Kconfig 57 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 && !NO_HZ_FULL
  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 && !NO_HZ_FULL
  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 && !NO_HZ_FULL
  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. select IRQ_WORK
  360. help
  361. This option selects the RCU implementation that is
  362. designed for very large SMP system with hundreds or
  363. thousands of CPUs. It also scales down nicely to
  364. smaller systems.
  365. config TREE_PREEMPT_RCU
  366. bool "Preemptible tree-based hierarchical RCU"
  367. depends on PREEMPT
  368. help
  369. This option selects the RCU implementation that is
  370. designed for very large SMP systems with hundreds or
  371. thousands of CPUs, but for which real-time response
  372. is also required. It also scales down nicely to
  373. smaller systems.
  374. Select this option if you are unsure.
  375. config TINY_RCU
  376. bool "UP-only small-memory-footprint RCU"
  377. depends on !PREEMPT && !SMP
  378. help
  379. This option selects the RCU implementation that is
  380. designed for UP systems from which real-time response
  381. is not required. This option greatly reduces the
  382. memory footprint of RCU.
  383. config TINY_PREEMPT_RCU
  384. bool "Preemptible UP-only small-memory-footprint RCU"
  385. depends on PREEMPT && !SMP
  386. help
  387. This option selects the RCU implementation that is designed
  388. for real-time UP systems. This option greatly reduces the
  389. memory footprint of RCU.
  390. endchoice
  391. config PREEMPT_RCU
  392. def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
  393. help
  394. This option enables preemptible-RCU code that is common between
  395. the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
  396. config RCU_STALL_COMMON
  397. def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
  398. help
  399. This option enables RCU CPU stall code that is common between
  400. the TINY and TREE variants of RCU. The purpose is to allow
  401. the tiny variants to disable RCU CPU stall warnings, while
  402. making these warnings mandatory for the tree variants.
  403. config CONTEXT_TRACKING
  404. bool
  405. config RCU_USER_QS
  406. bool "Consider userspace as in RCU extended quiescent state"
  407. depends on HAVE_CONTEXT_TRACKING && SMP
  408. select CONTEXT_TRACKING
  409. help
  410. This option sets hooks on kernel / userspace boundaries and
  411. puts RCU in extended quiescent state when the CPU runs in
  412. userspace. It means that when a CPU runs in userspace, it is
  413. excluded from the global RCU state machine and thus doesn't
  414. try to keep the timer tick on for RCU.
  415. Unless you want to hack and help the development of the full
  416. dynticks mode, you shouldn't enable this option. It also
  417. adds unnecessary overhead.
  418. If unsure say N
  419. config CONTEXT_TRACKING_FORCE
  420. bool "Force context tracking"
  421. depends on CONTEXT_TRACKING
  422. default CONTEXT_TRACKING
  423. help
  424. Probe on user/kernel boundaries by default in order to
  425. test the features that rely on it such as userspace RCU extended
  426. quiescent states.
  427. This test is there for debugging until we have a real user like the
  428. full dynticks mode.
  429. config RCU_FANOUT
  430. int "Tree-based hierarchical RCU fanout value"
  431. range 2 64 if 64BIT
  432. range 2 32 if !64BIT
  433. depends on TREE_RCU || TREE_PREEMPT_RCU
  434. default 64 if 64BIT
  435. default 32 if !64BIT
  436. help
  437. This option controls the fanout of hierarchical implementations
  438. of RCU, allowing RCU to work efficiently on machines with
  439. large numbers of CPUs. This value must be at least the fourth
  440. root of NR_CPUS, which allows NR_CPUS to be insanely large.
  441. The default value of RCU_FANOUT should be used for production
  442. systems, but if you are stress-testing the RCU implementation
  443. itself, small RCU_FANOUT values allow you to test large-system
  444. code paths on small(er) systems.
  445. Select a specific number if testing RCU itself.
  446. Take the default if unsure.
  447. config RCU_FANOUT_LEAF
  448. int "Tree-based hierarchical RCU leaf-level fanout value"
  449. range 2 RCU_FANOUT if 64BIT
  450. range 2 RCU_FANOUT if !64BIT
  451. depends on TREE_RCU || TREE_PREEMPT_RCU
  452. default 16
  453. help
  454. This option controls the leaf-level fanout of hierarchical
  455. implementations of RCU, and allows trading off cache misses
  456. against lock contention. Systems that synchronize their
  457. scheduling-clock interrupts for energy-efficiency reasons will
  458. want the default because the smaller leaf-level fanout keeps
  459. lock contention levels acceptably low. Very large systems
  460. (hundreds or thousands of CPUs) will instead want to set this
  461. value to the maximum value possible in order to reduce the
  462. number of cache misses incurred during RCU's grace-period
  463. initialization. These systems tend to run CPU-bound, and thus
  464. are not helped by synchronized interrupts, and thus tend to
  465. skew them, which reduces lock contention enough that large
  466. leaf-level fanouts work well.
  467. Select a specific number if testing RCU itself.
  468. Select the maximum permissible value for large systems.
  469. Take the default if unsure.
  470. config RCU_FANOUT_EXACT
  471. bool "Disable tree-based hierarchical RCU auto-balancing"
  472. depends on TREE_RCU || TREE_PREEMPT_RCU
  473. default n
  474. help
  475. This option forces use of the exact RCU_FANOUT value specified,
  476. regardless of imbalances in the hierarchy. This is useful for
  477. testing RCU itself, and might one day be useful on systems with
  478. strong NUMA behavior.
  479. Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
  480. Say N if unsure.
  481. config RCU_FAST_NO_HZ
  482. bool "Accelerate last non-dyntick-idle CPU's grace periods"
  483. depends on NO_HZ_COMMON && SMP
  484. default n
  485. help
  486. This option permits CPUs to enter dynticks-idle state even if
  487. they have RCU callbacks queued, and prevents RCU from waking
  488. these CPUs up more than roughly once every four jiffies (by
  489. default, you can adjust this using the rcutree.rcu_idle_gp_delay
  490. parameter), thus improving energy efficiency. On the other
  491. hand, this option increases the duration of RCU grace periods,
  492. for example, slowing down synchronize_rcu().
  493. Say Y if energy efficiency is critically important, and you
  494. don't care about increased grace-period durations.
