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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
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24config HAVE_IRQ_WORK
25 bool
26
27config IRQ_WORK
28 bool
29 depends on HAVE_IRQ_WORK
30
ff0cfc66 31menu "General setup"
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32
33config EXPERIMENTAL
34 bool "Prompt for development and/or incomplete code/drivers"
35 ---help---
36 Some of the various things that Linux supports (such as network
37 drivers, file systems, network protocols, etc.) can be in a state
38 of development where the functionality, stability, or the level of
39 testing is not yet high enough for general use. This is usually
40 known as the "alpha-test" phase among developers. If a feature is
41 currently in alpha-test, then the developers usually discourage
42 uninformed widespread use of this feature by the general public to
43 avoid "Why doesn't this work?" type mail messages. However, active
44 testing and use of these systems is welcomed. Just be aware that it
45 may not meet the normal level of reliability or it may fail to work
46 in some special cases. Detailed bug reports from people familiar
47 with the kernel internals are usually welcomed by the developers
48 (before submitting bug reports, please read the documents
49 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
50 <file:Documentation/BUG-HUNTING>, and
51 <file:Documentation/oops-tracing.txt> in the kernel source).
52
53 This option will also make obsoleted drivers available. These are
54 drivers that have been replaced by something else, and/or are
55 scheduled to be removed in a future kernel release.
56
57 Unless you intend to help test and develop a feature or driver that
58 falls into this category, or you have a situation that requires
59 using these features, you should probably say N here, which will
60 cause the configurator to present you with fewer choices. If
61 you say Y here, you will be offered the choice of using features or
62 drivers that are currently considered to be in the alpha-test phase.
63
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64config BROKEN
65 bool
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66
67config BROKEN_ON_SMP
68 bool
69 depends on BROKEN || !SMP
70 default y
71
72config LOCK_KERNEL
73 bool
74 depends on SMP || PREEMPT
75 default y
76
77config INIT_ENV_ARG_LIMIT
78 int
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79 default 32 if !UML
80 default 128 if UML
1da177e4 81 help
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82 Maximum of each of the number of arguments and environment
83 variables passed to init from the kernel command line.
1da177e4 84
1da177e4 85
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86config CROSS_COMPILE
87 string "Cross-compiler tool prefix"
88 help
89 Same as running 'make CROSS_COMPILE=prefix-' but stored for
90 default make runs in this kernel build directory. You don't
91 need to set this unless you want the configured kernel build
92 directory to select the cross-compiler automatically.
93
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94config LOCALVERSION
95 string "Local version - append to kernel release"
96 help
97 Append an extra string to the end of your kernel version.
98 This will show up when you type uname, for example.
99 The string you set here will be appended after the contents of
100 any files with a filename matching localversion* in your
101 object and source tree, in that order. Your total string can
102 be a maximum of 64 characters.
103
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104config LOCALVERSION_AUTO
105 bool "Automatically append version information to the version string"
106 default y
107 help
108 This will try to automatically determine if the current tree is a
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109 release tree by looking for git tags that belong to the current
110 top of tree revision.
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111
112 A string of the format -gxxxxxxxx will be added to the localversion
6e5a5420 113 if a git-based tree is found. The string generated by this will be
aaebf433 114 appended after any matching localversion* files, and after the value
6e5a5420 115 set in CONFIG_LOCALVERSION.
aaebf433 116
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117 (The actual string used here is the first eight characters produced
118 by running the command:
119
120 $ git rev-parse --verify HEAD
121
122 which is done within the script "scripts/setlocalversion".)
aaebf433 123
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124config HAVE_KERNEL_GZIP
125 bool
126
127config HAVE_KERNEL_BZIP2
128 bool
129
130config HAVE_KERNEL_LZMA
131 bool
132
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133config HAVE_KERNEL_LZO
134 bool
135
30d65dbf 136choice
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137 prompt "Kernel compression mode"
138 default KERNEL_GZIP
7dd65feb 139 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
2e9f3bdd 140 help
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141 The linux kernel is a kind of self-extracting executable.
142 Several compression algorithms are available, which differ
143 in efficiency, compression and decompression speed.
144 Compression speed is only relevant when building a kernel.
145 Decompression speed is relevant at each boot.
146
147 If you have any problems with bzip2 or lzma compressed
148 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
149 version of this functionality (bzip2 only), for 2.4, was
150 supplied by Christian Ludwig)
151
152 High compression options are mostly useful for users, who
153 are low on disk space (embedded systems), but for whom ram
154 size matters less.
155
156 If in doubt, select 'gzip'
157
158config KERNEL_GZIP
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159 bool "Gzip"
160 depends on HAVE_KERNEL_GZIP
161 help
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162 The old and tried gzip compression. It provides a good balance
163 between compression ratio and decompression speed.
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164
165config KERNEL_BZIP2
166 bool "Bzip2"
2e9f3bdd 167 depends on HAVE_KERNEL_BZIP2
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168 help
169 Its compression ratio and speed is intermediate.
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170 Decompression speed is slowest among the three. The kernel
171 size is about 10% smaller with bzip2, in comparison to gzip.
172 Bzip2 uses a large amount of memory. For modern kernels you
173 will need at least 8MB RAM or more for booting.
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174
175config KERNEL_LZMA
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176 bool "LZMA"
177 depends on HAVE_KERNEL_LZMA
178 help
179 The most recent compression algorithm.
180 Its ratio is best, decompression speed is between the other
181 two. Compression is slowest. The kernel size is about 33%
182 smaller with LZMA in comparison to gzip.
30d65dbf 183
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184config KERNEL_LZO
185 bool "LZO"
186 depends on HAVE_KERNEL_LZO
187 help
188 Its compression ratio is the poorest among the 4. The kernel
189 size is about about 10% bigger than gzip; however its speed
190 (both compression and decompression) is the fastest.
