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
  23 config HAVE_IRQ_WORK
  24         bool
  25
  26 config IRQ_WORK
  27         bool
  28         depends on HAVE_IRQ_WORK
  29
  30 menu "General setup"
  31
  32 config EXPERIMENTAL
  33         bool "Prompt for development and/or incomplete code/drivers"
  34         ---help---
  35           Some of the various things that Linux supports (such as network
  36           drivers, file systems, network protocols, etc.) can be in a state
  37           of development where the functionality, stability, or the level of
  38           testing is not yet high enough for general use. This is usually
  39           known as the "alpha-test" phase among developers. If a feature is
  40           currently in alpha-test, then the developers usually discourage
  41           uninformed widespread use of this feature by the general public to
  42           avoid "Why doesn't this work?" type mail messages. However, active
  43           testing and use of these systems is welcomed. Just be aware that it
  44           may not meet the normal level of reliability or it may fail to work
  45           in some special cases. Detailed bug reports from people familiar
  46           with the kernel internals are usually welcomed by the developers
  47           (before submitting bug reports, please read the documents
  48           <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  49           <file:Documentation/BUG-HUNTING>, and
  50           <file:Documentation/oops-tracing.txt> in the kernel source).
  51
  52           This option will also make obsoleted drivers available. These are
  53           drivers that have been replaced by something else, and/or are
  54           scheduled to be removed in a future kernel release.
  55
  56           Unless you intend to help test and develop a feature or driver that
  57           falls into this category, or you have a situation that requires
  58           using these features, you should probably say N here, which will
  59           cause the configurator to present you with fewer choices. If
  60           you say Y here, you will be offered the choice of using features or
  61           drivers that are currently considered to be in the alpha-test phase.
  62
  63 config BROKEN
  64         bool
  65
  66 config BROKEN_ON_SMP
  67         bool
  68         depends on BROKEN || !SMP
  69         default y
  70
  71 config INIT_ENV_ARG_LIMIT
  72         int
  73         default 32 if !UML
  74         default 128 if UML
  75         help
  76           Maximum of each of the number of arguments and environment
  77           variables passed to init from the kernel command line.
  78
  79
  80 config CROSS_COMPILE
  81         string "Cross-compiler tool prefix"
  82         help
  83           Same as running 'make CROSS_COMPILE=prefix-' but stored for
  84           default make runs in this kernel build directory.  You don't
  85           need to set this unless you want the configured kernel build
  86           directory to select the cross-compiler automatically.
  87
  88 config LOCALVERSION
  89         string "Local version - append to kernel release"
  90         help
  91           Append an extra string to the end of your kernel version.
  92           This will show up when you type uname, for example.
  93           The string you set here will be appended after the contents of
  94           any files with a filename matching localversion* in your
  95           object and source tree, in that order.  Your total string can
  96           be a maximum of 64 characters.
  97
  98 config LOCALVERSION_AUTO
  99         bool "Automatically append version information to the version string"
 100         default y
 101         help
 102           This will try to automatically determine if the current tree is a
 103           release tree by looking for git tags that belong to the current
 104           top of tree revision.
 105
 106           A string of the format -gxxxxxxxx will be added to the localversion
 107           if a git-based tree is found.  The string generated by this will be
 108           appended after any matching localversion* files, and after the value
 109           set in CONFIG_LOCALVERSION.
 110
 111           (The actual string used here is the first eight characters produced
 112           by running the command:
 113
 114             $ git rev-parse --verify HEAD
 115
 116           which is done within the script "scripts/setlocalversion".)
 117
 118 config HAVE_KERNEL_GZIP
 119         bool
 120
 121 config HAVE_KERNEL_BZIP2
 122         bool
 123
 124 config HAVE_KERNEL_LZMA
 125         bool
 126
 127 config HAVE_KERNEL_XZ
 128         bool
 129
 130 config HAVE_KERNEL_LZO
 131         bool
 132
 133 choice
 134         prompt "Kernel compression mode"
 135         default KERNEL_GZIP
 136         depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
 137         help
 138           The linux kernel is a kind of self-extracting executable.
 139           Several compression algorithms are available, which differ
 140           in efficiency, compression and decompression speed.
 141           Compression speed is only relevant when building a kernel.
 142           Decompression speed is relevant at each boot.
 143
 144           If you have any problems with bzip2 or lzma compressed
 145           kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
 146           version of this functionality (bzip2 only), for 2.4, was
 147           supplied by Christian Ludwig)
 148
 149           High compression options are mostly useful for users, who
 150           are low on disk space (embedded systems), but for whom ram
 151           size matters less.
 152
 153           If in doubt, select 'gzip'
 154
 155 config KERNEL_GZIP
 156         bool "Gzip"
 157         depends on HAVE_KERNEL_GZIP
 158         help
 159           The old and tried gzip compression. It provides a good balance
 160           between compression ratio and decompression speed.
 161
 162 config KERNEL_BZIP2
 163         bool "Bzip2"
 164         depends on HAVE_KERNEL_BZIP2
 165         help
 166           Its compression ratio and speed is intermediate.
 167           Decompression speed is slowest among the three.  The kernel
 168           size is about 10% smaller with bzip2, in comparison to gzip.
 169           Bzip2 uses a large amount of memory. For modern kernels you
 170           will need at least 8MB RAM or more for booting.
 171
 172 config KERNEL_LZMA
 173         bool "LZMA"
 174         depends on HAVE_KERNEL_LZMA
 175         help
 176           The most recent compression algorithm.
 177           Its ratio is best, decompression speed is between the other
 178           two. Compression is slowest.  The kernel size is about 33%
 179           smaller with LZMA in comparison to gzip.
 180
 181 config KERNEL_XZ
 182         bool "XZ"
 183         depends on HAVE_KERNEL_XZ
 184         help
 185           XZ uses the LZMA2 algorithm and instruction set specific
 186           BCJ filters which can improve compression ratio of executable
 187           code. The size of the kernel is about 30% smaller with XZ in
 188           comparison to gzip. On architectures for which there is a BCJ
 189           filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
 190           will create a few percent smaller kernel than plain LZMA.
 191
 192           The speed is about the same as with LZMA: The decompression
 193           speed of XZ is better than that of bzip2 but worse than gzip
 194           and LZO. Compression is slow.
