drivers: power: report battery voltage in AOSP compatible format
[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
b99b87f7 22
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23config IRQ_WORK
24 bool
e360adbe 25
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26config BUILDTIME_EXTABLE_SORT
27 bool
28
ff0cfc66 29menu "General setup"
1da177e4 30
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31config BROKEN
32 bool
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33
34config BROKEN_ON_SMP
35 bool
36 depends on BROKEN || !SMP
37 default y
38
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39config INIT_ENV_ARG_LIMIT
40 int
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41 default 32 if !UML
42 default 128 if UML
1da177e4 43 help
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44 Maximum of each of the number of arguments and environment
45 variables passed to init from the kernel command line.
1da177e4 46
1da177e4 47
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48config CROSS_COMPILE
49 string "Cross-compiler tool prefix"
50 help
51 Same as running 'make CROSS_COMPILE=prefix-' but stored for
52 default make runs in this kernel build directory. You don't
53 need to set this unless you want the configured kernel build
54 directory to select the cross-compiler automatically.
55
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56config LOCALVERSION
57 string "Local version - append to kernel release"
58 help
59 Append an extra string to the end of your kernel version.
60 This will show up when you type uname, for example.
61 The string you set here will be appended after the contents of
62 any files with a filename matching localversion* in your
63 object and source tree, in that order. Your total string can
64 be a maximum of 64 characters.
65
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66config LOCALVERSION_AUTO
67 bool "Automatically append version information to the version string"
68 default y
69 help
70 This will try to automatically determine if the current tree is a
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71 release tree by looking for git tags that belong to the current
72 top of tree revision.
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73
74 A string of the format -gxxxxxxxx will be added to the localversion
6e5a5420 75 if a git-based tree is found. The string generated by this will be
aaebf433 76 appended after any matching localversion* files, and after the value
6e5a5420 77 set in CONFIG_LOCALVERSION.
aaebf433 78
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79 (The actual string used here is the first eight characters produced
80 by running the command:
81
82 $ git rev-parse --verify HEAD
83
84 which is done within the script "scripts/setlocalversion".)
aaebf433 85
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86config HAVE_KERNEL_GZIP
87 bool
88
89config HAVE_KERNEL_BZIP2
90 bool
91
92config HAVE_KERNEL_LZMA
93 bool
94
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95config HAVE_KERNEL_XZ
96 bool
97
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98config HAVE_KERNEL_LZO
99 bool
100
30d65dbf 101choice
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102 prompt "Kernel compression mode"
103 default KERNEL_GZIP
3ebe1243 104 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
2e9f3bdd 105 help
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106 The linux kernel is a kind of self-extracting executable.
107 Several compression algorithms are available, which differ
108 in efficiency, compression and decompression speed.
109 Compression speed is only relevant when building a kernel.
110 Decompression speed is relevant at each boot.
111
112 If you have any problems with bzip2 or lzma compressed
113 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
114 version of this functionality (bzip2 only), for 2.4, was
115 supplied by Christian Ludwig)
116
117 High compression options are mostly useful for users, who
118 are low on disk space (embedded systems), but for whom ram
119 size matters less.
120
121 If in doubt, select 'gzip'
122
123config KERNEL_GZIP
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124 bool "Gzip"
125 depends on HAVE_KERNEL_GZIP
126 help
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127 The old and tried gzip compression. It provides a good balance
128 between compression ratio and decompression speed.
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129
130config KERNEL_BZIP2
131 bool "Bzip2"
2e9f3bdd 132 depends on HAVE_KERNEL_BZIP2
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133 help
134 Its compression ratio and speed is intermediate.
0a4dd35c 135 Decompression speed is slowest among the choices. The kernel
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136 size is about 10% smaller with bzip2, in comparison to gzip.
137 Bzip2 uses a large amount of memory. For modern kernels you
138 will need at least 8MB RAM or more for booting.
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139
140config KERNEL_LZMA
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141 bool "LZMA"
142 depends on HAVE_KERNEL_LZMA
143 help
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144 This compression algorithm's ratio is best. Decompression speed
145 is between gzip and bzip2. Compression is slowest.
146 The kernel size is about 33% smaller with LZMA in comparison to gzip.
30d65dbf 147
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148config KERNEL_XZ
149 bool "XZ"
150 depends on HAVE_KERNEL_XZ
151 help
152 XZ uses the LZMA2 algorithm and instruction set specific
153 BCJ filters which can improve compression ratio of executable
154 code. The size of the kernel is about 30% smaller with XZ in
155 comparison to gzip. On architectures for which there is a BCJ
156 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
157 will create a few percent smaller kernel than plain LZMA.
158
159 The speed is about the same as with LZMA: The decompression
160 speed of XZ is better than that of bzip2 but worse than gzip
161 and LZO. Compression is slow.
162
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163config KERNEL_LZO
164 bool "LZO"
165 depends on HAVE_KERNEL_LZO
166 help
0a4dd35c 167 Its compression ratio is the poorest among the choices. The kernel
681b3049 168 size is about 10% bigger than gzip; however its speed
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169 (both compression and decompression) is the fastest.
170
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171endchoice
172
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173config DEFAULT_HOSTNAME
174 string "Default hostname"
175 default "(none)"
176 help
177 This option determines the default system hostname before userspace
178 calls sethostname(2). The kernel traditionally uses "(none)" here,
179 but you may wish to use a different default here to make a minimal
180 system more usable with less configuration.
181
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182config SWAP
183 bool "Support for paging of anonymous memory (swap)"
9361401e 184 depends on MMU && BLOCK
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185 default y
186 help
187 This option allows you to choose whether you want to have support
92c3504e 188 for so called swap devices or swap files in your kernel that are
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189 used to provide more virtual memory than the actual RAM present
190 in your computer. If unsure say Y.
191
192config SYSVIPC
193 bool "System V IPC"
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194 ---help---
195 Inter Process Communication is a suite of library functions and
196 system calls which let processes (running programs) synchronize and
197 exchange information. It is generally considered to be a good thing,
198 and some programs won't run unless you say Y here. In particular, if
199 you want to run the DOS emulator dosemu under Linux (read the
200 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
201 you'll need to say Y here.
202
203 You can find documentation about IPC with "info ipc" and also in
204 section 6.4 of the Linux Programmer's Guide, available from
205 <http://www.tldp.org/guides.html>.
206
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207config SYSVIPC_SYSCTL
208 bool
209 depends on SYSVIPC
210 depends on SYSCTL
211 default y
212
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213config POSIX_MQUEUE
214 bool "POSIX Message Queues"
19c92399 215 depends on NET
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216 ---help---
217 POSIX variant of message queues is a part of IPC. In POSIX message
218 queues every message has a priority which decides about succession
219 of receiving it by a process. If you want to compile and run
220 programs written e.g. for Solaris with use of its POSIX message
b0e37650 221 queues (functions mq_*) say Y here.
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222
223 POSIX message queues are visible as a filesystem called 'mqueue'
224 and can be mounted somewhere if you want to do filesystem
225 operations on message queues.
226
227 If unsure, say Y.
228
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229config POSIX_MQUEUE_SYSCTL
230 bool
231 depends on POSIX_MQUEUE
232 depends on SYSCTL
233 default y
234
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235config FHANDLE
236 bool "open by fhandle syscalls"
237 select EXPORTFS
238 help
239 If you say Y here, a user level program will be able to map
240 file names to handle and then later use the handle for
241 different file system operations. This is useful in implementing
242 userspace file servers, which now track files using handles instead
243 of names. The handle would remain the same even if file names
244 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
245 syscalls.
246
247config AUDIT
248 bool "Auditing support"
249 depends on NET
250 help
251 Enable auditing infrastructure that can be used with another
252 kernel subsystem, such as SELinux (which requires this for
253 logging of avc messages output). Does not do system-call
254 auditing without CONFIG_AUDITSYSCALL.
255
256config AUDITSYSCALL
257 bool "Enable system-call auditing support"
258 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
259 default y if SECURITY_SELINUX
260 help
261 Enable low-overhead system-call auditing infrastructure that
262 can be used independently or with another kernel subsystem,
263 such as SELinux.
