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  42           drivers that have been replaced by something else, and/or are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 SWAP
 105         bool "Support for paging of anonymous memory (swap)"
 106         depends on MMU && BLOCK
 107         default y
 108         help
 109           This option allows you to choose whether you want to have support
 110           for so called swap devices or swap files in your kernel that are
 111           used to provide more virtual memory than the actual RAM present
 112           in your computer.  If unsure say Y.
 113
 114 config SYSVIPC
 115         bool "System V IPC"
 116         ---help---
 117           Inter Process Communication is a suite of library functions and
 118           system calls which let processes (running programs) synchronize and
 119           exchange information. It is generally considered to be a good thing,
 120           and some programs won't run unless you say Y here. In particular, if
 121           you want to run the DOS emulator dosemu under Linux (read the
 122           DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
 123           you'll need to say Y here.
 124
 125           You can find documentation about IPC with "info ipc" and also in
 126           section 6.4 of the Linux Programmer's Guide, available from
 127           <http://www.tldp.org/guides.html>.
 128
 129 config SYSVIPC_SYSCTL
 130         bool
 131         depends on SYSVIPC
 132         depends on SYSCTL
 133         default y
 134
 135 config POSIX_MQUEUE
 136         bool "POSIX Message Queues"
 137         depends on NET && EXPERIMENTAL
 138         ---help---
 139           POSIX variant of message queues is a part of IPC. In POSIX message
 140           queues every message has a priority which decides about succession
 141           of receiving it by a process. If you want to compile and run
 142           programs written e.g. for Solaris with use of its POSIX message
 143           queues (functions mq_*) say Y here.
 144
 145           POSIX message queues are visible as a filesystem called 'mqueue'
 146           and can be mounted somewhere if you want to do filesystem
 147           operations on message queues.
 148
 149           If unsure, say Y.
 150
 151 config BSD_PROCESS_ACCT
 152         bool "BSD Process Accounting"
 153         help
 154           If you say Y here, a user level program will be able to instruct the
 155           kernel (via a special system call) to write process accounting
 156           information to a file: whenever a process exits, information about
 157           that process will be appended to the file by the kernel.  The
 158           information includes things such as creation time, owning user,
 159           command name, memory usage, controlling terminal etc. (the complete
 160           list is in the struct acct in <file:include/linux/acct.h>).  It is
 161           up to the user level program to do useful things with this
 162           information.  This is generally a good idea, so say Y.
 163
 164 config BSD_PROCESS_ACCT_V3
 165         bool "BSD Process Accounting version 3 file format"
 166         depends on BSD_PROCESS_ACCT
 167         default n
 168         help
 169           If you say Y here, the process accounting information is written
 170           in a new file format that also logs the process IDs of each
 171           process and it's parent. Note that this file format is incompatible
 172           with previous v0/v1/v2 file formats, so you will need updated tools
 173           for processing it. A preliminary version of these tools is available
 174           at <http://www.gnu.org/software/acct/>.
 175
 176 config TASKSTATS
 177         bool "Export task/process statistics through netlink (EXPERIMENTAL)"
 178         depends on NET
 179         default n
 180         help
 181           Export selected statistics for tasks/processes through the
 182           generic netlink interface. Unlike BSD process accounting, the
 183           statistics are available during the lifetime of tasks/processes as
 184           responses to commands. Like BSD accounting, they are sent to user
 185           space on task exit.
 186
 187           Say N if unsure.
 188
 189 config TASK_DELAY_ACCT
 190         bool "Enable per-task delay accounting (EXPERIMENTAL)"
 191         depends on TASKSTATS
 192         help
 193           Collect information on time spent by a task waiting for system
 194           resources like cpu, synchronous block I/O completion and swapping
 195           in pages. Such statistics can help in setting a task's priorities
 196           relative to other tasks for cpu, io, rss limits etc.
 197
 198           Say N if unsure.
 199
 200 config TASK_XACCT
 201         bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
 202         depends on TASKSTATS
 203         help
 204           Collect extended task accounting data and send the data
 205           to userland for processing over the taskstats interface.
