7 option env="KERNELVERSION"
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"
28 depends on HAVE_IRQ_WORK
30 config BUILDTIME_EXTABLE_SORT
36 bool "Prompt for development and/or incomplete code/drivers"
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).
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56 drivers that have been replaced by something else, and/or are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.
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.
71 depends on BROKEN || !SMP
74 config INIT_ENV_ARG_LIMIT
79 Maximum of each of the number of arguments and environment
80 variables passed to init from the kernel command line.
84 string "Cross-compiler tool prefix"
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.
92 string "Local version - append to kernel release"
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.
101 config LOCALVERSION_AUTO
102 bool "Automatically append version information to the version string"
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.
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.
114 (The actual string used here is the first eight characters produced
115 by running the command:
117 $ git rev-parse --verify HEAD
119 which is done within the script "scripts/setlocalversion".)
121 config HAVE_KERNEL_GZIP
124 config HAVE_KERNEL_BZIP2
127 config HAVE_KERNEL_LZMA
130 config HAVE_KERNEL_XZ
133 config HAVE_KERNEL_LZO
137 prompt "Kernel compression mode"
139 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
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.
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)
152 High compression options are mostly useful for users, who
153 are low on disk space (embedded systems), but for whom ram
156 If in doubt, select 'gzip'
160 depends on HAVE_KERNEL_GZIP
162 The old and tried gzip compression. It provides a good balance
163 between compression ratio and decompression speed.
167 depends on HAVE_KERNEL_BZIP2
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.
177 depends on HAVE_KERNEL_LZMA
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.
185 depends on HAVE_KERNEL_XZ
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.
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.
200 depends on HAVE_KERNEL_LZO
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.
208 config DEFAULT_HOSTNAME
209 string "Default hostname"
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.
218 bool "Support for paging of anonymous memory (swap)"
219 depends on MMU && BLOCK
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.
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.
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>.
242 config SYSVIPC_SYSCTL
249 bool "POSIX Message Queues"
250 depends on NET && EXPERIMENTAL
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.
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.
264 config POSIX_MQUEUE_SYSCTL
266 depends on POSIX_MQUEUE
270 config BSD_PROCESS_ACCT
271 bool "BSD Process Accounting"
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.
283 config BSD_PROCESS_ACCT_V3
284 bool "BSD Process Accounting version 3 file format"
285 depends on BSD_PROCESS_ACCT
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/>.
296 bool "open by fhandle syscalls"
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)
308 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
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
320 config TASK_DELAY_ACCT
321 bool "Enable per-task delay accounting (EXPERIMENTAL)"
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.
332 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
335 Collect extended task accounting data and send the data
336 to userland for processing over the taskstats interface.
340 config TASK_IO_ACCOUNTING
341 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
342 depends on TASK_XACCT
344 Collect information on the number of bytes of storage I/O which this
350 bool "Auditing support"
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.
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
363 Enable low-overhead system-call auditing infrastructure that
364 can be used independently or with another kernel subsystem,
369 depends on AUDITSYSCALL
374 depends on AUDITSYSCALL
377 config AUDIT_LOGINUID_IMMUTABLE
378 bool "Make audit loginuid immutable"
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.
391 source "kernel/irq/Kconfig"
392 source "kernel/time/Kconfig"
397 prompt "RCU Implementation"
401 bool "Tree-based hierarchical RCU"
402 depends on !PREEMPT && SMP
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
409 config TREE_PREEMPT_RCU
410 bool "Preemptible tree-based hierarchical RCU"
411 depends on PREEMPT && SMP
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
420 bool "UP-only small-memory-footprint RCU"
421 depends on !PREEMPT && !SMP
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.
428 config TINY_PREEMPT_RCU
429 bool "Preemptible UP-only small-memory-footprint RCU"
430 depends on PREEMPT && !SMP
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.
439 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
441 This option enables preemptible-RCU code that is common between
442 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
445 bool "Consider userspace as in RCU extended quiescent state"
446 depends on HAVE_RCU_USER_QS && SMP
448 This option sets hooks on kernel / userspace boundaries and
449 puts RCU in extended quiescent state when the CPU runs in
450 userspace. It means that when a CPU runs in userspace, it is
451 excluded from the global RCU state machine and thus doesn't
452 to keep the timer tick on for RCU.
455 int "Tree-based hierarchical RCU fanout value"
458 depends on TREE_RCU || TREE_PREEMPT_RCU
462 This option controls the fanout of hierarchical implementations
463 of RCU, allowing RCU to work efficiently on machines with
464 large numbers of CPUs. This value must be at least the fourth
465 root of NR_CPUS, which allows NR_CPUS to be insanely large.
