Kconfig 56 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. config HAVE_IRQ_WORK
  20. bool
  21. config IRQ_WORK
  22. bool
  23. depends on HAVE_IRQ_WORK
  24. config BUILDTIME_EXTABLE_SORT
  25. bool
  26. menu "General setup"
  27. config EXPERIMENTAL
  28. bool "Prompt for development and/or incomplete code/drivers"
  29. ---help---
  30. Some of the various things that Linux supports (such as network
  31. drivers, file systems, network protocols, etc.) can be in a state
  32. of development where the functionality, stability, or the level of
  33. testing is not yet high enough for general use. This is usually
  34. known as the "alpha-test" phase among developers. If a feature is
  35. currently in alpha-test, then the developers usually discourage
  36. uninformed widespread use of this feature by the general public to
  37. avoid "Why doesn't this work?" type mail messages. However, active
  38. testing and use of these systems is welcomed. Just be aware that it
  39. may not meet the normal level of reliability or it may fail to work
  40. in some special cases. Detailed bug reports from people familiar
  41. with the kernel internals are usually welcomed by the developers
  42. (before submitting bug reports, please read the documents
  43. <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  44. <file:Documentation/BUG-HUNTING>, and
  45. <file:Documentation/oops-tracing.txt> in the kernel source).
  46. This option will also make obsoleted drivers available. These are
  47. drivers that have been replaced by something else, and/or are
  48. scheduled to be removed in a future kernel release.
  49. Unless you intend to help test and develop a feature or driver that
  50. falls into this category, or you have a situation that requires
  51. using these features, you should probably say N here, which will
  52. cause the configurator to present you with fewer choices. If
  53. you say Y here, you will be offered the choice of using features or
  54. drivers that are currently considered to be in the alpha-test phase.
  55. config BROKEN
  56. bool
  57. config BROKEN_ON_SMP
  58. bool
  59. depends on BROKEN || !SMP
  60. default y
  61. config INIT_ENV_ARG_LIMIT
  62. int
  63. default 32 if !UML
  64. default 128 if UML
  65. help
  66. Maximum of each of the number of arguments and environment
  67. variables passed to init from the kernel command line.
  68. config CROSS_COMPILE
  69. string "Cross-compiler tool prefix"
  70. help
  71. Same as running 'make CROSS_COMPILE=prefix-' but stored for
  72. default make runs in this kernel build directory. You don't
  73. need to set this unless you want the configured kernel build
  74. directory to select the cross-compiler automatically.
  75. config LOCALVERSION
  76. string "Local version - append to kernel release"
  77. help
  78. Append an extra string to the end of your kernel version.
  79. This will show up when you type uname, for example.
  80. The string you set here will be appended after the contents of
  81. any files with a filename matching localversion* in your
  82. object and source tree, in that order. Your total string can
  83. be a maximum of 64 characters.
  84. config LOCALVERSION_AUTO
  85. bool "Automatically append version information to the version string"
  86. default y
  87. help
  88. This will try to automatically determine if the current tree is a
  89. release tree by looking for git tags that belong to the current
  90. top of tree revision.
  91. A string of the format -gxxxxxxxx will be added to the localversion
  92. if a git-based tree is found. The string generated by this will be
  93. appended after any matching localversion* files, and after the value
  94. set in CONFIG_LOCALVERSION.
  95. (The actual string used here is the first eight characters produced
  96. by running the command:
  97. $ git rev-parse --verify HEAD
  98. which is done within the script "scripts/setlocalversion".)
  99. config HAVE_KERNEL_GZIP
  100. bool
  101. config HAVE_KERNEL_BZIP2
  102. bool
  103. config HAVE_KERNEL_LZMA
  104. bool
  105. config HAVE_KERNEL_XZ
  106. bool
  107. config HAVE_KERNEL_LZO
  108. bool
  109. choice
  110. prompt "Kernel compression mode"
  111. default KERNEL_GZIP
  112. depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
  113. help
  114. The linux kernel is a kind of self-extracting executable.
  115. Several compression algorithms are available, which differ
  116. in efficiency, compression and decompression speed.
  117. Compression speed is only relevant when building a kernel.
  118. Decompression speed is relevant at each boot.
  119. If you have any problems with bzip2 or lzma compressed
  120. kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
  121. version of this functionality (bzip2 only), for 2.4, was
  122. supplied by Christian Ludwig)
  123. High compression options are mostly useful for users, who
  124. are low on disk space (embedded systems), but for whom ram
  125. size matters less.
  126. If in doubt, select 'gzip'
  127. config KERNEL_GZIP
  128. bool "Gzip"
  129. depends on HAVE_KERNEL_GZIP
  130. help
  131. The old and tried gzip compression. It provides a good balance
  132. between compression ratio and decompression speed.
  133. config KERNEL_BZIP2
  134. bool "Bzip2"
  135. depends on HAVE_KERNEL_BZIP2
  136. help
  137. Its compression ratio and speed is intermediate.
  138. Decompression speed is slowest among the choices. The kernel
  139. size is about 10% smaller with bzip2, in comparison to gzip.
  140. Bzip2 uses a large amount of memory. For modern kernels you
  141. will need at least 8MB RAM or more for booting.
  142. config KERNEL_LZMA
  143. bool "LZMA"
  144. depends on HAVE_KERNEL_LZMA
  145. help
  146. This compression algorithm's ratio is best. Decompression speed
  147. is between gzip and bzip2. Compression is slowest.
  148. The kernel size is about 33% smaller with LZMA in comparison to gzip.
  149. config KERNEL_XZ
  150. bool "XZ"
  151. depends on HAVE_KERNEL_XZ
  152. help
  153. XZ uses the LZMA2 algorithm and instruction set specific
  154. BCJ filters which can improve compression ratio of executable
  155. code. The size of the kernel is about 30% smaller with XZ in
  156. comparison to gzip. On architectures for which there is a BCJ
  157. filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
  158. will create a few percent smaller kernel than plain LZMA.
  159. The speed is about the same as with LZMA: The decompression
  160. speed of XZ is better than that of bzip2 but worse than gzip
  161. and LZO. Compression is slow.
  162. config KERNEL_LZO
  163. bool "LZO"
  164. depends on HAVE_KERNEL_LZO
  165. help
  166. Its compression ratio is the poorest among the choices. The kernel
  167. size is about 10% bigger than gzip; however its speed
  168. (both compression and decompression) is the fastest.
  169. endchoice
  170. config DEFAULT_HOSTNAME
  171. string "Default hostname"
  172. default "(none)"
  173. help
  174. This option determines the default system hostname before userspace
  175. calls sethostname(2). The kernel traditionally uses "(none)" here,
  176. but you may wish to use a different default here to make a minimal
  177. system more usable with less configuration.
  178. config SWAP
  179. bool "Support for paging of anonymous memory (swap)"
  180. depends on MMU && BLOCK
  181. default y
  182. help
  183. This option allows you to choose whether you want to have support
  184. for so called swap devices or swap files in your kernel that are
  185. used to provide more virtual memory than the actual RAM present
  186. in your computer. If unsure say Y.
  187. config SYSVIPC
  188. bool "System V IPC"
  189. ---help---
  190. Inter Process Communication is a suite of library functions and
  191. system calls which let processes (running programs) synchronize and
  192. exchange information. It is generally considered to be a good thing,
  193. and some programs won't run unless you say Y here. In particular, if
  194. you want to run the DOS emulator dosemu under Linux (read the
  195. DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
  196. you'll need to say Y here.
  197. You can find documentation about IPC with "info ipc" and also in
  198. section 6.4 of the Linux Programmer's Guide, available from
  199. <http://www.tldp.org/guides.html>.
