Kconfig 60 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. config HAVE_KERNEL_LZ4
  91. bool
  92. choice
  93. prompt "Kernel compression mode"
  94. default KERNEL_GZIP
  95. depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
  96. help
  97. The linux kernel is a kind of self-extracting executable.
  98. Several compression algorithms are available, which differ
  99. in efficiency, compression and decompression speed.
  100. Compression speed is only relevant when building a kernel.
  101. Decompression speed is relevant at each boot.
  102. If you have any problems with bzip2 or lzma compressed
  103. kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
  104. version of this functionality (bzip2 only), for 2.4, was
  105. supplied by Christian Ludwig)
  106. High compression options are mostly useful for users, who
  107. are low on disk space (embedded systems), but for whom ram
  108. size matters less.
  109. If in doubt, select 'gzip'
  110. config KERNEL_GZIP
  111. bool "Gzip"
  112. depends on HAVE_KERNEL_GZIP
  113. help
  114. The old and tried gzip compression. It provides a good balance
  115. between compression ratio and decompression speed.
  116. config KERNEL_BZIP2
  117. bool "Bzip2"
  118. depends on HAVE_KERNEL_BZIP2
  119. help
  120. Its compression ratio and speed is intermediate.
  121. Decompression speed is slowest among the choices. The kernel
  122. size is about 10% smaller with bzip2, in comparison to gzip.
  123. Bzip2 uses a large amount of memory. For modern kernels you
  124. will need at least 8MB RAM or more for booting.
  125. config KERNEL_LZMA
  126. bool "LZMA"
  127. depends on HAVE_KERNEL_LZMA
  128. help
  129. This compression algorithm's ratio is best. Decompression speed
  130. is between gzip and bzip2. Compression is slowest.
  131. The kernel size is about 33% smaller with LZMA in comparison to gzip.
  132. config KERNEL_XZ
  133. bool "XZ"
  134. depends on HAVE_KERNEL_XZ
  135. help
  136. XZ uses the LZMA2 algorithm and instruction set specific
  137. BCJ filters which can improve compression ratio of executable
  138. code. The size of the kernel is about 30% smaller with XZ in
  139. comparison to gzip. On architectures for which there is a BCJ
  140. filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
  141. will create a few percent smaller kernel than plain LZMA.
  142. The speed is about the same as with LZMA: The decompression
  143. speed of XZ is better than that of bzip2 but worse than gzip
  144. and LZO. Compression is slow.
  145. config KERNEL_LZO
  146. bool "LZO"
  147. depends on HAVE_KERNEL_LZO
  148. help
  149. Its compression ratio is the poorest among the choices. The kernel
  150. size is about 10% bigger than gzip; however its speed
  151. (both compression and decompression) is the fastest.
  152. config KERNEL_LZ4
  153. bool "LZ4"
  154. depends on HAVE_KERNEL_LZ4
  155. help
  156. LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
  157. A preliminary version of LZ4 de/compression tool is available at
  158. <https://code.google.com/p/lz4/>.
  159. Its compression ratio is worse than LZO. The size of the kernel
  160. is about 8% bigger than LZO. But the decompression speed is
  161. faster than LZO.
  162. endchoice
  163. config DEFAULT_HOSTNAME
  164. string "Default hostname"
  165. default "(none)"
  166. help
  167. This option determines the default system hostname before userspace
  168. calls sethostname(2). The kernel traditionally uses "(none)" here,
  169. but you may wish to use a different default here to make a minimal
  170. system more usable with less configuration.
  171. config SWAP
  172. bool "Support for paging of anonymous memory (swap)"
  173. depends on MMU && BLOCK
  174. default y
  175. help
  176. This option allows you to choose whether you want to have support
  177. for so called swap devices or swap files in your kernel that are
  178. used to provide more virtual memory than the actual RAM present
  179. in your computer. If unsure say Y.
  180. config SYSVIPC
  181. bool "System V IPC"
  182. ---help---
  183. Inter Process Communication is a suite of library functions and
  184. system calls which let processes (running programs) synchronize and
  185. exchange information. It is generally considered to be a good thing,
  186. and some programs won't run unless you say Y here. In particular, if
  187. you want to run the DOS emulator dosemu under Linux (read the
  188. DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
  189. you'll need to say Y here.
  190. You can find documentation about IPC with "info ipc" and also in
  191. section 6.4 of the Linux Programmer's Guide, available from
  192. <http://www.tldp.org/guides.html>.
  193. config SYSVIPC_SYSCTL
  194. bool
  195. depends on SYSVIPC
  196. depends on SYSCTL
  197. default y
  198. config POSIX_MQUEUE
  199. bool "POSIX Message Queues"
  200. depends on NET
  201. ---help---
  202. POSIX variant of message queues is a part of IPC. In POSIX message
  203. queues every message has a priority which decides about succession
  204. of receiving it by a process. If you want to compile and run
  205. programs written e.g. for Solaris with use of its POSIX message
  206. queues (functions mq_*) say Y here.
  207. POSIX message queues are visible as a filesystem called 'mqueue'
  208. and can be mounted somewhere if you want to do filesystem
  209. operations on message queues.
  210. If unsure, say Y.
  211. config POSIX_MQUEUE_SYSCTL
  212. bool
  213. depends on POSIX_MQUEUE
  214. depends on SYSCTL
  215. default y
  216. config FHANDLE
  217. bool "open by fhandle syscalls"
  218. select EXPORTFS
  219. help
  220. If you say Y here, a user level program will be able to map
  221. file names to handle and then later use the handle for
  222. different file system operations. This is useful in implementing
  223. userspace file servers, which now track files using handles instead
  224. of names. The handle would remain the same even if file names
  225. get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
  226. syscalls.
  227. config AUDIT
  228. bool "Auditing support"
  229. depends on NET
  230. help
  231. Enable auditing infrastructure that can be used with another
  232. kernel subsystem, such as SELinux (which requires this for
  233. logging of avc messages output). Does not do system-call
  234. auditing without CONFIG_AUDITSYSCALL.
  235. config AUDITSYSCALL
  236. bool "Enable system-call auditing support"
  237. depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
  238. default y if SECURITY_SELINUX
  239. help
  240. Enable low-overhead system-call auditing infrastructure that
  241. can be used independently or with another kernel subsystem,
  242. such as SELinux.
  243. config AUDIT_WATCH
  244. def_bool y
  245. depends on AUDITSYSCALL
  246. select FSNOTIFY
  247. config AUDIT_TREE
  248. def_bool y
  249. depends on AUDITSYSCALL
  250. select FSNOTIFY
  251. config AUDIT_LOGINUID_IMMUTABLE
  252. bool "Make audit loginuid immutable"
  253. depends on AUDIT
  254. help
  255. The config option toggles if a task setting its loginuid requires
  256. CAP_SYS_AUDITCONTROL or if that task should require no special permissions
  257. but should instead only allow setting its loginuid if it was never
  258. previously set. On systems which use systemd or a similar central
  259. process to restart login services this should be set to true. On older
  260. systems in which an admin would typically have to directly stop and
  261. start processes this should be set to false. Setting this to true allows
  262. one to drop potentially dangerous capabilites from the login tasks,
  263. but may not be backwards compatible with older init systems.
  264. source "kernel/irq/Kconfig"
  265. source "kernel/time/Kconfig"
  266. menu "CPU/Task time and stats accounting"
  267. config VIRT_CPU_ACCOUNTING
  268. bool
  269. choice
  270. prompt "Cputime accounting"
  271. default TICK_CPU_ACCOUNTING if !PPC64
  272. default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
  273. # Kind of a stub config for the pure tick based cputime accounting
  274. config TICK_CPU_ACCOUNTING
  275. bool "Simple tick based cputime accounting"
  276. depends on !S390 && !NO_HZ_FULL
  277. help
  278. This is the basic tick based cputime accounting that maintains
  279. statistics about user, system and idle time spent on per jiffies
  280. granularity.