466 The default value of RCU_FANOUT should be used for production
467 systems, but if you are stress-testing the RCU implementation
468 itself, small RCU_FANOUT values allow you to test large-system
469 code paths on small(er) systems.
471 Select a specific number if testing RCU itself.
472 Take the default if unsure.
474 config RCU_FANOUT_LEAF
475 int "Tree-based hierarchical RCU leaf-level fanout value"
476 range 2 RCU_FANOUT if 64BIT
477 range 2 RCU_FANOUT if !64BIT
478 depends on TREE_RCU || TREE_PREEMPT_RCU
481 This option controls the leaf-level fanout of hierarchical
482 implementations of RCU, and allows trading off cache misses
483 against lock contention. Systems that synchronize their
484 scheduling-clock interrupts for energy-efficiency reasons will
485 want the default because the smaller leaf-level fanout keeps
486 lock contention levels acceptably low. Very large systems
487 (hundreds or thousands of CPUs) will instead want to set this
488 value to the maximum value possible in order to reduce the
489 number of cache misses incurred during RCU's grace-period
490 initialization. These systems tend to run CPU-bound, and thus
491 are not helped by synchronized interrupts, and thus tend to
492 skew them, which reduces lock contention enough that large
493 leaf-level fanouts work well.
495 Select a specific number if testing RCU itself.
497 Select the maximum permissible value for large systems.
499 Take the default if unsure.
501 config RCU_FANOUT_EXACT
502 bool "Disable tree-based hierarchical RCU auto-balancing"
503 depends on TREE_RCU || TREE_PREEMPT_RCU
506 This option forces use of the exact RCU_FANOUT value specified,
507 regardless of imbalances in the hierarchy. This is useful for
508 testing RCU itself, and might one day be useful on systems with
509 strong NUMA behavior.
511 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
515 config RCU_FAST_NO_HZ
516 bool "Accelerate last non-dyntick-idle CPU's grace periods"
517 depends on NO_HZ && SMP
520 This option causes RCU to attempt to accelerate grace periods
521 in order to allow CPUs to enter dynticks-idle state more
522 quickly. On the other hand, this option increases the overhead
523 of the dynticks-idle checking, particularly on systems with
524 large numbers of CPUs.
526 Say Y if energy efficiency is critically important, particularly
527 if you have relatively few CPUs.
529 Say N if you are unsure.
531 config TREE_RCU_TRACE
532 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
535 This option provides tracing for the TREE_RCU and
536 TREE_PREEMPT_RCU implementations, permitting Makefile to
537 trivially select kernel/rcutree_trace.c.
540 bool "Enable RCU priority boosting"
541 depends on RT_MUTEXES && PREEMPT_RCU
544 This option boosts the priority of preempted RCU readers that
545 block the current preemptible RCU grace period for too long.
546 This option also prevents heavy loads from blocking RCU
547 callback invocation for all flavors of RCU.
549 Say Y here if you are working with real-time apps or heavy loads
550 Say N here if you are unsure.
552 config RCU_BOOST_PRIO
553 int "Real-time priority to boost RCU readers to"
558 This option specifies the real-time priority to which long-term
559 preempted RCU readers are to be boosted. If you are working
560 with a real-time application that has one or more CPU-bound
561 threads running at a real-time priority level, you should set
562 RCU_BOOST_PRIO to a priority higher then the highest-priority
563 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
564 of 1 is appropriate in the common case, which is real-time
565 applications that do not have any CPU-bound threads.
567 Some real-time applications might not have a single real-time
568 thread that saturates a given CPU, but instead might have
569 multiple real-time threads that, taken together, fully utilize
570 that CPU. In this case, you should set RCU_BOOST_PRIO to
571 a priority higher than the lowest-priority thread that is
572 conspiring to prevent the CPU from running any non-real-time
573 tasks. For example, if one thread at priority 10 and another
574 thread at priority 5 are between themselves fully consuming
575 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
576 set to priority 6 or higher.
578 Specify the real-time priority, or take the default if unsure.
580 config RCU_BOOST_DELAY
581 int "Milliseconds to delay boosting after RCU grace-period start"
586 This option specifies the time to wait after the beginning of
587 a given grace period before priority-boosting preempted RCU
588 readers blocking that grace period. Note that any RCU reader
589 blocking an expedited RCU grace period is boosted immediately.
591 Accept the default if unsure.
593 endmenu # "RCU Subsystem"
596 tristate "Kernel .config support"
598 This option enables the complete Linux kernel ".config" file
599 contents to be saved in the kernel. It provides documentation
600 of which kernel options are used in a running kernel or in an
601 on-disk kernel. This information can be extracted from the kernel
602 image file with the script scripts/extract-ikconfig and used as
603 input to rebuild the current kernel or to build another kernel.
