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56 drivers that have been replaced by something else, and/or are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 VIRT_CPU_ACCOUNTING
271 bool "Deterministic task and CPU time accounting"
272 depends on HAVE_VIRT_CPU_ACCOUNTING
275 Select this option to enable more accurate task and CPU time
276 accounting. This is done by reading a CPU counter on each
277 kernel entry and exit and on transitions within the kernel
278 between system, softirq and hardirq state, so there is a
279 small performance impact. In the case of s390 or IBM POWER > 5,
280 this also enables accounting of stolen time on logically-partitioned
283 config BSD_PROCESS_ACCT
284 bool "BSD Process Accounting"
286 If you say Y here, a user level program will be able to instruct the
287 kernel (via a special system call) to write process accounting
288 information to a file: whenever a process exits, information about
289 that process will be appended to the file by the kernel. The
290 information includes things such as creation time, owning user,
291 command name, memory usage, controlling terminal etc. (the complete
292 list is in the struct acct in <file:include/linux/acct.h>). It is
293 up to the user level program to do useful things with this
294 information. This is generally a good idea, so say Y.
296 config BSD_PROCESS_ACCT_V3
297 bool "BSD Process Accounting version 3 file format"
298 depends on BSD_PROCESS_ACCT
301 If you say Y here, the process accounting information is written
302 in a new file format that also logs the process IDs of each
303 process and it's parent. Note that this file format is incompatible
304 with previous v0/v1/v2 file formats, so you will need updated tools
305 for processing it. A preliminary version of these tools is available
306 at <http://www.gnu.org/software/acct/>.
309 bool "open by fhandle syscalls"
312 If you say Y here, a user level program will be able to map
313 file names to handle and then later use the handle for
314 different file system operations. This is useful in implementing
315 userspace file servers, which now track files using handles instead
316 of names. The handle would remain the same even if file names
317 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
321 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
325 Export selected statistics for tasks/processes through the
326 generic netlink interface. Unlike BSD process accounting, the
327 statistics are available during the lifetime of tasks/processes as
328 responses to commands. Like BSD accounting, they are sent to user
333 config TASK_DELAY_ACCT
334 bool "Enable per-task delay accounting (EXPERIMENTAL)"
337 Collect information on time spent by a task waiting for system
338 resources like cpu, synchronous block I/O completion and swapping
339 in pages. Such statistics can help in setting a task's priorities
340 relative to other tasks for cpu, io, rss limits etc.
345 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
348 Collect extended task accounting data and send the data
349 to userland for processing over the taskstats interface.
353 config TASK_IO_ACCOUNTING
354 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
355 depends on TASK_XACCT
357 Collect information on the number of bytes of storage I/O which this
363 bool "Auditing support"
366 Enable auditing infrastructure that can be used with another
367 kernel subsystem, such as SELinux (which requires this for
368 logging of avc messages output). Does not do system-call
369 auditing without CONFIG_AUDITSYSCALL.
372 bool "Enable system-call auditing support"
373 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
374 default y if SECURITY_SELINUX
376 Enable low-overhead system-call auditing infrastructure that
377 can be used independently or with another kernel subsystem,
382 depends on AUDITSYSCALL
387 depends on AUDITSYSCALL
390 config AUDIT_LOGINUID_IMMUTABLE
391 bool "Make audit loginuid immutable"
394 The config option toggles if a task setting its loginuid requires
395 CAP_SYS_AUDITCONTROL or if that task should require no special permissions
396 but should instead only allow setting its loginuid if it was never
397 previously set. On systems which use systemd or a similar central
398 process to restart login services this should be set to true. On older
399 systems in which an admin would typically have to directly stop and
400 start processes this should be set to false. Setting this to true allows
401 one to drop potentially dangerous capabilites from the login tasks,
402 but may not be backwards compatible with older init systems.
404 source "kernel/irq/Kconfig"
405 source "kernel/time/Kconfig"
410 prompt "RCU Implementation"
414 bool "Tree-based hierarchical RCU"
415 depends on !PREEMPT && SMP
417 This option selects the RCU implementation that is
418 designed for very large SMP system with hundreds or
419 thousands of CPUs. It also scales down nicely to
422 config TREE_PREEMPT_RCU
423 bool "Preemptible tree-based hierarchical RCU"
424 depends on PREEMPT && SMP
426 This option selects the RCU implementation that is
427 designed for very large SMP systems with hundreds or
428 thousands of CPUs, but for which real-time response
429 is also required. It also scales down nicely to
433 bool "UP-only small-memory-footprint RCU"
434 depends on !PREEMPT && !SMP
436 This option selects the RCU implementation that is
437 designed for UP systems from which real-time response
438 is not required. This option greatly reduces the
439 memory footprint of RCU.
