Kconfig 38 KB

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  1. config ARCH
  2. string
  3. option env="ARCH"
  4. config KERNELVERSION
  5. string
  6. option env="KERNELVERSION"
  7. config DEFCONFIG_LIST
  8. string
  9. depends on !UML
  10. option defconfig_list
  11. default "/lib/modules/$UNAME_RELEASE/.config"
  12. default "/etc/kernel-config"
  13. default "/boot/config-$UNAME_RELEASE"
  14. default "$ARCH_DEFCONFIG"
  15. default "arch/$ARCH/defconfig"
  16. config CONSTRUCTORS
  17. bool
  18. depends on !UML
  19. default y
  20. menu "General setup"
  21. config EXPERIMENTAL
  22. bool "Prompt for development and/or incomplete code/drivers"
  23. ---help---
  24. Some of the various things that Linux supports (such as network
  25. drivers, file systems, network protocols, etc.) can be in a state
  26. of development where the functionality, stability, or the level of
  27. testing is not yet high enough for general use. This is usually
  28. known as the "alpha-test" phase among developers. If a feature is
  29. currently in alpha-test, then the developers usually discourage
  30. uninformed widespread use of this feature by the general public to
  31. avoid "Why doesn't this work?" type mail messages. However, active
  32. testing and use of these systems is welcomed. Just be aware that it
  33. may not meet the normal level of reliability or it may fail to work
  34. in some special cases. Detailed bug reports from people familiar
  35. with the kernel internals are usually welcomed by the developers
  36. (before submitting bug reports, please read the documents
  37. <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  38. <file:Documentation/BUG-HUNTING>, and
  39. <file:Documentation/oops-tracing.txt> in the kernel source).
  40. This option will also make obsoleted drivers available. These are
  41. drivers that have been replaced by something else, and/or are
  42. scheduled to be removed in a future kernel release.
  43. Unless you intend to help test and develop a feature or driver that
  44. falls into this category, or you have a situation that requires
  45. using these features, you should probably say N here, which will
  46. cause the configurator to present you with fewer choices. If
  47. you say Y here, you will be offered the choice of using features or
  48. drivers that are currently considered to be in the alpha-test phase.
  49. config BROKEN
  50. bool
  51. config BROKEN_ON_SMP
  52. bool
  53. depends on BROKEN || !SMP
  54. default y
  55. config LOCK_KERNEL
  56. bool
  57. depends on SMP || PREEMPT
  58. default y
  59. config INIT_ENV_ARG_LIMIT
  60. int
  61. default 32 if !UML
  62. default 128 if UML
  63. help
  64. Maximum of each of the number of arguments and environment
  65. variables passed to init from the kernel command line.
  66. config LOCALVERSION
  67. string "Local version - append to kernel release"
  68. help
  69. Append an extra string to the end of your kernel version.
  70. This will show up when you type uname, for example.
  71. The string you set here will be appended after the contents of
  72. any files with a filename matching localversion* in your
  73. object and source tree, in that order. Your total string can
  74. be a maximum of 64 characters.
  75. config LOCALVERSION_AUTO
  76. bool "Automatically append version information to the version string"
  77. default y
  78. help
  79. This will try to automatically determine if the current tree is a
  80. release tree by looking for git tags that belong to the current
  81. top of tree revision.
  82. A string of the format -gxxxxxxxx will be added to the localversion
  83. if a git-based tree is found. The string generated by this will be
  84. appended after any matching localversion* files, and after the value
  85. set in CONFIG_LOCALVERSION.
  86. (The actual string used here is the first eight characters produced
  87. by running the command:
  88. $ git rev-parse --verify HEAD
  89. which is done within the script "scripts/setlocalversion".)
  90. config HAVE_KERNEL_GZIP
  91. bool
  92. config HAVE_KERNEL_BZIP2
  93. bool
  94. config HAVE_KERNEL_LZMA
  95. bool
  96. choice
  97. prompt "Kernel compression mode"
  98. default KERNEL_GZIP
  99. depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
  100. help
  101. The linux kernel is a kind of self-extracting executable.
  102. Several compression algorithms are available, which differ
  103. in efficiency, compression and decompression speed.
  104. Compression speed is only relevant when building a kernel.
  105. Decompression speed is relevant at each boot.
  106. If you have any problems with bzip2 or lzma compressed
  107. kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
  108. version of this functionality (bzip2 only), for 2.4, was
  109. supplied by Christian Ludwig)
  110. High compression options are mostly useful for users, who
  111. are low on disk space (embedded systems), but for whom ram
  112. size matters less.
