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56 drivers that have been replaced by something else, and/or are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"
330 prompt "Cputime accounting"
331 default TICK_CPU_ACCOUNTING if !PPC64
332 default VIRT_CPU_ACCOUNTING if PPC64
334 # Kind of a stub config for the pure tick based cputime accounting
335 config TICK_CPU_ACCOUNTING
336 bool "Simple tick based cputime accounting"
339 This is the basic tick based cputime accounting that maintains
340 statistics about user, system and idle time spent on per jiffies
345 config VIRT_CPU_ACCOUNTING
346 bool "Deterministic task and CPU time accounting"
347 depends on HAVE_VIRT_CPU_ACCOUNTING
349 Select this option to enable more accurate task and CPU time
350 accounting. This is done by reading a CPU counter on each
351 kernel entry and exit and on transitions within the kernel
352 between system, softirq and hardirq state, so there is a
353 small performance impact. In the case of s390 or IBM POWER > 5,
354 this also enables accounting of stolen time on logically-partitioned
357 config IRQ_TIME_ACCOUNTING
358 bool "Fine granularity task level IRQ time accounting"
359 depends on HAVE_IRQ_TIME_ACCOUNTING
361 Select this option to enable fine granularity task irq time
362 accounting. This is done by reading a timestamp on each
363 transitions between softirq and hardirq state, so there can be a
364 small performance impact.
366 If in doubt, say N here.
370 config BSD_PROCESS_ACCT
371 bool "BSD Process Accounting"
373 If you say Y here, a user level program will be able to instruct the
374 kernel (via a special system call) to write process accounting
375 information to a file: whenever a process exits, information about
376 that process will be appended to the file by the kernel. The
377 information includes things such as creation time, owning user,
378 command name, memory usage, controlling terminal etc. (the complete
379 list is in the struct acct in <file:include/linux/acct.h>). It is
380 up to the user level program to do useful things with this
381 information. This is generally a good idea, so say Y.
383 config BSD_PROCESS_ACCT_V3
384 bool "BSD Process Accounting version 3 file format"
385 depends on BSD_PROCESS_ACCT
388 If you say Y here, the process accounting information is written
389 in a new file format that also logs the process IDs of each
390 process and it's parent. Note that this file format is incompatible
391 with previous v0/v1/v2 file formats, so you will need updated tools
392 for processing it. A preliminary version of these tools is available
393 at <http://www.gnu.org/software/acct/>.
396 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
400 Export selected statistics for tasks/processes through the
401 generic netlink interface. Unlike BSD process accounting, the
402 statistics are available during the lifetime of tasks/processes as
403 responses to commands. Like BSD accounting, they are sent to user
408 config TASK_DELAY_ACCT
409 bool "Enable per-task delay accounting (EXPERIMENTAL)"
412 Collect information on time spent by a task waiting for system
413 resources like cpu, synchronous block I/O completion and swapping
414 in pages. Such statistics can help in setting a task's priorities
415 relative to other tasks for cpu, io, rss limits etc.
420 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
423 Collect extended task accounting data and send the data
424 to userland for processing over the taskstats interface.
428 config TASK_IO_ACCOUNTING
429 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
430 depends on TASK_XACCT
432 Collect information on the number of bytes of storage I/O which this
437 endmenu # "CPU/Task time and stats accounting"
442 prompt "RCU Implementation"
446 bool "Tree-based hierarchical RCU"
447 depends on !PREEMPT && SMP
449 This option selects the RCU implementation that is
450 designed for very large SMP system with hundreds or
451 thousands of CPUs. It also scales down nicely to
454 config TREE_PREEMPT_RCU
455 bool "Preemptible tree-based hierarchical RCU"
456 depends on PREEMPT && SMP
458 This option selects the RCU implementation that is
459 designed for very large SMP systems with hundreds or
460 thousands of CPUs, but for which real-time response
461 is also required. It also scales down nicely to
465 bool "UP-only small-memory-footprint RCU"
466 depends on !PREEMPT && !SMP
468 This option selects the RCU implementation that is
469 designed for UP systems from which real-time response
470 is not required. This option greatly reduces the
471 memory footprint of RCU.
473 config TINY_PREEMPT_RCU
474 bool "Preemptible UP-only small-memory-footprint RCU"
475 depends on PREEMPT && !SMP
477 This option selects the RCU implementation that is designed
478 for real-time UP systems. This option greatly reduces the
479 memory footprint of RCU.
