Merge tag 'staging-3.9-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh...
[deliverable/linux.git] / init / Kconfig
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1config ARCH
2 string
3 option env="ARCH"
4
5config KERNELVERSION
6 string
7 option env="KERNELVERSION"
8
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9config DEFCONFIG_LIST
10 string
b2670eac 11 depends on !UML
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12 option defconfig_list
13 default "/lib/modules/$UNAME_RELEASE/.config"
14 default "/etc/kernel-config"
15 default "/boot/config-$UNAME_RELEASE"
73531905 16 default "$ARCH_DEFCONFIG"
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17 default "arch/$ARCH/defconfig"
18
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19config CONSTRUCTORS
20 bool
21 depends on !UML
b99b87f7 22
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23config IRQ_WORK
24 bool
e360adbe 25
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26config BUILDTIME_EXTABLE_SORT
27 bool
28
ff0cfc66 29menu "General setup"
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30
31config EXPERIMENTAL
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32 bool
33 default y
1da177e4 34
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35config BROKEN
36 bool
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37
38config BROKEN_ON_SMP
39 bool
40 depends on BROKEN || !SMP
41 default y
42
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43config INIT_ENV_ARG_LIMIT
44 int
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45 default 32 if !UML
46 default 128 if UML
1da177e4 47 help
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48 Maximum of each of the number of arguments and environment
49 variables passed to init from the kernel command line.
1da177e4 50
1da177e4 51
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52config CROSS_COMPILE
53 string "Cross-compiler tool prefix"
54 help
55 Same as running 'make CROSS_COMPILE=prefix-' but stored for
56 default make runs in this kernel build directory. You don't
57 need to set this unless you want the configured kernel build
58 directory to select the cross-compiler automatically.
59
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60config LOCALVERSION
61 string "Local version - append to kernel release"
62 help
63 Append an extra string to the end of your kernel version.
64 This will show up when you type uname, for example.
65 The string you set here will be appended after the contents of
66 any files with a filename matching localversion* in your
67 object and source tree, in that order. Your total string can
68 be a maximum of 64 characters.
69
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70config LOCALVERSION_AUTO
71 bool "Automatically append version information to the version string"
72 default y
73 help
74 This will try to automatically determine if the current tree is a
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75 release tree by looking for git tags that belong to the current
76 top of tree revision.
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77
78 A string of the format -gxxxxxxxx will be added to the localversion
6e5a5420 79 if a git-based tree is found. The string generated by this will be
aaebf433 80 appended after any matching localversion* files, and after the value
6e5a5420 81 set in CONFIG_LOCALVERSION.
aaebf433 82
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83 (The actual string used here is the first eight characters produced
84 by running the command:
85
86 $ git rev-parse --verify HEAD
87
88 which is done within the script "scripts/setlocalversion".)
aaebf433 89
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90config HAVE_KERNEL_GZIP
91 bool
92
93config HAVE_KERNEL_BZIP2
94 bool
95
96config HAVE_KERNEL_LZMA
97 bool
98
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99config HAVE_KERNEL_XZ
100 bool
101
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102config HAVE_KERNEL_LZO
103 bool
104
30d65dbf 105choice
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106 prompt "Kernel compression mode"
107 default KERNEL_GZIP
3ebe1243 108 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
2e9f3bdd 109 help
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110 The linux kernel is a kind of self-extracting executable.
111 Several compression algorithms are available, which differ
112 in efficiency, compression and decompression speed.
113 Compression speed is only relevant when building a kernel.
114 Decompression speed is relevant at each boot.
115
116 If you have any problems with bzip2 or lzma compressed
117 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
118 version of this functionality (bzip2 only), for 2.4, was
119 supplied by Christian Ludwig)
120
121 High compression options are mostly useful for users, who
122 are low on disk space (embedded systems), but for whom ram
123 size matters less.
124
125 If in doubt, select 'gzip'
126
127config KERNEL_GZIP
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128 bool "Gzip"
129 depends on HAVE_KERNEL_GZIP
130 help
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131 The old and tried gzip compression. It provides a good balance
132 between compression ratio and decompression speed.
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133
134config KERNEL_BZIP2
135 bool "Bzip2"
2e9f3bdd 136 depends on HAVE_KERNEL_BZIP2
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137 help
138 Its compression ratio and speed is intermediate.
0a4dd35c 139 Decompression speed is slowest among the choices. The kernel
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140 size is about 10% smaller with bzip2, in comparison to gzip.
141 Bzip2 uses a large amount of memory. For modern kernels you
142 will need at least 8MB RAM or more for booting.
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143
144config KERNEL_LZMA
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145 bool "LZMA"
146 depends on HAVE_KERNEL_LZMA
147 help
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148 This compression algorithm's ratio is best. Decompression speed
149 is between gzip and bzip2. Compression is slowest.
150 The kernel size is about 33% smaller with LZMA in comparison to gzip.
30d65dbf 151
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152config KERNEL_XZ
153 bool "XZ"
154 depends on HAVE_KERNEL_XZ
155 help
156 XZ uses the LZMA2 algorithm and instruction set specific
157 BCJ filters which can improve compression ratio of executable
158 code. The size of the kernel is about 30% smaller with XZ in
159 comparison to gzip. On architectures for which there is a BCJ
160 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
161 will create a few percent smaller kernel than plain LZMA.
162
163 The speed is about the same as with LZMA: The decompression
164 speed of XZ is better than that of bzip2 but worse than gzip
165 and LZO. Compression is slow.
166
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167config KERNEL_LZO
168 bool "LZO"
169 depends on HAVE_KERNEL_LZO
170 help
0a4dd35c 171 Its compression ratio is the poorest among the choices. The kernel
681b3049 172 size is about 10% bigger than gzip; however its speed
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173 (both compression and decompression) is the fastest.
174
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175endchoice
176
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177config DEFAULT_HOSTNAME
178 string "Default hostname"
179 default "(none)"
180 help
181 This option determines the default system hostname before userspace
182 calls sethostname(2). The kernel traditionally uses "(none)" here,
183 but you may wish to use a different default here to make a minimal
184 system more usable with less configuration.
185
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186config SWAP
187 bool "Support for paging of anonymous memory (swap)"
9361401e 188 depends on MMU && BLOCK
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189 default y
190 help
191 This option allows you to choose whether you want to have support
92c3504e 192 for so called swap devices or swap files in your kernel that are
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193 used to provide more virtual memory than the actual RAM present
194 in your computer. If unsure say Y.
195
196config SYSVIPC
197 bool "System V IPC"
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198 ---help---
199 Inter Process Communication is a suite of library functions and
200 system calls which let processes (running programs) synchronize and
201 exchange information. It is generally considered to be a good thing,
202 and some programs won't run unless you say Y here. In particular, if
203 you want to run the DOS emulator dosemu under Linux (read the
204 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
205 you'll need to say Y here.
206
207 You can find documentation about IPC with "info ipc" and also in
208 section 6.4 of the Linux Programmer's Guide, available from
209 <http://www.tldp.org/guides.html>.
210
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211config SYSVIPC_SYSCTL
212 bool
213 depends on SYSVIPC
214 depends on SYSCTL
215 default y
216
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217config POSIX_MQUEUE
218 bool "POSIX Message Queues"
19c92399 219 depends on NET
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220 ---help---
221 POSIX variant of message queues is a part of IPC. In POSIX message
222 queues every message has a priority which decides about succession
223 of receiving it by a process. If you want to compile and run
224 programs written e.g. for Solaris with use of its POSIX message
b0e37650 225 queues (functions mq_*) say Y here.
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226
227 POSIX message queues are visible as a filesystem called 'mqueue'
228 and can be mounted somewhere if you want to do filesystem
229 operations on message queues.
230
231 If unsure, say Y.
232
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233config POSIX_MQUEUE_SYSCTL
234 bool
235 depends on POSIX_MQUEUE
236 depends on SYSCTL
237 default y
238
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239config FHANDLE
240 bool "open by fhandle syscalls"
241 select EXPORTFS
242 help
243 If you say Y here, a user level program will be able to map
244 file names to handle and then later use the handle for
245 different file system operations. This is useful in implementing
246 userspace file servers, which now track files using handles instead
247 of names. The handle would remain the same even if file names
248 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
249 syscalls.