  113. If in doubt, select 'gzip'
  114. config KERNEL_GZIP
  115. bool "Gzip"
  116. depends on HAVE_KERNEL_GZIP
  117. help
  118. The old and tried gzip compression. Its compression ratio is
  119. the poorest among the 3 choices; however its speed (both
  120. compression and decompression) is the fastest.
  121. config KERNEL_BZIP2
  122. bool "Bzip2"
  123. depends on HAVE_KERNEL_BZIP2
  124. help
  125. Its compression ratio and speed is intermediate.
  126. Decompression speed is slowest among the three. The kernel
  127. size is about 10% smaller with bzip2, in comparison to gzip.
  128. Bzip2 uses a large amount of memory. For modern kernels you
  129. will need at least 8MB RAM or more for booting.
  130. config KERNEL_LZMA
  131. bool "LZMA"
  132. depends on HAVE_KERNEL_LZMA
  133. help
  134. The most recent compression algorithm.
  135. Its ratio is best, decompression speed is between the other
  136. two. Compression is slowest. The kernel size is about 33%
  137. smaller with LZMA in comparison to gzip.
  138. endchoice
  139. config SWAP
  140. bool "Support for paging of anonymous memory (swap)"
  141. depends on MMU && BLOCK
  142. default y
  143. help
  144. This option allows you to choose whether you want to have support
  145. for so called swap devices or swap files in your kernel that are
  146. used to provide more virtual memory than the actual RAM present
  147. in your computer. If unsure say Y.
  148. config SYSVIPC
  149. bool "System V IPC"
  150. ---help---
  151. Inter Process Communication is a suite of library functions and
  152. system calls which let processes (running programs) synchronize and
  153. exchange information. It is generally considered to be a good thing,
  154. and some programs won't run unless you say Y here. In particular, if
  155. you want to run the DOS emulator dosemu under Linux (read the
  156. DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
  157. you'll need to say Y here.
  158. You can find documentation about IPC with "info ipc" and also in
  159. section 6.4 of the Linux Programmer's Guide, available from
  160. <http://www.tldp.org/guides.html>.
  161. config SYSVIPC_SYSCTL
  162. bool
  163. depends on SYSVIPC
  164. depends on SYSCTL
  165. default y
  166. config POSIX_MQUEUE
  167. bool "POSIX Message Queues"
  168. depends on NET && EXPERIMENTAL
  169. ---help---
  170. POSIX variant of message queues is a part of IPC. In POSIX message
  171. queues every message has a priority which decides about succession
  172. of receiving it by a process. If you want to compile and run
  173. programs written e.g. for Solaris with use of its POSIX message
  174. queues (functions mq_*) say Y here.
  175. POSIX message queues are visible as a filesystem called 'mqueue'
  176. and can be mounted somewhere if you want to do filesystem
  177. operations on message queues.
  178. If unsure, say Y.
  179. config POSIX_MQUEUE_SYSCTL
  180. bool
  181. depends on POSIX_MQUEUE
  182. depends on SYSCTL
  183. default y
  184. config BSD_PROCESS_ACCT
  185. bool "BSD Process Accounting"
  186. help
  187. If you say Y here, a user level program will be able to instruct the
  188. kernel (via a special system call) to write process accounting
  189. information to a file: whenever a process exits, information about
  190. that process will be appended to the file by the kernel. The
  191. information includes things such as creation time, owning user,
  192. command name, memory usage, controlling terminal etc. (the complete
  193. list is in the struct acct in <file:include/linux/acct.h>). It is
  194. up to the user level program to do useful things with this
  195. information. This is generally a good idea, so say Y.
  196. config BSD_PROCESS_ACCT_V3
  197. bool "BSD Process Accounting version 3 file format"
  198. depends on BSD_PROCESS_ACCT
  199. default n
  200. help
  201. If you say Y here, the process accounting information is written
  202. in a new file format that also logs the process IDs of each
  203. process and it's parent. Note that this file format is incompatible
  204. with previous v0/v1/v2 file formats, so you will need updated tools
  205. for processing it. A preliminary version of these tools is available
  206. at <http://www.gnu.org/software/acct/>.
  207. config TASKSTATS
  208. bool "Export task/process statistics through netlink (EXPERIMENTAL)"
  209. depends on NET
  210. default n
  211. help
  212. Export selected statistics for tasks/processes through the
  213. generic netlink interface. Unlike BSD process accounting, the
  214. statistics are available during the lifetime of tasks/processes as
  215. responses to commands. Like BSD accounting, they are sent to user
  216. space on task exit.