604 It can also be extracted from a running kernel by reading
605 /proc/config.gz if enabled (below).
608 bool "Enable access to .config through /proc/config.gz"
609 depends on IKCONFIG && PROC_FS
611 This option enables access to the kernel configuration file
612 through /proc/config.gz.
615 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
619 Select kernel log buffer size as a power of 2.
629 # Architectures with an unreliable sched_clock() should select this:
631 config HAVE_UNSTABLE_SCHED_CLOCK
635 boolean "Control Group support"
638 This option adds support for grouping sets of processes together, for
639 use with process control subsystems such as Cpusets, CFS, memory
640 controls or device isolation.
642 - Documentation/scheduler/sched-design-CFS.txt (CFS)
643 - Documentation/cgroups/ (features for grouping, isolation
644 and resource control)
651 bool "Example debug cgroup subsystem"
654 This option enables a simple cgroup subsystem that
655 exports useful debugging information about the cgroups
660 config CGROUP_FREEZER
661 bool "Freezer cgroup subsystem"
663 Provides a way to freeze and unfreeze all tasks in a
667 bool "Device controller for cgroups"
669 Provides a cgroup implementing whitelists for devices which
670 a process in the cgroup can mknod or open.
673 bool "Cpuset support"
675 This option will let you create and manage CPUSETs which
676 allow dynamically partitioning a system into sets of CPUs and
677 Memory Nodes and assigning tasks to run only within those sets.
678 This is primarily useful on large SMP or NUMA systems.
682 config PROC_PID_CPUSET
683 bool "Include legacy /proc/<pid>/cpuset file"
687 config CGROUP_CPUACCT
688 bool "Simple CPU accounting cgroup subsystem"
690 Provides a simple Resource Controller for monitoring the
691 total CPU consumed by the tasks in a cgroup.
693 config RESOURCE_COUNTERS
694 bool "Resource counters"
696 This option enables controller independent resource accounting
697 infrastructure that works with cgroups.
700 bool "Memory Resource Controller for Control Groups"
701 depends on RESOURCE_COUNTERS
704 Provides a memory resource controller that manages both anonymous
705 memory and page cache. (See Documentation/cgroups/memory.txt)
707 Note that setting this option increases fixed memory overhead
708 associated with each page of memory in the system. By this,
709 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
710 usage tracking struct at boot. Total amount of this is printed out
713 Only enable when you're ok with these trade offs and really
714 sure you need the memory resource controller. Even when you enable
715 this, you can set "cgroup_disable=memory" at your boot option to
716 disable memory resource controller and you can avoid overheads.
717 (and lose benefits of memory resource controller)
719 This config option also selects MM_OWNER config option, which
720 could in turn add some fork/exit overhead.
723 bool "Memory Resource Controller Swap Extension"
724 depends on MEMCG && SWAP
726 Add swap management feature to memory resource controller. When you
727 enable this, you can limit mem+swap usage per cgroup. In other words,
728 when you disable this, memory resource controller has no cares to
729 usage of swap...a process can exhaust all of the swap. This extension
730 is useful when you want to avoid exhaustion swap but this itself
731 adds more overheads and consumes memory for remembering information.
732 Especially if you use 32bit system or small memory system, please
733 be careful about enabling this. When memory resource controller
734 is disabled by boot option, this will be automatically disabled and
735 there will be no overhead from this. Even when you set this config=y,
736 if boot option "swapaccount=0" is set, swap will not be accounted.
737 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
738 size is 4096bytes, 512k per 1Gbytes of swap.
739 config MEMCG_SWAP_ENABLED
740 bool "Memory Resource Controller Swap Extension enabled by default"
741 depends on MEMCG_SWAP
744 Memory Resource Controller Swap Extension comes with its price in
745 a bigger memory consumption. General purpose distribution kernels
746 which want to enable the feature but keep it disabled by default
747 and let the user enable it by swapaccount boot command line
748 parameter should have this option unselected.
749 For those who want to have the feature enabled by default should
750 select this option (if, for some reason, they need to disable it
751 then swapaccount=0 does the trick).
753 bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
754 depends on MEMCG && EXPERIMENTAL
757 The Kernel Memory extension for Memory Resource Controller can limit
758 the amount of memory used by kernel objects in the system. Those are
759 fundamentally different from the entities handled by the standard
760 Memory Controller, which are page-based, and can be swapped. Users of
761 the kmem extension can use it to guarantee that no group of processes
762 will ever exhaust kernel resources alone.