 206
 207           Say N if unsure.
 208
 209 config TASK_IO_ACCOUNTING
 210         bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
 211         depends on TASK_XACCT
 212         help
 213           Collect information on the number of bytes of storage I/O which this
 214           task has caused.
 215
 216           Say N if unsure.
 217
 218 config AUDIT
 219         bool "Auditing support"
 220         depends on NET
 221         help
 222           Enable auditing infrastructure that can be used with another
 223           kernel subsystem, such as SELinux (which requires this for
 224           logging of avc messages output).  Does not do system-call
 225           auditing without CONFIG_AUDITSYSCALL.
 226
 227 config AUDITSYSCALL
 228         bool "Enable system-call auditing support"
 229         depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
 230         default y if SECURITY_SELINUX
 231         help
 232           Enable low-overhead system-call auditing infrastructure that
 233           can be used independently or with another kernel subsystem,
 234           such as SELinux.  To use audit's filesystem watch feature, please
 235           ensure that INOTIFY is configured.
 236
 237 config AUDIT_TREE
 238         def_bool y
 239         depends on AUDITSYSCALL && INOTIFY
 240
 241 config IKCONFIG
 242         tristate "Kernel .config support"
 243         ---help---
 244           This option enables the complete Linux kernel ".config" file
 245           contents to be saved in the kernel. It provides documentation
 246           of which kernel options are used in a running kernel or in an
 247           on-disk kernel.  This information can be extracted from the kernel
 248           image file with the script scripts/extract-ikconfig and used as
 249           input to rebuild the current kernel or to build another kernel.
 250           It can also be extracted from a running kernel by reading
 251           /proc/config.gz if enabled (below).
 252
 253 config IKCONFIG_PROC
 254         bool "Enable access to .config through /proc/config.gz"
 255         depends on IKCONFIG && PROC_FS
 256         ---help---
 257           This option enables access to the kernel configuration file
 258           through /proc/config.gz.
 259
 260 config LOG_BUF_SHIFT
 261         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 262         range 12 21
 263         default 17
 264         help
 265           Select kernel log buffer size as a power of 2.
 266           Examples:
 267                      17 => 128 KB
 268                      16 => 64 KB
 269                      15 => 32 KB
 270                      14 => 16 KB
 271                      13 =>  8 KB
 272                      12 =>  4 KB
 273
 274 config CGROUPS
 275         bool "Control Group support"
 276         help
 277           This option will let you use process cgroup subsystems
 278           such as Cpusets
 279
 280           Say N if unsure.
 281
 282 config CGROUP_DEBUG
 283         bool "Example debug cgroup subsystem"
 284         depends on CGROUPS
 285         default n
 286         help
 287           This option enables a simple cgroup subsystem that
 288           exports useful debugging information about the cgroups
 289           framework
 290
 291           Say N if unsure
 292
 293 config CGROUP_NS
 294         bool "Namespace cgroup subsystem"
 295         depends on CGROUPS
 296         help
 297           Provides a simple namespace cgroup subsystem to
 298           provide hierarchical naming of sets of namespaces,
 299           for instance virtual servers and checkpoint/restart
 300           jobs.
 301
 302 config CGROUP_FREEZER
 303         bool "control group freezer subsystem"
 304         depends on CGROUPS
 305         help
 306           Provides a way to freeze and unfreeze all tasks in a
 307           cgroup.
 308
 309 config CGROUP_DEVICE
 310         bool "Device controller for cgroups"
 311         depends on CGROUPS && EXPERIMENTAL
 312         help
 313           Provides a cgroup implementing whitelists for devices which
 314           a process in the cgroup can mknod or open.
 315
 316 config CPUSETS
 317         bool "Cpuset support"
 318         depends on SMP && CGROUPS
 319         help
 320           This option will let you create and manage CPUSETs which
 321           allow dynamically partitioning a system into sets of CPUs and
 322           Memory Nodes and assigning tasks to run only within those sets.
 323           This is primarily useful on large SMP or NUMA systems.
 324
 325           Say N if unsure.
 326
 327 #
 328 # Architectures with an unreliable sched_clock() should select this:
 329 #
 330 config HAVE_UNSTABLE_SCHED_CLOCK
 331         bool
 332
 333 config GROUP_SCHED
 334         bool "Group CPU scheduler"
 335         depends on EXPERIMENTAL
 336         default n
 337         help
 338           This feature lets CPU scheduler recognize task groups and control CPU
 339           bandwidth allocation to such task groups.
