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 drivers that have been replaced by something else, and/or are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. config VIRT_CPU_ACCOUNTING
  275. bool
  276. choice
  277. prompt "Cputime accounting"
  278. default TICK_CPU_ACCOUNTING if !PPC64
  279. default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
  280. # Kind of a stub config for the pure tick based cputime accounting
  281. config TICK_CPU_ACCOUNTING
  282. bool "Simple tick based cputime accounting"
  283. depends on !S390
  284. help
  285. This is the basic tick based cputime accounting that maintains
  286. statistics about user, system and idle time spent on per jiffies
  287. granularity.
  288. If unsure, say Y.
  289. config VIRT_CPU_ACCOUNTING_NATIVE
  290. bool "Deterministic task and CPU time accounting"
  291. depends on HAVE_VIRT_CPU_ACCOUNTING
  292. select VIRT_CPU_ACCOUNTING
  293. help
  294. Select this option to enable more accurate task and CPU time
  295. accounting. This is done by reading a CPU counter on each
  296. kernel entry and exit and on transitions within the kernel
  297. between system, softirq and hardirq state, so there is a
  298. small performance impact. In the case of s390 or IBM POWER > 5,
  299. this also enables accounting of stolen time on logically-partitioned
  300. systems.
  301. config VIRT_CPU_ACCOUNTING_GEN
  302. bool "Full dynticks CPU time accounting"
  303. depends on HAVE_CONTEXT_TRACKING && 64BIT
  304. select VIRT_CPU_ACCOUNTING
  305. select CONTEXT_TRACKING
  306. help
  307. Select this option to enable task and CPU time accounting on full
  308. dynticks systems. This accounting is implemented by watching every
  309. kernel-user boundaries using the context tracking subsystem.
  310. The accounting is thus performed at the expense of some significant
  311. overhead.
  312. For now this is only useful if you are working on the full
  313. dynticks subsystem development.
  314. If unsure, say N.
  315. config IRQ_TIME_ACCOUNTING
  316. bool "Fine granularity task level IRQ time accounting"
  317. depends on HAVE_IRQ_TIME_ACCOUNTING
  318. help
  319. Select this option to enable fine granularity task irq time
  320. accounting. This is done by reading a timestamp on each
  321. transitions between softirq and hardirq state, so there can be a
  322. small performance impact.
  323. If in doubt, say N here.
  324. endchoice
  325. config BSD_PROCESS_ACCT
  326. bool "BSD Process Accounting"
  327. help
  328. If you say Y here, a user level program will be able to instruct the
  329. kernel (via a special system call) to write process accounting
  330. information to a file: whenever a process exits, information about
  331. that process will be appended to the file by the kernel. The
  332. information includes things such as creation time, owning user,
  333. command name, memory usage, controlling terminal etc. (the complete
  334. list is in the struct acct in <file:include/linux/acct.h>). It is
  335. up to the user level program to do useful things with this
  336. information. This is generally a good idea, so say Y.
  337. config BSD_PROCESS_ACCT_V3
  338. bool "BSD Process Accounting version 3 file format"
  339. depends on BSD_PROCESS_ACCT
  340. default n
  341. help
  342. If you say Y here, the process accounting information is written
  343. in a new file format that also logs the process IDs of each
  344. process and it's parent. Note that this file format is incompatible
  345. with previous v0/v1/v2 file formats, so you will need updated tools
  346. for processing it. A preliminary version of these tools is available
  347. at <http://www.gnu.org/software/acct/>.
  348. config TASKSTATS
  349. bool "Export task/process statistics through netlink (EXPERIMENTAL)"
  350. depends on NET
  351. default n
  352. help
  353. Export selected statistics for tasks/processes through the
  354. generic netlink interface. Unlike BSD process accounting, the
  355. statistics are available during the lifetime of tasks/processes as
  356. responses to commands. Like BSD accounting, they are sent to user
  357. space on task exit.
  358. Say N if unsure.
  359. config TASK_DELAY_ACCT
  360. bool "Enable per-task delay accounting (EXPERIMENTAL)"
  361. depends on TASKSTATS
  362. help
  363. Collect information on time spent by a task waiting for system
  364. resources like cpu, synchronous block I/O completion and swapping
  365. in pages. Such statistics can help in setting a task's priorities
  366. relative to other tasks for cpu, io, rss limits etc.
  367. Say N if unsure.
  368. config TASK_XACCT
  369. bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
  370. depends on TASKSTATS
  371. help
  372. Collect extended task accounting data and send the data
  373. to userland for processing over the taskstats interface.
  374. Say N if unsure.
  375. config TASK_IO_ACCOUNTING
  376. bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
  377. depends on TASK_XACCT
  378. help
  379. Collect information on the number of bytes of storage I/O which this
  380. task has caused.
  381. Say N if unsure.
  382. endmenu # "CPU/Task time and stats accounting"
  383. menu "RCU Subsystem"
  384. choice
  385. prompt "RCU Implementation"
  386. default TREE_RCU
  387. config TREE_RCU
  388. bool "Tree-based hierarchical RCU"
  389. depends on !PREEMPT && SMP
  390. help
  391. This option selects the RCU implementation that is
  392. designed for very large SMP system with hundreds or
  393. thousands of CPUs. It also scales down nicely to
  394. smaller systems.
  395. config TREE_PREEMPT_RCU
  396. bool "Preemptible tree-based hierarchical RCU"
  397. depends on PREEMPT && SMP
  398. help
  399. This option selects the RCU implementation that is
  400. designed for very large SMP systems with hundreds or
  401. thousands of CPUs, but for which real-time response
  402. is also required. It also scales down nicely to
  403. smaller systems.
  404. config TINY_RCU
  405. bool "UP-only small-memory-footprint RCU"
  406. depends on !PREEMPT && !SMP
  407. help
  408. This option selects the RCU implementation that is
  409. designed for UP systems from which real-time response
  410. is not required. This option greatly reduces the
  411. memory footprint of RCU.
  412. config TINY_PREEMPT_RCU
  413. bool "Preemptible UP-only small-memory-footprint RCU"
  414. depends on PREEMPT && !SMP
  415. help
  416. This option selects the RCU implementation that is designed
  417. for real-time UP systems. This option greatly reduces the
  418. memory footprint of RCU.
