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. select IRQ_WORK
  392. help
  393. This option selects the RCU implementation that is
  394. designed for very large SMP system with hundreds or
  395. thousands of CPUs. It also scales down nicely to
  396. smaller systems.
  397. config TREE_PREEMPT_RCU
  398. bool "Preemptible tree-based hierarchical RCU"
  399. depends on PREEMPT
  400. select IRQ_WORK
  401. help
  402. This option selects the RCU implementation that is
  403. designed for very large SMP systems with hundreds or
  404. thousands of CPUs, but for which real-time response
  405. is also required. It also scales down nicely to
  406. smaller systems.
  407. Select this option if you are unsure.
  408. config TINY_RCU
  409. bool "UP-only small-memory-footprint RCU"
  410. depends on !PREEMPT && !SMP
  411. help
  412. This option selects the RCU implementation that is
  413. designed for UP systems from which real-time response
  414. is not required. This option greatly reduces the
  415. memory footprint of RCU.
  416. endchoice
  417. config PREEMPT_RCU
  418. def_bool TREE_PREEMPT_RCU
  419. help
  420. This option enables preemptible-RCU code that is common between
  421. TREE_PREEMPT_RCU and, in the old days, TINY_PREEMPT_RCU.
  422. config RCU_STALL_COMMON
  423. def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
  424. help
  425. This option enables RCU CPU stall code that is common between
  426. the TINY and TREE variants of RCU. The purpose is to allow
  427. the tiny variants to disable RCU CPU stall warnings, while
  428. making these warnings mandatory for the tree variants.
  429. config CONTEXT_TRACKING
  430. bool
  431. config RCU_USER_QS
  432. bool "Consider userspace as in RCU extended quiescent state"
  433. depends on HAVE_CONTEXT_TRACKING && SMP
  434. select CONTEXT_TRACKING
  435. help
  436. This option sets hooks on kernel / userspace boundaries and
  437. puts RCU in extended quiescent state when the CPU runs in
  438. userspace. It means that when a CPU runs in userspace, it is
  439. excluded from the global RCU state machine and thus doesn't
  440. try to keep the timer tick on for RCU.
  441. Unless you want to hack and help the development of the full
  442. dynticks mode, you shouldn't enable this option. It also
  443. adds unnecessary overhead.
  444. If unsure say N
  445. config CONTEXT_TRACKING_FORCE
  446. bool "Force context tracking"
  447. depends on CONTEXT_TRACKING
  448. default y if !NO_HZ_FULL
  449. help
  450. The major pre-requirement for full dynticks to work is to
  451. support the context tracking subsystem. But there are also
  452. other dependencies to provide in order to make the full
  453. dynticks working.
  454. This option stands for testing when an arch implements the
  455. context tracking backend but doesn't yet fullfill all the
  456. requirements to make the full dynticks feature working.
  457. Without the full dynticks, there is no way to test the support
  458. for context tracking and the subsystems that rely on it: RCU
  459. userspace extended quiescent state and tickless cputime
  460. accounting. This option copes with the absence of the full
  461. dynticks subsystem by forcing the context tracking on all
  462. CPUs in the system.
  463. Say Y only if you're working on the development of an
  464. architecture backend for the context tracking.
  465. Say N otherwise, this option brings an overhead that you
  466. don't want in production.
  467. config RCU_FANOUT
  468. int "Tree-based hierarchical RCU fanout value"
  469. range 2 64 if 64BIT
  470. range 2 32 if !64BIT
  471. depends on TREE_RCU || TREE_PREEMPT_RCU
  472. default 64 if 64BIT
  473. default 32 if !64BIT
  474. help
  475. This option controls the fanout of hierarchical implementations
  476. of RCU, allowing RCU to work efficiently on machines with
  477. large numbers of CPUs. This value must be at least the fourth
  478. root of NR_CPUS, which allows NR_CPUS to be insanely large.
  479. The default value of RCU_FANOUT should be used for production
  480. systems, but if you are stress-testing the RCU implementation
  481. itself, small RCU_FANOUT values allow you to test large-system
  482. code paths on small(er) systems.
  483. Select a specific number if testing RCU itself.
  484. Take the default if unsure.
  485. config RCU_FANOUT_LEAF
  486. int "Tree-based hierarchical RCU leaf-level fanout value"
  487. range 2 RCU_FANOUT if 64BIT
  488. range 2 RCU_FANOUT if !64BIT
  489. depends on TREE_RCU || TREE_PREEMPT_RCU
  490. default 16
  491. help
  492. This option controls the leaf-level fanout of hierarchical
  493. implementations of RCU, and allows trading off cache misses
  494. against lock contention. Systems that synchronize their
  495. scheduling-clock interrupts for energy-efficiency reasons will
  496. want the default because the smaller leaf-level fanout keeps
  497. lock contention levels acceptably low. Very large systems
  498. (hundreds or thousands of CPUs) will instead want to set this
  499. value to the maximum value possible in order to reduce the
  500. number of cache misses incurred during RCU's grace-period
  501. initialization. These systems tend to run CPU-bound, and thus
  502. are not helped by synchronized interrupts, and thus tend to
  503. skew them, which reduces lock contention enough that large
  504. leaf-level fanouts work well.
  505. Select a specific number if testing RCU itself.
  506. Select the maximum permissible value for large systems.
  507. Take the default if unsure.
  508. config RCU_FANOUT_EXACT
  509. bool "Disable tree-based hierarchical RCU auto-balancing"
  510. depends on TREE_RCU || TREE_PREEMPT_RCU
  511. default n
  512. help
  513. This option forces use of the exact RCU_FANOUT value specified,
  514. regardless of imbalances in the hierarchy. This is useful for
  515. testing RCU itself, and might one day be useful on systems with
  516. strong NUMA behavior.
  517. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  518. Say N if unsure.
  519. config RCU_FAST_NO_HZ
  520. bool "Accelerate last non-dyntick-idle CPU's grace periods"
  521. depends on NO_HZ_COMMON && SMP
  522. default n
  523. help
  524. This option permits CPUs to enter dynticks-idle state even if
  525. they have RCU callbacks queued, and prevents RCU from waking
  526. these CPUs up more than roughly once every four jiffies (by
  527. default, you can adjust this using the rcutree.rcu_idle_gp_delay
  528. parameter), thus improving energy efficiency. On the other
  529. hand, this option increases the duration of RCU grace periods,
  530. for example, slowing down synchronize_rcu().
