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 menu "General setup"
  20
  21 config EXPERIMENTAL
  22         bool "Prompt for development and/or incomplete code/drivers"
  23         ---help---
  24           Some of the various things that Linux supports (such as network
  25           drivers, file systems, network protocols, etc.) can be in a state
  26           of development where the functionality, stability, or the level of
  27           testing is not yet high enough for general use. This is usually
  28           known as the "alpha-test" phase among developers. If a feature is
  29           currently in alpha-test, then the developers usually discourage
  30           uninformed widespread use of this feature by the general public to
  31           avoid "Why doesn't this work?" type mail messages. However, active
  32           testing and use of these systems is welcomed. Just be aware that it
  33           may not meet the normal level of reliability or it may fail to work
  34           in some special cases. Detailed bug reports from people familiar
  35           with the kernel internals are usually welcomed by the developers
  36           (before submitting bug reports, please read the documents
  37           <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  38           <file:Documentation/BUG-HUNTING>, and
  39           <file:Documentation/oops-tracing.txt> in the kernel source).
  40
  41           This option will also make obsoleted drivers available. These are
  42           drivers that have been replaced by something else, and/or are
  43           scheduled to be removed in a future kernel release.
  44
  45           Unless you intend to help test and develop a feature or driver that
  46           falls into this category, or you have a situation that requires
  47           using these features, you should probably say N here, which will
  48           cause the configurator to present you with fewer choices. If
  49           you say Y here, you will be offered the choice of using features or
  50           drivers that are currently considered to be in the alpha-test phase.
  51
  52 config BROKEN
  53         bool
  54
  55 config BROKEN_ON_SMP
  56         bool
  57         depends on BROKEN || !SMP
  58         default y
  59
  60 config LOCK_KERNEL
  61         bool
  62         depends on SMP || PREEMPT
  63         default y
  64
  65 config INIT_ENV_ARG_LIMIT
  66         int
  67         default 32 if !UML
  68         default 128 if UML
  69         help
  70           Maximum of each of the number of arguments and environment
  71           variables passed to init from the kernel command line.
  72
  73
  74 config LOCALVERSION
  75         string "Local version - append to kernel release"
  76         help
  77           Append an extra string to the end of your kernel version.
  78           This will show up when you type uname, for example.
  79           The string you set here will be appended after the contents of
  80           any files with a filename matching localversion* in your
  81           object and source tree, in that order.  Your total string can
  82           be a maximum of 64 characters.
  83
  84 config LOCALVERSION_AUTO
  85         bool "Automatically append version information to the version string"
  86         default y
  87         help
  88           This will try to automatically determine if the current tree is a
  89           release tree by looking for git tags that belong to the current
  90           top of tree revision.
  91
  92           A string of the format -gxxxxxxxx will be added to the localversion
  93           if a git-based tree is found.  The string generated by this will be
  94           appended after any matching localversion* files, and after the value
  95           set in CONFIG_LOCALVERSION.
  96
  97           (The actual string used here is the first eight characters produced
  98           by running the command:
  99
 100             $ git rev-parse --verify HEAD
 101
 102           which is done within the script "scripts/setlocalversion".)
 103
 104 config HAVE_KERNEL_GZIP
 105         bool
 106
 107 config HAVE_KERNEL_BZIP2
 108         bool
 109
 110 config HAVE_KERNEL_LZMA
 111         bool
 112
 113 choice
 114         prompt "Kernel compression mode"
 115         default KERNEL_GZIP
 116         depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
 117         help
 118           The linux kernel is a kind of self-extracting executable.
 119           Several compression algorithms are available, which differ
 120           in efficiency, compression and decompression speed.
 121           Compression speed is only relevant when building a kernel.
 122           Decompression speed is relevant at each boot.
 123
 124           If you have any problems with bzip2 or lzma compressed
 125           kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
 126           version of this functionality (bzip2 only), for 2.4, was
 127           supplied by Christian Ludwig)
 128
 129           High compression options are mostly useful for users, who
 130           are low on disk space (embedded systems), but for whom ram
 131           size matters less.
 132
 133           If in doubt, select 'gzip'
 134
 135 config KERNEL_GZIP
 136         bool "Gzip"
 137         depends on HAVE_KERNEL_GZIP
 138         help
 139           The old and tried gzip compression. Its compression ratio is
 140           the poorest among the 3 choices; however its speed (both
 141           compression and decompression) is the fastest.
