blob: df84625b1373648f0224307f381c2ba24524e2e0 [file] [log] [blame]
Roman Zippel80daa562008-01-14 04:51:16 +01001config ARCH
2 string
3 option env="ARCH"
4
5config KERNELVERSION
6 string
7 option env="KERNELVERSION"
8
Roman Zippelface4372006-06-08 22:12:45 -07009config DEFCONFIG_LIST
10 string
Paolo 'Blaisorblade' Giarrussob2670eac2006-10-19 23:28:23 -070011 depends on !UML
Roman Zippelface4372006-06-08 22:12:45 -070012 option defconfig_list
13 default "/lib/modules/$UNAME_RELEASE/.config"
14 default "/etc/kernel-config"
15 default "/boot/config-$UNAME_RELEASE"
Sam Ravnborg73531902008-05-25 23:03:18 +020016 default "$ARCH_DEFCONFIG"
Roman Zippelface4372006-06-08 22:12:45 -070017 default "arch/$ARCH/defconfig"
18
Al Boldiff0cfc62007-07-31 00:39:23 -070019menu "General setup"
Linus Torvalds1da177e2005-04-16 15:20:36 -070020
21config EXPERIMENTAL
22 bool "Prompt for development and/or incomplete code/drivers"
23 ---help---
24 Some of the various things that Linux supports (such as network
25 drivers, file systems, network protocols, etc.) can be in a state
26 of development where the functionality, stability, or the level of
27 testing is not yet high enough for general use. This is usually
28 known as the "alpha-test" phase among developers. If a feature is
29 currently in alpha-test, then the developers usually discourage
30 uninformed widespread use of this feature by the general public to
31 avoid "Why doesn't this work?" type mail messages. However, active
32 testing and use of these systems is welcomed. Just be aware that it
33 may not meet the normal level of reliability or it may fail to work
34 in some special cases. Detailed bug reports from people familiar
35 with the kernel internals are usually welcomed by the developers
36 (before submitting bug reports, please read the documents
37 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
38 <file:Documentation/BUG-HUNTING>, and
39 <file:Documentation/oops-tracing.txt> in the kernel source).
40
41 This option will also make obsoleted drivers available. These are
42 drivers that have been replaced by something else, and/or are
43 scheduled to be removed in a future kernel release.
44
45 Unless you intend to help test and develop a feature or driver that
46 falls into this category, or you have a situation that requires
47 using these features, you should probably say N here, which will
48 cause the configurator to present you with fewer choices. If
49 you say Y here, you will be offered the choice of using features or
50 drivers that are currently considered to be in the alpha-test phase.
51
Linus Torvalds1da177e2005-04-16 15:20:36 -070052config BROKEN
53 bool
Linus Torvalds1da177e2005-04-16 15:20:36 -070054
55config BROKEN_ON_SMP
56 bool
57 depends on BROKEN || !SMP
58 default y
59
60config LOCK_KERNEL
61 bool
62 depends on SMP || PREEMPT
63 default y
64
65config INIT_ENV_ARG_LIMIT
66 int
Adrian Bunkdd673bc2006-06-30 01:55:51 -070067 default 32 if !UML
68 default 128 if UML
Linus Torvalds1da177e2005-04-16 15:20:36 -070069 help
Randy Dunlap34ad92c2005-10-30 15:01:46 -080070 Maximum of each of the number of arguments and environment
71 variables passed to init from the kernel command line.
Linus Torvalds1da177e2005-04-16 15:20:36 -070072
Linus Torvalds1da177e2005-04-16 15:20:36 -070073
74config LOCALVERSION
75 string "Local version - append to kernel release"
76 help
77 Append an extra string to the end of your kernel version.
78 This will show up when you type uname, for example.
79 The string you set here will be appended after the contents of
80 any files with a filename matching localversion* in your
81 object and source tree, in that order. Your total string can
82 be a maximum of 64 characters.
83
Ryan Andersonaaebf432005-07-31 04:57:49 -040084config LOCALVERSION_AUTO
85 bool "Automatically append version information to the version string"
86 default y
87 help
88 This will try to automatically determine if the current tree is a
Robert P. J. Day6e5a5422007-05-01 23:08:11 +020089 release tree by looking for git tags that belong to the current
90 top of tree revision.
Ryan Andersonaaebf432005-07-31 04:57:49 -040091
92 A string of the format -gxxxxxxxx will be added to the localversion
Robert P. J. Day6e5a5422007-05-01 23:08:11 +020093 if a git-based tree is found. The string generated by this will be
Ryan Andersonaaebf432005-07-31 04:57:49 -040094 appended after any matching localversion* files, and after the value
Robert P. J. Day6e5a5422007-05-01 23:08:11 +020095 set in CONFIG_LOCALVERSION.
Ryan Andersonaaebf432005-07-31 04:57:49 -040096
Robert P. J. Day6e5a5422007-05-01 23:08:11 +020097 (The actual string used here is the first eight characters produced
98 by running the command:
99
100 $ git rev-parse --verify HEAD
101
102 which is done within the script "scripts/setlocalversion".)
Ryan Andersonaaebf432005-07-31 04:57:49 -0400103
Alain Knaff30d65db2009-01-04 22:46:17 +0100104choice
105 prompt "Kernel compression mode"
106 default KERNEL_GZIP
107 help
108 The linux kernel is a kind of self-extracting executable.
109 Several compression algorithms are available, which differ
110 in efficiency, compression and decompression speed.
111 Compression speed is only relevant when building a kernel.
112 Decompression speed is relevant at each boot.
113
114 If you have any problems with bzip2 or lzma compressed
115 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
116 version of this functionality (bzip2 only), for 2.4, was
117 supplied by Christian Ludwig)
118
119 High compression options are mostly useful for users, who
120 are low on disk space (embedded systems), but for whom ram
121 size matters less.
122
123 If in doubt, select 'gzip'
124
125config KERNEL_GZIP
126 bool "Gzip"
127 help
128 The old and tried gzip compression. Its compression ratio is
129 the poorest among the 3 choices; however its speed (both
130 compression and decompression) is the fastest.
131
132config KERNEL_BZIP2
133 bool "Bzip2"
134 help
135 Its compression ratio and speed is intermediate.
136 Decompression speed is slowest among the 3.
137 The kernel size is about 10 per cent smaller with bzip2,
138 in comparison to gzip.
139 Bzip2 uses a large amount of memory. For modern kernels
140 you will need at least 8MB RAM or more for booting.