 195
 196 config KERNEL_LZO
 197         bool "LZO"
 198         depends on HAVE_KERNEL_LZO
 199         help
 200           Its compression ratio is the poorest among the 4. The kernel
 201           size is about 10% bigger than gzip; however its speed
 202           (both compression and decompression) is the fastest.
 203
 204 endchoice
 205
 206 config DEFAULT_HOSTNAME
 207         string "Default hostname"
 208         default "(none)"
 209         help
 210           This option determines the default system hostname before userspace
 211           calls sethostname(2). The kernel traditionally uses "(none)" here,
 212           but you may wish to use a different default here to make a minimal
 213           system more usable with less configuration.
 214
 215 config SWAP
 216         bool "Support for paging of anonymous memory (swap)"
 217         depends on MMU && BLOCK
 218         default y
 219         help
 220           This option allows you to choose whether you want to have support
 221           for so called swap devices or swap files in your kernel that are
 222           used to provide more virtual memory than the actual RAM present
 223           in your computer.  If unsure say Y.
 224
 225 config SYSVIPC
 226         bool "System V IPC"
 227         ---help---
 228           Inter Process Communication is a suite of library functions and
 229           system calls which let processes (running programs) synchronize and
 230           exchange information. It is generally considered to be a good thing,
 231           and some programs won't run unless you say Y here. In particular, if
 232           you want to run the DOS emulator dosemu under Linux (read the
 233           DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
 234           you'll need to say Y here.
 235
 236           You can find documentation about IPC with "info ipc" and also in
 237           section 6.4 of the Linux Programmer's Guide, available from
 238           <http://www.tldp.org/guides.html>.
 239
 240 config SYSVIPC_SYSCTL
 241         bool
 242         depends on SYSVIPC
 243         depends on SYSCTL
 244         default y
 245
 246 config POSIX_MQUEUE
 247         bool "POSIX Message Queues"
 248         depends on NET && EXPERIMENTAL
 249         ---help---
 250           POSIX variant of message queues is a part of IPC. In POSIX message
 251           queues every message has a priority which decides about succession
 252           of receiving it by a process. If you want to compile and run
 253           programs written e.g. for Solaris with use of its POSIX message
 254           queues (functions mq_*) say Y here.
 255
 256           POSIX message queues are visible as a filesystem called 'mqueue'
 257           and can be mounted somewhere if you want to do filesystem
 258           operations on message queues.
 259
 260           If unsure, say Y.
 261
 262 config POSIX_MQUEUE_SYSCTL
 263         bool
 264         depends on POSIX_MQUEUE
 265         depends on SYSCTL
 266         default y
 267
 268 config BSD_PROCESS_ACCT
 269         bool "BSD Process Accounting"
 270         help
 271           If you say Y here, a user level program will be able to instruct the
 272           kernel (via a special system call) to write process accounting
 273           information to a file: whenever a process exits, information about
 274           that process will be appended to the file by the kernel.  The
 275           information includes things such as creation time, owning user,
 276           command name, memory usage, controlling terminal etc. (the complete
 277           list is in the struct acct in <file:include/linux/acct.h>).  It is
 278           up to the user level program to do useful things with this
 279           information.  This is generally a good idea, so say Y.
 280
 281 config BSD_PROCESS_ACCT_V3
 282         bool "BSD Process Accounting version 3 file format"
 283         depends on BSD_PROCESS_ACCT
 284         default n
 285         help
 286           If you say Y here, the process accounting information is written
 287           in a new file format that also logs the process IDs of each
 288           process and it's parent. Note that this file format is incompatible
 289           with previous v0/v1/v2 file formats, so you will need updated tools
 290           for processing it. A preliminary version of these tools is available
 291           at <http://www.gnu.org/software/acct/>.
 292
 293 config FHANDLE
 294         bool "open by fhandle syscalls"
 295         select EXPORTFS
 296         help
 297           If you say Y here, a user level program will be able to map
 298           file names to handle and then later use the handle for
 299           different file system operations. This is useful in implementing
 300           userspace file servers, which now track files using handles instead
 301           of names. The handle would remain the same even if file names
 302           get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
 303           syscalls.
 304
 305 config TASKSTATS
 306         bool "Export task/process statistics through netlink (EXPERIMENTAL)"
 307         depends on NET
 308         default n
 309         help
 310           Export selected statistics for tasks/processes through the
 311           generic netlink interface. Unlike BSD process accounting, the
 312           statistics are available during the lifetime of tasks/processes as
 313           responses to commands. Like BSD accounting, they are sent to user
 314           space on task exit.
 315
 316           Say N if unsure.
 317
 318 config TASK_DELAY_ACCT
 319         bool "Enable per-task delay accounting (EXPERIMENTAL)"
 320         depends on TASKSTATS
 321         help
 322           Collect information on time spent by a task waiting for system
 323           resources like cpu, synchronous block I/O completion and swapping
 324           in pages. Such statistics can help in setting a task's priorities
 325           relative to other tasks for cpu, io, rss limits etc.
 326
 327           Say N if unsure.
 328
 329 config TASK_XACCT
 330         bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
 331         depends on TASKSTATS
 332         help
 333           Collect extended task accounting data and send the data
 334           to userland for processing over the taskstats interface.
 335
 336           Say N if unsure.
 337
 338 config TASK_IO_ACCOUNTING
 339         bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
 340         depends on TASK_XACCT
 341         help
 342           Collect information on the number of bytes of storage I/O which this
 343           task has caused.
 344
 345           Say N if unsure.
 346
 347 config AUDIT
 348         bool "Auditing support"
 349         depends on NET
 350         help
 351           Enable auditing infrastructure that can be used with another
 352           kernel subsystem, such as SELinux (which requires this for
 353           logging of avc messages output).  Does not do system-call
 354           auditing without CONFIG_AUDITSYSCALL.
 355
 356 config AUDITSYSCALL
 357         bool "Enable system-call auditing support"
 358         depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
 359         default y if SECURITY_SELINUX
 360         help
 361           Enable low-overhead system-call auditing infrastructure that
 362           can be used independently or with another kernel subsystem,
 363           such as SELinux.
