linux/init/Kconfig
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   1config ARCH
   2        string
   3        option env="ARCH"
   4
   5config KERNELVERSION
   6        string
   7        option env="KERNELVERSION"
   8
   9config 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
  19config CONSTRUCTORS
  20        bool
  21        depends on !UML
  22
  23config HAVE_IRQ_WORK
  24        bool
  25
  26config IRQ_WORK
  27        bool
  28        depends on HAVE_IRQ_WORK
  29
  30config BUILDTIME_EXTABLE_SORT
  31        bool
  32
  33menu "General setup"
  34
  35config EXPERIMENTAL
  36        bool "Prompt for development and/or incomplete code/drivers"
  37        ---help---
  38          Some of the various things that Linux supports (such as network
  39          drivers, file systems, network protocols, etc.) can be in a state
  40          of development where the functionality, stability, or the level of
  41          testing is not yet high enough for general use. This is usually
  42          known as the "alpha-test" phase among developers. If a feature is
  43          currently in alpha-test, then the developers usually discourage
  44          uninformed widespread use of this feature by the general public to
  45          avoid "Why doesn't this work?" type mail messages. However, active
  46          testing and use of these systems is welcomed. Just be aware that it
  47          may not meet the normal level of reliability or it may fail to work
  48          in some special cases. Detailed bug reports from people familiar
  49          with the kernel internals are usually welcomed by the developers
  50          (before submitting bug reports, please read the documents
  51          <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
  52          <file:Documentation/BUG-HUNTING>, and
  53          <file:Documentation/oops-tracing.txt> in the kernel source).
  54
  55          This option will also make obsoleted drivers available. These are
  56          drivers that have been replaced by something else, and/or are
  57          scheduled to be removed in a future kernel release.
  58
  59          Unless you intend to help test and develop a feature or driver that
  60          falls into this category, or you have a situation that requires
  61          using these features, you should probably say N here, which will
  62          cause the configurator to present you with fewer choices. If
  63          you say Y here, you will be offered the choice of using features or
  64          drivers that are currently considered to be in the alpha-test phase.
  65
  66config BROKEN
  67        bool
  68
  69config BROKEN_ON_SMP
  70        bool
  71        depends on BROKEN || !SMP
  72        default y
  73
  74config INIT_ENV_ARG_LIMIT
  75        int
  76        default 32 if !UML
  77        default 128 if UML
  78        help
  79          Maximum of each of the number of arguments and environment
  80          variables passed to init from the kernel command line.
  81
  82
  83config CROSS_COMPILE
  84        string "Cross-compiler tool prefix"
  85        help
  86          Same as running 'make CROSS_COMPILE=prefix-' but stored for
  87          default make runs in this kernel build directory.  You don't
  88          need to set this unless you want the configured kernel build
  89          directory to select the cross-compiler automatically.
  90
  91config LOCALVERSION
  92        string "Local version - append to kernel release"
  93        help
  94          Append an extra string to the end of your kernel version.
  95          This will show up when you type uname, for example.
  96          The string you set here will be appended after the contents of
  97          any files with a filename matching localversion* in your
  98          object and source tree, in that order.  Your total string can
  99          be a maximum of 64 characters.
 100
 101config LOCALVERSION_AUTO
 102        bool "Automatically append version information to the version string"
 103        default y
 104        help
 105          This will try to automatically determine if the current tree is a
 106          release tree by looking for git tags that belong to the current
 107          top of tree revision.
 108
 109          A string of the format -gxxxxxxxx will be added to the localversion
 110          if a git-based tree is found.  The string generated by this will be
 111          appended after any matching localversion* files, and after the value
 112          set in CONFIG_LOCALVERSION.
 113
 114          (The actual string used here is the first eight characters produced
 115          by running the command:
 116
 117            $ git rev-parse --verify HEAD
 118
 119          which is done within the script "scripts/setlocalversion".)
 120
 121config HAVE_KERNEL_GZIP
 122        bool
 123
 124config HAVE_KERNEL_BZIP2
 125        bool
 126
 127config HAVE_KERNEL_LZMA
 128        bool
 129
 130config HAVE_KERNEL_XZ
 131        bool
 132
 133config HAVE_KERNEL_LZO
 134        bool
 135
 136choice
 137        prompt "Kernel compression mode"
 138        default KERNEL_GZIP
 139        depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
 140        help
 141          The linux kernel is a kind of self-extracting executable.
 142          Several compression algorithms are available, which differ
 143          in efficiency, compression and decompression speed.
 144          Compression speed is only relevant when building a kernel.
 145          Decompression speed is relevant at each boot.
 146
 147          If you have any problems with bzip2 or lzma compressed
 148          kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
 149          version of this functionality (bzip2 only), for 2.4, was
 150          supplied by Christian Ludwig)
 151
 152          High compression options are mostly useful for users, who
 153          are low on disk space (embedded systems), but for whom ram
 154          size matters less.
 155
 156          If in doubt, select 'gzip'
 157
 158config KERNEL_GZIP
 159        bool "Gzip"
 160        depends on HAVE_KERNEL_GZIP
 161        help
 162          The old and tried gzip compression. It provides a good balance
 163          between compression ratio and decompression speed.
 164
 165config KERNEL_BZIP2
 166        bool "Bzip2"
 167        depends on HAVE_KERNEL_BZIP2
 168        help
 169          Its compression ratio and speed is intermediate.
 170          Decompression speed is slowest among the choices.  The kernel
 171          size is about 10% smaller with bzip2, in comparison to gzip.
 172          Bzip2 uses a large amount of memory. For modern kernels you
 173          will need at least 8MB RAM or more for booting.
 174
 175config KERNEL_LZMA
 176        bool "LZMA"
 177        depends on HAVE_KERNEL_LZMA
 178        help
 179          This compression algorithm's ratio is best.  Decompression speed
 180          is between gzip and bzip2.  Compression is slowest.
 181          The kernel size is about 33% smaller with LZMA in comparison to gzip.
 182
 183config KERNEL_XZ
 184        bool "XZ"
 185        depends on HAVE_KERNEL_XZ
 186        help
 187          XZ uses the LZMA2 algorithm and instruction set specific
 188          BCJ filters which can improve compression ratio of executable
 189          code. The size of the kernel is about 30% smaller with XZ in
 190          comparison to gzip. On architectures for which there is a BCJ
 191          filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
 192          will create a few percent smaller kernel than plain LZMA.
 193
 194          The speed is about the same as with LZMA: The decompression
 195          speed of XZ is better than that of bzip2 but worse than gzip
 196          and LZO. Compression is slow.
 197
 198config KERNEL_LZO
 199        bool "LZO"
 200        depends on HAVE_KERNEL_LZO
 201        help
 202          Its compression ratio is the poorest among the choices. The kernel
 203          size is about 10% bigger than gzip; however its speed
 204          (both compression and decompression) is the fastest.
 205
 206endchoice
 207
 208config DEFAULT_HOSTNAME
 209        string "Default hostname"
 210        default "(none)"
 211        help
 212          This option determines the default system hostname before userspace
 213          calls sethostname(2). The kernel traditionally uses "(none)" here,
 214          but you may wish to use a different default here to make a minimal
 215          system more usable with less configuration.
