Kconfig 64 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 CROSS_MEMORY_ATTACH
  217. bool "Enable process_vm_readv/writev syscalls"
  218. depends on MMU
  219. default y
  220. help
  221. Enabling this option adds the system calls process_vm_readv and
  222. process_vm_writev which allow a process with the correct privileges
  223. to directly read from or write to another process' address space.
  224. See the man page for more details.
  225. config FHANDLE
  226. bool "open by fhandle syscalls"
  227. select EXPORTFS
  228. help
  229. If you say Y here, a user level program will be able to map
  230. file names to handle and then later use the handle for
  231. different file system operations. This is useful in implementing
  232. userspace file servers, which now track files using handles instead
  233. of names. The handle would remain the same even if file names
  234. get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
  235. syscalls.
  236. config USELIB
  237. bool "uselib syscall"
  238. default y
  239. help
  240. This option enables the uselib syscall, a system call used in the
  241. dynamic linker from libc5 and earlier. glibc does not use this
  242. system call. If you intend to run programs built on libc5 or
  243. earlier, you may need to enable this syscall. Current systems
  244. running glibc can safely disable this.
  245. config AUDIT
  246. bool "Auditing support"
  247. depends on NET
  248. help
  249. Enable auditing infrastructure that can be used with another
  250. kernel subsystem, such as SELinux (which requires this for
  251. logging of avc messages output). Does not do system-call
  252. auditing without CONFIG_AUDITSYSCALL.
  253. config HAVE_ARCH_AUDITSYSCALL
  254. bool
  255. config AUDITSYSCALL
  256. bool "Enable system-call auditing support"
  257. depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
  258. default y if SECURITY_SELINUX
  259. help
  260. Enable low-overhead system-call auditing infrastructure that
  261. can be used independently or with another kernel subsystem,
  262. such as SELinux.
  263. config AUDIT_WATCH
  264. def_bool y
  265. depends on AUDITSYSCALL
  266. select FSNOTIFY
  267. config AUDIT_TREE
  268. def_bool y
  269. depends on AUDITSYSCALL
  270. select FSNOTIFY
  271. source "kernel/irq/Kconfig"
  272. source "kernel/time/Kconfig"
  273. menu "CPU/Task time and stats accounting"
  274. config VIRT_CPU_ACCOUNTING
  275. bool
  276. choice
  277. prompt "Cputime accounting"
  278. default TICK_CPU_ACCOUNTING if !PPC64
  279. default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
  280. # Kind of a stub config for the pure tick based cputime accounting
  281. config TICK_CPU_ACCOUNTING
  282. bool "Simple tick based cputime accounting"
  283. depends on !S390 && !NO_HZ_FULL
  284. help
  285. This is the basic tick based cputime accounting that maintains
  286. statistics about user, system and idle time spent on per jiffies
  287. granularity.
  288. If unsure, say Y.
  289. config VIRT_CPU_ACCOUNTING_NATIVE
  290. bool "Deterministic task and CPU time accounting"
  291. depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
  292. select VIRT_CPU_ACCOUNTING
  293. help
  294. Select this option to enable more accurate task and CPU time
  295. accounting. This is done by reading a CPU counter on each
  296. kernel entry and exit and on transitions within the kernel
  297. between system, softirq and hardirq state, so there is a
  298. small performance impact. In the case of s390 or IBM POWER > 5,
  299. this also enables accounting of stolen time on logically-partitioned
  300. systems.
  301. config VIRT_CPU_ACCOUNTING_GEN
  302. bool "Full dynticks CPU time accounting"
  303. depends on HAVE_CONTEXT_TRACKING
  304. depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
  305. select VIRT_CPU_ACCOUNTING
  306. select CONTEXT_TRACKING
  307. help
  308. Select this option to enable task and CPU time accounting on full
  309. dynticks systems. This accounting is implemented by watching every
  310. kernel-user boundaries using the context tracking subsystem.
  311. The accounting is thus performed at the expense of some significant
  312. overhead.
  313. For now this is only useful if you are working on the full
  314. dynticks subsystem development.
  315. If unsure, say N.
  316. config IRQ_TIME_ACCOUNTING
  317. bool "Fine granularity task level IRQ time accounting"
  318. depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
  319. help
  320. Select this option to enable fine granularity task irq time
  321. accounting. This is done by reading a timestamp on each
  322. transitions between softirq and hardirq state, so there can be a
  323. small performance impact.
  324. If in doubt, say N here.
  325. endchoice
  326. config BSD_PROCESS_ACCT
  327. bool "BSD Process Accounting"
  328. help
  329. If you say Y here, a user level program will be able to instruct the
  330. kernel (via a special system call) to write process accounting
  331. information to a file: whenever a process exits, information about
  332. that process will be appended to the file by the kernel. The
  333. information includes things such as creation time, owning user,
  334. command name, memory usage, controlling terminal etc. (the complete
  335. list is in the struct acct in <file:include/linux/acct.h>). It is
  336. up to the user level program to do useful things with this
  337. information. This is generally a good idea, so say Y.
  338. config BSD_PROCESS_ACCT_V3
  339. bool "BSD Process Accounting version 3 file format"
  340. depends on BSD_PROCESS_ACCT
  341. default n
  342. help
  343. If you say Y here, the process accounting information is written
  344. in a new file format that also logs the process IDs of each
  345. process and it's parent. Note that this file format is incompatible
  346. with previous v0/v1/v2 file formats, so you will need updated tools
  347. for processing it. A preliminary version of these tools is available
  348. at <http://www.gnu.org/software/acct/>.
  349. config TASKSTATS
  350. bool "Export task/process statistics through netlink"
  351. depends on NET
  352. default n
  353. help
  354. Export selected statistics for tasks/processes through the
  355. generic netlink interface. Unlike BSD process accounting, the
  356. statistics are available during the lifetime of tasks/processes as
  357. responses to commands. Like BSD accounting, they are sent to user
  358. space on task exit.
  359. Say N if unsure.
  360. config TASK_DELAY_ACCT
  361. bool "Enable per-task delay accounting"
  362. depends on TASKSTATS
  363. help
  364. Collect information on time spent by a task waiting for system
  365. resources like cpu, synchronous block I/O completion and swapping
  366. in pages. Such statistics can help in setting a task's priorities
  367. relative to other tasks for cpu, io, rss limits etc.
  368. Say N if unsure.
  369. config TASK_XACCT
  370. bool "Enable extended accounting over taskstats"
  371. depends on TASKSTATS
  372. help
  373. Collect extended task accounting data and send the data
  374. to userland for processing over the taskstats interface.
  375. Say N if unsure.
  376. config TASK_IO_ACCOUNTING
  377. bool "Enable per-task storage I/O accounting"
  378. depends on TASK_XACCT
  379. help
  380. Collect information on the number of bytes of storage I/O which this
  381. task has caused.
  382. Say N if unsure.
  383. endmenu # "CPU/Task time and stats accounting"
  384. menu "RCU Subsystem"
  385. choice
  386. prompt "RCU Implementation"
  387. default TREE_RCU
  388. config TREE_RCU
  389. bool "Tree-based hierarchical RCU"
  390. depends on !PREEMPT && SMP
  391. help
  392. This option selects the RCU implementation that is
  393. designed for very large SMP system with hundreds or
  394. thousands of CPUs. It also scales down nicely to
  395. smaller systems.
  396. config PREEMPT_RCU
  397. bool "Preemptible tree-based hierarchical RCU"
  398. depends on PREEMPT
  399. help
  400. This option selects the RCU implementation that is
  401. designed for very large SMP systems with hundreds or
  402. thousands of CPUs, but for which real-time response
  403. is also required. It also scales down nicely to
  404. smaller systems.
