Merge branch 'for-john' of git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211
[deliverable/linux.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 IRQ_WORK
24 bool
25
26 config BUILDTIME_EXTABLE_SORT
27 bool
28
29 menu "General setup"
30
31 config EXPERIMENTAL
32 bool
33 default y
34
35 config BROKEN
36 bool
37
38 config BROKEN_ON_SMP
39 bool
40 depends on BROKEN || !SMP
41 default y
42
43 config INIT_ENV_ARG_LIMIT
44 int
45 default 32 if !UML
46 default 128 if UML
47 help
48 Maximum of each of the number of arguments and environment
49 variables passed to init from the kernel command line.
50
51
52 config CROSS_COMPILE
53 string "Cross-compiler tool prefix"
54 help
55 Same as running 'make CROSS_COMPILE=prefix-' but stored for
56 default make runs in this kernel build directory. You don't
57 need to set this unless you want the configured kernel build
58 directory to select the cross-compiler automatically.
59
60 config LOCALVERSION
61 string "Local version - append to kernel release"
62 help
63 Append an extra string to the end of your kernel version.
64 This will show up when you type uname, for example.
65 The string you set here will be appended after the contents of
66 any files with a filename matching localversion* in your
67 object and source tree, in that order. Your total string can
68 be a maximum of 64 characters.
69
70 config LOCALVERSION_AUTO
71 bool "Automatically append version information to the version string"
72 default y
73 help
74 This will try to automatically determine if the current tree is a
75 release tree by looking for git tags that belong to the current
76 top of tree revision.
77
78 A string of the format -gxxxxxxxx will be added to the localversion
79 if a git-based tree is found. The string generated by this will be
80 appended after any matching localversion* files, and after the value
81 set in CONFIG_LOCALVERSION.
82
83 (The actual string used here is the first eight characters produced
84 by running the command:
85
86 $ git rev-parse --verify HEAD
87
88 which is done within the script "scripts/setlocalversion".)
89
90 config HAVE_KERNEL_GZIP
91 bool
92
93 config HAVE_KERNEL_BZIP2
94 bool
95
96 config HAVE_KERNEL_LZMA
97 bool
98
99 config HAVE_KERNEL_XZ
100 bool
101
102 config HAVE_KERNEL_LZO
103 bool
104
105 choice
106 prompt "Kernel compression mode"
107 default KERNEL_GZIP
108 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
109 help
110 The linux kernel is a kind of self-extracting executable.
111 Several compression algorithms are available, which differ
112 in efficiency, compression and decompression speed.
113 Compression speed is only relevant when building a kernel.
114 Decompression speed is relevant at each boot.
115
116 If you have any problems with bzip2 or lzma compressed
117 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
118 version of this functionality (bzip2 only), for 2.4, was
119 supplied by Christian Ludwig)
120
121 High compression options are mostly useful for users, who
122 are low on disk space (embedded systems), but for whom ram
123 size matters less.
124
125 If in doubt, select 'gzip'
126
127 config KERNEL_GZIP
128 bool "Gzip"
129 depends on HAVE_KERNEL_GZIP
130 help
131 The old and tried gzip compression. It provides a good balance
132 between compression ratio and decompression speed.
133
134 config KERNEL_BZIP2
135 bool "Bzip2"
136 depends on HAVE_KERNEL_BZIP2
137 help
138 Its compression ratio and speed is intermediate.
139 Decompression speed is slowest among the choices. The kernel
140 size is about 10% smaller with bzip2, in comparison to gzip.
141 Bzip2 uses a large amount of memory. For modern kernels you
142 will need at least 8MB RAM or more for booting.
143
144 config KERNEL_LZMA
145 bool "LZMA"
146 depends on HAVE_KERNEL_LZMA
147 help
148 This compression algorithm's ratio is best. Decompression speed
149 is between gzip and bzip2. Compression is slowest.
150 The kernel size is about 33% smaller with LZMA in comparison to gzip.
151
152 config KERNEL_XZ
153 bool "XZ"
154 depends on HAVE_KERNEL_XZ
155 help
156 XZ uses the LZMA2 algorithm and instruction set specific
157 BCJ filters which can improve compression ratio of executable
158 code. The size of the kernel is about 30% smaller with XZ in
159 comparison to gzip. On architectures for which there is a BCJ
160 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
161 will create a few percent smaller kernel than plain LZMA.
162
163 The speed is about the same as with LZMA: The decompression
164 speed of XZ is better than that of bzip2 but worse than gzip
165 and LZO. Compression is slow.
166
167 config KERNEL_LZO
168 bool "LZO"
169 depends on HAVE_KERNEL_LZO
170 help
171 Its compression ratio is the poorest among the choices. The kernel
172 size is about 10% bigger than gzip; however its speed
173 (both compression and decompression) is the fastest.
174
175 endchoice
176
177 config DEFAULT_HOSTNAME
178 string "Default hostname"
179 default "(none)"
180 help
181 This option determines the default system hostname before userspace
182 calls sethostname(2). The kernel traditionally uses "(none)" here,
183 but you may wish to use a different default here to make a minimal
184 system more usable with less configuration.
185
186 config SWAP
187 bool "Support for paging of anonymous memory (swap)"
188 depends on MMU && BLOCK
189 default y
190 help
191 This option allows you to choose whether you want to have support
192 for so called swap devices or swap files in your kernel that are
193 used to provide more virtual memory than the actual RAM present
194 in your computer. If unsure say Y.
