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56 drivers that have been replaced by something else, and/or are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
271 bool "open by fhandle syscalls"
274 If you say Y here, a user level program will be able to map
275 file names to handle and then later use the handle for
276 different file system operations. This is useful in implementing
277 userspace file servers, which now track files using handles instead
278 of names. The handle would remain the same even if file names
279 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
283 bool "Auditing support"
286 Enable auditing infrastructure that can be used with another
287 kernel subsystem, such as SELinux (which requires this for
288 logging of avc messages output). Does not do system-call
289 auditing without CONFIG_AUDITSYSCALL.
292 bool "Enable system-call auditing support"
293 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
294 default y if SECURITY_SELINUX
296 Enable low-overhead system-call auditing infrastructure that
297 can be used independently or with another kernel subsystem,
302 depends on AUDITSYSCALL
307 depends on AUDITSYSCALL
310 config AUDIT_LOGINUID_IMMUTABLE
311 bool "Make audit loginuid immutable"
314 The config option toggles if a task setting its loginuid requires
315 CAP_SYS_AUDITCONTROL or if that task should require no special permissions
316 but should instead only allow setting its loginuid if it was never
317 previously set. On systems which use systemd or a similar central
318 process to restart login services this should be set to true. On older
319 systems in which an admin would typically have to directly stop and
320 start processes this should be set to false. Setting this to true allows
321 one to drop potentially dangerous capabilites from the login tasks,
322 but may not be backwards compatible with older init systems.
324 source "kernel/irq/Kconfig"
325 source "kernel/time/Kconfig"
327 menu "CPU/Task time and stats accounting"
329 config VIRT_CPU_ACCOUNTING
330 bool "Deterministic task and CPU time accounting"
331 depends on HAVE_VIRT_CPU_ACCOUNTING
334 Select this option to enable more accurate task and CPU time
335 accounting. This is done by reading a CPU counter on each
336 kernel entry and exit and on transitions within the kernel
337 between system, softirq and hardirq state, so there is a
338 small performance impact. In the case of s390 or IBM POWER > 5,
339 this also enables accounting of stolen time on logically-partitioned
342 config BSD_PROCESS_ACCT
343 bool "BSD Process Accounting"
345 If you say Y here, a user level program will be able to instruct the
346 kernel (via a special system call) to write process accounting
347 information to a file: whenever a process exits, information about
348 that process will be appended to the file by the kernel. The
349 information includes things such as creation time, owning user,
350 command name, memory usage, controlling terminal etc. (the complete
351 list is in the struct acct in <file:include/linux/acct.h>). It is
352 up to the user level program to do useful things with this
353 information. This is generally a good idea, so say Y.
355 config BSD_PROCESS_ACCT_V3
356 bool "BSD Process Accounting version 3 file format"
357 depends on BSD_PROCESS_ACCT
360 If you say Y here, the process accounting information is written
361 in a new file format that also logs the process IDs of each
362 process and it's parent. Note that this file format is incompatible
363 with previous v0/v1/v2 file formats, so you will need updated tools
364 for processing it. A preliminary version of these tools is available
365 at <http://www.gnu.org/software/acct/>.
368 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
372 Export selected statistics for tasks/processes through the
373 generic netlink interface. Unlike BSD process accounting, the
374 statistics are available during the lifetime of tasks/processes as
375 responses to commands. Like BSD accounting, they are sent to user
380 config TASK_DELAY_ACCT
381 bool "Enable per-task delay accounting (EXPERIMENTAL)"
384 Collect information on time spent by a task waiting for system
385 resources like cpu, synchronous block I/O completion and swapping
386 in pages. Such statistics can help in setting a task's priorities
387 relative to other tasks for cpu, io, rss limits etc.
392 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
395 Collect extended task accounting data and send the data
396 to userland for processing over the taskstats interface.
400 config TASK_IO_ACCOUNTING
401 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
402 depends on TASK_XACCT
404 Collect information on the number of bytes of storage I/O which this
409 endmenu # "CPU/Task time and stats accounting"
414 prompt "RCU Implementation"
418 bool "Tree-based hierarchical RCU"
419 depends on !PREEMPT && SMP
421 This option selects the RCU implementation that is
422 designed for very large SMP system with hundreds or
423 thousands of CPUs. It also scales down nicely to
426 config TREE_PREEMPT_RCU
427 bool "Preemptible tree-based hierarchical RCU"
428 depends on PREEMPT && SMP
430 This option selects the RCU implementation that is
431 designed for very large SMP systems with hundreds or
432 thousands of CPUs, but for which real-time response
433 is also required. It also scales down nicely to
437 bool "UP-only small-memory-footprint RCU"
438 depends on !PREEMPT && !SMP
440 This option selects the RCU implementation that is
441 designed for UP systems from which real-time response
442 is not required. This option greatly reduces the
443 memory footprint of RCU.