  531. Say Y if energy efficiency is critically important, and you
  532. don't care about increased grace-period durations.
  533. Say N if you are unsure.
  534. config TREE_RCU_TRACE
  535. def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
  536. select DEBUG_FS
  537. help
  538. This option provides tracing for the TREE_RCU and
  539. TREE_PREEMPT_RCU implementations, permitting Makefile to
  540. trivially select kernel/rcutree_trace.c.
  541. config RCU_BOOST
  542. bool "Enable RCU priority boosting"
  543. depends on RT_MUTEXES && PREEMPT_RCU
  544. default n
  545. help
  546. This option boosts the priority of preempted RCU readers that
  547. block the current preemptible RCU grace period for too long.
  548. This option also prevents heavy loads from blocking RCU
  549. callback invocation for all flavors of RCU.
  550. Say Y here if you are working with real-time apps or heavy loads
  551. Say N here if you are unsure.
  552. config RCU_BOOST_PRIO
  553. int "Real-time priority to boost RCU readers to"
  554. range 1 99
  555. depends on RCU_BOOST
  556. default 1
  557. help
  558. This option specifies the real-time priority to which long-term
  559. preempted RCU readers are to be boosted. If you are working
  560. with a real-time application that has one or more CPU-bound
  561. threads running at a real-time priority level, you should set
  562. RCU_BOOST_PRIO to a priority higher then the highest-priority
  563. real-time CPU-bound thread. The default RCU_BOOST_PRIO value
  564. of 1 is appropriate in the common case, which is real-time
  565. applications that do not have any CPU-bound threads.
  566. Some real-time applications might not have a single real-time
  567. thread that saturates a given CPU, but instead might have
  568. multiple real-time threads that, taken together, fully utilize
  569. that CPU. In this case, you should set RCU_BOOST_PRIO to
  570. a priority higher than the lowest-priority thread that is
  571. conspiring to prevent the CPU from running any non-real-time
  572. tasks. For example, if one thread at priority 10 and another
  573. thread at priority 5 are between themselves fully consuming
  574. the CPU time on a given CPU, then RCU_BOOST_PRIO should be
  575. set to priority 6 or higher.
  576. Specify the real-time priority, or take the default if unsure.
  577. config RCU_BOOST_DELAY
  578. int "Milliseconds to delay boosting after RCU grace-period start"
  579. range 0 3000
  580. depends on RCU_BOOST
  581. default 500
  582. help
  583. This option specifies the time to wait after the beginning of
  584. a given grace period before priority-boosting preempted RCU
  585. readers blocking that grace period. Note that any RCU reader
  586. blocking an expedited RCU grace period is boosted immediately.
  587. Accept the default if unsure.
  588. config RCU_NOCB_CPU
  589. bool "Offload RCU callback processing from boot-selected CPUs"
  590. depends on TREE_RCU || TREE_PREEMPT_RCU
  591. default n
  592. help
  593. Use this option to reduce OS jitter for aggressive HPC or
  594. real-time workloads. It can also be used to offload RCU
  595. callback invocation to energy-efficient CPUs in battery-powered
  596. asymmetric multiprocessors.
  597. This option offloads callback invocation from the set of
  598. CPUs specified at boot time by the rcu_nocbs parameter.
  599. For each such CPU, a kthread ("rcuox/N") will be created to
  600. invoke callbacks, where the "N" is the CPU being offloaded,
  601. and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
  602. "s" for RCU-sched. Nothing prevents this kthread from running
  603. on the specified CPUs, but (1) the kthreads may be preempted
  604. between each callback, and (2) affinity or cgroups can be used
  605. to force the kthreads to run on whatever set of CPUs is desired.
  606. Say Y here if you want to help to debug reduced OS jitter.
  607. Say N here if you are unsure.
  608. choice
  609. prompt "Build-forced no-CBs CPUs"
  610. default RCU_NOCB_CPU_NONE
  611. help
  612. This option allows no-CBs CPUs (whose RCU callbacks are invoked
  613. from kthreads rather than from softirq context) to be specified
  614. at build time. Additional no-CBs CPUs may be specified by
  615. the rcu_nocbs= boot parameter.
  616. config RCU_NOCB_CPU_NONE
  617. bool "No build_forced no-CBs CPUs"
  618. depends on RCU_NOCB_CPU && !NO_HZ_FULL_ALL
  619. help
  620. This option does not force any of the CPUs to be no-CBs CPUs.
  621. Only CPUs designated by the rcu_nocbs= boot parameter will be
  622. no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
  623. kthreads whose names begin with "rcuo". All other CPUs will
  624. invoke their own RCU callbacks in softirq context.
  625. Select this option if you want to choose no-CBs CPUs at
  626. boot time, for example, to allow testing of different no-CBs
  627. configurations without having to rebuild the kernel each time.
  628. config RCU_NOCB_CPU_ZERO
  629. bool "CPU 0 is a build_forced no-CBs CPU"
  630. depends on RCU_NOCB_CPU && !NO_HZ_FULL_ALL
  631. help
  632. This option forces CPU 0 to be a no-CBs CPU, so that its RCU
  633. callbacks are invoked by a per-CPU kthread whose name begins
  634. with "rcuo". Additional CPUs may be designated as no-CBs
  635. CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
  636. All other CPUs will invoke their own RCU callbacks in softirq
  637. context.
  638. Select this if CPU 0 needs to be a no-CBs CPU for real-time
  639. or energy-efficiency reasons, but the real reason it exists
  640. is to ensure that randconfig testing covers mixed systems.
  641. config RCU_NOCB_CPU_ALL
  642. bool "All CPUs are build_forced no-CBs CPUs"
  643. depends on RCU_NOCB_CPU
  644. help
  645. This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
  646. boot parameter will be ignored. All CPUs' RCU callbacks will
  647. be executed in the context of per-CPU rcuo kthreads created for
  648. this purpose. Assuming that the kthreads whose names start with
  649. "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
  650. on the remaining CPUs, but might decrease memory locality during
  651. RCU-callback invocation, thus potentially degrading throughput.
  652. Select this if all CPUs need to be no-CBs CPUs for real-time
  653. or energy-efficiency reasons.