195
196 config SYSVIPC
197 bool "System V IPC"
198 ---help---
199 Inter Process Communication is a suite of library functions and
200 system calls which let processes (running programs) synchronize and
201 exchange information. It is generally considered to be a good thing,
202 and some programs won't run unless you say Y here. In particular, if
203 you want to run the DOS emulator dosemu under Linux (read the
204 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
205 you'll need to say Y here.
206
207 You can find documentation about IPC with "info ipc" and also in
208 section 6.4 of the Linux Programmer's Guide, available from
209 <http://www.tldp.org/guides.html>.
210
211 config SYSVIPC_SYSCTL
212 bool
213 depends on SYSVIPC
214 depends on SYSCTL
215 default y
216
217 config POSIX_MQUEUE
218 bool "POSIX Message Queues"
219 depends on NET
220 ---help---
221 POSIX variant of message queues is a part of IPC. In POSIX message
222 queues every message has a priority which decides about succession
223 of receiving it by a process. If you want to compile and run
224 programs written e.g. for Solaris with use of its POSIX message
225 queues (functions mq_*) say Y here.
226
227 POSIX message queues are visible as a filesystem called 'mqueue'
228 and can be mounted somewhere if you want to do filesystem
229 operations on message queues.
230
231 If unsure, say Y.
232
233 config POSIX_MQUEUE_SYSCTL
234 bool
235 depends on POSIX_MQUEUE
236 depends on SYSCTL
237 default y
238
239 config FHANDLE
240 bool "open by fhandle syscalls"
241 select EXPORTFS
242 help
243 If you say Y here, a user level program will be able to map
244 file names to handle and then later use the handle for
245 different file system operations. This is useful in implementing
246 userspace file servers, which now track files using handles instead
247 of names. The handle would remain the same even if file names
248 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
249 syscalls.
250
251 config AUDIT
252 bool "Auditing support"
253 depends on NET
254 help
255 Enable auditing infrastructure that can be used with another
256 kernel subsystem, such as SELinux (which requires this for
257 logging of avc messages output). Does not do system-call
258 auditing without CONFIG_AUDITSYSCALL.
259
260 config AUDITSYSCALL
261 bool "Enable system-call auditing support"
262 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
263 default y if SECURITY_SELINUX
264 help
265 Enable low-overhead system-call auditing infrastructure that
266 can be used independently or with another kernel subsystem,
267 such as SELinux.
268
269 config AUDIT_WATCH
270 def_bool y
271 depends on AUDITSYSCALL
272 select FSNOTIFY
273
274 config AUDIT_TREE
275 def_bool y
276 depends on AUDITSYSCALL
277 select FSNOTIFY
278
279 config AUDIT_LOGINUID_IMMUTABLE
280 bool "Make audit loginuid immutable"
281 depends on AUDIT
282 help
283 The config option toggles if a task setting its loginuid requires
284 CAP_SYS_AUDITCONTROL or if that task should require no special permissions
285 but should instead only allow setting its loginuid if it was never
286 previously set. On systems which use systemd or a similar central
287 process to restart login services this should be set to true. On older
288 systems in which an admin would typically have to directly stop and
289 start processes this should be set to false. Setting this to true allows
290 one to drop potentially dangerous capabilites from the login tasks,
291 but may not be backwards compatible with older init systems.
292
293 source "kernel/irq/Kconfig"
294 source "kernel/time/Kconfig"
295
296 menu "CPU/Task time and stats accounting"
297
298 config VIRT_CPU_ACCOUNTING
299 bool
300
301 choice
302 prompt "Cputime accounting"
303 default TICK_CPU_ACCOUNTING if !PPC64
304 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
305
306 # Kind of a stub config for the pure tick based cputime accounting
307 config TICK_CPU_ACCOUNTING
308 bool "Simple tick based cputime accounting"
309 depends on !S390
310 help
311 This is the basic tick based cputime accounting that maintains
312 statistics about user, system and idle time spent on per jiffies
313 granularity.
314
315 If unsure, say Y.
316
317 config VIRT_CPU_ACCOUNTING_NATIVE
318 bool "Deterministic task and CPU time accounting"
319 depends on HAVE_VIRT_CPU_ACCOUNTING
320 select VIRT_CPU_ACCOUNTING
321 help
322 Select this option to enable more accurate task and CPU time
323 accounting. This is done by reading a CPU counter on each
324 kernel entry and exit and on transitions within the kernel
325 between system, softirq and hardirq state, so there is a
326 small performance impact. In the case of s390 or IBM POWER > 5,
327 this also enables accounting of stolen time on logically-partitioned
328 systems.
329
330 config VIRT_CPU_ACCOUNTING_GEN
331 bool "Full dynticks CPU time accounting"
332 depends on HAVE_CONTEXT_TRACKING && 64BIT
333 select VIRT_CPU_ACCOUNTING
334 select CONTEXT_TRACKING
335 help
336 Select this option to enable task and CPU time accounting on full
337 dynticks systems. This accounting is implemented by watching every
338 kernel-user boundaries using the context tracking subsystem.
339 The accounting is thus performed at the expense of some significant
340 overhead.
341
342 For now this is only useful if you are working on the full
343 dynticks subsystem development.
344
345 If unsure, say N.
346
347 config IRQ_TIME_ACCOUNTING
348 bool "Fine granularity task level IRQ time accounting"
349 depends on HAVE_IRQ_TIME_ACCOUNTING
350 help
351 Select this option to enable fine granularity task irq time
352 accounting. This is done by reading a timestamp on each
353 transitions between softirq and hardirq state, so there can be a
354 small performance impact.