  200. config SYSVIPC_SYSCTL
  201. bool
  202. depends on SYSVIPC
  203. depends on SYSCTL
  204. default y
  205. config POSIX_MQUEUE
  206. bool "POSIX Message Queues"
  207. depends on NET && EXPERIMENTAL
  208. ---help---
  209. POSIX variant of message queues is a part of IPC. In POSIX message
  210. queues every message has a priority which decides about succession
  211. of receiving it by a process. If you want to compile and run
  212. programs written e.g. for Solaris with use of its POSIX message
  213. queues (functions mq_*) say Y here.
  214. POSIX message queues are visible as a filesystem called 'mqueue'
  215. and can be mounted somewhere if you want to do filesystem
  216. operations on message queues.
  217. If unsure, say Y.
  218. config POSIX_MQUEUE_SYSCTL
  219. bool
  220. depends on POSIX_MQUEUE
  221. depends on SYSCTL
  222. default y
  223. config FHANDLE
  224. bool "open by fhandle syscalls"
  225. select EXPORTFS
  226. help
  227. If you say Y here, a user level program will be able to map
  228. file names to handle and then later use the handle for
  229. different file system operations. This is useful in implementing
  230. userspace file servers, which now track files using handles instead
  231. of names. The handle would remain the same even if file names
  232. get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
  233. syscalls.
  234. config AUDIT
  235. bool "Auditing support"
  236. depends on NET
  237. help
  238. Enable auditing infrastructure that can be used with another
  239. kernel subsystem, such as SELinux (which requires this for
  240. logging of avc messages output). Does not do system-call
  241. auditing without CONFIG_AUDITSYSCALL.
  242. config AUDITSYSCALL
  243. bool "Enable system-call auditing support"
  244. depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
  245. default y if SECURITY_SELINUX
  246. help
  247. Enable low-overhead system-call auditing infrastructure that
  248. can be used independently or with another kernel subsystem,
  249. such as SELinux.
  250. config AUDIT_WATCH
  251. def_bool y
  252. depends on AUDITSYSCALL
  253. select FSNOTIFY
  254. config AUDIT_TREE
  255. def_bool y
  256. depends on AUDITSYSCALL
  257. select FSNOTIFY
  258. config AUDIT_LOGINUID_IMMUTABLE
  259. bool "Make audit loginuid immutable"
  260. depends on AUDIT
  261. help
  262. The config option toggles if a task setting its loginuid requires
  263. CAP_SYS_AUDITCONTROL or if that task should require no special permissions
  264. but should instead only allow setting its loginuid if it was never
  265. previously set. On systems which use systemd or a similar central
  266. process to restart login services this should be set to true. On older
  267. systems in which an admin would typically have to directly stop and
  268. start processes this should be set to false. Setting this to true allows
  269. one to drop potentially dangerous capabilites from the login tasks,
  270. but may not be backwards compatible with older init systems.
  271. source "kernel/irq/Kconfig"
  272. source "kernel/time/Kconfig"
  273. menu "CPU/Task time and stats accounting"
  274. choice
  275. prompt "Cputime accounting"
  276. default TICK_CPU_ACCOUNTING if !PPC64
  277. default VIRT_CPU_ACCOUNTING if PPC64
  278. # Kind of a stub config for the pure tick based cputime accounting
  279. config TICK_CPU_ACCOUNTING
  280. bool "Simple tick based cputime accounting"
  281. depends on !S390
  282. help
  283. This is the basic tick based cputime accounting that maintains
  284. statistics about user, system and idle time spent on per jiffies
  285. granularity.
  286. If unsure, say Y.
  287. config VIRT_CPU_ACCOUNTING
  288. bool "Deterministic task and CPU time accounting"
  289. depends on HAVE_VIRT_CPU_ACCOUNTING
  290. help
  291. Select this option to enable more accurate task and CPU time
  292. accounting. This is done by reading a CPU counter on each
  293. kernel entry and exit and on transitions within the kernel
  294. between system, softirq and hardirq state, so there is a
  295. small performance impact. In the case of s390 or IBM POWER > 5,
  296. this also enables accounting of stolen time on logically-partitioned
  297. systems.
  298. config IRQ_TIME_ACCOUNTING
  299. bool "Fine granularity task level IRQ time accounting"
  300. depends on HAVE_IRQ_TIME_ACCOUNTING
  301. help
  302. Select this option to enable fine granularity task irq time
  303. accounting. This is done by reading a timestamp on each
  304. transitions between softirq and hardirq state, so there can be a
  305. small performance impact.
  306. If in doubt, say N here.
  307. endchoice
  308. config BSD_PROCESS_ACCT
  309. bool "BSD Process Accounting"
  310. help
  311. If you say Y here, a user level program will be able to instruct the
  312. kernel (via a special system call) to write process accounting
  313. information to a file: whenever a process exits, information about
  314. that process will be appended to the file by the kernel. The
  315. information includes things such as creation time, owning user,
  316. command name, memory usage, controlling terminal etc. (the complete
  317. list is in the struct acct in <file:include/linux/acct.h>). It is
  318. up to the user level program to do useful things with this
  319. information. This is generally a good idea, so say Y.
  320. config BSD_PROCESS_ACCT_V3
  321. bool "BSD Process Accounting version 3 file format"
  322. depends on BSD_PROCESS_ACCT
  323. default n
  324. help
  325. If you say Y here, the process accounting information is written
  326. in a new file format that also logs the process IDs of each
  327. process and it's parent. Note that this file format is incompatible
  328. with previous v0/v1/v2 file formats, so you will need updated tools
  329. for processing it. A preliminary version of these tools is available
  330. at <http://www.gnu.org/software/acct/>.
  331. config TASKSTATS
  332. bool "Export task/process statistics through netlink (EXPERIMENTAL)"
  333. depends on NET
  334. default n
  335. help
  336. Export selected statistics for tasks/processes through the
  337. generic netlink interface. Unlike BSD process accounting, the
  338. statistics are available during the lifetime of tasks/processes as
  339. responses to commands. Like BSD accounting, they are sent to user
  340. space on task exit.
  341. Say N if unsure.
  342. config TASK_DELAY_ACCT
  343. bool "Enable per-task delay accounting (EXPERIMENTAL)"
  344. depends on TASKSTATS
  345. help
  346. Collect information on time spent by a task waiting for system
  347. resources like cpu, synchronous block I/O completion and swapping
  348. in pages. Such statistics can help in setting a task's priorities
  349. relative to other tasks for cpu, io, rss limits etc.
  350. Say N if unsure.
  351. config TASK_XACCT
  352. bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
  353. depends on TASKSTATS
  354. help
  355. Collect extended task accounting data and send the data
  356. to userland for processing over the taskstats interface.
  357. Say N if unsure.
  358. config TASK_IO_ACCOUNTING
  359. bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
  360. depends on TASK_XACCT
  361. help
  362. Collect information on the number of bytes of storage I/O which this
  363. task has caused.
  364. Say N if unsure.
  365. endmenu # "CPU/Task time and stats accounting"
  366. menu "RCU Subsystem"
  367. choice
  368. prompt "RCU Implementation"
  369. default TREE_RCU
  370. config TREE_RCU
  371. bool "Tree-based hierarchical RCU"
  372. depends on !PREEMPT && SMP
  373. help
  374. This option selects the RCU implementation that is
  375. designed for very large SMP system with hundreds or
  376. thousands of CPUs. It also scales down nicely to
  377. smaller systems.
  378. config TREE_PREEMPT_RCU
  379. bool "Preemptible tree-based hierarchical RCU"
  380. depends on PREEMPT
  381. help
  382. This option selects the RCU implementation that is
  383. designed for very large SMP systems with hundreds or
  384. thousands of CPUs, but for which real-time response
  385. is also required. It also scales down nicely to
  386. smaller systems.