141
142config KERNEL_LZMA
143 bool "LZMA"
144 help
145 The most recent compression algorithm.
146 Its ratio is best, decompression speed is between the other
147 2. Compression is slowest.
148 The kernel size is about 33 per cent smaller with lzma,
149 in comparison to gzip.
150
151endchoice
152
153
Linus Torvalds1da177e2005-04-16 15:20:36 -0700154config SWAP
155 bool "Support for paging of anonymous memory (swap)"
David Howells93614012006-09-30 20:45:40 +0200156 depends on MMU && BLOCK
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157 default y
158 help
159 This option allows you to choose whether you want to have support
Jesper Juhl92c35042006-01-15 02:40:08 +0100160 for so called swap devices or swap files in your kernel that are
Linus Torvalds1da177e2005-04-16 15:20:36 -0700161 used to provide more virtual memory than the actual RAM present
162 in your computer. If unsure say Y.
163
164config SYSVIPC
165 bool "System V IPC"
Linus Torvalds1da177e2005-04-16 15:20:36 -0700166 ---help---
167 Inter Process Communication is a suite of library functions and
168 system calls which let processes (running programs) synchronize and
169 exchange information. It is generally considered to be a good thing,
170 and some programs won't run unless you say Y here. In particular, if
171 you want to run the DOS emulator dosemu under Linux (read the
172 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
173 you'll need to say Y here.
174
175 You can find documentation about IPC with "info ipc" and also in
176 section 6.4 of the Linux Programmer's Guide, available from
177 <http://www.tldp.org/guides.html>.
178
Eric W. Biedermana5494dc2007-02-14 00:34:06 -0800179config SYSVIPC_SYSCTL
180 bool
181 depends on SYSVIPC
182 depends on SYSCTL
183 default y
184
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185config POSIX_MQUEUE
186 bool "POSIX Message Queues"
187 depends on NET && EXPERIMENTAL
188 ---help---
189 POSIX variant of message queues is a part of IPC. In POSIX message
190 queues every message has a priority which decides about succession
191 of receiving it by a process. If you want to compile and run
192 programs written e.g. for Solaris with use of its POSIX message
Robert P. J. Dayb0e37652007-05-09 07:25:13 +0200193 queues (functions mq_*) say Y here.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194
195 POSIX message queues are visible as a filesystem called 'mqueue'
196 and can be mounted somewhere if you want to do filesystem
197 operations on message queues.
198
199 If unsure, say Y.
200
201config BSD_PROCESS_ACCT
202 bool "BSD Process Accounting"
203 help
204 If you say Y here, a user level program will be able to instruct the
205 kernel (via a special system call) to write process accounting
206 information to a file: whenever a process exits, information about
207 that process will be appended to the file by the kernel. The
208 information includes things such as creation time, owning user,
209 command name, memory usage, controlling terminal etc. (the complete
210 list is in the struct acct in <file:include/linux/acct.h>). It is
211 up to the user level program to do useful things with this
212 information. This is generally a good idea, so say Y.
213
214config BSD_PROCESS_ACCT_V3
215 bool "BSD Process Accounting version 3 file format"
216 depends on BSD_PROCESS_ACCT
217 default n
218 help
219 If you say Y here, the process accounting information is written
220 in a new file format that also logs the process IDs of each
221 process and it's parent. Note that this file format is incompatible
222 with previous v0/v1/v2 file formats, so you will need updated tools
223 for processing it. A preliminary version of these tools is available
S.Çağlar Onur37a4c942008-06-18 11:45:13 +0300224 at <http://www.gnu.org/software/acct/>.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700225
Shailabh Nagarc7572492006-07-14 00:24:40 -0700226config TASKSTATS
227 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
228 depends on NET
229 default n
230 help
231 Export selected statistics for tasks/processes through the
232 generic netlink interface. Unlike BSD process accounting, the
233 statistics are available during the lifetime of tasks/processes as
234 responses to commands. Like BSD accounting, they are sent to user
235 space on task exit.
236
237 Say N if unsure.
238
Shailabh Nagarca74e922006-07-14 00:24:36 -0700239config TASK_DELAY_ACCT
240 bool "Enable per-task delay accounting (EXPERIMENTAL)"
Shailabh Nagar6f449932006-07-14 00:24:41 -0700241 depends on TASKSTATS
Shailabh Nagarca74e922006-07-14 00:24:36 -0700242 help
243 Collect information on time spent by a task waiting for system
244 resources like cpu, synchronous block I/O completion and swapping
245 in pages. Such statistics can help in setting a task's priorities
246 relative to other tasks for cpu, io, rss limits etc.
247
248 Say N if unsure.
249
Alexey Dobriyan18f705f2007-02-10 01:46:44 -0800250config TASK_XACCT
251 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
252 depends on TASKSTATS
253 help
254 Collect extended task accounting data and send the data
255 to userland for processing over the taskstats interface.
256
257 Say N if unsure.
258
259config TASK_IO_ACCOUNTING
260 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
261 depends on TASK_XACCT
262 help
263 Collect information on the number of bytes of storage I/O which this
264 task has caused.
265
266 Say N if unsure.
267
Linus Torvalds1da177e2005-04-16 15:20:36 -0700268config AUDIT
269 bool "Auditing support"
Chris Wright804a6a492005-05-11 10:52:45 +0100270 depends on NET
Linus Torvalds1da177e2005-04-16 15:20:36 -0700271 help
272 Enable auditing infrastructure that can be used with another
273 kernel subsystem, such as SELinux (which requires this for
274 logging of avc messages output). Does not do system-call
275 auditing without CONFIG_AUDITSYSCALL.
276
277config AUDITSYSCALL
278 bool "Enable system-call auditing support"
Yuichi Nakamura1322b9d2007-11-10 19:21:34 +0900279 depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700280 default y if SECURITY_SELINUX
281 help
282 Enable low-overhead system-call auditing infrastructure that
283 can be used independently or with another kernel subsystem,
Amy Griffisf368c07d2006-04-07 16:55:56 -0400284 such as SELinux. To use audit's filesystem watch feature, please
285 ensure that INOTIFY is configured.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700286
Al Viro74c3cbe2007-07-22 08:04:18 -0400287config AUDIT_TREE
288 def_bool y
289 depends on AUDITSYSCALL && INOTIFY
290
Linus Torvalds1da177e2005-04-16 15:20:36 -0700291config IKCONFIG
Ross Birof2443ab2006-09-30 23:27:25 -0700292 tristate "Kernel .config support"
Linus Torvalds1da177e2005-04-16 15:20:36 -0700293 ---help---
294 This option enables the complete Linux kernel ".config" file
295 contents to be saved in the kernel. It provides documentation
296 of which kernel options are used in a running kernel or in an
297 on-disk kernel. This information can be extracted from the kernel
298 image file with the script scripts/extract-ikconfig and used as
299 input to rebuild the current kernel or to build another kernel.
