Root/init/Kconfig

1config ARCH
2    string
3    option env="ARCH"
4
5config KERNELVERSION
6    string
7    option env="KERNELVERSION"
8
9config 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
19config CONSTRUCTORS
20    bool
21    depends on !UML
22    default y
23
24config HAVE_IRQ_WORK
25    bool
26
27config IRQ_WORK
28    bool
29    depends on HAVE_IRQ_WORK
30
31menu "General setup"
32
33config EXPERIMENTAL
34    bool "Prompt for development and/or incomplete code/drivers"
35    ---help---
36      Some of the various things that Linux supports (such as network
37      drivers, file systems, network protocols, etc.) can be in a state
38      of development where the functionality, stability, or the level of
39      testing is not yet high enough for general use. This is usually
40      known as the "alpha-test" phase among developers. If a feature is
41      currently in alpha-test, then the developers usually discourage
42      uninformed widespread use of this feature by the general public to
43      avoid "Why doesn't this work?" type mail messages. However, active
44      testing and use of these systems is welcomed. Just be aware that it
45      may not meet the normal level of reliability or it may fail to work
46      in some special cases. Detailed bug reports from people familiar
47      with the kernel internals are usually welcomed by the developers
48      (before submitting bug reports, please read the documents
49      <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
50      <file:Documentation/BUG-HUNTING>, and
51      <file:Documentation/oops-tracing.txt> in the kernel source).
52
53      This option will also make obsoleted drivers available. These are
54      drivers that have been replaced by something else, and/or are
55      scheduled to be removed in a future kernel release.
56
57      Unless you intend to help test and develop a feature or driver that
58      falls into this category, or you have a situation that requires
59      using these features, you should probably say N here, which will
60      cause the configurator to present you with fewer choices. If
61      you say Y here, you will be offered the choice of using features or
62      drivers that are currently considered to be in the alpha-test phase.
63
64config BROKEN
65    bool
66
67config BROKEN_ON_SMP
68    bool
69    depends on BROKEN || !SMP
70    default y
71
72config LOCK_KERNEL
73    bool
74    depends on (SMP || PREEMPT) && BKL
75    default y
76
77config INIT_ENV_ARG_LIMIT
78    int
79    default 32 if !UML
80    default 128 if UML
81    help
82      Maximum of each of the number of arguments and environment
83      variables passed to init from the kernel command line.
84
85
86config CROSS_COMPILE
87    string "Cross-compiler tool prefix"
88    help
89      Same as running 'make CROSS_COMPILE=prefix-' but stored for
90      default make runs in this kernel build directory. You don't
91      need to set this unless you want the configured kernel build
92      directory to select the cross-compiler automatically.
93
94config LOCALVERSION
95    string "Local version - append to kernel release"
96    help
97      Append an extra string to the end of your kernel version.
98      This will show up when you type uname, for example.
99      The string you set here will be appended after the contents of
100      any files with a filename matching localversion* in your
101      object and source tree, in that order. Your total string can
102      be a maximum of 64 characters.
103
104config LOCALVERSION_AUTO
105    bool "Automatically append version information to the version string"
106    default y
107    help
108      This will try to automatically determine if the current tree is a
109      release tree by looking for git tags that belong to the current
110      top of tree revision.
111
112      A string of the format -gxxxxxxxx will be added to the localversion
113      if a git-based tree is found. The string generated by this will be
114      appended after any matching localversion* files, and after the value
115      set in CONFIG_LOCALVERSION.
116
117      (The actual string used here is the first eight characters produced
118      by running the command:
119
120        $ git rev-parse --verify HEAD
121
122      which is done within the script "scripts/setlocalversion".)
123
124config HAVE_KERNEL_GZIP
125    bool
126
127config HAVE_KERNEL_BZIP2
128    bool
129
130config HAVE_KERNEL_LZMA
131    bool
132
133config HAVE_KERNEL_LZO
134    bool
135
136choice
137    prompt "Kernel compression mode"
138    default KERNEL_GZIP
139    depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
140    help
141      The linux kernel is a kind of self-extracting executable.
142      Several compression algorithms are available, which differ
143      in efficiency, compression and decompression speed.
144      Compression speed is only relevant when building a kernel.
145      Decompression speed is relevant at each boot.
146
147      If you have any problems with bzip2 or lzma compressed
148      kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
149      version of this functionality (bzip2 only), for 2.4, was
150      supplied by Christian Ludwig)
151
152      High compression options are mostly useful for users, who
153      are low on disk space (embedded systems), but for whom ram
154      size matters less.
155
156      If in doubt, select 'gzip'
157
158config KERNEL_GZIP
159    bool "Gzip"
160    depends on HAVE_KERNEL_GZIP
161    help
162      The old and tried gzip compression. It provides a good balance
163      between compression ratio and decompression speed.
164
165config 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 three. The kernel
171      size is about 10% smaller with bzip2, in comparison to gzip.
172      Bzip2 uses a large amount of memory. For modern kernels you
173      will need at least 8MB RAM or more for booting.
174
175config KERNEL_LZMA
176    bool "LZMA"
177    depends on HAVE_KERNEL_LZMA
178    help
179      The most recent compression algorithm.
180      Its ratio is best, decompression speed is between the other
181      two. Compression is slowest. The kernel size is about 33%
182      smaller with LZMA in comparison to gzip.