 142
 143 config KERNEL_BZIP2
 144         bool "Bzip2"
 145         depends on HAVE_KERNEL_BZIP2
 146         help
 147           Its compression ratio and speed is intermediate.
 148           Decompression speed is slowest among the three.  The kernel
 149           size is about 10% smaller with bzip2, in comparison to gzip.
 150           Bzip2 uses a large amount of memory. For modern kernels you
 151           will need at least 8MB RAM or more for booting.
 152
 153 config KERNEL_LZMA
 154         bool "LZMA"
 155         depends on HAVE_KERNEL_LZMA
 156         help
 157           The most recent compression algorithm.
 158           Its ratio is best, decompression speed is between the other
 159           two. Compression is slowest.  The kernel size is about 33%
 160           smaller with LZMA in comparison to gzip.
 161
 162 endchoice
 163
 164 config SWAP
 165         bool "Support for paging of anonymous memory (swap)"
 166         depends on MMU && BLOCK
 167         default y
 168         help
 169           This option allows you to choose whether you want to have support
 170           for so called swap devices or swap files in your kernel that are
 171           used to provide more virtual memory than the actual RAM present
 172           in your computer.  If unsure say Y.
 173
 174 config SYSVIPC
 175         bool "System V IPC"
 176         ---help---
 177           Inter Process Communication is a suite of library functions and
 178           system calls which let processes (running programs) synchronize and
 179           exchange information. It is generally considered to be a good thing,
 180           and some programs won't run unless you say Y here. In particular, if
 181           you want to run the DOS emulator dosemu under Linux (read the
 182           DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
 183           you'll need to say Y here.
 184
 185           You can find documentation about IPC with "info ipc" and also in
 186           section 6.4 of the Linux Programmer's Guide, available from
 187           <http://www.tldp.org/guides.html>.
 188
 189 config SYSVIPC_SYSCTL
 190         bool
 191         depends on SYSVIPC
 192         depends on SYSCTL
 193         default y
 194
 195 config POSIX_MQUEUE
 196         bool "POSIX Message Queues"
 197         depends on NET && EXPERIMENTAL
 198         ---help---
 199           POSIX variant of message queues is a part of IPC. In POSIX message
 200           queues every message has a priority which decides about succession
 201           of receiving it by a process. If you want to compile and run
 202           programs written e.g. for Solaris with use of its POSIX message
 203           queues (functions mq_*) say Y here.
 204
 205           POSIX message queues are visible as a filesystem called 'mqueue'
 206           and can be mounted somewhere if you want to do filesystem
 207           operations on message queues.
 208
 209           If unsure, say Y.
 210
 211 config POSIX_MQUEUE_SYSCTL
 212         bool
 213         depends on POSIX_MQUEUE
 214         depends on SYSCTL
 215         default y
 216
 217 config BSD_PROCESS_ACCT
 218         bool "BSD Process Accounting"
 219         help
 220           If you say Y here, a user level program will be able to instruct the
 221           kernel (via a special system call) to write process accounting
 222           information to a file: whenever a process exits, information about
 223           that process will be appended to the file by the kernel.  The
 224           information includes things such as creation time, owning user,
 225           command name, memory usage, controlling terminal etc. (the complete
 226           list is in the struct acct in <file:include/linux/acct.h>).  It is
 227           up to the user level program to do useful things with this
 228           information.  This is generally a good idea, so say Y.
 229
 230 config BSD_PROCESS_ACCT_V3
 231         bool "BSD Process Accounting version 3 file format"
 232         depends on BSD_PROCESS_ACCT
 233         default n
 234         help
 235           If you say Y here, the process accounting information is written
 236           in a new file format that also logs the process IDs of each
 237           process and it's parent. Note that this file format is incompatible
 238           with previous v0/v1/v2 file formats, so you will need updated tools
 239           for processing it. A preliminary version of these tools is available
 240           at <http://www.gnu.org/software/acct/>.
 241
 242 config TASKSTATS
 243         bool "Export task/process statistics through netlink (EXPERIMENTAL)"
 244         depends on NET
 245         default n
 246         help
 247           Export selected statistics for tasks/processes through the
 248           generic netlink interface. Unlike BSD process accounting, the
 249           statistics are available during the lifetime of tasks/processes as
 250           responses to commands. Like BSD accounting, they are sent to user
 251           space on task exit.