764 config CGROUP_HUGETLB
765 bool "HugeTLB Resource Controller for Control Groups"
766 depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
769 Provides a cgroup Resource Controller for HugeTLB pages.
770 When you enable this, you can put a per cgroup limit on HugeTLB usage.
771 The limit is enforced during page fault. Since HugeTLB doesn't
772 support page reclaim, enforcing the limit at page fault time implies
773 that, the application will get SIGBUS signal if it tries to access
774 HugeTLB pages beyond its limit. This requires the application to know
775 beforehand how much HugeTLB pages it would require for its use. The
776 control group is tracked in the third page lru pointer. This means
777 that we cannot use the controller with huge page less than 3 pages.
780 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
781 depends on PERF_EVENTS && CGROUPS
783 This option extends the per-cpu mode to restrict monitoring to
784 threads which belong to the cgroup specified and run on the
789 menuconfig CGROUP_SCHED
790 bool "Group CPU scheduler"
793 This feature lets CPU scheduler recognize task groups and control CPU
794 bandwidth allocation to such task groups. It uses cgroups to group
798 config FAIR_GROUP_SCHED
799 bool "Group scheduling for SCHED_OTHER"
800 depends on CGROUP_SCHED
804 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
805 depends on EXPERIMENTAL
806 depends on FAIR_GROUP_SCHED
809 This option allows users to define CPU bandwidth rates (limits) for
810 tasks running within the fair group scheduler. Groups with no limit
811 set are considered to be unconstrained and will run with no
813 See tip/Documentation/scheduler/sched-bwc.txt for more information.
815 config RT_GROUP_SCHED
816 bool "Group scheduling for SCHED_RR/FIFO"
817 depends on EXPERIMENTAL
818 depends on CGROUP_SCHED
821 This feature lets you explicitly allocate real CPU bandwidth
822 to task groups. If enabled, it will also make it impossible to
823 schedule realtime tasks for non-root users until you allocate
824 realtime bandwidth for them.
825 See Documentation/scheduler/sched-rt-group.txt for more information.
830 bool "Block IO controller"
834 Generic block IO controller cgroup interface. This is the common
835 cgroup interface which should be used by various IO controlling
838 Currently, CFQ IO scheduler uses it to recognize task groups and
839 control disk bandwidth allocation (proportional time slice allocation)
840 to such task groups. It is also used by bio throttling logic in
841 block layer to implement upper limit in IO rates on a device.
843 This option only enables generic Block IO controller infrastructure.
844 One needs to also enable actual IO controlling logic/policy. For
845 enabling proportional weight division of disk bandwidth in CFQ, set
846 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
847 CONFIG_BLK_DEV_THROTTLING=y.
849 See Documentation/cgroups/blkio-controller.txt for more information.
851 config DEBUG_BLK_CGROUP
852 bool "Enable Block IO controller debugging"
853 depends on BLK_CGROUP
856 Enable some debugging help. Currently it exports additional stat
857 files in a cgroup which can be useful for debugging.
861 config CHECKPOINT_RESTORE
862 bool "Checkpoint/restore support" if EXPERT
865 Enables additional kernel features in a sake of checkpoint/restore.
866 In particular it adds auxiliary prctl codes to setup process text,
867 data and heap segment sizes, and a few additional /proc filesystem
870 If unsure, say N here.
872 menuconfig NAMESPACES
873 bool "Namespaces support" if EXPERT
876 Provides the way to make tasks work with different objects using
877 the same id. For example same IPC id may refer to different objects
878 or same user id or pid may refer to different tasks when used in
879 different namespaces.
887 In this namespace tasks see different info provided with the
892 depends on (SYSVIPC || POSIX_MQUEUE)
895 In this namespace tasks work with IPC ids which correspond to
896 different IPC objects in different namespaces.
899 bool "User namespace (EXPERIMENTAL)"
900 depends on EXPERIMENTAL
901 depends on UIDGID_CONVERTED
902 select UIDGID_STRICT_TYPE_CHECKS
906 This allows containers, i.e. vservers, to use user namespaces
907 to provide different user info for different servers.
911 bool "PID Namespaces"
914 Support process id namespaces. This allows having multiple
915 processes with the same pid as long as they are in different
916 pid namespaces. This is a building block of containers.
919 bool "Network namespace"
923 Allow user space to create what appear to be multiple instances
924 of the network stack.
928 config UIDGID_CONVERTED
929 # True if all of the selected software conmponents are known
930 # to have uid_t and gid_t converted to kuid_t and kgid_t
931 # where appropriate and are otherwise safe to use with
932 # the user namespace.