355
356 If in doubt, say N here.
357
358 endchoice
359
360 config BSD_PROCESS_ACCT
361 bool "BSD Process Accounting"
362 help
363 If you say Y here, a user level program will be able to instruct the
364 kernel (via a special system call) to write process accounting
365 information to a file: whenever a process exits, information about
366 that process will be appended to the file by the kernel. The
367 information includes things such as creation time, owning user,
368 command name, memory usage, controlling terminal etc. (the complete
369 list is in the struct acct in <file:include/linux/acct.h>). It is
370 up to the user level program to do useful things with this
371 information. This is generally a good idea, so say Y.
372
373 config BSD_PROCESS_ACCT_V3
374 bool "BSD Process Accounting version 3 file format"
375 depends on BSD_PROCESS_ACCT
376 default n
377 help
378 If you say Y here, the process accounting information is written
379 in a new file format that also logs the process IDs of each
380 process and it's parent. Note that this file format is incompatible
381 with previous v0/v1/v2 file formats, so you will need updated tools
382 for processing it. A preliminary version of these tools is available
383 at <http://www.gnu.org/software/acct/>.
384
385 config TASKSTATS
386 bool "Export task/process statistics through netlink"
387 depends on NET
388 default n
389 help
390 Export selected statistics for tasks/processes through the
391 generic netlink interface. Unlike BSD process accounting, the
392 statistics are available during the lifetime of tasks/processes as
393 responses to commands. Like BSD accounting, they are sent to user
394 space on task exit.
395
396 Say N if unsure.
397
398 config TASK_DELAY_ACCT
399 bool "Enable per-task delay accounting"
400 depends on TASKSTATS
401 help
402 Collect information on time spent by a task waiting for system
403 resources like cpu, synchronous block I/O completion and swapping
404 in pages. Such statistics can help in setting a task's priorities
405 relative to other tasks for cpu, io, rss limits etc.
406
407 Say N if unsure.
408
409 config TASK_XACCT
410 bool "Enable extended accounting over taskstats"
411 depends on TASKSTATS
412 help
413 Collect extended task accounting data and send the data
414 to userland for processing over the taskstats interface.
415
416 Say N if unsure.
417
418 config TASK_IO_ACCOUNTING
419 bool "Enable per-task storage I/O accounting"
420 depends on TASK_XACCT
421 help
422 Collect information on the number of bytes of storage I/O which this
423 task has caused.
424
425 Say N if unsure.
426
427 endmenu # "CPU/Task time and stats accounting"
428
429 menu "RCU Subsystem"
430
431 choice
432 prompt "RCU Implementation"
433 default TREE_RCU
434
435 config TREE_RCU
436 bool "Tree-based hierarchical RCU"
437 depends on !PREEMPT && SMP
438 help
439 This option selects the RCU implementation that is
440 designed for very large SMP system with hundreds or
441 thousands of CPUs. It also scales down nicely to
442 smaller systems.
443
444 config TREE_PREEMPT_RCU
445 bool "Preemptible tree-based hierarchical RCU"
446 depends on PREEMPT
447 help
448 This option selects the RCU implementation that is
449 designed for very large SMP systems with hundreds or
450 thousands of CPUs, but for which real-time response
451 is also required. It also scales down nicely to
452 smaller systems.
453
454 Select this option if you are unsure.
455
456 config TINY_RCU
457 bool "UP-only small-memory-footprint RCU"
458 depends on !PREEMPT && !SMP
459 help
460 This option selects the RCU implementation that is
461 designed for UP systems from which real-time response
462 is not required. This option greatly reduces the
463 memory footprint of RCU.
464
465 config TINY_PREEMPT_RCU
466 bool "Preemptible UP-only small-memory-footprint RCU"
467 depends on PREEMPT && !SMP
468 help
469 This option selects the RCU implementation that is designed
470 for real-time UP systems. This option greatly reduces the
471 memory footprint of RCU.
472
473 endchoice
474
475 config PREEMPT_RCU
476 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
477 help
478 This option enables preemptible-RCU code that is common between
479 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
480
481 config RCU_STALL_COMMON
482 def_bool ( TREE_RCU || TREE_PREEMPT_RCU || RCU_TRACE )
483 help
484 This option enables RCU CPU stall code that is common between
485 the TINY and TREE variants of RCU. The purpose is to allow
486 the tiny variants to disable RCU CPU stall warnings, while
487 making these warnings mandatory for the tree variants.
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"
884 depends on MEMCG
885 depends on SLUB || SLAB
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
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 FAIR_GROUP_SCHED
936 default n
937 help
938 This option allows users to define CPU bandwidth rates (limits) for
939 tasks running within the fair group scheduler. Groups with no limit
940 set are considered to be unconstrained and will run with no
941 restriction.
942 See tip/Documentation/scheduler/sched-bwc.txt for more information.
943
944 config RT_GROUP_SCHED
945 bool "Group scheduling for SCHED_RR/FIFO"
946 depends on CGROUP_SCHED
947 default n
948 help
949 This feature lets you explicitly allocate real CPU bandwidth
950 to task groups. If enabled, it will also make it impossible to
951 schedule realtime tasks for non-root users until you allocate
952 realtime bandwidth for them.
953 See Documentation/scheduler/sched-rt-group.txt for more information.
954
955 endif #CGROUP_SCHED
956
957 config BLK_CGROUP
958 bool "Block IO controller"
959 depends on BLOCK
960 default n
961 ---help---
962 Generic block IO controller cgroup interface. This is the common
963 cgroup interface which should be used by various IO controlling
964 policies.