  405. Select this option if you are unsure.
  406. config TINY_RCU
  407. bool "UP-only small-memory-footprint RCU"
  408. depends on !PREEMPT && !SMP
  409. help
  410. This option selects the RCU implementation that is
  411. designed for UP systems from which real-time response
  412. is not required. This option greatly reduces the
  413. memory footprint of RCU.
  414. endchoice
  415. config SRCU
  416. bool
  417. help
  418. This option selects the sleepable version of RCU. This version
  419. permits arbitrary sleeping or blocking within RCU read-side critical
  420. sections.
  421. config TASKS_RCU
  422. bool "Task_based RCU implementation using voluntary context switch"
  423. default n
  424. select SRCU
  425. help
  426. This option enables a task-based RCU implementation that uses
  427. only voluntary context switch (not preemption!), idle, and
  428. user-mode execution as quiescent states.
  429. If unsure, say N.
  430. config RCU_STALL_COMMON
  431. def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
  432. help
  433. This option enables RCU CPU stall code that is common between
  434. the TINY and TREE variants of RCU. The purpose is to allow
  435. the tiny variants to disable RCU CPU stall warnings, while
  436. making these warnings mandatory for the tree variants.
  437. config CONTEXT_TRACKING
  438. bool
  439. config RCU_USER_QS
  440. bool "Consider userspace as in RCU extended quiescent state"
  441. depends on HAVE_CONTEXT_TRACKING && SMP
  442. select CONTEXT_TRACKING
  443. help
  444. This option sets hooks on kernel / userspace boundaries and
  445. puts RCU in extended quiescent state when the CPU runs in
  446. userspace. It means that when a CPU runs in userspace, it is
  447. excluded from the global RCU state machine and thus doesn't
  448. try to keep the timer tick on for RCU.
  449. Unless you want to hack and help the development of the full
  450. dynticks mode, you shouldn't enable this option. It also
  451. adds unnecessary overhead.
  452. If unsure say N
  453. config CONTEXT_TRACKING_FORCE
  454. bool "Force context tracking"
  455. depends on CONTEXT_TRACKING
  456. default y if !NO_HZ_FULL
  457. help
  458. The major pre-requirement for full dynticks to work is to
  459. support the context tracking subsystem. But there are also
  460. other dependencies to provide in order to make the full
  461. dynticks working.
  462. This option stands for testing when an arch implements the
  463. context tracking backend but doesn't yet fullfill all the
  464. requirements to make the full dynticks feature working.
  465. Without the full dynticks, there is no way to test the support
  466. for context tracking and the subsystems that rely on it: RCU
  467. userspace extended quiescent state and tickless cputime
  468. accounting. This option copes with the absence of the full
  469. dynticks subsystem by forcing the context tracking on all
  470. CPUs in the system.
  471. Say Y only if you're working on the development of an
  472. architecture backend for the context tracking.
  473. Say N otherwise, this option brings an overhead that you
  474. don't want in production.
  475. config RCU_FANOUT
  476. int "Tree-based hierarchical RCU fanout value"
  477. range 2 64 if 64BIT
  478. range 2 32 if !64BIT
  479. depends on TREE_RCU || PREEMPT_RCU
  480. default 64 if 64BIT
  481. default 32 if !64BIT
  482. help
  483. This option controls the fanout of hierarchical implementations
  484. of RCU, allowing RCU to work efficiently on machines with
  485. large numbers of CPUs. This value must be at least the fourth
  486. root of NR_CPUS, which allows NR_CPUS to be insanely large.
  487. The default value of RCU_FANOUT should be used for production
  488. systems, but if you are stress-testing the RCU implementation
  489. itself, small RCU_FANOUT values allow you to test large-system
  490. code paths on small(er) systems.
  491. Select a specific number if testing RCU itself.
  492. Take the default if unsure.
  493. config RCU_FANOUT_LEAF
  494. int "Tree-based hierarchical RCU leaf-level fanout value"
  495. range 2 RCU_FANOUT if 64BIT
  496. range 2 RCU_FANOUT if !64BIT
  497. depends on TREE_RCU || PREEMPT_RCU
  498. default 16
  499. help
  500. This option controls the leaf-level fanout of hierarchical
  501. implementations of RCU, and allows trading off cache misses
  502. against lock contention. Systems that synchronize their
  503. scheduling-clock interrupts for energy-efficiency reasons will
  504. want the default because the smaller leaf-level fanout keeps
  505. lock contention levels acceptably low. Very large systems
  506. (hundreds or thousands of CPUs) will instead want to set this
  507. value to the maximum value possible in order to reduce the
  508. number of cache misses incurred during RCU's grace-period
  509. initialization. These systems tend to run CPU-bound, and thus
  510. are not helped by synchronized interrupts, and thus tend to
  511. skew them, which reduces lock contention enough that large
  512. leaf-level fanouts work well.
  513. Select a specific number if testing RCU itself.
  514. Select the maximum permissible value for large systems.
  515. Take the default if unsure.
  516. config RCU_FANOUT_EXACT
  517. bool "Disable tree-based hierarchical RCU auto-balancing"
  518. depends on TREE_RCU || PREEMPT_RCU
  519. default n
  520. help
  521. This option forces use of the exact RCU_FANOUT value specified,
  522. regardless of imbalances in the hierarchy. This is useful for
  523. testing RCU itself, and might one day be useful on systems with
  524. strong NUMA behavior.
  525. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  526. Say N if unsure.
  527. config RCU_FAST_NO_HZ
  528. bool "Accelerate last non-dyntick-idle CPU's grace periods"
  529. depends on NO_HZ_COMMON && SMP
  530. default n
  531. help
  532. This option permits CPUs to enter dynticks-idle state even if
  533. they have RCU callbacks queued, and prevents RCU from waking
  534. these CPUs up more than roughly once every four jiffies (by
  535. default, you can adjust this using the rcutree.rcu_idle_gp_delay
  536. parameter), thus improving energy efficiency. On the other
  537. hand, this option increases the duration of RCU grace periods,
  538. for example, slowing down synchronize_rcu().
  539. Say Y if energy efficiency is critically important, and you
  540. don't care about increased grace-period durations.
  541. Say N if you are unsure.
  542. config TREE_RCU_TRACE
  543. def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
  544. select DEBUG_FS
  545. help
  546. This option provides tracing for the TREE_RCU and
  547. PREEMPT_RCU implementations, permitting Makefile to
  548. trivially select kernel/rcutree_trace.c.
  549. config RCU_BOOST
  550. bool "Enable RCU priority boosting"
  551. depends on RT_MUTEXES && PREEMPT_RCU
  552. default n
  553. help
  554. This option boosts the priority of preempted RCU readers that
  555. block the current preemptible RCU grace period for too long.
  556. This option also prevents heavy loads from blocking RCU
  557. callback invocation for all flavors of RCU.
  558. Say Y here if you are working with real-time apps or heavy loads
  559. Say N here if you are unsure.
  560. config RCU_KTHREAD_PRIO
  561. int "Real-time priority to use for RCU worker threads"
  562. range 1 99 if RCU_BOOST
  563. range 0 99 if !RCU_BOOST
  564. default 1 if RCU_BOOST
  565. default 0 if !RCU_BOOST
  566. help
  567. This option specifies the SCHED_FIFO priority value that will be
  568. assigned to the rcuc/n and rcub/n threads and is also the value
  569. used for RCU_BOOST (if enabled). If you are working with a
  570. real-time application that has one or more CPU-bound threads
  571. running at a real-time priority level, you should set
  572. RCU_KTHREAD_PRIO to a priority higher than the highest-priority
  573. real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
  574. value of 1 is appropriate in the common case, which is real-time
  575. applications that do not have any CPU-bound threads.
  576. Some real-time applications might not have a single real-time
  577. thread that saturates a given CPU, but instead might have
  578. multiple real-time threads that, taken together, fully utilize
  579. that CPU. In this case, you should set RCU_KTHREAD_PRIO to
  580. a priority higher than the lowest-priority thread that is
  581. conspiring to prevent the CPU from running any non-real-time
  582. tasks. For example, if one thread at priority 10 and another
  583. thread at priority 5 are between themselves fully consuming
  584. the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
  585. set to priority 6 or higher.
