init/Kconfig

   1 config ARCH
   2         string
   3         option env="ARCH"
   4
   5 config KERNELVERSION
   6         string
   7         option env="KERNELVERSION"
   8
   9 config DEFCONFIG_LIST
  10         string
  11         depends on !UML
  12         option defconfig_list
  13         default "/lib/modules/$UNAME_RELEASE/.config"
  14         default "/etc/kernel-config"
  15         default "/boot/config-$UNAME_RELEASE"
  16         default "$ARCH_DEFCONFIG"
  17         default "arch/$ARCH/defconfig"
  18
  19 config CONSTRUCTORS
  20         bool
  21         depends on !UML
  22         default y
  23
  24 menu "General setup"
  25
  26 config EXPERIMENTAL
  27         bool "Prompt for development and/or incomplete code/drivers"
  28         ---help---
  29           Some of the various things that Linux supports (such as network
  30           drivers, file systems, network protocols, etc.) can be in a state
  31           of development where the functionality, stability, or the level of
  32           testing is not yet high enough for general use. This is usually
  33           known as the "alpha-test" phase among developers. If a feature is
  34           currently in alpha-test, then the developers usually discourage
  35           uninformed widespread use of this feature by the general public to
  36           avoid "Why doesn't this work?" type mail messages. However, active
  37           testing and use of these systems is welcomed. Just be aware that it
  38           may not meet the normal level of reliability or it may fail to work
  39           in some special cases. Detailed bug reports from people familiar
  40           with the kernel internals are usually welcomed by the developers
  41           (before submitting bug reports, please read the documents
  42           <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  43           <file:Documentation/BUG-HUNTING>, and
  44           <file:Documentation/oops-tracing.txt> in the kernel source).
  45
  46           This option will also make obsoleted drivers available. These are
  47           drivers that have been replaced by something else, and/or are
  48           scheduled to be removed in a future kernel release.
  49
  50           Unless you intend to help test and develop a feature or driver that
  51           falls into this category, or you have a situation that requires
  52           using these features, you should probably say N here, which will
  53           cause the configurator to present you with fewer choices. If
  54           you say Y here, you will be offered the choice of using features or
  55           drivers that are currently considered to be in the alpha-test phase.
  56
  57 config BROKEN
  58         bool
  59
  60 config BROKEN_ON_SMP
  61         bool
  62         depends on BROKEN || !SMP
  63         default y
  64
  65 config LOCK_KERNEL
  66         bool
  67         depends on SMP || PREEMPT
  68         default y
  69
  70 config INIT_ENV_ARG_LIMIT
  71         int
  72         default 32 if !UML
  73         default 128 if UML
  74         help
  75           Maximum of each of the number of arguments and environment
  76           variables passed to init from the kernel command line.
  77
  78
  79 config CROSS_COMPILE
  80         string "Cross-compiler tool prefix"
  81         help
  82           Same as running 'make CROSS_COMPILE=prefix-' but stored for
  83           default make runs in this kernel build directory.  You don't
  84           need to set this unless you want the configured kernel build
  85           directory to select the cross-compiler automatically.
  86
  87 config LOCALVERSION
  88         string "Local version - append to kernel release"
  89         help
  90           Append an extra string to the end of your kernel version.
  91           This will show up when you type uname, for example.
  92           The string you set here will be appended after the contents of
  93           any files with a filename matching localversion* in your
  94           object and source tree, in that order.  Your total string can
  95           be a maximum of 64 characters.
  96
  97 config LOCALVERSION_AUTO
  98         bool "Automatically append version information to the version string"
  99         default y
 100         help
 101           This will try to automatically determine if the current tree is a
 102           release tree by looking for git tags that belong to the current
 103           top of tree revision.
 104
 105           A string of the format -gxxxxxxxx will be added to the localversion
 106           if a git-based tree is found.  The string generated by this will be
 107           appended after any matching localversion* files, and after the value
 108           set in CONFIG_LOCALVERSION.
 109
 110           (The actual string used here is the first eight characters produced
 111           by running the command:
 112
 113             $ git rev-parse --verify HEAD
 114
 115           which is done within the script "scripts/setlocalversion".)
 116
 117 config HAVE_KERNEL_GZIP
 118         bool
 119
 120 config HAVE_KERNEL_BZIP2
 121         bool
 122
 123 config HAVE_KERNEL_LZMA
 124         bool
 125
 126 config HAVE_KERNEL_LZO
 127         bool
 128
 129 choice
 130         prompt "Kernel compression mode"
 131         default KERNEL_GZIP
 132         depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
 133         help
 134           The linux kernel is a kind of self-extracting executable.
 135           Several compression algorithms are available, which differ
 136           in efficiency, compression and decompression speed.
 137           Compression speed is only relevant when building a kernel.
 138           Decompression speed is relevant at each boot.
 139
 140           If you have any problems with bzip2 or lzma compressed
 141           kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
 142           version of this functionality (bzip2 only), for 2.4, was
 143           supplied by Christian Ludwig)
 144
 145           High compression options are mostly useful for users, who
 146           are low on disk space (embedded systems), but for whom ram
 147           size matters less.
 148
 149           If in doubt, select 'gzip'
 150
 151 config KERNEL_GZIP
 152         bool "Gzip"
 153         depends on HAVE_KERNEL_GZIP
 154         help
 155           The old and tried gzip compression. It provides a good balance
 156           between compression ratio and decompression speed.
 157
 158 config KERNEL_BZIP2
 159         bool "Bzip2"
 160         depends on HAVE_KERNEL_BZIP2
 161         help
 162           Its compression ratio and speed is intermediate.
 163           Decompression speed is slowest among the three.  The kernel
 164           size is about 10% smaller with bzip2, in comparison to gzip.
