Kconfig 58 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 IRQ_WORK
  20. bool
  21. config BUILDTIME_EXTABLE_SORT
  22. bool
  23. menu "General setup"
  24. config BROKEN
  25. bool
  26. config BROKEN_ON_SMP
  27. bool
  28. depends on BROKEN || !SMP
  29. default y
  30. config INIT_ENV_ARG_LIMIT
  31. int
  32. default 32 if !UML
  33. default 128 if UML
  34. help
  35. Maximum of each of the number of arguments and environment
  36. variables passed to init from the kernel command line.
  37. config CROSS_COMPILE
  38. string "Cross-compiler tool prefix"
  39. help
  40. Same as running 'make CROSS_COMPILE=prefix-' but stored for
  41. default make runs in this kernel build directory. You don't
  42. need to set this unless you want the configured kernel build
  43. directory to select the cross-compiler automatically.
  44. config COMPILE_TEST
  45. bool "Compile also drivers which will not load"
  46. default n
  47. help
  48. Some drivers can be compiled on a different platform than they are
  49. intended to be run on. Despite they cannot be loaded there (or even
  50. when they load they cannot be used due to missing HW support),
  51. developers still, opposing to distributors, might want to build such
  52. drivers to compile-test them.
  53. If you are a developer and want to build everything available, say Y
  54. here. If you are a user/distributor, say N here to exclude useless
  55. drivers to be distributed.
  56. config LOCALVERSION
  57. string "Local version - append to kernel release"
  58. help
  59. Append an extra string to the end of your kernel version.
  60. This will show up when you type uname, for example.
  61. The string you set here will be appended after the contents of
  62. any files with a filename matching localversion* in your
  63. object and source tree, in that order. Your total string can
  64. be a maximum of 64 characters.
  65. config LOCALVERSION_AUTO
  66. bool "Automatically append version information to the version string"
  67. default y
  68. help
  69. This will try to automatically determine if the current tree is a
  70. release tree by looking for git tags that belong to the current
  71. top of tree revision.
  72. A string of the format -gxxxxxxxx will be added to the localversion
  73. if a git-based tree is found. The string generated by this will be
  74. appended after any matching localversion* files, and after the value
  75. set in CONFIG_LOCALVERSION.
  76. (The actual string used here is the first eight characters produced
  77. by running the command:
  78. $ git rev-parse --verify HEAD
  79. which is done within the script "scripts/setlocalversion".)
  80. config HAVE_KERNEL_GZIP
  81. bool
  82. config HAVE_KERNEL_BZIP2
  83. bool
  84. config HAVE_KERNEL_LZMA
  85. bool
  86. config HAVE_KERNEL_XZ
  87. bool
  88. config HAVE_KERNEL_LZO
  89. bool
  90. choice
  91. prompt "Kernel compression mode"
  92. default KERNEL_GZIP
  93. depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
  94. help
  95. The linux kernel is a kind of self-extracting executable.
  96. Several compression algorithms are available, which differ
  97. in efficiency, compression and decompression speed.
  98. Compression speed is only relevant when building a kernel.
  99. Decompression speed is relevant at each boot.
  100. If you have any problems with bzip2 or lzma compressed
  101. kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
  102. version of this functionality (bzip2 only), for 2.4, was
  103. supplied by Christian Ludwig)
  104. High compression options are mostly useful for users, who
  105. are low on disk space (embedded systems), but for whom ram
  106. size matters less.
  107. If in doubt, select 'gzip'
  108. config KERNEL_GZIP
  109. bool "Gzip"
  110. depends on HAVE_KERNEL_GZIP
  111. help
  112. The old and tried gzip compression. It provides a good balance
  113. between compression ratio and decompression speed.
  114. config KERNEL_BZIP2
  115. bool "Bzip2"
  116. depends on HAVE_KERNEL_BZIP2
  117. help
  118. Its compression ratio and speed is intermediate.
  119. Decompression speed is slowest among the choices. The kernel
  120. size is about 10% smaller with bzip2, in comparison to gzip.
  121. Bzip2 uses a large amount of memory. For modern kernels you
  122. will need at least 8MB RAM or more for booting.
  123. config KERNEL_LZMA
  124. bool "LZMA"
  125. depends on HAVE_KERNEL_LZMA
  126. help
  127. This compression algorithm's ratio is best. Decompression speed
  128. is between gzip and bzip2. Compression is slowest.
  129. The kernel size is about 33% smaller with LZMA in comparison to gzip.
  130. config KERNEL_XZ
  131. bool "XZ"
  132. depends on HAVE_KERNEL_XZ
  133. help
  134. XZ uses the LZMA2 algorithm and instruction set specific
  135. BCJ filters which can improve compression ratio of executable
  136. code. The size of the kernel is about 30% smaller with XZ in
  137. comparison to gzip. On architectures for which there is a BCJ
  138. filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
  139. will create a few percent smaller kernel than plain LZMA.
  140. The speed is about the same as with LZMA: The decompression
  141. speed of XZ is better than that of bzip2 but worse than gzip
  142. and LZO. Compression is slow.
  143. config KERNEL_LZO
  144. bool "LZO"
  145. depends on HAVE_KERNEL_LZO
  146. help
  147. Its compression ratio is the poorest among the choices. The kernel
  148. size is about 10% bigger than gzip; however its speed
  149. (both compression and decompression) is the fastest.
  150. endchoice
  151. config DEFAULT_HOSTNAME
  152. string "Default hostname"
  153. default "(none)"
  154. help
  155. This option determines the default system hostname before userspace
  156. calls sethostname(2). The kernel traditionally uses "(none)" here,
  157. but you may wish to use a different default here to make a minimal
  158. system more usable with less configuration.
  159. config SWAP
  160. bool "Support for paging of anonymous memory (swap)"
  161. depends on MMU && BLOCK
  162. default y
  163. help
  164. This option allows you to choose whether you want to have support
  165. for so called swap devices or swap files in your kernel that are
  166. used to provide more virtual memory than the actual RAM present
  167. in your computer. If unsure say Y.
  168. config SYSVIPC
  169. bool "System V IPC"
  170. ---help---
  171. Inter Process Communication is a suite of library functions and
  172. system calls which let processes (running programs) synchronize and
  173. exchange information. It is generally considered to be a good thing,
  174. and some programs won't run unless you say Y here. In particular, if
  175. you want to run the DOS emulator dosemu under Linux (read the
  176. DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
  177. you'll need to say Y here.
  178. You can find documentation about IPC with "info ipc" and also in
  179. section 6.4 of the Linux Programmer's Guide, available from
  180. <http://www.tldp.org/guides.html>.
  181. config SYSVIPC_SYSCTL
  182. bool
  183. depends on SYSVIPC
  184. depends on SYSCTL
  185. default y
  186. config POSIX_MQUEUE
  187. bool "POSIX Message Queues"
  188. depends on NET
  189. ---help---
  190. POSIX variant of message queues is a part of IPC. In POSIX message
  191. queues every message has a priority which decides about succession
  192. of receiving it by a process. If you want to compile and run
  193. programs written e.g. for Solaris with use of its POSIX message
  194. queues (functions mq_*) say Y here.
  195. POSIX message queues are visible as a filesystem called 'mqueue'
  196. and can be mounted somewhere if you want to do filesystem
  197. operations on message queues.
  198. If unsure, say Y.
  199. config POSIX_MQUEUE_SYSCTL
  200. bool
  201. depends on POSIX_MQUEUE
  202. depends on SYSCTL
  203. default y
  204. config FHANDLE
  205. bool "open by fhandle syscalls"
  206. select EXPORTFS
  207. help
  208. If you say Y here, a user level program will be able to map
  209. file names to handle and then later use the handle for
  210. different file system operations. This is useful in implementing
  211. userspace file servers, which now track files using handles instead
  212. of names. The handle would remain the same even if file names
  213. get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
  214. syscalls.
