Kconfig 65 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 TASKS_RCU
  423. bool "Task_based RCU implementation using voluntary context switch"
  424. default n
  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 || TREE_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 || TREE_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 || TREE_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 || TREE_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 || TREE_PREEMPT_RCU )
  544. select DEBUG_FS
  545. help
  546. This option provides tracing for the TREE_RCU and
  547. TREE_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_BOOST_PRIO
  561. int "Real-time priority to boost RCU readers to"
  562. range 1 99
  563. depends on RCU_BOOST
  564. default 1
  565. help
  566. This option specifies the real-time priority to which long-term
  567. preempted RCU readers are to be boosted. If you are working
  568. with a real-time application that has one or more CPU-bound
  569. threads running at a real-time priority level, you should set
  570. RCU_BOOST_PRIO to a priority higher then the highest-priority
  571. real-time CPU-bound thread. The default RCU_BOOST_PRIO value
  572. of 1 is appropriate in the common case, which is real-time
  573. applications that do not have any CPU-bound threads.
  574. Some real-time applications might not have a single real-time
  575. thread that saturates a given CPU, but instead might have
  576. multiple real-time threads that, taken together, fully utilize
  577. that CPU. In this case, you should set RCU_BOOST_PRIO to
  578. a priority higher than the lowest-priority thread that is
  579. conspiring to prevent the CPU from running any non-real-time
  580. tasks. For example, if one thread at priority 10 and another
  581. thread at priority 5 are between themselves fully consuming
  582. the CPU time on a given CPU, then RCU_BOOST_PRIO should be
  583. set to priority 6 or higher.
  584. Specify the real-time priority, or take the default if unsure.
  585. config RCU_BOOST_DELAY
  586. int "Milliseconds to delay boosting after RCU grace-period start"
  587. range 0 3000
  588. depends on RCU_BOOST
  589. default 500
  590. help
  591. This option specifies the time to wait after the beginning of
  592. a given grace period before priority-boosting preempted RCU
  593. readers blocking that grace period. Note that any RCU reader
  594. blocking an expedited RCU grace period is boosted immediately.
  595. Accept the default if unsure.
  596. config RCU_NOCB_CPU
  597. bool "Offload RCU callback processing from boot-selected CPUs"
  598. depends on TREE_RCU || TREE_PREEMPT_RCU
  599. default n
  600. help
  601. Use this option to reduce OS jitter for aggressive HPC or
  602. real-time workloads. It can also be used to offload RCU
  603. callback invocation to energy-efficient CPUs in battery-powered
  604. asymmetric multiprocessors.
  605. This option offloads callback invocation from the set of
  606. CPUs specified at boot time by the rcu_nocbs parameter.
  607. For each such CPU, a kthread ("rcuox/N") will be created to
  608. invoke callbacks, where the "N" is the CPU being offloaded,
  609. and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
  610. "s" for RCU-sched. Nothing prevents this kthread from running
  611. on the specified CPUs, but (1) the kthreads may be preempted
  612. between each callback, and (2) affinity or cgroups can be used
  613. to force the kthreads to run on whatever set of CPUs is desired.
  614. Say Y here if you want to help to debug reduced OS jitter.
  615. Say N here if you are unsure.
  616. choice
  617. prompt "Build-forced no-CBs CPUs"
  618. default RCU_NOCB_CPU_NONE
  619. help
  620. This option allows no-CBs CPUs (whose RCU callbacks are invoked
  621. from kthreads rather than from softirq context) to be specified
  622. at build time. Additional no-CBs CPUs may be specified by
  623. the rcu_nocbs= boot parameter.
  624. config RCU_NOCB_CPU_NONE
  625. bool "No build_forced no-CBs CPUs"
  626. depends on RCU_NOCB_CPU
  627. help
  628. This option does not force any of the CPUs to be no-CBs CPUs.
  629. Only CPUs designated by the rcu_nocbs= boot parameter will be
  630. no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
  631. kthreads whose names begin with "rcuo". All other CPUs will
  632. invoke their own RCU callbacks in softirq context.
  633. Select this option if you want to choose no-CBs CPUs at
  634. boot time, for example, to allow testing of different no-CBs
  635. configurations without having to rebuild the kernel each time.
  636. config RCU_NOCB_CPU_ZERO
  637. bool "CPU 0 is a build_forced no-CBs CPU"
  638. depends on RCU_NOCB_CPU
  639. help
  640. This option forces CPU 0 to be a no-CBs CPU, so that its RCU
  641. callbacks are invoked by a per-CPU kthread whose name begins
  642. with "rcuo". Additional CPUs may be designated as no-CBs
  643. CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
  644. All other CPUs will invoke their own RCU callbacks in softirq
  645. context.
  646. Select this if CPU 0 needs to be a no-CBs CPU for real-time
  647. or energy-efficiency reasons, but the real reason it exists
  648. is to ensure that randconfig testing covers mixed systems.
  649. config RCU_NOCB_CPU_ALL
  650. bool "All CPUs are build_forced no-CBs CPUs"
  651. depends on RCU_NOCB_CPU
  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_DEFAULT_ENABLED
  757. bool "Automatically enable NUMA aware memory/task placement"
  758. default y
  759. depends on NUMA_BALANCING
  760. help
  761. If set, automatic NUMA balancing will be enabled if running on a NUMA
  762. machine.
