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