 165           Bzip2 uses a large amount of memory. For modern kernels you
 166           will need at least 8MB RAM or more for booting.
 167
 168 config KERNEL_LZMA
 169         bool "LZMA"
 170         depends on HAVE_KERNEL_LZMA
 171         help
 172           The most recent compression algorithm.
 173           Its ratio is best, decompression speed is between the other
 174           two. Compression is slowest.  The kernel size is about 33%
 175           smaller with LZMA in comparison to gzip.
 176
 177 config KERNEL_LZO
 178         bool "LZO"
 179         depends on HAVE_KERNEL_LZO
 180         help
 181           Its compression ratio is the poorest among the 4. The kernel
 182           size is about about 10% bigger than gzip; however its speed
 183           (both compression and decompression) is the fastest.
 184
 185 endchoice
 186
 187 config SWAP
 188         bool "Support for paging of anonymous memory (swap)"
 189         depends on MMU && BLOCK
 190         default y
 191         help
 192           This option allows you to choose whether you want to have support
 193           for so called swap devices or swap files in your kernel that are
 194           used to provide more virtual memory than the actual RAM present
 195           in your computer.  If unsure say Y.
 196
 197 config SYSVIPC
 198         bool "System V IPC"
 199         ---help---
 200           Inter Process Communication is a suite of library functions and
 201           system calls which let processes (running programs) synchronize and
 202           exchange information. It is generally considered to be a good thing,
 203           and some programs won't run unless you say Y here. In particular, if
 204           you want to run the DOS emulator dosemu under Linux (read the
 205           DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
 206           you'll need to say Y here.
 207
 208           You can find documentation about IPC with "info ipc" and also in
 209           section 6.4 of the Linux Programmer's Guide, available from
 210           <http://www.tldp.org/guides.html>.
 211
 212 config SYSVIPC_SYSCTL
 213         bool
 214         depends on SYSVIPC
 215         depends on SYSCTL
 216         default y
 217
 218 config POSIX_MQUEUE
 219         bool "POSIX Message Queues"
 220         depends on NET && EXPERIMENTAL
 221         ---help---
 222           POSIX variant of message queues is a part of IPC. In POSIX message
 223           queues every message has a priority which decides about succession
 224           of receiving it by a process. If you want to compile and run
 225           programs written e.g. for Solaris with use of its POSIX message
 226           queues (functions mq_*) say Y here.
 227
 228           POSIX message queues are visible as a filesystem called 'mqueue'
 229           and can be mounted somewhere if you want to do filesystem
 230           operations on message queues.
 231
 232           If unsure, say Y.
 233
 234 config POSIX_MQUEUE_SYSCTL
 235         bool
 236         depends on POSIX_MQUEUE
 237         depends on SYSCTL
 238         default y
 239
 240 config BSD_PROCESS_ACCT
 241         bool "BSD Process Accounting"
 242         help
 243           If you say Y here, a user level program will be able to instruct the
 244           kernel (via a special system call) to write process accounting
 245           information to a file: whenever a process exits, information about
 246           that process will be appended to the file by the kernel.  The
 247           information includes things such as creation time, owning user,
 248           command name, memory usage, controlling terminal etc. (the complete
 249           list is in the struct acct in <file:include/linux/acct.h>).  It is
 250           up to the user level program to do useful things with this
 251           information.  This is generally a good idea, so say Y.
 252
 253 config BSD_PROCESS_ACCT_V3
 254         bool "BSD Process Accounting version 3 file format"
 255         depends on BSD_PROCESS_ACCT
 256         default n
 257         help
 258           If you say Y here, the process accounting information is written
 259           in a new file format that also logs the process IDs of each
 260           process and it's parent. Note that this file format is incompatible
 261           with previous v0/v1/v2 file formats, so you will need updated tools
 262           for processing it. A preliminary version of these tools is available
 263           at <http://www.gnu.org/software/acct/>.
 264
 265 config TASKSTATS
 266         bool "Export task/process statistics through netlink (EXPERIMENTAL)"
 267         depends on NET
 268         default n
 269         help
 270           Export selected statistics for tasks/processes through the
 271           generic netlink interface. Unlike BSD process accounting, the
 272           statistics are available during the lifetime of tasks/processes as
 273           responses to commands. Like BSD accounting, they are sent to user
 274           space on task exit.
 275
 276           Say N if unsure.
 277
 278 config TASK_DELAY_ACCT
 279         bool "Enable per-task delay accounting (EXPERIMENTAL)"
 280         depends on TASKSTATS
 281         help
 282           Collect information on time spent by a task waiting for system
 283           resources like cpu, synchronous block I/O completion and swapping
 284           in pages. Such statistics can help in setting a task's priorities
 285           relative to other tasks for cpu, io, rss limits etc.
 286
 287           Say N if unsure.
 288
 289 config TASK_XACCT
 290         bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
 291         depends on TASKSTATS
 292         help
 293           Collect extended task accounting data and send the data
 294           to userland for processing over the taskstats interface.
 295
 296           Say N if unsure.
 297
 298 config TASK_IO_ACCOUNTING
 299         bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
 300         depends on TASK_XACCT
 301         help
 302           Collect information on the number of bytes of storage I/O which this
 303           task has caused.
 304
 305           Say N if unsure.
 306
 307 config AUDIT
 308         bool "Auditing support"
 309         depends on NET
 310         help
 311           Enable auditing infrastructure that can be used with another
 312           kernel subsystem, such as SELinux (which requires this for
 313           logging of avc messages output).  Does not do system-call
 314           auditing without CONFIG_AUDITSYSCALL.
 315
 316 config AUDITSYSCALL
 317         bool "Enable system-call auditing support"
 318         depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
 319         default y if SECURITY_SELINUX
 320         help
 321           Enable low-overhead system-call auditing infrastructure that
 322           can be used independently or with another kernel subsystem,
 323           such as SELinux.
