Kconfig 41 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. config HAVE_IRQ_WORK
  21. bool
  22. config IRQ_WORK
  23. bool
  24. depends on HAVE_IRQ_WORK
  25. menu "General setup"
  26. config EXPERIMENTAL
  27. bool "Prompt for development and/or incomplete code/drivers"
  28. ---help---
  29. Some of the various things that Linux supports (such as network
  30. drivers, file systems, network protocols, etc.) can be in a state
  31. of development where the functionality, stability, or the level of
  32. testing is not yet high enough for general use. This is usually
  33. known as the "alpha-test" phase among developers. If a feature is
  34. currently in alpha-test, then the developers usually discourage
  35. uninformed widespread use of this feature by the general public to
  36. avoid "Why doesn't this work?" type mail messages. However, active
  37. testing and use of these systems is welcomed. Just be aware that it
  38. may not meet the normal level of reliability or it may fail to work
  39. in some special cases. Detailed bug reports from people familiar
  40. with the kernel internals are usually welcomed by the developers
  41. (before submitting bug reports, please read the documents
  42. <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  43. <file:Documentation/BUG-HUNTING>, and
  44. <file:Documentation/oops-tracing.txt> in the kernel source).
  45. This option will also make obsoleted drivers available. These are
  46. drivers that have been replaced by something else, and/or are
  47. scheduled to be removed in a future kernel release.
  48. Unless you intend to help test and develop a feature or driver that
  49. falls into this category, or you have a situation that requires
  50. using these features, you should probably say N here, which will
  51. cause the configurator to present you with fewer choices. If
  52. you say Y here, you will be offered the choice of using features or
  53. drivers that are currently considered to be in the alpha-test phase.
  54. config BROKEN
  55. bool
  56. config BROKEN_ON_SMP
  57. bool
  58. depends on BROKEN || !SMP
  59. default y
  60. config LOCK_KERNEL
  61. bool
  62. depends on (SMP || PREEMPT) && BKL
  63. default y
  64. config INIT_ENV_ARG_LIMIT
  65. int
  66. default 32 if !UML
  67. default 128 if UML
  68. help
  69. Maximum of each of the number of arguments and environment
  70. variables passed to init from the kernel command line.
  71. config CROSS_COMPILE
  72. string "Cross-compiler tool prefix"
  73. help
  74. Same as running 'make CROSS_COMPILE=prefix-' but stored for
  75. default make runs in this kernel build directory. You don't
  76. need to set this unless you want the configured kernel build
  77. directory to select the cross-compiler automatically.
  78. config LOCALVERSION
  79. string "Local version - append to kernel release"
  80. help
  81. Append an extra string to the end of your kernel version.
  82. This will show up when you type uname, for example.
  83. The string you set here will be appended after the contents of
  84. any files with a filename matching localversion* in your
  85. object and source tree, in that order. Your total string can
  86. be a maximum of 64 characters.
  87. config LOCALVERSION_AUTO
  88. bool "Automatically append version information to the version string"
  89. default y
  90. help
  91. This will try to automatically determine if the current tree is a
  92. release tree by looking for git tags that belong to the current
  93. top of tree revision.
  94. A string of the format -gxxxxxxxx will be added to the localversion
  95. if a git-based tree is found. The string generated by this will be
  96. appended after any matching localversion* files, and after the value
  97. set in CONFIG_LOCALVERSION.
  98. (The actual string used here is the first eight characters produced
  99. by running the command:
  100. $ git rev-parse --verify HEAD
  101. which is done within the script "scripts/setlocalversion".)
  102. config HAVE_KERNEL_GZIP
  103. bool
  104. config HAVE_KERNEL_BZIP2
  105. bool
  106. config HAVE_KERNEL_LZMA
  107. bool
  108. config HAVE_KERNEL_LZO
  109. bool
  110. choice
  111. prompt "Kernel compression mode"
  112. default KERNEL_GZIP
  113. depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
  114. help
  115. The linux kernel is a kind of self-extracting executable.
  116. Several compression algorithms are available, which differ
  117. in efficiency, compression and decompression speed.
  118. Compression speed is only relevant when building a kernel.
  119. Decompression speed is relevant at each boot.
  120. If you have any problems with bzip2 or lzma compressed
  121. kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
  122. version of this functionality (bzip2 only), for 2.4, was
  123. supplied by Christian Ludwig)
  124. High compression options are mostly useful for users, who
  125. are low on disk space (embedded systems), but for whom ram
  126. size matters less.
  127. If in doubt, select 'gzip'
  128. config KERNEL_GZIP
  129. bool "Gzip"
  130. depends on HAVE_KERNEL_GZIP
  131. help
  132. The old and tried gzip compression. It provides a good balance
  133. between compression ratio and decompression speed.
  134. config KERNEL_BZIP2
  135. bool "Bzip2"
  136. depends on HAVE_KERNEL_BZIP2
  137. help
  138. Its compression ratio and speed is intermediate.
  139. Decompression speed is slowest among the three. The kernel
  140. size is about 10% smaller with bzip2, in comparison to gzip.
  141. Bzip2 uses a large amount of memory. For modern kernels you
  142. will need at least 8MB RAM or more for booting.
  143. config KERNEL_LZMA
  144. bool "LZMA"
  145. depends on HAVE_KERNEL_LZMA
  146. help
  147. The most recent compression algorithm.
  148. Its ratio is best, decompression speed is between the other
  149. two. Compression is slowest. The kernel size is about 33%
  150. smaller with LZMA in comparison to gzip.