 364
 365 config AUDIT_WATCH
 366         def_bool y
 367         depends on AUDITSYSCALL
 368         select FSNOTIFY
 369
 370 config AUDIT_TREE
 371         def_bool y
 372         depends on AUDITSYSCALL
 373         select FSNOTIFY
 374
 375 source "kernel/irq/Kconfig"
 376
 377 menu "RCU Subsystem"
 378
 379 choice
 380         prompt "RCU Implementation"
 381         default TREE_RCU
 382
 383 config TREE_RCU
 384         bool "Tree-based hierarchical RCU"
 385         depends on !PREEMPT && SMP
 386         help
 387           This option selects the RCU implementation that is
 388           designed for very large SMP system with hundreds or
 389           thousands of CPUs.  It also scales down nicely to
 390           smaller systems.
 391
 392 config TREE_PREEMPT_RCU
 393         bool "Preemptible tree-based hierarchical RCU"
 394         depends on PREEMPT && SMP
 395         help
 396           This option selects the RCU implementation that is
 397           designed for very large SMP systems with hundreds or
 398           thousands of CPUs, but for which real-time response
 399           is also required.  It also scales down nicely to
 400           smaller systems.
 401
 402 config TINY_RCU
 403         bool "UP-only small-memory-footprint RCU"
 404         depends on !PREEMPT && !SMP
 405         help
 406           This option selects the RCU implementation that is
 407           designed for UP systems from which real-time response
 408           is not required.  This option greatly reduces the
 409           memory footprint of RCU.
 410
 411 config TINY_PREEMPT_RCU
 412         bool "Preemptible UP-only small-memory-footprint RCU"
 413         depends on PREEMPT && !SMP
 414         help
 415           This option selects the RCU implementation that is designed
 416           for real-time UP systems.  This option greatly reduces the
 417           memory footprint of RCU.
 418
 419 endchoice
 420
 421 config PREEMPT_RCU
 422         def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
 423         help
 424           This option enables preemptible-RCU code that is common between
 425           the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
 426
 427 config RCU_TRACE
 428         bool "Enable tracing for RCU"
 429         help
 430           This option provides tracing in RCU which presents stats
 431           in debugfs for debugging RCU implementation.
 432
 433           Say Y here if you want to enable RCU tracing
 434           Say N if you are unsure.
 435
 436 config RCU_FANOUT
 437         int "Tree-based hierarchical RCU fanout value"
 438         range 2 64 if 64BIT
 439         range 2 32 if !64BIT
 440         depends on TREE_RCU || TREE_PREEMPT_RCU
 441         default 64 if 64BIT
 442         default 32 if !64BIT
 443         help
 444           This option controls the fanout of hierarchical implementations
 445           of RCU, allowing RCU to work efficiently on machines with
 446           large numbers of CPUs.  This value must be at least the fourth
 447           root of NR_CPUS, which allows NR_CPUS to be insanely large.
 448           The default value of RCU_FANOUT should be used for production
 449           systems, but if you are stress-testing the RCU implementation
 450           itself, small RCU_FANOUT values allow you to test large-system
 451           code paths on small(er) systems.
 452
 453           Select a specific number if testing RCU itself.
 454           Take the default if unsure.
 455
 456 config RCU_FANOUT_EXACT
 457         bool "Disable tree-based hierarchical RCU auto-balancing"
 458         depends on TREE_RCU || TREE_PREEMPT_RCU
 459         default n
 460         help
 461           This option forces use of the exact RCU_FANOUT value specified,
 462           regardless of imbalances in the hierarchy.  This is useful for
 463           testing RCU itself, and might one day be useful on systems with
 464           strong NUMA behavior.
 465
 466           Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
 467
 468           Say N if unsure.
 469
 470 config RCU_FAST_NO_HZ
 471         bool "Accelerate last non-dyntick-idle CPU's grace periods"
 472         depends on NO_HZ && SMP
 473         default n
 474         help
 475           This option causes RCU to attempt to accelerate grace periods
 476           in order to allow CPUs to enter dynticks-idle state more
 477           quickly.  On the other hand, this option increases the overhead
 478           of the dynticks-idle checking, particularly on systems with
 479           large numbers of CPUs.
 480
 481           Say Y if energy efficiency is critically important, particularly
 482                 if you have relatively few CPUs.
 483
 484           Say N if you are unsure.
 485
 486 config TREE_RCU_TRACE
 487         def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
 488         select DEBUG_FS
 489         help
 490           This option provides tracing for the TREE_RCU and
 491           TREE_PREEMPT_RCU implementations, permitting Makefile to
 492           trivially select kernel/rcutree_trace.c.
 493
 494 config RCU_BOOST
 495         bool "Enable RCU priority boosting"
 496         depends on RT_MUTEXES && PREEMPT_RCU
 497         default n
 498         help
 499           This option boosts the priority of preempted RCU readers that
 500           block the current preemptible RCU grace period for too long.
 501           This option also prevents heavy loads from blocking RCU
 502           callback invocation for all flavors of RCU.
 503
 504           Say Y here if you are working with real-time apps or heavy loads
 505           Say N here if you are unsure.
 506
 507 config RCU_BOOST_PRIO
 508         int "Real-time priority to boost RCU readers to"
 509         range 1 99
 510         depends on RCU_BOOST
 511         default 1
 512         help
 513           This option specifies the real-time priority to which preempted
 514           RCU readers are to be boosted.  If you are working with CPU-bound
 515           real-time applications, you should specify a priority higher then
 516           the highest-priority CPU-bound application.
 517
 518           Specify the real-time priority, or take the default if unsure.
 519
 520 config RCU_BOOST_DELAY
 521         int "Milliseconds to delay boosting after RCU grace-period start"
 522         range 0 3000
 523         depends on RCU_BOOST
 524         default 500
 525         help
 526           This option specifies the time to wait after the beginning of
 527           a given grace period before priority-boosting preempted RCU
 528           readers blocking that grace period.  Note that any RCU reader
 529           blocking an expedited RCU grace period is boosted immediately.
 530
 531           Accept the default if unsure.
 532
 533 endmenu # "RCU Subsystem"
 534
 535 config IKCONFIG
 536         tristate "Kernel .config support"
 537         ---help---
 538           This option enables the complete Linux kernel ".config" file
 539           contents to be saved in the kernel. It provides documentation
 540           of which kernel options are used in a running kernel or in an
 541           on-disk kernel.  This information can be extracted from the kernel
 542           image file with the script scripts/extract-ikconfig and used as
 543           input to rebuild the current kernel or to build another kernel.