  419. endchoice
  420. config PREEMPT_RCU
  421. def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
  422. help
  423. This option enables preemptible-RCU code that is common between
  424. the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
  425. config CONTEXT_TRACKING
  426. bool
  427. config RCU_USER_QS
  428. bool "Consider userspace as in RCU extended quiescent state"
  429. depends on HAVE_CONTEXT_TRACKING && SMP
  430. select CONTEXT_TRACKING
  431. help
  432. This option sets hooks on kernel / userspace boundaries and
  433. puts RCU in extended quiescent state when the CPU runs in
  434. userspace. It means that when a CPU runs in userspace, it is
  435. excluded from the global RCU state machine and thus doesn't
  436. try to keep the timer tick on for RCU.
  437. Unless you want to hack and help the development of the full
  438. dynticks mode, you shouldn't enable this option. It also
  439. adds unnecessary overhead.
  440. If unsure say N
  441. config CONTEXT_TRACKING_FORCE
  442. bool "Force context tracking"
  443. depends on CONTEXT_TRACKING
  444. help
  445. Probe on user/kernel boundaries by default in order to
  446. test the features that rely on it such as userspace RCU extended
  447. quiescent states.
  448. This test is there for debugging until we have a real user like the
  449. full dynticks mode.
  450. config RCU_FANOUT
  451. int "Tree-based hierarchical RCU fanout value"
  452. range 2 64 if 64BIT
  453. range 2 32 if !64BIT
  454. depends on TREE_RCU || TREE_PREEMPT_RCU
  455. default 64 if 64BIT
  456. default 32 if !64BIT
  457. help
  458. This option controls the fanout of hierarchical implementations
  459. of RCU, allowing RCU to work efficiently on machines with
  460. large numbers of CPUs. This value must be at least the fourth
  461. root of NR_CPUS, which allows NR_CPUS to be insanely large.
  462. The default value of RCU_FANOUT should be used for production
  463. systems, but if you are stress-testing the RCU implementation
  464. itself, small RCU_FANOUT values allow you to test large-system
  465. code paths on small(er) systems.
  466. Select a specific number if testing RCU itself.
  467. Take the default if unsure.
  468. config RCU_FANOUT_LEAF
  469. int "Tree-based hierarchical RCU leaf-level fanout value"
  470. range 2 RCU_FANOUT if 64BIT
  471. range 2 RCU_FANOUT if !64BIT
  472. depends on TREE_RCU || TREE_PREEMPT_RCU
  473. default 16
  474. help
  475. This option controls the leaf-level fanout of hierarchical
  476. implementations of RCU, and allows trading off cache misses
  477. against lock contention. Systems that synchronize their
  478. scheduling-clock interrupts for energy-efficiency reasons will
  479. want the default because the smaller leaf-level fanout keeps
  480. lock contention levels acceptably low. Very large systems
  481. (hundreds or thousands of CPUs) will instead want to set this
  482. value to the maximum value possible in order to reduce the
  483. number of cache misses incurred during RCU's grace-period
  484. initialization. These systems tend to run CPU-bound, and thus
  485. are not helped by synchronized interrupts, and thus tend to
  486. skew them, which reduces lock contention enough that large
  487. leaf-level fanouts work well.
  488. Select a specific number if testing RCU itself.
  489. Select the maximum permissible value for large systems.
  490. Take the default if unsure.
  491. config RCU_FANOUT_EXACT
  492. bool "Disable tree-based hierarchical RCU auto-balancing"
  493. depends on TREE_RCU || TREE_PREEMPT_RCU
  494. default n
  495. help
  496. This option forces use of the exact RCU_FANOUT value specified,
  497. regardless of imbalances in the hierarchy. This is useful for
  498. testing RCU itself, and might one day be useful on systems with
  499. strong NUMA behavior.
  500. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  501. Say N if unsure.
  502. config RCU_FAST_NO_HZ
  503. bool "Accelerate last non-dyntick-idle CPU's grace periods"
  504. depends on NO_HZ && SMP
  505. default n
  506. help
  507. This option causes RCU to attempt to accelerate grace periods in
  508. order to allow CPUs to enter dynticks-idle state more quickly.
  509. On the other hand, this option increases the overhead of the
  510. dynticks-idle checking, thus degrading scheduling latency.
  511. Say Y if energy efficiency is critically important, and you don't
  512. care about real-time response.
  513. Say N if you are unsure.
  514. config TREE_RCU_TRACE
  515. def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
  516. select DEBUG_FS
  517. help
  518. This option provides tracing for the TREE_RCU and
  519. TREE_PREEMPT_RCU implementations, permitting Makefile to
  520. trivially select kernel/rcutree_trace.c.
  521. config RCU_BOOST
  522. bool "Enable RCU priority boosting"
  523. depends on RT_MUTEXES && PREEMPT_RCU
  524. default n
  525. help
  526. This option boosts the priority of preempted RCU readers that
  527. block the current preemptible RCU grace period for too long.
  528. This option also prevents heavy loads from blocking RCU
  529. callback invocation for all flavors of RCU.
  530. Say Y here if you are working with real-time apps or heavy loads
  531. Say N here if you are unsure.
  532. config RCU_BOOST_PRIO
  533. int "Real-time priority to boost RCU readers to"
  534. range 1 99
  535. depends on RCU_BOOST
  536. default 1
  537. help
  538. This option specifies the real-time priority to which long-term
  539. preempted RCU readers are to be boosted. If you are working
  540. with a real-time application that has one or more CPU-bound
  541. threads running at a real-time priority level, you should set
  542. RCU_BOOST_PRIO to a priority higher then the highest-priority
  543. real-time CPU-bound thread. The default RCU_BOOST_PRIO value
  544. of 1 is appropriate in the common case, which is real-time
  545. applications that do not have any CPU-bound threads.
  546. Some real-time applications might not have a single real-time
  547. thread that saturates a given CPU, but instead might have
  548. multiple real-time threads that, taken together, fully utilize
  549. that CPU. In this case, you should set RCU_BOOST_PRIO to
  550. a priority higher than the lowest-priority thread that is
  551. conspiring to prevent the CPU from running any non-real-time
  552. tasks. For example, if one thread at priority 10 and another
  553. thread at priority 5 are between themselves fully consuming
  554. the CPU time on a given CPU, then RCU_BOOST_PRIO should be
  555. set to priority 6 or higher.
  556. Specify the real-time priority, or take the default if unsure.
  557. config RCU_BOOST_DELAY
  558. int "Milliseconds to delay boosting after RCU grace-period start"
  559. range 0 3000
  560. depends on RCU_BOOST
  561. default 500
  562. help
  563. This option specifies the time to wait after the beginning of
  564. a given grace period before priority-boosting preempted RCU
  565. readers blocking that grace period. Note that any RCU reader
  566. blocking an expedited RCU grace period is boosted immediately.
