Merge tag 'mfd-3.8-1' of git://git.kernel.org/pub/scm/linux/kernel/git/sameo/mfd-2.6
[GitHub/mt8127/android_kernel_alcatel_ttab.git] / init / Kconfig
1 config ARCH
2 string
3 option env="ARCH"
4
5 config KERNELVERSION
6 string
7 option env="KERNELVERSION"
8
9 config DEFCONFIG_LIST
10 string
11 depends on !UML
12 option defconfig_list
13 default "/lib/modules/$UNAME_RELEASE/.config"
14 default "/etc/kernel-config"
15 default "/boot/config-$UNAME_RELEASE"
16 default "$ARCH_DEFCONFIG"
17 default "arch/$ARCH/defconfig"
18
19 config CONSTRUCTORS
20 bool
21 depends on !UML
22
23 config HAVE_IRQ_WORK
24 bool
25
26 config IRQ_WORK
27 bool
28 depends on HAVE_IRQ_WORK
29
30 config BUILDTIME_EXTABLE_SORT
31 bool
32
33 menu "General setup"
34
35 config EXPERIMENTAL
36 bool "Prompt for development and/or incomplete code/drivers"
37 ---help---
38 Some of the various things that Linux supports (such as network
39 drivers, file systems, network protocols, etc.) can be in a state
40 of development where the functionality, stability, or the level of
41 testing is not yet high enough for general use. This is usually
42 known as the "alpha-test" phase among developers. If a feature is
43 currently in alpha-test, then the developers usually discourage
44 uninformed widespread use of this feature by the general public to
45 avoid "Why doesn't this work?" type mail messages. However, active
46 testing and use of these systems is welcomed. Just be aware that it
47 may not meet the normal level of reliability or it may fail to work
48 in some special cases. Detailed bug reports from people familiar
49 with the kernel internals are usually welcomed by the developers
50 (before submitting bug reports, please read the documents
51 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
52 <file:Documentation/BUG-HUNTING>, and
53 <file:Documentation/oops-tracing.txt> in the kernel source).
54
55 This option will also make obsoleted drivers available. These are
56 drivers that have been replaced by something else, and/or are
57 scheduled to be removed in a future kernel release.
58
59 Unless you intend to help test and develop a feature or driver that
60 falls into this category, or you have a situation that requires
61 using these features, you should probably say N here, which will
62 cause the configurator to present you with fewer choices. If
63 you say Y here, you will be offered the choice of using features or
64 drivers that are currently considered to be in the alpha-test phase.
65
66 config BROKEN
67 bool
68
69 config BROKEN_ON_SMP
70 bool
71 depends on BROKEN || !SMP
72 default y
73
74 config INIT_ENV_ARG_LIMIT
75 int
76 default 32 if !UML
77 default 128 if UML
78 help
79 Maximum of each of the number of arguments and environment
80 variables passed to init from the kernel command line.
81
82
83 config CROSS_COMPILE
84 string "Cross-compiler tool prefix"
85 help
86 Same as running 'make CROSS_COMPILE=prefix-' but stored for
87 default make runs in this kernel build directory. You don't
88 need to set this unless you want the configured kernel build
89 directory to select the cross-compiler automatically.
90
91 config LOCALVERSION
92 string "Local version - append to kernel release"
93 help
94 Append an extra string to the end of your kernel version.
95 This will show up when you type uname, for example.
96 The string you set here will be appended after the contents of
97 any files with a filename matching localversion* in your
98 object and source tree, in that order. Your total string can
99 be a maximum of 64 characters.
100
101 config LOCALVERSION_AUTO
102 bool "Automatically append version information to the version string"
103 default y
104 help
105 This will try to automatically determine if the current tree is a
106 release tree by looking for git tags that belong to the current
107 top of tree revision.
108
109 A string of the format -gxxxxxxxx will be added to the localversion
110 if a git-based tree is found. The string generated by this will be
111 appended after any matching localversion* files, and after the value
112 set in CONFIG_LOCALVERSION.
113
114 (The actual string used here is the first eight characters produced
115 by running the command:
116
117 $ git rev-parse --verify HEAD
118
119 which is done within the script "scripts/setlocalversion".)
120
121 config HAVE_KERNEL_GZIP
122 bool
123
124 config HAVE_KERNEL_BZIP2
125 bool
126
127 config HAVE_KERNEL_LZMA
128 bool
129
130 config HAVE_KERNEL_XZ
131 bool
132
133 config HAVE_KERNEL_LZO
134 bool
135
136 choice
137 prompt "Kernel compression mode"
138 default KERNEL_GZIP
139 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
140 help
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
158 config KERNEL_GZIP
159 bool "Gzip"
160 depends on HAVE_KERNEL_GZIP
161 help
162 The old and tried gzip compression. It provides a good balance
163 between compression ratio and decompression speed.
164
165 config KERNEL_BZIP2
166 bool "Bzip2"
167 depends on HAVE_KERNEL_BZIP2
168 help
169 Its compression ratio and speed is intermediate.
170 Decompression speed is slowest among the choices. 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.
174
175 config KERNEL_LZMA
176 bool "LZMA"
177 depends on HAVE_KERNEL_LZMA
178 help
179 This compression algorithm's ratio is best. Decompression speed
180 is between gzip and bzip2. Compression is slowest.
181 The kernel size is about 33% smaller with LZMA in comparison to gzip.
182
183 config KERNEL_XZ
184 bool "XZ"
185 depends on HAVE_KERNEL_XZ
186 help
187 XZ uses the LZMA2 algorithm and instruction set specific
188 BCJ filters which can improve compression ratio of executable
189 code. The size of the kernel is about 30% smaller with XZ in
190 comparison to gzip. On architectures for which there is a BCJ
191 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
192 will create a few percent smaller kernel than plain LZMA.
193
194 The speed is about the same as with LZMA: The decompression
195 speed of XZ is better than that of bzip2 but worse than gzip
196 and LZO. Compression is slow.
197
198 config KERNEL_LZO
199 bool "LZO"
200 depends on HAVE_KERNEL_LZO
201 help
202 Its compression ratio is the poorest among the choices. The kernel
203 size is about 10% bigger than gzip; however its speed
204 (both compression and decompression) is the fastest.
205
206 endchoice
207
208 config DEFAULT_HOSTNAME
209 string "Default hostname"
210 default "(none)"
211 help
212 This option determines the default system hostname before userspace
213 calls sethostname(2). The kernel traditionally uses "(none)" here,
214 but you may wish to use a different default here to make a minimal
215 system more usable with less configuration.
216
217 config SWAP
218 bool "Support for paging of anonymous memory (swap)"
219 depends on MMU && BLOCK
220 default y
221 help
222 This option allows you to choose whether you want to have support
223 for so called swap devices or swap files in your kernel that are
224 used to provide more virtual memory than the actual RAM present
225 in your computer. If unsure say Y.
226
227 config SYSVIPC
228 bool "System V IPC"
229 ---help---
230 Inter Process Communication is a suite of library functions and
231 system calls which let processes (running programs) synchronize and
232 exchange information. It is generally considered to be a good thing,
233 and some programs won't run unless you say Y here. In particular, if
234 you want to run the DOS emulator dosemu under Linux (read the
235 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
236 you'll need to say Y here.
237
238 You can find documentation about IPC with "info ipc" and also in
239 section 6.4 of the Linux Programmer's Guide, available from
240 <http://www.tldp.org/guides.html>.