250
251config AUDIT
252 bool "Auditing support"
253 depends on NET
254 help
255 Enable auditing infrastructure that can be used with another
256 kernel subsystem, such as SELinux (which requires this for
257 logging of avc messages output). Does not do system-call
258 auditing without CONFIG_AUDITSYSCALL.
259
260config AUDITSYSCALL
261 bool "Enable system-call auditing support"
262 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
263 default y if SECURITY_SELINUX
264 help
265 Enable low-overhead system-call auditing infrastructure that
266 can be used independently or with another kernel subsystem,
267 such as SELinux.
268
269config AUDIT_WATCH
270 def_bool y
271 depends on AUDITSYSCALL
272 select FSNOTIFY
273
274config AUDIT_TREE
275 def_bool y
276 depends on AUDITSYSCALL
277 select FSNOTIFY
278
279config AUDIT_LOGINUID_IMMUTABLE
280 bool "Make audit loginuid immutable"
281 depends on AUDIT
282 help
283 The config option toggles if a task setting its loginuid requires
284 CAP_SYS_AUDITCONTROL or if that task should require no special permissions
285 but should instead only allow setting its loginuid if it was never
286 previously set. On systems which use systemd or a similar central
287 process to restart login services this should be set to true. On older
288 systems in which an admin would typically have to directly stop and
289 start processes this should be set to false. Setting this to true allows
290 one to drop potentially dangerous capabilites from the login tasks,
291 but may not be backwards compatible with older init systems.
292
293source "kernel/irq/Kconfig"
294source "kernel/time/Kconfig"
295
296menu "CPU/Task time and stats accounting"
297
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298config VIRT_CPU_ACCOUNTING
299 bool
300
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301choice
302 prompt "Cputime accounting"
303 default TICK_CPU_ACCOUNTING if !PPC64
02fc8d37 304 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
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305
306# Kind of a stub config for the pure tick based cputime accounting
307config TICK_CPU_ACCOUNTING
308 bool "Simple tick based cputime accounting"
309 depends on !S390
310 help
311 This is the basic tick based cputime accounting that maintains
312 statistics about user, system and idle time spent on per jiffies
313 granularity.
314
315 If unsure, say Y.
316
abf917cd 317config VIRT_CPU_ACCOUNTING_NATIVE
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318 bool "Deterministic task and CPU time accounting"
319 depends on HAVE_VIRT_CPU_ACCOUNTING
abf917cd 320 select VIRT_CPU_ACCOUNTING
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321 help
322 Select this option to enable more accurate task and CPU time
323 accounting. This is done by reading a CPU counter on each
324 kernel entry and exit and on transitions within the kernel
325 between system, softirq and hardirq state, so there is a
326 small performance impact. In the case of s390 or IBM POWER > 5,
327 this also enables accounting of stolen time on logically-partitioned
328 systems.
329
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330config VIRT_CPU_ACCOUNTING_GEN
331 bool "Full dynticks CPU time accounting"
332 depends on HAVE_CONTEXT_TRACKING && 64BIT
333 select VIRT_CPU_ACCOUNTING
334 select CONTEXT_TRACKING
335 help
336 Select this option to enable task and CPU time accounting on full
337 dynticks systems. This accounting is implemented by watching every
338 kernel-user boundaries using the context tracking subsystem.
339 The accounting is thus performed at the expense of some significant
340 overhead.
341
342 For now this is only useful if you are working on the full
343 dynticks subsystem development.
344
345 If unsure, say N.
346
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347config IRQ_TIME_ACCOUNTING
348 bool "Fine granularity task level IRQ time accounting"
349 depends on HAVE_IRQ_TIME_ACCOUNTING
350 help
351 Select this option to enable fine granularity task irq time
352 accounting. This is done by reading a timestamp on each
353 transitions between softirq and hardirq state, so there can be a
354 small performance impact.
355
356 If in doubt, say N here.
357
358endchoice
359
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360config BSD_PROCESS_ACCT
361 bool "BSD Process Accounting"
362 help
363 If you say Y here, a user level program will be able to instruct the
364 kernel (via a special system call) to write process accounting
365 information to a file: whenever a process exits, information about
366 that process will be appended to the file by the kernel. The
367 information includes things such as creation time, owning user,
368 command name, memory usage, controlling terminal etc. (the complete
369 list is in the struct acct in <file:include/linux/acct.h>). It is
370 up to the user level program to do useful things with this
371 information. This is generally a good idea, so say Y.
372
373config BSD_PROCESS_ACCT_V3
374 bool "BSD Process Accounting version 3 file format"
375 depends on BSD_PROCESS_ACCT
376 default n
377 help
378 If you say Y here, the process accounting information is written
379 in a new file format that also logs the process IDs of each
380 process and it's parent. Note that this file format is incompatible
381 with previous v0/v1/v2 file formats, so you will need updated tools
382 for processing it. A preliminary version of these tools is available
37a4c940 383 at <http://www.gnu.org/software/acct/>.
1da177e4 384
c757249a 385config TASKSTATS
19c92399 386 bool "Export task/process statistics through netlink"
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387 depends on NET
388 default n
389 help
390 Export selected statistics for tasks/processes through the
391 generic netlink interface. Unlike BSD process accounting, the
392 statistics are available during the lifetime of tasks/processes as
393 responses to commands. Like BSD accounting, they are sent to user
394 space on task exit.
395
396 Say N if unsure.
397
ca74e92b 398config TASK_DELAY_ACCT
19c92399 399 bool "Enable per-task delay accounting"
6f44993f 400 depends on TASKSTATS
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401 help
402 Collect information on time spent by a task waiting for system
403 resources like cpu, synchronous block I/O completion and swapping
404 in pages. Such statistics can help in setting a task's priorities
405 relative to other tasks for cpu, io, rss limits etc.
406
407 Say N if unsure.
408
18f705f4 409config TASK_XACCT
19c92399 410 bool "Enable extended accounting over taskstats"
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411 depends on TASKSTATS
412 help
413 Collect extended task accounting data and send the data
414 to userland for processing over the taskstats interface.
415
416 Say N if unsure.
417
418config TASK_IO_ACCOUNTING
19c92399 419 bool "Enable per-task storage I/O accounting"
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420 depends on TASK_XACCT
421 help
422 Collect information on the number of bytes of storage I/O which this
423 task has caused.
424
425 Say N if unsure.
426
391dc69c 427endmenu # "CPU/Task time and stats accounting"
d9817ebe 428
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429menu "RCU Subsystem"
430
431choice
432 prompt "RCU Implementation"
31c9a24e 433 default TREE_RCU
c903ff83 434
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435config TREE_RCU
436 bool "Tree-based hierarchical RCU"
687d7a96 437 depends on !PREEMPT && SMP
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438 help
439 This option selects the RCU implementation that is
440 designed for very large SMP system with hundreds or
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441 thousands of CPUs. It also scales down nicely to
442 smaller systems.
c903ff83 443
f41d911f 444config TREE_PREEMPT_RCU
a57eb940 445 bool "Preemptible tree-based hierarchical RCU"
9fc52d83 446 depends on PREEMPT
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447 help
448 This option selects the RCU implementation that is
449 designed for very large SMP systems with hundreds or
450 thousands of CPUs, but for which real-time response
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451 is also required. It also scales down nicely to
452 smaller systems.
f41d911f 453
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454 Select this option if you are unsure.
455
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456config TINY_RCU
457 bool "UP-only small-memory-footprint RCU"
8008e129 458 depends on !PREEMPT && !SMP
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459 help
460 This option selects the RCU implementation that is
461 designed for UP systems from which real-time response
462 is not required. This option greatly reduces the
463 memory footprint of RCU.
464
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465config TINY_PREEMPT_RCU
466 bool "Preemptible UP-only small-memory-footprint RCU"
8008e129 467 depends on PREEMPT && !SMP
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468 help
469 This option selects the RCU implementation that is designed
470 for real-time UP systems. This option greatly reduces the
471 memory footprint of RCU.
472
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473endchoice
474
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475config PREEMPT_RCU
476 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
477 help
478 This option enables preemptible-RCU code that is common between
479 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
480
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481config RCU_STALL_COMMON
482 def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
483 help
484 This option enables RCU CPU stall code that is common between
485 the TINY and TREE variants of RCU. The purpose is to allow
486 the tiny variants to disable RCU CPU stall warnings, while
487 making these warnings mandatory for the tree variants.
