rcu: Simplify rcu_pending()/rcu_check_callbacks() API
[linux-2.6-block.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
22 default y
23
ff0cfc66 24menu "General setup"
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25
26config EXPERIMENTAL
27 bool "Prompt for development and/or incomplete code/drivers"
28 ---help---
29 Some of the various things that Linux supports (such as network
30 drivers, file systems, network protocols, etc.) can be in a state
31 of development where the functionality, stability, or the level of
32 testing is not yet high enough for general use. This is usually
33 known as the "alpha-test" phase among developers. If a feature is
34 currently in alpha-test, then the developers usually discourage
35 uninformed widespread use of this feature by the general public to
36 avoid "Why doesn't this work?" type mail messages. However, active
37 testing and use of these systems is welcomed. Just be aware that it
38 may not meet the normal level of reliability or it may fail to work
39 in some special cases. Detailed bug reports from people familiar
40 with the kernel internals are usually welcomed by the developers
41 (before submitting bug reports, please read the documents
42 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
43 <file:Documentation/BUG-HUNTING>, and
44 <file:Documentation/oops-tracing.txt> in the kernel source).
45
46 This option will also make obsoleted drivers available. These are
47 drivers that have been replaced by something else, and/or are
48 scheduled to be removed in a future kernel release.
49
50 Unless you intend to help test and develop a feature or driver that
51 falls into this category, or you have a situation that requires
52 using these features, you should probably say N here, which will
53 cause the configurator to present you with fewer choices. If
54 you say Y here, you will be offered the choice of using features or
55 drivers that are currently considered to be in the alpha-test phase.
56
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57config BROKEN
58 bool
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59
60config BROKEN_ON_SMP
61 bool
62 depends on BROKEN || !SMP
63 default y
64
65config LOCK_KERNEL
66 bool
67 depends on SMP || PREEMPT
68 default y
69
70config INIT_ENV_ARG_LIMIT
71 int
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72 default 32 if !UML
73 default 128 if UML
1da177e4 74 help
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75 Maximum of each of the number of arguments and environment
76 variables passed to init from the kernel command line.
1da177e4 77
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78
79config LOCALVERSION
80 string "Local version - append to kernel release"
81 help
82 Append an extra string to the end of your kernel version.
83 This will show up when you type uname, for example.
84 The string you set here will be appended after the contents of
85 any files with a filename matching localversion* in your
86 object and source tree, in that order. Your total string can
87 be a maximum of 64 characters.
88
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89config LOCALVERSION_AUTO
90 bool "Automatically append version information to the version string"
91 default y
92 help
93 This will try to automatically determine if the current tree is a
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94 release tree by looking for git tags that belong to the current
95 top of tree revision.
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96
97 A string of the format -gxxxxxxxx will be added to the localversion
6e5a5420 98 if a git-based tree is found. The string generated by this will be
aaebf433 99 appended after any matching localversion* files, and after the value
6e5a5420 100 set in CONFIG_LOCALVERSION.
aaebf433 101
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102 (The actual string used here is the first eight characters produced
103 by running the command:
104
105 $ git rev-parse --verify HEAD
106
107 which is done within the script "scripts/setlocalversion".)
aaebf433 108
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109config HAVE_KERNEL_GZIP
110 bool
111
112config HAVE_KERNEL_BZIP2
113 bool
114
115config HAVE_KERNEL_LZMA
116 bool
117
30d65dbf 118choice
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119 prompt "Kernel compression mode"
120 default KERNEL_GZIP
121 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
122 help
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123 The linux kernel is a kind of self-extracting executable.
124 Several compression algorithms are available, which differ
125 in efficiency, compression and decompression speed.
126 Compression speed is only relevant when building a kernel.
127 Decompression speed is relevant at each boot.
128
129 If you have any problems with bzip2 or lzma compressed
130 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
131 version of this functionality (bzip2 only), for 2.4, was
132 supplied by Christian Ludwig)
133
134 High compression options are mostly useful for users, who
135 are low on disk space (embedded systems), but for whom ram
136 size matters less.
137
138 If in doubt, select 'gzip'
139
140config KERNEL_GZIP
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141 bool "Gzip"
142 depends on HAVE_KERNEL_GZIP
143 help
144 The old and tried gzip compression. Its compression ratio is
145 the poorest among the 3 choices; however its speed (both
146 compression and decompression) is the fastest.
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147
148config KERNEL_BZIP2
149 bool "Bzip2"
2e9f3bdd 150 depends on HAVE_KERNEL_BZIP2
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151 help
152 Its compression ratio and speed is intermediate.
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153 Decompression speed is slowest among the three. The kernel
154 size is about 10% smaller with bzip2, in comparison to gzip.
155 Bzip2 uses a large amount of memory. For modern kernels you
156 will need at least 8MB RAM or more for booting.
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157
158config KERNEL_LZMA
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159 bool "LZMA"
160 depends on HAVE_KERNEL_LZMA
161 help
162 The most recent compression algorithm.
163 Its ratio is best, decompression speed is between the other
164 two. Compression is slowest. The kernel size is about 33%
165 smaller with LZMA in comparison to gzip.
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166
167endchoice
168
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169config SWAP
170 bool "Support for paging of anonymous memory (swap)"
9361401e 171 depends on MMU && BLOCK
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172 default y
173 help
174 This option allows you to choose whether you want to have support
92c3504e 175 for so called swap devices or swap files in your kernel that are
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176 used to provide more virtual memory than the actual RAM present
177 in your computer. If unsure say Y.
