init/Kconfig

   1 config ARCH
   2         string
   3         option env="ARCH"
   4
   5 config KERNELVERSION
   6         string
   7         option env="KERNELVERSION"
   8
   9 config DEFCONFIG_LIST
  10         string
  11         depends on !UML
  12         option defconfig_list
  13         default "/lib/modules/$UNAME_RELEASE/.config"
  14         default "/etc/kernel-config"
  15         default "/boot/config-$UNAME_RELEASE"
  16         default "$ARCH_DEFCONFIG"
  17         default "arch/$ARCH/defconfig"
  18
  19 config CONSTRUCTORS
  20         bool
  21         depends on !UML
  22
  23 config HAVE_IRQ_WORK
  24         bool
  25
  26 config IRQ_WORK
  27         bool
  28         depends on HAVE_IRQ_WORK
  29
  30 config BUILDTIME_EXTABLE_SORT
  31         bool
  32
  33 menu "General setup"
  34
  35 config 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  56           drivers that have been replaced by something else, and/or are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
  66 config BROKEN
  67         bool
  68
  69 config BROKEN_ON_SMP
  70         bool
  71         depends on BROKEN || !SMP
  72         default y
  73
  74 config 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
  83 config 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
  91 config 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
 101 config 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
 121 config HAVE_KERNEL_GZIP
 122         bool
 123
 124 config HAVE_KERNEL_BZIP2
 125         bool
 126
 127 config HAVE_KERNEL_LZMA
 128         bool
 129
 130 config HAVE_KERNEL_XZ
 131         bool
 132
 133 config HAVE_KERNEL_LZO
 134         bool
 135
 136 choice
 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
 158 config 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
 165 config 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
 175 config 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
 183 config 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
 198 config 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
 206 endchoice
 207
 208 config 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
 217 config 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
 227 config 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
 242 config SYSVIPC_SYSCTL
 243         bool
 244         depends on SYSVIPC
 245         depends on SYSCTL
 246         default y
 247
 248 config 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
 264 config POSIX_MQUEUE_SYSCTL
 265         bool
 266         depends on POSIX_MQUEUE
 267         depends on SYSCTL
 268         default y
 269
 270 config 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
 283 config 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
 295 config 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
 307 config 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
 320 config 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
 331 config 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
 340 config 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
 349 config 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
 358 config 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
 367 config AUDIT_WATCH
 368         def_bool y
 369         depends on AUDITSYSCALL
 370         select FSNOTIFY
 371
 372 config AUDIT_TREE
 373         def_bool y
 374         depends on AUDITSYSCALL
 375         select FSNOTIFY
 376
 377 config 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
 391 source "kernel/irq/Kconfig"
 392 source "kernel/time/Kconfig"
 393
 394 menu "RCU Subsystem"
 395
 396 choice
 397         prompt "RCU Implementation"
 398         default TREE_RCU
 399
 400 config 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
 409 config 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
 419 config 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
 428 config 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
 436 endchoice
 437
 438 config 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
 444 config 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
 464 config 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
 491 config 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
 505 config 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
 521 config 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
 529 config 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
 542 config 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
 570 config 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
 583 endmenu # "RCU Subsystem"
 584
 585 config 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
 597 config 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
 604 config 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 #
 621 config HAVE_UNSTABLE_SCHED_CLOCK
 622         bool
 623
 624 menuconfig 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
 638 if CGROUPS
 639
 640 config 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
 650 config CGROUP_FREEZER
 651         bool "Freezer cgroup subsystem"
 652         help
 653           Provides a way to freeze and unfreeze all tasks in a
 654           cgroup.
 655
 656 config 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
 662 config 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
 672 config PROC_PID_CPUSET
 673         bool "Include legacy /proc/<pid>/cpuset file"
 674         depends on CPUSETS
 675         default y
 676
 677 config 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
 683 config RESOURCE_COUNTERS
 684         bool "Resource counters"
 685         help
 686           This option enables controller independent resource accounting
 687           infrastructure that works with cgroups.
 688
 689 config 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
 712 config 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.
 729 config 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).