  567. Accept the default if unsure.
  568. config RCU_NOCB_CPU
  569. bool "Offload RCU callback processing from boot-selected CPUs"
  570. depends on TREE_RCU || TREE_PREEMPT_RCU
  571. default n
  572. help
  573. Use this option to reduce OS jitter for aggressive HPC or
  574. real-time workloads. It can also be used to offload RCU
  575. callback invocation to energy-efficient CPUs in battery-powered
  576. asymmetric multiprocessors.
  577. This option offloads callback invocation from the set of
  578. CPUs specified at boot time by the rcu_nocbs parameter.
  579. For each such CPU, a kthread ("rcuoN") will be created to
  580. invoke callbacks, where the "N" is the CPU being offloaded.
  581. Nothing prevents this kthread from running on the specified
  582. CPUs, but (1) the kthreads may be preempted between each
  583. callback, and (2) affinity or cgroups can be used to force
  584. the kthreads to run on whatever set of CPUs is desired.
  585. Say Y here if you want reduced OS jitter on selected CPUs.
  586. Say N here if you are unsure.
  587. endmenu # "RCU Subsystem"
  588. config IKCONFIG
  589. tristate "Kernel .config support"
  590. ---help---
  591. This option enables the complete Linux kernel ".config" file
  592. contents to be saved in the kernel. It provides documentation
  593. of which kernel options are used in a running kernel or in an
  594. on-disk kernel. This information can be extracted from the kernel
  595. image file with the script scripts/extract-ikconfig and used as
  596. input to rebuild the current kernel or to build another kernel.
  597. It can also be extracted from a running kernel by reading
  598. /proc/config.gz if enabled (below).
  599. config IKCONFIG_PROC
  600. bool "Enable access to .config through /proc/config.gz"
  601. depends on IKCONFIG && PROC_FS
  602. ---help---
  603. This option enables access to the kernel configuration file
  604. through /proc/config.gz.
  605. config LOG_BUF_SHIFT
  606. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  607. range 12 21
  608. default 17
  609. help
  610. Select kernel log buffer size as a power of 2.
  611. Examples:
  612. 17 => 128 KB
  613. 16 => 64 KB
  614. 15 => 32 KB
  615. 14 => 16 KB
  616. 13 => 8 KB
  617. 12 => 4 KB
  618. #
  619. # Architectures with an unreliable sched_clock() should select this:
  620. #
  621. config HAVE_UNSTABLE_SCHED_CLOCK
  622. bool
  623. #
  624. # For architectures that want to enable the support for NUMA-affine scheduler
  625. # balancing logic:
  626. #
  627. config ARCH_SUPPORTS_NUMA_BALANCING
  628. bool
  629. # For architectures that (ab)use NUMA to represent different memory regions
  630. # all cpu-local but of different latencies, such as SuperH.
  631. #
  632. config ARCH_WANT_NUMA_VARIABLE_LOCALITY
  633. bool
  634. #
  635. # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
  636. config ARCH_WANTS_PROT_NUMA_PROT_NONE
  637. bool
  638. config ARCH_USES_NUMA_PROT_NONE
  639. bool
  640. default y
  641. depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
  642. depends on NUMA_BALANCING
  643. config NUMA_BALANCING_DEFAULT_ENABLED
  644. bool "Automatically enable NUMA aware memory/task placement"
  645. default y
  646. depends on NUMA_BALANCING
  647. help
  648. If set, autonumic NUMA balancing will be enabled if running on a NUMA
  649. machine.
  650. config NUMA_BALANCING
  651. bool "Memory placement aware NUMA scheduler"
  652. depends on ARCH_SUPPORTS_NUMA_BALANCING
  653. depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
  654. depends on SMP && NUMA && MIGRATION
  655. help
  656. This option adds support for automatic NUMA aware memory/task placement.
  657. The mechanism is quite primitive and is based on migrating memory when
  658. it is references to the node the task is running on.
  659. This system will be inactive on UMA systems.
  660. menuconfig CGROUPS
  661. boolean "Control Group support"
  662. depends on EVENTFD
  663. help
  664. This option adds support for grouping sets of processes together, for
  665. use with process control subsystems such as Cpusets, CFS, memory
  666. controls or device isolation.
  667. See
  668. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  669. - Documentation/cgroups/ (features for grouping, isolation
  670. and resource control)
  671. Say N if unsure.
  672. if CGROUPS
  673. config CGROUP_DEBUG
  674. bool "Example debug cgroup subsystem"
  675. default n
  676. help
  677. This option enables a simple cgroup subsystem that
  678. exports useful debugging information about the cgroups
  679. framework.
  680. Say N if unsure.
  681. config CGROUP_FREEZER
  682. bool "Freezer cgroup subsystem"
  683. help
  684. Provides a way to freeze and unfreeze all tasks in a
  685. cgroup.
  686. config CGROUP_DEVICE
  687. bool "Device controller for cgroups"
  688. help
  689. Provides a cgroup implementing whitelists for devices which
  690. a process in the cgroup can mknod or open.
  691. config CPUSETS
  692. bool "Cpuset support"
  693. help
  694. This option will let you create and manage CPUSETs which
  695. allow dynamically partitioning a system into sets of CPUs and
  696. Memory Nodes and assigning tasks to run only within those sets.
  697. This is primarily useful on large SMP or NUMA systems.
  698. Say N if unsure.
  699. config PROC_PID_CPUSET
  700. bool "Include legacy /proc/<pid>/cpuset file"
  701. depends on CPUSETS
  702. default y
  703. config CGROUP_CPUACCT
  704. bool "Simple CPU accounting cgroup subsystem"
  705. help
  706. Provides a simple Resource Controller for monitoring the
  707. total CPU consumed by the tasks in a cgroup.
  708. config RESOURCE_COUNTERS
  709. bool "Resource counters"
  710. help
  711. This option enables controller independent resource accounting
  712. infrastructure that works with cgroups.
  713. config MEMCG
  714. bool "Memory Resource Controller for Control Groups"
  715. depends on RESOURCE_COUNTERS
  716. select MM_OWNER
  717. help
  718. Provides a memory resource controller that manages both anonymous
  719. memory and page cache. (See Documentation/cgroups/memory.txt)
  720. Note that setting this option increases fixed memory overhead
  721. associated with each page of memory in the system. By this,
  722. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  723. usage tracking struct at boot. Total amount of this is printed out
  724. at boot.