 544           It can also be extracted from a running kernel by reading
 545           /proc/config.gz if enabled (below).
 546
 547 config IKCONFIG_PROC
 548         bool "Enable access to .config through /proc/config.gz"
 549         depends on IKCONFIG && PROC_FS
 550         ---help---
 551           This option enables access to the kernel configuration file
 552           through /proc/config.gz.
 553
 554 config LOG_BUF_SHIFT
 555         int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 556         range 12 21
 557         default 17
 558         help
 559           Select kernel log buffer size as a power of 2.
 560           Examples:
 561                      17 => 128 KB
 562                      16 => 64 KB
 563                      15 => 32 KB
 564                      14 => 16 KB
 565                      13 =>  8 KB
 566                      12 =>  4 KB
 567
 568 #
 569 # Architectures with an unreliable sched_clock() should select this:
 570 #
 571 config HAVE_UNSTABLE_SCHED_CLOCK
 572         bool
 573
 574 menuconfig CGROUPS
 575         boolean "Control Group support"
 576         depends on EVENTFD
 577         help
 578           This option adds support for grouping sets of processes together, for
 579           use with process control subsystems such as Cpusets, CFS, memory
 580           controls or device isolation.
 581           See
 582                 - Documentation/scheduler/sched-design-CFS.txt  (CFS)
 583                 - Documentation/cgroups/ (features for grouping, isolation
 584                                           and resource control)
 585
 586           Say N if unsure.
 587
 588 if CGROUPS
 589
 590 config CGROUP_DEBUG
 591         bool "Example debug cgroup subsystem"
 592         default n
 593         help
 594           This option enables a simple cgroup subsystem that
 595           exports useful debugging information about the cgroups
 596           framework.
 597
 598           Say N if unsure.
 599
 600 config CGROUP_FREEZER
 601         bool "Freezer cgroup subsystem"
 602         help
 603           Provides a way to freeze and unfreeze all tasks in a
 604           cgroup.
 605
 606 config CGROUP_DEVICE
 607         bool "Device controller for cgroups"
 608         help
 609           Provides a cgroup implementing whitelists for devices which
 610           a process in the cgroup can mknod or open.
 611
 612 config CPUSETS
 613         bool "Cpuset support"
 614         help
 615           This option will let you create and manage CPUSETs which
 616           allow dynamically partitioning a system into sets of CPUs and
 617           Memory Nodes and assigning tasks to run only within those sets.
 618           This is primarily useful on large SMP or NUMA systems.
 619
 620           Say N if unsure.
 621
 622 config PROC_PID_CPUSET
 623         bool "Include legacy /proc/<pid>/cpuset file"
 624         depends on CPUSETS
 625         default y
 626
 627 config CGROUP_CPUACCT
 628         bool "Simple CPU accounting cgroup subsystem"
 629         help
 630           Provides a simple Resource Controller for monitoring the
 631           total CPU consumed by the tasks in a cgroup.
 632
 633 config RESOURCE_COUNTERS
 634         bool "Resource counters"
 635         help
 636           This option enables controller independent resource accounting
 637           infrastructure that works with cgroups.
 638
 639 config CGROUP_MEM_RES_CTLR
 640         bool "Memory Resource Controller for Control Groups"
 641         depends on RESOURCE_COUNTERS
 642         select MM_OWNER
 643         help
 644           Provides a memory resource controller that manages both anonymous
 645           memory and page cache. (See Documentation/cgroups/memory.txt)
 646
 647           Note that setting this option increases fixed memory overhead
 648           associated with each page of memory in the system. By this,
 649           20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
 650           usage tracking struct at boot. Total amount of this is printed out
 651           at boot.
 652
 653           Only enable when you're ok with these trade offs and really
 654           sure you need the memory resource controller. Even when you enable
 655           this, you can set "cgroup_disable=memory" at your boot option to
 656           disable memory resource controller and you can avoid overheads.
 657           (and lose benefits of memory resource controller)
 658
 659           This config option also selects MM_OWNER config option, which
 660           could in turn add some fork/exit overhead.
 661
 662 config CGROUP_MEM_RES_CTLR_SWAP
 663         bool "Memory Resource Controller Swap Extension"
 664         depends on CGROUP_MEM_RES_CTLR && SWAP
 665         help
 666           Add swap management feature to memory resource controller. When you
 667           enable this, you can limit mem+swap usage per cgroup. In other words,
 668           when you disable this, memory resource controller has no cares to
 669           usage of swap...a process can exhaust all of the swap. This extension
 670           is useful when you want to avoid exhaustion swap but this itself
 671           adds more overheads and consumes memory for remembering information.
 672           Especially if you use 32bit system or small memory system, please
 673           be careful about enabling this. When memory resource controller
 674           is disabled by boot option, this will be automatically disabled and
 675           there will be no overhead from this. Even when you set this config=y,
 676           if boot option "swapaccount=0" is set, swap will not be accounted.
 677           Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
 678           size is 4096bytes, 512k per 1Gbytes of swap.
 679 config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
 680         bool "Memory Resource Controller Swap Extension enabled by default"
 681         depends on CGROUP_MEM_RES_CTLR_SWAP
 682         default y
 683         help
 684           Memory Resource Controller Swap Extension comes with its price in
 685           a bigger memory consumption. General purpose distribution kernels
 686           which want to enable the feature but keep it disabled by default
 687           and let the user enable it by swapaccount boot command line
 688           parameter should have this option unselected.
 689           For those who want to have the feature enabled by default should
 690           select this option (if, for some reason, they need to disable it
 691           then swapaccount=0 does the trick).
 692 config CGROUP_MEM_RES_CTLR_KMEM
 693         bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
 694         depends on CGROUP_MEM_RES_CTLR && EXPERIMENTAL
 695         default n
 696         help
 697           The Kernel Memory extension for Memory Resource Controller can limit
 698           the amount of memory used by kernel objects in the system. Those are
 699           fundamentally different from the entities handled by the standard
 700           Memory Controller, which are page-based, and can be swapped. Users of
 701           the kmem extension can use it to guarantee that no group of processes
 702           will ever exhaust kernel resources alone.