  654. endchoice
  655. endmenu # "RCU Subsystem"
  656. config BUILD_BIN2C
  657. bool
  658. default n
  659. config IKCONFIG
  660. tristate "Kernel .config support"
  661. select BUILD_BIN2C
  662. ---help---
  663. This option enables the complete Linux kernel ".config" file
  664. contents to be saved in the kernel. It provides documentation
  665. of which kernel options are used in a running kernel or in an
  666. on-disk kernel. This information can be extracted from the kernel
  667. image file with the script scripts/extract-ikconfig and used as
  668. input to rebuild the current kernel or to build another kernel.
  669. It can also be extracted from a running kernel by reading
  670. /proc/config.gz if enabled (below).
  671. config IKCONFIG_PROC
  672. bool "Enable access to .config through /proc/config.gz"
  673. depends on IKCONFIG && PROC_FS
  674. ---help---
  675. This option enables access to the kernel configuration file
  676. through /proc/config.gz.
  677. config LOG_BUF_SHIFT
  678. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  679. range 12 21
  680. default 17
  681. depends on PRINTK
  682. help
  683. Select the minimal kernel log buffer size as a power of 2.
  684. The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
  685. parameter, see below. Any higher size also might be forced
  686. by "log_buf_len" boot parameter.
  687. Examples:
  688. 17 => 128 KB
  689. 16 => 64 KB
  690. 15 => 32 KB
  691. 14 => 16 KB
  692. 13 => 8 KB
  693. 12 => 4 KB
  694. config LOG_CPU_MAX_BUF_SHIFT
  695. int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
  696. range 0 21
  697. default 12 if !BASE_SMALL
  698. default 0 if BASE_SMALL
  699. depends on PRINTK
  700. help
  701. This option allows to increase the default ring buffer size
  702. according to the number of CPUs. The value defines the contribution
  703. of each CPU as a power of 2. The used space is typically only few
  704. lines however it might be much more when problems are reported,
  705. e.g. backtraces.
  706. The increased size means that a new buffer has to be allocated and
  707. the original static one is unused. It makes sense only on systems
  708. with more CPUs. Therefore this value is used only when the sum of
  709. contributions is greater than the half of the default kernel ring
  710. buffer as defined by LOG_BUF_SHIFT. The default values are set
  711. so that more than 64 CPUs are needed to trigger the allocation.
  712. Also this option is ignored when "log_buf_len" kernel parameter is
  713. used as it forces an exact (power of two) size of the ring buffer.
  714. The number of possible CPUs is used for this computation ignoring
  715. hotplugging making the compuation optimal for the the worst case
  716. scenerio while allowing a simple algorithm to be used from bootup.
  717. Examples shift values and their meaning:
  718. 17 => 128 KB for each CPU
  719. 16 => 64 KB for each CPU
  720. 15 => 32 KB for each CPU
  721. 14 => 16 KB for each CPU
  722. 13 => 8 KB for each CPU
  723. 12 => 4 KB for each CPU
  724. #
  725. # Architectures with an unreliable sched_clock() should select this:
  726. #
  727. config HAVE_UNSTABLE_SCHED_CLOCK
  728. bool
  729. config GENERIC_SCHED_CLOCK
  730. bool
  731. #
  732. # For architectures that want to enable the support for NUMA-affine scheduler
  733. # balancing logic:
  734. #
  735. config ARCH_SUPPORTS_NUMA_BALANCING
  736. bool
  737. #
  738. # For architectures that know their GCC __int128 support is sound
  739. #
  740. config ARCH_SUPPORTS_INT128
  741. bool
  742. # For architectures that (ab)use NUMA to represent different memory regions
  743. # all cpu-local but of different latencies, such as SuperH.
  744. #
  745. config ARCH_WANT_NUMA_VARIABLE_LOCALITY
  746. bool
  747. config NUMA_BALANCING_DEFAULT_ENABLED
  748. bool "Automatically enable NUMA aware memory/task placement"
  749. default y
  750. depends on NUMA_BALANCING
  751. help
  752. If set, automatic NUMA balancing will be enabled if running on a NUMA
  753. machine.
  754. config NUMA_BALANCING
  755. bool "Memory placement aware NUMA scheduler"
  756. depends on ARCH_SUPPORTS_NUMA_BALANCING
  757. depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
  758. depends on SMP && NUMA && MIGRATION
  759. help
  760. This option adds support for automatic NUMA aware memory/task placement.
  761. The mechanism is quite primitive and is based on migrating memory when
  762. it has references to the node the task is running on.
  763. This system will be inactive on UMA systems.
  764. menuconfig CGROUPS
  765. boolean "Control Group support"
  766. select KERNFS
  767. help
  768. This option adds support for grouping sets of processes together, for
  769. use with process control subsystems such as Cpusets, CFS, memory
  770. controls or device isolation.
  771. See
  772. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  773. - Documentation/cgroups/ (features for grouping, isolation
  774. and resource control)
  775. Say N if unsure.
  776. if CGROUPS
  777. config CGROUP_DEBUG
  778. bool "Example debug cgroup subsystem"
  779. default n
  780. help
  781. This option enables a simple cgroup subsystem that
  782. exports useful debugging information about the cgroups
  783. framework.
  784. Say N if unsure.
  785. config CGROUP_FREEZER
  786. bool "Freezer cgroup subsystem"
  787. help
  788. Provides a way to freeze and unfreeze all tasks in a
  789. cgroup.
  790. config CGROUP_DEVICE
  791. bool "Device controller for cgroups"
  792. help
  793. Provides a cgroup implementing whitelists for devices which
  794. a process in the cgroup can mknod or open.
  795. config CPUSETS
  796. bool "Cpuset support"
  797. help
  798. This option will let you create and manage CPUSETs which
  799. allow dynamically partitioning a system into sets of CPUs and
  800. Memory Nodes and assigning tasks to run only within those sets.
  801. This is primarily useful on large SMP or NUMA systems.
  802. Say N if unsure.
  803. config PROC_PID_CPUSET
  804. bool "Include legacy /proc/<pid>/cpuset file"
  805. depends on CPUSETS
  806. default y
  807. config CGROUP_CPUACCT
  808. bool "Simple CPU accounting cgroup subsystem"
  809. help
  810. Provides a simple Resource Controller for monitoring the
  811. total CPU consumed by the tasks in a cgroup.
