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
23config HAVE_IRQ_WORK
24    bool
25
26config IRQ_WORK
27    bool
28    depends on HAVE_IRQ_WORK
29
30menu "General setup"
31
32config EXPERIMENTAL
33    bool "Prompt for development and/or incomplete code/drivers"
34    ---help---
35      Some of the various things that Linux supports (such as network
36      drivers, file systems, network protocols, etc.) can be in a state
37      of development where the functionality, stability, or the level of
38      testing is not yet high enough for general use. This is usually
39      known as the "alpha-test" phase among developers. If a feature is
40      currently in alpha-test, then the developers usually discourage
41      uninformed widespread use of this feature by the general public to
42      avoid "Why doesn't this work?" type mail messages. However, active
43      testing and use of these systems is welcomed. Just be aware that it
44      may not meet the normal level of reliability or it may fail to work
45      in some special cases. Detailed bug reports from people familiar
46      with the kernel internals are usually welcomed by the developers
47      (before submitting bug reports, please read the documents
48      <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
49      <file:Documentation/BUG-HUNTING>, and
50      <file:Documentation/oops-tracing.txt> in the kernel source).
51
52      This option will also make obsoleted drivers available. These are
53      drivers that have been replaced by something else, and/or are
54      scheduled to be removed in a future kernel release.
55
56      Unless you intend to help test and develop a feature or driver that
57      falls into this category, or you have a situation that requires
58      using these features, you should probably say N here, which will
59      cause the configurator to present you with fewer choices. If
60      you say Y here, you will be offered the choice of using features or
61      drivers that are currently considered to be in the alpha-test phase.
62
63config BROKEN
64    bool
65
66config BROKEN_ON_SMP
67    bool
68    depends on BROKEN || !SMP
69    default y
70
71config INIT_ENV_ARG_LIMIT
72    int
73    default 32 if !UML
74    default 128 if UML
75    help
76      Maximum of each of the number of arguments and environment
77      variables passed to init from the kernel command line.
78
79
80config CROSS_COMPILE
81    string "Cross-compiler tool prefix"
82    help
83      Same as running 'make CROSS_COMPILE=prefix-' but stored for
84      default make runs in this kernel build directory. You don't
85      need to set this unless you want the configured kernel build
86      directory to select the cross-compiler automatically.
87
88config LOCALVERSION
89    string "Local version - append to kernel release"
90    help
91      Append an extra string to the end of your kernel version.
92      This will show up when you type uname, for example.
93      The string you set here will be appended after the contents of
94      any files with a filename matching localversion* in your
95      object and source tree, in that order. Your total string can
96      be a maximum of 64 characters.
97
98config LOCALVERSION_AUTO
99    bool "Automatically append version information to the version string"
100    default y
101    help
102      This will try to automatically determine if the current tree is a
103      release tree by looking for git tags that belong to the current
104      top of tree revision.
105
106      A string of the format -gxxxxxxxx will be added to the localversion
107      if a git-based tree is found. The string generated by this will be
108      appended after any matching localversion* files, and after the value
109      set in CONFIG_LOCALVERSION.
110
111      (The actual string used here is the first eight characters produced
112      by running the command:
113
114        $ git rev-parse --verify HEAD
115
116      which is done within the script "scripts/setlocalversion".)
117
118config HAVE_KERNEL_GZIP
119    bool
120
121config HAVE_KERNEL_BZIP2
122    bool
123
124config HAVE_KERNEL_LZMA
125    bool
126
127config HAVE_KERNEL_XZ
128    bool
129
130config HAVE_KERNEL_LZO
131    bool
132
133choice
134    prompt "Kernel compression mode"
135    default KERNEL_GZIP
136    depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
137    help
138      The linux kernel is a kind of self-extracting executable.
139      Several compression algorithms are available, which differ
140      in efficiency, compression and decompression speed.
141      Compression speed is only relevant when building a kernel.
142      Decompression speed is relevant at each boot.
143
144      If you have any problems with bzip2 or lzma compressed
145      kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
146      version of this functionality (bzip2 only), for 2.4, was
147      supplied by Christian Ludwig)
148
149      High compression options are mostly useful for users, who
150      are low on disk space (embedded systems), but for whom ram
151      size matters less.
152
153      If in doubt, select 'gzip'
154
155config KERNEL_GZIP
156    bool "Gzip"
157    depends on HAVE_KERNEL_GZIP
158    help
159      The old and tried gzip compression. It provides a good balance
160      between compression ratio and decompression speed.
161
162config KERNEL_BZIP2
163    bool "Bzip2"
164    depends on HAVE_KERNEL_BZIP2
165    help
166      Its compression ratio and speed is intermediate.
167      Decompression speed is slowest among the three. The kernel
168      size is about 10% smaller with bzip2, in comparison to gzip.
169      Bzip2 uses a large amount of memory. For modern kernels you
170      will need at least 8MB RAM or more for booting.
171
172config KERNEL_LZMA
173    bool "LZMA"
174    depends on HAVE_KERNEL_LZMA
175    help
176      The most recent compression algorithm.
177      Its ratio is best, decompression speed is between the other
178      two. Compression is slowest. The kernel size is about 33%
179      smaller with LZMA in comparison to gzip.
180
181config KERNEL_XZ
182    bool "XZ"
183    depends on HAVE_KERNEL_XZ
184    help
185      XZ uses the LZMA2 algorithm and instruction set specific
186      BCJ filters which can improve compression ratio of executable
187      code. The size of the kernel is about 30% smaller with XZ in
188      comparison to gzip. On architectures for which there is a BCJ
189      filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
190      will create a few percent smaller kernel than plain LZMA.
191
192      The speed is about the same as with LZMA: The decompression
193      speed of XZ is better than that of bzip2 but worse than gzip
194      and LZO. Compression is slow.
