rcu: Mark Hierarchical RCU no longer experimental
[GitHub/mt8127/android_kernel_alcatel_ttab.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47 drivers that have been replaced by something else, and/or are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
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318
319config CLASSIC_RCU
320 bool "Classic RCU"
321 help
322 This option selects the classic RCU implementation that is
323 designed for best read-side performance on non-realtime
324 systems.
325
326 Select this option if you are unsure.
327
328config TREE_RCU
329 bool "Tree-based hierarchical RCU"
330 help
331 This option selects the RCU implementation that is
332 designed for very large SMP system with hundreds or
333 thousands of CPUs.
334
335config PREEMPT_RCU
336 bool "Preemptible RCU"
337 depends on PREEMPT
338 help
339 This option reduces the latency of the kernel by making certain
340 RCU sections preemptible. Normally RCU code is non-preemptible, if
341 this option is selected then read-only RCU sections become
342 preemptible. This helps latency, but may expose bugs due to
343 now-naive assumptions about each RCU read-side critical section
344 remaining on a given CPU through its execution.
345
346endchoice
347
348config RCU_TRACE
349 bool "Enable tracing for RCU"
350 depends on TREE_RCU || PREEMPT_RCU
351 help
352 This option provides tracing in RCU which presents stats
353 in debugfs for debugging RCU implementation.
354
355 Say Y here if you want to enable RCU tracing
356 Say N if you are unsure.
357
358config RCU_FANOUT
359 int "Tree-based hierarchical RCU fanout value"
360 range 2 64 if 64BIT
361 range 2 32 if !64BIT
362 depends on TREE_RCU
363 default 64 if 64BIT
364 default 32 if !64BIT
365 help
366 This option controls the fanout of hierarchical implementations
367 of RCU, allowing RCU to work efficiently on machines with
368 large numbers of CPUs. This value must be at least the cube
369 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
370 systems and up to 262,144 for 64-bit systems.
371
372 Select a specific number if testing RCU itself.
373 Take the default if unsure.
374
375config RCU_FANOUT_EXACT
376 bool "Disable tree-based hierarchical RCU auto-balancing"
377 depends on TREE_RCU
378 default n
379 help
380 This option forces use of the exact RCU_FANOUT value specified,
381 regardless of imbalances in the hierarchy. This is useful for
382 testing RCU itself, and might one day be useful on systems with
383 strong NUMA behavior.
384
385 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
386
387 Say N if unsure.
388
389config TREE_RCU_TRACE
390 def_bool RCU_TRACE && TREE_RCU
391 select DEBUG_FS
392 help
393 This option provides tracing for the TREE_RCU implementation,
394 permitting Makefile to trivially select kernel/rcutree_trace.c.
395
396config PREEMPT_RCU_TRACE
397 def_bool RCU_TRACE && PREEMPT_RCU
398 select DEBUG_FS
399 help
400 This option provides tracing for the PREEMPT_RCU implementation,
401 permitting Makefile to trivially select kernel/rcupreempt_trace.c.
402
403endmenu # "RCU Subsystem"
404
1da177e4 405config IKCONFIG
f2443ab6 406 tristate "Kernel .config support"
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407 ---help---
408 This option enables the complete Linux kernel ".config" file
409 contents to be saved in the kernel. It provides documentation
410 of which kernel options are used in a running kernel or in an
411 on-disk kernel. This information can be extracted from the kernel
412 image file with the script scripts/extract-ikconfig and used as
413 input to rebuild the current kernel or to build another kernel.
414 It can also be extracted from a running kernel by reading
415 /proc/config.gz if enabled (below).
416
417config IKCONFIG_PROC
418 bool "Enable access to .config through /proc/config.gz"
419 depends on IKCONFIG && PROC_FS
420 ---help---
421 This option enables access to the kernel configuration file
422 through /proc/config.gz.
