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54      drivers that have been replaced by something else, and/or are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_XZ
134    bool
135
136config HAVE_KERNEL_LZO
137    bool
138
139choice
140    prompt "Kernel compression mode"
141    default KERNEL_GZIP
142    depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
143    help
144      The linux kernel is a kind of self-extracting executable.
145      Several compression algorithms are available, which differ
146      in efficiency, compression and decompression speed.
147      Compression speed is only relevant when building a kernel.
148      Decompression speed is relevant at each boot.
149
150      If you have any problems with bzip2 or lzma compressed
151      kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
152      version of this functionality (bzip2 only), for 2.4, was
153      supplied by Christian Ludwig)
154
155      High compression options are mostly useful for users, who
156      are low on disk space (embedded systems), but for whom ram
157      size matters less.
158
159      If in doubt, select 'gzip'
160
161config KERNEL_GZIP
162    bool "Gzip"
163    depends on HAVE_KERNEL_GZIP
164    help
165      The old and tried gzip compression. It provides a good balance
166      between compression ratio and decompression speed.
167
168config KERNEL_BZIP2
169    bool "Bzip2"
170    depends on HAVE_KERNEL_BZIP2
171    help
172      Its compression ratio and speed is intermediate.
173      Decompression speed is slowest among the three. The kernel
174      size is about 10% smaller with bzip2, in comparison to gzip.
175      Bzip2 uses a large amount of memory. For modern kernels you
176      will need at least 8MB RAM or more for booting.
177
178config KERNEL_LZMA
179    bool "LZMA"
180    depends on HAVE_KERNEL_LZMA
181    help
182      The most recent compression algorithm.
183      Its ratio is best, decompression speed is between the other
184      two. Compression is slowest. The kernel size is about 33%
185      smaller with LZMA in comparison to gzip.
186
187config KERNEL_XZ
188    bool "XZ"
189    depends on HAVE_KERNEL_XZ
190    help
191      XZ uses the LZMA2 algorithm and instruction set specific
192      BCJ filters which can improve compression ratio of executable
193      code. The size of the kernel is about 30% smaller with XZ in
194      comparison to gzip. On architectures for which there is a BCJ
195      filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
196      will create a few percent smaller kernel than plain LZMA.
197
198      The speed is about the same as with LZMA: The decompression
199      speed of XZ is better than that of bzip2 but worse than gzip
200      and LZO. Compression is slow.
201
202config KERNEL_LZO
203    bool "LZO"
204    depends on HAVE_KERNEL_LZO
205    help
206      Its compression ratio is the poorest among the 4. The kernel
207      size is about 10% bigger than gzip; however its speed
208      (both compression and decompression) is the fastest.
209
210endchoice
211
212config SWAP
213    bool "Support for paging of anonymous memory (swap)"
214    depends on MMU && BLOCK
215    default y
216    help
217      This option allows you to choose whether you want to have support
218      for so called swap devices or swap files in your kernel that are
219      used to provide more virtual memory than the actual RAM present
220      in your computer. If unsure say Y.
221
222config SYSVIPC
223    bool "System V IPC"
224    ---help---
225      Inter Process Communication is a suite of library functions and
226      system calls which let processes (running programs) synchronize and
227      exchange information. It is generally considered to be a good thing,
228      and some programs won't run unless you say Y here. In particular, if
229      you want to run the DOS emulator dosemu under Linux (read the
230      DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
231      you'll need to say Y here.
232
233      You can find documentation about IPC with "info ipc" and also in
234      section 6.4 of the Linux Programmer's Guide, available from
235      <http://www.tldp.org/guides.html>.
236
237config SYSVIPC_SYSCTL
238    bool
239    depends on SYSVIPC
240    depends on SYSCTL
241    default y
242
243config POSIX_MQUEUE
244    bool "POSIX Message Queues"
245    depends on NET && EXPERIMENTAL
246    ---help---
247      POSIX variant of message queues is a part of IPC. In POSIX message
248      queues every message has a priority which decides about succession
249      of receiving it by a process. If you want to compile and run
250      programs written e.g. for Solaris with use of its POSIX message
251      queues (functions mq_*) say Y here.
252
253      POSIX message queues are visible as a filesystem called 'mqueue'
254      and can be mounted somewhere if you want to do filesystem
255      operations on message queues.
256
257      If unsure, say Y.
258
259config POSIX_MQUEUE_SYSCTL
260    bool
261    depends on POSIX_MQUEUE
262    depends on SYSCTL
263    default y
264
265config BSD_PROCESS_ACCT
266    bool "BSD Process Accounting"
267    help
268      If you say Y here, a user level program will be able to instruct the
269      kernel (via a special system call) to write process accounting
270      information to a file: whenever a process exits, information about
271      that process will be appended to the file by the kernel. The
272      information includes things such as creation time, owning user,
273      command name, memory usage, controlling terminal etc. (the complete
274      list is in the struct acct in <file:include/linux/acct.h>). It is
275      up to the user level program to do useful things with this
276      information. This is generally a good idea, so say Y.
