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  47           drivers that have been replaced by something else, and/or are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