484 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
486 This option enables preemptible-RCU code that is common between
487 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
490 bool "Consider userspace as in RCU extended quiescent state"
491 depends on HAVE_RCU_USER_QS && SMP
493 This option sets hooks on kernel / userspace boundaries and
494 puts RCU in extended quiescent state when the CPU runs in
495 userspace. It means that when a CPU runs in userspace, it is
496 excluded from the global RCU state machine and thus doesn't
497 to keep the timer tick on for RCU.
499 Unless you want to hack and help the development of the full
500 tickless feature, you shouldn't enable this option. It adds
501 unnecessary overhead.
505 config RCU_USER_QS_FORCE
506 bool "Force userspace extended QS by default"
507 depends on RCU_USER_QS
509 Set the hooks in user/kernel boundaries by default in order to
510 test this feature that treats userspace as an extended quiescent
511 state until we have a real user like a full adaptive nohz option.
513 Unless you want to hack and help the development of the full
514 tickless feature, you shouldn't enable this option. It adds
515 unnecessary overhead.
520 int "Tree-based hierarchical RCU fanout value"
523 depends on TREE_RCU || TREE_PREEMPT_RCU
527 This option controls the fanout of hierarchical implementations
528 of RCU, allowing RCU to work efficiently on machines with
529 large numbers of CPUs. This value must be at least the fourth
530 root of NR_CPUS, which allows NR_CPUS to be insanely large.
531 The default value of RCU_FANOUT should be used for production
532 systems, but if you are stress-testing the RCU implementation
533 itself, small RCU_FANOUT values allow you to test large-system
534 code paths on small(er) systems.
536 Select a specific number if testing RCU itself.
537 Take the default if unsure.
539 config RCU_FANOUT_LEAF
540 int "Tree-based hierarchical RCU leaf-level fanout value"
541 range 2 RCU_FANOUT if 64BIT
542 range 2 RCU_FANOUT if !64BIT
543 depends on TREE_RCU || TREE_PREEMPT_RCU
546 This option controls the leaf-level fanout of hierarchical
547 implementations of RCU, and allows trading off cache misses
548 against lock contention. Systems that synchronize their
549 scheduling-clock interrupts for energy-efficiency reasons will
550 want the default because the smaller leaf-level fanout keeps
551 lock contention levels acceptably low. Very large systems
552 (hundreds or thousands of CPUs) will instead want to set this
553 value to the maximum value possible in order to reduce the
554 number of cache misses incurred during RCU's grace-period
555 initialization. These systems tend to run CPU-bound, and thus
556 are not helped by synchronized interrupts, and thus tend to
557 skew them, which reduces lock contention enough that large
558 leaf-level fanouts work well.
560 Select a specific number if testing RCU itself.
562 Select the maximum permissible value for large systems.
564 Take the default if unsure.
566 config RCU_FANOUT_EXACT
567 bool "Disable tree-based hierarchical RCU auto-balancing"
568 depends on TREE_RCU || TREE_PREEMPT_RCU
571 This option forces use of the exact RCU_FANOUT value specified,
572 regardless of imbalances in the hierarchy. This is useful for
573 testing RCU itself, and might one day be useful on systems with
574 strong NUMA behavior.
576 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
580 config RCU_FAST_NO_HZ
581 bool "Accelerate last non-dyntick-idle CPU's grace periods"
582 depends on NO_HZ && SMP
585 This option causes RCU to attempt to accelerate grace periods
586 in order to allow CPUs to enter dynticks-idle state more
587 quickly. On the other hand, this option increases the overhead
588 of the dynticks-idle checking, particularly on systems with
589 large numbers of CPUs.
591 Say Y if energy efficiency is critically important, particularly
592 if you have relatively few CPUs.
594 Say N if you are unsure.
596 config TREE_RCU_TRACE
597 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
600 This option provides tracing for the TREE_RCU and
601 TREE_PREEMPT_RCU implementations, permitting Makefile to
602 trivially select kernel/rcutree_trace.c.
605 bool "Enable RCU priority boosting"
606 depends on RT_MUTEXES && PREEMPT_RCU
609 This option boosts the priority of preempted RCU readers that
610 block the current preemptible RCU grace period for too long.
611 This option also prevents heavy loads from blocking RCU
612 callback invocation for all flavors of RCU.