183
184config KERNEL_LZO
185    bool "LZO"
186    depends on HAVE_KERNEL_LZO
187    help
188      Its compression ratio is the poorest among the 4. The kernel
189      size is about 10% bigger than gzip; however its speed
190      (both compression and decompression) is the fastest.
191
192endchoice
193
194config SWAP
195    bool "Support for paging of anonymous memory (swap)"
196    depends on MMU && BLOCK
197    default y
198    help
199      This option allows you to choose whether you want to have support
200      for so called swap devices or swap files in your kernel that are
201      used to provide more virtual memory than the actual RAM present
202      in your computer. If unsure say Y.
203
204config SYSVIPC
205    bool "System V IPC"
206    ---help---
207      Inter Process Communication is a suite of library functions and
208      system calls which let processes (running programs) synchronize and
209      exchange information. It is generally considered to be a good thing,
210      and some programs won't run unless you say Y here. In particular, if
211      you want to run the DOS emulator dosemu under Linux (read the
212      DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
213      you'll need to say Y here.
214
215      You can find documentation about IPC with "info ipc" and also in
216      section 6.4 of the Linux Programmer's Guide, available from
217      <http://www.tldp.org/guides.html>.
218
219config SYSVIPC_SYSCTL
220    bool
221    depends on SYSVIPC
222    depends on SYSCTL
223    default y
224
225config POSIX_MQUEUE
226    bool "POSIX Message Queues"
227    depends on NET && EXPERIMENTAL
228    ---help---
229      POSIX variant of message queues is a part of IPC. In POSIX message
230      queues every message has a priority which decides about succession
231      of receiving it by a process. If you want to compile and run
232      programs written e.g. for Solaris with use of its POSIX message
233      queues (functions mq_*) say Y here.
234
235      POSIX message queues are visible as a filesystem called 'mqueue'
236      and can be mounted somewhere if you want to do filesystem
237      operations on message queues.
238
239      If unsure, say Y.
240
241config POSIX_MQUEUE_SYSCTL
242    bool
243    depends on POSIX_MQUEUE
244    depends on SYSCTL
245    default y
246
247config BSD_PROCESS_ACCT
248    bool "BSD Process Accounting"
249    help
250      If you say Y here, a user level program will be able to instruct the
251      kernel (via a special system call) to write process accounting
252      information to a file: whenever a process exits, information about
253      that process will be appended to the file by the kernel. The
254      information includes things such as creation time, owning user,
255      command name, memory usage, controlling terminal etc. (the complete
256      list is in the struct acct in <file:include/linux/acct.h>). It is
257      up to the user level program to do useful things with this
258      information. This is generally a good idea, so say Y.
259
260config BSD_PROCESS_ACCT_V3
261    bool "BSD Process Accounting version 3 file format"
262    depends on BSD_PROCESS_ACCT
263    default n
264    help
265      If you say Y here, the process accounting information is written
266      in a new file format that also logs the process IDs of each
267      process and it's parent. Note that this file format is incompatible
268      with previous v0/v1/v2 file formats, so you will need updated tools
269      for processing it. A preliminary version of these tools is available
270      at <http://www.gnu.org/software/acct/>.
271
272config TASKSTATS
273    bool "Export task/process statistics through netlink (EXPERIMENTAL)"
274    depends on NET
275    default n
276    help
277      Export selected statistics for tasks/processes through the
278      generic netlink interface. Unlike BSD process accounting, the
279      statistics are available during the lifetime of tasks/processes as
280      responses to commands. Like BSD accounting, they are sent to user
281      space on task exit.
282
283      Say N if unsure.
284
285config TASK_DELAY_ACCT
286    bool "Enable per-task delay accounting (EXPERIMENTAL)"
287    depends on TASKSTATS
288    help
289      Collect information on time spent by a task waiting for system
290      resources like cpu, synchronous block I/O completion and swapping
291      in pages. Such statistics can help in setting a task's priorities
292      relative to other tasks for cpu, io, rss limits etc.
293
294      Say N if unsure.
295
296config TASK_XACCT
297    bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
298    depends on TASKSTATS
299    help
300      Collect extended task accounting data and send the data
301      to userland for processing over the taskstats interface.
302
303      Say N if unsure.
304
305config TASK_IO_ACCOUNTING
306    bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
307    depends on TASK_XACCT
308    help
309      Collect information on the number of bytes of storage I/O which this
310      task has caused.
311
312      Say N if unsure.
313
314config AUDIT
315    bool "Auditing support"
316    depends on NET
317    help
318      Enable auditing infrastructure that can be used with another
319      kernel subsystem, such as SELinux (which requires this for
320      logging of avc messages output). Does not do system-call
321      auditing without CONFIG_AUDITSYSCALL.
322
323config AUDITSYSCALL
324    bool "Enable system-call auditing support"
325    depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
326    default y if SECURITY_SELINUX
327    help
328      Enable low-overhead system-call auditing infrastructure that
329      can be used independently or with another kernel subsystem,
330      such as SELinux.
331
332config AUDIT_WATCH
333    def_bool y
334    depends on AUDITSYSCALL
335    select FSNOTIFY
336
337config AUDIT_TREE
338    def_bool y
339    depends on AUDITSYSCALL
340    select FSNOTIFY
341
342source "kernel/irq/Kconfig"
343
344menu "RCU Subsystem"
345
346choice
347    prompt "RCU Implementation"
348    default TREE_RCU
349
350config TREE_RCU
351    bool "Tree-based hierarchical RCU"
352    depends on !PREEMPT && SMP
353    help
354      This option selects the RCU implementation that is
355      designed for very large SMP system with hundreds or
356      thousands of CPUs. It also scales down nicely to
357      smaller systems.
