1 config ARCH
2 string
3 option env="ARCH"
5 config KERNELVERSION
6 string
7 option env="KERNELVERSION"
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"
19 config CONSTRUCTORS
20 bool
21 depends on !UML
23 config HAVE_IRQ_WORK
24 bool
26 config IRQ_WORK
27 bool
28 depends on HAVE_IRQ_WORK
30 config BUILDTIME_EXTABLE_SORT
31 bool
33 menu "General setup"
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).
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56 drivers that have been replaced by something else, and/or are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.
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.
66 config BROKEN
67 bool
69 config BROKEN_ON_SMP
70 bool
71 depends on BROKEN || !SMP
72 default y
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.
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.
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.
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.
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.
114 (The actual string used here is the first eight characters produced
115 by running the command:
117 $ git rev-parse --verify HEAD
119 which is done within the script "scripts/setlocalversion".)
121 config HAVE_KERNEL_GZIP
122 bool
124 config HAVE_KERNEL_BZIP2
125 bool
127 config HAVE_KERNEL_LZMA
128 bool
130 config HAVE_KERNEL_XZ
131 bool
133 config HAVE_KERNEL_LZO
134 bool
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.
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)
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.
156 If in doubt, select 'gzip'
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.
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.
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.
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.
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.
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.
206 endchoice
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.
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.
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.
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>.
242 config SYSVIPC_SYSCTL
243 bool
244 depends on SYSVIPC
245 depends on SYSCTL
246 default y
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.
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.
262 If unsure, say Y.
264 config POSIX_MQUEUE_SYSCTL
265 bool
266 depends on POSIX_MQUEUE
267 depends on SYSCTL
268 default y
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.
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.
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.
300 config AUDIT_WATCH
301 def_bool y
302 depends on AUDITSYSCALL
303 select FSNOTIFY
305 config AUDIT_TREE
306 def_bool y
307 depends on AUDITSYSCALL
308 select FSNOTIFY
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.
324 source "kernel/irq/Kconfig"
325 source "kernel/time/Kconfig"
327 menu "CPU/Task time and stats accounting"
329 choice
330 prompt "Cputime accounting"
331 default TICK_CPU_ACCOUNTING if !PPC64
332 default VIRT_CPU_ACCOUNTING if PPC64
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.
343 If unsure, say Y.
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.
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.
366 If in doubt, say N here.
368 endchoice
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.
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/>.
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.
406 Say N if unsure.
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.
417 Say N if unsure.
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.
426 Say N if unsure.
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.
435 Say N if unsure.
437 endmenu # "CPU/Task time and stats accounting"
439 menu "RCU Subsystem"
441 choice
442 prompt "RCU Implementation"
443 default TREE_RCU
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.
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.
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.
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.
481 endchoice
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.
489 config RCU_USER_QS
490 bool "Consider userspace as in RCU extended quiescent state"
491 depends on HAVE_RCU_USER_QS && SMP
492 help
493 This option sets hooks on kernel / userspace boundaries and
494 puts RCU in extended quiescent state when the CPU runs in
495 userspace. It means that when a CPU runs in userspace, it is
496 excluded from the global RCU state machine and thus doesn't
497 to keep the timer tick on for RCU.
499 Unless you want to hack and help the development of the full
500 tickless feature, you shouldn't enable this option. It adds
501 unnecessary overhead.
503 If unsure say N
505 config RCU_USER_QS_FORCE
506 bool "Force userspace extended QS by default"
507 depends on RCU_USER_QS
508 help
509 Set the hooks in user/kernel boundaries by default in order to
510 test this feature that treats userspace as an extended quiescent
511 state until we have a real user like a full adaptive nohz option.
513 Unless you want to hack and help the development of the full
514 tickless feature, you shouldn't enable this option. It adds
515 unnecessary overhead.
517 If unsure say N
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.
536 Select a specific number if testing RCU itself.
537 Take the default if unsure.
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.
560 Select a specific number if testing RCU itself.
562 Select the maximum permissible value for large systems.
564 Take the default if unsure.
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.
576 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
578 Say N if unsure.
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
586 in order to allow CPUs to enter dynticks-idle state more
587 quickly. On the other hand, this option increases the overhead
588 of the dynticks-idle checking, particularly on systems with
589 large numbers of CPUs.
591 Say Y if energy efficiency is critically important, particularly
592 if you have relatively few CPUs.
594 Say N if you are unsure.
596 config TREE_RCU_TRACE
597 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
598 select DEBUG_FS
599 help
600 This option provides tracing for the TREE_RCU and
601 TREE_PREEMPT_RCU implementations, permitting Makefile to
602 trivially select kernel/rcutree_trace.c.
604 config RCU_BOOST
605 bool "Enable RCU priority boosting"
606 depends on RT_MUTEXES && PREEMPT_RCU
607 default n
608 help
609 This option boosts the priority of preempted RCU readers that
610 block the current preemptible RCU grace period for too long.
611 This option also prevents heavy loads from blocking RCU
612 callback invocation for all flavors of RCU.