445 config TINY_PREEMPT_RCU
446 bool "Preemptible UP-only small-memory-footprint RCU"
447 depends on PREEMPT && !SMP
449 This option selects the RCU implementation that is designed
450 for real-time UP systems. This option greatly reduces the
451 memory footprint of RCU.
456 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
458 This option enables preemptible-RCU code that is common between
459 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
462 int "Tree-based hierarchical RCU fanout value"
465 depends on TREE_RCU || TREE_PREEMPT_RCU
469 This option controls the fanout of hierarchical implementations
470 of RCU, allowing RCU to work efficiently on machines with
471 large numbers of CPUs. This value must be at least the fourth
472 root of NR_CPUS, which allows NR_CPUS to be insanely large.
473 The default value of RCU_FANOUT should be used for production
474 systems, but if you are stress-testing the RCU implementation
475 itself, small RCU_FANOUT values allow you to test large-system
476 code paths on small(er) systems.
478 Select a specific number if testing RCU itself.
479 Take the default if unsure.
481 config RCU_FANOUT_LEAF
482 int "Tree-based hierarchical RCU leaf-level fanout value"
483 range 2 RCU_FANOUT if 64BIT
484 range 2 RCU_FANOUT if !64BIT
485 depends on TREE_RCU || TREE_PREEMPT_RCU
488 This option controls the leaf-level fanout of hierarchical
489 implementations of RCU, and allows trading off cache misses
490 against lock contention. Systems that synchronize their
491 scheduling-clock interrupts for energy-efficiency reasons will
492 want the default because the smaller leaf-level fanout keeps
493 lock contention levels acceptably low. Very large systems
494 (hundreds or thousands of CPUs) will instead want to set this
495 value to the maximum value possible in order to reduce the
496 number of cache misses incurred during RCU's grace-period
497 initialization. These systems tend to run CPU-bound, and thus
498 are not helped by synchronized interrupts, and thus tend to
499 skew them, which reduces lock contention enough that large
500 leaf-level fanouts work well.
502 Select a specific number if testing RCU itself.
504 Select the maximum permissible value for large systems.
506 Take the default if unsure.
508 config RCU_FANOUT_EXACT
509 bool "Disable tree-based hierarchical RCU auto-balancing"
510 depends on TREE_RCU || TREE_PREEMPT_RCU
513 This option forces use of the exact RCU_FANOUT value specified,
514 regardless of imbalances in the hierarchy. This is useful for
515 testing RCU itself, and might one day be useful on systems with
516 strong NUMA behavior.
518 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
522 config RCU_FAST_NO_HZ
523 bool "Accelerate last non-dyntick-idle CPU's grace periods"
524 depends on NO_HZ && SMP
527 This option causes RCU to attempt to accelerate grace periods
528 in order to allow CPUs to enter dynticks-idle state more
529 quickly. On the other hand, this option increases the overhead
530 of the dynticks-idle checking, particularly on systems with
531 large numbers of CPUs.
533 Say Y if energy efficiency is critically important, particularly
534 if you have relatively few CPUs.
536 Say N if you are unsure.
538 config TREE_RCU_TRACE
539 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
542 This option provides tracing for the TREE_RCU and
543 TREE_PREEMPT_RCU implementations, permitting Makefile to
544 trivially select kernel/rcutree_trace.c.
547 bool "Enable RCU priority boosting"
548 depends on RT_MUTEXES && PREEMPT_RCU
551 This option boosts the priority of preempted RCU readers that
552 block the current preemptible RCU grace period for too long.
553 This option also prevents heavy loads from blocking RCU
554 callback invocation for all flavors of RCU.
556 Say Y here if you are working with real-time apps or heavy loads
557 Say N here if you are unsure.
559 config RCU_BOOST_PRIO
560 int "Real-time priority to boost RCU readers to"
565 This option specifies the real-time priority to which long-term
566 preempted RCU readers are to be boosted. If you are working
567 with a real-time application that has one or more CPU-bound
568 threads running at a real-time priority level, you should set
569 RCU_BOOST_PRIO to a priority higher then the highest-priority
570 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
571 of 1 is appropriate in the common case, which is real-time
572 applications that do not have any CPU-bound threads.
574 Some real-time applications might not have a single real-time
575 thread that saturates a given CPU, but instead might have
576 multiple real-time threads that, taken together, fully utilize
577 that CPU. In this case, you should set RCU_BOOST_PRIO to
578 a priority higher than the lowest-priority thread that is
579 conspiring to prevent the CPU from running any non-real-time
580 tasks. For example, if one thread at priority 10 and another
581 thread at priority 5 are between themselves fully consuming
582 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
583 set to priority 6 or higher.