423
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424config LOG_BUF_SHIFT
425 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
426 range 12 21
f17a32e9 427 default 17
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428 help
429 Select kernel log buffer size as a power of 2.
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430 Examples:
431 17 => 128 KB
432 16 => 64 KB
433 15 => 32 KB
434 14 => 16 KB
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435 13 => 8 KB
436 12 => 4 KB
437
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438#
439# Architectures with an unreliable sched_clock() should select this:
440#
441config HAVE_UNSTABLE_SCHED_CLOCK
442 bool
443
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444config GROUP_SCHED
445 bool "Group CPU scheduler"
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446 depends on EXPERIMENTAL
447 default n
29f59db3 448 help
fb615581 449 This feature lets CPU scheduler recognize task groups and control CPU
9b5b7751 450 bandwidth allocation to such task groups.
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451 In order to create a group from arbitrary set of processes, use
452 CONFIG_CGROUPS. (See Control Group support.)
29f59db3 453
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454config FAIR_GROUP_SCHED
455 bool "Group scheduling for SCHED_OTHER"
456 depends on GROUP_SCHED
aac6abca 457 default GROUP_SCHED
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458
459config RT_GROUP_SCHED
460 bool "Group scheduling for SCHED_RR/FIFO"
461 depends on EXPERIMENTAL
462 depends on GROUP_SCHED
463 default n
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464 help
465 This feature lets you explicitly allocate real CPU bandwidth
466 to users or control groups (depending on the "Basis for grouping tasks"
467 setting below. If enabled, it will also make it impossible to
468 schedule realtime tasks for non-root users until you allocate
469 realtime bandwidth for them.
2fe401e3 470 See Documentation/scheduler/sched-rt-group.txt for more information.
052f1dc7 471
24e377a8 472choice
052f1dc7 473 depends on GROUP_SCHED
24e377a8 474 prompt "Basis for grouping tasks"
052f1dc7 475 default USER_SCHED
24e377a8 476
052f1dc7 477config USER_SCHED
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478 bool "user id"
479 help
480 This option will choose userid as the basis for grouping
481 tasks, thus providing equal CPU bandwidth to each user.
24e377a8 482
052f1dc7 483config CGROUP_SCHED
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484 bool "Control groups"
485 depends on CGROUPS
486 help
487 This option allows you to create arbitrary task groups
488 using the "cgroup" pseudo filesystem and control
489 the cpu bandwidth allocated to each such task group.
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490 Refer to Documentation/cgroups/cgroups.txt for more
491 information on "cgroup" pseudo filesystem.
68318b8e 492
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493endchoice
494
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495menuconfig CGROUPS
496 boolean "Control Group support"
5cdc38f9 497 help
23964d2d 498 This option adds support for grouping sets of processes together, for
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499 use with process control subsystems such as Cpusets, CFS, memory
500 controls or device isolation.
501 See
5cdc38f9 502 - Documentation/scheduler/sched-design-CFS.txt (CFS)
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503 - Documentation/cgroups/ (features for grouping, isolation
504 and resource control)
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505
506 Say N if unsure.
507
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508if CGROUPS
509
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510config CGROUP_DEBUG
511 bool "Example debug cgroup subsystem"
512 depends on CGROUPS
513 default n
514 help
515 This option enables a simple cgroup subsystem that
516 exports useful debugging information about the cgroups
23964d2d 517 framework.
5cdc38f9 518
23964d2d 519 Say N if unsure.
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520
521config CGROUP_NS
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522 bool "Namespace cgroup subsystem"
523 depends on CGROUPS
524 help
525 Provides a simple namespace cgroup subsystem to
526 provide hierarchical naming of sets of namespaces,
527 for instance virtual servers and checkpoint/restart
528 jobs.
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529
530config CGROUP_FREEZER
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531 bool "Freezer cgroup subsystem"
532 depends on CGROUPS
533 help
534 Provides a way to freeze and unfreeze all tasks in a
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535 cgroup.
536
537config CGROUP_DEVICE
538 bool "Device controller for cgroups"
539 depends on CGROUPS && EXPERIMENTAL
540 help
541 Provides a cgroup implementing whitelists for devices which
542 a process in the cgroup can mknod or open.