965
966 Currently, CFQ IO scheduler uses it to recognize task groups and
967 control disk bandwidth allocation (proportional time slice allocation)
968 to such task groups. It is also used by bio throttling logic in
969 block layer to implement upper limit in IO rates on a device.
970
971 This option only enables generic Block IO controller infrastructure.
972 One needs to also enable actual IO controlling logic/policy. For
973 enabling proportional weight division of disk bandwidth in CFQ, set
974 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
975 CONFIG_BLK_DEV_THROTTLING=y.
976
977 See Documentation/cgroups/blkio-controller.txt for more information.
978
979 config DEBUG_BLK_CGROUP
980 bool "Enable Block IO controller debugging"
981 depends on BLK_CGROUP
982 default n
983 ---help---
984 Enable some debugging help. Currently it exports additional stat
985 files in a cgroup which can be useful for debugging.
986
987 endif # CGROUPS
988
989 config CHECKPOINT_RESTORE
990 bool "Checkpoint/restore support" if EXPERT
991 default n
992 help
993 Enables additional kernel features in a sake of checkpoint/restore.
994 In particular it adds auxiliary prctl codes to setup process text,
995 data and heap segment sizes, and a few additional /proc filesystem
996 entries.
997
998 If unsure, say N here.
999
1000 menuconfig NAMESPACES
1001 bool "Namespaces support" if EXPERT
1002 default !EXPERT
1003 help
1004 Provides the way to make tasks work with different objects using
1005 the same id. For example same IPC id may refer to different objects
1006 or same user id or pid may refer to different tasks when used in
1007 different namespaces.
1008
1009 if NAMESPACES
1010
1011 config UTS_NS
1012 bool "UTS namespace"
1013 default y
1014 help
1015 In this namespace tasks see different info provided with the
1016 uname() system call
1017
1018 config IPC_NS
1019 bool "IPC namespace"
1020 depends on (SYSVIPC || POSIX_MQUEUE)
1021 default y
1022 help
1023 In this namespace tasks work with IPC ids which correspond to
1024 different IPC objects in different namespaces.
1025
1026 config USER_NS
1027 bool "User namespace"
1028 depends on UIDGID_CONVERTED
1029 select UIDGID_STRICT_TYPE_CHECKS
1030
1031 default n
1032 help
1033 This allows containers, i.e. vservers, to use user namespaces
1034 to provide different user info for different servers.
1035
1036 When user namespaces are enabled in the kernel it is
1037 recommended that the MEMCG and MEMCG_KMEM options also be
1038 enabled and that user-space use the memory control groups to
1039 limit the amount of memory a memory unprivileged users can
1040 use.
1041
1042 If unsure, say N.
1043
1044 config PID_NS
1045 bool "PID Namespaces"
1046 default y
1047 help
1048 Support process id namespaces. This allows having multiple
1049 processes with the same pid as long as they are in different
1050 pid namespaces. This is a building block of containers.
1051
1052 config NET_NS
1053 bool "Network namespace"
1054 depends on NET
1055 default y
1056 help
1057 Allow user space to create what appear to be multiple instances
1058 of the network stack.
1059
1060 endif # NAMESPACES
1061
1062 config UIDGID_CONVERTED
1063 # True if all of the selected software conmponents are known
1064 # to have uid_t and gid_t converted to kuid_t and kgid_t
1065 # where appropriate and are otherwise safe to use with
1066 # the user namespace.
1067 bool
1068 default y
1069
1070 # Filesystems
1071 depends on XFS_FS = n
1072
1073 config UIDGID_STRICT_TYPE_CHECKS
1074 bool "Require conversions between uid/gids and their internal representation"
1075 depends on UIDGID_CONVERTED
1076 default n
1077 help
1078 While the nececessary conversions are being added to all subsystems this option allows
1079 the code to continue to build for unconverted subsystems.
1080
1081 Say Y here if you want the strict type checking enabled
1082
1083 config SCHED_AUTOGROUP
1084 bool "Automatic process group scheduling"
1085 select EVENTFD
1086 select CGROUPS
1087 select CGROUP_SCHED
1088 select FAIR_GROUP_SCHED
1089 help
1090 This option optimizes the scheduler for common desktop workloads by
1091 automatically creating and populating task groups. This separation
1092 of workloads isolates aggressive CPU burners (like build jobs) from
1093 desktop applications. Task group autogeneration is currently based
1094 upon task session.
1095
1096 config MM_OWNER
1097 bool
1098
1099 config SYSFS_DEPRECATED
1100 bool "Enable deprecated sysfs features to support old userspace tools"
1101 depends on SYSFS
1102 default n
1103 help
1104 This option adds code that switches the layout of the "block" class
1105 devices, to not show up in /sys/class/block/, but only in
1106 /sys/block/.
1107
1108 This switch is only active when the sysfs.deprecated=1 boot option is
1109 passed or the SYSFS_DEPRECATED_V2 option is set.
1110
1111 This option allows new kernels to run on old distributions and tools,
1112 which might get confused by /sys/class/block/. Since 2007/2008 all
1113 major distributions and tools handle this just fine.
1114
1115 Recent distributions and userspace tools after 2009/2010 depend on
1116 the existence of /sys/class/block/, and will not work with this
1117 option enabled.
1118
1119 Only if you are using a new kernel on an old distribution, you might
1120 need to say Y here.
