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  56          drivers that have been replaced by something else, and/or are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 && AEABI && !OABI_COMPAT))
 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 MEMCG
 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 MEMCG_SWAP
 713        bool "Memory Resource Controller Swap Extension"
 714        depends on MEMCG && 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 MEMCG_SWAP_ENABLED
 730        bool "Memory Resource Controller Swap Extension enabled by default"
 731        depends on MEMCG_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 MEMCG_KMEM
 743        bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
 744        depends on MEMCG && 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_HUGETLB
 755        bool "HugeTLB Resource Controller for Control Groups"
 756        depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
 757        default n
 758        help
 759          Provides a cgroup Resource Controller for HugeTLB pages.
 760          When you enable this, you can put a per cgroup limit on HugeTLB usage.
 761          The limit is enforced during page fault. Since HugeTLB doesn't
 762          support page reclaim, enforcing the limit at page fault time implies
 763          that, the application will get SIGBUS signal if it tries to access
 764          HugeTLB pages beyond its limit. This requires the application to know
 765          beforehand how much HugeTLB pages it would require for its use. The
 766          control group is tracked in the third page lru pointer. This means
 767          that we cannot use the controller with huge page less than 3 pages.
 768
 769config CGROUP_PERF
 770        bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
 771        depends on PERF_EVENTS && CGROUPS
 772        help
 773          This option extends the per-cpu mode to restrict monitoring to
 774          threads which belong to the cgroup specified and run on the
 775          designated cpu.
 776
 777          Say N if unsure.
 778
 779menuconfig CGROUP_SCHED
 780        bool "Group CPU scheduler"
 781        default n
 782        help
 783          This feature lets CPU scheduler recognize task groups and control CPU
 784          bandwidth allocation to such task groups. It uses cgroups to group
 785          tasks.
 786
 787if CGROUP_SCHED
 788config FAIR_GROUP_SCHED
 789        bool "Group scheduling for SCHED_OTHER"
 790        depends on CGROUP_SCHED
 791        default CGROUP_SCHED
 792
 793config CFS_BANDWIDTH
 794        bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
 795        depends on EXPERIMENTAL
 796        depends on FAIR_GROUP_SCHED
 797        default n
 798        help
 799          This option allows users to define CPU bandwidth rates (limits) for
 800          tasks running within the fair group scheduler.  Groups with no limit
 801          set are considered to be unconstrained and will run with no
 802          restriction.
 803          See tip/Documentation/scheduler/sched-bwc.txt for more information.
 804
 805config RT_GROUP_SCHED
 806        bool "Group scheduling for SCHED_RR/FIFO"
 807        depends on EXPERIMENTAL
 808        depends on CGROUP_SCHED
 809        default n
 810        help
 811          This feature lets you explicitly allocate real CPU bandwidth
 812          to task groups. If enabled, it will also make it impossible to
 813          schedule realtime tasks for non-root users until you allocate
 814          realtime bandwidth for them.
 815          See Documentation/scheduler/sched-rt-group.txt for more information.
 816
 817endif #CGROUP_SCHED
 818
 819config BLK_CGROUP
 820        bool "Block IO controller"
 821        depends on BLOCK
 822        default n
 823        ---help---
 824        Generic block IO controller cgroup interface. This is the common
 825        cgroup interface which should be used by various IO controlling
 826        policies.
 827
 828        Currently, CFQ IO scheduler uses it to recognize task groups and
 829        control disk bandwidth allocation (proportional time slice allocation)
 830        to such task groups. It is also used by bio throttling logic in
 831        block layer to implement upper limit in IO rates on a device.