264
265config AUDIT_WATCH
266 def_bool y
267 depends on AUDITSYSCALL
268 select FSNOTIFY
269
270config AUDIT_TREE
271 def_bool y
272 depends on AUDITSYSCALL
273 select FSNOTIFY
274
275config AUDIT_LOGINUID_IMMUTABLE
276 bool "Make audit loginuid immutable"
277 depends on AUDIT
278 help
279 The config option toggles if a task setting its loginuid requires
280 CAP_SYS_AUDITCONTROL or if that task should require no special permissions
281 but should instead only allow setting its loginuid if it was never
282 previously set. On systems which use systemd or a similar central
283 process to restart login services this should be set to true. On older
284 systems in which an admin would typically have to directly stop and
285 start processes this should be set to false. Setting this to true allows
286 one to drop potentially dangerous capabilites from the login tasks,
287 but may not be backwards compatible with older init systems.
288
289source "kernel/irq/Kconfig"
290source "kernel/time/Kconfig"
291
292menu "CPU/Task time and stats accounting"
293
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294config VIRT_CPU_ACCOUNTING
295 bool
296
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297choice
298 prompt "Cputime accounting"
299 default TICK_CPU_ACCOUNTING if !PPC64
02fc8d37 300 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
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301
302# Kind of a stub config for the pure tick based cputime accounting
303config TICK_CPU_ACCOUNTING
304 bool "Simple tick based cputime accounting"
c58b0df1 305 depends on !S390 && !NO_HZ_FULL
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306 help
307 This is the basic tick based cputime accounting that maintains
308 statistics about user, system and idle time spent on per jiffies
309 granularity.
310
311 If unsure, say Y.
312
abf917cd 313config VIRT_CPU_ACCOUNTING_NATIVE
b952741c 314 bool "Deterministic task and CPU time accounting"
c58b0df1 315 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
abf917cd 316 select VIRT_CPU_ACCOUNTING
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317 help
318 Select this option to enable more accurate task and CPU time
319 accounting. This is done by reading a CPU counter on each
320 kernel entry and exit and on transitions within the kernel
321 between system, softirq and hardirq state, so there is a
322 small performance impact. In the case of s390 or IBM POWER > 5,
323 this also enables accounting of stolen time on logically-partitioned
324 systems.
325
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326config VIRT_CPU_ACCOUNTING_GEN
327 bool "Full dynticks CPU time accounting"
328 depends on HAVE_CONTEXT_TRACKING && 64BIT
329 select VIRT_CPU_ACCOUNTING
330 select CONTEXT_TRACKING
331 help
332 Select this option to enable task and CPU time accounting on full
333 dynticks systems. This accounting is implemented by watching every
334 kernel-user boundaries using the context tracking subsystem.
335 The accounting is thus performed at the expense of some significant
336 overhead.
337
338 For now this is only useful if you are working on the full
339 dynticks subsystem development.
340
341 If unsure, say N.
342
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343config IRQ_TIME_ACCOUNTING
344 bool "Fine granularity task level IRQ time accounting"
c58b0df1 345 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
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346 help
347 Select this option to enable fine granularity task irq time
348 accounting. This is done by reading a timestamp on each
349 transitions between softirq and hardirq state, so there can be a
350 small performance impact.
351
352 If in doubt, say N here.
353
354endchoice
355
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356config BSD_PROCESS_ACCT
357 bool "BSD Process Accounting"
358 help
359 If you say Y here, a user level program will be able to instruct the
360 kernel (via a special system call) to write process accounting
361 information to a file: whenever a process exits, information about
362 that process will be appended to the file by the kernel. The
363 information includes things such as creation time, owning user,
364 command name, memory usage, controlling terminal etc. (the complete
365 list is in the struct acct in <file:include/linux/acct.h>). It is
366 up to the user level program to do useful things with this
367 information. This is generally a good idea, so say Y.
368
369config BSD_PROCESS_ACCT_V3
370 bool "BSD Process Accounting version 3 file format"
371 depends on BSD_PROCESS_ACCT
372 default n
373 help
374 If you say Y here, the process accounting information is written
375 in a new file format that also logs the process IDs of each
376 process and it's parent. Note that this file format is incompatible
377 with previous v0/v1/v2 file formats, so you will need updated tools
378 for processing it. A preliminary version of these tools is available
37a4c940 379 at <http://www.gnu.org/software/acct/>.
1da177e4 380
c757249a 381config TASKSTATS
19c92399 382 bool "Export task/process statistics through netlink"
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383 depends on NET
384 default n
385 help
386 Export selected statistics for tasks/processes through the
387 generic netlink interface. Unlike BSD process accounting, the
388 statistics are available during the lifetime of tasks/processes as
389 responses to commands. Like BSD accounting, they are sent to user
390 space on task exit.
391
392 Say N if unsure.
393
ca74e92b 394config TASK_DELAY_ACCT
19c92399 395 bool "Enable per-task delay accounting"
6f44993f 396 depends on TASKSTATS
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397 help
398 Collect information on time spent by a task waiting for system
399 resources like cpu, synchronous block I/O completion and swapping
400 in pages. Such statistics can help in setting a task's priorities
401 relative to other tasks for cpu, io, rss limits etc.
402
403 Say N if unsure.
404
18f705f4 405config TASK_XACCT
19c92399 406 bool "Enable extended accounting over taskstats"
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407 depends on TASKSTATS
408 help
409 Collect extended task accounting data and send the data
410 to userland for processing over the taskstats interface.
411
412 Say N if unsure.
413
414config TASK_IO_ACCOUNTING
19c92399 415 bool "Enable per-task storage I/O accounting"
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416 depends on TASK_XACCT
417 help
418 Collect information on the number of bytes of storage I/O which this
419 task has caused.
420
421 Say N if unsure.
422
391dc69c 423endmenu # "CPU/Task time and stats accounting"
d9817ebe 424
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425menu "RCU Subsystem"
426
427choice
428 prompt "RCU Implementation"
31c9a24e 429 default TREE_RCU
c903ff83 430
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431config TREE_RCU
432 bool "Tree-based hierarchical RCU"
687d7a96 433 depends on !PREEMPT && SMP
016a8d5b 434 select IRQ_WORK
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435 help
436 This option selects the RCU implementation that is
437 designed for very large SMP system with hundreds or
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438 thousands of CPUs. It also scales down nicely to
439 smaller systems.
c903ff83 440
f41d911f 441config TREE_PREEMPT_RCU
a57eb940 442 bool "Preemptible tree-based hierarchical RCU"
9fc52d83 443 depends on PREEMPT
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444 help
445 This option selects the RCU implementation that is
446 designed for very large SMP systems with hundreds or
447 thousands of CPUs, but for which real-time response
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448 is also required. It also scales down nicely to
449 smaller systems.
f41d911f 450
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451 Select this option if you are unsure.
452
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453config TINY_RCU
454 bool "UP-only small-memory-footprint RCU"
8008e129 455 depends on !PREEMPT && !SMP
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456 help
457 This option selects the RCU implementation that is
458 designed for UP systems from which real-time response
459 is not required. This option greatly reduces the
460 memory footprint of RCU.
461
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462config TINY_PREEMPT_RCU
463 bool "Preemptible UP-only small-memory-footprint RCU"
8008e129 464 depends on PREEMPT && !SMP
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465 help
466 This option selects the RCU implementation that is designed
467 for real-time UP systems. This option greatly reduces the
468 memory footprint of RCU.
469
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470endchoice
471
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472config PREEMPT_RCU
473 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
474 help
475 This option enables preemptible-RCU code that is common between
476 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
477
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478config RCU_STALL_COMMON
479 def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
480 help
481 This option enables RCU CPU stall code that is common between
482 the TINY and TREE variants of RCU. The purpose is to allow
483 the tiny variants to disable RCU CPU stall warnings, while
484 making these warnings mandatory for the tree variants.
485
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486config CONTEXT_TRACKING
487 bool
488
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489config RCU_USER_QS
490 bool "Consider userspace as in RCU extended quiescent state"
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491 depends on HAVE_CONTEXT_TRACKING && SMP
492 select CONTEXT_TRACKING
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493 help
494 This option sets hooks on kernel / userspace boundaries and
495 puts RCU in extended quiescent state when the CPU runs in
496 userspace. It means that when a CPU runs in userspace, it is
497 excluded from the global RCU state machine and thus doesn't
af71befa 498 try to keep the timer tick on for RCU.
2b1d5024 499
d677124b 500 Unless you want to hack and help the development of the full
91d1aa43 501 dynticks mode, you shouldn't enable this option. It also
af71befa 502 adds unnecessary overhead.
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503
504 If unsure say N
505
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506config CONTEXT_TRACKING_FORCE
507 bool "Force context tracking"
508 depends on CONTEXT_TRACKING
8b438766 509 default CONTEXT_TRACKING
1fd2b442 510 help
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511 Probe on user/kernel boundaries by default in order to
512 test the features that rely on it such as userspace RCU extended
513 quiescent states.