614 Say Y here if you are working with real-time apps or heavy loads
615 Say N here if you are unsure.
617 config RCU_BOOST_PRIO
618 int "Real-time priority to boost RCU readers to"
619 range 1 99
620 depends on RCU_BOOST
621 default 1
622 help
623 This option specifies the real-time priority to which long-term
624 preempted RCU readers are to be boosted. If you are working
625 with a real-time application that has one or more CPU-bound
626 threads running at a real-time priority level, you should set
627 RCU_BOOST_PRIO to a priority higher then the highest-priority
628 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
629 of 1 is appropriate in the common case, which is real-time
630 applications that do not have any CPU-bound threads.
632 Some real-time applications might not have a single real-time
633 thread that saturates a given CPU, but instead might have
634 multiple real-time threads that, taken together, fully utilize
635 that CPU. In this case, you should set RCU_BOOST_PRIO to
636 a priority higher than the lowest-priority thread that is
637 conspiring to prevent the CPU from running any non-real-time
638 tasks. For example, if one thread at priority 10 and another
639 thread at priority 5 are between themselves fully consuming
640 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
641 set to priority 6 or higher.
643 Specify the real-time priority, or take the default if unsure.
645 config RCU_BOOST_DELAY
646 int "Milliseconds to delay boosting after RCU grace-period start"
647 range 0 3000
648 depends on RCU_BOOST
649 default 500
650 help
651 This option specifies the time to wait after the beginning of
652 a given grace period before priority-boosting preempted RCU
653 readers blocking that grace period. Note that any RCU reader
654 blocking an expedited RCU grace period is boosted immediately.
656 Accept the default if unsure.
658 endmenu # "RCU Subsystem"
660 config IKCONFIG
661 tristate "Kernel .config support"
662 ---help---
663 This option enables the complete Linux kernel ".config" file
664 contents to be saved in the kernel. It provides documentation
665 of which kernel options are used in a running kernel or in an
666 on-disk kernel. This information can be extracted from the kernel
667 image file with the script scripts/extract-ikconfig and used as
668 input to rebuild the current kernel or to build another kernel.
669 It can also be extracted from a running kernel by reading
670 /proc/config.gz if enabled (below).
672 config IKCONFIG_PROC
673 bool "Enable access to .config through /proc/config.gz"
674 depends on IKCONFIG && PROC_FS
675 ---help---
676 This option enables access to the kernel configuration file
677 through /proc/config.gz.
679 config LOG_BUF_SHIFT
680 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
681 range 12 21
682 default 17
683 help
684 Select kernel log buffer size as a power of 2.
685 Examples:
686 17 => 128 KB
687 16 => 64 KB
688 15 => 32 KB
689 14 => 16 KB
690 13 => 8 KB
691 12 => 4 KB
693 #
694 # Architectures with an unreliable sched_clock() should select this:
695 #
696 config HAVE_UNSTABLE_SCHED_CLOCK
697 bool
699 #
700 # For architectures that want to enable the support for NUMA-affine scheduler
701 # balancing logic:
702 #
703 config ARCH_SUPPORTS_NUMA_BALANCING
704 bool
706 # For architectures that (ab)use NUMA to represent different memory regions
707 # all cpu-local but of different latencies, such as SuperH.
708 #
709 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
710 bool
712 #
713 # For architectures that are willing to define _PAGE_NUMA as _PAGE_PROTNONE
714 config ARCH_WANTS_PROT_NUMA_PROT_NONE
715 bool
717 config ARCH_USES_NUMA_PROT_NONE
718 bool
719 default y
720 depends on ARCH_WANTS_PROT_NUMA_PROT_NONE
721 depends on NUMA_BALANCING
723 config NUMA_BALANCING_DEFAULT_ENABLED
724 bool "Automatically enable NUMA aware memory/task placement"
725 default y
726 depends on NUMA_BALANCING
727 help
728 If set, autonumic NUMA balancing will be enabled if running on a NUMA
729 machine.
731 config NUMA_BALANCING
732 bool "Memory placement aware NUMA scheduler"
733 default y
734 depends on ARCH_SUPPORTS_NUMA_BALANCING
735 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
736 depends on SMP && NUMA && MIGRATION
737 help
738 This option adds support for automatic NUMA aware memory/task placement.
739 The mechanism is quite primitive and is based on migrating memory when
740 it is references to the node the task is running on.
742 This system will be inactive on UMA systems.
744 menuconfig CGROUPS
745 boolean "Control Group support"
746 depends on EVENTFD
747 help
748 This option adds support for grouping sets of processes together, for
749 use with process control subsystems such as Cpusets, CFS, memory
750 controls or device isolation.
751 See
752 - Documentation/scheduler/sched-design-CFS.txt (CFS)
753 - Documentation/cgroups/ (features for grouping, isolation
754 and resource control)
756 Say N if unsure.
758 if CGROUPS
760 config CGROUP_DEBUG
761 bool "Example debug cgroup subsystem"
762 default n
763 help
764 This option enables a simple cgroup subsystem that
765 exports useful debugging information about the cgroups
766 framework.
768 Say N if unsure.
770 config CGROUP_FREEZER
771 bool "Freezer cgroup subsystem"
772 help
773 Provides a way to freeze and unfreeze all tasks in a
774 cgroup.
776 config CGROUP_DEVICE
777 bool "Device controller for cgroups"
778 help
779 Provides a cgroup implementing whitelists for devices which
780 a process in the cgroup can mknod or open.