  151. config KERNEL_LZO
  152. bool "LZO"
  153. depends on HAVE_KERNEL_LZO
  154. help
  155. Its compression ratio is the poorest among the 4. The kernel
  156. size is about about 10% bigger than gzip; however its speed
  157. (both compression and decompression) is the fastest.
  158. endchoice
  159. config SWAP
  160. bool "Support for paging of anonymous memory (swap)"
  161. depends on MMU && BLOCK
  162. default y
  163. help
  164. This option allows you to choose whether you want to have support
  165. for so called swap devices or swap files in your kernel that are
  166. used to provide more virtual memory than the actual RAM present
  167. in your computer. If unsure say Y.
  168. config SYSVIPC
  169. bool "System V IPC"
  170. ---help---
  171. Inter Process Communication is a suite of library functions and
  172. system calls which let processes (running programs) synchronize and
  173. exchange information. It is generally considered to be a good thing,
  174. and some programs won't run unless you say Y here. In particular, if
  175. you want to run the DOS emulator dosemu under Linux (read the
  176. DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
  177. you'll need to say Y here.
  178. You can find documentation about IPC with "info ipc" and also in
  179. section 6.4 of the Linux Programmer's Guide, available from
  180. <http://www.tldp.org/guides.html>.
  181. config SYSVIPC_SYSCTL
  182. bool
  183. depends on SYSVIPC
  184. depends on SYSCTL
  185. default y
  186. config POSIX_MQUEUE
  187. bool "POSIX Message Queues"
  188. depends on NET && EXPERIMENTAL
  189. ---help---
  190. POSIX variant of message queues is a part of IPC. In POSIX message
  191. queues every message has a priority which decides about succession
  192. of receiving it by a process. If you want to compile and run
  193. programs written e.g. for Solaris with use of its POSIX message
  194. queues (functions mq_*) say Y here.
  195. POSIX message queues are visible as a filesystem called 'mqueue'
  196. and can be mounted somewhere if you want to do filesystem
  197. operations on message queues.
  198. If unsure, say Y.
  199. config POSIX_MQUEUE_SYSCTL
  200. bool
  201. depends on POSIX_MQUEUE
  202. depends on SYSCTL
  203. default y
  204. config BSD_PROCESS_ACCT
  205. bool "BSD Process Accounting"
  206. help
  207. If you say Y here, a user level program will be able to instruct the
  208. kernel (via a special system call) to write process accounting
  209. information to a file: whenever a process exits, information about
  210. that process will be appended to the file by the kernel. The
  211. information includes things such as creation time, owning user,
  212. command name, memory usage, controlling terminal etc. (the complete
  213. list is in the struct acct in <file:include/linux/acct.h>). It is
  214. up to the user level program to do useful things with this
  215. information. This is generally a good idea, so say Y.
  216. config BSD_PROCESS_ACCT_V3
  217. bool "BSD Process Accounting version 3 file format"
  218. depends on BSD_PROCESS_ACCT
  219. default n
  220. help
  221. If you say Y here, the process accounting information is written
  222. in a new file format that also logs the process IDs of each
  223. process and it's parent. Note that this file format is incompatible
  224. with previous v0/v1/v2 file formats, so you will need updated tools
  225. for processing it. A preliminary version of these tools is available
  226. at <http://www.gnu.org/software/acct/>.
  227. config TASKSTATS
  228. bool "Export task/process statistics through netlink (EXPERIMENTAL)"
  229. depends on NET
  230. default n
  231. help
  232. Export selected statistics for tasks/processes through the
  233. generic netlink interface. Unlike BSD process accounting, the
  234. statistics are available during the lifetime of tasks/processes as
  235. responses to commands. Like BSD accounting, they are sent to user
  236. space on task exit.
  237. Say N if unsure.
  238. config TASK_DELAY_ACCT
  239. bool "Enable per-task delay accounting (EXPERIMENTAL)"
  240. depends on TASKSTATS
  241. help
  242. Collect information on time spent by a task waiting for system
  243. resources like cpu, synchronous block I/O completion and swapping
  244. in pages. Such statistics can help in setting a task's priorities
  245. relative to other tasks for cpu, io, rss limits etc.
  246. Say N if unsure.
  247. config TASK_XACCT
  248. bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
  249. depends on TASKSTATS
  250. help
  251. Collect extended task accounting data and send the data
  252. to userland for processing over the taskstats interface.
  253. Say N if unsure.
  254. config TASK_IO_ACCOUNTING
  255. bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
  256. depends on TASK_XACCT
  257. help
  258. Collect information on the number of bytes of storage I/O which this
  259. task has caused.
  260. Say N if unsure.
  261. config AUDIT
  262. bool "Auditing support"
  263. depends on NET
  264. help
  265. Enable auditing infrastructure that can be used with another
  266. kernel subsystem, such as SELinux (which requires this for
  267. logging of avc messages output). Does not do system-call
  268. auditing without CONFIG_AUDITSYSCALL.
  269. config AUDITSYSCALL
  270. bool "Enable system-call auditing support"
  271. depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
  272. default y if SECURITY_SELINUX
  273. help
  274. Enable low-overhead system-call auditing infrastructure that
  275. can be used independently or with another kernel subsystem,
  276. such as SELinux.
