1042. unsure, say N.
  1043. config MODULE_SRCVERSION_ALL
  1044. bool "Source checksum for all modules"
  1045. help
  1046. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1047. field inserted into their modinfo section, which contains a
  1048. sum of the source files which made it. This helps maintainers
  1049. see exactly which source was used to build a module (since
  1050. others sometimes change the module source without updating
  1051. the version). With this option, such a "srcversion" field
  1052. will be created for all modules. If unsure, say N.
  1053. endif # MODULES
  1054. config INIT_ALL_POSSIBLE
  1055. bool
  1056. help
  1057. Back when each arch used to define their own cpu_online_map and
  1058. cpu_possible_map, some of them chose to initialize cpu_possible_map
  1059. with all 1s, and others with all 0s. When they were centralised,
  1060. it was better to provide this option than to break all the archs
  1061. and have several arch maintainers pursuing me down dark alleys.
  1062. config STOP_MACHINE
  1063. bool
  1064. default y
  1065. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1066. help
  1067. Need stop_machine() primitive.
  1068. source "block/Kconfig"
  1069. config PREEMPT_NOTIFIERS
  1070. bool
  1071. config PADATA
  1072. depends on SMP
  1073. bool
  1074. source "kernel/Kconfig.locks"