  725. Only enable when you're ok with these trade offs and really
  726. sure you need the memory resource controller. Even when you enable
  727. this, you can set "cgroup_disable=memory" at your boot option to
  728. disable memory resource controller and you can avoid overheads.
  729. (and lose benefits of memory resource controller)
  730. This config option also selects MM_OWNER config option, which
  731. could in turn add some fork/exit overhead.
  732. config MEMCG_SWAP
  733. bool "Memory Resource Controller Swap Extension"
  734. depends on MEMCG && SWAP
  735. help
  736. Add swap management feature to memory resource controller. When you
  737. enable this, you can limit mem+swap usage per cgroup. In other words,
  738. when you disable this, memory resource controller has no cares to
  739. usage of swap...a process can exhaust all of the swap. This extension
  740. is useful when you want to avoid exhaustion swap but this itself
  741. adds more overheads and consumes memory for remembering information.
  742. Especially if you use 32bit system or small memory system, please
  743. be careful about enabling this. When memory resource controller
  744. is disabled by boot option, this will be automatically disabled and
  745. there will be no overhead from this. Even when you set this config=y,
  746. if boot option "swapaccount=0" is set, swap will not be accounted.
  747. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  748. size is 4096bytes, 512k per 1Gbytes of swap.
  749. config MEMCG_SWAP_ENABLED
  750. bool "Memory Resource Controller Swap Extension enabled by default"
  751. depends on MEMCG_SWAP
  752. default y
  753. help
  754. Memory Resource Controller Swap Extension comes with its price in
  755. a bigger memory consumption. General purpose distribution kernels
  756. which want to enable the feature but keep it disabled by default
  757. and let the user enable it by swapaccount boot command line
  758. parameter should have this option unselected.
  759. For those who want to have the feature enabled by default should
  760. select this option (if, for some reason, they need to disable it
  761. then swapaccount=0 does the trick).
  762. config MEMCG_KMEM
  763. bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
  764. depends on MEMCG && EXPERIMENTAL
  765. depends on SLUB || SLAB
  766. help
  767. The Kernel Memory extension for Memory Resource Controller can limit
  768. the amount of memory used by kernel objects in the system. Those are
  769. fundamentally different from the entities handled by the standard
  770. Memory Controller, which are page-based, and can be swapped. Users of
  771. the kmem extension can use it to guarantee that no group of processes
  772. will ever exhaust kernel resources alone.
  773. config CGROUP_HUGETLB
  774. bool "HugeTLB Resource Controller for Control Groups"
  775. depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
  776. default n
  777. help
  778. Provides a cgroup Resource Controller for HugeTLB pages.
  779. When you enable this, you can put a per cgroup limit on HugeTLB usage.
  780. The limit is enforced during page fault. Since HugeTLB doesn't
  781. support page reclaim, enforcing the limit at page fault time implies
  782. that, the application will get SIGBUS signal if it tries to access
  783. HugeTLB pages beyond its limit. This requires the application to know
  784. beforehand how much HugeTLB pages it would require for its use. The
  785. control group is tracked in the third page lru pointer. This means
  786. that we cannot use the controller with huge page less than 3 pages.
  787. config CGROUP_PERF
  788. bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
  789. depends on PERF_EVENTS && CGROUPS
  790. help
  791. This option extends the per-cpu mode to restrict monitoring to
  792. threads which belong to the cgroup specified and run on the
  793. designated cpu.
  794. Say N if unsure.
  795. menuconfig CGROUP_SCHED
  796. bool "Group CPU scheduler"
  797. default n
  798. help
  799. This feature lets CPU scheduler recognize task groups and control CPU
  800. bandwidth allocation to such task groups. It uses cgroups to group
  801. tasks.
  802. if CGROUP_SCHED
  803. config FAIR_GROUP_SCHED
  804. bool "Group scheduling for SCHED_OTHER"
  805. depends on CGROUP_SCHED
  806. default CGROUP_SCHED
  807. config CFS_BANDWIDTH
  808. bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
  809. depends on EXPERIMENTAL
  810. depends on FAIR_GROUP_SCHED
  811. default n
  812. help
  813. This option allows users to define CPU bandwidth rates (limits) for
  814. tasks running within the fair group scheduler. Groups with no limit
  815. set are considered to be unconstrained and will run with no
  816. restriction.
  817. See tip/Documentation/scheduler/sched-bwc.txt for more information.
  818. config RT_GROUP_SCHED
  819. bool "Group scheduling for SCHED_RR/FIFO"
  820. depends on EXPERIMENTAL
  821. depends on CGROUP_SCHED
  822. default n
  823. help
  824. This feature lets you explicitly allocate real CPU bandwidth
  825. to task groups. If enabled, it will also make it impossible to
  826. schedule realtime tasks for non-root users until you allocate
  827. realtime bandwidth for them.
  828. See Documentation/scheduler/sched-rt-group.txt for more information.
  829. endif #CGROUP_SCHED
  830. config BLK_CGROUP
  831. bool "Block IO controller"
  832. depends on BLOCK
  833. default n
  834. ---help---
  835. Generic block IO controller cgroup interface. This is the common
  836. cgroup interface which should be used by various IO controlling
  837. policies.
  838. Currently, CFQ IO scheduler uses it to recognize task groups and
  839. control disk bandwidth allocation (proportional time slice allocation)
  840. to such task groups. It is also used by bio throttling logic in
  841. block layer to implement upper limit in IO rates on a device.
  842. This option only enables generic Block IO controller infrastructure.
  843. One needs to also enable actual IO controlling logic/policy. For
  844. enabling proportional weight division of disk bandwidth in CFQ, set
  845. CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
  846. CONFIG_BLK_DEV_THROTTLING=y.
  847. See Documentation/cgroups/blkio-controller.txt for more information.
  848. config DEBUG_BLK_CGROUP
  849. bool "Enable Block IO controller debugging"
  850. depends on BLK_CGROUP
  851. default n
  852. ---help---
  853. Enable some debugging help. Currently it exports additional stat
  854. files in a cgroup which can be useful for debugging.