585 Specify the real-time priority, or take the default if unsure.
587 config RCU_BOOST_DELAY
588 int "Milliseconds to delay boosting after RCU grace-period start"
593 This option specifies the time to wait after the beginning of
594 a given grace period before priority-boosting preempted RCU
595 readers blocking that grace period. Note that any RCU reader
596 blocking an expedited RCU grace period is boosted immediately.
598 Accept the default if unsure.
600 endmenu # "RCU Subsystem"
603 tristate "Kernel .config support"
605 This option enables the complete Linux kernel ".config" file
606 contents to be saved in the kernel. It provides documentation
607 of which kernel options are used in a running kernel or in an
608 on-disk kernel. This information can be extracted from the kernel
609 image file with the script scripts/extract-ikconfig and used as
610 input to rebuild the current kernel or to build another kernel.
611 It can also be extracted from a running kernel by reading
612 /proc/config.gz if enabled (below).
615 bool "Enable access to .config through /proc/config.gz"
616 depends on IKCONFIG && PROC_FS
618 This option enables access to the kernel configuration file
619 through /proc/config.gz.
622 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
626 Select kernel log buffer size as a power of 2.
636 # Architectures with an unreliable sched_clock() should select this:
638 config HAVE_UNSTABLE_SCHED_CLOCK
642 boolean "Control Group support"
645 This option adds support for grouping sets of processes together, for
646 use with process control subsystems such as Cpusets, CFS, memory
647 controls or device isolation.
649 - Documentation/scheduler/sched-design-CFS.txt (CFS)
650 - Documentation/cgroups/ (features for grouping, isolation
651 and resource control)
658 bool "Example debug cgroup subsystem"
661 This option enables a simple cgroup subsystem that
662 exports useful debugging information about the cgroups
667 config CGROUP_FREEZER
668 bool "Freezer cgroup subsystem"
670 Provides a way to freeze and unfreeze all tasks in a
674 bool "Device controller for cgroups"
676 Provides a cgroup implementing whitelists for devices which
677 a process in the cgroup can mknod or open.
680 bool "Cpuset support"
682 This option will let you create and manage CPUSETs which
683 allow dynamically partitioning a system into sets of CPUs and
684 Memory Nodes and assigning tasks to run only within those sets.
685 This is primarily useful on large SMP or NUMA systems.
689 config PROC_PID_CPUSET
690 bool "Include legacy /proc/<pid>/cpuset file"
694 config CGROUP_CPUACCT
695 bool "Simple CPU accounting cgroup subsystem"
697 Provides a simple Resource Controller for monitoring the
698 total CPU consumed by the tasks in a cgroup.
700 config RESOURCE_COUNTERS
701 bool "Resource counters"
703 This option enables controller independent resource accounting
704 infrastructure that works with cgroups.
707 bool "Memory Resource Controller for Control Groups"
708 depends on RESOURCE_COUNTERS
711 Provides a memory resource controller that manages both anonymous
712 memory and page cache. (See Documentation/cgroups/memory.txt)
714 Note that setting this option increases fixed memory overhead
715 associated with each page of memory in the system. By this,
716 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
717 usage tracking struct at boot. Total amount of this is printed out
720 Only enable when you're ok with these trade offs and really
721 sure you need the memory resource controller. Even when you enable
722 this, you can set "cgroup_disable=memory" at your boot option to
723 disable memory resource controller and you can avoid overheads.
724 (and lose benefits of memory resource controller)
726 This config option also selects MM_OWNER config option, which
727 could in turn add some fork/exit overhead.
730 bool "Memory Resource Controller Swap Extension"
731 depends on MEMCG && SWAP
733 Add swap management feature to memory resource controller. When you
734 enable this, you can limit mem+swap usage per cgroup. In other words,
735 when you disable this, memory resource controller has no cares to
736 usage of swap...a process can exhaust all of the swap. This extension
737 is useful when you want to avoid exhaustion swap but this itself
738 adds more overheads and consumes memory for remembering information.
739 Especially if you use 32bit system or small memory system, please
740 be careful about enabling this. When memory resource controller
741 is disabled by boot option, this will be automatically disabled and
742 there will be no overhead from this. Even when you set this config=y,
743 if boot option "swapaccount=0" is set, swap will not be accounted.
744 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
745 size is 4096bytes, 512k per 1Gbytes of swap.
746 config MEMCG_SWAP_ENABLED
747 bool "Memory Resource Controller Swap Extension enabled by default"
748 depends on MEMCG_SWAP
751 Memory Resource Controller Swap Extension comes with its price in
752 a bigger memory consumption. General purpose distribution kernels
753 which want to enable the feature but keep it disabled by default
754 and let the user enable it by swapaccount boot command line
755 parameter should have this option unselected.
756 For those who want to have the feature enabled by default should
757 select this option (if, for some reason, they need to disable it
758 then swapaccount=0 does the trick).
