init/Kconfig

   1 config ARCH
   2         string
   3         option env="ARCH"
   4
   5 config KERNELVERSION
   6         string
   7         option env="KERNELVERSION"
   8
   9 config DEFCONFIG_LIST
  10         string
  11         depends on !UML
  12         option defconfig_list
  13         default "/lib/modules/$UNAME_RELEASE/.config"
  14         default "/etc/kernel-config"
  15         default "/boot/config-$UNAME_RELEASE"
  16         default "$ARCH_DEFCONFIG"
  17         default "arch/$ARCH/defconfig"
  18
  19 config CONSTRUCTORS
  20         bool
  21         depends on !UML
  22         default y
  23
  24 menu "General setup"
  25
  26 config EXPERIMENTAL
  27         bool "Prompt for development and/or incomplete code/drivers"
  28         ---help---
  29           Some of the various things that Linux supports (such as network
  30           drivers, file systems, network protocols, etc.) can be in a state
  31           of development where the functionality, stability, or the level of
  32           testing is not yet high enough for general use. This is usually
  33           known as the "alpha-test" phase among developers. If a feature is
  34           currently in alpha-test, then the developers usually discourage
  35           uninformed widespread use of this feature by the general public to
  36           avoid "Why doesn't this work?" type mail messages. However, active
  37           testing and use of these systems is welcomed. Just be aware that it
  38           may not meet the normal level of reliability or it may fail to work
  39           in some special cases. Detailed bug reports from people familiar
  40           with the kernel internals are usually welcomed by the developers
  41           (before submitting bug reports, please read the documents
  42           <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  43           <file:Documentation/BUG-HUNTING>, and
  44           <file:Documentation/oops-tracing.txt> in the kernel source).
  45
  46           This option will also make obsoleted drivers available. These are
  47           drivers that have been replaced by something else, and/or are
  48           scheduled to be removed in a future kernel release.
  49
  50           Unless you intend to help test and develop a feature or driver that
  51           falls into this category, or you have a situation that requires
  52           using these features, you should probably say N here, which will
  53           cause the configurator to present you with fewer choices. If
  54           you say Y here, you will be offered the choice of using features or
  55           drivers that are currently considered to be in the alpha-test phase.
  56
  57 config BROKEN
  58         bool
  59
  60 config BROKEN_ON_SMP
  61         bool
  62         depends on BROKEN || !SMP
  63         default y
  64
  65 config LOCK_KERNEL
  66         bool
  67         depends on SMP || PREEMPT
  68         default y
  69
  70 config INIT_ENV_ARG_LIMIT
  71         int
  72         default 32 if !UML
  73         default 128 if UML
  74         help
  75           Maximum of each of the number of arguments and environment
  76           variables passed to init from the kernel command line.
  77
  78
  79 config CROSS_COMPILE
  80         string "Cross-compiler tool prefix"
  81         help
  82           Same as running 'make CROSS_COMPILE=prefix-' but stored for
  83           default make runs in this kernel build directory.  You don't
  84           need to set this unless you want the configured kernel build
  85           directory to select the cross-compiler automatically.
  86
  87 config LOCALVERSION
  88         string "Local version - append to kernel release"
  89         help
  90           Append an extra string to the end of your kernel version.
  91           This will show up when you type uname, for example.
  92           The string you set here will be appended after the contents of
  93           any files with a filename matching localversion* in your
  94           object and source tree, in that order.  Your total string can
  95           be a maximum of 64 characters.
  96
  97 config LOCALVERSION_AUTO
  98         bool "Automatically append version information to the version string"
  99         default y
 100         help
 101           This will try to automatically determine if the current tree is a
 102           release tree by looking for git tags that belong to the current
 103           top of tree revision.
 104
 105           A string of the format -gxxxxxxxx will be added to the localversion
 106           if a git-based tree is found.  The string generated by this will be
 107           appended after any matching localversion* files, and after the value
 108           set in CONFIG_LOCALVERSION.
 109
 110           (The actual string used here is the first eight characters produced
 111           by running the command:
 112
 113             $ git rev-parse --verify HEAD
 114
 115           which is done within the script "scripts/setlocalversion".)
 116
 117 config HAVE_KERNEL_GZIP
 118         bool
 119
 120 config HAVE_KERNEL_BZIP2
 121         bool
 122
 123 config HAVE_KERNEL_LZMA
 124         bool
 125
 126 config HAVE_KERNEL_LZO
 127         bool
 128
 129 choice
 130         prompt "Kernel compression mode"
 131         default KERNEL_GZIP
 132         depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
 133         help
 134           The linux kernel is a kind of self-extracting executable.
 135           Several compression algorithms are available, which differ
 136           in efficiency, compression and decompression speed.
 137           Compression speed is only relevant when building a kernel.
 138           Decompression speed is relevant at each boot.
 139
 140           If you have any problems with bzip2 or lzma compressed
 141           kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
 142           version of this functionality (bzip2 only), for 2.4, was
 143           supplied by Christian Ludwig)
 144
 145           High compression options are mostly useful for users, who
 146           are low on disk space (embedded systems), but for whom ram
 147           size matters less.
 148
 149           If in doubt, select 'gzip'
 150
 151 config KERNEL_GZIP
 152         bool "Gzip"
 153         depends on HAVE_KERNEL_GZIP
 154         help
 155           The old and tried gzip compression. It provides a good balance
 156           between compression ratio and decompression speed.
 157
 158 config KERNEL_BZIP2
 159         bool "Bzip2"
 160         depends on HAVE_KERNEL_BZIP2
 161         help
 162           Its compression ratio and speed is intermediate.
 163           Decompression speed is slowest among the three.  The kernel
 164           size is about 10% smaller with bzip2, in comparison to gzip.