191
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192endchoice
193
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194config SWAP
195 bool "Support for paging of anonymous memory (swap)"
9361401e 196 depends on MMU && BLOCK
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197 default y
198 help
199 This option allows you to choose whether you want to have support
92c3504e 200 for so called swap devices or swap files in your kernel that are
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201 used to provide more virtual memory than the actual RAM present
202 in your computer. If unsure say Y.
203
204config SYSVIPC
205 bool "System V IPC"
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206 ---help---
207 Inter Process Communication is a suite of library functions and
208 system calls which let processes (running programs) synchronize and
209 exchange information. It is generally considered to be a good thing,
210 and some programs won't run unless you say Y here. In particular, if
211 you want to run the DOS emulator dosemu under Linux (read the
212 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
213 you'll need to say Y here.
214
215 You can find documentation about IPC with "info ipc" and also in
216 section 6.4 of the Linux Programmer's Guide, available from
217 <http://www.tldp.org/guides.html>.
218
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219config SYSVIPC_SYSCTL
220 bool
221 depends on SYSVIPC
222 depends on SYSCTL
223 default y
224
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225config POSIX_MQUEUE
226 bool "POSIX Message Queues"
227 depends on NET && EXPERIMENTAL
228 ---help---
229 POSIX variant of message queues is a part of IPC. In POSIX message
230 queues every message has a priority which decides about succession
231 of receiving it by a process. If you want to compile and run
232 programs written e.g. for Solaris with use of its POSIX message
b0e37650 233 queues (functions mq_*) say Y here.
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234
235 POSIX message queues are visible as a filesystem called 'mqueue'
236 and can be mounted somewhere if you want to do filesystem
237 operations on message queues.
238
239 If unsure, say Y.
240
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241config POSIX_MQUEUE_SYSCTL
242 bool
243 depends on POSIX_MQUEUE
244 depends on SYSCTL
245 default y
246
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247config BSD_PROCESS_ACCT
248 bool "BSD Process Accounting"
249 help
250 If you say Y here, a user level program will be able to instruct the
251 kernel (via a special system call) to write process accounting
252 information to a file: whenever a process exits, information about
253 that process will be appended to the file by the kernel. The
254 information includes things such as creation time, owning user,
255 command name, memory usage, controlling terminal etc. (the complete
256 list is in the struct acct in <file:include/linux/acct.h>). It is
257 up to the user level program to do useful things with this
258 information. This is generally a good idea, so say Y.
259
260config BSD_PROCESS_ACCT_V3
261 bool "BSD Process Accounting version 3 file format"
262 depends on BSD_PROCESS_ACCT
263 default n
264 help
265 If you say Y here, the process accounting information is written
266 in a new file format that also logs the process IDs of each
267 process and it's parent. Note that this file format is incompatible
268 with previous v0/v1/v2 file formats, so you will need updated tools
269 for processing it. A preliminary version of these tools is available
37a4c940 270 at <http://www.gnu.org/software/acct/>.
1da177e4 271
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272config TASKSTATS
273 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
274 depends on NET
275 default n
276 help
277 Export selected statistics for tasks/processes through the
278 generic netlink interface. Unlike BSD process accounting, the
279 statistics are available during the lifetime of tasks/processes as
280 responses to commands. Like BSD accounting, they are sent to user
281 space on task exit.
282
283 Say N if unsure.
284
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285config TASK_DELAY_ACCT
286 bool "Enable per-task delay accounting (EXPERIMENTAL)"
6f44993f 287 depends on TASKSTATS
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288 help
289 Collect information on time spent by a task waiting for system
290 resources like cpu, synchronous block I/O completion and swapping
291 in pages. Such statistics can help in setting a task's priorities
292 relative to other tasks for cpu, io, rss limits etc.
293
294 Say N if unsure.
295
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296config TASK_XACCT
297 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
298 depends on TASKSTATS
299 help
300 Collect extended task accounting data and send the data
301 to userland for processing over the taskstats interface.
302
303 Say N if unsure.
304
305config TASK_IO_ACCOUNTING
306 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
307 depends on TASK_XACCT
308 help
309 Collect information on the number of bytes of storage I/O which this
310 task has caused.
311
312 Say N if unsure.
313
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314config AUDIT
315 bool "Auditing support"
804a6a49 316 depends on NET
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317 help
318 Enable auditing infrastructure that can be used with another
319 kernel subsystem, such as SELinux (which requires this for
320 logging of avc messages output). Does not do system-call
321 auditing without CONFIG_AUDITSYSCALL.
322
323config AUDITSYSCALL
324 bool "Enable system-call auditing support"
022382a5 325 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
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326 default y if SECURITY_SELINUX
327 help
328 Enable low-overhead system-call auditing infrastructure that
329 can be used independently or with another kernel subsystem,
67640b60 330 such as SELinux.
1da177e4 331
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332config AUDIT_WATCH
333 def_bool y
334 depends on AUDITSYSCALL
335 select FSNOTIFY
1da177e4 336
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337config AUDIT_TREE
338 def_bool y
63c882a0 339 depends on AUDITSYSCALL
28a3a7eb 340 select FSNOTIFY
74c3cbe3 341
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342menu "RCU Subsystem"
343
344choice
345 prompt "RCU Implementation"
31c9a24e 346 default TREE_RCU
c903ff83 347
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348config TREE_RCU
349 bool "Tree-based hierarchical RCU"
687d7a96 350 depends on !PREEMPT && SMP
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351 help
352 This option selects the RCU implementation that is
353 designed for very large SMP system with hundreds or
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354 thousands of CPUs. It also scales down nicely to
355 smaller systems.
c903ff83 356
f41d911f 357config TREE_PREEMPT_RCU
a57eb940 358 bool "Preemptible tree-based hierarchical RCU"
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359 depends on PREEMPT
360 help
361 This option selects the RCU implementation that is
362 designed for very large SMP systems with hundreds or
363 thousands of CPUs, but for which real-time response
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364 is also required. It also scales down nicely to
365 smaller systems.
f41d911f 366
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367config TINY_RCU
368 bool "UP-only small-memory-footprint RCU"
369 depends on !SMP
370 help
371 This option selects the RCU implementation that is
372 designed for UP systems from which real-time response
373 is not required. This option greatly reduces the
374 memory footprint of RCU.