760 bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
761 depends on MEMCG && EXPERIMENTAL
764 The Kernel Memory extension for Memory Resource Controller can limit
765 the amount of memory used by kernel objects in the system. Those are
766 fundamentally different from the entities handled by the standard
767 Memory Controller, which are page-based, and can be swapped. Users of
768 the kmem extension can use it to guarantee that no group of processes
769 will ever exhaust kernel resources alone.
771 config CGROUP_HUGETLB
772 bool "HugeTLB Resource Controller for Control Groups"
773 depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
776 Provides a cgroup Resource Controller for HugeTLB pages.
777 When you enable this, you can put a per cgroup limit on HugeTLB usage.
778 The limit is enforced during page fault. Since HugeTLB doesn't
779 support page reclaim, enforcing the limit at page fault time implies
780 that, the application will get SIGBUS signal if it tries to access
781 HugeTLB pages beyond its limit. This requires the application to know
782 beforehand how much HugeTLB pages it would require for its use. The
783 control group is tracked in the third page lru pointer. This means
784 that we cannot use the controller with huge page less than 3 pages.
787 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
788 depends on PERF_EVENTS && CGROUPS
790 This option extends the per-cpu mode to restrict monitoring to
791 threads which belong to the cgroup specified and run on the
796 menuconfig CGROUP_SCHED
797 bool "Group CPU scheduler"
800 This feature lets CPU scheduler recognize task groups and control CPU
801 bandwidth allocation to such task groups. It uses cgroups to group
805 config FAIR_GROUP_SCHED
806 bool "Group scheduling for SCHED_OTHER"
807 depends on CGROUP_SCHED
811 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
812 depends on EXPERIMENTAL
813 depends on FAIR_GROUP_SCHED
816 This option allows users to define CPU bandwidth rates (limits) for
817 tasks running within the fair group scheduler. Groups with no limit
818 set are considered to be unconstrained and will run with no
820 See tip/Documentation/scheduler/sched-bwc.txt for more information.
822 config RT_GROUP_SCHED
823 bool "Group scheduling for SCHED_RR/FIFO"
824 depends on EXPERIMENTAL
825 depends on CGROUP_SCHED
828 This feature lets you explicitly allocate real CPU bandwidth
829 to task groups. If enabled, it will also make it impossible to
830 schedule realtime tasks for non-root users until you allocate
831 realtime bandwidth for them.
832 See Documentation/scheduler/sched-rt-group.txt for more information.
837 bool "Block IO controller"
841 Generic block IO controller cgroup interface. This is the common
842 cgroup interface which should be used by various IO controlling
845 Currently, CFQ IO scheduler uses it to recognize task groups and
846 control disk bandwidth allocation (proportional time slice allocation)
847 to such task groups. It is also used by bio throttling logic in
848 block layer to implement upper limit in IO rates on a device.
850 This option only enables generic Block IO controller infrastructure.
851 One needs to also enable actual IO controlling logic/policy. For
852 enabling proportional weight division of disk bandwidth in CFQ, set
853 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
854 CONFIG_BLK_DEV_THROTTLING=y.
856 See Documentation/cgroups/blkio-controller.txt for more information.
858 config DEBUG_BLK_CGROUP
859 bool "Enable Block IO controller debugging"
860 depends on BLK_CGROUP
863 Enable some debugging help. Currently it exports additional stat
864 files in a cgroup which can be useful for debugging.
868 config CHECKPOINT_RESTORE
869 bool "Checkpoint/restore support" if EXPERT
872 Enables additional kernel features in a sake of checkpoint/restore.
873 In particular it adds auxiliary prctl codes to setup process text,
874 data and heap segment sizes, and a few additional /proc filesystem
877 If unsure, say N here.
879 menuconfig NAMESPACES
880 bool "Namespaces support" if EXPERT
883 Provides the way to make tasks work with different objects using
884 the same id. For example same IPC id may refer to different objects
885 or same user id or pid may refer to different tasks when used in
886 different namespaces.
894 In this namespace tasks see different info provided with the
899 depends on (SYSVIPC || POSIX_MQUEUE)
902 In this namespace tasks work with IPC ids which correspond to
903 different IPC objects in different namespaces.
906 bool "User namespace (EXPERIMENTAL)"
907 depends on EXPERIMENTAL
908 depends on UIDGID_CONVERTED
909 select UIDGID_STRICT_TYPE_CHECKS
913 This allows containers, i.e. vservers, to use user namespaces
914 to provide different user info for different servers.
918 bool "PID Namespaces"
921 Support process id namespaces. This allows having multiple
922 processes with the same pid as long as they are in different
923 pid namespaces. This is a building block of containers.
926 bool "Network namespace"
930 Allow user space to create what appear to be multiple instances
931 of the network stack.