 340
 341 config FAIR_GROUP_SCHED
 342         bool "Group scheduling for SCHED_OTHER"
 343         depends on GROUP_SCHED
 344         default GROUP_SCHED
 345
 346 config RT_GROUP_SCHED
 347         bool "Group scheduling for SCHED_RR/FIFO"
 348         depends on EXPERIMENTAL
 349         depends on GROUP_SCHED
 350         default n
 351         help
 352           This feature lets you explicitly allocate real CPU bandwidth
 353           to users or control groups (depending on the "Basis for grouping tasks"
 354           setting below. If enabled, it will also make it impossible to
 355           schedule realtime tasks for non-root users until you allocate
 356           realtime bandwidth for them.
 357           See Documentation/scheduler/sched-rt-group.txt for more information.
 358
 359 choice
 360         depends on GROUP_SCHED
 361         prompt "Basis for grouping tasks"
 362         default USER_SCHED
 363
 364 config USER_SCHED
 365         bool "user id"
 366         help
 367           This option will choose userid as the basis for grouping
 368           tasks, thus providing equal CPU bandwidth to each user.
 369
 370 config CGROUP_SCHED
 371         bool "Control groups"
 372         depends on CGROUPS
 373         help
 374           This option allows you to create arbitrary task groups
 375           using the "cgroup" pseudo filesystem and control
 376           the cpu bandwidth allocated to each such task group.
 377           Refer to Documentation/cgroups.txt for more information
 378           on "cgroup" pseudo filesystem.
 379
 380 endchoice
 381
 382 config CGROUP_CPUACCT
 383         bool "Simple CPU accounting cgroup subsystem"
 384         depends on CGROUPS
 385         help
 386           Provides a simple Resource Controller for monitoring the
 387           total CPU consumed by the tasks in a cgroup
 388
 389 config RESOURCE_COUNTERS
 390         bool "Resource counters"
 391         help
 392           This option enables controller independent resource accounting
 393           infrastructure that works with cgroups
 394         depends on CGROUPS
 395
 396 config MM_OWNER
 397         bool
 398
 399 config CGROUP_MEM_RES_CTLR
 400         bool "Memory Resource Controller for Control Groups"
 401         depends on CGROUPS && RESOURCE_COUNTERS
 402         select MM_OWNER
 403         help
 404           Provides a memory resource controller that manages both anonymous
 405           memory and page cache. (See Documentation/controllers/memory.txt)
 406
 407           Note that setting this option increases fixed memory overhead
 408           associated with each page of memory in the system. By this,
 409           20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
 410           usage tracking struct at boot. Total amount of this is printed out
 411           at boot.
 412
 413           Only enable when you're ok with these trade offs and really
 414           sure you need the memory resource controller. Even when you enable
 415           this, you can set "cgroup_disable=memory" at your boot option to
 416           disable memory resource controller and you can avoid overheads.
 417           (and lose benefits of memory resource contoller)
 418
 419           This config option also selects MM_OWNER config option, which
 420           could in turn add some fork/exit overhead.
 421
 422 config SYSFS_DEPRECATED
 423         bool
 424
 425 config SYSFS_DEPRECATED_V2
 426         bool "Create deprecated sysfs layout for older userspace tools"
 427         depends on SYSFS
 428         default y
 429         select SYSFS_DEPRECATED
 430         help
 431           This option switches the layout of sysfs to the deprecated
 432           version.
 433
 434           The current sysfs layout features a unified device tree at
 435           /sys/devices/, which is able to express a hierarchy between
 436           class devices. If the deprecated option is set to Y, the
 437           unified device tree is split into a bus device tree at
 438           /sys/devices/ and several individual class device trees at
 439           /sys/class/. The class and bus devices will be connected by
 440           "<subsystem>:<name>" and the "device" links. The "block"
 441           class devices, will not show up in /sys/class/block/. Some
 442           subsystems will suppress the creation of some devices which
 443           depend on the unified device tree.