300 It can also be extracted from a running kernel by reading
301 /proc/config.gz if enabled (below).
302
303config IKCONFIG_PROC
304 bool "Enable access to .config through /proc/config.gz"
305 depends on IKCONFIG && PROC_FS
306 ---help---
307 This option enables access to the kernel configuration file
308 through /proc/config.gz.
309
Alistair John Strachan794543a2007-05-08 00:31:15 -0700310config LOG_BUF_SHIFT
311 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
312 range 12 21
Adrian Bunkf17a32e2008-04-29 00:58:58 -0700313 default 17
Alistair John Strachan794543a2007-05-08 00:31:15 -0700314 help
315 Select kernel log buffer size as a power of 2.
Adrian Bunkf17a32e2008-04-29 00:58:58 -0700316 Examples:
317 17 => 128 KB
318 16 => 64 KB
319 15 => 32 KB
320 14 => 16 KB
Alistair John Strachan794543a2007-05-08 00:31:15 -0700321 13 => 8 KB
322 12 => 4 KB
323
Paul Menageddbcc7e2007-10-18 23:39:30 -0700324config CGROUPS
325 bool "Control Group support"
326 help
327 This option will let you use process cgroup subsystems
328 such as Cpusets
329
330 Say N if unsure.
331
Paul Menage006cb992007-10-18 23:39:43 -0700332config CGROUP_DEBUG
333 bool "Example debug cgroup subsystem"
334 depends on CGROUPS
Paul Menage418d7d82008-04-29 01:00:05 -0700335 default n
Paul Menage006cb992007-10-18 23:39:43 -0700336 help
337 This option enables a simple cgroup subsystem that
338 exports useful debugging information about the cgroups
339 framework
340
341 Say N if unsure
342
Serge E. Hallyn858d72e2007-10-18 23:39:45 -0700343config CGROUP_NS
344 bool "Namespace cgroup subsystem"
345 depends on CGROUPS
346 help
347 Provides a simple namespace cgroup subsystem to
348 provide hierarchical naming of sets of namespaces,
349 for instance virtual servers and checkpoint/restart
350 jobs.
351
Matt Helsleydc52ddc2008-10-18 20:27:21 -0700352config CGROUP_FREEZER
353 bool "control group freezer subsystem"
354 depends on CGROUPS
355 help
356 Provides a way to freeze and unfreeze all tasks in a
357 cgroup.
358
Serge E. Hallyn08ce5f12008-04-29 01:00:10 -0700359config CGROUP_DEVICE
360 bool "Device controller for cgroups"
361 depends on CGROUPS && EXPERIMENTAL
362 help
363 Provides a cgroup implementing whitelists for devices which
364 a process in the cgroup can mknod or open.
365
Linus Torvalds1da177e2005-04-16 15:20:36 -0700366config CPUSETS
367 bool "Cpuset support"
Paul Menage8793d852007-10-18 23:39:39 -0700368 depends on SMP && CGROUPS
Linus Torvalds1da177e2005-04-16 15:20:36 -0700369 help
Randy Dunlapd9fd8a62005-07-27 11:45:11 -0700370 This option will let you create and manage CPUSETs which
Linus Torvalds1da177e2005-04-16 15:20:36 -0700371 allow dynamically partitioning a system into sets of CPUs and
372 Memory Nodes and assigning tasks to run only within those sets.
373 This is primarily useful on large SMP or NUMA systems.
374
375 Say N if unsure.
376
Ingo Molnara5574cf2008-05-05 23:19:50 +0200377#
378# Architectures with an unreliable sched_clock() should select this:
379#
380config HAVE_UNSTABLE_SCHED_CLOCK
381 bool
382
Peter Zijlstra052f1dc2008-02-13 15:45:40 +0100383config GROUP_SCHED
384 bool "Group CPU scheduler"
Parag Warudkaraac6abc2008-05-03 20:42:34 -0400385 depends on EXPERIMENTAL
386 default n
Srivatsa Vaddagiri29f59db2007-10-15 17:00:07 +0200387 help
Srivatsa Vaddagirifb615582007-10-15 17:00:12 +0200388 This feature lets CPU scheduler recognize task groups and control CPU
Srivatsa Vaddagiri9b5b7752007-10-15 17:00:09 +0200389 bandwidth allocation to such task groups.
Srivatsa Vaddagiri29f59db2007-10-15 17:00:07 +0200390
Peter Zijlstra052f1dc2008-02-13 15:45:40 +0100391config FAIR_GROUP_SCHED
392 bool "Group scheduling for SCHED_OTHER"
393 depends on GROUP_SCHED
Parag Warudkaraac6abc2008-05-03 20:42:34 -0400394 default GROUP_SCHED
Srivatsa Vaddagiri24e377a2007-10-15 17:00:09 +0200395
Peter Zijlstra052f1dc2008-02-13 15:45:40 +0100396config RT_GROUP_SCHED
397 bool "Group scheduling for SCHED_RR/FIFO"
398 depends on EXPERIMENTAL
399 depends on GROUP_SCHED
400 default n
Viktor Radnaib9b158f2008-04-19 19:45:01 +0200401 help
402 This feature lets you explicitly allocate real CPU bandwidth
403 to users or control groups (depending on the "Basis for grouping tasks"
404 setting below. If enabled, it will also make it impossible to
405 schedule realtime tasks for non-root users until you allocate
406 realtime bandwidth for them.
Adrian Knoth2fe401e2008-11-12 16:23:55 -0800407 See Documentation/scheduler/sched-rt-group.txt for more information.
Peter Zijlstra052f1dc2008-02-13 15:45:40 +0100408
409choice
410 depends on GROUP_SCHED
411 prompt "Basis for grouping tasks"
412 default USER_SCHED
413
414config USER_SCHED
Srivatsa Vaddagirifb615582007-10-15 17:00:12 +0200415 bool "user id"
416 help
417 This option will choose userid as the basis for grouping
418 tasks, thus providing equal CPU bandwidth to each user.
Srivatsa Vaddagiri24e377a2007-10-15 17:00:09 +0200419
Peter Zijlstra052f1dc2008-02-13 15:45:40 +0100420config CGROUP_SCHED
Srivatsa Vaddagiri68318b82007-10-18 23:41:03 -0700421 bool "Control groups"
422 depends on CGROUPS
423 help
424 This option allows you to create arbitrary task groups
425 using the "cgroup" pseudo filesystem and control
426 the cpu bandwidth allocated to each such task group.