358
359config TREE_PREEMPT_RCU
360    bool "Preemptible tree-based hierarchical RCU"
361    depends on PREEMPT
362    help
363      This option selects the RCU implementation that is
364      designed for very large SMP systems with hundreds or
365      thousands of CPUs, but for which real-time response
366      is also required. It also scales down nicely to
367      smaller systems.
368
369config TINY_RCU
370    bool "UP-only small-memory-footprint RCU"
371    depends on !SMP
372    help
373      This option selects the RCU implementation that is
374      designed for UP systems from which real-time response
375      is not required. This option greatly reduces the
376      memory footprint of RCU.
377
378config TINY_PREEMPT_RCU
379    bool "Preemptible UP-only small-memory-footprint RCU"
380    depends on !SMP && PREEMPT
381    help
382      This option selects the RCU implementation that is designed
383      for real-time UP systems. This option greatly reduces the
384      memory footprint of RCU.
385
386endchoice
387
388config PREEMPT_RCU
389    def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
390    help
391      This option enables preemptible-RCU code that is common between
392      the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
393
394config RCU_TRACE
395    bool "Enable tracing for RCU"
396    depends on TREE_RCU || TREE_PREEMPT_RCU
397    help
398      This option provides tracing in RCU which presents stats
399      in debugfs for debugging RCU implementation.
400
401      Say Y here if you want to enable RCU tracing
402      Say N if you are unsure.
403
404config RCU_FANOUT
405    int "Tree-based hierarchical RCU fanout value"
406    range 2 64 if 64BIT
407    range 2 32 if !64BIT
408    depends on TREE_RCU || TREE_PREEMPT_RCU
409    default 64 if 64BIT
410    default 32 if !64BIT
411    help
412      This option controls the fanout of hierarchical implementations
413      of RCU, allowing RCU to work efficiently on machines with
414      large numbers of CPUs. This value must be at least the fourth
415      root of NR_CPUS, which allows NR_CPUS to be insanely large.
416      The default value of RCU_FANOUT should be used for production
417      systems, but if you are stress-testing the RCU implementation
418      itself, small RCU_FANOUT values allow you to test large-system
419      code paths on small(er) systems.
420
421      Select a specific number if testing RCU itself.
422      Take the default if unsure.
423
424config RCU_FANOUT_EXACT
425    bool "Disable tree-based hierarchical RCU auto-balancing"
426    depends on TREE_RCU || TREE_PREEMPT_RCU
427    default n
428    help
429      This option forces use of the exact RCU_FANOUT value specified,
430      regardless of imbalances in the hierarchy. This is useful for
431      testing RCU itself, and might one day be useful on systems with
432      strong NUMA behavior.
433
434      Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
435
436      Say N if unsure.
437
438config RCU_FAST_NO_HZ
439    bool "Accelerate last non-dyntick-idle CPU's grace periods"
440    depends on TREE_RCU && NO_HZ && SMP
441    default n
442    help
443      This option causes RCU to attempt to accelerate grace periods
444      in order to allow the final CPU to enter dynticks-idle state
445      more quickly. On the other hand, this option increases the
446      overhead of the dynticks-idle checking, particularly on systems
447      with large numbers of CPUs.
448
449      Say Y if energy efficiency is critically important, particularly
450          if you have relatively few CPUs.
451
452      Say N if you are unsure.
453
454config TREE_RCU_TRACE
455    def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
456    select DEBUG_FS
457    help
458      This option provides tracing for the TREE_RCU and
459      TREE_PREEMPT_RCU implementations, permitting Makefile to
460      trivially select kernel/rcutree_trace.c.
461
462endmenu # "RCU Subsystem"
463
464config IKCONFIG
465    tristate "Kernel .config support"
466    ---help---
467      This option enables the complete Linux kernel ".config" file
468      contents to be saved in the kernel. It provides documentation
469      of which kernel options are used in a running kernel or in an
470      on-disk kernel. This information can be extracted from the kernel
471      image file with the script scripts/extract-ikconfig and used as
472      input to rebuild the current kernel or to build another kernel.
473      It can also be extracted from a running kernel by reading
474      /proc/config.gz if enabled (below).
475
476config IKCONFIG_PROC
477    bool "Enable access to .config through /proc/config.gz"
478    depends on IKCONFIG && PROC_FS
479    ---help---
480      This option enables access to the kernel configuration file
481      through /proc/config.gz.
482
483config LOG_BUF_SHIFT
484    int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
485    range 12 21
486    default 17
487    help
488      Select kernel log buffer size as a power of 2.
489      Examples:
490               17 => 128 KB
491             16 => 64 KB
492                 15 => 32 KB
493                 14 => 16 KB
494             13 => 8 KB
495             12 => 4 KB
496
497#
498# Architectures with an unreliable sched_clock() should select this:
499#
500config HAVE_UNSTABLE_SCHED_CLOCK
501    bool
502
503menuconfig CGROUPS
504    boolean "Control Group support"
505    depends on EVENTFD
506    help
507      This option adds support for grouping sets of processes together, for
508      use with process control subsystems such as Cpusets, CFS, memory
509      controls or device isolation.