178
179config SYSVIPC
180 bool "System V IPC"
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181 ---help---
182 Inter Process Communication is a suite of library functions and
183 system calls which let processes (running programs) synchronize and
184 exchange information. It is generally considered to be a good thing,
185 and some programs won't run unless you say Y here. In particular, if
186 you want to run the DOS emulator dosemu under Linux (read the
187 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
188 you'll need to say Y here.
189
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
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194config SYSVIPC_SYSCTL
195 bool
196 depends on SYSVIPC
197 depends on SYSCTL
198 default y
199
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200config POSIX_MQUEUE
201 bool "POSIX Message Queues"
202 depends on NET && EXPERIMENTAL
203 ---help---
204 POSIX variant of message queues is a part of IPC. In POSIX message
205 queues every message has a priority which decides about succession
206 of receiving it by a process. If you want to compile and run
207 programs written e.g. for Solaris with use of its POSIX message
b0e37650 208 queues (functions mq_*) say Y here.
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209
210 POSIX message queues are visible as a filesystem called 'mqueue'
211 and can be mounted somewhere if you want to do filesystem
212 operations on message queues.
213
214 If unsure, say Y.
215
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216config POSIX_MQUEUE_SYSCTL
217 bool
218 depends on POSIX_MQUEUE
219 depends on SYSCTL
220 default y
221
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222config BSD_PROCESS_ACCT
223 bool "BSD Process Accounting"
224 help
225 If you say Y here, a user level program will be able to instruct the
226 kernel (via a special system call) to write process accounting
227 information to a file: whenever a process exits, information about
228 that process will be appended to the file by the kernel. The
229 information includes things such as creation time, owning user,
230 command name, memory usage, controlling terminal etc. (the complete
231 list is in the struct acct in <file:include/linux/acct.h>). It is
232 up to the user level program to do useful things with this
233 information. This is generally a good idea, so say Y.
234
235config BSD_PROCESS_ACCT_V3
236 bool "BSD Process Accounting version 3 file format"
237 depends on BSD_PROCESS_ACCT
238 default n
239 help
240 If you say Y here, the process accounting information is written
241 in a new file format that also logs the process IDs of each
242 process and it's parent. Note that this file format is incompatible
243 with previous v0/v1/v2 file formats, so you will need updated tools
244 for processing it. A preliminary version of these tools is available
37a4c940 245 at <http://www.gnu.org/software/acct/>.
1da177e4 246
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247config TASKSTATS
248 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
249 depends on NET
250 default n
251 help
252 Export selected statistics for tasks/processes through the
253 generic netlink interface. Unlike BSD process accounting, the
254 statistics are available during the lifetime of tasks/processes as
255 responses to commands. Like BSD accounting, they are sent to user
256 space on task exit.
257
258 Say N if unsure.
259
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260config TASK_DELAY_ACCT
261 bool "Enable per-task delay accounting (EXPERIMENTAL)"
6f44993f 262 depends on TASKSTATS
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263 help
264 Collect information on time spent by a task waiting for system
265 resources like cpu, synchronous block I/O completion and swapping
266 in pages. Such statistics can help in setting a task's priorities
267 relative to other tasks for cpu, io, rss limits etc.
268
269 Say N if unsure.
270
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271config TASK_XACCT
272 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
273 depends on TASKSTATS
274 help
275 Collect extended task accounting data and send the data
276 to userland for processing over the taskstats interface.
277
278 Say N if unsure.
279
280config TASK_IO_ACCOUNTING
281 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
282 depends on TASK_XACCT
283 help
284 Collect information on the number of bytes of storage I/O which this
285 task has caused.
286
287 Say N if unsure.
288
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289config AUDIT
290 bool "Auditing support"
804a6a49 291 depends on NET
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292 help
293 Enable auditing infrastructure that can be used with another
294 kernel subsystem, such as SELinux (which requires this for
295 logging of avc messages output). Does not do system-call
296 auditing without CONFIG_AUDITSYSCALL.
297
298config AUDITSYSCALL
299 bool "Enable system-call auditing support"
1322b9de 300 depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
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301 default y if SECURITY_SELINUX
302 help
303 Enable low-overhead system-call auditing infrastructure that
304 can be used independently or with another kernel subsystem,
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305 such as SELinux. To use audit's filesystem watch feature, please
306 ensure that INOTIFY is configured.
1da177e4 307
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308config AUDIT_TREE
309 def_bool y
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310 depends on AUDITSYSCALL
311 select INOTIFY
74c3cbe3 312
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313menu "RCU Subsystem"
314
315choice
316 prompt "RCU Implementation"
31c9a24e 317 default TREE_RCU
c903ff83 318
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319config TREE_RCU
320 bool "Tree-based hierarchical RCU"
321 help
322 This option selects the RCU implementation that is
323 designed for very large SMP system with hundreds or
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324 thousands of CPUs. It also scales down nicely to
325 smaller systems.
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326
327config PREEMPT_RCU
328 bool "Preemptible RCU"
329 depends on PREEMPT
330 help
331 This option reduces the latency of the kernel by making certain
332 RCU sections preemptible. Normally RCU code is non-preemptible, if
333 this option is selected then read-only RCU sections become
334 preemptible. This helps latency, but may expose bugs due to
335 now-naive assumptions about each RCU read-side critical section
336 remaining on a given CPU through its execution.