 324
 325 config AUDIT_WATCH
 326         def_bool y
 327         depends on AUDITSYSCALL
 328         select FSNOTIFY
 329
 330 config AUDIT_TREE
 331         def_bool y
 332         depends on AUDITSYSCALL
 333         select FSNOTIFY
 334
 335 menu "RCU Subsystem"
 336
 337 choice
 338         prompt "RCU Implementation"
 339         default TREE_RCU
 340
 341 config TREE_RCU
 342         bool "Tree-based hierarchical RCU"
 343         depends on !PREEMPT && SMP
 344         help
 345           This option selects the RCU implementation that is
 346           designed for very large SMP system with hundreds or
 347           thousands of CPUs.  It also scales down nicely to
 348           smaller systems.
 349
 350 config TREE_PREEMPT_RCU
 351         bool "Preemptible tree-based hierarchical RCU"
 352         depends on PREEMPT
 353         help
 354           This option selects the RCU implementation that is
 355           designed for very large SMP systems with hundreds or
 356           thousands of CPUs, but for which real-time response
 357           is also required.  It also scales down nicely to
 358           smaller systems.
 359
 360 config TINY_RCU
 361         bool "UP-only small-memory-footprint RCU"
 362         depends on !SMP
 363         help
 364           This option selects the RCU implementation that is
 365           designed for UP systems from which real-time response
 366           is not required.  This option greatly reduces the
 367           memory footprint of RCU.
 368
 369 config TINY_PREEMPT_RCU
 370         bool "Preemptible UP-only small-memory-footprint RCU"
 371         depends on !SMP && PREEMPT
 372         help
 373           This option selects the RCU implementation that is designed
 374           for real-time UP systems.  This option greatly reduces the
 375           memory footprint of RCU.
 376
 377 endchoice
 378
 379 config PREEMPT_RCU
 380         def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
 381         help
 382           This option enables preemptible-RCU code that is common between
 383           the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
 384
 385 config RCU_TRACE
 386         bool "Enable tracing for RCU"
 387         depends on TREE_RCU || TREE_PREEMPT_RCU
 388         help
 389           This option provides tracing in RCU which presents stats
 390           in debugfs for debugging RCU implementation.
 391
 392           Say Y here if you want to enable RCU tracing
 393           Say N if you are unsure.
 394
 395 config RCU_FANOUT
 396         int "Tree-based hierarchical RCU fanout value"
 397         range 2 64 if 64BIT
 398         range 2 32 if !64BIT
 399         depends on TREE_RCU || TREE_PREEMPT_RCU
 400         default 64 if 64BIT
 401         default 32 if !64BIT
 402         help
 403           This option controls the fanout of hierarchical implementations
 404           of RCU, allowing RCU to work efficiently on machines with
 405           large numbers of CPUs.  This value must be at least the fourth
 406           root of NR_CPUS, which allows NR_CPUS to be insanely large.
 407           The default value of RCU_FANOUT should be used for production
 408           systems, but if you are stress-testing the RCU implementation
 409           itself, small RCU_FANOUT values allow you to test large-system
 410           code paths on small(er) systems.
 411
 412           Select a specific number if testing RCU itself.
 413           Take the default if unsure.
 414
 415 config RCU_FANOUT_EXACT
 416         bool "Disable tree-based hierarchical RCU auto-balancing"
 417         depends on TREE_RCU || TREE_PREEMPT_RCU
 418         default n
 419         help
 420           This option forces use of the exact RCU_FANOUT value specified,
 421           regardless of imbalances in the hierarchy.  This is useful for
 422           testing RCU itself, and might one day be useful on systems with
 423           strong NUMA behavior.
 424
 425           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
 426
 427           Say N if unsure.
 428
 429 config RCU_FAST_NO_HZ
 430         bool "Accelerate last non-dyntick-idle CPU's grace periods"
 431         depends on TREE_RCU && NO_HZ && SMP
 432         default n
 433         help
 434           This option causes RCU to attempt to accelerate grace periods
 435           in order to allow the final CPU to enter dynticks-idle state
 436           more quickly.  On the other hand, this option increases the
 437           overhead of the dynticks-idle checking, particularly on systems
 438           with large numbers of CPUs.
 439
 440           Say Y if energy efficiency is critically important, particularly
 441                 if you have relatively few CPUs.
 442
 443           Say N if you are unsure.
 444
 445 config TREE_RCU_TRACE
 446         def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
 447         select DEBUG_FS
 448         help
 449           This option provides tracing for the TREE_RCU and
 450           TREE_PREEMPT_RCU implementations, permitting Makefile to
 451           trivially select kernel/rcutree_trace.c.
 452
 453 endmenu # "RCU Subsystem"
 454
 455 config IKCONFIG
 456         tristate "Kernel .config support"
 457         ---help---
 458           This option enables the complete Linux kernel ".config" file
 459           contents to be saved in the kernel. It provides documentation
 460           of which kernel options are used in a running kernel or in an
 461           on-disk kernel.  This information can be extracted from the kernel
 462           image file with the script scripts/extract-ikconfig and used as
 463           input to rebuild the current kernel or to build another kernel.
 464           It can also be extracted from a running kernel by reading
 465           /proc/config.gz if enabled (below).
 466
 467 config IKCONFIG_PROC
 468         bool "Enable access to .config through /proc/config.gz"
 469         depends on IKCONFIG && PROC_FS
 470         ---help---
 471           This option enables access to the kernel configuration file
 472           through /proc/config.gz.