277
278config BSD_PROCESS_ACCT_V3
279    bool "BSD Process Accounting version 3 file format"
280    depends on BSD_PROCESS_ACCT
281    default n
282    help
283      If you say Y here, the process accounting information is written
284      in a new file format that also logs the process IDs of each
285      process and it's parent. Note that this file format is incompatible
286      with previous v0/v1/v2 file formats, so you will need updated tools
287      for processing it. A preliminary version of these tools is available
288      at <http://www.gnu.org/software/acct/>.
289
290config TASKSTATS
291    bool "Export task/process statistics through netlink (EXPERIMENTAL)"
292    depends on NET
293    default n
294    help
295      Export selected statistics for tasks/processes through the
296      generic netlink interface. Unlike BSD process accounting, the
297      statistics are available during the lifetime of tasks/processes as
298      responses to commands. Like BSD accounting, they are sent to user
299      space on task exit.
300
301      Say N if unsure.
302
303config TASK_DELAY_ACCT
304    bool "Enable per-task delay accounting (EXPERIMENTAL)"
305    depends on TASKSTATS
306    help
307      Collect information on time spent by a task waiting for system
308      resources like cpu, synchronous block I/O completion and swapping
309      in pages. Such statistics can help in setting a task's priorities
310      relative to other tasks for cpu, io, rss limits etc.
311
312      Say N if unsure.
313
314config TASK_XACCT
315    bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
316    depends on TASKSTATS
317    help
318      Collect extended task accounting data and send the data
319      to userland for processing over the taskstats interface.
320
321      Say N if unsure.
322
323config TASK_IO_ACCOUNTING
324    bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
325    depends on TASK_XACCT
326    help
327      Collect information on the number of bytes of storage I/O which this
328      task has caused.
329
330      Say N if unsure.
331
332config AUDIT
333    bool "Auditing support"
334    depends on NET
335    help
336      Enable auditing infrastructure that can be used with another
337      kernel subsystem, such as SELinux (which requires this for
338      logging of avc messages output). Does not do system-call
339      auditing without CONFIG_AUDITSYSCALL.
340
341config AUDITSYSCALL
342    bool "Enable system-call auditing support"
343    depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
344    default y if SECURITY_SELINUX
345    help
346      Enable low-overhead system-call auditing infrastructure that
347      can be used independently or with another kernel subsystem,
348      such as SELinux.
349
350config AUDIT_WATCH
351    def_bool y
352    depends on AUDITSYSCALL
353    select FSNOTIFY
354
355config AUDIT_TREE
356    def_bool y
357    depends on AUDITSYSCALL
358    select FSNOTIFY
359
360source "kernel/irq/Kconfig"
361
362menu "RCU Subsystem"
363
364choice
365    prompt "RCU Implementation"
366    default TREE_RCU
367
368config TREE_RCU
369    bool "Tree-based hierarchical RCU"
370    depends on !PREEMPT && SMP
371    help
372      This option selects the RCU implementation that is
373      designed for very large SMP system with hundreds or
374      thousands of CPUs. It also scales down nicely to
375      smaller systems.
376
377config TREE_PREEMPT_RCU
378    bool "Preemptible tree-based hierarchical RCU"
379    depends on PREEMPT
380    help
381      This option selects the RCU implementation that is
382      designed for very large SMP systems with hundreds or
383      thousands of CPUs, but for which real-time response
384      is also required. It also scales down nicely to
385      smaller systems.
386
387config TINY_RCU
388    bool "UP-only small-memory-footprint RCU"
389    depends on !SMP
390    help
391      This option selects the RCU implementation that is
392      designed for UP systems from which real-time response
393      is not required. This option greatly reduces the
394      memory footprint of RCU.
395
396config TINY_PREEMPT_RCU
397    bool "Preemptible UP-only small-memory-footprint RCU"
398    depends on !SMP && PREEMPT
399    help
400      This option selects the RCU implementation that is designed
401      for real-time UP systems. This option greatly reduces the
402      memory footprint of RCU.
403
404endchoice
405
406config PREEMPT_RCU
407    def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
408    help
409      This option enables preemptible-RCU code that is common between
410      the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
411
412config RCU_TRACE
413    bool "Enable tracing for RCU"
414    help
415      This option provides tracing in RCU which presents stats
416      in debugfs for debugging RCU implementation.
417
418      Say Y here if you want to enable RCU tracing
419      Say N if you are unsure.
420
421config RCU_FANOUT
422    int "Tree-based hierarchical RCU fanout value"
423    range 2 64 if 64BIT
424    range 2 32 if !64BIT
425    depends on TREE_RCU || TREE_PREEMPT_RCU
426    default 64 if 64BIT
427    default 32 if !64BIT
428    help
429      This option controls the fanout of hierarchical implementations
430      of RCU, allowing RCU to work efficiently on machines with
431      large numbers of CPUs. This value must be at least the fourth
432      root of NR_CPUS, which allows NR_CPUS to be insanely large.
433      The default value of RCU_FANOUT should be used for production
434      systems, but if you are stress-testing the RCU implementation
435      itself, small RCU_FANOUT values allow you to test large-system
436      code paths on small(er) systems.
437
438      Select a specific number if testing RCU itself.
439      Take the default if unsure.
440
441config RCU_FANOUT_EXACT
442    bool "Disable tree-based hierarchical RCU auto-balancing"
443    depends on TREE_RCU || TREE_PREEMPT_RCU
444    default n
445    help
446      This option forces use of the exact RCU_FANOUT value specified,
447      regardless of imbalances in the hierarchy. This is useful for
448      testing RCU itself, and might one day be useful on systems with
449      strong NUMA behavior.