782 config CPUSETS
783 bool "Cpuset support"
784 help
785 This option will let you create and manage CPUSETs which
786 allow dynamically partitioning a system into sets of CPUs and
787 Memory Nodes and assigning tasks to run only within those sets.
788 This is primarily useful on large SMP or NUMA systems.
790 Say N if unsure.
792 config PROC_PID_CPUSET
793 bool "Include legacy /proc/<pid>/cpuset file"
794 depends on CPUSETS
795 default y
797 config CGROUP_CPUACCT
798 bool "Simple CPU accounting cgroup subsystem"
799 help
800 Provides a simple Resource Controller for monitoring the
801 total CPU consumed by the tasks in a cgroup.
803 config RESOURCE_COUNTERS
804 bool "Resource counters"
805 help
806 This option enables controller independent resource accounting
807 infrastructure that works with cgroups.
809 config MEMCG
810 bool "Memory Resource Controller for Control Groups"
811 depends on RESOURCE_COUNTERS
812 select MM_OWNER
813 help
814 Provides a memory resource controller that manages both anonymous
815 memory and page cache. (See Documentation/cgroups/memory.txt)
817 Note that setting this option increases fixed memory overhead
818 associated with each page of memory in the system. By this,
819 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
820 usage tracking struct at boot. Total amount of this is printed out
821 at boot.
823 Only enable when you're ok with these trade offs and really
824 sure you need the memory resource controller. Even when you enable
825 this, you can set "cgroup_disable=memory" at your boot option to
826 disable memory resource controller and you can avoid overheads.
827 (and lose benefits of memory resource controller)
829 This config option also selects MM_OWNER config option, which
830 could in turn add some fork/exit overhead.
832 config MEMCG_SWAP
833 bool "Memory Resource Controller Swap Extension"
834 depends on MEMCG && SWAP
835 help
836 Add swap management feature to memory resource controller. When you
837 enable this, you can limit mem+swap usage per cgroup. In other words,
838 when you disable this, memory resource controller has no cares to
839 usage of swap...a process can exhaust all of the swap. This extension
840 is useful when you want to avoid exhaustion swap but this itself
841 adds more overheads and consumes memory for remembering information.
842 Especially if you use 32bit system or small memory system, please
843 be careful about enabling this. When memory resource controller
844 is disabled by boot option, this will be automatically disabled and
845 there will be no overhead from this. Even when you set this config=y,
846 if boot option "swapaccount=0" is set, swap will not be accounted.
847 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
848 size is 4096bytes, 512k per 1Gbytes of swap.
849 config MEMCG_SWAP_ENABLED
850 bool "Memory Resource Controller Swap Extension enabled by default"
851 depends on MEMCG_SWAP
852 default y
853 help
854 Memory Resource Controller Swap Extension comes with its price in
855 a bigger memory consumption. General purpose distribution kernels
856 which want to enable the feature but keep it disabled by default
857 and let the user enable it by swapaccount boot command line
858 parameter should have this option unselected.
859 For those who want to have the feature enabled by default should
860 select this option (if, for some reason, they need to disable it
861 then swapaccount=0 does the trick).
862 config MEMCG_KMEM
863 bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
864 depends on MEMCG && EXPERIMENTAL
865 default n
866 help
867 The Kernel Memory extension for Memory Resource Controller can limit
868 the amount of memory used by kernel objects in the system. Those are
869 fundamentally different from the entities handled by the standard
870 Memory Controller, which are page-based, and can be swapped. Users of
871 the kmem extension can use it to guarantee that no group of processes
872 will ever exhaust kernel resources alone.
874 config CGROUP_HUGETLB
875 bool "HugeTLB Resource Controller for Control Groups"
876 depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
877 default n
878 help
879 Provides a cgroup Resource Controller for HugeTLB pages.
880 When you enable this, you can put a per cgroup limit on HugeTLB usage.
881 The limit is enforced during page fault. Since HugeTLB doesn't
882 support page reclaim, enforcing the limit at page fault time implies
883 that, the application will get SIGBUS signal if it tries to access
884 HugeTLB pages beyond its limit. This requires the application to know
885 beforehand how much HugeTLB pages it would require for its use. The
886 control group is tracked in the third page lru pointer. This means
887 that we cannot use the controller with huge page less than 3 pages.
889 config CGROUP_PERF
890 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
891 depends on PERF_EVENTS && CGROUPS
892 help
893 This option extends the per-cpu mode to restrict monitoring to
894 threads which belong to the cgroup specified and run on the
895 designated cpu.
897 Say N if unsure.
899 menuconfig CGROUP_SCHED
900 bool "Group CPU scheduler"
901 default n
902 help
903 This feature lets CPU scheduler recognize task groups and control CPU
904 bandwidth allocation to such task groups. It uses cgroups to group
905 tasks.
907 if CGROUP_SCHED
908 config FAIR_GROUP_SCHED
909 bool "Group scheduling for SCHED_OTHER"
910 depends on CGROUP_SCHED
911 default CGROUP_SCHED
913 config CFS_BANDWIDTH
914 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
915 depends on EXPERIMENTAL
916 depends on FAIR_GROUP_SCHED
917 default n
918 help
919 This option allows users to define CPU bandwidth rates (limits) for
920 tasks running within the fair group scheduler. Groups with no limit
921 set are considered to be unconstrained and will run with no
922 restriction.