936 # List of kernel pieces that need user namespace work
938 depends on SYSVIPC = n
943 depends on AUDITSYSCALL = n
944 depends on TASKSTATS = n
945 depends on TRACING = n
946 depends on FS_POSIX_ACL = n
948 depends on QUOTACTL = n
949 depends on DEBUG_CREDENTIALS = n
950 depends on BSD_PROCESS_ACCT = n
952 depends on PROC_EVENTS = n
956 depends on NET_9P = n
958 depends on PHONET = n
959 depends on NET_CLS_FLOW = n
960 depends on NETFILTER_XT_MATCH_OWNER = n
961 depends on NETFILTER_XT_MATCH_RECENT = n
962 depends on NETFILTER_XT_TARGET_LOG = n
963 depends on NETFILTER_NETLINK_LOG = n
966 depends on IP_SCTP = n
967 depends on AF_RXRPC = n
969 depends on NET_KEY = n
970 depends on INET_DIAG = n
971 depends on DNS_RESOLVER = n
976 depends on USB_DEVICEFS = n
977 depends on USB_GADGETFS = n
978 depends on USB_FUNCTIONFS = n
979 depends on DEVTMPFS = n
983 depends on ADFS_FS = n
984 depends on AFFS_FS = n
985 depends on AFS_FS = n
986 depends on AUTOFS4_FS = n
987 depends on BEFS_FS = n
988 depends on BFS_FS = n
989 depends on BTRFS_FS = n
990 depends on CEPH_FS = n
992 depends on CODA_FS = n
993 depends on CONFIGFS_FS = n
994 depends on CRAMFS = n
995 depends on DEBUG_FS = n
996 depends on ECRYPT_FS = n
997 depends on EFS_FS = n
998 depends on EXOFS_FS = n
999 depends on FAT_FS = n
1000 depends on FUSE_FS = n
1001 depends on GFS2_FS = n
1002 depends on HFS_FS = n
1003 depends on HFSPLUS_FS = n
1004 depends on HPFS_FS = n
1005 depends on HUGETLBFS = n
1006 depends on ISO9660_FS = n
1007 depends on JFFS2_FS = n
1008 depends on JFS_FS = n
1009 depends on LOGFS = n
1010 depends on MINIX_FS = n
1011 depends on NCP_FS = n
1013 depends on NFS_FS = n
1014 depends on NILFS2_FS = n
1015 depends on NTFS_FS = n
1016 depends on OCFS2_FS = n
1017 depends on OMFS_FS = n
1018 depends on QNX4FS_FS = n
1019 depends on QNX6FS_FS = n
1020 depends on REISERFS_FS = n
1021 depends on SQUASHFS = n
1022 depends on SYSV_FS = n
1023 depends on UBIFS_FS = n
1024 depends on UDF_FS = n
1025 depends on UFS_FS = n
1026 depends on VXFS_FS = n
1027 depends on XFS_FS = n
1029 depends on !UML || HOSTFS = n
1031 # The rare drivers that won't build
1033 depends on AIRO_CS = n
1035 depends on INFINIBAND_QIB = n
1036 depends on BLK_DEV_LOOP = n
1037 depends on ANDROID_BINDER_IPC = n
1040 depends on SECURITY_TOMOYO = n
1041 depends on SECURITY_APPARMOR = n
1043 config UIDGID_STRICT_TYPE_CHECKS
1044 bool "Require conversions between uid/gids and their internal representation"
1045 depends on UIDGID_CONVERTED
1048 While the nececessary conversions are being added to all subsystems this option allows
1049 the code to continue to build for unconverted subsystems.
1051 Say Y here if you want the strict type checking enabled
1053 config SCHED_AUTOGROUP
1054 bool "Automatic process group scheduling"
1058 select FAIR_GROUP_SCHED
1060 This option optimizes the scheduler for common desktop workloads by
1061 automatically creating and populating task groups. This separation
1062 of workloads isolates aggressive CPU burners (like build jobs) from
1063 desktop applications. Task group autogeneration is currently based
1069 config SYSFS_DEPRECATED
1070 bool "Enable deprecated sysfs features to support old userspace tools"
1074 This option adds code that switches the layout of the "block" class
1075 devices, to not show up in /sys/class/block/, but only in
1078 This switch is only active when the sysfs.deprecated=1 boot option is
1079 passed or the SYSFS_DEPRECATED_V2 option is set.
1081 This option allows new kernels to run on old distributions and tools,
1082 which might get confused by /sys/class/block/. Since 2007/2008 all
1083 major distributions and tools handle this just fine.