  215. config AUDIT
  216. bool "Auditing support"
  217. depends on NET
  218. help
  219. Enable auditing infrastructure that can be used with another
  220. kernel subsystem, such as SELinux (which requires this for
  221. logging of avc messages output). Does not do system-call
  222. auditing without CONFIG_AUDITSYSCALL.
  223. config AUDITSYSCALL
  224. bool "Enable system-call auditing support"
  225. depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
  226. default y if SECURITY_SELINUX
  227. help
  228. Enable low-overhead system-call auditing infrastructure that
  229. can be used independently or with another kernel subsystem,
  230. such as SELinux.
  231. config AUDIT_WATCH
  232. def_bool y
  233. depends on AUDITSYSCALL
  234. select FSNOTIFY
  235. config AUDIT_TREE
  236. def_bool y
  237. depends on AUDITSYSCALL
  238. select FSNOTIFY
  239. config AUDIT_LOGINUID_IMMUTABLE
  240. bool "Make audit loginuid immutable"
  241. depends on AUDIT
  242. help
  243. The config option toggles if a task setting its loginuid requires
  244. CAP_SYS_AUDITCONTROL or if that task should require no special permissions
  245. but should instead only allow setting its loginuid if it was never
  246. previously set. On systems which use systemd or a similar central
  247. process to restart login services this should be set to true. On older
  248. systems in which an admin would typically have to directly stop and
  249. start processes this should be set to false. Setting this to true allows
  250. one to drop potentially dangerous capabilites from the login tasks,
  251. but may not be backwards compatible with older init systems.
  252. source "kernel/irq/Kconfig"
  253. source "kernel/time/Kconfig"
  254. menu "CPU/Task time and stats accounting"
  255. config VIRT_CPU_ACCOUNTING
  256. bool
  257. choice
  258. prompt "Cputime accounting"
  259. default TICK_CPU_ACCOUNTING if !PPC64
  260. default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
  261. # Kind of a stub config for the pure tick based cputime accounting
  262. config TICK_CPU_ACCOUNTING
  263. bool "Simple tick based cputime accounting"
  264. depends on !S390 && !NO_HZ_FULL
  265. help
  266. This is the basic tick based cputime accounting that maintains
  267. statistics about user, system and idle time spent on per jiffies
  268. granularity.
  269. If unsure, say Y.
  270. config VIRT_CPU_ACCOUNTING_NATIVE
  271. bool "Deterministic task and CPU time accounting"
  272. depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
  273. select VIRT_CPU_ACCOUNTING
  274. help
  275. Select this option to enable more accurate task and CPU time
  276. accounting. This is done by reading a CPU counter on each
  277. kernel entry and exit and on transitions within the kernel
  278. between system, softirq and hardirq state, so there is a
  279. small performance impact. In the case of s390 or IBM POWER > 5,
  280. this also enables accounting of stolen time on logically-partitioned
  281. systems.
  282. config VIRT_CPU_ACCOUNTING_GEN
  283. bool "Full dynticks CPU time accounting"
  284. depends on HAVE_CONTEXT_TRACKING && 64BIT
  285. select VIRT_CPU_ACCOUNTING
  286. select CONTEXT_TRACKING
  287. help
  288. Select this option to enable task and CPU time accounting on full
  289. dynticks systems. This accounting is implemented by watching every
  290. kernel-user boundaries using the context tracking subsystem.
  291. The accounting is thus performed at the expense of some significant
  292. overhead.
  293. For now this is only useful if you are working on the full
  294. dynticks subsystem development.
  295. If unsure, say N.
  296. config IRQ_TIME_ACCOUNTING
  297. bool "Fine granularity task level IRQ time accounting"
  298. depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
  299. help
  300. Select this option to enable fine granularity task irq time
  301. accounting. This is done by reading a timestamp on each
  302. transitions between softirq and hardirq state, so there can be a
  303. small performance impact.
  304. If in doubt, say N here.
  305. endchoice
  306. config BSD_PROCESS_ACCT
  307. bool "BSD Process Accounting"
  308. help
  309. If you say Y here, a user level program will be able to instruct the
  310. kernel (via a special system call) to write process accounting
  311. information to a file: whenever a process exits, information about
  312. that process will be appended to the file by the kernel. The
  313. information includes things such as creation time, owning user,
  314. command name, memory usage, controlling terminal etc. (the complete
  315. list is in the struct acct in <file:include/linux/acct.h>). It is
  316. up to the user level program to do useful things with this
  317. information. This is generally a good idea, so say Y.
  318. config BSD_PROCESS_ACCT_V3
  319. bool "BSD Process Accounting version 3 file format"
  320. depends on BSD_PROCESS_ACCT
  321. default n
  322. help
  323. If you say Y here, the process accounting information is written
  324. in a new file format that also logs the process IDs of each
  325. process and it's parent. Note that this file format is incompatible
  326. with previous v0/v1/v2 file formats, so you will need updated tools
  327. for processing it. A preliminary version of these tools is available
  328. at <http://www.gnu.org/software/acct/>.
  329. config TASKSTATS
  330. bool "Export task/process statistics through netlink"
  331. depends on NET
  332. default n
  333. help
  334. Export selected statistics for tasks/processes through the
  335. generic netlink interface. Unlike BSD process accounting, the
  336. statistics are available during the lifetime of tasks/processes as
  337. responses to commands. Like BSD accounting, they are sent to user
  338. space on task exit.
  339. Say N if unsure.
  340. config TASK_DELAY_ACCT
  341. bool "Enable per-task delay accounting"
  342. depends on TASKSTATS
  343. help
  344. Collect information on time spent by a task waiting for system
  345. resources like cpu, synchronous block I/O completion and swapping
  346. in pages. Such statistics can help in setting a task's priorities
  347. relative to other tasks for cpu, io, rss limits etc.
  348. Say N if unsure.
  349. config TASK_XACCT
  350. bool "Enable extended accounting over taskstats"
  351. depends on TASKSTATS
  352. help
  353. Collect extended task accounting data and send the data
  354. to userland for processing over the taskstats interface.
  355. Say N if unsure.
  356. config TASK_IO_ACCOUNTING
  357. bool "Enable per-task storage I/O accounting"
  358. depends on TASK_XACCT
  359. help
  360. Collect information on the number of bytes of storage I/O which this
  361. task has caused.
  362. Say N if unsure.
  363. endmenu # "CPU/Task time and stats accounting"
  364. menu "RCU Subsystem"
  365. choice
  366. prompt "RCU Implementation"
  367. default TREE_RCU
  368. config TREE_RCU
  369. bool "Tree-based hierarchical RCU"
  370. depends on !PREEMPT && SMP
  371. select IRQ_WORK
  372. help
  373. This option selects the RCU implementation that is
  374. designed for very large SMP system with hundreds or
  375. thousands of CPUs. It also scales down nicely to
  376. smaller systems.
  377. config TREE_PREEMPT_RCU
  378. bool "Preemptible tree-based hierarchical RCU"
  379. depends on PREEMPT
  380. help
  381. This option selects the RCU implementation that is
  382. designed for very large SMP systems with hundreds or
  383. thousands of CPUs, but for which real-time response
  384. is also required. It also scales down nicely to
  385. smaller systems.
  386. Select this option if you are unsure.
  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. endchoice
  396. config PREEMPT_RCU
  397. def_bool TREE_PREEMPT_RCU
  398. help
  399. This option enables preemptible-RCU code that is common between
  400. the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
  401. config RCU_STALL_COMMON
  402. def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
  403. help
  404. This option enables RCU CPU stall code that is common between
  405. the TINY and TREE variants of RCU. The purpose is to allow
  406. the tiny variants to disable RCU CPU stall warnings, while
  407. making these warnings mandatory for the tree variants.
  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. default CONTEXT_TRACKING
  428. help
  429. Probe on user/kernel boundaries by default in order to
  430. test the features that rely on it such as userspace RCU extended
  431. quiescent states.
  432. This test is there for debugging until we have a real user like the
  433. full dynticks mode.