  586. Specify the real-time priority, or take the default if unsure.
  587. config RCU_BOOST_DELAY
  588. int "Milliseconds to delay boosting after RCU grace-period start"
  589. range 0 3000
  590. depends on RCU_BOOST
  591. default 500
  592. help
  593. This option specifies the time to wait after the beginning of
  594. a given grace period before priority-boosting preempted RCU
  595. readers blocking that grace period. Note that any RCU reader
  596. blocking an expedited RCU grace period is boosted immediately.
  597. Accept the default if unsure.
  598. config RCU_NOCB_CPU
  599. bool "Offload RCU callback processing from boot-selected CPUs"
  600. depends on TREE_RCU || PREEMPT_RCU
  601. default n
  602. help
  603. Use this option to reduce OS jitter for aggressive HPC or
  604. real-time workloads. It can also be used to offload RCU
  605. callback invocation to energy-efficient CPUs in battery-powered
  606. asymmetric multiprocessors.
  607. This option offloads callback invocation from the set of
  608. CPUs specified at boot time by the rcu_nocbs parameter.
  609. For each such CPU, a kthread ("rcuox/N") will be created to
  610. invoke callbacks, where the "N" is the CPU being offloaded,
  611. and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
  612. "s" for RCU-sched. Nothing prevents this kthread from running
  613. on the specified CPUs, but (1) the kthreads may be preempted
  614. between each callback, and (2) affinity or cgroups can be used
  615. to force the kthreads to run on whatever set of CPUs is desired.
  616. Say Y here if you want to help to debug reduced OS jitter.
  617. Say N here if you are unsure.
  618. choice
  619. prompt "Build-forced no-CBs CPUs"
  620. default RCU_NOCB_CPU_NONE
  621. depends on RCU_NOCB_CPU
  622. help
  623. This option allows no-CBs CPUs (whose RCU callbacks are invoked
  624. from kthreads rather than from softirq context) to be specified
  625. at build time. Additional no-CBs CPUs may be specified by
  626. the rcu_nocbs= boot parameter.
  627. config RCU_NOCB_CPU_NONE
  628. bool "No build_forced no-CBs CPUs"
  629. help
  630. This option does not force any of the CPUs to be no-CBs CPUs.
  631. Only CPUs designated by the rcu_nocbs= boot parameter will be
  632. no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
  633. kthreads whose names begin with "rcuo". All other CPUs will
  634. invoke their own RCU callbacks in softirq context.
  635. Select this option if you want to choose no-CBs CPUs at
  636. boot time, for example, to allow testing of different no-CBs
  637. configurations without having to rebuild the kernel each time.
  638. config RCU_NOCB_CPU_ZERO
  639. bool "CPU 0 is a build_forced no-CBs CPU"
  640. help
  641. This option forces CPU 0 to be a no-CBs CPU, so that its RCU
  642. callbacks are invoked by a per-CPU kthread whose name begins
  643. with "rcuo". Additional CPUs may be designated as no-CBs
  644. CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
  645. All other CPUs will invoke their own RCU callbacks in softirq
  646. context.
  647. Select this if CPU 0 needs to be a no-CBs CPU for real-time
  648. or energy-efficiency reasons, but the real reason it exists
  649. is to ensure that randconfig testing covers mixed systems.
  650. config RCU_NOCB_CPU_ALL
  651. bool "All CPUs are build_forced no-CBs CPUs"
  652. help
  653. This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
  654. boot parameter will be ignored. All CPUs' RCU callbacks will
  655. be executed in the context of per-CPU rcuo kthreads created for
  656. this purpose. Assuming that the kthreads whose names start with
  657. "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
  658. on the remaining CPUs, but might decrease memory locality during
  659. RCU-callback invocation, thus potentially degrading throughput.
  660. Select this if all CPUs need to be no-CBs CPUs for real-time
  661. or energy-efficiency reasons.
  662. endchoice
  663. endmenu # "RCU Subsystem"
  664. config BUILD_BIN2C
  665. bool
  666. default n
  667. config IKCONFIG
  668. tristate "Kernel .config support"
  669. select BUILD_BIN2C
  670. ---help---
  671. This option enables the complete Linux kernel ".config" file
  672. contents to be saved in the kernel. It provides documentation
  673. of which kernel options are used in a running kernel or in an
  674. on-disk kernel. This information can be extracted from the kernel
  675. image file with the script scripts/extract-ikconfig and used as
  676. input to rebuild the current kernel or to build another kernel.
  677. It can also be extracted from a running kernel by reading
  678. /proc/config.gz if enabled (below).
  679. config IKCONFIG_PROC
  680. bool "Enable access to .config through /proc/config.gz"
  681. depends on IKCONFIG && PROC_FS
  682. ---help---
  683. This option enables access to the kernel configuration file
  684. through /proc/config.gz.
  685. config LOG_BUF_SHIFT
  686. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  687. range 12 21
  688. default 17
  689. depends on PRINTK
  690. help
  691. Select the minimal kernel log buffer size as a power of 2.
  692. The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
  693. parameter, see below. Any higher size also might be forced
  694. by "log_buf_len" boot parameter.
  695. Examples:
  696. 17 => 128 KB
  697. 16 => 64 KB
  698. 15 => 32 KB
  699. 14 => 16 KB
  700. 13 => 8 KB
  701. 12 => 4 KB
  702. config LOG_CPU_MAX_BUF_SHIFT
  703. int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
  704. depends on SMP
  705. range 0 21
  706. default 12 if !BASE_SMALL
  707. default 0 if BASE_SMALL
  708. depends on PRINTK
  709. help
  710. This option allows to increase the default ring buffer size
  711. according to the number of CPUs. The value defines the contribution
  712. of each CPU as a power of 2. The used space is typically only few
  713. lines however it might be much more when problems are reported,
  714. e.g. backtraces.
  715. The increased size means that a new buffer has to be allocated and
  716. the original static one is unused. It makes sense only on systems
  717. with more CPUs. Therefore this value is used only when the sum of
  718. contributions is greater than the half of the default kernel ring
  719. buffer as defined by LOG_BUF_SHIFT. The default values are set
  720. so that more than 64 CPUs are needed to trigger the allocation.
  721. Also this option is ignored when "log_buf_len" kernel parameter is
  722. used as it forces an exact (power of two) size of the ring buffer.
  723. The number of possible CPUs is used for this computation ignoring
  724. hotplugging making the compuation optimal for the the worst case
  725. scenerio while allowing a simple algorithm to be used from bootup.
  726. Examples shift values and their meaning:
  727. 17 => 128 KB for each CPU
  728. 16 => 64 KB for each CPU
  729. 15 => 32 KB for each CPU
  730. 14 => 16 KB for each CPU
  731. 13 => 8 KB for each CPU
  732. 12 => 4 KB for each CPU
  733. #
  734. # Architectures with an unreliable sched_clock() should select this:
  735. #
  736. config HAVE_UNSTABLE_SCHED_CLOCK
  737. bool
  738. config GENERIC_SCHED_CLOCK
  739. bool
  740. #
  741. # For architectures that want to enable the support for NUMA-affine scheduler
  742. # balancing logic:
  743. #
  744. config ARCH_SUPPORTS_NUMA_BALANCING
  745. bool
  746. #
  747. # For architectures that know their GCC __int128 support is sound
  748. #
  749. config ARCH_SUPPORTS_INT128
  750. bool
  751. # For architectures that (ab)use NUMA to represent different memory regions
  752. # all cpu-local but of different latencies, such as SuperH.