 703
 704 config CGROUP_PERF
 705         bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
 706         depends on PERF_EVENTS && CGROUPS
 707         help
 708           This option extends the per-cpu mode to restrict monitoring to
 709           threads which belong to the cgroup specified and run on the
 710           designated cpu.
 711
 712           Say N if unsure.
 713
 714 menuconfig CGROUP_SCHED
 715         bool "Group CPU scheduler"
 716         default n
 717         help
 718           This feature lets CPU scheduler recognize task groups and control CPU
 719           bandwidth allocation to such task groups. It uses cgroups to group
 720           tasks.
 721
 722 if CGROUP_SCHED
 723 config FAIR_GROUP_SCHED
 724         bool "Group scheduling for SCHED_OTHER"
 725         depends on CGROUP_SCHED
 726         default CGROUP_SCHED
 727
 728 config CFS_BANDWIDTH
 729         bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
 730         depends on EXPERIMENTAL
 731         depends on FAIR_GROUP_SCHED
 732         default n
 733         help
 734           This option allows users to define CPU bandwidth rates (limits) for
 735           tasks running within the fair group scheduler.  Groups with no limit
 736           set are considered to be unconstrained and will run with no
 737           restriction.
 738           See tip/Documentation/scheduler/sched-bwc.txt for more information.
 739
 740 config RT_GROUP_SCHED
 741         bool "Group scheduling for SCHED_RR/FIFO"
 742         depends on EXPERIMENTAL
 743         depends on CGROUP_SCHED
 744         default n
 745         help
 746           This feature lets you explicitly allocate real CPU bandwidth
 747           to task groups. If enabled, it will also make it impossible to
 748           schedule realtime tasks for non-root users until you allocate
 749           realtime bandwidth for them.
 750           See Documentation/scheduler/sched-rt-group.txt for more information.
 751
 752 endif #CGROUP_SCHED
 753
 754 config BLK_CGROUP
 755         tristate "Block IO controller"
 756         depends on BLOCK
 757         default n
 758         ---help---
 759         Generic block IO controller cgroup interface. This is the common
 760         cgroup interface which should be used by various IO controlling
 761         policies.
 762
 763         Currently, CFQ IO scheduler uses it to recognize task groups and
 764         control disk bandwidth allocation (proportional time slice allocation)
 765         to such task groups. It is also used by bio throttling logic in
 766         block layer to implement upper limit in IO rates on a device.
 767
 768         This option only enables generic Block IO controller infrastructure.
 769         One needs to also enable actual IO controlling logic/policy. For
 770         enabling proportional weight division of disk bandwidth in CFQ, set
 771         CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
 772         CONFIG_BLK_DEV_THROTTLING=y.
 773
 774         See Documentation/cgroups/blkio-controller.txt for more information.
 775
 776 config DEBUG_BLK_CGROUP
 777         bool "Enable Block IO controller debugging"
 778         depends on BLK_CGROUP
 779         default n
 780         ---help---
 781         Enable some debugging help. Currently it exports additional stat
 782         files in a cgroup which can be useful for debugging.
 783
 784 endif # CGROUPS
 785
 786 menuconfig NAMESPACES
 787         bool "Namespaces support" if EXPERT
 788         default !EXPERT
 789         help
 790           Provides the way to make tasks work with different objects using
 791           the same id. For example same IPC id may refer to different objects
 792           or same user id or pid may refer to different tasks when used in
 793           different namespaces.
 794
 795 if NAMESPACES
 796
 797 config UTS_NS
 798         bool "UTS namespace"
 799         default y
 800         help
 801           In this namespace tasks see different info provided with the
 802           uname() system call
 803
 804 config IPC_NS
 805         bool "IPC namespace"
 806         depends on (SYSVIPC || POSIX_MQUEUE)
 807         default y
 808         help
 809           In this namespace tasks work with IPC ids which correspond to
 810           different IPC objects in different namespaces.
 811
 812 config USER_NS
 813         bool "User namespace (EXPERIMENTAL)"
 814         depends on EXPERIMENTAL
 815         default y
 816         help
 817           This allows containers, i.e. vservers, to use user namespaces
 818           to provide different user info for different servers.
 819           If unsure, say N.
 820
 821 config PID_NS
 822         bool "PID Namespaces"
 823         default y
 824         help
 825           Support process id namespaces.  This allows having multiple
 826           processes with the same pid as long as they are in different
 827           pid namespaces.  This is a building block of containers.
 828
 829 config NET_NS
 830         bool "Network namespace"
 831         depends on NET
 832         default y
 833         help
 834           Allow user space to create what appear to be multiple instances
 835           of the network stack.
 836
 837 endif # NAMESPACES
 838
 839 config SCHED_AUTOGROUP
 840         bool "Automatic process group scheduling"
 841         select EVENTFD
 842         select CGROUPS
 843         select CGROUP_SCHED
 844         select FAIR_GROUP_SCHED
 845         help
 846           This option optimizes the scheduler for common desktop workloads by
 847           automatically creating and populating task groups.  This separation
 848           of workloads isolates aggressive CPU burners (like build jobs) from
 849           desktop applications.  Task group autogeneration is currently based
 850           upon task session.
 851
 852 config MM_OWNER
 853         bool
 854
 855 config SYSFS_DEPRECATED
 856         bool "Enable deprecated sysfs features to support old userspace tools"
 857         depends on SYSFS
 858         default n
 859         help
 860           This option adds code that switches the layout of the "block" class
 861           devices, to not show up in /sys/class/block/, but only in
 862           /sys/block/.
 863
 864           This switch is only active when the sysfs.deprecated=1 boot option is
 865           passed or the SYSFS_DEPRECATED_V2 option is set.
 866
 867           This option allows new kernels to run on old distributions and tools,
 868           which might get confused by /sys/class/block/. Since 2007/2008 all
 869           major distributions and tools handle this just fine.
 870
 871           Recent distributions and userspace tools after 2009/2010 depend on
 872           the existence of /sys/class/block/, and will not work with this
 873           option enabled.
 874
 875           Only if you are using a new kernel on an old distribution, you might
 876           need to say Y here.