 252
 253           Say N if unsure.
 254
 255 config TASK_DELAY_ACCT
 256         bool "Enable per-task delay accounting (EXPERIMENTAL)"
 257         depends on TASKSTATS
 258         help
 259           Collect information on time spent by a task waiting for system
 260           resources like cpu, synchronous block I/O completion and swapping
 261           in pages. Such statistics can help in setting a task's priorities
 262           relative to other tasks for cpu, io, rss limits etc.
 263
 264           Say N if unsure.
 265
 266 config TASK_XACCT
 267         bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
 268         depends on TASKSTATS
 269         help
 270           Collect extended task accounting data and send the data
 271           to userland for processing over the taskstats interface.
 272
 273           Say N if unsure.
 274
 275 config TASK_IO_ACCOUNTING
 276         bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
 277         depends on TASK_XACCT
 278         help
 279           Collect information on the number of bytes of storage I/O which this
 280           task has caused.
 281
 282           Say N if unsure.
 283
 284 config AUDIT
 285         bool "Auditing support"
 286         depends on NET
 287         help
 288           Enable auditing infrastructure that can be used with another
 289           kernel subsystem, such as SELinux (which requires this for
 290           logging of avc messages output).  Does not do system-call
 291           auditing without CONFIG_AUDITSYSCALL.
 292
 293 config AUDITSYSCALL
 294         bool "Enable system-call auditing support"
 295         depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
 296         default y if SECURITY_SELINUX
 297         help
 298           Enable low-overhead system-call auditing infrastructure that
 299           can be used independently or with another kernel subsystem,
 300           such as SELinux.  To use audit's filesystem watch feature, please
 301           ensure that INOTIFY is configured.
 302
 303 config AUDIT_TREE
 304         def_bool y
 305         depends on AUDITSYSCALL && INOTIFY
 306
 307 menu "RCU Subsystem"
 308
 309 choice
 310         prompt "RCU Implementation"
 311         default CLASSIC_RCU
 312
 313 config CLASSIC_RCU
 314         bool "Classic RCU"
 315         help
 316           This option selects the classic RCU implementation that is
 317           designed for best read-side performance on non-realtime
 318           systems.
 319
 320           Select this option if you are unsure.
 321
 322 config TREE_RCU
 323         bool "Tree-based hierarchical RCU"
 324         help
 325           This option selects the RCU implementation that is
 326           designed for very large SMP system with hundreds or
 327           thousands of CPUs.
 328
 329 config PREEMPT_RCU
 330         bool "Preemptible RCU"
 331         depends on PREEMPT
 332         help
 333           This option reduces the latency of the kernel by making certain
 334           RCU sections preemptible. Normally RCU code is non-preemptible, if
 335           this option is selected then read-only RCU sections become
 336           preemptible. This helps latency, but may expose bugs due to
 337           now-naive assumptions about each RCU read-side critical section
 338           remaining on a given CPU through its execution.
 339
 340 endchoice
 341
 342 config RCU_TRACE
 343         bool "Enable tracing for RCU"
 344         depends on TREE_RCU || PREEMPT_RCU
 345         help
 346           This option provides tracing in RCU which presents stats
 347           in debugfs for debugging RCU implementation.
 348
 349           Say Y here if you want to enable RCU tracing
 350           Say N if you are unsure.
 351
 352 config RCU_FANOUT
 353         int "Tree-based hierarchical RCU fanout value"
 354         range 2 64 if 64BIT
 355         range 2 32 if !64BIT
 356         depends on TREE_RCU
 357         default 64 if 64BIT
 358         default 32 if !64BIT
 359         help
 360           This option controls the fanout of hierarchical implementations
 361           of RCU, allowing RCU to work efficiently on machines with
 362           large numbers of CPUs.  This value must be at least the cube
 363           root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
 364           systems and up to 262,144 for 64-bit systems.
 365
 366           Select a specific number if testing RCU itself.
 367           Take the default if unsure.
 368
 369 config RCU_FANOUT_EXACT
 370         bool "Disable tree-based hierarchical RCU auto-balancing"
 371         depends on TREE_RCU
 372         default n
 373         help
 374           This option forces use of the exact RCU_FANOUT value specified,
 375           regardless of imbalances in the hierarchy.  This is useful for
 376           testing RCU itself, and might one day be useful on systems with
 377           strong NUMA behavior.