923 See tip/Documentation/scheduler/sched-bwc.txt for more information.
925 config RT_GROUP_SCHED
926 bool "Group scheduling for SCHED_RR/FIFO"
927 depends on EXPERIMENTAL
928 depends on CGROUP_SCHED
929 default n
930 help
931 This feature lets you explicitly allocate real CPU bandwidth
932 to task groups. If enabled, it will also make it impossible to
933 schedule realtime tasks for non-root users until you allocate
934 realtime bandwidth for them.
935 See Documentation/scheduler/sched-rt-group.txt for more information.
937 endif #CGROUP_SCHED
939 config BLK_CGROUP
940 bool "Block IO controller"
941 depends on BLOCK
942 default n
943 ---help---
944 Generic block IO controller cgroup interface. This is the common
945 cgroup interface which should be used by various IO controlling
946 policies.
948 Currently, CFQ IO scheduler uses it to recognize task groups and
949 control disk bandwidth allocation (proportional time slice allocation)
950 to such task groups. It is also used by bio throttling logic in
951 block layer to implement upper limit in IO rates on a device.
953 This option only enables generic Block IO controller infrastructure.
954 One needs to also enable actual IO controlling logic/policy. For
955 enabling proportional weight division of disk bandwidth in CFQ, set
956 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
957 CONFIG_BLK_DEV_THROTTLING=y.
959 See Documentation/cgroups/blkio-controller.txt for more information.
961 config DEBUG_BLK_CGROUP
962 bool "Enable Block IO controller debugging"
963 depends on BLK_CGROUP
964 default n
965 ---help---
966 Enable some debugging help. Currently it exports additional stat
967 files in a cgroup which can be useful for debugging.
969 endif # CGROUPS
971 config CHECKPOINT_RESTORE
972 bool "Checkpoint/restore support" if EXPERT
973 default n
974 help
975 Enables additional kernel features in a sake of checkpoint/restore.
976 In particular it adds auxiliary prctl codes to setup process text,
977 data and heap segment sizes, and a few additional /proc filesystem
978 entries.
980 If unsure, say N here.
982 menuconfig NAMESPACES
983 bool "Namespaces support" if EXPERT
984 default !EXPERT
985 help
986 Provides the way to make tasks work with different objects using
987 the same id. For example same IPC id may refer to different objects
988 or same user id or pid may refer to different tasks when used in
989 different namespaces.
991 if NAMESPACES
993 config UTS_NS
994 bool "UTS namespace"
995 default y
996 help
997 In this namespace tasks see different info provided with the
998 uname() system call
1000 config IPC_NS
1001 bool "IPC namespace"
1002 depends on (SYSVIPC || POSIX_MQUEUE)
1003 default y
1004 help
1005 In this namespace tasks work with IPC ids which correspond to
1006 different IPC objects in different namespaces.
1008 config USER_NS
1009 bool "User namespace (EXPERIMENTAL)"
1010 depends on EXPERIMENTAL
1011 depends on UIDGID_CONVERTED
1012 select UIDGID_STRICT_TYPE_CHECKS
1014 default n
1015 help
1016 This allows containers, i.e. vservers, to use user namespaces
1017 to provide different user info for different servers.
1018 If unsure, say N.
1020 config PID_NS
1021 bool "PID Namespaces"
1022 default y
1023 help
1024 Support process id namespaces. This allows having multiple
1025 processes with the same pid as long as they are in different
1026 pid namespaces. This is a building block of containers.
1028 config NET_NS
1029 bool "Network namespace"
1030 depends on NET
1031 default y
1032 help
1033 Allow user space to create what appear to be multiple instances
1034 of the network stack.
1036 endif # NAMESPACES
1038 config UIDGID_CONVERTED
1039 # True if all of the selected software conmponents are known
1040 # to have uid_t and gid_t converted to kuid_t and kgid_t
1041 # where appropriate and are otherwise safe to use with
1042 # the user namespace.
1043 bool
1044 default y
1046 # Networking
1047 depends on NET_9P = n
1049 # Filesystems
1050 depends on 9P_FS = n
1051 depends on AFS_FS = n
1052 depends on AUTOFS4_FS = n
1053 depends on CEPH_FS = n
1054 depends on CIFS = n
1055 depends on CODA_FS = n
1056 depends on FUSE_FS = n
1057 depends on GFS2_FS = n
1058 depends on NCP_FS = n
1059 depends on NFSD = n
1060 depends on NFS_FS = n
1061 depends on OCFS2_FS = n
1062 depends on XFS_FS = n
1064 config UIDGID_STRICT_TYPE_CHECKS
1065 bool "Require conversions between uid/gids and their internal representation"
1066 depends on UIDGID_CONVERTED
1067 default n
1068 help
1069 While the nececessary conversions are being added to all subsystems this option allows
1070 the code to continue to build for unconverted subsystems.
1072 Say Y here if you want the strict type checking enabled
1074 config SCHED_AUTOGROUP
1075 bool "Automatic process group scheduling"
1076 select EVENTFD
1077 select CGROUPS
1078 select CGROUP_SCHED
1079 select FAIR_GROUP_SCHED
1080 help
1081 This option optimizes the scheduler for common desktop workloads by
1082 automatically creating and populating task groups. This separation
1083 of workloads isolates aggressive CPU burners (like build jobs) from
1084 desktop applications. Task group autogeneration is currently based
1085 upon task session.