 216
 217config SWAP
 218        bool "Support for paging of anonymous memory (swap)"
 219        depends on MMU && BLOCK
 220        default y
 221        help
 222          This option allows you to choose whether you want to have support
 223          for so called swap devices or swap files in your kernel that are
 224          used to provide more virtual memory than the actual RAM present
 225          in your computer.  If unsure say Y.
 226
 227config SYSVIPC
 228        bool "System V IPC"
 229        ---help---
 230          Inter Process Communication is a suite of library functions and
 231          system calls which let processes (running programs) synchronize and
 232          exchange information. It is generally considered to be a good thing,
 233          and some programs won't run unless you say Y here. In particular, if
 234          you want to run the DOS emulator dosemu under Linux (read the
 235          DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
 236          you'll need to say Y here.
 237
 238          You can find documentation about IPC with "info ipc" and also in
 239          section 6.4 of the Linux Programmer's Guide, available from
 240          <http://www.tldp.org/guides.html>.
 241
 242config SYSVIPC_SYSCTL
 243        bool
 244        depends on SYSVIPC
 245        depends on SYSCTL
 246        default y
 247
 248config POSIX_MQUEUE
 249        bool "POSIX Message Queues"
 250        depends on NET && EXPERIMENTAL
 251        ---help---
 252          POSIX variant of message queues is a part of IPC. In POSIX message
 253          queues every message has a priority which decides about succession
 254          of receiving it by a process. If you want to compile and run
 255          programs written e.g. for Solaris with use of its POSIX message
 256          queues (functions mq_*) say Y here.
 257
 258          POSIX message queues are visible as a filesystem called 'mqueue'
 259          and can be mounted somewhere if you want to do filesystem
 260          operations on message queues.
 261
 262          If unsure, say Y.
 263
 264config POSIX_MQUEUE_SYSCTL
 265        bool
 266        depends on POSIX_MQUEUE
 267        depends on SYSCTL
 268        default y
 269
 270config BSD_PROCESS_ACCT
 271        bool "BSD Process Accounting"
 272        help
 273          If you say Y here, a user level program will be able to instruct the
 274          kernel (via a special system call) to write process accounting
 275          information to a file: whenever a process exits, information about
 276          that process will be appended to the file by the kernel.  The
 277          information includes things such as creation time, owning user,
 278          command name, memory usage, controlling terminal etc. (the complete
 279          list is in the struct acct in <file:include/linux/acct.h>).  It is
 280          up to the user level program to do useful things with this
 281          information.  This is generally a good idea, so say Y.
 282
 283config BSD_PROCESS_ACCT_V3
 284        bool "BSD Process Accounting version 3 file format"
 285        depends on BSD_PROCESS_ACCT
 286        default n
 287        help
 288          If you say Y here, the process accounting information is written
 289          in a new file format that also logs the process IDs of each
 290          process and it's parent. Note that this file format is incompatible
 291          with previous v0/v1/v2 file formats, so you will need updated tools
 292          for processing it. A preliminary version of these tools is available
 293          at <http://www.gnu.org/software/acct/>.
 294
 295config FHANDLE
 296        bool "open by fhandle syscalls"
 297        select EXPORTFS
 298        help
 299          If you say Y here, a user level program will be able to map
 300          file names to handle and then later use the handle for
 301          different file system operations. This is useful in implementing
 302          userspace file servers, which now track files using handles instead
 303          of names. The handle would remain the same even if file names
 304          get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
 305          syscalls.
 306
 307config TASKSTATS
 308        bool "Export task/process statistics through netlink (EXPERIMENTAL)"
 309        depends on NET
 310        default n
 311        help
 312          Export selected statistics for tasks/processes through the
 313          generic netlink interface. Unlike BSD process accounting, the
 314          statistics are available during the lifetime of tasks/processes as
 315          responses to commands. Like BSD accounting, they are sent to user
 316          space on task exit.
 317
 318          Say N if unsure.
 319
 320config TASK_DELAY_ACCT
 321        bool "Enable per-task delay accounting (EXPERIMENTAL)"
 322        depends on TASKSTATS
 323        help
 324          Collect information on time spent by a task waiting for system
 325          resources like cpu, synchronous block I/O completion and swapping
 326          in pages. Such statistics can help in setting a task's priorities
 327          relative to other tasks for cpu, io, rss limits etc.
 328
 329          Say N if unsure.
 330
 331config TASK_XACCT
 332        bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
 333        depends on TASKSTATS
 334        help
 335          Collect extended task accounting data and send the data
 336          to userland for processing over the taskstats interface.
 337
 338          Say N if unsure.
 339
 340config TASK_IO_ACCOUNTING
 341        bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
 342        depends on TASK_XACCT
 343        help
 344          Collect information on the number of bytes of storage I/O which this
 345          task has caused.
 346
 347          Say N if unsure.
 348
 349config AUDIT
 350        bool "Auditing support"
 351        depends on NET
 352        help
 353          Enable auditing infrastructure that can be used with another
 354          kernel subsystem, such as SELinux (which requires this for
 355          logging of avc messages output).  Does not do system-call
 356          auditing without CONFIG_AUDITSYSCALL.
 357
 358config AUDITSYSCALL
 359        bool "Enable system-call auditing support"
 360        depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || ARM)
 361        default y if SECURITY_SELINUX
 362        help
 363          Enable low-overhead system-call auditing infrastructure that
 364          can be used independently or with another kernel subsystem,
 365          such as SELinux.
 366
 367config AUDIT_WATCH
 368        def_bool y
 369        depends on AUDITSYSCALL
 370        select FSNOTIFY
 371
 372config AUDIT_TREE
 373        def_bool y
 374        depends on AUDITSYSCALL
 375        select FSNOTIFY
 376
 377config AUDIT_LOGINUID_IMMUTABLE
 378        bool "Make audit loginuid immutable"
 379        depends on AUDIT
 380        help
 381          The config option toggles if a task setting its loginuid requires
 382          CAP_SYS_AUDITCONTROL or if that task should require no special permissions
 383          but should instead only allow setting its loginuid if it was never
 384          previously set.  On systems which use systemd or a similar central
 385          process to restart login services this should be set to true.  On older
 386          systems in which an admin would typically have to directly stop and
 387          start processes this should be set to false.  Setting this to true allows
 388          one to drop potentially dangerous capabilites from the login tasks,
 389          but may not be backwards compatible with older init systems.
 390
 391source "kernel/irq/Kconfig"
 392source "kernel/time/Kconfig"
 393
 394menu "RCU Subsystem"
 395
 396choice
 397        prompt "RCU Implementation"
 398        default TREE_RCU
 399
 400config TREE_RCU
 401        bool "Tree-based hierarchical RCU"
 402        depends on !PREEMPT && SMP
 403        help
 404          This option selects the RCU implementation that is
 405          designed for very large SMP system with hundreds or
 406          thousands of CPUs.  It also scales down nicely to
 407          smaller systems.