195
196config KERNEL_LZO
197    bool "LZO"
198    depends on HAVE_KERNEL_LZO
199    help
200      Its compression ratio is the poorest among the 4. The kernel
201      size is about 10% bigger than gzip; however its speed
202      (both compression and decompression) is the fastest.
203
204endchoice
205
206config DEFAULT_HOSTNAME
207    string "Default hostname"
208    default "(none)"
209    help
210      This option determines the default system hostname before userspace
211      calls sethostname(2). The kernel traditionally uses "(none)" here,
212      but you may wish to use a different default here to make a minimal
213      system more usable with less configuration.
214
215config SWAP
216    bool "Support for paging of anonymous memory (swap)"
217    depends on MMU && BLOCK
218    default y
219    help
220      This option allows you to choose whether you want to have support
221      for so called swap devices or swap files in your kernel that are
222      used to provide more virtual memory than the actual RAM present
223      in your computer. If unsure say Y.
224
225config SYSVIPC
226    bool "System V IPC"
227    ---help---
228      Inter Process Communication is a suite of library functions and
229      system calls which let processes (running programs) synchronize and
230      exchange information. It is generally considered to be a good thing,
231      and some programs won't run unless you say Y here. In particular, if
232      you want to run the DOS emulator dosemu under Linux (read the
233      DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
234      you'll need to say Y here.
235
236      You can find documentation about IPC with "info ipc" and also in
237      section 6.4 of the Linux Programmer's Guide, available from
238      <http://www.tldp.org/guides.html>.
239
240config SYSVIPC_SYSCTL
241    bool
242    depends on SYSVIPC
243    depends on SYSCTL
244    default y
245
246config POSIX_MQUEUE
247    bool "POSIX Message Queues"
248    depends on NET && EXPERIMENTAL
249    ---help---
250      POSIX variant of message queues is a part of IPC. In POSIX message
251      queues every message has a priority which decides about succession
252      of receiving it by a process. If you want to compile and run
253      programs written e.g. for Solaris with use of its POSIX message
254      queues (functions mq_*) say Y here.
255
256      POSIX message queues are visible as a filesystem called 'mqueue'
257      and can be mounted somewhere if you want to do filesystem
258      operations on message queues.
259
260      If unsure, say Y.
261
262config POSIX_MQUEUE_SYSCTL
263    bool
264    depends on POSIX_MQUEUE
265    depends on SYSCTL
266    default y
267
268config BSD_PROCESS_ACCT
269    bool "BSD Process Accounting"
270    help
271      If you say Y here, a user level program will be able to instruct the
272      kernel (via a special system call) to write process accounting
273      information to a file: whenever a process exits, information about
274      that process will be appended to the file by the kernel. The
275      information includes things such as creation time, owning user,
276      command name, memory usage, controlling terminal etc. (the complete
277      list is in the struct acct in <file:include/linux/acct.h>). It is
278      up to the user level program to do useful things with this
279      information. This is generally a good idea, so say Y.
280
281config BSD_PROCESS_ACCT_V3
282    bool "BSD Process Accounting version 3 file format"
283    depends on BSD_PROCESS_ACCT
284    default n
285    help
286      If you say Y here, the process accounting information is written
287      in a new file format that also logs the process IDs of each
288      process and it's parent. Note that this file format is incompatible
289      with previous v0/v1/v2 file formats, so you will need updated tools
290      for processing it. A preliminary version of these tools is available
291      at <http://www.gnu.org/software/acct/>.
292
293config FHANDLE
294    bool "open by fhandle syscalls"
295    select EXPORTFS
296    help
297      If you say Y here, a user level program will be able to map
298      file names to handle and then later use the handle for
299      different file system operations. This is useful in implementing
300      userspace file servers, which now track files using handles instead
301      of names. The handle would remain the same even if file names
302      get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
303      syscalls.
304
305config TASKSTATS
306    bool "Export task/process statistics through netlink (EXPERIMENTAL)"
307    depends on NET
308    default n
309    help
310      Export selected statistics for tasks/processes through the
311      generic netlink interface. Unlike BSD process accounting, the
312      statistics are available during the lifetime of tasks/processes as
313      responses to commands. Like BSD accounting, they are sent to user
314      space on task exit.
315
316      Say N if unsure.
317
318config TASK_DELAY_ACCT
319    bool "Enable per-task delay accounting (EXPERIMENTAL)"
320    depends on TASKSTATS
321    help
322      Collect information on time spent by a task waiting for system
323      resources like cpu, synchronous block I/O completion and swapping
324      in pages. Such statistics can help in setting a task's priorities
325      relative to other tasks for cpu, io, rss limits etc.
326
327      Say N if unsure.
328
329config TASK_XACCT
330    bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
331    depends on TASKSTATS
332    help
333      Collect extended task accounting data and send the data
334      to userland for processing over the taskstats interface.
335
336      Say N if unsure.
337
338config TASK_IO_ACCOUNTING
339    bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
340    depends on TASK_XACCT
341    help
342      Collect information on the number of bytes of storage I/O which this
343      task has caused.
344
345      Say N if unsure.
346
347config AUDIT
348    bool "Auditing support"
349    depends on NET
350    help
351      Enable auditing infrastructure that can be used with another
352      kernel subsystem, such as SELinux (which requires this for
353      logging of avc messages output). Does not do system-call
354      auditing without CONFIG_AUDITSYSCALL.
355
356config AUDITSYSCALL
357    bool "Enable system-call auditing support"
358    depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
359    default y if SECURITY_SELINUX
360    help
361      Enable low-overhead system-call auditing infrastructure that
362      can be used independently or with another kernel subsystem,
363      such as SELinux.