 742 config 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
 754 config 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
 769 config 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
 779 menuconfig 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
 787 if CGROUP_SCHED
 788 config FAIR_GROUP_SCHED
 789         bool "Group scheduling for SCHED_OTHER"
 790         depends on CGROUP_SCHED
 791         default CGROUP_SCHED
 792
 793 config 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
 805 config 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
 817 endif #CGROUP_SCHED
 818
 819 config 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
 841 config 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
 849 endif # CGROUPS
 850
 851 config 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
 862 menuconfig 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
 871 if NAMESPACES
 872
 873 config 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
 880 config 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
 888 config 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
 900 config 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
 908 config 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
 916 endif # NAMESPACES
 917
 918 config 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         # Networking
 927         depends on NET_9P = n
 928
 929         # Filesystems
 930         depends on 9P_FS = n
 931         depends on AFS_FS = n
 932         depends on AUTOFS4_FS = n
 933         depends on CEPH_FS = n
 934         depends on CIFS = n
 935         depends on CODA_FS = n
 936         depends on FUSE_FS = n
 937         depends on GFS2_FS = n
 938         depends on JFS_FS = n
 939         depends on NCP_FS = n
 940         depends on NFSD = n
 941         depends on NFS_FS = n
 942         depends on OCFS2_FS = n
 943         depends on REISERFS_FS = n
 944         depends on SQUASHFS = n
 945         depends on UBIFS_FS = n
 946         depends on UDF_FS = n
 947         depends on UFS_FS = n
 948         depends on XFS_FS = n
 949
 950 config UIDGID_STRICT_TYPE_CHECKS
 951         bool "Require conversions between uid/gids and their internal representation"
 952         depends on UIDGID_CONVERTED
 953         default n
 954         help
 955          While the nececessary conversions are being added to all subsystems this option allows
 956          the code to continue to build for unconverted subsystems.
 957
 958          Say Y here if you want the strict type checking enabled
 959
 960 config SCHED_AUTOGROUP
 961         bool "Automatic process group scheduling"
 962         select EVENTFD
 963         select CGROUPS
 964         select CGROUP_SCHED
 965         select FAIR_GROUP_SCHED
 966         help
 967           This option optimizes the scheduler for common desktop workloads by
 968           automatically creating and populating task groups.  This separation
 969           of workloads isolates aggressive CPU burners (like build jobs) from
 970           desktop applications.  Task group autogeneration is currently based
 971           upon task session.
 972
 973 config MM_OWNER
 974         bool
 975
 976 config SYSFS_DEPRECATED
 977         bool "Enable deprecated sysfs features to support old userspace tools"
 978         depends on SYSFS
 979         default n
 980         help
 981           This option adds code that switches the layout of the "block" class
 982           devices, to not show up in /sys/class/block/, but only in
 983           /sys/block/.
 984
 985           This switch is only active when the sysfs.deprecated=1 boot option is
 986           passed or the SYSFS_DEPRECATED_V2 option is set.
 987
 988           This option allows new kernels to run on old distributions and tools,
 989           which might get confused by /sys/class/block/. Since 2007/2008 all
 990           major distributions and tools handle this just fine.
 991
 992           Recent distributions and userspace tools after 2009/2010 depend on
 993           the existence of /sys/class/block/, and will not work with this
 994           option enabled.
 995
 996           Only if you are using a new kernel on an old distribution, you might
 997           need to say Y here.
 998
 999 config SYSFS_DEPRECATED_V2
1000         bool "Enable deprecated sysfs features by default"
1001         default n
1002         depends on SYSFS
1003         depends on SYSFS_DEPRECATED
1004         help
1005           Enable deprecated sysfs by default.
1006
1007           See the CONFIG_SYSFS_DEPRECATED option for more details about this
1008           option.
1009
1010           Only if you are using a new kernel on an old distribution, you might
1011           need to say Y here. Even then, odds are you would not need it
1012           enabled, you can always pass the boot option if absolutely necessary.
1013
1014 config RELAY
1015         bool "Kernel->user space relay support (formerly relayfs)"
1016         help
1017           This option enables support for relay interface support in
1018           certain file systems (such as debugfs).
1019           It is designed to provide an efficient mechanism for tools and
1020           facilities to relay large amounts of data from kernel space to
1021           user space.
1022
1023           If unsure, say N.
1024
1025 config BLK_DEV_INITRD
1026         bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1027         depends on BROKEN || !FRV
1028         help
1029           The initial RAM filesystem is a ramfs which is loaded by the
1030           boot loader (loadlin or lilo) and that is mounted as root
1031           before the normal boot procedure. It is typically used to
1032           load modules needed to mount the "real" root file system,
1033           etc. See <file:Documentation/initrd.txt> for details.