  387. Select this option if you are unsure.
  388. config TINY_RCU
  389. bool "UP-only small-memory-footprint RCU"
  390. depends on !PREEMPT && !SMP
  391. help
  392. This option selects the RCU implementation that is
  393. designed for UP systems from which real-time response
  394. is not required. This option greatly reduces the
  395. memory footprint of RCU.
  396. config TINY_PREEMPT_RCU
  397. bool "Preemptible UP-only small-memory-footprint RCU"
  398. depends on PREEMPT && !SMP
  399. help
  400. This option selects the RCU implementation that is designed
  401. for real-time UP systems. This option greatly reduces the
  402. memory footprint of RCU.
  403. endchoice
  404. config PREEMPT_RCU
  405. def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
  406. help
  407. This option enables preemptible-RCU code that is common between
  408. the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
  409. config RCU_STALL_COMMON
  410. def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
  411. help
  412. This option enables RCU CPU stall code that is common between
  413. the TINY and TREE variants of RCU. The purpose is to allow
  414. the tiny variants to disable RCU CPU stall warnings, while
  415. making these warnings mandatory for the tree variants.
  416. config CONTEXT_TRACKING
  417. bool
  418. config RCU_USER_QS
  419. bool "Consider userspace as in RCU extended quiescent state"
  420. depends on HAVE_CONTEXT_TRACKING && SMP
  421. select CONTEXT_TRACKING
  422. help
  423. This option sets hooks on kernel / userspace boundaries and
  424. puts RCU in extended quiescent state when the CPU runs in
  425. userspace. It means that when a CPU runs in userspace, it is
  426. excluded from the global RCU state machine and thus doesn't
  427. try to keep the timer tick on for RCU.
  428. Unless you want to hack and help the development of the full
  429. dynticks mode, you shouldn't enable this option. It also
  430. adds unnecessary overhead.
  431. If unsure say N
  432. config CONTEXT_TRACKING_FORCE
  433. bool "Force context tracking"
  434. depends on CONTEXT_TRACKING
  435. help
  436. Probe on user/kernel boundaries by default in order to
  437. test the features that rely on it such as userspace RCU extended
  438. quiescent states.
  439. This test is there for debugging until we have a real user like the
  440. full dynticks mode.
  441. config RCU_FANOUT
  442. int "Tree-based hierarchical RCU fanout value"
  443. range 2 64 if 64BIT
  444. range 2 32 if !64BIT
  445. depends on TREE_RCU || TREE_PREEMPT_RCU
  446. default 64 if 64BIT
  447. default 32 if !64BIT
  448. help
  449. This option controls the fanout of hierarchical implementations
  450. of RCU, allowing RCU to work efficiently on machines with
  451. large numbers of CPUs. This value must be at least the fourth
  452. root of NR_CPUS, which allows NR_CPUS to be insanely large.
  453. The default value of RCU_FANOUT should be used for production
  454. systems, but if you are stress-testing the RCU implementation
  455. itself, small RCU_FANOUT values allow you to test large-system
  456. code paths on small(er) systems.
  457. Select a specific number if testing RCU itself.
  458. Take the default if unsure.
  459. config RCU_FANOUT_LEAF
  460. int "Tree-based hierarchical RCU leaf-level fanout value"
  461. range 2 RCU_FANOUT if 64BIT
  462. range 2 RCU_FANOUT if !64BIT
  463. depends on TREE_RCU || TREE_PREEMPT_RCU
  464. default 16
  465. help
  466. This option controls the leaf-level fanout of hierarchical
  467. implementations of RCU, and allows trading off cache misses
  468. against lock contention. Systems that synchronize their
  469. scheduling-clock interrupts for energy-efficiency reasons will
  470. want the default because the smaller leaf-level fanout keeps
  471. lock contention levels acceptably low. Very large systems
  472. (hundreds or thousands of CPUs) will instead want to set this
  473. value to the maximum value possible in order to reduce the
  474. number of cache misses incurred during RCU's grace-period
  475. initialization. These systems tend to run CPU-bound, and thus
  476. are not helped by synchronized interrupts, and thus tend to
  477. skew them, which reduces lock contention enough that large
  478. leaf-level fanouts work well.
  479. Select a specific number if testing RCU itself.
  480. Select the maximum permissible value for large systems.
  481. Take the default if unsure.
  482. config RCU_FANOUT_EXACT
  483. bool "Disable tree-based hierarchical RCU auto-balancing"
  484. depends on TREE_RCU || TREE_PREEMPT_RCU
  485. default n
  486. help
  487. This option forces use of the exact RCU_FANOUT value specified,
  488. regardless of imbalances in the hierarchy. This is useful for
  489. testing RCU itself, and might one day be useful on systems with
  490. strong NUMA behavior.
  491. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  492. Say N if unsure.
  493. config RCU_FAST_NO_HZ
  494. bool "Accelerate last non-dyntick-idle CPU's grace periods"
  495. depends on NO_HZ && SMP
  496. default n
  497. help
  498. This option causes RCU to attempt to accelerate grace periods in
  499. order to allow CPUs to enter dynticks-idle state more quickly.
  500. On the other hand, this option increases the overhead of the
  501. dynticks-idle checking, thus degrading scheduling latency.
  502. Say Y if energy efficiency is critically important, and you don't
  503. care about real-time response.
  504. Say N if you are unsure.
  505. config TREE_RCU_TRACE
  506. def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
  507. select DEBUG_FS
  508. help
  509. This option provides tracing for the TREE_RCU and
  510. TREE_PREEMPT_RCU implementations, permitting Makefile to
  511. trivially select kernel/rcutree_trace.c.
  512. config RCU_BOOST
  513. bool "Enable RCU priority boosting"
  514. depends on RT_MUTEXES && PREEMPT_RCU
  515. default n
  516. help
  517. This option boosts the priority of preempted RCU readers that
  518. block the current preemptible RCU grace period for too long.
  519. This option also prevents heavy loads from blocking RCU
  520. callback invocation for all flavors of RCU.
  521. Say Y here if you are working with real-time apps or heavy loads
  522. Say N here if you are unsure.
  523. config RCU_BOOST_PRIO
  524. int "Real-time priority to boost RCU readers to"
  525. range 1 99
  526. depends on RCU_BOOST
  527. default 1
  528. help
  529. This option specifies the real-time priority to which long-term
  530. preempted RCU readers are to be boosted. If you are working
  531. with a real-time application that has one or more CPU-bound
  532. threads running at a real-time priority level, you should set
  533. RCU_BOOST_PRIO to a priority higher then the highest-priority
  534. real-time CPU-bound thread. The default RCU_BOOST_PRIO value
  535. of 1 is appropriate in the common case, which is real-time
  536. applications that do not have any CPU-bound threads.
  537. Some real-time applications might not have a single real-time
  538. thread that saturates a given CPU, but instead might have
  539. multiple real-time threads that, taken together, fully utilize
  540. that CPU. In this case, you should set RCU_BOOST_PRIO to
  541. a priority higher than the lowest-priority thread that is
  542. conspiring to prevent the CPU from running any non-real-time
  543. tasks. For example, if one thread at priority 10 and another
  544. thread at priority 5 are between themselves fully consuming
  545. the CPU time on a given CPU, then RCU_BOOST_PRIO should be
  546. set to priority 6 or higher.
  547. Specify the real-time priority, or take the default if unsure.
  548. config RCU_BOOST_DELAY
  549. int "Milliseconds to delay boosting after RCU grace-period start"
  550. range 0 3000
  551. depends on RCU_BOOST
  552. default 500
  553. help
  554. This option specifies the time to wait after the beginning of
  555. a given grace period before priority-boosting preempted RCU
  556. readers blocking that grace period. Note that any RCU reader
  557. blocking an expedited RCU grace period is boosted immediately.
