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  41           drivers that have been replaced by something else, and/or are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 PROC_PID_CPUSET
 401         bool "Include legacy /proc/<pid>/cpuset file"
 402         depends on CPUSETS
 403         default y
 404
 405 config RELAY
 406         bool "Kernel->user space relay support (formerly relayfs)"
 407         help
 408           This option enables support for relay interface support in
 409           certain file systems (such as debugfs).
 410           It is designed to provide an efficient mechanism for tools and
 411           facilities to relay large amounts of data from kernel space to
 412           user space.
 413
 414           If unsure, say N.
 415
 416 config BLK_DEV_INITRD
 417         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 418         depends on BROKEN || !FRV
 419         help
 420           The initial RAM filesystem is a ramfs which is loaded by the
 421           boot loader (loadlin or lilo) and that is mounted as root
 422           before the normal boot procedure. It is typically used to
 423           load modules needed to mount the "real" root file system,
 424           etc. See <file:Documentation/initrd.txt> for details.
 425
 426           If RAM disk support (BLK_DEV_RAM) is also included, this
 427           also enables initial RAM disk (initrd) support and adds
 428           15 Kbytes (more on some other architectures) to the kernel size.
 429
 430           If unsure say Y.
 431
 432 if BLK_DEV_INITRD
 433
 434 source "usr/Kconfig"
 435
 436 endif
 437
 438 config CC_OPTIMIZE_FOR_SIZE
 439         bool "Optimize for size (Look out for broken compilers!)"
 440         default y
 441         depends on ARM || H8300 || SUPERH || EXPERIMENTAL
 442         help
 443           Enabling this option will pass "-Os" instead of "-O2" to gcc
 444           resulting in a smaller kernel.
 445
 446           WARNING: some versions of gcc may generate incorrect code with this
 447           option.  If problems are observed, a gcc upgrade may be needed.
 448
 449           If unsure, say N.
 450
 451 config SYSCTL
 452         bool
 453
 454 menuconfig EMBEDDED
 455         bool "Configure standard kernel features (for small systems)"
 456         help
 457           This option allows certain base kernel options and settings
 458           to be disabled or tweaked. This is for specialized
 459           environments which can tolerate a "non-standard" kernel.
 460           Only use this if you really know what you are doing.
 461
 462 config UID16
 463         bool "Enable 16-bit UID system calls" if EMBEDDED
 464         depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && SPARC32_COMPAT) || UML || (X86_64 && IA32_EMULATION)
 465         default y
 466         help
 467           This enables the legacy 16-bit UID syscall wrappers.
 468
 469 config SYSCTL_SYSCALL
 470         bool "Sysctl syscall support" if EMBEDDED
 471         default y
 472         select SYSCTL
 473         ---help---
 474           sys_sysctl uses binary paths that have been found challenging
 475           to properly maintain and use.  The interface in /proc/sys
 476           using paths with ascii names is now the primary path to this
 477           information.
 478
 479           Almost nothing using the binary sysctl interface so if you are
 480           trying to save some space it is probably safe to disable this,
 481           making your kernel marginally smaller.
 482
 483           If unsure say Y here.
 484
 485 config KALLSYMS
 486          bool "Load all symbols for debugging/ksymoops" if EMBEDDED
 487          default y
 488          help
 489            Say Y here to let the kernel print out symbolic crash information and
 490            symbolic stack backtraces. This increases the size of the kernel
 491            somewhat, as all symbols have to be loaded into the kernel image.
 492
 493 config KALLSYMS_ALL
 494         bool "Include all symbols in kallsyms"
 495         depends on DEBUG_KERNEL && KALLSYMS
 496         help
 497            Normally kallsyms only contains the symbols of functions, for nicer
 498            OOPS messages.  Some debuggers can use kallsyms for other
 499            symbols too: say Y here to include all symbols, if you need them
 500            and you don't care about adding 300k to the size of your kernel.