337
338endchoice
339
340config RCU_TRACE
341 bool "Enable tracing for RCU"
342 depends on TREE_RCU || PREEMPT_RCU
343 help
344 This option provides tracing in RCU which presents stats
345 in debugfs for debugging RCU implementation.
346
347 Say Y here if you want to enable RCU tracing
348 Say N if you are unsure.
349
350config RCU_FANOUT
351 int "Tree-based hierarchical RCU fanout value"
352 range 2 64 if 64BIT
353 range 2 32 if !64BIT
354 depends on TREE_RCU
355 default 64 if 64BIT
356 default 32 if !64BIT
357 help
358 This option controls the fanout of hierarchical implementations
359 of RCU, allowing RCU to work efficiently on machines with
360 large numbers of CPUs. This value must be at least the cube
361 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
362 systems and up to 262,144 for 64-bit systems.
363
364 Select a specific number if testing RCU itself.
365 Take the default if unsure.
366
367config RCU_FANOUT_EXACT
368 bool "Disable tree-based hierarchical RCU auto-balancing"
369 depends on TREE_RCU
370 default n
371 help
372 This option forces use of the exact RCU_FANOUT value specified,
373 regardless of imbalances in the hierarchy. This is useful for
374 testing RCU itself, and might one day be useful on systems with
375 strong NUMA behavior.
376
377 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
378
379 Say N if unsure.
380
381config TREE_RCU_TRACE
382 def_bool RCU_TRACE && TREE_RCU
383 select DEBUG_FS
384 help
385 This option provides tracing for the TREE_RCU implementation,
386 permitting Makefile to trivially select kernel/rcutree_trace.c.
387
388config PREEMPT_RCU_TRACE
389 def_bool RCU_TRACE && PREEMPT_RCU
390 select DEBUG_FS
391 help
392 This option provides tracing for the PREEMPT_RCU implementation,
393 permitting Makefile to trivially select kernel/rcupreempt_trace.c.
394
395endmenu # "RCU Subsystem"
396
1da177e4 397config IKCONFIG
f2443ab6 398 tristate "Kernel .config support"
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399 ---help---
400 This option enables the complete Linux kernel ".config" file
401 contents to be saved in the kernel. It provides documentation
402 of which kernel options are used in a running kernel or in an
403 on-disk kernel. This information can be extracted from the kernel
404 image file with the script scripts/extract-ikconfig and used as
405 input to rebuild the current kernel or to build another kernel.
406 It can also be extracted from a running kernel by reading
407 /proc/config.gz if enabled (below).
408
409config IKCONFIG_PROC
410 bool "Enable access to .config through /proc/config.gz"
411 depends on IKCONFIG && PROC_FS
412 ---help---
413 This option enables access to the kernel configuration file
414 through /proc/config.gz.
415
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416config LOG_BUF_SHIFT
417 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
418 range 12 21
f17a32e9 419 default 17
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420 help
421 Select kernel log buffer size as a power of 2.
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422 Examples:
423 17 => 128 KB
424 16 => 64 KB
425 15 => 32 KB
426 14 => 16 KB
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427 13 => 8 KB
428 12 => 4 KB
429
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430#
431# Architectures with an unreliable sched_clock() should select this:
432#
433config HAVE_UNSTABLE_SCHED_CLOCK
434 bool
435
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436config GROUP_SCHED
437 bool "Group CPU scheduler"
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438 depends on EXPERIMENTAL
439 default n
29f59db3 440 help
fb615581 441 This feature lets CPU scheduler recognize task groups and control CPU
9b5b7751 442 bandwidth allocation to such task groups.
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443 In order to create a group from arbitrary set of processes, use
444 CONFIG_CGROUPS. (See Control Group support.)
29f59db3 445
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446config FAIR_GROUP_SCHED
447 bool "Group scheduling for SCHED_OTHER"
448 depends on GROUP_SCHED
aac6abca 449 default GROUP_SCHED
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450
451config RT_GROUP_SCHED
452 bool "Group scheduling for SCHED_RR/FIFO"
453 depends on EXPERIMENTAL
454 depends on GROUP_SCHED
455 default n
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456 help
457 This feature lets you explicitly allocate real CPU bandwidth
458 to users or control groups (depending on the "Basis for grouping tasks"
459 setting below. If enabled, it will also make it impossible to
460 schedule realtime tasks for non-root users until you allocate
461 realtime bandwidth for them.
2fe401e3 462 See Documentation/scheduler/sched-rt-group.txt for more information.
052f1dc7 463
24e377a8 464choice
052f1dc7 465 depends on GROUP_SCHED
24e377a8 466 prompt "Basis for grouping tasks"
052f1dc7 467 default USER_SCHED
24e377a8 468
052f1dc7 469config USER_SCHED
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470 bool "user id"
471 help
472 This option will choose userid as the basis for grouping
473 tasks, thus providing equal CPU bandwidth to each user.
24e377a8 474
052f1dc7 475config CGROUP_SCHED
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476 bool "Control groups"
477 depends on CGROUPS
478 help
479 This option allows you to create arbitrary task groups
480 using the "cgroup" pseudo filesystem and control
481 the cpu bandwidth allocated to each such task group.
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482 Refer to Documentation/cgroups/cgroups.txt for more
483 information on "cgroup" pseudo filesystem.