543
544config CPUSETS
545 bool "Cpuset support"
db7f47cf 546 depends on CGROUPS
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547 help
548 This option will let you create and manage CPUSETs which
549 allow dynamically partitioning a system into sets of CPUs and
550 Memory Nodes and assigning tasks to run only within those sets.
551 This is primarily useful on large SMP or NUMA systems.
552
553 Say N if unsure.
554
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555config PROC_PID_CPUSET
556 bool "Include legacy /proc/<pid>/cpuset file"
557 depends on CPUSETS
558 default y
559
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560config CGROUP_CPUACCT
561 bool "Simple CPU accounting cgroup subsystem"
562 depends on CGROUPS
563 help
564 Provides a simple Resource Controller for monitoring the
23964d2d 565 total CPU consumed by the tasks in a cgroup.
d842de87 566
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567config RESOURCE_COUNTERS
568 bool "Resource counters"
569 help
570 This option enables controller independent resource accounting
23964d2d 571 infrastructure that works with cgroups.
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572 depends on CGROUPS
573
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574config CGROUP_MEM_RES_CTLR
575 bool "Memory Resource Controller for Control Groups"
576 depends on CGROUPS && RESOURCE_COUNTERS
cf475ad2 577 select MM_OWNER
00f0b825 578 help
84ad6d70 579 Provides a memory resource controller that manages both anonymous
21acb9ca 580 memory and page cache. (See Documentation/cgroups/memory.txt)
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581
582 Note that setting this option increases fixed memory overhead
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583 associated with each page of memory in the system. By this,
584 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
585 usage tracking struct at boot. Total amount of this is printed out
586 at boot.
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587
588 Only enable when you're ok with these trade offs and really
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589 sure you need the memory resource controller. Even when you enable
590 this, you can set "cgroup_disable=memory" at your boot option to
591 disable memory resource controller and you can avoid overheads.
c9d5409f 592 (and lose benefits of memory resource controller)
00f0b825 593
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594 This config option also selects MM_OWNER config option, which
595 could in turn add some fork/exit overhead.
596
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597config CGROUP_MEM_RES_CTLR_SWAP
598 bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
599 depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
600 help
601 Add swap management feature to memory resource controller. When you
602 enable this, you can limit mem+swap usage per cgroup. In other words,
603 when you disable this, memory resource controller has no cares to
604 usage of swap...a process can exhaust all of the swap. This extension
605 is useful when you want to avoid exhaustion swap but this itself
606 adds more overheads and consumes memory for remembering information.
607 Especially if you use 32bit system or small memory system, please
608 be careful about enabling this. When memory resource controller
609 is disabled by boot option, this will be automatically disabled and
610 there will be no overhead from this. Even when you set this config=y,
611 if boot option "noswapaccount" is set, swap will not be accounted.
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612 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
613 size is 4096bytes, 512k per 1Gbytes of swap.
c077719b 614
23964d2d 615endif # CGROUPS
c077719b 616
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617config MM_OWNER
618 bool
5cdc38f9 619
88a22c98 620config SYSFS_DEPRECATED
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621 bool
622
623config SYSFS_DEPRECATED_V2
f6ee649f 624 bool "remove sysfs features which may confuse old userspace tools"
9148fe87 625 depends on SYSFS
f6ee649f 626 default n
d47846c5 627 select SYSFS_DEPRECATED
88a22c98 628 help
fce3e804 629 This option switches the layout of sysfs to the deprecated
f6ee649f 630 version. Do not use it on recent distributions.
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631
632 The current sysfs layout features a unified device tree at
633 /sys/devices/, which is able to express a hierarchy between
634 class devices. If the deprecated option is set to Y, the
635 unified device tree is split into a bus device tree at
636 /sys/devices/ and several individual class device trees at
637 /sys/class/. The class and bus devices will be connected by
638 "<subsystem>:<name>" and the "device" links. The "block"
639 class devices, will not show up in /sys/class/block/. Some
640 subsystems will suppress the creation of some devices which
641 depend on the unified device tree.
642
643 This option is not a pure compatibility option that can
644 be safely enabled on newer distributions. It will change the
645 layout of sysfs to the non-extensible deprecated version,
646 and disable some features, which can not be exported without
647 confusing older userspace tools. Since 2007/2008 all major
648 distributions do not enable this option, and ship no tools which
649 depend on the deprecated layout or this option.