1087 config MM_OWNER
1088 bool
1090 config SYSFS_DEPRECATED
1091 bool "Enable deprecated sysfs features to support old userspace tools"
1092 depends on SYSFS
1093 default n
1094 help
1095 This option adds code that switches the layout of the "block" class
1096 devices, to not show up in /sys/class/block/, but only in
1097 /sys/block/.
1099 This switch is only active when the sysfs.deprecated=1 boot option is
1100 passed or the SYSFS_DEPRECATED_V2 option is set.
1102 This option allows new kernels to run on old distributions and tools,
1103 which might get confused by /sys/class/block/. Since 2007/2008 all
1104 major distributions and tools handle this just fine.
1106 Recent distributions and userspace tools after 2009/2010 depend on
1107 the existence of /sys/class/block/, and will not work with this
1108 option enabled.
1110 Only if you are using a new kernel on an old distribution, you might
1111 need to say Y here.
1113 config SYSFS_DEPRECATED_V2
1114 bool "Enable deprecated sysfs features by default"
1115 default n
1116 depends on SYSFS
1117 depends on SYSFS_DEPRECATED
1118 help
1119 Enable deprecated sysfs by default.
1121 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1122 option.
1124 Only if you are using a new kernel on an old distribution, you might
1125 need to say Y here. Even then, odds are you would not need it
1126 enabled, you can always pass the boot option if absolutely necessary.
1128 config RELAY
1129 bool "Kernel->user space relay support (formerly relayfs)"
1130 help
1131 This option enables support for relay interface support in
1132 certain file systems (such as debugfs).
1133 It is designed to provide an efficient mechanism for tools and
1134 facilities to relay large amounts of data from kernel space to
1135 user space.
1137 If unsure, say N.
1139 config BLK_DEV_INITRD
1140 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1141 depends on BROKEN || !FRV
1142 help
1143 The initial RAM filesystem is a ramfs which is loaded by the
1144 boot loader (loadlin or lilo) and that is mounted as root
1145 before the normal boot procedure. It is typically used to
1146 load modules needed to mount the "real" root file system,
1147 etc. See <file:Documentation/initrd.txt> for details.
1149 If RAM disk support (BLK_DEV_RAM) is also included, this
1150 also enables initial RAM disk (initrd) support and adds
1151 15 Kbytes (more on some other architectures) to the kernel size.
1153 If unsure say Y.
1155 if BLK_DEV_INITRD
1157 source "usr/Kconfig"
1159 endif
1161 config CC_OPTIMIZE_FOR_SIZE
1162 bool "Optimize for size"
1163 help
1164 Enabling this option will pass "-Os" instead of "-O2" to gcc
1165 resulting in a smaller kernel.
1167 If unsure, say Y.
1169 config SYSCTL
1170 bool
1172 config ANON_INODES
1173 bool
1175 menuconfig EXPERT
1176 bool "Configure standard kernel features (expert users)"
1177 # Unhide debug options, to make the on-by-default options visible
1178 select DEBUG_KERNEL
1179 help
1180 This option allows certain base kernel options and settings
1181 to be disabled or tweaked. This is for specialized
1182 environments which can tolerate a "non-standard" kernel.
1183 Only use this if you really know what you are doing.
1185 config HAVE_UID16
1186 bool
1188 config UID16
1189 bool "Enable 16-bit UID system calls" if EXPERT
1190 depends on HAVE_UID16
1191 default y
1192 help
1193 This enables the legacy 16-bit UID syscall wrappers.
1195 config SYSCTL_SYSCALL
1196 bool "Sysctl syscall support" if EXPERT
1197 depends on PROC_SYSCTL
1198 default n
1199 select SYSCTL
1200 ---help---
1201 sys_sysctl uses binary paths that have been found challenging
1202 to properly maintain and use. The interface in /proc/sys
1203 using paths with ascii names is now the primary path to this
1204 information.
1206 Almost nothing using the binary sysctl interface so if you are
1207 trying to save some space it is probably safe to disable this,
1208 making your kernel marginally smaller.
1210 If unsure say N here.
1212 config SYSCTL_EXCEPTION_TRACE
1213 bool
1214 help
1215 Enable support for /proc/sys/debug/exception-trace.
1217 config KALLSYMS
1218 bool "Load all symbols for debugging/ksymoops" if EXPERT
1219 default y
1220 help
1221 Say Y here to let the kernel print out symbolic crash information and
1222 symbolic stack backtraces. This increases the size of the kernel
1223 somewhat, as all symbols have to be loaded into the kernel image.
1225 config KALLSYMS_ALL
1226 bool "Include all symbols in kallsyms"
1227 depends on DEBUG_KERNEL && KALLSYMS
1228 help
1229 Normally kallsyms only contains the symbols of functions for nicer
1230 OOPS messages and backtraces (i.e., symbols from the text and inittext
1231 sections). This is sufficient for most cases. And only in very rare
1232 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1233 names of variables from the data sections, etc).
1235 This option makes sure that all symbols are loaded into the kernel
1236 image (i.e., symbols from all sections) in cost of increased kernel
1237 size (depending on the kernel configuration, it may be 300KiB or
1238 something like this).