364
365config AUDIT_WATCH
366    def_bool y
367    depends on AUDITSYSCALL
368    select FSNOTIFY
369
370config AUDIT_TREE
371    def_bool y
372    depends on AUDITSYSCALL
373    select FSNOTIFY
374
375source "kernel/irq/Kconfig"
376
377menu "RCU Subsystem"
378
379choice
380    prompt "RCU Implementation"
381    default TREE_RCU
382
383config TREE_RCU
384    bool "Tree-based hierarchical RCU"
385    depends on !PREEMPT && SMP
386    help
387      This option selects the RCU implementation that is
388      designed for very large SMP system with hundreds or
389      thousands of CPUs. It also scales down nicely to
390      smaller systems.
391
392config TREE_PREEMPT_RCU
393    bool "Preemptible tree-based hierarchical RCU"
394    depends on PREEMPT
395    help
396      This option selects the RCU implementation that is
397      designed for very large SMP systems with hundreds or
398      thousands of CPUs, but for which real-time response
399      is also required. It also scales down nicely to
400      smaller systems.
401
402config TINY_RCU
403    bool "UP-only small-memory-footprint RCU"
404    depends on !SMP
405    help
406      This option selects the RCU implementation that is
407      designed for UP systems from which real-time response
408      is not required. This option greatly reduces the
409      memory footprint of RCU.
410
411config TINY_PREEMPT_RCU
412    bool "Preemptible UP-only small-memory-footprint RCU"
413    depends on !SMP && PREEMPT
414    help
415      This option selects the RCU implementation that is designed
416      for real-time UP systems. This option greatly reduces the
417      memory footprint of RCU.
418
419endchoice
420
421config PREEMPT_RCU
422    def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
423    help
424      This option enables preemptible-RCU code that is common between
425      the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
426
427config RCU_TRACE
428    bool "Enable tracing for RCU"
429    help
430      This option provides tracing in RCU which presents stats
431      in debugfs for debugging RCU implementation.
432
433      Say Y here if you want to enable RCU tracing
434      Say N if you are unsure.
435
436config RCU_FANOUT
437    int "Tree-based hierarchical RCU fanout value"
438    range 2 64 if 64BIT
439    range 2 32 if !64BIT
440    depends on TREE_RCU || TREE_PREEMPT_RCU
441    default 64 if 64BIT
442    default 32 if !64BIT
443    help
444      This option controls the fanout of hierarchical implementations
445      of RCU, allowing RCU to work efficiently on machines with
446      large numbers of CPUs. This value must be at least the fourth
447      root of NR_CPUS, which allows NR_CPUS to be insanely large.
448      The default value of RCU_FANOUT should be used for production
449      systems, but if you are stress-testing the RCU implementation
450      itself, small RCU_FANOUT values allow you to test large-system
451      code paths on small(er) systems.
452
453      Select a specific number if testing RCU itself.
454      Take the default if unsure.
455
456config RCU_FANOUT_EXACT
457    bool "Disable tree-based hierarchical RCU auto-balancing"
458    depends on TREE_RCU || TREE_PREEMPT_RCU
459    default n
460    help
461      This option forces use of the exact RCU_FANOUT value specified,
462      regardless of imbalances in the hierarchy. This is useful for
463      testing RCU itself, and might one day be useful on systems with
464      strong NUMA behavior.
465
466      Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
467
468      Say N if unsure.
469
470config RCU_FAST_NO_HZ
471    bool "Accelerate last non-dyntick-idle CPU's grace periods"
472    depends on TREE_RCU && NO_HZ && SMP
473    default n
474    help
475      This option causes RCU to attempt to accelerate grace periods
476      in order to allow the final CPU to enter dynticks-idle state
477      more quickly. On the other hand, this option increases the
478      overhead of the dynticks-idle checking, particularly on systems
479      with large numbers of CPUs.
480
481      Say Y if energy efficiency is critically important, particularly
482          if you have relatively few CPUs.
483
484      Say N if you are unsure.
485
486config TREE_RCU_TRACE
487    def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
488    select DEBUG_FS
489    help
490      This option provides tracing for the TREE_RCU and
491      TREE_PREEMPT_RCU implementations, permitting Makefile to
492      trivially select kernel/rcutree_trace.c.
493
494config RCU_BOOST
495    bool "Enable RCU priority boosting"
496    depends on RT_MUTEXES && PREEMPT_RCU
497    default n
498    help
499      This option boosts the priority of preempted RCU readers that
500      block the current preemptible RCU grace period for too long.
501      This option also prevents heavy loads from blocking RCU
502      callback invocation for all flavors of RCU.
503
504      Say Y here if you are working with real-time apps or heavy loads
505      Say N here if you are unsure.
506
507config RCU_BOOST_PRIO
508    int "Real-time priority to boost RCU readers to"
509    range 1 99
510    depends on RCU_BOOST
511    default 1
512    help
513      This option specifies the real-time priority to which preempted
514      RCU readers are to be boosted. If you are working with CPU-bound
515      real-time applications, you should specify a priority higher then
516      the highest-priority CPU-bound application.
517
518      Specify the real-time priority, or take the default if unsure.
519
520config RCU_BOOST_DELAY
521    int "Milliseconds to delay boosting after RCU grace-period start"
522    range 0 3000
523    depends on RCU_BOOST
524    default 500
525    help
526      This option specifies the time to wait after the beginning of
527      a given grace period before priority-boosting preempted RCU
528      readers blocking that grace period. Note that any RCU reader
529      blocking an expedited RCU grace period is boosted immediately.
530
531      Accept the default if unsure.
532
533endmenu # "RCU Subsystem"
534
535config IKCONFIG
536    tristate "Kernel .config support"
537    ---help---
538      This option enables the complete Linux kernel ".config" file
539      contents to be saved in the kernel. It provides documentation
540      of which kernel options are used in a running kernel or in an
541      on-disk kernel. This information can be extracted from the kernel
542      image file with the script scripts/extract-ikconfig and used as
543      input to rebuild the current kernel or to build another kernel.