  434. config RCU_FANOUT
  435. int "Tree-based hierarchical RCU fanout value"
  436. range 2 64 if 64BIT
  437. range 2 32 if !64BIT
  438. depends on TREE_RCU || TREE_PREEMPT_RCU
  439. default 64 if 64BIT
  440. default 32 if !64BIT
  441. help
  442. This option controls the fanout of hierarchical implementations
  443. of RCU, allowing RCU to work efficiently on machines with
  444. large numbers of CPUs. This value must be at least the fourth
  445. root of NR_CPUS, which allows NR_CPUS to be insanely large.
  446. The default value of RCU_FANOUT should be used for production
  447. systems, but if you are stress-testing the RCU implementation
  448. itself, small RCU_FANOUT values allow you to test large-system
  449. code paths on small(er) systems.
  450. Select a specific number if testing RCU itself.
  451. Take the default if unsure.
  452. config RCU_FANOUT_LEAF
  453. int "Tree-based hierarchical RCU leaf-level fanout value"
  454. range 2 RCU_FANOUT if 64BIT
  455. range 2 RCU_FANOUT if !64BIT
  456. depends on TREE_RCU || TREE_PREEMPT_RCU
  457. default 16
  458. help
  459. This option controls the leaf-level fanout of hierarchical
  460. implementations of RCU, and allows trading off cache misses
  461. against lock contention. Systems that synchronize their
  462. scheduling-clock interrupts for energy-efficiency reasons will
  463. want the default because the smaller leaf-level fanout keeps
  464. lock contention levels acceptably low. Very large systems
  465. (hundreds or thousands of CPUs) will instead want to set this
  466. value to the maximum value possible in order to reduce the
  467. number of cache misses incurred during RCU's grace-period
  468. initialization. These systems tend to run CPU-bound, and thus
  469. are not helped by synchronized interrupts, and thus tend to
  470. skew them, which reduces lock contention enough that large
  471. leaf-level fanouts work well.
  472. Select a specific number if testing RCU itself.
  473. Select the maximum permissible value for large systems.
  474. Take the default if unsure.
  475. config RCU_FANOUT_EXACT
  476. bool "Disable tree-based hierarchical RCU auto-balancing"
  477. depends on TREE_RCU || TREE_PREEMPT_RCU
  478. default n
  479. help
  480. This option forces use of the exact RCU_FANOUT value specified,
  481. regardless of imbalances in the hierarchy. This is useful for
  482. testing RCU itself, and might one day be useful on systems with
  483. strong NUMA behavior.
  484. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  485. Say N if unsure.
  486. config RCU_FAST_NO_HZ
  487. bool "Accelerate last non-dyntick-idle CPU's grace periods"
  488. depends on NO_HZ_COMMON && SMP
  489. default n
  490. help
  491. This option permits CPUs to enter dynticks-idle state even if
  492. they have RCU callbacks queued, and prevents RCU from waking
  493. these CPUs up more than roughly once every four jiffies (by
  494. default, you can adjust this using the rcutree.rcu_idle_gp_delay
  495. parameter), thus improving energy efficiency. On the other
  496. hand, this option increases the duration of RCU grace periods,
  497. for example, slowing down synchronize_rcu().
  498. Say Y if energy efficiency is critically important, and you
  499. don't care about increased grace-period durations.
  500. Say N if you are unsure.
  501. config TREE_RCU_TRACE
  502. def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
  503. select DEBUG_FS
  504. help
  505. This option provides tracing for the TREE_RCU and
  506. TREE_PREEMPT_RCU implementations, permitting Makefile to
  507. trivially select kernel/rcutree_trace.c.
  508. config RCU_BOOST
  509. bool "Enable RCU priority boosting"
  510. depends on RT_MUTEXES && PREEMPT_RCU
  511. default n
  512. help
  513. This option boosts the priority of preempted RCU readers that
  514. block the current preemptible RCU grace period for too long.
  515. This option also prevents heavy loads from blocking RCU
  516. callback invocation for all flavors of RCU.
  517. Say Y here if you are working with real-time apps or heavy loads
  518. Say N here if you are unsure.
  519. config RCU_BOOST_PRIO
  520. int "Real-time priority to boost RCU readers to"
  521. range 1 99
  522. depends on RCU_BOOST
  523. default 1
  524. help
  525. This option specifies the real-time priority to which long-term
  526. preempted RCU readers are to be boosted. If you are working
  527. with a real-time application that has one or more CPU-bound
  528. threads running at a real-time priority level, you should set
  529. RCU_BOOST_PRIO to a priority higher then the highest-priority
  530. real-time CPU-bound thread. The default RCU_BOOST_PRIO value
  531. of 1 is appropriate in the common case, which is real-time
  532. applications that do not have any CPU-bound threads.
  533. Some real-time applications might not have a single real-time
  534. thread that saturates a given CPU, but instead might have
  535. multiple real-time threads that, taken together, fully utilize
  536. that CPU. In this case, you should set RCU_BOOST_PRIO to
  537. a priority higher than the lowest-priority thread that is
  538. conspiring to prevent the CPU from running any non-real-time
  539. tasks. For example, if one thread at priority 10 and another
  540. thread at priority 5 are between themselves fully consuming
  541. the CPU time on a given CPU, then RCU_BOOST_PRIO should be
  542. set to priority 6 or higher.
  543. Specify the real-time priority, or take the default if unsure.
  544. config RCU_BOOST_DELAY
  545. int "Milliseconds to delay boosting after RCU grace-period start"
  546. range 0 3000
  547. depends on RCU_BOOST
  548. default 500
  549. help
  550. This option specifies the time to wait after the beginning of
  551. a given grace period before priority-boosting preempted RCU
  552. readers blocking that grace period. Note that any RCU reader
  553. blocking an expedited RCU grace period is boosted immediately.
  554. Accept the default if unsure.
  555. config RCU_NOCB_CPU
  556. bool "Offload RCU callback processing from boot-selected CPUs"
  557. depends on TREE_RCU || TREE_PREEMPT_RCU
  558. default n
  559. help
  560. Use this option to reduce OS jitter for aggressive HPC or
  561. real-time workloads. It can also be used to offload RCU
  562. callback invocation to energy-efficient CPUs in battery-powered
  563. asymmetric multiprocessors.
  564. This option offloads callback invocation from the set of
  565. CPUs specified at boot time by the rcu_nocbs parameter.
  566. For each such CPU, a kthread ("rcuox/N") will be created to
  567. invoke callbacks, where the "N" is the CPU being offloaded,
  568. and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
  569. "s" for RCU-sched. Nothing prevents this kthread from running
  570. on the specified CPUs, but (1) the kthreads may be preempted
  571. between each callback, and (2) affinity or cgroups can be used
  572. to force the kthreads to run on whatever set of CPUs is desired.
  573. Say Y here if you want to help to debug reduced OS jitter.
  574. Say N here if you are unsure.
  575. choice
  576. prompt "Build-forced no-CBs CPUs"
  577. default RCU_NOCB_CPU_NONE
  578. help
  579. This option allows no-CBs CPUs (whose RCU callbacks are invoked
  580. from kthreads rather than from softirq context) to be specified
  581. at build time. Additional no-CBs CPUs may be specified by
  582. the rcu_nocbs= boot parameter.
  583. config RCU_NOCB_CPU_NONE
  584. bool "No build_forced no-CBs CPUs"
  585. depends on RCU_NOCB_CPU && !NO_HZ_FULL
  586. help
  587. This option does not force any of the CPUs to be no-CBs CPUs.
  588. Only CPUs designated by the rcu_nocbs= boot parameter will be
  589. no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
  590. kthreads whose names begin with "rcuo". All other CPUs will
  591. invoke their own RCU callbacks in softirq context.
  592. Select this option if you want to choose no-CBs CPUs at
  593. boot time, for example, to allow testing of different no-CBs
  594. configurations without having to rebuild the kernel each time.