450
451      Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
452
453      Say N if unsure.
454
455config RCU_FAST_NO_HZ
456    bool "Accelerate last non-dyntick-idle CPU's grace periods"
457    depends on TREE_RCU && NO_HZ && SMP
458    default n
459    help
460      This option causes RCU to attempt to accelerate grace periods
461      in order to allow the final CPU to enter dynticks-idle state
462      more quickly. On the other hand, this option increases the
463      overhead of the dynticks-idle checking, particularly on systems
464      with large numbers of CPUs.
465
466      Say Y if energy efficiency is critically important, particularly
467          if you have relatively few CPUs.
468
469      Say N if you are unsure.
470
471config TREE_RCU_TRACE
472    def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
473    select DEBUG_FS
474    help
475      This option provides tracing for the TREE_RCU and
476      TREE_PREEMPT_RCU implementations, permitting Makefile to
477      trivially select kernel/rcutree_trace.c.
478
479config RCU_BOOST
480    bool "Enable RCU priority boosting"
481    depends on RT_MUTEXES && TINY_PREEMPT_RCU
482    default n
483    help
484      This option boosts the priority of preempted RCU readers that
485      block the current preemptible RCU grace period for too long.
486      This option also prevents heavy loads from blocking RCU
487      callback invocation for all flavors of RCU.
488
489      Say Y here if you are working with real-time apps or heavy loads
490      Say N here if you are unsure.
491
492config RCU_BOOST_PRIO
493    int "Real-time priority to boost RCU readers to"
494    range 1 99
495    depends on RCU_BOOST
496    default 1
497    help
498      This option specifies the real-time priority to which preempted
499      RCU readers are to be boosted. If you are working with CPU-bound
500      real-time applications, you should specify a priority higher then
501      the highest-priority CPU-bound application.
502
503      Specify the real-time priority, or take the default if unsure.
504
505config RCU_BOOST_DELAY
506    int "Milliseconds to delay boosting after RCU grace-period start"
507    range 0 3000
508    depends on RCU_BOOST
509    default 500
510    help
511      This option specifies the time to wait after the beginning of
512      a given grace period before priority-boosting preempted RCU
513      readers blocking that grace period. Note that any RCU reader
514      blocking an expedited RCU grace period is boosted immediately.
515
516      Accept the default if unsure.
517
518endmenu # "RCU Subsystem"
519
520config IKCONFIG
521    tristate "Kernel .config support"
522    ---help---
523      This option enables the complete Linux kernel ".config" file
524      contents to be saved in the kernel. It provides documentation
525      of which kernel options are used in a running kernel or in an
526      on-disk kernel. This information can be extracted from the kernel
527      image file with the script scripts/extract-ikconfig and used as
528      input to rebuild the current kernel or to build another kernel.
529      It can also be extracted from a running kernel by reading
530      /proc/config.gz if enabled (below).
531
532config IKCONFIG_PROC
533    bool "Enable access to .config through /proc/config.gz"
534    depends on IKCONFIG && PROC_FS
535    ---help---
536      This option enables access to the kernel configuration file
537      through /proc/config.gz.
538
539config LOG_BUF_SHIFT
540    int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
541    range 12 21
542    default 17
543    help
544      Select kernel log buffer size as a power of 2.
545      Examples:
546               17 => 128 KB
547             16 => 64 KB
548                 15 => 32 KB
549                 14 => 16 KB
550             13 => 8 KB
551             12 => 4 KB
552
553#
554# Architectures with an unreliable sched_clock() should select this:
555#
556config HAVE_UNSTABLE_SCHED_CLOCK
557    bool
558
559menuconfig CGROUPS
560    boolean "Control Group support"
561    depends on EVENTFD
562    help
563      This option adds support for grouping sets of processes together, for
564      use with process control subsystems such as Cpusets, CFS, memory
565      controls or device isolation.
566      See
567        - Documentation/scheduler/sched-design-CFS.txt (CFS)
568        - Documentation/cgroups/ (features for grouping, isolation
569                      and resource control)
570
571      Say N if unsure.
572
573if CGROUPS
574
575config CGROUP_DEBUG
576    bool "Example debug cgroup subsystem"
577    default n
578    help
579      This option enables a simple cgroup subsystem that
580      exports useful debugging information about the cgroups
581      framework.
582
583      Say N if unsure.
584
585config CGROUP_NS
586    bool "Namespace cgroup subsystem"
587    help
588      Provides a simple namespace cgroup subsystem to
589      provide hierarchical naming of sets of namespaces,
590      for instance virtual servers and checkpoint/restart
591      jobs.
592
593config CGROUP_FREEZER
594    bool "Freezer cgroup subsystem"
595    help
596      Provides a way to freeze and unfreeze all tasks in a
597      cgroup.
598
599config CGROUP_DEVICE
600    bool "Device controller for cgroups"
601    help
602      Provides a cgroup implementing whitelists for devices which
603      a process in the cgroup can mknod or open.