544      It can also be extracted from a running kernel by reading
545      /proc/config.gz if enabled (below).
546
547config IKCONFIG_PROC
548    bool "Enable access to .config through /proc/config.gz"
549    depends on IKCONFIG && PROC_FS
550    ---help---
551      This option enables access to the kernel configuration file
552      through /proc/config.gz.
553
554config LOG_BUF_SHIFT
555    int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
556    range 12 21
557    default 17
558    help
559      Select kernel log buffer size as a power of 2.
560      Examples:
561               17 => 128 KB
562             16 => 64 KB
563                 15 => 32 KB
564                 14 => 16 KB
565             13 => 8 KB
566             12 => 4 KB
567
568#
569# Architectures with an unreliable sched_clock() should select this:
570#
571config HAVE_UNSTABLE_SCHED_CLOCK
572    bool
573
574menuconfig CGROUPS
575    boolean "Control Group support"
576    depends on EVENTFD
577    help
578      This option adds support for grouping sets of processes together, for
579      use with process control subsystems such as Cpusets, CFS, memory
580      controls or device isolation.
581      See
582        - Documentation/scheduler/sched-design-CFS.txt (CFS)
583        - Documentation/cgroups/ (features for grouping, isolation
584                      and resource control)
585
586      Say N if unsure.
587
588if CGROUPS
589
590config CGROUP_DEBUG
591    bool "Example debug cgroup subsystem"
592    default n
593    help
594      This option enables a simple cgroup subsystem that
595      exports useful debugging information about the cgroups
596      framework.
597
598      Say N if unsure.
599
600config CGROUP_FREEZER
601    bool "Freezer cgroup subsystem"
602    help
603      Provides a way to freeze and unfreeze all tasks in a
604      cgroup.
605
606config CGROUP_DEVICE
607    bool "Device controller for cgroups"
608    help
609      Provides a cgroup implementing whitelists for devices which
610      a process in the cgroup can mknod or open.
611
612config CPUSETS
613    bool "Cpuset support"
614    help
615      This option will let you create and manage CPUSETs which
616      allow dynamically partitioning a system into sets of CPUs and
617      Memory Nodes and assigning tasks to run only within those sets.
618      This is primarily useful on large SMP or NUMA systems.
619
620      Say N if unsure.
621
622config PROC_PID_CPUSET
623    bool "Include legacy /proc/<pid>/cpuset file"
624    depends on CPUSETS
625    default y
626
627config CGROUP_CPUACCT
628    bool "Simple CPU accounting cgroup subsystem"
629    help
630      Provides a simple Resource Controller for monitoring the
631      total CPU consumed by the tasks in a cgroup.
632
633config RESOURCE_COUNTERS
634    bool "Resource counters"
635    help
636      This option enables controller independent resource accounting
637      infrastructure that works with cgroups.
638
639config CGROUP_MEM_RES_CTLR
640    bool "Memory Resource Controller for Control Groups"
641    depends on RESOURCE_COUNTERS
642    select MM_OWNER
643    help
644      Provides a memory resource controller that manages both anonymous
645      memory and page cache. (See Documentation/cgroups/memory.txt)
646
647      Note that setting this option increases fixed memory overhead
648      associated with each page of memory in the system. By this,
649      20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
650      usage tracking struct at boot. Total amount of this is printed out
651      at boot.
652
653      Only enable when you're ok with these trade offs and really
654      sure you need the memory resource controller. Even when you enable
655      this, you can set "cgroup_disable=memory" at your boot option to
656      disable memory resource controller and you can avoid overheads.
657      (and lose benefits of memory resource controller)
658
659      This config option also selects MM_OWNER config option, which
660      could in turn add some fork/exit overhead.
661
662config CGROUP_MEM_RES_CTLR_SWAP
663    bool "Memory Resource Controller Swap Extension"
664    depends on CGROUP_MEM_RES_CTLR && SWAP
665    help
666      Add swap management feature to memory resource controller. When you
667      enable this, you can limit mem+swap usage per cgroup. In other words,
668      when you disable this, memory resource controller has no cares to
669      usage of swap...a process can exhaust all of the swap. This extension
670      is useful when you want to avoid exhaustion swap but this itself
671      adds more overheads and consumes memory for remembering information.
672      Especially if you use 32bit system or small memory system, please
673      be careful about enabling this. When memory resource controller
674      is disabled by boot option, this will be automatically disabled and
675      there will be no overhead from this. Even when you set this config=y,
676      if boot option "swapaccount=0" is set, swap will not be accounted.
677      Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
678      size is 4096bytes, 512k per 1Gbytes of swap.
679config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
680    bool "Memory Resource Controller Swap Extension enabled by default"
681    depends on CGROUP_MEM_RES_CTLR_SWAP
682    default y
683    help
684      Memory Resource Controller Swap Extension comes with its price in
685      a bigger memory consumption. General purpose distribution kernels
686      which want to enable the feature but keep it disabled by default
687      and let the user enable it by swapaccount boot command line
688      parameter should have this option unselected.
689      For those who want to have the feature enabled by default should
690      select this option (if, for some reason, they need to disable it
691      then swapaccount=0 does the trick).
692
693config CGROUP_PERF
694    bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
695    depends on PERF_EVENTS && CGROUPS
696    help
697      This option extends the per-cpu mode to restrict monitoring to
698      threads which belong to the cgroup specified and run on the
699      designated cpu.
700
701      Say N if unsure.
702
703menuconfig CGROUP_SCHED
704    bool "Group CPU scheduler"
705    depends on EXPERIMENTAL
706    default n
707    help
708      This feature lets CPU scheduler recognize task groups and control CPU
709      bandwidth allocation to such task groups. It uses cgroups to group
710      tasks.