  763. config NUMA_BALANCING
  764. bool "Memory placement aware NUMA scheduler"
  765. depends on ARCH_SUPPORTS_NUMA_BALANCING
  766. depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
  767. depends on SMP && NUMA && MIGRATION
  768. help
  769. This option adds support for automatic NUMA aware memory/task placement.
  770. The mechanism is quite primitive and is based on migrating memory when
  771. it has references to the node the task is running on.
  772. This system will be inactive on UMA systems.
  773. menuconfig CGROUPS
  774. boolean "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 RESOURCE_COUNTERS
  822. bool "Resource counters"
  823. help
  824. This option enables controller independent resource accounting
  825. infrastructure that works with cgroups.
  826. config MEMCG
  827. bool "Memory Resource Controller for Control Groups"
  828. depends on RESOURCE_COUNTERS
  829. select EVENTFD
  830. help
  831. Provides a memory resource controller that manages both anonymous
  832. memory and page cache. (See Documentation/cgroups/memory.txt)
  833. Note that setting this option increases fixed memory overhead
  834. associated with each page of memory in the system. By this,
  835. 8(16)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  836. usage tracking struct at boot. Total amount of this is printed out
  837. at boot.
  838. Only enable when you're ok with these trade offs and really
  839. sure you need the memory resource controller. Even when you enable
  840. this, you can set "cgroup_disable=memory" at your boot option to
  841. disable memory resource controller and you can avoid overheads.
  842. (and lose benefits of memory resource controller)
  843. config MEMCG_SWAP
  844. bool "Memory Resource Controller Swap Extension"
  845. depends on MEMCG && SWAP
  846. help
  847. Add swap management feature to memory resource controller. When you
  848. enable this, you can limit mem+swap usage per cgroup. In other words,
  849. when you disable this, memory resource controller has no cares to
  850. usage of swap...a process can exhaust all of the swap. This extension
  851. is useful when you want to avoid exhaustion swap but this itself
  852. adds more overheads and consumes memory for remembering information.
  853. Especially if you use 32bit system or small memory system, please
  854. be careful about enabling this. When memory resource controller
  855. is disabled by boot option, this will be automatically disabled and
  856. there will be no overhead from this. Even when you set this config=y,
  857. if boot option "swapaccount=0" is set, swap will not be accounted.
  858. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  859. size is 4096bytes, 512k per 1Gbytes of swap.
  860. config MEMCG_SWAP_ENABLED
  861. bool "Memory Resource Controller Swap Extension enabled by default"
  862. depends on MEMCG_SWAP
  863. default y
  864. help
  865. Memory Resource Controller Swap Extension comes with its price in
  866. a bigger memory consumption. General purpose distribution kernels
  867. which want to enable the feature but keep it disabled by default
  868. and let the user enable it by swapaccount=1 boot command line
  869. parameter should have this option unselected.
  870. For those who want to have the feature enabled by default should
  871. select this option (if, for some reason, they need to disable it
  872. then swapaccount=0 does the trick).
  873. config MEMCG_KMEM
  874. bool "Memory Resource Controller Kernel Memory accounting"
  875. depends on MEMCG
  876. depends on SLUB || SLAB
  877. help
  878. The Kernel Memory extension for Memory Resource Controller can limit
  879. the amount of memory used by kernel objects in the system. Those are
  880. fundamentally different from the entities handled by the standard
  881. Memory Controller, which are page-based, and can be swapped. Users of
  882. the kmem extension can use it to guarantee that no group of processes
  883. will ever exhaust kernel resources alone.
  884. WARNING: Current implementation lacks reclaim support. That means
  885. allocation attempts will fail when close to the limit even if there
  886. are plenty of kmem available for reclaim. That makes this option
  887. unusable in real life so DO NOT SELECT IT unless for development
  888. purposes.
  889. config CGROUP_HUGETLB
  890. bool "HugeTLB Resource Controller for Control Groups"
  891. depends on RESOURCE_COUNTERS && HUGETLB_PAGE
  892. default n
  893. help
  894. Provides a cgroup Resource Controller for HugeTLB pages.
  895. When you enable this, you can put a per cgroup limit on HugeTLB usage.
  896. The limit is enforced during page fault. Since HugeTLB doesn't
  897. support page reclaim, enforcing the limit at page fault time implies
  898. that, the application will get SIGBUS signal if it tries to access
  899. HugeTLB pages beyond its limit. This requires the application to know
  900. beforehand how much HugeTLB pages it would require for its use. The
  901. control group is tracked in the third page lru pointer. This means
  902. that we cannot use the controller with huge page less than 3 pages.
  903. config CGROUP_PERF
  904. bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
  905. depends on PERF_EVENTS && CGROUPS
  906. help
  907. This option extends the per-cpu mode to restrict monitoring to
  908. threads which belong to the cgroup specified and run on the
  909. designated cpu.
  910. Say N if unsure.
  911. menuconfig CGROUP_SCHED
  912. bool "Group CPU scheduler"
  913. default n
  914. help
  915. This feature lets CPU scheduler recognize task groups and control CPU
  916. bandwidth allocation to such task groups. It uses cgroups to group
  917. tasks.
  918. if CGROUP_SCHED
  919. config FAIR_GROUP_SCHED
  920. bool "Group scheduling for SCHED_OTHER"
  921. depends on CGROUP_SCHED
  922. default CGROUP_SCHED
  923. config CFS_BANDWIDTH
  924. bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
  925. depends on FAIR_GROUP_SCHED
  926. default n
  927. help
  928. This option allows users to define CPU bandwidth rates (limits) for
  929. tasks running within the fair group scheduler. Groups with no limit
  930. set are considered to be unconstrained and will run with no
  931. restriction.