935 config UIDGID_CONVERTED
936 # True if all of the selected software conmponents are known
937 # to have uid_t and gid_t converted to kuid_t and kgid_t
938 # where appropriate and are otherwise safe to use with
939 # the user namespace.
943 # List of kernel pieces that need user namespace work
945 depends on SYSVIPC = n
950 depends on AUDITSYSCALL = n
951 depends on TASKSTATS = n
952 depends on TRACING = n
953 depends on FS_POSIX_ACL = n
955 depends on QUOTACTL = n
956 depends on DEBUG_CREDENTIALS = n
957 depends on BSD_PROCESS_ACCT = n
959 depends on PROC_EVENTS = n
963 depends on NET_9P = n
965 depends on PHONET = n
966 depends on NET_CLS_FLOW = n
967 depends on NETFILTER_XT_MATCH_OWNER = n
968 depends on NETFILTER_XT_MATCH_RECENT = n
969 depends on NETFILTER_XT_TARGET_LOG = n
970 depends on NETFILTER_NETLINK_LOG = n
973 depends on IP_SCTP = n
974 depends on AF_RXRPC = n
976 depends on NET_KEY = n
977 depends on INET_DIAG = n
978 depends on DNS_RESOLVER = n
983 depends on USB_DEVICEFS = n
984 depends on USB_GADGETFS = n
985 depends on USB_FUNCTIONFS = n
986 depends on DEVTMPFS = n
990 depends on ADFS_FS = n
991 depends on AFFS_FS = n
992 depends on AFS_FS = n
993 depends on AUTOFS4_FS = n
994 depends on BEFS_FS = n
995 depends on BFS_FS = n
996 depends on BTRFS_FS = n
997 depends on CEPH_FS = n
999 depends on CODA_FS = n
1000 depends on CONFIGFS_FS = n
1001 depends on CRAMFS = n
1002 depends on DEBUG_FS = n
1003 depends on ECRYPT_FS = n
1004 depends on EFS_FS = n
1005 depends on EXOFS_FS = n
1006 depends on FAT_FS = n
1007 depends on FUSE_FS = n
1008 depends on GFS2_FS = n
1009 depends on HFS_FS = n
1010 depends on HFSPLUS_FS = n
1011 depends on HPFS_FS = n
1012 depends on HUGETLBFS = n
1013 depends on ISO9660_FS = n
1014 depends on JFFS2_FS = n
1015 depends on JFS_FS = n
1016 depends on LOGFS = n
1017 depends on MINIX_FS = n
1018 depends on NCP_FS = n
1020 depends on NFS_FS = n
1021 depends on NILFS2_FS = n
1022 depends on NTFS_FS = n
1023 depends on OCFS2_FS = n
1024 depends on OMFS_FS = n
1025 depends on QNX4FS_FS = n
1026 depends on QNX6FS_FS = n
1027 depends on REISERFS_FS = n
1028 depends on SQUASHFS = n
1029 depends on SYSV_FS = n
1030 depends on UBIFS_FS = n
1031 depends on UDF_FS = n
1032 depends on UFS_FS = n
1033 depends on VXFS_FS = n
1034 depends on XFS_FS = n
1036 depends on !UML || HOSTFS = n
1038 # The rare drivers that won't build
1040 depends on AIRO_CS = n
1042 depends on INFINIBAND_QIB = n
1043 depends on BLK_DEV_LOOP = n
1044 depends on ANDROID_BINDER_IPC = n
1047 depends on SECURITY_TOMOYO = n
1048 depends on SECURITY_APPARMOR = n
1050 config UIDGID_STRICT_TYPE_CHECKS
1051 bool "Require conversions between uid/gids and their internal representation"
1052 depends on UIDGID_CONVERTED
1055 While the nececessary conversions are being added to all subsystems this option allows
1056 the code to continue to build for unconverted subsystems.
1058 Say Y here if you want the strict type checking enabled
1060 config SCHED_AUTOGROUP
1061 bool "Automatic process group scheduling"
1065 select FAIR_GROUP_SCHED
1067 This option optimizes the scheduler for common desktop workloads by
1068 automatically creating and populating task groups. This separation
1069 of workloads isolates aggressive CPU burners (like build jobs) from
1070 desktop applications. Task group autogeneration is currently based
1076 config SYSFS_DEPRECATED
1077 bool "Enable deprecated sysfs features to support old userspace tools"
1081 This option adds code that switches the layout of the "block" class
1082 devices, to not show up in /sys/class/block/, but only in
1085 This switch is only active when the sysfs.deprecated=1 boot option is
1086 passed or the SYSFS_DEPRECATED_V2 option is set.
1088 This option allows new kernels to run on old distributions and tools,
1089 which might get confused by /sys/class/block/. Since 2007/2008 all
1090 major distributions and tools handle this just fine.