614 Say Y here if you are working with real-time apps or heavy loads
615 Say N here if you are unsure.
617 config RCU_BOOST_PRIO
618 int "Real-time priority to boost RCU readers to"
623 This option specifies the real-time priority to which long-term
624 preempted RCU readers are to be boosted. If you are working
625 with a real-time application that has one or more CPU-bound
626 threads running at a real-time priority level, you should set
627 RCU_BOOST_PRIO to a priority higher then the highest-priority
628 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
629 of 1 is appropriate in the common case, which is real-time
630 applications that do not have any CPU-bound threads.
632 Some real-time applications might not have a single real-time
633 thread that saturates a given CPU, but instead might have
634 multiple real-time threads that, taken together, fully utilize
635 that CPU. In this case, you should set RCU_BOOST_PRIO to
636 a priority higher than the lowest-priority thread that is
637 conspiring to prevent the CPU from running any non-real-time
638 tasks. For example, if one thread at priority 10 and another
639 thread at priority 5 are between themselves fully consuming
640 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
641 set to priority 6 or higher.
643 Specify the real-time priority, or take the default if unsure.
645 config RCU_BOOST_DELAY
646 int "Milliseconds to delay boosting after RCU grace-period start"
651 This option specifies the time to wait after the beginning of
652 a given grace period before priority-boosting preempted RCU
653 readers blocking that grace period. Note that any RCU reader
654 blocking an expedited RCU grace period is boosted immediately.
656 Accept the default if unsure.
658 endmenu # "RCU Subsystem"
661 tristate "Kernel .config support"
663 This option enables the complete Linux kernel ".config" file
664 contents to be saved in the kernel. It provides documentation
665 of which kernel options are used in a running kernel or in an
666 on-disk kernel. This information can be extracted from the kernel
667 image file with the script scripts/extract-ikconfig and used as
668 input to rebuild the current kernel or to build another kernel.
669 It can also be extracted from a running kernel by reading
670 /proc/config.gz if enabled (below).
673 bool "Enable access to .config through /proc/config.gz"
674 depends on IKCONFIG && PROC_FS
676 This option enables access to the kernel configuration file
677 through /proc/config.gz.
680 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
684 Select kernel log buffer size as a power of 2.
694 # Architectures with an unreliable sched_clock() should select this:
696 config HAVE_UNSTABLE_SCHED_CLOCK
700 boolean "Control Group support"
703 This option adds support for grouping sets of processes together, for
704 use with process control subsystems such as Cpusets, CFS, memory
705 controls or device isolation.
707 - Documentation/scheduler/sched-design-CFS.txt (CFS)
708 - Documentation/cgroups/ (features for grouping, isolation
709 and resource control)
716 bool "Example debug cgroup subsystem"
719 This option enables a simple cgroup subsystem that
720 exports useful debugging information about the cgroups
725 config CGROUP_FREEZER
726 bool "Freezer cgroup subsystem"
728 Provides a way to freeze and unfreeze all tasks in a
732 bool "Device controller for cgroups"
734 Provides a cgroup implementing whitelists for devices which
735 a process in the cgroup can mknod or open.
738 bool "Cpuset support"
740 This option will let you create and manage CPUSETs which
741 allow dynamically partitioning a system into sets of CPUs and
742 Memory Nodes and assigning tasks to run only within those sets.
743 This is primarily useful on large SMP or NUMA systems.
747 config PROC_PID_CPUSET
748 bool "Include legacy /proc/<pid>/cpuset file"
752 config CGROUP_CPUACCT
753 bool "Simple CPU accounting cgroup subsystem"
755 Provides a simple Resource Controller for monitoring the
756 total CPU consumed by the tasks in a cgroup.
758 config RESOURCE_COUNTERS
759 bool "Resource counters"
761 This option enables controller independent resource accounting
762 infrastructure that works with cgroups.
765 bool "Memory Resource Controller for Control Groups"
766 depends on RESOURCE_COUNTERS
769 Provides a memory resource controller that manages both anonymous
770 memory and page cache. (See Documentation/cgroups/memory.txt)
772 Note that setting this option increases fixed memory overhead
773 associated with each page of memory in the system. By this,
774 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
775 usage tracking struct at boot. Total amount of this is printed out
778 Only enable when you're ok with these trade offs and really
779 sure you need the memory resource controller. Even when you enable
780 this, you can set "cgroup_disable=memory" at your boot option to
781 disable memory resource controller and you can avoid overheads.
782 (and lose benefits of memory resource controller)
784 This config option also selects MM_OWNER config option, which
785 could in turn add some fork/exit overhead.