 444
 445           This option is not a pure compatibility option that can
 446           be safely enabled on newer distributions. It will change the
 447           layout of sysfs to the non-extensible deprecated version,
 448           and disable some features, which can not be exported without
 449           confusing older userspace tools. Since 2007/2008 all major
 450           distributions do not enable this option, and ship no tools which
 451           depend on the deprecated layout or this option.
 452
 453           If you are using a new kernel on an older distribution, or use
 454           older userspace tools, you might need to say Y here. Do not say Y,
 455           if the original kernel, that came with your distribution, has
 456           this option set to N.
 457
 458 config PROC_PID_CPUSET
 459         bool "Include legacy /proc/<pid>/cpuset file"
 460         depends on CPUSETS
 461         default y
 462
 463 config RELAY
 464         bool "Kernel->user space relay support (formerly relayfs)"
 465         help
 466           This option enables support for relay interface support in
 467           certain file systems (such as debugfs).
 468           It is designed to provide an efficient mechanism for tools and
 469           facilities to relay large amounts of data from kernel space to
 470           user space.
 471
 472           If unsure, say N.
 473
 474 config NAMESPACES
 475         bool "Namespaces support" if EMBEDDED
 476         default !EMBEDDED
 477         help
 478           Provides the way to make tasks work with different objects using
 479           the same id. For example same IPC id may refer to different objects
 480           or same user id or pid may refer to different tasks when used in
 481           different namespaces.
 482
 483 config UTS_NS
 484         bool "UTS namespace"
 485         depends on NAMESPACES
 486         help
 487           In this namespace tasks see different info provided with the
 488           uname() system call
 489
 490 config IPC_NS
 491         bool "IPC namespace"
 492         depends on NAMESPACES && SYSVIPC
 493         help
 494           In this namespace tasks work with IPC ids which correspond to
 495           different IPC objects in different namespaces
 496
 497 config USER_NS
 498         bool "User namespace (EXPERIMENTAL)"
 499         depends on NAMESPACES && EXPERIMENTAL
 500         help
 501           This allows containers, i.e. vservers, to use user namespaces
 502           to provide different user info for different servers.
 503           If unsure, say N.
 504
 505 config PID_NS
 506         bool "PID Namespaces (EXPERIMENTAL)"
 507         default n
 508         depends on NAMESPACES && EXPERIMENTAL
 509         help
 510           Support process id namespaces.  This allows having multiple
 511           process with the same pid as long as they are in different
 512           pid namespaces.  This is a building block of containers.
 513
 514           Unless you want to work with an experimental feature
 515           say N here.
 516
 517 config BLK_DEV_INITRD
 518         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 519         depends on BROKEN || !FRV
 520         help
 521           The initial RAM filesystem is a ramfs which is loaded by the
 522           boot loader (loadlin or lilo) and that is mounted as root
 523           before the normal boot procedure. It is typically used to
 524           load modules needed to mount the "real" root file system,
 525           etc. See <file:Documentation/initrd.txt> for details.
 526
 527           If RAM disk support (BLK_DEV_RAM) is also included, this
 528           also enables initial RAM disk (initrd) support and adds
 529           15 Kbytes (more on some other architectures) to the kernel size.
 530
 531           If unsure say Y.
 532
 533 if BLK_DEV_INITRD
 534
 535 source "usr/Kconfig"
 536
 537 endif
 538
 539 config CC_OPTIMIZE_FOR_SIZE
 540         bool "Optimize for size"
 541         default y
 542         help
 543           Enabling this option will pass "-Os" instead of "-O2" to gcc
 544           resulting in a smaller kernel.
 545
 546           If unsure, say Y.
 547
 548 config SYSCTL
 549         bool
 550
 551 menuconfig EMBEDDED
 552         bool "Configure standard kernel features (for small systems)"
 553         help
 554           This option allows certain base kernel options and settings
 555           to be disabled or tweaked. This is for specialized
 556           environments which can tolerate a "non-standard" kernel.