650
651 If you are using a new kernel on an older distribution, or use
652 older userspace tools, you might need to say Y here. Do not say Y,
653 if the original kernel, that came with your distribution, has
654 this option set to N.
88a22c98 655
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656config RELAY
657 bool "Kernel->user space relay support (formerly relayfs)"
658 help
659 This option enables support for relay interface support in
660 certain file systems (such as debugfs).
661 It is designed to provide an efficient mechanism for tools and
662 facilities to relay large amounts of data from kernel space to
663 user space.
664
665 If unsure, say N.
666
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PE
667config NAMESPACES
668 bool "Namespaces support" if EMBEDDED
669 default !EMBEDDED
670 help
671 Provides the way to make tasks work with different objects using
672 the same id. For example same IPC id may refer to different objects
673 or same user id or pid may refer to different tasks when used in
674 different namespaces.
675
58bfdd6d
PE
676config UTS_NS
677 bool "UTS namespace"
678 depends on NAMESPACES
679 help
680 In this namespace tasks see different info provided with the
681 uname() system call
682
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PE
683config IPC_NS
684 bool "IPC namespace"
614b84cf 685 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
ae5e1b22
PE
686 help
687 In this namespace tasks work with IPC ids which correspond to
614b84cf 688 different IPC objects in different namespaces.
ae5e1b22 689
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PE
690config USER_NS
691 bool "User namespace (EXPERIMENTAL)"
692 depends on NAMESPACES && EXPERIMENTAL
693 help
694 This allows containers, i.e. vservers, to use user namespaces
695 to provide different user info for different servers.
696 If unsure, say N.
697
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PE
698config PID_NS
699 bool "PID Namespaces (EXPERIMENTAL)"
700 default n
701 depends on NAMESPACES && EXPERIMENTAL
702 help
12d2b8f9 703 Support process id namespaces. This allows having multiple
692105b8 704 processes with the same pid as long as they are in different
74bd59bb
PE
705 pid namespaces. This is a building block of containers.
706
707 Unless you want to work with an experimental feature
708 say N here.
709
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MH
710config NET_NS
711 bool "Network namespace"
712 default n
713 depends on NAMESPACES && EXPERIMENTAL && NET
714 help
715 Allow user space to create what appear to be multiple instances
716 of the network stack.
717
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DG
718config BLK_DEV_INITRD
719 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
720 depends on BROKEN || !FRV
721 help
722 The initial RAM filesystem is a ramfs which is loaded by the
723 boot loader (loadlin or lilo) and that is mounted as root
724 before the normal boot procedure. It is typically used to
725 load modules needed to mount the "real" root file system,
726 etc. See <file:Documentation/initrd.txt> for details.
727
728 If RAM disk support (BLK_DEV_RAM) is also included, this
729 also enables initial RAM disk (initrd) support and adds
730 15 Kbytes (more on some other architectures) to the kernel size.
731
732 If unsure say Y.
733
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JPS
734if BLK_DEV_INITRD
735
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SR
736source "usr/Kconfig"
737
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JPS
738endif
739
c45b4f1f 740config CC_OPTIMIZE_FOR_SIZE
96fffeb4 741 bool "Optimize for size"
c45b4f1f 742 default y
c45b4f1f
LT
743 help
744 Enabling this option will pass "-Os" instead of "-O2" to gcc
745 resulting in a smaller kernel.
746
775a7229 747 If unsure, say Y.
c45b4f1f 748
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RD
749config SYSCTL
750 bool
751
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752config ANON_INODES
753 bool
754
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755menuconfig EMBEDDED
756 bool "Configure standard kernel features (for small systems)"
757 help
758 This option allows certain base kernel options and settings
759 to be disabled or tweaked. This is for specialized
760 environments which can tolerate a "non-standard" kernel.