 832
 833        This option only enables generic Block IO controller infrastructure.
 834        One needs to also enable actual IO controlling logic/policy. For
 835        enabling proportional weight division of disk bandwidth in CFQ, set
 836        CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
 837        CONFIG_BLK_DEV_THROTTLING=y.
 838
 839        See Documentation/cgroups/blkio-controller.txt for more information.
 840
 841config DEBUG_BLK_CGROUP
 842        bool "Enable Block IO controller debugging"
 843        depends on BLK_CGROUP
 844        default n
 845        ---help---
 846        Enable some debugging help. Currently it exports additional stat
 847        files in a cgroup which can be useful for debugging.
 848
 849endif # CGROUPS
 850
 851config CHECKPOINT_RESTORE
 852        bool "Checkpoint/restore support" if EXPERT
 853        default n
 854        help
 855          Enables additional kernel features in a sake of checkpoint/restore.
 856          In particular it adds auxiliary prctl codes to setup process text,
 857          data and heap segment sizes, and a few additional /proc filesystem
 858          entries.
 859
 860          If unsure, say N here.
 861
 862menuconfig NAMESPACES
 863        bool "Namespaces support" if EXPERT
 864        default !EXPERT
 865        help
 866          Provides the way to make tasks work with different objects using
 867          the same id. For example same IPC id may refer to different objects
 868          or same user id or pid may refer to different tasks when used in
 869          different namespaces.
 870
 871if NAMESPACES
 872
 873config UTS_NS
 874        bool "UTS namespace"
 875        default y
 876        help
 877          In this namespace tasks see different info provided with the
 878          uname() system call
 879
 880config IPC_NS
 881        bool "IPC namespace"
 882        depends on (SYSVIPC || POSIX_MQUEUE)
 883        default y
 884        help
 885          In this namespace tasks work with IPC ids which correspond to
 886          different IPC objects in different namespaces.
 887
 888config USER_NS
 889        bool "User namespace (EXPERIMENTAL)"
 890        depends on EXPERIMENTAL
 891        depends on UIDGID_CONVERTED
 892        select UIDGID_STRICT_TYPE_CHECKS
 893
 894        default n
 895        help
 896          This allows containers, i.e. vservers, to use user namespaces
 897          to provide different user info for different servers.
 898          If unsure, say N.
 899
 900config PID_NS
 901        bool "PID Namespaces"
 902        default y
 903        help
 904          Support process id namespaces.  This allows having multiple
 905          processes with the same pid as long as they are in different
 906          pid namespaces.  This is a building block of containers.
 907
 908config NET_NS
 909        bool "Network namespace"
 910        depends on NET
 911        default y
 912        help
 913          Allow user space to create what appear to be multiple instances
 914          of the network stack.
 915
 916endif # NAMESPACES
 917
 918config UIDGID_CONVERTED
 919        # True if all of the selected software conmponents are known
 920        # to have uid_t and gid_t converted to kuid_t and kgid_t
 921        # where appropriate and are otherwise safe to use with
 922        # the user namespace.
 923        bool
 924        default y
 925
 926        # List of kernel pieces that need user namespace work
 927        # Features
 928        depends on SYSVIPC = n
 929        depends on IMA = n
 930        depends on EVM = n
 931        depends on KEYS = n
 932        depends on AUDIT = n
 933        depends on AUDITSYSCALL = n
 934        depends on TASKSTATS = n
 935        depends on TRACING = n
 936        depends on FS_POSIX_ACL = n
 937        depends on QUOTA = n
 938        depends on QUOTACTL = n
 939        depends on DEBUG_CREDENTIALS = n
 940        depends on BSD_PROCESS_ACCT = n
 941        depends on DRM = n
 942        depends on PROC_EVENTS = n
 943