1092 Recent distributions and userspace tools after 2009/2010 depend on
1093 the existence of /sys/class/block/, and will not work with this
1096 Only if you are using a new kernel on an old distribution, you might
1099 config SYSFS_DEPRECATED_V2
1100 bool "Enable deprecated sysfs features by default"
1103 depends on SYSFS_DEPRECATED
1105 Enable deprecated sysfs by default.
1107 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1110 Only if you are using a new kernel on an old distribution, you might
1111 need to say Y here. Even then, odds are you would not need it
1112 enabled, you can always pass the boot option if absolutely necessary.
1115 bool "Kernel->user space relay support (formerly relayfs)"
1117 This option enables support for relay interface support in
1118 certain file systems (such as debugfs).
1119 It is designed to provide an efficient mechanism for tools and
1120 facilities to relay large amounts of data from kernel space to
1125 config BLK_DEV_INITRD
1126 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1127 depends on BROKEN || !FRV
1129 The initial RAM filesystem is a ramfs which is loaded by the
1130 boot loader (loadlin or lilo) and that is mounted as root
1131 before the normal boot procedure. It is typically used to
1132 load modules needed to mount the "real" root file system,
1133 etc. See <file:Documentation/initrd.txt> for details.
1135 If RAM disk support (BLK_DEV_RAM) is also included, this
1136 also enables initial RAM disk (initrd) support and adds
1137 15 Kbytes (more on some other architectures) to the kernel size.
1143 source "usr/Kconfig"
1147 config CC_OPTIMIZE_FOR_SIZE
1148 bool "Optimize for size"
1150 Enabling this option will pass "-Os" instead of "-O2" to gcc
1151 resulting in a smaller kernel.
1162 bool "Configure standard kernel features (expert users)"
1163 # Unhide debug options, to make the on-by-default options visible
1166 This option allows certain base kernel options and settings
1167 to be disabled or tweaked. This is for specialized
1168 environments which can tolerate a "non-standard" kernel.
1169 Only use this if you really know what you are doing.
1172 bool "Enable 16-bit UID system calls" if EXPERT
1173 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
1176 This enables the legacy 16-bit UID syscall wrappers.
1178 config SYSCTL_SYSCALL
1179 bool "Sysctl syscall support" if EXPERT
1180 depends on PROC_SYSCTL
1184 sys_sysctl uses binary paths that have been found challenging
1185 to properly maintain and use. The interface in /proc/sys
1186 using paths with ascii names is now the primary path to this
1189 Almost nothing using the binary sysctl interface so if you are
1190 trying to save some space it is probably safe to disable this,
1191 making your kernel marginally smaller.
1193 If unsure say N here.
1196 bool "Load all symbols for debugging/ksymoops" if EXPERT
1199 Say Y here to let the kernel print out symbolic crash information and
1200 symbolic stack backtraces. This increases the size of the kernel
1201 somewhat, as all symbols have to be loaded into the kernel image.
1204 bool "Include all symbols in kallsyms"
1205 depends on DEBUG_KERNEL && KALLSYMS
1207 Normally kallsyms only contains the symbols of functions for nicer
1208 OOPS messages and backtraces (i.e., symbols from the text and inittext
1209 sections). This is sufficient for most cases. And only in very rare
1210 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1211 names of variables from the data sections, etc).
1213 This option makes sure that all symbols are loaded into the kernel
1214 image (i.e., symbols from all sections) in cost of increased kernel
1215 size (depending on the kernel configuration, it may be 300KiB or
1216 something like this).
1218 Say N unless you really need all symbols.
1221 bool "Support for hot-pluggable devices" if EXPERT
1224 This option is provided for the case where no hotplug or uevent
1225 capabilities is wanted by the kernel. You should only consider
1226 disabling this option for embedded systems that do not use modules, a
1227 dynamic /dev tree, or dynamic device discovery. Just say Y.
1231 bool "Enable support for printk" if EXPERT
1233 This option enables normal printk support. Removing it
1234 eliminates most of the message strings from the kernel image
1235 and makes the kernel more or less silent. As this makes it
1236 very difficult to diagnose system problems, saying N here is
1237 strongly discouraged.
1240 bool "BUG() support" if EXPERT
1243 Disabling this option eliminates support for BUG and WARN, reducing
1244 the size of your kernel image and potentially quietly ignoring
1245 numerous fatal conditions. You should only consider disabling this
1246 option for embedded systems with no facilities for reporting errors.
1251 bool "Enable ELF core dumps" if EXPERT
1253 Enable support for generating core dumps. Disabling saves about 4k.
1256 config PCSPKR_PLATFORM
1257 bool "Enable PC-Speaker support" if EXPERT
1258 depends on HAVE_PCSPKR_PLATFORM
1262 This option allows to disable the internal PC-Speaker
1263 support, saving some memory.