  495. Say N if you are unsure.
  496. config TREE_RCU_TRACE
  497. def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
  498. select DEBUG_FS
  499. help
  500. This option provides tracing for the TREE_RCU and
  501. TREE_PREEMPT_RCU implementations, permitting Makefile to
  502. trivially select kernel/rcutree_trace.c.
  503. config RCU_BOOST
  504. bool "Enable RCU priority boosting"
  505. depends on RT_MUTEXES && PREEMPT_RCU
  506. default n
  507. help
  508. This option boosts the priority of preempted RCU readers that
  509. block the current preemptible RCU grace period for too long.
  510. This option also prevents heavy loads from blocking RCU
  511. callback invocation for all flavors of RCU.
  512. Say Y here if you are working with real-time apps or heavy loads
  513. Say N here if you are unsure.
  514. config RCU_BOOST_PRIO
  515. int "Real-time priority to boost RCU readers to"
  516. range 1 99
  517. depends on RCU_BOOST
  518. default 1
  519. help
  520. This option specifies the real-time priority to which long-term
  521. preempted RCU readers are to be boosted. If you are working
  522. with a real-time application that has one or more CPU-bound
  523. threads running at a real-time priority level, you should set
  524. RCU_BOOST_PRIO to a priority higher then the highest-priority
  525. real-time CPU-bound thread. The default RCU_BOOST_PRIO value
  526. of 1 is appropriate in the common case, which is real-time
  527. applications that do not have any CPU-bound threads.
  528. Some real-time applications might not have a single real-time
  529. thread that saturates a given CPU, but instead might have
  530. multiple real-time threads that, taken together, fully utilize
  531. that CPU. In this case, you should set RCU_BOOST_PRIO to
  532. a priority higher than the lowest-priority thread that is
  533. conspiring to prevent the CPU from running any non-real-time
  534. tasks. For example, if one thread at priority 10 and another
  535. thread at priority 5 are between themselves fully consuming
  536. the CPU time on a given CPU, then RCU_BOOST_PRIO should be
  537. set to priority 6 or higher.
  538. Specify the real-time priority, or take the default if unsure.
  539. config RCU_BOOST_DELAY
  540. int "Milliseconds to delay boosting after RCU grace-period start"
  541. range 0 3000
  542. depends on RCU_BOOST
  543. default 500
  544. help
  545. This option specifies the time to wait after the beginning of
  546. a given grace period before priority-boosting preempted RCU
  547. readers blocking that grace period. Note that any RCU reader
  548. blocking an expedited RCU grace period is boosted immediately.
  549. Accept the default if unsure.
  550. config RCU_NOCB_CPU
  551. bool "Offload RCU callback processing from boot-selected CPUs (EXPERIMENTAL"
  552. depends on TREE_RCU || TREE_PREEMPT_RCU
  553. default n
  554. help
  555. Use this option to reduce OS jitter for aggressive HPC or
  556. real-time workloads. It can also be used to offload RCU
  557. callback invocation to energy-efficient CPUs in battery-powered
  558. asymmetric multiprocessors.
  559. This option offloads callback invocation from the set of
  560. CPUs specified at boot time by the rcu_nocbs parameter.
  561. For each such CPU, a kthread ("rcuox/N") will be created to
  562. invoke callbacks, where the "N" is the CPU being offloaded,
  563. and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
  564. "s" for RCU-sched. Nothing prevents this kthread from running
  565. on the specified CPUs, but (1) the kthreads may be preempted
  566. between each callback, and (2) affinity or cgroups can be used
  567. to force the kthreads to run on whatever set of CPUs is desired.
  568. Say Y here if you want to help to debug reduced OS jitter.
  569. Say N here if you are unsure.
  570. choice
  571. prompt "Build-forced no-CBs CPUs"
  572. default RCU_NOCB_CPU_NONE
  573. help
  574. This option allows no-CBs CPUs to be specified at build time.
  575. Additional no-CBs CPUs may be specified by the rcu_nocbs=
  576. boot parameter.
  577. config RCU_NOCB_CPU_NONE
  578. bool "No build_forced no-CBs CPUs"
  579. depends on RCU_NOCB_CPU && !NO_HZ_FULL
  580. help
  581. This option does not force any of the CPUs to be no-CBs CPUs.
  582. Only CPUs designated by the rcu_nocbs= boot parameter will be
  583. no-CBs CPUs.
  584. config RCU_NOCB_CPU_ZERO
  585. bool "CPU 0 is a build_forced no-CBs CPU"
  586. depends on RCU_NOCB_CPU && !NO_HZ_FULL
  587. help
  588. This option forces CPU 0 to be a no-CBs CPU. Additional CPUs
  589. may be designated as no-CBs CPUs using the rcu_nocbs= boot
  590. parameter will be no-CBs CPUs.
  591. Select this if CPU 0 needs to be a no-CBs CPU for real-time
  592. or energy-efficiency reasons.
  593. config RCU_NOCB_CPU_ALL
  594. bool "All CPUs are build_forced no-CBs CPUs"
  595. depends on RCU_NOCB_CPU
  596. help
  597. This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
  598. boot parameter will be ignored.
  599. Select this if all CPUs need to be no-CBs CPUs for real-time
  600. or energy-efficiency reasons.
  601. endchoice
  602. endmenu # "RCU Subsystem"
  603. config IKCONFIG
  604. tristate "Kernel .config support"
  605. ---help---
  606. This option enables the complete Linux kernel ".config" file
  607. contents to be saved in the kernel. It provides documentation
  608. of which kernel options are used in a running kernel or in an
  609. on-disk kernel. This information can be extracted from the kernel
  610. image file with the script scripts/extract-ikconfig and used as
  611. input to rebuild the current kernel or to build another kernel.
  612. It can also be extracted from a running kernel by reading
  613. /proc/config.gz if enabled (below).
  614. config IKCONFIG_PROC
  615. bool "Enable access to .config through /proc/config.gz"
  616. depends on IKCONFIG && PROC_FS
  617. ---help---
  618. This option enables access to the kernel configuration file
  619. through /proc/config.gz.