604
605config CPUSETS
606    bool "Cpuset support"
607    help
608      This option will let you create and manage CPUSETs which
609      allow dynamically partitioning a system into sets of CPUs and
610      Memory Nodes and assigning tasks to run only within those sets.
611      This is primarily useful on large SMP or NUMA systems.
612
613      Say N if unsure.
614
615config PROC_PID_CPUSET
616    bool "Include legacy /proc/<pid>/cpuset file"
617    depends on CPUSETS
618    default y
619
620config CGROUP_CPUACCT
621    bool "Simple CPU accounting cgroup subsystem"
622    help
623      Provides a simple Resource Controller for monitoring the
624      total CPU consumed by the tasks in a cgroup.
625
626config RESOURCE_COUNTERS
627    bool "Resource counters"
628    help
629      This option enables controller independent resource accounting
630      infrastructure that works with cgroups.
631
632config CGROUP_MEM_RES_CTLR
633    bool "Memory Resource Controller for Control Groups"
634    depends on RESOURCE_COUNTERS
635    select MM_OWNER
636    help
637      Provides a memory resource controller that manages both anonymous
638      memory and page cache. (See Documentation/cgroups/memory.txt)
639
640      Note that setting this option increases fixed memory overhead
641      associated with each page of memory in the system. By this,
642      20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
643      usage tracking struct at boot. Total amount of this is printed out
644      at boot.
645
646      Only enable when you're ok with these trade offs and really
647      sure you need the memory resource controller. Even when you enable
648      this, you can set "cgroup_disable=memory" at your boot option to
649      disable memory resource controller and you can avoid overheads.
650      (and lose benefits of memory resource controller)
651
652      This config option also selects MM_OWNER config option, which
653      could in turn add some fork/exit overhead.
654
655config CGROUP_MEM_RES_CTLR_SWAP
656    bool "Memory Resource Controller Swap Extension"
657    depends on CGROUP_MEM_RES_CTLR && SWAP
658    help
659      Add swap management feature to memory resource controller. When you
660      enable this, you can limit mem+swap usage per cgroup. In other words,
661      when you disable this, memory resource controller has no cares to
662      usage of swap...a process can exhaust all of the swap. This extension
663      is useful when you want to avoid exhaustion swap but this itself
664      adds more overheads and consumes memory for remembering information.
665      Especially if you use 32bit system or small memory system, please
666      be careful about enabling this. When memory resource controller
667      is disabled by boot option, this will be automatically disabled and
668      there will be no overhead from this. Even when you set this config=y,
669      if boot option "noswapaccount" is set, swap will not be accounted.
670      Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
671      size is 4096bytes, 512k per 1Gbytes of swap.
672config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
673    bool "Memory Resource Controller Swap Extension enabled by default"
674    depends on CGROUP_MEM_RES_CTLR_SWAP
675    default y
676    help
677      Memory Resource Controller Swap Extension comes with its price in
678      a bigger memory consumption. General purpose distribution kernels
679      which want to enable the feature but keep it disabled by default
680      and let the user enable it by swapaccount boot command line
681      parameter should have this option unselected.
682      For those who want to have the feature enabled by default should
683      select this option (if, for some reason, they need to disable it
684      then noswapaccount does the trick).
685
686menuconfig CGROUP_SCHED
687    bool "Group CPU scheduler"
688    depends on EXPERIMENTAL
689    default n
690    help
691      This feature lets CPU scheduler recognize task groups and control CPU
692      bandwidth allocation to such task groups. It uses cgroups to group
693      tasks.
694
695if CGROUP_SCHED
696config FAIR_GROUP_SCHED
697    bool "Group scheduling for SCHED_OTHER"
698    depends on CGROUP_SCHED
699    default CGROUP_SCHED
700
701config RT_GROUP_SCHED
702    bool "Group scheduling for SCHED_RR/FIFO"
703    depends on EXPERIMENTAL
704    depends on CGROUP_SCHED
705    default n
706    help
707      This feature lets you explicitly allocate real CPU bandwidth
708      to task groups. If enabled, it will also make it impossible to
709      schedule realtime tasks for non-root users until you allocate
710      realtime bandwidth for them.
711      See Documentation/scheduler/sched-rt-group.txt for more information.
712
713endif #CGROUP_SCHED
714
715config BLK_CGROUP
716    tristate "Block IO controller"
717    depends on BLOCK
718    default n
719    ---help---
720    Generic block IO controller cgroup interface. This is the common
721    cgroup interface which should be used by various IO controlling
722    policies.
723
724    Currently, CFQ IO scheduler uses it to recognize task groups and
725    control disk bandwidth allocation (proportional time slice allocation)
726    to such task groups. It is also used by bio throttling logic in
727    block layer to implement upper limit in IO rates on a device.
728
729    This option only enables generic Block IO controller infrastructure.
730    One needs to also enable actual IO controlling logic/policy. For
731    enabling proportional weight division of disk bandwidth in CFQ seti
732    CONFIG_CFQ_GROUP_IOSCHED=y and for enabling throttling policy set
733    CONFIG_BLK_THROTTLE=y.
734
735    See Documentation/cgroups/blkio-controller.txt for more information.
736
737config DEBUG_BLK_CGROUP
738    bool "Enable Block IO controller debugging"
739    depends on BLK_CGROUP
740    default n
741    ---help---
742    Enable some debugging help. Currently it exports additional stat
743    files in a cgroup which can be useful for debugging.