711
712if CGROUP_SCHED
713config FAIR_GROUP_SCHED
714    bool "Group scheduling for SCHED_OTHER"
715    depends on CGROUP_SCHED
716    default CGROUP_SCHED
717
718config RT_GROUP_SCHED
719    bool "Group scheduling for SCHED_RR/FIFO"
720    depends on EXPERIMENTAL
721    depends on CGROUP_SCHED
722    default n
723    help
724      This feature lets you explicitly allocate real CPU bandwidth
725      to task groups. If enabled, it will also make it impossible to
726      schedule realtime tasks for non-root users until you allocate
727      realtime bandwidth for them.
728      See Documentation/scheduler/sched-rt-group.txt for more information.
729
730endif #CGROUP_SCHED
731
732config BLK_CGROUP
733    tristate "Block IO controller"
734    depends on BLOCK
735    default n
736    ---help---
737    Generic block IO controller cgroup interface. This is the common
738    cgroup interface which should be used by various IO controlling
739    policies.
740
741    Currently, CFQ IO scheduler uses it to recognize task groups and
742    control disk bandwidth allocation (proportional time slice allocation)
743    to such task groups. It is also used by bio throttling logic in
744    block layer to implement upper limit in IO rates on a device.
745
746    This option only enables generic Block IO controller infrastructure.
747    One needs to also enable actual IO controlling logic/policy. For
748    enabling proportional weight division of disk bandwidth in CFQ, set
749    CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
750    CONFIG_BLK_DEV_THROTTLING=y.
751
752    See Documentation/cgroups/blkio-controller.txt for more information.
753
754config DEBUG_BLK_CGROUP
755    bool "Enable Block IO controller debugging"
756    depends on BLK_CGROUP
757    default n
758    ---help---
759    Enable some debugging help. Currently it exports additional stat
760    files in a cgroup which can be useful for debugging.
761
762endif # CGROUPS
763
764menuconfig NAMESPACES
765    bool "Namespaces support" if EXPERT
766    default !EXPERT
767    help
768      Provides the way to make tasks work with different objects using
769      the same id. For example same IPC id may refer to different objects
770      or same user id or pid may refer to different tasks when used in
771      different namespaces.
772
773if NAMESPACES
774
775config UTS_NS
776    bool "UTS namespace"
777    default y
778    help
779      In this namespace tasks see different info provided with the
780      uname() system call
781
782config IPC_NS
783    bool "IPC namespace"
784    depends on (SYSVIPC || POSIX_MQUEUE)
785    default y
786    help
787      In this namespace tasks work with IPC ids which correspond to
788      different IPC objects in different namespaces.
789
790config USER_NS
791    bool "User namespace (EXPERIMENTAL)"
792    depends on EXPERIMENTAL
793    default y
794    help
795      This allows containers, i.e. vservers, to use user namespaces
796      to provide different user info for different servers.
797      If unsure, say N.
798
799config PID_NS
800    bool "PID Namespaces"
801    default y
802    help
803      Support process id namespaces. This allows having multiple
804      processes with the same pid as long as they are in different
805      pid namespaces. This is a building block of containers.
806
807config NET_NS
808    bool "Network namespace"
809    depends on NET
810    default y
811    help
812      Allow user space to create what appear to be multiple instances
813      of the network stack.
814
815endif # NAMESPACES
816
817config SCHED_AUTOGROUP
818    bool "Automatic process group scheduling"
819    select EVENTFD
820    select CGROUPS
821    select CGROUP_SCHED
822    select FAIR_GROUP_SCHED
823    help
824      This option optimizes the scheduler for common desktop workloads by
825      automatically creating and populating task groups. This separation
826      of workloads isolates aggressive CPU burners (like build jobs) from
827      desktop applications. Task group autogeneration is currently based
828      upon task session.
829
830config MM_OWNER
831    bool
832
833config SYSFS_DEPRECATED
834    bool "Enable deprecated sysfs features to support old userspace tools"
835    depends on SYSFS
836    default n
837    help
838      This option adds code that switches the layout of the "block" class
839      devices, to not show up in /sys/class/block/, but only in
840      /sys/block/.
841
842      This switch is only active when the sysfs.deprecated=1 boot option is
843      passed or the SYSFS_DEPRECATED_V2 option is set.
844
845      This option allows new kernels to run on old distributions and tools,
846      which might get confused by /sys/class/block/. Since 2007/2008 all
847      major distributions and tools handle this just fine.
848
849      Recent distributions and userspace tools after 2009/2010 depend on
850      the existence of /sys/class/block/, and will not work with this
851      option enabled.
852
853      Only if you are using a new kernel on an old distribution, you might
854      need to say Y here.
855
856config SYSFS_DEPRECATED_V2
857    bool "Enable deprecated sysfs features by default"
858    default n
859    depends on SYSFS
860    depends on SYSFS_DEPRECATED
861    help
862      Enable deprecated sysfs by default.
863
864      See the CONFIG_SYSFS_DEPRECATED option for more details about this
865      option.
866
867      Only if you are using a new kernel on an old distribution, you might
868      need to say Y here. Even then, odds are you would not need it
869      enabled, you can always pass the boot option if absolutely necessary.
870
871config RELAY
872    bool "Kernel->user space relay support (formerly relayfs)"
873    help
874      This option enables support for relay interface support in
875      certain file systems (such as debugfs).
876      It is designed to provide an efficient mechanism for tools and
877      facilities to relay large amounts of data from kernel space to
878      user space.
879
880      If unsure, say N.
881
882config BLK_DEV_INITRD
883    bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
884    depends on BROKEN || !FRV
885    help
886      The initial RAM filesystem is a ramfs which is loaded by the
887      boot loader (loadlin or lilo) and that is mounted as root
888      before the normal boot procedure. It is typically used to
889      load modules needed to mount the "real" root file system,
890      etc. See <file:Documentation/initrd.txt> for details.