 408
 409config TREE_PREEMPT_RCU
 410        bool "Preemptible tree-based hierarchical RCU"
 411        depends on PREEMPT && SMP
 412        help
 413          This option selects the RCU implementation that is
 414          designed for very large SMP systems with hundreds or
 415          thousands of CPUs, but for which real-time response
 416          is also required.  It also scales down nicely to
 417          smaller systems.
 418
 419config TINY_RCU
 420        bool "UP-only small-memory-footprint RCU"
 421        depends on !PREEMPT && !SMP
 422        help
 423          This option selects the RCU implementation that is
 424          designed for UP systems from which real-time response
 425          is not required.  This option greatly reduces the
 426          memory footprint of RCU.
 427
 428config TINY_PREEMPT_RCU
 429        bool "Preemptible UP-only small-memory-footprint RCU"
 430        depends on PREEMPT && !SMP
 431        help
 432          This option selects the RCU implementation that is designed
 433          for real-time UP systems.  This option greatly reduces the
 434          memory footprint of RCU.
 435
 436endchoice
 437
 438config PREEMPT_RCU
 439        def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
 440        help
 441          This option enables preemptible-RCU code that is common between
 442          the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
 443
 444config RCU_FANOUT
 445        int "Tree-based hierarchical RCU fanout value"
 446        range 2 64 if 64BIT
 447        range 2 32 if !64BIT
 448        depends on TREE_RCU || TREE_PREEMPT_RCU
 449        default 64 if 64BIT
 450        default 32 if !64BIT
 451        help
 452          This option controls the fanout of hierarchical implementations
 453          of RCU, allowing RCU to work efficiently on machines with
 454          large numbers of CPUs.  This value must be at least the fourth
 455          root of NR_CPUS, which allows NR_CPUS to be insanely large.
 456          The default value of RCU_FANOUT should be used for production
 457          systems, but if you are stress-testing the RCU implementation
 458          itself, small RCU_FANOUT values allow you to test large-system
 459          code paths on small(er) systems.
 460
 461          Select a specific number if testing RCU itself.
 462          Take the default if unsure.
 463
 464config RCU_FANOUT_LEAF
 465        int "Tree-based hierarchical RCU leaf-level fanout value"
 466        range 2 RCU_FANOUT if 64BIT
 467        range 2 RCU_FANOUT if !64BIT
 468        depends on TREE_RCU || TREE_PREEMPT_RCU
 469        default 16
 470        help
 471          This option controls the leaf-level fanout of hierarchical
 472          implementations of RCU, and allows trading off cache misses
 473          against lock contention.  Systems that synchronize their
 474          scheduling-clock interrupts for energy-efficiency reasons will
 475          want the default because the smaller leaf-level fanout keeps
 476          lock contention levels acceptably low.  Very large systems
 477          (hundreds or thousands of CPUs) will instead want to set this
 478          value to the maximum value possible in order to reduce the
 479          number of cache misses incurred during RCU's grace-period
 480          initialization.  These systems tend to run CPU-bound, and thus
 481          are not helped by synchronized interrupts, and thus tend to
 482          skew them, which reduces lock contention enough that large
 483          leaf-level fanouts work well.
 484
 485          Select a specific number if testing RCU itself.
 486
 487          Select the maximum permissible value for large systems.
 488
 489          Take the default if unsure.
 490
 491config RCU_FANOUT_EXACT
 492        bool "Disable tree-based hierarchical RCU auto-balancing"
 493        depends on TREE_RCU || TREE_PREEMPT_RCU
 494        default n
 495        help
 496          This option forces use of the exact RCU_FANOUT value specified,
 497          regardless of imbalances in the hierarchy.  This is useful for
 498          testing RCU itself, and might one day be useful on systems with
 499          strong NUMA behavior.
 500
 501          Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
 502
 503          Say N if unsure.
 504
 505config RCU_FAST_NO_HZ
 506        bool "Accelerate last non-dyntick-idle CPU's grace periods"
 507        depends on NO_HZ && SMP
 508        default n
 509        help
 510          This option causes RCU to attempt to accelerate grace periods
 511          in order to allow CPUs to enter dynticks-idle state more
 512          quickly.  On the other hand, this option increases the overhead
 513          of the dynticks-idle checking, particularly on systems with
 514          large numbers of CPUs.
 515
 516          Say Y if energy efficiency is critically important, particularly
 517                if you have relatively few CPUs.
 518
 519          Say N if you are unsure.
 520
 521config TREE_RCU_TRACE
 522        def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
 523        select DEBUG_FS
 524        help
 525          This option provides tracing for the TREE_RCU and
 526          TREE_PREEMPT_RCU implementations, permitting Makefile to
 527          trivially select kernel/rcutree_trace.c.
 528
 529config RCU_BOOST
 530        bool "Enable RCU priority boosting"
 531        depends on RT_MUTEXES && PREEMPT_RCU
 532        default n
 533        help
 534          This option boosts the priority of preempted RCU readers that
 535          block the current preemptible RCU grace period for too long.
 536          This option also prevents heavy loads from blocking RCU
 537          callback invocation for all flavors of RCU.
 538
 539          Say Y here if you are working with real-time apps or heavy loads
 540          Say N here if you are unsure.
 541
 542config RCU_BOOST_PRIO
 543        int "Real-time priority to boost RCU readers to"
 544        range 1 99
 545        depends on RCU_BOOST
 546        default 1
 547        help
 548          This option specifies the real-time priority to which long-term
 549          preempted RCU readers are to be boosted.  If you are working
 550          with a real-time application that has one or more CPU-bound
 551          threads running at a real-time priority level, you should set
 552          RCU_BOOST_PRIO to a priority higher then the highest-priority
 553          real-time CPU-bound thread.  The default RCU_BOOST_PRIO value
 554          of 1 is appropriate in the common case, which is real-time
 555          applications that do not have any CPU-bound threads.
 556
 557          Some real-time applications might not have a single real-time
 558          thread that saturates a given CPU, but instead might have
 559          multiple real-time threads that, taken together, fully utilize
 560          that CPU.  In this case, you should set RCU_BOOST_PRIO to
 561          a priority higher than the lowest-priority thread that is
 562          conspiring to prevent the CPU from running any non-real-time
 563          tasks.  For example, if one thread at priority 10 and another
 564          thread at priority 5 are between themselves fully consuming
 565          the CPU time on a given CPU, then RCU_BOOST_PRIO should be
 566          set to priority 6 or higher.
 567
 568          Specify the real-time priority, or take the default if unsure.
 569
 570config RCU_BOOST_DELAY
 571        int "Milliseconds to delay boosting after RCU grace-period start"
 572        range 0 3000
 573        depends on RCU_BOOST
 574        default 500
 575        help
 576          This option specifies the time to wait after the beginning of
 577          a given grace period before priority-boosting preempted RCU
 578          readers blocking that grace period.  Note that any RCU reader
 579          blocking an expedited RCU grace period is boosted immediately.
 580
 581          Accept the default if unsure.
 582
 583endmenu # "RCU Subsystem"
 584
 585config IKCONFIG
 586        tristate "Kernel .config support"
 587        ---help---
 588          This option enables the complete Linux kernel ".config" file
 589          contents to be saved in the kernel. It provides documentation
 590          of which kernel options are used in a running kernel or in an
 591          on-disk kernel.  This information can be extracted from the kernel
 592          image file with the script scripts/extract-ikconfig and used as
 593          input to rebuild the current kernel or to build another kernel.