514 This test is there for debugging until we have a real user like the
515 full dynticks mode.
d677124b 516
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517config RCU_FANOUT
518 int "Tree-based hierarchical RCU fanout value"
519 range 2 64 if 64BIT
520 range 2 32 if !64BIT
f41d911f 521 depends on TREE_RCU || TREE_PREEMPT_RCU
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522 default 64 if 64BIT
523 default 32 if !64BIT
524 help
525 This option controls the fanout of hierarchical implementations
526 of RCU, allowing RCU to work efficiently on machines with
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527 large numbers of CPUs. This value must be at least the fourth
528 root of NR_CPUS, which allows NR_CPUS to be insanely large.
529 The default value of RCU_FANOUT should be used for production
530 systems, but if you are stress-testing the RCU implementation
531 itself, small RCU_FANOUT values allow you to test large-system
532 code paths on small(er) systems.
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533
534 Select a specific number if testing RCU itself.
535 Take the default if unsure.
536
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537config RCU_FANOUT_LEAF
538 int "Tree-based hierarchical RCU leaf-level fanout value"
539 range 2 RCU_FANOUT if 64BIT
540 range 2 RCU_FANOUT if !64BIT
541 depends on TREE_RCU || TREE_PREEMPT_RCU
542 default 16
543 help
544 This option controls the leaf-level fanout of hierarchical
545 implementations of RCU, and allows trading off cache misses
546 against lock contention. Systems that synchronize their
547 scheduling-clock interrupts for energy-efficiency reasons will
548 want the default because the smaller leaf-level fanout keeps
549 lock contention levels acceptably low. Very large systems
550 (hundreds or thousands of CPUs) will instead want to set this
551 value to the maximum value possible in order to reduce the
552 number of cache misses incurred during RCU's grace-period
553 initialization. These systems tend to run CPU-bound, and thus
554 are not helped by synchronized interrupts, and thus tend to
555 skew them, which reduces lock contention enough that large
556 leaf-level fanouts work well.
557
558 Select a specific number if testing RCU itself.
559
560 Select the maximum permissible value for large systems.
561
562 Take the default if unsure.
563
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564config RCU_FANOUT_EXACT
565 bool "Disable tree-based hierarchical RCU auto-balancing"
f41d911f 566 depends on TREE_RCU || TREE_PREEMPT_RCU
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567 default n
568 help
569 This option forces use of the exact RCU_FANOUT value specified,
570 regardless of imbalances in the hierarchy. This is useful for
571 testing RCU itself, and might one day be useful on systems with
572 strong NUMA behavior.
573
574 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
575
576 Say N if unsure.
577
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578config RCU_FAST_NO_HZ
579 bool "Accelerate last non-dyntick-idle CPU's grace periods"
3451d024 580 depends on NO_HZ_COMMON && SMP
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581 default n
582 help
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583 This option permits CPUs to enter dynticks-idle state even if
584 they have RCU callbacks queued, and prevents RCU from waking
585 these CPUs up more than roughly once every four jiffies (by
586 default, you can adjust this using the rcutree.rcu_idle_gp_delay
587 parameter), thus improving energy efficiency. On the other
588 hand, this option increases the duration of RCU grace periods,
589 for example, slowing down synchronize_rcu().
ba49df47 590
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591 Say Y if energy efficiency is critically important, and you
592 don't care about increased grace-period durations.
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593
594 Say N if you are unsure.
595
c903ff83 596config TREE_RCU_TRACE
f41d911f 597 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
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598 select DEBUG_FS
599 help
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600 This option provides tracing for the TREE_RCU and
601 TREE_PREEMPT_RCU implementations, permitting Makefile to
602 trivially select kernel/rcutree_trace.c.
c903ff83 603
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604config RCU_BOOST
605 bool "Enable RCU priority boosting"
27f4d280 606 depends on RT_MUTEXES && PREEMPT_RCU
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607 default n
608 help
609 This option boosts the priority of preempted RCU readers that
610 block the current preemptible RCU grace period for too long.
611 This option also prevents heavy loads from blocking RCU
612 callback invocation for all flavors of RCU.
613
614 Say Y here if you are working with real-time apps or heavy loads
615 Say N here if you are unsure.
616
617config RCU_BOOST_PRIO
618 int "Real-time priority to boost RCU readers to"
619 range 1 99
620 depends on RCU_BOOST
621 default 1
622 help
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623 This option specifies the real-time priority to which long-term
624 preempted RCU readers are to be boosted. If you are working
625 with a real-time application that has one or more CPU-bound
626 threads running at a real-time priority level, you should set
627 RCU_BOOST_PRIO to a priority higher then the highest-priority
628 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
629 of 1 is appropriate in the common case, which is real-time
630 applications that do not have any CPU-bound threads.
631
632 Some real-time applications might not have a single real-time
633 thread that saturates a given CPU, but instead might have
634 multiple real-time threads that, taken together, fully utilize
635 that CPU. In this case, you should set RCU_BOOST_PRIO to
636 a priority higher than the lowest-priority thread that is
637 conspiring to prevent the CPU from running any non-real-time
638 tasks. For example, if one thread at priority 10 and another
639 thread at priority 5 are between themselves fully consuming
640 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
641 set to priority 6 or higher.
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642
643 Specify the real-time priority, or take the default if unsure.
644
645config RCU_BOOST_DELAY
646 int "Milliseconds to delay boosting after RCU grace-period start"
647 range 0 3000
648 depends on RCU_BOOST
649 default 500
650 help
651 This option specifies the time to wait after the beginning of
652 a given grace period before priority-boosting preempted RCU
653 readers blocking that grace period. Note that any RCU reader
654 blocking an expedited RCU grace period is boosted immediately.
655
656 Accept the default if unsure.
657
3fbfbf7a 658config RCU_NOCB_CPU
34ed6246 659 bool "Offload RCU callback processing from boot-selected CPUs (EXPERIMENTAL"
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660 depends on TREE_RCU || TREE_PREEMPT_RCU
661 default n
662 help
663 Use this option to reduce OS jitter for aggressive HPC or
664 real-time workloads. It can also be used to offload RCU
665 callback invocation to energy-efficient CPUs in battery-powered
666 asymmetric multiprocessors.
667
668 This option offloads callback invocation from the set of
669 CPUs specified at boot time by the rcu_nocbs parameter.
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670 For each such CPU, a kthread ("rcuox/N") will be created to
671 invoke callbacks, where the "N" is the CPU being offloaded,
672 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
673 "s" for RCU-sched. Nothing prevents this kthread from running
674 on the specified CPUs, but (1) the kthreads may be preempted
675 between each callback, and (2) affinity or cgroups can be used
676 to force the kthreads to run on whatever set of CPUs is desired.
3fbfbf7a 677
34ed6246 678 Say Y here if you want to help to debug reduced OS jitter.
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679 Say N here if you are unsure.
680
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681choice
682 prompt "Build-forced no-CBs CPUs"
683 default RCU_NOCB_CPU_NONE
684 help
685 This option allows no-CBs CPUs to be specified at build time.
686 Additional no-CBs CPUs may be specified by the rcu_nocbs=
687 boot parameter.
688
689config RCU_NOCB_CPU_NONE
690 bool "No build_forced no-CBs CPUs"
73c30828 691 depends on RCU_NOCB_CPU && !NO_HZ_FULL
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692 help
693 This option does not force any of the CPUs to be no-CBs CPUs.
694 Only CPUs designated by the rcu_nocbs= boot parameter will be
695 no-CBs CPUs.
696
697config RCU_NOCB_CPU_ZERO
698 bool "CPU 0 is a build_forced no-CBs CPU"
73c30828 699 depends on RCU_NOCB_CPU && !NO_HZ_FULL
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700 help
701 This option forces CPU 0 to be a no-CBs CPU. Additional CPUs
702 may be designated as no-CBs CPUs using the rcu_nocbs= boot
703 parameter will be no-CBs CPUs.
704
705 Select this if CPU 0 needs to be a no-CBs CPU for real-time
706 or energy-efficiency reasons.
707
708config RCU_NOCB_CPU_ALL
709 bool "All CPUs are build_forced no-CBs CPUs"
710 depends on RCU_NOCB_CPU
711 help
712 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
713 boot parameter will be ignored.
714
715 Select this if all CPUs need to be no-CBs CPUs for real-time
716 or energy-efficiency reasons.