 944        # Networking
 945        depends on NET = n
 946        depends on NET_9P = n
 947        depends on IPX = n
 948        depends on PHONET = n
 949        depends on NET_CLS_FLOW = n
 950        depends on NETFILTER_XT_MATCH_OWNER = n
 951        depends on NETFILTER_XT_MATCH_RECENT = n
 952        depends on NETFILTER_XT_TARGET_LOG = n
 953        depends on NETFILTER_NETLINK_LOG = n
 954        depends on INET = n
 955        depends on IPV6 = n
 956        depends on IP_SCTP = n
 957        depends on AF_RXRPC = n
 958        depends on LLC2 = n
 959        depends on NET_KEY = n
 960        depends on INET_DIAG = n
 961        depends on DNS_RESOLVER = n
 962        depends on AX25 = n
 963        depends on ATALK = n
 964
 965        # Filesystems
 966        depends on USB_DEVICEFS = n
 967        depends on USB_GADGETFS = n
 968        depends on USB_FUNCTIONFS = n
 969        depends on DEVTMPFS = n
 970        depends on XENFS = n
 971
 972        depends on 9P_FS = n
 973        depends on ADFS_FS = n
 974        depends on AFFS_FS = n
 975        depends on AFS_FS = n
 976        depends on AUTOFS4_FS = n
 977        depends on BEFS_FS = n
 978        depends on BFS_FS = n
 979        depends on BTRFS_FS = n
 980        depends on CEPH_FS = n
 981        depends on CIFS = n
 982        depends on CODA_FS = n
 983        depends on CONFIGFS_FS = n
 984        depends on CRAMFS = n
 985        depends on DEBUG_FS = n
 986        depends on ECRYPT_FS = n
 987        depends on EFS_FS = n
 988        depends on EXOFS_FS = n
 989        depends on FAT_FS = n
 990        depends on FUSE_FS = n
 991        depends on GFS2_FS = n
 992        depends on HFS_FS = n
 993        depends on HFSPLUS_FS = n
 994        depends on HPFS_FS = n
 995        depends on HUGETLBFS = n
 996        depends on ISO9660_FS = n
 997        depends on JFFS2_FS = n
 998        depends on JFS_FS = n
 999        depends on LOGFS = n
1000        depends on MINIX_FS = n
1001        depends on NCP_FS = n
1002        depends on NFSD = n
1003        depends on NFS_FS = n
1004        depends on NILFS2_FS = n
1005        depends on NTFS_FS = n
1006        depends on OCFS2_FS = n
1007        depends on OMFS_FS = n
1008        depends on QNX4FS_FS = n
1009        depends on QNX6FS_FS = n
1010        depends on REISERFS_FS = n
1011        depends on SQUASHFS = n
1012        depends on SYSV_FS = n
1013        depends on UBIFS_FS = n
1014        depends on UDF_FS = n
1015        depends on UFS_FS = n
1016        depends on VXFS_FS = n
1017        depends on XFS_FS = n
1018
1019        depends on !UML || HOSTFS = n
1020
1021        # The rare drivers that won't build
1022        depends on AIRO = n
1023        depends on AIRO_CS = n
1024        depends on TUN = n
1025        depends on INFINIBAND_QIB = n
1026        depends on BLK_DEV_LOOP = n
1027        depends on ANDROID_BINDER_IPC = n
1028
1029        # Security modules
1030        depends on SECURITY_TOMOYO = n
1031        depends on SECURITY_APPARMOR = n
1032
1033config UIDGID_STRICT_TYPE_CHECKS
1034        bool "Require conversions between uid/gids and their internal representation"
1035        depends on UIDGID_CONVERTED
1036        default n
1037        help
1038         While the nececessary conversions are being added to all subsystems this option allows
1039         the code to continue to build for unconverted subsystems.
1040
1041         Say Y here if you want the strict type checking enabled
1042
1043config SCHED_AUTOGROUP
1044        bool "Automatic process group scheduling"
1045        select EVENTFD
1046        select CGROUPS
1047        select CGROUP_SCHED
1048        select FAIR_GROUP_SCHED
1049        help
1050          This option optimizes the scheduler for common desktop workloads by
1051          automatically creating and populating task groups.  This separation
1052          of workloads isolates aggressive CPU burners (like build jobs) from
1053          desktop applications.  Task group autogeneration is currently based
1054          upon task session.