  932. See tip/Documentation/scheduler/sched-bwc.txt for more information.
  933. config RT_GROUP_SCHED
  934. bool "Group scheduling for SCHED_RR/FIFO"
  935. depends on CGROUP_SCHED
  936. default n
  937. help
  938. This feature lets you explicitly allocate real CPU bandwidth
  939. to task groups. If enabled, it will also make it impossible to
  940. schedule realtime tasks for non-root users until you allocate
  941. realtime bandwidth for them.
  942. See Documentation/scheduler/sched-rt-group.txt for more information.
  943. endif #CGROUP_SCHED
  944. config BLK_CGROUP
  945. bool "Block IO controller"
  946. depends on BLOCK
  947. default n
  948. ---help---
  949. Generic block IO controller cgroup interface. This is the common
  950. cgroup interface which should be used by various IO controlling
  951. policies.
  952. Currently, CFQ IO scheduler uses it to recognize task groups and
  953. control disk bandwidth allocation (proportional time slice allocation)
  954. to such task groups. It is also used by bio throttling logic in
  955. block layer to implement upper limit in IO rates on a device.
  956. This option only enables generic Block IO controller infrastructure.
  957. One needs to also enable actual IO controlling logic/policy. For
  958. enabling proportional weight division of disk bandwidth in CFQ, set
  959. CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
  960. CONFIG_BLK_DEV_THROTTLING=y.
  961. See Documentation/cgroups/blkio-controller.txt for more information.
  962. config DEBUG_BLK_CGROUP
  963. bool "Enable Block IO controller debugging"
  964. depends on BLK_CGROUP
  965. default n
  966. ---help---
  967. Enable some debugging help. Currently it exports additional stat
  968. files in a cgroup which can be useful for debugging.
  969. endif # CGROUPS
  970. config CHECKPOINT_RESTORE
  971. bool "Checkpoint/restore support" if EXPERT
  972. default n
  973. help
  974. Enables additional kernel features in a sake of checkpoint/restore.
  975. In particular it adds auxiliary prctl codes to setup process text,
  976. data and heap segment sizes, and a few additional /proc filesystem
  977. entries.
  978. If unsure, say N here.
  979. menuconfig NAMESPACES
  980. bool "Namespaces support" if EXPERT
  981. default !EXPERT
  982. help
  983. Provides the way to make tasks work with different objects using
  984. the same id. For example same IPC id may refer to different objects
  985. or same user id or pid may refer to different tasks when used in
  986. different namespaces.
  987. if NAMESPACES
  988. config UTS_NS
  989. bool "UTS namespace"
  990. default y
  991. help
  992. In this namespace tasks see different info provided with the
  993. uname() system call
  994. config IPC_NS
  995. bool "IPC namespace"
  996. depends on (SYSVIPC || POSIX_MQUEUE)
  997. default y
  998. help
  999. In this namespace tasks work with IPC ids which correspond to
  1000. different IPC objects in different namespaces.
  1001. config USER_NS
  1002. bool "User namespace"
  1003. default n
  1004. help
  1005. This allows containers, i.e. vservers, to use user namespaces
  1006. to provide different user info for different servers.
  1007. When user namespaces are enabled in the kernel it is
  1008. recommended that the MEMCG and MEMCG_KMEM options also be
  1009. enabled and that user-space use the memory control groups to
  1010. limit the amount of memory a memory unprivileged users can
  1011. use.
  1012. If unsure, say N.
  1013. config PID_NS
  1014. bool "PID Namespaces"
  1015. default y
  1016. help
  1017. Support process id namespaces. This allows having multiple
  1018. processes with the same pid as long as they are in different
  1019. pid namespaces. This is a building block of containers.
  1020. config NET_NS
  1021. bool "Network namespace"
  1022. depends on NET
  1023. default y
  1024. help
  1025. Allow user space to create what appear to be multiple instances
  1026. of the network stack.
  1027. endif # NAMESPACES
  1028. config SCHED_AUTOGROUP
  1029. bool "Automatic process group scheduling"
  1030. select CGROUPS
  1031. select CGROUP_SCHED
  1032. select FAIR_GROUP_SCHED
  1033. help
  1034. This option optimizes the scheduler for common desktop workloads by
  1035. automatically creating and populating task groups. This separation
  1036. of workloads isolates aggressive CPU burners (like build jobs) from
  1037. desktop applications. Task group autogeneration is currently based
  1038. upon task session.
  1039. config SYSFS_DEPRECATED
  1040. bool "Enable deprecated sysfs features to support old userspace tools"
  1041. depends on SYSFS
  1042. default n
  1043. help
  1044. This option adds code that switches the layout of the "block" class
  1045. devices, to not show up in /sys/class/block/, but only in
  1046. /sys/block/.
  1047. This switch is only active when the sysfs.deprecated=1 boot option is
  1048. passed or the SYSFS_DEPRECATED_V2 option is set.
  1049. This option allows new kernels to run on old distributions and tools,
  1050. which might get confused by /sys/class/block/. Since 2007/2008 all
  1051. major distributions and tools handle this just fine.
  1052. Recent distributions and userspace tools after 2009/2010 depend on
  1053. the existence of /sys/class/block/, and will not work with this
  1054. option enabled.
  1055. Only if you are using a new kernel on an old distribution, you might
  1056. need to say Y here.