  277. config AUDIT_WATCH
  278. def_bool y
  279. depends on AUDITSYSCALL
  280. select FSNOTIFY
  281. config AUDIT_TREE
  282. def_bool y
  283. depends on AUDITSYSCALL
  284. select FSNOTIFY
  285. source "kernel/irq/Kconfig"
  286. menu "RCU Subsystem"
  287. choice
  288. prompt "RCU Implementation"
  289. default TREE_RCU
  290. config TREE_RCU
  291. bool "Tree-based hierarchical RCU"
  292. depends on !PREEMPT && SMP
  293. help
  294. This option selects the RCU implementation that is
  295. designed for very large SMP system with hundreds or
  296. thousands of CPUs. It also scales down nicely to
  297. smaller systems.
  298. config TREE_PREEMPT_RCU
  299. bool "Preemptible tree-based hierarchical RCU"
  300. depends on PREEMPT
  301. help
  302. This option selects the RCU implementation that is
  303. designed for very large SMP systems with hundreds or
  304. thousands of CPUs, but for which real-time response
  305. is also required. It also scales down nicely to
  306. smaller systems.
  307. config TINY_RCU
  308. bool "UP-only small-memory-footprint RCU"
  309. depends on !SMP
  310. help
  311. This option selects the RCU implementation that is
  312. designed for UP systems from which real-time response
  313. is not required. This option greatly reduces the
  314. memory footprint of RCU.
  315. config TINY_PREEMPT_RCU
  316. bool "Preemptible UP-only small-memory-footprint RCU"
  317. depends on !SMP && PREEMPT
  318. help
  319. This option selects the RCU implementation that is designed
  320. for real-time UP systems. This option greatly reduces the
  321. memory footprint of RCU.
  322. endchoice
  323. config PREEMPT_RCU
  324. def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
  325. help
  326. This option enables preemptible-RCU code that is common between
  327. the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
  328. config RCU_TRACE
  329. bool "Enable tracing for RCU"
  330. depends on TREE_RCU || TREE_PREEMPT_RCU
  331. help
  332. This option provides tracing in RCU which presents stats
  333. in debugfs for debugging RCU implementation.
  334. Say Y here if you want to enable RCU tracing
  335. Say N if you are unsure.
  336. config RCU_FANOUT
  337. int "Tree-based hierarchical RCU fanout value"
  338. range 2 64 if 64BIT
  339. range 2 32 if !64BIT
  340. depends on TREE_RCU || TREE_PREEMPT_RCU
  341. default 64 if 64BIT
  342. default 32 if !64BIT
  343. help
  344. This option controls the fanout of hierarchical implementations
  345. of RCU, allowing RCU to work efficiently on machines with
  346. large numbers of CPUs. This value must be at least the fourth
  347. root of NR_CPUS, which allows NR_CPUS to be insanely large.
  348. The default value of RCU_FANOUT should be used for production
  349. systems, but if you are stress-testing the RCU implementation
  350. itself, small RCU_FANOUT values allow you to test large-system
  351. code paths on small(er) systems.
  352. Select a specific number if testing RCU itself.
  353. Take the default if unsure.
  354. config RCU_FANOUT_EXACT
  355. bool "Disable tree-based hierarchical RCU auto-balancing"
  356. depends on TREE_RCU || TREE_PREEMPT_RCU
  357. default n
  358. help
  359. This option forces use of the exact RCU_FANOUT value specified,
  360. regardless of imbalances in the hierarchy. This is useful for
  361. testing RCU itself, and might one day be useful on systems with
  362. strong NUMA behavior.
  363. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  364. Say N if unsure.
  365. config RCU_FAST_NO_HZ
  366. bool "Accelerate last non-dyntick-idle CPU's grace periods"
  367. depends on TREE_RCU && NO_HZ && SMP
  368. default n
  369. help
  370. This option causes RCU to attempt to accelerate grace periods
  371. in order to allow the final CPU to enter dynticks-idle state
  372. more quickly. On the other hand, this option increases the
  373. overhead of the dynticks-idle checking, particularly on systems
  374. with large numbers of CPUs.
  375. Say Y if energy efficiency is critically important, particularly
  376. if you have relatively few CPUs.
  377. Say N if you are unsure.
  378. config TREE_RCU_TRACE
  379. def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
  380. select DEBUG_FS
  381. help
  382. This option provides tracing for the TREE_RCU and
  383. TREE_PREEMPT_RCU implementations, permitting Makefile to
  384. trivially select kernel/rcutree_trace.c.
  385. endmenu # "RCU Subsystem"
  386. config IKCONFIG
  387. tristate "Kernel .config support"
  388. ---help---
  389. This option enables the complete Linux kernel ".config" file
  390. contents to be saved in the kernel. It provides documentation
  391. of which kernel options are used in a running kernel or in an
  392. on-disk kernel. This information can be extracted from the kernel
  393. image file with the script scripts/extract-ikconfig and used as
  394. input to rebuild the current kernel or to build another kernel.
  395. It can also be extracted from a running kernel by reading
  396. /proc/config.gz if enabled (below).
  397. config IKCONFIG_PROC
  398. bool "Enable access to .config through /proc/config.gz"
  399. depends on IKCONFIG && PROC_FS
  400. ---help---
  401. This option enables access to the kernel configuration file
  402. through /proc/config.gz.