510      See
511        - Documentation/scheduler/sched-design-CFS.txt (CFS)
512        - Documentation/cgroups/ (features for grouping, isolation
513                      and resource control)
514
515      Say N if unsure.
516
517if CGROUPS
518
519config CGROUP_DEBUG
520    bool "Example debug cgroup subsystem"
521    default n
522    help
523      This option enables a simple cgroup subsystem that
524      exports useful debugging information about the cgroups
525      framework.
526
527      Say N if unsure.
528
529config CGROUP_NS
530    bool "Namespace cgroup subsystem"
531    help
532      Provides a simple namespace cgroup subsystem to
533      provide hierarchical naming of sets of namespaces,
534      for instance virtual servers and checkpoint/restart
535      jobs.
536
537config CGROUP_FREEZER
538    bool "Freezer cgroup subsystem"
539    help
540      Provides a way to freeze and unfreeze all tasks in a
541      cgroup.
542
543config CGROUP_DEVICE
544    bool "Device controller for cgroups"
545    help
546      Provides a cgroup implementing whitelists for devices which
547      a process in the cgroup can mknod or open.
548
549config CPUSETS
550    bool "Cpuset support"
551    help
552      This option will let you create and manage CPUSETs which
553      allow dynamically partitioning a system into sets of CPUs and
554      Memory Nodes and assigning tasks to run only within those sets.
555      This is primarily useful on large SMP or NUMA systems.
556
557      Say N if unsure.
558
559config PROC_PID_CPUSET
560    bool "Include legacy /proc/<pid>/cpuset file"
561    depends on CPUSETS
562    default y
563
564config CGROUP_CPUACCT
565    bool "Simple CPU accounting cgroup subsystem"
566    help
567      Provides a simple Resource Controller for monitoring the
568      total CPU consumed by the tasks in a cgroup.
569
570config RESOURCE_COUNTERS
571    bool "Resource counters"
572    help
573      This option enables controller independent resource accounting
574      infrastructure that works with cgroups.
575
576config CGROUP_MEM_RES_CTLR
577    bool "Memory Resource Controller for Control Groups"
578    depends on RESOURCE_COUNTERS
579    select MM_OWNER
580    help
581      Provides a memory resource controller that manages both anonymous
582      memory and page cache. (See Documentation/cgroups/memory.txt)
583
584      Note that setting this option increases fixed memory overhead
585      associated with each page of memory in the system. By this,
586      20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
587      usage tracking struct at boot. Total amount of this is printed out
588      at boot.
589
590      Only enable when you're ok with these trade offs and really
591      sure you need the memory resource controller. Even when you enable
592      this, you can set "cgroup_disable=memory" at your boot option to
593      disable memory resource controller and you can avoid overheads.
594      (and lose benefits of memory resource controller)
595
596      This config option also selects MM_OWNER config option, which
597      could in turn add some fork/exit overhead.
598
599config CGROUP_MEM_RES_CTLR_SWAP
600    bool "Memory Resource Controller Swap Extension"
601    depends on CGROUP_MEM_RES_CTLR && SWAP
602    help
603      Add swap management feature to memory resource controller. When you
604      enable this, you can limit mem+swap usage per cgroup. In other words,
605      when you disable this, memory resource controller has no cares to
606      usage of swap...a process can exhaust all of the swap. This extension
607      is useful when you want to avoid exhaustion swap but this itself
608      adds more overheads and consumes memory for remembering information.
609      Especially if you use 32bit system or small memory system, please
610      be careful about enabling this. When memory resource controller
611      is disabled by boot option, this will be automatically disabled and
612      there will be no overhead from this. Even when you set this config=y,
613      if boot option "noswapaccount" is set, swap will not be accounted.
614      Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
615      size is 4096bytes, 512k per 1Gbytes of swap.
616config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
617    bool "Memory Resource Controller Swap Extension enabled by default"
618    depends on CGROUP_MEM_RES_CTLR_SWAP
619    default y
620    help
621      Memory Resource Controller Swap Extension comes with its price in
622      a bigger memory consumption. General purpose distribution kernels
623      which want to enable the feautre but keep it disabled by default
624      and let the user enable it by swapaccount boot command line
625      parameter should have this option unselected.
626      For those who want to have the feature enabled by default should
627      select this option (if, for some reason, they need to disable it
628      then noswapaccount does the trick).
629
630menuconfig CGROUP_SCHED
631    bool "Group CPU scheduler"
632    depends on EXPERIMENTAL
633    default n
634    help
635      This feature lets CPU scheduler recognize task groups and control CPU
636      bandwidth allocation to such task groups. It uses cgroups to group
637      tasks.
638
639if CGROUP_SCHED
640config FAIR_GROUP_SCHED
641    bool "Group scheduling for SCHED_OTHER"
642    depends on CGROUP_SCHED
643    default CGROUP_SCHED
644
645config RT_GROUP_SCHED
646    bool "Group scheduling for SCHED_RR/FIFO"
647    depends on EXPERIMENTAL
648    depends on CGROUP_SCHED
649    default n
650    help
651      This feature lets you explicitly allocate real CPU bandwidth
652      to task groups. If enabled, it will also make it impossible to
653      schedule realtime tasks for non-root users until you allocate
654      realtime bandwidth for them.