 165           Bzip2 uses a large amount of memory. For modern kernels you
 166           will need at least 8MB RAM or more for booting.
 167
 168 config KERNEL_LZMA
 169         bool "LZMA"
 170         depends on HAVE_KERNEL_LZMA
 171         help
 172           The most recent compression algorithm.
 173           Its ratio is best, decompression speed is between the other
 174           two. Compression is slowest.  The kernel size is about 33%
 175           smaller with LZMA in comparison to gzip.
 176
 177 config KERNEL_LZO
 178         bool "LZO"
 179         depends on HAVE_KERNEL_LZO
 180         help
 181           Its compression ratio is the poorest among the 4. The kernel
 182           size is about about 10% bigger than gzip; however its speed
 183           (both compression and decompression) is the fastest.
 184
 185 endchoice
 186
 187 config SWAP
 188         bool "Support for paging of anonymous memory (swap)"
 189         depends on MMU && BLOCK
 190         default y
 191         help
 192           This option allows you to choose whether you want to have support
 193           for so called swap devices or swap files in your kernel that are
 194           used to provide more virtual memory than the actual RAM present
 195           in your computer.  If unsure say Y.
 196
 197 config SYSVIPC
 198         bool "System V IPC"
 199         ---help---
 200           Inter Process Communication is a suite of library functions and
 201           system calls which let processes (running programs) synchronize and
 202           exchange information. It is generally considered to be a good thing,
 203           and some programs won't run unless you say Y here. In particular, if
 204           you want to run the DOS emulator dosemu under Linux (read the
 205           DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
 206           you'll need to say Y here.
 207
 208           You can find documentation about IPC with "info ipc" and also in
 209           section 6.4 of the Linux Programmer's Guide, available from
 210           <http://www.tldp.org/guides.html>.
 211
 212 config SYSVIPC_SYSCTL
 213         bool
 214         depends on SYSVIPC
 215         depends on SYSCTL
 216         default y
 217
 218 config POSIX_MQUEUE
 219         bool "POSIX Message Queues"
 220         depends on NET && EXPERIMENTAL
 221         ---help---
 222           POSIX variant of message queues is a part of IPC. In POSIX message
 223           queues every message has a priority which decides about succession
 224           of receiving it by a process. If you want to compile and run
 225           programs written e.g. for Solaris with use of its POSIX message
 226           queues (functions mq_*) say Y here.
 227
 228           POSIX message queues are visible as a filesystem called 'mqueue'
 229           and can be mounted somewhere if you want to do filesystem
 230           operations on message queues.
 231
 232           If unsure, say Y.
 233
 234 config POSIX_MQUEUE_SYSCTL
 235         bool
 236         depends on POSIX_MQUEUE
 237         depends on SYSCTL
 238         default y
 239
 240 config BSD_PROCESS_ACCT
 241         bool "BSD Process Accounting"
 242         help
 243           If you say Y here, a user level program will be able to instruct the
 244           kernel (via a special system call) to write process accounting
 245           information to a file: whenever a process exits, information about
 246           that process will be appended to the file by the kernel.  The
 247           information includes things such as creation time, owning user,
 248           command name, memory usage, controlling terminal etc. (the complete
 249           list is in the struct acct in <file:include/linux/acct.h>).  It is
 250           up to the user level program to do useful things with this
 251           information.  This is generally a good idea, so say Y.
 252
 253 config BSD_PROCESS_ACCT_V3
 254         bool "BSD Process Accounting version 3 file format"
 255         depends on BSD_PROCESS_ACCT
 256         default n
 257         help
 258           If you say Y here, the process accounting information is written
 259           in a new file format that also logs the process IDs of each
 260           process and it's parent. Note that this file format is incompatible
 261           with previous v0/v1/v2 file formats, so you will need updated tools
 262           for processing it. A preliminary version of these tools is available
 263           at <http://www.gnu.org/software/acct/>.
 264
 265 config TASKSTATS
 266         bool "Export task/process statistics through netlink (EXPERIMENTAL)"
 267         depends on NET
 268         default n
 269         help
 270           Export selected statistics for tasks/processes through the
 271           generic netlink interface. Unlike BSD process accounting, the
 272           statistics are available during the lifetime of tasks/processes as
 273           responses to commands. Like BSD accounting, they are sent to user
 274           space on task exit.
 275
 276           Say N if unsure.
 277
 278 config TASK_DELAY_ACCT
 279         bool "Enable per-task delay accounting (EXPERIMENTAL)"
 280         depends on TASKSTATS
 281         help
 282           Collect information on time spent by a task waiting for system
 283           resources like cpu, synchronous block I/O completion and swapping
 284           in pages. Such statistics can help in setting a task's priorities
 285           relative to other tasks for cpu, io, rss limits etc.
 286
 287           Say N if unsure.
 288
 289 config TASK_XACCT
 290         bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
 291         depends on TASKSTATS
 292         help
 293           Collect extended task accounting data and send the data
 294           to userland for processing over the taskstats interface.
 295
 296           Say N if unsure.
 297
 298 config TASK_IO_ACCOUNTING
 299         bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
 300         depends on TASK_XACCT
 301         help
 302           Collect information on the number of bytes of storage I/O which this
 303           task has caused.
 304
 305           Say N if unsure.
 306
 307 config AUDIT
 308         bool "Auditing support"
 309         depends on NET
 310         help
 311           Enable auditing infrastructure that can be used with another
 312           kernel subsystem, such as SELinux (which requires this for
 313           logging of avc messages output).  Does not do system-call
 314           auditing without CONFIG_AUDITSYSCALL.