241
242 config SYSVIPC_SYSCTL
243 bool
244 depends on SYSVIPC
245 depends on SYSCTL
246 default y
247
248 config POSIX_MQUEUE
249 bool "POSIX Message Queues"
250 depends on NET && EXPERIMENTAL
251 ---help---
252 POSIX variant of message queues is a part of IPC. In POSIX message
253 queues every message has a priority which decides about succession
254 of receiving it by a process. If you want to compile and run
255 programs written e.g. for Solaris with use of its POSIX message
256 queues (functions mq_*) say Y here.
257
258 POSIX message queues are visible as a filesystem called 'mqueue'
259 and can be mounted somewhere if you want to do filesystem
260 operations on message queues.
261
262 If unsure, say Y.
263
264 config POSIX_MQUEUE_SYSCTL
265 bool
266 depends on POSIX_MQUEUE
267 depends on SYSCTL
268 default y
269
270 config FHANDLE
271 bool "open by fhandle syscalls"
272 select EXPORTFS
273 help
274 If you say Y here, a user level program will be able to map
275 file names to handle and then later use the handle for
276 different file system operations. This is useful in implementing
277 userspace file servers, which now track files using handles instead
278 of names. The handle would remain the same even if file names
279 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
280 syscalls.
281
282 config AUDIT
283 bool "Auditing support"
284 depends on NET
285 help
286 Enable auditing infrastructure that can be used with another
287 kernel subsystem, such as SELinux (which requires this for
288 logging of avc messages output). Does not do system-call
289 auditing without CONFIG_AUDITSYSCALL.
290
291 config AUDITSYSCALL
292 bool "Enable system-call auditing support"
293 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
294 default y if SECURITY_SELINUX
295 help
296 Enable low-overhead system-call auditing infrastructure that
297 can be used independently or with another kernel subsystem,
298 such as SELinux.
299
300 config AUDIT_WATCH
301 def_bool y
302 depends on AUDITSYSCALL
303 select FSNOTIFY
304
305 config AUDIT_TREE
306 def_bool y
307 depends on AUDITSYSCALL
308 select FSNOTIFY
309
310 config AUDIT_LOGINUID_IMMUTABLE
311 bool "Make audit loginuid immutable"
312 depends on AUDIT
313 help
314 The config option toggles if a task setting its loginuid requires
315 CAP_SYS_AUDITCONTROL or if that task should require no special permissions
316 but should instead only allow setting its loginuid if it was never
317 previously set. On systems which use systemd or a similar central
318 process to restart login services this should be set to true. On older
319 systems in which an admin would typically have to directly stop and
320 start processes this should be set to false. Setting this to true allows
321 one to drop potentially dangerous capabilites from the login tasks,
322 but may not be backwards compatible with older init systems.
323
324 source "kernel/irq/Kconfig"
325 source "kernel/time/Kconfig"
326
327 menu "CPU/Task time and stats accounting"
328
329 choice
330 prompt "Cputime accounting"
331 default TICK_CPU_ACCOUNTING if !PPC64
332 default VIRT_CPU_ACCOUNTING if PPC64
333
334 # Kind of a stub config for the pure tick based cputime accounting
335 config TICK_CPU_ACCOUNTING
336 bool "Simple tick based cputime accounting"
337 depends on !S390
338 help
339 This is the basic tick based cputime accounting that maintains
340 statistics about user, system and idle time spent on per jiffies
341 granularity.
342
343 If unsure, say Y.
344
345 config VIRT_CPU_ACCOUNTING
346 bool "Deterministic task and CPU time accounting"
347 depends on HAVE_VIRT_CPU_ACCOUNTING
348 help
349 Select this option to enable more accurate task and CPU time
350 accounting. This is done by reading a CPU counter on each
351 kernel entry and exit and on transitions within the kernel
352 between system, softirq and hardirq state, so there is a
353 small performance impact. In the case of s390 or IBM POWER > 5,
354 this also enables accounting of stolen time on logically-partitioned
355 systems.
356
357 config IRQ_TIME_ACCOUNTING
358 bool "Fine granularity task level IRQ time accounting"
359 depends on HAVE_IRQ_TIME_ACCOUNTING
360 help
361 Select this option to enable fine granularity task irq time
362 accounting. This is done by reading a timestamp on each
363 transitions between softirq and hardirq state, so there can be a
364 small performance impact.
365
366 If in doubt, say N here.
367
368 endchoice
369
370 config BSD_PROCESS_ACCT
371 bool "BSD Process Accounting"
372 help
373 If you say Y here, a user level program will be able to instruct the
374 kernel (via a special system call) to write process accounting
375 information to a file: whenever a process exits, information about
376 that process will be appended to the file by the kernel. The
377 information includes things such as creation time, owning user,
378 command name, memory usage, controlling terminal etc. (the complete
379 list is in the struct acct in <file:include/linux/acct.h>). It is
380 up to the user level program to do useful things with this
381 information. This is generally a good idea, so say Y.
382
383 config BSD_PROCESS_ACCT_V3
384 bool "BSD Process Accounting version 3 file format"
385 depends on BSD_PROCESS_ACCT
386 default n
387 help
388 If you say Y here, the process accounting information is written
389 in a new file format that also logs the process IDs of each
390 process and it's parent. Note that this file format is incompatible
391 with previous v0/v1/v2 file formats, so you will need updated tools
392 for processing it. A preliminary version of these tools is available
393 at <http://www.gnu.org/software/acct/>.
394
395 config TASKSTATS
396 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
397 depends on NET
398 default n
399 help
400 Export selected statistics for tasks/processes through the
401 generic netlink interface. Unlike BSD process accounting, the
402 statistics are available during the lifetime of tasks/processes as
403 responses to commands. Like BSD accounting, they are sent to user
404 space on task exit.
405
406 Say N if unsure.
407
408 config TASK_DELAY_ACCT
409 bool "Enable per-task delay accounting (EXPERIMENTAL)"
410 depends on TASKSTATS
411 help
412 Collect information on time spent by a task waiting for system
413 resources like cpu, synchronous block I/O completion and swapping
414 in pages. Such statistics can help in setting a task's priorities
415 relative to other tasks for cpu, io, rss limits etc.
416
417 Say N if unsure.
418
419 config TASK_XACCT
420 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
421 depends on TASKSTATS
422 help
423 Collect extended task accounting data and send the data
424 to userland for processing over the taskstats interface.
425
426 Say N if unsure.
427
428 config TASK_IO_ACCOUNTING
429 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
430 depends on TASK_XACCT
431 help
432 Collect information on the number of bytes of storage I/O which this
433 task has caused.
434
435 Say N if unsure.
436
437 endmenu # "CPU/Task time and stats accounting"
438
439 menu "RCU Subsystem"
440
441 choice
442 prompt "RCU Implementation"
443 default TREE_RCU
444
445 config TREE_RCU
446 bool "Tree-based hierarchical RCU"
447 depends on !PREEMPT && SMP
448 help
449 This option selects the RCU implementation that is
450 designed for very large SMP system with hundreds or
451 thousands of CPUs. It also scales down nicely to
452 smaller systems.
453
454 config TREE_PREEMPT_RCU
455 bool "Preemptible tree-based hierarchical RCU"
456 depends on PREEMPT && SMP
457 help
458 This option selects the RCU implementation that is
459 designed for very large SMP systems with hundreds or
460 thousands of CPUs, but for which real-time response
461 is also required. It also scales down nicely to
462 smaller systems.
