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