1121
1122 config SYSFS_DEPRECATED_V2
1123 bool "Enable deprecated sysfs features by default"
1124 default n
1125 depends on SYSFS
1126 depends on SYSFS_DEPRECATED
1127 help
1128 Enable deprecated sysfs by default.
1129
1130 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1131 option.
1132
1133 Only if you are using a new kernel on an old distribution, you might
1134 need to say Y here. Even then, odds are you would not need it
1135 enabled, you can always pass the boot option if absolutely necessary.
1136
1137 config RELAY
1138 bool "Kernel->user space relay support (formerly relayfs)"
1139 help
1140 This option enables support for relay interface support in
1141 certain file systems (such as debugfs).
1142 It is designed to provide an efficient mechanism for tools and
1143 facilities to relay large amounts of data from kernel space to
1144 user space.
1145
1146 If unsure, say N.
1147
1148 config BLK_DEV_INITRD
1149 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1150 depends on BROKEN || !FRV
1151 help
1152 The initial RAM filesystem is a ramfs which is loaded by the
1153 boot loader (loadlin or lilo) and that is mounted as root
1154 before the normal boot procedure. It is typically used to
1155 load modules needed to mount the "real" root file system,
1156 etc. See <file:Documentation/initrd.txt> for details.
1157
1158 If RAM disk support (BLK_DEV_RAM) is also included, this
1159 also enables initial RAM disk (initrd) support and adds
1160 15 Kbytes (more on some other architectures) to the kernel size.
1161
1162 If unsure say Y.
1163
1164 if BLK_DEV_INITRD
1165
1166 source "usr/Kconfig"
1167
1168 endif
1169
1170 config CC_OPTIMIZE_FOR_SIZE
1171 bool "Optimize for size"
1172 help
1173 Enabling this option will pass "-Os" instead of "-O2" to gcc
1174 resulting in a smaller kernel.
1175
1176 If unsure, say N.
1177
1178 config SYSCTL
1179 bool
1180
1181 config ANON_INODES
1182 bool
1183
1184 menuconfig EXPERT
1185 bool "Configure standard kernel features (expert users)"
1186 # Unhide debug options, to make the on-by-default options visible
1187 select DEBUG_KERNEL
1188 help
1189 This option allows certain base kernel options and settings
1190 to be disabled or tweaked. This is for specialized
1191 environments which can tolerate a "non-standard" kernel.
1192 Only use this if you really know what you are doing.
1193
1194 config HAVE_UID16
1195 bool
1196
1197 config UID16
1198 bool "Enable 16-bit UID system calls" if EXPERT
1199 depends on HAVE_UID16
1200 default y
1201 help
1202 This enables the legacy 16-bit UID syscall wrappers.
1203
1204 config SYSCTL_SYSCALL
1205 bool "Sysctl syscall support" if EXPERT
1206 depends on PROC_SYSCTL
1207 default n
1208 select SYSCTL
1209 ---help---
1210 sys_sysctl uses binary paths that have been found challenging
1211 to properly maintain and use. The interface in /proc/sys
1212 using paths with ascii names is now the primary path to this
1213 information.
1214
1215 Almost nothing using the binary sysctl interface so if you are
1216 trying to save some space it is probably safe to disable this,
1217 making your kernel marginally smaller.
1218
1219 If unsure say N here.
1220
1221 config SYSCTL_EXCEPTION_TRACE
1222 bool
1223 help
1224 Enable support for /proc/sys/debug/exception-trace.
1225
1226 config SYSCTL_ARCH_UNALIGN_NO_WARN
1227 bool
1228 help
1229 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1230 Allows arch to define/use @no_unaligned_warning to possibly warn
1231 about unaligned access emulation going on under the hood.
1232
1233 config SYSCTL_ARCH_UNALIGN_ALLOW
1234 bool
1235 help
1236 Enable support for /proc/sys/kernel/unaligned-trap
1237 Allows arches to define/use @unaligned_enabled to runtime toggle
1238 the unaligned access emulation.
1239 see arch/parisc/kernel/unaligned.c for reference
1240
1241 config KALLSYMS
1242 bool "Load all symbols for debugging/ksymoops" if EXPERT
1243 default y
1244 help
1245 Say Y here to let the kernel print out symbolic crash information and
1246 symbolic stack backtraces. This increases the size of the kernel
1247 somewhat, as all symbols have to be loaded into the kernel image.
1248
1249 config KALLSYMS_ALL
1250 bool "Include all symbols in kallsyms"
1251 depends on DEBUG_KERNEL && KALLSYMS
1252 help
1253 Normally kallsyms only contains the symbols of functions for nicer
1254 OOPS messages and backtraces (i.e., symbols from the text and inittext
1255 sections). This is sufficient for most cases. And only in very rare
1256 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1257 names of variables from the data sections, etc).
1258
1259 This option makes sure that all symbols are loaded into the kernel
1260 image (i.e., symbols from all sections) in cost of increased kernel
1261 size (depending on the kernel configuration, it may be 300KiB or
1262 something like this).
1263
1264 Say N unless you really need all symbols.
1265
1266 config HOTPLUG
1267 def_bool y
1268
1269 config PRINTK
1270 default y
1271 bool "Enable support for printk" if EXPERT
1272 select IRQ_WORK
1273 help
1274 This option enables normal printk support. Removing it
1275 eliminates most of the message strings from the kernel image
1276 and makes the kernel more or less silent. As this makes it
1277 very difficult to diagnose system problems, saying N here is
1278 strongly discouraged.