463
464 config TINY_RCU
465 bool "UP-only small-memory-footprint RCU"
466 depends on !PREEMPT && !SMP
467 help
468 This option selects the RCU implementation that is
469 designed for UP systems from which real-time response
470 is not required. This option greatly reduces the
471 memory footprint of RCU.
472
473 config TINY_PREEMPT_RCU
474 bool "Preemptible UP-only small-memory-footprint RCU"
475 depends on PREEMPT && !SMP
476 help
477 This option selects the RCU implementation that is designed
478 for real-time UP systems. This option greatly reduces the
479 memory footprint of RCU.
480
481 endchoice
482
483 config PREEMPT_RCU
484 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
485 help
486 This option enables preemptible-RCU code that is common between
487 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
488
489 config CONTEXT_TRACKING
490 bool
491
492 config RCU_USER_QS
493 bool "Consider userspace as in RCU extended quiescent state"
494 depends on HAVE_CONTEXT_TRACKING && SMP
495 select CONTEXT_TRACKING
496 help
497 This option sets hooks on kernel / userspace boundaries and
498 puts RCU in extended quiescent state when the CPU runs in
499 userspace. It means that when a CPU runs in userspace, it is
500 excluded from the global RCU state machine and thus doesn't
501 try to keep the timer tick on for RCU.
502
503 Unless you want to hack and help the development of the full
504 dynticks mode, you shouldn't enable this option. It also
505 adds unnecessary overhead.
506
507 If unsure say N
508
509 config CONTEXT_TRACKING_FORCE
510 bool "Force context tracking"
511 depends on CONTEXT_TRACKING
512 help
513 Probe on user/kernel boundaries by default in order to
514 test the features that rely on it such as userspace RCU extended
515 quiescent states.
516 This test is there for debugging until we have a real user like the
517 full dynticks mode.
518
519 config RCU_FANOUT
520 int "Tree-based hierarchical RCU fanout value"
521 range 2 64 if 64BIT
522 range 2 32 if !64BIT
523 depends on TREE_RCU || TREE_PREEMPT_RCU
524 default 64 if 64BIT
525 default 32 if !64BIT
526 help
527 This option controls the fanout of hierarchical implementations
528 of RCU, allowing RCU to work efficiently on machines with
529 large numbers of CPUs. This value must be at least the fourth
530 root of NR_CPUS, which allows NR_CPUS to be insanely large.
531 The default value of RCU_FANOUT should be used for production
532 systems, but if you are stress-testing the RCU implementation
533 itself, small RCU_FANOUT values allow you to test large-system
534 code paths on small(er) systems.
535
536 Select a specific number if testing RCU itself.
537 Take the default if unsure.
538
539 config RCU_FANOUT_LEAF
540 int "Tree-based hierarchical RCU leaf-level fanout value"
541 range 2 RCU_FANOUT if 64BIT
542 range 2 RCU_FANOUT if !64BIT
543 depends on TREE_RCU || TREE_PREEMPT_RCU
544 default 16
545 help
546 This option controls the leaf-level fanout of hierarchical
547 implementations of RCU, and allows trading off cache misses
548 against lock contention. Systems that synchronize their
549 scheduling-clock interrupts for energy-efficiency reasons will
550 want the default because the smaller leaf-level fanout keeps
551 lock contention levels acceptably low. Very large systems
552 (hundreds or thousands of CPUs) will instead want to set this
553 value to the maximum value possible in order to reduce the
554 number of cache misses incurred during RCU's grace-period
555 initialization. These systems tend to run CPU-bound, and thus
556 are not helped by synchronized interrupts, and thus tend to
557 skew them, which reduces lock contention enough that large
558 leaf-level fanouts work well.
559
560 Select a specific number if testing RCU itself.
561
562 Select the maximum permissible value for large systems.
563
564 Take the default if unsure.
565
566 config RCU_FANOUT_EXACT
567 bool "Disable tree-based hierarchical RCU auto-balancing"
568 depends on TREE_RCU || TREE_PREEMPT_RCU
569 default n
570 help
571 This option forces use of the exact RCU_FANOUT value specified,
572 regardless of imbalances in the hierarchy. This is useful for
573 testing RCU itself, and might one day be useful on systems with
574 strong NUMA behavior.
575
576 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
577
578 Say N if unsure.
579
580 config RCU_FAST_NO_HZ
581 bool "Accelerate last non-dyntick-idle CPU's grace periods"
582 depends on NO_HZ && SMP
583 default n
584 help
585 This option causes RCU to attempt to accelerate grace periods in
586 order to allow CPUs to enter dynticks-idle state more quickly.
587 On the other hand, this option increases the overhead of the
588 dynticks-idle checking, thus degrading scheduling latency.
589
590 Say Y if energy efficiency is critically important, and you don't
591 care about real-time response.
592
593 Say N if you are unsure.
594
595 config TREE_RCU_TRACE
596 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
597 select DEBUG_FS
598 help
599 This option provides tracing for the TREE_RCU and
600 TREE_PREEMPT_RCU implementations, permitting Makefile to
601 trivially select kernel/rcutree_trace.c.
602
603 config RCU_BOOST
604 bool "Enable RCU priority boosting"
605 depends on RT_MUTEXES && PREEMPT_RCU
606 default n
607 help
608 This option boosts the priority of preempted RCU readers that
609 block the current preemptible RCU grace period for too long.
610 This option also prevents heavy loads from blocking RCU
611 callback invocation for all flavors of RCU.
612
613 Say Y here if you are working with real-time apps or heavy loads
614 Say N here if you are unsure.
615
616 config RCU_BOOST_PRIO
617 int "Real-time priority to boost RCU readers to"
618 range 1 99
619 depends on RCU_BOOST
620 default 1
621 help
622 This option specifies the real-time priority to which long-term
623 preempted RCU readers are to be boosted. If you are working
624 with a real-time application that has one or more CPU-bound
625 threads running at a real-time priority level, you should set
626 RCU_BOOST_PRIO to a priority higher then the highest-priority
627 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
628 of 1 is appropriate in the common case, which is real-time
629 applications that do not have any CPU-bound threads.
630
631 Some real-time applications might not have a single real-time
632 thread that saturates a given CPU, but instead might have
633 multiple real-time threads that, taken together, fully utilize
634 that CPU. In this case, you should set RCU_BOOST_PRIO to
635 a priority higher than the lowest-priority thread that is
636 conspiring to prevent the CPU from running any non-real-time
637 tasks. For example, if one thread at priority 10 and another
638 thread at priority 5 are between themselves fully consuming
639 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
640 set to priority 6 or higher.
641
642 Specify the real-time priority, or take the default if unsure.
643
644 config RCU_BOOST_DELAY
645 int "Milliseconds to delay boosting after RCU grace-period start"
646 range 0 3000
647 depends on RCU_BOOST
648 default 500
649 help
650 This option specifies the time to wait after the beginning of
651 a given grace period before priority-boosting preempted RCU
652 readers blocking that grace period. Note that any RCU reader
653 blocking an expedited RCU grace period is boosted immediately.
654
655 Accept the default if unsure.
656
657 config RCU_NOCB_CPU
658 bool "Offload RCU callback processing from boot-selected CPUs"
659 depends on TREE_RCU || TREE_PREEMPT_RCU
660 default n
661 help
662 Use this option to reduce OS jitter for aggressive HPC or
663 real-time workloads. It can also be used to offload RCU
664 callback invocation to energy-efficient CPUs in battery-powered
665 asymmetric multiprocessors.