1055
1056config MM_OWNER
1057        bool
1058
1059config SYSFS_DEPRECATED
1060        bool "Enable deprecated sysfs features to support old userspace tools"
1061        depends on SYSFS
1062        default n
1063        help
1064          This option adds code that switches the layout of the "block" class
1065          devices, to not show up in /sys/class/block/, but only in
1066          /sys/block/.
1067
1068          This switch is only active when the sysfs.deprecated=1 boot option is
1069          passed or the SYSFS_DEPRECATED_V2 option is set.
1070
1071          This option allows new kernels to run on old distributions and tools,
1072          which might get confused by /sys/class/block/. Since 2007/2008 all
1073          major distributions and tools handle this just fine.
1074
1075          Recent distributions and userspace tools after 2009/2010 depend on
1076          the existence of /sys/class/block/, and will not work with this
1077          option enabled.
1078
1079          Only if you are using a new kernel on an old distribution, you might
1080          need to say Y here.
1081
1082config SYSFS_DEPRECATED_V2
1083        bool "Enable deprecated sysfs features by default"
1084        default n
1085        depends on SYSFS
1086        depends on SYSFS_DEPRECATED
1087        help
1088          Enable deprecated sysfs by default.
1089
1090          See the CONFIG_SYSFS_DEPRECATED option for more details about this
1091          option.
1092
1093          Only if you are using a new kernel on an old distribution, you might
1094          need to say Y here. Even then, odds are you would not need it
1095          enabled, you can always pass the boot option if absolutely necessary.
1096
1097config RELAY
1098        bool "Kernel->user space relay support (formerly relayfs)"
1099        help
1100          This option enables support for relay interface support in
1101          certain file systems (such as debugfs).
1102          It is designed to provide an efficient mechanism for tools and
1103          facilities to relay large amounts of data from kernel space to
1104          user space.
1105
1106          If unsure, say N.
1107
1108config BLK_DEV_INITRD
1109        bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1110        depends on BROKEN || !FRV
1111        help
1112          The initial RAM filesystem is a ramfs which is loaded by the
1113          boot loader (loadlin or lilo) and that is mounted as root
1114          before the normal boot procedure. It is typically used to
1115          load modules needed to mount the "real" root file system,
1116          etc. See <file:Documentation/initrd.txt> for details.
1117
1118          If RAM disk support (BLK_DEV_RAM) is also included, this
1119          also enables initial RAM disk (initrd) support and adds
1120          15 Kbytes (more on some other architectures) to the kernel size.
1121
1122          If unsure say Y.
1123
1124if BLK_DEV_INITRD
1125
1126source "usr/Kconfig"
1127
1128endif
1129
1130config CC_OPTIMIZE_FOR_SIZE
1131        bool "Optimize for size"
1132        help
1133          Enabling this option will pass "-Os" instead of "-O2" to gcc
1134          resulting in a smaller kernel.
1135
1136          If unsure, say Y.
1137
1138config SYSCTL
1139        bool
1140
1141config ANON_INODES
1142        bool
1143
1144menuconfig EXPERT
1145        bool "Configure standard kernel features (expert users)"
1146        # Unhide debug options, to make the on-by-default options visible
1147        select DEBUG_KERNEL
1148        help
1149          This option allows certain base kernel options and settings
1150          to be disabled or tweaked. This is for specialized
1151          environments which can tolerate a "non-standard" kernel.
1152          Only use this if you really know what you are doing.
1153
1154config UID16
1155        bool "Enable 16-bit UID system calls" if EXPERT
1156        depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
1157        default y
1158        help
1159          This enables the legacy 16-bit UID syscall wrappers.
1160
1161config SYSCTL_SYSCALL
1162        bool "Sysctl syscall support" if EXPERT
1163        depends on PROC_SYSCTL
1164        default n
1165        select SYSCTL
1166        ---help---
1167          sys_sysctl uses binary paths that have been found challenging
1168          to properly maintain and use.  The interface in /proc/sys
1169          using paths with ascii names is now the primary path to this
1170          information.