488
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489config CONTEXT_TRACKING
490 bool
491
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492config RCU_USER_QS
493 bool "Consider userspace as in RCU extended quiescent state"
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494 depends on HAVE_CONTEXT_TRACKING && SMP
495 select CONTEXT_TRACKING
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496 help
497 This option sets hooks on kernel / userspace boundaries and
498 puts RCU in extended quiescent state when the CPU runs in
499 userspace. It means that when a CPU runs in userspace, it is
500 excluded from the global RCU state machine and thus doesn't
af71befa 501 try to keep the timer tick on for RCU.
2b1d5024 502
d677124b 503 Unless you want to hack and help the development of the full
91d1aa43 504 dynticks mode, you shouldn't enable this option. It also
af71befa 505 adds unnecessary overhead.
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506
507 If unsure say N
508
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509config CONTEXT_TRACKING_FORCE
510 bool "Force context tracking"
511 depends on CONTEXT_TRACKING
1fd2b442 512 help
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513 Probe on user/kernel boundaries by default in order to
514 test the features that rely on it such as userspace RCU extended
515 quiescent states.
516 This test is there for debugging until we have a real user like the
517 full dynticks mode.
d677124b 518
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519config RCU_FANOUT
520 int "Tree-based hierarchical RCU fanout value"
521 range 2 64 if 64BIT
522 range 2 32 if !64BIT
f41d911f 523 depends on TREE_RCU || TREE_PREEMPT_RCU
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524 default 64 if 64BIT
525 default 32 if !64BIT
526 help
527 This option controls the fanout of hierarchical implementations
528 of RCU, allowing RCU to work efficiently on machines with
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529 large numbers of CPUs. This value must be at least the fourth
530 root of NR_CPUS, which allows NR_CPUS to be insanely large.
531 The default value of RCU_FANOUT should be used for production
532 systems, but if you are stress-testing the RCU implementation
533 itself, small RCU_FANOUT values allow you to test large-system
534 code paths on small(er) systems.
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535
536 Select a specific number if testing RCU itself.
537 Take the default if unsure.
538
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539config RCU_FANOUT_LEAF
540 int "Tree-based hierarchical RCU leaf-level fanout value"
541 range 2 RCU_FANOUT if 64BIT
542 range 2 RCU_FANOUT if !64BIT
543 depends on TREE_RCU || TREE_PREEMPT_RCU
544 default 16
545 help
546 This option controls the leaf-level fanout of hierarchical
547 implementations of RCU, and allows trading off cache misses
548 against lock contention. Systems that synchronize their
549 scheduling-clock interrupts for energy-efficiency reasons will
550 want the default because the smaller leaf-level fanout keeps
551 lock contention levels acceptably low. Very large systems
552 (hundreds or thousands of CPUs) will instead want to set this
553 value to the maximum value possible in order to reduce the
554 number of cache misses incurred during RCU's grace-period
555 initialization. These systems tend to run CPU-bound, and thus
556 are not helped by synchronized interrupts, and thus tend to
557 skew them, which reduces lock contention enough that large
558 leaf-level fanouts work well.
559
560 Select a specific number if testing RCU itself.
561
562 Select the maximum permissible value for large systems.
563
564 Take the default if unsure.
565
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566config RCU_FANOUT_EXACT
567 bool "Disable tree-based hierarchical RCU auto-balancing"
f41d911f 568 depends on TREE_RCU || TREE_PREEMPT_RCU
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569 default n
570 help
571 This option forces use of the exact RCU_FANOUT value specified,
572 regardless of imbalances in the hierarchy. This is useful for
573 testing RCU itself, and might one day be useful on systems with
574 strong NUMA behavior.
575
576 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
577
578 Say N if unsure.
579
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580config RCU_FAST_NO_HZ
581 bool "Accelerate last non-dyntick-idle CPU's grace periods"
b807fbff 582 depends on NO_HZ && SMP
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583 default n
584 help
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585 This option causes RCU to attempt to accelerate grace periods in
586 order to allow CPUs to enter dynticks-idle state more quickly.
587 On the other hand, this option increases the overhead of the
588 dynticks-idle checking, thus degrading scheduling latency.
589
590 Say Y if energy efficiency is critically important, and you don't
591 care about real-time response.
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592
593 Say N if you are unsure.
594
c903ff83 595config TREE_RCU_TRACE
f41d911f 596 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
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597 select DEBUG_FS
598 help
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599 This option provides tracing for the TREE_RCU and
600 TREE_PREEMPT_RCU implementations, permitting Makefile to
601 trivially select kernel/rcutree_trace.c.
c903ff83 602
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603config RCU_BOOST
604 bool "Enable RCU priority boosting"
27f4d280 605 depends on RT_MUTEXES && PREEMPT_RCU
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606 default n
607 help
608 This option boosts the priority of preempted RCU readers that
609 block the current preemptible RCU grace period for too long.
610 This option also prevents heavy loads from blocking RCU
611 callback invocation for all flavors of RCU.
612
613 Say Y here if you are working with real-time apps or heavy loads
614 Say N here if you are unsure.
615
616config RCU_BOOST_PRIO
617 int "Real-time priority to boost RCU readers to"
618 range 1 99
619 depends on RCU_BOOST
620 default 1
621 help
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622 This option specifies the real-time priority to which long-term
623 preempted RCU readers are to be boosted. If you are working
624 with a real-time application that has one or more CPU-bound
625 threads running at a real-time priority level, you should set
626 RCU_BOOST_PRIO to a priority higher then the highest-priority
627 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
628 of 1 is appropriate in the common case, which is real-time
629 applications that do not have any CPU-bound threads.
630
631 Some real-time applications might not have a single real-time
632 thread that saturates a given CPU, but instead might have
633 multiple real-time threads that, taken together, fully utilize
634 that CPU. In this case, you should set RCU_BOOST_PRIO to
635 a priority higher than the lowest-priority thread that is
636 conspiring to prevent the CPU from running any non-real-time
637 tasks. For example, if one thread at priority 10 and another
638 thread at priority 5 are between themselves fully consuming
639 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
640 set to priority 6 or higher.
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641
642 Specify the real-time priority, or take the default if unsure.
643
644config RCU_BOOST_DELAY
645 int "Milliseconds to delay boosting after RCU grace-period start"
646 range 0 3000
647 depends on RCU_BOOST
648 default 500
649 help
650 This option specifies the time to wait after the beginning of
651 a given grace period before priority-boosting preempted RCU
652 readers blocking that grace period. Note that any RCU reader
653 blocking an expedited RCU grace period is boosted immediately.
654
655 Accept the default if unsure.
656
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657config RCU_NOCB_CPU
658 bool "Offload RCU callback processing from boot-selected CPUs"
659 depends on TREE_RCU || TREE_PREEMPT_RCU
660 default n
661 help
662 Use this option to reduce OS jitter for aggressive HPC or
663 real-time workloads. It can also be used to offload RCU
664 callback invocation to energy-efficient CPUs in battery-powered
665 asymmetric multiprocessors.
666
667 This option offloads callback invocation from the set of
668 CPUs specified at boot time by the rcu_nocbs parameter.
669 For each such CPU, a kthread ("rcuoN") will be created to
670 invoke callbacks, where the "N" is the CPU being offloaded.
671 Nothing prevents this kthread from running on the specified
672 CPUs, but (1) the kthreads may be preempted between each
673 callback, and (2) affinity or cgroups can be used to force
674 the kthreads to run on whatever set of CPUs is desired.
675
676 Say Y here if you want reduced OS jitter on selected CPUs.
677 Say N here if you are unsure.
678
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679endmenu # "RCU Subsystem"
680
1da177e4 681config IKCONFIG
f2443ab6 682 tristate "Kernel .config support"
1da177e4
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683 ---help---
684 This option enables the complete Linux kernel ".config" file
685 contents to be saved in the kernel. It provides documentation
686 of which kernel options are used in a running kernel or in an
687 on-disk kernel. This information can be extracted from the kernel
688 image file with the script scripts/extract-ikconfig and used as
689 input to rebuild the current kernel or to build another kernel.
690 It can also be extracted from a running kernel by reading
691 /proc/config.gz if enabled (below).