666
667 This option offloads callback invocation from the set of
668 CPUs specified at boot time by the rcu_nocbs parameter.
669 For each such CPU, a kthread ("rcuoN") will be created to
670 invoke callbacks, where the "N" is the CPU being offloaded.
671 Nothing prevents this kthread from running on the specified
672 CPUs, but (1) the kthreads may be preempted between each
673 callback, and (2) affinity or cgroups can be used to force
674 the kthreads to run on whatever set of CPUs is desired.
675
676 Say Y here if you want reduced OS jitter on selected CPUs.
677 Say N here if you are unsure.
678
679 endmenu # "RCU Subsystem"
680
681 config IKCONFIG
682 tristate "Kernel .config support"
683 ---help---
684 This option enables the complete Linux kernel ".config" file
685 contents to be saved in the kernel. It provides documentation
686 of which kernel options are used in a running kernel or in an
687 on-disk kernel. This information can be extracted from the kernel
688 image file with the script scripts/extract-ikconfig and used as
689 input to rebuild the current kernel or to build another kernel.
690 It can also be extracted from a running kernel by reading
691 /proc/config.gz if enabled (below).
692
693 config IKCONFIG_PROC
694 bool "Enable access to .config through /proc/config.gz"
695 depends on IKCONFIG && PROC_FS
696 ---help---
697 This option enables access to the kernel configuration file
698 through /proc/config.gz.
699
700 config LOG_BUF_SHIFT
701 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
702 range 12 21
703 default 17
704 help
705 Select kernel log buffer size as a power of 2.
706 Examples:
707 17 => 128 KB
708 16 => 64 KB
709 15 => 32 KB
710 14 => 16 KB
711 13 => 8 KB
712 12 => 4 KB
713
714 #
715 # Architectures with an unreliable sched_clock() should select this:
716 #
717 config HAVE_UNSTABLE_SCHED_CLOCK
718 bool
719
720 #
721 # For architectures that want to enable the support for NUMA-affine scheduler
722 # balancing logic:
723 #
724 config ARCH_SUPPORTS_NUMA_BALANCING
725 bool
726
727 # For architectures that (ab)use NUMA to represent different memory regions
728 # all cpu-local but of different latencies, such as SuperH.
729 #
730 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
731 bool
732
733 #
734 # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
735 config ARCH_WANTS_PROT_NUMA_PROT_NONE
736 bool
737
738 config ARCH_USES_NUMA_PROT_NONE
739 bool
740 default y
741 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
742 depends on NUMA_BALANCING
743
744 config NUMA_BALANCING_DEFAULT_ENABLED
745 bool "Automatically enable NUMA aware memory/task placement"
746 default y
747 depends on NUMA_BALANCING
748 help
749 If set, autonumic NUMA balancing will be enabled if running on a NUMA
750 machine.
751
752 config NUMA_BALANCING
753 bool "Memory placement aware NUMA scheduler"
754 depends on ARCH_SUPPORTS_NUMA_BALANCING
755 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
756 depends on SMP && NUMA && MIGRATION
757 help
758 This option adds support for automatic NUMA aware memory/task placement.
759 The mechanism is quite primitive and is based on migrating memory when
760 it is references to the node the task is running on.
761
762 This system will be inactive on UMA systems.
763
764 menuconfig CGROUPS
765 boolean "Control Group support"
766 depends on EVENTFD
767 help
768 This option adds support for grouping sets of processes together, for
769 use with process control subsystems such as Cpusets, CFS, memory
770 controls or device isolation.
771 See
772 - Documentation/scheduler/sched-design-CFS.txt (CFS)
773 - Documentation/cgroups/ (features for grouping, isolation
774 and resource control)
775
776 Say N if unsure.
777
778 if CGROUPS
779
780 config CGROUP_DEBUG
781 bool "Example debug cgroup subsystem"
782 default n
783 help
784 This option enables a simple cgroup subsystem that
785 exports useful debugging information about the cgroups
786 framework.
787
788 Say N if unsure.
789
790 config CGROUP_FREEZER
791 bool "Freezer cgroup subsystem"
792 help
793 Provides a way to freeze and unfreeze all tasks in a
794 cgroup.
795
796 config CGROUP_DEVICE
797 bool "Device controller for cgroups"
798 help
799 Provides a cgroup implementing whitelists for devices which
800 a process in the cgroup can mknod or open.
801
802 config CPUSETS
803 bool "Cpuset support"
804 help
805 This option will let you create and manage CPUSETs which
806 allow dynamically partitioning a system into sets of CPUs and
807 Memory Nodes and assigning tasks to run only within those sets.
808 This is primarily useful on large SMP or NUMA systems.
809
810 Say N if unsure.
811
812 config PROC_PID_CPUSET
813 bool "Include legacy /proc/<pid>/cpuset file"
814 depends on CPUSETS
815 default y
816
817 config CGROUP_CPUACCT
818 bool "Simple CPU accounting cgroup subsystem"
819 help
820 Provides a simple Resource Controller for monitoring the
821 total CPU consumed by the tasks in a cgroup.
822
823 config RESOURCE_COUNTERS
824 bool "Resource counters"
825 help
826 This option enables controller independent resource accounting
827 infrastructure that works with cgroups.
828
829 config MEMCG
830 bool "Memory Resource Controller for Control Groups"
831 depends on RESOURCE_COUNTERS
832 select MM_OWNER
833 help
834 Provides a memory resource controller that manages both anonymous
835 memory and page cache. (See Documentation/cgroups/memory.txt)
836
837 Note that setting this option increases fixed memory overhead
838 associated with each page of memory in the system. By this,
839 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
840 usage tracking struct at boot. Total amount of this is printed out
841 at boot.
842
843 Only enable when you're ok with these trade offs and really
844 sure you need the memory resource controller. Even when you enable
845 this, you can set "cgroup_disable=memory" at your boot option to
846 disable memory resource controller and you can avoid overheads.
847 (and lose benefits of memory resource controller)
848
849 This config option also selects MM_OWNER config option, which
850 could in turn add some fork/exit overhead.
851
852 config MEMCG_SWAP
853 bool "Memory Resource Controller Swap Extension"
854 depends on MEMCG && SWAP
855 help
856 Add swap management feature to memory resource controller. When you
857 enable this, you can limit mem+swap usage per cgroup. In other words,
858 when you disable this, memory resource controller has no cares to
859 usage of swap...a process can exhaust all of the swap. This extension
860 is useful when you want to avoid exhaustion swap but this itself
861 adds more overheads and consumes memory for remembering information.
862 Especially if you use 32bit system or small memory system, please
863 be careful about enabling this. When memory resource controller
864 is disabled by boot option, this will be automatically disabled and
865 there will be no overhead from this. Even when you set this config=y,
866 if boot option "swapaccount=0" is set, swap will not be accounted.
867 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
868 size is 4096bytes, 512k per 1Gbytes of swap.
869 config MEMCG_SWAP_ENABLED
870 bool "Memory Resource Controller Swap Extension enabled by default"
871 depends on MEMCG_SWAP
872 default y
873 help
874 Memory Resource Controller Swap Extension comes with its price in
875 a bigger memory consumption. General purpose distribution kernels
876 which want to enable the feature but keep it disabled by default
877 and let the user enable it by swapaccount boot command line
878 parameter should have this option unselected.
