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 drivers that have been replaced by something else, and/or are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