441 config TINY_PREEMPT_RCU
442 bool "Preemptible UP-only small-memory-footprint RCU"
443 depends on PREEMPT && !SMP
445 This option selects the RCU implementation that is designed
446 for real-time UP systems. This option greatly reduces the
447 memory footprint of RCU.
452 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
454 This option enables preemptible-RCU code that is common between
455 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
458 bool "Consider userspace as in RCU extended quiescent state"
459 depends on HAVE_RCU_USER_QS && SMP
461 This option sets hooks on kernel / userspace boundaries and
462 puts RCU in extended quiescent state when the CPU runs in
463 userspace. It means that when a CPU runs in userspace, it is
464 excluded from the global RCU state machine and thus doesn't
465 to keep the timer tick on for RCU.
467 config RCU_USER_QS_FORCE
468 bool "Force userspace extended QS by default"
469 depends on RCU_USER_QS
471 Set the hooks in user/kernel boundaries by default in order to
472 test this feature that treats userspace as an extended quiescent
473 state until we have a real user like a full adaptive nohz option.
476 int "Tree-based hierarchical RCU fanout value"
479 depends on TREE_RCU || TREE_PREEMPT_RCU
483 This option controls the fanout of hierarchical implementations
484 of RCU, allowing RCU to work efficiently on machines with
485 large numbers of CPUs. This value must be at least the fourth
486 root of NR_CPUS, which allows NR_CPUS to be insanely large.
487 The default value of RCU_FANOUT should be used for production
488 systems, but if you are stress-testing the RCU implementation
489 itself, small RCU_FANOUT values allow you to test large-system
490 code paths on small(er) systems.
492 Select a specific number if testing RCU itself.
493 Take the default if unsure.
495 config RCU_FANOUT_LEAF
496 int "Tree-based hierarchical RCU leaf-level fanout value"
497 range 2 RCU_FANOUT if 64BIT
498 range 2 RCU_FANOUT if !64BIT
499 depends on TREE_RCU || TREE_PREEMPT_RCU
502 This option controls the leaf-level fanout of hierarchical
503 implementations of RCU, and allows trading off cache misses
504 against lock contention. Systems that synchronize their
505 scheduling-clock interrupts for energy-efficiency reasons will
506 want the default because the smaller leaf-level fanout keeps
507 lock contention levels acceptably low. Very large systems
508 (hundreds or thousands of CPUs) will instead want to set this
509 value to the maximum value possible in order to reduce the
510 number of cache misses incurred during RCU's grace-period
511 initialization. These systems tend to run CPU-bound, and thus
512 are not helped by synchronized interrupts, and thus tend to
513 skew them, which reduces lock contention enough that large
514 leaf-level fanouts work well.
516 Select a specific number if testing RCU itself.
518 Select the maximum permissible value for large systems.
520 Take the default if unsure.
522 config RCU_FANOUT_EXACT
523 bool "Disable tree-based hierarchical RCU auto-balancing"
524 depends on TREE_RCU || TREE_PREEMPT_RCU
527 This option forces use of the exact RCU_FANOUT value specified,
528 regardless of imbalances in the hierarchy. This is useful for
529 testing RCU itself, and might one day be useful on systems with
530 strong NUMA behavior.
532 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
536 config RCU_FAST_NO_HZ
537 bool "Accelerate last non-dyntick-idle CPU's grace periods"
538 depends on NO_HZ && SMP
541 This option causes RCU to attempt to accelerate grace periods
542 in order to allow CPUs to enter dynticks-idle state more
543 quickly. On the other hand, this option increases the overhead
544 of the dynticks-idle checking, particularly on systems with
545 large numbers of CPUs.
547 Say Y if energy efficiency is critically important, particularly
548 if you have relatively few CPUs.
550 Say N if you are unsure.
552 config TREE_RCU_TRACE
553 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
556 This option provides tracing for the TREE_RCU and
557 TREE_PREEMPT_RCU implementations, permitting Makefile to
558 trivially select kernel/rcutree_trace.c.
561 bool "Enable RCU priority boosting"
562 depends on RT_MUTEXES && PREEMPT_RCU
565 This option boosts the priority of preempted RCU readers that
566 block the current preemptible RCU grace period for too long.
567 This option also prevents heavy loads from blocking RCU
568 callback invocation for all flavors of RCU.
570 Say Y here if you are working with real-time apps or heavy loads
571 Say N here if you are unsure.
573 config RCU_BOOST_PRIO
574 int "Real-time priority to boost RCU readers to"
579 This option specifies the real-time priority to which long-term
580 preempted RCU readers are to be boosted. If you are working
581 with a real-time application that has one or more CPU-bound
582 threads running at a real-time priority level, you should set
583 RCU_BOOST_PRIO to a priority higher then the highest-priority
584 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
585 of 1 is appropriate in the common case, which is real-time
586 applications that do not have any CPU-bound threads.