 557           Only use this if you really know what you are doing.
 558
 559 config UID16
 560         bool "Enable 16-bit UID system calls" if EMBEDDED
 561         depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
 562         default y
 563         help
 564           This enables the legacy 16-bit UID syscall wrappers.
 565
 566 config SYSCTL_SYSCALL
 567         bool "Sysctl syscall support" if EMBEDDED
 568         default y
 569         select SYSCTL
 570         ---help---
 571           sys_sysctl uses binary paths that have been found challenging
 572           to properly maintain and use.  The interface in /proc/sys
 573           using paths with ascii names is now the primary path to this
 574           information.
 575
 576           Almost nothing using the binary sysctl interface so if you are
 577           trying to save some space it is probably safe to disable this,
 578           making your kernel marginally smaller.
 579
 580           If unsure say Y here.
 581
 582 config KALLSYMS
 583          bool "Load all symbols for debugging/ksymoops" if EMBEDDED
 584          default y
 585          help
 586            Say Y here to let the kernel print out symbolic crash information and
 587            symbolic stack backtraces. This increases the size of the kernel
 588            somewhat, as all symbols have to be loaded into the kernel image.
 589
 590 config KALLSYMS_ALL
 591         bool "Include all symbols in kallsyms"
 592         depends on DEBUG_KERNEL && KALLSYMS
 593         help
 594            Normally kallsyms only contains the symbols of functions, for nicer
 595            OOPS messages.  Some debuggers can use kallsyms for other
 596            symbols too: say Y here to include all symbols, if you need them
 597            and you don't care about adding 300k to the size of your kernel.
 598
 599            Say N.
 600
 601 config KALLSYMS_STRIP_GENERATED
 602         bool "Strip machine generated symbols from kallsyms"
 603         depends on KALLSYMS_ALL
 604         default y
 605         help
 606           Say N if you want kallsyms to retain even machine generated symbols.
 607
 608 config KALLSYMS_EXTRA_PASS
 609         bool "Do an extra kallsyms pass"
 610         depends on KALLSYMS
 611         help
 612            If kallsyms is not working correctly, the build will fail with
 613            inconsistent kallsyms data.  If that occurs, log a bug report and
 614            turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
 615            Always say N here unless you find a bug in kallsyms, which must be
 616            reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
 617            you wait for kallsyms to be fixed.
 618
 619
 620 config HOTPLUG
 621         bool "Support for hot-pluggable devices" if EMBEDDED
 622         default y
 623         help
 624           This option is provided for the case where no hotplug or uevent
 625           capabilities is wanted by the kernel.  You should only consider
 626           disabling this option for embedded systems that do not use modules, a
 627           dynamic /dev tree, or dynamic device discovery.  Just say Y.
 628
 629 config PRINTK
 630         default y
 631         bool "Enable support for printk" if EMBEDDED
 632         help
 633           This option enables normal printk support. Removing it
 634           eliminates most of the message strings from the kernel image
 635           and makes the kernel more or less silent. As this makes it
 636           very difficult to diagnose system problems, saying N here is
 637           strongly discouraged.
 638
 639 config BUG
 640         bool "BUG() support" if EMBEDDED
 641         default y
 642         help
 643           Disabling this option eliminates support for BUG and WARN, reducing
 644           the size of your kernel image and potentially quietly ignoring
 645           numerous fatal conditions. You should only consider disabling this
 646           option for embedded systems with no facilities for reporting errors.
 647           Just say Y.
 648
 649 config ELF_CORE
 650         default y
 651         bool "Enable ELF core dumps" if EMBEDDED
 652         help
 653           Enable support for generating core dumps. Disabling saves about 4k.
 654
 655 config PCSPKR_PLATFORM
 656         bool "Enable PC-Speaker support" if EMBEDDED
 657         depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
 658         default y
 659         help
 660           This option allows to disable the internal PC-Speaker
 661           support, saving some memory.
 662
 663 config COMPAT_BRK
 664         bool "Disable heap randomization"
 665         default y
 666         help
 667           Randomizing heap placement makes heap exploits harder, but it
 668           also breaks ancient binaries (including anything libc5 based).
 669           This option changes the bootup default to heap randomization
 670           disabled, and can be overriden runtime by setting
 671           /proc/sys/kernel/randomize_va_space to 2.