1171
1172          Almost nothing using the binary sysctl interface so if you are
1173          trying to save some space it is probably safe to disable this,
1174          making your kernel marginally smaller.
1175
1176          If unsure say N here.
1177
1178config KALLSYMS
1179         bool "Load all symbols for debugging/ksymoops" if EXPERT
1180         default y
1181         help
1182           Say Y here to let the kernel print out symbolic crash information and
1183           symbolic stack backtraces. This increases the size of the kernel
1184           somewhat, as all symbols have to be loaded into the kernel image.
1185
1186config KALLSYMS_ALL
1187        bool "Include all symbols in kallsyms"
1188        depends on DEBUG_KERNEL && KALLSYMS
1189        help
1190           Normally kallsyms only contains the symbols of functions for nicer
1191           OOPS messages and backtraces (i.e., symbols from the text and inittext
1192           sections). This is sufficient for most cases. And only in very rare
1193           cases (e.g., when a debugger is used) all symbols are required (e.g.,
1194           names of variables from the data sections, etc).
1195
1196           This option makes sure that all symbols are loaded into the kernel
1197           image (i.e., symbols from all sections) in cost of increased kernel
1198           size (depending on the kernel configuration, it may be 300KiB or
1199           something like this).
1200
1201           Say N unless you really need all symbols.
1202
1203config HOTPLUG
1204        bool "Support for hot-pluggable devices" if EXPERT
1205        default y
1206        help
1207          This option is provided for the case where no hotplug or uevent
1208          capabilities is wanted by the kernel.  You should only consider
1209          disabling this option for embedded systems that do not use modules, a
1210          dynamic /dev tree, or dynamic device discovery.  Just say Y.
1211
1212config PRINTK
1213        default y
1214        bool "Enable support for printk" if EXPERT
1215        help
1216          This option enables normal printk support. Removing it
1217          eliminates most of the message strings from the kernel image
1218          and makes the kernel more or less silent. As this makes it
1219          very difficult to diagnose system problems, saying N here is
1220          strongly discouraged.
1221
1222config BUG
1223        bool "BUG() support" if EXPERT
1224        default y
1225        help
1226          Disabling this option eliminates support for BUG and WARN, reducing
1227          the size of your kernel image and potentially quietly ignoring
1228          numerous fatal conditions. You should only consider disabling this
1229          option for embedded systems with no facilities for reporting errors.
1230          Just say Y.
1231
1232config ELF_CORE
1233        default y
1234        bool "Enable ELF core dumps" if EXPERT
1235        help
1236          Enable support for generating core dumps. Disabling saves about 4k.
1237
1238
1239config PCSPKR_PLATFORM
1240        bool "Enable PC-Speaker support" if EXPERT
1241        depends on HAVE_PCSPKR_PLATFORM
1242        select I8253_LOCK
1243        default y
1244        help
1245          This option allows to disable the internal PC-Speaker
1246          support, saving some memory.
1247
1248config HAVE_PCSPKR_PLATFORM
1249        bool
1250
1251config BASE_FULL
1252        default y
1253        bool "Enable full-sized data structures for core" if EXPERT
1254        help
1255          Disabling this option reduces the size of miscellaneous core
1256          kernel data structures. This saves memory on small machines,
1257          but may reduce performance.
1258
1259config FUTEX
1260        bool "Enable futex support" if EXPERT
1261        default y
1262        select RT_MUTEXES
1263        help
1264          Disabling this option will cause the kernel to be built without
1265          support for "fast userspace mutexes".  The resulting kernel may not
1266          run glibc-based applications correctly.
1267
1268config EPOLL
1269        bool "Enable eventpoll support" if EXPERT
1270        default y
1271        select ANON_INODES
1272        help
1273          Disabling this option will cause the kernel to be built without
1274          support for epoll family of system calls.