788 bool "Memory Resource Controller Swap Extension"
789 depends on MEMCG && SWAP
791 Add swap management feature to memory resource controller. When you
792 enable this, you can limit mem+swap usage per cgroup. In other words,
793 when you disable this, memory resource controller has no cares to
794 usage of swap...a process can exhaust all of the swap. This extension
795 is useful when you want to avoid exhaustion swap but this itself
796 adds more overheads and consumes memory for remembering information.
797 Especially if you use 32bit system or small memory system, please
798 be careful about enabling this. When memory resource controller
799 is disabled by boot option, this will be automatically disabled and
800 there will be no overhead from this. Even when you set this config=y,
801 if boot option "swapaccount=0" is set, swap will not be accounted.
802 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
803 size is 4096bytes, 512k per 1Gbytes of swap.
804 config MEMCG_SWAP_ENABLED
805 bool "Memory Resource Controller Swap Extension enabled by default"
806 depends on MEMCG_SWAP
809 Memory Resource Controller Swap Extension comes with its price in
810 a bigger memory consumption. General purpose distribution kernels
811 which want to enable the feature but keep it disabled by default
812 and let the user enable it by swapaccount boot command line
813 parameter should have this option unselected.
814 For those who want to have the feature enabled by default should
815 select this option (if, for some reason, they need to disable it
816 then swapaccount=0 does the trick).
818 bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
819 depends on MEMCG && EXPERIMENTAL
822 The Kernel Memory extension for Memory Resource Controller can limit
823 the amount of memory used by kernel objects in the system. Those are
824 fundamentally different from the entities handled by the standard
825 Memory Controller, which are page-based, and can be swapped. Users of
826 the kmem extension can use it to guarantee that no group of processes
827 will ever exhaust kernel resources alone.
829 config CGROUP_HUGETLB
830 bool "HugeTLB Resource Controller for Control Groups"
831 depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
834 Provides a cgroup Resource Controller for HugeTLB pages.
835 When you enable this, you can put a per cgroup limit on HugeTLB usage.
836 The limit is enforced during page fault. Since HugeTLB doesn't
837 support page reclaim, enforcing the limit at page fault time implies
838 that, the application will get SIGBUS signal if it tries to access
839 HugeTLB pages beyond its limit. This requires the application to know
840 beforehand how much HugeTLB pages it would require for its use. The
841 control group is tracked in the third page lru pointer. This means
842 that we cannot use the controller with huge page less than 3 pages.
845 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
846 depends on PERF_EVENTS && CGROUPS
848 This option extends the per-cpu mode to restrict monitoring to
849 threads which belong to the cgroup specified and run on the
854 menuconfig CGROUP_SCHED
855 bool "Group CPU scheduler"
858 This feature lets CPU scheduler recognize task groups and control CPU
859 bandwidth allocation to such task groups. It uses cgroups to group
863 config FAIR_GROUP_SCHED
864 bool "Group scheduling for SCHED_OTHER"
865 depends on CGROUP_SCHED
869 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
870 depends on EXPERIMENTAL
871 depends on FAIR_GROUP_SCHED
874 This option allows users to define CPU bandwidth rates (limits) for
875 tasks running within the fair group scheduler. Groups with no limit
876 set are considered to be unconstrained and will run with no
878 See tip/Documentation/scheduler/sched-bwc.txt for more information.
880 config RT_GROUP_SCHED
881 bool "Group scheduling for SCHED_RR/FIFO"
882 depends on EXPERIMENTAL
883 depends on CGROUP_SCHED
886 This feature lets you explicitly allocate real CPU bandwidth
887 to task groups. If enabled, it will also make it impossible to
888 schedule realtime tasks for non-root users until you allocate
889 realtime bandwidth for them.
890 See Documentation/scheduler/sched-rt-group.txt for more information.
895 bool "Block IO controller"
899 Generic block IO controller cgroup interface. This is the common
900 cgroup interface which should be used by various IO controlling
903 Currently, CFQ IO scheduler uses it to recognize task groups and
904 control disk bandwidth allocation (proportional time slice allocation)
905 to such task groups. It is also used by bio throttling logic in
906 block layer to implement upper limit in IO rates on a device.