 315
 316 config AUDITSYSCALL
 317         bool "Enable system-call auditing support"
 318         depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
 319         default y if SECURITY_SELINUX
 320         help
 321           Enable low-overhead system-call auditing infrastructure that
 322           can be used independently or with another kernel subsystem,
 323           such as SELinux.  To use audit's filesystem watch feature, please
 324           ensure that INOTIFY is configured.
 325
 326 config AUDIT_TREE
 327         def_bool y
 328         depends on AUDITSYSCALL
 329         select INOTIFY
 330
 331 menu "RCU Subsystem"
 332
 333 choice
 334         prompt "RCU Implementation"
 335         default TREE_RCU
 336
 337 config TREE_RCU
 338         bool "Tree-based hierarchical RCU"
 339         help
 340           This option selects the RCU implementation that is
 341           designed for very large SMP system with hundreds or
 342           thousands of CPUs.  It also scales down nicely to
 343           smaller systems.
 344
 345 config TREE_PREEMPT_RCU
 346         bool "Preemptable tree-based hierarchical RCU"
 347         depends on PREEMPT
 348         help
 349           This option selects the RCU implementation that is
 350           designed for very large SMP systems with hundreds or
 351           thousands of CPUs, but for which real-time response
 352           is also required.  It also scales down nicely to
 353           smaller systems.
 354
 355 config TINY_RCU
 356         bool "UP-only small-memory-footprint RCU"
 357         depends on !SMP
 358         help
 359           This option selects the RCU implementation that is
 360           designed for UP systems from which real-time response
 361           is not required.  This option greatly reduces the
 362           memory footprint of RCU.
 363
 364 endchoice
 365
 366 config RCU_TRACE
 367         bool "Enable tracing for RCU"
 368         depends on TREE_RCU || TREE_PREEMPT_RCU
 369         help
 370           This option provides tracing in RCU which presents stats
 371           in debugfs for debugging RCU implementation.
 372
 373           Say Y here if you want to enable RCU tracing
 374           Say N if you are unsure.
 375
 376 config RCU_FANOUT
 377         int "Tree-based hierarchical RCU fanout value"
 378         range 2 64 if 64BIT
 379         range 2 32 if !64BIT
 380         depends on TREE_RCU || TREE_PREEMPT_RCU
 381         default 64 if 64BIT
 382         default 32 if !64BIT
 383         help
 384           This option controls the fanout of hierarchical implementations
 385           of RCU, allowing RCU to work efficiently on machines with
 386           large numbers of CPUs.  This value must be at least the cube
 387           root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
 388           systems and up to 262,144 for 64-bit systems.
 389
 390           Select a specific number if testing RCU itself.
 391           Take the default if unsure.
 392
 393 config RCU_FANOUT_EXACT
 394         bool "Disable tree-based hierarchical RCU auto-balancing"
 395         depends on TREE_RCU || TREE_PREEMPT_RCU
 396         default n
 397         help
 398           This option forces use of the exact RCU_FANOUT value specified,
 399           regardless of imbalances in the hierarchy.  This is useful for
 400           testing RCU itself, and might one day be useful on systems with
 401           strong NUMA behavior.
 402
 403           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
 404
 405           Say N if unsure.
 406
 407 config RCU_FAST_NO_HZ
 408         bool "Accelerate last non-dyntick-idle CPU's grace periods"
 409         depends on TREE_RCU && NO_HZ && SMP
 410         default n
 411         help
 412           This option causes RCU to attempt to accelerate grace periods
 413           in order to allow the final CPU to enter dynticks-idle state
 414           more quickly.  On the other hand, this option increases the
 415           overhead of the dynticks-idle checking, particularly on systems
 416           with large numbers of CPUs.
 417
 418           Say Y if energy efficiency is critically important, particularly
 419                 if you have relatively few CPUs.
 420
 421           Say N if you are unsure.
 422
 423 config TREE_RCU_TRACE
 424         def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
 425         select DEBUG_FS
 426         help
 427           This option provides tracing for the TREE_RCU and
 428           TREE_PREEMPT_RCU implementations, permitting Makefile to
 429           trivially select kernel/rcutree_trace.c.
 430
 431 endmenu # "RCU Subsystem"
 432
 433 config IKCONFIG
 434         tristate "Kernel .config support"
 435         ---help---
 436           This option enables the complete Linux kernel ".config" file
 437           contents to be saved in the kernel. It provides documentation
 438           of which kernel options are used in a running kernel or in an
 439           on-disk kernel.  This information can be extracted from the kernel
 440           image file with the script scripts/extract-ikconfig and used as
 441           input to rebuild the current kernel or to build another kernel.
 442           It can also be extracted from a running kernel by reading
 443           /proc/config.gz if enabled (below).
 444
 445 config IKCONFIG_PROC
 446         bool "Enable access to .config through /proc/config.gz"
 447         depends on IKCONFIG && PROC_FS
 448         ---help---
 449           This option enables access to the kernel configuration file
 450           through /proc/config.gz.
 451
 452 config LOG_BUF_SHIFT
 453         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 454         range 12 21
 455         default 17
 456         help
 457           Select kernel log buffer size as a power of 2.
 458           Examples:
 459                      17 => 128 KB
 460                      16 => 64 KB
 461                      15 => 32 KB
 462                      14 => 16 KB
 463                      13 =>  8 KB
 464                      12 =>  4 KB
 465
 466 #
 467 # Architectures with an unreliable sched_clock() should select this:
 468 #
 469 config HAVE_UNSTABLE_SCHED_CLOCK
 470         bool
 471
 472 menuconfig CGROUPS
 473         boolean "Control Group support"
 474         depends on EVENTFD
 475         help
 476           This option adds support for grouping sets of processes together, for
 477           use with process control subsystems such as Cpusets, CFS, memory
 478           controls or device isolation.