  620. config LOG_BUF_SHIFT
  621. int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
  622. range 12 21
  623. default 17
  624. help
  625. Select kernel log buffer size as a power of 2.
  626. Examples:
  627. 17 => 128 KB
  628. 16 => 64 KB
  629. 15 => 32 KB
  630. 14 => 16 KB
  631. 13 => 8 KB
  632. 12 => 4 KB
  633. #
  634. # Architectures with an unreliable sched_clock() should select this:
  635. #
  636. config HAVE_UNSTABLE_SCHED_CLOCK
  637. bool
  638. #
  639. # For architectures that want to enable the support for NUMA-affine scheduler
  640. # balancing logic:
  641. #
  642. config ARCH_SUPPORTS_NUMA_BALANCING
  643. bool
  644. # For architectures that (ab)use NUMA to represent different memory regions
  645. # all cpu-local but of different latencies, such as SuperH.
  646. #
  647. config ARCH_WANT_NUMA_VARIABLE_LOCALITY
  648. bool
  649. #
  650. # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
  651. config ARCH_WANTS_PROT_NUMA_PROT_NONE
  652. bool
  653. config ARCH_USES_NUMA_PROT_NONE
  654. bool
  655. default y
  656. depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
  657. depends on NUMA_BALANCING
  658. config NUMA_BALANCING_DEFAULT_ENABLED
  659. bool "Automatically enable NUMA aware memory/task placement"
  660. default y
  661. depends on NUMA_BALANCING
  662. help
  663. If set, autonumic NUMA balancing will be enabled if running on a NUMA
  664. machine.
  665. config NUMA_BALANCING
  666. bool "Memory placement aware NUMA scheduler"
  667. depends on ARCH_SUPPORTS_NUMA_BALANCING
  668. depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
  669. depends on SMP && NUMA && MIGRATION
  670. help
  671. This option adds support for automatic NUMA aware memory/task placement.
  672. The mechanism is quite primitive and is based on migrating memory when
  673. it is references to the node the task is running on.
  674. This system will be inactive on UMA systems.
  675. menuconfig CGROUPS
  676. boolean "Control Group support"
  677. depends on EVENTFD
  678. help
  679. This option adds support for grouping sets of processes together, for
  680. use with process control subsystems such as Cpusets, CFS, memory
  681. controls or device isolation.
  682. See
  683. - Documentation/scheduler/sched-design-CFS.txt (CFS)
  684. - Documentation/cgroups/ (features for grouping, isolation
  685. and resource control)
  686. Say N if unsure.
  687. if CGROUPS
  688. config CGROUP_DEBUG
  689. bool "Example debug cgroup subsystem"
  690. default n
  691. help
  692. This option enables a simple cgroup subsystem that
  693. exports useful debugging information about the cgroups
  694. framework.
  695. Say N if unsure.
  696. config CGROUP_FREEZER
  697. bool "Freezer cgroup subsystem"
  698. help
  699. Provides a way to freeze and unfreeze all tasks in a
  700. cgroup.
  701. config CGROUP_DEVICE
  702. bool "Device controller for cgroups"
  703. help
  704. Provides a cgroup implementing whitelists for devices which
  705. a process in the cgroup can mknod or open.
  706. config CPUSETS
  707. bool "Cpuset support"
  708. help
  709. This option will let you create and manage CPUSETs which
  710. allow dynamically partitioning a system into sets of CPUs and
  711. Memory Nodes and assigning tasks to run only within those sets.
  712. This is primarily useful on large SMP or NUMA systems.
  713. Say N if unsure.
  714. config PROC_PID_CPUSET
  715. bool "Include legacy /proc/<pid>/cpuset file"
  716. depends on CPUSETS
  717. default y
  718. config CGROUP_CPUACCT
  719. bool "Simple CPU accounting cgroup subsystem"
  720. help
  721. Provides a simple Resource Controller for monitoring the
  722. total CPU consumed by the tasks in a cgroup.
  723. config RESOURCE_COUNTERS
  724. bool "Resource counters"
  725. help
  726. This option enables controller independent resource accounting
  727. infrastructure that works with cgroups.
  728. config MEMCG
  729. bool "Memory Resource Controller for Control Groups"
  730. depends on RESOURCE_COUNTERS
  731. select MM_OWNER
  732. help
  733. Provides a memory resource controller that manages both anonymous
  734. memory and page cache. (See Documentation/cgroups/memory.txt)
  735. Note that setting this option increases fixed memory overhead
  736. associated with each page of memory in the system. By this,
  737. 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
  738. usage tracking struct at boot. Total amount of this is printed out
  739. at boot.
  740. Only enable when you're ok with these trade offs and really
  741. sure you need the memory resource controller. Even when you enable
  742. this, you can set "cgroup_disable=memory" at your boot option to
  743. disable memory resource controller and you can avoid overheads.
  744. (and lose benefits of memory resource controller)
  745. This config option also selects MM_OWNER config option, which
  746. could in turn add some fork/exit overhead.
  747. config MEMCG_SWAP
  748. bool "Memory Resource Controller Swap Extension"
  749. depends on MEMCG && SWAP
  750. help
  751. Add swap management feature to memory resource controller. When you
  752. enable this, you can limit mem+swap usage per cgroup. In other words,
  753. when you disable this, memory resource controller has no cares to
  754. usage of swap...a process can exhaust all of the swap. This extension
  755. is useful when you want to avoid exhaustion swap but this itself
  756. adds more overheads and consumes memory for remembering information.
  757. Especially if you use 32bit system or small memory system, please
  758. be careful about enabling this. When memory resource controller
  759. is disabled by boot option, this will be automatically disabled and
  760. there will be no overhead from this. Even when you set this config=y,
  761. if boot option "swapaccount=0" is set, swap will not be accounted.
  762. Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
  763. size is 4096bytes, 512k per 1Gbytes of swap.
  764. config MEMCG_SWAP_ENABLED
  765. bool "Memory Resource Controller Swap Extension enabled by default"
  766. depends on MEMCG_SWAP
  767. default y
  768. help
  769. Memory Resource Controller Swap Extension comes with its price in
  770. a bigger memory consumption. General purpose distribution kernels
  771. which want to enable the feature but keep it disabled by default
  772. and let the user enable it by swapaccount boot command line
  773. parameter should have this option unselected.
  774. For those who want to have the feature enabled by default should
  775. select this option (if, for some reason, they need to disable it
  776. then swapaccount=0 does the trick).