761 Only use this if you really know what you are doing.
762
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763config UID16
764 bool "Enable 16-bit UID system calls" if EMBEDDED
09337f50 765 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
ae81f9e3
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766 default y
767 help
768 This enables the legacy 16-bit UID syscall wrappers.
769
b89a8171 770config SYSCTL_SYSCALL
0847062a 771 bool "Sysctl syscall support" if EMBEDDED
13bb7e37 772 default y
b89a8171 773 select SYSCTL
ae81f9e3 774 ---help---
13bb7e37
EB
775 sys_sysctl uses binary paths that have been found challenging
776 to properly maintain and use. The interface in /proc/sys
777 using paths with ascii names is now the primary path to this
778 information.
b89a8171 779
13bb7e37
EB
780 Almost nothing using the binary sysctl interface so if you are
781 trying to save some space it is probably safe to disable this,
782 making your kernel marginally smaller.
b89a8171 783
13bb7e37 784 If unsure say Y here.
ae81f9e3 785
1da177e4 786config KALLSYMS
979c6a1e 787 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
1da177e4
LT
788 default y
789 help
790 Say Y here to let the kernel print out symbolic crash information and
791 symbolic stack backtraces. This increases the size of the kernel
792 somewhat, as all symbols have to be loaded into the kernel image.
793
794config KALLSYMS_ALL
795 bool "Include all symbols in kallsyms"
796 depends on DEBUG_KERNEL && KALLSYMS
797 help
798 Normally kallsyms only contains the symbols of functions, for nicer
799 OOPS messages. Some debuggers can use kallsyms for other
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JJ
800 symbols too: say Y here to include all symbols, if you need them
801 and you don't care about adding 300k to the size of your kernel.
1da177e4
LT
802
803 Say N.
804
805config KALLSYMS_EXTRA_PASS
806 bool "Do an extra kallsyms pass"
807 depends on KALLSYMS
808 help
809 If kallsyms is not working correctly, the build will fail with
810 inconsistent kallsyms data. If that occurs, log a bug report and
811 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
812 Always say N here unless you find a bug in kallsyms, which must be
813 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
814 you wait for kallsyms to be fixed.
815
d59745ce 816
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GKH
817config HOTPLUG
818 bool "Support for hot-pluggable devices" if EMBEDDED
819 default y
820 help
821 This option is provided for the case where no hotplug or uevent
822 capabilities is wanted by the kernel. You should only consider
823 disabling this option for embedded systems that do not use modules, a
824 dynamic /dev tree, or dynamic device discovery. Just say Y.
825
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MM
826config PRINTK
827 default y
828 bool "Enable support for printk" if EMBEDDED
829 help
830 This option enables normal printk support. Removing it
831 eliminates most of the message strings from the kernel image
832 and makes the kernel more or less silent. As this makes it
833 very difficult to diagnose system problems, saying N here is
834 strongly discouraged.
835
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MM
836config BUG
837 bool "BUG() support" if EMBEDDED
838 default y
839 help
840 Disabling this option eliminates support for BUG and WARN, reducing
841 the size of your kernel image and potentially quietly ignoring
842 numerous fatal conditions. You should only consider disabling this
843 option for embedded systems with no facilities for reporting errors.
844 Just say Y.
845
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MM
846config ELF_CORE
847 default y
848 bool "Enable ELF core dumps" if EMBEDDED
849 help
850 Enable support for generating core dumps. Disabling saves about 4k.
851
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SS
852config PCSPKR_PLATFORM
853 bool "Enable PC-Speaker support" if EMBEDDED
854 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
855 default y
856 help
857 This option allows to disable the internal PC-Speaker
858 support, saving some memory.
859
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LT
860config BASE_FULL
861 default y
862 bool "Enable full-sized data structures for core" if EMBEDDED
863 help
864 Disabling this option reduces the size of miscellaneous core
865 kernel data structures. This saves memory on small machines,
866 but may reduce performance.
867
868config FUTEX
869 bool "Enable futex support" if EMBEDDED
870 default y
23f78d4a 871 select RT_MUTEXES
1da177e4
LT
872 help
873 Disabling this option will cause the kernel to be built without
874 support for "fast userspace mutexes". The resulting kernel may not
875 run glibc-based applications correctly.