375
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376config TINY_PREEMPT_RCU
377 bool "Preemptible UP-only small-memory-footprint RCU"
378 depends on !SMP && PREEMPT
379 help
380 This option selects the RCU implementation that is designed
381 for real-time UP systems. This option greatly reduces the
382 memory footprint of RCU.
383
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384endchoice
385
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386config PREEMPT_RCU
387 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
388 help
389 This option enables preemptible-RCU code that is common between
390 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
391
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392config RCU_TRACE
393 bool "Enable tracing for RCU"
6b3ef48a 394 depends on TREE_RCU || TREE_PREEMPT_RCU
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395 help
396 This option provides tracing in RCU which presents stats
397 in debugfs for debugging RCU implementation.
398
399 Say Y here if you want to enable RCU tracing
400 Say N if you are unsure.
401
402config RCU_FANOUT
403 int "Tree-based hierarchical RCU fanout value"
404 range 2 64 if 64BIT
405 range 2 32 if !64BIT
f41d911f 406 depends on TREE_RCU || TREE_PREEMPT_RCU
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407 default 64 if 64BIT
408 default 32 if !64BIT
409 help
410 This option controls the fanout of hierarchical implementations
411 of RCU, allowing RCU to work efficiently on machines with
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412 large numbers of CPUs. This value must be at least the fourth
413 root of NR_CPUS, which allows NR_CPUS to be insanely large.
414 The default value of RCU_FANOUT should be used for production
415 systems, but if you are stress-testing the RCU implementation
416 itself, small RCU_FANOUT values allow you to test large-system
417 code paths on small(er) systems.
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418
419 Select a specific number if testing RCU itself.
420 Take the default if unsure.
421
422config RCU_FANOUT_EXACT
423 bool "Disable tree-based hierarchical RCU auto-balancing"
f41d911f 424 depends on TREE_RCU || TREE_PREEMPT_RCU
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425 default n
426 help
427 This option forces use of the exact RCU_FANOUT value specified,
428 regardless of imbalances in the hierarchy. This is useful for
429 testing RCU itself, and might one day be useful on systems with
430 strong NUMA behavior.
431
432 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
433
434 Say N if unsure.
435
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436config RCU_FAST_NO_HZ
437 bool "Accelerate last non-dyntick-idle CPU's grace periods"
438 depends on TREE_RCU && NO_HZ && SMP
439 default n
440 help
441 This option causes RCU to attempt to accelerate grace periods
442 in order to allow the final CPU to enter dynticks-idle state
443 more quickly. On the other hand, this option increases the
444 overhead of the dynticks-idle checking, particularly on systems
445 with large numbers of CPUs.
446
447 Say Y if energy efficiency is critically important, particularly
448 if you have relatively few CPUs.
449
450 Say N if you are unsure.
451
c903ff83 452config TREE_RCU_TRACE
f41d911f 453 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
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454 select DEBUG_FS
455 help
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456 This option provides tracing for the TREE_RCU and
457 TREE_PREEMPT_RCU implementations, permitting Makefile to
458 trivially select kernel/rcutree_trace.c.
c903ff83 459
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460endmenu # "RCU Subsystem"
461
1da177e4 462config IKCONFIG
f2443ab6 463 tristate "Kernel .config support"
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464 ---help---
465 This option enables the complete Linux kernel ".config" file
466 contents to be saved in the kernel. It provides documentation
467 of which kernel options are used in a running kernel or in an
468 on-disk kernel. This information can be extracted from the kernel
469 image file with the script scripts/extract-ikconfig and used as
470 input to rebuild the current kernel or to build another kernel.
471 It can also be extracted from a running kernel by reading
472 /proc/config.gz if enabled (below).
473
474config IKCONFIG_PROC
475 bool "Enable access to .config through /proc/config.gz"
476 depends on IKCONFIG && PROC_FS
477 ---help---
478 This option enables access to the kernel configuration file
479 through /proc/config.gz.
480
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481config LOG_BUF_SHIFT
482 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
483 range 12 21
f17a32e9 484 default 17
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485 help
486 Select kernel log buffer size as a power of 2.
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487 Examples:
488 17 => 128 KB
489 16 => 64 KB
490 15 => 32 KB
491 14 => 16 KB
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492 13 => 8 KB
493 12 => 4 KB
494
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495#
496# Architectures with an unreliable sched_clock() should select this:
497#
498config HAVE_UNSTABLE_SCHED_CLOCK
499 bool
500
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501menuconfig CGROUPS
502 boolean "Control Group support"
0dea1168 503 depends on EVENTFD
5cdc38f9 504 help
23964d2d 505 This option adds support for grouping sets of processes together, for
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506 use with process control subsystems such as Cpusets, CFS, memory
507 controls or device isolation.
508 See
5cdc38f9 509 - Documentation/scheduler/sched-design-CFS.txt (CFS)
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510 - Documentation/cgroups/ (features for grouping, isolation
511 and resource control)
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512
513 Say N if unsure.
514
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515if CGROUPS
516
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517config CGROUP_DEBUG
518 bool "Example debug cgroup subsystem"
519 depends on CGROUPS
520 default n
521 help
522 This option enables a simple cgroup subsystem that
523 exports useful debugging information about the cgroups
23964d2d 524 framework.
5cdc38f9 525
23964d2d 526 Say N if unsure.
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527
528config CGROUP_NS
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529 bool "Namespace cgroup subsystem"
530 depends on CGROUPS
531 help
532 Provides a simple namespace cgroup subsystem to
533 provide hierarchical naming of sets of namespaces,
534 for instance virtual servers and checkpoint/restart
535 jobs.