717
718endchoice
719
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720endmenu # "RCU Subsystem"
721
1da177e4 722config IKCONFIG
f2443ab6 723 tristate "Kernel .config support"
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724 ---help---
725 This option enables the complete Linux kernel ".config" file
726 contents to be saved in the kernel. It provides documentation
727 of which kernel options are used in a running kernel or in an
728 on-disk kernel. This information can be extracted from the kernel
729 image file with the script scripts/extract-ikconfig and used as
730 input to rebuild the current kernel or to build another kernel.
731 It can also be extracted from a running kernel by reading
732 /proc/config.gz if enabled (below).
733
734config IKCONFIG_PROC
735 bool "Enable access to .config through /proc/config.gz"
736 depends on IKCONFIG && PROC_FS
737 ---help---
738 This option enables access to the kernel configuration file
739 through /proc/config.gz.
740
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741config LOG_BUF_SHIFT
742 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
743 range 12 21
f17a32e9 744 default 17
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745 help
746 Select kernel log buffer size as a power of 2.
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747 Examples:
748 17 => 128 KB
749 16 => 64 KB
750 15 => 32 KB
751 14 => 16 KB
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752 13 => 8 KB
753 12 => 4 KB
754
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755#
756# Architectures with an unreliable sched_clock() should select this:
757#
758config HAVE_UNSTABLE_SCHED_CLOCK
759 bool
760
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761config GENERIC_SCHED_CLOCK
762 bool
763
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764#
765# For architectures that want to enable the support for NUMA-affine scheduler
766# balancing logic:
767#
768config ARCH_SUPPORTS_NUMA_BALANCING
769 bool
770
771# For architectures that (ab)use NUMA to represent different memory regions
772# all cpu-local but of different latencies, such as SuperH.
773#
774config ARCH_WANT_NUMA_VARIABLE_LOCALITY
775 bool
776
777#
778# For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
779config ARCH_WANTS_PROT_NUMA_PROT_NONE
780 bool
781
782config ARCH_USES_NUMA_PROT_NONE
783 bool
784 default y
785 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
786 depends on NUMA_BALANCING
787
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788config NUMA_BALANCING_DEFAULT_ENABLED
789 bool "Automatically enable NUMA aware memory/task placement"
790 default y
791 depends on NUMA_BALANCING
792 help
793 If set, autonumic NUMA balancing will be enabled if running on a NUMA
794 machine.
795
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796config NUMA_BALANCING
797 bool "Memory placement aware NUMA scheduler"
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798 depends on ARCH_SUPPORTS_NUMA_BALANCING
799 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
800 depends on SMP && NUMA && MIGRATION
801 help
802 This option adds support for automatic NUMA aware memory/task placement.
803 The mechanism is quite primitive and is based on migrating memory when
804 it is references to the node the task is running on.
805
806 This system will be inactive on UMA systems.
807
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808menuconfig CGROUPS
809 boolean "Control Group support"
0dea1168 810 depends on EVENTFD
5cdc38f9 811 help
23964d2d 812 This option adds support for grouping sets of processes together, for
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813 use with process control subsystems such as Cpusets, CFS, memory
814 controls or device isolation.
815 See
5cdc38f9 816 - Documentation/scheduler/sched-design-CFS.txt (CFS)
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817 - Documentation/cgroups/ (features for grouping, isolation
818 and resource control)
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819
820 Say N if unsure.
821
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822if CGROUPS
823
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824config CGROUP_DEBUG
825 bool "Example debug cgroup subsystem"
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826 default n
827 help
828 This option enables a simple cgroup subsystem that
829 exports useful debugging information about the cgroups
23964d2d 830 framework.
5cdc38f9 831
23964d2d 832 Say N if unsure.
5cdc38f9 833
5cdc38f9 834config CGROUP_FREEZER
23964d2d 835 bool "Freezer cgroup subsystem"
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836 help
837 Provides a way to freeze and unfreeze all tasks in a
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838 cgroup.
839
840config CGROUP_DEVICE
841 bool "Device controller for cgroups"
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842 help
843 Provides a cgroup implementing whitelists for devices which
844 a process in the cgroup can mknod or open.
845
846config CPUSETS
847 bool "Cpuset support"
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848 help
849 This option will let you create and manage CPUSETs which
850 allow dynamically partitioning a system into sets of CPUs and
851 Memory Nodes and assigning tasks to run only within those sets.
852 This is primarily useful on large SMP or NUMA systems.
853
854 Say N if unsure.
855
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856config PROC_PID_CPUSET
857 bool "Include legacy /proc/<pid>/cpuset file"
858 depends on CPUSETS
859 default y
860
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861config CGROUP_CPUACCT
862 bool "Simple CPU accounting cgroup subsystem"
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863 help
864 Provides a simple Resource Controller for monitoring the
23964d2d 865 total CPU consumed by the tasks in a cgroup.
d842de87 866
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867config RESOURCE_COUNTERS
868 bool "Resource counters"
869 help
870 This option enables controller independent resource accounting
23964d2d 871 infrastructure that works with cgroups.
e552b661 872
c255a458 873config MEMCG
00f0b825 874 bool "Memory Resource Controller for Control Groups"
79ae9c29 875 depends on RESOURCE_COUNTERS
cf475ad2 876 select MM_OWNER
00f0b825 877 help
84ad6d70 878 Provides a memory resource controller that manages both anonymous
21acb9ca 879 memory and page cache. (See Documentation/cgroups/memory.txt)
00f0b825
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880
881 Note that setting this option increases fixed memory overhead
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882 associated with each page of memory in the system. By this,
883 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
884 usage tracking struct at boot. Total amount of this is printed out
885 at boot.
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886
887 Only enable when you're ok with these trade offs and really
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888 sure you need the memory resource controller. Even when you enable
889 this, you can set "cgroup_disable=memory" at your boot option to
890 disable memory resource controller and you can avoid overheads.
c9d5409f 891 (and lose benefits of memory resource controller)
00f0b825 892
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893 This config option also selects MM_OWNER config option, which
894 could in turn add some fork/exit overhead.
895
c255a458 896config MEMCG_SWAP
65e0e811 897 bool "Memory Resource Controller Swap Extension"
c255a458 898 depends on MEMCG && SWAP
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899 help
900 Add swap management feature to memory resource controller. When you
901 enable this, you can limit mem+swap usage per cgroup. In other words,
902 when you disable this, memory resource controller has no cares to
903 usage of swap...a process can exhaust all of the swap. This extension
904 is useful when you want to avoid exhaustion swap but this itself
905 adds more overheads and consumes memory for remembering information.
906 Especially if you use 32bit system or small memory system, please
907 be careful about enabling this. When memory resource controller
908 is disabled by boot option, this will be automatically disabled and
909 there will be no overhead from this. Even when you set this config=y,
00a66d29 910 if boot option "swapaccount=0" is set, swap will not be accounted.
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911 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
912 size is 4096bytes, 512k per 1Gbytes of swap.
c255a458 913config MEMCG_SWAP_ENABLED
a42c390c 914 bool "Memory Resource Controller Swap Extension enabled by default"
c255a458 915 depends on MEMCG_SWAP
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MH
916 default y
917 help
918 Memory Resource Controller Swap Extension comes with its price in
919 a bigger memory consumption. General purpose distribution kernels
43d547f9 920 which want to enable the feature but keep it disabled by default
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921 and let the user enable it by swapaccount boot command line
922 parameter should have this option unselected.
923 For those who want to have the feature enabled by default should
924 select this option (if, for some reason, they need to disable it
00a66d29 925 then swapaccount=0 does the trick).
c255a458 926config MEMCG_KMEM
19c92399
KC
927 bool "Memory Resource Controller Kernel Memory accounting"
928 depends on MEMCG
510fc4e1 929 depends on SLUB || SLAB
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GC
930 help
931 The Kernel Memory extension for Memory Resource Controller can limit
932 the amount of memory used by kernel objects in the system. Those are
933 fundamentally different from the entities handled by the standard
934 Memory Controller, which are page-based, and can be swapped. Users of
935 the kmem extension can use it to guarantee that no group of processes
936 will ever exhaust kernel resources alone.
c077719b 937
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938config CGROUP_HUGETLB
939 bool "HugeTLB Resource Controller for Control Groups"
19c92399 940 depends on RESOURCE_COUNTERS && HUGETLB_PAGE
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941 default n
942 help
943 Provides a cgroup Resource Controller for HugeTLB pages.
944 When you enable this, you can put a per cgroup limit on HugeTLB usage.
945 The limit is enforced during page fault. Since HugeTLB doesn't
946 support page reclaim, enforcing the limit at page fault time implies
947 that, the application will get SIGBUS signal if it tries to access
948 HugeTLB pages beyond its limit. This requires the application to know
949 beforehand how much HugeTLB pages it would require for its use. The
950 control group is tracked in the third page lru pointer. This means
951 that we cannot use the controller with huge page less than 3 pages.