 378
 379           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
 380
 381           Say N if unsure.
 382
 383 config TREE_RCU_TRACE
 384         def_bool RCU_TRACE && TREE_RCU
 385         select DEBUG_FS
 386         help
 387           This option provides tracing for the TREE_RCU implementation,
 388           permitting Makefile to trivially select kernel/rcutree_trace.c.
 389
 390 config PREEMPT_RCU_TRACE
 391         def_bool RCU_TRACE && PREEMPT_RCU
 392         select DEBUG_FS
 393         help
 394           This option provides tracing for the PREEMPT_RCU implementation,
 395           permitting Makefile to trivially select kernel/rcupreempt_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 "Create deprecated sysfs layout for older userspace tools"
 619         depends on SYSFS
 620         default y
 621         select SYSFS_DEPRECATED
 622         help
 623           This option switches the layout of sysfs to the deprecated
 624           version.
 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 STRIP_ASM_SYMS
 812         bool "Strip assembler-generated symbols during link"
 813         default n
 814         help
 815           Strip internal assembler-generated symbols during a link (symbols
 816           that look like '.Lxxx') so they don't pollute the output of
 817           get_wchan() and suchlike.
 818
 819 config HOTPLUG
 820         bool "Support for hot-pluggable devices" if EMBEDDED
 821         default y
 822         help
 823           This option is provided for the case where no hotplug or uevent
 824           capabilities is wanted by the kernel.  You should only consider
 825           disabling this option for embedded systems that do not use modules, a
 826           dynamic /dev tree, or dynamic device discovery.  Just say Y.
 827
 828 config PRINTK
 829         default y
 830         bool "Enable support for printk" if EMBEDDED
 831         help
 832           This option enables normal printk support. Removing it
 833           eliminates most of the message strings from the kernel image
 834           and makes the kernel more or less silent. As this makes it
 835           very difficult to diagnose system problems, saying N here is
 836           strongly discouraged.
 837
 838 config BUG
 839         bool "BUG() support" if EMBEDDED
 840         default y
 841         help
 842           Disabling this option eliminates support for BUG and WARN, reducing
 843           the size of your kernel image and potentially quietly ignoring
 844           numerous fatal conditions. You should only consider disabling this
 845           option for embedded systems with no facilities for reporting errors.
 846           Just say Y.
 847
 848 config ELF_CORE
 849         default y
 850         bool "Enable ELF core dumps" if EMBEDDED
 851         help
 852           Enable support for generating core dumps. Disabling saves about 4k.
 853
 854 config PCSPKR_PLATFORM
 855         bool "Enable PC-Speaker support" if EMBEDDED
 856         depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
 857         default y
 858         help
 859           This option allows to disable the internal PC-Speaker
 860           support, saving some memory.
 861
 862 config BASE_FULL
 863         default y
 864         bool "Enable full-sized data structures for core" if EMBEDDED
 865         help
 866           Disabling this option reduces the size of miscellaneous core
 867           kernel data structures. This saves memory on small machines,
 868           but may reduce performance.
 869
 870 config FUTEX
 871         bool "Enable futex support" if EMBEDDED
 872         default y
 873         select RT_MUTEXES
 874         help
 875           Disabling this option will cause the kernel to be built without
 876           support for "fast userspace mutexes".  The resulting kernel may not
 877           run glibc-based applications correctly.
 878
 879 config EPOLL
 880         bool "Enable eventpoll support" if EMBEDDED
 881         default y
 882         select ANON_INODES
 883         help
 884           Disabling this option will cause the kernel to be built without
 885           support for epoll family of system calls.
 886
 887 config SIGNALFD
 888         bool "Enable signalfd() system call" if EMBEDDED
 889         select ANON_INODES
 890         default y
 891         help
 892           Enable the signalfd() system call that allows to receive signals
 893           on a file descriptor.
 894
 895           If unsure, say Y.
 896
 897 config TIMERFD
 898         bool "Enable timerfd() system call" if EMBEDDED
 899         select ANON_INODES
 900         default y
 901         help
 902           Enable the timerfd() system call that allows to receive timer
 903           events on a file descriptor.