1240 Say N unless you really need all symbols.
1242 config HOTPLUG
1243 def_bool y
1245 config PRINTK
1246 default y
1247 bool "Enable support for printk" if EXPERT
1248 help
1249 This option enables normal printk support. Removing it
1250 eliminates most of the message strings from the kernel image
1251 and makes the kernel more or less silent. As this makes it
1252 very difficult to diagnose system problems, saying N here is
1253 strongly discouraged.
1255 config BUG
1256 bool "BUG() support" if EXPERT
1257 default y
1258 help
1259 Disabling this option eliminates support for BUG and WARN, reducing
1260 the size of your kernel image and potentially quietly ignoring
1261 numerous fatal conditions. You should only consider disabling this
1262 option for embedded systems with no facilities for reporting errors.
1263 Just say Y.
1265 config ELF_CORE
1266 depends on COREDUMP
1267 default y
1268 bool "Enable ELF core dumps" if EXPERT
1269 help
1270 Enable support for generating core dumps. Disabling saves about 4k.
1273 config PCSPKR_PLATFORM
1274 bool "Enable PC-Speaker support" if EXPERT
1275 depends on HAVE_PCSPKR_PLATFORM
1276 select I8253_LOCK
1277 default y
1278 help
1279 This option allows to disable the internal PC-Speaker
1280 support, saving some memory.
1282 config HAVE_PCSPKR_PLATFORM
1283 bool
1285 config BASE_FULL
1286 default y
1287 bool "Enable full-sized data structures for core" if EXPERT
1288 help
1289 Disabling this option reduces the size of miscellaneous core
1290 kernel data structures. This saves memory on small machines,
1291 but may reduce performance.
1293 config FUTEX
1294 bool "Enable futex support" if EXPERT
1295 default y
1296 select RT_MUTEXES
1297 help
1298 Disabling this option will cause the kernel to be built without
1299 support for "fast userspace mutexes". The resulting kernel may not
1300 run glibc-based applications correctly.
1302 config EPOLL
1303 bool "Enable eventpoll support" if EXPERT
1304 default y
1305 select ANON_INODES
1306 help
1307 Disabling this option will cause the kernel to be built without
1308 support for epoll family of system calls.
1310 config SIGNALFD
1311 bool "Enable signalfd() system call" if EXPERT
1312 select ANON_INODES
1313 default y
1314 help
1315 Enable the signalfd() system call that allows to receive signals
1316 on a file descriptor.
1318 If unsure, say Y.
1320 config TIMERFD
1321 bool "Enable timerfd() system call" if EXPERT
1322 select ANON_INODES
1323 default y
1324 help
1325 Enable the timerfd() system call that allows to receive timer
1326 events on a file descriptor.
1328 If unsure, say Y.
1330 config EVENTFD
1331 bool "Enable eventfd() system call" if EXPERT
1332 select ANON_INODES
1333 default y
1334 help
1335 Enable the eventfd() system call that allows to receive both
1336 kernel notification (ie. KAIO) or userspace notifications.
1338 If unsure, say Y.
1340 config SHMEM
1341 bool "Use full shmem filesystem" if EXPERT
1342 default y
1343 depends on MMU
1344 help
1345 The shmem is an internal filesystem used to manage shared memory.
1346 It is backed by swap and manages resource limits. It is also exported
1347 to userspace as tmpfs if TMPFS is enabled. Disabling this
1348 option replaces shmem and tmpfs with the much simpler ramfs code,
1349 which may be appropriate on small systems without swap.
1351 config AIO
1352 bool "Enable AIO support" if EXPERT
1353 default y
1354 help
1355 This option enables POSIX asynchronous I/O which may by used
1356 by some high performance threaded applications. Disabling
1357 this option saves about 7k.
1359 config EMBEDDED
1360 bool "Embedded system"
1361 select EXPERT
1362 help
1363 This option should be enabled if compiling the kernel for
1364 an embedded system so certain expert options are available
1365 for configuration.
1367 config HAVE_PERF_EVENTS
1368 bool
1369 help
1370 See tools/perf/design.txt for details.
1372 config PERF_USE_VMALLOC
1373 bool
1374 help
1375 See tools/perf/design.txt for details
1377 menu "Kernel Performance Events And Counters"
1379 config PERF_EVENTS
1380 bool "Kernel performance events and counters"
1381 default y if PROFILING
1382 depends on HAVE_PERF_EVENTS
1383 select ANON_INODES
1384 select IRQ_WORK
1385 help
1386 Enable kernel support for various performance events provided
1387 by software and hardware.
1389 Software events are supported either built-in or via the
1390 use of generic tracepoints.
1392 Most modern CPUs support performance events via performance
1393 counter registers. These registers count the number of certain
1394 types of hw events: such as instructions executed, cachemisses
1395 suffered, or branches mis-predicted - without slowing down the
1396 kernel or applications. These registers can also trigger interrupts
1397 when a threshold number of events have passed - and can thus be
1398 used to profile the code that runs on that CPU.
1400 The Linux Performance Event subsystem provides an abstraction of
1401 these software and hardware event capabilities, available via a
1402 system call and used by the "perf" utility in tools/perf/. It
1403 provides per task and per CPU counters, and it provides event
1404 capabilities on top of those.