427 Refer to Documentation/cgroups.txt for more information
428 on "cgroup" pseudo filesystem.
429
Srivatsa Vaddagiri24e377a2007-10-15 17:00:09 +0200430endchoice
431
Srivatsa Vaddagirid842de82007-12-02 20:04:49 +0100432config CGROUP_CPUACCT
433 bool "Simple CPU accounting cgroup subsystem"
434 depends on CGROUPS
435 help
436 Provides a simple Resource Controller for monitoring the
437 total CPU consumed by the tasks in a cgroup
438
Pavel Emelianove552b662008-02-07 00:13:49 -0800439config RESOURCE_COUNTERS
440 bool "Resource counters"
441 help
442 This option enables controller independent resource accounting
443 infrastructure that works with cgroups
444 depends on CGROUPS
445
Balbir Singhcf475ad2008-04-29 01:00:16 -0700446config MM_OWNER
447 bool
448
Balbir Singh00f0b822008-03-04 14:28:39 -0800449config CGROUP_MEM_RES_CTLR
450 bool "Memory Resource Controller for Control Groups"
451 depends on CGROUPS && RESOURCE_COUNTERS
Balbir Singhcf475ad2008-04-29 01:00:16 -0700452 select MM_OWNER
Balbir Singh00f0b822008-03-04 14:28:39 -0800453 help
KAMEZAWA Hiroyuki84ad6d72008-10-29 14:01:06 -0700454 Provides a memory resource controller that manages both anonymous
455 memory and page cache. (See Documentation/controllers/memory.txt)
Balbir Singh00f0b822008-03-04 14:28:39 -0800456
457 Note that setting this option increases fixed memory overhead
KAMEZAWA Hiroyuki84ad6d72008-10-29 14:01:06 -0700458 associated with each page of memory in the system. By this,
459 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
460 usage tracking struct at boot. Total amount of this is printed out
461 at boot.
Balbir Singh00f0b822008-03-04 14:28:39 -0800462
463 Only enable when you're ok with these trade offs and really
KAMEZAWA Hiroyuki84ad6d72008-10-29 14:01:06 -0700464 sure you need the memory resource controller. Even when you enable
465 this, you can set "cgroup_disable=memory" at your boot option to
466 disable memory resource controller and you can avoid overheads.
467 (and lose benefits of memory resource contoller)
Balbir Singh00f0b822008-03-04 14:28:39 -0800468
Balbir Singhcf475ad2008-04-29 01:00:16 -0700469 This config option also selects MM_OWNER config option, which
470 could in turn add some fork/exit overhead.
471
Kay Sievers88a22c92006-09-14 11:23:28 +0200472config SYSFS_DEPRECATED
Ingo Molnard47846c2008-03-04 14:54:47 +0100473 bool
474
475config SYSFS_DEPRECATED_V2
Kay Sievers88a22c92006-09-14 11:23:28 +0200476 bool "Create deprecated sysfs files"
Randy Dunlap9148fe82007-12-31 10:05:34 -0800477 depends on SYSFS
Kay Sievers88a22c92006-09-14 11:23:28 +0200478 default y
Ingo Molnard47846c2008-03-04 14:54:47 +0100479 select SYSFS_DEPRECATED
Kay Sievers88a22c92006-09-14 11:23:28 +0200480 help
481 This option creates deprecated symlinks such as the
482 "device"-link, the <subsystem>:<name>-link, and the
483 "bus"-link. It may also add deprecated key in the
484 uevent environment.
485 None of these features or values should be used today, as
486 they export driver core implementation details to userspace
487 or export properties which can't be kept stable across kernel
488 releases.
489
490 If enabled, this option will also move any device structures
David Sterba3dde6ad2007-05-09 07:12:20 +0200491 that belong to a class, back into the /sys/class hierarchy, in
Greg Kroah-Hartman024440d2008-03-03 14:47:13 -0800492 order to support older versions of udev and some userspace
493 programs.
Kay Sievers88a22c92006-09-14 11:23:28 +0200494
Greg Kroah-Hartman024440d2008-03-03 14:47:13 -0800495 If you are using a distro with the most recent userspace
496 packages, it should be safe to say N here.
Kay Sievers88a22c92006-09-14 11:23:28 +0200497
Paul Menage8793d852007-10-18 23:39:39 -0700498config PROC_PID_CPUSET
499 bool "Include legacy /proc/<pid>/cpuset file"
500 depends on CPUSETS
501 default y
502
Jens Axboeb86ff9812006-03-23 19:56:55 +0100503config RELAY
504 bool "Kernel->user space relay support (formerly relayfs)"
505 help
506 This option enables support for relay interface support in
507 certain file systems (such as debugfs).
508 It is designed to provide an efficient mechanism for tools and
509 facilities to relay large amounts of data from kernel space to
510 user space.
511
512 If unsure, say N.
513
Pavel Emelyanovc5289a62008-02-08 04:18:19 -0800514config NAMESPACES
515 bool "Namespaces support" if EMBEDDED
516 default !EMBEDDED
517 help
518 Provides the way to make tasks work with different objects using
519 the same id. For example same IPC id may refer to different objects
520 or same user id or pid may refer to different tasks when used in
521 different namespaces.
522
Pavel Emelyanov58bfdd6d2008-02-08 04:18:21 -0800523config UTS_NS
524 bool "UTS namespace"
525 depends on NAMESPACES
526 help
527 In this namespace tasks see different info provided with the
528 uname() system call
529
Pavel Emelyanovae5e1b22008-02-08 04:18:22 -0800530config IPC_NS
531 bool "IPC namespace"
532 depends on NAMESPACES && SYSVIPC
533 help
534 In this namespace tasks work with IPC ids which correspond to
535 different IPC objects in different namespaces
536
Pavel Emelyanovaee16ce2008-02-08 04:18:23 -0800537config USER_NS
538 bool "User namespace (EXPERIMENTAL)"
539 depends on NAMESPACES && EXPERIMENTAL
540 help
541 This allows containers, i.e. vservers, to use user namespaces
542 to provide different user info for different servers.
543 If unsure, say N.
544
Pavel Emelyanov74bd59b2008-02-08 04:18:24 -0800545config PID_NS
546 bool "PID Namespaces (EXPERIMENTAL)"
547 default n
548 depends on NAMESPACES && EXPERIMENTAL
549 help
Heikki Orsila12d2b8f2008-07-06 15:48:02 +0300550 Support process id namespaces. This allows having multiple
Pavel Emelyanov74bd59b2008-02-08 04:18:24 -0800551 process with the same pid as long as they are in different
552 pid namespaces. This is a building block of containers.