655      See Documentation/scheduler/sched-rt-group.txt for more information.
656
657endif #CGROUP_SCHED
658
659config BLK_CGROUP
660    tristate "Block IO controller"
661    depends on BLOCK
662    default n
663    ---help---
664    Generic block IO controller cgroup interface. This is the common
665    cgroup interface which should be used by various IO controlling
666    policies.
667
668    Currently, CFQ IO scheduler uses it to recognize task groups and
669    control disk bandwidth allocation (proportional time slice allocation)
670    to such task groups. It is also used by bio throttling logic in
671    block layer to implement upper limit in IO rates on a device.
672
673    This option only enables generic Block IO controller infrastructure.
674    One needs to also enable actual IO controlling logic/policy. For
675    enabling proportional weight division of disk bandwidth in CFQ seti
676    CONFIG_CFQ_GROUP_IOSCHED=y and for enabling throttling policy set
677    CONFIG_BLK_THROTTLE=y.
678
679    See Documentation/cgroups/blkio-controller.txt for more information.
680
681config DEBUG_BLK_CGROUP
682    bool "Enable Block IO controller debugging"
683    depends on BLK_CGROUP
684    default n
685    ---help---
686    Enable some debugging help. Currently it exports additional stat
687    files in a cgroup which can be useful for debugging.
688
689endif # CGROUPS
690
691menuconfig NAMESPACES
692    bool "Namespaces support" if EMBEDDED
693    default !EMBEDDED
694    help
695      Provides the way to make tasks work with different objects using
696      the same id. For example same IPC id may refer to different objects
697      or same user id or pid may refer to different tasks when used in
698      different namespaces.
699
700if NAMESPACES
701
702config UTS_NS
703    bool "UTS namespace"
704    default y
705    help
706      In this namespace tasks see different info provided with the
707      uname() system call
708
709config IPC_NS
710    bool "IPC namespace"
711    depends on (SYSVIPC || POSIX_MQUEUE)
712    default y
713    help
714      In this namespace tasks work with IPC ids which correspond to
715      different IPC objects in different namespaces.
716
717config USER_NS
718    bool "User namespace (EXPERIMENTAL)"
719    depends on EXPERIMENTAL
720    default y
721    help
722      This allows containers, i.e. vservers, to use user namespaces
723      to provide different user info for different servers.
724      If unsure, say N.
725
726config PID_NS
727    bool "PID Namespaces"
728    default y
729    help
730      Support process id namespaces. This allows having multiple
731      processes with the same pid as long as they are in different
732      pid namespaces. This is a building block of containers.
733
734config NET_NS
735    bool "Network namespace"
736    depends on NET
737    default y
738    help
739      Allow user space to create what appear to be multiple instances
740      of the network stack.
741
742endif # NAMESPACES
743
744config MM_OWNER
745    bool
746
747config SYSFS_DEPRECATED
748    bool "enable deprecated sysfs features to support old userspace tools"
749    depends on SYSFS
750    default n
751    help
752      This option adds code that switches the layout of the "block" class
753      devices, to not show up in /sys/class/block/, but only in
754      /sys/block/.
755
756      This switch is only active when the sysfs.deprecated=1 boot option is
757      passed or the SYSFS_DEPRECATED_V2 option is set.
758
759      This option allows new kernels to run on old distributions and tools,
760      which might get confused by /sys/class/block/. Since 2007/2008 all
761      major distributions and tools handle this just fine.
762
763      Recent distributions and userspace tools after 2009/2010 depend on
764      the existence of /sys/class/block/, and will not work with this
765      option enabled.
766
767      Only if you are using a new kernel on an old distribution, you might
768      need to say Y here.
769
770config SYSFS_DEPRECATED_V2
771    bool "enabled deprecated sysfs features by default"
772    default n
773    depends on SYSFS
774    depends on SYSFS_DEPRECATED
775    help
776      Enable deprecated sysfs by default.
777
778      See the CONFIG_SYSFS_DEPRECATED option for more details about this
779      option.
780
781      Only if you are using a new kernel on an old distribution, you might
782      need to say Y here. Even then, odds are you would not need it
783      enabled, you can always pass the boot option if absolutely necessary.
784
785config RELAY
786    bool "Kernel->user space relay support (formerly relayfs)"
787    help
788      This option enables support for relay interface support in
789      certain file systems (such as debugfs).
790      It is designed to provide an efficient mechanism for tools and
791      facilities to relay large amounts of data from kernel space to
792      user space.
793
794      If unsure, say N.
795
796config BLK_DEV_INITRD
797    bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
798    depends on BROKEN || !FRV
799    help
800      The initial RAM filesystem is a ramfs which is loaded by the
801      boot loader (loadlin or lilo) and that is mounted as root
802      before the normal boot procedure. It is typically used to
803      load modules needed to mount the "real" root file system,
804      etc. See <file:Documentation/initrd.txt> for details.
805
806      If RAM disk support (BLK_DEV_RAM) is also included, this
807      also enables initial RAM disk (initrd) support and adds
808      15 Kbytes (more on some other architectures) to the kernel size.
809
810      If unsure say Y.
811
812if BLK_DEV_INITRD
813
814source "usr/Kconfig"
815
816endif
817
818config CC_OPTIMIZE_FOR_SIZE
819    bool "Optimize for size"
820    default y
821    help
822      Enabling this option will pass "-Os" instead of "-O2" to gcc
823      resulting in a smaller kernel.