  777. config MEMCG_KMEM
  778. bool "Memory Resource Controller Kernel Memory accounting"
  779. depends on MEMCG
  780. depends on SLUB || SLAB
  781. help
  782. The Kernel Memory extension for Memory Resource Controller can limit
  783. the amount of memory used by kernel objects in the system. Those are
  784. fundamentally different from the entities handled by the standard
  785. Memory Controller, which are page-based, and can be swapped. Users of
  786. the kmem extension can use it to guarantee that no group of processes
  787. will ever exhaust kernel resources alone.
  788. config CGROUP_HUGETLB
  789. bool "HugeTLB Resource Controller for Control Groups"
  790. depends on RESOURCE_COUNTERS && HUGETLB_PAGE
  791. default n
  792. help
  793. Provides a cgroup Resource Controller for HugeTLB pages.
  794. When you enable this, you can put a per cgroup limit on HugeTLB usage.
  795. The limit is enforced during page fault. Since HugeTLB doesn't
  796. support page reclaim, enforcing the limit at page fault time implies
  797. that, the application will get SIGBUS signal if it tries to access
  798. HugeTLB pages beyond its limit. This requires the application to know
  799. beforehand how much HugeTLB pages it would require for its use. The
  800. control group is tracked in the third page lru pointer. This means
  801. that we cannot use the controller with huge page less than 3 pages.
  802. config CGROUP_PERF
  803. bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
  804. depends on PERF_EVENTS && CGROUPS
  805. help
  806. This option extends the per-cpu mode to restrict monitoring to
  807. threads which belong to the cgroup specified and run on the
  808. designated cpu.
  809. Say N if unsure.
  810. menuconfig CGROUP_SCHED
  811. bool "Group CPU scheduler"
  812. default n
  813. help
  814. This feature lets CPU scheduler recognize task groups and control CPU
  815. bandwidth allocation to such task groups. It uses cgroups to group
  816. tasks.
  817. if CGROUP_SCHED
  818. config FAIR_GROUP_SCHED
  819. bool "Group scheduling for SCHED_OTHER"
  820. depends on CGROUP_SCHED
  821. default CGROUP_SCHED
  822. config CFS_BANDWIDTH
  823. bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
  824. depends on FAIR_GROUP_SCHED
  825. default n
  826. help
  827. This option allows users to define CPU bandwidth rates (limits) for
  828. tasks running within the fair group scheduler. Groups with no limit
  829. set are considered to be unconstrained and will run with no
  830. restriction.
  831. See tip/Documentation/scheduler/sched-bwc.txt for more information.
  832. config RT_GROUP_SCHED
  833. bool "Group scheduling for SCHED_RR/FIFO"
  834. depends on CGROUP_SCHED
  835. default n
  836. help
  837. This feature lets you explicitly allocate real CPU bandwidth
  838. to task groups. If enabled, it will also make it impossible to
  839. schedule realtime tasks for non-root users until you allocate
  840. realtime bandwidth for them.
  841. See Documentation/scheduler/sched-rt-group.txt for more information.
  842. endif #CGROUP_SCHED
  843. config BLK_CGROUP
  844. bool "Block IO controller"
  845. depends on BLOCK
  846. default n
  847. ---help---
  848. Generic block IO controller cgroup interface. This is the common
  849. cgroup interface which should be used by various IO controlling
  850. policies.
  851. Currently, CFQ IO scheduler uses it to recognize task groups and
  852. control disk bandwidth allocation (proportional time slice allocation)
  853. to such task groups. It is also used by bio throttling logic in
  854. block layer to implement upper limit in IO rates on a device.
  855. This option only enables generic Block IO controller infrastructure.
  856. One needs to also enable actual IO controlling logic/policy. For
  857. enabling proportional weight division of disk bandwidth in CFQ, set
  858. CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
  859. CONFIG_BLK_DEV_THROTTLING=y.
  860. See Documentation/cgroups/blkio-controller.txt for more information.
  861. config DEBUG_BLK_CGROUP
  862. bool "Enable Block IO controller debugging"
  863. depends on BLK_CGROUP
  864. default n
  865. ---help---
  866. Enable some debugging help. Currently it exports additional stat
  867. files in a cgroup which can be useful for debugging.
  868. endif # CGROUPS
  869. config CHECKPOINT_RESTORE
  870. bool "Checkpoint/restore support" if EXPERT
  871. default n
  872. help
  873. Enables additional kernel features in a sake of checkpoint/restore.
  874. In particular it adds auxiliary prctl codes to setup process text,
  875. data and heap segment sizes, and a few additional /proc filesystem
  876. entries.
  877. If unsure, say N here.
  878. menuconfig NAMESPACES
  879. bool "Namespaces support" if EXPERT
  880. default !EXPERT
  881. help
  882. Provides the way to make tasks work with different objects using
  883. the same id. For example same IPC id may refer to different objects
  884. or same user id or pid may refer to different tasks when used in
  885. different namespaces.
  886. if NAMESPACES
  887. config UTS_NS
  888. bool "UTS namespace"
  889. default y
  890. help
  891. In this namespace tasks see different info provided with the
  892. uname() system call
  893. config IPC_NS
  894. bool "IPC namespace"
  895. depends on (SYSVIPC || POSIX_MQUEUE)
  896. default y
  897. help
  898. In this namespace tasks work with IPC ids which correspond to
  899. different IPC objects in different namespaces.
  900. config USER_NS
  901. bool "User namespace"
  902. depends on UIDGID_CONVERTED
  903. select UIDGID_STRICT_TYPE_CHECKS
  904. default n
  905. help
  906. This allows containers, i.e. vservers, to use user namespaces
  907. to provide different user info for different servers.
  908. When user namespaces are enabled in the kernel it is
  909. recommended that the MEMCG and MEMCG_KMEM options also be
  910. enabled and that user-space use the memory control groups to
  911. limit the amount of memory a memory unprivileged users can
  912. use.
  913. If unsure, say N.
  914. config PID_NS
  915. bool "PID Namespaces"
  916. default y
  917. help
  918. Support process id namespaces. This allows having multiple
  919. processes with the same pid as long as they are in different
  920. pid namespaces. This is a building block of containers.
  921. config NET_NS
  922. bool "Network namespace"
  923. depends on NET
  924. default y
  925. help
  926. Allow user space to create what appear to be multiple instances
  927. of the network stack.