  217. Say N if unsure.
  218. config TASK_DELAY_ACCT
  219. bool "Enable per-task delay accounting (EXPERIMENTAL)"
  220. depends on TASKSTATS
  221. help
  222. Collect information on time spent by a task waiting for system
  223. resources like cpu, synchronous block I/O completion and swapping
  224. in pages. Such statistics can help in setting a task's priorities
  225. relative to other tasks for cpu, io, rss limits etc.
  226. Say N if unsure.
  227. config TASK_XACCT
  228. bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
  229. depends on TASKSTATS
  230. help
  231. Collect extended task accounting data and send the data
  232. to userland for processing over the taskstats interface.
  233. Say N if unsure.
  234. config TASK_IO_ACCOUNTING
  235. bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
  236. depends on TASK_XACCT
  237. help
  238. Collect information on the number of bytes of storage I/O which this
  239. task has caused.
  240. Say N if unsure.
  241. config AUDIT
  242. bool "Auditing support"
  243. depends on NET
  244. help
  245. Enable auditing infrastructure that can be used with another
  246. kernel subsystem, such as SELinux (which requires this for
  247. logging of avc messages output). Does not do system-call
  248. auditing without CONFIG_AUDITSYSCALL.
  249. config AUDITSYSCALL
  250. bool "Enable system-call auditing support"
  251. depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
  252. default y if SECURITY_SELINUX
  253. help
  254. Enable low-overhead system-call auditing infrastructure that
  255. can be used independently or with another kernel subsystem,
  256. such as SELinux. To use audit's filesystem watch feature, please
  257. ensure that INOTIFY is configured.
  258. config AUDIT_TREE
  259. def_bool y
  260. depends on AUDITSYSCALL
  261. select INOTIFY
  262. menu "RCU Subsystem"
  263. choice
  264. prompt "RCU Implementation"
  265. default TREE_RCU
  266. config CLASSIC_RCU
  267. bool "Classic RCU"
  268. help
  269. This option selects the classic RCU implementation that is
  270. designed for best read-side performance on non-realtime
  271. systems.
  272. Select this option if you are unsure.
  273. config TREE_RCU
  274. bool "Tree-based hierarchical RCU"
  275. help
  276. This option selects the RCU implementation that is
  277. designed for very large SMP system with hundreds or
  278. thousands of CPUs.
  279. config PREEMPT_RCU
  280. bool "Preemptible RCU"
  281. depends on PREEMPT
  282. help
  283. This option reduces the latency of the kernel by making certain
  284. RCU sections preemptible. Normally RCU code is non-preemptible, if
  285. this option is selected then read-only RCU sections become
  286. preemptible. This helps latency, but may expose bugs due to
  287. now-naive assumptions about each RCU read-side critical section
  288. remaining on a given CPU through its execution.
  289. endchoice
  290. config RCU_TRACE
  291. bool "Enable tracing for RCU"
  292. depends on TREE_RCU || PREEMPT_RCU
  293. help
  294. This option provides tracing in RCU which presents stats
  295. in debugfs for debugging RCU implementation.
  296. Say Y here if you want to enable RCU tracing
  297. Say N if you are unsure.
  298. config RCU_FANOUT
  299. int "Tree-based hierarchical RCU fanout value"
  300. range 2 64 if 64BIT
  301. range 2 32 if !64BIT
  302. depends on TREE_RCU
  303. default 64 if 64BIT
  304. default 32 if !64BIT
  305. help
  306. This option controls the fanout of hierarchical implementations
  307. of RCU, allowing RCU to work efficiently on machines with
  308. large numbers of CPUs. This value must be at least the cube
  309. root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
  310. systems and up to 262,144 for 64-bit systems.
  311. Select a specific number if testing RCU itself.
  312. Take the default if unsure.
  313. config RCU_FANOUT_EXACT
  314. bool "Disable tree-based hierarchical RCU auto-balancing"
  315. depends on TREE_RCU
  316. default n
  317. help
  318. This option forces use of the exact RCU_FANOUT value specified,
  319. regardless of imbalances in the hierarchy. This is useful for
  320. testing RCU itself, and might one day be useful on systems with
  321. strong NUMA behavior.
  322. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  323. Say N if unsure.
  324. config TREE_RCU_TRACE
  325. def_bool RCU_TRACE && TREE_RCU
  326. select DEBUG_FS
  327. help
  328. This option provides tracing for the TREE_RCU implementation,
  329. permitting Makefile to trivially select kernel/rcutree_trace.c.
  330. config PREEMPT_RCU_TRACE
  331. def_bool RCU_TRACE && PREEMPT_RCU
  332. select DEBUG_FS
  333. help
  334. This option provides tracing for the PREEMPT_RCU implementation,
  335. permitting Makefile to trivially select kernel/rcupreempt_trace.c.