824
825      If unsure, say Y.
826
827config SYSCTL
828    bool
829
830config ANON_INODES
831    bool
832
833menuconfig EMBEDDED
834    bool "Configure standard kernel features (for small systems)"
835    help
836      This option allows certain base kernel options and settings
837          to be disabled or tweaked. This is for specialized
838          environments which can tolerate a "non-standard" kernel.
839          Only use this if you really know what you are doing.
840
841config UID16
842    bool "Enable 16-bit UID system calls" if EMBEDDED
843    depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
844    default y
845    help
846      This enables the legacy 16-bit UID syscall wrappers.
847
848config SYSCTL_SYSCALL
849    bool "Sysctl syscall support" if EMBEDDED
850    depends on PROC_SYSCTL
851    default y
852    select SYSCTL
853    ---help---
854      sys_sysctl uses binary paths that have been found challenging
855      to properly maintain and use. The interface in /proc/sys
856      using paths with ascii names is now the primary path to this
857      information.
858
859      Almost nothing using the binary sysctl interface so if you are
860      trying to save some space it is probably safe to disable this,
861      making your kernel marginally smaller.
862
863      If unsure say Y here.
864
865config KALLSYMS
866     bool "Load all symbols for debugging/ksymoops" if EMBEDDED
867     default y
868     help
869       Say Y here to let the kernel print out symbolic crash information and
870       symbolic stack backtraces. This increases the size of the kernel
871       somewhat, as all symbols have to be loaded into the kernel image.
872
873config KALLSYMS_ALL
874    bool "Include all symbols in kallsyms"
875    depends on DEBUG_KERNEL && KALLSYMS
876    help
877       Normally kallsyms only contains the symbols of functions, for nicer
878       OOPS messages. Some debuggers can use kallsyms for other
879       symbols too: say Y here to include all symbols, if you need them
880       and you don't care about adding 300k to the size of your kernel.
881
882       Say N.
883
884config KALLSYMS_EXTRA_PASS
885    bool "Do an extra kallsyms pass"
886    depends on KALLSYMS
887    help
888       If kallsyms is not working correctly, the build will fail with
889       inconsistent kallsyms data. If that occurs, log a bug report and
890       turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
891       Always say N here unless you find a bug in kallsyms, which must be
892       reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
893       you wait for kallsyms to be fixed.
894
895
896config HOTPLUG
897    bool "Support for hot-pluggable devices" if EMBEDDED
898    default y
899    help
900      This option is provided for the case where no hotplug or uevent
901      capabilities is wanted by the kernel. You should only consider
902      disabling this option for embedded systems that do not use modules, a
903      dynamic /dev tree, or dynamic device discovery. Just say Y.
904
905config PRINTK
906    default y
907    bool "Enable support for printk" if EMBEDDED
908    help
909      This option enables normal printk support. Removing it
910      eliminates most of the message strings from the kernel image
911      and makes the kernel more or less silent. As this makes it
912      very difficult to diagnose system problems, saying N here is
913      strongly discouraged.
914
915config BUG
916    bool "BUG() support" if EMBEDDED
917    default y
918    help
919          Disabling this option eliminates support for BUG and WARN, reducing
920          the size of your kernel image and potentially quietly ignoring
921          numerous fatal conditions. You should only consider disabling this
922          option for embedded systems with no facilities for reporting errors.
923          Just say Y.
924
925config ELF_CORE
926    default y
927    bool "Enable ELF core dumps" if EMBEDDED
928    help
929      Enable support for generating core dumps. Disabling saves about 4k.
930
931config PCSPKR_PLATFORM
932    bool "Enable PC-Speaker support" if EMBEDDED
933    depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
934    default y
935    help
936          This option allows to disable the internal PC-Speaker
937          support, saving some memory.
938
939config BASE_FULL
940    default y
941    bool "Enable full-sized data structures for core" if EMBEDDED
942    help
943      Disabling this option reduces the size of miscellaneous core
944      kernel data structures. This saves memory on small machines,
945      but may reduce performance.
946
947config FUTEX
948    bool "Enable futex support" if EMBEDDED
949    default y
950    select RT_MUTEXES
951    help
952      Disabling this option will cause the kernel to be built without
953      support for "fast userspace mutexes". The resulting kernel may not
954      run glibc-based applications correctly.
955
956config EPOLL
957    bool "Enable eventpoll support" if EMBEDDED
958    default y
959    select ANON_INODES
960    help
961      Disabling this option will cause the kernel to be built without
962      support for epoll family of system calls.
963
964config SIGNALFD
965    bool "Enable signalfd() system call" if EMBEDDED
966    select ANON_INODES
967    default y
968    help
969      Enable the signalfd() system call that allows to receive signals
970      on a file descriptor.
971
972      If unsure, say Y.
973
974config TIMERFD
975    bool "Enable timerfd() system call" if EMBEDDED
976    select ANON_INODES
977    default y
978    help
979      Enable the timerfd() system call that allows to receive timer
980      events on a file descriptor.
981
982      If unsure, say Y.
983
984config EVENTFD
985    bool "Enable eventfd() system call" if EMBEDDED
986    select ANON_INODES
987    default y
988    help
989      Enable the eventfd() system call that allows to receive both
990      kernel notification (ie. KAIO) or userspace notifications.