  403. config LOG_BUF_SHIFT
  404. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  405. range 12 21
  406. default 17
  407. help
  408. Select kernel log buffer size as a power of 2.
  409. Examples:
  410. 17 => 128 KB
  411. 16 => 64 KB
  412. 15 => 32 KB
  413. 14 => 16 KB
  414. 13 => 8 KB
  415. 12 => 4 KB
  416. #
  417. # Architectures with an unreliable sched_clock() should select this:
  418. #
  419. config HAVE_UNSTABLE_SCHED_CLOCK
  420. bool
  421. menuconfig CGROUPS
  422. boolean "Control Group support"
  423. depends on EVENTFD
  424. help
  425. This option adds support for grouping sets of processes together, for
  426. use with process control subsystems such as Cpusets, CFS, memory
  427. controls or device isolation.
  428. See
  429. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  430. - Documentation/cgroups/ (features for grouping, isolation
  431. and resource control)
  432. Say N if unsure.
  433. if CGROUPS
  434. config CGROUP_DEBUG
  435. bool "Example debug cgroup subsystem"
  436. depends on CGROUPS
  437. default n
  438. help
  439. This option enables a simple cgroup subsystem that
  440. exports useful debugging information about the cgroups
  441. framework.
  442. Say N if unsure.
  443. config CGROUP_NS
  444. bool "Namespace cgroup subsystem"
  445. depends on CGROUPS
  446. help
  447. Provides a simple namespace cgroup subsystem to
  448. provide hierarchical naming of sets of namespaces,
  449. for instance virtual servers and checkpoint/restart
  450. jobs.
  451. config CGROUP_FREEZER
  452. bool "Freezer cgroup subsystem"
  453. depends on CGROUPS
  454. help
  455. Provides a way to freeze and unfreeze all tasks in a
  456. cgroup.
  457. config CGROUP_DEVICE
  458. bool "Device controller for cgroups"
  459. depends on CGROUPS && EXPERIMENTAL
  460. help
  461. Provides a cgroup implementing whitelists for devices which
  462. a process in the cgroup can mknod or open.
  463. config CPUSETS
  464. bool "Cpuset support"
  465. depends on CGROUPS
  466. help
  467. This option will let you create and manage CPUSETs which
  468. allow dynamically partitioning a system into sets of CPUs and
  469. Memory Nodes and assigning tasks to run only within those sets.
  470. This is primarily useful on large SMP or NUMA systems.
  471. Say N if unsure.
  472. config PROC_PID_CPUSET
  473. bool "Include legacy /proc/<pid>/cpuset file"
  474. depends on CPUSETS
  475. default y
  476. config CGROUP_CPUACCT
  477. bool "Simple CPU accounting cgroup subsystem"
  478. depends on CGROUPS
  479. help
  480. Provides a simple Resource Controller for monitoring the
  481. total CPU consumed by the tasks in a cgroup.
  482. config RESOURCE_COUNTERS
  483. bool "Resource counters"
  484. help
  485. This option enables controller independent resource accounting
  486. infrastructure that works with cgroups.
  487. depends on CGROUPS
  488. config CGROUP_MEM_RES_CTLR
  489. bool "Memory Resource Controller for Control Groups"
  490. depends on CGROUPS && RESOURCE_COUNTERS
  491. select MM_OWNER
  492. help
  493. Provides a memory resource controller that manages both anonymous
  494. memory and page cache. (See Documentation/cgroups/memory.txt)
  495. Note that setting this option increases fixed memory overhead
  496. associated with each page of memory in the system. By this,
  497. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  498. usage tracking struct at boot. Total amount of this is printed out
  499. at boot.
  500. Only enable when you're ok with these trade offs and really
  501. sure you need the memory resource controller. Even when you enable
  502. this, you can set "cgroup_disable=memory" at your boot option to
  503. disable memory resource controller and you can avoid overheads.
  504. (and lose benefits of memory resource controller)
  505. This config option also selects MM_OWNER config option, which
  506. could in turn add some fork/exit overhead.
  507. config CGROUP_MEM_RES_CTLR_SWAP
  508. bool "Memory Resource Controller Swap Extension"
  509. depends on CGROUP_MEM_RES_CTLR && SWAP
  510. help
  511. Add swap management feature to memory resource controller. When you
  512. enable this, you can limit mem+swap usage per cgroup. In other words,
  513. when you disable this, memory resource controller has no cares to
  514. usage of swap...a process can exhaust all of the swap. This extension
  515. is useful when you want to avoid exhaustion swap but this itself
  516. adds more overheads and consumes memory for remembering information.
  517. Especially if you use 32bit system or small memory system, please
  518. be careful about enabling this. When memory resource controller
  519. is disabled by boot option, this will be automatically disabled and
  520. there will be no overhead from this. Even when you set this config=y,
  521. if boot option "noswapaccount" is set, swap will not be accounted.
  522. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  523. size is 4096bytes, 512k per 1Gbytes of swap.
  524. menuconfig CGROUP_SCHED
  525. bool "Group CPU scheduler"
  526. depends on EXPERIMENTAL && CGROUPS
  527. default n
  528. help
  529. This feature lets CPU scheduler recognize task groups and control CPU
  530. bandwidth allocation to such task groups. It uses cgroups to group
  531. tasks.
  532. if CGROUP_SCHED
  533. config FAIR_GROUP_SCHED
  534. bool "Group scheduling for SCHED_OTHER"
  535. depends on CGROUP_SCHED
  536. default CGROUP_SCHED
  537. config RT_GROUP_SCHED
  538. bool "Group scheduling for SCHED_RR/FIFO"
  539. depends on EXPERIMENTAL
  540. depends on CGROUP_SCHED
  541. default n
  542. help
  543. This feature lets you explicitly allocate real CPU bandwidth
  544. to task groups. If enabled, it will also make it impossible to
  545. schedule realtime tasks for non-root users until you allocate
  546. realtime bandwidth for them.