 473
 474 config LOG_BUF_SHIFT
 475         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 476         range 12 21
 477         default 17
 478         help
 479           Select kernel log buffer size as a power of 2.
 480           Examples:
 481                      17 => 128 KB
 482                      16 => 64 KB
 483                      15 => 32 KB
 484                      14 => 16 KB
 485                      13 =>  8 KB
 486                      12 =>  4 KB
 487
 488 #
 489 # Architectures with an unreliable sched_clock() should select this:
 490 #
 491 config HAVE_UNSTABLE_SCHED_CLOCK
 492         bool
 493
 494 menuconfig CGROUPS
 495         boolean "Control Group support"
 496         depends on EVENTFD
 497         help
 498           This option adds support for grouping sets of processes together, for
 499           use with process control subsystems such as Cpusets, CFS, memory
 500           controls or device isolation.
 501           See
 502                 - Documentation/scheduler/sched-design-CFS.txt  (CFS)
 503                 - Documentation/cgroups/ (features for grouping, isolation
 504                                           and resource control)
 505
 506           Say N if unsure.
 507
 508 if CGROUPS
 509
 510 config CGROUP_DEBUG
 511         bool "Example debug cgroup subsystem"
 512         depends on CGROUPS
 513         default n
 514         help
 515           This option enables a simple cgroup subsystem that
 516           exports useful debugging information about the cgroups
 517           framework.
 518
 519           Say N if unsure.
 520
 521 config CGROUP_NS
 522         bool "Namespace cgroup subsystem"
 523         depends on CGROUPS
 524         help
 525           Provides a simple namespace cgroup subsystem to
 526           provide hierarchical naming of sets of namespaces,
 527           for instance virtual servers and checkpoint/restart
 528           jobs.
 529
 530 config CGROUP_FREEZER
 531         bool "Freezer cgroup subsystem"
 532         depends on CGROUPS
 533         help
 534           Provides a way to freeze and unfreeze all tasks in a
 535           cgroup.
 536
 537 config CGROUP_DEVICE
 538         bool "Device controller for cgroups"
 539         depends on CGROUPS && EXPERIMENTAL
 540         help
 541           Provides a cgroup implementing whitelists for devices which
 542           a process in the cgroup can mknod or open.
 543
 544 config CPUSETS
 545         bool "Cpuset support"
 546         depends on CGROUPS
 547         help
 548           This option will let you create and manage CPUSETs which
 549           allow dynamically partitioning a system into sets of CPUs and
 550           Memory Nodes and assigning tasks to run only within those sets.
 551           This is primarily useful on large SMP or NUMA systems.
 552
 553           Say N if unsure.
 554
 555 config PROC_PID_CPUSET
 556         bool "Include legacy /proc/<pid>/cpuset file"
 557         depends on CPUSETS
 558         default y
 559
 560 config CGROUP_CPUACCT
 561         bool "Simple CPU accounting cgroup subsystem"
 562         depends on CGROUPS
 563         help
 564           Provides a simple Resource Controller for monitoring the
 565           total CPU consumed by the tasks in a cgroup.
 566
 567 config RESOURCE_COUNTERS
 568         bool "Resource counters"
 569         help
 570           This option enables controller independent resource accounting
 571           infrastructure that works with cgroups.
 572         depends on CGROUPS
 573
 574 config CGROUP_MEM_RES_CTLR
 575         bool "Memory Resource Controller for Control Groups"
 576         depends on CGROUPS && RESOURCE_COUNTERS
 577         select MM_OWNER
 578         help
 579           Provides a memory resource controller that manages both anonymous
 580           memory and page cache. (See Documentation/cgroups/memory.txt)
 581
 582           Note that setting this option increases fixed memory overhead
 583           associated with each page of memory in the system. By this,
 584           20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
 585           usage tracking struct at boot. Total amount of this is printed out
 586           at boot.
 587
 588           Only enable when you're ok with these trade offs and really
 589           sure you need the memory resource controller. Even when you enable
 590           this, you can set "cgroup_disable=memory" at your boot option to
 591           disable memory resource controller and you can avoid overheads.
 592           (and lose benefits of memory resource controller)
 593
 594           This config option also selects MM_OWNER config option, which
 595           could in turn add some fork/exit overhead.
 596
 597 config CGROUP_MEM_RES_CTLR_SWAP
 598         bool "Memory Resource Controller Swap Extension"
 599         depends on CGROUP_MEM_RES_CTLR && SWAP
 600         help
 601           Add swap management feature to memory resource controller. When you
 602           enable this, you can limit mem+swap usage per cgroup. In other words,
 603           when you disable this, memory resource controller has no cares to
 604           usage of swap...a process can exhaust all of the swap. This extension
 605           is useful when you want to avoid exhaustion swap but this itself
 606           adds more overheads and consumes memory for remembering information.
 607           Especially if you use 32bit system or small memory system, please
 608           be careful about enabling this. When memory resource controller
 609           is disabled by boot option, this will be automatically disabled and
 610           there will be no overhead from this. Even when you set this config=y,
 611           if boot option "noswapaccount" is set, swap will not be accounted.
 612           Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
 613           size is 4096bytes, 512k per 1Gbytes of swap.
 614
 615 menuconfig CGROUP_SCHED
 616         bool "Group CPU scheduler"
 617         depends on EXPERIMENTAL && CGROUPS
 618         default n
 619         help
 620           This feature lets CPU scheduler recognize task groups and control CPU
 621           bandwidth allocation to such task groups. It uses cgroups to group
 622           tasks.