1265 config HAVE_PCSPKR_PLATFORM
1270 bool "Enable full-sized data structures for core" if EXPERT
1272 Disabling this option reduces the size of miscellaneous core
1273 kernel data structures. This saves memory on small machines,
1274 but may reduce performance.
1277 bool "Enable futex support" if EXPERT
1281 Disabling this option will cause the kernel to be built without
1282 support for "fast userspace mutexes". The resulting kernel may not
1283 run glibc-based applications correctly.
1286 bool "Enable eventpoll support" if EXPERT
1290 Disabling this option will cause the kernel to be built without
1291 support for epoll family of system calls.
1294 bool "Enable signalfd() system call" if EXPERT
1298 Enable the signalfd() system call that allows to receive signals
1299 on a file descriptor.
1304 bool "Enable timerfd() system call" if EXPERT
1308 Enable the timerfd() system call that allows to receive timer
1309 events on a file descriptor.
1314 bool "Enable eventfd() system call" if EXPERT
1318 Enable the eventfd() system call that allows to receive both
1319 kernel notification (ie. KAIO) or userspace notifications.
1324 bool "Use full shmem filesystem" if EXPERT
1328 The shmem is an internal filesystem used to manage shared memory.
1329 It is backed by swap and manages resource limits. It is also exported
1330 to userspace as tmpfs if TMPFS is enabled. Disabling this
1331 option replaces shmem and tmpfs with the much simpler ramfs code,
1332 which may be appropriate on small systems without swap.
1335 bool "Enable AIO support" if EXPERT
1338 This option enables POSIX asynchronous I/O which may by used
1339 by some high performance threaded applications. Disabling
1340 this option saves about 7k.
1343 bool "Embedded system"
1346 This option should be enabled if compiling the kernel for
1347 an embedded system so certain expert options are available
1350 config HAVE_PERF_EVENTS
1353 See tools/perf/design.txt for details.
1355 config PERF_USE_VMALLOC
1358 See tools/perf/design.txt for details
1360 menu "Kernel Performance Events And Counters"
1363 bool "Kernel performance events and counters"
1364 default y if PROFILING
1365 depends on HAVE_PERF_EVENTS
1369 Enable kernel support for various performance events provided
1370 by software and hardware.
1372 Software events are supported either built-in or via the
1373 use of generic tracepoints.
1375 Most modern CPUs support performance events via performance
1376 counter registers. These registers count the number of certain
1377 types of hw events: such as instructions executed, cachemisses
1378 suffered, or branches mis-predicted - without slowing down the
1379 kernel or applications. These registers can also trigger interrupts
1380 when a threshold number of events have passed - and can thus be
1381 used to profile the code that runs on that CPU.
1383 The Linux Performance Event subsystem provides an abstraction of
1384 these software and hardware event capabilities, available via a
1385 system call and used by the "perf" utility in tools/perf/. It
1386 provides per task and per CPU counters, and it provides event
1387 capabilities on top of those.
1391 config DEBUG_PERF_USE_VMALLOC
1393 bool "Debug: use vmalloc to back perf mmap() buffers"
1394 depends on PERF_EVENTS && DEBUG_KERNEL
1395 select PERF_USE_VMALLOC
1397 Use vmalloc memory to back perf mmap() buffers.
1399 Mostly useful for debugging the vmalloc code on platforms
1400 that don't require it.
1406 config VM_EVENT_COUNTERS
1408 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1410 VM event counters are needed for event counts to be shown.
1411 This option allows the disabling of the VM event counters
1412 on EXPERT systems. /proc/vmstat will only show page counts
1413 if VM event counters are disabled.
1417 bool "Enable PCI quirk workarounds" if EXPERT
1420 This enables workarounds for various PCI chipset
1421 bugs/quirks. Disable this only if your target machine is
1422 unaffected by PCI quirks.
1426 bool "Enable SLUB debugging support" if EXPERT
1427 depends on SLUB && SYSFS
1429 SLUB has extensive debug support features. Disabling these can
1430 result in significant savings in code size. This also disables
1431 SLUB sysfs support. /sys/slab will not exist and there will be
1432 no support for cache validation etc.
1435 bool "Disable heap randomization"
1438 Randomizing heap placement makes heap exploits harder, but it
1439 also breaks ancient binaries (including anything libc5 based).
1440 This option changes the bootup default to heap randomization
1441 disabled, and can be overridden at runtime by setting
1442 /proc/sys/kernel/randomize_va_space to 2.
1444 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1447 prompt "Choose SLAB allocator"
1450 This option allows to select a slab allocator.
1455 The regular slab allocator that is established and known to work
1456 well in all environments. It organizes cache hot objects in
1457 per cpu and per node queues.