68318b8e 484
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485endchoice
486
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487menuconfig CGROUPS
488 boolean "Control Group support"
5cdc38f9 489 help
23964d2d 490 This option adds support for grouping sets of processes together, for
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491 use with process control subsystems such as Cpusets, CFS, memory
492 controls or device isolation.
493 See
5cdc38f9 494 - Documentation/scheduler/sched-design-CFS.txt (CFS)
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495 - Documentation/cgroups/ (features for grouping, isolation
496 and resource control)
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497
498 Say N if unsure.
499
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500if CGROUPS
501
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502config CGROUP_DEBUG
503 bool "Example debug cgroup subsystem"
504 depends on CGROUPS
505 default n
506 help
507 This option enables a simple cgroup subsystem that
508 exports useful debugging information about the cgroups
23964d2d 509 framework.
5cdc38f9 510
23964d2d 511 Say N if unsure.
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512
513config CGROUP_NS
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514 bool "Namespace cgroup subsystem"
515 depends on CGROUPS
516 help
517 Provides a simple namespace cgroup subsystem to
518 provide hierarchical naming of sets of namespaces,
519 for instance virtual servers and checkpoint/restart
520 jobs.
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521
522config CGROUP_FREEZER
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523 bool "Freezer cgroup subsystem"
524 depends on CGROUPS
525 help
526 Provides a way to freeze and unfreeze all tasks in a
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527 cgroup.
528
529config CGROUP_DEVICE
530 bool "Device controller for cgroups"
531 depends on CGROUPS && EXPERIMENTAL
532 help
533 Provides a cgroup implementing whitelists for devices which
534 a process in the cgroup can mknod or open.
535
536config CPUSETS
537 bool "Cpuset support"
db7f47cf 538 depends on CGROUPS
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539 help
540 This option will let you create and manage CPUSETs which
541 allow dynamically partitioning a system into sets of CPUs and
542 Memory Nodes and assigning tasks to run only within those sets.
543 This is primarily useful on large SMP or NUMA systems.
544
545 Say N if unsure.
546
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547config PROC_PID_CPUSET
548 bool "Include legacy /proc/<pid>/cpuset file"
549 depends on CPUSETS
550 default y
551
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552config CGROUP_CPUACCT
553 bool "Simple CPU accounting cgroup subsystem"
554 depends on CGROUPS
555 help
556 Provides a simple Resource Controller for monitoring the
23964d2d 557 total CPU consumed by the tasks in a cgroup.
d842de87 558
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559config RESOURCE_COUNTERS
560 bool "Resource counters"
561 help
562 This option enables controller independent resource accounting
23964d2d 563 infrastructure that works with cgroups.
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564 depends on CGROUPS
565
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566config CGROUP_MEM_RES_CTLR
567 bool "Memory Resource Controller for Control Groups"
568 depends on CGROUPS && RESOURCE_COUNTERS
cf475ad2 569 select MM_OWNER
00f0b825 570 help
84ad6d70 571 Provides a memory resource controller that manages both anonymous
21acb9ca 572 memory and page cache. (See Documentation/cgroups/memory.txt)
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573
574 Note that setting this option increases fixed memory overhead
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575 associated with each page of memory in the system. By this,
576 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
577 usage tracking struct at boot. Total amount of this is printed out
578 at boot.
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579
580 Only enable when you're ok with these trade offs and really
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581 sure you need the memory resource controller. Even when you enable
582 this, you can set "cgroup_disable=memory" at your boot option to
583 disable memory resource controller and you can avoid overheads.
c9d5409f 584 (and lose benefits of memory resource controller)
00f0b825 585
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586 This config option also selects MM_OWNER config option, which
587 could in turn add some fork/exit overhead.
588
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589config CGROUP_MEM_RES_CTLR_SWAP
590 bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
591 depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
592 help
593 Add swap management feature to memory resource controller. When you
594 enable this, you can limit mem+swap usage per cgroup. In other words,
595 when you disable this, memory resource controller has no cares to
596 usage of swap...a process can exhaust all of the swap. This extension
597 is useful when you want to avoid exhaustion swap but this itself
598 adds more overheads and consumes memory for remembering information.
599 Especially if you use 32bit system or small memory system, please
600 be careful about enabling this. When memory resource controller
601 is disabled by boot option, this will be automatically disabled and
602 there will be no overhead from this. Even when you set this config=y,
603 if boot option "noswapaccount" is set, swap will not be accounted.
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604 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
605 size is 4096bytes, 512k per 1Gbytes of swap.
c077719b 606
23964d2d 607endif # CGROUPS
c077719b 608
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609config MM_OWNER
610 bool
5cdc38f9 611
88a22c98 612config SYSFS_DEPRECATED
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613 bool
614
615config SYSFS_DEPRECATED_V2
f6ee649f 616 bool "remove sysfs features which may confuse old userspace tools"
9148fe87 617 depends on SYSFS
f6ee649f 618 default n
d47846c5 619 select SYSFS_DEPRECATED
88a22c98 620 help
fce3e804 621 This option switches the layout of sysfs to the deprecated
f6ee649f 622 version. Do not use it on recent distributions.