  753. #
  754. config ARCH_WANT_NUMA_VARIABLE_LOCALITY
  755. bool
  756. config NUMA_BALANCING
  757. bool "Memory placement aware NUMA scheduler"
  758. depends on ARCH_SUPPORTS_NUMA_BALANCING
  759. depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
  760. depends on SMP && NUMA && MIGRATION
  761. help
  762. This option adds support for automatic NUMA aware memory/task placement.
  763. The mechanism is quite primitive and is based on migrating memory when
  764. it has references to the node the task is running on.
  765. This system will be inactive on UMA systems.
  766. config NUMA_BALANCING_DEFAULT_ENABLED
  767. bool "Automatically enable NUMA aware memory/task placement"
  768. default y
  769. depends on NUMA_BALANCING
  770. help
  771. If set, automatic NUMA balancing will be enabled if running on a NUMA
  772. machine.
  773. menuconfig CGROUPS
  774. bool "Control Group support"
  775. select KERNFS
  776. help
  777. This option adds support for grouping sets of processes together, for
  778. use with process control subsystems such as Cpusets, CFS, memory
  779. controls or device isolation.
  780. See
  781. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  782. - Documentation/cgroups/ (features for grouping, isolation
  783. and resource control)
  784. Say N if unsure.
  785. if CGROUPS
  786. config CGROUP_DEBUG
  787. bool "Example debug cgroup subsystem"
  788. default n
  789. help
  790. This option enables a simple cgroup subsystem that
  791. exports useful debugging information about the cgroups
  792. framework.
  793. Say N if unsure.
  794. config CGROUP_FREEZER
  795. bool "Freezer cgroup subsystem"
  796. help
  797. Provides a way to freeze and unfreeze all tasks in a
  798. cgroup.
  799. config CGROUP_DEVICE
  800. bool "Device controller for cgroups"
  801. help
  802. Provides a cgroup implementing whitelists for devices which
  803. a process in the cgroup can mknod or open.
  804. config CPUSETS
  805. bool "Cpuset support"
  806. help
  807. This option will let you create and manage CPUSETs which
  808. allow dynamically partitioning a system into sets of CPUs and
  809. Memory Nodes and assigning tasks to run only within those sets.
  810. This is primarily useful on large SMP or NUMA systems.
  811. Say N if unsure.
  812. config PROC_PID_CPUSET
  813. bool "Include legacy /proc/<pid>/cpuset file"
  814. depends on CPUSETS
  815. default y
  816. config CGROUP_CPUACCT
  817. bool "Simple CPU accounting cgroup subsystem"
  818. help
  819. Provides a simple Resource Controller for monitoring the
  820. total CPU consumed by the tasks in a cgroup.
  821. config PAGE_COUNTER
  822. bool
  823. config MEMCG
  824. bool "Memory Resource Controller for Control Groups"
  825. select PAGE_COUNTER
  826. select EVENTFD
  827. help
  828. Provides a memory resource controller that manages both anonymous
  829. memory and page cache. (See Documentation/cgroups/memory.txt)
  830. config MEMCG_SWAP
  831. bool "Memory Resource Controller Swap Extension"
  832. depends on MEMCG && SWAP
  833. help
  834. Add swap management feature to memory resource controller. When you
  835. enable this, you can limit mem+swap usage per cgroup. In other words,
  836. when you disable this, memory resource controller has no cares to
  837. usage of swap...a process can exhaust all of the swap. This extension
  838. is useful when you want to avoid exhaustion swap but this itself
  839. adds more overheads and consumes memory for remembering information.
  840. Especially if you use 32bit system or small memory system, please
  841. be careful about enabling this. When memory resource controller
  842. is disabled by boot option, this will be automatically disabled and
  843. there will be no overhead from this. Even when you set this config=y,
  844. if boot option "swapaccount=0" is set, swap will not be accounted.
  845. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  846. size is 4096bytes, 512k per 1Gbytes of swap.
  847. config MEMCG_SWAP_ENABLED
  848. bool "Memory Resource Controller Swap Extension enabled by default"
  849. depends on MEMCG_SWAP
  850. default y
  851. help
  852. Memory Resource Controller Swap Extension comes with its price in
  853. a bigger memory consumption. General purpose distribution kernels
  854. which want to enable the feature but keep it disabled by default
  855. and let the user enable it by swapaccount=1 boot command line
  856. parameter should have this option unselected.
  857. For those who want to have the feature enabled by default should
  858. select this option (if, for some reason, they need to disable it
  859. then swapaccount=0 does the trick).
  860. config MEMCG_KMEM
  861. bool "Memory Resource Controller Kernel Memory accounting"
  862. depends on MEMCG
  863. depends on SLUB || SLAB
  864. help
  865. The Kernel Memory extension for Memory Resource Controller can limit
  866. the amount of memory used by kernel objects in the system. Those are
  867. fundamentally different from the entities handled by the standard
  868. Memory Controller, which are page-based, and can be swapped. Users of
  869. the kmem extension can use it to guarantee that no group of processes
  870. will ever exhaust kernel resources alone.
  871. WARNING: Current implementation lacks reclaim support. That means
  872. allocation attempts will fail when close to the limit even if there
  873. are plenty of kmem available for reclaim. That makes this option
  874. unusable in real life so DO NOT SELECT IT unless for development
  875. purposes.
  876. config CGROUP_HUGETLB
  877. bool "HugeTLB Resource Controller for Control Groups"
  878. depends on HUGETLB_PAGE
  879. select PAGE_COUNTER
  880. default n
  881. help
  882. Provides a cgroup Resource Controller for HugeTLB pages.
  883. When you enable this, you can put a per cgroup limit on HugeTLB usage.
  884. The limit is enforced during page fault. Since HugeTLB doesn't
  885. support page reclaim, enforcing the limit at page fault time implies
  886. that, the application will get SIGBUS signal if it tries to access
  887. HugeTLB pages beyond its limit. This requires the application to know
  888. beforehand how much HugeTLB pages it would require for its use. The
  889. control group is tracked in the third page lru pointer. This means
  890. that we cannot use the controller with huge page less than 3 pages.
  891. config CGROUP_PERF
  892. bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
  893. depends on PERF_EVENTS && CGROUPS
  894. help
  895. This option extends the per-cpu mode to restrict monitoring to
  896. threads which belong to the cgroup specified and run on the
  897. designated cpu.
  898. Say N if unsure.
  899. menuconfig CGROUP_SCHED
  900. bool "Group CPU scheduler"
  901. default n
  902. help
  903. This feature lets CPU scheduler recognize task groups and control CPU
  904. bandwidth allocation to such task groups. It uses cgroups to group
  905. tasks.
  906. if CGROUP_SCHED
  907. config FAIR_GROUP_SCHED
  908. bool "Group scheduling for SCHED_OTHER"
  909. depends on CGROUP_SCHED
  910. default CGROUP_SCHED
  911. config CFS_BANDWIDTH
  912. bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
  913. depends on FAIR_GROUP_SCHED
  914. default n
  915. help
  916. This option allows users to define CPU bandwidth rates (limits) for
  917. tasks running within the fair group scheduler. Groups with no limit
  918. set are considered to be unconstrained and will run with no
  919. restriction.
  920. See tip/Documentation/scheduler/sched-bwc.txt for more information.
  921. config RT_GROUP_SCHED
  922. bool "Group scheduling for SCHED_RR/FIFO"
  923. depends on CGROUP_SCHED
  924. default n
  925. help
  926. This feature lets you explicitly allocate real CPU bandwidth
  927. to task groups. If enabled, it will also make it impossible to
  928. schedule realtime tasks for non-root users until you allocate
  929. realtime bandwidth for them.
  930. See Documentation/scheduler/sched-rt-group.txt for more information.
  931. endif #CGROUP_SCHED
  932. config BLK_CGROUP
  933. bool "Block IO controller"
  934. depends on BLOCK
  935. default n
  936. ---help---
  937. Generic block IO controller cgroup interface. This is the common
  938. cgroup interface which should be used by various IO controlling
  939. policies.