891
892      If RAM disk support (BLK_DEV_RAM) is also included, this
893      also enables initial RAM disk (initrd) support and adds
894      15 Kbytes (more on some other architectures) to the kernel size.
895
896      If unsure say Y.
897
898if BLK_DEV_INITRD
899
900source "usr/Kconfig"
901
902endif
903
904config CC_OPTIMIZE_FOR_SIZE
905    bool "Optimize for size"
906    help
907      Enabling this option will pass "-Os" instead of "-O2" to gcc
908      resulting in a smaller kernel.
909
910      If unsure, say Y.
911
912config SYSCTL
913    bool
914
915config ANON_INODES
916    bool
917
918menuconfig EXPERT
919    bool "Configure standard kernel features (expert users)"
920    # Unhide debug options, to make the on-by-default options visible
921    select DEBUG_KERNEL
922    help
923      This option allows certain base kernel options and settings
924          to be disabled or tweaked. This is for specialized
925          environments which can tolerate a "non-standard" kernel.
926          Only use this if you really know what you are doing.
927
928config UID16
929    bool "Enable 16-bit UID system calls" if EXPERT
930    depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
931    default y
932    help
933      This enables the legacy 16-bit UID syscall wrappers.
934
935config SYSCTL_SYSCALL
936    bool "Sysctl syscall support" if EXPERT
937    depends on PROC_SYSCTL
938    default y
939    select SYSCTL
940    ---help---
941      sys_sysctl uses binary paths that have been found challenging
942      to properly maintain and use. The interface in /proc/sys
943      using paths with ascii names is now the primary path to this
944      information.
945
946      Almost nothing using the binary sysctl interface so if you are
947      trying to save some space it is probably safe to disable this,
948      making your kernel marginally smaller.
949
950      If unsure say Y here.
951
952config KALLSYMS
953     bool "Load all symbols for debugging/ksymoops" if EXPERT
954     default y
955     help
956       Say Y here to let the kernel print out symbolic crash information and
957       symbolic stack backtraces. This increases the size of the kernel
958       somewhat, as all symbols have to be loaded into the kernel image.
959
960config KALLSYMS_ALL
961    bool "Include all symbols in kallsyms"
962    depends on DEBUG_KERNEL && KALLSYMS
963    help
964       Normally kallsyms only contains the symbols of functions for nicer
965       OOPS messages and backtraces (i.e., symbols from the text and inittext
966       sections). This is sufficient for most cases. And only in very rare
967       cases (e.g., when a debugger is used) all symbols are required (e.g.,
968       names of variables from the data sections, etc).
969
970       This option makes sure that all symbols are loaded into the kernel
971       image (i.e., symbols from all sections) in cost of increased kernel
972       size (depending on the kernel configuration, it may be 300KiB or
973       something like this).
974
975       Say N unless you really need all symbols.
976
977config HOTPLUG
978    bool "Support for hot-pluggable devices" if EXPERT
979    default y
980    help
981      This option is provided for the case where no hotplug or uevent
982      capabilities is wanted by the kernel. You should only consider
983      disabling this option for embedded systems that do not use modules, a
984      dynamic /dev tree, or dynamic device discovery. Just say Y.
985
986config PRINTK
987    default y
988    bool "Enable support for printk" if EXPERT
989    help
990      This option enables normal printk support. Removing it
991      eliminates most of the message strings from the kernel image
992      and makes the kernel more or less silent. As this makes it
993      very difficult to diagnose system problems, saying N here is
994      strongly discouraged.
995
996config BUG
997    bool "BUG() support" if EXPERT
998    default y
999    help
1000          Disabling this option eliminates support for BUG and WARN, reducing
1001          the size of your kernel image and potentially quietly ignoring
1002          numerous fatal conditions. You should only consider disabling this
1003          option for embedded systems with no facilities for reporting errors.
1004          Just say Y.
1005
1006config ELF_CORE
1007    default y
1008    bool "Enable ELF core dumps" if EXPERT
1009    help
1010      Enable support for generating core dumps. Disabling saves about 4k.
1011
1012
1013config PCSPKR_PLATFORM
1014    bool "Enable PC-Speaker support" if EXPERT
1015    depends on HAVE_PCSPKR_PLATFORM
1016    select I8253_LOCK
1017    default y
1018    help
1019          This option allows to disable the internal PC-Speaker
1020          support, saving some memory.
1021
1022config HAVE_PCSPKR_PLATFORM
1023    bool
1024
1025config BASE_FULL
1026    default y
1027    bool "Enable full-sized data structures for core" if EXPERT
1028    help
1029      Disabling this option reduces the size of miscellaneous core
1030      kernel data structures. This saves memory on small machines,
1031      but may reduce performance.
1032
1033config FUTEX
1034    bool "Enable futex support" if EXPERT
1035    default y
1036    select RT_MUTEXES
1037    help
1038      Disabling this option will cause the kernel to be built without
1039      support for "fast userspace mutexes". The resulting kernel may not
1040      run glibc-based applications correctly.
1041
1042config EPOLL
1043    bool "Enable eventpoll support" if EXPERT
1044    default y
1045    select ANON_INODES
1046    help
1047      Disabling this option will cause the kernel to be built without
1048      support for epoll family of system calls.
1049
1050config SIGNALFD
1051    bool "Enable signalfd() system call" if EXPERT
1052    select ANON_INODES
1053    default y
1054    help
1055      Enable the signalfd() system call that allows to receive signals
1056      on a file descriptor.
1057
1058      If unsure, say Y.
1059
1060config TIMERFD
1061    bool "Enable timerfd() system call" if EXPERT
1062    select ANON_INODES
1063    default y
1064    help
1065      Enable the timerfd() system call that allows to receive timer
1066      events on a file descriptor.