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623
624 The current sysfs layout features a unified device tree at
625 /sys/devices/, which is able to express a hierarchy between
626 class devices. If the deprecated option is set to Y, the
627 unified device tree is split into a bus device tree at
628 /sys/devices/ and several individual class device trees at
629 /sys/class/. The class and bus devices will be connected by
630 "<subsystem>:<name>" and the "device" links. The "block"
631 class devices, will not show up in /sys/class/block/. Some
632 subsystems will suppress the creation of some devices which
633 depend on the unified device tree.
634
635 This option is not a pure compatibility option that can
636 be safely enabled on newer distributions. It will change the
637 layout of sysfs to the non-extensible deprecated version,
638 and disable some features, which can not be exported without
639 confusing older userspace tools. Since 2007/2008 all major
640 distributions do not enable this option, and ship no tools which
641 depend on the deprecated layout or this option.
642
643 If you are using a new kernel on an older distribution, or use
644 older userspace tools, you might need to say Y here. Do not say Y,
645 if the original kernel, that came with your distribution, has
646 this option set to N.
88a22c98 647
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648config RELAY
649 bool "Kernel->user space relay support (formerly relayfs)"
650 help
651 This option enables support for relay interface support in
652 certain file systems (such as debugfs).
653 It is designed to provide an efficient mechanism for tools and
654 facilities to relay large amounts of data from kernel space to
655 user space.
656
657 If unsure, say N.
658
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PE
659config NAMESPACES
660 bool "Namespaces support" if EMBEDDED
661 default !EMBEDDED
662 help
663 Provides the way to make tasks work with different objects using
664 the same id. For example same IPC id may refer to different objects
665 or same user id or pid may refer to different tasks when used in
666 different namespaces.
667
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PE
668config UTS_NS
669 bool "UTS namespace"
670 depends on NAMESPACES
671 help
672 In this namespace tasks see different info provided with the
673 uname() system call
674
ae5e1b22
PE
675config IPC_NS
676 bool "IPC namespace"
614b84cf 677 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
ae5e1b22
PE
678 help
679 In this namespace tasks work with IPC ids which correspond to
614b84cf 680 different IPC objects in different namespaces.
ae5e1b22 681
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PE
682config USER_NS
683 bool "User namespace (EXPERIMENTAL)"
684 depends on NAMESPACES && EXPERIMENTAL
685 help
686 This allows containers, i.e. vservers, to use user namespaces
687 to provide different user info for different servers.
688 If unsure, say N.
689
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PE
690config PID_NS
691 bool "PID Namespaces (EXPERIMENTAL)"
692 default n
693 depends on NAMESPACES && EXPERIMENTAL
694 help
12d2b8f9 695 Support process id namespaces. This allows having multiple
692105b8 696 processes with the same pid as long as they are in different
74bd59bb
PE
697 pid namespaces. This is a building block of containers.
698
699 Unless you want to work with an experimental feature
700 say N here.
701
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MH
702config NET_NS
703 bool "Network namespace"
704 default n
705 depends on NAMESPACES && EXPERIMENTAL && NET
706 help
707 Allow user space to create what appear to be multiple instances
708 of the network stack.
709
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DG
710config BLK_DEV_INITRD
711 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
712 depends on BROKEN || !FRV
713 help
714 The initial RAM filesystem is a ramfs which is loaded by the
715 boot loader (loadlin or lilo) and that is mounted as root
716 before the normal boot procedure. It is typically used to
717 load modules needed to mount the "real" root file system,
718 etc. See <file:Documentation/initrd.txt> for details.
719
720 If RAM disk support (BLK_DEV_RAM) is also included, this
721 also enables initial RAM disk (initrd) support and adds
722 15 Kbytes (more on some other architectures) to the kernel size.
723
724 If unsure say Y.
725
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JPS
726if BLK_DEV_INITRD
727
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SR
728source "usr/Kconfig"
729
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JPS
730endif
731
c45b4f1f 732config CC_OPTIMIZE_FOR_SIZE
96fffeb4 733 bool "Optimize for size"
c45b4f1f 734 default y
c45b4f1f
LT
735 help
736 Enabling this option will pass "-Os" instead of "-O2" to gcc
737 resulting in a smaller kernel.
738
775a7229 739 If unsure, say Y.
c45b4f1f 740
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RD
741config SYSCTL
742 bool
743
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RD
744config ANON_INODES
745 bool
746
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LT
747menuconfig EMBEDDED
748 bool "Configure standard kernel features (for small systems)"
749 help
750 This option allows certain base kernel options and settings
751 to be disabled or tweaked. This is for specialized
752 environments which can tolerate a "non-standard" kernel.
753 Only use this if you really know what you are doing.
754
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CE
755config UID16
756 bool "Enable 16-bit UID system calls" if EMBEDDED
09337f50 757 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
ae81f9e3
CE
758 default y
759 help
760 This enables the legacy 16-bit UID syscall wrappers.
761
b89a8171 762config SYSCTL_SYSCALL
0847062a 763 bool "Sysctl syscall support" if EMBEDDED
13bb7e37 764 default y
b89a8171 765 select SYSCTL
ae81f9e3 766 ---help---
13bb7e37
EB
767 sys_sysctl uses binary paths that have been found challenging
768 to properly maintain and use. The interface in /proc/sys
769 using paths with ascii names is now the primary path to this
770 information.
b89a8171 771
13bb7e37
EB
772 Almost nothing using the binary sysctl interface so if you are
773 trying to save some space it is probably safe to disable this,
774 making your kernel marginally smaller.
b89a8171 775
13bb7e37 776 If unsure say Y here.
ae81f9e3 777
1da177e4 778config KALLSYMS
979c6a1e 779 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
1da177e4
LT
780 default y
781 help
782 Say Y here to let the kernel print out symbolic crash information and
783 symbolic stack backtraces. This increases the size of the kernel
784 somewhat, as all symbols have to be loaded into the kernel image.