  595. config RCU_NOCB_CPU_ZERO
  596. bool "CPU 0 is a build_forced no-CBs CPU"
  597. depends on RCU_NOCB_CPU && !NO_HZ_FULL
  598. help
  599. This option forces CPU 0 to be a no-CBs CPU, so that its RCU
  600. callbacks are invoked by a per-CPU kthread whose name begins
  601. with "rcuo". Additional CPUs may be designated as no-CBs
  602. CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
  603. All other CPUs will invoke their own RCU callbacks in softirq
  604. context.
  605. Select this if CPU 0 needs to be a no-CBs CPU for real-time
  606. or energy-efficiency reasons, but the real reason it exists
  607. is to ensure that randconfig testing covers mixed systems.
  608. config RCU_NOCB_CPU_ALL
  609. bool "All CPUs are build_forced no-CBs CPUs"
  610. depends on RCU_NOCB_CPU
  611. help
  612. This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
  613. boot parameter will be ignored. All CPUs' RCU callbacks will
  614. be executed in the context of per-CPU rcuo kthreads created for
  615. this purpose. Assuming that the kthreads whose names start with
  616. "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
  617. on the remaining CPUs, but might decrease memory locality during
  618. RCU-callback invocation, thus potentially degrading throughput.
  619. Select this if all CPUs need to be no-CBs CPUs for real-time
  620. or energy-efficiency reasons.
  621. endchoice
  622. endmenu # "RCU Subsystem"
  623. config IKCONFIG
  624. tristate "Kernel .config support"
  625. ---help---
  626. This option enables the complete Linux kernel ".config" file
  627. contents to be saved in the kernel. It provides documentation
  628. of which kernel options are used in a running kernel or in an
  629. on-disk kernel. This information can be extracted from the kernel
  630. image file with the script scripts/extract-ikconfig and used as
  631. input to rebuild the current kernel or to build another kernel.
  632. It can also be extracted from a running kernel by reading
  633. /proc/config.gz if enabled (below).
  634. config IKCONFIG_PROC
  635. bool "Enable access to .config through /proc/config.gz"
  636. depends on IKCONFIG && PROC_FS
  637. ---help---
  638. This option enables access to the kernel configuration file
  639. through /proc/config.gz.
  640. config LOG_BUF_SHIFT
  641. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  642. range 12 21
  643. default 17
  644. help
  645. Select kernel log buffer size as a power of 2.
  646. Examples:
  647. 17 => 128 KB
  648. 16 => 64 KB
  649. 15 => 32 KB
  650. 14 => 16 KB
  651. 13 => 8 KB
  652. 12 => 4 KB
  653. #
  654. # Architectures with an unreliable sched_clock() should select this:
  655. #
  656. config HAVE_UNSTABLE_SCHED_CLOCK
  657. bool
  658. #
  659. # For architectures that want to enable the support for NUMA-affine scheduler
  660. # balancing logic:
  661. #
  662. config ARCH_SUPPORTS_NUMA_BALANCING
  663. bool
  664. # For architectures that (ab)use NUMA to represent different memory regions
  665. # all cpu-local but of different latencies, such as SuperH.
  666. #
  667. config ARCH_WANT_NUMA_VARIABLE_LOCALITY
  668. bool
  669. #
  670. # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
  671. config ARCH_WANTS_PROT_NUMA_PROT_NONE
  672. bool
  673. config ARCH_USES_NUMA_PROT_NONE
  674. bool
  675. default y
  676. depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
  677. depends on NUMA_BALANCING
  678. config NUMA_BALANCING_DEFAULT_ENABLED
  679. bool "Automatically enable NUMA aware memory/task placement"
  680. default y
  681. depends on NUMA_BALANCING
  682. help
  683. If set, autonumic NUMA balancing will be enabled if running on a NUMA
  684. machine.
  685. config NUMA_BALANCING
  686. bool "Memory placement aware NUMA scheduler"
  687. depends on ARCH_SUPPORTS_NUMA_BALANCING
  688. depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
  689. depends on SMP && NUMA && MIGRATION
  690. help
  691. This option adds support for automatic NUMA aware memory/task placement.
  692. The mechanism is quite primitive and is based on migrating memory when
  693. it is references to the node the task is running on.
  694. This system will be inactive on UMA systems.
  695. menuconfig CGROUPS
  696. boolean "Control Group support"
  697. depends on EVENTFD
  698. help
  699. This option adds support for grouping sets of processes together, for
  700. use with process control subsystems such as Cpusets, CFS, memory
  701. controls or device isolation.
  702. See
  703. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  704. - Documentation/cgroups/ (features for grouping, isolation
  705. and resource control)
  706. Say N if unsure.
  707. if CGROUPS
  708. config CGROUP_DEBUG
  709. bool "Example debug cgroup subsystem"
  710. default n
  711. help
  712. This option enables a simple cgroup subsystem that
  713. exports useful debugging information about the cgroups
  714. framework.
  715. Say N if unsure.
  716. config CGROUP_FREEZER
  717. bool "Freezer cgroup subsystem"
  718. help
  719. Provides a way to freeze and unfreeze all tasks in a
  720. cgroup.
  721. config CGROUP_DEVICE
  722. bool "Device controller for cgroups"
  723. help
  724. Provides a cgroup implementing whitelists for devices which
  725. a process in the cgroup can mknod or open.
  726. config CPUSETS
  727. bool "Cpuset support"
  728. help
  729. This option will let you create and manage CPUSETs which
  730. allow dynamically partitioning a system into sets of CPUs and
  731. Memory Nodes and assigning tasks to run only within those sets.
  732. This is primarily useful on large SMP or NUMA systems.
  733. Say N if unsure.
  734. config PROC_PID_CPUSET
  735. bool "Include legacy /proc/<pid>/cpuset file"
  736. depends on CPUSETS
  737. default y
  738. config CGROUP_CPUACCT
  739. bool "Simple CPU accounting cgroup subsystem"
  740. help
  741. Provides a simple Resource Controller for monitoring the
  742. total CPU consumed by the tasks in a cgroup.
  743. config RESOURCE_COUNTERS
  744. bool "Resource counters"
  745. help
  746. This option enables controller independent resource accounting
  747. infrastructure that works with cgroups.
  748. config MEMCG
  749. bool "Memory Resource Controller for Control Groups"
  750. depends on RESOURCE_COUNTERS
  751. select MM_OWNER
  752. help
  753. Provides a memory resource controller that manages both anonymous
  754. memory and page cache. (See Documentation/cgroups/memory.txt)
  755. Note that setting this option increases fixed memory overhead
  756. associated with each page of memory in the system. By this,
  757. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  758. usage tracking struct at boot. Total amount of this is printed out
  759. at boot.
  760. Only enable when you're ok with these trade offs and really
  761. sure you need the memory resource controller. Even when you enable
  762. this, you can set "cgroup_disable=memory" at your boot option to
  763. disable memory resource controller and you can avoid overheads.
  764. (and lose benefits of memory resource controller)
  765. This config option also selects MM_OWNER config option, which
  766. could in turn add some fork/exit overhead.
  767. config MEMCG_SWAP
  768. bool "Memory Resource Controller Swap Extension"
  769. depends on MEMCG && SWAP
  770. help
  771. Add swap management feature to memory resource controller. When you
  772. enable this, you can limit mem+swap usage per cgroup. In other words,
  773. when you disable this, memory resource controller has no cares to
  774. usage of swap...a process can exhaust all of the swap. This extension
  775. is useful when you want to avoid exhaustion swap but this itself
  776. adds more overheads and consumes memory for remembering information.
  777. Especially if you use 32bit system or small memory system, please
  778. be careful about enabling this. When memory resource controller
  779. is disabled by boot option, this will be automatically disabled and
  780. there will be no overhead from this. Even when you set this config=y,
  781. if boot option "swapaccount=0" is set, swap will not be accounted.
  782. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  783. size is 4096bytes, 512k per 1Gbytes of swap.