 877
 878 config SYSFS_DEPRECATED_V2
 879         bool "Enable deprecated sysfs features by default"
 880         default n
 881         depends on SYSFS
 882         depends on SYSFS_DEPRECATED
 883         help
 884           Enable deprecated sysfs by default.
 885
 886           See the CONFIG_SYSFS_DEPRECATED option for more details about this
 887           option.
 888
 889           Only if you are using a new kernel on an old distribution, you might
 890           need to say Y here. Even then, odds are you would not need it
 891           enabled, you can always pass the boot option if absolutely necessary.
 892
 893 config RELAY
 894         bool "Kernel->user space relay support (formerly relayfs)"
 895         help
 896           This option enables support for relay interface support in
 897           certain file systems (such as debugfs).
 898           It is designed to provide an efficient mechanism for tools and
 899           facilities to relay large amounts of data from kernel space to
 900           user space.
 901
 902           If unsure, say N.
 903
 904 config BLK_DEV_INITRD
 905         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
 906         depends on BROKEN || !FRV
 907         help
 908           The initial RAM filesystem is a ramfs which is loaded by the
 909           boot loader (loadlin or lilo) and that is mounted as root
 910           before the normal boot procedure. It is typically used to
 911           load modules needed to mount the "real" root file system,
 912           etc. See <file:Documentation/initrd.txt> for details.
 913
 914           If RAM disk support (BLK_DEV_RAM) is also included, this
 915           also enables initial RAM disk (initrd) support and adds
 916           15 Kbytes (more on some other architectures) to the kernel size.
 917
 918           If unsure say Y.
 919
 920 if BLK_DEV_INITRD
 921
 922 source "usr/Kconfig"
 923
 924 endif
 925
 926 config CC_OPTIMIZE_FOR_SIZE
 927         bool "Optimize for size"
 928         help
 929           Enabling this option will pass "-Os" instead of "-O2" to gcc
 930           resulting in a smaller kernel.
 931
 932           If unsure, say Y.
 933
 934 config SYSCTL
 935         bool
 936
 937 config ANON_INODES
 938         bool
 939
 940 menuconfig EXPERT
 941         bool "Configure standard kernel features (expert users)"
 942         # Unhide debug options, to make the on-by-default options visible
 943         select DEBUG_KERNEL
 944         help
 945           This option allows certain base kernel options and settings
 946           to be disabled or tweaked. This is for specialized
 947           environments which can tolerate a "non-standard" kernel.
 948           Only use this if you really know what you are doing.
 949
 950 config UID16
 951         bool "Enable 16-bit UID system calls" if EXPERT
 952         depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
 953         default y
 954         help
 955           This enables the legacy 16-bit UID syscall wrappers.
 956
 957 config SYSCTL_SYSCALL
 958         bool "Sysctl syscall support" if EXPERT
 959         depends on PROC_SYSCTL
 960         default n
 961         select SYSCTL
 962         ---help---
 963           sys_sysctl uses binary paths that have been found challenging
 964           to properly maintain and use.  The interface in /proc/sys
 965           using paths with ascii names is now the primary path to this
 966           information.
 967
 968           Almost nothing using the binary sysctl interface so if you are
 969           trying to save some space it is probably safe to disable this,
 970           making your kernel marginally smaller.
 971
 972           If unsure say N here.
 973
 974 config KALLSYMS
 975          bool "Load all symbols for debugging/ksymoops" if EXPERT
 976          default y
 977          help
 978            Say Y here to let the kernel print out symbolic crash information and
 979            symbolic stack backtraces. This increases the size of the kernel
 980            somewhat, as all symbols have to be loaded into the kernel image.
 981
 982 config KALLSYMS_ALL
 983         bool "Include all symbols in kallsyms"
 984         depends on DEBUG_KERNEL && KALLSYMS
 985         help
 986            Normally kallsyms only contains the symbols of functions for nicer
 987            OOPS messages and backtraces (i.e., symbols from the text and inittext
 988            sections). This is sufficient for most cases. And only in very rare
 989            cases (e.g., when a debugger is used) all symbols are required (e.g.,
 990            names of variables from the data sections, etc).
 991
 992            This option makes sure that all symbols are loaded into the kernel
 993            image (i.e., symbols from all sections) in cost of increased kernel
 994            size (depending on the kernel configuration, it may be 300KiB or
 995            something like this).
 996
 997            Say N unless you really need all symbols.
 998
 999 config HOTPLUG
1000         bool "Support for hot-pluggable devices" if EXPERT
1001         default y
1002         help
1003           This option is provided for the case where no hotplug or uevent
1004           capabilities is wanted by the kernel.  You should only consider
1005           disabling this option for embedded systems that do not use modules, a
1006           dynamic /dev tree, or dynamic device discovery.  Just say Y.
1007
1008 config PRINTK
1009         default y
1010         bool "Enable support for printk" if EXPERT
1011         help
1012           This option enables normal printk support. Removing it
1013           eliminates most of the message strings from the kernel image
1014           and makes the kernel more or less silent. As this makes it
1015           very difficult to diagnose system problems, saying N here is
1016           strongly discouraged.
1017
1018 config BUG
1019         bool "BUG() support" if EXPERT
1020         default y
1021         help
1022           Disabling this option eliminates support for BUG and WARN, reducing
1023           the size of your kernel image and potentially quietly ignoring
1024           numerous fatal conditions. You should only consider disabling this
1025           option for embedded systems with no facilities for reporting errors.
1026           Just say Y.
1027
1028 config ELF_CORE
1029         default y
1030         bool "Enable ELF core dumps" if EXPERT
1031         help
1032           Enable support for generating core dumps. Disabling saves about 4k.
1033
1034
1035 config PCSPKR_PLATFORM
1036         bool "Enable PC-Speaker support" if EXPERT
1037         depends on HAVE_PCSPKR_PLATFORM
1038         select I8253_LOCK
1039         default y
1040         help
1041           This option allows to disable the internal PC-Speaker
1042           support, saving some memory.
1043
1044 config HAVE_PCSPKR_PLATFORM
1045         bool
1046
1047 config BASE_FULL
1048         default y
1049         bool "Enable full-sized data structures for core" if EXPERT
1050         help
1051           Disabling this option reduces the size of miscellaneous core
1052           kernel data structures. This saves memory on small machines,
1053           but may reduce performance.