952
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953config CGROUP_PERF
954 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
955 depends on PERF_EVENTS && CGROUPS
956 help
957 This option extends the per-cpu mode to restrict monitoring to
2d0f2520 958 threads which belong to the cgroup specified and run on the
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SE
959 designated cpu.
960
961 Say N if unsure.
962
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963menuconfig CGROUP_SCHED
964 bool "Group CPU scheduler"
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DG
965 default n
966 help
967 This feature lets CPU scheduler recognize task groups and control CPU
968 bandwidth allocation to such task groups. It uses cgroups to group
969 tasks.
970
971if CGROUP_SCHED
972config FAIR_GROUP_SCHED
973 bool "Group scheduling for SCHED_OTHER"
974 depends on CGROUP_SCHED
975 default CGROUP_SCHED
976
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PT
977config CFS_BANDWIDTH
978 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
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979 depends on FAIR_GROUP_SCHED
980 default n
981 help
982 This option allows users to define CPU bandwidth rates (limits) for
983 tasks running within the fair group scheduler. Groups with no limit
984 set are considered to be unconstrained and will run with no
985 restriction.
986 See tip/Documentation/scheduler/sched-bwc.txt for more information.
987
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988config RT_GROUP_SCHED
989 bool "Group scheduling for SCHED_RR/FIFO"
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DG
990 depends on CGROUP_SCHED
991 default n
992 help
993 This feature lets you explicitly allocate real CPU bandwidth
32bd7eb5 994 to task groups. If enabled, it will also make it impossible to
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DG
995 schedule realtime tasks for non-root users until you allocate
996 realtime bandwidth for them.
997 See Documentation/scheduler/sched-rt-group.txt for more information.
998
999endif #CGROUP_SCHED
1000
afc24d49 1001config BLK_CGROUP
32e380ae 1002 bool "Block IO controller"
79ae9c29 1003 depends on BLOCK
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VG
1004 default n
1005 ---help---
1006 Generic block IO controller cgroup interface. This is the common
1007 cgroup interface which should be used by various IO controlling
1008 policies.
1009
1010 Currently, CFQ IO scheduler uses it to recognize task groups and
1011 control disk bandwidth allocation (proportional time slice allocation)
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1012 to such task groups. It is also used by bio throttling logic in
1013 block layer to implement upper limit in IO rates on a device.
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VG
1014
1015 This option only enables generic Block IO controller infrastructure.
e43473b7 1016 One needs to also enable actual IO controlling logic/policy. For
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1017 enabling proportional weight division of disk bandwidth in CFQ, set
1018 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
c5e0591a 1019 CONFIG_BLK_DEV_THROTTLING=y.
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VG
1020
1021 See Documentation/cgroups/blkio-controller.txt for more information.
1022
1023config DEBUG_BLK_CGROUP
1024 bool "Enable Block IO controller debugging"
1025 depends on BLK_CGROUP
1026 default n
1027 ---help---
1028 Enable some debugging help. Currently it exports additional stat
1029 files in a cgroup which can be useful for debugging.
1030
23964d2d 1031endif # CGROUPS
c077719b 1032
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CG
1033config CHECKPOINT_RESTORE
1034 bool "Checkpoint/restore support" if EXPERT
1035 default n
1036 help
1037 Enables additional kernel features in a sake of checkpoint/restore.
1038 In particular it adds auxiliary prctl codes to setup process text,
1039 data and heap segment sizes, and a few additional /proc filesystem
1040 entries.
1041
1042 If unsure, say N here.
1043
8dd2a82c 1044menuconfig NAMESPACES
6a108a14
DR
1045 bool "Namespaces support" if EXPERT
1046 default !EXPERT
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1047 help
1048 Provides the way to make tasks work with different objects using
1049 the same id. For example same IPC id may refer to different objects
1050 or same user id or pid may refer to different tasks when used in
1051 different namespaces.
1052
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DL
1053if NAMESPACES
1054
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PE
1055config UTS_NS
1056 bool "UTS namespace"
17a6d441 1057 default y
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1058 help
1059 In this namespace tasks see different info provided with the
1060 uname() system call
1061
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1062config IPC_NS
1063 bool "IPC namespace"
8dd2a82c 1064 depends on (SYSVIPC || POSIX_MQUEUE)
17a6d441 1065 default y
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1066 help
1067 In this namespace tasks work with IPC ids which correspond to
614b84cf 1068 different IPC objects in different namespaces.
ae5e1b22 1069
aee16ce7 1070config USER_NS
19c92399 1071 bool "User namespace"
e1c972b6 1072 depends on UIDGID_CONVERTED
5673a94c 1073 select UIDGID_STRICT_TYPE_CHECKS
e1c972b6 1074
5673a94c 1075 default n
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1076 help
1077 This allows containers, i.e. vservers, to use user namespaces
1078 to provide different user info for different servers.
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1079
1080 When user namespaces are enabled in the kernel it is
1081 recommended that the MEMCG and MEMCG_KMEM options also be
1082 enabled and that user-space use the memory control groups to
1083 limit the amount of memory a memory unprivileged users can
1084 use.
1085
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1086 If unsure, say N.
1087
74bd59bb 1088config PID_NS
9bd38c2c 1089 bool "PID Namespaces"
17a6d441 1090 default y
74bd59bb 1091 help
12d2b8f9 1092 Support process id namespaces. This allows having multiple
692105b8 1093 processes with the same pid as long as they are in different
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1094 pid namespaces. This is a building block of containers.
1095
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1096config NET_NS
1097 bool "Network namespace"
8dd2a82c 1098 depends on NET
17a6d441 1099 default y
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1100 help
1101 Allow user space to create what appear to be multiple instances
1102 of the network stack.
1103
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DL
1104endif # NAMESPACES
1105
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EB
1106config UIDGID_CONVERTED
1107 # True if all of the selected software conmponents are known
1108 # to have uid_t and gid_t converted to kuid_t and kgid_t
1109 # where appropriate and are otherwise safe to use with
1110 # the user namespace.
1111 bool
1112 default y
1113
e1c972b6 1114 # Filesystems
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EB
1115 depends on XFS_FS = n
1116
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1117config UIDGID_STRICT_TYPE_CHECKS
1118 bool "Require conversions between uid/gids and their internal representation"
e1c972b6 1119 depends on UIDGID_CONVERTED
5673a94c
EB
1120 default n
1121 help
1122 While the nececessary conversions are being added to all subsystems this option allows
1123 the code to continue to build for unconverted subsystems.
1124
1125 Say Y here if you want the strict type checking enabled
1126
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1127config SCHED_AUTOGROUP
1128 bool "Automatic process group scheduling"
1129 select EVENTFD
1130 select CGROUPS
1131 select CGROUP_SCHED
1132 select FAIR_GROUP_SCHED
1133 help
1134 This option optimizes the scheduler for common desktop workloads by
1135 automatically creating and populating task groups. This separation
1136 of workloads isolates aggressive CPU burners (like build jobs) from
1137 desktop applications. Task group autogeneration is currently based
1138 upon task session.
1139
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DL
1140config MM_OWNER
1141 bool
1142
1143config SYSFS_DEPRECATED
5d6a4ea5 1144 bool "Enable deprecated sysfs features to support old userspace tools"
7af37bec
DL
1145 depends on SYSFS
1146 default n
1147 help
1148 This option adds code that switches the layout of the "block" class
1149 devices, to not show up in /sys/class/block/, but only in
1150 /sys/block/.
1151
1152 This switch is only active when the sysfs.deprecated=1 boot option is
1153 passed or the SYSFS_DEPRECATED_V2 option is set.
1154
1155 This option allows new kernels to run on old distributions and tools,
1156 which might get confused by /sys/class/block/. Since 2007/2008 all
1157 major distributions and tools handle this just fine.
1158
1159 Recent distributions and userspace tools after 2009/2010 depend on
1160 the existence of /sys/class/block/, and will not work with this
1161 option enabled.
1162
1163 Only if you are using a new kernel on an old distribution, you might
1164 need to say Y here.
1165
1166config SYSFS_DEPRECATED_V2
5d6a4ea5 1167 bool "Enable deprecated sysfs features by default"
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DL
1168 default n
1169 depends on SYSFS
1170 depends on SYSFS_DEPRECATED
1171 help
1172 Enable deprecated sysfs by default.
1173
1174 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1175 option.