692
693config IKCONFIG_PROC
694 bool "Enable access to .config through /proc/config.gz"
695 depends on IKCONFIG && PROC_FS
696 ---help---
697 This option enables access to the kernel configuration file
698 through /proc/config.gz.
699
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700config LOG_BUF_SHIFT
701 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
702 range 12 21
f17a32e9 703 default 17
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704 help
705 Select kernel log buffer size as a power of 2.
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706 Examples:
707 17 => 128 KB
708 16 => 64 KB
709 15 => 32 KB
710 14 => 16 KB
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711 13 => 8 KB
712 12 => 4 KB
713
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714#
715# Architectures with an unreliable sched_clock() should select this:
716#
717config HAVE_UNSTABLE_SCHED_CLOCK
718 bool
719
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720#
721# For architectures that want to enable the support for NUMA-affine scheduler
722# balancing logic:
723#
724config ARCH_SUPPORTS_NUMA_BALANCING
725 bool
726
727# For architectures that (ab)use NUMA to represent different memory regions
728# all cpu-local but of different latencies, such as SuperH.
729#
730config ARCH_WANT_NUMA_VARIABLE_LOCALITY
731 bool
732
733#
734# For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
735config ARCH_WANTS_PROT_NUMA_PROT_NONE
736 bool
737
738config ARCH_USES_NUMA_PROT_NONE
739 bool
740 default y
741 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
742 depends on NUMA_BALANCING
743
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744config NUMA_BALANCING_DEFAULT_ENABLED
745 bool "Automatically enable NUMA aware memory/task placement"
746 default y
747 depends on NUMA_BALANCING
748 help
749 If set, autonumic NUMA balancing will be enabled if running on a NUMA
750 machine.
751
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752config NUMA_BALANCING
753 bool "Memory placement aware NUMA scheduler"
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754 depends on ARCH_SUPPORTS_NUMA_BALANCING
755 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
756 depends on SMP && NUMA && MIGRATION
757 help
758 This option adds support for automatic NUMA aware memory/task placement.
759 The mechanism is quite primitive and is based on migrating memory when
760 it is references to the node the task is running on.
761
762 This system will be inactive on UMA systems.
763
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764menuconfig CGROUPS
765 boolean "Control Group support"
0dea1168 766 depends on EVENTFD
5cdc38f9 767 help
23964d2d 768 This option adds support for grouping sets of processes together, for
5cdc38f9
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769 use with process control subsystems such as Cpusets, CFS, memory
770 controls or device isolation.
771 See
5cdc38f9 772 - Documentation/scheduler/sched-design-CFS.txt (CFS)
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773 - Documentation/cgroups/ (features for grouping, isolation
774 and resource control)
5cdc38f9
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775
776 Say N if unsure.
777
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778if CGROUPS
779
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780config CGROUP_DEBUG
781 bool "Example debug cgroup subsystem"
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782 default n
783 help
784 This option enables a simple cgroup subsystem that
785 exports useful debugging information about the cgroups
23964d2d 786 framework.
5cdc38f9 787
23964d2d 788 Say N if unsure.
5cdc38f9 789
5cdc38f9 790config CGROUP_FREEZER
23964d2d 791 bool "Freezer cgroup subsystem"
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792 help
793 Provides a way to freeze and unfreeze all tasks in a
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794 cgroup.
795
796config CGROUP_DEVICE
797 bool "Device controller for cgroups"
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798 help
799 Provides a cgroup implementing whitelists for devices which
800 a process in the cgroup can mknod or open.
801
802config CPUSETS
803 bool "Cpuset support"
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804 help
805 This option will let you create and manage CPUSETs which
806 allow dynamically partitioning a system into sets of CPUs and
807 Memory Nodes and assigning tasks to run only within those sets.
808 This is primarily useful on large SMP or NUMA systems.
809
810 Say N if unsure.
811
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812config PROC_PID_CPUSET
813 bool "Include legacy /proc/<pid>/cpuset file"
814 depends on CPUSETS
815 default y
816
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817config CGROUP_CPUACCT
818 bool "Simple CPU accounting cgroup subsystem"
d842de87
SV
819 help
820 Provides a simple Resource Controller for monitoring the
23964d2d 821 total CPU consumed by the tasks in a cgroup.
d842de87 822
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823config RESOURCE_COUNTERS
824 bool "Resource counters"
825 help
826 This option enables controller independent resource accounting
23964d2d 827 infrastructure that works with cgroups.
e552b661 828
c255a458 829config MEMCG
00f0b825 830 bool "Memory Resource Controller for Control Groups"
79ae9c29 831 depends on RESOURCE_COUNTERS
cf475ad2 832 select MM_OWNER
00f0b825 833 help
84ad6d70 834 Provides a memory resource controller that manages both anonymous
21acb9ca 835 memory and page cache. (See Documentation/cgroups/memory.txt)
00f0b825
BS
836
837 Note that setting this option increases fixed memory overhead
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838 associated with each page of memory in the system. By this,
839 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
840 usage tracking struct at boot. Total amount of this is printed out
841 at boot.
00f0b825
BS
842
843 Only enable when you're ok with these trade offs and really
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844 sure you need the memory resource controller. Even when you enable
845 this, you can set "cgroup_disable=memory" at your boot option to
846 disable memory resource controller and you can avoid overheads.
c9d5409f 847 (and lose benefits of memory resource controller)
00f0b825 848
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849 This config option also selects MM_OWNER config option, which
850 could in turn add some fork/exit overhead.
851
c255a458 852config MEMCG_SWAP
65e0e811 853 bool "Memory Resource Controller Swap Extension"
c255a458 854 depends on MEMCG && SWAP
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855 help
856 Add swap management feature to memory resource controller. When you
857 enable this, you can limit mem+swap usage per cgroup. In other words,
858 when you disable this, memory resource controller has no cares to
859 usage of swap...a process can exhaust all of the swap. This extension
860 is useful when you want to avoid exhaustion swap but this itself
861 adds more overheads and consumes memory for remembering information.
862 Especially if you use 32bit system or small memory system, please
863 be careful about enabling this. When memory resource controller
864 is disabled by boot option, this will be automatically disabled and
865 there will be no overhead from this. Even when you set this config=y,
00a66d29 866 if boot option "swapaccount=0" is set, swap will not be accounted.
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KH
867 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
868 size is 4096bytes, 512k per 1Gbytes of swap.
c255a458 869config MEMCG_SWAP_ENABLED
a42c390c 870 bool "Memory Resource Controller Swap Extension enabled by default"
c255a458 871 depends on MEMCG_SWAP
a42c390c
MH
872 default y
873 help
874 Memory Resource Controller Swap Extension comes with its price in
875 a bigger memory consumption. General purpose distribution kernels
43d547f9 876 which want to enable the feature but keep it disabled by default
a42c390c
MH
877 and let the user enable it by swapaccount boot command line
878 parameter should have this option unselected.
879 For those who want to have the feature enabled by default should
880 select this option (if, for some reason, they need to disable it
00a66d29 881 then swapaccount=0 does the trick).
c255a458 882config MEMCG_KMEM
19c92399
KC
883 bool "Memory Resource Controller Kernel Memory accounting"
884 depends on MEMCG
510fc4e1 885 depends on SLUB || SLAB
e5671dfa
GC
886 help
887 The Kernel Memory extension for Memory Resource Controller can limit
888 the amount of memory used by kernel objects in the system. Those are
889 fundamentally different from the entities handled by the standard
890 Memory Controller, which are page-based, and can be swapped. Users of
891 the kmem extension can use it to guarantee that no group of processes
892 will ever exhaust kernel resources alone.
c077719b 893
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894config CGROUP_HUGETLB
895 bool "HugeTLB Resource Controller for Control Groups"
19c92399 896 depends on RESOURCE_COUNTERS && HUGETLB_PAGE
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897 default n
898 help
899 Provides a cgroup Resource Controller for HugeTLB pages.
900 When you enable this, you can put a per cgroup limit on HugeTLB usage.
901 The limit is enforced during page fault. Since HugeTLB doesn't
902 support page reclaim, enforcing the limit at page fault time implies
903 that, the application will get SIGBUS signal if it tries to access
904 HugeTLB pages beyond its limit. This requires the application to know
905 beforehand how much HugeTLB pages it would require for its use. The
906 control group is tracked in the third page lru pointer. This means
907 that we cannot use the controller with huge page less than 3 pages.