  812. config RESOURCE_COUNTERS
  813. bool "Resource counters"
  814. help
  815. This option enables controller independent resource accounting
  816. infrastructure that works with cgroups.
  817. config MEMCG
  818. bool "Memory Resource Controller for Control Groups"
  819. depends on RESOURCE_COUNTERS
  820. select EVENTFD
  821. help
  822. Provides a memory resource controller that manages both anonymous
  823. memory and page cache. (See Documentation/cgroups/memory.txt)
  824. Note that setting this option increases fixed memory overhead
  825. associated with each page of memory in the system. By this,
  826. 8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  827. usage tracking struct at boot. Total amount of this is printed out
  828. at boot.
  829. Only enable when you're ok with these trade offs and really
  830. sure you need the memory resource controller. Even when you enable
  831. this, you can set "cgroup_disable=memory" at your boot option to
  832. disable memory resource controller and you can avoid overheads.
  833. (and lose benefits of memory resource controller)
  834. config MEMCG_SWAP
  835. bool "Memory Resource Controller Swap Extension"
  836. depends on MEMCG && SWAP
  837. help
  838. Add swap management feature to memory resource controller. When you
  839. enable this, you can limit mem+swap usage per cgroup. In other words,
  840. when you disable this, memory resource controller has no cares to
  841. usage of swap...a process can exhaust all of the swap. This extension
  842. is useful when you want to avoid exhaustion swap but this itself
  843. adds more overheads and consumes memory for remembering information.
  844. Especially if you use 32bit system or small memory system, please
  845. be careful about enabling this. When memory resource controller
  846. is disabled by boot option, this will be automatically disabled and
  847. there will be no overhead from this. Even when you set this config=y,
  848. if boot option "swapaccount=0" is set, swap will not be accounted.
  849. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  850. size is 4096bytes, 512k per 1Gbytes of swap.
  851. config MEMCG_SWAP_ENABLED
  852. bool "Memory Resource Controller Swap Extension enabled by default"
  853. depends on MEMCG_SWAP
  854. default y
  855. help
  856. Memory Resource Controller Swap Extension comes with its price in
  857. a bigger memory consumption. General purpose distribution kernels
  858. which want to enable the feature but keep it disabled by default
  859. and let the user enable it by swapaccount=1 boot command line
  860. parameter should have this option unselected.
  861. For those who want to have the feature enabled by default should
  862. select this option (if, for some reason, they need to disable it
  863. then swapaccount=0 does the trick).
  864. config MEMCG_KMEM
  865. bool "Memory Resource Controller Kernel Memory accounting"
  866. depends on MEMCG
  867. depends on SLUB || SLAB
  868. help
  869. The Kernel Memory extension for Memory Resource Controller can limit
  870. the amount of memory used by kernel objects in the system. Those are
  871. fundamentally different from the entities handled by the standard
  872. Memory Controller, which are page-based, and can be swapped. Users of
  873. the kmem extension can use it to guarantee that no group of processes
  874. will ever exhaust kernel resources alone.
  875. WARNING: Current implementation lacks reclaim support. That means
  876. allocation attempts will fail when close to the limit even if there
  877. are plenty of kmem available for reclaim. That makes this option
  878. unusable in real life so DO NOT SELECT IT unless for development
  879. purposes.
  880. config CGROUP_HUGETLB
  881. bool "HugeTLB Resource Controller for Control Groups"
  882. depends on RESOURCE_COUNTERS && HUGETLB_PAGE
  883. default n
  884. help
  885. Provides a cgroup Resource Controller for HugeTLB pages.
  886. When you enable this, you can put a per cgroup limit on HugeTLB usage.
  887. The limit is enforced during page fault. Since HugeTLB doesn't
  888. support page reclaim, enforcing the limit at page fault time implies
  889. that, the application will get SIGBUS signal if it tries to access
  890. HugeTLB pages beyond its limit. This requires the application to know
  891. beforehand how much HugeTLB pages it would require for its use. The
  892. control group is tracked in the third page lru pointer. This means
  893. that we cannot use the controller with huge page less than 3 pages.
  894. config CGROUP_PERF
  895. bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
  896. depends on PERF_EVENTS && CGROUPS
  897. help
  898. This option extends the per-cpu mode to restrict monitoring to
  899. threads which belong to the cgroup specified and run on the
  900. designated cpu.
  901. Say N if unsure.
  902. menuconfig CGROUP_SCHED
  903. bool "Group CPU scheduler"
  904. default n
  905. help
  906. This feature lets CPU scheduler recognize task groups and control CPU
  907. bandwidth allocation to such task groups. It uses cgroups to group
  908. tasks.
  909. if CGROUP_SCHED
  910. config FAIR_GROUP_SCHED
  911. bool "Group scheduling for SCHED_OTHER"
  912. depends on CGROUP_SCHED
  913. default CGROUP_SCHED
  914. config CFS_BANDWIDTH
  915. bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
  916. depends on FAIR_GROUP_SCHED
  917. default n
  918. help
  919. This option allows users to define CPU bandwidth rates (limits) for
  920. tasks running within the fair group scheduler. Groups with no limit
  921. set are considered to be unconstrained and will run with no
  922. restriction.
  923. See tip/Documentation/scheduler/sched-bwc.txt for more information.
  924. config RT_GROUP_SCHED
  925. bool "Group scheduling for SCHED_RR/FIFO"
  926. depends on CGROUP_SCHED
  927. default n
  928. help
  929. This feature lets you explicitly allocate real CPU bandwidth
  930. to task groups. If enabled, it will also make it impossible to
  931. schedule realtime tasks for non-root users until you allocate
  932. realtime bandwidth for them.
  933. See Documentation/scheduler/sched-rt-group.txt for more information.
  934. endif #CGROUP_SCHED
  935. config BLK_CGROUP
  936. bool "Block IO controller"
  937. depends on BLOCK
  938. default n
  939. ---help---
  940. Generic block IO controller cgroup interface. This is the common
  941. cgroup interface which should be used by various IO controlling
  942. policies.