1085 Recent distributions and userspace tools after 2009/2010 depend on
1086 the existence of /sys/class/block/, and will not work with this
1089 Only if you are using a new kernel on an old distribution, you might
1092 config SYSFS_DEPRECATED_V2
1093 bool "Enable deprecated sysfs features by default"
1096 depends on SYSFS_DEPRECATED
1098 Enable deprecated sysfs by default.
1100 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1103 Only if you are using a new kernel on an old distribution, you might
1104 need to say Y here. Even then, odds are you would not need it
1105 enabled, you can always pass the boot option if absolutely necessary.
1108 bool "Kernel->user space relay support (formerly relayfs)"
1110 This option enables support for relay interface support in
1111 certain file systems (such as debugfs).
1112 It is designed to provide an efficient mechanism for tools and
1113 facilities to relay large amounts of data from kernel space to
1118 config BLK_DEV_INITRD
1119 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1120 depends on BROKEN || !FRV
1122 The initial RAM filesystem is a ramfs which is loaded by the
1123 boot loader (loadlin or lilo) and that is mounted as root
1124 before the normal boot procedure. It is typically used to
1125 load modules needed to mount the "real" root file system,
1126 etc. See <file:Documentation/initrd.txt> for details.
1128 If RAM disk support (BLK_DEV_RAM) is also included, this
1129 also enables initial RAM disk (initrd) support and adds
1130 15 Kbytes (more on some other architectures) to the kernel size.
1136 source "usr/Kconfig"
1140 config CC_OPTIMIZE_FOR_SIZE
1141 bool "Optimize for size"
1143 Enabling this option will pass "-Os" instead of "-O2" to gcc
1144 resulting in a smaller kernel.
1155 bool "Configure standard kernel features (expert users)"
1156 # Unhide debug options, to make the on-by-default options visible
1159 This option allows certain base kernel options and settings
1160 to be disabled or tweaked. This is for specialized
1161 environments which can tolerate a "non-standard" kernel.
1162 Only use this if you really know what you are doing.
1165 bool "Enable 16-bit UID system calls" if EXPERT
1166 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
1169 This enables the legacy 16-bit UID syscall wrappers.
1171 config SYSCTL_SYSCALL
1172 bool "Sysctl syscall support" if EXPERT
1173 depends on PROC_SYSCTL
1177 sys_sysctl uses binary paths that have been found challenging
1178 to properly maintain and use. The interface in /proc/sys
1179 using paths with ascii names is now the primary path to this
1182 Almost nothing using the binary sysctl interface so if you are
1183 trying to save some space it is probably safe to disable this,
1184 making your kernel marginally smaller.
1186 If unsure say N here.
1189 bool "Load all symbols for debugging/ksymoops" if EXPERT
1192 Say Y here to let the kernel print out symbolic crash information and
1193 symbolic stack backtraces. This increases the size of the kernel
1194 somewhat, as all symbols have to be loaded into the kernel image.
1197 bool "Include all symbols in kallsyms"
1198 depends on DEBUG_KERNEL && KALLSYMS
1200 Normally kallsyms only contains the symbols of functions for nicer
1201 OOPS messages and backtraces (i.e., symbols from the text and inittext
1202 sections). This is sufficient for most cases. And only in very rare
1203 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1204 names of variables from the data sections, etc).
1206 This option makes sure that all symbols are loaded into the kernel
1207 image (i.e., symbols from all sections) in cost of increased kernel
1208 size (depending on the kernel configuration, it may be 300KiB or
1209 something like this).
1211 Say N unless you really need all symbols.
1214 bool "Support for hot-pluggable devices" if EXPERT
1217 This option is provided for the case where no hotplug or uevent
1218 capabilities is wanted by the kernel. You should only consider
1219 disabling this option for embedded systems that do not use modules, a
1220 dynamic /dev tree, or dynamic device discovery. Just say Y.
1224 bool "Enable support for printk" if EXPERT
1226 This option enables normal printk support. Removing it
1227 eliminates most of the message strings from the kernel image
1228 and makes the kernel more or less silent. As this makes it
1229 very difficult to diagnose system problems, saying N here is
1230 strongly discouraged.
1233 bool "BUG() support" if EXPERT
1236 Disabling this option eliminates support for BUG and WARN, reducing
1237 the size of your kernel image and potentially quietly ignoring
1238 numerous fatal conditions. You should only consider disabling this
1239 option for embedded systems with no facilities for reporting errors.
1244 bool "Enable ELF core dumps" if EXPERT
1246 Enable support for generating core dumps. Disabling saves about 4k.
1249 config PCSPKR_PLATFORM
1250 bool "Enable PC-Speaker support" if EXPERT
1251 depends on HAVE_PCSPKR_PLATFORM
1255 This option allows to disable the internal PC-Speaker
1256 support, saving some memory.
1258 config HAVE_PCSPKR_PLATFORM
1263 bool "Enable full-sized data structures for core" if EXPERT
1265 Disabling this option reduces the size of miscellaneous core
1266 kernel data structures. This saves memory on small machines,
1267 but may reduce performance.