 594          It can also be extracted from a running kernel by reading
 595          /proc/config.gz if enabled (below).
 596
 597config IKCONFIG_PROC
 598        bool "Enable access to .config through /proc/config.gz"
 599        depends on IKCONFIG && PROC_FS
 600        ---help---
 601          This option enables access to the kernel configuration file
 602          through /proc/config.gz.
 603
 604config LOG_BUF_SHIFT
 605        int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
 606        range 12 21
 607        default 17
 608        help
 609          Select kernel log buffer size as a power of 2.
 610          Examples:
 611                     17 => 128 KB
 612                     16 => 64 KB
 613                     15 => 32 KB
 614                     14 => 16 KB
 615                     13 =>  8 KB
 616                     12 =>  4 KB
 617
 618#
 619# Architectures with an unreliable sched_clock() should select this:
 620#
 621config HAVE_UNSTABLE_SCHED_CLOCK
 622        bool
 623
 624menuconfig CGROUPS
 625        boolean "Control Group support"
 626        depends on EVENTFD
 627        help
 628          This option adds support for grouping sets of processes together, for
 629          use with process control subsystems such as Cpusets, CFS, memory
 630          controls or device isolation.
 631          See
 632                - Documentation/scheduler/sched-design-CFS.txt  (CFS)
 633                - Documentation/cgroups/ (features for grouping, isolation
 634                                          and resource control)
 635
 636          Say N if unsure.
 637
 638if CGROUPS
 639
 640config CGROUP_DEBUG
 641        bool "Example debug cgroup subsystem"
 642        default n
 643        help
 644          This option enables a simple cgroup subsystem that
 645          exports useful debugging information about the cgroups
 646          framework.
 647
 648          Say N if unsure.
 649
 650config CGROUP_FREEZER
 651        bool "Freezer cgroup subsystem"
 652        help
 653          Provides a way to freeze and unfreeze all tasks in a
 654          cgroup.
 655
 656config CGROUP_DEVICE
 657        bool "Device controller for cgroups"
 658        help
 659          Provides a cgroup implementing whitelists for devices which
 660          a process in the cgroup can mknod or open.
 661
 662config CPUSETS
 663        bool "Cpuset support"
 664        help
 665          This option will let you create and manage CPUSETs which
 666          allow dynamically partitioning a system into sets of CPUs and
 667          Memory Nodes and assigning tasks to run only within those sets.
 668          This is primarily useful on large SMP or NUMA systems.
 669
 670          Say N if unsure.
 671
 672config PROC_PID_CPUSET
 673        bool "Include legacy /proc/<pid>/cpuset file"
 674        depends on CPUSETS
 675        default y
 676
 677config CGROUP_CPUACCT
 678        bool "Simple CPU accounting cgroup subsystem"
 679        help
 680          Provides a simple Resource Controller for monitoring the
 681          total CPU consumed by the tasks in a cgroup.
 682
 683config RESOURCE_COUNTERS
 684        bool "Resource counters"
 685        help
 686          This option enables controller independent resource accounting
 687          infrastructure that works with cgroups.
 688
 689config CGROUP_MEM_RES_CTLR
 690        bool "Memory Resource Controller for Control Groups"
 691        depends on RESOURCE_COUNTERS
 692        select MM_OWNER
 693        help
 694          Provides a memory resource controller that manages both anonymous
 695          memory and page cache. (See Documentation/cgroups/memory.txt)
 696
 697          Note that setting this option increases fixed memory overhead
 698          associated with each page of memory in the system. By this,
 699          20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
 700          usage tracking struct at boot. Total amount of this is printed out
 701          at boot.
 702
 703          Only enable when you're ok with these trade offs and really
 704          sure you need the memory resource controller. Even when you enable
 705          this, you can set "cgroup_disable=memory" at your boot option to
 706          disable memory resource controller and you can avoid overheads.
 707          (and lose benefits of memory resource controller)
 708
 709          This config option also selects MM_OWNER config option, which
 710          could in turn add some fork/exit overhead.
 711
 712config CGROUP_MEM_RES_CTLR_SWAP
 713        bool "Memory Resource Controller Swap Extension"
 714        depends on CGROUP_MEM_RES_CTLR && SWAP
 715        help
 716          Add swap management feature to memory resource controller. When you
 717          enable this, you can limit mem+swap usage per cgroup. In other words,
 718          when you disable this, memory resource controller has no cares to
 719          usage of swap...a process can exhaust all of the swap. This extension
 720          is useful when you want to avoid exhaustion swap but this itself
 721          adds more overheads and consumes memory for remembering information.
 722          Especially if you use 32bit system or small memory system, please
 723          be careful about enabling this. When memory resource controller
 724          is disabled by boot option, this will be automatically disabled and
 725          there will be no overhead from this. Even when you set this config=y,
 726          if boot option "swapaccount=0" is set, swap will not be accounted.
 727          Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
 728          size is 4096bytes, 512k per 1Gbytes of swap.
 729config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
 730        bool "Memory Resource Controller Swap Extension enabled by default"
 731        depends on CGROUP_MEM_RES_CTLR_SWAP
 732        default y
 733        help
 734          Memory Resource Controller Swap Extension comes with its price in
 735          a bigger memory consumption. General purpose distribution kernels
 736          which want to enable the feature but keep it disabled by default
 737          and let the user enable it by swapaccount boot command line
 738          parameter should have this option unselected.
 739          For those who want to have the feature enabled by default should
 740          select this option (if, for some reason, they need to disable it
 741          then swapaccount=0 does the trick).
 742config CGROUP_MEM_RES_CTLR_KMEM
 743        bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
 744        depends on CGROUP_MEM_RES_CTLR && EXPERIMENTAL
 745        default n
 746        help
 747          The Kernel Memory extension for Memory Resource Controller can limit
 748          the amount of memory used by kernel objects in the system. Those are
 749          fundamentally different from the entities handled by the standard
 750          Memory Controller, which are page-based, and can be swapped. Users of
 751          the kmem extension can use it to guarantee that no group of processes
 752          will ever exhaust kernel resources alone.
 753
 754config CGROUP_PERF
 755        bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
 756        depends on PERF_EVENTS && CGROUPS
 757        help
 758          This option extends the per-cpu mode to restrict monitoring to
 759          threads which belong to the cgroup specified and run on the
 760          designated cpu.
 761
 762          Say N if unsure.
 763
 764menuconfig CGROUP_SCHED
 765        bool "Group CPU scheduler"
 766        default n
 767        help
 768          This feature lets CPU scheduler recognize task groups and control CPU
 769          bandwidth allocation to such task groups. It uses cgroups to group
 770          tasks.
 771
 772if CGROUP_SCHED
 773config FAIR_GROUP_SCHED
 774        bool "Group scheduling for SCHED_OTHER"
 775        depends on CGROUP_SCHED
 776        default CGROUP_SCHED
 777
 778config CFS_BANDWIDTH
 779        bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
 780        depends on EXPERIMENTAL
 781        depends on FAIR_GROUP_SCHED
 782        default n
 783        help
 784          This option allows users to define CPU bandwidth rates (limits) for
 785          tasks running within the fair group scheduler.  Groups with no limit
 786          set are considered to be unconstrained and will run with no
 787          restriction.