  928. endif # NAMESPACES
  929. config UIDGID_CONVERTED
  930. # True if all of the selected software conmponents are known
  931. # to have uid_t and gid_t converted to kuid_t and kgid_t
  932. # where appropriate and are otherwise safe to use with
  933. # the user namespace.
  934. bool
  935. default y
  936. # Filesystems
  937. depends on XFS_FS = n
  938. config UIDGID_STRICT_TYPE_CHECKS
  939. bool "Require conversions between uid/gids and their internal representation"
  940. depends on UIDGID_CONVERTED
  941. default n
  942. help
  943. While the nececessary conversions are being added to all subsystems this option allows
  944. the code to continue to build for unconverted subsystems.
  945. Say Y here if you want the strict type checking enabled
  946. config SCHED_AUTOGROUP
  947. bool "Automatic process group scheduling"
  948. select EVENTFD
  949. select CGROUPS
  950. select CGROUP_SCHED
  951. select FAIR_GROUP_SCHED
  952. help
  953. This option optimizes the scheduler for common desktop workloads by
  954. automatically creating and populating task groups. This separation
  955. of workloads isolates aggressive CPU burners (like build jobs) from
  956. desktop applications. Task group autogeneration is currently based
  957. upon task session.
  958. config MM_OWNER
  959. bool
  960. config SYSFS_DEPRECATED
  961. bool "Enable deprecated sysfs features to support old userspace tools"
  962. depends on SYSFS
  963. default n
  964. help
  965. This option adds code that switches the layout of the "block" class
  966. devices, to not show up in /sys/class/block/, but only in
  967. /sys/block/.
  968. This switch is only active when the sysfs.deprecated=1 boot option is
  969. passed or the SYSFS_DEPRECATED_V2 option is set.
  970. This option allows new kernels to run on old distributions and tools,
  971. which might get confused by /sys/class/block/. Since 2007/2008 all
  972. major distributions and tools handle this just fine.
  973. Recent distributions and userspace tools after 2009/2010 depend on
  974. the existence of /sys/class/block/, and will not work with this
  975. option enabled.
  976. Only if you are using a new kernel on an old distribution, you might
  977. need to say Y here.
  978. config SYSFS_DEPRECATED_V2
  979. bool "Enable deprecated sysfs features by default"
  980. default n
  981. depends on SYSFS
  982. depends on SYSFS_DEPRECATED
  983. help
  984. Enable deprecated sysfs by default.
  985. See the CONFIG_SYSFS_DEPRECATED option for more details about this
  986. option.
  987. Only if you are using a new kernel on an old distribution, you might
  988. need to say Y here. Even then, odds are you would not need it
  989. enabled, you can always pass the boot option if absolutely necessary.
  990. config RELAY
  991. bool "Kernel->user space relay support (formerly relayfs)"
  992. help
  993. This option enables support for relay interface support in
  994. certain file systems (such as debugfs).
  995. It is designed to provide an efficient mechanism for tools and
  996. facilities to relay large amounts of data from kernel space to
  997. user space.
  998. If unsure, say N.
  999. config BLK_DEV_INITRD
  1000. bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
  1001. depends on BROKEN || !FRV
  1002. help
  1003. The initial RAM filesystem is a ramfs which is loaded by the
  1004. boot loader (loadlin or lilo) and that is mounted as root
  1005. before the normal boot procedure. It is typically used to
  1006. load modules needed to mount the "real" root file system,
  1007. etc. See <file:Documentation/initrd.txt> for details.
  1008. If RAM disk support (BLK_DEV_RAM) is also included, this
  1009. also enables initial RAM disk (initrd) support and adds
  1010. 15 Kbytes (more on some other architectures) to the kernel size.
  1011. If unsure say Y.
  1012. if BLK_DEV_INITRD
  1013. source "usr/Kconfig"
  1014. endif
  1015. config CC_OPTIMIZE_FOR_SIZE
  1016. bool "Optimize for size"
  1017. help
  1018. Enabling this option will pass "-Os" instead of "-O2" to gcc
  1019. resulting in a smaller kernel.
  1020. If unsure, say N.
  1021. config SYSCTL
  1022. bool
  1023. config ANON_INODES
  1024. bool
  1025. config HAVE_UID16
  1026. bool
  1027. config SYSCTL_EXCEPTION_TRACE
  1028. bool
  1029. help
  1030. Enable support for /proc/sys/debug/exception-trace.
  1031. config SYSCTL_ARCH_UNALIGN_NO_WARN
  1032. bool
  1033. help
  1034. Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
  1035. Allows arch to define/use @no_unaligned_warning to possibly warn
  1036. about unaligned access emulation going on under the hood.
  1037. config SYSCTL_ARCH_UNALIGN_ALLOW
  1038. bool
  1039. help
  1040. Enable support for /proc/sys/kernel/unaligned-trap
  1041. Allows arches to define/use @unaligned_enabled to runtime toggle
  1042. the unaligned access emulation.
  1043. see arch/parisc/kernel/unaligned.c for reference
  1044. config HOTPLUG
  1045. def_bool y
  1046. config HAVE_PCSPKR_PLATFORM
  1047. bool
  1048. menuconfig EXPERT
  1049. bool "Configure standard kernel features (expert users)"
  1050. # Unhide debug options, to make the on-by-default options visible
  1051. select DEBUG_KERNEL
  1052. help
  1053. This option allows certain base kernel options and settings
  1054. to be disabled or tweaked. This is for specialized
  1055. environments which can tolerate a "non-standard" kernel.
  1056. Only use this if you really know what you are doing.
  1057. config UID16
  1058. bool "Enable 16-bit UID system calls" if EXPERT
  1059. depends on HAVE_UID16
  1060. default y
  1061. help
  1062. This enables the legacy 16-bit UID syscall wrappers.
  1063. config SYSCTL_SYSCALL
  1064. bool "Sysctl syscall support" if EXPERT
  1065. depends on PROC_SYSCTL
  1066. default n
  1067. select SYSCTL
  1068. ---help---
  1069. sys_sysctl uses binary paths that have been found challenging
  1070. to properly maintain and use. The interface in /proc/sys
  1071. using paths with ascii names is now the primary path to this
  1072. information.