1176
1177 Only if you are using a new kernel on an old distribution, you might
1178 need to say Y here. Even then, odds are you would not need it
1179 enabled, you can always pass the boot option if absolutely necessary.
1180
1181config RELAY
1182 bool "Kernel->user space relay support (formerly relayfs)"
1183 help
1184 This option enables support for relay interface support in
1185 certain file systems (such as debugfs).
1186 It is designed to provide an efficient mechanism for tools and
1187 facilities to relay large amounts of data from kernel space to
1188 user space.
1189
1190 If unsure, say N.
1191
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1192config BLK_DEV_INITRD
1193 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1194 depends on BROKEN || !FRV
1195 help
1196 The initial RAM filesystem is a ramfs which is loaded by the
1197 boot loader (loadlin or lilo) and that is mounted as root
1198 before the normal boot procedure. It is typically used to
1199 load modules needed to mount the "real" root file system,
1200 etc. See <file:Documentation/initrd.txt> for details.
1201
1202 If RAM disk support (BLK_DEV_RAM) is also included, this
1203 also enables initial RAM disk (initrd) support and adds
1204 15 Kbytes (more on some other architectures) to the kernel size.
1205
1206 If unsure say Y.
1207
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1208if BLK_DEV_INITRD
1209
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1210source "usr/Kconfig"
1211
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1212endif
1213
c45b4f1f 1214config CC_OPTIMIZE_FOR_SIZE
96fffeb4 1215 bool "Optimize for size"
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LT
1216 help
1217 Enabling this option will pass "-Os" instead of "-O2" to gcc
1218 resulting in a smaller kernel.
1219
3a55fb0d 1220 If unsure, say N.
c45b4f1f 1221
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1222config SYSCTL
1223 bool
1224
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1225config ANON_INODES
1226 bool
1227
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1228config HAVE_UID16
1229 bool
1230
1231config SYSCTL_EXCEPTION_TRACE
1232 bool
1233 help
1234 Enable support for /proc/sys/debug/exception-trace.
1235
1236config SYSCTL_ARCH_UNALIGN_NO_WARN
1237 bool
1238 help
1239 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1240 Allows arch to define/use @no_unaligned_warning to possibly warn
1241 about unaligned access emulation going on under the hood.
1242
1243config SYSCTL_ARCH_UNALIGN_ALLOW
1244 bool
1245 help
1246 Enable support for /proc/sys/kernel/unaligned-trap
1247 Allows arches to define/use @unaligned_enabled to runtime toggle
1248 the unaligned access emulation.
1249 see arch/parisc/kernel/unaligned.c for reference
1250
1251config HOTPLUG
1252 def_bool y
1253
1254config HAVE_PCSPKR_PLATFORM
1255 bool
1256
6fa3eb70
S
1257config PANIC_TIMEOUT
1258 int "Default panic timeout"
1259 default 0
1260 help
1261 Set default panic timeout.
1262
6a108a14
DR
1263menuconfig EXPERT
1264 bool "Configure standard kernel features (expert users)"
f505c553
JT
1265 # Unhide debug options, to make the on-by-default options visible
1266 select DEBUG_KERNEL
1da177e4
LT
1267 help
1268 This option allows certain base kernel options and settings
1269 to be disabled or tweaked. This is for specialized
1270 environments which can tolerate a "non-standard" kernel.
1271 Only use this if you really know what you are doing.
1272
ae81f9e3 1273config UID16
6a108a14 1274 bool "Enable 16-bit UID system calls" if EXPERT
af1839eb 1275 depends on HAVE_UID16
ae81f9e3
CE
1276 default y
1277 help
1278 This enables the legacy 16-bit UID syscall wrappers.
1279
b89a8171 1280config SYSCTL_SYSCALL
6a108a14 1281 bool "Sysctl syscall support" if EXPERT
26a7034b 1282 depends on PROC_SYSCTL
c736de60 1283 default n
b89a8171 1284 select SYSCTL
ae81f9e3 1285 ---help---
13bb7e37
EB
1286 sys_sysctl uses binary paths that have been found challenging
1287 to properly maintain and use. The interface in /proc/sys
1288 using paths with ascii names is now the primary path to this
1289 information.
b89a8171 1290
13bb7e37
EB
1291 Almost nothing using the binary sysctl interface so if you are
1292 trying to save some space it is probably safe to disable this,
1293 making your kernel marginally smaller.
b89a8171 1294
c736de60 1295 If unsure say N here.
ae81f9e3 1296
1da177e4 1297config KALLSYMS
6a108a14 1298 bool "Load all symbols for debugging/ksymoops" if EXPERT
1da177e4
LT
1299 default y
1300 help
1301 Say Y here to let the kernel print out symbolic crash information and
1302 symbolic stack backtraces. This increases the size of the kernel
1303 somewhat, as all symbols have to be loaded into the kernel image.
1304
1305config KALLSYMS_ALL
1306 bool "Include all symbols in kallsyms"
1307 depends on DEBUG_KERNEL && KALLSYMS
1308 help
71a83ec7
AB
1309 Normally kallsyms only contains the symbols of functions for nicer
1310 OOPS messages and backtraces (i.e., symbols from the text and inittext
1311 sections). This is sufficient for most cases. And only in very rare
1312 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1313 names of variables from the data sections, etc).
1314
1315 This option makes sure that all symbols are loaded into the kernel
1316 image (i.e., symbols from all sections) in cost of increased kernel
1317 size (depending on the kernel configuration, it may be 300KiB or
1318 something like this).
1319
1320 Say N unless you really need all symbols.
d59745ce
MM
1321
1322config PRINTK
1323 default y
6a108a14 1324 bool "Enable support for printk" if EXPERT
74876a98 1325 select IRQ_WORK
d59745ce
MM
1326 help
1327 This option enables normal printk support. Removing it
1328 eliminates most of the message strings from the kernel image
1329 and makes the kernel more or less silent. As this makes it
1330 very difficult to diagnose system problems, saying N here is
1331 strongly discouraged.
1332
c8538a7a 1333config BUG
6a108a14 1334 bool "BUG() support" if EXPERT
c8538a7a
MM
1335 default y
1336 help
1337 Disabling this option eliminates support for BUG and WARN, reducing
1338 the size of your kernel image and potentially quietly ignoring
1339 numerous fatal conditions. You should only consider disabling this
1340 option for embedded systems with no facilities for reporting errors.
1341 Just say Y.
1342
708e9a79 1343config ELF_CORE
046d662f 1344 depends on COREDUMP
708e9a79 1345 default y
6a108a14 1346 bool "Enable ELF core dumps" if EXPERT
708e9a79
MM
1347 help
1348 Enable support for generating core dumps. Disabling saves about 4k.
1349
8761f1ab 1350
e5e1d3cb 1351config PCSPKR_PLATFORM
6a108a14 1352 bool "Enable PC-Speaker support" if EXPERT
8761f1ab 1353 depends on HAVE_PCSPKR_PLATFORM
15f304b6 1354 select I8253_LOCK
e5e1d3cb
SS
1355 default y
1356 help
1357 This option allows to disable the internal PC-Speaker
1358 support, saving some memory.
1359
1da177e4
LT
1360config BASE_FULL
1361 default y
6a108a14 1362 bool "Enable full-sized data structures for core" if EXPERT
1da177e4
LT
1363 help
1364 Disabling this option reduces the size of miscellaneous core
1365 kernel data structures. This saves memory on small machines,
1366 but may reduce performance.
1367
1368config FUTEX
6a108a14 1369 bool "Enable futex support" if EXPERT
1da177e4 1370 default y
23f78d4a 1371 select RT_MUTEXES
1da177e4
LT
1372 help
1373 Disabling this option will cause the kernel to be built without
1374 support for "fast userspace mutexes". The resulting kernel may not
1375 run glibc-based applications correctly.
1376
f26c70a4
HC
1377config HAVE_FUTEX_CMPXCHG
1378 bool
0000372a 1379 depends on FUTEX
f26c70a4
HC
1380 help
1381 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1382 is implemented and always working. This removes a couple of runtime
1383 checks.
1384
1da177e4 1385config EPOLL
6a108a14 1386 bool "Enable eventpoll support" if EXPERT
1da177e4 1387 default y
448e3cee 1388 select ANON_INODES
1da177e4
LT
1389 help
1390 Disabling this option will cause the kernel to be built without
1391 support for epoll family of system calls.
1392
fba2afaa 1393config SIGNALFD
6a108a14 1394 bool "Enable signalfd() system call" if EXPERT
448e3cee 1395 select ANON_INODES
fba2afaa
DL
1396 default y
1397 help
1398 Enable the signalfd() system call that allows to receive signals
1399 on a file descriptor.