  1057. config SYSFS_DEPRECATED_V2
  1058. bool "Enable deprecated sysfs features by default"
  1059. default n
  1060. depends on SYSFS
  1061. depends on SYSFS_DEPRECATED
  1062. help
  1063. Enable deprecated sysfs by default.
  1064. See the CONFIG_SYSFS_DEPRECATED option for more details about this
  1065. option.
  1066. Only if you are using a new kernel on an old distribution, you might
  1067. need to say Y here. Even then, odds are you would not need it
  1068. enabled, you can always pass the boot option if absolutely necessary.
  1069. config RELAY
  1070. bool "Kernel->user space relay support (formerly relayfs)"
  1071. help
  1072. This option enables support for relay interface support in
  1073. certain file systems (such as debugfs).
  1074. It is designed to provide an efficient mechanism for tools and
  1075. facilities to relay large amounts of data from kernel space to
  1076. user space.
  1077. If unsure, say N.
  1078. config BLK_DEV_INITRD
  1079. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  1080. depends on BROKEN || !FRV
  1081. help
  1082. The initial RAM filesystem is a ramfs which is loaded by the
  1083. boot loader (loadlin or lilo) and that is mounted as root
  1084. before the normal boot procedure. It is typically used to
  1085. load modules needed to mount the "real" root file system,
  1086. etc. See <file:Documentation/initrd.txt> for details.
  1087. If RAM disk support (BLK_DEV_RAM) is also included, this
  1088. also enables initial RAM disk (initrd) support and adds
  1089. 15 Kbytes (more on some other architectures) to the kernel size.
  1090. If unsure say Y.
  1091. if BLK_DEV_INITRD
  1092. source "usr/Kconfig"
  1093. endif
  1094. config CC_OPTIMIZE_FOR_SIZE
  1095. bool "Optimize for size"
  1096. help
  1097. Enabling this option will pass "-Os" instead of "-O2" to gcc
  1098. resulting in a smaller kernel.
  1099. If unsure, say N.
  1100. config SYSCTL
  1101. bool
  1102. config ANON_INODES
  1103. bool
  1104. config HAVE_UID16
  1105. bool
  1106. config SYSCTL_EXCEPTION_TRACE
  1107. bool
  1108. help
  1109. Enable support for /proc/sys/debug/exception-trace.
  1110. config SYSCTL_ARCH_UNALIGN_NO_WARN
  1111. bool
  1112. help
  1113. Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
  1114. Allows arch to define/use @no_unaligned_warning to possibly warn
  1115. about unaligned access emulation going on under the hood.
  1116. config SYSCTL_ARCH_UNALIGN_ALLOW
  1117. bool
  1118. help
  1119. Enable support for /proc/sys/kernel/unaligned-trap
  1120. Allows arches to define/use @unaligned_enabled to runtime toggle
  1121. the unaligned access emulation.
  1122. see arch/parisc/kernel/unaligned.c for reference
  1123. config HAVE_PCSPKR_PLATFORM
  1124. bool
  1125. # interpreter that classic socket filters depend on
  1126. config BPF
  1127. bool
  1128. menuconfig EXPERT
  1129. bool "Configure standard kernel features (expert users)"
  1130. # Unhide debug options, to make the on-by-default options visible
  1131. select DEBUG_KERNEL
  1132. help
  1133. This option allows certain base kernel options and settings
  1134. to be disabled or tweaked. This is for specialized
  1135. environments which can tolerate a "non-standard" kernel.
  1136. Only use this if you really know what you are doing.
  1137. config UID16
  1138. bool "Enable 16-bit UID system calls" if EXPERT
  1139. depends on HAVE_UID16
  1140. default y
  1141. help
  1142. This enables the legacy 16-bit UID syscall wrappers.
  1143. config SGETMASK_SYSCALL
  1144. bool "sgetmask/ssetmask syscalls support" if EXPERT
  1145. def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
  1146. ---help---
  1147. sys_sgetmask and sys_ssetmask are obsolete system calls
  1148. no longer supported in libc but still enabled by default in some
  1149. architectures.
  1150. If unsure, leave the default option here.
  1151. config SYSFS_SYSCALL
  1152. bool "Sysfs syscall support" if EXPERT
  1153. default y
  1154. ---help---
  1155. sys_sysfs is an obsolete system call no longer supported in libc.
  1156. Note that disabling this option is more secure but might break
  1157. compatibility with some systems.
  1158. If unsure say Y here.
  1159. config SYSCTL_SYSCALL
  1160. bool "Sysctl syscall support" if EXPERT
  1161. depends on PROC_SYSCTL
  1162. default n
  1163. select SYSCTL
  1164. ---help---
  1165. sys_sysctl uses binary paths that have been found challenging
  1166. to properly maintain and use. The interface in /proc/sys
  1167. using paths with ascii names is now the primary path to this
  1168. information.
  1169. Almost nothing using the binary sysctl interface so if you are
  1170. trying to save some space it is probably safe to disable this,
  1171. making your kernel marginally smaller.
  1172. If unsure say N here.
  1173. config KALLSYMS
  1174. bool "Load all symbols for debugging/ksymoops" if EXPERT
  1175. default y
  1176. help
  1177. Say Y here to let the kernel print out symbolic crash information and
  1178. symbolic stack backtraces. This increases the size of the kernel
  1179. somewhat, as all symbols have to be loaded into the kernel image.