  855. endif # CGROUPS
  856. config CHECKPOINT_RESTORE
  857. bool "Checkpoint/restore support" if EXPERT
  858. default n
  859. help
  860. Enables additional kernel features in a sake of checkpoint/restore.
  861. In particular it adds auxiliary prctl codes to setup process text,
  862. data and heap segment sizes, and a few additional /proc filesystem
  863. entries.
  864. If unsure, say N here.
  865. menuconfig NAMESPACES
  866. bool "Namespaces support" if EXPERT
  867. default !EXPERT
  868. help
  869. Provides the way to make tasks work with different objects using
  870. the same id. For example same IPC id may refer to different objects
  871. or same user id or pid may refer to different tasks when used in
  872. different namespaces.
  873. if NAMESPACES
  874. config UTS_NS
  875. bool "UTS namespace"
  876. default y
  877. help
  878. In this namespace tasks see different info provided with the
  879. uname() system call
  880. config IPC_NS
  881. bool "IPC namespace"
  882. depends on (SYSVIPC || POSIX_MQUEUE)
  883. default y
  884. help
  885. In this namespace tasks work with IPC ids which correspond to
  886. different IPC objects in different namespaces.
  887. config USER_NS
  888. bool "User namespace (EXPERIMENTAL)"
  889. depends on EXPERIMENTAL
  890. depends on UIDGID_CONVERTED
  891. select UIDGID_STRICT_TYPE_CHECKS
  892. default n
  893. help
  894. This allows containers, i.e. vservers, to use user namespaces
  895. to provide different user info for different servers.
  896. If unsure, say N.
  897. config PID_NS
  898. bool "PID Namespaces"
  899. default y
  900. help
  901. Support process id namespaces. This allows having multiple
  902. processes with the same pid as long as they are in different
  903. pid namespaces. This is a building block of containers.
  904. config NET_NS
  905. bool "Network namespace"
  906. depends on NET
  907. default y
  908. help
  909. Allow user space to create what appear to be multiple instances
  910. of the network stack.
  911. endif # NAMESPACES
  912. config UIDGID_CONVERTED
  913. # True if all of the selected software conmponents are known
  914. # to have uid_t and gid_t converted to kuid_t and kgid_t
  915. # where appropriate and are otherwise safe to use with
  916. # the user namespace.
  917. bool
  918. default y
  919. # Networking
  920. depends on NET_9P = n
  921. # Filesystems
  922. depends on 9P_FS = n
  923. depends on AFS_FS = n
  924. depends on CEPH_FS = n
  925. depends on CIFS = n
  926. depends on CODA_FS = n
  927. depends on GFS2_FS = n
  928. depends on NCP_FS = n
  929. depends on NFSD = n
  930. depends on NFS_FS = n
  931. depends on OCFS2_FS = n
  932. depends on XFS_FS = n
  933. config UIDGID_STRICT_TYPE_CHECKS
  934. bool "Require conversions between uid/gids and their internal representation"
  935. depends on UIDGID_CONVERTED
  936. default n
  937. help
  938. While the nececessary conversions are being added to all subsystems this option allows
  939. the code to continue to build for unconverted subsystems.
  940. Say Y here if you want the strict type checking enabled
  941. config SCHED_AUTOGROUP
  942. bool "Automatic process group scheduling"
  943. select EVENTFD
  944. select CGROUPS
  945. select CGROUP_SCHED
  946. select FAIR_GROUP_SCHED
  947. help
  948. This option optimizes the scheduler for common desktop workloads by
  949. automatically creating and populating task groups. This separation
  950. of workloads isolates aggressive CPU burners (like build jobs) from
  951. desktop applications. Task group autogeneration is currently based
  952. upon task session.
  953. config MM_OWNER
  954. bool
  955. config SYSFS_DEPRECATED
  956. bool "Enable deprecated sysfs features to support old userspace tools"
  957. depends on SYSFS
  958. default n
  959. help
  960. This option adds code that switches the layout of the "block" class
  961. devices, to not show up in /sys/class/block/, but only in
  962. /sys/block/.
  963. This switch is only active when the sysfs.deprecated=1 boot option is
  964. passed or the SYSFS_DEPRECATED_V2 option is set.
  965. This option allows new kernels to run on old distributions and tools,
  966. which might get confused by /sys/class/block/. Since 2007/2008 all
  967. major distributions and tools handle this just fine.
  968. Recent distributions and userspace tools after 2009/2010 depend on
  969. the existence of /sys/class/block/, and will not work with this
  970. option enabled.
  971. Only if you are using a new kernel on an old distribution, you might
  972. need to say Y here.
  973. config SYSFS_DEPRECATED_V2
  974. bool "Enable deprecated sysfs features by default"
  975. default n
  976. depends on SYSFS
  977. depends on SYSFS_DEPRECATED
  978. help
  979. Enable deprecated sysfs by default.
  980. See the CONFIG_SYSFS_DEPRECATED option for more details about this
  981. option.
  982. Only if you are using a new kernel on an old distribution, you might
  983. need to say Y here. Even then, odds are you would not need it
  984. enabled, you can always pass the boot option if absolutely necessary.
  985. config RELAY
  986. bool "Kernel->user space relay support (formerly relayfs)"
  987. help
  988. This option enables support for relay interface support in
  989. certain file systems (such as debugfs).
  990. It is designed to provide an efficient mechanism for tools and
  991. facilities to relay large amounts of data from kernel space to
  992. user space.
  993. If unsure, say N.
  994. config BLK_DEV_INITRD
  995. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  996. depends on BROKEN || !FRV
  997. help
  998. The initial RAM filesystem is a ramfs which is loaded by the
  999. boot loader (loadlin or lilo) and that is mounted as root
  1000. before the normal boot procedure. It is typically used to
  1001. load modules needed to mount the "real" root file system,
  1002. etc. See <file:Documentation/initrd.txt> for details.
  1003. If RAM disk support (BLK_DEV_RAM) is also included, this
  1004. also enables initial RAM disk (initrd) support and adds
  1005. 15 Kbytes (more on some other architectures) to the kernel size.
  1006. If unsure say Y.
  1007. if BLK_DEV_INITRD
  1008. source "usr/Kconfig"
  1009. endif
  1010. config CC_OPTIMIZE_FOR_SIZE
  1011. bool "Optimize for size"
  1012. help
  1013. Enabling this option will pass "-Os" instead of "-O2" to gcc
  1014. resulting in a smaller kernel.