908
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SE
909config CGROUP_PERF
910 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
911 depends on PERF_EVENTS && CGROUPS
912 help
913 This option extends the per-cpu mode to restrict monitoring to
2d0f2520 914 threads which belong to the cgroup specified and run on the
e5d1367f
SE
915 designated cpu.
916
917 Say N if unsure.
918
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DG
919menuconfig CGROUP_SCHED
920 bool "Group CPU scheduler"
7c941438
DG
921 default n
922 help
923 This feature lets CPU scheduler recognize task groups and control CPU
924 bandwidth allocation to such task groups. It uses cgroups to group
925 tasks.
926
927if CGROUP_SCHED
928config FAIR_GROUP_SCHED
929 bool "Group scheduling for SCHED_OTHER"
930 depends on CGROUP_SCHED
931 default CGROUP_SCHED
932
ab84d31e
PT
933config CFS_BANDWIDTH
934 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
ab84d31e
PT
935 depends on FAIR_GROUP_SCHED
936 default n
937 help
938 This option allows users to define CPU bandwidth rates (limits) for
939 tasks running within the fair group scheduler. Groups with no limit
940 set are considered to be unconstrained and will run with no
941 restriction.
942 See tip/Documentation/scheduler/sched-bwc.txt for more information.
943
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DG
944config RT_GROUP_SCHED
945 bool "Group scheduling for SCHED_RR/FIFO"
7c941438
DG
946 depends on CGROUP_SCHED
947 default n
948 help
949 This feature lets you explicitly allocate real CPU bandwidth
32bd7eb5 950 to task groups. If enabled, it will also make it impossible to
7c941438
DG
951 schedule realtime tasks for non-root users until you allocate
952 realtime bandwidth for them.
953 See Documentation/scheduler/sched-rt-group.txt for more information.
954
955endif #CGROUP_SCHED
956
afc24d49 957config BLK_CGROUP
32e380ae 958 bool "Block IO controller"
79ae9c29 959 depends on BLOCK
afc24d49
VG
960 default n
961 ---help---
962 Generic block IO controller cgroup interface. This is the common
963 cgroup interface which should be used by various IO controlling
964 policies.
965
966 Currently, CFQ IO scheduler uses it to recognize task groups and
967 control disk bandwidth allocation (proportional time slice allocation)
e43473b7
VG
968 to such task groups. It is also used by bio throttling logic in
969 block layer to implement upper limit in IO rates on a device.
afc24d49
VG
970
971 This option only enables generic Block IO controller infrastructure.
e43473b7 972 One needs to also enable actual IO controlling logic/policy. For
79e2e759
MW
973 enabling proportional weight division of disk bandwidth in CFQ, set
974 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
c5e0591a 975 CONFIG_BLK_DEV_THROTTLING=y.
afc24d49
VG
976
977 See Documentation/cgroups/blkio-controller.txt for more information.
978
979config DEBUG_BLK_CGROUP
980 bool "Enable Block IO controller debugging"
981 depends on BLK_CGROUP
982 default n
983 ---help---
984 Enable some debugging help. Currently it exports additional stat
985 files in a cgroup which can be useful for debugging.
986
23964d2d 987endif # CGROUPS
c077719b 988
067bce1a
CG
989config CHECKPOINT_RESTORE
990 bool "Checkpoint/restore support" if EXPERT
991 default n
992 help
993 Enables additional kernel features in a sake of checkpoint/restore.
994 In particular it adds auxiliary prctl codes to setup process text,
995 data and heap segment sizes, and a few additional /proc filesystem
996 entries.
997
998 If unsure, say N here.
999
8dd2a82c 1000menuconfig NAMESPACES
6a108a14
DR
1001 bool "Namespaces support" if EXPERT
1002 default !EXPERT
c5289a69
PE
1003 help
1004 Provides the way to make tasks work with different objects using
1005 the same id. For example same IPC id may refer to different objects
1006 or same user id or pid may refer to different tasks when used in
1007 different namespaces.
1008
8dd2a82c
DL
1009if NAMESPACES
1010
58bfdd6d
PE
1011config UTS_NS
1012 bool "UTS namespace"
17a6d441 1013 default y
58bfdd6d
PE
1014 help
1015 In this namespace tasks see different info provided with the
1016 uname() system call
1017
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PE
1018config IPC_NS
1019 bool "IPC namespace"
8dd2a82c 1020 depends on (SYSVIPC || POSIX_MQUEUE)
17a6d441 1021 default y
ae5e1b22
PE
1022 help
1023 In this namespace tasks work with IPC ids which correspond to
614b84cf 1024 different IPC objects in different namespaces.
ae5e1b22 1025
aee16ce7 1026config USER_NS
19c92399 1027 bool "User namespace"
e1c972b6 1028 depends on UIDGID_CONVERTED
5673a94c 1029 select UIDGID_STRICT_TYPE_CHECKS
e1c972b6 1030
5673a94c 1031 default n
aee16ce7
PE
1032 help
1033 This allows containers, i.e. vservers, to use user namespaces
1034 to provide different user info for different servers.
1035 If unsure, say N.
1036
74bd59bb 1037config PID_NS
9bd38c2c 1038 bool "PID Namespaces"
17a6d441 1039 default y
74bd59bb 1040 help
12d2b8f9 1041 Support process id namespaces. This allows having multiple
692105b8 1042 processes with the same pid as long as they are in different
74bd59bb
PE
1043 pid namespaces. This is a building block of containers.
1044
d6eb633f
MH
1045config NET_NS
1046 bool "Network namespace"
8dd2a82c 1047 depends on NET
17a6d441 1048 default y
d6eb633f
MH
1049 help
1050 Allow user space to create what appear to be multiple instances
1051 of the network stack.
1052
8dd2a82c
DL
1053endif # NAMESPACES
1054
e1c972b6
EB
1055config UIDGID_CONVERTED
1056 # True if all of the selected software conmponents are known
1057 # to have uid_t and gid_t converted to kuid_t and kgid_t
1058 # where appropriate and are otherwise safe to use with
1059 # the user namespace.
1060 bool
1061 default y
1062
e1c972b6 1063 # Networking
e1c972b6 1064 depends on NET_9P = n
e1c972b6
EB
1065
1066 # Filesystems
e1c972b6 1067 depends on 9P_FS = n
e1c972b6 1068 depends on AFS_FS = n
e1c972b6
EB
1069 depends on CEPH_FS = n
1070 depends on CIFS = n
1071 depends on CODA_FS = n
e1c972b6 1072 depends on GFS2_FS = n
e1c972b6
EB
1073 depends on NCP_FS = n
1074 depends on NFSD = n
1075 depends on NFS_FS = n
e1c972b6 1076 depends on OCFS2_FS = n
e1c972b6
EB
1077 depends on XFS_FS = n
1078
5673a94c
EB
1079config UIDGID_STRICT_TYPE_CHECKS
1080 bool "Require conversions between uid/gids and their internal representation"
e1c972b6 1081 depends on UIDGID_CONVERTED
5673a94c
EB
1082 default n
1083 help
1084 While the nececessary conversions are being added to all subsystems this option allows
1085 the code to continue to build for unconverted subsystems.
1086
1087 Say Y here if you want the strict type checking enabled
1088
5091faa4
MG
1089config SCHED_AUTOGROUP
1090 bool "Automatic process group scheduling"
1091 select EVENTFD
1092 select CGROUPS
1093 select CGROUP_SCHED
1094 select FAIR_GROUP_SCHED
1095 help
1096 This option optimizes the scheduler for common desktop workloads by
1097 automatically creating and populating task groups. This separation
1098 of workloads isolates aggressive CPU burners (like build jobs) from
1099 desktop applications. Task group autogeneration is currently based
1100 upon task session.
1101
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1102config MM_OWNER
1103 bool
1104
1105config SYSFS_DEPRECATED
5d6a4ea5 1106 bool "Enable deprecated sysfs features to support old userspace tools"
7af37bec
DL
1107 depends on SYSFS
1108 default n
1109 help
1110 This option adds code that switches the layout of the "block" class
1111 devices, to not show up in /sys/class/block/, but only in
1112 /sys/block/.