588 Some real-time applications might not have a single real-time
589 thread that saturates a given CPU, but instead might have
590 multiple real-time threads that, taken together, fully utilize
591 that CPU. In this case, you should set RCU_BOOST_PRIO to
592 a priority higher than the lowest-priority thread that is
593 conspiring to prevent the CPU from running any non-real-time
594 tasks. For example, if one thread at priority 10 and another
595 thread at priority 5 are between themselves fully consuming
596 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
597 set to priority 6 or higher.
599 Specify the real-time priority, or take the default if unsure.
601 config RCU_BOOST_DELAY
602 int "Milliseconds to delay boosting after RCU grace-period start"
607 This option specifies the time to wait after the beginning of
608 a given grace period before priority-boosting preempted RCU
609 readers blocking that grace period. Note that any RCU reader
610 blocking an expedited RCU grace period is boosted immediately.
612 Accept the default if unsure.
614 endmenu # "RCU Subsystem"
617 tristate "Kernel .config support"
619 This option enables the complete Linux kernel ".config" file
620 contents to be saved in the kernel. It provides documentation
621 of which kernel options are used in a running kernel or in an
622 on-disk kernel. This information can be extracted from the kernel
623 image file with the script scripts/extract-ikconfig and used as
624 input to rebuild the current kernel or to build another kernel.
625 It can also be extracted from a running kernel by reading
626 /proc/config.gz if enabled (below).
629 bool "Enable access to .config through /proc/config.gz"
630 depends on IKCONFIG && PROC_FS
632 This option enables access to the kernel configuration file
633 through /proc/config.gz.
636 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
640 Select kernel log buffer size as a power of 2.
650 # Architectures with an unreliable sched_clock() should select this:
652 config HAVE_UNSTABLE_SCHED_CLOCK
656 boolean "Control Group support"
659 This option adds support for grouping sets of processes together, for
660 use with process control subsystems such as Cpusets, CFS, memory
661 controls or device isolation.
663 - Documentation/scheduler/sched-design-CFS.txt (CFS)
664 - Documentation/cgroups/ (features for grouping, isolation
665 and resource control)
672 bool "Example debug cgroup subsystem"
675 This option enables a simple cgroup subsystem that
676 exports useful debugging information about the cgroups
681 config CGROUP_FREEZER
682 bool "Freezer cgroup subsystem"
684 Provides a way to freeze and unfreeze all tasks in a
688 bool "Device controller for cgroups"
690 Provides a cgroup implementing whitelists for devices which
691 a process in the cgroup can mknod or open.
694 bool "Cpuset support"
696 This option will let you create and manage CPUSETs which
697 allow dynamically partitioning a system into sets of CPUs and
698 Memory Nodes and assigning tasks to run only within those sets.
699 This is primarily useful on large SMP or NUMA systems.
703 config PROC_PID_CPUSET
704 bool "Include legacy /proc/<pid>/cpuset file"
708 config CGROUP_CPUACCT
709 bool "Simple CPU accounting cgroup subsystem"
711 Provides a simple Resource Controller for monitoring the
712 total CPU consumed by the tasks in a cgroup.
714 config RESOURCE_COUNTERS
715 bool "Resource counters"
717 This option enables controller independent resource accounting
718 infrastructure that works with cgroups.
721 bool "Memory Resource Controller for Control Groups"
722 depends on RESOURCE_COUNTERS
725 Provides a memory resource controller that manages both anonymous
726 memory and page cache. (See Documentation/cgroups/memory.txt)
728 Note that setting this option increases fixed memory overhead
729 associated with each page of memory in the system. By this,
730 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
731 usage tracking struct at boot. Total amount of this is printed out
734 Only enable when you're ok with these trade offs and really
735 sure you need the memory resource controller. Even when you enable
736 this, you can set "cgroup_disable=memory" at your boot option to
737 disable memory resource controller and you can avoid overheads.
738 (and lose benefits of memory resource controller)
740 This config option also selects MM_OWNER config option, which
741 could in turn add some fork/exit overhead.
744 bool "Memory Resource Controller Swap Extension"
745 depends on MEMCG && SWAP
747 Add swap management feature to memory resource controller. When you
748 enable this, you can limit mem+swap usage per cgroup. In other words,
749 when you disable this, memory resource controller has no cares to
750 usage of swap...a process can exhaust all of the swap. This extension
751 is useful when you want to avoid exhaustion swap but this itself
752 adds more overheads and consumes memory for remembering information.