  943. Currently, CFQ IO scheduler uses it to recognize task groups and
  944. control disk bandwidth allocation (proportional time slice allocation)
  945. to such task groups. It is also used by bio throttling logic in
  946. block layer to implement upper limit in IO rates on a device.
  947. This option only enables generic Block IO controller infrastructure.
  948. One needs to also enable actual IO controlling logic/policy. For
  949. enabling proportional weight division of disk bandwidth in CFQ, set
  950. CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
  951. CONFIG_BLK_DEV_THROTTLING=y.
  952. See Documentation/cgroups/blkio-controller.txt for more information.
  953. config DEBUG_BLK_CGROUP
  954. bool "Enable Block IO controller debugging"
  955. depends on BLK_CGROUP
  956. default n
  957. ---help---
  958. Enable some debugging help. Currently it exports additional stat
  959. files in a cgroup which can be useful for debugging.
  960. endif # CGROUPS
  961. config CHECKPOINT_RESTORE
  962. bool "Checkpoint/restore support" if EXPERT
  963. default n
  964. help
  965. Enables additional kernel features in a sake of checkpoint/restore.
  966. In particular it adds auxiliary prctl codes to setup process text,
  967. data and heap segment sizes, and a few additional /proc filesystem
  968. entries.
  969. If unsure, say N here.
  970. menuconfig NAMESPACES
  971. bool "Namespaces support" if EXPERT
  972. default !EXPERT
  973. help
  974. Provides the way to make tasks work with different objects using
  975. the same id. For example same IPC id may refer to different objects
  976. or same user id or pid may refer to different tasks when used in
  977. different namespaces.
  978. if NAMESPACES
  979. config UTS_NS
  980. bool "UTS namespace"
  981. default y
  982. help
  983. In this namespace tasks see different info provided with the
  984. uname() system call
  985. config IPC_NS
  986. bool "IPC namespace"
  987. depends on (SYSVIPC || POSIX_MQUEUE)
  988. default y
  989. help
  990. In this namespace tasks work with IPC ids which correspond to
  991. different IPC objects in different namespaces.
  992. config USER_NS
  993. bool "User namespace"
  994. default n
  995. help
  996. This allows containers, i.e. vservers, to use user namespaces
  997. to provide different user info for different servers.
  998. When user namespaces are enabled in the kernel it is
  999. recommended that the MEMCG and MEMCG_KMEM options also be
  1000. enabled and that user-space use the memory control groups to
  1001. limit the amount of memory a memory unprivileged users can
  1002. use.
  1003. If unsure, say N.
  1004. config PID_NS
  1005. bool "PID Namespaces"
  1006. default y
  1007. help
  1008. Support process id namespaces. This allows having multiple
  1009. processes with the same pid as long as they are in different
  1010. pid namespaces. This is a building block of containers.
  1011. config NET_NS
  1012. bool "Network namespace"
  1013. depends on NET
  1014. default y
  1015. help
  1016. Allow user space to create what appear to be multiple instances
  1017. of the network stack.
  1018. endif # NAMESPACES
  1019. config SCHED_AUTOGROUP
  1020. bool "Automatic process group scheduling"
  1021. select CGROUPS
  1022. select CGROUP_SCHED
  1023. select FAIR_GROUP_SCHED
  1024. help
  1025. This option optimizes the scheduler for common desktop workloads by
  1026. automatically creating and populating task groups. This separation
  1027. of workloads isolates aggressive CPU burners (like build jobs) from
  1028. desktop applications. Task group autogeneration is currently based
  1029. upon task session.
  1030. config SYSFS_DEPRECATED
  1031. bool "Enable deprecated sysfs features to support old userspace tools"
  1032. depends on SYSFS
  1033. default n
  1034. help
  1035. This option adds code that switches the layout of the "block" class
  1036. devices, to not show up in /sys/class/block/, but only in
  1037. /sys/block/.
  1038. This switch is only active when the sysfs.deprecated=1 boot option is
  1039. passed or the SYSFS_DEPRECATED_V2 option is set.
  1040. This option allows new kernels to run on old distributions and tools,
  1041. which might get confused by /sys/class/block/. Since 2007/2008 all
  1042. major distributions and tools handle this just fine.
  1043. Recent distributions and userspace tools after 2009/2010 depend on
  1044. the existence of /sys/class/block/, and will not work with this
  1045. option enabled.
  1046. Only if you are using a new kernel on an old distribution, you might
  1047. need to say Y here.
  1048. config SYSFS_DEPRECATED_V2
  1049. bool "Enable deprecated sysfs features by default"
  1050. default n
  1051. depends on SYSFS
  1052. depends on SYSFS_DEPRECATED
  1053. help
  1054. Enable deprecated sysfs by default.
  1055. See the CONFIG_SYSFS_DEPRECATED option for more details about this
  1056. option.
  1057. Only if you are using a new kernel on an old distribution, you might
  1058. need to say Y here. Even then, odds are you would not need it
  1059. enabled, you can always pass the boot option if absolutely necessary.
  1060. config RELAY
  1061. bool "Kernel->user space relay support (formerly relayfs)"
  1062. help
  1063. This option enables support for relay interface support in
  1064. certain file systems (such as debugfs).
  1065. It is designed to provide an efficient mechanism for tools and
  1066. facilities to relay large amounts of data from kernel space to
  1067. user space.
  1068. If unsure, say N.
  1069. config BLK_DEV_INITRD
  1070. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  1071. depends on BROKEN || !FRV
  1072. help
  1073. The initial RAM filesystem is a ramfs which is loaded by the
  1074. boot loader (loadlin or lilo) and that is mounted as root
  1075. before the normal boot procedure. It is typically used to
  1076. load modules needed to mount the "real" root file system,
  1077. etc. See <file:Documentation/initrd.txt> for details.
  1078. If RAM disk support (BLK_DEV_RAM) is also included, this
  1079. also enables initial RAM disk (initrd) support and adds
  1080. 15 Kbytes (more on some other architectures) to the kernel size.
