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/$ARCH/defconfig"
  17
  18 menu "General setup"
  19
  20 config EXPERIMENTAL
  21         bool "Prompt for development and/or incomplete code/drivers"
  22         ---help---
  23           Some of the various things that Linux supports (such as network
  24           drivers, file systems, network protocols, etc.) can be in a state
  25           of development where the functionality, stability, or the level of
  26           testing is not yet high enough for general use. This is usually
  27           known as the "alpha-test" phase among developers. If a feature is
  28           currently in alpha-test, then the developers usually discourage
  29           uninformed widespread use of this feature by the general public to
  30           avoid "Why doesn't this work?" type mail messages. However, active
  31           testing and use of these systems is welcomed. Just be aware that it
  32           may not meet the normal level of reliability or it may fail to work
  33           in some special cases. Detailed bug reports from people familiar
  34           with the kernel internals are usually welcomed by the developers
  35           (before submitting bug reports, please read the documents
  36           <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  37           <file:Documentation/BUG-HUNTING>, and
  38           <file:Documentation/oops-tracing.txt> in the kernel source).
  39
  40           This option will also make obsoleted drivers available. These are
  41           drivers that have been replaced by something else, and/or are
  42           scheduled to be removed in a future kernel release.
  43
  44           Unless you intend to help test and develop a feature or driver that
  45           falls into this category, or you have a situation that requires
  46           using these features, you should probably say N here, which will
  47           cause the configurator to present you with fewer choices. If
  48           you say Y here, you will be offered the choice of using features or
  49           drivers that are currently considered to be in the alpha-test phase.
  50
  51 config BROKEN
  52         bool
  53
  54 config BROKEN_ON_SMP
  55         bool
  56         depends on BROKEN || !SMP
  57         default y
  58
  59 config LOCK_KERNEL
  60         bool
  61         depends on SMP || PREEMPT
  62         default y
  63
  64 config INIT_ENV_ARG_LIMIT
  65         int
  66         default 32 if !UML
  67         default 128 if UML
  68         help
  69           Maximum of each of the number of arguments and environment
  70           variables passed to init from the kernel command line.
  71
  72
  73 config LOCALVERSION
  74         string "Local version - append to kernel release"
  75         help
  76           Append an extra string to the end of your kernel version.
  77           This will show up when you type uname, for example.
  78           The string you set here will be appended after the contents of
  79           any files with a filename matching localversion* in your
  80           object and source tree, in that order.  Your total string can
  81           be a maximum of 64 characters.
  82
  83 config LOCALVERSION_AUTO
  84         bool "Automatically append version information to the version string"
  85         default y
  86         help
  87           This will try to automatically determine if the current tree is a
  88           release tree by looking for git tags that belong to the current
  89           top of tree revision.
  90
  91           A string of the format -gxxxxxxxx will be added to the localversion
  92           if a git-based tree is found.  The string generated by this will be
  93           appended after any matching localversion* files, and after the value
  94           set in CONFIG_LOCALVERSION.
  95
  96           (The actual string used here is the first eight characters produced
  97           by running the command:
  98
  99             $ git rev-parse --verify HEAD
 100
 101           which is done within the script "scripts/setlocalversion".)
 102
 103 config SWAP
 104         bool "Support for paging of anonymous memory (swap)"
 105         depends on MMU && BLOCK
 106         default y
 107         help
 108           This option allows you to choose whether you want to have support
 109           for so called swap devices or swap files in your kernel that are
 110           used to provide more virtual memory than the actual RAM present
 111           in your computer.  If unsure say Y.
 112
 113 config SYSVIPC
 114         bool "System V IPC"
 115         ---help---
 116           Inter Process Communication is a suite of library functions and
 117           system calls which let processes (running programs) synchronize and
 118           exchange information. It is generally considered to be a good thing,
 119           and some programs won't run unless you say Y here. In particular, if
 120           you want to run the DOS emulator dosemu under Linux (read the
 121           DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
 122           you'll need to say Y here.
 123
 124           You can find documentation about IPC with "info ipc" and also in
 125           section 6.4 of the Linux Programmer's Guide, available from
 126           <http://www.tldp.org/guides.html>.