753 Especially if you use 32bit system or small memory system, please
754 be careful about enabling this. When memory resource controller
755 is disabled by boot option, this will be automatically disabled and
756 there will be no overhead from this. Even when you set this config=y,
757 if boot option "swapaccount=0" is set, swap will not be accounted.
758 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
759 size is 4096bytes, 512k per 1Gbytes of swap.
760 config MEMCG_SWAP_ENABLED
761 bool "Memory Resource Controller Swap Extension enabled by default"
762 depends on MEMCG_SWAP
765 Memory Resource Controller Swap Extension comes with its price in
766 a bigger memory consumption. General purpose distribution kernels
767 which want to enable the feature but keep it disabled by default
768 and let the user enable it by swapaccount boot command line
769 parameter should have this option unselected.
770 For those who want to have the feature enabled by default should
771 select this option (if, for some reason, they need to disable it
772 then swapaccount=0 does the trick).
774 bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
775 depends on MEMCG && EXPERIMENTAL
778 The Kernel Memory extension for Memory Resource Controller can limit
779 the amount of memory used by kernel objects in the system. Those are
780 fundamentally different from the entities handled by the standard
781 Memory Controller, which are page-based, and can be swapped. Users of
782 the kmem extension can use it to guarantee that no group of processes
783 will ever exhaust kernel resources alone.
785 config CGROUP_HUGETLB
786 bool "HugeTLB Resource Controller for Control Groups"
787 depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
790 Provides a cgroup Resource Controller for HugeTLB pages.
791 When you enable this, you can put a per cgroup limit on HugeTLB usage.
792 The limit is enforced during page fault. Since HugeTLB doesn't
793 support page reclaim, enforcing the limit at page fault time implies
794 that, the application will get SIGBUS signal if it tries to access
795 HugeTLB pages beyond its limit. This requires the application to know
796 beforehand how much HugeTLB pages it would require for its use. The
797 control group is tracked in the third page lru pointer. This means
798 that we cannot use the controller with huge page less than 3 pages.
801 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
802 depends on PERF_EVENTS && CGROUPS
804 This option extends the per-cpu mode to restrict monitoring to
805 threads which belong to the cgroup specified and run on the
810 menuconfig CGROUP_SCHED
811 bool "Group CPU scheduler"
814 This feature lets CPU scheduler recognize task groups and control CPU
815 bandwidth allocation to such task groups. It uses cgroups to group
819 config FAIR_GROUP_SCHED
820 bool "Group scheduling for SCHED_OTHER"
821 depends on CGROUP_SCHED
825 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
826 depends on EXPERIMENTAL
827 depends on FAIR_GROUP_SCHED
830 This option allows users to define CPU bandwidth rates (limits) for
831 tasks running within the fair group scheduler. Groups with no limit
832 set are considered to be unconstrained and will run with no
834 See tip/Documentation/scheduler/sched-bwc.txt for more information.
836 config RT_GROUP_SCHED
837 bool "Group scheduling for SCHED_RR/FIFO"
838 depends on EXPERIMENTAL
839 depends on CGROUP_SCHED
842 This feature lets you explicitly allocate real CPU bandwidth
843 to task groups. If enabled, it will also make it impossible to
844 schedule realtime tasks for non-root users until you allocate
845 realtime bandwidth for them.
846 See Documentation/scheduler/sched-rt-group.txt for more information.
851 bool "Block IO controller"
855 Generic block IO controller cgroup interface. This is the common
856 cgroup interface which should be used by various IO controlling
859 Currently, CFQ IO scheduler uses it to recognize task groups and
860 control disk bandwidth allocation (proportional time slice allocation)
861 to such task groups. It is also used by bio throttling logic in
862 block layer to implement upper limit in IO rates on a device.
864 This option only enables generic Block IO controller infrastructure.
865 One needs to also enable actual IO controlling logic/policy. For
866 enabling proportional weight division of disk bandwidth in CFQ, set
867 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
868 CONFIG_BLK_DEV_THROTTLING=y.
870 See Documentation/cgroups/blkio-controller.txt for more information.
872 config DEBUG_BLK_CGROUP
873 bool "Enable Block IO controller debugging"
874 depends on BLK_CGROUP
877 Enable some debugging help. Currently it exports additional stat
878 files in a cgroup which can be useful for debugging.
882 config CHECKPOINT_RESTORE
883 bool "Checkpoint/restore support" if EXPERT
886 Enables additional kernel features in a sake of checkpoint/restore.
887 In particular it adds auxiliary prctl codes to setup process text,
888 data and heap segment sizes, and a few additional /proc filesystem
891 If unsure, say N here.
893 menuconfig NAMESPACES
894 bool "Namespaces support" if EXPERT
897 Provides the way to make tasks work with different objects using
898 the same id. For example same IPC id may refer to different objects
899 or same user id or pid may refer to different tasks when used in
900 different namespaces.