553
554 Unless you want to work with an experimental feature
555 say N here.
556
Dimitri Gorokhovikf9916332007-03-06 01:42:17 -0800557config BLK_DEV_INITRD
558 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
559 depends on BROKEN || !FRV
560 help
561 The initial RAM filesystem is a ramfs which is loaded by the
562 boot loader (loadlin or lilo) and that is mounted as root
563 before the normal boot procedure. It is typically used to
564 load modules needed to mount the "real" root file system,
565 etc. See <file:Documentation/initrd.txt> for details.
566
567 If RAM disk support (BLK_DEV_RAM) is also included, this
568 also enables initial RAM disk (initrd) support and adds
569 15 Kbytes (more on some other architectures) to the kernel size.
570
571 If unsure say Y.
572
Jean-Paul Samanc33df4e2007-02-10 01:44:43 -0800573if BLK_DEV_INITRD
574
Sam Ravnborgdbec4862005-08-10 20:44:50 +0200575source "usr/Kconfig"
576
Jean-Paul Samanc33df4e2007-02-10 01:44:43 -0800577endif
578
Linus Torvaldsc45b4f12005-12-14 18:52:21 -0800579config CC_OPTIMIZE_FOR_SIZE
Ingo Molnar96fffeb2008-04-28 01:39:43 +0200580 bool "Optimize for size"
Linus Torvaldsc45b4f12005-12-14 18:52:21 -0800581 default y
Linus Torvaldsc45b4f12005-12-14 18:52:21 -0800582 help
583 Enabling this option will pass "-Os" instead of "-O2" to gcc
584 resulting in a smaller kernel.
585
jkacur775a7222008-07-16 00:31:16 +0200586 If unsure, say Y.
Linus Torvaldsc45b4f12005-12-14 18:52:21 -0800587
Randy Dunlap08470622006-09-30 23:28:13 -0700588config SYSCTL
589 bool
590
Linus Torvalds1da177e2005-04-16 15:20:36 -0700591menuconfig EMBEDDED
592 bool "Configure standard kernel features (for small systems)"
593 help
594 This option allows certain base kernel options and settings
595 to be disabled or tweaked. This is for specialized
596 environments which can tolerate a "non-standard" kernel.
597 Only use this if you really know what you are doing.
598
Chuck Ebbertae81f9e2006-09-16 12:15:53 -0700599config UID16
600 bool "Enable 16-bit UID system calls" if EMBEDDED
David S. Miller09337f52008-04-26 03:17:12 -0700601 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
Chuck Ebbertae81f9e2006-09-16 12:15:53 -0700602 default y
603 help
604 This enables the legacy 16-bit UID syscall wrappers.
605
Eric W. Biedermanb89a8172006-09-27 01:51:04 -0700606config SYSCTL_SYSCALL
Randy Dunlap08470622006-09-30 23:28:13 -0700607 bool "Sysctl syscall support" if EMBEDDED
Eric W. Biederman13bb7e32006-11-08 17:44:51 -0800608 default y
Eric W. Biedermanb89a8172006-09-27 01:51:04 -0700609 select SYSCTL
610 ---help---
Eric W. Biederman13bb7e32006-11-08 17:44:51 -0800611 sys_sysctl uses binary paths that have been found challenging
612 to properly maintain and use. The interface in /proc/sys
613 using paths with ascii names is now the primary path to this
614 information.
Eric W. Biedermanb89a8172006-09-27 01:51:04 -0700615
Eric W. Biederman13bb7e32006-11-08 17:44:51 -0800616 Almost nothing using the binary sysctl interface so if you are
617 trying to save some space it is probably safe to disable this,
618 making your kernel marginally smaller.
Eric W. Biedermanb89a8172006-09-27 01:51:04 -0700619
Eric W. Biederman13bb7e32006-11-08 17:44:51 -0800620 If unsure say Y here.
Chuck Ebbertae81f9e2006-09-16 12:15:53 -0700621
Linus Torvalds1da177e2005-04-16 15:20:36 -0700622config KALLSYMS
Jesper Juhl979c6a12006-12-12 19:25:11 +0100623 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
Linus Torvalds1da177e2005-04-16 15:20:36 -0700624 default y
625 help
626 Say Y here to let the kernel print out symbolic crash information and
627 symbolic stack backtraces. This increases the size of the kernel
628 somewhat, as all symbols have to be loaded into the kernel image.
629
630config KALLSYMS_ALL
631 bool "Include all symbols in kallsyms"
632 depends on DEBUG_KERNEL && KALLSYMS
633 help
634 Normally kallsyms only contains the symbols of functions, for nicer
635 OOPS messages. Some debuggers can use kallsyms for other
Jesper Juhlf9f97bc2005-07-20 05:43:05 +0200636 symbols too: say Y here to include all symbols, if you need them
637 and you don't care about adding 300k to the size of your kernel.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700638
639 Say N.
640
Jan Beulich9bb48242008-12-16 11:30:08 +0000641config KALLSYMS_STRIP_GENERATED
642 bool "Strip machine generated symbols from kallsyms"
643 depends on KALLSYMS_ALL
644 default y
645 help
646 Say N if you want kallsyms to retain even machine generated symbols.
647
Linus Torvalds1da177e2005-04-16 15:20:36 -0700648config KALLSYMS_EXTRA_PASS
649 bool "Do an extra kallsyms pass"
650 depends on KALLSYMS
651 help
652 If kallsyms is not working correctly, the build will fail with
653 inconsistent kallsyms data. If that occurs, log a bug report and
654 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
655 Always say N here unless you find a bug in kallsyms, which must be
656 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
657 you wait for kallsyms to be fixed.
658
Matt Mackalld59745c2005-05-01 08:59:02 -0700659
Greg Kroah-Hartman712f47c2005-11-16 11:27:07 -0800660config HOTPLUG
661 bool "Support for hot-pluggable devices" if EMBEDDED
662 default y
663 help
664 This option is provided for the case where no hotplug or uevent
665 capabilities is wanted by the kernel. You should only consider
666 disabling this option for embedded systems that do not use modules, a
667 dynamic /dev tree, or dynamic device discovery. Just say Y.
668
Matt Mackalld59745c2005-05-01 08:59:02 -0700669config PRINTK
670 default y
671 bool "Enable support for printk" if EMBEDDED
672 help
673 This option enables normal printk support. Removing it
674 eliminates most of the message strings from the kernel image
675 and makes the kernel more or less silent. As this makes it
676 very difficult to diagnose system problems, saying N here is
677 strongly discouraged.