1067
1068      If unsure, say Y.
1069
1070config EVENTFD
1071    bool "Enable eventfd() system call" if EXPERT
1072    select ANON_INODES
1073    default y
1074    help
1075      Enable the eventfd() system call that allows to receive both
1076      kernel notification (ie. KAIO) or userspace notifications.
1077
1078      If unsure, say Y.
1079
1080config SHMEM
1081    bool "Use full shmem filesystem" if EXPERT
1082    default y
1083    depends on MMU
1084    help
1085      The shmem is an internal filesystem used to manage shared memory.
1086      It is backed by swap and manages resource limits. It is also exported
1087      to userspace as tmpfs if TMPFS is enabled. Disabling this
1088      option replaces shmem and tmpfs with the much simpler ramfs code,
1089      which may be appropriate on small systems without swap.
1090
1091config AIO
1092    bool "Enable AIO support" if EXPERT
1093    default y
1094    help
1095      This option enables POSIX asynchronous I/O which may by used
1096          by some high performance threaded applications. Disabling
1097          this option saves about 7k.
1098
1099config EMBEDDED
1100    bool "Embedded system"
1101    select EXPERT
1102    help
1103      This option should be enabled if compiling the kernel for
1104      an embedded system so certain expert options are available
1105      for configuration.
1106
1107config HAVE_PERF_EVENTS
1108    bool
1109    help
1110      See tools/perf/design.txt for details.
1111
1112config PERF_USE_VMALLOC
1113    bool
1114    help
1115      See tools/perf/design.txt for details
1116
1117menu "Kernel Performance Events And Counters"
1118
1119config PERF_EVENTS
1120    bool "Kernel performance events and counters"
1121    default y if (PROFILING || PERF_COUNTERS)
1122    depends on HAVE_PERF_EVENTS
1123    select ANON_INODES
1124    select IRQ_WORK
1125    help
1126      Enable kernel support for various performance events provided
1127      by software and hardware.
1128
1129      Software events are supported either built-in or via the
1130      use of generic tracepoints.
1131
1132      Most modern CPUs support performance events via performance
1133      counter registers. These registers count the number of certain
1134      types of hw events: such as instructions executed, cachemisses
1135      suffered, or branches mis-predicted - without slowing down the
1136      kernel or applications. These registers can also trigger interrupts
1137      when a threshold number of events have passed - and can thus be
1138      used to profile the code that runs on that CPU.
1139
1140      The Linux Performance Event subsystem provides an abstraction of
1141      these software and hardware event capabilities, available via a
1142      system call and used by the "perf" utility in tools/perf/. It
1143      provides per task and per CPU counters, and it provides event
1144      capabilities on top of those.
1145
1146      Say Y if unsure.
1147
1148config PERF_COUNTERS
1149    bool "Kernel performance counters (old config option)"
1150    depends on HAVE_PERF_EVENTS
1151    help
1152      This config has been obsoleted by the PERF_EVENTS
1153      config option - please see that one for details.
1154
1155      It has no effect on the kernel whether you enable
1156      it or not, it is a compatibility placeholder.
1157
1158      Say N if unsure.
1159
1160config DEBUG_PERF_USE_VMALLOC
1161    default n
1162    bool "Debug: use vmalloc to back perf mmap() buffers"
1163    depends on PERF_EVENTS && DEBUG_KERNEL
1164    select PERF_USE_VMALLOC
1165    help
1166     Use vmalloc memory to back perf mmap() buffers.
1167
1168     Mostly useful for debugging the vmalloc code on platforms
1169     that don't require it.
1170
1171     Say N if unsure.
1172
1173endmenu
1174
1175config VM_EVENT_COUNTERS
1176    default y
1177    bool "Enable VM event counters for /proc/vmstat" if EXPERT
1178    help
1179      VM event counters are needed for event counts to be shown.
1180      This option allows the disabling of the VM event counters
1181      on EXPERT systems. /proc/vmstat will only show page counts
1182      if VM event counters are disabled.
1183
1184config PCI_QUIRKS
1185    default y
1186    bool "Enable PCI quirk workarounds" if EXPERT
1187    depends on PCI
1188    help
1189      This enables workarounds for various PCI chipset
1190          bugs/quirks. Disable this only if your target machine is
1191          unaffected by PCI quirks.
1192
1193config SLUB_DEBUG
1194    default y
1195    bool "Enable SLUB debugging support" if EXPERT
1196    depends on SLUB && SYSFS
1197    help
1198      SLUB has extensive debug support features. Disabling these can
1199      result in significant savings in code size. This also disables
1200      SLUB sysfs support. /sys/slab will not exist and there will be
1201      no support for cache validation etc.
1202
1203config COMPAT_BRK
1204    bool "Disable heap randomization"
1205    default y
1206    help
1207      Randomizing heap placement makes heap exploits harder, but it
1208      also breaks ancient binaries (including anything libc5 based).
1209      This option changes the bootup default to heap randomization
1210      disabled, and can be overridden at runtime by setting
1211      /proc/sys/kernel/randomize_va_space to 2.
1212
1213      On non-ancient distros (post-2000 ones) N is usually a safe choice.
1214
1215choice
1216    prompt "Choose SLAB allocator"
1217    default SLUB
1218    help
1219       This option allows to select a slab allocator.
1220
1221config SLAB
1222    bool "SLAB"
1223    help
1224      The regular slab allocator that is established and known to work
1225      well in all environments. It organizes cache hot objects in
1226      per cpu and per node queues.
1227
1228config SLUB
1229    bool "SLUB (Unqueued Allocator)"
1230    help
1231       SLUB is a slab allocator that minimizes cache line usage
1232       instead of managing queues of cached objects (SLAB approach).