1406 Say Y if unsure.
1408 config DEBUG_PERF_USE_VMALLOC
1409 default n
1410 bool "Debug: use vmalloc to back perf mmap() buffers"
1411 depends on PERF_EVENTS && DEBUG_KERNEL
1412 select PERF_USE_VMALLOC
1413 help
1414 Use vmalloc memory to back perf mmap() buffers.
1416 Mostly useful for debugging the vmalloc code on platforms
1417 that don't require it.
1419 Say N if unsure.
1421 endmenu
1423 config VM_EVENT_COUNTERS
1424 default y
1425 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1426 help
1427 VM event counters are needed for event counts to be shown.
1428 This option allows the disabling of the VM event counters
1429 on EXPERT systems. /proc/vmstat will only show page counts
1430 if VM event counters are disabled.
1432 config PCI_QUIRKS
1433 default y
1434 bool "Enable PCI quirk workarounds" if EXPERT
1435 depends on PCI
1436 help
1437 This enables workarounds for various PCI chipset
1438 bugs/quirks. Disable this only if your target machine is
1439 unaffected by PCI quirks.
1441 config SLUB_DEBUG
1442 default y
1443 bool "Enable SLUB debugging support" if EXPERT
1444 depends on SLUB && SYSFS
1445 help
1446 SLUB has extensive debug support features. Disabling these can
1447 result in significant savings in code size. This also disables
1448 SLUB sysfs support. /sys/slab will not exist and there will be
1449 no support for cache validation etc.
1451 config COMPAT_BRK
1452 bool "Disable heap randomization"
1453 default y
1454 help
1455 Randomizing heap placement makes heap exploits harder, but it
1456 also breaks ancient binaries (including anything libc5 based).
1457 This option changes the bootup default to heap randomization
1458 disabled, and can be overridden at runtime by setting
1459 /proc/sys/kernel/randomize_va_space to 2.
1461 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1463 choice
1464 prompt "Choose SLAB allocator"
1465 default SLUB
1466 help
1467 This option allows to select a slab allocator.
1469 config SLAB
1470 bool "SLAB"
1471 help
1472 The regular slab allocator that is established and known to work
1473 well in all environments. It organizes cache hot objects in
1474 per cpu and per node queues.
1476 config SLUB
1477 bool "SLUB (Unqueued Allocator)"
1478 help
1479 SLUB is a slab allocator that minimizes cache line usage
1480 instead of managing queues of cached objects (SLAB approach).
1481 Per cpu caching is realized using slabs of objects instead
1482 of queues of objects. SLUB can use memory efficiently
1483 and has enhanced diagnostics. SLUB is the default choice for
1484 a slab allocator.
1486 config SLOB
1487 depends on EXPERT
1488 bool "SLOB (Simple Allocator)"
1489 help
1490 SLOB replaces the stock allocator with a drastically simpler
1491 allocator. SLOB is generally more space efficient but
1492 does not perform as well on large systems.
1494 endchoice
1496 config MMAP_ALLOW_UNINITIALIZED
1497 bool "Allow mmapped anonymous memory to be uninitialized"
1498 depends on EXPERT && !MMU
1499 default n
1500 help
1501 Normally, and according to the Linux spec, anonymous memory obtained
1502 from mmap() has it's contents cleared before it is passed to
1503 userspace. Enabling this config option allows you to request that
1504 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1505 providing a huge performance boost. If this option is not enabled,
1506 then the flag will be ignored.
1508 This is taken advantage of by uClibc's malloc(), and also by
1509 ELF-FDPIC binfmt's brk and stack allocator.
1511 Because of the obvious security issues, this option should only be
1512 enabled on embedded devices where you control what is run in
1513 userspace. Since that isn't generally a problem on no-MMU systems,
1514 it is normally safe to say Y here.
1516 See Documentation/nommu-mmap.txt for more information.
1518 config PROFILING
1519 bool "Profiling support"
1520 help
1521 Say Y here to enable the extended profiling support mechanisms used
1522 by profilers such as OProfile.
1524 #
1525 # Place an empty function call at each tracepoint site. Can be
1526 # dynamically changed for a probe function.
1527 #
1528 config TRACEPOINTS
1529 bool
1531 source "arch/Kconfig"
1533 endmenu # General setup
1535 config HAVE_GENERIC_DMA_COHERENT
1536 bool
1537 default n
1539 config SLABINFO
1540 bool
1541 depends on PROC_FS
1542 depends on SLAB || SLUB_DEBUG
1543 default y
1545 config RT_MUTEXES
1546 boolean
1548 config BASE_SMALL
1549 int
1550 default 0 if BASE_FULL
1551 default 1 if !BASE_FULL
1553 menuconfig MODULES
1554 bool "Enable loadable module support"
1555 help
1556 Kernel modules are small pieces of compiled code which can
1557 be inserted in the running kernel, rather than being
1558 permanently built into the kernel. You use the "modprobe"
1559 tool to add (and sometimes remove) them. If you say Y here,
1560 many parts of the kernel can be built as modules (by
1561 answering M instead of Y where indicated): this is most
1562 useful for infrequently used options which are not required
1563 for booting. For more information, see the man pages for
1564 modprobe, lsmod, modinfo, insmod and rmmod.