908 In this namespace tasks see different info provided with the
913 depends on (SYSVIPC || POSIX_MQUEUE)
916 In this namespace tasks work with IPC ids which correspond to
917 different IPC objects in different namespaces.
920 bool "User namespace (EXPERIMENTAL)"
921 depends on EXPERIMENTAL
922 depends on UIDGID_CONVERTED
923 select UIDGID_STRICT_TYPE_CHECKS
927 This allows containers, i.e. vservers, to use user namespaces
928 to provide different user info for different servers.
932 bool "PID Namespaces"
935 Support process id namespaces. This allows having multiple
936 processes with the same pid as long as they are in different
937 pid namespaces. This is a building block of containers.
940 bool "Network namespace"
944 Allow user space to create what appear to be multiple instances
945 of the network stack.
949 config UIDGID_CONVERTED
950 # True if all of the selected software conmponents are known
951 # to have uid_t and gid_t converted to kuid_t and kgid_t
952 # where appropriate and are otherwise safe to use with
953 # the user namespace.
957 # List of kernel pieces that need user namespace work
963 depends on AUDITSYSCALL = n
964 depends on TASKSTATS = n
965 depends on TRACING = n
966 depends on FS_POSIX_ACL = n
968 depends on QUOTACTL = n
969 depends on BSD_PROCESS_ACCT = n
972 depends on NET_9P = n
973 depends on AF_RXRPC = n
974 depends on DNS_RESOLVER = 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 ECRYPT_FS = n
996 depends on EFS_FS = n
997 depends on EXOFS_FS = n
998 depends on FAT_FS = n
999 depends on FUSE_FS = n
1000 depends on GFS2_FS = n
1001 depends on HFS_FS = n
1002 depends on HFSPLUS_FS = n
1003 depends on HPFS_FS = n
1004 depends on HUGETLBFS = n
1005 depends on ISO9660_FS = n
1006 depends on JFFS2_FS = n
1007 depends on JFS_FS = n
1008 depends on LOGFS = n
1009 depends on MINIX_FS = n
1010 depends on NCP_FS = n
1012 depends on NFS_FS = n
1013 depends on NILFS2_FS = n
1014 depends on NTFS_FS = n
1015 depends on OCFS2_FS = n
1016 depends on OMFS_FS = n
1017 depends on QNX4FS_FS = n
1018 depends on QNX6FS_FS = n
1019 depends on REISERFS_FS = n
1020 depends on SQUASHFS = n
1021 depends on SYSV_FS = n
1022 depends on UBIFS_FS = n
1023 depends on UDF_FS = n
1024 depends on UFS_FS = n
1025 depends on VXFS_FS = n
1026 depends on XFS_FS = n
1028 depends on !UML || HOSTFS = n
1030 # The rare drivers that won't build
1031 depends on INFINIBAND_QIB = n
1032 depends on BLK_DEV_LOOP = n
1033 depends on ANDROID_BINDER_IPC = n
1036 depends on SECURITY_TOMOYO = n
1037 depends on SECURITY_APPARMOR = n
1039 config UIDGID_STRICT_TYPE_CHECKS
1040 bool "Require conversions between uid/gids and their internal representation"
1041 depends on UIDGID_CONVERTED
1044 While the nececessary conversions are being added to all subsystems this option allows
1045 the code to continue to build for unconverted subsystems.
1047 Say Y here if you want the strict type checking enabled
1049 config SCHED_AUTOGROUP
1050 bool "Automatic process group scheduling"
1054 select FAIR_GROUP_SCHED
1056 This option optimizes the scheduler for common desktop workloads by
1057 automatically creating and populating task groups. This separation
1058 of workloads isolates aggressive CPU burners (like build jobs) from
1059 desktop applications. Task group autogeneration is currently based
1065 config SYSFS_DEPRECATED
1066 bool "Enable deprecated sysfs features to support old userspace tools"
1070 This option adds code that switches the layout of the "block" class
1071 devices, to not show up in /sys/class/block/, but only in
1074 This switch is only active when the sysfs.deprecated=1 boot option is
1075 passed or the SYSFS_DEPRECATED_V2 option is set.
1077 This option allows new kernels to run on old distributions and tools,
1078 which might get confused by /sys/class/block/. Since 2007/2008 all
1079 major distributions and tools handle this just fine.