1275
1276config SIGNALFD
1277        bool "Enable signalfd() system call" if EXPERT
1278        select ANON_INODES
1279        default y
1280        help
1281          Enable the signalfd() system call that allows to receive signals
1282          on a file descriptor.
1283
1284          If unsure, say Y.
1285
1286config TIMERFD
1287        bool "Enable timerfd() system call" if EXPERT
1288        select ANON_INODES
1289        default y
1290        help
1291          Enable the timerfd() system call that allows to receive timer
1292          events on a file descriptor.
1293
1294          If unsure, say Y.
1295
1296config EVENTFD
1297        bool "Enable eventfd() system call" if EXPERT
1298        select ANON_INODES
1299        default y
1300        help
1301          Enable the eventfd() system call that allows to receive both
1302          kernel notification (ie. KAIO) or userspace notifications.
1303
1304          If unsure, say Y.
1305
1306config SHMEM
1307        bool "Use full shmem filesystem" if EXPERT
1308        default y
1309        depends on MMU
1310        help
1311          The shmem is an internal filesystem used to manage shared memory.
1312          It is backed by swap and manages resource limits. It is also exported
1313          to userspace as tmpfs if TMPFS is enabled. Disabling this
1314          option replaces shmem and tmpfs with the much simpler ramfs code,
1315          which may be appropriate on small systems without swap.
1316
1317config AIO
1318        bool "Enable AIO support" if EXPERT
1319        default y
1320        help
1321          This option enables POSIX asynchronous I/O which may by used
1322          by some high performance threaded applications. Disabling
1323          this option saves about 7k.
1324
1325config EMBEDDED
1326        bool "Embedded system"
1327        select EXPERT
1328        help
1329          This option should be enabled if compiling the kernel for
1330          an embedded system so certain expert options are available
1331          for configuration.
1332
1333config HAVE_PERF_EVENTS
1334        bool
1335        help
1336          See tools/perf/design.txt for details.
1337
1338config PERF_USE_VMALLOC
1339        bool
1340        help
1341          See tools/perf/design.txt for details
1342
1343menu "Kernel Performance Events And Counters"
1344
1345config PERF_EVENTS
1346        bool "Kernel performance events and counters"
1347        default y if PROFILING
1348        depends on HAVE_PERF_EVENTS
1349        select ANON_INODES
1350        select IRQ_WORK
1351        help
1352          Enable kernel support for various performance events provided
1353          by software and hardware.
1354
1355          Software events are supported either built-in or via the
1356          use of generic tracepoints.
1357
1358          Most modern CPUs support performance events via performance
1359          counter registers. These registers count the number of certain
1360          types of hw events: such as instructions executed, cachemisses
1361          suffered, or branches mis-predicted - without slowing down the
1362          kernel or applications. These registers can also trigger interrupts
1363          when a threshold number of events have passed - and can thus be
1364          used to profile the code that runs on that CPU.
1365
1366          The Linux Performance Event subsystem provides an abstraction of
1367          these software and hardware event capabilities, available via a
1368          system call and used by the "perf" utility in tools/perf/. It
1369          provides per task and per CPU counters, and it provides event
1370          capabilities on top of those.
1371
1372          Say Y if unsure.
1373
1374config DEBUG_PERF_USE_VMALLOC
1375        default n
1376        bool "Debug: use vmalloc to back perf mmap() buffers"
1377        depends on PERF_EVENTS && DEBUG_KERNEL
1378        select PERF_USE_VMALLOC
1379        help
1380         Use vmalloc memory to back perf mmap() buffers.
1381
1382         Mostly useful for debugging the vmalloc code on platforms
1383         that don't require it.