1034
1035           If RAM disk support (BLK_DEV_RAM) is also included, this
1036           also enables initial RAM disk (initrd) support and adds
1037           15 Kbytes (more on some other architectures) to the kernel size.
1038
1039           If unsure say Y.
1040
1041 if BLK_DEV_INITRD
1042
1043 source "usr/Kconfig"
1044
1045 endif
1046
1047 config CC_OPTIMIZE_FOR_SIZE
1048         bool "Optimize for size"
1049         help
1050           Enabling this option will pass "-Os" instead of "-O2" to gcc
1051           resulting in a smaller kernel.
1052
1053           If unsure, say Y.
1054
1055 config SYSCTL
1056         bool
1057
1058 config ANON_INODES
1059         bool
1060
1061 menuconfig EXPERT
1062         bool "Configure standard kernel features (expert users)"
1063         # Unhide debug options, to make the on-by-default options visible
1064         select DEBUG_KERNEL
1065         help
1066           This option allows certain base kernel options and settings
1067           to be disabled or tweaked. This is for specialized
1068           environments which can tolerate a "non-standard" kernel.
1069           Only use this if you really know what you are doing.
1070
1071 config UID16
1072         bool "Enable 16-bit UID system calls" if EXPERT
1073         depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
1074         default y
1075         help
1076           This enables the legacy 16-bit UID syscall wrappers.
1077
1078 config SYSCTL_SYSCALL
1079         bool "Sysctl syscall support" if EXPERT
1080         depends on PROC_SYSCTL
1081         default n
1082         select SYSCTL
1083         ---help---
1084           sys_sysctl uses binary paths that have been found challenging
1085           to properly maintain and use.  The interface in /proc/sys
1086           using paths with ascii names is now the primary path to this
1087           information.
1088
1089           Almost nothing using the binary sysctl interface so if you are
1090           trying to save some space it is probably safe to disable this,
1091           making your kernel marginally smaller.
1092
1093           If unsure say N here.
1094
1095 config KALLSYMS
1096          bool "Load all symbols for debugging/ksymoops" if EXPERT
1097          default y
1098          help
1099            Say Y here to let the kernel print out symbolic crash information and
1100            symbolic stack backtraces. This increases the size of the kernel
1101            somewhat, as all symbols have to be loaded into the kernel image.
1102
1103 config KALLSYMS_ALL
1104         bool "Include all symbols in kallsyms"
1105         depends on DEBUG_KERNEL && KALLSYMS
1106         help
1107            Normally kallsyms only contains the symbols of functions for nicer
1108            OOPS messages and backtraces (i.e., symbols from the text and inittext
1109            sections). This is sufficient for most cases. And only in very rare
1110            cases (e.g., when a debugger is used) all symbols are required (e.g.,
1111            names of variables from the data sections, etc).
1112
1113            This option makes sure that all symbols are loaded into the kernel
1114            image (i.e., symbols from all sections) in cost of increased kernel
1115            size (depending on the kernel configuration, it may be 300KiB or
1116            something like this).
1117
1118            Say N unless you really need all symbols.
1119
1120 config HOTPLUG
1121         bool "Support for hot-pluggable devices" if EXPERT
1122         default y
1123         help
1124           This option is provided for the case where no hotplug or uevent
1125           capabilities is wanted by the kernel.  You should only consider
1126           disabling this option for embedded systems that do not use modules, a
1127           dynamic /dev tree, or dynamic device discovery.  Just say Y.
1128
1129 config PRINTK
1130         default y
1131         bool "Enable support for printk" if EXPERT
1132         help
1133           This option enables normal printk support. Removing it
1134           eliminates most of the message strings from the kernel image
1135           and makes the kernel more or less silent. As this makes it
1136           very difficult to diagnose system problems, saying N here is
1137           strongly discouraged.
1138
1139 config BUG
1140         bool "BUG() support" if EXPERT
1141         default y
1142         help
1143           Disabling this option eliminates support for BUG and WARN, reducing
1144           the size of your kernel image and potentially quietly ignoring
1145           numerous fatal conditions. You should only consider disabling this
1146           option for embedded systems with no facilities for reporting errors.