1081 Recent distributions and userspace tools after 2009/2010 depend on
1082 the existence of /sys/class/block/, and will not work with this
1085 Only if you are using a new kernel on an old distribution, you might
1088 config SYSFS_DEPRECATED_V2
1089 bool "Enable deprecated sysfs features by default"
1092 depends on SYSFS_DEPRECATED
1094 Enable deprecated sysfs by default.
1096 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1099 Only if you are using a new kernel on an old distribution, you might
1100 need to say Y here. Even then, odds are you would not need it
1101 enabled, you can always pass the boot option if absolutely necessary.
1104 bool "Kernel->user space relay support (formerly relayfs)"
1106 This option enables support for relay interface support in
1107 certain file systems (such as debugfs).
1108 It is designed to provide an efficient mechanism for tools and
1109 facilities to relay large amounts of data from kernel space to
1114 config BLK_DEV_INITRD
1115 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1116 depends on BROKEN || !FRV
1118 The initial RAM filesystem is a ramfs which is loaded by the
1119 boot loader (loadlin or lilo) and that is mounted as root
1120 before the normal boot procedure. It is typically used to
1121 load modules needed to mount the "real" root file system,
1122 etc. See <file:Documentation/initrd.txt> for details.
1124 If RAM disk support (BLK_DEV_RAM) is also included, this
1125 also enables initial RAM disk (initrd) support and adds
1126 15 Kbytes (more on some other architectures) to the kernel size.
1132 source "usr/Kconfig"
1136 config CC_OPTIMIZE_FOR_SIZE
1137 bool "Optimize for size"
1139 Enabling this option will pass "-Os" instead of "-O2" to gcc
1140 resulting in a smaller kernel.
1151 bool "Configure standard kernel features (expert users)"
1152 # Unhide debug options, to make the on-by-default options visible
1155 This option allows certain base kernel options and settings
1156 to be disabled or tweaked. This is for specialized
1157 environments which can tolerate a "non-standard" kernel.
1158 Only use this if you really know what you are doing.
1161 bool "Enable 16-bit UID system calls" if EXPERT
1162 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION) \
1163 || AARCH32_EMULATION
1166 This enables the legacy 16-bit UID syscall wrappers.
1168 config SYSCTL_SYSCALL
1169 bool "Sysctl syscall support" if EXPERT
1170 depends on PROC_SYSCTL
1174 sys_sysctl uses binary paths that have been found challenging
1175 to properly maintain and use. The interface in /proc/sys
1176 using paths with ascii names is now the primary path to this
1179 Almost nothing using the binary sysctl interface so if you are
1180 trying to save some space it is probably safe to disable this,
1181 making your kernel marginally smaller.
1183 If unsure say N here.
1186 bool "Load all symbols for debugging/ksymoops" if EXPERT
1189 Say Y here to let the kernel print out symbolic crash information and
1190 symbolic stack backtraces. This increases the size of the kernel
1191 somewhat, as all symbols have to be loaded into the kernel image.
1194 bool "Include all symbols in kallsyms"
1195 depends on DEBUG_KERNEL && KALLSYMS
1197 Normally kallsyms only contains the symbols of functions for nicer
1198 OOPS messages and backtraces (i.e., symbols from the text and inittext
1199 sections). This is sufficient for most cases. And only in very rare
1200 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1201 names of variables from the data sections, etc).
1203 This option makes sure that all symbols are loaded into the kernel
1204 image (i.e., symbols from all sections) in cost of increased kernel
1205 size (depending on the kernel configuration, it may be 300KiB or
1206 something like this).
1208 Say N unless you really need all symbols.
1215 bool "Enable support for printk" if EXPERT
1217 This option enables normal printk support. Removing it
1218 eliminates most of the message strings from the kernel image
1219 and makes the kernel more or less silent. As this makes it
1220 very difficult to diagnose system problems, saying N here is
1221 strongly discouraged.
1224 bool "BUG() support" if EXPERT
1227 Disabling this option eliminates support for BUG and WARN, reducing
1228 the size of your kernel image and potentially quietly ignoring
1229 numerous fatal conditions. You should only consider disabling this
1230 option for embedded systems with no facilities for reporting errors.
1236 bool "Enable ELF core dumps" if EXPERT
1238 Enable support for generating core dumps. Disabling saves about 4k.
1241 config PCSPKR_PLATFORM
1242 bool "Enable PC-Speaker support" if EXPERT
1243 depends on HAVE_PCSPKR_PLATFORM
1247 This option allows to disable the internal PC-Speaker
1248 support, saving some memory.
1250 config HAVE_PCSPKR_PLATFORM
1255 bool "Enable full-sized data structures for core" if EXPERT
1257 Disabling this option reduces the size of miscellaneous core
1258 kernel data structures. This saves memory on small machines,
1259 but may reduce performance.