 904
 905           If unsure, say Y.
 906
 907 config EVENTFD
 908         bool "Enable eventfd() system call" if EMBEDDED
 909         select ANON_INODES
 910         default y
 911         help
 912           Enable the eventfd() system call that allows to receive both
 913           kernel notification (ie. KAIO) or userspace notifications.
 914
 915           If unsure, say Y.
 916
 917 config SHMEM
 918         bool "Use full shmem filesystem" if EMBEDDED
 919         default y
 920         depends on MMU
 921         help
 922           The shmem is an internal filesystem used to manage shared memory.
 923           It is backed by swap and manages resource limits. It is also exported
 924           to userspace as tmpfs if TMPFS is enabled. Disabling this
 925           option replaces shmem and tmpfs with the much simpler ramfs code,
 926           which may be appropriate on small systems without swap.
 927
 928 config AIO
 929         bool "Enable AIO support" if EMBEDDED
 930         default y
 931         help
 932           This option enables POSIX asynchronous I/O which may by used
 933           by some high performance threaded applications. Disabling
 934           this option saves about 7k.
 935
 936 config VM_EVENT_COUNTERS
 937         default y
 938         bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
 939         help
 940           VM event counters are needed for event counts to be shown.
 941           This option allows the disabling of the VM event counters
 942           on EMBEDDED systems.  /proc/vmstat will only show page counts
 943           if VM event counters are disabled.
 944
 945 config PCI_QUIRKS
 946         default y
 947         bool "Enable PCI quirk workarounds" if EMBEDDED
 948         depends on PCI
 949         help
 950           This enables workarounds for various PCI chipset
 951           bugs/quirks. Disable this only if your target machine is
 952           unaffected by PCI quirks.
 953
 954 config SLUB_DEBUG
 955         default y
 956         bool "Enable SLUB debugging support" if EMBEDDED
 957         depends on SLUB && SYSFS
 958         help
 959           SLUB has extensive debug support features. Disabling these can
 960           result in significant savings in code size. This also disables
 961           SLUB sysfs support. /sys/slab will not exist and there will be
 962           no support for cache validation etc.
 963
 964 config COMPAT_BRK
 965         bool "Disable heap randomization"
 966         default y
 967         help
 968           Randomizing heap placement makes heap exploits harder, but it
 969           also breaks ancient binaries (including anything libc5 based).
 970           This option changes the bootup default to heap randomization
 971           disabled, and can be overridden at runtime by setting
 972           /proc/sys/kernel/randomize_va_space to 2.
 973
 974           On non-ancient distros (post-2000 ones) N is usually a safe choice.
 975
 976 choice
 977         prompt "Choose SLAB allocator"
 978         default SLUB
 979         help
 980            This option allows to select a slab allocator.
 981
 982 config SLAB
 983         bool "SLAB"
 984         help
 985           The regular slab allocator that is established and known to work
 986           well in all environments. It organizes cache hot objects in
 987           per cpu and per node queues.
 988
 989 config SLUB
 990         bool "SLUB (Unqueued Allocator)"
 991         help
 992            SLUB is a slab allocator that minimizes cache line usage
 993            instead of managing queues of cached objects (SLAB approach).
 994            Per cpu caching is realized using slabs of objects instead
 995            of queues of objects. SLUB can use memory efficiently
 996            and has enhanced diagnostics. SLUB is the default choice for
 997            a slab allocator.
 998
 999 config SLOB
1000         depends on EMBEDDED
1001         bool "SLOB (Simple Allocator)"
1002         help
1003            SLOB replaces the stock allocator with a drastically simpler
1004            allocator. SLOB is generally more space efficient but
1005            does not perform as well on large systems.
1006
1007 endchoice
1008
1009 config PROFILING
1010         bool "Profiling support (EXPERIMENTAL)"
1011         help
1012           Say Y here to enable the extended profiling support mechanisms used
1013           by profilers such as OProfile.
1014
1015 #
1016 # Place an empty function call at each tracepoint site. Can be
1017 # dynamically changed for a probe function.
1018 #
1019 config TRACEPOINTS
1020         bool
1021
1022 config MARKERS
1023         bool "Activate markers"
1024         select TRACEPOINTS
1025         help
1026           Place an empty function call at each marker site. Can be
1027           dynamically changed for a probe function.