  1180. config KALLSYMS_ALL
  1181. bool "Include all symbols in kallsyms"
  1182. depends on DEBUG_KERNEL && KALLSYMS
  1183. help
  1184. Normally kallsyms only contains the symbols of functions for nicer
  1185. OOPS messages and backtraces (i.e., symbols from the text and inittext
  1186. sections). This is sufficient for most cases. And only in very rare
  1187. cases (e.g., when a debugger is used) all symbols are required (e.g.,
  1188. names of variables from the data sections, etc).
  1189. This option makes sure that all symbols are loaded into the kernel
  1190. image (i.e., symbols from all sections) in cost of increased kernel
  1191. size (depending on the kernel configuration, it may be 300KiB or
  1192. something like this).
  1193. Say N unless you really need all symbols.
  1194. config PRINTK
  1195. default y
  1196. bool "Enable support for printk" if EXPERT
  1197. select IRQ_WORK
  1198. help
  1199. This option enables normal printk support. Removing it
  1200. eliminates most of the message strings from the kernel image
  1201. and makes the kernel more or less silent. As this makes it
  1202. very difficult to diagnose system problems, saying N here is
  1203. strongly discouraged.
  1204. config BUG
  1205. bool "BUG() support" if EXPERT
  1206. default y
  1207. help
  1208. Disabling this option eliminates support for BUG and WARN, reducing
  1209. the size of your kernel image and potentially quietly ignoring
  1210. numerous fatal conditions. You should only consider disabling this
  1211. option for embedded systems with no facilities for reporting errors.
  1212. Just say Y.
  1213. config ELF_CORE
  1214. depends on COREDUMP
  1215. default y
  1216. bool "Enable ELF core dumps" if EXPERT
  1217. help
  1218. Enable support for generating core dumps. Disabling saves about 4k.
  1219. config PCSPKR_PLATFORM
  1220. bool "Enable PC-Speaker support" if EXPERT
  1221. depends on HAVE_PCSPKR_PLATFORM
  1222. select I8253_LOCK
  1223. default y
  1224. help
  1225. This option allows to disable the internal PC-Speaker
  1226. support, saving some memory.
  1227. config BASE_FULL
  1228. default y
  1229. bool "Enable full-sized data structures for core" if EXPERT
  1230. help
  1231. Disabling this option reduces the size of miscellaneous core
  1232. kernel data structures. This saves memory on small machines,
  1233. but may reduce performance.
  1234. config FUTEX
  1235. bool "Enable futex support" if EXPERT
  1236. default y
  1237. select RT_MUTEXES
  1238. help
  1239. Disabling this option will cause the kernel to be built without
  1240. support for "fast userspace mutexes". The resulting kernel may not
  1241. run glibc-based applications correctly.
  1242. config HAVE_FUTEX_CMPXCHG
  1243. bool
  1244. depends on FUTEX
  1245. help
  1246. Architectures should select this if futex_atomic_cmpxchg_inatomic()
  1247. is implemented and always working. This removes a couple of runtime
  1248. checks.
  1249. config EPOLL
  1250. bool "Enable eventpoll support" if EXPERT
  1251. default y
  1252. select ANON_INODES
  1253. help
  1254. Disabling this option will cause the kernel to be built without
  1255. support for epoll family of system calls.
  1256. config SIGNALFD
  1257. bool "Enable signalfd() system call" if EXPERT
  1258. select ANON_INODES
  1259. default y
  1260. help
  1261. Enable the signalfd() system call that allows to receive signals
  1262. on a file descriptor.
  1263. If unsure, say Y.
  1264. config TIMERFD
  1265. bool "Enable timerfd() system call" if EXPERT
  1266. select ANON_INODES
  1267. default y
  1268. help
  1269. Enable the timerfd() system call that allows to receive timer
  1270. events on a file descriptor.
  1271. If unsure, say Y.
  1272. config EVENTFD
  1273. bool "Enable eventfd() system call" if EXPERT
  1274. select ANON_INODES
  1275. default y
  1276. help
  1277. Enable the eventfd() system call that allows to receive both
  1278. kernel notification (ie. KAIO) or userspace notifications.
  1279. If unsure, say Y.
  1280. # syscall, maps, verifier
  1281. config BPF_SYSCALL
  1282. bool "Enable bpf() system call" if EXPERT
  1283. select ANON_INODES
  1284. select BPF
  1285. default n
  1286. help
  1287. Enable the bpf() system call that allows to manipulate eBPF
  1288. programs and maps via file descriptors.
  1289. config SHMEM
  1290. bool "Use full shmem filesystem" if EXPERT
  1291. default y
  1292. depends on MMU
  1293. help
  1294. The shmem is an internal filesystem used to manage shared memory.
  1295. It is backed by swap and manages resource limits. It is also exported
  1296. to userspace as tmpfs if TMPFS is enabled. Disabling this
  1297. option replaces shmem and tmpfs with the much simpler ramfs code,
  1298. which may be appropriate on small systems without swap.
  1299. config AIO
  1300. bool "Enable AIO support" if EXPERT
  1301. default y
  1302. help
  1303. This option enables POSIX asynchronous I/O which may by used
  1304. by some high performance threaded applications. Disabling
  1305. this option saves about 7k.
  1306. config ADVISE_SYSCALLS
  1307. bool "Enable madvise/fadvise syscalls" if EXPERT
  1308. default y
  1309. help
  1310. This option enables the madvise and fadvise syscalls, used by
  1311. applications to advise the kernel about their future memory or file
  1312. usage, improving performance. If building an embedded system where no
  1313. applications use these syscalls, you can disable this option to save
  1314. space.