  1015. If unsure, say N.
  1016. config SYSCTL
  1017. bool
  1018. config ANON_INODES
  1019. bool
  1020. menuconfig EXPERT
  1021. bool "Configure standard kernel features (expert users)"
  1022. # Unhide debug options, to make the on-by-default options visible
  1023. select DEBUG_KERNEL
  1024. help
  1025. This option allows certain base kernel options and settings
  1026. to be disabled or tweaked. This is for specialized
  1027. environments which can tolerate a "non-standard" kernel.
  1028. Only use this if you really know what you are doing.
  1029. config HAVE_UID16
  1030. bool
  1031. config UID16
  1032. bool "Enable 16-bit UID system calls" if EXPERT
  1033. depends on HAVE_UID16
  1034. default y
  1035. help
  1036. This enables the legacy 16-bit UID syscall wrappers.
  1037. config SYSCTL_SYSCALL
  1038. bool "Sysctl syscall support" if EXPERT
  1039. depends on PROC_SYSCTL
  1040. default n
  1041. select SYSCTL
  1042. ---help---
  1043. sys_sysctl uses binary paths that have been found challenging
  1044. to properly maintain and use. The interface in /proc/sys
  1045. using paths with ascii names is now the primary path to this
  1046. information.
  1047. Almost nothing using the binary sysctl interface so if you are
  1048. trying to save some space it is probably safe to disable this,
  1049. making your kernel marginally smaller.
  1050. If unsure say N here.
  1051. config SYSCTL_EXCEPTION_TRACE
  1052. bool
  1053. help
  1054. Enable support for /proc/sys/debug/exception-trace.
  1055. config KALLSYMS
  1056. bool "Load all symbols for debugging/ksymoops" if EXPERT
  1057. default y
  1058. help
  1059. Say Y here to let the kernel print out symbolic crash information and
  1060. symbolic stack backtraces. This increases the size of the kernel
  1061. somewhat, as all symbols have to be loaded into the kernel image.
  1062. config KALLSYMS_ALL
  1063. bool "Include all symbols in kallsyms"
  1064. depends on DEBUG_KERNEL && KALLSYMS
  1065. help
  1066. Normally kallsyms only contains the symbols of functions for nicer
  1067. OOPS messages and backtraces (i.e., symbols from the text and inittext
  1068. sections). This is sufficient for most cases. And only in very rare
  1069. cases (e.g., when a debugger is used) all symbols are required (e.g.,
  1070. names of variables from the data sections, etc).
  1071. This option makes sure that all symbols are loaded into the kernel
  1072. image (i.e., symbols from all sections) in cost of increased kernel
  1073. size (depending on the kernel configuration, it may be 300KiB or
  1074. something like this).
  1075. Say N unless you really need all symbols.
  1076. config HOTPLUG
  1077. def_bool y
  1078. config PRINTK
  1079. default y
  1080. bool "Enable support for printk" if EXPERT
  1081. help
  1082. This option enables normal printk support. Removing it
  1083. eliminates most of the message strings from the kernel image
  1084. and makes the kernel more or less silent. As this makes it
  1085. very difficult to diagnose system problems, saying N here is
  1086. strongly discouraged.
  1087. config BUG
  1088. bool "BUG() support" if EXPERT
  1089. default y
  1090. help
  1091. Disabling this option eliminates support for BUG and WARN, reducing
  1092. the size of your kernel image and potentially quietly ignoring
  1093. numerous fatal conditions. You should only consider disabling this
  1094. option for embedded systems with no facilities for reporting errors.
  1095. Just say Y.
  1096. config ELF_CORE
  1097. depends on COREDUMP
  1098. default y
  1099. bool "Enable ELF core dumps" if EXPERT
  1100. help
  1101. Enable support for generating core dumps. Disabling saves about 4k.
  1102. config PCSPKR_PLATFORM
  1103. bool "Enable PC-Speaker support" if EXPERT
  1104. depends on HAVE_PCSPKR_PLATFORM
  1105. select I8253_LOCK
  1106. default y
  1107. help
  1108. This option allows to disable the internal PC-Speaker
  1109. support, saving some memory.
  1110. config HAVE_PCSPKR_PLATFORM
  1111. bool
  1112. config BASE_FULL
  1113. default y
  1114. bool "Enable full-sized data structures for core" if EXPERT
  1115. help
  1116. Disabling this option reduces the size of miscellaneous core
  1117. kernel data structures. This saves memory on small machines,
  1118. but may reduce performance.
  1119. config FUTEX
  1120. bool "Enable futex support" if EXPERT
  1121. default y
  1122. select RT_MUTEXES
  1123. help
  1124. Disabling this option will cause the kernel to be built without
  1125. support for "fast userspace mutexes". The resulting kernel may not
  1126. run glibc-based applications correctly.
  1127. config EPOLL
  1128. bool "Enable eventpoll support" if EXPERT
  1129. default y
  1130. select ANON_INODES
  1131. help
  1132. Disabling this option will cause the kernel to be built without
  1133. support for epoll family of system calls.
  1134. config SIGNALFD
  1135. bool "Enable signalfd() system call" if EXPERT
  1136. select ANON_INODES
  1137. default y
  1138. help
  1139. Enable the signalfd() system call that allows to receive signals
  1140. on a file descriptor.
  1141. If unsure, say Y.
  1142. config TIMERFD
  1143. bool "Enable timerfd() system call" if EXPERT
  1144. select ANON_INODES
  1145. default y
  1146. help
  1147. Enable the timerfd() system call that allows to receive timer
  1148. events on a file descriptor.
  1149. If unsure, say Y.
  1150. config EVENTFD
  1151. bool "Enable eventfd() system call" if EXPERT
  1152. select ANON_INODES
  1153. default y
  1154. help
  1155. Enable the eventfd() system call that allows to receive both
  1156. kernel notification (ie. KAIO) or userspace notifications.
  1157. If unsure, say Y.
  1158. config SHMEM
  1159. bool "Use full shmem filesystem" if EXPERT
  1160. default y
  1161. depends on MMU
  1162. help
  1163. The shmem is an internal filesystem used to manage shared memory.
  1164. It is backed by swap and manages resource limits. It is also exported
  1165. to userspace as tmpfs if TMPFS is enabled. Disabling this
  1166. option replaces shmem and tmpfs with the much simpler ramfs code,
  1167. which may be appropriate on small systems without swap.
  1168. config AIO
  1169. bool "Enable AIO support" if EXPERT
  1170. default y
  1171. help
  1172. This option enables POSIX asynchronous I/O which may by used
  1173. by some high performance threaded applications. Disabling
  1174. this option saves about 7k.