991
992      If unsure, say Y.
993
994config SHMEM
995    bool "Use full shmem filesystem" if EMBEDDED
996    default y
997    depends on MMU
998    help
999      The shmem is an internal filesystem used to manage shared memory.
1000      It is backed by swap and manages resource limits. It is also exported
1001      to userspace as tmpfs if TMPFS is enabled. Disabling this
1002      option replaces shmem and tmpfs with the much simpler ramfs code,
1003      which may be appropriate on small systems without swap.
1004
1005config AIO
1006    bool "Enable AIO support" if EMBEDDED
1007    default y
1008    help
1009      This option enables POSIX asynchronous I/O which may by used
1010          by some high performance threaded applications. Disabling
1011          this option saves about 7k.
1012
1013config HAVE_PERF_EVENTS
1014    bool
1015    help
1016      See tools/perf/design.txt for details.
1017
1018config PERF_USE_VMALLOC
1019    bool
1020    help
1021      See tools/perf/design.txt for details
1022
1023menu "Kernel Performance Events And Counters"
1024
1025config PERF_EVENTS
1026    bool "Kernel performance events and counters"
1027    default y if (PROFILING || PERF_COUNTERS)
1028    depends on HAVE_PERF_EVENTS
1029    select ANON_INODES
1030    select IRQ_WORK
1031    help
1032      Enable kernel support for various performance events provided
1033      by software and hardware.
1034
1035      Software events are supported either built-in or via the
1036      use of generic tracepoints.
1037
1038      Most modern CPUs support performance events via performance
1039      counter registers. These registers count the number of certain
1040      types of hw events: such as instructions executed, cachemisses
1041      suffered, or branches mis-predicted - without slowing down the
1042      kernel or applications. These registers can also trigger interrupts
1043      when a threshold number of events have passed - and can thus be
1044      used to profile the code that runs on that CPU.
1045
1046      The Linux Performance Event subsystem provides an abstraction of
1047      these software and hardware event capabilities, available via a
1048      system call and used by the "perf" utility in tools/perf/. It
1049      provides per task and per CPU counters, and it provides event
1050      capabilities on top of those.
1051
1052      Say Y if unsure.
1053
1054config PERF_COUNTERS
1055    bool "Kernel performance counters (old config option)"
1056    depends on HAVE_PERF_EVENTS
1057    help
1058      This config has been obsoleted by the PERF_EVENTS
1059      config option - please see that one for details.
1060
1061      It has no effect on the kernel whether you enable
1062      it or not, it is a compatibility placeholder.
1063
1064      Say N if unsure.
1065
1066config DEBUG_PERF_USE_VMALLOC
1067    default n
1068    bool "Debug: use vmalloc to back perf mmap() buffers"
1069    depends on PERF_EVENTS && DEBUG_KERNEL
1070    select PERF_USE_VMALLOC
1071    help
1072     Use vmalloc memory to back perf mmap() buffers.
1073
1074     Mostly useful for debugging the vmalloc code on platforms
1075     that don't require it.
1076
1077     Say N if unsure.
1078
1079endmenu
1080
1081config VM_EVENT_COUNTERS
1082    default y
1083    bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1084    help
1085      VM event counters are needed for event counts to be shown.
1086      This option allows the disabling of the VM event counters
1087      on EMBEDDED systems. /proc/vmstat will only show page counts
1088      if VM event counters are disabled.
1089
1090config PCI_QUIRKS
1091    default y
1092    bool "Enable PCI quirk workarounds" if EMBEDDED
1093    depends on PCI
1094    help
1095      This enables workarounds for various PCI chipset
1096          bugs/quirks. Disable this only if your target machine is
1097          unaffected by PCI quirks.
1098
1099config SLUB_DEBUG
1100    default y
1101    bool "Enable SLUB debugging support" if EMBEDDED
1102    depends on SLUB && SYSFS
1103    help
1104      SLUB has extensive debug support features. Disabling these can
1105      result in significant savings in code size. This also disables
1106      SLUB sysfs support. /sys/slab will not exist and there will be
1107      no support for cache validation etc.
1108
1109config COMPAT_BRK
1110    bool "Disable heap randomization"
1111    default y
1112    help
1113      Randomizing heap placement makes heap exploits harder, but it
1114      also breaks ancient binaries (including anything libc5 based).
1115      This option changes the bootup default to heap randomization
1116      disabled, and can be overridden at runtime by setting
1117      /proc/sys/kernel/randomize_va_space to 2.
1118
1119      On non-ancient distros (post-2000 ones) N is usually a safe choice.
1120
1121choice
1122    prompt "Choose SLAB allocator"
1123    default SLUB
1124    help
1125       This option allows to select a slab allocator.
1126
1127config SLAB
1128    bool "SLAB"
1129    help
1130      The regular slab allocator that is established and known to work
1131      well in all environments. It organizes cache hot objects in
1132      per cpu and per node queues.
1133
1134config SLUB
1135    bool "SLUB (Unqueued Allocator)"
1136    help
1137       SLUB is a slab allocator that minimizes cache line usage
1138       instead of managing queues of cached objects (SLAB approach).
1139       Per cpu caching is realized using slabs of objects instead
1140       of queues of objects. SLUB can use memory efficiently
1141       and has enhanced diagnostics. SLUB is the default choice for
1142       a slab allocator.
1143
1144config SLOB
1145    depends on EMBEDDED
1146    bool "SLOB (Simple Allocator)"
1147    help
1148       SLOB replaces the stock allocator with a drastically simpler
1149       allocator. SLOB is generally more space efficient but
1150       does not perform as well on large systems.