 623
 624 if CGROUP_SCHED
 625 config FAIR_GROUP_SCHED
 626         bool "Group scheduling for SCHED_OTHER"
 627         depends on CGROUP_SCHED
 628         default CGROUP_SCHED
 629
 630 config RT_GROUP_SCHED
 631         bool "Group scheduling for SCHED_RR/FIFO"
 632         depends on EXPERIMENTAL
 633         depends on CGROUP_SCHED
 634         default n
 635         help
 636           This feature lets you explicitly allocate real CPU bandwidth
 637           to task groups. If enabled, it will also make it impossible to
 638           schedule realtime tasks for non-root users until you allocate
 639           realtime bandwidth for them.
 640           See Documentation/scheduler/sched-rt-group.txt for more information.
 641
 642 endif #CGROUP_SCHED
 643
 644 config BLK_CGROUP
 645         tristate "Block IO controller"
 646         depends on CGROUPS && BLOCK
 647         default n
 648         ---help---
 649         Generic block IO controller cgroup interface. This is the common
 650         cgroup interface which should be used by various IO controlling
 651         policies.
 652
 653         Currently, CFQ IO scheduler uses it to recognize task groups and
 654         control disk bandwidth allocation (proportional time slice allocation)
 655         to such task groups.
 656
 657         This option only enables generic Block IO controller infrastructure.
 658         One needs to also enable actual IO controlling logic in CFQ for it
 659         to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
 660
 661         See Documentation/cgroups/blkio-controller.txt for more information.
 662
 663 config DEBUG_BLK_CGROUP
 664         bool "Enable Block IO controller debugging"
 665         depends on BLK_CGROUP
 666         default n
 667         ---help---
 668         Enable some debugging help. Currently it exports additional stat
 669         files in a cgroup which can be useful for debugging.
 670
 671 endif # CGROUPS
 672
 673 config MM_OWNER
 674         bool
 675
 676 config SYSFS_DEPRECATED
 677         bool
 678
 679 config SYSFS_DEPRECATED_V2
 680         bool "enable deprecated sysfs features to support old userspace tools"
 681         depends on SYSFS
 682         default n
 683         select SYSFS_DEPRECATED
 684         help
 685           This option switches the layout of sysfs to the deprecated
 686           version. Do not use it on recent distributions.
 687
 688           The current sysfs layout features a unified device tree at
 689           /sys/devices/, which is able to express a hierarchy between
 690           class devices. If the deprecated option is set to Y, the
 691           unified device tree is split into a bus device tree at
 692           /sys/devices/ and several individual class device trees at
 693           /sys/class/. The class and bus devices will be connected by
 694           "<subsystem>:<name>" and the "device" links. The "block"
 695           class devices, will not show up in /sys/class/block/. Some
 696           subsystems will suppress the creation of some devices which
 697           depend on the unified device tree.
 698
 699           This option is not a pure compatibility option that can
 700           be safely enabled on newer distributions. It will change the
 701           layout of sysfs to the non-extensible deprecated version,
 702           and disable some features, which can not be exported without
 703           confusing older userspace tools. Since 2007/2008 all major
 704           distributions do not enable this option, and ship no tools which
 705           depend on the deprecated layout or this option.
 706
 707           If you are using a new kernel on an older distribution, or use
 708           older userspace tools, you might need to say Y here. Do not say Y,
 709           if the original kernel, that came with your distribution, has
 710           this option set to N.
 711
 712 config RELAY
 713         bool "Kernel->user space relay support (formerly relayfs)"
 714         help
 715           This option enables support for relay interface support in
 716           certain file systems (such as debugfs).
 717           It is designed to provide an efficient mechanism for tools and
 718           facilities to relay large amounts of data from kernel space to
 719           user space.
 720
 721           If unsure, say N.
 722
 723 config NAMESPACES
 724         bool "Namespaces support" if EMBEDDED
 725         default !EMBEDDED
 726         help
 727           Provides the way to make tasks work with different objects using
 728           the same id. For example same IPC id may refer to different objects
 729           or same user id or pid may refer to different tasks when used in
 730           different namespaces.
 731
 732 config UTS_NS
 733         bool "UTS namespace"
 734         depends on NAMESPACES
 735         help
 736           In this namespace tasks see different info provided with the
 737           uname() system call
 738
 739 config IPC_NS
 740         bool "IPC namespace"
 741         depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
 742         help
 743           In this namespace tasks work with IPC ids which correspond to
 744           different IPC objects in different namespaces.
 745
 746 config USER_NS
 747         bool "User namespace (EXPERIMENTAL)"
 748         depends on NAMESPACES && EXPERIMENTAL
 749         help
 750           This allows containers, i.e. vservers, to use user namespaces
 751           to provide different user info for different servers.
 752           If unsure, say N.
 753
 754 config PID_NS
 755         bool "PID Namespaces (EXPERIMENTAL)"
 756         default n
 757         depends on NAMESPACES && EXPERIMENTAL
 758         help
 759           Support process id namespaces.  This allows having multiple
 760           processes with the same pid as long as they are in different
 761           pid namespaces.  This is a building block of containers.
 762
 763           Unless you want to work with an experimental feature
 764           say N here.
 765
 766 config NET_NS
 767         bool "Network namespace"
 768         default n
 769         depends on NAMESPACES && EXPERIMENTAL && NET
 770         help
 771           Allow user space to create what appear to be multiple instances
 772           of the network stack.
 773
 774 config BLK_DEV_INITRD
 775         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 776         depends on BROKEN || !FRV
 777         help
 778           The initial RAM filesystem is a ramfs which is loaded by the
 779           boot loader (loadlin or lilo) and that is mounted as root
 780           before the normal boot procedure. It is typically used to
 781           load modules needed to mount the "real" root file system,
 782           etc. See <file:Documentation/initrd.txt> for details.
 783
 784           If RAM disk support (BLK_DEV_RAM) is also included, this
 785           also enables initial RAM disk (initrd) support and adds
 786           15 Kbytes (more on some other architectures) to the kernel size.