  336. endmenu # "RCU Subsystem"
  337. config IKCONFIG
  338. tristate "Kernel .config support"
  339. ---help---
  340. This option enables the complete Linux kernel ".config" file
  341. contents to be saved in the kernel. It provides documentation
  342. of which kernel options are used in a running kernel or in an
  343. on-disk kernel. This information can be extracted from the kernel
  344. image file with the script scripts/extract-ikconfig and used as
  345. input to rebuild the current kernel or to build another kernel.
  346. It can also be extracted from a running kernel by reading
  347. /proc/config.gz if enabled (below).
  348. config IKCONFIG_PROC
  349. bool "Enable access to .config through /proc/config.gz"
  350. depends on IKCONFIG && PROC_FS
  351. ---help---
  352. This option enables access to the kernel configuration file
  353. through /proc/config.gz.
  354. config LOG_BUF_SHIFT
  355. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  356. range 12 21
  357. default 17
  358. help
  359. Select kernel log buffer size as a power of 2.
  360. Examples:
  361. 17 => 128 KB
  362. 16 => 64 KB
  363. 15 => 32 KB
  364. 14 => 16 KB
  365. 13 => 8 KB
  366. 12 => 4 KB
  367. #
  368. # Architectures with an unreliable sched_clock() should select this:
  369. #
  370. config HAVE_UNSTABLE_SCHED_CLOCK
  371. bool
  372. config GROUP_SCHED
  373. bool "Group CPU scheduler"
  374. depends on EXPERIMENTAL
  375. default n
  376. help
  377. This feature lets CPU scheduler recognize task groups and control CPU
  378. bandwidth allocation to such task groups.
  379. In order to create a group from arbitrary set of processes, use
  380. CONFIG_CGROUPS. (See Control Group support.)
  381. config FAIR_GROUP_SCHED
  382. bool "Group scheduling for SCHED_OTHER"
  383. depends on GROUP_SCHED
  384. default GROUP_SCHED
  385. config RT_GROUP_SCHED
  386. bool "Group scheduling for SCHED_RR/FIFO"
  387. depends on EXPERIMENTAL
  388. depends on GROUP_SCHED
  389. default n
  390. help
  391. This feature lets you explicitly allocate real CPU bandwidth
  392. to users or control groups (depending on the "Basis for grouping tasks"
  393. setting below. If enabled, it will also make it impossible to
  394. schedule realtime tasks for non-root users until you allocate
  395. realtime bandwidth for them.
  396. See Documentation/scheduler/sched-rt-group.txt for more information.
  397. choice
  398. depends on GROUP_SCHED
  399. prompt "Basis for grouping tasks"
  400. default USER_SCHED
  401. config USER_SCHED
  402. bool "user id"
  403. help
  404. This option will choose userid as the basis for grouping
  405. tasks, thus providing equal CPU bandwidth to each user.
  406. config CGROUP_SCHED
  407. bool "Control groups"
  408. depends on CGROUPS
  409. help
  410. This option allows you to create arbitrary task groups
  411. using the "cgroup" pseudo filesystem and control
  412. the cpu bandwidth allocated to each such task group.
  413. Refer to Documentation/cgroups/cgroups.txt for more
  414. information on "cgroup" pseudo filesystem.
  415. endchoice
  416. menuconfig CGROUPS
  417. boolean "Control Group support"
  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(EXPERIMENTAL)"
  503. depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
  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. endif # CGROUPS
  519. config MM_OWNER
  520. bool
  521. config SYSFS_DEPRECATED
  522. bool
  523. config SYSFS_DEPRECATED_V2
  524. bool "remove sysfs features which may confuse old userspace tools"
  525. depends on SYSFS
  526. default n
  527. select SYSFS_DEPRECATED
  528. help
  529. This option switches the layout of sysfs to the deprecated
  530. version. Do not use it on recent distributions.
  531. The current sysfs layout features a unified device tree at
  532. /sys/devices/, which is able to express a hierarchy between
  533. class devices. If the deprecated option is set to Y, the
  534. unified device tree is split into a bus device tree at
  535. /sys/devices/ and several individual class device trees at
  536. /sys/class/. The class and bus devices will be connected by
  537. "<subsystem>:<name>" and the "device" links. The "block"
  538. class devices, will not show up in /sys/class/block/. Some
  539. subsystems will suppress the creation of some devices which
  540. depend on the unified device tree.