  547. See Documentation/scheduler/sched-rt-group.txt for more information.
  548. endif #CGROUP_SCHED
  549. config BLK_CGROUP
  550. tristate "Block IO controller"
  551. depends on CGROUPS && BLOCK
  552. default n
  553. ---help---
  554. Generic block IO controller cgroup interface. This is the common
  555. cgroup interface which should be used by various IO controlling
  556. policies.
  557. Currently, CFQ IO scheduler uses it to recognize task groups and
  558. control disk bandwidth allocation (proportional time slice allocation)
  559. to such task groups.
  560. This option only enables generic Block IO controller infrastructure.
  561. One needs to also enable actual IO controlling logic in CFQ for it
  562. to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
  563. See Documentation/cgroups/blkio-controller.txt for more information.
  564. config DEBUG_BLK_CGROUP
  565. bool "Enable Block IO controller debugging"
  566. depends on BLK_CGROUP
  567. default n
  568. ---help---
  569. Enable some debugging help. Currently it exports additional stat
  570. files in a cgroup which can be useful for debugging.
  571. endif # CGROUPS
  572. config MM_OWNER
  573. bool
  574. config SYSFS_DEPRECATED
  575. bool
  576. config SYSFS_DEPRECATED_V2
  577. bool "enable deprecated sysfs features to support old userspace tools"
  578. depends on SYSFS
  579. default n
  580. select SYSFS_DEPRECATED
  581. help
  582. This option switches the layout of sysfs to the deprecated
  583. version. Do not use it on recent distributions.
  584. The current sysfs layout features a unified device tree at
  585. /sys/devices/, which is able to express a hierarchy between
  586. class devices. If the deprecated option is set to Y, the
  587. unified device tree is split into a bus device tree at
  588. /sys/devices/ and several individual class device trees at
  589. /sys/class/. The class and bus devices will be connected by
  590. "<subsystem>:<name>" and the "device" links. The "block"
  591. class devices, will not show up in /sys/class/block/. Some
  592. subsystems will suppress the creation of some devices which
  593. depend on the unified device tree.
  594. This option is not a pure compatibility option that can
  595. be safely enabled on newer distributions. It will change the
  596. layout of sysfs to the non-extensible deprecated version,
  597. and disable some features, which can not be exported without
  598. confusing older userspace tools. Since 2007/2008 all major
  599. distributions do not enable this option, and ship no tools which
  600. depend on the deprecated layout or this option.
  601. If you are using a new kernel on an older distribution, or use
  602. older userspace tools, you might need to say Y here. Do not say Y,
  603. if the original kernel, that came with your distribution, has
  604. this option set to N.
  605. config RELAY
  606. bool "Kernel->user space relay support (formerly relayfs)"
  607. help
  608. This option enables support for relay interface support in
  609. certain file systems (such as debugfs).
  610. It is designed to provide an efficient mechanism for tools and
  611. facilities to relay large amounts of data from kernel space to
  612. user space.
  613. If unsure, say N.
  614. config NAMESPACES
  615. bool "Namespaces support" if EMBEDDED
  616. default !EMBEDDED
  617. help
  618. Provides the way to make tasks work with different objects using
  619. the same id. For example same IPC id may refer to different objects
  620. or same user id or pid may refer to different tasks when used in
  621. different namespaces.
  622. config UTS_NS
  623. bool "UTS namespace"
  624. depends on NAMESPACES
  625. help
  626. In this namespace tasks see different info provided with the
  627. uname() system call
  628. config IPC_NS
  629. bool "IPC namespace"
  630. depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
  631. help
  632. In this namespace tasks work with IPC ids which correspond to
  633. different IPC objects in different namespaces.
  634. config USER_NS
  635. bool "User namespace (EXPERIMENTAL)"
  636. depends on NAMESPACES && EXPERIMENTAL
  637. help
  638. This allows containers, i.e. vservers, to use user namespaces
  639. to provide different user info for different servers.
  640. If unsure, say N.
  641. config PID_NS
  642. bool "PID Namespaces (EXPERIMENTAL)"
  643. default n
  644. depends on NAMESPACES && EXPERIMENTAL
  645. help
  646. Support process id namespaces. This allows having multiple
  647. processes with the same pid as long as they are in different
  648. pid namespaces. This is a building block of containers.
  649. Unless you want to work with an experimental feature
  650. say N here.
  651. config NET_NS
  652. bool "Network namespace"
  653. default n
  654. depends on NAMESPACES && EXPERIMENTAL && NET
  655. help
  656. Allow user space to create what appear to be multiple instances
  657. of the network stack.
  658. config BLK_DEV_INITRD
  659. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  660. depends on BROKEN || !FRV
  661. help
  662. The initial RAM filesystem is a ramfs which is loaded by the
  663. boot loader (loadlin or lilo) and that is mounted as root
  664. before the normal boot procedure. It is typically used to
  665. load modules needed to mount the "real" root file system,
  666. etc. See <file:Documentation/initrd.txt> for details.
  667. If RAM disk support (BLK_DEV_RAM) is also included, this
  668. also enables initial RAM disk (initrd) support and adds
  669. 15 Kbytes (more on some other architectures) to the kernel size.