876
877config EPOLL
878 bool "Enable eventpoll support" if EMBEDDED
879 default y
448e3cee 880 select ANON_INODES
1da177e4
LT
881 help
882 Disabling this option will cause the kernel to be built without
883 support for epoll family of system calls.
884
fba2afaa
DL
885config SIGNALFD
886 bool "Enable signalfd() system call" if EMBEDDED
448e3cee 887 select ANON_INODES
fba2afaa
DL
888 default y
889 help
890 Enable the signalfd() system call that allows to receive signals
891 on a file descriptor.
892
893 If unsure, say Y.
894
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DL
895config TIMERFD
896 bool "Enable timerfd() system call" if EMBEDDED
448e3cee 897 select ANON_INODES
b215e283
DL
898 default y
899 help
900 Enable the timerfd() system call that allows to receive timer
901 events on a file descriptor.
902
903 If unsure, say Y.
904
e1ad7468
DL
905config EVENTFD
906 bool "Enable eventfd() system call" if EMBEDDED
448e3cee 907 select ANON_INODES
e1ad7468
DL
908 default y
909 help
910 Enable the eventfd() system call that allows to receive both
911 kernel notification (ie. KAIO) or userspace notifications.
912
913 If unsure, say Y.
914
1da177e4
LT
915config SHMEM
916 bool "Use full shmem filesystem" if EMBEDDED
917 default y
918 depends on MMU
919 help
920 The shmem is an internal filesystem used to manage shared memory.
921 It is backed by swap and manages resource limits. It is also exported
922 to userspace as tmpfs if TMPFS is enabled. Disabling this
923 option replaces shmem and tmpfs with the much simpler ramfs code,
924 which may be appropriate on small systems without swap.
925
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TP
926config AIO
927 bool "Enable AIO support" if EMBEDDED
928 default y
929 help
930 This option enables POSIX asynchronous I/O which may by used
931 by some high performance threaded applications. Disabling
932 this option saves about 7k.
933
0793a61d
TG
934config HAVE_PERF_COUNTERS
935 bool
018df72d
MF
936 help
937 See tools/perf/design.txt for details.
0793a61d
TG
938
939menu "Performance Counters"
940
941config PERF_COUNTERS
942 bool "Kernel Performance Counters"
943 depends on HAVE_PERF_COUNTERS
4c59e467 944 select ANON_INODES
0793a61d
TG
945 help
946 Enable kernel support for performance counter hardware.
947
948 Performance counters are special hardware registers available
949 on most modern CPUs. These registers count the number of certain
950 types of hw events: such as instructions executed, cachemisses
951 suffered, or branches mis-predicted - without slowing down the
952 kernel or applications. These registers can also trigger interrupts
953 when a threshold number of events have passed - and can thus be
954 used to profile the code that runs on that CPU.
955
956 The Linux Performance Counter subsystem provides an abstraction of
957 these hardware capabilities, available via a system call. It
958 provides per task and per CPU counters, and it provides event
959 capabilities on top of those.
960
961 Say Y if unsure.
962
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PZ
963config EVENT_PROFILE
964 bool "Tracepoint profile sources"
965 depends on PERF_COUNTERS && EVENT_TRACER
966 default y
967
0793a61d
TG
968endmenu
969
f8891e5e
CL
970config VM_EVENT_COUNTERS
971 default y
972 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
973 help
2aea4fb6
PJ
974 VM event counters are needed for event counts to be shown.
975 This option allows the disabling of the VM event counters
976 on EMBEDDED systems. /proc/vmstat will only show page counts
977 if VM event counters are disabled.
f8891e5e 978
3d137310
TP
979config PCI_QUIRKS
980 default y
61cfc7e4
GU
981 bool "Enable PCI quirk workarounds" if EMBEDDED
982 depends on PCI
3d137310
TP
983 help
984 This enables workarounds for various PCI chipset
985 bugs/quirks. Disable this only if your target machine is
986 unaffected by PCI quirks.