1262 bool "Enable futex support" if EXPERT
1266 Disabling this option will cause the kernel to be built without
1267 support for "fast userspace mutexes". The resulting kernel may not
1268 run glibc-based applications correctly.
1271 bool "Enable eventpoll support" if EXPERT
1275 Disabling this option will cause the kernel to be built without
1276 support for epoll family of system calls.
1279 bool "Enable signalfd() system call" if EXPERT
1283 Enable the signalfd() system call that allows to receive signals
1284 on a file descriptor.
1289 bool "Enable timerfd() system call" if EXPERT
1293 Enable the timerfd() system call that allows to receive timer
1294 events on a file descriptor.
1299 bool "Enable eventfd() system call" if EXPERT
1303 Enable the eventfd() system call that allows to receive both
1304 kernel notification (ie. KAIO) or userspace notifications.
1309 bool "Use full shmem filesystem" if EXPERT
1313 The shmem is an internal filesystem used to manage shared memory.
1314 It is backed by swap and manages resource limits. It is also exported
1315 to userspace as tmpfs if TMPFS is enabled. Disabling this
1316 option replaces shmem and tmpfs with the much simpler ramfs code,
1317 which may be appropriate on small systems without swap.
1320 bool "Enable AIO support" if EXPERT
1323 This option enables POSIX asynchronous I/O which may by used
1324 by some high performance threaded applications. Disabling
1325 this option saves about 7k.
1328 bool "Embedded system"
1331 This option should be enabled if compiling the kernel for
1332 an embedded system so certain expert options are available
1335 config HAVE_PERF_EVENTS
1338 See tools/perf/design.txt for details.
1340 config PERF_USE_VMALLOC
1343 See tools/perf/design.txt for details
1345 menu "Kernel Performance Events And Counters"
1348 bool "Kernel performance events and counters"
1349 default y if PROFILING
1350 depends on HAVE_PERF_EVENTS
1354 Enable kernel support for various performance events provided
1355 by software and hardware.
1357 Software events are supported either built-in or via the
1358 use of generic tracepoints.
1360 Most modern CPUs support performance events via performance
1361 counter registers. These registers count the number of certain
1362 types of hw events: such as instructions executed, cachemisses
1363 suffered, or branches mis-predicted - without slowing down the
1364 kernel or applications. These registers can also trigger interrupts
1365 when a threshold number of events have passed - and can thus be
1366 used to profile the code that runs on that CPU.
1368 The Linux Performance Event subsystem provides an abstraction of
1369 these software and hardware event capabilities, available via a
1370 system call and used by the "perf" utility in tools/perf/. It
1371 provides per task and per CPU counters, and it provides event
1372 capabilities on top of those.
1376 config DEBUG_PERF_USE_VMALLOC
1378 bool "Debug: use vmalloc to back perf mmap() buffers"
1379 depends on PERF_EVENTS && DEBUG_KERNEL
1380 select PERF_USE_VMALLOC
1382 Use vmalloc memory to back perf mmap() buffers.
1384 Mostly useful for debugging the vmalloc code on platforms
1385 that don't require it.
1391 config VM_EVENT_COUNTERS
1393 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1395 VM event counters are needed for event counts to be shown.
1396 This option allows the disabling of the VM event counters
1397 on EXPERT systems. /proc/vmstat will only show page counts
1398 if VM event counters are disabled.
1402 bool "Enable PCI quirk workarounds" if EXPERT
1405 This enables workarounds for various PCI chipset
1406 bugs/quirks. Disable this only if your target machine is
1407 unaffected by PCI quirks.
1411 bool "Enable SLUB debugging support" if EXPERT
1412 depends on SLUB && SYSFS
1414 SLUB has extensive debug support features. Disabling these can
1415 result in significant savings in code size. This also disables
1416 SLUB sysfs support. /sys/slab will not exist and there will be
1417 no support for cache validation etc.
1420 bool "Disable heap randomization"
1423 Randomizing heap placement makes heap exploits harder, but it
1424 also breaks ancient binaries (including anything libc5 based).
1425 This option changes the bootup default to heap randomization
1426 disabled, and can be overridden at runtime by setting
1427 /proc/sys/kernel/randomize_va_space to 2.
1429 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1432 prompt "Choose SLAB allocator"
1435 This option allows to select a slab allocator.
1440 The regular slab allocator that is established and known to work
1441 well in all environments. It organizes cache hot objects in
1442 per cpu and per node queues.
1445 bool "SLUB (Unqueued Allocator)"
1447 SLUB is a slab allocator that minimizes cache line usage
1448 instead of managing queues of cached objects (SLAB approach).