  1175. config EMBEDDED
  1176. bool "Embedded system"
  1177. select EXPERT
  1178. help
  1179. This option should be enabled if compiling the kernel for
  1180. an embedded system so certain expert options are available
  1181. for configuration.
  1182. config HAVE_PERF_EVENTS
  1183. bool
  1184. help
  1185. See tools/perf/design.txt for details.
  1186. config PERF_USE_VMALLOC
  1187. bool
  1188. help
  1189. See tools/perf/design.txt for details
  1190. menu "Kernel Performance Events And Counters"
  1191. config PERF_EVENTS
  1192. bool "Kernel performance events and counters"
  1193. default y if PROFILING
  1194. depends on HAVE_PERF_EVENTS
  1195. select ANON_INODES
  1196. select IRQ_WORK
  1197. help
  1198. Enable kernel support for various performance events provided
  1199. by software and hardware.
  1200. Software events are supported either built-in or via the
  1201. use of generic tracepoints.
  1202. Most modern CPUs support performance events via performance
  1203. counter registers. These registers count the number of certain
  1204. types of hw events: such as instructions executed, cachemisses
  1205. suffered, or branches mis-predicted - without slowing down the
  1206. kernel or applications. These registers can also trigger interrupts
  1207. when a threshold number of events have passed - and can thus be
  1208. used to profile the code that runs on that CPU.
  1209. The Linux Performance Event subsystem provides an abstraction of
  1210. these software and hardware event capabilities, available via a
  1211. system call and used by the "perf" utility in tools/perf/. It
  1212. provides per task and per CPU counters, and it provides event
  1213. capabilities on top of those.
  1214. Say Y if unsure.
  1215. config DEBUG_PERF_USE_VMALLOC
  1216. default n
  1217. bool "Debug: use vmalloc to back perf mmap() buffers"
  1218. depends on PERF_EVENTS && DEBUG_KERNEL
  1219. select PERF_USE_VMALLOC
  1220. help
  1221. Use vmalloc memory to back perf mmap() buffers.
  1222. Mostly useful for debugging the vmalloc code on platforms
  1223. that don't require it.
  1224. Say N if unsure.
  1225. endmenu
  1226. config VM_EVENT_COUNTERS
  1227. default y
  1228. bool "Enable VM event counters for /proc/vmstat" if EXPERT
  1229. help
  1230. VM event counters are needed for event counts to be shown.
  1231. This option allows the disabling of the VM event counters
  1232. on EXPERT systems. /proc/vmstat will only show page counts
  1233. if VM event counters are disabled.
  1234. config PCI_QUIRKS
  1235. default y
  1236. bool "Enable PCI quirk workarounds" if EXPERT
  1237. depends on PCI
  1238. help
  1239. This enables workarounds for various PCI chipset
  1240. bugs/quirks. Disable this only if your target machine is
  1241. unaffected by PCI quirks.
  1242. config SLUB_DEBUG
  1243. default y
  1244. bool "Enable SLUB debugging support" if EXPERT
  1245. depends on SLUB && SYSFS
  1246. help
  1247. SLUB has extensive debug support features. Disabling these can
  1248. result in significant savings in code size. This also disables
  1249. SLUB sysfs support. /sys/slab will not exist and there will be
  1250. no support for cache validation etc.
  1251. config COMPAT_BRK
  1252. bool "Disable heap randomization"
  1253. default y
  1254. help
  1255. Randomizing heap placement makes heap exploits harder, but it
  1256. also breaks ancient binaries (including anything libc5 based).
  1257. This option changes the bootup default to heap randomization
  1258. disabled, and can be overridden at runtime by setting
  1259. /proc/sys/kernel/randomize_va_space to 2.
  1260. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  1261. choice
  1262. prompt "Choose SLAB allocator"
  1263. default SLUB
  1264. help
  1265. This option allows to select a slab allocator.
  1266. config SLAB
  1267. bool "SLAB"
  1268. help
  1269. The regular slab allocator that is established and known to work
  1270. well in all environments. It organizes cache hot objects in
  1271. per cpu and per node queues.
  1272. config SLUB
  1273. bool "SLUB (Unqueued Allocator)"
  1274. help
  1275. SLUB is a slab allocator that minimizes cache line usage
  1276. instead of managing queues of cached objects (SLAB approach).
  1277. Per cpu caching is realized using slabs of objects instead
  1278. of queues of objects. SLUB can use memory efficiently
  1279. and has enhanced diagnostics. SLUB is the default choice for
  1280. a slab allocator.
  1281. config SLOB
  1282. depends on EXPERT
  1283. bool "SLOB (Simple Allocator)"
  1284. help
  1285. SLOB replaces the stock allocator with a drastically simpler
  1286. allocator. SLOB is generally more space efficient but
  1287. does not perform as well on large systems.
  1288. endchoice
  1289. config MMAP_ALLOW_UNINITIALIZED
  1290. bool "Allow mmapped anonymous memory to be uninitialized"
  1291. depends on EXPERT && !MMU
  1292. default n
  1293. help
  1294. Normally, and according to the Linux spec, anonymous memory obtained
  1295. from mmap() has it's contents cleared before it is passed to
  1296. userspace. Enabling this config option allows you to request that
  1297. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  1298. providing a huge performance boost. If this option is not enabled,
  1299. then the flag will be ignored.
  1300. This is taken advantage of by uClibc's malloc(), and also by
  1301. ELF-FDPIC binfmt's brk and stack allocator.
  1302. Because of the obvious security issues, this option should only be
  1303. enabled on embedded devices where you control what is run in
  1304. userspace. Since that isn't generally a problem on no-MMU systems,
  1305. it is normally safe to say Y here.
  1306. See Documentation/nommu-mmap.txt for more information.
  1307. config PROFILING
  1308. bool "Profiling support"
  1309. help
  1310. Say Y here to enable the extended profiling support mechanisms used
  1311. by profilers such as OProfile.
  1312. #
  1313. # Place an empty function call at each tracepoint site. Can be
  1314. # dynamically changed for a probe function.