 788          See tip/Documentation/scheduler/sched-bwc.txt for more information.
 789
 790config RT_GROUP_SCHED
 791        bool "Group scheduling for SCHED_RR/FIFO"
 792        depends on EXPERIMENTAL
 793        depends on CGROUP_SCHED
 794        default n
 795        help
 796          This feature lets you explicitly allocate real CPU bandwidth
 797          to task groups. If enabled, it will also make it impossible to
 798          schedule realtime tasks for non-root users until you allocate
 799          realtime bandwidth for them.
 800          See Documentation/scheduler/sched-rt-group.txt for more information.
 801
 802endif #CGROUP_SCHED
 803
 804config BLK_CGROUP
 805        bool "Block IO controller"
 806        depends on BLOCK
 807        default n
 808        ---help---
 809        Generic block IO controller cgroup interface. This is the common
 810        cgroup interface which should be used by various IO controlling
 811        policies.
 812
 813        Currently, CFQ IO scheduler uses it to recognize task groups and
 814        control disk bandwidth allocation (proportional time slice allocation)
 815        to such task groups. It is also used by bio throttling logic in
 816        block layer to implement upper limit in IO rates on a device.
 817
 818        This option only enables generic Block IO controller infrastructure.
 819        One needs to also enable actual IO controlling logic/policy. For
 820        enabling proportional weight division of disk bandwidth in CFQ, set
 821        CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
 822        CONFIG_BLK_DEV_THROTTLING=y.
 823
 824        See Documentation/cgroups/blkio-controller.txt for more information.
 825
 826config DEBUG_BLK_CGROUP
 827        bool "Enable Block IO controller debugging"
 828        depends on BLK_CGROUP
 829        default n
 830        ---help---
 831        Enable some debugging help. Currently it exports additional stat
 832        files in a cgroup which can be useful for debugging.
 833
 834endif # CGROUPS
 835
 836config CHECKPOINT_RESTORE
 837        bool "Checkpoint/restore support" if EXPERT
 838        default n
 839        help
 840          Enables additional kernel features in a sake of checkpoint/restore.
 841          In particular it adds auxiliary prctl codes to setup process text,
 842          data and heap segment sizes, and a few additional /proc filesystem
 843          entries.
 844
 845          If unsure, say N here.
 846
 847menuconfig NAMESPACES
 848        bool "Namespaces support" if EXPERT
 849        default !EXPERT
 850        help
 851          Provides the way to make tasks work with different objects using
 852          the same id. For example same IPC id may refer to different objects
 853          or same user id or pid may refer to different tasks when used in
 854          different namespaces.
 855
 856if NAMESPACES
 857
 858config UTS_NS
 859        bool "UTS namespace"
 860        default y
 861        help
 862          In this namespace tasks see different info provided with the
 863          uname() system call
 864
 865config IPC_NS
 866        bool "IPC namespace"
 867        depends on (SYSVIPC || POSIX_MQUEUE)
 868        default y
 869        help
 870          In this namespace tasks work with IPC ids which correspond to
 871          different IPC objects in different namespaces.
 872
 873config USER_NS
 874        bool "User namespace (EXPERIMENTAL)"
 875        depends on EXPERIMENTAL
 876        depends on UIDGID_CONVERTED
 877        select UIDGID_STRICT_TYPE_CHECKS
 878
 879        default n
 880        help
 881          This allows containers, i.e. vservers, to use user namespaces
 882          to provide different user info for different servers.
 883          If unsure, say N.
 884
 885config PID_NS
 886        bool "PID Namespaces"
 887        default y
 888        help
 889          Support process id namespaces.  This allows having multiple
 890          processes with the same pid as long as they are in different
 891          pid namespaces.  This is a building block of containers.
 892
 893config NET_NS
 894        bool "Network namespace"
 895        depends on NET
 896        default y
 897        help
 898          Allow user space to create what appear to be multiple instances
 899          of the network stack.
 900
 901endif # NAMESPACES
 902
 903config UIDGID_CONVERTED
 904        # True if all of the selected software conmponents are known
 905        # to have uid_t and gid_t converted to kuid_t and kgid_t
 906        # where appropriate and are otherwise safe to use with
 907        # the user namespace.
 908        bool
 909        default y
 910
 911        # List of kernel pieces that need user namespace work
 912        # Features
 913        depends on SYSVIPC = n
 914        depends on IMA = n
 915        depends on EVM = n
 916        depends on KEYS = n
 917        depends on AUDIT = n
 918        depends on AUDITSYSCALL = n
 919        depends on TASKSTATS = n
 920        depends on TRACING = n
 921        depends on FS_POSIX_ACL = n
 922        depends on QUOTA = n
 923        depends on QUOTACTL = n
 924        depends on DEBUG_CREDENTIALS = n
 925        depends on BSD_PROCESS_ACCT = n
 926        depends on DRM = n
 927        depends on PROC_EVENTS = n
 928
 929        # Networking
 930        depends on NET = n
 931        depends on NET_9P = n
 932        depends on IPX = n
 933        depends on PHONET = n
 934        depends on NET_CLS_FLOW = n
 935        depends on NETFILTER_XT_MATCH_OWNER = n
 936        depends on NETFILTER_XT_MATCH_RECENT = n
 937        depends on NETFILTER_XT_TARGET_LOG = n
 938        depends on NETFILTER_NETLINK_LOG = n
 939        depends on INET = n
 940        depends on IPV6 = n
 941        depends on IP_SCTP = n
 942        depends on AF_RXRPC = n
 943        depends on LLC2 = n
 944        depends on NET_KEY = n
 945        depends on INET_DIAG = n
 946        depends on DNS_RESOLVER = n
 947        depends on AX25 = n
 948        depends on ATALK = n
 949
 950        # Filesystems
 951        depends on USB_DEVICEFS = n
 952        depends on USB_GADGETFS = n
 953        depends on USB_FUNCTIONFS = n
 954        depends on DEVTMPFS = n
 955        depends on XENFS = n
 956
 957        depends on 9P_FS = n
 958        depends on ADFS_FS = n
 959        depends on AFFS_FS = n
 960        depends on AFS_FS = n
 961        depends on AUTOFS4_FS = n
 962        depends on BEFS_FS = n
 963        depends on BFS_FS = n
 964        depends on BTRFS_FS = n
 965        depends on CEPH_FS = n
 966        depends on CIFS = n
 967        depends on CODA_FS = n
 968        depends on CONFIGFS_FS = n
 969        depends on CRAMFS = n
 970        depends on DEBUG_FS = n
 971        depends on ECRYPT_FS = n
 972        depends on EFS_FS = n
 973        depends on EXOFS_FS = n
 974        depends on FAT_FS = n
 975        depends on FUSE_FS = n
 976        depends on GFS2_FS = n
 977        depends on HFS_FS = n
 978        depends on HFSPLUS_FS = n
 979        depends on HPFS_FS = n
 980        depends on HUGETLBFS = n
 981        depends on ISO9660_FS = n
 982        depends on JFFS2_FS = n
 983        depends on JFS_FS = n
 984        depends on LOGFS = n
 985        depends on MINIX_FS = n
 986        depends on NCP_FS = n
 987        depends on NFSD = n
 988        depends on NFS_FS = n
 989        depends on NILFS2_FS = n
 990        depends on NTFS_FS = n
 991        depends on OCFS2_FS = n
 992        depends on OMFS_FS = n
 993        depends on QNX4FS_FS = n
 994        depends on QNX6FS_FS = n
 995        depends on REISERFS_FS = n
 996        depends on SQUASHFS = n
 997        depends on SYSV_FS = n
 998        depends on UBIFS_FS = n
 999        depends on UDF_FS = n
1000        depends on UFS_FS = n
1001        depends on VXFS_FS = n
1002        depends on XFS_FS = n
1003
1004        depends on !UML || HOSTFS = n
1005
1006        # The rare drivers that won't build
1007        depends on AIRO = n
1008        depends on AIRO_CS = n
1009        depends on TUN = n
1010        depends on INFINIBAND_QIB = n
1011        depends on BLK_DEV_LOOP = n
1012        depends on ANDROID_BINDER_IPC = n
1013
1014        # Security modules
1015        depends on SECURITY_TOMOYO = n
1016        depends on SECURITY_APPARMOR = n
1017
1018config UIDGID_STRICT_TYPE_CHECKS
1019        bool "Require conversions between uid/gids and their internal representation"
1020        depends on UIDGID_CONVERTED
1021        default n
1022        help
1023         While the nececessary conversions are being added to all subsystems this option allows
1024         the code to continue to build for unconverted subsystems.