  1073. Almost nothing using the binary sysctl interface so if you are
  1074. trying to save some space it is probably safe to disable this,
  1075. making your kernel marginally smaller.
  1076. If unsure say N here.
  1077. config KALLSYMS
  1078. bool "Load all symbols for debugging/ksymoops" if EXPERT
  1079. default y
  1080. help
  1081. Say Y here to let the kernel print out symbolic crash information and
  1082. symbolic stack backtraces. This increases the size of the kernel
  1083. somewhat, as all symbols have to be loaded into the kernel image.
  1084. config KALLSYMS_ALL
  1085. bool "Include all symbols in kallsyms"
  1086. depends on DEBUG_KERNEL && KALLSYMS
  1087. help
  1088. Normally kallsyms only contains the symbols of functions for nicer
  1089. OOPS messages and backtraces (i.e., symbols from the text and inittext
  1090. sections). This is sufficient for most cases. And only in very rare
  1091. cases (e.g., when a debugger is used) all symbols are required (e.g.,
  1092. names of variables from the data sections, etc).
  1093. This option makes sure that all symbols are loaded into the kernel
  1094. image (i.e., symbols from all sections) in cost of increased kernel
  1095. size (depending on the kernel configuration, it may be 300KiB or
  1096. something like this).
  1097. Say N unless you really need all symbols.
  1098. config PRINTK
  1099. default y
  1100. bool "Enable support for printk" if EXPERT
  1101. select IRQ_WORK
  1102. help
  1103. This option enables normal printk support. Removing it
  1104. eliminates most of the message strings from the kernel image
  1105. and makes the kernel more or less silent. As this makes it
  1106. very difficult to diagnose system problems, saying N here is
  1107. strongly discouraged.
  1108. config BUG
  1109. bool "BUG() support" if EXPERT
  1110. default y
  1111. help
  1112. Disabling this option eliminates support for BUG and WARN, reducing
  1113. the size of your kernel image and potentially quietly ignoring
  1114. numerous fatal conditions. You should only consider disabling this
  1115. option for embedded systems with no facilities for reporting errors.
  1116. Just say Y.
  1117. config ELF_CORE
  1118. depends on COREDUMP
  1119. default y
  1120. bool "Enable ELF core dumps" if EXPERT
  1121. help
  1122. Enable support for generating core dumps. Disabling saves about 4k.
  1123. config PCSPKR_PLATFORM
  1124. bool "Enable PC-Speaker support" if EXPERT
  1125. depends on HAVE_PCSPKR_PLATFORM
  1126. select I8253_LOCK
  1127. default y
  1128. help
  1129. This option allows to disable the internal PC-Speaker
  1130. support, saving some memory.
  1131. config BASE_FULL
  1132. default y
  1133. bool "Enable full-sized data structures for core" if EXPERT
  1134. help
  1135. Disabling this option reduces the size of miscellaneous core
  1136. kernel data structures. This saves memory on small machines,
  1137. but may reduce performance.
  1138. config FUTEX
  1139. bool "Enable futex support" if EXPERT
  1140. default y
  1141. select RT_MUTEXES
  1142. help
  1143. Disabling this option will cause the kernel to be built without
  1144. support for "fast userspace mutexes". The resulting kernel may not
  1145. run glibc-based applications correctly.
  1146. config EPOLL
  1147. bool "Enable eventpoll support" if EXPERT
  1148. default y
  1149. select ANON_INODES
  1150. help
  1151. Disabling this option will cause the kernel to be built without
  1152. support for epoll family of system calls.
  1153. config SIGNALFD
  1154. bool "Enable signalfd() system call" if EXPERT
  1155. select ANON_INODES
  1156. default y
  1157. help
  1158. Enable the signalfd() system call that allows to receive signals
  1159. on a file descriptor.
  1160. If unsure, say Y.
  1161. config TIMERFD
  1162. bool "Enable timerfd() system call" if EXPERT
  1163. select ANON_INODES
  1164. default y
  1165. help
  1166. Enable the timerfd() system call that allows to receive timer
  1167. events on a file descriptor.
  1168. If unsure, say Y.
  1169. config EVENTFD
  1170. bool "Enable eventfd() system call" if EXPERT
  1171. select ANON_INODES
  1172. default y
  1173. help
  1174. Enable the eventfd() system call that allows to receive both
  1175. kernel notification (ie. KAIO) or userspace notifications.
  1176. If unsure, say Y.
  1177. config SHMEM
  1178. bool "Use full shmem filesystem" if EXPERT
  1179. default y
  1180. depends on MMU
  1181. help
  1182. The shmem is an internal filesystem used to manage shared memory.
  1183. It is backed by swap and manages resource limits. It is also exported
  1184. to userspace as tmpfs if TMPFS is enabled. Disabling this
  1185. option replaces shmem and tmpfs with the much simpler ramfs code,
  1186. which may be appropriate on small systems without swap.
  1187. config AIO
  1188. bool "Enable AIO support" if EXPERT
  1189. default y
  1190. help
  1191. This option enables POSIX asynchronous I/O which may by used
  1192. by some high performance threaded applications. Disabling
  1193. this option saves about 7k.
  1194. config PCI_QUIRKS
  1195. default y
  1196. bool "Enable PCI quirk workarounds" if EXPERT
  1197. depends on PCI
  1198. help
  1199. This enables workarounds for various PCI chipset
  1200. bugs/quirks. Disable this only if your target machine is
  1201. unaffected by PCI quirks.
  1202. config EMBEDDED
  1203. bool "Embedded system"
  1204. select EXPERT
  1205. help
  1206. This option should be enabled if compiling the kernel for
  1207. an embedded system so certain expert options are available
  1208. for configuration.
  1209. config HAVE_PERF_EVENTS
  1210. bool
  1211. help
  1212. See tools/perf/design.txt for details.
  1213. config PERF_USE_VMALLOC
  1214. bool
  1215. help
  1216. See tools/perf/design.txt for details
  1217. menu "Kernel Performance Events And Counters"
  1218. config PERF_EVENTS
  1219. bool "Kernel performance events and counters"
  1220. default y if PROFILING
  1221. depends on HAVE_PERF_EVENTS
  1222. select ANON_INODES
  1223. select IRQ_WORK
  1224. help
  1225. Enable kernel support for various performance events provided
  1226. by software and hardware.