  784. config MEMCG_SWAP_ENABLED
  785. bool "Memory Resource Controller Swap Extension enabled by default"
  786. depends on MEMCG_SWAP
  787. default y
  788. help
  789. Memory Resource Controller Swap Extension comes with its price in
  790. a bigger memory consumption. General purpose distribution kernels
  791. which want to enable the feature but keep it disabled by default
  792. and let the user enable it by swapaccount boot command line
  793. parameter should have this option unselected.
  794. For those who want to have the feature enabled by default should
  795. select this option (if, for some reason, they need to disable it
  796. then swapaccount=0 does the trick).
  797. config MEMCG_KMEM
  798. bool "Memory Resource Controller Kernel Memory accounting"
  799. depends on MEMCG
  800. depends on SLUB || SLAB
  801. help
  802. The Kernel Memory extension for Memory Resource Controller can limit
  803. the amount of memory used by kernel objects in the system. Those are
  804. fundamentally different from the entities handled by the standard
  805. Memory Controller, which are page-based, and can be swapped. Users of
  806. the kmem extension can use it to guarantee that no group of processes
  807. will ever exhaust kernel resources alone.
  808. config CGROUP_HUGETLB
  809. bool "HugeTLB Resource Controller for Control Groups"
  810. depends on RESOURCE_COUNTERS && HUGETLB_PAGE
  811. default n
  812. help
  813. Provides a cgroup Resource Controller for HugeTLB pages.
  814. When you enable this, you can put a per cgroup limit on HugeTLB usage.
  815. The limit is enforced during page fault. Since HugeTLB doesn't
  816. support page reclaim, enforcing the limit at page fault time implies
  817. that, the application will get SIGBUS signal if it tries to access
  818. HugeTLB pages beyond its limit. This requires the application to know
  819. beforehand how much HugeTLB pages it would require for its use. The
  820. control group is tracked in the third page lru pointer. This means
  821. that we cannot use the controller with huge page less than 3 pages.
  822. config CGROUP_PERF
  823. bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
  824. depends on PERF_EVENTS && CGROUPS
  825. help
  826. This option extends the per-cpu mode to restrict monitoring to
  827. threads which belong to the cgroup specified and run on the
  828. designated cpu.
  829. Say N if unsure.
  830. menuconfig CGROUP_SCHED
  831. bool "Group CPU scheduler"
  832. default n
  833. help
  834. This feature lets CPU scheduler recognize task groups and control CPU
  835. bandwidth allocation to such task groups. It uses cgroups to group
  836. tasks.
  837. if CGROUP_SCHED
  838. config FAIR_GROUP_SCHED
  839. bool "Group scheduling for SCHED_OTHER"
  840. depends on CGROUP_SCHED
  841. default CGROUP_SCHED
  842. config CFS_BANDWIDTH
  843. bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
  844. depends on FAIR_GROUP_SCHED
  845. default n
  846. help
  847. This option allows users to define CPU bandwidth rates (limits) for
  848. tasks running within the fair group scheduler. Groups with no limit
  849. set are considered to be unconstrained and will run with no
  850. restriction.
  851. See tip/Documentation/scheduler/sched-bwc.txt for more information.
  852. config RT_GROUP_SCHED
  853. bool "Group scheduling for SCHED_RR/FIFO"
  854. depends on CGROUP_SCHED
  855. default n
  856. help
  857. This feature lets you explicitly allocate real CPU bandwidth
  858. to task groups. If enabled, it will also make it impossible to
  859. schedule realtime tasks for non-root users until you allocate
  860. realtime bandwidth for them.
  861. See Documentation/scheduler/sched-rt-group.txt for more information.
  862. endif #CGROUP_SCHED
  863. config BLK_CGROUP
  864. bool "Block IO controller"
  865. depends on BLOCK
  866. default n
  867. ---help---
  868. Generic block IO controller cgroup interface. This is the common
  869. cgroup interface which should be used by various IO controlling
  870. policies.
  871. Currently, CFQ IO scheduler uses it to recognize task groups and
  872. control disk bandwidth allocation (proportional time slice allocation)
  873. to such task groups. It is also used by bio throttling logic in
  874. block layer to implement upper limit in IO rates on a device.
  875. This option only enables generic Block IO controller infrastructure.
  876. One needs to also enable actual IO controlling logic/policy. For
  877. enabling proportional weight division of disk bandwidth in CFQ, set
  878. CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
  879. CONFIG_BLK_DEV_THROTTLING=y.
  880. See Documentation/cgroups/blkio-controller.txt for more information.
  881. config DEBUG_BLK_CGROUP
  882. bool "Enable Block IO controller debugging"
  883. depends on BLK_CGROUP
  884. default n
  885. ---help---
  886. Enable some debugging help. Currently it exports additional stat
  887. files in a cgroup which can be useful for debugging.
  888. endif # CGROUPS
  889. config CHECKPOINT_RESTORE
  890. bool "Checkpoint/restore support" if EXPERT
  891. default n
  892. help
  893. Enables additional kernel features in a sake of checkpoint/restore.
  894. In particular it adds auxiliary prctl codes to setup process text,
  895. data and heap segment sizes, and a few additional /proc filesystem
  896. entries.
  897. If unsure, say N here.
  898. menuconfig NAMESPACES
  899. bool "Namespaces support" if EXPERT
  900. default !EXPERT
  901. help
  902. Provides the way to make tasks work with different objects using
  903. the same id. For example same IPC id may refer to different objects
  904. or same user id or pid may refer to different tasks when used in
  905. different namespaces.
  906. if NAMESPACES
  907. config UTS_NS
  908. bool "UTS namespace"
  909. default y
  910. help
  911. In this namespace tasks see different info provided with the
  912. uname() system call
  913. config IPC_NS
  914. bool "IPC namespace"
  915. depends on (SYSVIPC || POSIX_MQUEUE)
  916. default y
  917. help
  918. In this namespace tasks work with IPC ids which correspond to
  919. different IPC objects in different namespaces.
  920. config USER_NS
  921. bool "User namespace"
  922. depends on UIDGID_CONVERTED
  923. select UIDGID_STRICT_TYPE_CHECKS
  924. default n
  925. help
  926. This allows containers, i.e. vservers, to use user namespaces
  927. to provide different user info for different servers.
  928. When user namespaces are enabled in the kernel it is
  929. recommended that the MEMCG and MEMCG_KMEM options also be
  930. enabled and that user-space use the memory control groups to
  931. limit the amount of memory a memory unprivileged users can
  932. use.
  933. If unsure, say N.
  934. config PID_NS
  935. bool "PID Namespaces"
  936. default y
  937. help
  938. Support process id namespaces. This allows having multiple
  939. processes with the same pid as long as they are in different
  940. pid namespaces. This is a building block of containers.
  941. config NET_NS
  942. bool "Network namespace"
  943. depends on NET
  944. default y
  945. help
  946. Allow user space to create what appear to be multiple instances
  947. of the network stack.
  948. endif # NAMESPACES
  949. config UIDGID_CONVERTED
  950. # True if all of the selected software conmponents are known
  951. # to have uid_t and gid_t converted to kuid_t and kgid_t
  952. # where appropriate and are otherwise safe to use with
  953. # the user namespace.
  954. bool
  955. default y
  956. # Filesystems
  957. depends on XFS_FS = n
  958. config UIDGID_STRICT_TYPE_CHECKS
  959. bool "Require conversions between uid/gids and their internal representation"
  960. depends on UIDGID_CONVERTED
  961. default n
  962. help
  963. While the nececessary conversions are being added to all subsystems this option allows
  964. the code to continue to build for unconverted subsystems.
  965. Say Y here if you want the strict type checking enabled
  966. config SCHED_AUTOGROUP
  967. bool "Automatic process group scheduling"
  968. select EVENTFD
  969. select CGROUPS
  970. select CGROUP_SCHED
  971. select FAIR_GROUP_SCHED
  972. help
  973. This option optimizes the scheduler for common desktop workloads by
  974. automatically creating and populating task groups. This separation
  975. of workloads isolates aggressive CPU burners (like build jobs) from
  976. desktop applications. Task group autogeneration is currently based
  977. upon task session.