879 For those who want to have the feature enabled by default should
880 select this option (if, for some reason, they need to disable it
881 then swapaccount=0 does the trick).
882 config MEMCG_KMEM
883 bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
884 depends on MEMCG && EXPERIMENTAL
885 default n
886 help
887 The Kernel Memory extension for Memory Resource Controller can limit
888 the amount of memory used by kernel objects in the system. Those are
889 fundamentally different from the entities handled by the standard
890 Memory Controller, which are page-based, and can be swapped. Users of
891 the kmem extension can use it to guarantee that no group of processes
892 will ever exhaust kernel resources alone.
893
894 config CGROUP_HUGETLB
895 bool "HugeTLB Resource Controller for Control Groups"
896 depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
897 default n
898 help
899 Provides a cgroup Resource Controller for HugeTLB pages.
900 When you enable this, you can put a per cgroup limit on HugeTLB usage.
901 The limit is enforced during page fault. Since HugeTLB doesn't
902 support page reclaim, enforcing the limit at page fault time implies
903 that, the application will get SIGBUS signal if it tries to access
904 HugeTLB pages beyond its limit. This requires the application to know
905 beforehand how much HugeTLB pages it would require for its use. The
906 control group is tracked in the third page lru pointer. This means
907 that we cannot use the controller with huge page less than 3 pages.
908
909 config CGROUP_PERF
910 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
911 depends on PERF_EVENTS && CGROUPS
912 help
913 This option extends the per-cpu mode to restrict monitoring to
914 threads which belong to the cgroup specified and run on the
915 designated cpu.
916
917 Say N if unsure.
918
919 menuconfig CGROUP_SCHED
920 bool "Group CPU scheduler"
921 default n
922 help
923 This feature lets CPU scheduler recognize task groups and control CPU
924 bandwidth allocation to such task groups. It uses cgroups to group
925 tasks.
926
927 if CGROUP_SCHED
928 config FAIR_GROUP_SCHED
929 bool "Group scheduling for SCHED_OTHER"
930 depends on CGROUP_SCHED
931 default CGROUP_SCHED
932
933 config CFS_BANDWIDTH
934 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
935 depends on EXPERIMENTAL
936 depends on FAIR_GROUP_SCHED
937 default n
938 help
939 This option allows users to define CPU bandwidth rates (limits) for
940 tasks running within the fair group scheduler. Groups with no limit
941 set are considered to be unconstrained and will run with no
942 restriction.
943 See tip/Documentation/scheduler/sched-bwc.txt for more information.
944
945 config RT_GROUP_SCHED
946 bool "Group scheduling for SCHED_RR/FIFO"
947 depends on EXPERIMENTAL
948 depends on CGROUP_SCHED
949 default n
950 help
951 This feature lets you explicitly allocate real CPU bandwidth
952 to task groups. If enabled, it will also make it impossible to
953 schedule realtime tasks for non-root users until you allocate
954 realtime bandwidth for them.
955 See Documentation/scheduler/sched-rt-group.txt for more information.
956
957 endif #CGROUP_SCHED
958
959 config BLK_CGROUP
960 bool "Block IO controller"
961 depends on BLOCK
962 default n
963 ---help---
964 Generic block IO controller cgroup interface. This is the common
965 cgroup interface which should be used by various IO controlling
966 policies.
967
968 Currently, CFQ IO scheduler uses it to recognize task groups and
969 control disk bandwidth allocation (proportional time slice allocation)
970 to such task groups. It is also used by bio throttling logic in
971 block layer to implement upper limit in IO rates on a device.
972
973 This option only enables generic Block IO controller infrastructure.
974 One needs to also enable actual IO controlling logic/policy. For
975 enabling proportional weight division of disk bandwidth in CFQ, set
976 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
977 CONFIG_BLK_DEV_THROTTLING=y.
978
979 See Documentation/cgroups/blkio-controller.txt for more information.
980
981 config DEBUG_BLK_CGROUP
982 bool "Enable Block IO controller debugging"
983 depends on BLK_CGROUP
984 default n
985 ---help---
986 Enable some debugging help. Currently it exports additional stat
987 files in a cgroup which can be useful for debugging.
988
989 endif # CGROUPS
990
991 config CHECKPOINT_RESTORE
992 bool "Checkpoint/restore support" if EXPERT
993 default n
994 help
995 Enables additional kernel features in a sake of checkpoint/restore.
996 In particular it adds auxiliary prctl codes to setup process text,
997 data and heap segment sizes, and a few additional /proc filesystem
998 entries.
999
1000 If unsure, say N here.
1001
1002 menuconfig NAMESPACES
1003 bool "Namespaces support" if EXPERT
1004 default !EXPERT
1005 help
1006 Provides the way to make tasks work with different objects using
1007 the same id. For example same IPC id may refer to different objects
1008 or same user id or pid may refer to different tasks when used in
1009 different namespaces.
1010
1011 if NAMESPACES
1012
1013 config UTS_NS
1014 bool "UTS namespace"
1015 default y
1016 help
1017 In this namespace tasks see different info provided with the
1018 uname() system call
1019
1020 config IPC_NS
1021 bool "IPC namespace"
1022 depends on (SYSVIPC || POSIX_MQUEUE)
1023 default y
1024 help
1025 In this namespace tasks work with IPC ids which correspond to
1026 different IPC objects in different namespaces.
1027
1028 config USER_NS
1029 bool "User namespace (EXPERIMENTAL)"
1030 depends on EXPERIMENTAL
1031 depends on UIDGID_CONVERTED
1032 select UIDGID_STRICT_TYPE_CHECKS
1033
1034 default n
1035 help
1036 This allows containers, i.e. vservers, to use user namespaces
1037 to provide different user info for different servers.
1038 If unsure, say N.
1039
1040 config PID_NS
1041 bool "PID Namespaces"
1042 default y
1043 help
1044 Support process id namespaces. This allows having multiple
1045 processes with the same pid as long as they are in different
1046 pid namespaces. This is a building block of containers.
1047
1048 config NET_NS
1049 bool "Network namespace"
1050 depends on NET
1051 default y
1052 help
1053 Allow user space to create what appear to be multiple instances
1054 of the network stack.
1055
1056 endif # NAMESPACES
1057
1058 config UIDGID_CONVERTED
1059 # True if all of the selected software conmponents are known
1060 # to have uid_t and gid_t converted to kuid_t and kgid_t
1061 # where appropriate and are otherwise safe to use with
1062 # the user namespace.
1063 bool
1064 default y
1065
1066 # Networking
1067 depends on NET_9P = n
1068
1069 # Filesystems
1070 depends on 9P_FS = n
1071 depends on AFS_FS = n
1072 depends on AUTOFS4_FS = n
1073 depends on CEPH_FS = n
1074 depends on CIFS = n
1075 depends on CODA_FS = n
1076 depends on FUSE_FS = n
1077 depends on GFS2_FS = n
1078 depends on NCP_FS = n
1079 depends on NFSD = n
1080 depends on NFS_FS = n
1081 depends on OCFS2_FS = n
1082 depends on XFS_FS = n
1083
1084 config UIDGID_STRICT_TYPE_CHECKS
1085 bool "Require conversions between uid/gids and their internal representation"
1086 depends on UIDGID_CONVERTED
1087 default n
1088 help
1089 While the nececessary conversions are being added to all subsystems this option allows
1090 the code to continue to build for unconverted subsystems.
