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  47           drivers that have been replaced by something else, and/or are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