  281. If unsure, say Y.
  282. config VIRT_CPU_ACCOUNTING_NATIVE
  283. bool "Deterministic task and CPU time accounting"
  284. depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
  285. select VIRT_CPU_ACCOUNTING
  286. help
  287. Select this option to enable more accurate task and CPU time
  288. accounting. This is done by reading a CPU counter on each
  289. kernel entry and exit and on transitions within the kernel
  290. between system, softirq and hardirq state, so there is a
  291. small performance impact. In the case of s390 or IBM POWER > 5,
  292. this also enables accounting of stolen time on logically-partitioned
  293. systems.
  294. config VIRT_CPU_ACCOUNTING_GEN
  295. bool "Full dynticks CPU time accounting"
  296. depends on HAVE_CONTEXT_TRACKING && 64BIT
  297. select VIRT_CPU_ACCOUNTING
  298. select CONTEXT_TRACKING
  299. help
  300. Select this option to enable task and CPU time accounting on full
  301. dynticks systems. This accounting is implemented by watching every
  302. kernel-user boundaries using the context tracking subsystem.
  303. The accounting is thus performed at the expense of some significant
  304. overhead.
  305. For now this is only useful if you are working on the full
  306. dynticks subsystem development.
  307. If unsure, say N.
  308. config IRQ_TIME_ACCOUNTING
  309. bool "Fine granularity task level IRQ time accounting"
  310. depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
  311. help
  312. Select this option to enable fine granularity task irq time
  313. accounting. This is done by reading a timestamp on each
  314. transitions between softirq and hardirq state, so there can be a
  315. small performance impact.
  316. If in doubt, say N here.
  317. endchoice
  318. config BSD_PROCESS_ACCT
  319. bool "BSD Process Accounting"
  320. help
  321. If you say Y here, a user level program will be able to instruct the
  322. kernel (via a special system call) to write process accounting
  323. information to a file: whenever a process exits, information about
  324. that process will be appended to the file by the kernel. The
  325. information includes things such as creation time, owning user,
  326. command name, memory usage, controlling terminal etc. (the complete
  327. list is in the struct acct in <file:include/linux/acct.h>). It is
  328. up to the user level program to do useful things with this
  329. information. This is generally a good idea, so say Y.
  330. config BSD_PROCESS_ACCT_V3
  331. bool "BSD Process Accounting version 3 file format"
  332. depends on BSD_PROCESS_ACCT
  333. default n
  334. help
  335. If you say Y here, the process accounting information is written
  336. in a new file format that also logs the process IDs of each
  337. process and it's parent. Note that this file format is incompatible
  338. with previous v0/v1/v2 file formats, so you will need updated tools
  339. for processing it. A preliminary version of these tools is available
  340. at <http://www.gnu.org/software/acct/>.
  341. config TASKSTATS
  342. bool "Export task/process statistics through netlink"
  343. depends on NET
  344. default n
  345. help
  346. Export selected statistics for tasks/processes through the
  347. generic netlink interface. Unlike BSD process accounting, the
  348. statistics are available during the lifetime of tasks/processes as
  349. responses to commands. Like BSD accounting, they are sent to user
  350. space on task exit.
  351. Say N if unsure.
  352. config TASK_DELAY_ACCT
  353. bool "Enable per-task delay accounting"
  354. depends on TASKSTATS
  355. help
  356. Collect information on time spent by a task waiting for system
  357. resources like cpu, synchronous block I/O completion and swapping
  358. in pages. Such statistics can help in setting a task's priorities
  359. relative to other tasks for cpu, io, rss limits etc.
  360. Say N if unsure.
  361. config TASK_XACCT
  362. bool "Enable extended accounting over taskstats"
  363. depends on TASKSTATS
  364. help
  365. Collect extended task accounting data and send the data
  366. to userland for processing over the taskstats interface.
  367. Say N if unsure.
  368. config TASK_IO_ACCOUNTING
  369. bool "Enable per-task storage I/O accounting"
  370. depends on TASK_XACCT
  371. help
  372. Collect information on the number of bytes of storage I/O which this
  373. task has caused.
  374. Say N if unsure.
  375. endmenu # "CPU/Task time and stats accounting"
  376. menu "RCU Subsystem"
  377. choice
  378. prompt "RCU Implementation"
  379. default TREE_RCU
  380. config TREE_RCU
  381. bool "Tree-based hierarchical RCU"
  382. depends on !PREEMPT && SMP
  383. select IRQ_WORK
  384. help
  385. This option selects the RCU implementation that is
  386. designed for very large SMP system with hundreds or
  387. thousands of CPUs. It also scales down nicely to
  388. smaller systems.
  389. config TREE_PREEMPT_RCU
  390. bool "Preemptible tree-based hierarchical RCU"
  391. depends on PREEMPT
  392. help
  393. This option selects the RCU implementation that is
  394. designed for very large SMP systems with hundreds or
  395. thousands of CPUs, but for which real-time response
  396. is also required. It also scales down nicely to
  397. smaller systems.
  398. Select this option if you are unsure.
  399. config TINY_RCU
  400. bool "UP-only small-memory-footprint RCU"
  401. depends on !PREEMPT && !SMP
  402. help
  403. This option selects the RCU implementation that is
  404. designed for UP systems from which real-time response
  405. is not required. This option greatly reduces the
  406. memory footprint of RCU.
  407. endchoice
  408. config PREEMPT_RCU
  409. def_bool TREE_PREEMPT_RCU
  410. help
  411. This option enables preemptible-RCU code that is common between
  412. the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
  413. config RCU_STALL_COMMON
  414. def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
  415. help
  416. This option enables RCU CPU stall code that is common between
  417. the TINY and TREE variants of RCU. The purpose is to allow
  418. the tiny variants to disable RCU CPU stall warnings, while
  419. making these warnings mandatory for the tree variants.
  420. config CONTEXT_TRACKING
  421. bool
  422. config RCU_USER_QS
  423. bool "Consider userspace as in RCU extended quiescent state"
  424. depends on HAVE_CONTEXT_TRACKING && SMP
  425. select CONTEXT_TRACKING
  426. help
  427. This option sets hooks on kernel / userspace boundaries and
  428. puts RCU in extended quiescent state when the CPU runs in
  429. userspace. It means that when a CPU runs in userspace, it is
  430. excluded from the global RCU state machine and thus doesn't
  431. try to keep the timer tick on for RCU.
  432. Unless you want to hack and help the development of the full
  433. dynticks mode, you shouldn't enable this option. It also
  434. adds unnecessary overhead.
  435. If unsure say N
  436. config CONTEXT_TRACKING_FORCE
  437. bool "Force context tracking"
  438. depends on CONTEXT_TRACKING
  439. default y if !NO_HZ_FULL
  440. help
  441. The major pre-requirement for full dynticks to work is to
  442. support the context tracking subsystem. But there are also
  443. other dependencies to provide in order to make the full
  444. dynticks working.
  445. This option stands for testing when an arch implements the
  446. context tracking backend but doesn't yet fullfill all the
  447. requirements to make the full dynticks feature working.
  448. Without the full dynticks, there is no way to test the support
  449. for context tracking and the subsystems that rely on it: RCU
  450. userspace extended quiescent state and tickless cputime
  451. accounting. This option copes with the absence of the full
  452. dynticks subsystem by forcing the context tracking on all
  453. CPUs in the system.
  454. Say Y only if you're working on the developpement of an
  455. architecture backend for the context tracking.
  456. Say N otherwise, this option brings an overhead that you
  457. don't want in production.
  458. config RCU_FANOUT
  459. int "Tree-based hierarchical RCU fanout value"
  460. range 2 64 if 64BIT
  461. range 2 32 if !64BIT
  462. depends on TREE_RCU || TREE_PREEMPT_RCU
  463. default 64 if 64BIT
  464. default 32 if !64BIT
  465. help
  466. This option controls the fanout of hierarchical implementations
  467. of RCU, allowing RCU to work efficiently on machines with
  468. large numbers of CPUs. This value must be at least the fourth
  469. root of NR_CPUS, which allows NR_CPUS to be insanely large.