  670. If unsure say Y.
  671. if BLK_DEV_INITRD
  672. source "usr/Kconfig"
  673. endif
  674. config CC_OPTIMIZE_FOR_SIZE
  675. bool "Optimize for size"
  676. default y
  677. help
  678. Enabling this option will pass "-Os" instead of "-O2" to gcc
  679. resulting in a smaller kernel.
  680. If unsure, say Y.
  681. config SYSCTL
  682. bool
  683. config ANON_INODES
  684. bool
  685. menuconfig EMBEDDED
  686. bool "Configure standard kernel features (for small systems)"
  687. help
  688. This option allows certain base kernel options and settings
  689. to be disabled or tweaked. This is for specialized
  690. environments which can tolerate a "non-standard" kernel.
  691. Only use this if you really know what you are doing.
  692. config UID16
  693. bool "Enable 16-bit UID system calls" if EMBEDDED
  694. depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
  695. default y
  696. help
  697. This enables the legacy 16-bit UID syscall wrappers.
  698. config SYSCTL_SYSCALL
  699. bool "Sysctl syscall support" if EMBEDDED
  700. depends on PROC_SYSCTL
  701. default y
  702. select SYSCTL
  703. ---help---
  704. sys_sysctl uses binary paths that have been found challenging
  705. to properly maintain and use. The interface in /proc/sys
  706. using paths with ascii names is now the primary path to this
  707. information.
  708. Almost nothing using the binary sysctl interface so if you are
  709. trying to save some space it is probably safe to disable this,
  710. making your kernel marginally smaller.
  711. If unsure say Y here.
  712. config KALLSYMS
  713. bool "Load all symbols for debugging/ksymoops" if EMBEDDED
  714. default y
  715. help
  716. Say Y here to let the kernel print out symbolic crash information and
  717. symbolic stack backtraces. This increases the size of the kernel
  718. somewhat, as all symbols have to be loaded into the kernel image.
  719. config KALLSYMS_ALL
  720. bool "Include all symbols in kallsyms"
  721. depends on DEBUG_KERNEL && KALLSYMS
  722. help
  723. Normally kallsyms only contains the symbols of functions, for nicer
  724. OOPS messages. Some debuggers can use kallsyms for other
  725. symbols too: say Y here to include all symbols, if you need them
  726. and you don't care about adding 300k to the size of your kernel.
  727. Say N.
  728. config KALLSYMS_EXTRA_PASS
  729. bool "Do an extra kallsyms pass"
  730. depends on KALLSYMS
  731. help
  732. If kallsyms is not working correctly, the build will fail with
  733. inconsistent kallsyms data. If that occurs, log a bug report and
  734. turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
  735. Always say N here unless you find a bug in kallsyms, which must be
  736. reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
  737. you wait for kallsyms to be fixed.
  738. config HOTPLUG
  739. bool "Support for hot-pluggable devices" if EMBEDDED
  740. default y
  741. help
  742. This option is provided for the case where no hotplug or uevent
  743. capabilities is wanted by the kernel. You should only consider
  744. disabling this option for embedded systems that do not use modules, a
  745. dynamic /dev tree, or dynamic device discovery. Just say Y.
  746. config PRINTK
  747. default y
  748. bool "Enable support for printk" if EMBEDDED
  749. help
  750. This option enables normal printk support. Removing it
  751. eliminates most of the message strings from the kernel image
  752. and makes the kernel more or less silent. As this makes it
  753. very difficult to diagnose system problems, saying N here is
  754. strongly discouraged.
  755. config BUG
  756. bool "BUG() support" if EMBEDDED
  757. default y
  758. help
  759. Disabling this option eliminates support for BUG and WARN, reducing
  760. the size of your kernel image and potentially quietly ignoring
  761. numerous fatal conditions. You should only consider disabling this
  762. option for embedded systems with no facilities for reporting errors.
  763. Just say Y.
  764. config ELF_CORE
  765. default y
  766. bool "Enable ELF core dumps" if EMBEDDED
  767. help
  768. Enable support for generating core dumps. Disabling saves about 4k.
  769. config PCSPKR_PLATFORM
  770. bool "Enable PC-Speaker support" if EMBEDDED
  771. depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
  772. default y
  773. help
  774. This option allows to disable the internal PC-Speaker
  775. support, saving some memory.
  776. config BASE_FULL
  777. default y
  778. bool "Enable full-sized data structures for core" if EMBEDDED
  779. help
  780. Disabling this option reduces the size of miscellaneous core
  781. kernel data structures. This saves memory on small machines,
  782. but may reduce performance.
  783. config FUTEX
  784. bool "Enable futex support" if EMBEDDED
  785. default y
  786. select RT_MUTEXES
  787. help
  788. Disabling this option will cause the kernel to be built without
  789. support for "fast userspace mutexes". The resulting kernel may not
  790. run glibc-based applications correctly.
  791. config EPOLL
  792. bool "Enable eventpoll support" if EMBEDDED
  793. default y
  794. select ANON_INODES
  795. help
  796. Disabling this option will cause the kernel to be built without
  797. support for epoll family of system calls.
  798. config SIGNALFD
  799. bool "Enable signalfd() system call" if EMBEDDED
  800. select ANON_INODES
  801. default y
  802. help
  803. Enable the signalfd() system call that allows to receive signals
  804. on a file descriptor.
  805. If unsure, say Y.
  806. config TIMERFD
  807. bool "Enable timerfd() system call" if EMBEDDED
  808. select ANON_INODES
  809. default y
  810. help
  811. Enable the timerfd() system call that allows to receive timer
  812. events on a file descriptor.