1054
1055 config FUTEX
1056         bool "Enable futex support" if EXPERT
1057         default y
1058         select RT_MUTEXES
1059         help
1060           Disabling this option will cause the kernel to be built without
1061           support for "fast userspace mutexes".  The resulting kernel may not
1062           run glibc-based applications correctly.
1063
1064 config EPOLL
1065         bool "Enable eventpoll support" if EXPERT
1066         default y
1067         select ANON_INODES
1068         help
1069           Disabling this option will cause the kernel to be built without
1070           support for epoll family of system calls.
1071
1072 config SIGNALFD
1073         bool "Enable signalfd() system call" if EXPERT
1074         select ANON_INODES
1075         default y
1076         help
1077           Enable the signalfd() system call that allows to receive signals
1078           on a file descriptor.
1079
1080           If unsure, say Y.
1081
1082 config TIMERFD
1083         bool "Enable timerfd() system call" if EXPERT
1084         select ANON_INODES
1085         default y
1086         help
1087           Enable the timerfd() system call that allows to receive timer
1088           events on a file descriptor.
1089
1090           If unsure, say Y.
1091
1092 config EVENTFD
1093         bool "Enable eventfd() system call" if EXPERT
1094         select ANON_INODES
1095         default y
1096         help
1097           Enable the eventfd() system call that allows to receive both
1098           kernel notification (ie. KAIO) or userspace notifications.
1099
1100           If unsure, say Y.
1101
1102 config SHMEM
1103         bool "Use full shmem filesystem" if EXPERT
1104         default y
1105         depends on MMU
1106         help
1107           The shmem is an internal filesystem used to manage shared memory.
1108           It is backed by swap and manages resource limits. It is also exported
1109           to userspace as tmpfs if TMPFS is enabled. Disabling this
1110           option replaces shmem and tmpfs with the much simpler ramfs code,
1111           which may be appropriate on small systems without swap.
1112
1113 config AIO
1114         bool "Enable AIO support" if EXPERT
1115         default y
1116         help
1117           This option enables POSIX asynchronous I/O which may by used
1118           by some high performance threaded applications. Disabling
1119           this option saves about 7k.
1120
1121 config EMBEDDED
1122         bool "Embedded system"
1123         select EXPERT
1124         help
1125           This option should be enabled if compiling the kernel for
1126           an embedded system so certain expert options are available
1127           for configuration.
1128
1129 config HAVE_PERF_EVENTS
1130         bool
1131         help
1132           See tools/perf/design.txt for details.
1133
1134 config PERF_USE_VMALLOC
1135         bool
1136         help
1137           See tools/perf/design.txt for details
1138
1139 menu "Kernel Performance Events And Counters"
1140
1141 config PERF_EVENTS
1142         bool "Kernel performance events and counters"
1143         default y if (PROFILING || PERF_COUNTERS)
1144         depends on HAVE_PERF_EVENTS
1145         select ANON_INODES
1146         select IRQ_WORK
1147         help
1148           Enable kernel support for various performance events provided
1149           by software and hardware.
1150
1151           Software events are supported either built-in or via the
1152           use of generic tracepoints.
1153
1154           Most modern CPUs support performance events via performance
1155           counter registers. These registers count the number of certain
1156           types of hw events: such as instructions executed, cachemisses
1157           suffered, or branches mis-predicted - without slowing down the
1158           kernel or applications. These registers can also trigger interrupts
1159           when a threshold number of events have passed - and can thus be
1160           used to profile the code that runs on that CPU.
1161
1162           The Linux Performance Event subsystem provides an abstraction of
1163           these software and hardware event capabilities, available via a
1164           system call and used by the "perf" utility in tools/perf/. It
1165           provides per task and per CPU counters, and it provides event
1166           capabilities on top of those.
1167
1168           Say Y if unsure.
1169
1170 config PERF_COUNTERS
1171         bool "Kernel performance counters (old config option)"
1172         depends on HAVE_PERF_EVENTS
1173         help
1174           This config has been obsoleted by the PERF_EVENTS
1175           config option - please see that one for details.
1176
1177           It has no effect on the kernel whether you enable
1178           it or not, it is a compatibility placeholder.
1179
1180           Say N if unsure.
1181
1182 config DEBUG_PERF_USE_VMALLOC
1183         default n
1184         bool "Debug: use vmalloc to back perf mmap() buffers"
1185         depends on PERF_EVENTS && DEBUG_KERNEL
1186         select PERF_USE_VMALLOC
1187         help
1188          Use vmalloc memory to back perf mmap() buffers.
1189
1190          Mostly useful for debugging the vmalloc code on platforms
1191          that don't require it.
1192
1193          Say N if unsure.
1194
1195 endmenu
1196
1197 config VM_EVENT_COUNTERS
1198         default y
1199         bool "Enable VM event counters for /proc/vmstat" if EXPERT
1200         help
1201           VM event counters are needed for event counts to be shown.
1202           This option allows the disabling of the VM event counters
1203           on EXPERT systems.  /proc/vmstat will only show page counts
1204           if VM event counters are disabled.
1205
1206 config PCI_QUIRKS
1207         default y
1208         bool "Enable PCI quirk workarounds" if EXPERT
1209         depends on PCI
1210         help
1211           This enables workarounds for various PCI chipset
1212           bugs/quirks. Disable this only if your target machine is
1213           unaffected by PCI quirks.
1214
1215 config SLUB_DEBUG
1216         default y
1217         bool "Enable SLUB debugging support" if EXPERT
1218         depends on SLUB && SYSFS
1219         help
1220           SLUB has extensive debug support features. Disabling these can
1221           result in significant savings in code size. This also disables
1222           SLUB sysfs support. /sys/slab will not exist and there will be
1223           no support for cache validation etc.
1224
1225 config COMPAT_BRK
1226         bool "Disable heap randomization"
1227         default y
1228         help
1229           Randomizing heap placement makes heap exploits harder, but it
1230           also breaks ancient binaries (including anything libc5 based).
1231           This option changes the bootup default to heap randomization
1232           disabled, and can be overridden at runtime by setting
1233           /proc/sys/kernel/randomize_va_space to 2.
1234
1235           On non-ancient distros (post-2000 ones) N is usually a safe choice.
1236
1237 choice
1238         prompt "Choose SLAB allocator"
1239         default SLUB
1240         help
1241            This option allows to select a slab allocator.
1242
1243 config SLAB
1244         bool "SLAB"
1245         help
1246           The regular slab allocator that is established and known to work
1247           well in all environments. It organizes cache hot objects in
1248           per cpu and per node queues.