1279
1280 config BUG
1281 bool "BUG() support" if EXPERT
1282 default y
1283 help
1284 Disabling this option eliminates support for BUG and WARN, reducing
1285 the size of your kernel image and potentially quietly ignoring
1286 numerous fatal conditions. You should only consider disabling this
1287 option for embedded systems with no facilities for reporting errors.
1288 Just say Y.
1289
1290 config ELF_CORE
1291 depends on COREDUMP
1292 default y
1293 bool "Enable ELF core dumps" if EXPERT
1294 help
1295 Enable support for generating core dumps. Disabling saves about 4k.
1296
1297
1298 config PCSPKR_PLATFORM
1299 bool "Enable PC-Speaker support" if EXPERT
1300 depends on HAVE_PCSPKR_PLATFORM
1301 select I8253_LOCK
1302 default y
1303 help
1304 This option allows to disable the internal PC-Speaker
1305 support, saving some memory.
1306
1307 config HAVE_PCSPKR_PLATFORM
1308 bool
1309
1310 config BASE_FULL
1311 default y
1312 bool "Enable full-sized data structures for core" if EXPERT
1313 help
1314 Disabling this option reduces the size of miscellaneous core
1315 kernel data structures. This saves memory on small machines,
1316 but may reduce performance.
1317
1318 config FUTEX
1319 bool "Enable futex support" if EXPERT
1320 default y
1321 select RT_MUTEXES
1322 help
1323 Disabling this option will cause the kernel to be built without
1324 support for "fast userspace mutexes". The resulting kernel may not
1325 run glibc-based applications correctly.
1326
1327 config EPOLL
1328 bool "Enable eventpoll support" if EXPERT
1329 default y
1330 select ANON_INODES
1331 help
1332 Disabling this option will cause the kernel to be built without
1333 support for epoll family of system calls.
1334
1335 config SIGNALFD
1336 bool "Enable signalfd() system call" if EXPERT
1337 select ANON_INODES
1338 default y
1339 help
1340 Enable the signalfd() system call that allows to receive signals
1341 on a file descriptor.
1342
1343 If unsure, say Y.
1344
1345 config TIMERFD
1346 bool "Enable timerfd() system call" if EXPERT
1347 select ANON_INODES
1348 default y
1349 help
1350 Enable the timerfd() system call that allows to receive timer
1351 events on a file descriptor.
1352
1353 If unsure, say Y.
1354
1355 config EVENTFD
1356 bool "Enable eventfd() system call" if EXPERT
1357 select ANON_INODES
1358 default y
1359 help
1360 Enable the eventfd() system call that allows to receive both
1361 kernel notification (ie. KAIO) or userspace notifications.
1362
1363 If unsure, say Y.
1364
1365 config SHMEM
1366 bool "Use full shmem filesystem" if EXPERT
1367 default y
1368 depends on MMU
1369 help
1370 The shmem is an internal filesystem used to manage shared memory.
1371 It is backed by swap and manages resource limits. It is also exported
1372 to userspace as tmpfs if TMPFS is enabled. Disabling this
1373 option replaces shmem and tmpfs with the much simpler ramfs code,
1374 which may be appropriate on small systems without swap.
1375
1376 config AIO
1377 bool "Enable AIO support" if EXPERT
1378 default y
1379 help
1380 This option enables POSIX asynchronous I/O which may by used
1381 by some high performance threaded applications. Disabling
1382 this option saves about 7k.
1383
1384 config EMBEDDED
1385 bool "Embedded system"
1386 select EXPERT
1387 help
1388 This option should be enabled if compiling the kernel for
1389 an embedded system so certain expert options are available
1390 for configuration.
1391
1392 config HAVE_PERF_EVENTS
1393 bool
1394 help
1395 See tools/perf/design.txt for details.
1396
1397 config PERF_USE_VMALLOC
1398 bool
1399 help
1400 See tools/perf/design.txt for details
1401
1402 menu "Kernel Performance Events And Counters"
1403
1404 config PERF_EVENTS
1405 bool "Kernel performance events and counters"
1406 default y if PROFILING
1407 depends on HAVE_PERF_EVENTS
1408 select ANON_INODES
1409 select IRQ_WORK
1410 help
1411 Enable kernel support for various performance events provided
1412 by software and hardware.
1413
1414 Software events are supported either built-in or via the
1415 use of generic tracepoints.
1416
1417 Most modern CPUs support performance events via performance
1418 counter registers. These registers count the number of certain
1419 types of hw events: such as instructions executed, cachemisses
1420 suffered, or branches mis-predicted - without slowing down the
1421 kernel or applications. These registers can also trigger interrupts
1422 when a threshold number of events have passed - and can thus be
1423 used to profile the code that runs on that CPU.
1424
1425 The Linux Performance Event subsystem provides an abstraction of
1426 these software and hardware event capabilities, available via a
1427 system call and used by the "perf" utility in tools/perf/. It
1428 provides per task and per CPU counters, and it provides event
1429 capabilities on top of those.
1430
1431 Say Y if unsure.
1432
1433 config DEBUG_PERF_USE_VMALLOC
1434 default n
1435 bool "Debug: use vmalloc to back perf mmap() buffers"
1436 depends on PERF_EVENTS && DEBUG_KERNEL
1437 select PERF_USE_VMALLOC
1438 help
1439 Use vmalloc memory to back perf mmap() buffers.
1440
1441 Mostly useful for debugging the vmalloc code on platforms
1442 that don't require it.
1443
1444 Say N if unsure.
1445
1446 endmenu
1447
1448 config VM_EVENT_COUNTERS
1449 default y
1450 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1451 help
1452 VM event counters are needed for event counts to be shown.
1453 This option allows the disabling of the VM event counters
1454 on EXPERT systems. /proc/vmstat will only show page counts
1455 if VM event counters are disabled.