  940. Currently, CFQ IO scheduler uses it to recognize task groups and
  941. control disk bandwidth allocation (proportional time slice allocation)
  942. to such task groups. It is also used by bio throttling logic in
  943. block layer to implement upper limit in IO rates on a device.
  944. This option only enables generic Block IO controller infrastructure.
  945. One needs to also enable actual IO controlling logic/policy. For
  946. enabling proportional weight division of disk bandwidth in CFQ, set
  947. CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
  948. CONFIG_BLK_DEV_THROTTLING=y.
  949. See Documentation/cgroups/blkio-controller.txt for more information.
  950. config DEBUG_BLK_CGROUP
  951. bool "Enable Block IO controller debugging"
  952. depends on BLK_CGROUP
  953. default n
  954. ---help---
  955. Enable some debugging help. Currently it exports additional stat
  956. files in a cgroup which can be useful for debugging.
  957. endif # CGROUPS
  958. config CHECKPOINT_RESTORE
  959. bool "Checkpoint/restore support" if EXPERT
  960. default n
  961. help
  962. Enables additional kernel features in a sake of checkpoint/restore.
  963. In particular it adds auxiliary prctl codes to setup process text,
  964. data and heap segment sizes, and a few additional /proc filesystem
  965. entries.
  966. If unsure, say N here.
  967. menuconfig NAMESPACES
  968. bool "Namespaces support" if EXPERT
  969. default !EXPERT
  970. help
  971. Provides the way to make tasks work with different objects using
  972. the same id. For example same IPC id may refer to different objects
  973. or same user id or pid may refer to different tasks when used in
  974. different namespaces.
  975. if NAMESPACES
  976. config UTS_NS
  977. bool "UTS namespace"
  978. default y
  979. help
  980. In this namespace tasks see different info provided with the
  981. uname() system call
  982. config IPC_NS
  983. bool "IPC namespace"
  984. depends on (SYSVIPC || POSIX_MQUEUE)
  985. default y
  986. help
  987. In this namespace tasks work with IPC ids which correspond to
  988. different IPC objects in different namespaces.
  989. config USER_NS
  990. bool "User namespace"
  991. default n
  992. help
  993. This allows containers, i.e. vservers, to use user namespaces
  994. to provide different user info for different servers.
  995. When user namespaces are enabled in the kernel it is
  996. recommended that the MEMCG and MEMCG_KMEM options also be
  997. enabled and that user-space use the memory control groups to
  998. limit the amount of memory a memory unprivileged users can
  999. use.
  1000. If unsure, say N.
  1001. config PID_NS
  1002. bool "PID Namespaces"
  1003. default y
  1004. help
  1005. Support process id namespaces. This allows having multiple
  1006. processes with the same pid as long as they are in different
  1007. pid namespaces. This is a building block of containers.
  1008. config NET_NS
  1009. bool "Network namespace"
  1010. depends on NET
  1011. default y
  1012. help
  1013. Allow user space to create what appear to be multiple instances
  1014. of the network stack.
  1015. endif # NAMESPACES
  1016. config SCHED_AUTOGROUP
  1017. bool "Automatic process group scheduling"
  1018. select CGROUPS
  1019. select CGROUP_SCHED
  1020. select FAIR_GROUP_SCHED
  1021. help
  1022. This option optimizes the scheduler for common desktop workloads by
  1023. automatically creating and populating task groups. This separation
  1024. of workloads isolates aggressive CPU burners (like build jobs) from
  1025. desktop applications. Task group autogeneration is currently based
  1026. upon task session.
  1027. config SYSFS_DEPRECATED
  1028. bool "Enable deprecated sysfs features to support old userspace tools"
  1029. depends on SYSFS
  1030. default n
  1031. help
  1032. This option adds code that switches the layout of the "block" class
  1033. devices, to not show up in /sys/class/block/, but only in
  1034. /sys/block/.
  1035. This switch is only active when the sysfs.deprecated=1 boot option is
  1036. passed or the SYSFS_DEPRECATED_V2 option is set.
  1037. This option allows new kernels to run on old distributions and tools,
  1038. which might get confused by /sys/class/block/. Since 2007/2008 all
  1039. major distributions and tools handle this just fine.
  1040. Recent distributions and userspace tools after 2009/2010 depend on
  1041. the existence of /sys/class/block/, and will not work with this
  1042. option enabled.
  1043. Only if you are using a new kernel on an old distribution, you might
  1044. need to say Y here.
  1045. config SYSFS_DEPRECATED_V2
  1046. bool "Enable deprecated sysfs features by default"
  1047. default n
  1048. depends on SYSFS
  1049. depends on SYSFS_DEPRECATED
  1050. help
  1051. Enable deprecated sysfs by default.
  1052. See the CONFIG_SYSFS_DEPRECATED option for more details about this
  1053. option.
  1054. Only if you are using a new kernel on an old distribution, you might
  1055. need to say Y here. Even then, odds are you would not need it
  1056. enabled, you can always pass the boot option if absolutely necessary.
  1057. config RELAY
  1058. bool "Kernel->user space relay support (formerly relayfs)"
  1059. help
  1060. This option enables support for relay interface support in
  1061. certain file systems (such as debugfs).
  1062. It is designed to provide an efficient mechanism for tools and
  1063. facilities to relay large amounts of data from kernel space to
  1064. user space.
  1065. If unsure, say N.
  1066. config BLK_DEV_INITRD
  1067. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  1068. depends on BROKEN || !FRV
  1069. help
  1070. The initial RAM filesystem is a ramfs which is loaded by the
  1071. boot loader (loadlin or lilo) and that is mounted as root
  1072. before the normal boot procedure. It is typically used to
  1073. load modules needed to mount the "real" root file system,
  1074. etc. See <file:Documentation/initrd.txt> for details.
  1075. If RAM disk support (BLK_DEV_RAM) is also included, this
  1076. also enables initial RAM disk (initrd) support and adds
  1077. 15 Kbytes (more on some other architectures) to the kernel size.
  1078. If unsure say Y.
  1079. if BLK_DEV_INITRD
  1080. source "usr/Kconfig"
  1081. endif
  1082. config CC_OPTIMIZE_FOR_SIZE
  1083. bool "Optimize for size"
  1084. help
  1085. Enabling this option will pass "-Os" instead of "-O2" to
  1086. your compiler resulting in a smaller kernel.
  1087. If unsure, say N.
  1088. config SYSCTL
  1089. bool
  1090. config ANON_INODES
  1091. bool
  1092. config HAVE_UID16
  1093. bool
  1094. config SYSCTL_EXCEPTION_TRACE
  1095. bool
  1096. help
  1097. Enable support for /proc/sys/debug/exception-trace.
  1098. config SYSCTL_ARCH_UNALIGN_NO_WARN
  1099. bool
  1100. help
  1101. Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
  1102. Allows arch to define/use @no_unaligned_warning to possibly warn
  1103. about unaligned access emulation going on under the hood.
  1104. config SYSCTL_ARCH_UNALIGN_ALLOW
  1105. bool
  1106. help
  1107. Enable support for /proc/sys/kernel/unaligned-trap
  1108. Allows arches to define/use @unaligned_enabled to runtime toggle
  1109. the unaligned access emulation.
  1110. see arch/parisc/kernel/unaligned.c for reference
  1111. config HAVE_PCSPKR_PLATFORM
  1112. bool
  1113. # interpreter that classic socket filters depend on
  1114. config BPF
  1115. bool
  1116. menuconfig EXPERT
  1117. bool "Configure standard kernel features (expert users)"
  1118. # Unhide debug options, to make the on-by-default options visible
  1119. select DEBUG_KERNEL
  1120. help
  1121. This option allows certain base kernel options and settings
  1122. to be disabled or tweaked. This is for specialized
  1123. environments which can tolerate a "non-standard" kernel.