  541. This option is not a pure compatibility option that can
  542. be safely enabled on newer distributions. It will change the
  543. layout of sysfs to the non-extensible deprecated version,
  544. and disable some features, which can not be exported without
  545. confusing older userspace tools. Since 2007/2008 all major
  546. distributions do not enable this option, and ship no tools which
  547. depend on the deprecated layout or this option.
  548. If you are using a new kernel on an older distribution, or use
  549. older userspace tools, you might need to say Y here. Do not say Y,
  550. if the original kernel, that came with your distribution, has
  551. this option set to N.
  552. config RELAY
  553. bool "Kernel->user space relay support (formerly relayfs)"
  554. help
  555. This option enables support for relay interface support in
  556. certain file systems (such as debugfs).
  557. It is designed to provide an efficient mechanism for tools and
  558. facilities to relay large amounts of data from kernel space to
  559. user space.
  560. If unsure, say N.
  561. config NAMESPACES
  562. bool "Namespaces support" if EMBEDDED
  563. default !EMBEDDED
  564. help
  565. Provides the way to make tasks work with different objects using
  566. the same id. For example same IPC id may refer to different objects
  567. or same user id or pid may refer to different tasks when used in
  568. different namespaces.
  569. config UTS_NS
  570. bool "UTS namespace"
  571. depends on NAMESPACES
  572. help
  573. In this namespace tasks see different info provided with the
  574. uname() system call
  575. config IPC_NS
  576. bool "IPC namespace"
  577. depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
  578. help
  579. In this namespace tasks work with IPC ids which correspond to
  580. different IPC objects in different namespaces.
  581. config USER_NS
  582. bool "User namespace (EXPERIMENTAL)"
  583. depends on NAMESPACES && EXPERIMENTAL
  584. help
  585. This allows containers, i.e. vservers, to use user namespaces
  586. to provide different user info for different servers.
  587. If unsure, say N.
  588. config PID_NS
  589. bool "PID Namespaces (EXPERIMENTAL)"
  590. default n
  591. depends on NAMESPACES && EXPERIMENTAL
  592. help
  593. Support process id namespaces. This allows having multiple
  594. processes with the same pid as long as they are in different
  595. pid namespaces. This is a building block of containers.
  596. Unless you want to work with an experimental feature
  597. say N here.
  598. config NET_NS
  599. bool "Network namespace"
  600. default n
  601. depends on NAMESPACES && EXPERIMENTAL && NET
  602. help
  603. Allow user space to create what appear to be multiple instances
  604. of the network stack.
  605. config BLK_DEV_INITRD
  606. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  607. depends on BROKEN || !FRV
  608. help
  609. The initial RAM filesystem is a ramfs which is loaded by the
  610. boot loader (loadlin or lilo) and that is mounted as root
  611. before the normal boot procedure. It is typically used to
  612. load modules needed to mount the "real" root file system,
  613. etc. See <file:Documentation/initrd.txt> for details.
  614. If RAM disk support (BLK_DEV_RAM) is also included, this
  615. also enables initial RAM disk (initrd) support and adds
  616. 15 Kbytes (more on some other architectures) to the kernel size.
  617. If unsure say Y.
  618. if BLK_DEV_INITRD
  619. source "usr/Kconfig"
  620. endif
  621. config CC_OPTIMIZE_FOR_SIZE
  622. bool "Optimize for size"
  623. default y
  624. help
  625. Enabling this option will pass "-Os" instead of "-O2" to gcc
  626. resulting in a smaller kernel.
  627. If unsure, say Y.
  628. config SYSCTL
  629. bool
  630. config ANON_INODES
  631. bool
  632. menuconfig EMBEDDED
  633. bool "Configure standard kernel features (for small systems)"
  634. help
  635. This option allows certain base kernel options and settings
  636. to be disabled or tweaked. This is for specialized
  637. environments which can tolerate a "non-standard" kernel.
  638. Only use this if you really know what you are doing.
  639. config UID16
  640. bool "Enable 16-bit UID system calls" if EMBEDDED
  641. depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
  642. default y
  643. help
  644. This enables the legacy 16-bit UID syscall wrappers.
  645. config SYSCTL_SYSCALL
  646. bool "Sysctl syscall support" if EMBEDDED
  647. default y
  648. select SYSCTL
  649. ---help---
  650. sys_sysctl uses binary paths that have been found challenging
  651. to properly maintain and use. The interface in /proc/sys
  652. using paths with ascii names is now the primary path to this
  653. information.
  654. Almost nothing using the binary sysctl interface so if you are
  655. trying to save some space it is probably safe to disable this,
  656. making your kernel marginally smaller.