1091
1092 Say Y here if you want the strict type checking enabled
1093
1094 config SCHED_AUTOGROUP
1095 bool "Automatic process group scheduling"
1096 select EVENTFD
1097 select CGROUPS
1098 select CGROUP_SCHED
1099 select FAIR_GROUP_SCHED
1100 help
1101 This option optimizes the scheduler for common desktop workloads by
1102 automatically creating and populating task groups. This separation
1103 of workloads isolates aggressive CPU burners (like build jobs) from
1104 desktop applications. Task group autogeneration is currently based
1105 upon task session.
1106
1107 config MM_OWNER
1108 bool
1109
1110 config SYSFS_DEPRECATED
1111 bool "Enable deprecated sysfs features to support old userspace tools"
1112 depends on SYSFS
1113 default n
1114 help
1115 This option adds code that switches the layout of the "block" class
1116 devices, to not show up in /sys/class/block/, but only in
1117 /sys/block/.
1118
1119 This switch is only active when the sysfs.deprecated=1 boot option is
1120 passed or the SYSFS_DEPRECATED_V2 option is set.
1121
1122 This option allows new kernels to run on old distributions and tools,
1123 which might get confused by /sys/class/block/. Since 2007/2008 all
1124 major distributions and tools handle this just fine.
1125
1126 Recent distributions and userspace tools after 2009/2010 depend on
1127 the existence of /sys/class/block/, and will not work with this
1128 option enabled.
1129
1130 Only if you are using a new kernel on an old distribution, you might
1131 need to say Y here.
1132
1133 config SYSFS_DEPRECATED_V2
1134 bool "Enable deprecated sysfs features by default"
1135 default n
1136 depends on SYSFS
1137 depends on SYSFS_DEPRECATED
1138 help
1139 Enable deprecated sysfs by default.
1140
1141 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1142 option.
1143
1144 Only if you are using a new kernel on an old distribution, you might
1145 need to say Y here. Even then, odds are you would not need it
1146 enabled, you can always pass the boot option if absolutely necessary.
1147
1148 config RELAY
1149 bool "Kernel->user space relay support (formerly relayfs)"
1150 help
1151 This option enables support for relay interface support in
1152 certain file systems (such as debugfs).
1153 It is designed to provide an efficient mechanism for tools and
1154 facilities to relay large amounts of data from kernel space to
1155 user space.
1156
1157 If unsure, say N.
1158
1159 config BLK_DEV_INITRD
1160 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1161 depends on BROKEN || !FRV
1162 help
1163 The initial RAM filesystem is a ramfs which is loaded by the
1164 boot loader (loadlin or lilo) and that is mounted as root
1165 before the normal boot procedure. It is typically used to
1166 load modules needed to mount the "real" root file system,
1167 etc. See <file:Documentation/initrd.txt> for details.
1168
1169 If RAM disk support (BLK_DEV_RAM) is also included, this
1170 also enables initial RAM disk (initrd) support and adds
1171 15 Kbytes (more on some other architectures) to the kernel size.
1172
1173 If unsure say Y.
1174
1175 if BLK_DEV_INITRD
1176
1177 source "usr/Kconfig"
1178
1179 endif
1180
1181 config CC_OPTIMIZE_FOR_SIZE
1182 bool "Optimize for size"
1183 help
1184 Enabling this option will pass "-Os" instead of "-O2" to gcc
1185 resulting in a smaller kernel.
1186
1187 If unsure, say Y.
1188
1189 config SYSCTL
1190 bool
1191
1192 config ANON_INODES
1193 bool
1194
1195 menuconfig EXPERT
1196 bool "Configure standard kernel features (expert users)"
1197 # Unhide debug options, to make the on-by-default options visible
1198 select DEBUG_KERNEL
1199 help
1200 This option allows certain base kernel options and settings
1201 to be disabled or tweaked. This is for specialized
1202 environments which can tolerate a "non-standard" kernel.
1203 Only use this if you really know what you are doing.
1204
1205 config HAVE_UID16
1206 bool
1207
1208 config UID16
1209 bool "Enable 16-bit UID system calls" if EXPERT
1210 depends on HAVE_UID16
1211 default y
1212 help
1213 This enables the legacy 16-bit UID syscall wrappers.
1214
1215 config SYSCTL_SYSCALL
1216 bool "Sysctl syscall support" if EXPERT
1217 depends on PROC_SYSCTL
1218 default n
1219 select SYSCTL
1220 ---help---
1221 sys_sysctl uses binary paths that have been found challenging
1222 to properly maintain and use. The interface in /proc/sys
1223 using paths with ascii names is now the primary path to this
1224 information.
1225
1226 Almost nothing using the binary sysctl interface so if you are
1227 trying to save some space it is probably safe to disable this,
1228 making your kernel marginally smaller.
1229
1230 If unsure say N here.
1231
1232 config SYSCTL_EXCEPTION_TRACE
1233 bool
1234 help
1235 Enable support for /proc/sys/debug/exception-trace.
1236
1237 config KALLSYMS
1238 bool "Load all symbols for debugging/ksymoops" if EXPERT
1239 default y
1240 help
1241 Say Y here to let the kernel print out symbolic crash information and
1242 symbolic stack backtraces. This increases the size of the kernel
1243 somewhat, as all symbols have to be loaded into the kernel image.
1244
1245 config KALLSYMS_ALL
1246 bool "Include all symbols in kallsyms"
1247 depends on DEBUG_KERNEL && KALLSYMS
1248 help
1249 Normally kallsyms only contains the symbols of functions for nicer
1250 OOPS messages and backtraces (i.e., symbols from the text and inittext
1251 sections). This is sufficient for most cases. And only in very rare
1252 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1253 names of variables from the data sections, etc).
1254
1255 This option makes sure that all symbols are loaded into the kernel
1256 image (i.e., symbols from all sections) in cost of increased kernel
1257 size (depending on the kernel configuration, it may be 300KiB or
1258 something like this).
1259
1260 Say N unless you really need all symbols.
1261
1262 config HOTPLUG
1263 def_bool y
1264
1265 config PRINTK
1266 default y
1267 bool "Enable support for printk" if EXPERT
1268 help
1269 This option enables normal printk support. Removing it
1270 eliminates most of the message strings from the kernel image
1271 and makes the kernel more or less silent. As this makes it
1272 very difficult to diagnose system problems, saying N here is
1273 strongly discouraged.
1274
1275 config BUG
1276 bool "BUG() support" if EXPERT
1277 default y
1278 help
1279 Disabling this option eliminates support for BUG and WARN, reducing
1280 the size of your kernel image and potentially quietly ignoring
1281 numerous fatal conditions. You should only consider disabling this
1282 option for embedded systems with no facilities for reporting errors.
1283 Just say Y.
1284
1285 config ELF_CORE
1286 depends on COREDUMP
1287 default y
1288 bool "Enable ELF core dumps" if EXPERT
1289 help
1290 Enable support for generating core dumps. Disabling saves about 4k.
1291
1292
1293 config PCSPKR_PLATFORM
1294 bool "Enable PC-Speaker support" if EXPERT
1295 depends on HAVE_PCSPKR_PLATFORM
1296 select I8253_LOCK
1297 default y
1298 help
1299 This option allows to disable the internal PC-Speaker
1300 support, saving some memory.