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536
537config CGROUP_FREEZER
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538 bool "Freezer cgroup subsystem"
539 depends on CGROUPS
540 help
541 Provides a way to freeze and unfreeze all tasks in a
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542 cgroup.
543
544config CGROUP_DEVICE
545 bool "Device controller for cgroups"
546 depends on CGROUPS && EXPERIMENTAL
547 help
548 Provides a cgroup implementing whitelists for devices which
549 a process in the cgroup can mknod or open.
550
551config CPUSETS
552 bool "Cpuset support"
db7f47cf 553 depends on CGROUPS
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554 help
555 This option will let you create and manage CPUSETs which
556 allow dynamically partitioning a system into sets of CPUs and
557 Memory Nodes and assigning tasks to run only within those sets.
558 This is primarily useful on large SMP or NUMA systems.
559
560 Say N if unsure.
561
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562config PROC_PID_CPUSET
563 bool "Include legacy /proc/<pid>/cpuset file"
564 depends on CPUSETS
565 default y
566
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567config CGROUP_CPUACCT
568 bool "Simple CPU accounting cgroup subsystem"
569 depends on CGROUPS
570 help
571 Provides a simple Resource Controller for monitoring the
23964d2d 572 total CPU consumed by the tasks in a cgroup.
d842de87 573
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574config RESOURCE_COUNTERS
575 bool "Resource counters"
576 help
577 This option enables controller independent resource accounting
23964d2d 578 infrastructure that works with cgroups.
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579 depends on CGROUPS
580
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581config CGROUP_MEM_RES_CTLR
582 bool "Memory Resource Controller for Control Groups"
583 depends on CGROUPS && RESOURCE_COUNTERS
cf475ad2 584 select MM_OWNER
00f0b825 585 help
84ad6d70 586 Provides a memory resource controller that manages both anonymous
21acb9ca 587 memory and page cache. (See Documentation/cgroups/memory.txt)
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588
589 Note that setting this option increases fixed memory overhead
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590 associated with each page of memory in the system. By this,
591 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
592 usage tracking struct at boot. Total amount of this is printed out
593 at boot.
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594
595 Only enable when you're ok with these trade offs and really
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596 sure you need the memory resource controller. Even when you enable
597 this, you can set "cgroup_disable=memory" at your boot option to
598 disable memory resource controller and you can avoid overheads.
c9d5409f 599 (and lose benefits of memory resource controller)
00f0b825 600
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601 This config option also selects MM_OWNER config option, which
602 could in turn add some fork/exit overhead.
603
c077719b 604config CGROUP_MEM_RES_CTLR_SWAP
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605 bool "Memory Resource Controller Swap Extension"
606 depends on CGROUP_MEM_RES_CTLR && SWAP
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607 help
608 Add swap management feature to memory resource controller. When you
609 enable this, you can limit mem+swap usage per cgroup. In other words,
610 when you disable this, memory resource controller has no cares to
611 usage of swap...a process can exhaust all of the swap. This extension
612 is useful when you want to avoid exhaustion swap but this itself
613 adds more overheads and consumes memory for remembering information.
614 Especially if you use 32bit system or small memory system, please
615 be careful about enabling this. When memory resource controller
616 is disabled by boot option, this will be automatically disabled and
617 there will be no overhead from this. Even when you set this config=y,
618 if boot option "noswapaccount" is set, swap will not be accounted.
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619 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
620 size is 4096bytes, 512k per 1Gbytes of swap.
c077719b 621
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622menuconfig CGROUP_SCHED
623 bool "Group CPU scheduler"
624 depends on EXPERIMENTAL && CGROUPS
625 default n
626 help
627 This feature lets CPU scheduler recognize task groups and control CPU
628 bandwidth allocation to such task groups. It uses cgroups to group
629 tasks.
630
631if CGROUP_SCHED
632config FAIR_GROUP_SCHED
633 bool "Group scheduling for SCHED_OTHER"
634 depends on CGROUP_SCHED
635 default CGROUP_SCHED
636
637config RT_GROUP_SCHED
638 bool "Group scheduling for SCHED_RR/FIFO"
639 depends on EXPERIMENTAL
640 depends on CGROUP_SCHED
641 default n
642 help
643 This feature lets you explicitly allocate real CPU bandwidth
32bd7eb5 644 to task groups. If enabled, it will also make it impossible to
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645 schedule realtime tasks for non-root users until you allocate
646 realtime bandwidth for them.
647 See Documentation/scheduler/sched-rt-group.txt for more information.
648
649endif #CGROUP_SCHED
650
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651config BLK_CGROUP
652 tristate "Block IO controller"
653 depends on CGROUPS && BLOCK
654 default n
655 ---help---
656 Generic block IO controller cgroup interface. This is the common
657 cgroup interface which should be used by various IO controlling
658 policies.
659
660 Currently, CFQ IO scheduler uses it to recognize task groups and
661 control disk bandwidth allocation (proportional time slice allocation)
662 to such task groups.
663
664 This option only enables generic Block IO controller infrastructure.
665 One needs to also enable actual IO controlling logic in CFQ for it
666 to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
667
668 See Documentation/cgroups/blkio-controller.txt for more information.
669
670config DEBUG_BLK_CGROUP
671 bool "Enable Block IO controller debugging"
672 depends on BLK_CGROUP
673 default n
674 ---help---
675 Enable some debugging help. Currently it exports additional stat
676 files in a cgroup which can be useful for debugging.