  470. The default value of RCU_FANOUT should be used for production
  471. systems, but if you are stress-testing the RCU implementation
  472. itself, small RCU_FANOUT values allow you to test large-system
  473. code paths on small(er) systems.
  474. Select a specific number if testing RCU itself.
  475. Take the default if unsure.
  476. config RCU_FANOUT_LEAF
  477. int "Tree-based hierarchical RCU leaf-level fanout value"
  478. range 2 RCU_FANOUT if 64BIT
  479. range 2 RCU_FANOUT if !64BIT
  480. depends on TREE_RCU || TREE_PREEMPT_RCU
  481. default 16
  482. help
  483. This option controls the leaf-level fanout of hierarchical
  484. implementations of RCU, and allows trading off cache misses
  485. against lock contention. Systems that synchronize their
  486. scheduling-clock interrupts for energy-efficiency reasons will
  487. want the default because the smaller leaf-level fanout keeps
  488. lock contention levels acceptably low. Very large systems
  489. (hundreds or thousands of CPUs) will instead want to set this
  490. value to the maximum value possible in order to reduce the
  491. number of cache misses incurred during RCU's grace-period
  492. initialization. These systems tend to run CPU-bound, and thus
  493. are not helped by synchronized interrupts, and thus tend to
  494. skew them, which reduces lock contention enough that large
  495. leaf-level fanouts work well.
  496. Select a specific number if testing RCU itself.
  497. Select the maximum permissible value for large systems.
  498. Take the default if unsure.
  499. config RCU_FANOUT_EXACT
  500. bool "Disable tree-based hierarchical RCU auto-balancing"
  501. depends on TREE_RCU || TREE_PREEMPT_RCU
  502. default n
  503. help
  504. This option forces use of the exact RCU_FANOUT value specified,
  505. regardless of imbalances in the hierarchy. This is useful for
  506. testing RCU itself, and might one day be useful on systems with
  507. strong NUMA behavior.
  508. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  509. Say N if unsure.
  510. config RCU_FAST_NO_HZ
  511. bool "Accelerate last non-dyntick-idle CPU's grace periods"
  512. depends on NO_HZ_COMMON && SMP
  513. default n
  514. help
  515. This option permits CPUs to enter dynticks-idle state even if
  516. they have RCU callbacks queued, and prevents RCU from waking
  517. these CPUs up more than roughly once every four jiffies (by
  518. default, you can adjust this using the rcutree.rcu_idle_gp_delay
  519. parameter), thus improving energy efficiency. On the other
  520. hand, this option increases the duration of RCU grace periods,
  521. for example, slowing down synchronize_rcu().
  522. Say Y if energy efficiency is critically important, and you
  523. don't care about increased grace-period durations.
  524. Say N if you are unsure.
  525. config TREE_RCU_TRACE
  526. def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
  527. select DEBUG_FS
  528. help
  529. This option provides tracing for the TREE_RCU and
  530. TREE_PREEMPT_RCU implementations, permitting Makefile to
  531. trivially select kernel/rcutree_trace.c.
  532. config RCU_BOOST
  533. bool "Enable RCU priority boosting"
  534. depends on RT_MUTEXES && PREEMPT_RCU
  535. default n
  536. help
  537. This option boosts the priority of preempted RCU readers that
  538. block the current preemptible RCU grace period for too long.
  539. This option also prevents heavy loads from blocking RCU
  540. callback invocation for all flavors of RCU.
  541. Say Y here if you are working with real-time apps or heavy loads
  542. Say N here if you are unsure.
  543. config RCU_BOOST_PRIO
  544. int "Real-time priority to boost RCU readers to"
  545. range 1 99
  546. depends on RCU_BOOST
  547. default 1
  548. help
  549. This option specifies the real-time priority to which long-term
  550. preempted RCU readers are to be boosted. If you are working
  551. with a real-time application that has one or more CPU-bound
  552. threads running at a real-time priority level, you should set
  553. RCU_BOOST_PRIO to a priority higher then the highest-priority
  554. real-time CPU-bound thread. The default RCU_BOOST_PRIO value
  555. of 1 is appropriate in the common case, which is real-time
  556. applications that do not have any CPU-bound threads.
  557. Some real-time applications might not have a single real-time
  558. thread that saturates a given CPU, but instead might have
  559. multiple real-time threads that, taken together, fully utilize
  560. that CPU. In this case, you should set RCU_BOOST_PRIO to
  561. a priority higher than the lowest-priority thread that is
  562. conspiring to prevent the CPU from running any non-real-time
  563. tasks. For example, if one thread at priority 10 and another
  564. thread at priority 5 are between themselves fully consuming
  565. the CPU time on a given CPU, then RCU_BOOST_PRIO should be
  566. set to priority 6 or higher.
  567. Specify the real-time priority, or take the default if unsure.
  568. config RCU_BOOST_DELAY
  569. int "Milliseconds to delay boosting after RCU grace-period start"
  570. range 0 3000
  571. depends on RCU_BOOST
  572. default 500
  573. help
  574. This option specifies the time to wait after the beginning of
  575. a given grace period before priority-boosting preempted RCU
  576. readers blocking that grace period. Note that any RCU reader
  577. blocking an expedited RCU grace period is boosted immediately.
  578. Accept the default if unsure.
  579. config RCU_NOCB_CPU
  580. bool "Offload RCU callback processing from boot-selected CPUs"
  581. depends on TREE_RCU || TREE_PREEMPT_RCU
  582. default n
  583. help
  584. Use this option to reduce OS jitter for aggressive HPC or
  585. real-time workloads. It can also be used to offload RCU
  586. callback invocation to energy-efficient CPUs in battery-powered
  587. asymmetric multiprocessors.
  588. This option offloads callback invocation from the set of
  589. CPUs specified at boot time by the rcu_nocbs parameter.
  590. For each such CPU, a kthread ("rcuox/N") will be created to
  591. invoke callbacks, where the "N" is the CPU being offloaded,
  592. and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
  593. "s" for RCU-sched. Nothing prevents this kthread from running
  594. on the specified CPUs, but (1) the kthreads may be preempted
  595. between each callback, and (2) affinity or cgroups can be used
  596. to force the kthreads to run on whatever set of CPUs is desired.
  597. Say Y here if you want to help to debug reduced OS jitter.
  598. Say N here if you are unsure.
  599. choice
  600. prompt "Build-forced no-CBs CPUs"
  601. default RCU_NOCB_CPU_NONE
  602. help
  603. This option allows no-CBs CPUs (whose RCU callbacks are invoked
  604. from kthreads rather than from softirq context) to be specified
  605. at build time. Additional no-CBs CPUs may be specified by
  606. the rcu_nocbs= boot parameter.
  607. config RCU_NOCB_CPU_NONE
  608. bool "No build_forced no-CBs CPUs"
  609. depends on RCU_NOCB_CPU && !NO_HZ_FULL
  610. help
  611. This option does not force any of the CPUs to be no-CBs CPUs.
  612. Only CPUs designated by the rcu_nocbs= boot parameter will be
  613. no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
  614. kthreads whose names begin with "rcuo". All other CPUs will
  615. invoke their own RCU callbacks in softirq context.
  616. Select this option if you want to choose no-CBs CPUs at
  617. boot time, for example, to allow testing of different no-CBs
  618. configurations without having to rebuild the kernel each time.
  619. config RCU_NOCB_CPU_ZERO
  620. bool "CPU 0 is a build_forced no-CBs CPU"
  621. depends on RCU_NOCB_CPU && !NO_HZ_FULL
  622. help
  623. This option forces CPU 0 to be a no-CBs CPU, so that its RCU
  624. callbacks are invoked by a per-CPU kthread whose name begins
  625. with "rcuo". Additional CPUs may be designated as no-CBs
  626. CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
  627. All other CPUs will invoke their own RCU callbacks in softirq
  628. context.
