Kconfig 59 KB

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