677
23964d2d 678endif # CGROUPS
c077719b 679
23964d2d
LZ
680config MM_OWNER
681 bool
5cdc38f9 682
88a22c98 683config SYSFS_DEPRECATED
d47846c5
IM
684 bool
685
686config SYSFS_DEPRECATED_V2
9e9868a7 687 bool "enable deprecated sysfs features to support old userspace tools"
9148fe87 688 depends on SYSFS
f6ee649f 689 default n
d47846c5 690 select SYSFS_DEPRECATED
88a22c98 691 help
fce3e804 692 This option switches the layout of sysfs to the deprecated
f6ee649f 693 version. Do not use it on recent distributions.
fce3e804
KS
694
695 The current sysfs layout features a unified device tree at
696 /sys/devices/, which is able to express a hierarchy between
697 class devices. If the deprecated option is set to Y, the
698 unified device tree is split into a bus device tree at
699 /sys/devices/ and several individual class device trees at
700 /sys/class/. The class and bus devices will be connected by
701 "<subsystem>:<name>" and the "device" links. The "block"
702 class devices, will not show up in /sys/class/block/. Some
703 subsystems will suppress the creation of some devices which
704 depend on the unified device tree.
705
706 This option is not a pure compatibility option that can
707 be safely enabled on newer distributions. It will change the
708 layout of sysfs to the non-extensible deprecated version,
709 and disable some features, which can not be exported without
710 confusing older userspace tools. Since 2007/2008 all major
711 distributions do not enable this option, and ship no tools which
712 depend on the deprecated layout or this option.
713
714 If you are using a new kernel on an older distribution, or use
715 older userspace tools, you might need to say Y here. Do not say Y,
716 if the original kernel, that came with your distribution, has
717 this option set to N.
88a22c98 718
b86ff981
JA
719config RELAY
720 bool "Kernel->user space relay support (formerly relayfs)"
721 help
722 This option enables support for relay interface support in
723 certain file systems (such as debugfs).
724 It is designed to provide an efficient mechanism for tools and
725 facilities to relay large amounts of data from kernel space to
726 user space.
727
728 If unsure, say N.
729
c5289a69
PE
730config NAMESPACES
731 bool "Namespaces support" if EMBEDDED
732 default !EMBEDDED
733 help
734 Provides the way to make tasks work with different objects using
735 the same id. For example same IPC id may refer to different objects
736 or same user id or pid may refer to different tasks when used in
737 different namespaces.
738
58bfdd6d
PE
739config UTS_NS
740 bool "UTS namespace"
741 depends on NAMESPACES
742 help
743 In this namespace tasks see different info provided with the
744 uname() system call
745
ae5e1b22
PE
746config IPC_NS
747 bool "IPC namespace"
614b84cf 748 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
ae5e1b22
PE
749 help
750 In this namespace tasks work with IPC ids which correspond to
614b84cf 751 different IPC objects in different namespaces.
ae5e1b22 752
aee16ce7
PE
753config USER_NS
754 bool "User namespace (EXPERIMENTAL)"
755 depends on NAMESPACES && EXPERIMENTAL
756 help
757 This allows containers, i.e. vservers, to use user namespaces
758 to provide different user info for different servers.
759 If unsure, say N.
760
74bd59bb
PE
761config PID_NS
762 bool "PID Namespaces (EXPERIMENTAL)"
763 default n
764 depends on NAMESPACES && EXPERIMENTAL
765 help
12d2b8f9 766 Support process id namespaces. This allows having multiple
692105b8 767 processes with the same pid as long as they are in different
74bd59bb
PE
768 pid namespaces. This is a building block of containers.
769
770 Unless you want to work with an experimental feature
771 say N here.
772
d6eb633f
MH
773config NET_NS
774 bool "Network namespace"
775 default n
776 depends on NAMESPACES && EXPERIMENTAL && NET
777 help
778 Allow user space to create what appear to be multiple instances
779 of the network stack.
780
f991633d
DG
781config BLK_DEV_INITRD
782 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
783 depends on BROKEN || !FRV
784 help
785 The initial RAM filesystem is a ramfs which is loaded by the
786 boot loader (loadlin or lilo) and that is mounted as root
787 before the normal boot procedure. It is typically used to
788 load modules needed to mount the "real" root file system,
789 etc. See <file:Documentation/initrd.txt> for details.
790
791 If RAM disk support (BLK_DEV_RAM) is also included, this
792 also enables initial RAM disk (initrd) support and adds
793 15 Kbytes (more on some other architectures) to the kernel size.
794
795 If unsure say Y.
796
c33df4ea
JPS
797if BLK_DEV_INITRD
798
dbec4866
SR
799source "usr/Kconfig"
800
c33df4ea
JPS
801endif
802
c45b4f1f 803config CC_OPTIMIZE_FOR_SIZE
96fffeb4 804 bool "Optimize for size"
c45b4f1f 805 default y
c45b4f1f
LT
806 help
807 Enabling this option will pass "-Os" instead of "-O2" to gcc
808 resulting in a smaller kernel.
809
775a7229 810 If unsure, say Y.
c45b4f1f 811
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RD
812config SYSCTL
813 bool
814
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RD
815config ANON_INODES
816 bool
817
1da177e4
LT
818menuconfig EMBEDDED
819 bool "Configure standard kernel features (for small systems)"
820 help
821 This option allows certain base kernel options and settings
822 to be disabled or tweaked. This is for specialized
823 environments which can tolerate a "non-standard" kernel.
824 Only use this if you really know what you are doing.
825
ae81f9e3
CE
826config UID16
827 bool "Enable 16-bit UID system calls" if EMBEDDED
09337f50 828 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
ae81f9e3
CE
829 default y
830 help
831 This enables the legacy 16-bit UID syscall wrappers.
832
b89a8171 833config SYSCTL_SYSCALL
0847062a 834 bool "Sysctl syscall support" if EMBEDDED
26a7034b 835 depends on PROC_SYSCTL
13bb7e37 836 default y
b89a8171 837 select SYSCTL
ae81f9e3 838 ---help---
13bb7e37
EB
839 sys_sysctl uses binary paths that have been found challenging
840 to properly maintain and use. The interface in /proc/sys
841 using paths with ascii names is now the primary path to this
842 information.
b89a8171 843
13bb7e37
EB
844 Almost nothing using the binary sysctl interface so if you are
845 trying to save some space it is probably safe to disable this,
846 making your kernel marginally smaller.
b89a8171 847
13bb7e37 848 If unsure say Y here.
ae81f9e3 849
1da177e4 850config KALLSYMS
979c6a1e 851 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
1da177e4
LT
852 default y
853 help
854 Say Y here to let the kernel print out symbolic crash information and
855 symbolic stack backtraces. This increases the size of the kernel
856 somewhat, as all symbols have to be loaded into the kernel image.