908 This option only enables generic Block IO controller infrastructure.
909 One needs to also enable actual IO controlling logic/policy. For
910 enabling proportional weight division of disk bandwidth in CFQ, set
911 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
912 CONFIG_BLK_DEV_THROTTLING=y.
914 See Documentation/cgroups/blkio-controller.txt for more information.
916 config DEBUG_BLK_CGROUP
917 bool "Enable Block IO controller debugging"
918 depends on BLK_CGROUP
921 Enable some debugging help. Currently it exports additional stat
922 files in a cgroup which can be useful for debugging.
926 config CHECKPOINT_RESTORE
927 bool "Checkpoint/restore support" if EXPERT
930 Enables additional kernel features in a sake of checkpoint/restore.
931 In particular it adds auxiliary prctl codes to setup process text,
932 data and heap segment sizes, and a few additional /proc filesystem
935 If unsure, say N here.
937 menuconfig NAMESPACES
938 bool "Namespaces support" if EXPERT
941 Provides the way to make tasks work with different objects using
942 the same id. For example same IPC id may refer to different objects
943 or same user id or pid may refer to different tasks when used in
944 different namespaces.
952 In this namespace tasks see different info provided with the
957 depends on (SYSVIPC || POSIX_MQUEUE)
960 In this namespace tasks work with IPC ids which correspond to
961 different IPC objects in different namespaces.
964 bool "User namespace (EXPERIMENTAL)"
965 depends on EXPERIMENTAL
966 depends on UIDGID_CONVERTED
967 select UIDGID_STRICT_TYPE_CHECKS
971 This allows containers, i.e. vservers, to use user namespaces
972 to provide different user info for different servers.
976 bool "PID Namespaces"
979 Support process id namespaces. This allows having multiple
980 processes with the same pid as long as they are in different
981 pid namespaces. This is a building block of containers.
984 bool "Network namespace"
988 Allow user space to create what appear to be multiple instances
989 of the network stack.
993 config UIDGID_CONVERTED
994 # True if all of the selected software conmponents are known
995 # to have uid_t and gid_t converted to kuid_t and kgid_t
996 # where appropriate and are otherwise safe to use with
997 # the user namespace.
1002 depends on NET_9P = n
1005 depends on 9P_FS = n
1006 depends on AFS_FS = n
1007 depends on AUTOFS4_FS = n
1008 depends on CEPH_FS = n
1010 depends on CODA_FS = n
1011 depends on FUSE_FS = n
1012 depends on GFS2_FS = n
1013 depends on NCP_FS = n
1015 depends on NFS_FS = n
1016 depends on OCFS2_FS = n
1017 depends on XFS_FS = n
1019 config UIDGID_STRICT_TYPE_CHECKS
1020 bool "Require conversions between uid/gids and their internal representation"
1021 depends on UIDGID_CONVERTED
1024 While the nececessary conversions are being added to all subsystems this option allows
1025 the code to continue to build for unconverted subsystems.
1027 Say Y here if you want the strict type checking enabled
1029 config SCHED_AUTOGROUP
1030 bool "Automatic process group scheduling"
1034 select FAIR_GROUP_SCHED
1036 This option optimizes the scheduler for common desktop workloads by
1037 automatically creating and populating task groups. This separation
1038 of workloads isolates aggressive CPU burners (like build jobs) from
1039 desktop applications. Task group autogeneration is currently based
1045 config SYSFS_DEPRECATED
1046 bool "Enable deprecated sysfs features to support old userspace tools"
1050 This option adds code that switches the layout of the "block" class
1051 devices, to not show up in /sys/class/block/, but only in
1054 This switch is only active when the sysfs.deprecated=1 boot option is
1055 passed or the SYSFS_DEPRECATED_V2 option is set.
1057 This option allows new kernels to run on old distributions and tools,
1058 which might get confused by /sys/class/block/. Since 2007/2008 all
1059 major distributions and tools handle this just fine.
1061 Recent distributions and userspace tools after 2009/2010 depend on
1062 the existence of /sys/class/block/, and will not work with this
1065 Only if you are using a new kernel on an old distribution, you might
1068 config SYSFS_DEPRECATED_V2
1069 bool "Enable deprecated sysfs features by default"
1072 depends on SYSFS_DEPRECATED
1074 Enable deprecated sysfs by default.
1076 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1079 Only if you are using a new kernel on an old distribution, you might
1080 need to say Y here. Even then, odds are you would not need it
1081 enabled, you can always pass the boot option if absolutely necessary.
1084 bool "Kernel->user space relay support (formerly relayfs)"
1086 This option enables support for relay interface support in
1087 certain file systems (such as debugfs).