  1315. config PCI_QUIRKS
  1316. default y
  1317. bool "Enable PCI quirk workarounds" if EXPERT
  1318. depends on PCI
  1319. help
  1320. This enables workarounds for various PCI chipset
  1321. bugs/quirks. Disable this only if your target machine is
  1322. unaffected by PCI quirks.
  1323. config EMBEDDED
  1324. bool "Embedded system"
  1325. option allnoconfig_y
  1326. select EXPERT
  1327. help
  1328. This option should be enabled if compiling the kernel for
  1329. an embedded system so certain expert options are available
  1330. for configuration.
  1331. config HAVE_PERF_EVENTS
  1332. bool
  1333. help
  1334. See tools/perf/design.txt for details.
  1335. config PERF_USE_VMALLOC
  1336. bool
  1337. help
  1338. See tools/perf/design.txt for details
  1339. menu "Kernel Performance Events And Counters"
  1340. config PERF_EVENTS
  1341. bool "Kernel performance events and counters"
  1342. default y if PROFILING
  1343. depends on HAVE_PERF_EVENTS
  1344. select ANON_INODES
  1345. select IRQ_WORK
  1346. help
  1347. Enable kernel support for various performance events provided
  1348. by software and hardware.
  1349. Software events are supported either built-in or via the
  1350. use of generic tracepoints.
  1351. Most modern CPUs support performance events via performance
  1352. counter registers. These registers count the number of certain
  1353. types of hw events: such as instructions executed, cachemisses
  1354. suffered, or branches mis-predicted - without slowing down the
  1355. kernel or applications. These registers can also trigger interrupts
  1356. when a threshold number of events have passed - and can thus be
  1357. used to profile the code that runs on that CPU.
  1358. The Linux Performance Event subsystem provides an abstraction of
  1359. these software and hardware event capabilities, available via a
  1360. system call and used by the "perf" utility in tools/perf/. It
  1361. provides per task and per CPU counters, and it provides event
  1362. capabilities on top of those.
  1363. Say Y if unsure.
  1364. config DEBUG_PERF_USE_VMALLOC
  1365. default n
  1366. bool "Debug: use vmalloc to back perf mmap() buffers"
  1367. depends on PERF_EVENTS && DEBUG_KERNEL
  1368. select PERF_USE_VMALLOC
  1369. help
  1370. Use vmalloc memory to back perf mmap() buffers.
  1371. Mostly useful for debugging the vmalloc code on platforms
  1372. that don't require it.
  1373. Say N if unsure.
  1374. endmenu
  1375. config VM_EVENT_COUNTERS
  1376. default y
  1377. bool "Enable VM event counters for /proc/vmstat" if EXPERT
  1378. help
  1379. VM event counters are needed for event counts to be shown.
  1380. This option allows the disabling of the VM event counters
  1381. on EXPERT systems. /proc/vmstat will only show page counts
  1382. if VM event counters are disabled.
  1383. config SLUB_DEBUG
  1384. default y
  1385. bool "Enable SLUB debugging support" if EXPERT
  1386. depends on SLUB && SYSFS
  1387. help
  1388. SLUB has extensive debug support features. Disabling these can
  1389. result in significant savings in code size. This also disables
  1390. SLUB sysfs support. /sys/slab will not exist and there will be
  1391. no support for cache validation etc.
  1392. config COMPAT_BRK
  1393. bool "Disable heap randomization"
  1394. default y
  1395. help
  1396. Randomizing heap placement makes heap exploits harder, but it
  1397. also breaks ancient binaries (including anything libc5 based).
  1398. This option changes the bootup default to heap randomization
  1399. disabled, and can be overridden at runtime by setting
  1400. /proc/sys/kernel/randomize_va_space to 2.
  1401. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  1402. choice
  1403. prompt "Choose SLAB allocator"
  1404. default SLUB
  1405. help
  1406. This option allows to select a slab allocator.
  1407. config SLAB
  1408. bool "SLAB"
  1409. help
  1410. The regular slab allocator that is established and known to work
  1411. well in all environments. It organizes cache hot objects in
  1412. per cpu and per node queues.
  1413. config SLUB
  1414. bool "SLUB (Unqueued Allocator)"
  1415. help
  1416. SLUB is a slab allocator that minimizes cache line usage
  1417. instead of managing queues of cached objects (SLAB approach).
  1418. Per cpu caching is realized using slabs of objects instead
  1419. of queues of objects. SLUB can use memory efficiently
  1420. and has enhanced diagnostics. SLUB is the default choice for
  1421. a slab allocator.
  1422. config SLOB
  1423. depends on EXPERT
  1424. bool "SLOB (Simple Allocator)"
  1425. help
  1426. SLOB replaces the stock allocator with a drastically simpler
  1427. allocator. SLOB is generally more space efficient but
  1428. does not perform as well on large systems.
  1429. endchoice
  1430. config SLUB_CPU_PARTIAL
  1431. default y
  1432. depends on SLUB && SMP
  1433. bool "SLUB per cpu partial cache"
  1434. help
  1435. Per cpu partial caches accellerate objects allocation and freeing
  1436. that is local to a processor at the price of more indeterminism
  1437. in the latency of the free. On overflow these caches will be cleared
  1438. which requires the taking of locks that may cause latency spikes.