  1124. Only use this if you really know what you are doing.
  1125. config UID16
  1126. bool "Enable 16-bit UID system calls" if EXPERT
  1127. depends on HAVE_UID16
  1128. default y
  1129. help
  1130. This enables the legacy 16-bit UID syscall wrappers.
  1131. config SGETMASK_SYSCALL
  1132. bool "sgetmask/ssetmask syscalls support" if EXPERT
  1133. def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
  1134. ---help---
  1135. sys_sgetmask and sys_ssetmask are obsolete system calls
  1136. no longer supported in libc but still enabled by default in some
  1137. architectures.
  1138. If unsure, leave the default option here.
  1139. config SYSFS_SYSCALL
  1140. bool "Sysfs syscall support" if EXPERT
  1141. default y
  1142. ---help---
  1143. sys_sysfs is an obsolete system call no longer supported in libc.
  1144. Note that disabling this option is more secure but might break
  1145. compatibility with some systems.
  1146. If unsure say Y here.
  1147. config SYSCTL_SYSCALL
  1148. bool "Sysctl syscall support" if EXPERT
  1149. depends on PROC_SYSCTL
  1150. default n
  1151. select SYSCTL
  1152. ---help---
  1153. sys_sysctl uses binary paths that have been found challenging
  1154. to properly maintain and use. The interface in /proc/sys
  1155. using paths with ascii names is now the primary path to this
  1156. information.
  1157. Almost nothing using the binary sysctl interface so if you are
  1158. trying to save some space it is probably safe to disable this,
  1159. making your kernel marginally smaller.
  1160. If unsure say N here.
  1161. config KALLSYMS
  1162. bool "Load all symbols for debugging/ksymoops" if EXPERT
  1163. default y
  1164. help
  1165. Say Y here to let the kernel print out symbolic crash information and
  1166. symbolic stack backtraces. This increases the size of the kernel
  1167. somewhat, as all symbols have to be loaded into the kernel image.
  1168. config KALLSYMS_ALL
  1169. bool "Include all symbols in kallsyms"
  1170. depends on DEBUG_KERNEL && KALLSYMS
  1171. help
  1172. Normally kallsyms only contains the symbols of functions for nicer
  1173. OOPS messages and backtraces (i.e., symbols from the text and inittext
  1174. sections). This is sufficient for most cases. And only in very rare
  1175. cases (e.g., when a debugger is used) all symbols are required (e.g.,
  1176. names of variables from the data sections, etc).
  1177. This option makes sure that all symbols are loaded into the kernel
  1178. image (i.e., symbols from all sections) in cost of increased kernel
  1179. size (depending on the kernel configuration, it may be 300KiB or
  1180. something like this).
  1181. Say N unless you really need all symbols.
  1182. config PRINTK
  1183. default y
  1184. bool "Enable support for printk" if EXPERT
  1185. select IRQ_WORK
  1186. help
  1187. This option enables normal printk support. Removing it
  1188. eliminates most of the message strings from the kernel image
  1189. and makes the kernel more or less silent. As this makes it
  1190. very difficult to diagnose system problems, saying N here is
  1191. strongly discouraged.
  1192. config BUG
  1193. bool "BUG() support" if EXPERT
  1194. default y
  1195. help
  1196. Disabling this option eliminates support for BUG and WARN, reducing
  1197. the size of your kernel image and potentially quietly ignoring
  1198. numerous fatal conditions. You should only consider disabling this
  1199. option for embedded systems with no facilities for reporting errors.
  1200. Just say Y.
  1201. config ELF_CORE
  1202. depends on COREDUMP
  1203. default y
  1204. bool "Enable ELF core dumps" if EXPERT
  1205. help
  1206. Enable support for generating core dumps. Disabling saves about 4k.
  1207. config PCSPKR_PLATFORM
  1208. bool "Enable PC-Speaker support" if EXPERT
  1209. depends on HAVE_PCSPKR_PLATFORM
  1210. select I8253_LOCK
  1211. default y
  1212. help
  1213. This option allows to disable the internal PC-Speaker
  1214. support, saving some memory.
  1215. config BASE_FULL
  1216. default y
  1217. bool "Enable full-sized data structures for core" if EXPERT
  1218. help
  1219. Disabling this option reduces the size of miscellaneous core
  1220. kernel data structures. This saves memory on small machines,
  1221. but may reduce performance.
  1222. config FUTEX
  1223. bool "Enable futex support" if EXPERT
  1224. default y
  1225. select RT_MUTEXES
  1226. help
  1227. Disabling this option will cause the kernel to be built without
  1228. support for "fast userspace mutexes". The resulting kernel may not
  1229. run glibc-based applications correctly.
  1230. config HAVE_FUTEX_CMPXCHG
  1231. bool
  1232. depends on FUTEX
  1233. help
  1234. Architectures should select this if futex_atomic_cmpxchg_inatomic()
  1235. is implemented and always working. This removes a couple of runtime
  1236. checks.
  1237. config EPOLL
  1238. bool "Enable eventpoll support" if EXPERT
  1239. default y
  1240. select ANON_INODES
  1241. help
  1242. Disabling this option will cause the kernel to be built without
  1243. support for epoll family of system calls.
  1244. config SIGNALFD
  1245. bool "Enable signalfd() system call" if EXPERT
  1246. select ANON_INODES
  1247. default y
  1248. help
  1249. Enable the signalfd() system call that allows to receive signals
  1250. on a file descriptor.
  1251. If unsure, say Y.
  1252. config TIMERFD
  1253. bool "Enable timerfd() system call" if EXPERT
  1254. select ANON_INODES
  1255. default y
  1256. help
  1257. Enable the timerfd() system call that allows to receive timer
  1258. events on a file descriptor.
  1259. If unsure, say Y.
  1260. config EVENTFD
  1261. bool "Enable eventfd() system call" if EXPERT
  1262. select ANON_INODES
  1263. default y
  1264. help
  1265. Enable the eventfd() system call that allows to receive both
  1266. kernel notification (ie. KAIO) or userspace notifications.
  1267. If unsure, say Y.
  1268. # syscall, maps, verifier
  1269. config BPF_SYSCALL
  1270. bool "Enable bpf() system call" if EXPERT
  1271. select ANON_INODES
  1272. select BPF
  1273. default n
  1274. help
  1275. Enable the bpf() system call that allows to manipulate eBPF
  1276. programs and maps via file descriptors.
  1277. config SHMEM
  1278. bool "Use full shmem filesystem" if EXPERT
  1279. default y
  1280. depends on MMU
  1281. help
  1282. The shmem is an internal filesystem used to manage shared memory.
  1283. It is backed by swap and manages resource limits. It is also exported
  1284. to userspace as tmpfs if TMPFS is enabled. Disabling this
  1285. option replaces shmem and tmpfs with the much simpler ramfs code,
  1286. which may be appropriate on small systems without swap.
  1287. config AIO
  1288. bool "Enable AIO support" if EXPERT
  1289. default y
  1290. help
  1291. This option enables POSIX asynchronous I/O which may by used
  1292. by some high performance threaded applications. Disabling
  1293. this option saves about 7k.
  1294. config ADVISE_SYSCALLS
  1295. bool "Enable madvise/fadvise syscalls" if EXPERT
  1296. default y
  1297. help
  1298. This option enables the madvise and fadvise syscalls, used by
  1299. applications to advise the kernel about their future memory or file
  1300. usage, improving performance. If building an embedded system where no
  1301. applications use these syscalls, you can disable this option to save
  1302. space.
  1303. config PCI_QUIRKS
  1304. default y
  1305. bool "Enable PCI quirk workarounds" if EXPERT
  1306. depends on PCI
  1307. help
  1308. This enables workarounds for various PCI chipset
  1309. bugs/quirks. Disable this only if your target machine is
  1310. unaffected by PCI quirks.