1088 It is designed to provide an efficient mechanism for tools and
1089 facilities to relay large amounts of data from kernel space to
1094 config BLK_DEV_INITRD
1095 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1096 depends on BROKEN || !FRV
1098 The initial RAM filesystem is a ramfs which is loaded by the
1099 boot loader (loadlin or lilo) and that is mounted as root
1100 before the normal boot procedure. It is typically used to
1101 load modules needed to mount the "real" root file system,
1102 etc. See <file:Documentation/initrd.txt> for details.
1104 If RAM disk support (BLK_DEV_RAM) is also included, this
1105 also enables initial RAM disk (initrd) support and adds
1106 15 Kbytes (more on some other architectures) to the kernel size.
1112 source "usr/Kconfig"
1116 config CC_OPTIMIZE_FOR_SIZE
1117 bool "Optimize for size"
1119 Enabling this option will pass "-Os" instead of "-O2" to gcc
1120 resulting in a smaller kernel.
1131 bool "Configure standard kernel features (expert users)"
1132 # Unhide debug options, to make the on-by-default options visible
1135 This option allows certain base kernel options and settings
1136 to be disabled or tweaked. This is for specialized
1137 environments which can tolerate a "non-standard" kernel.
1138 Only use this if you really know what you are doing.
1144 bool "Enable 16-bit UID system calls" if EXPERT
1145 depends on HAVE_UID16
1148 This enables the legacy 16-bit UID syscall wrappers.
1150 config SYSCTL_SYSCALL
1151 bool "Sysctl syscall support" if EXPERT
1152 depends on PROC_SYSCTL
1156 sys_sysctl uses binary paths that have been found challenging
1157 to properly maintain and use. The interface in /proc/sys
1158 using paths with ascii names is now the primary path to this
1161 Almost nothing using the binary sysctl interface so if you are
1162 trying to save some space it is probably safe to disable this,
1163 making your kernel marginally smaller.
1165 If unsure say N here.
1167 config SYSCTL_EXCEPTION_TRACE
1170 Enable support for /proc/sys/debug/exception-trace.
1173 bool "Load all symbols for debugging/ksymoops" if EXPERT
1176 Say Y here to let the kernel print out symbolic crash information and
1177 symbolic stack backtraces. This increases the size of the kernel
1178 somewhat, as all symbols have to be loaded into the kernel image.
1181 bool "Include all symbols in kallsyms"
1182 depends on DEBUG_KERNEL && KALLSYMS
1184 Normally kallsyms only contains the symbols of functions for nicer
1185 OOPS messages and backtraces (i.e., symbols from the text and inittext
1186 sections). This is sufficient for most cases. And only in very rare
1187 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1188 names of variables from the data sections, etc).
1190 This option makes sure that all symbols are loaded into the kernel
1191 image (i.e., symbols from all sections) in cost of increased kernel
1192 size (depending on the kernel configuration, it may be 300KiB or
1193 something like this).
1195 Say N unless you really need all symbols.
1202 bool "Enable support for printk" if EXPERT
1204 This option enables normal printk support. Removing it
1205 eliminates most of the message strings from the kernel image
1206 and makes the kernel more or less silent. As this makes it
1207 very difficult to diagnose system problems, saying N here is
1208 strongly discouraged.
1211 bool "BUG() support" if EXPERT
1214 Disabling this option eliminates support for BUG and WARN, reducing
1215 the size of your kernel image and potentially quietly ignoring
1216 numerous fatal conditions. You should only consider disabling this
1217 option for embedded systems with no facilities for reporting errors.
1223 bool "Enable ELF core dumps" if EXPERT
1225 Enable support for generating core dumps. Disabling saves about 4k.
1228 config PCSPKR_PLATFORM
1229 bool "Enable PC-Speaker support" if EXPERT
1230 depends on HAVE_PCSPKR_PLATFORM
1234 This option allows to disable the internal PC-Speaker
1235 support, saving some memory.
1237 config HAVE_PCSPKR_PLATFORM
1242 bool "Enable full-sized data structures for core" if EXPERT
1244 Disabling this option reduces the size of miscellaneous core
1245 kernel data structures. This saves memory on small machines,
1246 but may reduce performance.
1249 bool "Enable futex support" if EXPERT
1253 Disabling this option will cause the kernel to be built without
1254 support for "fast userspace mutexes". The resulting kernel may not
1255 run glibc-based applications correctly.