  1439. Typically one would choose no for a realtime system.
  1440. config MMAP_ALLOW_UNINITIALIZED
  1441. bool "Allow mmapped anonymous memory to be uninitialized"
  1442. depends on EXPERT && !MMU
  1443. default n
  1444. help
  1445. Normally, and according to the Linux spec, anonymous memory obtained
  1446. from mmap() has it's contents cleared before it is passed to
  1447. userspace. Enabling this config option allows you to request that
  1448. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  1449. providing a huge performance boost. If this option is not enabled,
  1450. then the flag will be ignored.
  1451. This is taken advantage of by uClibc's malloc(), and also by
  1452. ELF-FDPIC binfmt's brk and stack allocator.
  1453. Because of the obvious security issues, this option should only be
  1454. enabled on embedded devices where you control what is run in
  1455. userspace. Since that isn't generally a problem on no-MMU systems,
  1456. it is normally safe to say Y here.
  1457. See Documentation/nommu-mmap.txt for more information.
  1458. config SYSTEM_TRUSTED_KEYRING
  1459. bool "Provide system-wide ring of trusted keys"
  1460. depends on KEYS
  1461. help
  1462. Provide a system keyring to which trusted keys can be added. Keys in
  1463. the keyring are considered to be trusted. Keys may be added at will
  1464. by the kernel from compiled-in data and from hardware key stores, but
  1465. userspace may only add extra keys if those keys can be verified by
  1466. keys already in the keyring.
  1467. Keys in this keyring are used by module signature checking.
  1468. config PROFILING
  1469. bool "Profiling support"
  1470. help
  1471. Say Y here to enable the extended profiling support mechanisms used
  1472. by profilers such as OProfile.
  1473. #
  1474. # Place an empty function call at each tracepoint site. Can be
  1475. # dynamically changed for a probe function.
  1476. #
  1477. config TRACEPOINTS
  1478. bool
  1479. source "arch/Kconfig"
  1480. endmenu # General setup
  1481. config HAVE_GENERIC_DMA_COHERENT
  1482. bool
  1483. default n
  1484. config SLABINFO
  1485. bool
  1486. depends on PROC_FS
  1487. depends on SLAB || SLUB_DEBUG
  1488. default y
  1489. config RT_MUTEXES
  1490. boolean
  1491. config BASE_SMALL
  1492. int
  1493. default 0 if BASE_FULL
  1494. default 1 if !BASE_FULL
  1495. menuconfig MODULES
  1496. bool "Enable loadable module support"
  1497. option modules
  1498. help
  1499. Kernel modules are small pieces of compiled code which can
  1500. be inserted in the running kernel, rather than being
  1501. permanently built into the kernel. You use the "modprobe"
  1502. tool to add (and sometimes remove) them. If you say Y here,
  1503. many parts of the kernel can be built as modules (by
  1504. answering M instead of Y where indicated): this is most
  1505. useful for infrequently used options which are not required
  1506. for booting. For more information, see the man pages for
  1507. modprobe, lsmod, modinfo, insmod and rmmod.
  1508. If you say Y here, you will need to run "make
  1509. modules_install" to put the modules under /lib/modules/
  1510. where modprobe can find them (you may need to be root to do
  1511. this).
  1512. If unsure, say Y.
  1513. if MODULES
  1514. config MODULE_FORCE_LOAD
  1515. bool "Forced module loading"
  1516. default n
  1517. help
  1518. Allow loading of modules without version information (ie. modprobe
  1519. --force). Forced module loading sets the 'F' (forced) taint flag and
  1520. is usually a really bad idea.
  1521. config MODULE_UNLOAD
  1522. bool "Module unloading"
  1523. help
  1524. Without this option you will not be able to unload any
  1525. modules (note that some modules may not be unloadable
  1526. anyway), which makes your kernel smaller, faster
  1527. and simpler. If unsure, say Y.
  1528. config MODULE_FORCE_UNLOAD
  1529. bool "Forced module unloading"
  1530. depends on MODULE_UNLOAD
  1531. help
  1532. This option allows you to force a module to unload, even if the
  1533. kernel believes it is unsafe: the kernel will remove the module
  1534. without waiting for anyone to stop using it (using the -f option to
  1535. rmmod). This is mainly for kernel developers and desperate users.
  1536. If unsure, say N.
  1537. config MODVERSIONS
  1538. bool "Module versioning support"
  1539. help
  1540. Usually, you have to use modules compiled with your kernel.
  1541. Saying Y here makes it sometimes possible to use modules
  1542. compiled for different kernels, by adding enough information
  1543. to the modules to (hopefully) spot any changes which would
  1544. make them incompatible with the kernel you are running. If
  1545. unsure, say N.
  1546. config MODULE_SRCVERSION_ALL
  1547. bool "Source checksum for all modules"
  1548. help
  1549. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1550. field inserted into their modinfo section, which contains a
  1551. sum of the source files which made it. This helps maintainers
  1552. see exactly which source was used to build a module (since
  1553. others sometimes change the module source without updating
  1554. the version). With this option, such a "srcversion" field
  1555. will be created for all modules. If unsure, say N.