857
858config KALLSYMS_ALL
859 bool "Include all symbols in kallsyms"
860 depends on DEBUG_KERNEL && KALLSYMS
861 help
862 Normally kallsyms only contains the symbols of functions, for nicer
863 OOPS messages. Some debuggers can use kallsyms for other
f9f97bc0
JJ
864 symbols too: say Y here to include all symbols, if you need them
865 and you don't care about adding 300k to the size of your kernel.
1da177e4
LT
866
867 Say N.
868
869config KALLSYMS_EXTRA_PASS
870 bool "Do an extra kallsyms pass"
871 depends on KALLSYMS
872 help
873 If kallsyms is not working correctly, the build will fail with
874 inconsistent kallsyms data. If that occurs, log a bug report and
875 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
876 Always say N here unless you find a bug in kallsyms, which must be
877 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
878 you wait for kallsyms to be fixed.
879
d59745ce 880
712f47ce
GKH
881config HOTPLUG
882 bool "Support for hot-pluggable devices" if EMBEDDED
883 default y
884 help
885 This option is provided for the case where no hotplug or uevent
886 capabilities is wanted by the kernel. You should only consider
887 disabling this option for embedded systems that do not use modules, a
888 dynamic /dev tree, or dynamic device discovery. Just say Y.
889
d59745ce
MM
890config PRINTK
891 default y
892 bool "Enable support for printk" if EMBEDDED
893 help
894 This option enables normal printk support. Removing it
895 eliminates most of the message strings from the kernel image
896 and makes the kernel more or less silent. As this makes it
897 very difficult to diagnose system problems, saying N here is
898 strongly discouraged.
899
c8538a7a
MM
900config BUG
901 bool "BUG() support" if EMBEDDED
902 default y
903 help
904 Disabling this option eliminates support for BUG and WARN, reducing
905 the size of your kernel image and potentially quietly ignoring
906 numerous fatal conditions. You should only consider disabling this
907 option for embedded systems with no facilities for reporting errors.
908 Just say Y.
909
708e9a79
MM
910config ELF_CORE
911 default y
912 bool "Enable ELF core dumps" if EMBEDDED
913 help
914 Enable support for generating core dumps. Disabling saves about 4k.
915
e5e1d3cb
SS
916config PCSPKR_PLATFORM
917 bool "Enable PC-Speaker support" if EMBEDDED
918 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
919 default y
920 help
921 This option allows to disable the internal PC-Speaker
922 support, saving some memory.
923
1da177e4
LT
924config BASE_FULL
925 default y
926 bool "Enable full-sized data structures for core" if EMBEDDED
927 help
928 Disabling this option reduces the size of miscellaneous core
929 kernel data structures. This saves memory on small machines,
930 but may reduce performance.
931
932config FUTEX
933 bool "Enable futex support" if EMBEDDED
934 default y
23f78d4a 935 select RT_MUTEXES
1da177e4
LT
936 help
937 Disabling this option will cause the kernel to be built without
938 support for "fast userspace mutexes". The resulting kernel may not
939 run glibc-based applications correctly.
940
941config EPOLL
942 bool "Enable eventpoll support" if EMBEDDED
943 default y
448e3cee 944 select ANON_INODES
1da177e4
LT
945 help
946 Disabling this option will cause the kernel to be built without
947 support for epoll family of system calls.
948
fba2afaa
DL
949config SIGNALFD
950 bool "Enable signalfd() system call" if EMBEDDED
448e3cee 951 select ANON_INODES
fba2afaa
DL
952 default y
953 help
954 Enable the signalfd() system call that allows to receive signals
955 on a file descriptor.
956
957 If unsure, say Y.
958
b215e283
DL
959config TIMERFD
960 bool "Enable timerfd() system call" if EMBEDDED
448e3cee 961 select ANON_INODES
b215e283
DL
962 default y
963 help
964 Enable the timerfd() system call that allows to receive timer
965 events on a file descriptor.
966
967 If unsure, say Y.
968
e1ad7468
DL
969config EVENTFD
970 bool "Enable eventfd() system call" if EMBEDDED
448e3cee 971 select ANON_INODES
e1ad7468
DL
972 default y
973 help
974 Enable the eventfd() system call that allows to receive both
975 kernel notification (ie. KAIO) or userspace notifications.
976
977 If unsure, say Y.
978
1da177e4
LT
979config SHMEM
980 bool "Use full shmem filesystem" if EMBEDDED
981 default y
982 depends on MMU
983 help
984 The shmem is an internal filesystem used to manage shared memory.
985 It is backed by swap and manages resource limits. It is also exported
986 to userspace as tmpfs if TMPFS is enabled. Disabling this
987 option replaces shmem and tmpfs with the much simpler ramfs code,
988 which may be appropriate on small systems without swap.
989
ebf3f09c
TP
990config AIO
991 bool "Enable AIO support" if EMBEDDED
992 default y
993 help
994 This option enables POSIX asynchronous I/O which may by used
995 by some high performance threaded applications. Disabling
996 this option saves about 7k.