1400
1401 If unsure, say Y.
1402
b215e283 1403config TIMERFD
6a108a14 1404 bool "Enable timerfd() system call" if EXPERT
448e3cee 1405 select ANON_INODES
b215e283
DL
1406 default y
1407 help
1408 Enable the timerfd() system call that allows to receive timer
1409 events on a file descriptor.
1410
1411 If unsure, say Y.
1412
e1ad7468 1413config EVENTFD
6a108a14 1414 bool "Enable eventfd() system call" if EXPERT
448e3cee 1415 select ANON_INODES
e1ad7468
DL
1416 default y
1417 help
1418 Enable the eventfd() system call that allows to receive both
1419 kernel notification (ie. KAIO) or userspace notifications.
1420
1421 If unsure, say Y.
1422
1da177e4 1423config SHMEM
6a108a14 1424 bool "Use full shmem filesystem" if EXPERT
1da177e4
LT
1425 default y
1426 depends on MMU
1427 help
1428 The shmem is an internal filesystem used to manage shared memory.
1429 It is backed by swap and manages resource limits. It is also exported
1430 to userspace as tmpfs if TMPFS is enabled. Disabling this
1431 option replaces shmem and tmpfs with the much simpler ramfs code,
1432 which may be appropriate on small systems without swap.
1433
ebf3f09c 1434config AIO
6a108a14 1435 bool "Enable AIO support" if EXPERT
ebf3f09c
TP
1436 default y
1437 help
1438 This option enables POSIX asynchronous I/O which may by used
657a5209
MF
1439 by some high performance threaded applications. Disabling
1440 this option saves about 7k.
1441
1442config PCI_QUIRKS
1443 default y
1444 bool "Enable PCI quirk workarounds" if EXPERT
1445 depends on PCI
1446 help
1447 This enables workarounds for various PCI chipset
1448 bugs/quirks. Disable this only if your target machine is
1449 unaffected by PCI quirks.
ebf3f09c 1450
6befe5f6
RD
1451config EMBEDDED
1452 bool "Embedded system"
1453 select EXPERT
1454 help
1455 This option should be enabled if compiling the kernel for
1456 an embedded system so certain expert options are available
1457 for configuration.
1458
cdd6c482 1459config HAVE_PERF_EVENTS
0793a61d 1460 bool
018df72d
MF
1461 help
1462 See tools/perf/design.txt for details.
0793a61d 1463
906010b2
PZ
1464config PERF_USE_VMALLOC
1465 bool
1466 help
1467 See tools/perf/design.txt for details
1468
57c0c15b 1469menu "Kernel Performance Events And Counters"
0793a61d 1470
cdd6c482 1471config PERF_EVENTS
57c0c15b 1472 bool "Kernel performance events and counters"
392d65a9 1473 default y if PROFILING
cdd6c482 1474 depends on HAVE_PERF_EVENTS
4c59e467 1475 select ANON_INODES
e360adbe 1476 select IRQ_WORK
0793a61d 1477 help
57c0c15b
IM
1478 Enable kernel support for various performance events provided
1479 by software and hardware.
0793a61d 1480
dd77038d 1481 Software events are supported either built-in or via the
57c0c15b 1482 use of generic tracepoints.
0793a61d 1483
57c0c15b
IM
1484 Most modern CPUs support performance events via performance
1485 counter registers. These registers count the number of certain
0793a61d
TG
1486 types of hw events: such as instructions executed, cachemisses
1487 suffered, or branches mis-predicted - without slowing down the
1488 kernel or applications. These registers can also trigger interrupts
1489 when a threshold number of events have passed - and can thus be
1490 used to profile the code that runs on that CPU.
1491
57c0c15b 1492 The Linux Performance Event subsystem provides an abstraction of
dd77038d 1493 these software and hardware event capabilities, available via a
57c0c15b 1494 system call and used by the "perf" utility in tools/perf/. It
0793a61d
TG
1495 provides per task and per CPU counters, and it provides event
1496 capabilities on top of those.
1497
1498 Say Y if unsure.
1499
906010b2
PZ
1500config DEBUG_PERF_USE_VMALLOC
1501 default n
1502 bool "Debug: use vmalloc to back perf mmap() buffers"
1503 depends on PERF_EVENTS && DEBUG_KERNEL
1504 select PERF_USE_VMALLOC
1505 help
1506 Use vmalloc memory to back perf mmap() buffers.
1507
1508 Mostly useful for debugging the vmalloc code on platforms
1509 that don't require it.
1510
1511 Say N if unsure.
1512
0793a61d
TG
1513endmenu
1514
f8891e5e
CL
1515config VM_EVENT_COUNTERS
1516 default y
6a108a14 1517 bool "Enable VM event counters for /proc/vmstat" if EXPERT
f8891e5e 1518 help
2aea4fb6
PJ
1519 VM event counters are needed for event counts to be shown.
1520 This option allows the disabling of the VM event counters
6a108a14 1521 on EXPERT systems. /proc/vmstat will only show page counts
2aea4fb6 1522 if VM event counters are disabled.
f8891e5e 1523
41ecc55b
CL
1524config SLUB_DEBUG
1525 default y
6a108a14 1526 bool "Enable SLUB debugging support" if EXPERT
f6acb635 1527 depends on SLUB && SYSFS
41ecc55b
CL
1528 help
1529 SLUB has extensive debug support features. Disabling these can
1530 result in significant savings in code size. This also disables
1531 SLUB sysfs support. /sys/slab will not exist and there will be
1532 no support for cache validation etc.
1533
b943c460
RD
1534config COMPAT_BRK
1535 bool "Disable heap randomization"
1536 default y
1537 help
1538 Randomizing heap placement makes heap exploits harder, but it
1539 also breaks ancient binaries (including anything libc5 based).
1540 This option changes the bootup default to heap randomization
692105b8 1541 disabled, and can be overridden at runtime by setting
b943c460
RD
1542 /proc/sys/kernel/randomize_va_space to 2.
1543
1544 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1545
81819f0f
CL
1546choice
1547 prompt "Choose SLAB allocator"
a0acd820 1548 default SLUB
81819f0f
CL
1549 help
1550 This option allows to select a slab allocator.
1551
1552config SLAB
1553 bool "SLAB"
1554 help
1555 The regular slab allocator that is established and known to work
34013886 1556 well in all environments. It organizes cache hot objects in
02f56210 1557 per cpu and per node queues.
81819f0f
CL
1558
1559config SLUB
81819f0f
CL
1560 bool "SLUB (Unqueued Allocator)"
1561 help
1562 SLUB is a slab allocator that minimizes cache line usage
1563 instead of managing queues of cached objects (SLAB approach).
1564 Per cpu caching is realized using slabs of objects instead
1565 of queues of objects. SLUB can use memory efficiently
02f56210
SA
1566 and has enhanced diagnostics. SLUB is the default choice for
1567 a slab allocator.
81819f0f
CL
1568
1569config SLOB
6a108a14 1570 depends on EXPERT
81819f0f
CL
1571 bool "SLOB (Simple Allocator)"
1572 help
37291458
MM
1573 SLOB replaces the stock allocator with a drastically simpler
1574 allocator. SLOB is generally more space efficient but
1575 does not perform as well on large systems.
81819f0f
CL
1576
1577endchoice
1578
ea637639
JZ
1579config MMAP_ALLOW_UNINITIALIZED
1580 bool "Allow mmapped anonymous memory to be uninitialized"
6a108a14 1581 depends on EXPERT && !MMU
ea637639
JZ
1582 default n
1583 help
1584 Normally, and according to the Linux spec, anonymous memory obtained
1585 from mmap() has it's contents cleared before it is passed to
1586 userspace. Enabling this config option allows you to request that
1587 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1588 providing a huge performance boost. If this option is not enabled,
1589 then the flag will be ignored.
1590
1591 This is taken advantage of by uClibc's malloc(), and also by
1592 ELF-FDPIC binfmt's brk and stack allocator.
1593
1594 Because of the obvious security issues, this option should only be
1595 enabled on embedded devices where you control what is run in
1596 userspace. Since that isn't generally a problem on no-MMU systems,
1597 it is normally safe to say Y here.
1598
1599 See Documentation/nommu-mmap.txt for more information.
1600
125e5645 1601config PROFILING
b309a294 1602 bool "Profiling support"
125e5645
MD
1603 help
1604 Say Y here to enable the extended profiling support mechanisms used
1605 by profilers such as OProfile.