 787
 788           If unsure say Y.
 789
 790 if BLK_DEV_INITRD
 791
 792 source "usr/Kconfig"
 793
 794 endif
 795
 796 config CC_OPTIMIZE_FOR_SIZE
 797         bool "Optimize for size"
 798         default y
 799         help
 800           Enabling this option will pass "-Os" instead of "-O2" to gcc
 801           resulting in a smaller kernel.
 802
 803           If unsure, say Y.
 804
 805 config SYSCTL
 806         bool
 807
 808 config ANON_INODES
 809         bool
 810
 811 menuconfig EMBEDDED
 812         bool "Configure standard kernel features (for small systems)"
 813         help
 814           This option allows certain base kernel options and settings
 815           to be disabled or tweaked. This is for specialized
 816           environments which can tolerate a "non-standard" kernel.
 817           Only use this if you really know what you are doing.
 818
 819 config UID16
 820         bool "Enable 16-bit UID system calls" if EMBEDDED
 821         depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
 822         default y
 823         help
 824           This enables the legacy 16-bit UID syscall wrappers.
 825
 826 config SYSCTL_SYSCALL
 827         bool "Sysctl syscall support" if EMBEDDED
 828         depends on PROC_SYSCTL
 829         default y
 830         select SYSCTL
 831         ---help---
 832           sys_sysctl uses binary paths that have been found challenging
 833           to properly maintain and use.  The interface in /proc/sys
 834           using paths with ascii names is now the primary path to this
 835           information.
 836
 837           Almost nothing using the binary sysctl interface so if you are
 838           trying to save some space it is probably safe to disable this,
 839           making your kernel marginally smaller.
 840
 841           If unsure say Y here.
 842
 843 config KALLSYMS
 844          bool "Load all symbols for debugging/ksymoops" if EMBEDDED
 845          default y
 846          help
 847            Say Y here to let the kernel print out symbolic crash information and
 848            symbolic stack backtraces. This increases the size of the kernel
 849            somewhat, as all symbols have to be loaded into the kernel image.
 850
 851 config KALLSYMS_ALL
 852         bool "Include all symbols in kallsyms"
 853         depends on DEBUG_KERNEL && KALLSYMS
 854         help
 855            Normally kallsyms only contains the symbols of functions, for nicer
 856            OOPS messages.  Some debuggers can use kallsyms for other
 857            symbols too: say Y here to include all symbols, if you need them
 858            and you don't care about adding 300k to the size of your kernel.
 859
 860            Say N.
 861
 862 config KALLSYMS_EXTRA_PASS
 863         bool "Do an extra kallsyms pass"
 864         depends on KALLSYMS
 865         help
 866            If kallsyms is not working correctly, the build will fail with
 867            inconsistent kallsyms data.  If that occurs, log a bug report and
 868            turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
 869            Always say N here unless you find a bug in kallsyms, which must be
 870            reported.  KALLSYMS_EXTRA_PASS is only a temporary workaround while
 871            you wait for kallsyms to be fixed.
 872
 873
 874 config HOTPLUG
 875         bool "Support for hot-pluggable devices" if EMBEDDED
 876         default y
 877         help
 878           This option is provided for the case where no hotplug or uevent
 879           capabilities is wanted by the kernel.  You should only consider
 880           disabling this option for embedded systems that do not use modules, a
 881           dynamic /dev tree, or dynamic device discovery.  Just say Y.
 882
 883 config PRINTK
 884         default y
 885         bool "Enable support for printk" if EMBEDDED
 886         help
 887           This option enables normal printk support. Removing it
 888           eliminates most of the message strings from the kernel image
 889           and makes the kernel more or less silent. As this makes it
 890           very difficult to diagnose system problems, saying N here is
 891           strongly discouraged.
 892
 893 config BUG
 894         bool "BUG() support" if EMBEDDED
 895         default y
 896         help
 897           Disabling this option eliminates support for BUG and WARN, reducing
 898           the size of your kernel image and potentially quietly ignoring
 899           numerous fatal conditions. You should only consider disabling this
 900           option for embedded systems with no facilities for reporting errors.
 901           Just say Y.
 902
 903 config ELF_CORE
 904         default y
 905         bool "Enable ELF core dumps" if EMBEDDED
 906         help
 907           Enable support for generating core dumps. Disabling saves about 4k.
 908
 909 config PCSPKR_PLATFORM
 910         bool "Enable PC-Speaker support" if EMBEDDED
 911         depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
 912         default y
 913         help
 914           This option allows to disable the internal PC-Speaker
 915           support, saving some memory.
 916
 917 config BASE_FULL
 918         default y
 919         bool "Enable full-sized data structures for core" if EMBEDDED
 920         help
 921           Disabling this option reduces the size of miscellaneous core
 922           kernel data structures. This saves memory on small machines,
 923           but may reduce performance.
 924
 925 config FUTEX
 926         bool "Enable futex support" if EMBEDDED
 927         default y
 928         select RT_MUTEXES
 929         help
 930           Disabling this option will cause the kernel to be built without
 931           support for "fast userspace mutexes".  The resulting kernel may not
 932           run glibc-based applications correctly.
 933
 934 config EPOLL
 935         bool "Enable eventpoll support" if EMBEDDED
 936         default y
 937         select ANON_INODES
 938         help
 939           Disabling this option will cause the kernel to be built without
 940           support for epoll family of system calls.
 941
 942 config SIGNALFD
 943         bool "Enable signalfd() system call" if EMBEDDED
 944         select ANON_INODES
 945         default y
 946         help
 947           Enable the signalfd() system call that allows to receive signals
 948           on a file descriptor.