 127
 128 config SYSVIPC_SYSCTL
 129         bool
 130         depends on SYSVIPC
 131         depends on SYSCTL
 132         default y
 133
 134 config POSIX_MQUEUE
 135         bool "POSIX Message Queues"
 136         depends on NET && EXPERIMENTAL
 137         ---help---
 138           POSIX variant of message queues is a part of IPC. In POSIX message
 139           queues every message has a priority which decides about succession
 140           of receiving it by a process. If you want to compile and run
 141           programs written e.g. for Solaris with use of its POSIX message
 142           queues (functions mq_*) say Y here.
 143
 144           POSIX message queues are visible as a filesystem called 'mqueue'
 145           and can be mounted somewhere if you want to do filesystem
 146           operations on message queues.
 147
 148           If unsure, say Y.
 149
 150 config BSD_PROCESS_ACCT
 151         bool "BSD Process Accounting"
 152         help
 153           If you say Y here, a user level program will be able to instruct the
 154           kernel (via a special system call) to write process accounting
 155           information to a file: whenever a process exits, information about
 156           that process will be appended to the file by the kernel.  The
 157           information includes things such as creation time, owning user,
 158           command name, memory usage, controlling terminal etc. (the complete
 159           list is in the struct acct in <file:include/linux/acct.h>).  It is
 160           up to the user level program to do useful things with this
 161           information.  This is generally a good idea, so say Y.
 162
 163 config BSD_PROCESS_ACCT_V3
 164         bool "BSD Process Accounting version 3 file format"
 165         depends on BSD_PROCESS_ACCT
 166         default n
 167         help
 168           If you say Y here, the process accounting information is written
 169           in a new file format that also logs the process IDs of each
 170           process and it's parent. Note that this file format is incompatible
 171           with previous v0/v1/v2 file formats, so you will need updated tools
 172           for processing it. A preliminary version of these tools is available
 173           at <http://www.physik3.uni-rostock.de/tim/kernel/utils/acct/>.
 174
 175 config TASKSTATS
 176         bool "Export task/process statistics through netlink (EXPERIMENTAL)"
 177         depends on NET
 178         default n
 179         help
 180           Export selected statistics for tasks/processes through the
 181           generic netlink interface. Unlike BSD process accounting, the
 182           statistics are available during the lifetime of tasks/processes as
 183           responses to commands. Like BSD accounting, they are sent to user
 184           space on task exit.
 185
 186           Say N if unsure.
 187
 188 config TASK_DELAY_ACCT
 189         bool "Enable per-task delay accounting (EXPERIMENTAL)"
 190         depends on TASKSTATS
 191         help
 192           Collect information on time spent by a task waiting for system
 193           resources like cpu, synchronous block I/O completion and swapping
 194           in pages. Such statistics can help in setting a task's priorities
 195           relative to other tasks for cpu, io, rss limits etc.
 196
 197           Say N if unsure.
 198
 199 config TASK_XACCT
 200         bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
 201         depends on TASKSTATS
 202         help
 203           Collect extended task accounting data and send the data
 204           to userland for processing over the taskstats interface.
 205
 206           Say N if unsure.
 207
 208 config TASK_IO_ACCOUNTING
 209         bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
 210         depends on TASK_XACCT
 211         help
 212           Collect information on the number of bytes of storage I/O which this
 213           task has caused.
 214
 215           Say N if unsure.
 216
 217 config USER_NS
 218         bool "User Namespaces (EXPERIMENTAL)"
 219         default n
 220         depends on EXPERIMENTAL
 221         help
 222           Support user namespaces.  This allows containers, i.e.
 223           vservers, to use user namespaces to provide different
 224           user info for different servers.  If unsure, say N.
 225
 226 config PID_NS
 227         bool "PID Namespaces (EXPERIMENTAL)"
 228         default n
 229         depends on EXPERIMENTAL
 230         help
 231           Suport process id namespaces.  This allows having multiple
 232           process with the same pid as long as they are in different
 233           pid namespaces.  This is a building block of containers.
 234
 235           Unless you want to work with an experimental feature
 236           say N here.
 237
 238 config AUDIT
 239         bool "Auditing support"
 240         depends on NET
 241         help
 242           Enable auditing infrastructure that can be used with another
 243           kernel subsystem, such as SELinux (which requires this for
 244           logging of avc messages output).  Does not do system-call
 245           auditing without CONFIG_AUDITSYSCALL.