  813. If unsure, say Y.
  814. config EVENTFD
  815. bool "Enable eventfd() system call" if EMBEDDED
  816. select ANON_INODES
  817. default y
  818. help
  819. Enable the eventfd() system call that allows to receive both
  820. kernel notification (ie. KAIO) or userspace notifications.
  821. If unsure, say Y.
  822. config SHMEM
  823. bool "Use full shmem filesystem" if EMBEDDED
  824. default y
  825. depends on MMU
  826. help
  827. The shmem is an internal filesystem used to manage shared memory.
  828. It is backed by swap and manages resource limits. It is also exported
  829. to userspace as tmpfs if TMPFS is enabled. Disabling this
  830. option replaces shmem and tmpfs with the much simpler ramfs code,
  831. which may be appropriate on small systems without swap.
  832. config AIO
  833. bool "Enable AIO support" if EMBEDDED
  834. default y
  835. help
  836. This option enables POSIX asynchronous I/O which may by used
  837. by some high performance threaded applications. Disabling
  838. this option saves about 7k.
  839. config HAVE_PERF_EVENTS
  840. bool
  841. help
  842. See tools/perf/design.txt for details.
  843. config PERF_USE_VMALLOC
  844. bool
  845. help
  846. See tools/perf/design.txt for details
  847. menu "Kernel Performance Events And Counters"
  848. config PERF_EVENTS
  849. bool "Kernel performance events and counters"
  850. default y if (PROFILING || PERF_COUNTERS)
  851. depends on HAVE_PERF_EVENTS
  852. select ANON_INODES
  853. select IRQ_WORK
  854. help
  855. Enable kernel support for various performance events provided
  856. by software and hardware.
  857. Software events are supported either built-in or via the
  858. use of generic tracepoints.
  859. Most modern CPUs support performance events via performance
  860. counter registers. These registers count the number of certain
  861. types of hw events: such as instructions executed, cachemisses
  862. suffered, or branches mis-predicted - without slowing down the
  863. kernel or applications. These registers can also trigger interrupts
  864. when a threshold number of events have passed - and can thus be
  865. used to profile the code that runs on that CPU.
  866. The Linux Performance Event subsystem provides an abstraction of
  867. these software and hardware event capabilities, available via a
  868. system call and used by the "perf" utility in tools/perf/. It
  869. provides per task and per CPU counters, and it provides event
  870. capabilities on top of those.
  871. Say Y if unsure.
  872. config PERF_COUNTERS
  873. bool "Kernel performance counters (old config option)"
  874. depends on HAVE_PERF_EVENTS
  875. help
  876. This config has been obsoleted by the PERF_EVENTS
  877. config option - please see that one for details.
  878. It has no effect on the kernel whether you enable
  879. it or not, it is a compatibility placeholder.
  880. Say N if unsure.
  881. config DEBUG_PERF_USE_VMALLOC
  882. default n
  883. bool "Debug: use vmalloc to back perf mmap() buffers"
  884. depends on PERF_EVENTS && DEBUG_KERNEL
  885. select PERF_USE_VMALLOC
  886. help
  887. Use vmalloc memory to back perf mmap() buffers.
  888. Mostly useful for debugging the vmalloc code on platforms
  889. that don't require it.
  890. Say N if unsure.
  891. endmenu
  892. config VM_EVENT_COUNTERS
  893. default y
  894. bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
  895. help
  896. VM event counters are needed for event counts to be shown.
  897. This option allows the disabling of the VM event counters
  898. on EMBEDDED systems. /proc/vmstat will only show page counts
  899. if VM event counters are disabled.
  900. config PCI_QUIRKS
  901. default y
  902. bool "Enable PCI quirk workarounds" if EMBEDDED
  903. depends on PCI
  904. help
  905. This enables workarounds for various PCI chipset
  906. bugs/quirks. Disable this only if your target machine is
  907. unaffected by PCI quirks.
  908. config SLUB_DEBUG
  909. default y
  910. bool "Enable SLUB debugging support" if EMBEDDED
  911. depends on SLUB && SYSFS
  912. help
  913. SLUB has extensive debug support features. Disabling these can
  914. result in significant savings in code size. This also disables
  915. SLUB sysfs support. /sys/slab will not exist and there will be
  916. no support for cache validation etc.
  917. config COMPAT_BRK
  918. bool "Disable heap randomization"
  919. default y
  920. help
  921. Randomizing heap placement makes heap exploits harder, but it
  922. also breaks ancient binaries (including anything libc5 based).
  923. This option changes the bootup default to heap randomization
  924. disabled, and can be overridden at runtime by setting
  925. /proc/sys/kernel/randomize_va_space to 2.
  926. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  927. choice
  928. prompt "Choose SLAB allocator"
  929. default SLUB
  930. help
  931. This option allows to select a slab allocator.
  932. config SLAB
  933. bool "SLAB"
  934. help
  935. The regular slab allocator that is established and known to work
  936. well in all environments. It organizes cache hot objects in
  937. per cpu and per node queues.
  938. config SLUB
  939. bool "SLUB (Unqueued Allocator)"
  940. help
  941. SLUB is a slab allocator that minimizes cache line usage
  942. instead of managing queues of cached objects (SLAB approach).
  943. Per cpu caching is realized using slabs of objects instead
  944. of queues of objects. SLUB can use memory efficiently
  945. and has enhanced diagnostics. SLUB is the default choice for
  946. a slab allocator.