1270 bool "Enable futex support" if EXPERT
1274 Disabling this option will cause the kernel to be built without
1275 support for "fast userspace mutexes". The resulting kernel may not
1276 run glibc-based applications correctly.
1279 bool "Enable eventpoll support" if EXPERT
1283 Disabling this option will cause the kernel to be built without
1284 support for epoll family of system calls.
1287 bool "Enable signalfd() system call" if EXPERT
1291 Enable the signalfd() system call that allows to receive signals
1292 on a file descriptor.
1297 bool "Enable timerfd() system call" if EXPERT
1301 Enable the timerfd() system call that allows to receive timer
1302 events on a file descriptor.
1307 bool "Enable eventfd() system call" if EXPERT
1311 Enable the eventfd() system call that allows to receive both
1312 kernel notification (ie. KAIO) or userspace notifications.
1317 bool "Use full shmem filesystem" if EXPERT
1321 The shmem is an internal filesystem used to manage shared memory.
1322 It is backed by swap and manages resource limits. It is also exported
1323 to userspace as tmpfs if TMPFS is enabled. Disabling this
1324 option replaces shmem and tmpfs with the much simpler ramfs code,
1325 which may be appropriate on small systems without swap.
1328 bool "Enable AIO support" if EXPERT
1331 This option enables POSIX asynchronous I/O which may by used
1332 by some high performance threaded applications. Disabling
1333 this option saves about 7k.
1336 bool "Embedded system"
1339 This option should be enabled if compiling the kernel for
1340 an embedded system so certain expert options are available
1343 config HAVE_PERF_EVENTS
1346 See tools/perf/design.txt for details.
1348 config PERF_USE_VMALLOC
1351 See tools/perf/design.txt for details
1353 menu "Kernel Performance Events And Counters"
1356 bool "Kernel performance events and counters"
1357 default y if PROFILING
1358 depends on HAVE_PERF_EVENTS
1362 Enable kernel support for various performance events provided
1363 by software and hardware.
1365 Software events are supported either built-in or via the
1366 use of generic tracepoints.
1368 Most modern CPUs support performance events via performance
1369 counter registers. These registers count the number of certain
1370 types of hw events: such as instructions executed, cachemisses
1371 suffered, or branches mis-predicted - without slowing down the
1372 kernel or applications. These registers can also trigger interrupts
1373 when a threshold number of events have passed - and can thus be
1374 used to profile the code that runs on that CPU.
1376 The Linux Performance Event subsystem provides an abstraction of
1377 these software and hardware event capabilities, available via a
1378 system call and used by the "perf" utility in tools/perf/. It
1379 provides per task and per CPU counters, and it provides event
1380 capabilities on top of those.
1384 config DEBUG_PERF_USE_VMALLOC
1386 bool "Debug: use vmalloc to back perf mmap() buffers"
1387 depends on PERF_EVENTS && DEBUG_KERNEL
1388 select PERF_USE_VMALLOC
1390 Use vmalloc memory to back perf mmap() buffers.
1392 Mostly useful for debugging the vmalloc code on platforms
1393 that don't require it.
1399 config VM_EVENT_COUNTERS
1401 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1403 VM event counters are needed for event counts to be shown.
1404 This option allows the disabling of the VM event counters
1405 on EXPERT systems. /proc/vmstat will only show page counts
1406 if VM event counters are disabled.
1410 bool "Enable PCI quirk workarounds" if EXPERT
1413 This enables workarounds for various PCI chipset
1414 bugs/quirks. Disable this only if your target machine is
1415 unaffected by PCI quirks.
1419 bool "Enable SLUB debugging support" if EXPERT
1420 depends on SLUB && SYSFS
1422 SLUB has extensive debug support features. Disabling these can
1423 result in significant savings in code size. This also disables
1424 SLUB sysfs support. /sys/slab will not exist and there will be
1425 no support for cache validation etc.
1428 bool "Disable heap randomization"
1431 Randomizing heap placement makes heap exploits harder, but it
1432 also breaks ancient binaries (including anything libc5 based).
1433 This option changes the bootup default to heap randomization
1434 disabled, and can be overridden at runtime by setting
1435 /proc/sys/kernel/randomize_va_space to 2.
1437 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1440 prompt "Choose SLAB allocator"
1443 This option allows to select a slab allocator.
1448 The regular slab allocator that is established and known to work
1449 well in all environments. It organizes cache hot objects in
1450 per cpu and per node queues.
1453 bool "SLUB (Unqueued Allocator)"
1455 SLUB is a slab allocator that minimizes cache line usage
1456 instead of managing queues of cached objects (SLAB approach).