 949
 950           If unsure, say Y.
 951
 952 config TIMERFD
 953         bool "Enable timerfd() system call" if EMBEDDED
 954         select ANON_INODES
 955         default y
 956         help
 957           Enable the timerfd() system call that allows to receive timer
 958           events on a file descriptor.
 959
 960           If unsure, say Y.
 961
 962 config EVENTFD
 963         bool "Enable eventfd() system call" if EMBEDDED
 964         select ANON_INODES
 965         default y
 966         help
 967           Enable the eventfd() system call that allows to receive both
 968           kernel notification (ie. KAIO) or userspace notifications.
 969
 970           If unsure, say Y.
 971
 972 config SHMEM
 973         bool "Use full shmem filesystem" if EMBEDDED
 974         default y
 975         depends on MMU
 976         help
 977           The shmem is an internal filesystem used to manage shared memory.
 978           It is backed by swap and manages resource limits. It is also exported
 979           to userspace as tmpfs if TMPFS is enabled. Disabling this
 980           option replaces shmem and tmpfs with the much simpler ramfs code,
 981           which may be appropriate on small systems without swap.
 982
 983 config AIO
 984         bool "Enable AIO support" if EMBEDDED
 985         default y
 986         help
 987           This option enables POSIX asynchronous I/O which may by used
 988           by some high performance threaded applications. Disabling
 989           this option saves about 7k.
 990
 991 config HAVE_PERF_EVENTS
 992         bool
 993         help
 994           See tools/perf/design.txt for details.
 995
 996 config PERF_USE_VMALLOC
 997         bool
 998         help
 999           See tools/perf/design.txt for details
1000
1001 menu "Kernel Performance Events And Counters"
1002
1003 config PERF_EVENTS
1004         bool "Kernel performance events and counters"
1005         default y if (PROFILING || PERF_COUNTERS)
1006         depends on HAVE_PERF_EVENTS
1007         select ANON_INODES
1008         help
1009           Enable kernel support for various performance events provided
1010           by software and hardware.
1011
1012           Software events are supported either built-in or via the
1013           use of generic tracepoints.
1014
1015           Most modern CPUs support performance events via performance
1016           counter registers. These registers count the number of certain
1017           types of hw events: such as instructions executed, cachemisses
1018           suffered, or branches mis-predicted - without slowing down the
1019           kernel or applications. These registers can also trigger interrupts
1020           when a threshold number of events have passed - and can thus be
1021           used to profile the code that runs on that CPU.
1022
1023           The Linux Performance Event subsystem provides an abstraction of
1024           these software and hardware event capabilities, available via a
1025           system call and used by the "perf" utility in tools/perf/. It
1026           provides per task and per CPU counters, and it provides event
1027           capabilities on top of those.
1028
1029           Say Y if unsure.
1030
1031 config PERF_COUNTERS
1032         bool "Kernel performance counters (old config option)"
1033         depends on HAVE_PERF_EVENTS
1034         help
1035           This config has been obsoleted by the PERF_EVENTS
1036           config option - please see that one for details.
1037
1038           It has no effect on the kernel whether you enable
1039           it or not, it is a compatibility placeholder.
1040
1041           Say N if unsure.
1042
1043 config DEBUG_PERF_USE_VMALLOC
1044         default n
1045         bool "Debug: use vmalloc to back perf mmap() buffers"
1046         depends on PERF_EVENTS && DEBUG_KERNEL
1047         select PERF_USE_VMALLOC
1048         help
1049          Use vmalloc memory to back perf mmap() buffers.
1050
1051          Mostly useful for debugging the vmalloc code on platforms
1052          that don't require it.
1053
1054          Say N if unsure.
1055
1056 endmenu
1057
1058 config VM_EVENT_COUNTERS
1059         default y
1060         bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1061         help
1062           VM event counters are needed for event counts to be shown.
1063           This option allows the disabling of the VM event counters
1064           on EMBEDDED systems.  /proc/vmstat will only show page counts
1065           if VM event counters are disabled.
1066
1067 config PCI_QUIRKS
1068         default y
1069         bool "Enable PCI quirk workarounds" if EMBEDDED
1070         depends on PCI
1071         help
1072           This enables workarounds for various PCI chipset
1073           bugs/quirks. Disable this only if your target machine is
1074           unaffected by PCI quirks.
1075
1076 config SLUB_DEBUG
1077         default y
1078         bool "Enable SLUB debugging support" if EMBEDDED
1079         depends on SLUB && SYSFS
1080         help
1081           SLUB has extensive debug support features. Disabling these can
1082           result in significant savings in code size. This also disables
1083           SLUB sysfs support. /sys/slab will not exist and there will be
1084           no support for cache validation etc.
1085
1086 config COMPAT_BRK
1087         bool "Disable heap randomization"
1088         default y
1089         help
1090           Randomizing heap placement makes heap exploits harder, but it
1091           also breaks ancient binaries (including anything libc5 based).
1092           This option changes the bootup default to heap randomization
1093           disabled, and can be overridden at runtime by setting
1094           /proc/sys/kernel/randomize_va_space to 2.
1095
1096           On non-ancient distros (post-2000 ones) N is usually a safe choice.
1097
1098 choice
1099         prompt "Choose SLAB allocator"
1100         default SLUB
1101         help
1102            This option allows to select a slab allocator.
1103
1104 config SLAB
1105         bool "SLAB"
1106         help
1107           The regular slab allocator that is established and known to work
1108           well in all environments. It organizes cache hot objects in
1109           per cpu and per node queues.
1110
1111 config SLUB
1112         bool "SLUB (Unqueued Allocator)"
1113         help
1114            SLUB is a slab allocator that minimizes cache line usage
1115            instead of managing queues of cached objects (SLAB approach).
1116            Per cpu caching is realized using slabs of objects instead
1117            of queues of objects. SLUB can use memory efficiently
1118            and has enhanced diagnostics. SLUB is the default choice for
1119            a slab allocator.