1025
1026         Say Y here if you want the strict type checking enabled
1027
1028config SCHED_AUTOGROUP
1029        bool "Automatic process group scheduling"
1030        select EVENTFD
1031        select CGROUPS
1032        select CGROUP_SCHED
1033        select FAIR_GROUP_SCHED
1034        help
1035          This option optimizes the scheduler for common desktop workloads by
1036          automatically creating and populating task groups.  This separation
1037          of workloads isolates aggressive CPU burners (like build jobs) from
1038          desktop applications.  Task group autogeneration is currently based
1039          upon task session.
1040
1041config MM_OWNER
1042        bool
1043
1044config SYSFS_DEPRECATED
1045        bool "Enable deprecated sysfs features to support old userspace tools"
1046        depends on SYSFS
1047        default n
1048        help
1049          This option adds code that switches the layout of the "block" class
1050          devices, to not show up in /sys/class/block/, but only in
1051          /sys/block/.
1052
1053          This switch is only active when the sysfs.deprecated=1 boot option is
1054          passed or the SYSFS_DEPRECATED_V2 option is set.
1055
1056          This option allows new kernels to run on old distributions and tools,
1057          which might get confused by /sys/class/block/. Since 2007/2008 all
1058          major distributions and tools handle this just fine.
1059
1060          Recent distributions and userspace tools after 2009/2010 depend on
1061          the existence of /sys/class/block/, and will not work with this
1062          option enabled.
1063
1064          Only if you are using a new kernel on an old distribution, you might
1065          need to say Y here.
1066
1067config SYSFS_DEPRECATED_V2
1068        bool "Enable deprecated sysfs features by default"
1069        default n
1070        depends on SYSFS
1071        depends on SYSFS_DEPRECATED
1072        help
1073          Enable deprecated sysfs by default.
1074
1075          See the CONFIG_SYSFS_DEPRECATED option for more details about this
1076          option.
1077
1078          Only if you are using a new kernel on an old distribution, you might
1079          need to say Y here. Even then, odds are you would not need it
1080          enabled, you can always pass the boot option if absolutely necessary.
1081
1082config RELAY
1083        bool "Kernel->user space relay support (formerly relayfs)"
1084        help
1085          This option enables support for relay interface support in
1086          certain file systems (such as debugfs).
1087          It is designed to provide an efficient mechanism for tools and
1088          facilities to relay large amounts of data from kernel space to
1089          user space.
1090
1091          If unsure, say N.
1092
1093config BLK_DEV_INITRD
1094        bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1095        depends on BROKEN || !FRV
1096        help
1097          The initial RAM filesystem is a ramfs which is loaded by the
1098          boot loader (loadlin or lilo) and that is mounted as root
1099          before the normal boot procedure. It is typically used to
1100          load modules needed to mount the "real" root file system,
1101          etc. See <file:Documentation/initrd.txt> for details.
1102
1103          If RAM disk support (BLK_DEV_RAM) is also included, this
1104          also enables initial RAM disk (initrd) support and adds
1105          15 Kbytes (more on some other architectures) to the kernel size.
1106
1107          If unsure say Y.
1108
1109if BLK_DEV_INITRD
1110
1111source "usr/Kconfig"
1112
1113endif
1114
1115config CC_OPTIMIZE_FOR_SIZE
1116        bool "Optimize for size"
1117        help
1118          Enabling this option will pass "-Os" instead of "-O2" to gcc
1119          resulting in a smaller kernel.
1120
1121          If unsure, say Y.
1122
1123config SYSCTL
1124        bool
1125
1126config ANON_INODES
1127        bool
1128
1129menuconfig EXPERT
1130        bool "Configure standard kernel features (expert users)"
1131        # Unhide debug options, to make the on-by-default options visible
1132        select DEBUG_KERNEL
1133        help
1134          This option allows certain base kernel options and settings
1135          to be disabled or tweaked. This is for specialized
1136          environments which can tolerate a "non-standard" kernel.
1137          Only use this if you really know what you are doing.
1138
1139config UID16
1140        bool "Enable 16-bit UID system calls" if EXPERT
1141        depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
1142        default y
1143        help
1144          This enables the legacy 16-bit UID syscall wrappers.
1145
1146config SYSCTL_SYSCALL
1147        bool "Sysctl syscall support" if EXPERT
1148        depends on PROC_SYSCTL
1149        default n
1150        select SYSCTL
1151        ---help---
1152          sys_sysctl uses binary paths that have been found challenging
1153          to properly maintain and use.  The interface in /proc/sys
1154          using paths with ascii names is now the primary path to this
1155          information.
1156
1157          Almost nothing using the binary sysctl interface so if you are
1158          trying to save some space it is probably safe to disable this,
1159          making your kernel marginally smaller.
1160
1161          If unsure say N here.
1162
1163config KALLSYMS
1164         bool "Load all symbols for debugging/ksymoops" if EXPERT
1165         default y
1166         help
1167           Say Y here to let the kernel print out symbolic crash information and
1168           symbolic stack backtraces. This increases the size of the kernel
1169           somewhat, as all symbols have to be loaded into the kernel image.
1170
1171config KALLSYMS_ALL
1172        bool "Include all symbols in kallsyms"
1173        depends on DEBUG_KERNEL && KALLSYMS
1174        help
1175           Normally kallsyms only contains the symbols of functions for nicer
1176           OOPS messages and backtraces (i.e., symbols from the text and inittext
1177           sections). This is sufficient for most cases. And only in very rare
1178           cases (e.g., when a debugger is used) all symbols are required (e.g.,
1179           names of variables from the data sections, etc).