785
786config KALLSYMS_ALL
787 bool "Include all symbols in kallsyms"
788 depends on DEBUG_KERNEL && KALLSYMS
789 help
790 Normally kallsyms only contains the symbols of functions, for nicer
791 OOPS messages. Some debuggers can use kallsyms for other
f9f97bc0
JJ
792 symbols too: say Y here to include all symbols, if you need them
793 and you don't care about adding 300k to the size of your kernel.
1da177e4
LT
794
795 Say N.
796
797config KALLSYMS_EXTRA_PASS
798 bool "Do an extra kallsyms pass"
799 depends on KALLSYMS
800 help
801 If kallsyms is not working correctly, the build will fail with
802 inconsistent kallsyms data. If that occurs, log a bug report and
803 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
804 Always say N here unless you find a bug in kallsyms, which must be
805 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
806 you wait for kallsyms to be fixed.
807
d59745ce 808
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GKH
809config HOTPLUG
810 bool "Support for hot-pluggable devices" if EMBEDDED
811 default y
812 help
813 This option is provided for the case where no hotplug or uevent
814 capabilities is wanted by the kernel. You should only consider
815 disabling this option for embedded systems that do not use modules, a
816 dynamic /dev tree, or dynamic device discovery. Just say Y.
817
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MM
818config PRINTK
819 default y
820 bool "Enable support for printk" if EMBEDDED
821 help
822 This option enables normal printk support. Removing it
823 eliminates most of the message strings from the kernel image
824 and makes the kernel more or less silent. As this makes it
825 very difficult to diagnose system problems, saying N here is
826 strongly discouraged.
827
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MM
828config BUG
829 bool "BUG() support" if EMBEDDED
830 default y
831 help
832 Disabling this option eliminates support for BUG and WARN, reducing
833 the size of your kernel image and potentially quietly ignoring
834 numerous fatal conditions. You should only consider disabling this
835 option for embedded systems with no facilities for reporting errors.
836 Just say Y.
837
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MM
838config ELF_CORE
839 default y
840 bool "Enable ELF core dumps" if EMBEDDED
841 help
842 Enable support for generating core dumps. Disabling saves about 4k.
843
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SS
844config PCSPKR_PLATFORM
845 bool "Enable PC-Speaker support" if EMBEDDED
846 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
847 default y
848 help
849 This option allows to disable the internal PC-Speaker
850 support, saving some memory.
851
1da177e4
LT
852config BASE_FULL
853 default y
854 bool "Enable full-sized data structures for core" if EMBEDDED
855 help
856 Disabling this option reduces the size of miscellaneous core
857 kernel data structures. This saves memory on small machines,
858 but may reduce performance.
859
860config FUTEX
861 bool "Enable futex support" if EMBEDDED
862 default y
23f78d4a 863 select RT_MUTEXES
1da177e4
LT
864 help
865 Disabling this option will cause the kernel to be built without
866 support for "fast userspace mutexes". The resulting kernel may not
867 run glibc-based applications correctly.
868
869config EPOLL
870 bool "Enable eventpoll support" if EMBEDDED
871 default y
448e3cee 872 select ANON_INODES
1da177e4
LT
873 help
874 Disabling this option will cause the kernel to be built without
875 support for epoll family of system calls.
876
fba2afaa
DL
877config SIGNALFD
878 bool "Enable signalfd() system call" if EMBEDDED
448e3cee 879 select ANON_INODES
fba2afaa
DL
880 default y
881 help
882 Enable the signalfd() system call that allows to receive signals
883 on a file descriptor.
884
885 If unsure, say Y.
886
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DL
887config TIMERFD
888 bool "Enable timerfd() system call" if EMBEDDED
448e3cee 889 select ANON_INODES
b215e283
DL
890 default y
891 help
892 Enable the timerfd() system call that allows to receive timer
893 events on a file descriptor.
894
895 If unsure, say Y.
896
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DL
897config EVENTFD
898 bool "Enable eventfd() system call" if EMBEDDED
448e3cee 899 select ANON_INODES
e1ad7468
DL
900 default y
901 help
902 Enable the eventfd() system call that allows to receive both
903 kernel notification (ie. KAIO) or userspace notifications.
904
905 If unsure, say Y.
906
1da177e4
LT
907config SHMEM
908 bool "Use full shmem filesystem" if EMBEDDED
909 default y
910 depends on MMU
911 help
912 The shmem is an internal filesystem used to manage shared memory.
913 It is backed by swap and manages resource limits. It is also exported
914 to userspace as tmpfs if TMPFS is enabled. Disabling this
915 option replaces shmem and tmpfs with the much simpler ramfs code,
916 which may be appropriate on small systems without swap.
917
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TP
918config AIO
919 bool "Enable AIO support" if EMBEDDED
920 default y
921 help
922 This option enables POSIX asynchronous I/O which may by used
923 by some high performance threaded applications. Disabling
924 this option saves about 7k.