 501
 502            Say N.
 503
 504 config KALLSYMS_EXTRA_PASS
 505         bool "Do an extra kallsyms pass"
 506         depends on KALLSYMS
 507         help
 508            If kallsyms is not working correctly, the build will fail with
 509            inconsistent kallsyms data.  If that occurs, log a bug report and
 510            turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
 511            Always say N here unless you find a bug in kallsyms, which must be
 512            reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
 513            you wait for kallsyms to be fixed.
 514
 515
 516 config HOTPLUG
 517         bool "Support for hot-pluggable devices" if EMBEDDED
 518         default y
 519         help
 520           This option is provided for the case where no hotplug or uevent
 521           capabilities is wanted by the kernel.  You should only consider
 522           disabling this option for embedded systems that do not use modules, a
 523           dynamic /dev tree, or dynamic device discovery.  Just say Y.
 524
 525 config PRINTK
 526         default y
 527         bool "Enable support for printk" if EMBEDDED
 528         help
 529           This option enables normal printk support. Removing it
 530           eliminates most of the message strings from the kernel image
 531           and makes the kernel more or less silent. As this makes it
 532           very difficult to diagnose system problems, saying N here is
 533           strongly discouraged.
 534
 535 config BUG
 536         bool "BUG() support" if EMBEDDED
 537         default y
 538         help
 539           Disabling this option eliminates support for BUG and WARN, reducing
 540           the size of your kernel image and potentially quietly ignoring
 541           numerous fatal conditions. You should only consider disabling this
 542           option for embedded systems with no facilities for reporting errors.
 543           Just say Y.
 544
 545 config ELF_CORE
 546         default y
 547         bool "Enable ELF core dumps" if EMBEDDED
 548         help
 549           Enable support for generating core dumps. Disabling saves about 4k.
 550
 551 config COMPAT_BRK
 552         bool "Disable heap randomization"
 553         default y
 554         help
 555           Randomizing heap placement makes heap exploits harder, but it
 556           also breaks ancient binaries (including anything libc5 based).
 557           This option changes the bootup default to heap randomization
 558           disabled, and can be overriden runtime by setting
 559           /proc/sys/kernel/randomize_va_space to 2.
 560
 561           On non-ancient distros (post-2000 ones) Y is usually a safe choice.
 562
 563 config BASE_FULL
 564         default y
 565         bool "Enable full-sized data structures for core" if EMBEDDED
 566         help
 567           Disabling this option reduces the size of miscellaneous core
 568           kernel data structures. This saves memory on small machines,
 569           but may reduce performance.
 570
 571 config FUTEX
 572         bool "Enable futex support" if EMBEDDED
 573         default y
 574         select RT_MUTEXES
 575         help
 576           Disabling this option will cause the kernel to be built without
 577           support for "fast userspace mutexes".  The resulting kernel may not
 578           run glibc-based applications correctly.
 579
 580 config ANON_INODES
 581         bool
 582
 583 config EPOLL
 584         bool "Enable eventpoll support" if EMBEDDED
 585         default y
 586         select ANON_INODES
 587         help
 588           Disabling this option will cause the kernel to be built without
 589           support for epoll family of system calls.
 590
 591 config SIGNALFD
 592         bool "Enable signalfd() system call" if EMBEDDED
 593         select ANON_INODES
 594         default y
 595         help
 596           Enable the signalfd() system call that allows to receive signals
 597           on a file descriptor.
 598
 599           If unsure, say Y.
 600
 601 config TIMERFD
 602         bool "Enable timerfd() system call" if EMBEDDED
 603         select ANON_INODES
 604         default y
 605         help
 606           Enable the timerfd() system call that allows to receive timer
 607           events on a file descriptor.
 608
 609           If unsure, say Y.
 610
 611 config EVENTFD
 612         bool "Enable eventfd() system call" if EMBEDDED
 613         select ANON_INODES
 614         default y
 615         help
 616           Enable the eventfd() system call that allows to receive both
 617           kernel notification (ie. KAIO) or userspace notifications.