  558. Accept the default if unsure.
  559. config RCU_NOCB_CPU
  560. bool "Offload RCU callback processing from boot-selected CPUs"
  561. depends on TREE_RCU || TREE_PREEMPT_RCU
  562. default n
  563. help
  564. Use this option to reduce OS jitter for aggressive HPC or
  565. real-time workloads. It can also be used to offload RCU
  566. callback invocation to energy-efficient CPUs in battery-powered
  567. asymmetric multiprocessors.
  568. This option offloads callback invocation from the set of
  569. CPUs specified at boot time by the rcu_nocbs parameter.
  570. For each such CPU, a kthread ("rcuoN") will be created to
  571. invoke callbacks, where the "N" is the CPU being offloaded.
  572. Nothing prevents this kthread from running on the specified
  573. CPUs, but (1) the kthreads may be preempted between each
  574. callback, and (2) affinity or cgroups can be used to force
  575. the kthreads to run on whatever set of CPUs is desired.
  576. Say Y here if you want reduced OS jitter on selected CPUs.
  577. Say N here if you are unsure.
  578. endmenu # "RCU Subsystem"
  579. config IKCONFIG
  580. tristate "Kernel .config support"
  581. ---help---
  582. This option enables the complete Linux kernel ".config" file
  583. contents to be saved in the kernel. It provides documentation
  584. of which kernel options are used in a running kernel or in an
  585. on-disk kernel. This information can be extracted from the kernel
  586. image file with the script scripts/extract-ikconfig and used as
  587. input to rebuild the current kernel or to build another kernel.
  588. It can also be extracted from a running kernel by reading
  589. /proc/config.gz if enabled (below).
  590. config IKCONFIG_PROC
  591. bool "Enable access to .config through /proc/config.gz"
  592. depends on IKCONFIG && PROC_FS
  593. ---help---
  594. This option enables access to the kernel configuration file
  595. through /proc/config.gz.
  596. config LOG_BUF_SHIFT
  597. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  598. range 12 21
  599. default 17
  600. help
  601. Select kernel log buffer size as a power of 2.
  602. Examples:
  603. 17 => 128 KB
  604. 16 => 64 KB
  605. 15 => 32 KB
  606. 14 => 16 KB
  607. 13 => 8 KB
  608. 12 => 4 KB
  609. #
  610. # Architectures with an unreliable sched_clock() should select this:
  611. #
  612. config HAVE_UNSTABLE_SCHED_CLOCK
  613. bool
  614. #
  615. # For architectures that want to enable the support for NUMA-affine scheduler
  616. # balancing logic:
  617. #
  618. config ARCH_SUPPORTS_NUMA_BALANCING
  619. bool
  620. # For architectures that (ab)use NUMA to represent different memory regions
  621. # all cpu-local but of different latencies, such as SuperH.
  622. #
  623. config ARCH_WANT_NUMA_VARIABLE_LOCALITY
  624. bool
  625. #
  626. # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
  627. config ARCH_WANTS_PROT_NUMA_PROT_NONE
  628. bool
  629. config ARCH_USES_NUMA_PROT_NONE
  630. bool
  631. default y
  632. depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
  633. depends on NUMA_BALANCING
  634. config NUMA_BALANCING_DEFAULT_ENABLED
  635. bool "Automatically enable NUMA aware memory/task placement"
  636. default y
  637. depends on NUMA_BALANCING
  638. help
  639. If set, autonumic NUMA balancing will be enabled if running on a NUMA
  640. machine.
  641. config NUMA_BALANCING
  642. bool "Memory placement aware NUMA scheduler"
  643. depends on ARCH_SUPPORTS_NUMA_BALANCING
  644. depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
  645. depends on SMP && NUMA && MIGRATION
  646. help
  647. This option adds support for automatic NUMA aware memory/task placement.
  648. The mechanism is quite primitive and is based on migrating memory when
  649. it is references to the node the task is running on.
  650. This system will be inactive on UMA systems.
  651. menuconfig CGROUPS
  652. boolean "Control Group support"
  653. depends on EVENTFD
  654. help
  655. This option adds support for grouping sets of processes together, for
  656. use with process control subsystems such as Cpusets, CFS, memory
  657. controls or device isolation.
  658. See
  659. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  660. - Documentation/cgroups/ (features for grouping, isolation
  661. and resource control)
  662. Say N if unsure.
  663. if CGROUPS
  664. config CGROUP_DEBUG
  665. bool "Example debug cgroup subsystem"
  666. default n
  667. help
  668. This option enables a simple cgroup subsystem that
  669. exports useful debugging information about the cgroups
  670. framework.
  671. Say N if unsure.
  672. config CGROUP_FREEZER
  673. bool "Freezer cgroup subsystem"
  674. help
  675. Provides a way to freeze and unfreeze all tasks in a
  676. cgroup.
  677. config CGROUP_DEVICE
  678. bool "Device controller for cgroups"
  679. help
  680. Provides a cgroup implementing whitelists for devices which
  681. a process in the cgroup can mknod or open.
  682. config CPUSETS
  683. bool "Cpuset support"
  684. help
  685. This option will let you create and manage CPUSETs which
  686. allow dynamically partitioning a system into sets of CPUs and
  687. Memory Nodes and assigning tasks to run only within those sets.
  688. This is primarily useful on large SMP or NUMA systems.
  689. Say N if unsure.
  690. config PROC_PID_CPUSET
  691. bool "Include legacy /proc/<pid>/cpuset file"
  692. depends on CPUSETS
  693. default y
  694. config CGROUP_CPUACCT
  695. bool "Simple CPU accounting cgroup subsystem"
  696. help
  697. Provides a simple Resource Controller for monitoring the
  698. total CPU consumed by the tasks in a cgroup.
  699. config RESOURCE_COUNTERS
  700. bool "Resource counters"
  701. help
  702. This option enables controller independent resource accounting
  703. infrastructure that works with cgroups.
  704. config MEMCG
  705. bool "Memory Resource Controller for Control Groups"
  706. depends on RESOURCE_COUNTERS
  707. select MM_OWNER
  708. help
  709. Provides a memory resource controller that manages both anonymous
  710. memory and page cache. (See Documentation/cgroups/memory.txt)
  711. Note that setting this option increases fixed memory overhead
  712. associated with each page of memory in the system. By this,
  713. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  714. usage tracking struct at boot. Total amount of this is printed out
  715. at boot.
  716. Only enable when you're ok with these trade offs and really
  717. sure you need the memory resource controller. Even when you enable
  718. this, you can set "cgroup_disable=memory" at your boot option to
  719. disable memory resource controller and you can avoid overheads.
  720. (and lose benefits of memory resource controller)
  721. This config option also selects MM_OWNER config option, which
  722. could in turn add some fork/exit overhead.
  723. config MEMCG_SWAP
  724. bool "Memory Resource Controller Swap Extension"
  725. depends on MEMCG && SWAP
  726. help
  727. Add swap management feature to memory resource controller. When you
  728. enable this, you can limit mem+swap usage per cgroup. In other words,
  729. when you disable this, memory resource controller has no cares to
  730. usage of swap...a process can exhaust all of the swap. This extension
  731. is useful when you want to avoid exhaustion swap but this itself
  732. adds more overheads and consumes memory for remembering information.
  733. Especially if you use 32bit system or small memory system, please
  734. be careful about enabling this. When memory resource controller
  735. is disabled by boot option, this will be automatically disabled and
  736. there will be no overhead from this. Even when you set this config=y,
  737. if boot option "swapaccount=0" is set, swap will not be accounted.