987
41ecc55b
CL
988config SLUB_DEBUG
989 default y
990 bool "Enable SLUB debugging support" if EMBEDDED
f6acb635 991 depends on SLUB && SYSFS
41ecc55b
CL
992 help
993 SLUB has extensive debug support features. Disabling these can
994 result in significant savings in code size. This also disables
995 SLUB sysfs support. /sys/slab will not exist and there will be
996 no support for cache validation etc.
997
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RD
998config STRIP_ASM_SYMS
999 bool "Strip assembler-generated symbols during link"
1000 default n
1001 help
1002 Strip internal assembler-generated symbols during a link (symbols
1003 that look like '.Lxxx') so they don't pollute the output of
1004 get_wchan() and suchlike.
1005
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RD
1006config COMPAT_BRK
1007 bool "Disable heap randomization"
1008 default y
1009 help
1010 Randomizing heap placement makes heap exploits harder, but it
1011 also breaks ancient binaries (including anything libc5 based).
1012 This option changes the bootup default to heap randomization
692105b8 1013 disabled, and can be overridden at runtime by setting
b943c460
RD
1014 /proc/sys/kernel/randomize_va_space to 2.
1015
1016 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1017
81819f0f
CL
1018choice
1019 prompt "Choose SLAB allocator"
a0acd820 1020 default SLUB
81819f0f
CL
1021 help
1022 This option allows to select a slab allocator.
1023
1024config SLAB
1025 bool "SLAB"
1026 help
1027 The regular slab allocator that is established and known to work
34013886 1028 well in all environments. It organizes cache hot objects in
02f56210 1029 per cpu and per node queues.
81819f0f
CL
1030
1031config SLUB
81819f0f
CL
1032 bool "SLUB (Unqueued Allocator)"
1033 help
1034 SLUB is a slab allocator that minimizes cache line usage
1035 instead of managing queues of cached objects (SLAB approach).
1036 Per cpu caching is realized using slabs of objects instead
1037 of queues of objects. SLUB can use memory efficiently
02f56210
SA
1038 and has enhanced diagnostics. SLUB is the default choice for
1039 a slab allocator.
81819f0f
CL
1040
1041config SLOB
84a01c2f 1042 depends on EMBEDDED
81819f0f
CL
1043 bool "SLOB (Simple Allocator)"
1044 help
37291458
MM
1045 SLOB replaces the stock allocator with a drastically simpler
1046 allocator. SLOB is generally more space efficient but
1047 does not perform as well on large systems.
81819f0f
CL
1048
1049endchoice
1050
125e5645
MD
1051config PROFILING
1052 bool "Profiling support (EXPERIMENTAL)"
1053 help
1054 Say Y here to enable the extended profiling support mechanisms used
1055 by profilers such as OProfile.
1056
5f87f112
IM
1057#
1058# Place an empty function call at each tracepoint site. Can be
1059# dynamically changed for a probe function.
1060#
97e1c18e 1061config TRACEPOINTS
5f87f112 1062 bool
97e1c18e 1063
125e5645
MD
1064config MARKERS
1065 bool "Activate markers"
91f73f90 1066 select TRACEPOINTS
125e5645
MD
1067 help
1068 Place an empty function call at each marker site. Can be
1069 dynamically changed for a probe function.
1070
fb32e03f
MD
1071source "arch/Kconfig"
1072
07fe7cb7
DH
1073config SLOW_WORK
1074 default n
1c2d008c 1075 bool
07fe7cb7
DH
1076 help
1077 The slow work thread pool provides a number of dynamically allocated
1078 threads that can be used by the kernel to perform operations that
1079 take a relatively long time.
1080
1081 An example of this would be CacheFiles doing a path lookup followed
1082 by a series of mkdirs and a create call, all of which have to touch
1083 disk.