1120
1121 config SLOB
1122         depends on EMBEDDED
1123         bool "SLOB (Simple Allocator)"
1124         help
1125            SLOB replaces the stock allocator with a drastically simpler
1126            allocator. SLOB is generally more space efficient but
1127            does not perform as well on large systems.
1128
1129 endchoice
1130
1131 config MMAP_ALLOW_UNINITIALIZED
1132         bool "Allow mmapped anonymous memory to be uninitialized"
1133         depends on EMBEDDED && !MMU
1134         default n
1135         help
1136           Normally, and according to the Linux spec, anonymous memory obtained
1137           from mmap() has it's contents cleared before it is passed to
1138           userspace.  Enabling this config option allows you to request that
1139           mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1140           providing a huge performance boost.  If this option is not enabled,
1141           then the flag will be ignored.
1142
1143           This is taken advantage of by uClibc's malloc(), and also by
1144           ELF-FDPIC binfmt's brk and stack allocator.
1145
1146           Because of the obvious security issues, this option should only be
1147           enabled on embedded devices where you control what is run in
1148           userspace.  Since that isn't generally a problem on no-MMU systems,
1149           it is normally safe to say Y here.
1150
1151           See Documentation/nommu-mmap.txt for more information.
1152
1153 config PROFILING
1154         bool "Profiling support"
1155         help
1156           Say Y here to enable the extended profiling support mechanisms used
1157           by profilers such as OProfile.
1158
1159 #
1160 # Place an empty function call at each tracepoint site. Can be
1161 # dynamically changed for a probe function.
1162 #
1163 config TRACEPOINTS
1164         bool
1165
1166 source "arch/Kconfig"
1167
1168 endmenu         # General setup
1169
1170 config HAVE_GENERIC_DMA_COHERENT
1171         bool
1172         default n
1173
1174 config SLABINFO
1175         bool
1176         depends on PROC_FS
1177         depends on SLAB || SLUB_DEBUG
1178         default y
1179
1180 config RT_MUTEXES
1181         boolean
1182
1183 config BASE_SMALL
1184         int
1185         default 0 if BASE_FULL
1186         default 1 if !BASE_FULL
1187
1188 menuconfig MODULES
1189         bool "Enable loadable module support"
1190         help
1191           Kernel modules are small pieces of compiled code which can
1192           be inserted in the running kernel, rather than being
1193           permanently built into the kernel.  You use the "modprobe"
1194           tool to add (and sometimes remove) them.  If you say Y here,
1195           many parts of the kernel can be built as modules (by
1196           answering M instead of Y where indicated): this is most
1197           useful for infrequently used options which are not required
1198           for booting.  For more information, see the man pages for
1199           modprobe, lsmod, modinfo, insmod and rmmod.
1200
1201           If you say Y here, you will need to run "make
1202           modules_install" to put the modules under /lib/modules/
1203           where modprobe can find them (you may need to be root to do
1204           this).
1205
1206           If unsure, say Y.
1207
1208 if MODULES
1209
1210 config MODULE_FORCE_LOAD
1211         bool "Forced module loading"
1212         default n
1213         help
1214           Allow loading of modules without version information (ie. modprobe
1215           --force).  Forced module loading sets the 'F' (forced) taint flag and
1216           is usually a really bad idea.
1217
1218 config MODULE_UNLOAD
1219         bool "Module unloading"
1220         help
1221           Without this option you will not be able to unload any
1222           modules (note that some modules may not be unloadable
1223           anyway), which makes your kernel smaller, faster
1224           and simpler.  If unsure, say Y.
1225
1226 config MODULE_FORCE_UNLOAD
1227         bool "Forced module unloading"
1228         depends on MODULE_UNLOAD && EXPERIMENTAL
1229         help
1230           This option allows you to force a module to unload, even if the
1231           kernel believes it is unsafe: the kernel will remove the module
1232           without waiting for anyone to stop using it (using the -f option to
1233           rmmod).  This is mainly for kernel developers and desperate users.
1234           If unsure, say N.
1235
1236 config MODVERSIONS
1237         bool "Module versioning support"
1238         help
1239           Usually, you have to use modules compiled with your kernel.
1240           Saying Y here makes it sometimes possible to use modules
1241           compiled for different kernels, by adding enough information
1242           to the modules to (hopefully) spot any changes which would
1243           make them incompatible with the kernel you are running.  If
1244           unsure, say N.
1245
1246 config MODULE_SRCVERSION_ALL
1247         bool "Source checksum for all modules"
1248         help
1249           Modules which contain a MODULE_VERSION get an extra "srcversion"
1250           field inserted into their modinfo section, which contains a
1251           sum of the source files which made it.  This helps maintainers
1252           see exactly which source was used to build a module (since
1253           others sometimes change the module source without updating
1254           the version).  With this option, such a "srcversion" field
1255           will be created for all modules.  If unsure, say N.
1256
1257 endif # MODULES
1258
1259 config INIT_ALL_POSSIBLE
1260         bool
1261         help
1262           Back when each arch used to define their own cpu_online_map and
1263           cpu_possible_map, some of them chose to initialize cpu_possible_map
1264           with all 1s, and others with all 0s.  When they were centralised,
1265           it was better to provide this option than to break all the archs
1266           and have several arch maintainers pursuing me down dark alleys.
1267
1268 config STOP_MACHINE
1269         bool
1270         default y
1271         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1272         help
1273           Need stop_machine() primitive.
1274
1275 source "block/Kconfig"
1276
1277 config PREEMPT_NOTIFIERS
1278         bool
1279
1280 config PADATA
1281         depends on SMP
1282         bool
1283
1284 source "kernel/Kconfig.locks"