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 drivers that have been replaced by something else, and/or are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