1028
1029 source "arch/Kconfig"
1030
1031 config SLOW_WORK
1032         default n
1033         bool
1034         help
1035           The slow work thread pool provides a number of dynamically allocated
1036           threads that can be used by the kernel to perform operations that
1037           take a relatively long time.
1038
1039           An example of this would be CacheFiles doing a path lookup followed
1040           by a series of mkdirs and a create call, all of which have to touch
1041           disk.
1042
1043           See Documentation/slow-work.txt.
1044
1045 endmenu         # General setup
1046
1047 config HAVE_GENERIC_DMA_COHERENT
1048         bool
1049         default n
1050
1051 config SLABINFO
1052         bool
1053         depends on PROC_FS
1054         depends on SLAB || SLUB_DEBUG
1055         default y
1056
1057 config RT_MUTEXES
1058         boolean
1059
1060 config BASE_SMALL
1061         int
1062         default 0 if BASE_FULL
1063         default 1 if !BASE_FULL
1064
1065 menuconfig MODULES
1066         bool "Enable loadable module support"
1067         help
1068           Kernel modules are small pieces of compiled code which can
1069           be inserted in the running kernel, rather than being
1070           permanently built into the kernel.  You use the "modprobe"
1071           tool to add (and sometimes remove) them.  If you say Y here,
1072           many parts of the kernel can be built as modules (by
1073           answering M instead of Y where indicated): this is most
1074           useful for infrequently used options which are not required
1075           for booting.  For more information, see the man pages for
1076           modprobe, lsmod, modinfo, insmod and rmmod.
1077
1078           If you say Y here, you will need to run "make
1079           modules_install" to put the modules under /lib/modules/
1080           where modprobe can find them (you may need to be root to do
1081           this).
1082
1083           If unsure, say Y.
1084
1085 if MODULES
1086
1087 config MODULE_FORCE_LOAD
1088         bool "Forced module loading"
1089         default n
1090         help
1091           Allow loading of modules without version information (ie. modprobe
1092           --force).  Forced module loading sets the 'F' (forced) taint flag and
1093           is usually a really bad idea.
1094
1095 config MODULE_UNLOAD
1096         bool "Module unloading"
1097         help
1098           Without this option you will not be able to unload any
1099           modules (note that some modules may not be unloadable
1100           anyway), which makes your kernel smaller, faster
1101           and simpler.  If unsure, say Y.
1102
1103 config MODULE_FORCE_UNLOAD
1104         bool "Forced module unloading"
1105         depends on MODULE_UNLOAD && EXPERIMENTAL
1106         help
1107           This option allows you to force a module to unload, even if the
1108           kernel believes it is unsafe: the kernel will remove the module
1109           without waiting for anyone to stop using it (using the -f option to
1110           rmmod).  This is mainly for kernel developers and desperate users.
1111           If unsure, say N.
1112
1113 config MODVERSIONS
1114         bool "Module versioning support"
1115         help
1116           Usually, you have to use modules compiled with your kernel.
1117           Saying Y here makes it sometimes possible to use modules
1118           compiled for different kernels, by adding enough information
1119           to the modules to (hopefully) spot any changes which would
1120           make them incompatible with the kernel you are running.  If
1121           unsure, say N.
1122
1123 config MODULE_SRCVERSION_ALL
1124         bool "Source checksum for all modules"
1125         help
1126           Modules which contain a MODULE_VERSION get an extra "srcversion"
1127           field inserted into their modinfo section, which contains a
1128           sum of the source files which made it.  This helps maintainers
1129           see exactly which source was used to build a module (since
1130           others sometimes change the module source without updating
1131           the version).  With this option, such a "srcversion" field
1132           will be created for all modules.  If unsure, say N.
1133
1134 endif # MODULES
1135
1136 config INIT_ALL_POSSIBLE
1137         bool
1138         help
1139           Back when each arch used to define their own cpu_online_map and
1140           cpu_possible_map, some of them chose to initialize cpu_possible_map
1141           with all 1s, and others with all 0s.  When they were centralised,
1142           it was better to provide this option than to break all the archs
1143           and have several arch maintainers pursuing me down dark alleys.
1144
1145 config STOP_MACHINE
1146         bool
1147         default y
1148         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1149         help
1150           Need stop_machine() primitive.
1151
1152 source "block/Kconfig"
1153
1154 config PREEMPT_NOTIFIERS
1155         bool
1156