 246
 247 config AUDITSYSCALL
 248         bool "Enable system-call auditing support"
 249         depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
 250         default y if SECURITY_SELINUX
 251         help
 252           Enable low-overhead system-call auditing infrastructure that
 253           can be used independently or with another kernel subsystem,
 254           such as SELinux.  To use audit's filesystem watch feature, please
 255           ensure that INOTIFY is configured.
 256
 257 config AUDIT_TREE
 258         def_bool y
 259         depends on AUDITSYSCALL && INOTIFY
 260
 261 config IKCONFIG
 262         tristate "Kernel .config support"
 263         ---help---
 264           This option enables the complete Linux kernel ".config" file
 265           contents to be saved in the kernel. It provides documentation
 266           of which kernel options are used in a running kernel or in an
 267           on-disk kernel.  This information can be extracted from the kernel
 268           image file with the script scripts/extract-ikconfig and used as
 269           input to rebuild the current kernel or to build another kernel.
 270           It can also be extracted from a running kernel by reading
 271           /proc/config.gz if enabled (below).
 272
 273 config IKCONFIG_PROC
 274         bool "Enable access to .config through /proc/config.gz"
 275         depends on IKCONFIG && PROC_FS
 276         ---help---
 277           This option enables access to the kernel configuration file
 278           through /proc/config.gz.
 279
 280 config LOG_BUF_SHIFT
 281         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 282         range 12 21
 283         default 17 if S390 || LOCKDEP
 284         default 16 if X86_NUMAQ || IA64
 285         default 15 if SMP
 286         default 14
 287         help
 288           Select kernel log buffer size as a power of 2.
 289           Defaults and Examples:
 290                      17 => 128 KB for S/390
 291                      16 => 64 KB for x86 NUMAQ or IA-64
 292                      15 => 32 KB for SMP
 293                      14 => 16 KB for uniprocessor
 294                      13 =>  8 KB
 295                      12 =>  4 KB
 296
 297 config CGROUPS
 298         bool "Control Group support"
 299         help
 300           This option will let you use process cgroup subsystems
 301           such as Cpusets
 302
 303           Say N if unsure.
 304
 305 config CGROUP_DEBUG
 306         bool "Example debug cgroup subsystem"
 307         depends on CGROUPS
 308         help
 309           This option enables a simple cgroup subsystem that
 310           exports useful debugging information about the cgroups
 311           framework
 312
 313           Say N if unsure
 314
 315 config CGROUP_NS
 316         bool "Namespace cgroup subsystem"
 317         depends on CGROUPS
 318         help
 319           Provides a simple namespace cgroup subsystem to
 320           provide hierarchical naming of sets of namespaces,
 321           for instance virtual servers and checkpoint/restart
 322           jobs.
 323
 324 config CPUSETS
 325         bool "Cpuset support"
 326         depends on SMP && CGROUPS
 327         help
 328           This option will let you create and manage CPUSETs which
 329           allow dynamically partitioning a system into sets of CPUs and
 330           Memory Nodes and assigning tasks to run only within those sets.
 331           This is primarily useful on large SMP or NUMA systems.
 332
 333           Say N if unsure.
 334
 335 config FAIR_GROUP_SCHED
 336         bool "Fair group CPU scheduler"
 337         default y
 338         help
 339           This feature lets CPU scheduler recognize task groups and control CPU
 340           bandwidth allocation to such task groups.
 341
 342 choice
 343         depends on FAIR_GROUP_SCHED
 344         prompt "Basis for grouping tasks"
 345         default FAIR_USER_SCHED
 346
 347 config FAIR_USER_SCHED
 348         bool "user id"
 349         help
 350           This option will choose userid as the basis for grouping
 351           tasks, thus providing equal CPU bandwidth to each user.
 352
 353 config FAIR_CGROUP_SCHED
 354         bool "Control groups"
 355         depends on CGROUPS
 356         help
 357           This option allows you to create arbitrary task groups
 358           using the "cgroup" pseudo filesystem and control
 359           the cpu bandwidth allocated to each such task group.
 360           Refer to Documentation/cgroups.txt for more information
 361           on "cgroup" pseudo filesystem.