  657. If unsure say Y here.
  658. config KALLSYMS
  659. bool "Load all symbols for debugging/ksymoops" if EMBEDDED
  660. default y
  661. help
  662. Say Y here to let the kernel print out symbolic crash information and
  663. symbolic stack backtraces. This increases the size of the kernel
  664. somewhat, as all symbols have to be loaded into the kernel image.
  665. config KALLSYMS_ALL
  666. bool "Include all symbols in kallsyms"
  667. depends on DEBUG_KERNEL && KALLSYMS
  668. help
  669. Normally kallsyms only contains the symbols of functions, for nicer
  670. OOPS messages. Some debuggers can use kallsyms for other
  671. symbols too: say Y here to include all symbols, if you need them
  672. and you don't care about adding 300k to the size of your kernel.
  673. Say N.
  674. config KALLSYMS_EXTRA_PASS
  675. bool "Do an extra kallsyms pass"
  676. depends on KALLSYMS
  677. help
  678. If kallsyms is not working correctly, the build will fail with
  679. inconsistent kallsyms data. If that occurs, log a bug report and
  680. turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
  681. Always say N here unless you find a bug in kallsyms, which must be
  682. reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
  683. you wait for kallsyms to be fixed.
  684. config HOTPLUG
  685. bool "Support for hot-pluggable devices" if EMBEDDED
  686. default y
  687. help
  688. This option is provided for the case where no hotplug or uevent
  689. capabilities is wanted by the kernel. You should only consider
  690. disabling this option for embedded systems that do not use modules, a
  691. dynamic /dev tree, or dynamic device discovery. Just say Y.
  692. config PRINTK
  693. default y
  694. bool "Enable support for printk" if EMBEDDED
  695. help
  696. This option enables normal printk support. Removing it
  697. eliminates most of the message strings from the kernel image
  698. and makes the kernel more or less silent. As this makes it
  699. very difficult to diagnose system problems, saying N here is
  700. strongly discouraged.
  701. config BUG
  702. bool "BUG() support" if EMBEDDED
  703. default y
  704. help
  705. Disabling this option eliminates support for BUG and WARN, reducing
  706. the size of your kernel image and potentially quietly ignoring
  707. numerous fatal conditions. You should only consider disabling this
  708. option for embedded systems with no facilities for reporting errors.
  709. Just say Y.
  710. config ELF_CORE
  711. default y
  712. bool "Enable ELF core dumps" if EMBEDDED
  713. help
  714. Enable support for generating core dumps. Disabling saves about 4k.
  715. config PCSPKR_PLATFORM
  716. bool "Enable PC-Speaker support" if EMBEDDED
  717. depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
  718. default y
  719. help
  720. This option allows to disable the internal PC-Speaker
  721. support, saving some memory.
  722. config BASE_FULL
  723. default y
  724. bool "Enable full-sized data structures for core" if EMBEDDED
  725. help
  726. Disabling this option reduces the size of miscellaneous core
  727. kernel data structures. This saves memory on small machines,
  728. but may reduce performance.
  729. config FUTEX
  730. bool "Enable futex support" if EMBEDDED
  731. default y
  732. select RT_MUTEXES
  733. help
  734. Disabling this option will cause the kernel to be built without
  735. support for "fast userspace mutexes". The resulting kernel may not
  736. run glibc-based applications correctly.
  737. config EPOLL
  738. bool "Enable eventpoll support" if EMBEDDED
  739. default y
  740. select ANON_INODES
  741. help
  742. Disabling this option will cause the kernel to be built without
  743. support for epoll family of system calls.
  744. config SIGNALFD
  745. bool "Enable signalfd() system call" if EMBEDDED
  746. select ANON_INODES
  747. default y
  748. help
  749. Enable the signalfd() system call that allows to receive signals
  750. on a file descriptor.
  751. If unsure, say Y.
  752. config TIMERFD
  753. bool "Enable timerfd() system call" if EMBEDDED
  754. select ANON_INODES
  755. default y
  756. help
  757. Enable the timerfd() system call that allows to receive timer
  758. events on a file descriptor.
  759. If unsure, say Y.
  760. config EVENTFD
  761. bool "Enable eventfd() system call" if EMBEDDED
  762. select ANON_INODES
  763. default y
  764. help
  765. Enable the eventfd() system call that allows to receive both
  766. kernel notification (ie. KAIO) or userspace notifications.
  767. If unsure, say Y.
  768. config SHMEM
  769. bool "Use full shmem filesystem" if EMBEDDED
  770. default y
  771. depends on MMU
  772. help
  773. The shmem is an internal filesystem used to manage shared memory.
  774. It is backed by swap and manages resource limits. It is also exported
  775. to userspace as tmpfs if TMPFS is enabled. Disabling this
  776. option replaces shmem and tmpfs with the much simpler ramfs code,
  777. which may be appropriate on small systems without swap.