1113
1114 This switch is only active when the sysfs.deprecated=1 boot option is
1115 passed or the SYSFS_DEPRECATED_V2 option is set.
1116
1117 This option allows new kernels to run on old distributions and tools,
1118 which might get confused by /sys/class/block/. Since 2007/2008 all
1119 major distributions and tools handle this just fine.
1120
1121 Recent distributions and userspace tools after 2009/2010 depend on
1122 the existence of /sys/class/block/, and will not work with this
1123 option enabled.
1124
1125 Only if you are using a new kernel on an old distribution, you might
1126 need to say Y here.
1127
1128config SYSFS_DEPRECATED_V2
5d6a4ea5 1129 bool "Enable deprecated sysfs features by default"
7af37bec
DL
1130 default n
1131 depends on SYSFS
1132 depends on SYSFS_DEPRECATED
1133 help
1134 Enable deprecated sysfs by default.
1135
1136 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1137 option.
1138
1139 Only if you are using a new kernel on an old distribution, you might
1140 need to say Y here. Even then, odds are you would not need it
1141 enabled, you can always pass the boot option if absolutely necessary.
1142
1143config RELAY
1144 bool "Kernel->user space relay support (formerly relayfs)"
1145 help
1146 This option enables support for relay interface support in
1147 certain file systems (such as debugfs).
1148 It is designed to provide an efficient mechanism for tools and
1149 facilities to relay large amounts of data from kernel space to
1150 user space.
1151
1152 If unsure, say N.
1153
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DG
1154config BLK_DEV_INITRD
1155 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1156 depends on BROKEN || !FRV
1157 help
1158 The initial RAM filesystem is a ramfs which is loaded by the
1159 boot loader (loadlin or lilo) and that is mounted as root
1160 before the normal boot procedure. It is typically used to
1161 load modules needed to mount the "real" root file system,
1162 etc. See <file:Documentation/initrd.txt> for details.
1163
1164 If RAM disk support (BLK_DEV_RAM) is also included, this
1165 also enables initial RAM disk (initrd) support and adds
1166 15 Kbytes (more on some other architectures) to the kernel size.
1167
1168 If unsure say Y.
1169
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JPS
1170if BLK_DEV_INITRD
1171
dbec4866
SR
1172source "usr/Kconfig"
1173
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JPS
1174endif
1175
c45b4f1f 1176config CC_OPTIMIZE_FOR_SIZE
96fffeb4 1177 bool "Optimize for size"
c45b4f1f
LT
1178 help
1179 Enabling this option will pass "-Os" instead of "-O2" to gcc
1180 resulting in a smaller kernel.
1181
3a55fb0d 1182 If unsure, say N.
c45b4f1f 1183
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RD
1184config SYSCTL
1185 bool
1186
b943c460
RD
1187config ANON_INODES
1188 bool
1189
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DR
1190menuconfig EXPERT
1191 bool "Configure standard kernel features (expert users)"
f505c553
JT
1192 # Unhide debug options, to make the on-by-default options visible
1193 select DEBUG_KERNEL
1da177e4
LT
1194 help
1195 This option allows certain base kernel options and settings
1196 to be disabled or tweaked. This is for specialized
1197 environments which can tolerate a "non-standard" kernel.
1198 Only use this if you really know what you are doing.
1199
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1200config HAVE_UID16
1201 bool
1202
ae81f9e3 1203config UID16
6a108a14 1204 bool "Enable 16-bit UID system calls" if EXPERT
af1839eb 1205 depends on HAVE_UID16
ae81f9e3
CE
1206 default y
1207 help
1208 This enables the legacy 16-bit UID syscall wrappers.
1209
b89a8171 1210config SYSCTL_SYSCALL
6a108a14 1211 bool "Sysctl syscall support" if EXPERT
26a7034b 1212 depends on PROC_SYSCTL
c736de60 1213 default n
b89a8171 1214 select SYSCTL
ae81f9e3 1215 ---help---
13bb7e37
EB
1216 sys_sysctl uses binary paths that have been found challenging
1217 to properly maintain and use. The interface in /proc/sys
1218 using paths with ascii names is now the primary path to this
1219 information.
b89a8171 1220
13bb7e37
EB
1221 Almost nothing using the binary sysctl interface so if you are
1222 trying to save some space it is probably safe to disable this,
1223 making your kernel marginally smaller.
b89a8171 1224
c736de60 1225 If unsure say N here.
ae81f9e3 1226
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CM
1227config SYSCTL_EXCEPTION_TRACE
1228 bool
1229 help
1230 Enable support for /proc/sys/debug/exception-trace.
1231
1da177e4 1232config KALLSYMS
6a108a14 1233 bool "Load all symbols for debugging/ksymoops" if EXPERT
1da177e4
LT
1234 default y
1235 help
1236 Say Y here to let the kernel print out symbolic crash information and
1237 symbolic stack backtraces. This increases the size of the kernel
1238 somewhat, as all symbols have to be loaded into the kernel image.
1239
1240config KALLSYMS_ALL
1241 bool "Include all symbols in kallsyms"
1242 depends on DEBUG_KERNEL && KALLSYMS
1243 help
71a83ec7
AB
1244 Normally kallsyms only contains the symbols of functions for nicer
1245 OOPS messages and backtraces (i.e., symbols from the text and inittext
1246 sections). This is sufficient for most cases. And only in very rare
1247 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1248 names of variables from the data sections, etc).
1249
1250 This option makes sure that all symbols are loaded into the kernel
1251 image (i.e., symbols from all sections) in cost of increased kernel
1252 size (depending on the kernel configuration, it may be 300KiB or
1253 something like this).
1254
1255 Say N unless you really need all symbols.
d59745ce 1256
712f47ce 1257config HOTPLUG
45f035ab 1258 def_bool y
712f47ce 1259
d59745ce
MM
1260config PRINTK
1261 default y
6a108a14 1262 bool "Enable support for printk" if EXPERT
74876a98 1263 select IRQ_WORK
d59745ce
MM
1264 help
1265 This option enables normal printk support. Removing it
1266 eliminates most of the message strings from the kernel image
1267 and makes the kernel more or less silent. As this makes it
1268 very difficult to diagnose system problems, saying N here is
1269 strongly discouraged.
1270
c8538a7a 1271config BUG
6a108a14 1272 bool "BUG() support" if EXPERT
c8538a7a
MM
1273 default y
1274 help
1275 Disabling this option eliminates support for BUG and WARN, reducing
1276 the size of your kernel image and potentially quietly ignoring
1277 numerous fatal conditions. You should only consider disabling this
1278 option for embedded systems with no facilities for reporting errors.
1279 Just say Y.
1280
708e9a79 1281config ELF_CORE
046d662f 1282 depends on COREDUMP
708e9a79 1283 default y
6a108a14 1284 bool "Enable ELF core dumps" if EXPERT
708e9a79
MM
1285 help
1286 Enable support for generating core dumps. Disabling saves about 4k.
1287
8761f1ab 1288
e5e1d3cb 1289config PCSPKR_PLATFORM
6a108a14 1290 bool "Enable PC-Speaker support" if EXPERT
8761f1ab 1291 depends on HAVE_PCSPKR_PLATFORM
15f304b6 1292 select I8253_LOCK
e5e1d3cb
SS
1293 default y
1294 help
1295 This option allows to disable the internal PC-Speaker
1296 support, saving some memory.
1297
8761f1ab
RB
1298config HAVE_PCSPKR_PLATFORM
1299 bool
1300
1da177e4
LT
1301config BASE_FULL
1302 default y
6a108a14 1303 bool "Enable full-sized data structures for core" if EXPERT
1da177e4
LT
1304 help
1305 Disabling this option reduces the size of miscellaneous core
1306 kernel data structures. This saves memory on small machines,
1307 but may reduce performance.
1308
1309config FUTEX
6a108a14 1310 bool "Enable futex support" if EXPERT
1da177e4 1311 default y
23f78d4a 1312 select RT_MUTEXES
1da177e4
LT
1313 help
1314 Disabling this option will cause the kernel to be built without
1315 support for "fast userspace mutexes". The resulting kernel may not
1316 run glibc-based applications correctly.
1317
1318config EPOLL
6a108a14 1319 bool "Enable eventpoll support" if EXPERT
1da177e4 1320 default y
448e3cee 1321 select ANON_INODES
1da177e4
LT
1322 help
1323 Disabling this option will cause the kernel to be built without
1324 support for epoll family of system calls.