1180
1181           This option makes sure that all symbols are loaded into the kernel
1182           image (i.e., symbols from all sections) in cost of increased kernel
1183           size (depending on the kernel configuration, it may be 300KiB or
1184           something like this).
1185
1186           Say N unless you really need all symbols.
1187
1188config HOTPLUG
1189        bool "Support for hot-pluggable devices" if EXPERT
1190        default y
1191        help
1192          This option is provided for the case where no hotplug or uevent
1193          capabilities is wanted by the kernel.  You should only consider
1194          disabling this option for embedded systems that do not use modules, a
1195          dynamic /dev tree, or dynamic device discovery.  Just say Y.
1196
1197config PRINTK
1198        default y
1199        bool "Enable support for printk" if EXPERT
1200        help
1201          This option enables normal printk support. Removing it
1202          eliminates most of the message strings from the kernel image
1203          and makes the kernel more or less silent. As this makes it
1204          very difficult to diagnose system problems, saying N here is
1205          strongly discouraged.
1206
1207config BUG
1208        bool "BUG() support" if EXPERT
1209        default y
1210        help
1211          Disabling this option eliminates support for BUG and WARN, reducing
1212          the size of your kernel image and potentially quietly ignoring
1213          numerous fatal conditions. You should only consider disabling this
1214          option for embedded systems with no facilities for reporting errors.
1215          Just say Y.
1216
1217config ELF_CORE
1218        default y
1219        bool "Enable ELF core dumps" if EXPERT
1220        help
1221          Enable support for generating core dumps. Disabling saves about 4k.
1222
1223
1224config PCSPKR_PLATFORM
1225        bool "Enable PC-Speaker support" if EXPERT
1226        depends on HAVE_PCSPKR_PLATFORM
1227        select I8253_LOCK
1228        default y
1229        help
1230          This option allows to disable the internal PC-Speaker
1231          support, saving some memory.
1232
1233config HAVE_PCSPKR_PLATFORM
1234        bool
1235
1236config BASE_FULL
1237        default y
1238        bool "Enable full-sized data structures for core" if EXPERT
1239        help
1240          Disabling this option reduces the size of miscellaneous core
1241          kernel data structures. This saves memory on small machines,
1242          but may reduce performance.
1243
1244config FUTEX
1245        bool "Enable futex support" if EXPERT
1246        default y
1247        select RT_MUTEXES
1248        help
1249          Disabling this option will cause the kernel to be built without
1250          support for "fast userspace mutexes".  The resulting kernel may not
1251          run glibc-based applications correctly.
1252
1253config EPOLL
1254        bool "Enable eventpoll support" if EXPERT
1255        default y
1256        select ANON_INODES
1257        help
1258          Disabling this option will cause the kernel to be built without
1259          support for epoll family of system calls.
1260
1261config SIGNALFD
1262        bool "Enable signalfd() system call" if EXPERT
1263        select ANON_INODES
1264        default y
1265        help
1266          Enable the signalfd() system call that allows to receive signals
1267          on a file descriptor.
1268
1269          If unsure, say Y.
1270
1271config TIMERFD
1272        bool "Enable timerfd() system call" if EXPERT
1273        select ANON_INODES
1274        default y
1275        help
1276          Enable the timerfd() system call that allows to receive timer
1277          events on a file descriptor.
1278
1279          If unsure, say Y.
1280
1281config EVENTFD
1282        bool "Enable eventfd() system call" if EXPERT
1283        select ANON_INODES
1284        default y
1285        help
1286          Enable the eventfd() system call that allows to receive both
1287          kernel notification (ie. KAIO) or userspace notifications.
1288
1289          If unsure, say Y.
1290
1291config SHMEM
1292        bool "Use full shmem filesystem" if EXPERT
1293        default y
1294        depends on MMU
1295        help
1296          The shmem is an internal filesystem used to manage shared memory.
1297          It is backed by swap and manages resource limits. It is also exported
1298          to userspace as tmpfs if TMPFS is enabled. Disabling this
1299          option replaces shmem and tmpfs with the much simpler ramfs code,
1300          which may be appropriate on small systems without swap.
1301
1302config AIO
1303        bool "Enable AIO support" if EXPERT
1304        default y
1305        help
1306          This option enables POSIX asynchronous I/O which may by used
1307          by some high performance threaded applications. Disabling
1308          this option saves about 7k.
1309
1310config EMBEDDED
1311        bool "Embedded system"
1312        select EXPERT
1313        help
1314          This option should be enabled if compiling the kernel for
1315          an embedded system so certain expert options are available
1316          for configuration.
1317
1318config HAVE_PERF_EVENTS
1319        bool
1320        help
1321          See tools/perf/design.txt for details.
1322
1323config PERF_USE_VMALLOC
1324        bool
1325        help
1326          See tools/perf/design.txt for details
1327
1328menu "Kernel Performance Events And Counters"
1329
1330config PERF_EVENTS
1331        bool "Kernel performance events and counters"
1332        default y if PROFILING
1333        depends on HAVE_PERF_EVENTS
1334        select ANON_INODES
1335        select IRQ_WORK
1336        help
1337          Enable kernel support for various performance events provided
1338          by software and hardware.
1339
1340          Software events are supported either built-in or via the
1341          use of generic tracepoints.
1342
1343          Most modern CPUs support performance events via performance
1344          counter registers. These registers count the number of certain
1345          types of hw events: such as instructions executed, cachemisses
1346          suffered, or branches mis-predicted - without slowing down the
1347          kernel or applications. These registers can also trigger interrupts
1348          when a threshold number of events have passed - and can thus be
1349          used to profile the code that runs on that CPU.
1350
1351          The Linux Performance Event subsystem provides an abstraction of
1352          these software and hardware event capabilities, available via a
1353          system call and used by the "perf" utility in tools/perf/. It
1354          provides per task and per CPU counters, and it provides event
1355          capabilities on top of those.
1356
1357          Say Y if unsure.
1358
1359config DEBUG_PERF_USE_VMALLOC
1360        default n
1361        bool "Debug: use vmalloc to back perf mmap() buffers"
1362        depends on PERF_EVENTS && DEBUG_KERNEL
1363        select PERF_USE_VMALLOC
1364        help
1365         Use vmalloc memory to back perf mmap() buffers.
1366
1367         Mostly useful for debugging the vmalloc code on platforms
1368         that don't require it.
1369
1370         Say N if unsure.
1371
1372endmenu
1373
1374config VM_EVENT_COUNTERS
1375        default y
1376        bool "Enable VM event counters for /proc/vmstat" if EXPERT
1377        help
1378          VM event counters are needed for event counts to be shown.
1379          This option allows the disabling of the VM event counters
1380          on EXPERT systems.  /proc/vmstat will only show page counts
1381          if VM event counters are disabled.
1382
1383config PCI_QUIRKS
1384        default y
1385        bool "Enable PCI quirk workarounds" if EXPERT
1386        depends on PCI
1387        help
1388          This enables workarounds for various PCI chipset
1389          bugs/quirks. Disable this only if your target machine is
1390          unaffected by PCI quirks.