1456
1457 config PCI_QUIRKS
1458 default y
1459 bool "Enable PCI quirk workarounds" if EXPERT
1460 depends on PCI
1461 help
1462 This enables workarounds for various PCI chipset
1463 bugs/quirks. Disable this only if your target machine is
1464 unaffected by PCI quirks.
1465
1466 config SLUB_DEBUG
1467 default y
1468 bool "Enable SLUB debugging support" if EXPERT
1469 depends on SLUB && SYSFS
1470 help
1471 SLUB has extensive debug support features. Disabling these can
1472 result in significant savings in code size. This also disables
1473 SLUB sysfs support. /sys/slab will not exist and there will be
1474 no support for cache validation etc.
1475
1476 config COMPAT_BRK
1477 bool "Disable heap randomization"
1478 default y
1479 help
1480 Randomizing heap placement makes heap exploits harder, but it
1481 also breaks ancient binaries (including anything libc5 based).
1482 This option changes the bootup default to heap randomization
1483 disabled, and can be overridden at runtime by setting
1484 /proc/sys/kernel/randomize_va_space to 2.
1485
1486 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1487
1488 choice
1489 prompt "Choose SLAB allocator"
1490 default SLUB
1491 help
1492 This option allows to select a slab allocator.
1493
1494 config SLAB
1495 bool "SLAB"
1496 help
1497 The regular slab allocator that is established and known to work
1498 well in all environments. It organizes cache hot objects in
1499 per cpu and per node queues.
1500
1501 config SLUB
1502 bool "SLUB (Unqueued Allocator)"
1503 help
1504 SLUB is a slab allocator that minimizes cache line usage
1505 instead of managing queues of cached objects (SLAB approach).
1506 Per cpu caching is realized using slabs of objects instead
1507 of queues of objects. SLUB can use memory efficiently
1508 and has enhanced diagnostics. SLUB is the default choice for
1509 a slab allocator.
1510
1511 config SLOB
1512 depends on EXPERT
1513 bool "SLOB (Simple Allocator)"
1514 help
1515 SLOB replaces the stock allocator with a drastically simpler
1516 allocator. SLOB is generally more space efficient but
1517 does not perform as well on large systems.
1518
1519 endchoice
1520
1521 config MMAP_ALLOW_UNINITIALIZED
1522 bool "Allow mmapped anonymous memory to be uninitialized"
1523 depends on EXPERT && !MMU
1524 default n
1525 help
1526 Normally, and according to the Linux spec, anonymous memory obtained
1527 from mmap() has it's contents cleared before it is passed to
1528 userspace. Enabling this config option allows you to request that
1529 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1530 providing a huge performance boost. If this option is not enabled,
1531 then the flag will be ignored.
1532
1533 This is taken advantage of by uClibc's malloc(), and also by
1534 ELF-FDPIC binfmt's brk and stack allocator.
1535
1536 Because of the obvious security issues, this option should only be
1537 enabled on embedded devices where you control what is run in
1538 userspace. Since that isn't generally a problem on no-MMU systems,
1539 it is normally safe to say Y here.
1540
1541 See Documentation/nommu-mmap.txt for more information.
1542
1543 config PROFILING
1544 bool "Profiling support"
1545 help
1546 Say Y here to enable the extended profiling support mechanisms used
1547 by profilers such as OProfile.
1548
1549 #
1550 # Place an empty function call at each tracepoint site. Can be
1551 # dynamically changed for a probe function.
1552 #
1553 config TRACEPOINTS
1554 bool
1555
1556 source "arch/Kconfig"
1557
1558 endmenu # General setup
1559
1560 config HAVE_GENERIC_DMA_COHERENT
1561 bool
1562 default n
1563
1564 config SLABINFO
1565 bool
1566 depends on PROC_FS
1567 depends on SLAB || SLUB_DEBUG
1568 default y
1569
1570 config RT_MUTEXES
1571 boolean
1572
1573 config BASE_SMALL
1574 int
1575 default 0 if BASE_FULL
1576 default 1 if !BASE_FULL
1577
1578 menuconfig MODULES
1579 bool "Enable loadable module support"
1580 help
1581 Kernel modules are small pieces of compiled code which can
1582 be inserted in the running kernel, rather than being
1583 permanently built into the kernel. You use the "modprobe"
1584 tool to add (and sometimes remove) them. If you say Y here,
1585 many parts of the kernel can be built as modules (by
1586 answering M instead of Y where indicated): this is most
1587 useful for infrequently used options which are not required
1588 for booting. For more information, see the man pages for
1589 modprobe, lsmod, modinfo, insmod and rmmod.
1590
1591 If you say Y here, you will need to run "make
1592 modules_install" to put the modules under /lib/modules/
1593 where modprobe can find them (you may need to be root to do
1594 this).
1595
1596 If unsure, say Y.
1597
1598 if MODULES
1599
1600 config MODULE_FORCE_LOAD
1601 bool "Forced module loading"
1602 default n
1603 help
1604 Allow loading of modules without version information (ie. modprobe
1605 --force). Forced module loading sets the 'F' (forced) taint flag and
1606 is usually a really bad idea.
1607
1608 config MODULE_UNLOAD
1609 bool "Module unloading"
1610 help
1611 Without this option you will not be able to unload any
1612 modules (note that some modules may not be unloadable
1613 anyway), which makes your kernel smaller, faster
1614 and simpler. If unsure, say Y.