1301
1302 config HAVE_PCSPKR_PLATFORM
1303 bool
1304
1305 config BASE_FULL
1306 default y
1307 bool "Enable full-sized data structures for core" if EXPERT
1308 help
1309 Disabling this option reduces the size of miscellaneous core
1310 kernel data structures. This saves memory on small machines,
1311 but may reduce performance.
1312
1313 config FUTEX
1314 bool "Enable futex support" if EXPERT
1315 default y
1316 select RT_MUTEXES
1317 help
1318 Disabling this option will cause the kernel to be built without
1319 support for "fast userspace mutexes". The resulting kernel may not
1320 run glibc-based applications correctly.
1321
1322 config EPOLL
1323 bool "Enable eventpoll support" if EXPERT
1324 default y
1325 select ANON_INODES
1326 help
1327 Disabling this option will cause the kernel to be built without
1328 support for epoll family of system calls.
1329
1330 config SIGNALFD
1331 bool "Enable signalfd() system call" if EXPERT
1332 select ANON_INODES
1333 default y
1334 help
1335 Enable the signalfd() system call that allows to receive signals
1336 on a file descriptor.
1337
1338 If unsure, say Y.
1339
1340 config TIMERFD
1341 bool "Enable timerfd() system call" if EXPERT
1342 select ANON_INODES
1343 default y
1344 help
1345 Enable the timerfd() system call that allows to receive timer
1346 events on a file descriptor.
1347
1348 If unsure, say Y.
1349
1350 config EVENTFD
1351 bool "Enable eventfd() system call" if EXPERT
1352 select ANON_INODES
1353 default y
1354 help
1355 Enable the eventfd() system call that allows to receive both
1356 kernel notification (ie. KAIO) or userspace notifications.
1357
1358 If unsure, say Y.
1359
1360 config SHMEM
1361 bool "Use full shmem filesystem" if EXPERT
1362 default y
1363 depends on MMU
1364 help
1365 The shmem is an internal filesystem used to manage shared memory.
1366 It is backed by swap and manages resource limits. It is also exported
1367 to userspace as tmpfs if TMPFS is enabled. Disabling this
1368 option replaces shmem and tmpfs with the much simpler ramfs code,
1369 which may be appropriate on small systems without swap.
1370
1371 config AIO
1372 bool "Enable AIO support" if EXPERT
1373 default y
1374 help
1375 This option enables POSIX asynchronous I/O which may by used
1376 by some high performance threaded applications. Disabling
1377 this option saves about 7k.
1378
1379 config EMBEDDED
1380 bool "Embedded system"
1381 select EXPERT
1382 help
1383 This option should be enabled if compiling the kernel for
1384 an embedded system so certain expert options are available
1385 for configuration.
1386
1387 config HAVE_PERF_EVENTS
1388 bool
1389 help
1390 See tools/perf/design.txt for details.
1391
1392 config PERF_USE_VMALLOC
1393 bool
1394 help
1395 See tools/perf/design.txt for details
1396
1397 menu "Kernel Performance Events And Counters"
1398
1399 config PERF_EVENTS
1400 bool "Kernel performance events and counters"
1401 default y if PROFILING
1402 depends on HAVE_PERF_EVENTS
1403 select ANON_INODES
1404 select IRQ_WORK
1405 help
1406 Enable kernel support for various performance events provided
1407 by software and hardware.
1408
1409 Software events are supported either built-in or via the
1410 use of generic tracepoints.
1411
1412 Most modern CPUs support performance events via performance
1413 counter registers. These registers count the number of certain
1414 types of hw events: such as instructions executed, cachemisses
1415 suffered, or branches mis-predicted - without slowing down the
1416 kernel or applications. These registers can also trigger interrupts
1417 when a threshold number of events have passed - and can thus be
1418 used to profile the code that runs on that CPU.
1419
1420 The Linux Performance Event subsystem provides an abstraction of
1421 these software and hardware event capabilities, available via a
1422 system call and used by the "perf" utility in tools/perf/. It
1423 provides per task and per CPU counters, and it provides event
1424 capabilities on top of those.
1425
1426 Say Y if unsure.
1427
1428 config DEBUG_PERF_USE_VMALLOC
1429 default n
1430 bool "Debug: use vmalloc to back perf mmap() buffers"
1431 depends on PERF_EVENTS && DEBUG_KERNEL
1432 select PERF_USE_VMALLOC
1433 help
1434 Use vmalloc memory to back perf mmap() buffers.
1435
1436 Mostly useful for debugging the vmalloc code on platforms
1437 that don't require it.
1438
1439 Say N if unsure.
1440
1441 endmenu
1442
1443 config VM_EVENT_COUNTERS
1444 default y
1445 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1446 help
1447 VM event counters are needed for event counts to be shown.
1448 This option allows the disabling of the VM event counters
1449 on EXPERT systems. /proc/vmstat will only show page counts
1450 if VM event counters are disabled.
1451
1452 config PCI_QUIRKS
1453 default y
1454 bool "Enable PCI quirk workarounds" if EXPERT
1455 depends on PCI
1456 help
1457 This enables workarounds for various PCI chipset
1458 bugs/quirks. Disable this only if your target machine is
1459 unaffected by PCI quirks.
1460
1461 config SLUB_DEBUG
1462 default y
1463 bool "Enable SLUB debugging support" if EXPERT
1464 depends on SLUB && SYSFS
1465 help
1466 SLUB has extensive debug support features. Disabling these can
1467 result in significant savings in code size. This also disables
1468 SLUB sysfs support. /sys/slab will not exist and there will be
1469 no support for cache validation etc.
1470
1471 config COMPAT_BRK
1472 bool "Disable heap randomization"
1473 default y
1474 help
1475 Randomizing heap placement makes heap exploits harder, but it
1476 also breaks ancient binaries (including anything libc5 based).
1477 This option changes the bootup default to heap randomization
1478 disabled, and can be overridden at runtime by setting
1479 /proc/sys/kernel/randomize_va_space to 2.
1480
1481 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1482
1483 choice
1484 prompt "Choose SLAB allocator"
1485 default SLUB
1486 help
1487 This option allows to select a slab allocator.
1488
1489 config SLAB
1490 bool "SLAB"
1491 help
1492 The regular slab allocator that is established and known to work
1493 well in all environments. It organizes cache hot objects in
1494 per cpu and per node queues.
1495
1496 config SLUB
1497 bool "SLUB (Unqueued Allocator)"
1498 help
1499 SLUB is a slab allocator that minimizes cache line usage
1500 instead of managing queues of cached objects (SLAB approach).
1501 Per cpu caching is realized using slabs of objects instead
1502 of queues of objects. SLUB can use memory efficiently
1503 and has enhanced diagnostics. SLUB is the default choice for
1504 a slab allocator.
1505
1506 config SLOB
1507 depends on EXPERT
1508 bool "SLOB (Simple Allocator)"
1509 help
1510 SLOB replaces the stock allocator with a drastically simpler
1511 allocator. SLOB is generally more space efficient but
1512 does not perform as well on large systems.
1513
1514 endchoice
1515
1516 config MMAP_ALLOW_UNINITIALIZED
1517 bool "Allow mmapped anonymous memory to be uninitialized"
1518 depends on EXPERT && !MMU
1519 default n
1520 help
1521 Normally, and according to the Linux spec, anonymous memory obtained
1522 from mmap() has it's contents cleared before it is passed to
1523 userspace. Enabling this config option allows you to request that
1524 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1525 providing a huge performance boost. If this option is not enabled,
1526 then the flag will be ignored.