744
745endif # CGROUPS
746
747menuconfig NAMESPACES
748    bool "Namespaces support" if EXPERT
749    default !EXPERT
750    help
751      Provides the way to make tasks work with different objects using
752      the same id. For example same IPC id may refer to different objects
753      or same user id or pid may refer to different tasks when used in
754      different namespaces.
755
756if NAMESPACES
757
758config UTS_NS
759    bool "UTS namespace"
760    default y
761    help
762      In this namespace tasks see different info provided with the
763      uname() system call
764
765config IPC_NS
766    bool "IPC namespace"
767    depends on (SYSVIPC || POSIX_MQUEUE)
768    default y
769    help
770      In this namespace tasks work with IPC ids which correspond to
771      different IPC objects in different namespaces.
772
773config USER_NS
774    bool "User namespace (EXPERIMENTAL)"
775    depends on EXPERIMENTAL
776    default y
777    help
778      This allows containers, i.e. vservers, to use user namespaces
779      to provide different user info for different servers.
780      If unsure, say N.
781
782config PID_NS
783    bool "PID Namespaces"
784    default y
785    help
786      Support process id namespaces. This allows having multiple
787      processes with the same pid as long as they are in different
788      pid namespaces. This is a building block of containers.
789
790config NET_NS
791    bool "Network namespace"
792    depends on NET
793    default y
794    help
795      Allow user space to create what appear to be multiple instances
796      of the network stack.
797
798endif # NAMESPACES
799
800config SCHED_AUTOGROUP
801    bool "Automatic process group scheduling"
802    select EVENTFD
803    select CGROUPS
804    select CGROUP_SCHED
805    select FAIR_GROUP_SCHED
806    help
807      This option optimizes the scheduler for common desktop workloads by
808      automatically creating and populating task groups. This separation
809      of workloads isolates aggressive CPU burners (like build jobs) from
810      desktop applications. Task group autogeneration is currently based
811      upon task session.
812
813config MM_OWNER
814    bool
815
816config SYSFS_DEPRECATED
817    bool "enable deprecated sysfs features to support old userspace tools"
818    depends on SYSFS
819    default n
820    help
821      This option adds code that switches the layout of the "block" class
822      devices, to not show up in /sys/class/block/, but only in
823      /sys/block/.
824
825      This switch is only active when the sysfs.deprecated=1 boot option is
826      passed or the SYSFS_DEPRECATED_V2 option is set.
827
828      This option allows new kernels to run on old distributions and tools,
829      which might get confused by /sys/class/block/. Since 2007/2008 all
830      major distributions and tools handle this just fine.
831
832      Recent distributions and userspace tools after 2009/2010 depend on
833      the existence of /sys/class/block/, and will not work with this
834      option enabled.
835
836      Only if you are using a new kernel on an old distribution, you might
837      need to say Y here.
838
839config SYSFS_DEPRECATED_V2
840    bool "enabled deprecated sysfs features by default"
841    default n
842    depends on SYSFS
843    depends on SYSFS_DEPRECATED
844    help
845      Enable deprecated sysfs by default.
846
847      See the CONFIG_SYSFS_DEPRECATED option for more details about this
848      option.
849
850      Only if you are using a new kernel on an old distribution, you might
851      need to say Y here. Even then, odds are you would not need it
852      enabled, you can always pass the boot option if absolutely necessary.
853
854config RELAY
855    bool "Kernel->user space relay support (formerly relayfs)"
856    help
857      This option enables support for relay interface support in
858      certain file systems (such as debugfs).
859      It is designed to provide an efficient mechanism for tools and
860      facilities to relay large amounts of data from kernel space to
861      user space.
862
863      If unsure, say N.
864
865config BLK_DEV_INITRD
866    bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
867    depends on BROKEN || !FRV
868    help
869      The initial RAM filesystem is a ramfs which is loaded by the
870      boot loader (loadlin or lilo) and that is mounted as root
871      before the normal boot procedure. It is typically used to
872      load modules needed to mount the "real" root file system,
873      etc. See <file:Documentation/initrd.txt> for details.
874
875      If RAM disk support (BLK_DEV_RAM) is also included, this
876      also enables initial RAM disk (initrd) support and adds
877      15 Kbytes (more on some other architectures) to the kernel size.
878
879      If unsure say Y.
880
881if BLK_DEV_INITRD
882
883source "usr/Kconfig"
884
885endif
886
887config CC_OPTIMIZE_FOR_SIZE
888    bool "Optimize for size"
889    default y
890    help
891      Enabling this option will pass "-Os" instead of "-O2" to gcc
892      resulting in a smaller kernel.
893
894      If unsure, say Y.
895
896config SYSCTL
897    bool
898
899config ANON_INODES
900    bool
901
902menuconfig EXPERT
903    bool "Configure standard kernel features (expert users)"
904    help
905      This option allows certain base kernel options and settings
906          to be disabled or tweaked. This is for specialized
907          environments which can tolerate a "non-standard" kernel.
908          Only use this if you really know what you are doing.
909
910config EMBEDDED
911    bool "Embedded system"
912    select EXPERT
913    help
914      This option should be enabled if compiling the kernel for
915      an embedded system so certain expert options are available
916      for configuration.