 479           See
 480                 - Documentation/scheduler/sched-design-CFS.txt  (CFS)
 481                 - Documentation/cgroups/ (features for grouping, isolation
 482                                           and resource control)
 483
 484           Say N if unsure.
 485
 486 if CGROUPS
 487
 488 config CGROUP_DEBUG
 489         bool "Example debug cgroup subsystem"
 490         depends on CGROUPS
 491         default n
 492         help
 493           This option enables a simple cgroup subsystem that
 494           exports useful debugging information about the cgroups
 495           framework.
 496
 497           Say N if unsure.
 498
 499 config CGROUP_NS
 500         bool "Namespace cgroup subsystem"
 501         depends on CGROUPS
 502         help
 503           Provides a simple namespace cgroup subsystem to
 504           provide hierarchical naming of sets of namespaces,
 505           for instance virtual servers and checkpoint/restart
 506           jobs.
 507
 508 config CGROUP_FREEZER
 509         bool "Freezer cgroup subsystem"
 510         depends on CGROUPS
 511         help
 512           Provides a way to freeze and unfreeze all tasks in a
 513           cgroup.
 514
 515 config CGROUP_DEVICE
 516         bool "Device controller for cgroups"
 517         depends on CGROUPS && EXPERIMENTAL
 518         help
 519           Provides a cgroup implementing whitelists for devices which
 520           a process in the cgroup can mknod or open.
 521
 522 config CPUSETS
 523         bool "Cpuset support"
 524         depends on CGROUPS
 525         help
 526           This option will let you create and manage CPUSETs which
 527           allow dynamically partitioning a system into sets of CPUs and
 528           Memory Nodes and assigning tasks to run only within those sets.
 529           This is primarily useful on large SMP or NUMA systems.
 530
 531           Say N if unsure.
 532
 533 config PROC_PID_CPUSET
 534         bool "Include legacy /proc/<pid>/cpuset file"
 535         depends on CPUSETS
 536         default y
 537
 538 config CGROUP_CPUACCT
 539         bool "Simple CPU accounting cgroup subsystem"
 540         depends on CGROUPS
 541         help
 542           Provides a simple Resource Controller for monitoring the
 543           total CPU consumed by the tasks in a cgroup.
 544
 545 config RESOURCE_COUNTERS
 546         bool "Resource counters"
 547         help
 548           This option enables controller independent resource accounting
 549           infrastructure that works with cgroups.
 550         depends on CGROUPS
 551
 552 config CGROUP_MEM_RES_CTLR
 553         bool "Memory Resource Controller for Control Groups"
 554         depends on CGROUPS && RESOURCE_COUNTERS
 555         select MM_OWNER
 556         help
 557           Provides a memory resource controller that manages both anonymous
 558           memory and page cache. (See Documentation/cgroups/memory.txt)
 559
 560           Note that setting this option increases fixed memory overhead
 561           associated with each page of memory in the system. By this,
 562           20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
 563           usage tracking struct at boot. Total amount of this is printed out
 564           at boot.
 565
 566           Only enable when you're ok with these trade offs and really
 567           sure you need the memory resource controller. Even when you enable
 568           this, you can set "cgroup_disable=memory" at your boot option to
 569           disable memory resource controller and you can avoid overheads.
 570           (and lose benefits of memory resource controller)
 571
 572           This config option also selects MM_OWNER config option, which
 573           could in turn add some fork/exit overhead.
 574
 575 config CGROUP_MEM_RES_CTLR_SWAP
 576         bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
 577         depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
 578         help
 579           Add swap management feature to memory resource controller. When you
 580           enable this, you can limit mem+swap usage per cgroup. In other words,
 581           when you disable this, memory resource controller has no cares to
 582           usage of swap...a process can exhaust all of the swap. This extension
 583           is useful when you want to avoid exhaustion swap but this itself
 584           adds more overheads and consumes memory for remembering information.
 585           Especially if you use 32bit system or small memory system, please
 586           be careful about enabling this. When memory resource controller
 587           is disabled by boot option, this will be automatically disabled and
 588           there will be no overhead from this. Even when you set this config=y,
 589           if boot option "noswapaccount" is set, swap will not be accounted.
 590           Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
 591           size is 4096bytes, 512k per 1Gbytes of swap.
 592
 593 menuconfig CGROUP_SCHED
 594         bool "Group CPU scheduler"
 595         depends on EXPERIMENTAL && CGROUPS
 596         default n
 597         help
 598           This feature lets CPU scheduler recognize task groups and control CPU
 599           bandwidth allocation to such task groups. It uses cgroups to group
 600           tasks.
 601
 602 if CGROUP_SCHED
 603 config FAIR_GROUP_SCHED
 604         bool "Group scheduling for SCHED_OTHER"
 605         depends on CGROUP_SCHED
 606         default CGROUP_SCHED
 607
 608 config RT_GROUP_SCHED
 609         bool "Group scheduling for SCHED_RR/FIFO"
 610         depends on EXPERIMENTAL
 611         depends on CGROUP_SCHED
 612         default n
 613         help
 614           This feature lets you explicitly allocate real CPU bandwidth
 615           to task groups. If enabled, it will also make it impossible to
 616           schedule realtime tasks for non-root users until you allocate
 617           realtime bandwidth for them.
 618           See Documentation/scheduler/sched-rt-group.txt for more information.
 619
 620 endif #CGROUP_SCHED
 621
 622 config BLK_CGROUP
 623         tristate "Block IO controller"
 624         depends on CGROUPS && BLOCK
 625         default n
 626         ---help---
 627         Generic block IO controller cgroup interface. This is the common
 628         cgroup interface which should be used by various IO controlling
 629         policies.