  629. Select this if CPU 0 needs to be a no-CBs CPU for real-time
  630. or energy-efficiency reasons, but the real reason it exists
  631. is to ensure that randconfig testing covers mixed systems.
  632. config RCU_NOCB_CPU_ALL
  633. bool "All CPUs are build_forced no-CBs CPUs"
  634. depends on RCU_NOCB_CPU
  635. help
  636. This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
  637. boot parameter will be ignored. All CPUs' RCU callbacks will
  638. be executed in the context of per-CPU rcuo kthreads created for
  639. this purpose. Assuming that the kthreads whose names start with
  640. "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
  641. on the remaining CPUs, but might decrease memory locality during
  642. RCU-callback invocation, thus potentially degrading throughput.
  643. Select this if all CPUs need to be no-CBs CPUs for real-time
  644. or energy-efficiency reasons.
  645. endchoice
  646. endmenu # "RCU Subsystem"
  647. config IKCONFIG
  648. tristate "Kernel .config support"
  649. ---help---
  650. This option enables the complete Linux kernel ".config" file
  651. contents to be saved in the kernel. It provides documentation
  652. of which kernel options are used in a running kernel or in an
  653. on-disk kernel. This information can be extracted from the kernel
  654. image file with the script scripts/extract-ikconfig and used as
  655. input to rebuild the current kernel or to build another kernel.
  656. It can also be extracted from a running kernel by reading
  657. /proc/config.gz if enabled (below).
  658. config IKCONFIG_PROC
  659. bool "Enable access to .config through /proc/config.gz"
  660. depends on IKCONFIG && PROC_FS
  661. ---help---
  662. This option enables access to the kernel configuration file
  663. through /proc/config.gz.
  664. config LOG_BUF_SHIFT
  665. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  666. range 12 21
  667. default 17
  668. help
  669. Select kernel log buffer size as a power of 2.
  670. Examples:
  671. 17 => 128 KB
  672. 16 => 64 KB
  673. 15 => 32 KB
  674. 14 => 16 KB
  675. 13 => 8 KB
  676. 12 => 4 KB
  677. #
  678. # Architectures with an unreliable sched_clock() should select this:
  679. #
  680. config HAVE_UNSTABLE_SCHED_CLOCK
  681. bool
  682. config GENERIC_SCHED_CLOCK
  683. bool
  684. #
  685. # For architectures that want to enable the support for NUMA-affine scheduler
  686. # balancing logic:
  687. #
  688. config ARCH_SUPPORTS_NUMA_BALANCING
  689. bool
  690. # For architectures that (ab)use NUMA to represent different memory regions
  691. # all cpu-local but of different latencies, such as SuperH.
  692. #
  693. config ARCH_WANT_NUMA_VARIABLE_LOCALITY
  694. bool
  695. #
  696. # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
  697. config ARCH_WANTS_PROT_NUMA_PROT_NONE
  698. bool
  699. config ARCH_USES_NUMA_PROT_NONE
  700. bool
  701. default y
  702. depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
  703. depends on NUMA_BALANCING
  704. config NUMA_BALANCING_DEFAULT_ENABLED
  705. bool "Automatically enable NUMA aware memory/task placement"
  706. default y
  707. depends on NUMA_BALANCING
  708. help
  709. If set, autonumic NUMA balancing will be enabled if running on a NUMA
  710. machine.
  711. config NUMA_BALANCING
  712. bool "Memory placement aware NUMA scheduler"
  713. depends on ARCH_SUPPORTS_NUMA_BALANCING
  714. depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
  715. depends on SMP && NUMA && MIGRATION
  716. help
  717. This option adds support for automatic NUMA aware memory/task placement.
  718. The mechanism is quite primitive and is based on migrating memory when
  719. it is references to the node the task is running on.
  720. This system will be inactive on UMA systems.
  721. menuconfig CGROUPS
  722. boolean "Control Group support"
  723. depends on EVENTFD
  724. help
  725. This option adds support for grouping sets of processes together, for
  726. use with process control subsystems such as Cpusets, CFS, memory
  727. controls or device isolation.
  728. See
  729. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  730. - Documentation/cgroups/ (features for grouping, isolation
  731. and resource control)
  732. Say N if unsure.
  733. if CGROUPS
  734. config CGROUP_DEBUG
  735. bool "Example debug cgroup subsystem"
  736. default n
  737. help
  738. This option enables a simple cgroup subsystem that
  739. exports useful debugging information about the cgroups
  740. framework.
  741. Say N if unsure.
  742. config CGROUP_FREEZER
  743. bool "Freezer cgroup subsystem"
  744. help
  745. Provides a way to freeze and unfreeze all tasks in a
  746. cgroup.
  747. config CGROUP_DEVICE
  748. bool "Device controller for cgroups"
  749. help
  750. Provides a cgroup implementing whitelists for devices which
  751. a process in the cgroup can mknod or open.
  752. config CPUSETS
  753. bool "Cpuset support"
  754. help
  755. This option will let you create and manage CPUSETs which
  756. allow dynamically partitioning a system into sets of CPUs and
  757. Memory Nodes and assigning tasks to run only within those sets.
  758. This is primarily useful on large SMP or NUMA systems.
  759. Say N if unsure.
  760. config PROC_PID_CPUSET
  761. bool "Include legacy /proc/<pid>/cpuset file"
  762. depends on CPUSETS
  763. default y
  764. config CGROUP_CPUACCT
  765. bool "Simple CPU accounting cgroup subsystem"
  766. help
  767. Provides a simple Resource Controller for monitoring the
  768. total CPU consumed by the tasks in a cgroup.
  769. config RESOURCE_COUNTERS
  770. bool "Resource counters"
  771. help
  772. This option enables controller independent resource accounting
  773. infrastructure that works with cgroups.
  774. config MEMCG
  775. bool "Memory Resource Controller for Control Groups"
  776. depends on RESOURCE_COUNTERS
  777. select MM_OWNER
  778. help
  779. Provides a memory resource controller that manages both anonymous
  780. memory and page cache. (See Documentation/cgroups/memory.txt)
  781. Note that setting this option increases fixed memory overhead
  782. associated with each page of memory in the system. By this,
  783. 8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  784. usage tracking struct at boot. Total amount of this is printed out
  785. at boot.
  786. Only enable when you're ok with these trade offs and really
  787. sure you need the memory resource controller. Even when you enable
  788. this, you can set "cgroup_disable=memory" at your boot option to
  789. disable memory resource controller and you can avoid overheads.
  790. (and lose benefits of memory resource controller)
  791. This config option also selects MM_OWNER config option, which
  792. could in turn add some fork/exit overhead.
  793. config MEMCG_SWAP
  794. bool "Memory Resource Controller Swap Extension"
  795. depends on MEMCG && SWAP
  796. help
  797. Add swap management feature to memory resource controller. When you
  798. enable this, you can limit mem+swap usage per cgroup. In other words,
  799. when you disable this, memory resource controller has no cares to
  800. usage of swap...a process can exhaust all of the swap. This extension
  801. is useful when you want to avoid exhaustion swap but this itself
  802. adds more overheads and consumes memory for remembering information.
  803. Especially if you use 32bit system or small memory system, please
  804. be careful about enabling this. When memory resource controller
  805. is disabled by boot option, this will be automatically disabled and
  806. there will be no overhead from this. Even when you set this config=y,
  807. if boot option "swapaccount=0" is set, swap will not be accounted.
  808. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  809. size is 4096bytes, 512k per 1Gbytes of swap.
  810. config MEMCG_SWAP_ENABLED
  811. bool "Memory Resource Controller Swap Extension enabled by default"
  812. depends on MEMCG_SWAP
  813. default y
  814. help
  815. Memory Resource Controller Swap Extension comes with its price in
  816. a bigger memory consumption. General purpose distribution kernels
  817. which want to enable the feature but keep it disabled by default
  818. and let the user enable it by swapaccount boot command line
  819. parameter should have this option unselected.