1384
1385         Say N if unsure.
1386
1387endmenu
1388
1389config VM_EVENT_COUNTERS
1390        default y
1391        bool "Enable VM event counters for /proc/vmstat" if EXPERT
1392        help
1393          VM event counters are needed for event counts to be shown.
1394          This option allows the disabling of the VM event counters
1395          on EXPERT systems.  /proc/vmstat will only show page counts
1396          if VM event counters are disabled.
1397
1398config PCI_QUIRKS
1399        default y
1400        bool "Enable PCI quirk workarounds" if EXPERT
1401        depends on PCI
1402        help
1403          This enables workarounds for various PCI chipset
1404          bugs/quirks. Disable this only if your target machine is
1405          unaffected by PCI quirks.
1406
1407config SLUB_DEBUG
1408        default y
1409        bool "Enable SLUB debugging support" if EXPERT
1410        depends on SLUB && SYSFS
1411        help
1412          SLUB has extensive debug support features. Disabling these can
1413          result in significant savings in code size. This also disables
1414          SLUB sysfs support. /sys/slab will not exist and there will be
1415          no support for cache validation etc.
1416
1417config COMPAT_BRK
1418        bool "Disable heap randomization"
1419        default y
1420        help
1421          Randomizing heap placement makes heap exploits harder, but it
1422          also breaks ancient binaries (including anything libc5 based).
1423          This option changes the bootup default to heap randomization
1424          disabled, and can be overridden at runtime by setting
1425          /proc/sys/kernel/randomize_va_space to 2.
1426
1427          On non-ancient distros (post-2000 ones) N is usually a safe choice.
1428
1429choice
1430        prompt "Choose SLAB allocator"
1431        default SLUB
1432        help
1433           This option allows to select a slab allocator.
1434
1435config SLAB
1436        bool "SLAB"
1437        help
1438          The regular slab allocator that is established and known to work
1439          well in all environments. It organizes cache hot objects in
1440          per cpu and per node queues.
1441
1442config SLUB
1443        bool "SLUB (Unqueued Allocator)"
1444        help
1445           SLUB is a slab allocator that minimizes cache line usage
1446           instead of managing queues of cached objects (SLAB approach).
1447           Per cpu caching is realized using slabs of objects instead
1448           of queues of objects. SLUB can use memory efficiently
1449           and has enhanced diagnostics. SLUB is the default choice for
1450           a slab allocator.
1451
1452config SLOB
1453        depends on EXPERT
1454        bool "SLOB (Simple Allocator)"
1455        help
1456           SLOB replaces the stock allocator with a drastically simpler
1457           allocator. SLOB is generally more space efficient but
1458           does not perform as well on large systems.
1459
1460endchoice
1461
1462config MMAP_ALLOW_UNINITIALIZED
1463        bool "Allow mmapped anonymous memory to be uninitialized"
1464        depends on EXPERT && !MMU
1465        default n
1466        help
1467          Normally, and according to the Linux spec, anonymous memory obtained
1468          from mmap() has it's contents cleared before it is passed to
1469          userspace.  Enabling this config option allows you to request that
1470          mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1471          providing a huge performance boost.  If this option is not enabled,
1472          then the flag will be ignored.
1473
1474          This is taken advantage of by uClibc's malloc(), and also by
1475          ELF-FDPIC binfmt's brk and stack allocator.
1476
1477          Because of the obvious security issues, this option should only be
1478          enabled on embedded devices where you control what is run in
1479          userspace.  Since that isn't generally a problem on no-MMU systems,
1480          it is normally safe to say Y here.
1481
1482          See Documentation/nommu-mmap.txt for more information.
1483
1484config PROFILING
1485        bool "Profiling support"
1486        help
1487          Say Y here to enable the extended profiling support mechanisms used
1488          by profilers such as OProfile.
1489
1490#
1491# Place an empty function call at each tracepoint site. Can be
1492# dynamically changed for a probe function.