 630
 631         Currently, CFQ IO scheduler uses it to recognize task groups and
 632         control disk bandwidth allocation (proportional time slice allocation)
 633         to such task groups.
 634
 635         This option only enables generic Block IO controller infrastructure.
 636         One needs to also enable actual IO controlling logic in CFQ for it
 637         to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
 638
 639         See Documentation/cgroups/blkio-controller.txt for more information.
 640
 641 config DEBUG_BLK_CGROUP
 642         bool "Enable Block IO controller debugging"
 643         depends on BLK_CGROUP
 644         default n
 645         ---help---
 646         Enable some debugging help. Currently it exports additional stat
 647         files in a cgroup which can be useful for debugging.
 648
 649 endif # CGROUPS
 650
 651 config MM_OWNER
 652         bool
 653
 654 config SYSFS_DEPRECATED
 655         bool
 656
 657 config SYSFS_DEPRECATED_V2
 658         bool "enable deprecated sysfs features to support old userspace tools"
 659         depends on SYSFS
 660         default n
 661         select SYSFS_DEPRECATED
 662         help
 663           This option switches the layout of sysfs to the deprecated
 664           version. Do not use it on recent distributions.
 665
 666           The current sysfs layout features a unified device tree at
 667           /sys/devices/, which is able to express a hierarchy between
 668           class devices. If the deprecated option is set to Y, the
 669           unified device tree is split into a bus device tree at
 670           /sys/devices/ and several individual class device trees at
 671           /sys/class/. The class and bus devices will be connected by
 672           "<subsystem>:<name>" and the "device" links. The "block"
 673           class devices, will not show up in /sys/class/block/. Some
 674           subsystems will suppress the creation of some devices which
 675           depend on the unified device tree.
 676
 677           This option is not a pure compatibility option that can
 678           be safely enabled on newer distributions. It will change the
 679           layout of sysfs to the non-extensible deprecated version,
 680           and disable some features, which can not be exported without
 681           confusing older userspace tools. Since 2007/2008 all major
 682           distributions do not enable this option, and ship no tools which
 683           depend on the deprecated layout or this option.
 684
 685           If you are using a new kernel on an older distribution, or use
 686           older userspace tools, you might need to say Y here. Do not say Y,
 687           if the original kernel, that came with your distribution, has
 688           this option set to N.
 689
 690 config RELAY
 691         bool "Kernel->user space relay support (formerly relayfs)"
 692         help
 693           This option enables support for relay interface support in
 694           certain file systems (such as debugfs).
 695           It is designed to provide an efficient mechanism for tools and
 696           facilities to relay large amounts of data from kernel space to
 697           user space.
 698
 699           If unsure, say N.
 700
 701 config NAMESPACES
 702         bool "Namespaces support" if EMBEDDED
 703         default !EMBEDDED
 704         help
 705           Provides the way to make tasks work with different objects using
 706           the same id. For example same IPC id may refer to different objects
 707           or same user id or pid may refer to different tasks when used in
 708           different namespaces.
 709
 710 config UTS_NS
 711         bool "UTS namespace"
 712         depends on NAMESPACES
 713         help
 714           In this namespace tasks see different info provided with the
 715           uname() system call
 716
 717 config IPC_NS
 718         bool "IPC namespace"
 719         depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
 720         help
 721           In this namespace tasks work with IPC ids which correspond to
 722           different IPC objects in different namespaces.
 723
 724 config USER_NS
 725         bool "User namespace (EXPERIMENTAL)"
 726         depends on NAMESPACES && EXPERIMENTAL
 727         help
 728           This allows containers, i.e. vservers, to use user namespaces
 729           to provide different user info for different servers.
 730           If unsure, say N.
 731
 732 config PID_NS
 733         bool "PID Namespaces (EXPERIMENTAL)"
 734         default n
 735         depends on NAMESPACES && EXPERIMENTAL
 736         help
 737           Support process id namespaces.  This allows having multiple
 738           processes with the same pid as long as they are in different
 739           pid namespaces.  This is a building block of containers.
 740
 741           Unless you want to work with an experimental feature
 742           say N here.
 743
 744 config NET_NS
 745         bool "Network namespace"
 746         default n
 747         depends on NAMESPACES && EXPERIMENTAL && NET
 748         help
 749           Allow user space to create what appear to be multiple instances
 750           of the network stack.
 751
 752 config BLK_DEV_INITRD
 753         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 754         depends on BROKEN || !FRV
 755         help
 756           The initial RAM filesystem is a ramfs which is loaded by the
 757           boot loader (loadlin or lilo) and that is mounted as root
 758           before the normal boot procedure. It is typically used to
 759           load modules needed to mount the "real" root file system,
 760           etc. See <file:Documentation/initrd.txt> for details.
 761
 762           If RAM disk support (BLK_DEV_RAM) is also included, this
 763           also enables initial RAM disk (initrd) support and adds
 764           15 Kbytes (more on some other architectures) to the kernel size.
 765
 766           If unsure say Y.
 767
 768 if BLK_DEV_INITRD
 769
 770 source "usr/Kconfig"
 771
 772 endif
 773
 774 config CC_OPTIMIZE_FOR_SIZE
 775         bool "Optimize for size"
 776         default y
 777         help
 778           Enabling this option will pass "-Os" instead of "-O2" to gcc
 779           resulting in a smaller kernel.
 780
 781           If unsure, say Y.
 782
 783 config SYSCTL
 784         bool
 785
 786 config ANON_INODES
 787         bool
 788
 789 menuconfig EMBEDDED
 790         bool "Configure standard kernel features (for small systems)"
 791         help
 792           This option allows certain base kernel options and settings
 793           to be disabled or tweaked. This is for specialized
 794           environments which can tolerate a "non-standard" kernel.