1325
fba2afaa 1326config SIGNALFD
6a108a14 1327 bool "Enable signalfd() system call" if EXPERT
448e3cee 1328 select ANON_INODES
fba2afaa
DL
1329 default y
1330 help
1331 Enable the signalfd() system call that allows to receive signals
1332 on a file descriptor.
1333
1334 If unsure, say Y.
1335
b215e283 1336config TIMERFD
6a108a14 1337 bool "Enable timerfd() system call" if EXPERT
448e3cee 1338 select ANON_INODES
b215e283
DL
1339 default y
1340 help
1341 Enable the timerfd() system call that allows to receive timer
1342 events on a file descriptor.
1343
1344 If unsure, say Y.
1345
e1ad7468 1346config EVENTFD
6a108a14 1347 bool "Enable eventfd() system call" if EXPERT
448e3cee 1348 select ANON_INODES
e1ad7468
DL
1349 default y
1350 help
1351 Enable the eventfd() system call that allows to receive both
1352 kernel notification (ie. KAIO) or userspace notifications.
1353
1354 If unsure, say Y.
1355
1da177e4 1356config SHMEM
6a108a14 1357 bool "Use full shmem filesystem" if EXPERT
1da177e4
LT
1358 default y
1359 depends on MMU
1360 help
1361 The shmem is an internal filesystem used to manage shared memory.
1362 It is backed by swap and manages resource limits. It is also exported
1363 to userspace as tmpfs if TMPFS is enabled. Disabling this
1364 option replaces shmem and tmpfs with the much simpler ramfs code,
1365 which may be appropriate on small systems without swap.
1366
ebf3f09c 1367config AIO
6a108a14 1368 bool "Enable AIO support" if EXPERT
ebf3f09c
TP
1369 default y
1370 help
1371 This option enables POSIX asynchronous I/O which may by used
1372 by some high performance threaded applications. Disabling
1373 this option saves about 7k.
1374
6befe5f6
RD
1375config EMBEDDED
1376 bool "Embedded system"
1377 select EXPERT
1378 help
1379 This option should be enabled if compiling the kernel for
1380 an embedded system so certain expert options are available
1381 for configuration.
1382
cdd6c482 1383config HAVE_PERF_EVENTS
0793a61d 1384 bool
018df72d
MF
1385 help
1386 See tools/perf/design.txt for details.
0793a61d 1387
906010b2
PZ
1388config PERF_USE_VMALLOC
1389 bool
1390 help
1391 See tools/perf/design.txt for details
1392
57c0c15b 1393menu "Kernel Performance Events And Counters"
0793a61d 1394
cdd6c482 1395config PERF_EVENTS
57c0c15b 1396 bool "Kernel performance events and counters"
392d65a9 1397 default y if PROFILING
cdd6c482 1398 depends on HAVE_PERF_EVENTS
4c59e467 1399 select ANON_INODES
e360adbe 1400 select IRQ_WORK
0793a61d 1401 help
57c0c15b
IM
1402 Enable kernel support for various performance events provided
1403 by software and hardware.
0793a61d 1404
dd77038d 1405 Software events are supported either built-in or via the
57c0c15b 1406 use of generic tracepoints.
0793a61d 1407
57c0c15b
IM
1408 Most modern CPUs support performance events via performance
1409 counter registers. These registers count the number of certain
0793a61d
TG
1410 types of hw events: such as instructions executed, cachemisses
1411 suffered, or branches mis-predicted - without slowing down the
1412 kernel or applications. These registers can also trigger interrupts
1413 when a threshold number of events have passed - and can thus be
1414 used to profile the code that runs on that CPU.
1415
57c0c15b 1416 The Linux Performance Event subsystem provides an abstraction of
dd77038d 1417 these software and hardware event capabilities, available via a
57c0c15b 1418 system call and used by the "perf" utility in tools/perf/. It
0793a61d
TG
1419 provides per task and per CPU counters, and it provides event
1420 capabilities on top of those.
1421
1422 Say Y if unsure.
1423
906010b2
PZ
1424config DEBUG_PERF_USE_VMALLOC
1425 default n
1426 bool "Debug: use vmalloc to back perf mmap() buffers"
1427 depends on PERF_EVENTS && DEBUG_KERNEL
1428 select PERF_USE_VMALLOC
1429 help
1430 Use vmalloc memory to back perf mmap() buffers.
1431
1432 Mostly useful for debugging the vmalloc code on platforms
1433 that don't require it.
1434
1435 Say N if unsure.
1436
0793a61d
TG
1437endmenu
1438
f8891e5e
CL
1439config VM_EVENT_COUNTERS
1440 default y
6a108a14 1441 bool "Enable VM event counters for /proc/vmstat" if EXPERT
f8891e5e 1442 help
2aea4fb6
PJ
1443 VM event counters are needed for event counts to be shown.
1444 This option allows the disabling of the VM event counters
6a108a14 1445 on EXPERT systems. /proc/vmstat will only show page counts
2aea4fb6 1446 if VM event counters are disabled.
f8891e5e 1447
3d137310
TP
1448config PCI_QUIRKS
1449 default y
6a108a14 1450 bool "Enable PCI quirk workarounds" if EXPERT
61cfc7e4 1451 depends on PCI
3d137310
TP
1452 help
1453 This enables workarounds for various PCI chipset
1454 bugs/quirks. Disable this only if your target machine is
1455 unaffected by PCI quirks.
1456
41ecc55b
CL
1457config SLUB_DEBUG
1458 default y
6a108a14 1459 bool "Enable SLUB debugging support" if EXPERT
f6acb635 1460 depends on SLUB && SYSFS
41ecc55b
CL
1461 help
1462 SLUB has extensive debug support features. Disabling these can
1463 result in significant savings in code size. This also disables
1464 SLUB sysfs support. /sys/slab will not exist and there will be
1465 no support for cache validation etc.
1466
b943c460
RD
1467config COMPAT_BRK
1468 bool "Disable heap randomization"
1469 default y
1470 help
1471 Randomizing heap placement makes heap exploits harder, but it
1472 also breaks ancient binaries (including anything libc5 based).
1473 This option changes the bootup default to heap randomization
692105b8 1474 disabled, and can be overridden at runtime by setting
b943c460
RD
1475 /proc/sys/kernel/randomize_va_space to 2.
1476
1477 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1478
81819f0f
CL
1479choice
1480 prompt "Choose SLAB allocator"
a0acd820 1481 default SLUB
81819f0f
CL
1482 help
1483 This option allows to select a slab allocator.
1484
1485config SLAB
1486 bool "SLAB"
1487 help
1488 The regular slab allocator that is established and known to work
34013886 1489 well in all environments. It organizes cache hot objects in
02f56210 1490 per cpu and per node queues.
81819f0f
CL
1491
1492config SLUB
81819f0f
CL
1493 bool "SLUB (Unqueued Allocator)"
1494 help
1495 SLUB is a slab allocator that minimizes cache line usage
1496 instead of managing queues of cached objects (SLAB approach).
1497 Per cpu caching is realized using slabs of objects instead
1498 of queues of objects. SLUB can use memory efficiently
02f56210
SA
1499 and has enhanced diagnostics. SLUB is the default choice for
1500 a slab allocator.
81819f0f
CL
1501
1502config SLOB
6a108a14 1503 depends on EXPERT
81819f0f
CL
1504 bool "SLOB (Simple Allocator)"
1505 help
37291458
MM
1506 SLOB replaces the stock allocator with a drastically simpler
1507 allocator. SLOB is generally more space efficient but
1508 does not perform as well on large systems.
81819f0f
CL
1509
1510endchoice
1511
ea637639
JZ
1512config MMAP_ALLOW_UNINITIALIZED
1513 bool "Allow mmapped anonymous memory to be uninitialized"
6a108a14 1514 depends on EXPERT && !MMU
ea637639
JZ
1515 default n
1516 help
1517 Normally, and according to the Linux spec, anonymous memory obtained
1518 from mmap() has it's contents cleared before it is passed to
1519 userspace. Enabling this config option allows you to request that
1520 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1521 providing a huge performance boost. If this option is not enabled,
1522 then the flag will be ignored.