1566 If you say Y here, you will need to run "make
1567 modules_install" to put the modules under /lib/modules/
1568 where modprobe can find them (you may need to be root to do
1569 this).
1571 If unsure, say Y.
1573 if MODULES
1575 config MODULE_FORCE_LOAD
1576 bool "Forced module loading"
1577 default n
1578 help
1579 Allow loading of modules without version information (ie. modprobe
1580 --force). Forced module loading sets the 'F' (forced) taint flag and
1581 is usually a really bad idea.
1583 config MODULE_UNLOAD
1584 bool "Module unloading"
1585 help
1586 Without this option you will not be able to unload any
1587 modules (note that some modules may not be unloadable
1588 anyway), which makes your kernel smaller, faster
1589 and simpler. If unsure, say Y.
1591 config MODULE_FORCE_UNLOAD
1592 bool "Forced module unloading"
1593 depends on MODULE_UNLOAD && EXPERIMENTAL
1594 help
1595 This option allows you to force a module to unload, even if the
1596 kernel believes it is unsafe: the kernel will remove the module
1597 without waiting for anyone to stop using it (using the -f option to
1598 rmmod). This is mainly for kernel developers and desperate users.
1599 If unsure, say N.
1601 config MODVERSIONS
1602 bool "Module versioning support"
1603 help
1604 Usually, you have to use modules compiled with your kernel.
1605 Saying Y here makes it sometimes possible to use modules
1606 compiled for different kernels, by adding enough information
1607 to the modules to (hopefully) spot any changes which would
1608 make them incompatible with the kernel you are running. If
1609 unsure, say N.
1611 config MODULE_SRCVERSION_ALL
1612 bool "Source checksum for all modules"
1613 help
1614 Modules which contain a MODULE_VERSION get an extra "srcversion"
1615 field inserted into their modinfo section, which contains a
1616 sum of the source files which made it. This helps maintainers
1617 see exactly which source was used to build a module (since
1618 others sometimes change the module source without updating
1619 the version). With this option, such a "srcversion" field
1620 will be created for all modules. If unsure, say N.
1622 config MODULE_SIG
1623 bool "Module signature verification"
1624 depends on MODULES
1625 select KEYS
1626 select CRYPTO
1627 select ASYMMETRIC_KEY_TYPE
1628 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1629 select PUBLIC_KEY_ALGO_RSA
1630 select ASN1
1631 select OID_REGISTRY
1632 select X509_CERTIFICATE_PARSER
1633 help
1634 Check modules for valid signatures upon load: the signature
1635 is simply appended to the module. For more information see
1636 Documentation/module-signing.txt.
1638 !!!WARNING!!! If you enable this option, you MUST make sure that the
1639 module DOES NOT get stripped after being signed. This includes the
1640 debuginfo strip done by some packagers (such as rpmbuild) and
1641 inclusion into an initramfs that wants the module size reduced.
1643 config MODULE_SIG_FORCE
1644 bool "Require modules to be validly signed"
1645 depends on MODULE_SIG
1646 help
1647 Reject unsigned modules or signed modules for which we don't have a
1648 key. Without this, such modules will simply taint the kernel.
1650 choice
1651 prompt "Which hash algorithm should modules be signed with?"
1652 depends on MODULE_SIG
1653 help
1654 This determines which sort of hashing algorithm will be used during
1655 signature generation. This algorithm _must_ be built into the kernel
1656 directly so that signature verification can take place. It is not
1657 possible to load a signed module containing the algorithm to check
1658 the signature on that module.
1660 config MODULE_SIG_SHA1
1661 bool "Sign modules with SHA-1"
1662 select CRYPTO_SHA1
1664 config MODULE_SIG_SHA224
1665 bool "Sign modules with SHA-224"
1666 select CRYPTO_SHA256
1668 config MODULE_SIG_SHA256
1669 bool "Sign modules with SHA-256"
1670 select CRYPTO_SHA256
1672 config MODULE_SIG_SHA384
1673 bool "Sign modules with SHA-384"
1674 select CRYPTO_SHA512
1676 config MODULE_SIG_SHA512
1677 bool "Sign modules with SHA-512"
1678 select CRYPTO_SHA512
1680 endchoice
1682 endif # MODULES
1684 config INIT_ALL_POSSIBLE
1685 bool
1686 help
1687 Back when each arch used to define their own cpu_online_mask and
1688 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1689 with all 1s, and others with all 0s. When they were centralised,
1690 it was better to provide this option than to break all the archs
1691 and have several arch maintainers pursuing me down dark alleys.
1693 config STOP_MACHINE
1694 bool
1695 default y
1696 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1697 help
1698 Need stop_machine() primitive.
1700 source "block/Kconfig"
1702 config PREEMPT_NOTIFIERS
1703 bool
1705 config PADATA
1706 depends on SMP
1707 bool
1709 # Can be selected by architectures with broken toolchains
1710 # that get confused by correct const<->read_only section
1711 # mappings
1712 config BROKEN_RODATA
1713 bool
1715 config ASN1
1716 tristate
1717 help
1718 Build a simple ASN.1 grammar compiler that produces a bytecode output
1719 that can be interpreted by the ASN.1 stream decoder and used to
1720 inform it as to what tags are to be expected in a stream and what
1721 functions to call on what tags.
1723 source "kernel/Kconfig.locks"