1615
1616 config MODULE_FORCE_UNLOAD
1617 bool "Forced module unloading"
1618 depends on MODULE_UNLOAD
1619 help
1620 This option allows you to force a module to unload, even if the
1621 kernel believes it is unsafe: the kernel will remove the module
1622 without waiting for anyone to stop using it (using the -f option to
1623 rmmod). This is mainly for kernel developers and desperate users.
1624 If unsure, say N.
1625
1626 config MODVERSIONS
1627 bool "Module versioning support"
1628 help
1629 Usually, you have to use modules compiled with your kernel.
1630 Saying Y here makes it sometimes possible to use modules
1631 compiled for different kernels, by adding enough information
1632 to the modules to (hopefully) spot any changes which would
1633 make them incompatible with the kernel you are running. If
1634 unsure, say N.
1635
1636 config MODULE_SRCVERSION_ALL
1637 bool "Source checksum for all modules"
1638 help
1639 Modules which contain a MODULE_VERSION get an extra "srcversion"
1640 field inserted into their modinfo section, which contains a
1641 sum of the source files which made it. This helps maintainers
1642 see exactly which source was used to build a module (since
1643 others sometimes change the module source without updating
1644 the version). With this option, such a "srcversion" field
1645 will be created for all modules. If unsure, say N.
1646
1647 config MODULE_SIG
1648 bool "Module signature verification"
1649 depends on MODULES
1650 select KEYS
1651 select CRYPTO
1652 select ASYMMETRIC_KEY_TYPE
1653 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1654 select PUBLIC_KEY_ALGO_RSA
1655 select ASN1
1656 select OID_REGISTRY
1657 select X509_CERTIFICATE_PARSER
1658 help
1659 Check modules for valid signatures upon load: the signature
1660 is simply appended to the module. For more information see
1661 Documentation/module-signing.txt.
1662
1663 !!!WARNING!!! If you enable this option, you MUST make sure that the
1664 module DOES NOT get stripped after being signed. This includes the
1665 debuginfo strip done by some packagers (such as rpmbuild) and
1666 inclusion into an initramfs that wants the module size reduced.
1667
1668 config MODULE_SIG_FORCE
1669 bool "Require modules to be validly signed"
1670 depends on MODULE_SIG
1671 help
1672 Reject unsigned modules or signed modules for which we don't have a
1673 key. Without this, such modules will simply taint the kernel.
1674
1675 config MODULE_SIG_ALL
1676 bool "Automatically sign all modules"
1677 default y
1678 depends on MODULE_SIG
1679 help
1680 Sign all modules during make modules_install. Without this option,
1681 modules must be signed manually, using the scripts/sign-file tool.
1682
1683 comment "Do not forget to sign required modules with scripts/sign-file"
1684 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1685
1686 choice
1687 prompt "Which hash algorithm should modules be signed with?"
1688 depends on MODULE_SIG
1689 help
1690 This determines which sort of hashing algorithm will be used during
1691 signature generation. This algorithm _must_ be built into the kernel
1692 directly so that signature verification can take place. It is not
1693 possible to load a signed module containing the algorithm to check
1694 the signature on that module.
1695
1696 config MODULE_SIG_SHA1
1697 bool "Sign modules with SHA-1"
1698 select CRYPTO_SHA1
1699
1700 config MODULE_SIG_SHA224
1701 bool "Sign modules with SHA-224"
1702 select CRYPTO_SHA256
1703
1704 config MODULE_SIG_SHA256
1705 bool "Sign modules with SHA-256"
1706 select CRYPTO_SHA256
1707
1708 config MODULE_SIG_SHA384
1709 bool "Sign modules with SHA-384"
1710 select CRYPTO_SHA512
1711
1712 config MODULE_SIG_SHA512
1713 bool "Sign modules with SHA-512"
1714 select CRYPTO_SHA512
1715
1716 endchoice
1717
1718 config MODULE_SIG_HASH
1719 string
1720 depends on MODULE_SIG
1721 default "sha1" if MODULE_SIG_SHA1
1722 default "sha224" if MODULE_SIG_SHA224
1723 default "sha256" if MODULE_SIG_SHA256
1724 default "sha384" if MODULE_SIG_SHA384
1725 default "sha512" if MODULE_SIG_SHA512
1726
1727 endif # MODULES
1728
1729 config INIT_ALL_POSSIBLE
1730 bool
1731 help
1732 Back when each arch used to define their own cpu_online_mask and
1733 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1734 with all 1s, and others with all 0s. When they were centralised,
1735 it was better to provide this option than to break all the archs
1736 and have several arch maintainers pursuing me down dark alleys.
1737
1738 config STOP_MACHINE
1739 bool
1740 default y
1741 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1742 help
1743 Need stop_machine() primitive.
1744
1745 source "block/Kconfig"
1746
1747 config PREEMPT_NOTIFIERS
1748 bool
1749
1750 config PADATA
1751 depends on SMP
1752 bool
1753
1754 # Can be selected by architectures with broken toolchains
1755 # that get confused by correct const<->read_only section
1756 # mappings
1757 config BROKEN_RODATA
1758 bool
1759
1760 config ASN1
1761 tristate
1762 help
1763 Build a simple ASN.1 grammar compiler that produces a bytecode output
1764 that can be interpreted by the ASN.1 stream decoder and used to
1765 inform it as to what tags are to be expected in a stream and what
1766 functions to call on what tags.
1767
1768 source "kernel/Kconfig.locks"
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