  1311. config EMBEDDED
  1312. bool "Embedded system"
  1313. option allnoconfig_y
  1314. select EXPERT
  1315. help
  1316. This option should be enabled if compiling the kernel for
  1317. an embedded system so certain expert options are available
  1318. for configuration.
  1319. config HAVE_PERF_EVENTS
  1320. bool
  1321. help
  1322. See tools/perf/design.txt for details.
  1323. config PERF_USE_VMALLOC
  1324. bool
  1325. help
  1326. See tools/perf/design.txt for details
  1327. menu "Kernel Performance Events And Counters"
  1328. config PERF_EVENTS
  1329. bool "Kernel performance events and counters"
  1330. default y if PROFILING
  1331. depends on HAVE_PERF_EVENTS
  1332. select ANON_INODES
  1333. select IRQ_WORK
  1334. select SRCU
  1335. help
  1336. Enable kernel support for various performance events provided
  1337. by software and hardware.
  1338. Software events are supported either built-in or via the
  1339. use of generic tracepoints.
  1340. Most modern CPUs support performance events via performance
  1341. counter registers. These registers count the number of certain
  1342. types of hw events: such as instructions executed, cachemisses
  1343. suffered, or branches mis-predicted - without slowing down the
  1344. kernel or applications. These registers can also trigger interrupts
  1345. when a threshold number of events have passed - and can thus be
  1346. used to profile the code that runs on that CPU.
  1347. The Linux Performance Event subsystem provides an abstraction of
  1348. these software and hardware event capabilities, available via a
  1349. system call and used by the "perf" utility in tools/perf/. It
  1350. provides per task and per CPU counters, and it provides event
  1351. capabilities on top of those.
  1352. Say Y if unsure.
  1353. config DEBUG_PERF_USE_VMALLOC
  1354. default n
  1355. bool "Debug: use vmalloc to back perf mmap() buffers"
  1356. depends on PERF_EVENTS && DEBUG_KERNEL
  1357. select PERF_USE_VMALLOC
  1358. help
  1359. Use vmalloc memory to back perf mmap() buffers.
  1360. Mostly useful for debugging the vmalloc code on platforms
  1361. that don't require it.
  1362. Say N if unsure.
  1363. endmenu
  1364. config VM_EVENT_COUNTERS
  1365. default y
  1366. bool "Enable VM event counters for /proc/vmstat" if EXPERT
  1367. help
  1368. VM event counters are needed for event counts to be shown.
  1369. This option allows the disabling of the VM event counters
  1370. on EXPERT systems. /proc/vmstat will only show page counts
  1371. if VM event counters are disabled.
  1372. config SLUB_DEBUG
  1373. default y
  1374. bool "Enable SLUB debugging support" if EXPERT
  1375. depends on SLUB && SYSFS
  1376. help
  1377. SLUB has extensive debug support features. Disabling these can
  1378. result in significant savings in code size. This also disables
  1379. SLUB sysfs support. /sys/slab will not exist and there will be
  1380. no support for cache validation etc.
  1381. config COMPAT_BRK
  1382. bool "Disable heap randomization"
  1383. default y
  1384. help
  1385. Randomizing heap placement makes heap exploits harder, but it
  1386. also breaks ancient binaries (including anything libc5 based).
  1387. This option changes the bootup default to heap randomization
  1388. disabled, and can be overridden at runtime by setting
  1389. /proc/sys/kernel/randomize_va_space to 2.
  1390. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  1391. choice
  1392. prompt "Choose SLAB allocator"
  1393. default SLUB
  1394. help
  1395. This option allows to select a slab allocator.
  1396. config SLAB
  1397. bool "SLAB"
  1398. help
  1399. The regular slab allocator that is established and known to work
  1400. well in all environments. It organizes cache hot objects in
  1401. per cpu and per node queues.
  1402. config SLUB
  1403. bool "SLUB (Unqueued Allocator)"
  1404. help
  1405. SLUB is a slab allocator that minimizes cache line usage
  1406. instead of managing queues of cached objects (SLAB approach).
  1407. Per cpu caching is realized using slabs of objects instead
  1408. of queues of objects. SLUB can use memory efficiently
  1409. and has enhanced diagnostics. SLUB is the default choice for
  1410. a slab allocator.
  1411. config SLOB
  1412. depends on EXPERT
  1413. bool "SLOB (Simple Allocator)"
  1414. help
  1415. SLOB replaces the stock allocator with a drastically simpler
  1416. allocator. SLOB is generally more space efficient but
  1417. does not perform as well on large systems.
  1418. endchoice
  1419. config SLUB_CPU_PARTIAL
  1420. default y
  1421. depends on SLUB && SMP
  1422. bool "SLUB per cpu partial cache"
  1423. help
  1424. Per cpu partial caches accellerate objects allocation and freeing
  1425. that is local to a processor at the price of more indeterminism
  1426. in the latency of the free. On overflow these caches will be cleared
  1427. which requires the taking of locks that may cause latency spikes.
  1428. Typically one would choose no for a realtime system.
  1429. config MMAP_ALLOW_UNINITIALIZED
  1430. bool "Allow mmapped anonymous memory to be uninitialized"
  1431. depends on EXPERT && !MMU
  1432. default n
  1433. help
  1434. Normally, and according to the Linux spec, anonymous memory obtained
  1435. from mmap() has it's contents cleared before it is passed to
  1436. userspace. Enabling this config option allows you to request that
  1437. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  1438. providing a huge performance boost. If this option is not enabled,
  1439. then the flag will be ignored.
  1440. This is taken advantage of by uClibc's malloc(), and also by
  1441. ELF-FDPIC binfmt's brk and stack allocator.
  1442. Because of the obvious security issues, this option should only be
  1443. enabled on embedded devices where you control what is run in
  1444. userspace. Since that isn't generally a problem on no-MMU systems,
  1445. it is normally safe to say Y here.
  1446. See Documentation/nommu-mmap.txt for more information.
  1447. config SYSTEM_TRUSTED_KEYRING
  1448. bool "Provide system-wide ring of trusted keys"
  1449. depends on KEYS
  1450. help
  1451. Provide a system keyring to which trusted keys can be added. Keys in
  1452. the keyring are considered to be trusted. Keys may be added at will
  1453. by the kernel from compiled-in data and from hardware key stores, but
  1454. userspace may only add extra keys if those keys can be verified by
  1455. keys already in the keyring.
  1456. Keys in this keyring are used by module signature checking.
  1457. config PROFILING
  1458. bool "Profiling support"
  1459. help
  1460. Say Y here to enable the extended profiling support mechanisms used
  1461. by profilers such as OProfile.
  1462. #
  1463. # Place an empty function call at each tracepoint site. Can be
  1464. # dynamically changed for a probe function.
  1465. #
  1466. config TRACEPOINTS
  1467. bool
  1468. source "arch/Kconfig"
  1469. endmenu # General setup
  1470. config HAVE_GENERIC_DMA_COHERENT
  1471. bool
  1472. default n
  1473. config SLABINFO
  1474. bool
  1475. depends on PROC_FS
  1476. depends on SLAB || SLUB_DEBUG
  1477. default y
  1478. config RT_MUTEXES
  1479. bool
  1480. config BASE_SMALL
  1481. int
  1482. default 0 if BASE_FULL
  1483. default 1 if !BASE_FULL
  1484. menuconfig MODULES
  1485. bool "Enable loadable module support"
  1486. option modules
  1487. help
  1488. Kernel modules are small pieces of compiled code which can
  1489. be inserted in the running kernel, rather than being
  1490. permanently built into the kernel. You use the "modprobe"
  1491. tool to add (and sometimes remove) them. If you say Y here,
  1492. many parts of the kernel can be built as modules (by
  1493. answering M instead of Y where indicated): this is most
  1494. useful for infrequently used options which are not required
  1495. for booting. For more information, see the man pages for
  1496. modprobe, lsmod, modinfo, insmod and rmmod.