997
cdd6c482 998config HAVE_PERF_EVENTS
0793a61d 999 bool
018df72d
MF
1000 help
1001 See tools/perf/design.txt for details.
0793a61d 1002
906010b2
PZ
1003config PERF_USE_VMALLOC
1004 bool
1005 help
1006 See tools/perf/design.txt for details
1007
57c0c15b 1008menu "Kernel Performance Events And Counters"
0793a61d 1009
cdd6c482 1010config PERF_EVENTS
57c0c15b
IM
1011 bool "Kernel performance events and counters"
1012 default y if (PROFILING || PERF_COUNTERS)
cdd6c482 1013 depends on HAVE_PERF_EVENTS
4c59e467 1014 select ANON_INODES
e360adbe 1015 select IRQ_WORK
0793a61d 1016 help
57c0c15b
IM
1017 Enable kernel support for various performance events provided
1018 by software and hardware.
0793a61d 1019
dd77038d 1020 Software events are supported either built-in or via the
57c0c15b 1021 use of generic tracepoints.
0793a61d 1022
57c0c15b
IM
1023 Most modern CPUs support performance events via performance
1024 counter registers. These registers count the number of certain
0793a61d
TG
1025 types of hw events: such as instructions executed, cachemisses
1026 suffered, or branches mis-predicted - without slowing down the
1027 kernel or applications. These registers can also trigger interrupts
1028 when a threshold number of events have passed - and can thus be
1029 used to profile the code that runs on that CPU.
1030
57c0c15b 1031 The Linux Performance Event subsystem provides an abstraction of
dd77038d 1032 these software and hardware event capabilities, available via a
57c0c15b 1033 system call and used by the "perf" utility in tools/perf/. It
0793a61d
TG
1034 provides per task and per CPU counters, and it provides event
1035 capabilities on top of those.
1036
1037 Say Y if unsure.
1038
57c0c15b
IM
1039config PERF_COUNTERS
1040 bool "Kernel performance counters (old config option)"
1041 depends on HAVE_PERF_EVENTS
1042 help
1043 This config has been obsoleted by the PERF_EVENTS
1044 config option - please see that one for details.
1045
1046 It has no effect on the kernel whether you enable
1047 it or not, it is a compatibility placeholder.
1048
1049 Say N if unsure.
1050
906010b2
PZ
1051config DEBUG_PERF_USE_VMALLOC
1052 default n
1053 bool "Debug: use vmalloc to back perf mmap() buffers"
1054 depends on PERF_EVENTS && DEBUG_KERNEL
1055 select PERF_USE_VMALLOC
1056 help
1057 Use vmalloc memory to back perf mmap() buffers.
1058
1059 Mostly useful for debugging the vmalloc code on platforms
1060 that don't require it.
1061
1062 Say N if unsure.
1063
0793a61d
TG
1064endmenu
1065
f8891e5e
CL
1066config VM_EVENT_COUNTERS
1067 default y
1068 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1069 help
2aea4fb6
PJ
1070 VM event counters are needed for event counts to be shown.
1071 This option allows the disabling of the VM event counters
1072 on EMBEDDED systems. /proc/vmstat will only show page counts
1073 if VM event counters are disabled.
f8891e5e 1074
3d137310
TP
1075config PCI_QUIRKS
1076 default y
61cfc7e4
GU
1077 bool "Enable PCI quirk workarounds" if EMBEDDED
1078 depends on PCI
3d137310
TP
1079 help
1080 This enables workarounds for various PCI chipset
1081 bugs/quirks. Disable this only if your target machine is
1082 unaffected by PCI quirks.
1083
41ecc55b
CL
1084config SLUB_DEBUG
1085 default y
1086 bool "Enable SLUB debugging support" if EMBEDDED
f6acb635 1087 depends on SLUB && SYSFS
41ecc55b
CL
1088 help
1089 SLUB has extensive debug support features. Disabling these can
1090 result in significant savings in code size. This also disables
1091 SLUB sysfs support. /sys/slab will not exist and there will be
1092 no support for cache validation etc.
1093
b943c460
RD
1094config COMPAT_BRK
1095 bool "Disable heap randomization"
1096 default y
1097 help
1098 Randomizing heap placement makes heap exploits harder, but it
1099 also breaks ancient binaries (including anything libc5 based).
1100 This option changes the bootup default to heap randomization
692105b8 1101 disabled, and can be overridden at runtime by setting
b943c460
RD
1102 /proc/sys/kernel/randomize_va_space to 2.
1103
1104 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1105
81819f0f
CL
1106choice
1107 prompt "Choose SLAB allocator"
a0acd820 1108 default SLUB
81819f0f
CL
1109 help
1110 This option allows to select a slab allocator.
1111
1112config SLAB
1113 bool "SLAB"
1114 help
1115 The regular slab allocator that is established and known to work
34013886 1116 well in all environments. It organizes cache hot objects in
02f56210 1117 per cpu and per node queues.
81819f0f
CL
1118
1119config SLUB
81819f0f
CL
1120 bool "SLUB (Unqueued Allocator)"
1121 help
1122 SLUB is a slab allocator that minimizes cache line usage
1123 instead of managing queues of cached objects (SLAB approach).
1124 Per cpu caching is realized using slabs of objects instead
1125 of queues of objects. SLUB can use memory efficiently
02f56210
SA
1126 and has enhanced diagnostics. SLUB is the default choice for
1127 a slab allocator.
81819f0f
CL
1128
1129config SLOB
84a01c2f 1130 depends on EMBEDDED
81819f0f
CL
1131 bool "SLOB (Simple Allocator)"
1132 help
37291458
MM
1133 SLOB replaces the stock allocator with a drastically simpler
1134 allocator. SLOB is generally more space efficient but
1135 does not perform as well on large systems.