  1081. If unsure say Y.
  1082. if BLK_DEV_INITRD
  1083. source "usr/Kconfig"
  1084. endif
  1085. config CC_OPTIMIZE_FOR_SIZE
  1086. bool "Optimize for size"
  1087. help
  1088. Enabling this option will pass "-Os" instead of "-O2" to gcc
  1089. resulting in a smaller kernel.
  1090. If unsure, say N.
  1091. config SYSCTL
  1092. bool
  1093. config ANON_INODES
  1094. bool
  1095. config HAVE_UID16
  1096. bool
  1097. config SYSCTL_EXCEPTION_TRACE
  1098. bool
  1099. help
  1100. Enable support for /proc/sys/debug/exception-trace.
  1101. config SYSCTL_ARCH_UNALIGN_NO_WARN
  1102. bool
  1103. help
  1104. Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
  1105. Allows arch to define/use @no_unaligned_warning to possibly warn
  1106. about unaligned access emulation going on under the hood.
  1107. config SYSCTL_ARCH_UNALIGN_ALLOW
  1108. bool
  1109. help
  1110. Enable support for /proc/sys/kernel/unaligned-trap
  1111. Allows arches to define/use @unaligned_enabled to runtime toggle
  1112. the unaligned access emulation.
  1113. see arch/parisc/kernel/unaligned.c for reference
  1114. config HAVE_PCSPKR_PLATFORM
  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. config SHMEM
  1269. bool "Use full shmem filesystem" if EXPERT
  1270. default y
  1271. depends on MMU
  1272. help
  1273. The shmem is an internal filesystem used to manage shared memory.
  1274. It is backed by swap and manages resource limits. It is also exported
  1275. to userspace as tmpfs if TMPFS is enabled. Disabling this
  1276. option replaces shmem and tmpfs with the much simpler ramfs code,
  1277. which may be appropriate on small systems without swap.
  1278. config AIO
  1279. bool "Enable AIO support" if EXPERT
  1280. default y
  1281. help
  1282. This option enables POSIX asynchronous I/O which may by used
  1283. by some high performance threaded applications. Disabling
  1284. this option saves about 7k.
  1285. config ADVISE_SYSCALLS
  1286. bool "Enable madvise/fadvise syscalls" if EXPERT
  1287. default y
  1288. help
  1289. This option enables the madvise and fadvise syscalls, used by
  1290. applications to advise the kernel about their future memory or file
  1291. usage, improving performance. If building an embedded system where no
  1292. applications use these syscalls, you can disable this option to save
  1293. space.
  1294. config PCI_QUIRKS
  1295. default y
  1296. bool "Enable PCI quirk workarounds" if EXPERT
  1297. depends on PCI
  1298. help
  1299. This enables workarounds for various PCI chipset
  1300. bugs/quirks. Disable this only if your target machine is
  1301. unaffected by PCI quirks.
  1302. config EMBEDDED
  1303. bool "Embedded system"
  1304. option allnoconfig_y
  1305. select EXPERT
  1306. help
  1307. This option should be enabled if compiling the kernel for
  1308. an embedded system so certain expert options are available
  1309. for configuration.
  1310. config HAVE_PERF_EVENTS
  1311. bool
  1312. help
  1313. See tools/perf/design.txt for details.
  1314. config PERF_USE_VMALLOC
  1315. bool
  1316. help
  1317. See tools/perf/design.txt for details
  1318. menu "Kernel Performance Events And Counters"
  1319. config PERF_EVENTS
  1320. bool "Kernel performance events and counters"
  1321. default y if PROFILING
  1322. depends on HAVE_PERF_EVENTS
  1323. select ANON_INODES
  1324. select IRQ_WORK
  1325. help
  1326. Enable kernel support for various performance events provided
  1327. by software and hardware.
  1328. Software events are supported either built-in or via the
  1329. use of generic tracepoints.
  1330. Most modern CPUs support performance events via performance
  1331. counter registers. These registers count the number of certain
  1332. types of hw events: such as instructions executed, cachemisses
  1333. suffered, or branches mis-predicted - without slowing down the
  1334. kernel or applications. These registers can also trigger interrupts
  1335. when a threshold number of events have passed - and can thus be
  1336. used to profile the code that runs on that CPU.
  1337. The Linux Performance Event subsystem provides an abstraction of
  1338. these software and hardware event capabilities, available via a
  1339. system call and used by the "perf" utility in tools/perf/. It
  1340. provides per task and per CPU counters, and it provides event
  1341. capabilities on top of those.
  1342. Say Y if unsure.
  1343. config DEBUG_PERF_USE_VMALLOC
  1344. default n
  1345. bool "Debug: use vmalloc to back perf mmap() buffers"
  1346. depends on PERF_EVENTS && DEBUG_KERNEL
  1347. select PERF_USE_VMALLOC
  1348. help
  1349. Use vmalloc memory to back perf mmap() buffers.
  1350. Mostly useful for debugging the vmalloc code on platforms
  1351. that don't require it.
  1352. Say N if unsure.
  1353. endmenu
  1354. config VM_EVENT_COUNTERS
  1355. default y
  1356. bool "Enable VM event counters for /proc/vmstat" if EXPERT
  1357. help
  1358. VM event counters are needed for event counts to be shown.
  1359. This option allows the disabling of the VM event counters
  1360. on EXPERT systems. /proc/vmstat will only show page counts
  1361. if VM event counters are disabled.
  1362. config SLUB_DEBUG
  1363. default y
  1364. bool "Enable SLUB debugging support" if EXPERT
  1365. depends on SLUB && SYSFS
  1366. help
  1367. SLUB has extensive debug support features. Disabling these can
  1368. result in significant savings in code size. This also disables
  1369. SLUB sysfs support. /sys/slab will not exist and there will be
  1370. no support for cache validation etc.
  1371. config COMPAT_BRK
  1372. bool "Disable heap randomization"
  1373. default y
  1374. help
  1375. Randomizing heap placement makes heap exploits harder, but it
  1376. also breaks ancient binaries (including anything libc5 based).
  1377. This option changes the bootup default to heap randomization
  1378. disabled, and can be overridden at runtime by setting
  1379. /proc/sys/kernel/randomize_va_space to 2.