 362
 363 endchoice
 364
 365 config CGROUP_CPUACCT
 366         bool "Simple CPU accounting cgroup subsystem"
 367         depends on CGROUPS
 368         help
 369           Provides a simple Resource Controller for monitoring the
 370           total CPU consumed by the tasks in a cgroup
 371
 372 config RESOURCE_COUNTERS
 373         bool "Resource counters"
 374         help
 375           This option enables controller independent resource accounting
 376           infrastructure that works with cgroups
 377         depends on CGROUPS
 378
 379 config SYSFS_DEPRECATED
 380         bool "Create deprecated sysfs files"
 381         depends on SYSFS
 382         default y
 383         help
 384           This option creates deprecated symlinks such as the
 385           "device"-link, the <subsystem>:<name>-link, and the
 386           "bus"-link. It may also add deprecated key in the
 387           uevent environment.
 388           None of these features or values should be used today, as
 389           they export driver core implementation details to userspace
 390           or export properties which can't be kept stable across kernel
 391           releases.
 392
 393           If enabled, this option will also move any device structures
 394           that belong to a class, back into the /sys/class hierarchy, in
 395           order to support older versions of udev.
 396
 397           If you are using a distro that was released in 2006 or later,
 398           it should be safe to say N here.
 399
 400 config CGROUP_MEM_CONT
 401         bool "Memory controller for cgroups"
 402         depends on CGROUPS && RESOURCE_COUNTERS
 403         help
 404           Provides a memory controller that manages both page cache and
 405           RSS memory.
 406
 407 config PROC_PID_CPUSET
 408         bool "Include legacy /proc/<pid>/cpuset file"
 409         depends on CPUSETS
 410         default y
 411
 412 config RELAY
 413         bool "Kernel->user space relay support (formerly relayfs)"
 414         help
 415           This option enables support for relay interface support in
 416           certain file systems (such as debugfs).
 417           It is designed to provide an efficient mechanism for tools and
 418           facilities to relay large amounts of data from kernel space to
 419           user space.
 420
 421           If unsure, say N.
 422
 423 config BLK_DEV_INITRD
 424         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 425         depends on BROKEN || !FRV
 426         help
 427           The initial RAM filesystem is a ramfs which is loaded by the
 428           boot loader (loadlin or lilo) and that is mounted as root
 429           before the normal boot procedure. It is typically used to
 430           load modules needed to mount the "real" root file system,
 431           etc. See <file:Documentation/initrd.txt> for details.
 432
 433           If RAM disk support (BLK_DEV_RAM) is also included, this
 434           also enables initial RAM disk (initrd) support and adds
 435           15 Kbytes (more on some other architectures) to the kernel size.
 436
 437           If unsure say Y.
 438
 439 if BLK_DEV_INITRD
 440
 441 source "usr/Kconfig"
 442
 443 endif
 444
 445 config CC_OPTIMIZE_FOR_SIZE
 446         bool "Optimize for size (Look out for broken compilers!)"
 447         default y
 448         depends on ARM || H8300 || SUPERH || EXPERIMENTAL
 449         help
 450           Enabling this option will pass "-Os" instead of "-O2" to gcc
 451           resulting in a smaller kernel.
 452
 453           WARNING: some versions of gcc may generate incorrect code with this
 454           option.  If problems are observed, a gcc upgrade may be needed.
 455
 456           If unsure, say N.
 457
 458 config SYSCTL
 459         bool
 460
 461 menuconfig EMBEDDED
 462         bool "Configure standard kernel features (for small systems)"
 463         help
 464           This option allows certain base kernel options and settings
 465           to be disabled or tweaked. This is for specialized
 466           environments which can tolerate a "non-standard" kernel.
 467           Only use this if you really know what you are doing.
 468
 469 config UID16
 470         bool "Enable 16-bit UID system calls" if EMBEDDED
 471         depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && SPARC32_COMPAT) || UML || (X86_64 && IA32_EMULATION)
 472         default y
 473         help
 474           This enables the legacy 16-bit UID syscall wrappers.
 475
 476 config SYSCTL_SYSCALL
 477         bool "Sysctl syscall support" if EMBEDDED
 478         default y
 479         select SYSCTL
 480         ---help---
 481           sys_sysctl uses binary paths that have been found challenging
 482           to properly maintain and use.  The interface in /proc/sys
 483           using paths with ascii names is now the primary path to this
 484           information.
 485
 486           Almost nothing using the binary sysctl interface so if you are
 487           trying to save some space it is probably safe to disable this,
 488           making your kernel marginally smaller.