1457 Per cpu caching is realized using slabs of objects instead
1458 of queues of objects. SLUB can use memory efficiently
1459 and has enhanced diagnostics. SLUB is the default choice for
1464 bool "SLOB (Simple Allocator)"
1466 SLOB replaces the stock allocator with a drastically simpler
1467 allocator. SLOB is generally more space efficient but
1468 does not perform as well on large systems.
1472 config MMAP_ALLOW_UNINITIALIZED
1473 bool "Allow mmapped anonymous memory to be uninitialized"
1474 depends on EXPERT && !MMU
1477 Normally, and according to the Linux spec, anonymous memory obtained
1478 from mmap() has it's contents cleared before it is passed to
1479 userspace. Enabling this config option allows you to request that
1480 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1481 providing a huge performance boost. If this option is not enabled,
1482 then the flag will be ignored.
1484 This is taken advantage of by uClibc's malloc(), and also by
1485 ELF-FDPIC binfmt's brk and stack allocator.
1487 Because of the obvious security issues, this option should only be
1488 enabled on embedded devices where you control what is run in
1489 userspace. Since that isn't generally a problem on no-MMU systems,
1490 it is normally safe to say Y here.
1492 See Documentation/nommu-mmap.txt for more information.
1495 bool "Profiling support"
1497 Say Y here to enable the extended profiling support mechanisms used
1498 by profilers such as OProfile.
1501 # Place an empty function call at each tracepoint site. Can be
1502 # dynamically changed for a probe function.
1507 source "arch/Kconfig"
1509 endmenu # General setup
1511 config HAVE_GENERIC_DMA_COHERENT
1518 depends on SLAB || SLUB_DEBUG
1526 default 0 if BASE_FULL
1527 default 1 if !BASE_FULL
1530 bool "Enable loadable module support"
1532 Kernel modules are small pieces of compiled code which can
1533 be inserted in the running kernel, rather than being
1534 permanently built into the kernel. You use the "modprobe"
1535 tool to add (and sometimes remove) them. If you say Y here,
1536 many parts of the kernel can be built as modules (by
1537 answering M instead of Y where indicated): this is most
1538 useful for infrequently used options which are not required
1539 for booting. For more information, see the man pages for
1540 modprobe, lsmod, modinfo, insmod and rmmod.
1542 If you say Y here, you will need to run "make
1543 modules_install" to put the modules under /lib/modules/
1544 where modprobe can find them (you may need to be root to do
1551 config MODULE_FORCE_LOAD
1552 bool "Forced module loading"
1555 Allow loading of modules without version information (ie. modprobe
1556 --force). Forced module loading sets the 'F' (forced) taint flag and
1557 is usually a really bad idea.
1559 config MODULE_UNLOAD
1560 bool "Module unloading"
1562 Without this option you will not be able to unload any
1563 modules (note that some modules may not be unloadable
1564 anyway), which makes your kernel smaller, faster
1565 and simpler. If unsure, say Y.
1567 config MODULE_FORCE_UNLOAD
1568 bool "Forced module unloading"
1569 depends on MODULE_UNLOAD && EXPERIMENTAL
1571 This option allows you to force a module to unload, even if the
1572 kernel believes it is unsafe: the kernel will remove the module
1573 without waiting for anyone to stop using it (using the -f option to
1574 rmmod). This is mainly for kernel developers and desperate users.
1578 bool "Module versioning support"
1580 Usually, you have to use modules compiled with your kernel.
1581 Saying Y here makes it sometimes possible to use modules
1582 compiled for different kernels, by adding enough information
1583 to the modules to (hopefully) spot any changes which would
1584 make them incompatible with the kernel you are running. If
1587 config MODULE_SRCVERSION_ALL
1588 bool "Source checksum for all modules"
1590 Modules which contain a MODULE_VERSION get an extra "srcversion"
1591 field inserted into their modinfo section, which contains a
1592 sum of the source files which made it. This helps maintainers
1593 see exactly which source was used to build a module (since
1594 others sometimes change the module source without updating
1595 the version). With this option, such a "srcversion" field
1596 will be created for all modules. If unsure, say N.
1600 config INIT_ALL_POSSIBLE
1603 Back when each arch used to define their own cpu_online_mask and
1604 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1605 with all 1s, and others with all 0s. When they were centralised,
1606 it was better to provide this option than to break all the archs
1607 and have several arch maintainers pursuing me down dark alleys.
1612 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1614 Need stop_machine() primitive.
1616 source "block/Kconfig"
1618 config PREEMPT_NOTIFIERS
1625 source "kernel/Kconfig.locks"