1084
1c2d008c
DH
1085 See Documentation/slow-work.txt.
1086
1da177e4
LT
1087endmenu # General setup
1088
ee7e5516
DES
1089config HAVE_GENERIC_DMA_COHERENT
1090 bool
1091 default n
1092
158a9624
LT
1093config SLABINFO
1094 bool
1095 depends on PROC_FS
0f389ec6 1096 depends on SLAB || SLUB_DEBUG
158a9624
LT
1097 default y
1098
ae81f9e3
CE
1099config RT_MUTEXES
1100 boolean
ae81f9e3 1101
1da177e4
LT
1102config BASE_SMALL
1103 int
1104 default 0 if BASE_FULL
1105 default 1 if !BASE_FULL
1106
66da5733 1107menuconfig MODULES
1da177e4
LT
1108 bool "Enable loadable module support"
1109 help
1110 Kernel modules are small pieces of compiled code which can
1111 be inserted in the running kernel, rather than being
1112 permanently built into the kernel. You use the "modprobe"
1113 tool to add (and sometimes remove) them. If you say Y here,
1114 many parts of the kernel can be built as modules (by
1115 answering M instead of Y where indicated): this is most
1116 useful for infrequently used options which are not required
1117 for booting. For more information, see the man pages for
1118 modprobe, lsmod, modinfo, insmod and rmmod.
1119
1120 If you say Y here, you will need to run "make
1121 modules_install" to put the modules under /lib/modules/
1122 where modprobe can find them (you may need to be root to do
1123 this).
1124
1125 If unsure, say Y.
1126
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RD
1127if MODULES
1128
826e4506
LT
1129config MODULE_FORCE_LOAD
1130 bool "Forced module loading"
826e4506
LT
1131 default n
1132 help
91e37a79
RR
1133 Allow loading of modules without version information (ie. modprobe
1134 --force). Forced module loading sets the 'F' (forced) taint flag and
1135 is usually a really bad idea.
826e4506 1136
1da177e4
LT
1137config MODULE_UNLOAD
1138 bool "Module unloading"
1da177e4
LT
1139 help
1140 Without this option you will not be able to unload any
1141 modules (note that some modules may not be unloadable
f7f5b675
DV
1142 anyway), which makes your kernel smaller, faster
1143 and simpler. If unsure, say Y.
1da177e4
LT
1144
1145config MODULE_FORCE_UNLOAD
1146 bool "Forced module unloading"
1147 depends on MODULE_UNLOAD && EXPERIMENTAL
1148 help
1149 This option allows you to force a module to unload, even if the
1150 kernel believes it is unsafe: the kernel will remove the module
1151 without waiting for anyone to stop using it (using the -f option to
1152 rmmod). This is mainly for kernel developers and desperate users.
1153 If unsure, say N.
1154
1da177e4 1155config MODVERSIONS
0d541643 1156 bool "Module versioning support"
1da177e4
LT
1157 help
1158 Usually, you have to use modules compiled with your kernel.
1159 Saying Y here makes it sometimes possible to use modules
1160 compiled for different kernels, by adding enough information
1161 to the modules to (hopefully) spot any changes which would
1162 make them incompatible with the kernel you are running. If
1163 unsure, say N.
1164
1165config MODULE_SRCVERSION_ALL
1166 bool "Source checksum for all modules"
1da177e4
LT
1167 help
1168 Modules which contain a MODULE_VERSION get an extra "srcversion"
1169 field inserted into their modinfo section, which contains a
1170 sum of the source files which made it. This helps maintainers
1171 see exactly which source was used to build a module (since
1172 others sometimes change the module source without updating
1173 the version). With this option, such a "srcversion" field
1174 will be created for all modules. If unsure, say N.
1175
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RD
1176endif # MODULES
1177
98a79d6a
RR
1178config INIT_ALL_POSSIBLE
1179 bool
1180 help
1181 Back when each arch used to define their own cpu_online_map and
1182 cpu_possible_map, some of them chose to initialize cpu_possible_map
1183 with all 1s, and others with all 0s. When they were centralised,
1184 it was better to provide this option than to break all the archs
692105b8 1185 and have several arch maintainers pursuing me down dark alleys.
98a79d6a 1186
1da177e4
LT
1187config STOP_MACHINE
1188 bool
1189 default y
1190 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1191 help
1192 Need stop_machine() primitive.
3a65dfe8 1193
3a65dfe8 1194source "block/Kconfig"
e98c3202
AK
1195
1196config PREEMPT_NOTIFIERS
1197 bool
e260be67 1198