925
0793a61d
TG
926config HAVE_PERF_COUNTERS
927 bool
018df72d
MF
928 help
929 See tools/perf/design.txt for details.
0793a61d
TG
930
931menu "Performance Counters"
932
933config PERF_COUNTERS
934 bool "Kernel Performance Counters"
f2654260 935 default y if PROFILING
0793a61d 936 depends on HAVE_PERF_COUNTERS
4c59e467 937 select ANON_INODES
0793a61d
TG
938 help
939 Enable kernel support for performance counter hardware.
940
941 Performance counters are special hardware registers available
942 on most modern CPUs. These registers count the number of certain
943 types of hw events: such as instructions executed, cachemisses
944 suffered, or branches mis-predicted - without slowing down the
945 kernel or applications. These registers can also trigger interrupts
946 when a threshold number of events have passed - and can thus be
947 used to profile the code that runs on that CPU.
948
949 The Linux Performance Counter subsystem provides an abstraction of
950 these hardware capabilities, available via a system call. It
951 provides per task and per CPU counters, and it provides event
952 capabilities on top of those.
953
954 Say Y if unsure.
955
e077df4f 956config EVENT_PROFILE
470a1396 957 bool "Tracepoint profiling sources"
d4d7d0b9 958 depends on PERF_COUNTERS && EVENT_TRACING
e077df4f 959 default y
470a1396
PZ
960 help
961 Allow the use of tracepoints as software performance counters.
962
963 When this is enabled, you can create perf counters based on
964 tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID
965 found in debugfs://tracing/events/*/*/id. (The -e/--events
966 option to the perf tool can parse and interpret symbolic
967 tracepoints, in the subsystem:tracepoint_name format.)
e077df4f 968
0793a61d
TG
969endmenu
970
f8891e5e
CL
971config VM_EVENT_COUNTERS
972 default y
973 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
974 help
2aea4fb6
PJ
975 VM event counters are needed for event counts to be shown.
976 This option allows the disabling of the VM event counters
977 on EMBEDDED systems. /proc/vmstat will only show page counts
978 if VM event counters are disabled.
f8891e5e 979
3d137310
TP
980config PCI_QUIRKS
981 default y
61cfc7e4
GU
982 bool "Enable PCI quirk workarounds" if EMBEDDED
983 depends on PCI
3d137310
TP
984 help
985 This enables workarounds for various PCI chipset
986 bugs/quirks. Disable this only if your target machine is
987 unaffected by PCI quirks.
988
41ecc55b
CL
989config SLUB_DEBUG
990 default y
991 bool "Enable SLUB debugging support" if EMBEDDED
f6acb635 992 depends on SLUB && SYSFS
41ecc55b
CL
993 help
994 SLUB has extensive debug support features. Disabling these can
995 result in significant savings in code size. This also disables
996 SLUB sysfs support. /sys/slab will not exist and there will be
997 no support for cache validation etc.
998
a9eb5223
RD
999config STRIP_ASM_SYMS
1000 bool "Strip assembler-generated symbols during link"
1001 default n
1002 help
1003 Strip internal assembler-generated symbols during a link (symbols
1004 that look like '.Lxxx') so they don't pollute the output of
1005 get_wchan() and suchlike.
1006
b943c460
RD
1007config COMPAT_BRK
1008 bool "Disable heap randomization"
1009 default y
1010 help
1011 Randomizing heap placement makes heap exploits harder, but it
1012 also breaks ancient binaries (including anything libc5 based).
1013 This option changes the bootup default to heap randomization
692105b8 1014 disabled, and can be overridden at runtime by setting
b943c460
RD
1015 /proc/sys/kernel/randomize_va_space to 2.
1016
1017 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1018
81819f0f
CL
1019choice
1020 prompt "Choose SLAB allocator"
a0acd820 1021 default SLUB
81819f0f
CL
1022 help
1023 This option allows to select a slab allocator.
1024
1025config SLAB
1026 bool "SLAB"
1027 help
1028 The regular slab allocator that is established and known to work
34013886 1029 well in all environments. It organizes cache hot objects in
02f56210 1030 per cpu and per node queues.
81819f0f
CL
1031
1032config SLUB
81819f0f
CL
1033 bool "SLUB (Unqueued Allocator)"
1034 help
1035 SLUB is a slab allocator that minimizes cache line usage
1036 instead of managing queues of cached objects (SLAB approach).
1037 Per cpu caching is realized using slabs of objects instead
1038 of queues of objects. SLUB can use memory efficiently
02f56210
SA
1039 and has enhanced diagnostics. SLUB is the default choice for
1040 a slab allocator.
81819f0f
CL
1041
1042config SLOB
84a01c2f 1043 depends on EMBEDDED
81819f0f
CL
1044 bool "SLOB (Simple Allocator)"
1045 help
37291458
MM
1046 SLOB replaces the stock allocator with a drastically simpler
1047 allocator. SLOB is generally more space efficient but
1048 does not perform as well on large systems.
81819f0f
CL
1049
1050endchoice
1051
125e5645
MD
1052config PROFILING
1053 bool "Profiling support (EXPERIMENTAL)"
1054 help
1055 Say Y here to enable the extended profiling support mechanisms used
1056 by profilers such as OProfile.
1057
5f87f112
IM
1058#
1059# Place an empty function call at each tracepoint site. Can be
1060# dynamically changed for a probe function.