1523
1524 This is taken advantage of by uClibc's malloc(), and also by
1525 ELF-FDPIC binfmt's brk and stack allocator.
1526
1527 Because of the obvious security issues, this option should only be
1528 enabled on embedded devices where you control what is run in
1529 userspace. Since that isn't generally a problem on no-MMU systems,
1530 it is normally safe to say Y here.
1531
1532 See Documentation/nommu-mmap.txt for more information.
1533
125e5645 1534config PROFILING
b309a294 1535 bool "Profiling support"
125e5645
MD
1536 help
1537 Say Y here to enable the extended profiling support mechanisms used
1538 by profilers such as OProfile.
1539
5f87f112
IM
1540#
1541# Place an empty function call at each tracepoint site. Can be
1542# dynamically changed for a probe function.
1543#
97e1c18e 1544config TRACEPOINTS
5f87f112 1545 bool
97e1c18e 1546
fb32e03f
MD
1547source "arch/Kconfig"
1548
1da177e4
LT
1549endmenu # General setup
1550
ee7e5516
DB
1551config HAVE_GENERIC_DMA_COHERENT
1552 bool
1553 default n
1554
158a9624
LT
1555config SLABINFO
1556 bool
1557 depends on PROC_FS
0f389ec6 1558 depends on SLAB || SLUB_DEBUG
158a9624
LT
1559 default y
1560
ae81f9e3
CE
1561config RT_MUTEXES
1562 boolean
ae81f9e3 1563
1da177e4
LT
1564config BASE_SMALL
1565 int
1566 default 0 if BASE_FULL
1567 default 1 if !BASE_FULL
1568
66da5733 1569menuconfig MODULES
1da177e4
LT
1570 bool "Enable loadable module support"
1571 help
1572 Kernel modules are small pieces of compiled code which can
1573 be inserted in the running kernel, rather than being
1574 permanently built into the kernel. You use the "modprobe"
1575 tool to add (and sometimes remove) them. If you say Y here,
1576 many parts of the kernel can be built as modules (by
1577 answering M instead of Y where indicated): this is most
1578 useful for infrequently used options which are not required
1579 for booting. For more information, see the man pages for
1580 modprobe, lsmod, modinfo, insmod and rmmod.
1581
1582 If you say Y here, you will need to run "make
1583 modules_install" to put the modules under /lib/modules/
1584 where modprobe can find them (you may need to be root to do
1585 this).
1586
1587 If unsure, say Y.
1588
0b0de144
RD
1589if MODULES
1590
826e4506
LT
1591config MODULE_FORCE_LOAD
1592 bool "Forced module loading"
826e4506
LT
1593 default n
1594 help
91e37a79
RR
1595 Allow loading of modules without version information (ie. modprobe
1596 --force). Forced module loading sets the 'F' (forced) taint flag and
1597 is usually a really bad idea.
826e4506 1598
1da177e4
LT
1599config MODULE_UNLOAD
1600 bool "Module unloading"
1da177e4
LT
1601 help
1602 Without this option you will not be able to unload any
1603 modules (note that some modules may not be unloadable
f7f5b675
DV
1604 anyway), which makes your kernel smaller, faster
1605 and simpler. If unsure, say Y.
1da177e4
LT
1606
1607config MODULE_FORCE_UNLOAD
1608 bool "Forced module unloading"
19c92399 1609 depends on MODULE_UNLOAD
1da177e4
LT
1610 help
1611 This option allows you to force a module to unload, even if the
1612 kernel believes it is unsafe: the kernel will remove the module
1613 without waiting for anyone to stop using it (using the -f option to
1614 rmmod). This is mainly for kernel developers and desperate users.
1615 If unsure, say N.
1616
1da177e4 1617config MODVERSIONS
0d541643 1618 bool "Module versioning support"
1da177e4
LT
1619 help
1620 Usually, you have to use modules compiled with your kernel.
1621 Saying Y here makes it sometimes possible to use modules
1622 compiled for different kernels, by adding enough information
1623 to the modules to (hopefully) spot any changes which would
1624 make them incompatible with the kernel you are running. If
1625 unsure, say N.
1626
1627config MODULE_SRCVERSION_ALL
1628 bool "Source checksum for all modules"
1da177e4
LT
1629 help
1630 Modules which contain a MODULE_VERSION get an extra "srcversion"
1631 field inserted into their modinfo section, which contains a
1632 sum of the source files which made it. This helps maintainers
1633 see exactly which source was used to build a module (since
1634 others sometimes change the module source without updating
1635 the version). With this option, such a "srcversion" field
1636 will be created for all modules. If unsure, say N.
1637
106a4ee2
RR
1638config MODULE_SIG
1639 bool "Module signature verification"
1640 depends on MODULES
48ba2462
DH
1641 select KEYS
1642 select CRYPTO
1643 select ASYMMETRIC_KEY_TYPE
1644 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1645 select PUBLIC_KEY_ALGO_RSA
1646 select ASN1
1647 select OID_REGISTRY
1648 select X509_CERTIFICATE_PARSER
106a4ee2
RR
1649 help
1650 Check modules for valid signatures upon load: the signature
1651 is simply appended to the module. For more information see
1652 Documentation/module-signing.txt.
1653
ea0b6dcf
DH
1654 !!!WARNING!!! If you enable this option, you MUST make sure that the
1655 module DOES NOT get stripped after being signed. This includes the
1656 debuginfo strip done by some packagers (such as rpmbuild) and
1657 inclusion into an initramfs that wants the module size reduced.
1658
106a4ee2
RR
1659config MODULE_SIG_FORCE
1660 bool "Require modules to be validly signed"
1661 depends on MODULE_SIG
1662 help
1663 Reject unsigned modules or signed modules for which we don't have a
1664 key. Without this, such modules will simply taint the kernel.
ea0b6dcf
DH
1665
1666choice
1667 prompt "Which hash algorithm should modules be signed with?"
1668 depends on MODULE_SIG
1669 help
1670 This determines which sort of hashing algorithm will be used during
1671 signature generation. This algorithm _must_ be built into the kernel
1672 directly so that signature verification can take place. It is not
1673 possible to load a signed module containing the algorithm to check
1674 the signature on that module.
1675
1676config MODULE_SIG_SHA1
1677 bool "Sign modules with SHA-1"
1678 select CRYPTO_SHA1
1679
1680config MODULE_SIG_SHA224
1681 bool "Sign modules with SHA-224"
1682 select CRYPTO_SHA256
1683
1684config MODULE_SIG_SHA256
1685 bool "Sign modules with SHA-256"
1686 select CRYPTO_SHA256
1687
1688config MODULE_SIG_SHA384
1689 bool "Sign modules with SHA-384"
1690 select CRYPTO_SHA512
1691
1692config MODULE_SIG_SHA512
1693 bool "Sign modules with SHA-512"
1694 select CRYPTO_SHA512
1695
1696endchoice
1697
0b0de144
RD
1698endif # MODULES
1699
98a79d6a
RR
1700config INIT_ALL_POSSIBLE
1701 bool
1702 help
5f054e31
RR
1703 Back when each arch used to define their own cpu_online_mask and
1704 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
98a79d6a
RR
1705 with all 1s, and others with all 0s. When they were centralised,
1706 it was better to provide this option than to break all the archs
692105b8 1707 and have several arch maintainers pursuing me down dark alleys.
98a79d6a 1708
1da177e4
LT
1709config STOP_MACHINE
1710 bool
1711 default y
1712 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1713 help
1714 Need stop_machine() primitive.
3a65dfe8 1715
3a65dfe8 1716source "block/Kconfig"
e98c3202
AK
1717
1718config PREEMPT_NOTIFIERS
1719 bool
e260be67 1720
16295bec
SK
1721config PADATA
1722 depends on SMP
1723 bool
1724
754b7b63
AK
1725# Can be selected by architectures with broken toolchains
1726# that get confused by correct const<->read_only section
1727# mappings
1728config BROKEN_RODATA
1729 bool
1730
4520c6a4
DH
1731config ASN1
1732 tristate
1733 help
1734 Build a simple ASN.1 grammar compiler that produces a bytecode output
1735 that can be interpreted by the ASN.1 stream decoder and used to
1736 inform it as to what tags are to be expected in a stream and what
1737 functions to call on what tags.
1738
6beb0009 1739source "kernel/Kconfig.locks"
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