1527
1528 This is taken advantage of by uClibc's malloc(), and also by
1529 ELF-FDPIC binfmt's brk and stack allocator.
1530
1531 Because of the obvious security issues, this option should only be
1532 enabled on embedded devices where you control what is run in
1533 userspace. Since that isn't generally a problem on no-MMU systems,
1534 it is normally safe to say Y here.
1535
1536 See Documentation/nommu-mmap.txt for more information.
1537
1538 config PROFILING
1539 bool "Profiling support"
1540 help
1541 Say Y here to enable the extended profiling support mechanisms used
1542 by profilers such as OProfile.
1543
1544 #
1545 # Place an empty function call at each tracepoint site. Can be
1546 # dynamically changed for a probe function.
1547 #
1548 config TRACEPOINTS
1549 bool
1550
1551 source "arch/Kconfig"
1552
1553 endmenu # General setup
1554
1555 config HAVE_GENERIC_DMA_COHERENT
1556 bool
1557 default n
1558
1559 config SLABINFO
1560 bool
1561 depends on PROC_FS
1562 depends on SLAB || SLUB_DEBUG
1563 default y
1564
1565 config RT_MUTEXES
1566 boolean
1567
1568 config BASE_SMALL
1569 int
1570 default 0 if BASE_FULL
1571 default 1 if !BASE_FULL
1572
1573 menuconfig MODULES
1574 bool "Enable loadable module support"
1575 help
1576 Kernel modules are small pieces of compiled code which can
1577 be inserted in the running kernel, rather than being
1578 permanently built into the kernel. You use the "modprobe"
1579 tool to add (and sometimes remove) them. If you say Y here,
1580 many parts of the kernel can be built as modules (by
1581 answering M instead of Y where indicated): this is most
1582 useful for infrequently used options which are not required
1583 for booting. For more information, see the man pages for
1584 modprobe, lsmod, modinfo, insmod and rmmod.
1585
1586 If you say Y here, you will need to run "make
1587 modules_install" to put the modules under /lib/modules/
1588 where modprobe can find them (you may need to be root to do
1589 this).
1590
1591 If unsure, say Y.
1592
1593 if MODULES
1594
1595 config MODULE_FORCE_LOAD
1596 bool "Forced module loading"
1597 default n
1598 help
1599 Allow loading of modules without version information (ie. modprobe
1600 --force). Forced module loading sets the 'F' (forced) taint flag and
1601 is usually a really bad idea.
1602
1603 config MODULE_UNLOAD
1604 bool "Module unloading"
1605 help
1606 Without this option you will not be able to unload any
1607 modules (note that some modules may not be unloadable
1608 anyway), which makes your kernel smaller, faster
1609 and simpler. If unsure, say Y.
1610
1611 config MODULE_FORCE_UNLOAD
1612 bool "Forced module unloading"
1613 depends on MODULE_UNLOAD && EXPERIMENTAL
1614 help
1615 This option allows you to force a module to unload, even if the
1616 kernel believes it is unsafe: the kernel will remove the module
1617 without waiting for anyone to stop using it (using the -f option to
1618 rmmod). This is mainly for kernel developers and desperate users.
1619 If unsure, say N.
1620
1621 config MODVERSIONS
1622 bool "Module versioning support"
1623 help
1624 Usually, you have to use modules compiled with your kernel.
1625 Saying Y here makes it sometimes possible to use modules
1626 compiled for different kernels, by adding enough information
1627 to the modules to (hopefully) spot any changes which would
1628 make them incompatible with the kernel you are running. If
1629 unsure, say N.
1630
1631 config MODULE_SRCVERSION_ALL
1632 bool "Source checksum for all modules"
1633 help
1634 Modules which contain a MODULE_VERSION get an extra "srcversion"
1635 field inserted into their modinfo section, which contains a
1636 sum of the source files which made it. This helps maintainers
1637 see exactly which source was used to build a module (since
1638 others sometimes change the module source without updating
1639 the version). With this option, such a "srcversion" field
1640 will be created for all modules. If unsure, say N.
1641
1642 config MODULE_SIG
1643 bool "Module signature verification"
1644 depends on MODULES
1645 select KEYS
1646 select CRYPTO
1647 select ASYMMETRIC_KEY_TYPE
1648 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1649 select PUBLIC_KEY_ALGO_RSA
1650 select ASN1
1651 select OID_REGISTRY
1652 select X509_CERTIFICATE_PARSER
1653 help
1654 Check modules for valid signatures upon load: the signature
1655 is simply appended to the module. For more information see
1656 Documentation/module-signing.txt.
1657
1658 !!!WARNING!!! If you enable this option, you MUST make sure that the
1659 module DOES NOT get stripped after being signed. This includes the
1660 debuginfo strip done by some packagers (such as rpmbuild) and
1661 inclusion into an initramfs that wants the module size reduced.
1662
1663 config MODULE_SIG_FORCE
1664 bool "Require modules to be validly signed"
1665 depends on MODULE_SIG
1666 help
1667 Reject unsigned modules or signed modules for which we don't have a
1668 key. Without this, such modules will simply taint the kernel.
1669
1670 choice
1671 prompt "Which hash algorithm should modules be signed with?"
1672 depends on MODULE_SIG
1673 help
1674 This determines which sort of hashing algorithm will be used during
1675 signature generation. This algorithm _must_ be built into the kernel
1676 directly so that signature verification can take place. It is not
1677 possible to load a signed module containing the algorithm to check
1678 the signature on that module.
1679
1680 config MODULE_SIG_SHA1
1681 bool "Sign modules with SHA-1"
1682 select CRYPTO_SHA1
1683
1684 config MODULE_SIG_SHA224
1685 bool "Sign modules with SHA-224"
1686 select CRYPTO_SHA256
1687
1688 config MODULE_SIG_SHA256
1689 bool "Sign modules with SHA-256"
1690 select CRYPTO_SHA256
1691
1692 config MODULE_SIG_SHA384
1693 bool "Sign modules with SHA-384"
1694 select CRYPTO_SHA512
1695
1696 config MODULE_SIG_SHA512
1697 bool "Sign modules with SHA-512"
1698 select CRYPTO_SHA512
1699
1700 endchoice
1701
1702 endif # MODULES
1703
1704 config INIT_ALL_POSSIBLE
1705 bool
1706 help
1707 Back when each arch used to define their own cpu_online_mask and
1708 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1709 with all 1s, and others with all 0s. When they were centralised,
1710 it was better to provide this option than to break all the archs
1711 and have several arch maintainers pursuing me down dark alleys.
1712
1713 config STOP_MACHINE
1714 bool
1715 default y
1716 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1717 help
1718 Need stop_machine() primitive.
1719
1720 source "block/Kconfig"
1721
1722 config PREEMPT_NOTIFIERS
1723 bool
1724
1725 config PADATA
1726 depends on SMP
1727 bool
1728
1729 # Can be selected by architectures with broken toolchains
1730 # that get confused by correct const<->read_only section
1731 # mappings
1732 config BROKEN_RODATA
1733 bool
1734
1735 config ASN1
1736 tristate
1737 help
1738 Build a simple ASN.1 grammar compiler that produces a bytecode output
1739 that can be interpreted by the ASN.1 stream decoder and used to
1740 inform it as to what tags are to be expected in a stream and what
1741 functions to call on what tags.
1742
1743 source "kernel/Kconfig.locks"