1460 bool "SLUB (Unqueued Allocator)"
1462 SLUB is a slab allocator that minimizes cache line usage
1463 instead of managing queues of cached objects (SLAB approach).
1464 Per cpu caching is realized using slabs of objects instead
1465 of queues of objects. SLUB can use memory efficiently
1466 and has enhanced diagnostics. SLUB is the default choice for
1471 bool "SLOB (Simple Allocator)"
1473 SLOB replaces the stock allocator with a drastically simpler
1474 allocator. SLOB is generally more space efficient but
1475 does not perform as well on large systems.
1479 config MMAP_ALLOW_UNINITIALIZED
1480 bool "Allow mmapped anonymous memory to be uninitialized"
1481 depends on EXPERT && !MMU
1484 Normally, and according to the Linux spec, anonymous memory obtained
1485 from mmap() has it's contents cleared before it is passed to
1486 userspace. Enabling this config option allows you to request that
1487 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1488 providing a huge performance boost. If this option is not enabled,
1489 then the flag will be ignored.
1491 This is taken advantage of by uClibc's malloc(), and also by
1492 ELF-FDPIC binfmt's brk and stack allocator.
1494 Because of the obvious security issues, this option should only be
1495 enabled on embedded devices where you control what is run in
1496 userspace. Since that isn't generally a problem on no-MMU systems,
1497 it is normally safe to say Y here.
1499 See Documentation/nommu-mmap.txt for more information.
1502 bool "Profiling support"
1504 Say Y here to enable the extended profiling support mechanisms used
1505 by profilers such as OProfile.
1508 # Place an empty function call at each tracepoint site. Can be
1509 # dynamically changed for a probe function.
1514 source "arch/Kconfig"
1516 endmenu # General setup
1518 config HAVE_GENERIC_DMA_COHERENT
1525 depends on SLAB || SLUB_DEBUG
1533 default 0 if BASE_FULL
1534 default 1 if !BASE_FULL
1537 bool "Enable loadable module support"
1539 Kernel modules are small pieces of compiled code which can
1540 be inserted in the running kernel, rather than being
1541 permanently built into the kernel. You use the "modprobe"
1542 tool to add (and sometimes remove) them. If you say Y here,
1543 many parts of the kernel can be built as modules (by
1544 answering M instead of Y where indicated): this is most
1545 useful for infrequently used options which are not required
1546 for booting. For more information, see the man pages for
1547 modprobe, lsmod, modinfo, insmod and rmmod.
1549 If you say Y here, you will need to run "make
1550 modules_install" to put the modules under /lib/modules/
1551 where modprobe can find them (you may need to be root to do
1558 config MODULE_FORCE_LOAD
1559 bool "Forced module loading"
1562 Allow loading of modules without version information (ie. modprobe
1563 --force). Forced module loading sets the 'F' (forced) taint flag and
1564 is usually a really bad idea.
1566 config MODULE_UNLOAD
1567 bool "Module unloading"
1569 Without this option you will not be able to unload any
1570 modules (note that some modules may not be unloadable
1571 anyway), which makes your kernel smaller, faster
1572 and simpler. If unsure, say Y.
1574 config MODULE_FORCE_UNLOAD
1575 bool "Forced module unloading"
1576 depends on MODULE_UNLOAD && EXPERIMENTAL
1578 This option allows you to force a module to unload, even if the
1579 kernel believes it is unsafe: the kernel will remove the module
1580 without waiting for anyone to stop using it (using the -f option to
1581 rmmod). This is mainly for kernel developers and desperate users.
1585 bool "Module versioning support"
1587 Usually, you have to use modules compiled with your kernel.
1588 Saying Y here makes it sometimes possible to use modules
1589 compiled for different kernels, by adding enough information
1590 to the modules to (hopefully) spot any changes which would
1591 make them incompatible with the kernel you are running. If
1594 config MODULE_SRCVERSION_ALL
1595 bool "Source checksum for all modules"
1597 Modules which contain a MODULE_VERSION get an extra "srcversion"
1598 field inserted into their modinfo section, which contains a
1599 sum of the source files which made it. This helps maintainers
1600 see exactly which source was used to build a module (since
1601 others sometimes change the module source without updating
1602 the version). With this option, such a "srcversion" field
1603 will be created for all modules. If unsure, say N.
1607 config INIT_ALL_POSSIBLE
1610 Back when each arch used to define their own cpu_online_mask and
1611 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1612 with all 1s, and others with all 0s. When they were centralised,
1613 it was better to provide this option than to break all the archs
1614 and have several arch maintainers pursuing me down dark alleys.
1619 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1621 Need stop_machine() primitive.
1623 source "block/Kconfig"
1625 config PREEMPT_NOTIFIERS
1632 source "kernel/Kconfig.locks"
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