678
Matt Mackallc8538a72005-05-01 08:59:01 -0700679config BUG
680 bool "BUG() support" if EMBEDDED
681 default y
682 help
683 Disabling this option eliminates support for BUG and WARN, reducing
684 the size of your kernel image and potentially quietly ignoring
685 numerous fatal conditions. You should only consider disabling this
686 option for embedded systems with no facilities for reporting errors.
687 Just say Y.
688
Matt Mackall708e9a72006-01-08 01:05:25 -0800689config ELF_CORE
690 default y
691 bool "Enable ELF core dumps" if EMBEDDED
692 help
693 Enable support for generating core dumps. Disabling saves about 4k.
694
Stas Sergeeve5e1d3c2008-05-07 12:39:56 +0200695config PCSPKR_PLATFORM
696 bool "Enable PC-Speaker support" if EMBEDDED
697 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
698 default y
699 help
700 This option allows to disable the internal PC-Speaker
701 support, saving some memory.
702
Ingo Molnar32a93232008-02-06 22:39:44 +0100703config COMPAT_BRK
704 bool "Disable heap randomization"
705 default y
706 help
707 Randomizing heap placement makes heap exploits harder, but it
708 also breaks ancient binaries (including anything libc5 based).
709 This option changes the bootup default to heap randomization
710 disabled, and can be overriden runtime by setting
711 /proc/sys/kernel/randomize_va_space to 2.
712
Ingo Molnar166124f2008-02-09 23:24:09 +0100713 On non-ancient distros (post-2000 ones) N is usually a safe choice.
Ingo Molnar32a93232008-02-06 22:39:44 +0100714
Linus Torvalds1da177e2005-04-16 15:20:36 -0700715config BASE_FULL
716 default y
717 bool "Enable full-sized data structures for core" if EMBEDDED
718 help
719 Disabling this option reduces the size of miscellaneous core
720 kernel data structures. This saves memory on small machines,
721 but may reduce performance.
722
723config FUTEX
724 bool "Enable futex support" if EMBEDDED
725 default y
Ingo Molnar23f78d4a2006-06-27 02:54:53 -0700726 select RT_MUTEXES
Linus Torvalds1da177e2005-04-16 15:20:36 -0700727 help
728 Disabling this option will cause the kernel to be built without
729 support for "fast userspace mutexes". The resulting kernel may not
730 run glibc-based applications correctly.
731
Davide Libenzi5dc8bf82007-05-10 22:23:11 -0700732config ANON_INODES
Adrian Bunk448e3ce2007-07-31 00:39:10 -0700733 bool
Davide Libenzi5dc8bf82007-05-10 22:23:11 -0700734
Linus Torvalds1da177e2005-04-16 15:20:36 -0700735config EPOLL
736 bool "Enable eventpoll support" if EMBEDDED
737 default y
Adrian Bunk448e3ce2007-07-31 00:39:10 -0700738 select ANON_INODES
Linus Torvalds1da177e2005-04-16 15:20:36 -0700739 help
740 Disabling this option will cause the kernel to be built without
741 support for epoll family of system calls.
742
Davide Libenzifba2afa2007-05-10 22:23:13 -0700743config SIGNALFD
744 bool "Enable signalfd() system call" if EMBEDDED
Adrian Bunk448e3ce2007-07-31 00:39:10 -0700745 select ANON_INODES
Davide Libenzifba2afa2007-05-10 22:23:13 -0700746 default y
747 help
748 Enable the signalfd() system call that allows to receive signals
749 on a file descriptor.
750
751 If unsure, say Y.
752
Davide Libenzib215e282007-05-10 22:23:16 -0700753config TIMERFD
754 bool "Enable timerfd() system call" if EMBEDDED
Adrian Bunk448e3ce2007-07-31 00:39:10 -0700755 select ANON_INODES
Davide Libenzib215e282007-05-10 22:23:16 -0700756 default y
757 help
758 Enable the timerfd() system call that allows to receive timer
759 events on a file descriptor.
760
761 If unsure, say Y.
762
Davide Libenzie1ad7462007-05-10 22:23:19 -0700763config EVENTFD
764 bool "Enable eventfd() system call" if EMBEDDED
Adrian Bunk448e3ce2007-07-31 00:39:10 -0700765 select ANON_INODES
Davide Libenzie1ad7462007-05-10 22:23:19 -0700766 default y
767 help
768 Enable the eventfd() system call that allows to receive both
769 kernel notification (ie. KAIO) or userspace notifications.
770
771 If unsure, say Y.
772
Linus Torvalds1da177e2005-04-16 15:20:36 -0700773config SHMEM
774 bool "Use full shmem filesystem" if EMBEDDED
775 default y
776 depends on MMU
777 help
778 The shmem is an internal filesystem used to manage shared memory.
779 It is backed by swap and manages resource limits. It is also exported
780 to userspace as tmpfs if TMPFS is enabled. Disabling this
781 option replaces shmem and tmpfs with the much simpler ramfs code,
782 which may be appropriate on small systems without swap.
783
Thomas Petazzoniebf3f092008-10-15 22:05:12 -0700784config AIO
785 bool "Enable AIO support" if EMBEDDED
786 default y
787 help
788 This option enables POSIX asynchronous I/O which may by used
789 by some high performance threaded applications. Disabling
790 this option saves about 7k.
791
Christoph Lameterf8891e52006-06-30 01:55:45 -0700792config VM_EVENT_COUNTERS
793 default y
794 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
795 help
Paul Jackson2aea4fb2006-12-22 01:06:10 -0800796 VM event counters are needed for event counts to be shown.
797 This option allows the disabling of the VM event counters
798 on EMBEDDED systems. /proc/vmstat will only show page counts
799 if VM event counters are disabled.
Christoph Lameterf8891e52006-06-30 01:55:45 -0700800
Thomas Petazzoni3d137312008-08-19 10:28:24 +0200801config PCI_QUIRKS
802 default y
Geert Uytterhoeven61cfc7e2008-10-22 08:53:25 +0200803 bool "Enable PCI quirk workarounds" if EMBEDDED
804 depends on PCI
Thomas Petazzoni3d137312008-08-19 10:28:24 +0200805 help
806 This enables workarounds for various PCI chipset
807 bugs/quirks. Disable this only if your target machine is
808 unaffected by PCI quirks.