  778. config AIO
  779. bool "Enable AIO support" if EMBEDDED
  780. default y
  781. help
  782. This option enables POSIX asynchronous I/O which may by used
  783. by some high performance threaded applications. Disabling
  784. this option saves about 7k.
  785. config HAVE_PERF_COUNTERS
  786. bool
  787. help
  788. See tools/perf/design.txt for details.
  789. menu "Performance Counters"
  790. config PERF_COUNTERS
  791. bool "Kernel Performance Counters"
  792. depends on HAVE_PERF_COUNTERS
  793. select ANON_INODES
  794. help
  795. Enable kernel support for performance counter hardware.
  796. Performance counters are special hardware registers available
  797. on most modern CPUs. These registers count the number of certain
  798. types of hw events: such as instructions executed, cachemisses
  799. suffered, or branches mis-predicted - without slowing down the
  800. kernel or applications. These registers can also trigger interrupts
  801. when a threshold number of events have passed - and can thus be
  802. used to profile the code that runs on that CPU.
  803. The Linux Performance Counter subsystem provides an abstraction of
  804. these hardware capabilities, available via a system call. It
  805. provides per task and per CPU counters, and it provides event
  806. capabilities on top of those.
  807. Say Y if unsure.
  808. config EVENT_PROFILE
  809. bool "Tracepoint profile sources"
  810. depends on PERF_COUNTERS && EVENT_TRACING
  811. default y
  812. endmenu
  813. config VM_EVENT_COUNTERS
  814. default y
  815. bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
  816. help
  817. VM event counters are needed for event counts to be shown.
  818. This option allows the disabling of the VM event counters
  819. on EMBEDDED systems. /proc/vmstat will only show page counts
  820. if VM event counters are disabled.
  821. config PCI_QUIRKS
  822. default y
  823. bool "Enable PCI quirk workarounds" if EMBEDDED
  824. depends on PCI
  825. help
  826. This enables workarounds for various PCI chipset
  827. bugs/quirks. Disable this only if your target machine is
  828. unaffected by PCI quirks.
  829. config SLUB_DEBUG
  830. default y
  831. bool "Enable SLUB debugging support" if EMBEDDED
  832. depends on SLUB && SYSFS
  833. help
  834. SLUB has extensive debug support features. Disabling these can
  835. result in significant savings in code size. This also disables
  836. SLUB sysfs support. /sys/slab will not exist and there will be
  837. no support for cache validation etc.
  838. config STRIP_ASM_SYMS
  839. bool "Strip assembler-generated symbols during link"
  840. default n
  841. help
  842. Strip internal assembler-generated symbols during a link (symbols
  843. that look like '.Lxxx') so they don't pollute the output of
  844. get_wchan() and suchlike.
  845. config COMPAT_BRK
  846. bool "Disable heap randomization"
  847. default y
  848. help
  849. Randomizing heap placement makes heap exploits harder, but it
  850. also breaks ancient binaries (including anything libc5 based).
  851. This option changes the bootup default to heap randomization
  852. disabled, and can be overridden at runtime by setting
  853. /proc/sys/kernel/randomize_va_space to 2.
  854. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  855. choice
  856. prompt "Choose SLAB allocator"
  857. default SLUB
  858. help
  859. This option allows to select a slab allocator.
  860. config SLAB
  861. bool "SLAB"
  862. help
  863. The regular slab allocator that is established and known to work
  864. well in all environments. It organizes cache hot objects in
  865. per cpu and per node queues.
  866. config SLUB
  867. bool "SLUB (Unqueued Allocator)"
  868. help
  869. SLUB is a slab allocator that minimizes cache line usage
  870. instead of managing queues of cached objects (SLAB approach).
  871. Per cpu caching is realized using slabs of objects instead
  872. of queues of objects. SLUB can use memory efficiently
  873. and has enhanced diagnostics. SLUB is the default choice for
  874. a slab allocator.
  875. config SLOB
  876. depends on EMBEDDED
  877. bool "SLOB (Simple Allocator)"
  878. help
  879. SLOB replaces the stock allocator with a drastically simpler
  880. allocator. SLOB is generally more space efficient but
  881. does not perform as well on large systems.
  882. endchoice
  883. config PROFILING
  884. bool "Profiling support (EXPERIMENTAL)"
  885. help
  886. Say Y here to enable the extended profiling support mechanisms used
  887. by profilers such as OProfile.