 672
 673           On non-ancient distros (post-2000 ones) N is usually a safe choice.
 674
 675 config BASE_FULL
 676         default y
 677         bool "Enable full-sized data structures for core" if EMBEDDED
 678         help
 679           Disabling this option reduces the size of miscellaneous core
 680           kernel data structures. This saves memory on small machines,
 681           but may reduce performance.
 682
 683 config FUTEX
 684         bool "Enable futex support" if EMBEDDED
 685         default y
 686         select RT_MUTEXES
 687         help
 688           Disabling this option will cause the kernel to be built without
 689           support for "fast userspace mutexes".  The resulting kernel may not
 690           run glibc-based applications correctly.
 691
 692 config ANON_INODES
 693         bool
 694
 695 config EPOLL
 696         bool "Enable eventpoll support" if EMBEDDED
 697         default y
 698         select ANON_INODES
 699         help
 700           Disabling this option will cause the kernel to be built without
 701           support for epoll family of system calls.
 702
 703 config SIGNALFD
 704         bool "Enable signalfd() system call" if EMBEDDED
 705         select ANON_INODES
 706         default y
 707         help
 708           Enable the signalfd() system call that allows to receive signals
 709           on a file descriptor.
 710
 711           If unsure, say Y.
 712
 713 config TIMERFD
 714         bool "Enable timerfd() system call" if EMBEDDED
 715         select ANON_INODES
 716         default y
 717         help
 718           Enable the timerfd() system call that allows to receive timer
 719           events on a file descriptor.
 720
 721           If unsure, say Y.
 722
 723 config EVENTFD
 724         bool "Enable eventfd() system call" if EMBEDDED
 725         select ANON_INODES
 726         default y
 727         help
 728           Enable the eventfd() system call that allows to receive both
 729           kernel notification (ie. KAIO) or userspace notifications.
 730
 731           If unsure, say Y.
 732
 733 config SHMEM
 734         bool "Use full shmem filesystem" if EMBEDDED
 735         default y
 736         depends on MMU
 737         help
 738           The shmem is an internal filesystem used to manage shared memory.
 739           It is backed by swap and manages resource limits. It is also exported
 740           to userspace as tmpfs if TMPFS is enabled. Disabling this
 741           option replaces shmem and tmpfs with the much simpler ramfs code,
 742           which may be appropriate on small systems without swap.
 743
 744 config AIO
 745         bool "Enable AIO support" if EMBEDDED
 746         default y
 747         help
 748           This option enables POSIX asynchronous I/O which may by used
 749           by some high performance threaded applications. Disabling
 750           this option saves about 7k.
 751
 752 config VM_EVENT_COUNTERS
 753         default y
 754         bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
 755         help
 756           VM event counters are needed for event counts to be shown.
 757           This option allows the disabling of the VM event counters
 758           on EMBEDDED systems.  /proc/vmstat will only show page counts
 759           if VM event counters are disabled.
 760
 761 config PCI_QUIRKS
 762         default y
 763         bool "Enable PCI quirk workarounds" if EMBEDDED
 764         depends on PCI
 765         help
 766           This enables workarounds for various PCI chipset
 767           bugs/quirks. Disable this only if your target machine is
 768           unaffected by PCI quirks.
 769
 770 config SLUB_DEBUG
 771         default y
 772         bool "Enable SLUB debugging support" if EMBEDDED
 773         depends on SLUB && SYSFS
 774         help
 775           SLUB has extensive debug support features. Disabling these can
 776           result in significant savings in code size. This also disables
 777           SLUB sysfs support. /sys/slab will not exist and there will be
 778           no support for cache validation etc.
 779
 780 choice
 781         prompt "Choose SLAB allocator"
 782         default SLUB
 783         help
 784            This option allows to select a slab allocator.
 785
 786 config SLAB
 787         bool "SLAB"
 788         help
 789           The regular slab allocator that is established and known to work
 790           well in all environments. It organizes cache hot objects in
 791           per cpu and per node queues.
 792
 793 config SLUB
 794         bool "SLUB (Unqueued Allocator)"
 795         help
 796            SLUB is a slab allocator that minimizes cache line usage
 797            instead of managing queues of cached objects (SLAB approach).