  738. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  739. size is 4096bytes, 512k per 1Gbytes of swap.
  740. config MEMCG_SWAP_ENABLED
  741. bool "Memory Resource Controller Swap Extension enabled by default"
  742. depends on MEMCG_SWAP
  743. default y
  744. help
  745. Memory Resource Controller Swap Extension comes with its price in
  746. a bigger memory consumption. General purpose distribution kernels
  747. which want to enable the feature but keep it disabled by default
  748. and let the user enable it by swapaccount boot command line
  749. parameter should have this option unselected.
  750. For those who want to have the feature enabled by default should
  751. select this option (if, for some reason, they need to disable it
  752. then swapaccount=0 does the trick).
  753. config MEMCG_KMEM
  754. bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
  755. depends on MEMCG && EXPERIMENTAL
  756. depends on SLUB || SLAB
  757. help
  758. The Kernel Memory extension for Memory Resource Controller can limit
  759. the amount of memory used by kernel objects in the system. Those are
  760. fundamentally different from the entities handled by the standard
  761. Memory Controller, which are page-based, and can be swapped. Users of
  762. the kmem extension can use it to guarantee that no group of processes
  763. will ever exhaust kernel resources alone.
  764. config CGROUP_HUGETLB
  765. bool "HugeTLB Resource Controller for Control Groups"
  766. depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
  767. default n
  768. help
  769. Provides a cgroup Resource Controller for HugeTLB pages.
  770. When you enable this, you can put a per cgroup limit on HugeTLB usage.
  771. The limit is enforced during page fault. Since HugeTLB doesn't
  772. support page reclaim, enforcing the limit at page fault time implies
  773. that, the application will get SIGBUS signal if it tries to access
  774. HugeTLB pages beyond its limit. This requires the application to know
  775. beforehand how much HugeTLB pages it would require for its use. The
  776. control group is tracked in the third page lru pointer. This means
  777. that we cannot use the controller with huge page less than 3 pages.
  778. config CGROUP_PERF
  779. bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
  780. depends on PERF_EVENTS && CGROUPS
  781. help
  782. This option extends the per-cpu mode to restrict monitoring to
  783. threads which belong to the cgroup specified and run on the
  784. designated cpu.
  785. Say N if unsure.
  786. menuconfig CGROUP_SCHED
  787. bool "Group CPU scheduler"
  788. default n
  789. help
  790. This feature lets CPU scheduler recognize task groups and control CPU
  791. bandwidth allocation to such task groups. It uses cgroups to group
  792. tasks.
  793. if CGROUP_SCHED
  794. config FAIR_GROUP_SCHED
  795. bool "Group scheduling for SCHED_OTHER"
  796. depends on CGROUP_SCHED
  797. default CGROUP_SCHED
  798. config CFS_BANDWIDTH
  799. bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
  800. depends on EXPERIMENTAL
  801. depends on FAIR_GROUP_SCHED
  802. default n
  803. help
  804. This option allows users to define CPU bandwidth rates (limits) for
  805. tasks running within the fair group scheduler. Groups with no limit
  806. set are considered to be unconstrained and will run with no
  807. restriction.
  808. See tip/Documentation/scheduler/sched-bwc.txt for more information.
  809. config RT_GROUP_SCHED
  810. bool "Group scheduling for SCHED_RR/FIFO"
  811. depends on EXPERIMENTAL
  812. depends on CGROUP_SCHED
  813. default n
  814. help
  815. This feature lets you explicitly allocate real CPU bandwidth
  816. to task groups. If enabled, it will also make it impossible to
  817. schedule realtime tasks for non-root users until you allocate
  818. realtime bandwidth for them.
  819. See Documentation/scheduler/sched-rt-group.txt for more information.
  820. endif #CGROUP_SCHED
  821. config BLK_CGROUP
  822. bool "Block IO controller"
  823. depends on BLOCK
  824. default n
  825. ---help---
  826. Generic block IO controller cgroup interface. This is the common
  827. cgroup interface which should be used by various IO controlling
  828. policies.
  829. Currently, CFQ IO scheduler uses it to recognize task groups and
  830. control disk bandwidth allocation (proportional time slice allocation)
  831. to such task groups. It is also used by bio throttling logic in
  832. block layer to implement upper limit in IO rates on a device.
  833. This option only enables generic Block IO controller infrastructure.
  834. One needs to also enable actual IO controlling logic/policy. For
  835. enabling proportional weight division of disk bandwidth in CFQ, set
  836. CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
  837. CONFIG_BLK_DEV_THROTTLING=y.
  838. See Documentation/cgroups/blkio-controller.txt for more information.
  839. config DEBUG_BLK_CGROUP
  840. bool "Enable Block IO controller debugging"
  841. depends on BLK_CGROUP
  842. default n
  843. ---help---
  844. Enable some debugging help. Currently it exports additional stat
  845. files in a cgroup which can be useful for debugging.
  846. endif # CGROUPS
  847. config CHECKPOINT_RESTORE
  848. bool "Checkpoint/restore support" if EXPERT
  849. default n
  850. help
  851. Enables additional kernel features in a sake of checkpoint/restore.
  852. In particular it adds auxiliary prctl codes to setup process text,
  853. data and heap segment sizes, and a few additional /proc filesystem
  854. entries.
  855. If unsure, say N here.
  856. menuconfig NAMESPACES
  857. bool "Namespaces support" if EXPERT
  858. default !EXPERT
  859. help
  860. Provides the way to make tasks work with different objects using
  861. the same id. For example same IPC id may refer to different objects
  862. or same user id or pid may refer to different tasks when used in
  863. different namespaces.
  864. if NAMESPACES
  865. config UTS_NS
  866. bool "UTS namespace"
  867. default y
  868. help
  869. In this namespace tasks see different info provided with the
  870. uname() system call
  871. config IPC_NS
  872. bool "IPC namespace"
  873. depends on (SYSVIPC || POSIX_MQUEUE)
  874. default y
  875. help
  876. In this namespace tasks work with IPC ids which correspond to
  877. different IPC objects in different namespaces.
  878. config USER_NS
  879. bool "User namespace (EXPERIMENTAL)"
  880. depends on EXPERIMENTAL
  881. depends on UIDGID_CONVERTED
  882. select UIDGID_STRICT_TYPE_CHECKS
  883. default n
  884. help
  885. This allows containers, i.e. vservers, to use user namespaces
  886. to provide different user info for different servers.
  887. If unsure, say N.
  888. config PID_NS
  889. bool "PID Namespaces"
  890. default y
  891. help
  892. Support process id namespaces. This allows having multiple
  893. processes with the same pid as long as they are in different
  894. pid namespaces. This is a building block of containers.
  895. config NET_NS
  896. bool "Network namespace"
  897. depends on NET
  898. default y
  899. help
  900. Allow user space to create what appear to be multiple instances
  901. of the network stack.
  902. endif # NAMESPACES
  903. config UIDGID_CONVERTED
  904. # True if all of the selected software conmponents are known
  905. # to have uid_t and gid_t converted to kuid_t and kgid_t
  906. # where appropriate and are otherwise safe to use with
  907. # the user namespace.
  908. bool
  909. default y
  910. # Networking
  911. depends on NET_9P = n
  912. # Filesystems
  913. depends on 9P_FS = n
  914. depends on AFS_FS = n
  915. depends on CEPH_FS = n
  916. depends on CIFS = n
  917. depends on CODA_FS = n
  918. depends on GFS2_FS = n
  919. depends on NCP_FS = n
  920. depends on NFSD = n
  921. depends on NFS_FS = n
  922. depends on OCFS2_FS = n
  923. depends on XFS_FS = n
  924. config UIDGID_STRICT_TYPE_CHECKS
  925. bool "Require conversions between uid/gids and their internal representation"
  926. depends on UIDGID_CONVERTED
  927. default n
  928. help
  929. While the nececessary conversions are being added to all subsystems this option allows
  930. the code to continue to build for unconverted subsystems.