1147           Just say Y.
1148
1149 config ELF_CORE
1150         default y
1151         bool "Enable ELF core dumps" if EXPERT
1152         help
1153           Enable support for generating core dumps. Disabling saves about 4k.
1154
1155
1156 config PCSPKR_PLATFORM
1157         bool "Enable PC-Speaker support" if EXPERT
1158         depends on HAVE_PCSPKR_PLATFORM
1159         select I8253_LOCK
1160         default y
1161         help
1162           This option allows to disable the internal PC-Speaker
1163           support, saving some memory.
1164
1165 config HAVE_PCSPKR_PLATFORM
1166         bool
1167
1168 config BASE_FULL
1169         default y
1170         bool "Enable full-sized data structures for core" if EXPERT
1171         help
1172           Disabling this option reduces the size of miscellaneous core
1173           kernel data structures. This saves memory on small machines,
1174           but may reduce performance.
1175
1176 config FUTEX
1177         bool "Enable futex support" if EXPERT
1178         default y
1179         select RT_MUTEXES
1180         help
1181           Disabling this option will cause the kernel to be built without
1182           support for "fast userspace mutexes".  The resulting kernel may not
1183           run glibc-based applications correctly.
1184
1185 config EPOLL
1186         bool "Enable eventpoll support" if EXPERT
1187         default y
1188         select ANON_INODES
1189         help
1190           Disabling this option will cause the kernel to be built without
1191           support for epoll family of system calls.
1192
1193 config SIGNALFD
1194         bool "Enable signalfd() system call" if EXPERT
1195         select ANON_INODES
1196         default y
1197         help
1198           Enable the signalfd() system call that allows to receive signals
1199           on a file descriptor.
1200
1201           If unsure, say Y.
1202
1203 config TIMERFD
1204         bool "Enable timerfd() system call" if EXPERT
1205         select ANON_INODES
1206         default y
1207         help
1208           Enable the timerfd() system call that allows to receive timer
1209           events on a file descriptor.
1210
1211           If unsure, say Y.
1212
1213 config EVENTFD
1214         bool "Enable eventfd() system call" if EXPERT
1215         select ANON_INODES
1216         default y
1217         help
1218           Enable the eventfd() system call that allows to receive both
1219           kernel notification (ie. KAIO) or userspace notifications.
1220
1221           If unsure, say Y.
1222
1223 config SHMEM
1224         bool "Use full shmem filesystem" if EXPERT
1225         default y
1226         depends on MMU
1227         help
1228           The shmem is an internal filesystem used to manage shared memory.
1229           It is backed by swap and manages resource limits. It is also exported
1230           to userspace as tmpfs if TMPFS is enabled. Disabling this
1231           option replaces shmem and tmpfs with the much simpler ramfs code,
1232           which may be appropriate on small systems without swap.
1233
1234 config AIO
1235         bool "Enable AIO support" if EXPERT
1236         default y
1237         help
1238           This option enables POSIX asynchronous I/O which may by used
1239           by some high performance threaded applications. Disabling
1240           this option saves about 7k.
1241
1242 config EMBEDDED
1243         bool "Embedded system"
1244         select EXPERT
1245         help
1246           This option should be enabled if compiling the kernel for
1247           an embedded system so certain expert options are available
1248           for configuration.
1249
1250 config HAVE_PERF_EVENTS
1251         bool
1252         help
1253           See tools/perf/design.txt for details.
1254
1255 config PERF_USE_VMALLOC
1256         bool
1257         help
1258           See tools/perf/design.txt for details
1259
1260 menu "Kernel Performance Events And Counters"
1261
1262 config PERF_EVENTS
1263         bool "Kernel performance events and counters"
1264         default y if PROFILING
1265         depends on HAVE_PERF_EVENTS
1266         select ANON_INODES
1267         select IRQ_WORK
1268         help
1269           Enable kernel support for various performance events provided
1270           by software and hardware.
1271
1272           Software events are supported either built-in or via the
1273           use of generic tracepoints.
1274
1275           Most modern CPUs support performance events via performance
1276           counter registers. These registers count the number of certain
1277           types of hw events: such as instructions executed, cachemisses
1278           suffered, or branches mis-predicted - without slowing down the
1279           kernel or applications. These registers can also trigger interrupts
1280           when a threshold number of events have passed - and can thus be
1281           used to profile the code that runs on that CPU.
