Kconfig 60 KB

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