1233       Per cpu caching is realized using slabs of objects instead
1234       of queues of objects. SLUB can use memory efficiently
1235       and has enhanced diagnostics. SLUB is the default choice for
1236       a slab allocator.
1237
1238config SLOB
1239    depends on EXPERT
1240    bool "SLOB (Simple Allocator)"
1241    help
1242       SLOB replaces the stock allocator with a drastically simpler
1243       allocator. SLOB is generally more space efficient but
1244       does not perform as well on large systems.
1245
1246endchoice
1247
1248config MMAP_ALLOW_UNINITIALIZED
1249    bool "Allow mmapped anonymous memory to be uninitialized"
1250    depends on EXPERT && !MMU
1251    default n
1252    help
1253      Normally, and according to the Linux spec, anonymous memory obtained
1254      from mmap() has it's contents cleared before it is passed to
1255      userspace. Enabling this config option allows you to request that
1256      mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1257      providing a huge performance boost. If this option is not enabled,
1258      then the flag will be ignored.
1259
1260      This is taken advantage of by uClibc's malloc(), and also by
1261      ELF-FDPIC binfmt's brk and stack allocator.
1262
1263      Because of the obvious security issues, this option should only be
1264      enabled on embedded devices where you control what is run in
1265      userspace. Since that isn't generally a problem on no-MMU systems,
1266      it is normally safe to say Y here.
1267
1268      See Documentation/nommu-mmap.txt for more information.
1269
1270config PROFILING
1271    bool "Profiling support"
1272    help
1273      Say Y here to enable the extended profiling support mechanisms used
1274      by profilers such as OProfile.
1275
1276#
1277# Place an empty function call at each tracepoint site. Can be
1278# dynamically changed for a probe function.
1279#
1280config TRACEPOINTS
1281    bool
1282
1283source "arch/Kconfig"
1284
1285endmenu # General setup
1286
1287config HAVE_GENERIC_DMA_COHERENT
1288    bool
1289    default n
1290
1291config SLABINFO
1292    bool
1293    depends on PROC_FS
1294    depends on SLAB || SLUB_DEBUG
1295    default y
1296
1297config RT_MUTEXES
1298    boolean
1299
1300config BASE_SMALL
1301    int
1302    default 0 if BASE_FULL
1303    default 1 if !BASE_FULL
1304
1305menuconfig MODULES
1306    bool "Enable loadable module support"
1307    help
1308      Kernel modules are small pieces of compiled code which can
1309      be inserted in the running kernel, rather than being
1310      permanently built into the kernel. You use the "modprobe"
1311      tool to add (and sometimes remove) them. If you say Y here,
1312      many parts of the kernel can be built as modules (by
1313      answering M instead of Y where indicated): this is most
1314      useful for infrequently used options which are not required
1315      for booting. For more information, see the man pages for
1316      modprobe, lsmod, modinfo, insmod and rmmod.
1317
1318      If you say Y here, you will need to run "make
1319      modules_install" to put the modules under /lib/modules/
1320      where modprobe can find them (you may need to be root to do
1321      this).
1322
1323      If unsure, say Y.
1324
1325if MODULES
1326
1327config MODULE_FORCE_LOAD
1328    bool "Forced module loading"
1329    default n
1330    help
1331      Allow loading of modules without version information (ie. modprobe
1332      --force). Forced module loading sets the 'F' (forced) taint flag and
1333      is usually a really bad idea.
1334
1335config MODULE_UNLOAD
1336    bool "Module unloading"
1337    help
1338      Without this option you will not be able to unload any
1339      modules (note that some modules may not be unloadable
1340      anyway), which makes your kernel smaller, faster
1341      and simpler. If unsure, say Y.
1342
1343config MODULE_FORCE_UNLOAD
1344    bool "Forced module unloading"
1345    depends on MODULE_UNLOAD && EXPERIMENTAL
1346    help
1347      This option allows you to force a module to unload, even if the
1348      kernel believes it is unsafe: the kernel will remove the module
1349      without waiting for anyone to stop using it (using the -f option to
1350      rmmod). This is mainly for kernel developers and desperate users.
1351      If unsure, say N.
1352
1353config MODVERSIONS
1354    bool "Module versioning support"
1355    help
1356      Usually, you have to use modules compiled with your kernel.
1357      Saying Y here makes it sometimes possible to use modules
1358      compiled for different kernels, by adding enough information
1359      to the modules to (hopefully) spot any changes which would
1360      make them incompatible with the kernel you are running. If
1361      unsure, say N.
1362
1363config MODULE_SRCVERSION_ALL
1364    bool "Source checksum for all modules"
1365    help
1366      Modules which contain a MODULE_VERSION get an extra "srcversion"
1367      field inserted into their modinfo section, which contains a
1368          sum of the source files which made it. This helps maintainers
1369      see exactly which source was used to build a module (since
1370      others sometimes change the module source without updating
1371      the version). With this option, such a "srcversion" field
1372      will be created for all modules. If unsure, say N.
1373
1374endif # MODULES
1375
1376config INIT_ALL_POSSIBLE
1377    bool
1378    help
1379      Back when each arch used to define their own cpu_online_map and
1380      cpu_possible_map, some of them chose to initialize cpu_possible_map
1381      with all 1s, and others with all 0s. When they were centralised,
1382      it was better to provide this option than to break all the archs
1383      and have several arch maintainers pursuing me down dark alleys.
1384
1385config STOP_MACHINE
1386    bool
1387    default y
1388    depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1389    help
1390      Need stop_machine() primitive.
1391
1392source "block/Kconfig"
1393
1394config PREEMPT_NOTIFIERS
1395    bool
1396
1397config PADATA
1398    depends on SMP
1399    bool
1400
1401source "kernel/Kconfig.locks"
1402

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