 795           Only use this if you really know what you are doing.
 796
 797 config UID16
 798         bool "Enable 16-bit UID system calls" if EMBEDDED
 799         depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
 800         default y
 801         help
 802           This enables the legacy 16-bit UID syscall wrappers.
 803
 804 config SYSCTL_SYSCALL
 805         bool "Sysctl syscall support" if EMBEDDED
 806         depends on PROC_SYSCTL
 807         default y
 808         select SYSCTL
 809         ---help---
 810           sys_sysctl uses binary paths that have been found challenging
 811           to properly maintain and use.  The interface in /proc/sys
 812           using paths with ascii names is now the primary path to this
 813           information.
 814
 815           Almost nothing using the binary sysctl interface so if you are
 816           trying to save some space it is probably safe to disable this,
 817           making your kernel marginally smaller.
 818
 819           If unsure say Y here.
 820
 821 config KALLSYMS
 822          bool "Load all symbols for debugging/ksymoops" if EMBEDDED
 823          default y
 824          help
 825            Say Y here to let the kernel print out symbolic crash information and
 826            symbolic stack backtraces. This increases the size of the kernel
 827            somewhat, as all symbols have to be loaded into the kernel image.
 828
 829 config KALLSYMS_ALL
 830         bool "Include all symbols in kallsyms"
 831         depends on DEBUG_KERNEL && KALLSYMS
 832         help
 833            Normally kallsyms only contains the symbols of functions, for nicer
 834            OOPS messages.  Some debuggers can use kallsyms for other
 835            symbols too: say Y here to include all symbols, if you need them
 836            and you don't care about adding 300k to the size of your kernel.
 837
 838            Say N.
 839
 840 config KALLSYMS_EXTRA_PASS
 841         bool "Do an extra kallsyms pass"
 842         depends on KALLSYMS
 843         help
 844            If kallsyms is not working correctly, the build will fail with
 845            inconsistent kallsyms data.  If that occurs, log a bug report and
 846            turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
 847            Always say N here unless you find a bug in kallsyms, which must be
 848            reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
 849            you wait for kallsyms to be fixed.
 850
 851
 852 config HOTPLUG
 853         bool "Support for hot-pluggable devices" if EMBEDDED
 854         default y
 855         help
 856           This option is provided for the case where no hotplug or uevent
 857           capabilities is wanted by the kernel.  You should only consider
 858           disabling this option for embedded systems that do not use modules, a
 859           dynamic /dev tree, or dynamic device discovery.  Just say Y.
 860
 861 config PRINTK
 862         default y
 863         bool "Enable support for printk" if EMBEDDED
 864         help
 865           This option enables normal printk support. Removing it
 866           eliminates most of the message strings from the kernel image
 867           and makes the kernel more or less silent. As this makes it
 868           very difficult to diagnose system problems, saying N here is
 869           strongly discouraged.
 870
 871 config BUG
 872         bool "BUG() support" if EMBEDDED
 873         default y
 874         help
 875           Disabling this option eliminates support for BUG and WARN, reducing
 876           the size of your kernel image and potentially quietly ignoring
 877           numerous fatal conditions. You should only consider disabling this
 878           option for embedded systems with no facilities for reporting errors.
 879           Just say Y.
 880
 881 config ELF_CORE
 882         default y
 883         bool "Enable ELF core dumps" if EMBEDDED
 884         help
 885           Enable support for generating core dumps. Disabling saves about 4k.
 886
 887 config PCSPKR_PLATFORM
 888         bool "Enable PC-Speaker support" if EMBEDDED
 889         depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
 890         default y
 891         help
 892           This option allows to disable the internal PC-Speaker
 893           support, saving some memory.
 894
 895 config BASE_FULL
 896         default y
 897         bool "Enable full-sized data structures for core" if EMBEDDED
 898         help
 899           Disabling this option reduces the size of miscellaneous core
 900           kernel data structures. This saves memory on small machines,
 901           but may reduce performance.
 902
 903 config FUTEX
 904         bool "Enable futex support" if EMBEDDED
 905         default y
 906         select RT_MUTEXES
 907         help
 908           Disabling this option will cause the kernel to be built without
 909           support for "fast userspace mutexes".  The resulting kernel may not
 910           run glibc-based applications correctly.
 911
 912 config EPOLL
 913         bool "Enable eventpoll support" if EMBEDDED
 914         default y
 915         select ANON_INODES
 916         help
 917           Disabling this option will cause the kernel to be built without
 918           support for epoll family of system calls.
 919
 920 config SIGNALFD
 921         bool "Enable signalfd() system call" if EMBEDDED
 922         select ANON_INODES
 923         default y
 924         help
 925           Enable the signalfd() system call that allows to receive signals
 926           on a file descriptor.
 927
 928           If unsure, say Y.
 929
 930 config TIMERFD
 931         bool "Enable timerfd() system call" if EMBEDDED
 932         select ANON_INODES
 933         default y
 934         help
 935           Enable the timerfd() system call that allows to receive timer
 936           events on a file descriptor.
 937
 938           If unsure, say Y.
 939
 940 config EVENTFD
 941         bool "Enable eventfd() system call" if EMBEDDED
 942         select ANON_INODES
 943         default y
 944         help
 945           Enable the eventfd() system call that allows to receive both
 946           kernel notification (ie. KAIO) or userspace notifications.
 947
 948           If unsure, say Y.
 949
 950 config SHMEM
 951         bool "Use full shmem filesystem" if EMBEDDED
 952         default y
 953         depends on MMU
 954         help
 955           The shmem is an internal filesystem used to manage shared memory.
 956           It is backed by swap and manages resource limits. It is also exported
 957           to userspace as tmpfs if TMPFS is enabled. Disabling this
 958           option replaces shmem and tmpfs with the much simpler ramfs code,
 959           which may be appropriate on small systems without swap.