  947. config SLOB
  948. depends on EMBEDDED
  949. bool "SLOB (Simple Allocator)"
  950. help
  951. SLOB replaces the stock allocator with a drastically simpler
  952. allocator. SLOB is generally more space efficient but
  953. does not perform as well on large systems.
  954. endchoice
  955. config MMAP_ALLOW_UNINITIALIZED
  956. bool "Allow mmapped anonymous memory to be uninitialized"
  957. depends on EMBEDDED && !MMU
  958. default n
  959. help
  960. Normally, and according to the Linux spec, anonymous memory obtained
  961. from mmap() has it's contents cleared before it is passed to
  962. userspace. Enabling this config option allows you to request that
  963. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  964. providing a huge performance boost. If this option is not enabled,
  965. then the flag will be ignored.
  966. This is taken advantage of by uClibc's malloc(), and also by
  967. ELF-FDPIC binfmt's brk and stack allocator.
  968. Because of the obvious security issues, this option should only be
  969. enabled on embedded devices where you control what is run in
  970. userspace. Since that isn't generally a problem on no-MMU systems,
  971. it is normally safe to say Y here.
  972. See Documentation/nommu-mmap.txt for more information.
  973. config PROFILING
  974. bool "Profiling support"
  975. help
  976. Say Y here to enable the extended profiling support mechanisms used
  977. by profilers such as OProfile.
  978. #
  979. # Place an empty function call at each tracepoint site. Can be
  980. # dynamically changed for a probe function.
  981. #
  982. config TRACEPOINTS
  983. bool
  984. source "arch/Kconfig"
  985. endmenu # General setup
  986. config HAVE_GENERIC_DMA_COHERENT
  987. bool
  988. default n
  989. config SLABINFO
  990. bool
  991. depends on PROC_FS
  992. depends on SLAB || SLUB_DEBUG
  993. default y
  994. config RT_MUTEXES
  995. boolean
  996. config BASE_SMALL
  997. int
  998. default 0 if BASE_FULL
  999. default 1 if !BASE_FULL
  1000. menuconfig MODULES
  1001. bool "Enable loadable module support"
  1002. help
  1003. Kernel modules are small pieces of compiled code which can
  1004. be inserted in the running kernel, rather than being
  1005. permanently built into the kernel. You use the "modprobe"
  1006. tool to add (and sometimes remove) them. If you say Y here,
  1007. many parts of the kernel can be built as modules (by
  1008. answering M instead of Y where indicated): this is most
  1009. useful for infrequently used options which are not required
  1010. for booting. For more information, see the man pages for
  1011. modprobe, lsmod, modinfo, insmod and rmmod.
  1012. If you say Y here, you will need to run "make
  1013. modules_install" to put the modules under /lib/modules/
  1014. where modprobe can find them (you may need to be root to do
  1015. this).
  1016. If unsure, say Y.
  1017. if MODULES
  1018. config MODULE_FORCE_LOAD
  1019. bool "Forced module loading"
  1020. default n
  1021. help
  1022. Allow loading of modules without version information (ie. modprobe
  1023. --force). Forced module loading sets the 'F' (forced) taint flag and
  1024. is usually a really bad idea.
  1025. config MODULE_UNLOAD
  1026. bool "Module unloading"
  1027. help
  1028. Without this option you will not be able to unload any
  1029. modules (note that some modules may not be unloadable
  1030. anyway), which makes your kernel smaller, faster
  1031. and simpler. If unsure, say Y.
  1032. config MODULE_FORCE_UNLOAD
  1033. bool "Forced module unloading"
  1034. depends on MODULE_UNLOAD && EXPERIMENTAL
  1035. help
  1036. This option allows you to force a module to unload, even if the
  1037. kernel believes it is unsafe: the kernel will remove the module
  1038. without waiting for anyone to stop using it (using the -f option to
  1039. rmmod). This is mainly for kernel developers and desperate users.
  1040. If unsure, say N.
  1041. config MODVERSIONS
  1042. bool "Module versioning support"
  1043. help
  1044. Usually, you have to use modules compiled with your kernel.
  1045. Saying Y here makes it sometimes possible to use modules
  1046. compiled for different kernels, by adding enough information
  1047. to the modules to (hopefully) spot any changes which would
  1048. make them incompatible with the kernel you are running. If
  1049. unsure, say N.
  1050. config MODULE_SRCVERSION_ALL
  1051. bool "Source checksum for all modules"
  1052. help
  1053. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1054. field inserted into their modinfo section, which contains a
  1055. sum of the source files which made it. This helps maintainers
  1056. see exactly which source was used to build a module (since
  1057. others sometimes change the module source without updating
  1058. the version). With this option, such a "srcversion" field
  1059. will be created for all modules. If unsure, say N.
  1060. endif # MODULES
  1061. config INIT_ALL_POSSIBLE
  1062. bool
  1063. help
  1064. Back when each arch used to define their own cpu_online_map and
  1065. cpu_possible_map, some of them chose to initialize cpu_possible_map
  1066. with all 1s, and others with all 0s. When they were centralised,
  1067. it was better to provide this option than to break all the archs
  1068. and have several arch maintainers pursuing me down dark alleys.
  1069. config STOP_MACHINE
  1070. bool
  1071. default y
  1072. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1073. help
  1074. Need stop_machine() primitive.
  1075. source "block/Kconfig"
  1076. config PREEMPT_NOTIFIERS
  1077. bool
  1078. config PADATA
  1079. depends on SMP
  1080. bool
  1081. source "kernel/Kconfig.locks"