 618
 619           If unsure, say Y.
 620
 621 config SHMEM
 622         bool "Use full shmem filesystem" if EMBEDDED
 623         default y
 624         depends on MMU
 625         help
 626           The shmem is an internal filesystem used to manage shared memory.
 627           It is backed by swap and manages resource limits. It is also exported
 628           to userspace as tmpfs if TMPFS is enabled. Disabling this
 629           option replaces shmem and tmpfs with the much simpler ramfs code,
 630           which may be appropriate on small systems without swap.
 631
 632 config VM_EVENT_COUNTERS
 633         default y
 634         bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
 635         help
 636           VM event counters are needed for event counts to be shown.
 637           This option allows the disabling of the VM event counters
 638           on EMBEDDED systems.  /proc/vmstat will only show page counts
 639           if VM event counters are disabled.
 640
 641 config SLUB_DEBUG
 642         default y
 643         bool "Enable SLUB debugging support" if EMBEDDED
 644         depends on SLUB
 645         help
 646           SLUB has extensive debug support features. Disabling these can
 647           result in significant savings in code size. This also disables
 648           SLUB sysfs support. /sys/slab will not exist and there will be
 649           no support for cache validation etc.
 650
 651 choice
 652         prompt "Choose SLAB allocator"
 653         default SLUB
 654         help
 655            This option allows to select a slab allocator.
 656
 657 config SLAB
 658         bool "SLAB"
 659         help
 660           The regular slab allocator that is established and known to work
 661           well in all environments. It organizes cache hot objects in
 662           per cpu and per node queues. SLAB is the default choice for
 663           a slab allocator.
 664
 665 config SLUB
 666         bool "SLUB (Unqueued Allocator)"
 667         help
 668            SLUB is a slab allocator that minimizes cache line usage
 669            instead of managing queues of cached objects (SLAB approach).
 670            Per cpu caching is realized using slabs of objects instead
 671            of queues of objects. SLUB can use memory efficiently
 672            and has enhanced diagnostics.
 673
 674 config SLOB
 675         depends on EMBEDDED
 676         bool "SLOB (Simple Allocator)"
 677         help
 678            SLOB replaces the stock allocator with a drastically simpler
 679            allocator. SLOB is generally more space efficient but
 680            does not perform as well on large systems.
 681
 682 endchoice
 683
 684 config PROFILING
 685         bool "Profiling support (EXPERIMENTAL)"
 686         help
 687           Say Y here to enable the extended profiling support mechanisms used
 688           by profilers such as OProfile.
 689
 690 config MARKERS
 691         bool "Activate markers"
 692         help
 693           Place an empty function call at each marker site. Can be
 694           dynamically changed for a probe function.
 695
 696 source "arch/Kconfig"
 697
 698 config PROC_PAGE_MONITOR
 699         default y
 700         depends on PROC_FS && MMU
 701         bool "Enable /proc page monitoring" if EMBEDDED
 702         help
 703           Various /proc files exist to monitor process memory utilization:
 704           /proc/pid/smaps, /proc/pid/clear_refs, /proc/pid/pagemap,
 705           /proc/kpagecount, and /proc/kpageflags. Disabling these
 706           interfaces will reduce the size of the kernel by approximately 4kb.
 707
 708 endmenu         # General setup
 709
 710 config SLABINFO
 711         bool
 712         depends on PROC_FS
 713         depends on SLAB || SLUB
 714         default y
 715
 716 config RT_MUTEXES
 717         boolean
 718         select PLIST
 719
 720 config TINY_SHMEM
 721         default !SHMEM
 722         bool
 723
 724 config BASE_SMALL
 725         int
 726         default 0 if BASE_FULL
 727         default 1 if !BASE_FULL
 728
 729 menuconfig MODULES
 730         bool "Enable loadable module support"
 731         help
 732           Kernel modules are small pieces of compiled code which can
 733           be inserted in the running kernel, rather than being
 734           permanently built into the kernel.  You use the "modprobe"
 735           tool to add (and sometimes remove) them.  If you say Y here,
 736           many parts of the kernel can be built as modules (by
 737           answering M instead of Y where indicated): this is most
 738           useful for infrequently used options which are not required
 739           for booting.  For more information, see the man pages for
 740           modprobe, lsmod, modinfo, insmod and rmmod.