 960
 961 config AIO
 962         bool "Enable AIO support" if EMBEDDED
 963         default y
 964         help
 965           This option enables POSIX asynchronous I/O which may by used
 966           by some high performance threaded applications. Disabling
 967           this option saves about 7k.
 968
 969 config HAVE_PERF_EVENTS
 970         bool
 971         help
 972           See tools/perf/design.txt for details.
 973
 974 config PERF_USE_VMALLOC
 975         bool
 976         help
 977           See tools/perf/design.txt for details
 978
 979 menu "Kernel Performance Events And Counters"
 980
 981 config PERF_EVENTS
 982         bool "Kernel performance events and counters"
 983         default y if (PROFILING || PERF_COUNTERS)
 984         depends on HAVE_PERF_EVENTS
 985         select ANON_INODES
 986         help
 987           Enable kernel support for various performance events provided
 988           by software and hardware.
 989
 990           Software events are supported either built-in or via the
 991           use of generic tracepoints.
 992
 993           Most modern CPUs support performance events via performance
 994           counter registers. These registers count the number of certain
 995           types of hw events: such as instructions executed, cachemisses
 996           suffered, or branches mis-predicted - without slowing down the
 997           kernel or applications. These registers can also trigger interrupts
 998           when a threshold number of events have passed - and can thus be
 999           used to profile the code that runs on that CPU.
1000
1001           The Linux Performance Event subsystem provides an abstraction of
1002           these software and hardware event capabilities, available via a
1003           system call and used by the "perf" utility in tools/perf/. It
1004           provides per task and per CPU counters, and it provides event
1005           capabilities on top of those.
1006
1007           Say Y if unsure.
1008
1009 config PERF_COUNTERS
1010         bool "Kernel performance counters (old config option)"
1011         depends on HAVE_PERF_EVENTS
1012         help
1013           This config has been obsoleted by the PERF_EVENTS
1014           config option - please see that one for details.
1015
1016           It has no effect on the kernel whether you enable
1017           it or not, it is a compatibility placeholder.
1018
1019           Say N if unsure.
1020
1021 config DEBUG_PERF_USE_VMALLOC
1022         default n
1023         bool "Debug: use vmalloc to back perf mmap() buffers"
1024         depends on PERF_EVENTS && DEBUG_KERNEL
1025         select PERF_USE_VMALLOC
1026         help
1027          Use vmalloc memory to back perf mmap() buffers.
1028
1029          Mostly useful for debugging the vmalloc code on platforms
1030          that don't require it.
1031
1032          Say N if unsure.
1033
1034 endmenu
1035
1036 config VM_EVENT_COUNTERS
1037         default y
1038         bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1039         help
1040           VM event counters are needed for event counts to be shown.
1041           This option allows the disabling of the VM event counters
1042           on EMBEDDED systems.  /proc/vmstat will only show page counts
1043           if VM event counters are disabled.
1044
1045 config PCI_QUIRKS
1046         default y
1047         bool "Enable PCI quirk workarounds" if EMBEDDED
1048         depends on PCI
1049         help
1050           This enables workarounds for various PCI chipset
1051           bugs/quirks. Disable this only if your target machine is
1052           unaffected by PCI quirks.
1053
1054 config SLUB_DEBUG
1055         default y
1056         bool "Enable SLUB debugging support" if EMBEDDED
1057         depends on SLUB && SYSFS
1058         help
1059           SLUB has extensive debug support features. Disabling these can
1060           result in significant savings in code size. This also disables
1061           SLUB sysfs support. /sys/slab will not exist and there will be
1062           no support for cache validation etc.
1063
1064 config COMPAT_BRK
1065         bool "Disable heap randomization"
1066         default y
1067         help
1068           Randomizing heap placement makes heap exploits harder, but it
1069           also breaks ancient binaries (including anything libc5 based).
1070           This option changes the bootup default to heap randomization
1071           disabled, and can be overridden at runtime by setting
1072           /proc/sys/kernel/randomize_va_space to 2.
1073
1074           On non-ancient distros (post-2000 ones) N is usually a safe choice.
1075
1076 choice
1077         prompt "Choose SLAB allocator"
1078         default SLUB
1079         help
1080            This option allows to select a slab allocator.
1081
1082 config SLAB
1083         bool "SLAB"
1084         help
1085           The regular slab allocator that is established and known to work
1086           well in all environments. It organizes cache hot objects in
1087           per cpu and per node queues.
1088
1089 config SLUB
1090         bool "SLUB (Unqueued Allocator)"
1091         help
1092            SLUB is a slab allocator that minimizes cache line usage
1093            instead of managing queues of cached objects (SLAB approach).
1094            Per cpu caching is realized using slabs of objects instead
1095            of queues of objects. SLUB can use memory efficiently
1096            and has enhanced diagnostics. SLUB is the default choice for
1097            a slab allocator.
1098
1099 config SLOB
1100         depends on EMBEDDED
1101         bool "SLOB (Simple Allocator)"
1102         help
1103            SLOB replaces the stock allocator with a drastically simpler
1104            allocator. SLOB is generally more space efficient but
1105            does not perform as well on large systems.
1106
1107 endchoice
1108
1109 config MMAP_ALLOW_UNINITIALIZED
1110         bool "Allow mmapped anonymous memory to be uninitialized"
1111         depends on EMBEDDED && !MMU
1112         default n
1113         help
1114           Normally, and according to the Linux spec, anonymous memory obtained
1115           from mmap() has it's contents cleared before it is passed to
1116           userspace.  Enabling this config option allows you to request that
1117           mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1118           providing a huge performance boost.  If this option is not enabled,
1119           then the flag will be ignored.