  820. For those who want to have the feature enabled by default should
  821. select this option (if, for some reason, they need to disable it
  822. then swapaccount=0 does the trick).
  823. config MEMCG_KMEM
  824. bool "Memory Resource Controller Kernel Memory accounting"
  825. depends on MEMCG
  826. depends on SLUB || SLAB
  827. help
  828. The Kernel Memory extension for Memory Resource Controller can limit
  829. the amount of memory used by kernel objects in the system. Those are
  830. fundamentally different from the entities handled by the standard
  831. Memory Controller, which are page-based, and can be swapped. Users of
  832. the kmem extension can use it to guarantee that no group of processes
  833. will ever exhaust kernel resources alone.
  834. config CGROUP_HUGETLB
  835. bool "HugeTLB Resource Controller for Control Groups"
  836. depends on RESOURCE_COUNTERS && HUGETLB_PAGE
  837. default n
  838. help
  839. Provides a cgroup Resource Controller for HugeTLB pages.
  840. When you enable this, you can put a per cgroup limit on HugeTLB usage.
  841. The limit is enforced during page fault. Since HugeTLB doesn't
  842. support page reclaim, enforcing the limit at page fault time implies
  843. that, the application will get SIGBUS signal if it tries to access
  844. HugeTLB pages beyond its limit. This requires the application to know
  845. beforehand how much HugeTLB pages it would require for its use. The
  846. control group is tracked in the third page lru pointer. This means
  847. that we cannot use the controller with huge page less than 3 pages.
  848. config CGROUP_PERF
  849. bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
  850. depends on PERF_EVENTS && CGROUPS
  851. help
  852. This option extends the per-cpu mode to restrict monitoring to
  853. threads which belong to the cgroup specified and run on the
  854. designated cpu.
  855. Say N if unsure.
  856. menuconfig CGROUP_SCHED
  857. bool "Group CPU scheduler"
  858. default n
  859. help
  860. This feature lets CPU scheduler recognize task groups and control CPU
  861. bandwidth allocation to such task groups. It uses cgroups to group
  862. tasks.
  863. if CGROUP_SCHED
  864. config FAIR_GROUP_SCHED
  865. bool "Group scheduling for SCHED_OTHER"
  866. depends on CGROUP_SCHED
  867. default CGROUP_SCHED
  868. config CFS_BANDWIDTH
  869. bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
  870. depends on FAIR_GROUP_SCHED
  871. default n
  872. help
  873. This option allows users to define CPU bandwidth rates (limits) for
  874. tasks running within the fair group scheduler. Groups with no limit
  875. set are considered to be unconstrained and will run with no
  876. restriction.
  877. See tip/Documentation/scheduler/sched-bwc.txt for more information.
  878. config RT_GROUP_SCHED
  879. bool "Group scheduling for SCHED_RR/FIFO"
  880. depends on CGROUP_SCHED
  881. default n
  882. help
  883. This feature lets you explicitly allocate real CPU bandwidth
  884. to task groups. If enabled, it will also make it impossible to
  885. schedule realtime tasks for non-root users until you allocate
  886. realtime bandwidth for them.
  887. See Documentation/scheduler/sched-rt-group.txt for more information.
  888. endif #CGROUP_SCHED
  889. config BLK_CGROUP
  890. bool "Block IO controller"
  891. depends on BLOCK
  892. default n
  893. ---help---
  894. Generic block IO controller cgroup interface. This is the common
  895. cgroup interface which should be used by various IO controlling
  896. policies.
  897. Currently, CFQ IO scheduler uses it to recognize task groups and
  898. control disk bandwidth allocation (proportional time slice allocation)
  899. to such task groups. It is also used by bio throttling logic in
  900. block layer to implement upper limit in IO rates on a device.
  901. This option only enables generic Block IO controller infrastructure.
  902. One needs to also enable actual IO controlling logic/policy. For
  903. enabling proportional weight division of disk bandwidth in CFQ, set
  904. CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
  905. CONFIG_BLK_DEV_THROTTLING=y.
  906. See Documentation/cgroups/blkio-controller.txt for more information.
  907. config DEBUG_BLK_CGROUP
  908. bool "Enable Block IO controller debugging"
  909. depends on BLK_CGROUP
  910. default n
  911. ---help---
  912. Enable some debugging help. Currently it exports additional stat
  913. files in a cgroup which can be useful for debugging.
  914. endif # CGROUPS
  915. config CHECKPOINT_RESTORE
  916. bool "Checkpoint/restore support" if EXPERT
  917. default n
  918. help
  919. Enables additional kernel features in a sake of checkpoint/restore.
  920. In particular it adds auxiliary prctl codes to setup process text,
  921. data and heap segment sizes, and a few additional /proc filesystem
  922. entries.
  923. If unsure, say N here.
  924. menuconfig NAMESPACES
  925. bool "Namespaces support" if EXPERT
  926. default !EXPERT
  927. help
  928. Provides the way to make tasks work with different objects using
  929. the same id. For example same IPC id may refer to different objects
  930. or same user id or pid may refer to different tasks when used in
  931. different namespaces.
  932. if NAMESPACES
  933. config UTS_NS
  934. bool "UTS namespace"
  935. default y
  936. help
  937. In this namespace tasks see different info provided with the
  938. uname() system call
  939. config IPC_NS
  940. bool "IPC namespace"
  941. depends on (SYSVIPC || POSIX_MQUEUE)
  942. default y
  943. help
  944. In this namespace tasks work with IPC ids which correspond to
  945. different IPC objects in different namespaces.
  946. config USER_NS
  947. bool "User namespace"
  948. depends on UIDGID_CONVERTED
  949. select UIDGID_STRICT_TYPE_CHECKS
  950. default n
  951. help
  952. This allows containers, i.e. vservers, to use user namespaces
  953. to provide different user info for different servers.
  954. When user namespaces are enabled in the kernel it is
  955. recommended that the MEMCG and MEMCG_KMEM options also be
  956. enabled and that user-space use the memory control groups to
  957. limit the amount of memory a memory unprivileged users can
  958. use.
  959. If unsure, say N.
  960. config PID_NS
  961. bool "PID Namespaces"
  962. default y
  963. help
  964. Support process id namespaces. This allows having multiple
  965. processes with the same pid as long as they are in different
  966. pid namespaces. This is a building block of containers.
  967. config NET_NS
  968. bool "Network namespace"
  969. depends on NET
  970. default y
  971. help
  972. Allow user space to create what appear to be multiple instances
  973. of the network stack.
  974. endif # NAMESPACES
  975. config UIDGID_CONVERTED
  976. # True if all of the selected software conmponents are known
  977. # to have uid_t and gid_t converted to kuid_t and kgid_t
  978. # where appropriate and are otherwise safe to use with
  979. # the user namespace.
  980. bool
  981. default y
  982. # Filesystems
  983. depends on XFS_FS = n
  984. config UIDGID_STRICT_TYPE_CHECKS
  985. bool "Require conversions between uid/gids and their internal representation"
  986. depends on UIDGID_CONVERTED
  987. default n
  988. help
  989. While the nececessary conversions are being added to all subsystems this option allows
  990. the code to continue to build for unconverted subsystems.
  991. Say Y here if you want the strict type checking enabled
  992. config SCHED_AUTOGROUP
  993. bool "Automatic process group scheduling"
  994. select EVENTFD
  995. select CGROUPS
  996. select CGROUP_SCHED
  997. select FAIR_GROUP_SCHED
  998. help
  999. This option optimizes the scheduler for common desktop workloads by
  1000. automatically creating and populating task groups. This separation
  1001. of workloads isolates aggressive CPU burners (like build jobs) from
  1002. desktop applications. Task group autogeneration is currently based
  1003. upon task session.
  1004. config MM_OWNER
  1005. bool
  1006. config SYSFS_DEPRECATED
  1007. bool "Enable deprecated sysfs features to support old userspace tools"
  1008. depends on SYSFS
  1009. default n
  1010. help
  1011. This option adds code that switches the layout of the "block" class
  1012. devices, to not show up in /sys/class/block/, but only in
  1013. /sys/block/.