  1556. config MODULE_SIG
  1557. bool "Module signature verification"
  1558. depends on MODULES
  1559. select SYSTEM_TRUSTED_KEYRING
  1560. select KEYS
  1561. select CRYPTO
  1562. select ASYMMETRIC_KEY_TYPE
  1563. select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  1564. select PUBLIC_KEY_ALGO_RSA
  1565. select ASN1
  1566. select OID_REGISTRY
  1567. select X509_CERTIFICATE_PARSER
  1568. help
  1569. Check modules for valid signatures upon load: the signature
  1570. is simply appended to the module. For more information see
  1571. Documentation/module-signing.txt.
  1572. !!!WARNING!!! If you enable this option, you MUST make sure that the
  1573. module DOES NOT get stripped after being signed. This includes the
  1574. debuginfo strip done by some packagers (such as rpmbuild) and
  1575. inclusion into an initramfs that wants the module size reduced.
  1576. config MODULE_SIG_FORCE
  1577. bool "Require modules to be validly signed"
  1578. depends on MODULE_SIG
  1579. help
  1580. Reject unsigned modules or signed modules for which we don't have a
  1581. key. Without this, such modules will simply taint the kernel.
  1582. config MODULE_SIG_ALL
  1583. bool "Automatically sign all modules"
  1584. default y
  1585. depends on MODULE_SIG
  1586. help
  1587. Sign all modules during make modules_install. Without this option,
  1588. modules must be signed manually, using the scripts/sign-file tool.
  1589. comment "Do not forget to sign required modules with scripts/sign-file"
  1590. depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
  1591. choice
  1592. prompt "Which hash algorithm should modules be signed with?"
  1593. depends on MODULE_SIG
  1594. help
  1595. This determines which sort of hashing algorithm will be used during
  1596. signature generation. This algorithm _must_ be built into the kernel
  1597. directly so that signature verification can take place. It is not
  1598. possible to load a signed module containing the algorithm to check
  1599. the signature on that module.
  1600. config MODULE_SIG_SHA1
  1601. bool "Sign modules with SHA-1"
  1602. select CRYPTO_SHA1
  1603. config MODULE_SIG_SHA224
  1604. bool "Sign modules with SHA-224"
  1605. select CRYPTO_SHA256
  1606. config MODULE_SIG_SHA256
  1607. bool "Sign modules with SHA-256"
  1608. select CRYPTO_SHA256
  1609. config MODULE_SIG_SHA384
  1610. bool "Sign modules with SHA-384"
  1611. select CRYPTO_SHA512
  1612. config MODULE_SIG_SHA512
  1613. bool "Sign modules with SHA-512"
  1614. select CRYPTO_SHA512
  1615. endchoice
  1616. config MODULE_SIG_HASH
  1617. string
  1618. depends on MODULE_SIG
  1619. default "sha1" if MODULE_SIG_SHA1
  1620. default "sha224" if MODULE_SIG_SHA224
  1621. default "sha256" if MODULE_SIG_SHA256
  1622. default "sha384" if MODULE_SIG_SHA384
  1623. default "sha512" if MODULE_SIG_SHA512
  1624. config MODULE_COMPRESS
  1625. bool "Compress modules on installation"
  1626. depends on MODULES
  1627. help
  1628. This option compresses the kernel modules when 'make
  1629. modules_install' is run.
  1630. The modules will be compressed either using gzip or xz depend on the
  1631. choice made in "Compression algorithm".
  1632. module-init-tools has support for gzip format while kmod handle gzip
  1633. and xz compressed modules.
  1634. When a kernel module is installed from outside of the main kernel
  1635. source and uses the Kbuild system for installing modules then that
  1636. kernel module will also be compressed when it is installed.
  1637. This option provides little benefit when the modules are to be used inside
  1638. an initrd or initramfs, it generally is more efficient to compress the whole
  1639. initrd or initramfs instead.
  1640. This is fully compatible with signed modules while the signed module is
  1641. compressed. module-init-tools or kmod handles decompression and provide to
  1642. other layer the uncompressed but signed payload.
  1643. choice
  1644. prompt "Compression algorithm"
  1645. depends on MODULE_COMPRESS
  1646. default MODULE_COMPRESS_GZIP
  1647. help
  1648. This determines which sort of compression will be used during
  1649. 'make modules_install'.
  1650. GZIP (default) and XZ are supported.
  1651. config MODULE_COMPRESS_GZIP
  1652. bool "GZIP"
  1653. config MODULE_COMPRESS_XZ
  1654. bool "XZ"
  1655. endchoice
  1656. endif # MODULES
  1657. config INIT_ALL_POSSIBLE
  1658. bool
  1659. help
  1660. Back when each arch used to define their own cpu_online_mask and
  1661. cpu_possible_mask, some of them chose to initialize cpu_possible_mask
  1662. with all 1s, and others with all 0s. When they were centralised,
  1663. it was better to provide this option than to break all the archs
  1664. and have several arch maintainers pursuing me down dark alleys.
  1665. config STOP_MACHINE
  1666. bool
  1667. default y
  1668. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1669. help
  1670. Need stop_machine() primitive.
  1671. source "block/Kconfig"
  1672. config PREEMPT_NOTIFIERS
  1673. bool
  1674. config PADATA
  1675. depends on SMP
  1676. bool
  1677. # Can be selected by architectures with broken toolchains
  1678. # that get confused by correct const<->read_only section
  1679. # mappings
  1680. config BROKEN_RODATA
  1681. bool
  1682. config ASN1
  1683. tristate
  1684. help
  1685. Build a simple ASN.1 grammar compiler that produces a bytecode output
  1686. that can be interpreted by the ASN.1 stream decoder and used to
  1687. inform it as to what tags are to be expected in a stream and what
  1688. functions to call on what tags.
  1689. source "kernel/Kconfig.locks"