  1227. Software events are supported either built-in or via the
  1228. use of generic tracepoints.
  1229. Most modern CPUs support performance events via performance
  1230. counter registers. These registers count the number of certain
  1231. types of hw events: such as instructions executed, cachemisses
  1232. suffered, or branches mis-predicted - without slowing down the
  1233. kernel or applications. These registers can also trigger interrupts
  1234. when a threshold number of events have passed - and can thus be
  1235. used to profile the code that runs on that CPU.
  1236. The Linux Performance Event subsystem provides an abstraction of
  1237. these software and hardware event capabilities, available via a
  1238. system call and used by the "perf" utility in tools/perf/. It
  1239. provides per task and per CPU counters, and it provides event
  1240. capabilities on top of those.
  1241. Say Y if unsure.
  1242. config DEBUG_PERF_USE_VMALLOC
  1243. default n
  1244. bool "Debug: use vmalloc to back perf mmap() buffers"
  1245. depends on PERF_EVENTS && DEBUG_KERNEL
  1246. select PERF_USE_VMALLOC
  1247. help
  1248. Use vmalloc memory to back perf mmap() buffers.
  1249. Mostly useful for debugging the vmalloc code on platforms
  1250. that don't require it.
  1251. Say N if unsure.
  1252. endmenu
  1253. config VM_EVENT_COUNTERS
  1254. default y
  1255. bool "Enable VM event counters for /proc/vmstat" if EXPERT
  1256. help
  1257. VM event counters are needed for event counts to be shown.
  1258. This option allows the disabling of the VM event counters
  1259. on EXPERT systems. /proc/vmstat will only show page counts
  1260. if VM event counters are disabled.
  1261. config SLUB_DEBUG
  1262. default y
  1263. bool "Enable SLUB debugging support" if EXPERT
  1264. depends on SLUB && SYSFS
  1265. help
  1266. SLUB has extensive debug support features. Disabling these can
  1267. result in significant savings in code size. This also disables
  1268. SLUB sysfs support. /sys/slab will not exist and there will be
  1269. no support for cache validation etc.
  1270. config COMPAT_BRK
  1271. bool "Disable heap randomization"
  1272. default y
  1273. help
  1274. Randomizing heap placement makes heap exploits harder, but it
  1275. also breaks ancient binaries (including anything libc5 based).
  1276. This option changes the bootup default to heap randomization
  1277. disabled, and can be overridden at runtime by setting
  1278. /proc/sys/kernel/randomize_va_space to 2.
  1279. On non-ancient distros (post-2000 ones) N is usually a safe choice.
  1280. choice
  1281. prompt "Choose SLAB allocator"
  1282. default SLUB
  1283. help
  1284. This option allows to select a slab allocator.
  1285. config SLAB
  1286. bool "SLAB"
  1287. help
  1288. The regular slab allocator that is established and known to work
  1289. well in all environments. It organizes cache hot objects in
  1290. per cpu and per node queues.
  1291. config SLUB
  1292. bool "SLUB (Unqueued Allocator)"
  1293. help
  1294. SLUB is a slab allocator that minimizes cache line usage
  1295. instead of managing queues of cached objects (SLAB approach).
  1296. Per cpu caching is realized using slabs of objects instead
  1297. of queues of objects. SLUB can use memory efficiently
  1298. and has enhanced diagnostics. SLUB is the default choice for
  1299. a slab allocator.
  1300. config SLOB
  1301. depends on EXPERT
  1302. bool "SLOB (Simple Allocator)"
  1303. help
  1304. SLOB replaces the stock allocator with a drastically simpler
  1305. allocator. SLOB is generally more space efficient but
  1306. does not perform as well on large systems.
  1307. endchoice
  1308. config MMAP_ALLOW_UNINITIALIZED
  1309. bool "Allow mmapped anonymous memory to be uninitialized"
  1310. depends on EXPERT && !MMU
  1311. default n
  1312. help
  1313. Normally, and according to the Linux spec, anonymous memory obtained
  1314. from mmap() has it's contents cleared before it is passed to
  1315. userspace. Enabling this config option allows you to request that
  1316. mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
  1317. providing a huge performance boost. If this option is not enabled,
  1318. then the flag will be ignored.
  1319. This is taken advantage of by uClibc's malloc(), and also by
  1320. ELF-FDPIC binfmt's brk and stack allocator.
  1321. Because of the obvious security issues, this option should only be
  1322. enabled on embedded devices where you control what is run in
  1323. userspace. Since that isn't generally a problem on no-MMU systems,
  1324. it is normally safe to say Y here.
  1325. See Documentation/nommu-mmap.txt for more information.
  1326. config PROFILING
  1327. bool "Profiling support"
  1328. help
  1329. Say Y here to enable the extended profiling support mechanisms used
  1330. by profilers such as OProfile.
  1331. #
  1332. # Place an empty function call at each tracepoint site. Can be
  1333. # dynamically changed for a probe function.
  1334. #
  1335. config TRACEPOINTS
  1336. bool
  1337. source "arch/Kconfig"
  1338. endmenu # General setup
  1339. config HAVE_GENERIC_DMA_COHERENT
  1340. bool
  1341. default n
  1342. config SLABINFO
  1343. bool
  1344. depends on PROC_FS
  1345. depends on SLAB || SLUB_DEBUG
  1346. default y
  1347. config RT_MUTEXES
  1348. boolean
  1349. config BASE_SMALL
  1350. int
  1351. default 0 if BASE_FULL
  1352. default 1 if !BASE_FULL
  1353. menuconfig MODULES
  1354. bool "Enable loadable module support"
  1355. help
  1356. Kernel modules are small pieces of compiled code which can
  1357. be inserted in the running kernel, rather than being
  1358. permanently built into the kernel. You use the "modprobe"
  1359. tool to add (and sometimes remove) them. If you say Y here,
  1360. many parts of the kernel can be built as modules (by
  1361. answering M instead of Y where indicated): this is most
  1362. useful for infrequently used options which are not required
  1363. for booting. For more information, see the man pages for
  1364. modprobe, lsmod, modinfo, insmod and rmmod.
  1365. If you say Y here, you will need to run "make
  1366. modules_install" to put the modules under /lib/modules/
  1367. where modprobe can find them (you may need to be root to do
  1368. this).