1249
1250 config SLUB
1251         bool "SLUB (Unqueued Allocator)"
1252         help
1253            SLUB is a slab allocator that minimizes cache line usage
1254            instead of managing queues of cached objects (SLAB approach).
1255            Per cpu caching is realized using slabs of objects instead
1256            of queues of objects. SLUB can use memory efficiently
1257            and has enhanced diagnostics. SLUB is the default choice for
1258            a slab allocator.
1259
1260 config SLOB
1261         depends on EXPERT
1262         bool "SLOB (Simple Allocator)"
1263         help
1264            SLOB replaces the stock allocator with a drastically simpler
1265            allocator. SLOB is generally more space efficient but
1266            does not perform as well on large systems.
1267
1268 endchoice
1269
1270 config MMAP_ALLOW_UNINITIALIZED
1271         bool "Allow mmapped anonymous memory to be uninitialized"
1272         depends on EXPERT && !MMU
1273         default n
1274         help
1275           Normally, and according to the Linux spec, anonymous memory obtained
1276           from mmap() has it's contents cleared before it is passed to
1277           userspace.  Enabling this config option allows you to request that
1278           mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1279           providing a huge performance boost.  If this option is not enabled,
1280           then the flag will be ignored.
1281
1282           This is taken advantage of by uClibc's malloc(), and also by
1283           ELF-FDPIC binfmt's brk and stack allocator.
1284
1285           Because of the obvious security issues, this option should only be
1286           enabled on embedded devices where you control what is run in
1287           userspace.  Since that isn't generally a problem on no-MMU systems,
1288           it is normally safe to say Y here.
1289
1290           See Documentation/nommu-mmap.txt for more information.
1291
1292 config PROFILING
1293         bool "Profiling support"
1294         help
1295           Say Y here to enable the extended profiling support mechanisms used
1296           by profilers such as OProfile.
1297
1298 #
1299 # Place an empty function call at each tracepoint site. Can be
1300 # dynamically changed for a probe function.
1301 #
1302 config TRACEPOINTS
1303         bool
1304
1305 source "arch/Kconfig"
1306
1307 endmenu         # General setup
1308
1309 config HAVE_GENERIC_DMA_COHERENT
1310         bool
1311         default n
1312
1313 config SLABINFO
1314         bool
1315         depends on PROC_FS
1316         depends on SLAB || SLUB_DEBUG
1317         default y
1318
1319 config RT_MUTEXES
1320         boolean
1321
1322 config BASE_SMALL
1323         int
1324         default 0 if BASE_FULL
1325         default 1 if !BASE_FULL
1326
1327 menuconfig MODULES
1328         bool "Enable loadable module support"
1329         help
1330           Kernel modules are small pieces of compiled code which can
1331           be inserted in the running kernel, rather than being
1332           permanently built into the kernel.  You use the "modprobe"
1333           tool to add (and sometimes remove) them.  If you say Y here,
1334           many parts of the kernel can be built as modules (by
1335           answering M instead of Y where indicated): this is most
1336           useful for infrequently used options which are not required
1337           for booting.  For more information, see the man pages for
1338           modprobe, lsmod, modinfo, insmod and rmmod.
1339
1340           If you say Y here, you will need to run "make
1341           modules_install" to put the modules under /lib/modules/
1342           where modprobe can find them (you may need to be root to do
1343           this).
1344
1345           If unsure, say Y.
1346
1347 if MODULES
1348
1349 config MODULE_FORCE_LOAD
1350         bool "Forced module loading"
1351         default n
1352         help
1353           Allow loading of modules without version information (ie. modprobe
1354           --force).  Forced module loading sets the 'F' (forced) taint flag and
1355           is usually a really bad idea.
1356
1357 config MODULE_UNLOAD
1358         bool "Module unloading"
1359         help
1360           Without this option you will not be able to unload any
1361           modules (note that some modules may not be unloadable
1362           anyway), which makes your kernel smaller, faster
1363           and simpler.  If unsure, say Y.
1364
1365 config MODULE_FORCE_UNLOAD
1366         bool "Forced module unloading"
1367         depends on MODULE_UNLOAD && EXPERIMENTAL
1368         help
1369           This option allows you to force a module to unload, even if the
1370           kernel believes it is unsafe: the kernel will remove the module
1371           without waiting for anyone to stop using it (using the -f option to
1372           rmmod).  This is mainly for kernel developers and desperate users.
1373           If unsure, say N.
1374
1375 config MODVERSIONS
1376         bool "Module versioning support"
1377         help
1378           Usually, you have to use modules compiled with your kernel.
1379           Saying Y here makes it sometimes possible to use modules
1380           compiled for different kernels, by adding enough information
1381           to the modules to (hopefully) spot any changes which would
1382           make them incompatible with the kernel you are running.  If
1383           unsure, say N.
1384
1385 config MODULE_SRCVERSION_ALL
1386         bool "Source checksum for all modules"
1387         help
1388           Modules which contain a MODULE_VERSION get an extra "srcversion"
1389           field inserted into their modinfo section, which contains a
1390           sum of the source files which made it.  This helps maintainers
1391           see exactly which source was used to build a module (since
1392           others sometimes change the module source without updating
1393           the version).  With this option, such a "srcversion" field
1394           will be created for all modules.  If unsure, say N.
1395
1396 endif # MODULES
1397
1398 config INIT_ALL_POSSIBLE
1399         bool
1400         help
1401           Back when each arch used to define their own cpu_online_map and
1402           cpu_possible_map, some of them chose to initialize cpu_possible_map
1403           with all 1s, and others with all 0s.  When they were centralised,
1404           it was better to provide this option than to break all the archs
1405           and have several arch maintainers pursuing me down dark alleys.
1406
1407 config STOP_MACHINE
1408         bool
1409         default y
1410         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1411         help
1412           Need stop_machine() primitive.
1413
1414 source "block/Kconfig"
1415
1416 config PREEMPT_NOTIFIERS
1417         bool
1418
1419 config PADATA
1420         depends on SMP
1421         bool
1422
1423 source "kernel/Kconfig.locks"