 489
 490           If unsure say Y here.
 491
 492 config KALLSYMS
 493          bool "Load all symbols for debugging/ksymoops" if EMBEDDED
 494          default y
 495          help
 496            Say Y here to let the kernel print out symbolic crash information and
 497            symbolic stack backtraces. This increases the size of the kernel
 498            somewhat, as all symbols have to be loaded into the kernel image.
 499
 500 config KALLSYMS_ALL
 501         bool "Include all symbols in kallsyms"
 502         depends on DEBUG_KERNEL && KALLSYMS
 503         help
 504            Normally kallsyms only contains the symbols of functions, for nicer
 505            OOPS messages.  Some debuggers can use kallsyms for other
 506            symbols too: say Y here to include all symbols, if you need them
 507            and you don't care about adding 300k to the size of your kernel.
 508
 509            Say N.
 510
 511 config KALLSYMS_EXTRA_PASS
 512         bool "Do an extra kallsyms pass"
 513         depends on KALLSYMS
 514         help
 515            If kallsyms is not working correctly, the build will fail with
 516            inconsistent kallsyms data.  If that occurs, log a bug report and
 517            turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
 518            Always say N here unless you find a bug in kallsyms, which must be
 519            reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
 520            you wait for kallsyms to be fixed.
 521
 522
 523 config HOTPLUG
 524         bool "Support for hot-pluggable devices" if EMBEDDED
 525         default y
 526         help
 527           This option is provided for the case where no hotplug or uevent
 528           capabilities is wanted by the kernel.  You should only consider
 529           disabling this option for embedded systems that do not use modules, a
 530           dynamic /dev tree, or dynamic device discovery.  Just say Y.
 531
 532 config PRINTK
 533         default y
 534         bool "Enable support for printk" if EMBEDDED
 535         help
 536           This option enables normal printk support. Removing it
 537           eliminates most of the message strings from the kernel image
 538           and makes the kernel more or less silent. As this makes it
 539           very difficult to diagnose system problems, saying N here is
 540           strongly discouraged.
 541
 542 config BUG
 543         bool "BUG() support" if EMBEDDED
 544         default y
 545         help
 546           Disabling this option eliminates support for BUG and WARN, reducing
 547           the size of your kernel image and potentially quietly ignoring
 548           numerous fatal conditions. You should only consider disabling this
 549           option for embedded systems with no facilities for reporting errors.
 550           Just say Y.
 551
 552 config ELF_CORE
 553         default y
 554         bool "Enable ELF core dumps" if EMBEDDED
 555         help
 556           Enable support for generating core dumps. Disabling saves about 4k.
 557
 558 config COMPAT_BRK
 559         bool "Disable heap randomization"
 560         default y
 561         help
 562           Randomizing heap placement makes heap exploits harder, but it
 563           also breaks ancient binaries (including anything libc5 based).
 564           This option changes the bootup default to heap randomization
 565           disabled, and can be overriden runtime by setting
 566           /proc/sys/kernel/randomize_va_space to 2.
 567
 568           On non-ancient distros (post-2000 ones) Y is usually a safe choice.
 569
 570 config BASE_FULL
 571         default y
 572         bool "Enable full-sized data structures for core" if EMBEDDED
 573         help
 574           Disabling this option reduces the size of miscellaneous core
 575           kernel data structures. This saves memory on small machines,
 576           but may reduce performance.
 577
 578 config FUTEX
 579         bool "Enable futex support" if EMBEDDED
 580         default y
 581         select RT_MUTEXES
 582         help
 583           Disabling this option will cause the kernel to be built without
 584           support for "fast userspace mutexes".  The resulting kernel may not
 585           run glibc-based applications correctly.
 586
 587 config ANON_INODES
 588         bool
 589
 590 config EPOLL
 591         bool "Enable eventpoll support" if EMBEDDED
 592         default y
 593         select ANON_INODES
 594         help
 595           Disabling this option will cause the kernel to be built without
 596           support for epoll family of system calls.
 597
 598 config SIGNALFD
 599         bool "Enable signalfd() system call" if EMBEDDED
 600         select ANON_INODES
 601         default y
 602         help
 603           Enable the signalfd() system call that allows to receive signals
 604           on a file descriptor.