  1014. This switch is only active when the sysfs.deprecated=1 boot option is
  1015. passed or the SYSFS_DEPRECATED_V2 option is set.
  1016. This option allows new kernels to run on old distributions and tools,
  1017. which might get confused by /sys/class/block/. Since 2007/2008 all
  1018. major distributions and tools handle this just fine.
  1019. Recent distributions and userspace tools after 2009/2010 depend on
  1020. the existence of /sys/class/block/, and will not work with this
  1021. option enabled.
  1022. Only if you are using a new kernel on an old distribution, you might
  1023. need to say Y here.
  1024. config SYSFS_DEPRECATED_V2
  1025. bool "Enable deprecated sysfs features by default"
  1026. default n
  1027. depends on SYSFS
  1028. depends on SYSFS_DEPRECATED
  1029. help
  1030. Enable deprecated sysfs by default.
  1031. See the CONFIG_SYSFS_DEPRECATED option for more details about this
  1032. option.
  1033. Only if you are using a new kernel on an old distribution, you might
  1034. need to say Y here. Even then, odds are you would not need it
  1035. enabled, you can always pass the boot option if absolutely necessary.
  1036. config RELAY
  1037. bool "Kernel->user space relay support (formerly relayfs)"
  1038. help
  1039. This option enables support for relay interface support in
  1040. certain file systems (such as debugfs).
  1041. It is designed to provide an efficient mechanism for tools and
  1042. facilities to relay large amounts of data from kernel space to
  1043. user space.
  1044. If unsure, say N.
  1045. config BLK_DEV_INITRD
  1046. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  1047. depends on BROKEN || !FRV
  1048. help
  1049. The initial RAM filesystem is a ramfs which is loaded by the
  1050. boot loader (loadlin or lilo) and that is mounted as root
  1051. before the normal boot procedure. It is typically used to
  1052. load modules needed to mount the "real" root file system,
  1053. etc. See <file:Documentation/initrd.txt> for details.
  1054. If RAM disk support (BLK_DEV_RAM) is also included, this
  1055. also enables initial RAM disk (initrd) support and adds
  1056. 15 Kbytes (more on some other architectures) to the kernel size.
  1057. If unsure say Y.
  1058. if BLK_DEV_INITRD
  1059. source "usr/Kconfig"
  1060. endif
  1061. config CC_OPTIMIZE_FOR_SIZE
  1062. bool "Optimize for size"
  1063. help
  1064. Enabling this option will pass "-Os" instead of "-O2" to gcc
  1065. resulting in a smaller kernel.
  1066. If unsure, say N.
  1067. config SYSCTL
  1068. bool
  1069. config ANON_INODES
  1070. bool
  1071. config HAVE_UID16
  1072. bool
  1073. config SYSCTL_EXCEPTION_TRACE
  1074. bool
  1075. help
  1076. Enable support for /proc/sys/debug/exception-trace.
  1077. config SYSCTL_ARCH_UNALIGN_NO_WARN
  1078. bool
  1079. help
  1080. Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
  1081. Allows arch to define/use @no_unaligned_warning to possibly warn
  1082. about unaligned access emulation going on under the hood.
  1083. config SYSCTL_ARCH_UNALIGN_ALLOW
  1084. bool
  1085. help
  1086. Enable support for /proc/sys/kernel/unaligned-trap
  1087. Allows arches to define/use @unaligned_enabled to runtime toggle
  1088. the unaligned access emulation.
  1089. see arch/parisc/kernel/unaligned.c for reference
  1090. config HAVE_PCSPKR_PLATFORM
  1091. bool
  1092. menuconfig EXPERT
  1093. bool "Configure standard kernel features (expert users)"
  1094. # Unhide debug options, to make the on-by-default options visible
  1095. select DEBUG_KERNEL
  1096. help
  1097. This option allows certain base kernel options and settings
  1098. to be disabled or tweaked. This is for specialized
  1099. environments which can tolerate a "non-standard" kernel.
  1100. Only use this if you really know what you are doing.
  1101. config UID16
  1102. bool "Enable 16-bit UID system calls" if EXPERT
  1103. depends on HAVE_UID16
  1104. default y
  1105. help
  1106. This enables the legacy 16-bit UID syscall wrappers.
  1107. config SYSCTL_SYSCALL
  1108. bool "Sysctl syscall support" if EXPERT
  1109. depends on PROC_SYSCTL
  1110. default n
  1111. select SYSCTL
  1112. ---help---
  1113. sys_sysctl uses binary paths that have been found challenging
  1114. to properly maintain and use. The interface in /proc/sys
  1115. using paths with ascii names is now the primary path to this
  1116. information.
  1117. Almost nothing using the binary sysctl interface so if you are
  1118. trying to save some space it is probably safe to disable this,
  1119. making your kernel marginally smaller.
  1120. If unsure say N here.
  1121. config KALLSYMS
  1122. bool "Load all symbols for debugging/ksymoops" if EXPERT
  1123. default y
  1124. help
  1125. Say Y here to let the kernel print out symbolic crash information and
  1126. symbolic stack backtraces. This increases the size of the kernel
  1127. somewhat, as all symbols have to be loaded into the kernel image.
  1128. config KALLSYMS_ALL
  1129. bool "Include all symbols in kallsyms"
  1130. depends on DEBUG_KERNEL && KALLSYMS
  1131. help
  1132. Normally kallsyms only contains the symbols of functions for nicer
  1133. OOPS messages and backtraces (i.e., symbols from the text and inittext
  1134. sections). This is sufficient for most cases. And only in very rare
  1135. cases (e.g., when a debugger is used) all symbols are required (e.g.,
  1136. names of variables from the data sections, etc).
  1137. This option makes sure that all symbols are loaded into the kernel
  1138. image (i.e., symbols from all sections) in cost of increased kernel
  1139. size (depending on the kernel configuration, it may be 300KiB or
  1140. something like this).
  1141. Say N unless you really need all symbols.
  1142. config PRINTK
  1143. default y
  1144. bool "Enable support for printk" if EXPERT
  1145. select IRQ_WORK
  1146. help
  1147. This option enables normal printk support. Removing it
  1148. eliminates most of the message strings from the kernel image
  1149. and makes the kernel more or less silent. As this makes it
  1150. very difficult to diagnose system problems, saying N here is
  1151. strongly discouraged.
  1152. config BUG
  1153. bool "BUG() support" if EXPERT
  1154. default y
  1155. help
  1156. Disabling this option eliminates support for BUG and WARN, reducing
  1157. the size of your kernel image and potentially quietly ignoring
  1158. numerous fatal conditions. You should only consider disabling this
  1159. option for embedded systems with no facilities for reporting errors.
  1160. Just say Y.
  1161. config ELF_CORE
  1162. depends on COREDUMP
  1163. default y
  1164. bool "Enable ELF core dumps" if EXPERT
  1165. help
  1166. Enable support for generating core dumps. Disabling saves about 4k.
  1167. config PCSPKR_PLATFORM
  1168. bool "Enable PC-Speaker support" if EXPERT
  1169. depends on HAVE_PCSPKR_PLATFORM
  1170. select I8253_LOCK
  1171. default y
  1172. help
  1173. This option allows to disable the internal PC-Speaker
  1174. support, saving some memory.
  1175. config BASE_FULL
  1176. default y
  1177. bool "Enable full-sized data structures for core" if EXPERT
  1178. help
  1179. Disabling this option reduces the size of miscellaneous core
  1180. kernel data structures. This saves memory on small machines,
  1181. but may reduce performance.
  1182. config FUTEX
  1183. bool "Enable futex support" if EXPERT
  1184. default y
  1185. select RT_MUTEXES
  1186. help
  1187. Disabling this option will cause the kernel to be built without
  1188. support for "fast userspace mutexes". The resulting kernel may not
  1189. run glibc-based applications correctly.