1282
1283           The Linux Performance Event subsystem provides an abstraction of
1284           these software and hardware event capabilities, available via a
1285           system call and used by the "perf" utility in tools/perf/. It
1286           provides per task and per CPU counters, and it provides event
1287           capabilities on top of those.
1288
1289           Say Y if unsure.
1290
1291 config DEBUG_PERF_USE_VMALLOC
1292         default n
1293         bool "Debug: use vmalloc to back perf mmap() buffers"
1294         depends on PERF_EVENTS && DEBUG_KERNEL
1295         select PERF_USE_VMALLOC
1296         help
1297          Use vmalloc memory to back perf mmap() buffers.
1298
1299          Mostly useful for debugging the vmalloc code on platforms
1300          that don't require it.
1301
1302          Say N if unsure.
1303
1304 endmenu
1305
1306 config VM_EVENT_COUNTERS
1307         default y
1308         bool "Enable VM event counters for /proc/vmstat" if EXPERT
1309         help
1310           VM event counters are needed for event counts to be shown.
1311           This option allows the disabling of the VM event counters
1312           on EXPERT systems.  /proc/vmstat will only show page counts
1313           if VM event counters are disabled.
1314
1315 config PCI_QUIRKS
1316         default y
1317         bool "Enable PCI quirk workarounds" if EXPERT
1318         depends on PCI
1319         help
1320           This enables workarounds for various PCI chipset
1321           bugs/quirks. Disable this only if your target machine is
1322           unaffected by PCI quirks.
1323
1324 config SLUB_DEBUG
1325         default y
1326         bool "Enable SLUB debugging support" if EXPERT
1327         depends on SLUB && SYSFS
1328         help
1329           SLUB has extensive debug support features. Disabling these can
1330           result in significant savings in code size. This also disables
1331           SLUB sysfs support. /sys/slab will not exist and there will be
1332           no support for cache validation etc.
1333
1334 config COMPAT_BRK
1335         bool "Disable heap randomization"
1336         default y
1337         help
1338           Randomizing heap placement makes heap exploits harder, but it
1339           also breaks ancient binaries (including anything libc5 based).
1340           This option changes the bootup default to heap randomization
1341           disabled, and can be overridden at runtime by setting
1342           /proc/sys/kernel/randomize_va_space to 2.
1343
1344           On non-ancient distros (post-2000 ones) N is usually a safe choice.
1345
1346 choice
1347         prompt "Choose SLAB allocator"
1348         default SLUB
1349         help
1350            This option allows to select a slab allocator.
1351
1352 config SLAB
1353         bool "SLAB"
1354         help
1355           The regular slab allocator that is established and known to work
1356           well in all environments. It organizes cache hot objects in
1357           per cpu and per node queues.
1358
1359 config SLUB
1360         bool "SLUB (Unqueued Allocator)"
1361         help
1362            SLUB is a slab allocator that minimizes cache line usage
1363            instead of managing queues of cached objects (SLAB approach).
1364            Per cpu caching is realized using slabs of objects instead
1365            of queues of objects. SLUB can use memory efficiently
1366            and has enhanced diagnostics. SLUB is the default choice for
1367            a slab allocator.
1368
1369 config SLOB
1370         depends on EXPERT
1371         bool "SLOB (Simple Allocator)"
1372         help
1373            SLOB replaces the stock allocator with a drastically simpler
1374            allocator. SLOB is generally more space efficient but
1375            does not perform as well on large systems.
1376
1377 endchoice
1378
1379 config MMAP_ALLOW_UNINITIALIZED
1380         bool "Allow mmapped anonymous memory to be uninitialized"
1381         depends on EXPERT && !MMU
1382         default n
1383         help
1384           Normally, and according to the Linux spec, anonymous memory obtained
1385           from mmap() has it's contents cleared before it is passed to
1386           userspace.  Enabling this config option allows you to request that
1387           mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1388           providing a huge performance boost.  If this option is not enabled,
1389           then the flag will be ignored.
1390
1391           This is taken advantage of by uClibc's malloc(), and also by
1392           ELF-FDPIC binfmt's brk and stack allocator.
1393
1394           Because of the obvious security issues, this option should only be
1395           enabled on embedded devices where you control what is run in
1396           userspace.  Since that isn't generally a problem on no-MMU systems,
1397           it is normally safe to say Y here.