1120
1121           This is taken advantage of by uClibc's malloc(), and also by
1122           ELF-FDPIC binfmt's brk and stack allocator.
1123
1124           Because of the obvious security issues, this option should only be
1125           enabled on embedded devices where you control what is run in
1126           userspace.  Since that isn't generally a problem on no-MMU systems,
1127           it is normally safe to say Y here.
1128
1129           See Documentation/nommu-mmap.txt for more information.
1130
1131 config PROFILING
1132         bool "Profiling support"
1133         help
1134           Say Y here to enable the extended profiling support mechanisms used
1135           by profilers such as OProfile.
1136
1137 #
1138 # Place an empty function call at each tracepoint site. Can be
1139 # dynamically changed for a probe function.
1140 #
1141 config TRACEPOINTS
1142         bool
1143
1144 source "arch/Kconfig"
1145
1146 config SLOW_WORK
1147         default n
1148         bool
1149         help
1150           The slow work thread pool provides a number of dynamically allocated
1151           threads that can be used by the kernel to perform operations that
1152           take a relatively long time.
1153
1154           An example of this would be CacheFiles doing a path lookup followed
1155           by a series of mkdirs and a create call, all of which have to touch
1156           disk.
1157
1158           See Documentation/slow-work.txt.
1159
1160 config SLOW_WORK_DEBUG
1161         bool "Slow work debugging through debugfs"
1162         default n
1163         depends on SLOW_WORK && DEBUG_FS
1164         help
1165           Display the contents of the slow work run queue through debugfs,
1166           including items currently executing.
1167
1168           See Documentation/slow-work.txt.
1169
1170 endmenu         # General setup
1171
1172 config HAVE_GENERIC_DMA_COHERENT
1173         bool
1174         default n
1175
1176 config SLABINFO
1177         bool
1178         depends on PROC_FS
1179         depends on SLAB || SLUB_DEBUG
1180         default y
1181
1182 config RT_MUTEXES
1183         boolean
1184
1185 config BASE_SMALL
1186         int
1187         default 0 if BASE_FULL
1188         default 1 if !BASE_FULL
1189
1190 menuconfig MODULES
1191         bool "Enable loadable module support"
1192         help
1193           Kernel modules are small pieces of compiled code which can
1194           be inserted in the running kernel, rather than being
1195           permanently built into the kernel.  You use the "modprobe"
1196           tool to add (and sometimes remove) them.  If you say Y here,
1197           many parts of the kernel can be built as modules (by
1198           answering M instead of Y where indicated): this is most
1199           useful for infrequently used options which are not required
1200           for booting.  For more information, see the man pages for
1201           modprobe, lsmod, modinfo, insmod and rmmod.
1202
1203           If you say Y here, you will need to run "make
1204           modules_install" to put the modules under /lib/modules/
1205           where modprobe can find them (you may need to be root to do
1206           this).
1207
1208           If unsure, say Y.
1209
1210 if MODULES
1211
1212 config MODULE_FORCE_LOAD
1213         bool "Forced module loading"
1214         default n
1215         help
1216           Allow loading of modules without version information (ie. modprobe
1217           --force).  Forced module loading sets the 'F' (forced) taint flag and
1218           is usually a really bad idea.
1219
1220 config MODULE_UNLOAD
1221         bool "Module unloading"
1222         help
1223           Without this option you will not be able to unload any
1224           modules (note that some modules may not be unloadable
1225           anyway), which makes your kernel smaller, faster
1226           and simpler.  If unsure, say Y.
1227
1228 config MODULE_FORCE_UNLOAD
1229         bool "Forced module unloading"
1230         depends on MODULE_UNLOAD && EXPERIMENTAL
1231         help
1232           This option allows you to force a module to unload, even if the
1233           kernel believes it is unsafe: the kernel will remove the module
1234           without waiting for anyone to stop using it (using the -f option to
1235           rmmod).  This is mainly for kernel developers and desperate users.
1236           If unsure, say N.
1237
1238 config MODVERSIONS
1239         bool "Module versioning support"
1240         help
1241           Usually, you have to use modules compiled with your kernel.
1242           Saying Y here makes it sometimes possible to use modules
1243           compiled for different kernels, by adding enough information
1244           to the modules to (hopefully) spot any changes which would
1245           make them incompatible with the kernel you are running.  If
1246           unsure, say N.
1247
1248 config MODULE_SRCVERSION_ALL
1249         bool "Source checksum for all modules"
1250         help
1251           Modules which contain a MODULE_VERSION get an extra "srcversion"
1252           field inserted into their modinfo section, which contains a
1253           sum of the source files which made it.  This helps maintainers
1254           see exactly which source was used to build a module (since
1255           others sometimes change the module source without updating
1256           the version).  With this option, such a "srcversion" field
1257           will be created for all modules.  If unsure, say N.
1258
1259 endif # MODULES
1260
1261 config INIT_ALL_POSSIBLE
1262         bool
1263         help
1264           Back when each arch used to define their own cpu_online_map and
1265           cpu_possible_map, some of them chose to initialize cpu_possible_map
1266           with all 1s, and others with all 0s.  When they were centralised,
1267           it was better to provide this option than to break all the archs
1268           and have several arch maintainers pursuing me down dark alleys.
1269
1270 config STOP_MACHINE
1271         bool
1272         default y
1273         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1274         help
1275           Need stop_machine() primitive.
1276
1277 source "block/Kconfig"
1278
1279 config PREEMPT_NOTIFIERS
1280         bool
1281
1282 config PADATA
1283         depends on SMP
1284         bool
1285
1286 source "kernel/Kconfig.locks"