 798            Per cpu caching is realized using slabs of objects instead
 799            of queues of objects. SLUB can use memory efficiently
 800            and has enhanced diagnostics. SLUB is the default choice for
 801            a slab allocator.
 802
 803 config SLOB
 804         depends on EMBEDDED
 805         bool "SLOB (Simple Allocator)"
 806         help
 807            SLOB replaces the stock allocator with a drastically simpler
 808            allocator. SLOB is generally more space efficient but
 809            does not perform as well on large systems.
 810
 811 endchoice
 812
 813 config PROFILING
 814         bool "Profiling support (EXPERIMENTAL)"
 815         help
 816           Say Y here to enable the extended profiling support mechanisms used
 817           by profilers such as OProfile.
 818
 819 #
 820 # Place an empty function call at each tracepoint site. Can be
 821 # dynamically changed for a probe function.
 822 #
 823 config TRACEPOINTS
 824         bool
 825
 826 config MARKERS
 827         bool "Activate markers"
 828         depends on TRACEPOINTS
 829         help
 830           Place an empty function call at each marker site. Can be
 831           dynamically changed for a probe function.
 832
 833 source "arch/Kconfig"
 834
 835 endmenu         # General setup
 836
 837 config HAVE_GENERIC_DMA_COHERENT
 838         bool
 839         default n
 840
 841 config SLABINFO
 842         bool
 843         depends on PROC_FS
 844         depends on SLAB || SLUB_DEBUG
 845         default y
 846
 847 config RT_MUTEXES
 848         boolean
 849         select PLIST
 850
 851 config BASE_SMALL
 852         int
 853         default 0 if BASE_FULL
 854         default 1 if !BASE_FULL
 855
 856 menuconfig MODULES
 857         bool "Enable loadable module support"
 858         help
 859           Kernel modules are small pieces of compiled code which can
 860           be inserted in the running kernel, rather than being
 861           permanently built into the kernel.  You use the "modprobe"
 862           tool to add (and sometimes remove) them.  If you say Y here,
 863           many parts of the kernel can be built as modules (by
 864           answering M instead of Y where indicated): this is most
 865           useful for infrequently used options which are not required
 866           for booting.  For more information, see the man pages for
 867           modprobe, lsmod, modinfo, insmod and rmmod.
 868
 869           If you say Y here, you will need to run "make
 870           modules_install" to put the modules under /lib/modules/
 871           where modprobe can find them (you may need to be root to do
 872           this).
 873
 874           If unsure, say Y.
 875
 876 if MODULES
 877
 878 config MODULE_FORCE_LOAD
 879         bool "Forced module loading"
 880         default n
 881         help
 882           Allow loading of modules without version information (ie. modprobe
 883           --force).  Forced module loading sets the 'F' (forced) taint flag and
 884           is usually a really bad idea.
 885
 886 config MODULE_UNLOAD
 887         bool "Module unloading"
 888         help
 889           Without this option you will not be able to unload any
 890           modules (note that some modules may not be unloadable
 891           anyway), which makes your kernel smaller, faster
 892           and simpler.  If unsure, say Y.
 893
 894 config MODULE_FORCE_UNLOAD
 895         bool "Forced module unloading"
 896         depends on MODULE_UNLOAD && EXPERIMENTAL
 897         help
 898           This option allows you to force a module to unload, even if the
 899           kernel believes it is unsafe: the kernel will remove the module
 900           without waiting for anyone to stop using it (using the -f option to
 901           rmmod).  This is mainly for kernel developers and desperate users.
 902           If unsure, say N.
 903
 904 config MODVERSIONS
 905         bool "Module versioning support"
 906         help
 907           Usually, you have to use modules compiled with your kernel.
 908           Saying Y here makes it sometimes possible to use modules
 909           compiled for different kernels, by adding enough information
 910           to the modules to (hopefully) spot any changes which would
 911           make them incompatible with the kernel you are running.  If
 912           unsure, say N.