1151
1152endchoice
1153
1154config MMAP_ALLOW_UNINITIALIZED
1155    bool "Allow mmapped anonymous memory to be uninitialized"
1156    depends on EMBEDDED && !MMU
1157    default n
1158    help
1159      Normally, and according to the Linux spec, anonymous memory obtained
1160      from mmap() has it's contents cleared before it is passed to
1161      userspace. Enabling this config option allows you to request that
1162      mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1163      providing a huge performance boost. If this option is not enabled,
1164      then the flag will be ignored.
1165
1166      This is taken advantage of by uClibc's malloc(), and also by
1167      ELF-FDPIC binfmt's brk and stack allocator.
1168
1169      Because of the obvious security issues, this option should only be
1170      enabled on embedded devices where you control what is run in
1171      userspace. Since that isn't generally a problem on no-MMU systems,
1172      it is normally safe to say Y here.
1173
1174      See Documentation/nommu-mmap.txt for more information.
1175
1176config PROFILING
1177    bool "Profiling support"
1178    help
1179      Say Y here to enable the extended profiling support mechanisms used
1180      by profilers such as OProfile.
1181
1182#
1183# Place an empty function call at each tracepoint site. Can be
1184# dynamically changed for a probe function.
1185#
1186config TRACEPOINTS
1187    bool
1188
1189source "arch/Kconfig"
1190
1191endmenu # General setup
1192
1193config HAVE_GENERIC_DMA_COHERENT
1194    bool
1195    default n
1196
1197config SLABINFO
1198    bool
1199    depends on PROC_FS
1200    depends on SLAB || SLUB_DEBUG
1201    default y
1202
1203config RT_MUTEXES
1204    boolean
1205
1206config BASE_SMALL
1207    int
1208    default 0 if BASE_FULL
1209    default 1 if !BASE_FULL
1210
1211menuconfig MODULES
1212    bool "Enable loadable module support"
1213    help
1214      Kernel modules are small pieces of compiled code which can
1215      be inserted in the running kernel, rather than being
1216      permanently built into the kernel. You use the "modprobe"
1217      tool to add (and sometimes remove) them. If you say Y here,
1218      many parts of the kernel can be built as modules (by
1219      answering M instead of Y where indicated): this is most
1220      useful for infrequently used options which are not required
1221      for booting. For more information, see the man pages for
1222      modprobe, lsmod, modinfo, insmod and rmmod.
1223
1224      If you say Y here, you will need to run "make
1225      modules_install" to put the modules under /lib/modules/
1226      where modprobe can find them (you may need to be root to do
1227      this).
1228
1229      If unsure, say Y.
1230
1231if MODULES
1232
1233config MODULE_FORCE_LOAD
1234    bool "Forced module loading"
1235    default n
1236    help
1237      Allow loading of modules without version information (ie. modprobe
1238      --force). Forced module loading sets the 'F' (forced) taint flag and
1239      is usually a really bad idea.
1240
1241config MODULE_UNLOAD
1242    bool "Module unloading"
1243    help
1244      Without this option you will not be able to unload any
1245      modules (note that some modules may not be unloadable
1246      anyway), which makes your kernel smaller, faster
1247      and simpler. If unsure, say Y.
1248
1249config MODULE_FORCE_UNLOAD
1250    bool "Forced module unloading"
1251    depends on MODULE_UNLOAD && EXPERIMENTAL
1252    help
1253      This option allows you to force a module to unload, even if the
1254      kernel believes it is unsafe: the kernel will remove the module
1255      without waiting for anyone to stop using it (using the -f option to
1256      rmmod). This is mainly for kernel developers and desperate users.
1257      If unsure, say N.
1258
1259config MODVERSIONS
1260    bool "Module versioning support"
1261    help
1262      Usually, you have to use modules compiled with your kernel.
1263      Saying Y here makes it sometimes possible to use modules
1264      compiled for different kernels, by adding enough information
1265      to the modules to (hopefully) spot any changes which would
1266      make them incompatible with the kernel you are running. If
1267      unsure, say N.
1268
1269config MODULE_SRCVERSION_ALL
1270    bool "Source checksum for all modules"
1271    help
1272      Modules which contain a MODULE_VERSION get an extra "srcversion"
1273      field inserted into their modinfo section, which contains a
1274          sum of the source files which made it. This helps maintainers
1275      see exactly which source was used to build a module (since
1276      others sometimes change the module source without updating
1277      the version). With this option, such a "srcversion" field
1278      will be created for all modules. If unsure, say N.
1279
1280endif # MODULES
1281
1282config INIT_ALL_POSSIBLE
1283    bool
1284    help
1285      Back when each arch used to define their own cpu_online_map and
1286      cpu_possible_map, some of them chose to initialize cpu_possible_map
1287      with all 1s, and others with all 0s. When they were centralised,
1288      it was better to provide this option than to break all the archs
1289      and have several arch maintainers pursuing me down dark alleys.
1290
1291config STOP_MACHINE
1292    bool
1293    default y
1294    depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1295    help
1296      Need stop_machine() primitive.
1297
1298source "block/Kconfig"
1299
1300config PREEMPT_NOTIFIERS
1301    bool
1302
1303config PADATA
1304    depends on SMP
1305    bool
1306
1307source "kernel/Kconfig.locks"
1308

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