1398
1399           See Documentation/nommu-mmap.txt for more information.
1400
1401 config PROFILING
1402         bool "Profiling support"
1403         help
1404           Say Y here to enable the extended profiling support mechanisms used
1405           by profilers such as OProfile.
1406
1407 #
1408 # Place an empty function call at each tracepoint site. Can be
1409 # dynamically changed for a probe function.
1410 #
1411 config TRACEPOINTS
1412         bool
1413
1414 source "arch/Kconfig"
1415
1416 endmenu         # General setup
1417
1418 config HAVE_GENERIC_DMA_COHERENT
1419         bool
1420         default n
1421
1422 config SLABINFO
1423         bool
1424         depends on PROC_FS
1425         depends on SLAB || SLUB_DEBUG
1426         default y
1427
1428 config RT_MUTEXES
1429         boolean
1430
1431 config BASE_SMALL
1432         int
1433         default 0 if BASE_FULL
1434         default 1 if !BASE_FULL
1435
1436 menuconfig MODULES
1437         bool "Enable loadable module support"
1438         help
1439           Kernel modules are small pieces of compiled code which can
1440           be inserted in the running kernel, rather than being
1441           permanently built into the kernel.  You use the "modprobe"
1442           tool to add (and sometimes remove) them.  If you say Y here,
1443           many parts of the kernel can be built as modules (by
1444           answering M instead of Y where indicated): this is most
1445           useful for infrequently used options which are not required
1446           for booting.  For more information, see the man pages for
1447           modprobe, lsmod, modinfo, insmod and rmmod.
1448
1449           If you say Y here, you will need to run "make
1450           modules_install" to put the modules under /lib/modules/
1451           where modprobe can find them (you may need to be root to do
1452           this).
1453
1454           If unsure, say Y.
1455
1456 if MODULES
1457
1458 config MODULE_FORCE_LOAD
1459         bool "Forced module loading"
1460         default n
1461         help
1462           Allow loading of modules without version information (ie. modprobe
1463           --force).  Forced module loading sets the 'F' (forced) taint flag and
1464           is usually a really bad idea.
1465
1466 config MODULE_UNLOAD
1467         bool "Module unloading"
1468         help
1469           Without this option you will not be able to unload any
1470           modules (note that some modules may not be unloadable
1471           anyway), which makes your kernel smaller, faster
1472           and simpler.  If unsure, say Y.
1473
1474 config MODULE_FORCE_UNLOAD
1475         bool "Forced module unloading"
1476         depends on MODULE_UNLOAD && EXPERIMENTAL
1477         help
1478           This option allows you to force a module to unload, even if the
1479           kernel believes it is unsafe: the kernel will remove the module
1480           without waiting for anyone to stop using it (using the -f option to
1481           rmmod).  This is mainly for kernel developers and desperate users.
1482           If unsure, say N.
1483
1484 config MODVERSIONS
1485         bool "Module versioning support"
1486         help
1487           Usually, you have to use modules compiled with your kernel.
1488           Saying Y here makes it sometimes possible to use modules
1489           compiled for different kernels, by adding enough information
1490           to the modules to (hopefully) spot any changes which would
1491           make them incompatible with the kernel you are running.  If
1492           unsure, say N.
1493
1494 config MODULE_SRCVERSION_ALL
1495         bool "Source checksum for all modules"
1496         help
1497           Modules which contain a MODULE_VERSION get an extra "srcversion"
1498           field inserted into their modinfo section, which contains a
1499           sum of the source files which made it.  This helps maintainers
1500           see exactly which source was used to build a module (since
1501           others sometimes change the module source without updating
1502           the version).  With this option, such a "srcversion" field
1503           will be created for all modules.  If unsure, say N.
1504
1505 endif # MODULES
1506
1507 config INIT_ALL_POSSIBLE
1508         bool
1509         help
1510           Back when each arch used to define their own cpu_online_mask and
1511           cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1512           with all 1s, and others with all 0s.  When they were centralised,
1513           it was better to provide this option than to break all the archs
1514           and have several arch maintainers pursuing me down dark alleys.
1515
1516 config STOP_MACHINE
1517         bool
1518         default y
1519         depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1520         help
1521           Need stop_machine() primitive.
1522
1523 source "block/Kconfig"
1524
1525 config PREEMPT_NOTIFIERS
1526         bool
1527
1528 config PADATA
1529         depends on SMP
1530         bool
1531
1532 source "kernel/Kconfig.locks"