 605
 606           If unsure, say Y.
 607
 608 config TIMERFD
 609         bool "Enable timerfd() system call" if EMBEDDED
 610         select ANON_INODES
 611         default y
 612         help
 613           Enable the timerfd() system call that allows to receive timer
 614           events on a file descriptor.
 615
 616           If unsure, say Y.
 617
 618 config EVENTFD
 619         bool "Enable eventfd() system call" if EMBEDDED
 620         select ANON_INODES
 621         default y
 622         help
 623           Enable the eventfd() system call that allows to receive both
 624           kernel notification (ie. KAIO) or userspace notifications.
 625
 626           If unsure, say Y.
 627
 628 config SHMEM
 629         bool "Use full shmem filesystem" if EMBEDDED
 630         default y
 631         depends on MMU
 632         help
 633           The shmem is an internal filesystem used to manage shared memory.
 634           It is backed by swap and manages resource limits. It is also exported
 635           to userspace as tmpfs if TMPFS is enabled. Disabling this
 636           option replaces shmem and tmpfs with the much simpler ramfs code,
 637           which may be appropriate on small systems without swap.
 638
 639 config VM_EVENT_COUNTERS
 640         default y
 641         bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
 642         help
 643           VM event counters are needed for event counts to be shown.
 644           This option allows the disabling of the VM event counters
 645           on EMBEDDED systems.  /proc/vmstat will only show page counts
 646           if VM event counters are disabled.
 647
 648 config SLUB_DEBUG
 649         default y
 650         bool "Enable SLUB debugging support" if EMBEDDED
 651         depends on SLUB
 652         help
 653           SLUB has extensive debug support features. Disabling these can
 654           result in significant savings in code size. This also disables
 655           SLUB sysfs support. /sys/slab will not exist and there will be
 656           no support for cache validation etc.
 657
 658 choice
 659         prompt "Choose SLAB allocator"
 660         default SLUB
 661         help
 662            This option allows to select a slab allocator.
 663
 664 config SLAB
 665         bool "SLAB"
 666         help
 667           The regular slab allocator that is established and known to work
 668           well in all environments. It organizes cache hot objects in
 669           per cpu and per node queues. SLAB is the default choice for
 670           a slab allocator.
 671
 672 config SLUB
 673         bool "SLUB (Unqueued Allocator)"
 674         help
 675            SLUB is a slab allocator that minimizes cache line usage
 676            instead of managing queues of cached objects (SLAB approach).
 677            Per cpu caching is realized using slabs of objects instead
 678            of queues of objects. SLUB can use memory efficiently
 679            and has enhanced diagnostics.
 680
 681 config SLOB
 682         depends on EMBEDDED
 683         bool "SLOB (Simple Allocator)"
 684         help
 685            SLOB replaces the stock allocator with a drastically simpler
 686            allocator. SLOB is generally more space efficient but
 687            does not perform as well on large systems.
 688
 689 endchoice
 690
 691 config PROFILING
 692         bool "Profiling support (EXPERIMENTAL)"
 693         help
 694           Say Y here to enable the extended profiling support mechanisms used
 695           by profilers such as OProfile.
 696
 697 config MARKERS
 698         bool "Activate markers"
 699         help
 700           Place an empty function call at each marker site. Can be
 701           dynamically changed for a probe function.
 702
 703 source "arch/Kconfig"
 704
 705 config PROC_PAGE_MONITOR
 706         default y
 707         depends on PROC_FS && MMU
 708         bool "Enable /proc page monitoring" if EMBEDDED
 709         help
 710           Various /proc files exist to monitor process memory utilization:
 711           /proc/pid/smaps, /proc/pid/clear_refs, /proc/pid/pagemap,
 712           /proc/kpagecount, and /proc/kpageflags. Disabling these
 713           interfaces will reduce the size of the kernel by approximately 4kb.
 714
 715 endmenu         # General setup
 716
 717 config SLABINFO
 718         bool
 719         depends on PROC_FS
 720         depends on SLAB || SLUB
 721         default y
 722
 723 config RT_MUTEXES
 724         boolean
 725         select PLIST
 726
 727 config TINY_SHMEM
 728         default !SHMEM
 729         bool
 730
 731 config BASE_SMALL
 732         int
 733         default 0 if BASE_FULL
 734         default 1 if !BASE_FULL
 735
 736 menuconfig MODULES
 737         bool "Enable loadable module support"
 738         help
 739           Kernel modules are small pieces of compiled code which can
 740           be inserted in the running kernel, rather than being
 741           permanently built into the kernel.  You use the "modprobe"
 742           tool to add (and sometimes remove) them.  If you say Y here,
 743           many parts of the kernel can be built as modules (by
 744           answering M instead of Y where indicated): this is most
 745           useful for infrequently used options which are not required
 746           for booting.  For more information, see the man pages for
 747           modprobe, lsmod, modinfo, insmod and rmmod.