809
Christoph Lameter41ecc552007-05-09 02:32:44 -0700810config SLUB_DEBUG
811 default y
812 bool "Enable SLUB debugging support" if EMBEDDED
Christoph Lameterf6acb632008-04-29 16:16:06 -0700813 depends on SLUB && SYSFS
Christoph Lameter41ecc552007-05-09 02:32:44 -0700814 help
815 SLUB has extensive debug support features. Disabling these can
816 result in significant savings in code size. This also disables
817 SLUB sysfs support. /sys/slab will not exist and there will be
818 no support for cache validation etc.
819
Christoph Lameter81819f02007-05-06 14:49:36 -0700820choice
821 prompt "Choose SLAB allocator"
Christoph Lametera0acd822007-07-17 04:03:32 -0700822 default SLUB
Christoph Lameter81819f02007-05-06 14:49:36 -0700823 help
824 This option allows to select a slab allocator.
825
826config SLAB
827 bool "SLAB"
828 help
829 The regular slab allocator that is established and known to work
Christoph Lameter34013882007-05-09 02:32:47 -0700830 well in all environments. It organizes cache hot objects in
Simon Arlott02f56212008-11-05 22:18:19 +0000831 per cpu and per node queues.
Christoph Lameter81819f02007-05-06 14:49:36 -0700832
833config SLUB
Christoph Lameter81819f02007-05-06 14:49:36 -0700834 bool "SLUB (Unqueued Allocator)"
835 help
836 SLUB is a slab allocator that minimizes cache line usage
837 instead of managing queues of cached objects (SLAB approach).
838 Per cpu caching is realized using slabs of objects instead
839 of queues of objects. SLUB can use memory efficiently
Simon Arlott02f56212008-11-05 22:18:19 +0000840 and has enhanced diagnostics. SLUB is the default choice for
841 a slab allocator.
Christoph Lameter81819f02007-05-06 14:49:36 -0700842
843config SLOB
Paul Mundt84a01c22007-07-15 23:38:24 -0700844 depends on EMBEDDED
Christoph Lameter81819f02007-05-06 14:49:36 -0700845 bool "SLOB (Simple Allocator)"
846 help
Matt Mackall37291452008-02-04 22:29:38 -0800847 SLOB replaces the stock allocator with a drastically simpler
848 allocator. SLOB is generally more space efficient but
849 does not perform as well on large systems.
Christoph Lameter81819f02007-05-06 14:49:36 -0700850
851endchoice
852
Mathieu Desnoyers125e5642008-02-02 15:10:36 -0500853config PROFILING
854 bool "Profiling support (EXPERIMENTAL)"
855 help
856 Say Y here to enable the extended profiling support mechanisms used
857 by profilers such as OProfile.
858
Ingo Molnar5f87f112008-07-23 14:15:22 +0200859#
860# Place an empty function call at each tracepoint site. Can be
861# dynamically changed for a probe function.
862#
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400863config TRACEPOINTS
Ingo Molnar5f87f112008-07-23 14:15:22 +0200864 bool
Mathieu Desnoyers97e1c182008-07-18 12:16:16 -0400865
Mathieu Desnoyers125e5642008-02-02 15:10:36 -0500866config MARKERS
867 bool "Activate markers"
Mathieu Desnoyersc1df1bd2008-11-14 17:47:39 -0500868 depends on TRACEPOINTS
Mathieu Desnoyers125e5642008-02-02 15:10:36 -0500869 help
870 Place an empty function call at each marker site. Can be
871 dynamically changed for a probe function.
872
Mathieu Desnoyersfb32e032008-02-02 15:10:33 -0500873source "arch/Kconfig"
874
Linus Torvalds1da177e2005-04-16 15:20:36 -0700875endmenu # General setup
876
Dmitry Baryshkovee7e5512008-06-29 14:18:46 +0400877config HAVE_GENERIC_DMA_COHERENT
878 bool
879 default n
880
Linus Torvalds158a9622008-01-02 13:04:48 -0800881config SLABINFO
882 bool
883 depends on PROC_FS
Christoph Lameter0f389ec2008-04-14 18:53:02 +0300884 depends on SLAB || SLUB_DEBUG
Linus Torvalds158a9622008-01-02 13:04:48 -0800885 default y
886
Chuck Ebbertae81f9e2006-09-16 12:15:53 -0700887config RT_MUTEXES
888 boolean
889 select PLIST
890
Linus Torvalds1da177e2005-04-16 15:20:36 -0700891config TINY_SHMEM
892 default !SHMEM
893 bool
894
895config BASE_SMALL
896 int
897 default 0 if BASE_FULL
898 default 1 if !BASE_FULL
899
Jan Engelhardt66da5732007-07-15 23:39:29 -0700900menuconfig MODULES
Linus Torvalds1da177e2005-04-16 15:20:36 -0700901 bool "Enable loadable module support"
902 help
903 Kernel modules are small pieces of compiled code which can
904 be inserted in the running kernel, rather than being
905 permanently built into the kernel. You use the "modprobe"
906 tool to add (and sometimes remove) them. If you say Y here,
907 many parts of the kernel can be built as modules (by
908 answering M instead of Y where indicated): this is most
909 useful for infrequently used options which are not required
910 for booting. For more information, see the man pages for
911 modprobe, lsmod, modinfo, insmod and rmmod.
912
913 If you say Y here, you will need to run "make
914 modules_install" to put the modules under /lib/modules/
915 where modprobe can find them (you may need to be root to do
916 this).
917
918 If unsure, say Y.
919
Robert P. J. Day0b0de142008-08-04 13:31:32 -0400920if MODULES
921
Linus Torvalds826e4502008-05-04 17:04:16 -0700922config MODULE_FORCE_LOAD
923 bool "Forced module loading"
Linus Torvalds826e4502008-05-04 17:04:16 -0700924 default n
925 help
Rusty Russell91e37a72008-05-09 16:25:28 +1000926 Allow loading of modules without version information (ie. modprobe
927 --force). Forced module loading sets the 'F' (forced) taint flag and
928 is usually a really bad idea.
Linus Torvalds826e4502008-05-04 17:04:16 -0700929
Linus Torvalds1da177e2005-04-16 15:20:36 -0700930config MODULE_UNLOAD
931 bool "Module unloading"
Linus Torvalds1da177e2005-04-16 15:20:36 -0700932 help
933 Without this option you will not be able to unload any
934 modules (note that some modules may not be unloadable
Denys Vlasenkof7f5b672008-07-22 19:24:26 -0500935 anyway), which makes your kernel smaller, faster
936 and simpler. If unsure, say Y.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700937
938config MODULE_FORCE_UNLOAD
939 bool "Forced module unloading"
940 depends on MODULE_UNLOAD && EXPERIMENTAL
941 help
942 This option allows you to force a module to unload, even if the
943 kernel believes it is unsafe: the kernel will remove the module
944 without waiting for anyone to stop using it (using the -f option to
945 rmmod). This is mainly for kernel developers and desperate users.