  931. Say Y here if you want the strict type checking enabled
  932. config SCHED_AUTOGROUP
  933. bool "Automatic process group scheduling"
  934. select EVENTFD
  935. select CGROUPS
  936. select CGROUP_SCHED
  937. select FAIR_GROUP_SCHED
  938. help
  939. This option optimizes the scheduler for common desktop workloads by
  940. automatically creating and populating task groups. This separation
  941. of workloads isolates aggressive CPU burners (like build jobs) from
  942. desktop applications. Task group autogeneration is currently based
  943. upon task session.
  944. config MM_OWNER
  945. bool
  946. config SYSFS_DEPRECATED
  947. bool "Enable deprecated sysfs features to support old userspace tools"
  948. depends on SYSFS
  949. default n
  950. help
  951. This option adds code that switches the layout of the "block" class
  952. devices, to not show up in /sys/class/block/, but only in
  953. /sys/block/.
  954. This switch is only active when the sysfs.deprecated=1 boot option is
  955. passed or the SYSFS_DEPRECATED_V2 option is set.
  956. This option allows new kernels to run on old distributions and tools,
  957. which might get confused by /sys/class/block/. Since 2007/2008 all
  958. major distributions and tools handle this just fine.
  959. Recent distributions and userspace tools after 2009/2010 depend on
  960. the existence of /sys/class/block/, and will not work with this
  961. option enabled.
  962. Only if you are using a new kernel on an old distribution, you might
  963. need to say Y here.
  964. config SYSFS_DEPRECATED_V2
  965. bool "Enable deprecated sysfs features by default"
  966. default n
  967. depends on SYSFS
  968. depends on SYSFS_DEPRECATED
  969. help
  970. Enable deprecated sysfs by default.
  971. See the CONFIG_SYSFS_DEPRECATED option for more details about this
  972. option.
  973. Only if you are using a new kernel on an old distribution, you might
  974. need to say Y here. Even then, odds are you would not need it
  975. enabled, you can always pass the boot option if absolutely necessary.
  976. config RELAY
  977. bool "Kernel->user space relay support (formerly relayfs)"
  978. help
  979. This option enables support for relay interface support in
  980. certain file systems (such as debugfs).
  981. It is designed to provide an efficient mechanism for tools and
  982. facilities to relay large amounts of data from kernel space to
  983. user space.
  984. If unsure, say N.
  985. config BLK_DEV_INITRD
  986. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  987. depends on BROKEN || !FRV
  988. help
  989. The initial RAM filesystem is a ramfs which is loaded by the
  990. boot loader (loadlin or lilo) and that is mounted as root
  991. before the normal boot procedure. It is typically used to
  992. load modules needed to mount the "real" root file system,
  993. etc. See <file:Documentation/initrd.txt> for details.
  994. If RAM disk support (BLK_DEV_RAM) is also included, this
  995. also enables initial RAM disk (initrd) support and adds
  996. 15 Kbytes (more on some other architectures) to the kernel size.
  997. If unsure say Y.
  998. if BLK_DEV_INITRD
  999. source "usr/Kconfig"
  1000. endif
  1001. config CC_OPTIMIZE_FOR_SIZE
  1002. bool "Optimize for size"
  1003. help
  1004. Enabling this option will pass "-Os" instead of "-O2" to gcc
  1005. resulting in a smaller kernel.
  1006. If unsure, say N.
  1007. config SYSCTL
  1008. bool
  1009. config ANON_INODES
  1010. bool
  1011. menuconfig EXPERT
  1012. bool "Configure standard kernel features (expert users)"
  1013. # Unhide debug options, to make the on-by-default options visible
  1014. select DEBUG_KERNEL
  1015. help
  1016. This option allows certain base kernel options and settings
  1017. to be disabled or tweaked. This is for specialized
  1018. environments which can tolerate a "non-standard" kernel.
  1019. Only use this if you really know what you are doing.
  1020. config HAVE_UID16
  1021. bool
  1022. config UID16
  1023. bool "Enable 16-bit UID system calls" if EXPERT
  1024. depends on HAVE_UID16
  1025. default y
  1026. help
  1027. This enables the legacy 16-bit UID syscall wrappers.
  1028. config SYSCTL_SYSCALL
  1029. bool "Sysctl syscall support" if EXPERT
  1030. depends on PROC_SYSCTL
  1031. default n
  1032. select SYSCTL
  1033. ---help---
  1034. sys_sysctl uses binary paths that have been found challenging
  1035. to properly maintain and use. The interface in /proc/sys
  1036. using paths with ascii names is now the primary path to this
  1037. information.
  1038. Almost nothing using the binary sysctl interface so if you are
  1039. trying to save some space it is probably safe to disable this,
  1040. making your kernel marginally smaller.
  1041. If unsure say N here.
  1042. config SYSCTL_EXCEPTION_TRACE
  1043. bool
  1044. help
  1045. Enable support for /proc/sys/debug/exception-trace.
  1046. config KALLSYMS
  1047. bool "Load all symbols for debugging/ksymoops" if EXPERT
  1048. default y
  1049. help
  1050. Say Y here to let the kernel print out symbolic crash information and
  1051. symbolic stack backtraces. This increases the size of the kernel
  1052. somewhat, as all symbols have to be loaded into the kernel image.
  1053. config KALLSYMS_ALL
  1054. bool "Include all symbols in kallsyms"
  1055. depends on DEBUG_KERNEL && KALLSYMS
  1056. help
  1057. Normally kallsyms only contains the symbols of functions for nicer
  1058. OOPS messages and backtraces (i.e., symbols from the text and inittext
  1059. sections). This is sufficient for most cases. And only in very rare
  1060. cases (e.g., when a debugger is used) all symbols are required (e.g.,
  1061. names of variables from the data sections, etc).
  1062. This option makes sure that all symbols are loaded into the kernel
  1063. image (i.e., symbols from all sections) in cost of increased kernel
  1064. size (depending on the kernel configuration, it may be 300KiB or
  1065. something like this).
  1066. Say N unless you really need all symbols.
  1067. config HOTPLUG
  1068. def_bool y
  1069. config PRINTK
  1070. default y
  1071. bool "Enable support for printk" if EXPERT
  1072. help
  1073. This option enables normal printk support. Removing it
  1074. eliminates most of the message strings from the kernel image
  1075. and makes the kernel more or less silent. As this makes it
  1076. very difficult to diagnose system problems, saying N here is
  1077. strongly discouraged.
  1078. config BUG
  1079. bool "BUG() support" if EXPERT
  1080. default y
  1081. help
  1082. Disabling this option eliminates support for BUG and WARN, reducing
  1083. the size of your kernel image and potentially quietly ignoring
  1084. numerous fatal conditions. You should only consider disabling this
  1085. option for embedded systems with no facilities for reporting errors.
  1086. Just say Y.
  1087. config ELF_CORE
  1088. depends on COREDUMP
  1089. default y
  1090. bool "Enable ELF core dumps" if EXPERT
  1091. help
  1092. Enable support for generating core dumps. Disabling saves about 4k.
  1093. config PCSPKR_PLATFORM
  1094. bool "Enable PC-Speaker support" if EXPERT
  1095. depends on HAVE_PCSPKR_PLATFORM
  1096. select I8253_LOCK
  1097. default y
  1098. help
  1099. This option allows to disable the internal PC-Speaker
  1100. support, saving some memory.