  1190. config EPOLL
  1191. bool "Enable eventpoll support" if EXPERT
  1192. default y
  1193. select ANON_INODES
  1194. help
  1195. Disabling this option will cause the kernel to be built without
  1196. support for epoll family of system calls.
  1197. config SIGNALFD
  1198. bool "Enable signalfd() system call" if EXPERT
  1199. select ANON_INODES
  1200. default y
  1201. help
  1202. Enable the signalfd() system call that allows to receive signals
  1203. on a file descriptor.
  1204. If unsure, say Y.
  1205. config TIMERFD
  1206. bool "Enable timerfd() system call" if EXPERT
  1207. select ANON_INODES
  1208. default y
  1209. help
  1210. Enable the timerfd() system call that allows to receive timer
  1211. events on a file descriptor.
  1212. If unsure, say Y.
  1213. config EVENTFD
  1214. bool "Enable eventfd() system call" if EXPERT
  1215. select ANON_INODES
  1216. default y
  1217. help
  1218. Enable the eventfd() system call that allows to receive both
  1219. kernel notification (ie. KAIO) or userspace notifications.
  1220. If unsure, say Y.
  1221. config SHMEM
  1222. bool "Use full shmem filesystem" if EXPERT
  1223. default y
  1224. depends on MMU
  1225. help
  1226. The shmem is an internal filesystem used to manage shared memory.
  1227. It is backed by swap and manages resource limits. It is also exported
  1228. to userspace as tmpfs if TMPFS is enabled. Disabling this
  1229. option replaces shmem and tmpfs with the much simpler ramfs code,
  1230. which may be appropriate on small systems without swap.
  1231. config AIO
  1232. bool "Enable AIO support" if EXPERT
  1233. default y
  1234. help
  1235. This option enables POSIX asynchronous I/O which may by used
  1236. by some high performance threaded applications. Disabling
  1237. this option saves about 7k.
  1238. config PCI_QUIRKS
  1239. default y
  1240. bool "Enable PCI quirk workarounds" if EXPERT
  1241. depends on PCI
  1242. help
  1243. This enables workarounds for various PCI chipset
  1244. bugs/quirks. Disable this only if your target machine is
  1245. unaffected by PCI quirks.
  1246. config EMBEDDED
  1247. bool "Embedded system"
  1248. select EXPERT
  1249. help
  1250. This option should be enabled if compiling the kernel for
  1251. an embedded system so certain expert options are available
  1252. for configuration.
  1253. config HAVE_PERF_EVENTS
  1254. bool
  1255. help
  1256. See tools/perf/design.txt for details.
  1257. config PERF_USE_VMALLOC
  1258. bool
  1259. help
  1260. See tools/perf/design.txt for details
  1261. menu "Kernel Performance Events And Counters"
  1262. config PERF_EVENTS
  1263. bool "Kernel performance events and counters"
  1264. default y if PROFILING
  1265. depends on HAVE_PERF_EVENTS
  1266. select ANON_INODES
  1267. select IRQ_WORK
  1268. help
  1269. Enable kernel support for various performance events provided
  1270. by software and hardware.
  1271. Software events are supported either built-in or via the
  1272. use of generic tracepoints.
  1273. Most modern CPUs support performance events via performance
  1274. counter registers. These registers count the number of certain
  1275. types of hw events: such as instructions executed, cachemisses
  1276. suffered, or branches mis-predicted - without slowing down the
  1277. kernel or applications. These registers can also trigger interrupts
  1278. when a threshold number of events have passed - and can thus be
  1279. used to profile the code that runs on that CPU.
  1280. The Linux Performance Event subsystem provides an abstraction of
  1281. these software and hardware event capabilities, available via a
  1282. system call and used by the "perf" utility in tools/perf/. It
  1283. provides per task and per CPU counters, and it provides event
  1284. capabilities on top of those.
  1285. Say Y if unsure.
  1286. config DEBUG_PERF_USE_VMALLOC
  1287. default n
  1288. bool "Debug: use vmalloc to back perf mmap() buffers"
  1289. depends on PERF_EVENTS && DEBUG_KERNEL
  1290. select PERF_USE_VMALLOC
  1291. help
  1292. Use vmalloc memory to back perf mmap() buffers.
  1293. Mostly useful for debugging the vmalloc code on platforms
  1294. that don't require it.
  1295. Say N if unsure.
  1296. endmenu
  1297. config VM_EVENT_COUNTERS
  1298. default y
  1299. bool "Enable VM event counters for /proc/vmstat" if EXPERT
  1300. help
  1301. VM event counters are needed for event counts to be shown.
  1302. This option allows the disabling of the VM event counters
  1303. on EXPERT systems. /proc/vmstat will only show page counts
  1304. if VM event counters are disabled.
  1305. config SLUB_DEBUG
  1306. default y
  1307. bool "Enable SLUB debugging support" if EXPERT
  1308. depends on SLUB && SYSFS
  1309. help
  1310. SLUB has extensive debug support features. Disabling these can
  1311. result in significant savings in code size. This also disables
  1312. SLUB sysfs support. /sys/slab will not exist and there will be
  1313. no support for cache validation etc.
  1314. config COMPAT_BRK
  1315. bool "Disable heap randomization"
  1316. default y
  1317. help
  1318. Randomizing heap placement makes heap exploits harder, but it
  1319. also breaks ancient binaries (including anything libc5 based).
  1320. This option changes the bootup default to heap randomization
  1321. disabled, and can be overridden at runtime by setting
  1322. /proc/sys/kernel/randomize_va_space to 2.
  1323. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  1324. choice
  1325. prompt "Choose SLAB allocator"
  1326. default SLUB
  1327. help
  1328. This option allows to select a slab allocator.
  1329. config SLAB
  1330. bool "SLAB"
  1331. help
  1332. The regular slab allocator that is established and known to work
  1333. well in all environments. It organizes cache hot objects in
  1334. per cpu and per node queues.
  1335. config SLUB
  1336. bool "SLUB (Unqueued Allocator)"
  1337. help
  1338. SLUB is a slab allocator that minimizes cache line usage
  1339. instead of managing queues of cached objects (SLAB approach).
  1340. Per cpu caching is realized using slabs of objects instead
  1341. of queues of objects. SLUB can use memory efficiently
  1342. and has enhanced diagnostics. SLUB is the default choice for
  1343. a slab allocator.
  1344. config SLOB
  1345. depends on EXPERT
  1346. bool "SLOB (Simple Allocator)"
  1347. help
  1348. SLOB replaces the stock allocator with a drastically simpler
  1349. allocator. SLOB is generally more space efficient but
  1350. does not perform as well on large systems.
  1351. endchoice
  1352. config SLUB_CPU_PARTIAL
  1353. default y
  1354. depends on SLUB
  1355. bool "SLUB per cpu partial cache"
  1356. help
  1357. Per cpu partial caches accellerate objects allocation and freeing
  1358. that is local to a processor at the price of more indeterminism
  1359. in the latency of the free. On overflow these caches will be cleared
  1360. which requires the taking of locks that may cause latency spikes.
  1361. Typically one would choose no for a realtime system.
  1362. config MMAP_ALLOW_UNINITIALIZED
  1363. bool "Allow mmapped anonymous memory to be uninitialized"
  1364. depends on EXPERT && !MMU
  1365. default n
  1366. help
  1367. Normally, and according to the Linux spec, anonymous memory obtained
  1368. from mmap() has it's contents cleared before it is passed to
  1369. userspace. Enabling this config option allows you to request that
  1370. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  1371. providing a huge performance boost. If this option is not enabled,
  1372. then the flag will be ignored.
  1373. This is taken advantage of by uClibc's malloc(), and also by
  1374. ELF-FDPIC binfmt's brk and stack allocator.
  1375. Because of the obvious security issues, this option should only be
  1376. enabled on embedded devices where you control what is run in
  1377. userspace. Since that isn't generally a problem on no-MMU systems,
  1378. it is normally safe to say Y here.