946 If unsure, say N.
947
Linus Torvalds1da177e2005-04-16 15:20:36 -0700948config MODVERSIONS
Sam Ravnborg0d541642005-12-26 23:04:02 +0100949 bool "Module versioning support"
Linus Torvalds1da177e2005-04-16 15:20:36 -0700950 help
951 Usually, you have to use modules compiled with your kernel.
952 Saying Y here makes it sometimes possible to use modules
953 compiled for different kernels, by adding enough information
954 to the modules to (hopefully) spot any changes which would
955 make them incompatible with the kernel you are running. If
956 unsure, say N.
957
958config MODULE_SRCVERSION_ALL
959 bool "Source checksum for all modules"
Linus Torvalds1da177e2005-04-16 15:20:36 -0700960 help
961 Modules which contain a MODULE_VERSION get an extra "srcversion"
962 field inserted into their modinfo section, which contains a
963 sum of the source files which made it. This helps maintainers
964 see exactly which source was used to build a module (since
965 others sometimes change the module source without updating
966 the version). With this option, such a "srcversion" field
967 will be created for all modules. If unsure, say N.
968
969config KMOD
Johannes Bergbaabaae2008-07-08 19:00:16 +0200970 def_bool y
Linus Torvalds1da177e2005-04-16 15:20:36 -0700971 help
Johannes Bergbaabaae2008-07-08 19:00:16 +0200972 This is being removed soon. These days, CONFIG_MODULES
973 implies CONFIG_KMOD, so use that instead.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700974
Robert P. J. Day0b0de142008-08-04 13:31:32 -0400975endif # MODULES
976
Rusty Russell98a79d62008-12-13 21:19:41 +1030977config INIT_ALL_POSSIBLE
978 bool
979 help
980 Back when each arch used to define their own cpu_online_map and
981 cpu_possible_map, some of them chose to initialize cpu_possible_map
982 with all 1s, and others with all 0s. When they were centralised,
983 it was better to provide this option than to break all the archs
984 and have several arch maintainers persuing me down dark alleys.
985
Linus Torvalds1da177e2005-04-16 15:20:36 -0700986config STOP_MACHINE
987 bool
988 default y
989 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
990 help
991 Need stop_machine() primitive.
Jens Axboe3a65dfe2005-11-04 08:43:35 +0100992
Jens Axboe3a65dfe2005-11-04 08:43:35 +0100993source "block/Kconfig"
Avi Kivitye98c3202007-10-16 23:27:31 -0700994
995config PREEMPT_NOTIFIERS
996 bool
Paul E. McKenneye260be62008-01-25 21:08:24 +0100997
Ingo Molnar12d79ba2008-12-25 09:31:28 +0100998choice
999 prompt "RCU Implementation"
1000 default CLASSIC_RCU
1001
Paul E. McKenneye260be62008-01-25 21:08:24 +01001002config CLASSIC_RCU
Ingo Molnar12d79ba2008-12-25 09:31:28 +01001003 bool "Classic RCU"
Paul E. McKenneye260be62008-01-25 21:08:24 +01001004 help
1005 This option selects the classic RCU implementation that is
1006 designed for best read-side performance on non-realtime
Ingo Molnar12d79ba2008-12-25 09:31:28 +01001007 systems.
1008
1009 Select this option if you are unsure.
1010
1011config TREE_RCU
1012 bool "Tree-based hierarchical RCU"
1013 help
1014 This option selects the RCU implementation that is
1015 designed for very large SMP system with hundreds or
1016 thousands of CPUs.
1017
1018config PREEMPT_RCU
1019 bool "Preemptible RCU"
1020 depends on PREEMPT
1021 help
1022 This option reduces the latency of the kernel by making certain
1023 RCU sections preemptible. Normally RCU code is non-preemptible, if
1024 this option is selected then read-only RCU sections become
1025 preemptible. This helps latency, but may expose bugs due to
1026 now-naive assumptions about each RCU read-side critical section
1027 remaining on a given CPU through its execution.
1028
1029endchoice
1030
1031config RCU_TRACE
1032 bool "Enable tracing for RCU"
1033 depends on TREE_RCU || PREEMPT_RCU
1034 help
1035 This option provides tracing in RCU which presents stats
1036 in debugfs for debugging RCU implementation.
1037
1038 Say Y here if you want to enable RCU tracing
1039 Say N if you are unsure.
1040
1041config RCU_FANOUT
1042 int "Tree-based hierarchical RCU fanout value"
1043 range 2 64 if 64BIT
1044 range 2 32 if !64BIT
1045 depends on TREE_RCU
1046 default 64 if 64BIT
1047 default 32 if !64BIT
1048 help
1049 This option controls the fanout of hierarchical implementations
1050 of RCU, allowing RCU to work efficiently on machines with
1051 large numbers of CPUs. This value must be at least the cube
1052 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
1053 systems and up to 262,144 for 64-bit systems.
1054
1055 Select a specific number if testing RCU itself.
1056 Take the default if unsure.
1057
1058config RCU_FANOUT_EXACT
1059 bool "Disable tree-based hierarchical RCU auto-balancing"
1060 depends on TREE_RCU
1061 default n
1062 help
1063 This option forces use of the exact RCU_FANOUT value specified,
1064 regardless of imbalances in the hierarchy. This is useful for
1065 testing RCU itself, and might one day be useful on systems with
1066 strong NUMA behavior.
1067
1068 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
1069
1070 Say N if unsure.
1071
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001072config TREE_RCU_TRACE
1073 def_bool RCU_TRACE && TREE_RCU
1074 select DEBUG_FS
Paul E. McKenneye260be62008-01-25 21:08:24 +01001075 help
Paul E. McKenney64db4cf2008-12-18 21:55:32 +01001076 This option provides tracing for the TREE_RCU implementation,
1077 permitting Makefile to trivially select kernel/rcutree_trace.c.
1078
1079config PREEMPT_RCU_TRACE
1080 def_bool RCU_TRACE && PREEMPT_RCU
1081 select DEBUG_FS
1082 help
1083 This option provides tracing for the PREEMPT_RCU implementation,
1084 permitting Makefile to trivially select kernel/rcupreempt_trace.c.