1606
5f87f112
IM
1607#
1608# Place an empty function call at each tracepoint site. Can be
1609# dynamically changed for a probe function.
1610#
97e1c18e 1611config TRACEPOINTS
5f87f112 1612 bool
97e1c18e 1613
fb32e03f
MD
1614source "arch/Kconfig"
1615
1da177e4
LT
1616endmenu # General setup
1617
ee7e5516
DES
1618config HAVE_GENERIC_DMA_COHERENT
1619 bool
1620 default n
1621
158a9624
LT
1622config SLABINFO
1623 bool
1624 depends on PROC_FS
0f389ec6 1625 depends on SLAB || SLUB_DEBUG
158a9624
LT
1626 default y
1627
ae81f9e3
CE
1628config RT_MUTEXES
1629 boolean
ae81f9e3 1630
1da177e4
LT
1631config BASE_SMALL
1632 int
1633 default 0 if BASE_FULL
1634 default 1 if !BASE_FULL
1635
66da5733 1636menuconfig MODULES
1da177e4
LT
1637 bool "Enable loadable module support"
1638 help
1639 Kernel modules are small pieces of compiled code which can
1640 be inserted in the running kernel, rather than being
1641 permanently built into the kernel. You use the "modprobe"
1642 tool to add (and sometimes remove) them. If you say Y here,
1643 many parts of the kernel can be built as modules (by
1644 answering M instead of Y where indicated): this is most
1645 useful for infrequently used options which are not required
1646 for booting. For more information, see the man pages for
1647 modprobe, lsmod, modinfo, insmod and rmmod.
1648
1649 If you say Y here, you will need to run "make
1650 modules_install" to put the modules under /lib/modules/
1651 where modprobe can find them (you may need to be root to do
1652 this).
1653
1654 If unsure, say Y.
1655
0b0de144
RD
1656if MODULES
1657
826e4506
LT
1658config MODULE_FORCE_LOAD
1659 bool "Forced module loading"
826e4506
LT
1660 default n
1661 help
91e37a79
RR
1662 Allow loading of modules without version information (ie. modprobe
1663 --force). Forced module loading sets the 'F' (forced) taint flag and
1664 is usually a really bad idea.
826e4506 1665
1da177e4
LT
1666config MODULE_UNLOAD
1667 bool "Module unloading"
1da177e4
LT
1668 help
1669 Without this option you will not be able to unload any
1670 modules (note that some modules may not be unloadable
f7f5b675
DV
1671 anyway), which makes your kernel smaller, faster
1672 and simpler. If unsure, say Y.
1da177e4
LT
1673
1674config MODULE_FORCE_UNLOAD
1675 bool "Forced module unloading"
19c92399 1676 depends on MODULE_UNLOAD
1da177e4
LT
1677 help
1678 This option allows you to force a module to unload, even if the
1679 kernel believes it is unsafe: the kernel will remove the module
1680 without waiting for anyone to stop using it (using the -f option to
1681 rmmod). This is mainly for kernel developers and desperate users.
1682 If unsure, say N.
1683
1da177e4 1684config MODVERSIONS
0d541643 1685 bool "Module versioning support"
1da177e4
LT
1686 help
1687 Usually, you have to use modules compiled with your kernel.
1688 Saying Y here makes it sometimes possible to use modules
1689 compiled for different kernels, by adding enough information
1690 to the modules to (hopefully) spot any changes which would
1691 make them incompatible with the kernel you are running. If
1692 unsure, say N.
1693
1694config MODULE_SRCVERSION_ALL
1695 bool "Source checksum for all modules"
1da177e4
LT
1696 help
1697 Modules which contain a MODULE_VERSION get an extra "srcversion"
1698 field inserted into their modinfo section, which contains a
1699 sum of the source files which made it. This helps maintainers
1700 see exactly which source was used to build a module (since
1701 others sometimes change the module source without updating
1702 the version). With this option, such a "srcversion" field
1703 will be created for all modules. If unsure, say N.
1704
106a4ee2
RR
1705config MODULE_SIG
1706 bool "Module signature verification"
1707 depends on MODULES
48ba2462
DH
1708 select KEYS
1709 select CRYPTO
1710 select ASYMMETRIC_KEY_TYPE
1711 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1712 select PUBLIC_KEY_ALGO_RSA
1713 select ASN1
1714 select OID_REGISTRY
1715 select X509_CERTIFICATE_PARSER
106a4ee2
RR
1716 help
1717 Check modules for valid signatures upon load: the signature
1718 is simply appended to the module. For more information see
1719 Documentation/module-signing.txt.
1720
ea0b6dcf
DH
1721 !!!WARNING!!! If you enable this option, you MUST make sure that the
1722 module DOES NOT get stripped after being signed. This includes the
1723 debuginfo strip done by some packagers (such as rpmbuild) and
1724 inclusion into an initramfs that wants the module size reduced.
1725
106a4ee2
RR
1726config MODULE_SIG_FORCE
1727 bool "Require modules to be validly signed"
1728 depends on MODULE_SIG
1729 help
1730 Reject unsigned modules or signed modules for which we don't have a
1731 key. Without this, such modules will simply taint the kernel.
ea0b6dcf 1732
d9d8d7ed
MM
1733config MODULE_SIG_ALL
1734 bool "Automatically sign all modules"
1735 default y
1736 depends on MODULE_SIG
1737 help
1738 Sign all modules during make modules_install. Without this option,
1739 modules must be signed manually, using the scripts/sign-file tool.
1740
1741comment "Do not forget to sign required modules with scripts/sign-file"
1742 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1743
ea0b6dcf
DH
1744choice
1745 prompt "Which hash algorithm should modules be signed with?"
1746 depends on MODULE_SIG
1747 help
1748 This determines which sort of hashing algorithm will be used during
1749 signature generation. This algorithm _must_ be built into the kernel
1750 directly so that signature verification can take place. It is not
1751 possible to load a signed module containing the algorithm to check
1752 the signature on that module.
1753
1754config MODULE_SIG_SHA1
1755 bool "Sign modules with SHA-1"
1756 select CRYPTO_SHA1
1757
1758config MODULE_SIG_SHA224
1759 bool "Sign modules with SHA-224"
1760 select CRYPTO_SHA256
1761
1762config MODULE_SIG_SHA256
1763 bool "Sign modules with SHA-256"
1764 select CRYPTO_SHA256
1765
1766config MODULE_SIG_SHA384
1767 bool "Sign modules with SHA-384"
1768 select CRYPTO_SHA512
1769
1770config MODULE_SIG_SHA512
1771 bool "Sign modules with SHA-512"
1772 select CRYPTO_SHA512
1773
1774endchoice
1775
22753674
MM
1776config MODULE_SIG_HASH
1777 string
1778 depends on MODULE_SIG
1779 default "sha1" if MODULE_SIG_SHA1
1780 default "sha224" if MODULE_SIG_SHA224
1781 default "sha256" if MODULE_SIG_SHA256
1782 default "sha384" if MODULE_SIG_SHA384
1783 default "sha512" if MODULE_SIG_SHA512
1784
0b0de144
RD
1785endif # MODULES
1786
98a79d6a
RR
1787config INIT_ALL_POSSIBLE
1788 bool
1789 help
5f054e31
RR
1790 Back when each arch used to define their own cpu_online_mask and
1791 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
98a79d6a
RR
1792 with all 1s, and others with all 0s. When they were centralised,
1793 it was better to provide this option than to break all the archs
692105b8 1794 and have several arch maintainers pursuing me down dark alleys.
98a79d6a 1795
1da177e4
LT
1796config STOP_MACHINE
1797 bool
1798 default y
1799 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1800 help
1801 Need stop_machine() primitive.
3a65dfe8 1802
3a65dfe8 1803source "block/Kconfig"
e98c3202
AK
1804
1805config PREEMPT_NOTIFIERS
1806 bool
e260be67 1807
16295bec
SK
1808config PADATA
1809 depends on SMP
1810 bool
1811
754b7b63
AK
1812# Can be selected by architectures with broken toolchains
1813# that get confused by correct const<->read_only section
1814# mappings
1815config BROKEN_RODATA
1816 bool
1817
4520c6a4
DH
1818config ASN1
1819 tristate
1820 help
1821 Build a simple ASN.1 grammar compiler that produces a bytecode output
1822 that can be interpreted by the ASN.1 stream decoder and used to
1823 inform it as to what tags are to be expected in a stream and what
1824 functions to call on what tags.
1825
6beb0009 1826source "kernel/Kconfig.locks"