917
918config UID16
919    bool "Enable 16-bit UID system calls" if EXPERT
920    depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
921    default y
922    help
923      This enables the legacy 16-bit UID syscall wrappers.
924
925config SYSCTL_SYSCALL
926    bool "Sysctl syscall support" if EXPERT
927    depends on PROC_SYSCTL
928    default y
929    select SYSCTL
930    ---help---
931      sys_sysctl uses binary paths that have been found challenging
932      to properly maintain and use. The interface in /proc/sys
933      using paths with ascii names is now the primary path to this
934      information.
935
936      Almost nothing using the binary sysctl interface so if you are
937      trying to save some space it is probably safe to disable this,
938      making your kernel marginally smaller.
939
940      If unsure say Y here.
941
942config KALLSYMS
943     bool "Load all symbols for debugging/ksymoops" if EXPERT
944     default y
945     help
946       Say Y here to let the kernel print out symbolic crash information and
947       symbolic stack backtraces. This increases the size of the kernel
948       somewhat, as all symbols have to be loaded into the kernel image.
949
950config KALLSYMS_ALL
951    bool "Include all symbols in kallsyms"
952    depends on DEBUG_KERNEL && KALLSYMS
953    help
954       Normally kallsyms only contains the symbols of functions, for nicer
955       OOPS messages. Some debuggers can use kallsyms for other
956       symbols too: say Y here to include all symbols, if you need them
957       and you don't care about adding 300k to the size of your kernel.
958
959       Say N.
960
961config KALLSYMS_EXTRA_PASS
962    bool "Do an extra kallsyms pass"
963    depends on KALLSYMS
964    help
965       If kallsyms is not working correctly, the build will fail with
966       inconsistent kallsyms data. If that occurs, log a bug report and
967       turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
968       Always say N here unless you find a bug in kallsyms, which must be
969       reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
970       you wait for kallsyms to be fixed.
971
972
973config HOTPLUG
974    bool "Support for hot-pluggable devices" if EXPERT
975    default y
976    help
977      This option is provided for the case where no hotplug or uevent
978      capabilities is wanted by the kernel. You should only consider
979      disabling this option for embedded systems that do not use modules, a
980      dynamic /dev tree, or dynamic device discovery. Just say Y.
981
982config PRINTK
983    default y
984    bool "Enable support for printk" if EXPERT
985    help
986      This option enables normal printk support. Removing it
987      eliminates most of the message strings from the kernel image
988      and makes the kernel more or less silent. As this makes it
989      very difficult to diagnose system problems, saying N here is
990      strongly discouraged.
991
992config BUG
993    bool "BUG() support" if EXPERT
994    default y
995    help
996          Disabling this option eliminates support for BUG and WARN, reducing
997          the size of your kernel image and potentially quietly ignoring
998          numerous fatal conditions. You should only consider disabling this
999          option for embedded systems with no facilities for reporting errors.
1000          Just say Y.
1001
1002config ELF_CORE
1003    default y
1004    bool "Enable ELF core dumps" if EXPERT
1005    help
1006      Enable support for generating core dumps. Disabling saves about 4k.
1007
1008config PCSPKR_PLATFORM
1009    bool "Enable PC-Speaker support" if EXPERT
1010    depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
1011    default y
1012    help
1013          This option allows to disable the internal PC-Speaker
1014          support, saving some memory.
1015
1016config BASE_FULL
1017    default y
1018    bool "Enable full-sized data structures for core" if EXPERT
1019    help
1020      Disabling this option reduces the size of miscellaneous core
1021      kernel data structures. This saves memory on small machines,
1022      but may reduce performance.
1023
1024config FUTEX
1025    bool "Enable futex support" if EXPERT
1026    default y
1027    select RT_MUTEXES
1028    help
1029      Disabling this option will cause the kernel to be built without
1030      support for "fast userspace mutexes". The resulting kernel may not
1031      run glibc-based applications correctly.
1032
1033config EPOLL
1034    bool "Enable eventpoll support" if EXPERT
1035    default y
1036    select ANON_INODES
1037    help
1038      Disabling this option will cause the kernel to be built without
1039      support for epoll family of system calls.
1040
1041config SIGNALFD
1042    bool "Enable signalfd() system call" if EXPERT
1043    select ANON_INODES
1044    default y
1045    help
1046      Enable the signalfd() system call that allows to receive signals
1047      on a file descriptor.
1048
1049      If unsure, say Y.
1050
1051config TIMERFD
1052    bool "Enable timerfd() system call" if EXPERT
1053    select ANON_INODES
1054    default y
1055    help
1056      Enable the timerfd() system call that allows to receive timer
1057      events on a file descriptor.
1058
1059      If unsure, say Y.
1060
1061config EVENTFD
1062    bool "Enable eventfd() system call" if EXPERT
1063    select ANON_INODES
1064    default y
1065    help
1066      Enable the eventfd() system call that allows to receive both
1067      kernel notification (ie. KAIO) or userspace notifications.
1068
1069      If unsure, say Y.
1070
1071config SHMEM
1072    bool "Use full shmem filesystem" if EXPERT
1073    default y
1074    depends on MMU
1075    help
1076      The shmem is an internal filesystem used to manage shared memory.
1077      It is backed by swap and manages resource limits. It is also exported
1078      to userspace as tmpfs if TMPFS is enabled. Disabling this
1079      option replaces shmem and tmpfs with the much simpler ramfs code,
1080      which may be appropriate on small systems without swap.