  1101. config HAVE_PCSPKR_PLATFORM
  1102. bool
  1103. config BASE_FULL
  1104. default y
  1105. bool "Enable full-sized data structures for core" if EXPERT
  1106. help
  1107. Disabling this option reduces the size of miscellaneous core
  1108. kernel data structures. This saves memory on small machines,
  1109. but may reduce performance.
  1110. config FUTEX
  1111. bool "Enable futex support" if EXPERT
  1112. default y
  1113. select RT_MUTEXES
  1114. help
  1115. Disabling this option will cause the kernel to be built without
  1116. support for "fast userspace mutexes". The resulting kernel may not
  1117. run glibc-based applications correctly.
  1118. config EPOLL
  1119. bool "Enable eventpoll support" if EXPERT
  1120. default y
  1121. select ANON_INODES
  1122. help
  1123. Disabling this option will cause the kernel to be built without
  1124. support for epoll family of system calls.
  1125. config SIGNALFD
  1126. bool "Enable signalfd() system call" if EXPERT
  1127. select ANON_INODES
  1128. default y
  1129. help
  1130. Enable the signalfd() system call that allows to receive signals
  1131. on a file descriptor.
  1132. If unsure, say Y.
  1133. config TIMERFD
  1134. bool "Enable timerfd() system call" if EXPERT
  1135. select ANON_INODES
  1136. default y
  1137. help
  1138. Enable the timerfd() system call that allows to receive timer
  1139. events on a file descriptor.
  1140. If unsure, say Y.
  1141. config EVENTFD
  1142. bool "Enable eventfd() system call" if EXPERT
  1143. select ANON_INODES
  1144. default y
  1145. help
  1146. Enable the eventfd() system call that allows to receive both
  1147. kernel notification (ie. KAIO) or userspace notifications.
  1148. If unsure, say Y.
  1149. config SHMEM
  1150. bool "Use full shmem filesystem" if EXPERT
  1151. default y
  1152. depends on MMU
  1153. help
  1154. The shmem is an internal filesystem used to manage shared memory.
  1155. It is backed by swap and manages resource limits. It is also exported
  1156. to userspace as tmpfs if TMPFS is enabled. Disabling this
  1157. option replaces shmem and tmpfs with the much simpler ramfs code,
  1158. which may be appropriate on small systems without swap.
  1159. config AIO
  1160. bool "Enable AIO support" if EXPERT
  1161. default y
  1162. help
  1163. This option enables POSIX asynchronous I/O which may by used
  1164. by some high performance threaded applications. Disabling
  1165. this option saves about 7k.
  1166. config EMBEDDED
  1167. bool "Embedded system"
  1168. select EXPERT
  1169. help
  1170. This option should be enabled if compiling the kernel for
  1171. an embedded system so certain expert options are available
  1172. for configuration.
  1173. config HAVE_PERF_EVENTS
  1174. bool
  1175. help
  1176. See tools/perf/design.txt for details.
  1177. config PERF_USE_VMALLOC
  1178. bool
  1179. help
  1180. See tools/perf/design.txt for details
  1181. menu "Kernel Performance Events And Counters"
  1182. config PERF_EVENTS
  1183. bool "Kernel performance events and counters"
  1184. default y if PROFILING
  1185. depends on HAVE_PERF_EVENTS
  1186. select ANON_INODES
  1187. select IRQ_WORK
  1188. help
  1189. Enable kernel support for various performance events provided
  1190. by software and hardware.
  1191. Software events are supported either built-in or via the
  1192. use of generic tracepoints.
  1193. Most modern CPUs support performance events via performance
  1194. counter registers. These registers count the number of certain
  1195. types of hw events: such as instructions executed, cachemisses
  1196. suffered, or branches mis-predicted - without slowing down the
  1197. kernel or applications. These registers can also trigger interrupts
  1198. when a threshold number of events have passed - and can thus be
  1199. used to profile the code that runs on that CPU.
  1200. The Linux Performance Event subsystem provides an abstraction of
  1201. these software and hardware event capabilities, available via a
  1202. system call and used by the "perf" utility in tools/perf/. It
  1203. provides per task and per CPU counters, and it provides event
  1204. capabilities on top of those.
  1205. Say Y if unsure.
  1206. config DEBUG_PERF_USE_VMALLOC
  1207. default n
  1208. bool "Debug: use vmalloc to back perf mmap() buffers"
  1209. depends on PERF_EVENTS && DEBUG_KERNEL
  1210. select PERF_USE_VMALLOC
  1211. help
  1212. Use vmalloc memory to back perf mmap() buffers.
  1213. Mostly useful for debugging the vmalloc code on platforms
  1214. that don't require it.
  1215. Say N if unsure.
  1216. endmenu
  1217. config VM_EVENT_COUNTERS
  1218. default y
  1219. bool "Enable VM event counters for /proc/vmstat" if EXPERT
  1220. help
  1221. VM event counters are needed for event counts to be shown.
  1222. This option allows the disabling of the VM event counters
  1223. on EXPERT systems. /proc/vmstat will only show page counts
  1224. if VM event counters are disabled.
  1225. config PCI_QUIRKS
  1226. default y
  1227. bool "Enable PCI quirk workarounds" if EXPERT
  1228. depends on PCI
  1229. help
  1230. This enables workarounds for various PCI chipset
  1231. bugs/quirks. Disable this only if your target machine is
  1232. unaffected by PCI quirks.
  1233. config SLUB_DEBUG
  1234. default y
  1235. bool "Enable SLUB debugging support" if EXPERT
  1236. depends on SLUB && SYSFS
  1237. help
  1238. SLUB has extensive debug support features. Disabling these can
  1239. result in significant savings in code size. This also disables
  1240. SLUB sysfs support. /sys/slab will not exist and there will be
  1241. no support for cache validation etc.
  1242. config COMPAT_BRK
  1243. bool "Disable heap randomization"
  1244. default y
  1245. help
  1246. Randomizing heap placement makes heap exploits harder, but it
  1247. also breaks ancient binaries (including anything libc5 based).
  1248. This option changes the bootup default to heap randomization
  1249. disabled, and can be overridden at runtime by setting
  1250. /proc/sys/kernel/randomize_va_space to 2.
  1251. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  1252. choice
  1253. prompt "Choose SLAB allocator"
  1254. default SLUB
  1255. help
  1256. This option allows to select a slab allocator.
  1257. config SLAB
  1258. bool "SLAB"
  1259. help
  1260. The regular slab allocator that is established and known to work
  1261. well in all environments. It organizes cache hot objects in
  1262. per cpu and per node queues.
  1263. config SLUB
  1264. bool "SLUB (Unqueued Allocator)"
  1265. help
  1266. SLUB is a slab allocator that minimizes cache line usage
  1267. instead of managing queues of cached objects (SLAB approach).
  1268. Per cpu caching is realized using slabs of objects instead
  1269. of queues of objects. SLUB can use memory efficiently
  1270. and has enhanced diagnostics. SLUB is the default choice for
  1271. a slab allocator.
  1272. config SLOB
  1273. depends on EXPERT
  1274. bool "SLOB (Simple Allocator)"
  1275. help
  1276. SLOB replaces the stock allocator with a drastically simpler
  1277. allocator. SLOB is generally more space efficient but
  1278. does not perform as well on large systems.
  1279. endchoice
  1280. config MMAP_ALLOW_UNINITIALIZED
  1281. bool "Allow mmapped anonymous memory to be uninitialized"
  1282. depends on EXPERT && !MMU
  1283. default n
  1284. help
  1285. Normally, and according to the Linux spec, anonymous memory obtained
  1286. from mmap() has it's contents cleared before it is passed to
  1287. userspace. Enabling this config option allows you to request that
  1288. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  1289. providing a huge performance boost. If this option is not enabled,
  1290. then the flag will be ignored.