81819f0f
CL
1136
1137endchoice
1138
ea637639
JZ
1139config MMAP_ALLOW_UNINITIALIZED
1140 bool "Allow mmapped anonymous memory to be uninitialized"
1141 depends on EMBEDDED && !MMU
1142 default n
1143 help
1144 Normally, and according to the Linux spec, anonymous memory obtained
1145 from mmap() has it's contents cleared before it is passed to
1146 userspace. Enabling this config option allows you to request that
1147 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1148 providing a huge performance boost. If this option is not enabled,
1149 then the flag will be ignored.
1150
1151 This is taken advantage of by uClibc's malloc(), and also by
1152 ELF-FDPIC binfmt's brk and stack allocator.
1153
1154 Because of the obvious security issues, this option should only be
1155 enabled on embedded devices where you control what is run in
1156 userspace. Since that isn't generally a problem on no-MMU systems,
1157 it is normally safe to say Y here.
1158
1159 See Documentation/nommu-mmap.txt for more information.
1160
125e5645 1161config PROFILING
b309a294 1162 bool "Profiling support"
125e5645
MD
1163 help
1164 Say Y here to enable the extended profiling support mechanisms used
1165 by profilers such as OProfile.
1166
5f87f112
IM
1167#
1168# Place an empty function call at each tracepoint site. Can be
1169# dynamically changed for a probe function.
1170#
97e1c18e 1171config TRACEPOINTS
5f87f112 1172 bool
97e1c18e 1173
fb32e03f
MD
1174source "arch/Kconfig"
1175
1da177e4
LT
1176endmenu # General setup
1177
ee7e5516
DES
1178config HAVE_GENERIC_DMA_COHERENT
1179 bool
1180 default n
1181
158a9624
LT
1182config SLABINFO
1183 bool
1184 depends on PROC_FS
0f389ec6 1185 depends on SLAB || SLUB_DEBUG
158a9624
LT
1186 default y
1187
ae81f9e3
CE
1188config RT_MUTEXES
1189 boolean
ae81f9e3 1190
1da177e4
LT
1191config BASE_SMALL
1192 int
1193 default 0 if BASE_FULL
1194 default 1 if !BASE_FULL
1195
66da5733 1196menuconfig MODULES
1da177e4
LT
1197 bool "Enable loadable module support"
1198 help
1199 Kernel modules are small pieces of compiled code which can
1200 be inserted in the running kernel, rather than being
1201 permanently built into the kernel. You use the "modprobe"
1202 tool to add (and sometimes remove) them. If you say Y here,
1203 many parts of the kernel can be built as modules (by
1204 answering M instead of Y where indicated): this is most
1205 useful for infrequently used options which are not required
1206 for booting. For more information, see the man pages for
1207 modprobe, lsmod, modinfo, insmod and rmmod.
1208
1209 If you say Y here, you will need to run "make
1210 modules_install" to put the modules under /lib/modules/
1211 where modprobe can find them (you may need to be root to do
1212 this).
1213
1214 If unsure, say Y.
1215
0b0de144
RD
1216if MODULES
1217
826e4506
LT
1218config MODULE_FORCE_LOAD
1219 bool "Forced module loading"
826e4506
LT
1220 default n
1221 help
91e37a79
RR
1222 Allow loading of modules without version information (ie. modprobe
1223 --force). Forced module loading sets the 'F' (forced) taint flag and
1224 is usually a really bad idea.
826e4506 1225
1da177e4
LT
1226config MODULE_UNLOAD
1227 bool "Module unloading"
1da177e4
LT
1228 help
1229 Without this option you will not be able to unload any
1230 modules (note that some modules may not be unloadable
f7f5b675
DV
1231 anyway), which makes your kernel smaller, faster
1232 and simpler. If unsure, say Y.
1da177e4
LT
1233
1234config MODULE_FORCE_UNLOAD
1235 bool "Forced module unloading"
1236 depends on MODULE_UNLOAD && EXPERIMENTAL
1237 help
1238 This option allows you to force a module to unload, even if the
1239 kernel believes it is unsafe: the kernel will remove the module
1240 without waiting for anyone to stop using it (using the -f option to
1241 rmmod). This is mainly for kernel developers and desperate users.
1242 If unsure, say N.
1243
1da177e4 1244config MODVERSIONS
0d541643 1245 bool "Module versioning support"
1da177e4
LT
1246 help
1247 Usually, you have to use modules compiled with your kernel.
1248 Saying Y here makes it sometimes possible to use modules
1249 compiled for different kernels, by adding enough information
1250 to the modules to (hopefully) spot any changes which would
1251 make them incompatible with the kernel you are running. If
1252 unsure, say N.
1253
1254config MODULE_SRCVERSION_ALL
1255 bool "Source checksum for all modules"
1da177e4
LT
1256 help
1257 Modules which contain a MODULE_VERSION get an extra "srcversion"
1258 field inserted into their modinfo section, which contains a
1259 sum of the source files which made it. This helps maintainers
1260 see exactly which source was used to build a module (since
1261 others sometimes change the module source without updating
1262 the version). With this option, such a "srcversion" field
1263 will be created for all modules. If unsure, say N.
1264
0b0de144
RD
1265endif # MODULES
1266
98a79d6a
RR
1267config INIT_ALL_POSSIBLE
1268 bool
1269 help
1270 Back when each arch used to define their own cpu_online_map and
1271 cpu_possible_map, some of them chose to initialize cpu_possible_map
1272 with all 1s, and others with all 0s. When they were centralised,
1273 it was better to provide this option than to break all the archs
692105b8 1274 and have several arch maintainers pursuing me down dark alleys.
98a79d6a 1275
1da177e4
LT
1276config STOP_MACHINE
1277 bool
1278 default y
1279 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1280 help
1281 Need stop_machine() primitive.
3a65dfe8 1282
3a65dfe8 1283source "block/Kconfig"
e98c3202
AK
1284
1285config PREEMPT_NOTIFIERS
1286 bool
e260be67 1287
16295bec
SK
1288config PADATA
1289 depends on SMP
1290 bool
1291
6beb0009 1292source "kernel/Kconfig.locks"