1061#
97e1c18e 1062config TRACEPOINTS
5f87f112 1063 bool
97e1c18e 1064
125e5645
MD
1065config MARKERS
1066 bool "Activate markers"
91f73f90 1067 select TRACEPOINTS
125e5645
MD
1068 help
1069 Place an empty function call at each marker site. Can be
1070 dynamically changed for a probe function.
1071
fb32e03f
MD
1072source "arch/Kconfig"
1073
07fe7cb7
DH
1074config SLOW_WORK
1075 default n
1c2d008c 1076 bool
07fe7cb7
DH
1077 help
1078 The slow work thread pool provides a number of dynamically allocated
1079 threads that can be used by the kernel to perform operations that
1080 take a relatively long time.
1081
1082 An example of this would be CacheFiles doing a path lookup followed
1083 by a series of mkdirs and a create call, all of which have to touch
1084 disk.
1085
1c2d008c
DH
1086 See Documentation/slow-work.txt.
1087
1da177e4
LT
1088endmenu # General setup
1089
ee7e5516
DB
1090config HAVE_GENERIC_DMA_COHERENT
1091 bool
1092 default n
1093
158a9624
LT
1094config SLABINFO
1095 bool
1096 depends on PROC_FS
0f389ec6 1097 depends on SLAB || SLUB_DEBUG
158a9624
LT
1098 default y
1099
ae81f9e3
CE
1100config RT_MUTEXES
1101 boolean
ae81f9e3 1102
1da177e4
LT
1103config BASE_SMALL
1104 int
1105 default 0 if BASE_FULL
1106 default 1 if !BASE_FULL
1107
66da5733 1108menuconfig MODULES
1da177e4
LT
1109 bool "Enable loadable module support"
1110 help
1111 Kernel modules are small pieces of compiled code which can
1112 be inserted in the running kernel, rather than being
1113 permanently built into the kernel. You use the "modprobe"
1114 tool to add (and sometimes remove) them. If you say Y here,
1115 many parts of the kernel can be built as modules (by
1116 answering M instead of Y where indicated): this is most
1117 useful for infrequently used options which are not required
1118 for booting. For more information, see the man pages for
1119 modprobe, lsmod, modinfo, insmod and rmmod.
1120
1121 If you say Y here, you will need to run "make
1122 modules_install" to put the modules under /lib/modules/
1123 where modprobe can find them (you may need to be root to do
1124 this).
1125
1126 If unsure, say Y.
1127
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RD
1128if MODULES
1129
826e4506
LT
1130config MODULE_FORCE_LOAD
1131 bool "Forced module loading"
826e4506
LT
1132 default n
1133 help
91e37a79
RR
1134 Allow loading of modules without version information (ie. modprobe
1135 --force). Forced module loading sets the 'F' (forced) taint flag and
1136 is usually a really bad idea.
826e4506 1137
1da177e4
LT
1138config MODULE_UNLOAD
1139 bool "Module unloading"
1da177e4
LT
1140 help
1141 Without this option you will not be able to unload any
1142 modules (note that some modules may not be unloadable
f7f5b675
DV
1143 anyway), which makes your kernel smaller, faster
1144 and simpler. If unsure, say Y.
1da177e4
LT
1145
1146config MODULE_FORCE_UNLOAD
1147 bool "Forced module unloading"
1148 depends on MODULE_UNLOAD && EXPERIMENTAL
1149 help
1150 This option allows you to force a module to unload, even if the
1151 kernel believes it is unsafe: the kernel will remove the module
1152 without waiting for anyone to stop using it (using the -f option to
1153 rmmod). This is mainly for kernel developers and desperate users.
1154 If unsure, say N.
1155
1da177e4 1156config MODVERSIONS
0d541643 1157 bool "Module versioning support"
1da177e4
LT
1158 help
1159 Usually, you have to use modules compiled with your kernel.
1160 Saying Y here makes it sometimes possible to use modules
1161 compiled for different kernels, by adding enough information
1162 to the modules to (hopefully) spot any changes which would
1163 make them incompatible with the kernel you are running. If
1164 unsure, say N.
1165
1166config MODULE_SRCVERSION_ALL
1167 bool "Source checksum for all modules"
1da177e4
LT
1168 help
1169 Modules which contain a MODULE_VERSION get an extra "srcversion"
1170 field inserted into their modinfo section, which contains a
1171 sum of the source files which made it. This helps maintainers
1172 see exactly which source was used to build a module (since
1173 others sometimes change the module source without updating
1174 the version). With this option, such a "srcversion" field
1175 will be created for all modules. If unsure, say N.
1176
0b0de144
RD
1177endif # MODULES
1178
98a79d6a
RR
1179config INIT_ALL_POSSIBLE
1180 bool
1181 help
1182 Back when each arch used to define their own cpu_online_map and
1183 cpu_possible_map, some of them chose to initialize cpu_possible_map
1184 with all 1s, and others with all 0s. When they were centralised,
1185 it was better to provide this option than to break all the archs
692105b8 1186 and have several arch maintainers pursuing me down dark alleys.
98a79d6a 1187
1da177e4
LT
1188config STOP_MACHINE
1189 bool
1190 default y
1191 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1192 help
1193 Need stop_machine() primitive.
3a65dfe8 1194
3a65dfe8 1195source "block/Kconfig"
e98c3202
AK
1196
1197config PREEMPT_NOTIFIERS
1198 bool
e260be67 1199