1258 bool "Enable eventpoll support" if EXPERT
1262 Disabling this option will cause the kernel to be built without
1263 support for epoll family of system calls.
1266 bool "Enable signalfd() system call" if EXPERT
1270 Enable the signalfd() system call that allows to receive signals
1271 on a file descriptor.
1276 bool "Enable timerfd() system call" if EXPERT
1280 Enable the timerfd() system call that allows to receive timer
1281 events on a file descriptor.
1286 bool "Enable eventfd() system call" if EXPERT
1290 Enable the eventfd() system call that allows to receive both
1291 kernel notification (ie. KAIO) or userspace notifications.
1296 bool "Use full shmem filesystem" if EXPERT
1300 The shmem is an internal filesystem used to manage shared memory.
1301 It is backed by swap and manages resource limits. It is also exported
1302 to userspace as tmpfs if TMPFS is enabled. Disabling this
1303 option replaces shmem and tmpfs with the much simpler ramfs code,
1304 which may be appropriate on small systems without swap.
1307 bool "Enable AIO support" if EXPERT
1310 This option enables POSIX asynchronous I/O which may by used
1311 by some high performance threaded applications. Disabling
1312 this option saves about 7k.
1315 bool "Embedded system"
1318 This option should be enabled if compiling the kernel for
1319 an embedded system so certain expert options are available
1322 config HAVE_PERF_EVENTS
1325 See tools/perf/design.txt for details.
1327 config PERF_USE_VMALLOC
1330 See tools/perf/design.txt for details
1332 menu "Kernel Performance Events And Counters"
1335 bool "Kernel performance events and counters"
1336 default y if PROFILING
1337 depends on HAVE_PERF_EVENTS
1341 Enable kernel support for various performance events provided
1342 by software and hardware.
1344 Software events are supported either built-in or via the
1345 use of generic tracepoints.
1347 Most modern CPUs support performance events via performance
1348 counter registers. These registers count the number of certain
1349 types of hw events: such as instructions executed, cachemisses
1350 suffered, or branches mis-predicted - without slowing down the
1351 kernel or applications. These registers can also trigger interrupts
1352 when a threshold number of events have passed - and can thus be
1353 used to profile the code that runs on that CPU.
1355 The Linux Performance Event subsystem provides an abstraction of
1356 these software and hardware event capabilities, available via a
1357 system call and used by the "perf" utility in tools/perf/. It
1358 provides per task and per CPU counters, and it provides event
1359 capabilities on top of those.
1363 config DEBUG_PERF_USE_VMALLOC
1365 bool "Debug: use vmalloc to back perf mmap() buffers"
1366 depends on PERF_EVENTS && DEBUG_KERNEL
1367 select PERF_USE_VMALLOC
1369 Use vmalloc memory to back perf mmap() buffers.
1371 Mostly useful for debugging the vmalloc code on platforms
1372 that don't require it.
1378 config VM_EVENT_COUNTERS
1380 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1382 VM event counters are needed for event counts to be shown.
1383 This option allows the disabling of the VM event counters
1384 on EXPERT systems. /proc/vmstat will only show page counts
1385 if VM event counters are disabled.
1389 bool "Enable PCI quirk workarounds" if EXPERT
1392 This enables workarounds for various PCI chipset
1393 bugs/quirks. Disable this only if your target machine is
1394 unaffected by PCI quirks.
1398 bool "Enable SLUB debugging support" if EXPERT
1399 depends on SLUB && SYSFS
1401 SLUB has extensive debug support features. Disabling these can
1402 result in significant savings in code size. This also disables
1403 SLUB sysfs support. /sys/slab will not exist and there will be
1404 no support for cache validation etc.
1407 bool "Disable heap randomization"
1410 Randomizing heap placement makes heap exploits harder, but it
1411 also breaks ancient binaries (including anything libc5 based).
1412 This option changes the bootup default to heap randomization
1413 disabled, and can be overridden at runtime by setting
1414 /proc/sys/kernel/randomize_va_space to 2.
1416 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1419 prompt "Choose SLAB allocator"
1422 This option allows to select a slab allocator.
1427 The regular slab allocator that is established and known to work
1428 well in all environments. It organizes cache hot objects in
1429 per cpu and per node queues.
1432 bool "SLUB (Unqueued Allocator)"
1434 SLUB is a slab allocator that minimizes cache line usage
1435 instead of managing queues of cached objects (SLAB approach).