  978. config MM_OWNER
  979. bool
  980. config SYSFS_DEPRECATED
  981. bool "Enable deprecated sysfs features to support old userspace tools"
  982. depends on SYSFS
  983. default n
  984. help
  985. This option adds code that switches the layout of the "block" class
  986. devices, to not show up in /sys/class/block/, but only in
  987. /sys/block/.
  988. This switch is only active when the sysfs.deprecated=1 boot option is
  989. passed or the SYSFS_DEPRECATED_V2 option is set.
  990. This option allows new kernels to run on old distributions and tools,
  991. which might get confused by /sys/class/block/. Since 2007/2008 all
  992. major distributions and tools handle this just fine.
  993. Recent distributions and userspace tools after 2009/2010 depend on
  994. the existence of /sys/class/block/, and will not work with this
  995. option enabled.
  996. Only if you are using a new kernel on an old distribution, you might
  997. need to say Y here.
  998. config SYSFS_DEPRECATED_V2
  999. bool "Enable deprecated sysfs features by default"
  1000. default n
  1001. depends on SYSFS
  1002. depends on SYSFS_DEPRECATED
  1003. help
  1004. Enable deprecated sysfs by default.
  1005. See the CONFIG_SYSFS_DEPRECATED option for more details about this
  1006. option.
  1007. Only if you are using a new kernel on an old distribution, you might
  1008. need to say Y here. Even then, odds are you would not need it
  1009. enabled, you can always pass the boot option if absolutely necessary.
  1010. config RELAY
  1011. bool "Kernel->user space relay support (formerly relayfs)"
  1012. help
  1013. This option enables support for relay interface support in
  1014. certain file systems (such as debugfs).
  1015. It is designed to provide an efficient mechanism for tools and
  1016. facilities to relay large amounts of data from kernel space to
  1017. user space.
  1018. If unsure, say N.
  1019. config BLK_DEV_INITRD
  1020. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  1021. depends on BROKEN || !FRV
  1022. help
  1023. The initial RAM filesystem is a ramfs which is loaded by the
  1024. boot loader (loadlin or lilo) and that is mounted as root
  1025. before the normal boot procedure. It is typically used to
  1026. load modules needed to mount the "real" root file system,
  1027. etc. See <file:Documentation/initrd.txt> for details.
  1028. If RAM disk support (BLK_DEV_RAM) is also included, this
  1029. also enables initial RAM disk (initrd) support and adds
  1030. 15 Kbytes (more on some other architectures) to the kernel size.
  1031. If unsure say Y.
  1032. if BLK_DEV_INITRD
  1033. source "usr/Kconfig"
  1034. endif
  1035. config CC_OPTIMIZE_FOR_SIZE
  1036. bool "Optimize for size"
  1037. help
  1038. Enabling this option will pass "-Os" instead of "-O2" to gcc
  1039. resulting in a smaller kernel.
  1040. If unsure, say N.
  1041. config SYSCTL
  1042. bool
  1043. config ANON_INODES
  1044. bool
  1045. config HAVE_UID16
  1046. bool
  1047. config SYSCTL_EXCEPTION_TRACE
  1048. bool
  1049. help
  1050. Enable support for /proc/sys/debug/exception-trace.
  1051. config SYSCTL_ARCH_UNALIGN_NO_WARN
  1052. bool
  1053. help
  1054. Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
  1055. Allows arch to define/use @no_unaligned_warning to possibly warn
  1056. about unaligned access emulation going on under the hood.
  1057. config SYSCTL_ARCH_UNALIGN_ALLOW
  1058. bool
  1059. help
  1060. Enable support for /proc/sys/kernel/unaligned-trap
  1061. Allows arches to define/use @unaligned_enabled to runtime toggle
  1062. the unaligned access emulation.
  1063. see arch/parisc/kernel/unaligned.c for reference
  1064. config HAVE_PCSPKR_PLATFORM
  1065. bool
  1066. menuconfig EXPERT
  1067. bool "Configure standard kernel features (expert users)"
  1068. # Unhide debug options, to make the on-by-default options visible
  1069. select DEBUG_KERNEL
  1070. help
  1071. This option allows certain base kernel options and settings
  1072. to be disabled or tweaked. This is for specialized
  1073. environments which can tolerate a "non-standard" kernel.
  1074. Only use this if you really know what you are doing.
  1075. config UID16
  1076. bool "Enable 16-bit UID system calls" if EXPERT
  1077. depends on HAVE_UID16
  1078. default y
  1079. help
  1080. This enables the legacy 16-bit UID syscall wrappers.
  1081. config SYSCTL_SYSCALL
  1082. bool "Sysctl syscall support" if EXPERT
  1083. depends on PROC_SYSCTL
  1084. default n
  1085. select SYSCTL
  1086. ---help---
  1087. sys_sysctl uses binary paths that have been found challenging
  1088. to properly maintain and use. The interface in /proc/sys
  1089. using paths with ascii names is now the primary path to this
  1090. information.
  1091. Almost nothing using the binary sysctl interface so if you are
  1092. trying to save some space it is probably safe to disable this,
  1093. making your kernel marginally smaller.
  1094. If unsure say N here.
  1095. config KALLSYMS
  1096. bool "Load all symbols for debugging/ksymoops" if EXPERT
  1097. default y
  1098. help
  1099. Say Y here to let the kernel print out symbolic crash information and
  1100. symbolic stack backtraces. This increases the size of the kernel
  1101. somewhat, as all symbols have to be loaded into the kernel image.
  1102. config KALLSYMS_ALL
  1103. bool "Include all symbols in kallsyms"
  1104. depends on DEBUG_KERNEL && KALLSYMS
  1105. help
  1106. Normally kallsyms only contains the symbols of functions for nicer
  1107. OOPS messages and backtraces (i.e., symbols from the text and inittext
  1108. sections). This is sufficient for most cases. And only in very rare
  1109. cases (e.g., when a debugger is used) all symbols are required (e.g.,
  1110. names of variables from the data sections, etc).
  1111. This option makes sure that all symbols are loaded into the kernel
  1112. image (i.e., symbols from all sections) in cost of increased kernel
  1113. size (depending on the kernel configuration, it may be 300KiB or
  1114. something like this).
  1115. Say N unless you really need all symbols.
  1116. config PRINTK
  1117. default y
  1118. bool "Enable support for printk" if EXPERT
  1119. select IRQ_WORK
  1120. help
  1121. This option enables normal printk support. Removing it
  1122. eliminates most of the message strings from the kernel image
  1123. and makes the kernel more or less silent. As this makes it
  1124. very difficult to diagnose system problems, saying N here is
  1125. strongly discouraged.
  1126. config BUG
  1127. bool "BUG() support" if EXPERT
  1128. default y
  1129. help
  1130. Disabling this option eliminates support for BUG and WARN, reducing
  1131. the size of your kernel image and potentially quietly ignoring
  1132. numerous fatal conditions. You should only consider disabling this
  1133. option for embedded systems with no facilities for reporting errors.
  1134. Just say Y.
  1135. config ELF_CORE
  1136. depends on COREDUMP
  1137. default y
  1138. bool "Enable ELF core dumps" if EXPERT
  1139. help
  1140. Enable support for generating core dumps. Disabling saves about 4k.
  1141. config PCSPKR_PLATFORM
  1142. bool "Enable PC-Speaker support" if EXPERT
  1143. depends on HAVE_PCSPKR_PLATFORM
  1144. select I8253_LOCK
  1145. default y
  1146. help
  1147. This option allows to disable the internal PC-Speaker
  1148. support, saving some memory.
  1149. config BASE_FULL
  1150. default y
  1151. bool "Enable full-sized data structures for core" if EXPERT
  1152. help
  1153. Disabling this option reduces the size of miscellaneous core
  1154. kernel data structures. This saves memory on small machines,
  1155. but may reduce performance.