  1291. This is taken advantage of by uClibc's malloc(), and also by
  1292. ELF-FDPIC binfmt's brk and stack allocator.
  1293. Because of the obvious security issues, this option should only be
  1294. enabled on embedded devices where you control what is run in
  1295. userspace. Since that isn't generally a problem on no-MMU systems,
  1296. it is normally safe to say Y here.
  1297. See Documentation/nommu-mmap.txt for more information.
  1298. config PROFILING
  1299. bool "Profiling support"
  1300. help
  1301. Say Y here to enable the extended profiling support mechanisms used
  1302. by profilers such as OProfile.
  1303. #
  1304. # Place an empty function call at each tracepoint site. Can be
  1305. # dynamically changed for a probe function.
  1306. #
  1307. config TRACEPOINTS
  1308. bool
  1309. source "arch/Kconfig"
  1310. endmenu # General setup
  1311. config HAVE_GENERIC_DMA_COHERENT
  1312. bool
  1313. default n
  1314. config SLABINFO
  1315. bool
  1316. depends on PROC_FS
  1317. depends on SLAB || SLUB_DEBUG
  1318. default y
  1319. config RT_MUTEXES
  1320. boolean
  1321. config BASE_SMALL
  1322. int
  1323. default 0 if BASE_FULL
  1324. default 1 if !BASE_FULL
  1325. menuconfig MODULES
  1326. bool "Enable loadable module support"
  1327. help
  1328. Kernel modules are small pieces of compiled code which can
  1329. be inserted in the running kernel, rather than being
  1330. permanently built into the kernel. You use the "modprobe"
  1331. tool to add (and sometimes remove) them. If you say Y here,
  1332. many parts of the kernel can be built as modules (by
  1333. answering M instead of Y where indicated): this is most
  1334. useful for infrequently used options which are not required
  1335. for booting. For more information, see the man pages for
  1336. modprobe, lsmod, modinfo, insmod and rmmod.
  1337. If you say Y here, you will need to run "make
  1338. modules_install" to put the modules under /lib/modules/
  1339. where modprobe can find them (you may need to be root to do
  1340. this).
  1341. If unsure, say Y.
  1342. if MODULES
  1343. config MODULE_FORCE_LOAD
  1344. bool "Forced module loading"
  1345. default n
  1346. help
  1347. Allow loading of modules without version information (ie. modprobe
  1348. --force). Forced module loading sets the 'F' (forced) taint flag and
  1349. is usually a really bad idea.
  1350. config MODULE_UNLOAD
  1351. bool "Module unloading"
  1352. help
  1353. Without this option you will not be able to unload any
  1354. modules (note that some modules may not be unloadable
  1355. anyway), which makes your kernel smaller, faster
  1356. and simpler. If unsure, say Y.
  1357. config MODULE_FORCE_UNLOAD
  1358. bool "Forced module unloading"
  1359. depends on MODULE_UNLOAD && EXPERIMENTAL
  1360. help
  1361. This option allows you to force a module to unload, even if the
  1362. kernel believes it is unsafe: the kernel will remove the module
  1363. without waiting for anyone to stop using it (using the -f option to
  1364. rmmod). This is mainly for kernel developers and desperate users.
  1365. If unsure, say N.
  1366. config MODVERSIONS
  1367. bool "Module versioning support"
  1368. help
  1369. Usually, you have to use modules compiled with your kernel.
  1370. Saying Y here makes it sometimes possible to use modules
  1371. compiled for different kernels, by adding enough information
  1372. to the modules to (hopefully) spot any changes which would
  1373. make them incompatible with the kernel you are running. If
  1374. unsure, say N.
  1375. config MODULE_SRCVERSION_ALL
  1376. bool "Source checksum for all modules"
  1377. help
  1378. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1379. field inserted into their modinfo section, which contains a
  1380. sum of the source files which made it. This helps maintainers
  1381. see exactly which source was used to build a module (since
  1382. others sometimes change the module source without updating
  1383. the version). With this option, such a "srcversion" field
  1384. will be created for all modules. If unsure, say N.
  1385. config MODULE_SIG
  1386. bool "Module signature verification"
  1387. depends on MODULES
  1388. select KEYS
  1389. select CRYPTO
  1390. select ASYMMETRIC_KEY_TYPE
  1391. select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  1392. select PUBLIC_KEY_ALGO_RSA
  1393. select ASN1
  1394. select OID_REGISTRY
  1395. select X509_CERTIFICATE_PARSER
  1396. help
  1397. Check modules for valid signatures upon load: the signature
  1398. is simply appended to the module. For more information see
  1399. Documentation/module-signing.txt.
  1400. !!!WARNING!!! If you enable this option, you MUST make sure that the
  1401. module DOES NOT get stripped after being signed. This includes the
  1402. debuginfo strip done by some packagers (such as rpmbuild) and
  1403. inclusion into an initramfs that wants the module size reduced.
  1404. config MODULE_SIG_FORCE
  1405. bool "Require modules to be validly signed"
  1406. depends on MODULE_SIG
  1407. help
  1408. Reject unsigned modules or signed modules for which we don't have a
  1409. key. Without this, such modules will simply taint the kernel.
  1410. choice
  1411. prompt "Which hash algorithm should modules be signed with?"
  1412. depends on MODULE_SIG
  1413. help
  1414. This determines which sort of hashing algorithm will be used during
  1415. signature generation. This algorithm _must_ be built into the kernel
  1416. directly so that signature verification can take place. It is not
  1417. possible to load a signed module containing the algorithm to check
  1418. the signature on that module.
  1419. config MODULE_SIG_SHA1
  1420. bool "Sign modules with SHA-1"
  1421. select CRYPTO_SHA1
  1422. config MODULE_SIG_SHA224
  1423. bool "Sign modules with SHA-224"
  1424. select CRYPTO_SHA256
  1425. config MODULE_SIG_SHA256
  1426. bool "Sign modules with SHA-256"
  1427. select CRYPTO_SHA256
  1428. config MODULE_SIG_SHA384
  1429. bool "Sign modules with SHA-384"
  1430. select CRYPTO_SHA512
  1431. config MODULE_SIG_SHA512
  1432. bool "Sign modules with SHA-512"
  1433. select CRYPTO_SHA512
  1434. endchoice
  1435. endif # MODULES
  1436. config INIT_ALL_POSSIBLE
  1437. bool
  1438. help
  1439. Back when each arch used to define their own cpu_online_mask and
  1440. cpu_possible_mask, some of them chose to initialize cpu_possible_mask
  1441. with all 1s, and others with all 0s. When they were centralised,
  1442. it was better to provide this option than to break all the archs
  1443. and have several arch maintainers pursuing me down dark alleys.
  1444. config STOP_MACHINE
  1445. bool
  1446. default y
  1447. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1448. help
  1449. Need stop_machine() primitive.
  1450. source "block/Kconfig"
  1451. config PREEMPT_NOTIFIERS
  1452. bool
  1453. config PADATA
  1454. depends on SMP
  1455. bool
  1456. # Can be selected by architectures with broken toolchains
  1457. # that get confused by correct const<->read_only section
  1458. # mappings
  1459. config BROKEN_RODATA
  1460. bool
  1461. config ASN1
  1462. tristate
  1463. help
  1464. Build a simple ASN.1 grammar compiler that produces a bytecode output
  1465. that can be interpreted by the ASN.1 stream decoder and used to
  1466. inform it as to what tags are to be expected in a stream and what
  1467. functions to call on what tags.
  1468. source "kernel/Kconfig.locks"