 748
 749           If you say Y here, you will need to run "make
 750           modules_install" to put the modules under /lib/modules/
 751           where modprobe can find them (you may need to be root to do
 752           this).
 753
 754           If unsure, say Y.
 755
 756 config MODULE_UNLOAD
 757         bool "Module unloading"
 758         depends on MODULES
 759         help
 760           Without this option you will not be able to unload any
 761           modules (note that some modules may not be unloadable
 762           anyway), which makes your kernel slightly smaller and
 763           simpler.  If unsure, say Y.
 764
 765 config MODULE_FORCE_UNLOAD
 766         bool "Forced module unloading"
 767         depends on MODULE_UNLOAD && EXPERIMENTAL
 768         help
 769           This option allows you to force a module to unload, even if the
 770           kernel believes it is unsafe: the kernel will remove the module
 771           without waiting for anyone to stop using it (using the -f option to
 772           rmmod).  This is mainly for kernel developers and desperate users.
 773           If unsure, say N.
 774
 775 config MODVERSIONS
 776         bool "Module versioning support"
 777         depends on MODULES
 778         help
 779           Usually, you have to use modules compiled with your kernel.
 780           Saying Y here makes it sometimes possible to use modules
 781           compiled for different kernels, by adding enough information
 782           to the modules to (hopefully) spot any changes which would
 783           make them incompatible with the kernel you are running.  If
 784           unsure, say N.
 785
 786 config MODULE_SRCVERSION_ALL
 787         bool "Source checksum for all modules"
 788         depends on MODULES
 789         help
 790           Modules which contain a MODULE_VERSION get an extra "srcversion"
 791           field inserted into their modinfo section, which contains a
 792           sum of the source files which made it.  This helps maintainers
 793           see exactly which source was used to build a module (since
 794           others sometimes change the module source without updating
 795           the version).  With this option, such a "srcversion" field
 796           will be created for all modules.  If unsure, say N.
 797
 798 config KMOD
 799         bool "Automatic kernel module loading"
 800         depends on MODULES
 801         help
 802           Normally when you have selected some parts of the kernel to
 803           be created as kernel modules, you must load them (using the
 804           "modprobe" command) before you can use them. If you say Y
 805           here, some parts of the kernel will be able to load modules
 806           automatically: when a part of the kernel needs a module, it
 807           runs modprobe with the appropriate arguments, thereby
 808           loading the module if it is available.  If unsure, say Y.
 809
 810 config STOP_MACHINE
 811         bool
 812         default y
 813         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
 814         help
 815           Need stop_machine() primitive.
 816
 817 source "block/Kconfig"
 818
 819 config PREEMPT_NOTIFIERS
 820         bool
 821
 822 choice
 823         prompt "RCU implementation type:"
 824         default CLASSIC_RCU
 825         help
 826           This allows you to choose either the classic RCU implementation
 827           that is designed for best read-side performance on non-realtime
 828           systems, or the preemptible RCU implementation for best latency
 829           on realtime systems.  Note that some kernel preemption modes
 830           will restrict your choice.
 831
 832           Select the default if you are unsure.
 833
 834 config CLASSIC_RCU
 835         bool "Classic RCU"
 836         help
 837           This option selects the classic RCU implementation that is
 838           designed for best read-side performance on non-realtime
 839           systems.
 840
 841           Say Y if you are unsure.
 842
 843 config PREEMPT_RCU
 844         bool "Preemptible RCU"
 845         depends on PREEMPT
 846         help
 847           This option reduces the latency of the kernel by making certain
 848           RCU sections preemptible. Normally RCU code is non-preemptible, if
 849           this option is selected then read-only RCU sections become
 850           preemptible. This helps latency, but may expose bugs due to
 851           now-naive assumptions about each RCU read-side critical section
 852           remaining on a given CPU through its execution.
 853
 854           Say N if you are unsure.
 855
 856 endchoice