 741
 742           If you say Y here, you will need to run "make
 743           modules_install" to put the modules under /lib/modules/
 744           where modprobe can find them (you may need to be root to do
 745           this).
 746
 747           If unsure, say Y.
 748
 749 config MODULE_UNLOAD
 750         bool "Module unloading"
 751         depends on MODULES
 752         help
 753           Without this option you will not be able to unload any
 754           modules (note that some modules may not be unloadable
 755           anyway), which makes your kernel slightly smaller and
 756           simpler.  If unsure, say Y.
 757
 758 config MODULE_FORCE_UNLOAD
 759         bool "Forced module unloading"
 760         depends on MODULE_UNLOAD && EXPERIMENTAL
 761         help
 762           This option allows you to force a module to unload, even if the
 763           kernel believes it is unsafe: the kernel will remove the module
 764           without waiting for anyone to stop using it (using the -f option to
 765           rmmod).  This is mainly for kernel developers and desperate users.
 766           If unsure, say N.
 767
 768 config MODVERSIONS
 769         bool "Module versioning support"
 770         depends on MODULES
 771         help
 772           Usually, you have to use modules compiled with your kernel.
 773           Saying Y here makes it sometimes possible to use modules
 774           compiled for different kernels, by adding enough information
 775           to the modules to (hopefully) spot any changes which would
 776           make them incompatible with the kernel you are running.  If
 777           unsure, say N.
 778
 779 config MODULE_SRCVERSION_ALL
 780         bool "Source checksum for all modules"
 781         depends on MODULES
 782         help
 783           Modules which contain a MODULE_VERSION get an extra "srcversion"
 784           field inserted into their modinfo section, which contains a
 785           sum of the source files which made it.  This helps maintainers
 786           see exactly which source was used to build a module (since
 787           others sometimes change the module source without updating
 788           the version).  With this option, such a "srcversion" field
 789           will be created for all modules.  If unsure, say N.
 790
 791 config KMOD
 792         bool "Automatic kernel module loading"
 793         depends on MODULES
 794         help
 795           Normally when you have selected some parts of the kernel to
 796           be created as kernel modules, you must load them (using the
 797           "modprobe" command) before you can use them. If you say Y
 798           here, some parts of the kernel will be able to load modules
 799           automatically: when a part of the kernel needs a module, it
 800           runs modprobe with the appropriate arguments, thereby
 801           loading the module if it is available.  If unsure, say Y.
 802
 803 config STOP_MACHINE
 804         bool
 805         default y
 806         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
 807         help
 808           Need stop_machine() primitive.
 809
 810 source "block/Kconfig"
 811
 812 config PREEMPT_NOTIFIERS
 813         bool
 814
 815 choice
 816         prompt "RCU implementation type:"
 817         default CLASSIC_RCU
 818         help
 819           This allows you to choose either the classic RCU implementation
 820           that is designed for best read-side performance on non-realtime
 821           systems, or the preemptible RCU implementation for best latency
 822           on realtime systems.  Note that some kernel preemption modes
 823           will restrict your choice.
 824
 825           Select the default if you are unsure.
 826
 827 config CLASSIC_RCU
 828         bool "Classic RCU"
 829         help
 830           This option selects the classic RCU implementation that is
 831           designed for best read-side performance on non-realtime
 832           systems.
 833
 834           Say Y if you are unsure.
 835
 836 config PREEMPT_RCU
 837         bool "Preemptible RCU"
 838         depends on PREEMPT
 839         help
 840           This option reduces the latency of the kernel by making certain
 841           RCU sections preemptible. Normally RCU code is non-preemptible, if
 842           this option is selected then read-only RCU sections become
 843           preemptible. This helps latency, but may expose bugs due to
 844           now-naive assumptions about each RCU read-side critical section
 845           remaining on a given CPU through its execution.
 846
 847           Say N if you are unsure.
 848
 849 endchoice