  1379. See Documentation/nommu-mmap.txt for more information.
  1380. config PROFILING
  1381. bool "Profiling support"
  1382. help
  1383. Say Y here to enable the extended profiling support mechanisms used
  1384. by profilers such as OProfile.
  1385. #
  1386. # Place an empty function call at each tracepoint site. Can be
  1387. # dynamically changed for a probe function.
  1388. #
  1389. config TRACEPOINTS
  1390. bool
  1391. source "arch/Kconfig"
  1392. endmenu # General setup
  1393. config HAVE_GENERIC_DMA_COHERENT
  1394. bool
  1395. default n
  1396. config SLABINFO
  1397. bool
  1398. depends on PROC_FS
  1399. depends on SLAB || SLUB_DEBUG
  1400. default y
  1401. config RT_MUTEXES
  1402. boolean
  1403. config BASE_SMALL
  1404. int
  1405. default 0 if BASE_FULL
  1406. default 1 if !BASE_FULL
  1407. menuconfig MODULES
  1408. bool "Enable loadable module support"
  1409. help
  1410. Kernel modules are small pieces of compiled code which can
  1411. be inserted in the running kernel, rather than being
  1412. permanently built into the kernel. You use the "modprobe"
  1413. tool to add (and sometimes remove) them. If you say Y here,
  1414. many parts of the kernel can be built as modules (by
  1415. answering M instead of Y where indicated): this is most
  1416. useful for infrequently used options which are not required
  1417. for booting. For more information, see the man pages for
  1418. modprobe, lsmod, modinfo, insmod and rmmod.
  1419. If you say Y here, you will need to run "make
  1420. modules_install" to put the modules under /lib/modules/
  1421. where modprobe can find them (you may need to be root to do
  1422. this).
  1423. If unsure, say Y.
  1424. if MODULES
  1425. config MODULE_FORCE_LOAD
  1426. bool "Forced module loading"
  1427. default n
  1428. help
  1429. Allow loading of modules without version information (ie. modprobe
  1430. --force). Forced module loading sets the 'F' (forced) taint flag and
  1431. is usually a really bad idea.
  1432. config MODULE_UNLOAD
  1433. bool "Module unloading"
  1434. help
  1435. Without this option you will not be able to unload any
  1436. modules (note that some modules may not be unloadable
  1437. anyway), which makes your kernel smaller, faster
  1438. and simpler. If unsure, say Y.
  1439. config MODULE_FORCE_UNLOAD
  1440. bool "Forced module unloading"
  1441. depends on MODULE_UNLOAD
  1442. help
  1443. This option allows you to force a module to unload, even if the
  1444. kernel believes it is unsafe: the kernel will remove the module
  1445. without waiting for anyone to stop using it (using the -f option to
  1446. rmmod). This is mainly for kernel developers and desperate users.
  1447. If unsure, say N.
  1448. config MODVERSIONS
  1449. bool "Module versioning support"
  1450. help
  1451. Usually, you have to use modules compiled with your kernel.
  1452. Saying Y here makes it sometimes possible to use modules
  1453. compiled for different kernels, by adding enough information
  1454. to the modules to (hopefully) spot any changes which would
  1455. make them incompatible with the kernel you are running. If
  1456. unsure, say N.
  1457. config MODULE_SRCVERSION_ALL
  1458. bool "Source checksum for all modules"
  1459. help
  1460. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1461. field inserted into their modinfo section, which contains a
  1462. sum of the source files which made it. This helps maintainers
  1463. see exactly which source was used to build a module (since
  1464. others sometimes change the module source without updating
  1465. the version). With this option, such a "srcversion" field
  1466. will be created for all modules. If unsure, say N.
  1467. config MODULE_SIG
  1468. bool "Module signature verification"
  1469. depends on MODULES
  1470. select KEYS
  1471. select CRYPTO
  1472. select ASYMMETRIC_KEY_TYPE
  1473. select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  1474. select PUBLIC_KEY_ALGO_RSA
  1475. select ASN1
  1476. select OID_REGISTRY
  1477. select X509_CERTIFICATE_PARSER
  1478. help
  1479. Check modules for valid signatures upon load: the signature
  1480. is simply appended to the module. For more information see
  1481. Documentation/module-signing.txt.
  1482. !!!WARNING!!! If you enable this option, you MUST make sure that the
  1483. module DOES NOT get stripped after being signed. This includes the
  1484. debuginfo strip done by some packagers (such as rpmbuild) and
  1485. inclusion into an initramfs that wants the module size reduced.
  1486. config MODULE_SIG_FORCE
  1487. bool "Require modules to be validly signed"
  1488. depends on MODULE_SIG
  1489. help
  1490. Reject unsigned modules or signed modules for which we don't have a
  1491. key. Without this, such modules will simply taint the kernel.
  1492. config MODULE_SIG_ALL
  1493. bool "Automatically sign all modules"
  1494. default y
  1495. depends on MODULE_SIG
  1496. help
  1497. Sign all modules during make modules_install. Without this option,
  1498. modules must be signed manually, using the scripts/sign-file tool.
  1499. comment "Do not forget to sign required modules with scripts/sign-file"
  1500. depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
  1501. choice
  1502. prompt "Which hash algorithm should modules be signed with?"
  1503. depends on MODULE_SIG
  1504. help
  1505. This determines which sort of hashing algorithm will be used during
  1506. signature generation. This algorithm _must_ be built into the kernel
  1507. directly so that signature verification can take place. It is not
  1508. possible to load a signed module containing the algorithm to check
  1509. the signature on that module.
  1510. config MODULE_SIG_SHA1
  1511. bool "Sign modules with SHA-1"
  1512. select CRYPTO_SHA1
  1513. config MODULE_SIG_SHA224
  1514. bool "Sign modules with SHA-224"
  1515. select CRYPTO_SHA256
  1516. config MODULE_SIG_SHA256
  1517. bool "Sign modules with SHA-256"
  1518. select CRYPTO_SHA256
  1519. config MODULE_SIG_SHA384
  1520. bool "Sign modules with SHA-384"
  1521. select CRYPTO_SHA512
  1522. config MODULE_SIG_SHA512
  1523. bool "Sign modules with SHA-512"
  1524. select CRYPTO_SHA512
  1525. endchoice
  1526. config MODULE_SIG_HASH
  1527. string
  1528. depends on MODULE_SIG
  1529. default "sha1" if MODULE_SIG_SHA1
  1530. default "sha224" if MODULE_SIG_SHA224
  1531. default "sha256" if MODULE_SIG_SHA256
  1532. default "sha384" if MODULE_SIG_SHA384
  1533. default "sha512" if MODULE_SIG_SHA512
  1534. endif # MODULES
  1535. config INIT_ALL_POSSIBLE
  1536. bool
  1537. help
  1538. Back when each arch used to define their own cpu_online_mask and
  1539. cpu_possible_mask, some of them chose to initialize cpu_possible_mask
  1540. with all 1s, and others with all 0s. When they were centralised,
  1541. it was better to provide this option than to break all the archs
  1542. and have several arch maintainers pursuing me down dark alleys.
  1543. config STOP_MACHINE
  1544. bool
  1545. default y
  1546. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1547. help
  1548. Need stop_machine() primitive.
  1549. source "block/Kconfig"
  1550. config PREEMPT_NOTIFIERS
  1551. bool
  1552. config PADATA
  1553. depends on SMP
  1554. bool
  1555. # Can be selected by architectures with broken toolchains
  1556. # that get confused by correct const<->read_only section
  1557. # mappings
  1558. config BROKEN_RODATA
  1559. bool
  1560. config ASN1
  1561. tristate
  1562. help
  1563. Build a simple ASN.1 grammar compiler that produces a bytecode output
  1564. that can be interpreted by the ASN.1 stream decoder and used to
  1565. inform it as to what tags are to be expected in a stream and what
  1566. functions to call on what tags.
  1567. source "kernel/Kconfig.locks"