1081
1082config AIO
1083    bool "Enable AIO support" if EXPERT
1084    default y
1085    help
1086      This option enables POSIX asynchronous I/O which may by used
1087          by some high performance threaded applications. Disabling
1088          this option saves about 7k.
1089
1090config HAVE_PERF_EVENTS
1091    bool
1092    help
1093      See tools/perf/design.txt for details.
1094
1095config PERF_USE_VMALLOC
1096    bool
1097    help
1098      See tools/perf/design.txt for details
1099
1100menu "Kernel Performance Events And Counters"
1101
1102config PERF_EVENTS
1103    bool "Kernel performance events and counters"
1104    default y if (PROFILING || PERF_COUNTERS)
1105    depends on HAVE_PERF_EVENTS
1106    select ANON_INODES
1107    select IRQ_WORK
1108    help
1109      Enable kernel support for various performance events provided
1110      by software and hardware.
1111
1112      Software events are supported either built-in or via the
1113      use of generic tracepoints.
1114
1115      Most modern CPUs support performance events via performance
1116      counter registers. These registers count the number of certain
1117      types of hw events: such as instructions executed, cachemisses
1118      suffered, or branches mis-predicted - without slowing down the
1119      kernel or applications. These registers can also trigger interrupts
1120      when a threshold number of events have passed - and can thus be
1121      used to profile the code that runs on that CPU.
1122
1123      The Linux Performance Event subsystem provides an abstraction of
1124      these software and hardware event capabilities, available via a
1125      system call and used by the "perf" utility in tools/perf/. It
1126      provides per task and per CPU counters, and it provides event
1127      capabilities on top of those.
1128
1129      Say Y if unsure.
1130
1131config PERF_COUNTERS
1132    bool "Kernel performance counters (old config option)"
1133    depends on HAVE_PERF_EVENTS
1134    help
1135      This config has been obsoleted by the PERF_EVENTS
1136      config option - please see that one for details.
1137
1138      It has no effect on the kernel whether you enable
1139      it or not, it is a compatibility placeholder.
1140
1141      Say N if unsure.
1142
1143config DEBUG_PERF_USE_VMALLOC
1144    default n
1145    bool "Debug: use vmalloc to back perf mmap() buffers"
1146    depends on PERF_EVENTS && DEBUG_KERNEL
1147    select PERF_USE_VMALLOC
1148    help
1149     Use vmalloc memory to back perf mmap() buffers.
1150
1151     Mostly useful for debugging the vmalloc code on platforms
1152     that don't require it.
1153
1154     Say N if unsure.
1155
1156endmenu
1157
1158config VM_EVENT_COUNTERS
1159    default y
1160    bool "Enable VM event counters for /proc/vmstat" if EXPERT
1161    help
1162      VM event counters are needed for event counts to be shown.
1163      This option allows the disabling of the VM event counters
1164      on EXPERT systems. /proc/vmstat will only show page counts
1165      if VM event counters are disabled.
1166
1167config PCI_QUIRKS
1168    default y
1169    bool "Enable PCI quirk workarounds" if EXPERT
1170    depends on PCI
1171    help
1172      This enables workarounds for various PCI chipset
1173          bugs/quirks. Disable this only if your target machine is
1174          unaffected by PCI quirks.
1175
1176config SLUB_DEBUG
1177    default y
1178    bool "Enable SLUB debugging support" if EXPERT
1179    depends on SLUB && SYSFS
1180    help
1181      SLUB has extensive debug support features. Disabling these can
1182      result in significant savings in code size. This also disables
1183      SLUB sysfs support. /sys/slab will not exist and there will be
1184      no support for cache validation etc.
1185
1186config COMPAT_BRK
1187    bool "Disable heap randomization"
1188    default y
1189    help
1190      Randomizing heap placement makes heap exploits harder, but it
1191      also breaks ancient binaries (including anything libc5 based).
1192      This option changes the bootup default to heap randomization
1193      disabled, and can be overridden at runtime by setting
1194      /proc/sys/kernel/randomize_va_space to 2.
1195
1196      On non-ancient distros (post-2000 ones) N is usually a safe choice.
1197
1198choice
1199    prompt "Choose SLAB allocator"
1200    default SLUB
1201    help
1202       This option allows to select a slab allocator.
1203
1204config SLAB
1205    bool "SLAB"
1206    help
1207      The regular slab allocator that is established and known to work
1208      well in all environments. It organizes cache hot objects in
1209      per cpu and per node queues.
1210
1211config SLUB
1212    bool "SLUB (Unqueued Allocator)"
1213    help
1214       SLUB is a slab allocator that minimizes cache line usage
1215       instead of managing queues of cached objects (SLAB approach).
1216       Per cpu caching is realized using slabs of objects instead
1217       of queues of objects. SLUB can use memory efficiently
1218       and has enhanced diagnostics. SLUB is the default choice for
1219       a slab allocator.
1220
1221config SLOB
1222    depends on EXPERT
1223    bool "SLOB (Simple Allocator)"
1224    help
1225       SLOB replaces the stock allocator with a drastically simpler
1226       allocator. SLOB is generally more space efficient but
1227       does not perform as well on large systems.