1449 Per cpu caching is realized using slabs of objects instead
1450 of queues of objects. SLUB can use memory efficiently
1451 and has enhanced diagnostics. SLUB is the default choice for
1456 bool "SLOB (Simple Allocator)"
1458 SLOB replaces the stock allocator with a drastically simpler
1459 allocator. SLOB is generally more space efficient but
1460 does not perform as well on large systems.
1464 config MMAP_ALLOW_UNINITIALIZED
1465 bool "Allow mmapped anonymous memory to be uninitialized"
1466 depends on EXPERT && !MMU
1469 Normally, and according to the Linux spec, anonymous memory obtained
1470 from mmap() has it's contents cleared before it is passed to
1471 userspace. Enabling this config option allows you to request that
1472 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1473 providing a huge performance boost. If this option is not enabled,
1474 then the flag will be ignored.
1476 This is taken advantage of by uClibc's malloc(), and also by
1477 ELF-FDPIC binfmt's brk and stack allocator.
1479 Because of the obvious security issues, this option should only be
1480 enabled on embedded devices where you control what is run in
1481 userspace. Since that isn't generally a problem on no-MMU systems,
1482 it is normally safe to say Y here.
1484 See Documentation/nommu-mmap.txt for more information.
1487 bool "Profiling support"
1489 Say Y here to enable the extended profiling support mechanisms used
1490 by profilers such as OProfile.
1493 # Place an empty function call at each tracepoint site. Can be
1494 # dynamically changed for a probe function.
1499 source "arch/Kconfig"
1501 endmenu # General setup
1503 config HAVE_GENERIC_DMA_COHERENT
1510 depends on SLAB || SLUB_DEBUG
1518 default 0 if BASE_FULL
1519 default 1 if !BASE_FULL
1522 bool "Enable loadable module support"
1524 Kernel modules are small pieces of compiled code which can
1525 be inserted in the running kernel, rather than being
1526 permanently built into the kernel. You use the "modprobe"
1527 tool to add (and sometimes remove) them. If you say Y here,
1528 many parts of the kernel can be built as modules (by
1529 answering M instead of Y where indicated): this is most
1530 useful for infrequently used options which are not required
1531 for booting. For more information, see the man pages for
1532 modprobe, lsmod, modinfo, insmod and rmmod.
1534 If you say Y here, you will need to run "make
1535 modules_install" to put the modules under /lib/modules/
1536 where modprobe can find them (you may need to be root to do
1543 config MODULE_FORCE_LOAD
1544 bool "Forced module loading"
1547 Allow loading of modules without version information (ie. modprobe
1548 --force). Forced module loading sets the 'F' (forced) taint flag and
1549 is usually a really bad idea.
1551 config MODULE_UNLOAD
1552 bool "Module unloading"
1554 Without this option you will not be able to unload any
1555 modules (note that some modules may not be unloadable
1556 anyway), which makes your kernel smaller, faster
1557 and simpler. If unsure, say Y.
1559 config MODULE_FORCE_UNLOAD
1560 bool "Forced module unloading"
1561 depends on MODULE_UNLOAD && EXPERIMENTAL
1563 This option allows you to force a module to unload, even if the
1564 kernel believes it is unsafe: the kernel will remove the module
1565 without waiting for anyone to stop using it (using the -f option to
1566 rmmod). This is mainly for kernel developers and desperate users.
1570 bool "Module versioning support"
1572 Usually, you have to use modules compiled with your kernel.
1573 Saying Y here makes it sometimes possible to use modules
1574 compiled for different kernels, by adding enough information
1575 to the modules to (hopefully) spot any changes which would
1576 make them incompatible with the kernel you are running. If
1579 config MODULE_SRCVERSION_ALL
1580 bool "Source checksum for all modules"
1582 Modules which contain a MODULE_VERSION get an extra "srcversion"
1583 field inserted into their modinfo section, which contains a
1584 sum of the source files which made it. This helps maintainers
1585 see exactly which source was used to build a module (since
1586 others sometimes change the module source without updating
1587 the version). With this option, such a "srcversion" field
1588 will be created for all modules. If unsure, say N.
1592 config INIT_ALL_POSSIBLE
1595 Back when each arch used to define their own cpu_online_mask and
1596 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1597 with all 1s, and others with all 0s. When they were centralised,
1598 it was better to provide this option than to break all the archs
1599 and have several arch maintainers pursuing me down dark alleys.
1604 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1606 Need stop_machine() primitive.
1608 source "block/Kconfig"
1610 config PREEMPT_NOTIFIERS
1617 # Can be selected by architectures with broken toolchains
1618 # that get confused by correct const<->read_only section
1620 config BROKEN_RODATA
1623 source "kernel/Kconfig.locks"