1493#
1494config TRACEPOINTS
1495        bool
1496
1497source "arch/Kconfig"
1498
1499endmenu         # General setup
1500
1501config HAVE_GENERIC_DMA_COHERENT
1502        bool
1503        default n
1504
1505config SLABINFO
1506        bool
1507        depends on PROC_FS
1508        depends on SLAB || SLUB_DEBUG
1509        default y
1510
1511config RT_MUTEXES
1512        boolean
1513
1514config BASE_SMALL
1515        int
1516        default 0 if BASE_FULL
1517        default 1 if !BASE_FULL
1518
1519menuconfig MODULES
1520        bool "Enable loadable module support"
1521        help
1522          Kernel modules are small pieces of compiled code which can
1523          be inserted in the running kernel, rather than being
1524          permanently built into the kernel.  You use the "modprobe"
1525          tool to add (and sometimes remove) them.  If you say Y here,
1526          many parts of the kernel can be built as modules (by
1527          answering M instead of Y where indicated): this is most
1528          useful for infrequently used options which are not required
1529          for booting.  For more information, see the man pages for
1530          modprobe, lsmod, modinfo, insmod and rmmod.
1531
1532          If you say Y here, you will need to run "make
1533          modules_install" to put the modules under /lib/modules/
1534          where modprobe can find them (you may need to be root to do
1535          this).
1536
1537          If unsure, say Y.
1538
1539if MODULES
1540
1541config MODULE_FORCE_LOAD
1542        bool "Forced module loading"
1543        default n
1544        help
1545          Allow loading of modules without version information (ie. modprobe
1546          --force).  Forced module loading sets the 'F' (forced) taint flag and
1547          is usually a really bad idea.
1548
1549config MODULE_UNLOAD
1550        bool "Module unloading"
1551        help
1552          Without this option you will not be able to unload any
1553          modules (note that some modules may not be unloadable
1554          anyway), which makes your kernel smaller, faster
1555          and simpler.  If unsure, say Y.
1556
1557config MODULE_FORCE_UNLOAD
1558        bool "Forced module unloading"
1559        depends on MODULE_UNLOAD && EXPERIMENTAL
1560        help
1561          This option allows you to force a module to unload, even if the
1562          kernel believes it is unsafe: the kernel will remove the module
1563          without waiting for anyone to stop using it (using the -f option to
1564          rmmod).  This is mainly for kernel developers and desperate users.
1565          If unsure, say N.
1566
1567config MODVERSIONS
1568        bool "Module versioning support"
1569        help
1570          Usually, you have to use modules compiled with your kernel.
1571          Saying Y here makes it sometimes possible to use modules
1572          compiled for different kernels, by adding enough information
1573          to the modules to (hopefully) spot any changes which would
1574          make them incompatible with the kernel you are running.  If
1575          unsure, say N.
1576
1577config MODULE_SRCVERSION_ALL
1578        bool "Source checksum for all modules"
1579        help
1580          Modules which contain a MODULE_VERSION get an extra "srcversion"
1581          field inserted into their modinfo section, which contains a
1582          sum of the source files which made it.  This helps maintainers
1583          see exactly which source was used to build a module (since
1584          others sometimes change the module source without updating
1585          the version).  With this option, such a "srcversion" field
1586          will be created for all modules.  If unsure, say N.
1587
1588endif # MODULES
1589
1590config INIT_ALL_POSSIBLE
1591        bool
1592        help
1593          Back when each arch used to define their own cpu_online_mask and
1594          cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1595          with all 1s, and others with all 0s.  When they were centralised,
1596          it was better to provide this option than to break all the archs
1597          and have several arch maintainers pursuing me down dark alleys.
1598
1599config STOP_MACHINE
1600        bool
1601        default y
1602        depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1603        help
1604          Need stop_machine() primitive.
1605
1606source "block/Kconfig"
1607
1608config PREEMPT_NOTIFIERS
1609        bool
1610
1611config PADATA
1612        depends on SMP
1613        bool
1614
1615source "kernel/Kconfig.locks"
1616
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