  1369. If unsure, say Y.
  1370. if MODULES
  1371. config MODULE_FORCE_LOAD
  1372. bool "Forced module loading"
  1373. default n
  1374. help
  1375. Allow loading of modules without version information (ie. modprobe
  1376. --force). Forced module loading sets the 'F' (forced) taint flag and
  1377. is usually a really bad idea.
  1378. config MODULE_UNLOAD
  1379. bool "Module unloading"
  1380. help
  1381. Without this option you will not be able to unload any
  1382. modules (note that some modules may not be unloadable
  1383. anyway), which makes your kernel smaller, faster
  1384. and simpler. If unsure, say Y.
  1385. config MODULE_FORCE_UNLOAD
  1386. bool "Forced module unloading"
  1387. depends on MODULE_UNLOAD
  1388. help
  1389. This option allows you to force a module to unload, even if the
  1390. kernel believes it is unsafe: the kernel will remove the module
  1391. without waiting for anyone to stop using it (using the -f option to
  1392. rmmod). This is mainly for kernel developers and desperate users.
  1393. If unsure, say N.
  1394. config MODVERSIONS
  1395. bool "Module versioning support"
  1396. help
  1397. Usually, you have to use modules compiled with your kernel.
  1398. Saying Y here makes it sometimes possible to use modules
  1399. compiled for different kernels, by adding enough information
  1400. to the modules to (hopefully) spot any changes which would
  1401. make them incompatible with the kernel you are running. If
  1402. unsure, say N.
  1403. config MODULE_SRCVERSION_ALL
  1404. bool "Source checksum for all modules"
  1405. help
  1406. Modules which contain a MODULE_VERSION get an extra "srcversion"
  1407. field inserted into their modinfo section, which contains a
  1408. sum of the source files which made it. This helps maintainers
  1409. see exactly which source was used to build a module (since
  1410. others sometimes change the module source without updating
  1411. the version). With this option, such a "srcversion" field
  1412. will be created for all modules. If unsure, say N.
  1413. config MODULE_SIG
  1414. bool "Module signature verification"
  1415. depends on MODULES
  1416. select KEYS
  1417. select CRYPTO
  1418. select ASYMMETRIC_KEY_TYPE
  1419. select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
  1420. select PUBLIC_KEY_ALGO_RSA
  1421. select ASN1
  1422. select OID_REGISTRY
  1423. select X509_CERTIFICATE_PARSER
  1424. help
  1425. Check modules for valid signatures upon load: the signature
  1426. is simply appended to the module. For more information see
  1427. Documentation/module-signing.txt.
  1428. !!!WARNING!!! If you enable this option, you MUST make sure that the
  1429. module DOES NOT get stripped after being signed. This includes the
  1430. debuginfo strip done by some packagers (such as rpmbuild) and
  1431. inclusion into an initramfs that wants the module size reduced.
  1432. config MODULE_SIG_FORCE
  1433. bool "Require modules to be validly signed"
  1434. depends on MODULE_SIG
  1435. help
  1436. Reject unsigned modules or signed modules for which we don't have a
  1437. key. Without this, such modules will simply taint the kernel.
  1438. config MODULE_SIG_ALL
  1439. bool "Automatically sign all modules"
  1440. default y
  1441. depends on MODULE_SIG
  1442. help
  1443. Sign all modules during make modules_install. Without this option,
  1444. modules must be signed manually, using the scripts/sign-file tool.
  1445. comment "Do not forget to sign required modules with scripts/sign-file"
  1446. depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
  1447. choice
  1448. prompt "Which hash algorithm should modules be signed with?"
  1449. depends on MODULE_SIG
  1450. help
  1451. This determines which sort of hashing algorithm will be used during
  1452. signature generation. This algorithm _must_ be built into the kernel
  1453. directly so that signature verification can take place. It is not
  1454. possible to load a signed module containing the algorithm to check
  1455. the signature on that module.
  1456. config MODULE_SIG_SHA1
  1457. bool "Sign modules with SHA-1"
  1458. select CRYPTO_SHA1
  1459. config MODULE_SIG_SHA224
  1460. bool "Sign modules with SHA-224"
  1461. select CRYPTO_SHA256
  1462. config MODULE_SIG_SHA256
  1463. bool "Sign modules with SHA-256"
  1464. select CRYPTO_SHA256
  1465. config MODULE_SIG_SHA384
  1466. bool "Sign modules with SHA-384"
  1467. select CRYPTO_SHA512
  1468. config MODULE_SIG_SHA512
  1469. bool "Sign modules with SHA-512"
  1470. select CRYPTO_SHA512
  1471. endchoice
  1472. config MODULE_SIG_HASH
  1473. string
  1474. depends on MODULE_SIG
  1475. default "sha1" if MODULE_SIG_SHA1
  1476. default "sha224" if MODULE_SIG_SHA224
  1477. default "sha256" if MODULE_SIG_SHA256
  1478. default "sha384" if MODULE_SIG_SHA384
  1479. default "sha512" if MODULE_SIG_SHA512
  1480. endif # MODULES
  1481. config INIT_ALL_POSSIBLE
  1482. bool
  1483. help
  1484. Back when each arch used to define their own cpu_online_mask and
  1485. cpu_possible_mask, some of them chose to initialize cpu_possible_mask
  1486. with all 1s, and others with all 0s. When they were centralised,
  1487. it was better to provide this option than to break all the archs
  1488. and have several arch maintainers pursuing me down dark alleys.
  1489. config STOP_MACHINE
  1490. bool
  1491. default y
  1492. depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
  1493. help
  1494. Need stop_machine() primitive.
  1495. source "block/Kconfig"
  1496. config PREEMPT_NOTIFIERS
  1497. bool
  1498. config PADATA
  1499. depends on SMP
  1500. bool
  1501. # Can be selected by architectures with broken toolchains
  1502. # that get confused by correct const<->read_only section
  1503. # mappings
  1504. config BROKEN_RODATA
  1505. bool
  1506. config ASN1
  1507. tristate
  1508. help
  1509. Build a simple ASN.1 grammar compiler that produces a bytecode output
  1510. that can be interpreted by the ASN.1 stream decoder and used to
  1511. inform it as to what tags are to be expected in a stream and what
  1512. functions to call on what tags.
  1513. source "kernel/Kconfig.locks"