  1497. If you say Y here, you will need to run "make
  1498. modules_install" to put the modules under /lib/modules/
  1499. where modprobe can find them (you may need to be root to do
  1500. this).
  1501. If unsure, say Y.
  1502. if MODULES
  1503. config MODULE_FORCE_LOAD
  1504. bool "Forced module loading"
  1505. default n
  1506. help
  1507. Allow loading of modules without version information (ie. modprobe
  1508. --force). Forced module loading sets the 'F' (forced) taint flag and
  1509. is usually a really bad idea.
  1510. config MODULE_UNLOAD
  1511. bool "Module unloading"
  1512. help
  1513. Without this option you will not be able to unload any
  1514. modules (note that some modules may not be unloadable
  1515. anyway), which makes your kernel smaller, faster
  1516. and simpler. If unsure, say Y.
  1517. config MODULE_FORCE_UNLOAD
  1518. bool "Forced module unloading"
  1519. depends on MODULE_UNLOAD
  1520. help
  1521. This option allows you to force a module to unload, even if the
  1522. kernel believes it is unsafe: the kernel will remove the module
  1523. without waiting for anyone to stop using it (using the -f option to
  1524. rmmod). This is mainly for kernel developers and desperate users.
  1525. If unsure, say N.
  1526. config MODVERSIONS
  1527. bool "Module versioning support"
  1528. help
  1529. Usually, you have to use modules compiled with your kernel.
  1530. Saying Y here makes it sometimes possible to use modules
  1531. compiled for different kernels, by adding enough information
  1532. to the modules to (hopefully) spot any changes which would
  1533. make them incompatible with the kernel you are running. If
  1534. unsure, say N.
  1535. config MODULE_SRCVERSION_ALL
  1536. bool "Source checksum for all modules"
  1537. help
  1538. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1539. field inserted into their modinfo section, which contains a
  1540. sum of the source files which made it. This helps maintainers
  1541. see exactly which source was used to build a module (since
  1542. others sometimes change the module source without updating
  1543. the version). With this option, such a "srcversion" field
  1544. will be created for all modules. If unsure, say N.
  1545. config MODULE_SIG
  1546. bool "Module signature verification"
  1547. depends on MODULES
  1548. select SYSTEM_TRUSTED_KEYRING
  1549. select KEYS
  1550. select CRYPTO
  1551. select ASYMMETRIC_KEY_TYPE
  1552. select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  1553. select PUBLIC_KEY_ALGO_RSA
  1554. select ASN1
  1555. select OID_REGISTRY
  1556. select X509_CERTIFICATE_PARSER
  1557. help
  1558. Check modules for valid signatures upon load: the signature
  1559. is simply appended to the module. For more information see
  1560. Documentation/module-signing.txt.
  1561. !!!WARNING!!! If you enable this option, you MUST make sure that the
  1562. module DOES NOT get stripped after being signed. This includes the
  1563. debuginfo strip done by some packagers (such as rpmbuild) and
  1564. inclusion into an initramfs that wants the module size reduced.
  1565. config MODULE_SIG_FORCE
  1566. bool "Require modules to be validly signed"
  1567. depends on MODULE_SIG
  1568. help
  1569. Reject unsigned modules or signed modules for which we don't have a
  1570. key. Without this, such modules will simply taint the kernel.
  1571. config MODULE_SIG_ALL
  1572. bool "Automatically sign all modules"
  1573. default y
  1574. depends on MODULE_SIG
  1575. help
  1576. Sign all modules during make modules_install. Without this option,
  1577. modules must be signed manually, using the scripts/sign-file tool.
  1578. comment "Do not forget to sign required modules with scripts/sign-file"
  1579. depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
  1580. choice
  1581. prompt "Which hash algorithm should modules be signed with?"
  1582. depends on MODULE_SIG
  1583. help
  1584. This determines which sort of hashing algorithm will be used during
  1585. signature generation. This algorithm _must_ be built into the kernel
  1586. directly so that signature verification can take place. It is not
  1587. possible to load a signed module containing the algorithm to check
  1588. the signature on that module.
  1589. config MODULE_SIG_SHA1
  1590. bool "Sign modules with SHA-1"
  1591. select CRYPTO_SHA1
  1592. config MODULE_SIG_SHA224
  1593. bool "Sign modules with SHA-224"
  1594. select CRYPTO_SHA256
  1595. config MODULE_SIG_SHA256
  1596. bool "Sign modules with SHA-256"
  1597. select CRYPTO_SHA256
  1598. config MODULE_SIG_SHA384
  1599. bool "Sign modules with SHA-384"
  1600. select CRYPTO_SHA512
  1601. config MODULE_SIG_SHA512
  1602. bool "Sign modules with SHA-512"
  1603. select CRYPTO_SHA512
  1604. endchoice
  1605. config MODULE_SIG_HASH
  1606. string
  1607. depends on MODULE_SIG
  1608. default "sha1" if MODULE_SIG_SHA1
  1609. default "sha224" if MODULE_SIG_SHA224
  1610. default "sha256" if MODULE_SIG_SHA256
  1611. default "sha384" if MODULE_SIG_SHA384
  1612. default "sha512" if MODULE_SIG_SHA512
  1613. config MODULE_COMPRESS
  1614. bool "Compress modules on installation"
  1615. depends on MODULES
  1616. help
  1617. This option compresses the kernel modules when 'make
  1618. modules_install' is run.
  1619. The modules will be compressed either using gzip or xz depend on the
  1620. choice made in "Compression algorithm".
  1621. module-init-tools has support for gzip format while kmod handle gzip
  1622. and xz compressed modules.
  1623. When a kernel module is installed from outside of the main kernel
  1624. source and uses the Kbuild system for installing modules then that
  1625. kernel module will also be compressed when it is installed.
  1626. This option provides little benefit when the modules are to be used inside
  1627. an initrd or initramfs, it generally is more efficient to compress the whole
  1628. initrd or initramfs instead.
  1629. This is fully compatible with signed modules while the signed module is
  1630. compressed. module-init-tools or kmod handles decompression and provide to
  1631. other layer the uncompressed but signed payload.
  1632. choice
  1633. prompt "Compression algorithm"
  1634. depends on MODULE_COMPRESS
  1635. default MODULE_COMPRESS_GZIP
  1636. help
  1637. This determines which sort of compression will be used during
  1638. 'make modules_install'.
  1639. GZIP (default) and XZ are supported.
  1640. config MODULE_COMPRESS_GZIP
  1641. bool "GZIP"
  1642. config MODULE_COMPRESS_XZ
  1643. bool "XZ"
  1644. endchoice
  1645. endif # MODULES
  1646. config INIT_ALL_POSSIBLE
  1647. bool
  1648. help
  1649. Back when each arch used to define their own cpu_online_mask and
  1650. cpu_possible_mask, some of them chose to initialize cpu_possible_mask
  1651. with all 1s, and others with all 0s. When they were centralised,
  1652. it was better to provide this option than to break all the archs
  1653. and have several arch maintainers pursuing me down dark alleys.
  1654. config STOP_MACHINE
  1655. bool
  1656. default y
  1657. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1658. help
  1659. Need stop_machine() primitive.
  1660. source "block/Kconfig"
  1661. config PREEMPT_NOTIFIERS
  1662. bool
  1663. config PADATA
  1664. depends on SMP
  1665. bool
  1666. # Can be selected by architectures with broken toolchains
  1667. # that get confused by correct const<->read_only section
  1668. # mappings
  1669. config BROKEN_RODATA
  1670. bool
  1671. config ASN1
  1672. tristate
  1673. help
  1674. Build a simple ASN.1 grammar compiler that produces a bytecode output
  1675. that can be interpreted by the ASN.1 stream decoder and used to
  1676. inform it as to what tags are to be expected in a stream and what
  1677. functions to call on what tags.
  1678. source "kernel/Kconfig.locks"