  1315. #
  1316. config TRACEPOINTS
  1317. bool
  1318. source "arch/Kconfig"
  1319. endmenu # General setup
  1320. config HAVE_GENERIC_DMA_COHERENT
  1321. bool
  1322. default n
  1323. config SLABINFO
  1324. bool
  1325. depends on PROC_FS
  1326. depends on SLAB || SLUB_DEBUG
  1327. default y
  1328. config RT_MUTEXES
  1329. boolean
  1330. config BASE_SMALL
  1331. int
  1332. default 0 if BASE_FULL
  1333. default 1 if !BASE_FULL
  1334. menuconfig MODULES
  1335. bool "Enable loadable module support"
  1336. help
  1337. Kernel modules are small pieces of compiled code which can
  1338. be inserted in the running kernel, rather than being
  1339. permanently built into the kernel. You use the "modprobe"
  1340. tool to add (and sometimes remove) them. If you say Y here,
  1341. many parts of the kernel can be built as modules (by
  1342. answering M instead of Y where indicated): this is most
  1343. useful for infrequently used options which are not required
  1344. for booting. For more information, see the man pages for
  1345. modprobe, lsmod, modinfo, insmod and rmmod.
  1346. If you say Y here, you will need to run "make
  1347. modules_install" to put the modules under /lib/modules/
  1348. where modprobe can find them (you may need to be root to do
  1349. this).
  1350. If unsure, say Y.
  1351. if MODULES
  1352. config MODULE_FORCE_LOAD
  1353. bool "Forced module loading"
  1354. default n
  1355. help
  1356. Allow loading of modules without version information (ie. modprobe
  1357. --force). Forced module loading sets the 'F' (forced) taint flag and
  1358. is usually a really bad idea.
  1359. config MODULE_UNLOAD
  1360. bool "Module unloading"
  1361. help
  1362. Without this option you will not be able to unload any
  1363. modules (note that some modules may not be unloadable
  1364. anyway), which makes your kernel smaller, faster
  1365. and simpler. If unsure, say Y.
  1366. config MODULE_FORCE_UNLOAD
  1367. bool "Forced module unloading"
  1368. depends on MODULE_UNLOAD && EXPERIMENTAL
  1369. help
  1370. This option allows you to force a module to unload, even if the
  1371. kernel believes it is unsafe: the kernel will remove the module
  1372. without waiting for anyone to stop using it (using the -f option to
  1373. rmmod). This is mainly for kernel developers and desperate users.
  1374. If unsure, say N.
  1375. config MODVERSIONS
  1376. bool "Module versioning support"
  1377. help
  1378. Usually, you have to use modules compiled with your kernel.
  1379. Saying Y here makes it sometimes possible to use modules
  1380. compiled for different kernels, by adding enough information
  1381. to the modules to (hopefully) spot any changes which would
  1382. make them incompatible with the kernel you are running. If
  1383. unsure, say N.
  1384. config MODULE_SRCVERSION_ALL
  1385. bool "Source checksum for all modules"
  1386. help
  1387. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1388. field inserted into their modinfo section, which contains a
  1389. sum of the source files which made it. This helps maintainers
  1390. see exactly which source was used to build a module (since
  1391. others sometimes change the module source without updating
  1392. the version). With this option, such a "srcversion" field
  1393. will be created for all modules. If unsure, say N.
  1394. config MODULE_SIG
  1395. bool "Module signature verification"
  1396. depends on MODULES
  1397. select KEYS
  1398. select CRYPTO
  1399. select ASYMMETRIC_KEY_TYPE
  1400. select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  1401. select PUBLIC_KEY_ALGO_RSA
  1402. select ASN1
  1403. select OID_REGISTRY
  1404. select X509_CERTIFICATE_PARSER
  1405. help
  1406. Check modules for valid signatures upon load: the signature
  1407. is simply appended to the module. For more information see
  1408. Documentation/module-signing.txt.
  1409. !!!WARNING!!! If you enable this option, you MUST make sure that the
  1410. module DOES NOT get stripped after being signed. This includes the
  1411. debuginfo strip done by some packagers (such as rpmbuild) and
  1412. inclusion into an initramfs that wants the module size reduced.
  1413. config MODULE_SIG_FORCE
  1414. bool "Require modules to be validly signed"
  1415. depends on MODULE_SIG
  1416. help
  1417. Reject unsigned modules or signed modules for which we don't have a
  1418. key. Without this, such modules will simply taint the kernel.
  1419. choice
  1420. prompt "Which hash algorithm should modules be signed with?"
  1421. depends on MODULE_SIG
  1422. help
  1423. This determines which sort of hashing algorithm will be used during
  1424. signature generation. This algorithm _must_ be built into the kernel
  1425. directly so that signature verification can take place. It is not
  1426. possible to load a signed module containing the algorithm to check
  1427. the signature on that module.
  1428. config MODULE_SIG_SHA1
  1429. bool "Sign modules with SHA-1"
  1430. select CRYPTO_SHA1
  1431. config MODULE_SIG_SHA224
  1432. bool "Sign modules with SHA-224"
  1433. select CRYPTO_SHA256
  1434. config MODULE_SIG_SHA256
  1435. bool "Sign modules with SHA-256"
  1436. select CRYPTO_SHA256
  1437. config MODULE_SIG_SHA384
  1438. bool "Sign modules with SHA-384"
  1439. select CRYPTO_SHA512
  1440. config MODULE_SIG_SHA512
  1441. bool "Sign modules with SHA-512"
  1442. select CRYPTO_SHA512
  1443. endchoice
  1444. endif # MODULES
  1445. config INIT_ALL_POSSIBLE
  1446. bool
  1447. help
  1448. Back when each arch used to define their own cpu_online_mask and
  1449. cpu_possible_mask, some of them chose to initialize cpu_possible_mask
  1450. with all 1s, and others with all 0s. When they were centralised,
  1451. it was better to provide this option than to break all the archs
  1452. and have several arch maintainers pursuing me down dark alleys.
  1453. config STOP_MACHINE
  1454. bool
  1455. default y
  1456. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1457. help
  1458. Need stop_machine() primitive.
  1459. source "block/Kconfig"
  1460. config PREEMPT_NOTIFIERS
  1461. bool
  1462. config PADATA
  1463. depends on SMP
  1464. bool
  1465. # Can be selected by architectures with broken toolchains
  1466. # that get confused by correct const<->read_only section
  1467. # mappings
  1468. config BROKEN_RODATA
  1469. bool
  1470. config ASN1
  1471. tristate
  1472. help
  1473. Build a simple ASN.1 grammar compiler that produces a bytecode output
  1474. that can be interpreted by the ASN.1 stream decoder and used to
  1475. inform it as to what tags are to be expected in a stream and what
  1476. functions to call on what tags.
  1477. source "kernel/Kconfig.locks"