  1156. config FUTEX
  1157. bool "Enable futex support" if EXPERT
  1158. default y
  1159. select RT_MUTEXES
  1160. help
  1161. Disabling this option will cause the kernel to be built without
  1162. support for "fast userspace mutexes". The resulting kernel may not
  1163. run glibc-based applications correctly.
  1164. config EPOLL
  1165. bool "Enable eventpoll support" if EXPERT
  1166. default y
  1167. select ANON_INODES
  1168. help
  1169. Disabling this option will cause the kernel to be built without
  1170. support for epoll family of system calls.
  1171. config SIGNALFD
  1172. bool "Enable signalfd() system call" if EXPERT
  1173. select ANON_INODES
  1174. default y
  1175. help
  1176. Enable the signalfd() system call that allows to receive signals
  1177. on a file descriptor.
  1178. If unsure, say Y.
  1179. config TIMERFD
  1180. bool "Enable timerfd() system call" if EXPERT
  1181. select ANON_INODES
  1182. default y
  1183. help
  1184. Enable the timerfd() system call that allows to receive timer
  1185. events on a file descriptor.
  1186. If unsure, say Y.
  1187. config EVENTFD
  1188. bool "Enable eventfd() system call" if EXPERT
  1189. select ANON_INODES
  1190. default y
  1191. help
  1192. Enable the eventfd() system call that allows to receive both
  1193. kernel notification (ie. KAIO) or userspace notifications.
  1194. If unsure, say Y.
  1195. config SHMEM
  1196. bool "Use full shmem filesystem" if EXPERT
  1197. default y
  1198. depends on MMU
  1199. help
  1200. The shmem is an internal filesystem used to manage shared memory.
  1201. It is backed by swap and manages resource limits. It is also exported
  1202. to userspace as tmpfs if TMPFS is enabled. Disabling this
  1203. option replaces shmem and tmpfs with the much simpler ramfs code,
  1204. which may be appropriate on small systems without swap.
  1205. config AIO
  1206. bool "Enable AIO support" if EXPERT
  1207. default y
  1208. help
  1209. This option enables POSIX asynchronous I/O which may by used
  1210. by some high performance threaded applications. Disabling
  1211. this option saves about 7k.
  1212. config PCI_QUIRKS
  1213. default y
  1214. bool "Enable PCI quirk workarounds" if EXPERT
  1215. depends on PCI
  1216. help
  1217. This enables workarounds for various PCI chipset
  1218. bugs/quirks. Disable this only if your target machine is
  1219. unaffected by PCI quirks.
  1220. config EMBEDDED
  1221. bool "Embedded system"
  1222. select EXPERT
  1223. help
  1224. This option should be enabled if compiling the kernel for
  1225. an embedded system so certain expert options are available
  1226. for configuration.
  1227. config HAVE_PERF_EVENTS
  1228. bool
  1229. help
  1230. See tools/perf/design.txt for details.
  1231. config PERF_USE_VMALLOC
  1232. bool
  1233. help
  1234. See tools/perf/design.txt for details
  1235. menu "Kernel Performance Events And Counters"
  1236. config PERF_EVENTS
  1237. bool "Kernel performance events and counters"
  1238. default y if PROFILING
  1239. depends on HAVE_PERF_EVENTS
  1240. select ANON_INODES
  1241. select IRQ_WORK
  1242. help
  1243. Enable kernel support for various performance events provided
  1244. by software and hardware.
  1245. Software events are supported either built-in or via the
  1246. use of generic tracepoints.
  1247. Most modern CPUs support performance events via performance
  1248. counter registers. These registers count the number of certain
  1249. types of hw events: such as instructions executed, cachemisses
  1250. suffered, or branches mis-predicted - without slowing down the
  1251. kernel or applications. These registers can also trigger interrupts
  1252. when a threshold number of events have passed - and can thus be
  1253. used to profile the code that runs on that CPU.
  1254. The Linux Performance Event subsystem provides an abstraction of
  1255. these software and hardware event capabilities, available via a
  1256. system call and used by the "perf" utility in tools/perf/. It
  1257. provides per task and per CPU counters, and it provides event
  1258. capabilities on top of those.
  1259. Say Y if unsure.
  1260. config DEBUG_PERF_USE_VMALLOC
  1261. default n
  1262. bool "Debug: use vmalloc to back perf mmap() buffers"
  1263. depends on PERF_EVENTS && DEBUG_KERNEL
  1264. select PERF_USE_VMALLOC
  1265. help
  1266. Use vmalloc memory to back perf mmap() buffers.
  1267. Mostly useful for debugging the vmalloc code on platforms
  1268. that don't require it.
  1269. Say N if unsure.
  1270. endmenu
  1271. config VM_EVENT_COUNTERS
  1272. default y
  1273. bool "Enable VM event counters for /proc/vmstat" if EXPERT
  1274. help
  1275. VM event counters are needed for event counts to be shown.
  1276. This option allows the disabling of the VM event counters
  1277. on EXPERT systems. /proc/vmstat will only show page counts
  1278. if VM event counters are disabled.
  1279. config SLUB_DEBUG
  1280. default y
  1281. bool "Enable SLUB debugging support" if EXPERT
  1282. depends on SLUB && SYSFS
  1283. help
  1284. SLUB has extensive debug support features. Disabling these can
  1285. result in significant savings in code size. This also disables
  1286. SLUB sysfs support. /sys/slab will not exist and there will be
  1287. no support for cache validation etc.
  1288. config COMPAT_BRK
  1289. bool "Disable heap randomization"
  1290. default y
  1291. help
  1292. Randomizing heap placement makes heap exploits harder, but it
  1293. also breaks ancient binaries (including anything libc5 based).
  1294. This option changes the bootup default to heap randomization
  1295. disabled, and can be overridden at runtime by setting
  1296. /proc/sys/kernel/randomize_va_space to 2.
  1297. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  1298. choice
  1299. prompt "Choose SLAB allocator"
  1300. default SLUB
  1301. help
  1302. This option allows to select a slab allocator.
  1303. config SLAB
  1304. bool "SLAB"
  1305. help
  1306. The regular slab allocator that is established and known to work
  1307. well in all environments. It organizes cache hot objects in
  1308. per cpu and per node queues.
  1309. config SLUB
  1310. bool "SLUB (Unqueued Allocator)"
  1311. help
  1312. SLUB is a slab allocator that minimizes cache line usage
  1313. instead of managing queues of cached objects (SLAB approach).
  1314. Per cpu caching is realized using slabs of objects instead
  1315. of queues of objects. SLUB can use memory efficiently
  1316. and has enhanced diagnostics. SLUB is the default choice for
  1317. a slab allocator.
  1318. config SLOB
  1319. depends on EXPERT
  1320. bool "SLOB (Simple Allocator)"
  1321. help
  1322. SLOB replaces the stock allocator with a drastically simpler
  1323. allocator. SLOB is generally more space efficient but
  1324. does not perform as well on large systems.
  1325. endchoice
  1326. config MMAP_ALLOW_UNINITIALIZED
  1327. bool "Allow mmapped anonymous memory to be uninitialized"
  1328. depends on EXPERT && !MMU
  1329. default n
  1330. help
  1331. Normally, and according to the Linux spec, anonymous memory obtained
  1332. from mmap() has it's contents cleared before it is passed to
  1333. userspace. Enabling this config option allows you to request that
  1334. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  1335. providing a huge performance boost. If this option is not enabled,
  1336. then the flag will be ignored.
  1337. This is taken advantage of by uClibc's malloc(), and also by
  1338. ELF-FDPIC binfmt's brk and stack allocator.
  1339. Because of the obvious security issues, this option should only be
  1340. enabled on embedded devices where you control what is run in
  1341. userspace. Since that isn't generally a problem on no-MMU systems,
  1342. it is normally safe to say Y here.