1391
1392config SLUB_DEBUG
1393        default y
1394        bool "Enable SLUB debugging support" if EXPERT
1395        depends on SLUB && SYSFS
1396        help
1397          SLUB has extensive debug support features. Disabling these can
1398          result in significant savings in code size. This also disables
1399          SLUB sysfs support. /sys/slab will not exist and there will be
1400          no support for cache validation etc.
1401
1402config COMPAT_BRK
1403        bool "Disable heap randomization"
1404        default y
1405        help
1406          Randomizing heap placement makes heap exploits harder, but it
1407          also breaks ancient binaries (including anything libc5 based).
1408          This option changes the bootup default to heap randomization
1409          disabled, and can be overridden at runtime by setting
1410          /proc/sys/kernel/randomize_va_space to 2.
1411
1412          On non-ancient distros (post-2000 ones) N is usually a safe choice.
1413
1414choice
1415        prompt "Choose SLAB allocator"
1416        default SLUB
1417        help
1418           This option allows to select a slab allocator.
1419
1420config SLAB
1421        bool "SLAB"
1422        help
1423          The regular slab allocator that is established and known to work
1424          well in all environments. It organizes cache hot objects in
1425          per cpu and per node queues.
1426
1427config SLUB
1428        bool "SLUB (Unqueued Allocator)"
1429        help
1430           SLUB is a slab allocator that minimizes cache line usage
1431           instead of managing queues of cached objects (SLAB approach).
1432           Per cpu caching is realized using slabs of objects instead
1433           of queues of objects. SLUB can use memory efficiently
1434           and has enhanced diagnostics. SLUB is the default choice for
1435           a slab allocator.
1436
1437config SLOB
1438        depends on EXPERT
1439        bool "SLOB (Simple Allocator)"
1440        help
1441           SLOB replaces the stock allocator with a drastically simpler
1442           allocator. SLOB is generally more space efficient but
1443           does not perform as well on large systems.
1444
1445endchoice
1446
1447config MMAP_ALLOW_UNINITIALIZED
1448        bool "Allow mmapped anonymous memory to be uninitialized"
1449        depends on EXPERT && !MMU
1450        default n
1451        help
1452          Normally, and according to the Linux spec, anonymous memory obtained
1453          from mmap() has it's contents cleared before it is passed to
1454          userspace.  Enabling this config option allows you to request that
1455          mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1456          providing a huge performance boost.  If this option is not enabled,
1457          then the flag will be ignored.
1458
1459          This is taken advantage of by uClibc's malloc(), and also by
1460          ELF-FDPIC binfmt's brk and stack allocator.
1461
1462          Because of the obvious security issues, this option should only be
1463          enabled on embedded devices where you control what is run in
1464          userspace.  Since that isn't generally a problem on no-MMU systems,
1465          it is normally safe to say Y here.
1466
1467          See Documentation/nommu-mmap.txt for more information.
1468
1469config PROFILING
1470        bool "Profiling support"
1471        help
1472          Say Y here to enable the extended profiling support mechanisms used
1473          by profilers such as OProfile.
1474
1475#
1476# Place an empty function call at each tracepoint site. Can be
1477# dynamically changed for a probe function.
1478#
1479config TRACEPOINTS
1480        bool
1481
1482source "arch/Kconfig"
1483
1484endmenu         # General setup
1485
1486config HAVE_GENERIC_DMA_COHERENT
1487        bool
1488        default n
1489
1490config SLABINFO
1491        bool
1492        depends on PROC_FS
1493        depends on SLAB || SLUB_DEBUG
1494        default y
1495
1496config RT_MUTEXES
1497        boolean
1498
1499config BASE_SMALL
1500        int
1501        default 0 if BASE_FULL
1502        default 1 if !BASE_FULL
1503
1504menuconfig MODULES
1505        bool "Enable loadable module support"
1506        help
1507          Kernel modules are small pieces of compiled code which can
1508          be inserted in the running kernel, rather than being
1509          permanently built into the kernel.  You use the "modprobe"
1510          tool to add (and sometimes remove) them.  If you say Y here,
1511          many parts of the kernel can be built as modules (by
1512          answering M instead of Y where indicated): this is most
1513          useful for infrequently used options which are not required
1514          for booting.  For more information, see the man pages for
1515          modprobe, lsmod, modinfo, insmod and rmmod.
1516
1517          If you say Y here, you will need to run "make
1518          modules_install" to put the modules under /lib/modules/
1519          where modprobe can find them (you may need to be root to do
1520          this).
1521
1522          If unsure, say Y.
1523
1524if MODULES
1525
1526config MODULE_FORCE_LOAD
1527        bool "Forced module loading"
1528        default n
1529        help
1530          Allow loading of modules without version information (ie. modprobe
1531          --force).  Forced module loading sets the 'F' (forced) taint flag and
1532          is usually a really bad idea.
1533
1534config MODULE_UNLOAD
1535        bool "Module unloading"
1536        help
1537          Without this option you will not be able to unload any
1538          modules (note that some modules may not be unloadable
1539          anyway), which makes your kernel smaller, faster
1540          and simpler.  If unsure, say Y.
1541
1542config MODULE_FORCE_UNLOAD
1543        bool "Forced module unloading"
1544        depends on MODULE_UNLOAD && EXPERIMENTAL
1545        help
1546          This option allows you to force a module to unload, even if the
1547          kernel believes it is unsafe: the kernel will remove the module
1548          without waiting for anyone to stop using it (using the -f option to
1549          rmmod).  This is mainly for kernel developers and desperate users.
1550          If unsure, say N.
1551
1552config MODVERSIONS
1553        bool "Module versioning support"
1554        help
1555          Usually, you have to use modules compiled with your kernel.
1556          Saying Y here makes it sometimes possible to use modules
1557          compiled for different kernels, by adding enough information
1558          to the modules to (hopefully) spot any changes which would
1559          make them incompatible with the kernel you are running.  If
1560          unsure, say N.
1561
1562config MODULE_SRCVERSION_ALL
1563        bool "Source checksum for all modules"
1564        help
1565          Modules which contain a MODULE_VERSION get an extra "srcversion"
1566          field inserted into their modinfo section, which contains a
1567          sum of the source files which made it.  This helps maintainers
1568          see exactly which source was used to build a module (since
1569          others sometimes change the module source without updating
1570          the version).  With this option, such a "srcversion" field
1571          will be created for all modules.  If unsure, say N.
1572
1573endif # MODULES
1574
1575config INIT_ALL_POSSIBLE
1576        bool
1577        help
1578          Back when each arch used to define their own cpu_online_mask and
1579          cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1580          with all 1s, and others with all 0s.  When they were centralised,
1581          it was better to provide this option than to break all the archs
1582          and have several arch maintainers pursuing me down dark alleys.
1583
1584config STOP_MACHINE
1585        bool
1586        default y
1587        depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1588        help
1589          Need stop_machine() primitive.
1590
1591source "block/Kconfig"
1592
1593config PREEMPT_NOTIFIERS
1594        bool
1595
1596config PADATA
1597        depends on SMP
1598        bool
1599
1600source "kernel/Kconfig.locks"
1601
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