 913
 914 config MODULE_SRCVERSION_ALL
 915         bool "Source checksum for all modules"
 916         help
 917           Modules which contain a MODULE_VERSION get an extra "srcversion"
 918           field inserted into their modinfo section, which contains a
 919           sum of the source files which made it.  This helps maintainers
 920           see exactly which source was used to build a module (since
 921           others sometimes change the module source without updating
 922           the version).  With this option, such a "srcversion" field
 923           will be created for all modules.  If unsure, say N.
 924
 925 endif # MODULES
 926
 927 config INIT_ALL_POSSIBLE
 928         bool
 929         help
 930           Back when each arch used to define their own cpu_online_map and
 931           cpu_possible_map, some of them chose to initialize cpu_possible_map
 932           with all 1s, and others with all 0s.  When they were centralised,
 933           it was better to provide this option than to break all the archs
 934           and have several arch maintainers persuing me down dark alleys.
 935
 936 config STOP_MACHINE
 937         bool
 938         default y
 939         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
 940         help
 941           Need stop_machine() primitive.
 942
 943 source "block/Kconfig"
 944
 945 config PREEMPT_NOTIFIERS
 946         bool
 947
 948 choice
 949         prompt "RCU Implementation"
 950         default CLASSIC_RCU
 951
 952 config CLASSIC_RCU
 953         bool "Classic RCU"
 954         help
 955           This option selects the classic RCU implementation that is
 956           designed for best read-side performance on non-realtime
 957           systems.
 958
 959           Select this option if you are unsure.
 960
 961 config TREE_RCU
 962         bool "Tree-based hierarchical RCU"
 963         help
 964           This option selects the RCU implementation that is
 965           designed for very large SMP system with hundreds or
 966           thousands of CPUs.
 967
 968 config PREEMPT_RCU
 969         bool "Preemptible RCU"
 970         depends on PREEMPT
 971         help
 972           This option reduces the latency of the kernel by making certain
 973           RCU sections preemptible. Normally RCU code is non-preemptible, if
 974           this option is selected then read-only RCU sections become
 975           preemptible. This helps latency, but may expose bugs due to
 976           now-naive assumptions about each RCU read-side critical section
 977           remaining on a given CPU through its execution.
 978
 979 endchoice
 980
 981 config RCU_TRACE
 982         bool "Enable tracing for RCU"
 983         depends on TREE_RCU || PREEMPT_RCU
 984         help
 985           This option provides tracing in RCU which presents stats
 986           in debugfs for debugging RCU implementation.
 987
 988           Say Y here if you want to enable RCU tracing
 989           Say N if you are unsure.
 990
 991 config RCU_FANOUT
 992         int "Tree-based hierarchical RCU fanout value"
 993         range 2 64 if 64BIT
 994         range 2 32 if !64BIT
 995         depends on TREE_RCU
 996         default 64 if 64BIT
 997         default 32 if !64BIT
 998         help
 999           This option controls the fanout of hierarchical implementations
1000           of RCU, allowing RCU to work efficiently on machines with
1001           large numbers of CPUs.  This value must be at least the cube
1002           root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
1003           systems and up to 262,144 for 64-bit systems.
1004
1005           Select a specific number if testing RCU itself.
1006           Take the default if unsure.
1007
1008 config RCU_FANOUT_EXACT
1009         bool "Disable tree-based hierarchical RCU auto-balancing"
1010         depends on TREE_RCU
1011         default n
1012         help
1013           This option forces use of the exact RCU_FANOUT value specified,
1014           regardless of imbalances in the hierarchy.  This is useful for
1015           testing RCU itself, and might one day be useful on systems with
1016           strong NUMA behavior.
1017
1018           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
1019
1020           Say N if unsure.
1021
1022 config TREE_RCU_TRACE
1023         def_bool RCU_TRACE && TREE_RCU
1024         select DEBUG_FS
1025         help
1026           This option provides tracing for the TREE_RCU implementation,
1027           permitting Makefile to trivially select kernel/rcutree_trace.c.
1028
1029 config PREEMPT_RCU_TRACE
1030         def_bool RCU_TRACE && PREEMPT_RCU
1031         select DEBUG_FS
1032         help
1033           This option provides tracing for the PREEMPT_RCU implementation,
1034           permitting Makefile to trivially select kernel/rcupreempt_trace.c.