  1343. See Documentation/nommu-mmap.txt for more information.
  1344. config PROFILING
  1345. bool "Profiling support"
  1346. help
  1347. Say Y here to enable the extended profiling support mechanisms used
  1348. by profilers such as OProfile.
  1349. #
  1350. # Place an empty function call at each tracepoint site. Can be
  1351. # dynamically changed for a probe function.
  1352. #
  1353. config TRACEPOINTS
  1354. bool
  1355. source "arch/Kconfig"
  1356. endmenu # General setup
  1357. config HAVE_GENERIC_DMA_COHERENT
  1358. bool
  1359. default n
  1360. config SLABINFO
  1361. bool
  1362. depends on PROC_FS
  1363. depends on SLAB || SLUB_DEBUG
  1364. default y
  1365. config RT_MUTEXES
  1366. boolean
  1367. config BASE_SMALL
  1368. int
  1369. default 0 if BASE_FULL
  1370. default 1 if !BASE_FULL
  1371. menuconfig MODULES
  1372. bool "Enable loadable module support"
  1373. help
  1374. Kernel modules are small pieces of compiled code which can
  1375. be inserted in the running kernel, rather than being
  1376. permanently built into the kernel. You use the "modprobe"
  1377. tool to add (and sometimes remove) them. If you say Y here,
  1378. many parts of the kernel can be built as modules (by
  1379. answering M instead of Y where indicated): this is most
  1380. useful for infrequently used options which are not required
  1381. for booting. For more information, see the man pages for
  1382. modprobe, lsmod, modinfo, insmod and rmmod.
  1383. If you say Y here, you will need to run "make
  1384. modules_install" to put the modules under /lib/modules/
  1385. where modprobe can find them (you may need to be root to do
  1386. this).
  1387. If unsure, say Y.
  1388. if MODULES
  1389. config MODULE_FORCE_LOAD
  1390. bool "Forced module loading"
  1391. default n
  1392. help
  1393. Allow loading of modules without version information (ie. modprobe
  1394. --force). Forced module loading sets the 'F' (forced) taint flag and
  1395. is usually a really bad idea.
  1396. config MODULE_UNLOAD
  1397. bool "Module unloading"
  1398. help
  1399. Without this option you will not be able to unload any
  1400. modules (note that some modules may not be unloadable
  1401. anyway), which makes your kernel smaller, faster
  1402. and simpler. If unsure, say Y.
  1403. config MODULE_FORCE_UNLOAD
  1404. bool "Forced module unloading"
  1405. depends on MODULE_UNLOAD
  1406. help
  1407. This option allows you to force a module to unload, even if the
  1408. kernel believes it is unsafe: the kernel will remove the module
  1409. without waiting for anyone to stop using it (using the -f option to
  1410. rmmod). This is mainly for kernel developers and desperate users.
  1411. If unsure, say N.
  1412. config MODVERSIONS
  1413. bool "Module versioning support"
  1414. help
  1415. Usually, you have to use modules compiled with your kernel.
  1416. Saying Y here makes it sometimes possible to use modules
  1417. compiled for different kernels, by adding enough information
  1418. to the modules to (hopefully) spot any changes which would
  1419. make them incompatible with the kernel you are running. If
  1420. unsure, say N.
  1421. config MODULE_SRCVERSION_ALL
  1422. bool "Source checksum for all modules"
  1423. help
  1424. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1425. field inserted into their modinfo section, which contains a
  1426. sum of the source files which made it. This helps maintainers
  1427. see exactly which source was used to build a module (since
  1428. others sometimes change the module source without updating
  1429. the version). With this option, such a "srcversion" field
  1430. will be created for all modules. If unsure, say N.
  1431. config MODULE_SIG
  1432. bool "Module signature verification"
  1433. depends on MODULES
  1434. select KEYS
  1435. select CRYPTO
  1436. select ASYMMETRIC_KEY_TYPE
  1437. select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  1438. select PUBLIC_KEY_ALGO_RSA
  1439. select ASN1
  1440. select OID_REGISTRY
  1441. select X509_CERTIFICATE_PARSER
  1442. help
  1443. Check modules for valid signatures upon load: the signature
  1444. is simply appended to the module. For more information see
  1445. Documentation/module-signing.txt.
  1446. !!!WARNING!!! If you enable this option, you MUST make sure that the
  1447. module DOES NOT get stripped after being signed. This includes the
  1448. debuginfo strip done by some packagers (such as rpmbuild) and
  1449. inclusion into an initramfs that wants the module size reduced.
  1450. config MODULE_SIG_FORCE
  1451. bool "Require modules to be validly signed"
  1452. depends on MODULE_SIG
  1453. help
  1454. Reject unsigned modules or signed modules for which we don't have a
  1455. key. Without this, such modules will simply taint the kernel.
  1456. config MODULE_SIG_ALL
  1457. bool "Automatically sign all modules"
  1458. default y
  1459. depends on MODULE_SIG
  1460. help
  1461. Sign all modules during make modules_install. Without this option,
  1462. modules must be signed manually, using the scripts/sign-file tool.
  1463. comment "Do not forget to sign required modules with scripts/sign-file"
  1464. depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
  1465. choice
  1466. prompt "Which hash algorithm should modules be signed with?"
  1467. depends on MODULE_SIG
  1468. help
  1469. This determines which sort of hashing algorithm will be used during
  1470. signature generation. This algorithm _must_ be built into the kernel
  1471. directly so that signature verification can take place. It is not
  1472. possible to load a signed module containing the algorithm to check
  1473. the signature on that module.
  1474. config MODULE_SIG_SHA1
  1475. bool "Sign modules with SHA-1"
  1476. select CRYPTO_SHA1
  1477. config MODULE_SIG_SHA224
  1478. bool "Sign modules with SHA-224"
  1479. select CRYPTO_SHA256
  1480. config MODULE_SIG_SHA256
  1481. bool "Sign modules with SHA-256"
  1482. select CRYPTO_SHA256
  1483. config MODULE_SIG_SHA384
  1484. bool "Sign modules with SHA-384"
  1485. select CRYPTO_SHA512
  1486. config MODULE_SIG_SHA512
  1487. bool "Sign modules with SHA-512"
  1488. select CRYPTO_SHA512
  1489. endchoice
  1490. config MODULE_SIG_HASH
  1491. string
  1492. depends on MODULE_SIG
  1493. default "sha1" if MODULE_SIG_SHA1
  1494. default "sha224" if MODULE_SIG_SHA224
  1495. default "sha256" if MODULE_SIG_SHA256
  1496. default "sha384" if MODULE_SIG_SHA384
  1497. default "sha512" if MODULE_SIG_SHA512
  1498. endif # MODULES
  1499. config INIT_ALL_POSSIBLE
  1500. bool
  1501. help
  1502. Back when each arch used to define their own cpu_online_mask and
  1503. cpu_possible_mask, some of them chose to initialize cpu_possible_mask
  1504. with all 1s, and others with all 0s. When they were centralised,
  1505. it was better to provide this option than to break all the archs
  1506. and have several arch maintainers pursuing me down dark alleys.
  1507. config STOP_MACHINE
  1508. bool
  1509. default y
  1510. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1511. help
  1512. Need stop_machine() primitive.
  1513. source "block/Kconfig"
  1514. config PREEMPT_NOTIFIERS
  1515. bool
  1516. config PADATA
  1517. depends on SMP
  1518. bool
  1519. # Can be selected by architectures with broken toolchains
  1520. # that get confused by correct const<->read_only section
  1521. # mappings
  1522. config BROKEN_RODATA
  1523. bool
  1524. config ASN1
  1525. tristate
  1526. help
  1527. Build a simple ASN.1 grammar compiler that produces a bytecode output
  1528. that can be interpreted by the ASN.1 stream decoder and used to
  1529. inform it as to what tags are to be expected in a stream and what
  1530. functions to call on what tags.
  1531. source "kernel/Kconfig.locks"