1228
1229endchoice
1230
1231config MMAP_ALLOW_UNINITIALIZED
1232    bool "Allow mmapped anonymous memory to be uninitialized"
1233    depends on EXPERT && !MMU
1234    default n
1235    help
1236      Normally, and according to the Linux spec, anonymous memory obtained
1237      from mmap() has it's contents cleared before it is passed to
1238      userspace. Enabling this config option allows you to request that
1239      mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1240      providing a huge performance boost. If this option is not enabled,
1241      then the flag will be ignored.
1242
1243      This is taken advantage of by uClibc's malloc(), and also by
1244      ELF-FDPIC binfmt's brk and stack allocator.
1245
1246      Because of the obvious security issues, this option should only be
1247      enabled on embedded devices where you control what is run in
1248      userspace. Since that isn't generally a problem on no-MMU systems,
1249      it is normally safe to say Y here.
1250
1251      See Documentation/nommu-mmap.txt for more information.
1252
1253config PROFILING
1254    bool "Profiling support"
1255    help
1256      Say Y here to enable the extended profiling support mechanisms used
1257      by profilers such as OProfile.
1258
1259#
1260# Place an empty function call at each tracepoint site. Can be
1261# dynamically changed for a probe function.
1262#
1263config TRACEPOINTS
1264    bool
1265
1266source "arch/Kconfig"
1267
1268endmenu # General setup
1269
1270config HAVE_GENERIC_DMA_COHERENT
1271    bool
1272    default n
1273
1274config SLABINFO
1275    bool
1276    depends on PROC_FS
1277    depends on SLAB || SLUB_DEBUG
1278    default y
1279
1280config RT_MUTEXES
1281    boolean
1282
1283config BASE_SMALL
1284    int
1285    default 0 if BASE_FULL
1286    default 1 if !BASE_FULL
1287
1288menuconfig MODULES
1289    bool "Enable loadable module support"
1290    help
1291      Kernel modules are small pieces of compiled code which can
1292      be inserted in the running kernel, rather than being
1293      permanently built into the kernel. You use the "modprobe"
1294      tool to add (and sometimes remove) them. If you say Y here,
1295      many parts of the kernel can be built as modules (by
1296      answering M instead of Y where indicated): this is most
1297      useful for infrequently used options which are not required
1298      for booting. For more information, see the man pages for
1299      modprobe, lsmod, modinfo, insmod and rmmod.
1300
1301      If you say Y here, you will need to run "make
1302      modules_install" to put the modules under /lib/modules/
1303      where modprobe can find them (you may need to be root to do
1304      this).
1305
1306      If unsure, say Y.
1307
1308if MODULES
1309
1310config MODULE_FORCE_LOAD
1311    bool "Forced module loading"
1312    default n
1313    help
1314      Allow loading of modules without version information (ie. modprobe
1315      --force). Forced module loading sets the 'F' (forced) taint flag and
1316      is usually a really bad idea.
1317
1318config MODULE_UNLOAD
1319    bool "Module unloading"
1320    help
1321      Without this option you will not be able to unload any
1322      modules (note that some modules may not be unloadable
1323      anyway), which makes your kernel smaller, faster
1324      and simpler. If unsure, say Y.
1325
1326config MODULE_FORCE_UNLOAD
1327    bool "Forced module unloading"
1328    depends on MODULE_UNLOAD && EXPERIMENTAL
1329    help
1330      This option allows you to force a module to unload, even if the
1331      kernel believes it is unsafe: the kernel will remove the module
1332      without waiting for anyone to stop using it (using the -f option to
1333      rmmod). This is mainly for kernel developers and desperate users.
1334      If unsure, say N.
1335
1336config MODVERSIONS
1337    bool "Module versioning support"
1338    help
1339      Usually, you have to use modules compiled with your kernel.
1340      Saying Y here makes it sometimes possible to use modules
1341      compiled for different kernels, by adding enough information
1342      to the modules to (hopefully) spot any changes which would
1343      make them incompatible with the kernel you are running. If
1344      unsure, say N.
1345
1346config MODULE_SRCVERSION_ALL
1347    bool "Source checksum for all modules"
1348    help
1349      Modules which contain a MODULE_VERSION get an extra "srcversion"
1350      field inserted into their modinfo section, which contains a
1351          sum of the source files which made it. This helps maintainers
1352      see exactly which source was used to build a module (since
1353      others sometimes change the module source without updating
1354      the version). With this option, such a "srcversion" field
1355      will be created for all modules. If unsure, say N.
1356
1357endif # MODULES
1358
1359config INIT_ALL_POSSIBLE
1360    bool
1361    help
1362      Back when each arch used to define their own cpu_online_map and
1363      cpu_possible_map, some of them chose to initialize cpu_possible_map
1364      with all 1s, and others with all 0s. When they were centralised,
1365      it was better to provide this option than to break all the archs
1366      and have several arch maintainers pursuing me down dark alleys.
1367
1368config STOP_MACHINE
1369    bool
1370    default y
1371    depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1372    help
1373      Need stop_machine() primitive.
1374
1375source "block/Kconfig"
1376
1377config PREEMPT_NOTIFIERS
1378    bool
1379
1380config PADATA
1381    depends on SMP
1382    bool
1383
1384source "kernel/Kconfig.locks"
1385

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