  888. #
  889. # Place an empty function call at each tracepoint site. Can be
  890. # dynamically changed for a probe function.
  891. #
  892. config TRACEPOINTS
  893. bool
  894. config MARKERS
  895. bool "Activate markers"
  896. select TRACEPOINTS
  897. help
  898. Place an empty function call at each marker site. Can be
  899. dynamically changed for a probe function.
  900. source "arch/Kconfig"
  901. config SLOW_WORK
  902. default n
  903. bool
  904. help
  905. The slow work thread pool provides a number of dynamically allocated
  906. threads that can be used by the kernel to perform operations that
  907. take a relatively long time.
  908. An example of this would be CacheFiles doing a path lookup followed
  909. by a series of mkdirs and a create call, all of which have to touch
  910. disk.
  911. See Documentation/slow-work.txt.
  912. endmenu # General setup
  913. config HAVE_GENERIC_DMA_COHERENT
  914. bool
  915. default n
  916. config SLABINFO
  917. bool
  918. depends on PROC_FS
  919. depends on SLAB || SLUB_DEBUG
  920. default y
  921. config RT_MUTEXES
  922. boolean
  923. config BASE_SMALL
  924. int
  925. default 0 if BASE_FULL
  926. default 1 if !BASE_FULL
  927. menuconfig MODULES
  928. bool "Enable loadable module support"
  929. help
  930. Kernel modules are small pieces of compiled code which can
  931. be inserted in the running kernel, rather than being
  932. permanently built into the kernel. You use the "modprobe"
  933. tool to add (and sometimes remove) them. If you say Y here,
  934. many parts of the kernel can be built as modules (by
  935. answering M instead of Y where indicated): this is most
  936. useful for infrequently used options which are not required
  937. for booting. For more information, see the man pages for
  938. modprobe, lsmod, modinfo, insmod and rmmod.
  939. If you say Y here, you will need to run "make
  940. modules_install" to put the modules under /lib/modules/
  941. where modprobe can find them (you may need to be root to do
  942. this).
  943. If unsure, say Y.
  944. if MODULES
  945. config MODULE_FORCE_LOAD
  946. bool "Forced module loading"
  947. default n
  948. help
  949. Allow loading of modules without version information (ie. modprobe
  950. --force). Forced module loading sets the 'F' (forced) taint flag and
  951. is usually a really bad idea.
  952. config MODULE_UNLOAD
  953. bool "Module unloading"
  954. help
  955. Without this option you will not be able to unload any
  956. modules (note that some modules may not be unloadable
  957. anyway), which makes your kernel smaller, faster
  958. and simpler. If unsure, say Y.
  959. config MODULE_FORCE_UNLOAD
  960. bool "Forced module unloading"
  961. depends on MODULE_UNLOAD && EXPERIMENTAL
  962. help
  963. This option allows you to force a module to unload, even if the
  964. kernel believes it is unsafe: the kernel will remove the module
  965. without waiting for anyone to stop using it (using the -f option to
  966. rmmod). This is mainly for kernel developers and desperate users.
  967. If unsure, say N.
  968. config MODVERSIONS
  969. bool "Module versioning support"
  970. help
  971. Usually, you have to use modules compiled with your kernel.
  972. Saying Y here makes it sometimes possible to use modules
  973. compiled for different kernels, by adding enough information
  974. to the modules to (hopefully) spot any changes which would
  975. make them incompatible with the kernel you are running. If
  976. unsure, say N.
  977. config MODULE_SRCVERSION_ALL
  978. bool "Source checksum for all modules"
  979. help
  980. Modules which contain a MODULE_VERSION get an extra "srcversion"
  981. field inserted into their modinfo section, which contains a
  982. sum of the source files which made it. This helps maintainers
  983. see exactly which source was used to build a module (since
  984. others sometimes change the module source without updating
  985. the version). With this option, such a "srcversion" field
  986. will be created for all modules. If unsure, say N.
  987. endif # MODULES
  988. config INIT_ALL_POSSIBLE
  989. bool
  990. help
  991. Back when each arch used to define their own cpu_online_map and
  992. cpu_possible_map, some of them chose to initialize cpu_possible_map
  993. with all 1s, and others with all 0s. When they were centralised,
  994. it was better to provide this option than to break all the archs
  995. and have several arch maintainers pursuing me down dark alleys.
  996. config STOP_MACHINE
  997. bool
  998. default y
  999. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1000. help
  1001. Need stop_machine() primitive.
  1002. source "block/Kconfig"
  1003. config PREEMPT_NOTIFIERS
  1004. bool