  1380. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  1381. choice
  1382. prompt "Choose SLAB allocator"
  1383. default SLUB
  1384. help
  1385. This option allows to select a slab allocator.
  1386. config SLAB
  1387. bool "SLAB"
  1388. help
  1389. The regular slab allocator that is established and known to work
  1390. well in all environments. It organizes cache hot objects in
  1391. per cpu and per node queues.
  1392. config SLUB
  1393. bool "SLUB (Unqueued Allocator)"
  1394. help
  1395. SLUB is a slab allocator that minimizes cache line usage
  1396. instead of managing queues of cached objects (SLAB approach).
  1397. Per cpu caching is realized using slabs of objects instead
  1398. of queues of objects. SLUB can use memory efficiently
  1399. and has enhanced diagnostics. SLUB is the default choice for
  1400. a slab allocator.
  1401. config SLOB
  1402. depends on EXPERT
  1403. bool "SLOB (Simple Allocator)"
  1404. help
  1405. SLOB replaces the stock allocator with a drastically simpler
  1406. allocator. SLOB is generally more space efficient but
  1407. does not perform as well on large systems.
  1408. endchoice
  1409. config SLUB_CPU_PARTIAL
  1410. default y
  1411. depends on SLUB && SMP
  1412. bool "SLUB per cpu partial cache"
  1413. help
  1414. Per cpu partial caches accellerate objects allocation and freeing
  1415. that is local to a processor at the price of more indeterminism
  1416. in the latency of the free. On overflow these caches will be cleared
  1417. which requires the taking of locks that may cause latency spikes.
  1418. Typically one would choose no for a realtime system.
  1419. config MMAP_ALLOW_UNINITIALIZED
  1420. bool "Allow mmapped anonymous memory to be uninitialized"
  1421. depends on EXPERT && !MMU
  1422. default n
  1423. help
  1424. Normally, and according to the Linux spec, anonymous memory obtained
  1425. from mmap() has it's contents cleared before it is passed to
  1426. userspace. Enabling this config option allows you to request that
  1427. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  1428. providing a huge performance boost. If this option is not enabled,
  1429. then the flag will be ignored.
  1430. This is taken advantage of by uClibc's malloc(), and also by
  1431. ELF-FDPIC binfmt's brk and stack allocator.
  1432. Because of the obvious security issues, this option should only be
  1433. enabled on embedded devices where you control what is run in
  1434. userspace. Since that isn't generally a problem on no-MMU systems,
  1435. it is normally safe to say Y here.
  1436. See Documentation/nommu-mmap.txt for more information.
  1437. config SYSTEM_TRUSTED_KEYRING
  1438. bool "Provide system-wide ring of trusted keys"
  1439. depends on KEYS
  1440. help
  1441. Provide a system keyring to which trusted keys can be added. Keys in
  1442. the keyring are considered to be trusted. Keys may be added at will
  1443. by the kernel from compiled-in data and from hardware key stores, but
  1444. userspace may only add extra keys if those keys can be verified by
  1445. keys already in the keyring.
  1446. Keys in this keyring are used by module signature checking.
  1447. config PROFILING
  1448. bool "Profiling support"
  1449. help
  1450. Say Y here to enable the extended profiling support mechanisms used
  1451. by profilers such as OProfile.
  1452. #
  1453. # Place an empty function call at each tracepoint site. Can be
  1454. # dynamically changed for a probe function.
  1455. #
  1456. config TRACEPOINTS
  1457. bool
  1458. source "arch/Kconfig"
  1459. endmenu # General setup
  1460. config HAVE_GENERIC_DMA_COHERENT
  1461. bool
  1462. default n
  1463. config SLABINFO
  1464. bool
  1465. depends on PROC_FS
  1466. depends on SLAB || SLUB_DEBUG
  1467. default y
  1468. config RT_MUTEXES
  1469. boolean
  1470. config BASE_SMALL
  1471. int
  1472. default 0 if BASE_FULL
  1473. default 1 if !BASE_FULL
  1474. menuconfig MODULES
  1475. bool "Enable loadable module support"
  1476. option modules
  1477. help
  1478. Kernel modules are small pieces of compiled code which can
  1479. be inserted in the running kernel, rather than being
  1480. permanently built into the kernel. You use the "modprobe"
  1481. tool to add (and sometimes remove) them. If you say Y here,
  1482. many parts of the kernel can be built as modules (by
  1483. answering M instead of Y where indicated): this is most
  1484. useful for infrequently used options which are not required
  1485. for booting. For more information, see the man pages for
  1486. modprobe, lsmod, modinfo, insmod and rmmod.
  1487. If you say Y here, you will need to run "make
  1488. modules_install" to put the modules under /lib/modules/
  1489. where modprobe can find them (you may need to be root to do
  1490. this).
  1491. If unsure, say Y.
  1492. if MODULES
  1493. config MODULE_FORCE_LOAD
  1494. bool "Forced module loading"
  1495. default n
  1496. help
  1497. Allow loading of modules without version information (ie. modprobe
  1498. --force). Forced module loading sets the 'F' (forced) taint flag and
  1499. is usually a really bad idea.
  1500. config MODULE_UNLOAD
  1501. bool "Module unloading"
  1502. help
  1503. Without this option you will not be able to unload any
  1504. modules (note that some modules may not be unloadable
  1505. anyway), which makes your kernel smaller, faster
  1506. and simpler. If unsure, say Y.
  1507. config MODULE_FORCE_UNLOAD
  1508. bool "Forced module unloading"
  1509. depends on MODULE_UNLOAD
  1510. help
  1511. This option allows you to force a module to unload, even if the
  1512. kernel believes it is unsafe: the kernel will remove the module
  1513. without waiting for anyone to stop using it (using the -f option to
  1514. rmmod). This is mainly for kernel developers and desperate users.
  1515. If unsure, say N.
  1516. config MODVERSIONS
  1517. bool "Module versioning support"
  1518. help
  1519. Usually, you have to use modules compiled with your kernel.
  1520. Saying Y here makes it sometimes possible to use modules
  1521. compiled for different kernels, by adding enough information
  1522. to the modules to (hopefully) spot any changes which would
  1523. make them incompatible with the kernel you are running. If
  1524. unsure, say N.
  1525. config MODULE_SRCVERSION_ALL
  1526. bool "Source checksum for all modules"
  1527. help
  1528. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1529. field inserted into their modinfo section, which contains a
  1530. sum of the source files which made it. This helps maintainers
  1531. see exactly which source was used to build a module (since
  1532. others sometimes change the module source without updating
  1533. the version). With this option, such a "srcversion" field
  1534. will be created for all modules. If unsure, say N.
  1535. config MODULE_SIG
  1536. bool "Module signature verification"
  1537. depends on MODULES
  1538. select SYSTEM_TRUSTED_KEYRING
  1539. select KEYS
  1540. select CRYPTO
  1541. select ASYMMETRIC_KEY_TYPE
  1542. select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  1543. select PUBLIC_KEY_ALGO_RSA
  1544. select ASN1
  1545. select OID_REGISTRY
  1546. select X509_CERTIFICATE_PARSER
  1547. help
  1548. Check modules for valid signatures upon load: the signature
  1549. is simply appended to the module. For more information see
  1550. Documentation/module-signing.txt.
  1551. !!!WARNING!!! If you enable this option, you MUST make sure that the
  1552. module DOES NOT get stripped after being signed. This includes the
  1553. debuginfo strip done by some packagers (such as rpmbuild) and
  1554. inclusion into an initramfs that wants the module size reduced.
  1555. config MODULE_SIG_FORCE
  1556. bool "Require modules to be validly signed"
  1557. depends on MODULE_SIG
  1558. help
  1559. Reject unsigned modules or signed modules for which we don't have a
  1560. key. Without this, such modules will simply taint the kernel.
  1561. config MODULE_SIG_ALL
  1562. bool "Automatically sign all modules"
  1563. default y
  1564. depends on MODULE_SIG
  1565. help
  1566. Sign all modules during make modules_install. Without this option,
  1567. modules must be signed manually, using the scripts/sign-file tool.
  1568. comment "Do not forget to sign required modules with scripts/sign-file"
  1569. depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
  1570. choice
  1571. prompt "Which hash algorithm should modules be signed with?"
  1572. depends on MODULE_SIG
  1573. help
  1574. This determines which sort of hashing algorithm will be used during
  1575. signature generation. This algorithm _must_ be built into the kernel
  1576. directly so that signature verification can take place. It is not
  1577. possible to load a signed module containing the algorithm to check
  1578. the signature on that module.
  1579. config MODULE_SIG_SHA1
  1580. bool "Sign modules with SHA-1"
  1581. select CRYPTO_SHA1
  1582. config MODULE_SIG_SHA224
  1583. bool "Sign modules with SHA-224"
  1584. select CRYPTO_SHA256
  1585. config MODULE_SIG_SHA256
  1586. bool "Sign modules with SHA-256"
  1587. select CRYPTO_SHA256
  1588. config MODULE_SIG_SHA384
  1589. bool "Sign modules with SHA-384"
  1590. select CRYPTO_SHA512
  1591. config MODULE_SIG_SHA512
  1592. bool "Sign modules with SHA-512"
  1593. select CRYPTO_SHA512
  1594. endchoice
  1595. config MODULE_SIG_HASH
  1596. string
  1597. depends on MODULE_SIG
  1598. default "sha1" if MODULE_SIG_SHA1
  1599. default "sha224" if MODULE_SIG_SHA224
  1600. default "sha256" if MODULE_SIG_SHA256
  1601. default "sha384" if MODULE_SIG_SHA384
  1602. default "sha512" if MODULE_SIG_SHA512
  1603. config MODULE_COMPRESS
  1604. bool "Compress modules on installation"
  1605. depends on MODULES
  1606. help
  1607. This option compresses the kernel modules when 'make
  1608. modules_install' is run.
  1609. The modules will be compressed either using gzip or xz depend on the
  1610. choice made in "Compression algorithm".
  1611. module-init-tools has support for gzip format while kmod handle gzip
  1612. and xz compressed modules.
  1613. When a kernel module is installed from outside of the main kernel
  1614. source and uses the Kbuild system for installing modules then that
  1615. kernel module will also be compressed when it is installed.
  1616. This option provides little benefit when the modules are to be used inside
  1617. an initrd or initramfs, it generally is more efficient to compress the whole
  1618. initrd or initramfs instead.
  1619. This is fully compatible with signed modules while the signed module is
  1620. compressed. module-init-tools or kmod handles decompression and provide to
  1621. other layer the uncompressed but signed payload.
  1622. choice
  1623. prompt "Compression algorithm"
  1624. depends on MODULE_COMPRESS
  1625. default MODULE_COMPRESS_GZIP
  1626. help
  1627. This determines which sort of compression will be used during
  1628. 'make modules_install'.
  1629. GZIP (default) and XZ are supported.
  1630. config MODULE_COMPRESS_GZIP
  1631. bool "GZIP"
  1632. config MODULE_COMPRESS_XZ
  1633. bool "XZ"
  1634. endchoice
  1635. endif # MODULES
  1636. config INIT_ALL_POSSIBLE
  1637. bool
  1638. help
  1639. Back when each arch used to define their own cpu_online_mask and
  1640. cpu_possible_mask, some of them chose to initialize cpu_possible_mask
  1641. with all 1s, and others with all 0s. When they were centralised,
  1642. it was better to provide this option than to break all the archs
  1643. and have several arch maintainers pursuing me down dark alleys.
  1644. config STOP_MACHINE
  1645. bool
  1646. default y
  1647. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1648. help
  1649. Need stop_machine() primitive.
  1650. source "block/Kconfig"
  1651. config PREEMPT_NOTIFIERS
  1652. bool
  1653. config PADATA
  1654. depends on SMP
  1655. bool
  1656. # Can be selected by architectures with broken toolchains
  1657. # that get confused by correct const<->read_only section
  1658. # mappings
  1659. config BROKEN_RODATA
  1660. bool
  1661. config ASN1
  1662. tristate
  1663. help
  1664. Build a simple ASN.1 grammar compiler that produces a bytecode output
  1665. that can be interpreted by the ASN.1 stream decoder and used to
  1666. inform it as to what tags are to be expected in a stream and what
  1667. functions to call on what tags.
  1668. source "kernel/Kconfig.locks"