1436 Per cpu caching is realized using slabs of objects instead
1437 of queues of objects. SLUB can use memory efficiently
1438 and has enhanced diagnostics. SLUB is the default choice for
1443 bool "SLOB (Simple Allocator)"
1445 SLOB replaces the stock allocator with a drastically simpler
1446 allocator. SLOB is generally more space efficient but
1447 does not perform as well on large systems.
1451 config MMAP_ALLOW_UNINITIALIZED
1452 bool "Allow mmapped anonymous memory to be uninitialized"
1453 depends on EXPERT && !MMU
1456 Normally, and according to the Linux spec, anonymous memory obtained
1457 from mmap() has it's contents cleared before it is passed to
1458 userspace. Enabling this config option allows you to request that
1459 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1460 providing a huge performance boost. If this option is not enabled,
1461 then the flag will be ignored.
1463 This is taken advantage of by uClibc's malloc(), and also by
1464 ELF-FDPIC binfmt's brk and stack allocator.
1466 Because of the obvious security issues, this option should only be
1467 enabled on embedded devices where you control what is run in
1468 userspace. Since that isn't generally a problem on no-MMU systems,
1469 it is normally safe to say Y here.
1471 See Documentation/nommu-mmap.txt for more information.
1474 bool "Profiling support"
1476 Say Y here to enable the extended profiling support mechanisms used
1477 by profilers such as OProfile.
1480 # Place an empty function call at each tracepoint site. Can be
1481 # dynamically changed for a probe function.
1486 source "arch/Kconfig"
1488 endmenu # General setup
1490 config HAVE_GENERIC_DMA_COHERENT
1497 depends on SLAB || SLUB_DEBUG
1505 default 0 if BASE_FULL
1506 default 1 if !BASE_FULL
1509 bool "Enable loadable module support"
1511 Kernel modules are small pieces of compiled code which can
1512 be inserted in the running kernel, rather than being
1513 permanently built into the kernel. You use the "modprobe"
1514 tool to add (and sometimes remove) them. If you say Y here,
1515 many parts of the kernel can be built as modules (by
1516 answering M instead of Y where indicated): this is most
1517 useful for infrequently used options which are not required
1518 for booting. For more information, see the man pages for
1519 modprobe, lsmod, modinfo, insmod and rmmod.
1521 If you say Y here, you will need to run "make
1522 modules_install" to put the modules under /lib/modules/
1523 where modprobe can find them (you may need to be root to do
1530 config MODULE_FORCE_LOAD
1531 bool "Forced module loading"
1534 Allow loading of modules without version information (ie. modprobe
1535 --force). Forced module loading sets the 'F' (forced) taint flag and
1536 is usually a really bad idea.
1538 config MODULE_UNLOAD
1539 bool "Module unloading"
1541 Without this option you will not be able to unload any
1542 modules (note that some modules may not be unloadable
1543 anyway), which makes your kernel smaller, faster
1544 and simpler. If unsure, say Y.
1546 config MODULE_FORCE_UNLOAD
1547 bool "Forced module unloading"
1548 depends on MODULE_UNLOAD && EXPERIMENTAL
1550 This option allows you to force a module to unload, even if the
1551 kernel believes it is unsafe: the kernel will remove the module
1552 without waiting for anyone to stop using it (using the -f option to
1553 rmmod). This is mainly for kernel developers and desperate users.
1557 bool "Module versioning support"
1559 Usually, you have to use modules compiled with your kernel.
1560 Saying Y here makes it sometimes possible to use modules
1561 compiled for different kernels, by adding enough information
1562 to the modules to (hopefully) spot any changes which would
1563 make them incompatible with the kernel you are running. If
1566 config MODULE_SRCVERSION_ALL
1567 bool "Source checksum for all modules"
1569 Modules which contain a MODULE_VERSION get an extra "srcversion"
1570 field inserted into their modinfo section, which contains a
1571 sum of the source files which made it. This helps maintainers
1572 see exactly which source was used to build a module (since
1573 others sometimes change the module source without updating
1574 the version). With this option, such a "srcversion" field
1575 will be created for all modules. If unsure, say N.
1578 bool "Module signature verification"
1582 select ASYMMETRIC_KEY_TYPE
1583 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1584 select PUBLIC_KEY_ALGO_RSA
1587 select X509_CERTIFICATE_PARSER
1589 Check modules for valid signatures upon load: the signature
1590 is simply appended to the module. For more information see
1591 Documentation/module-signing.txt.
1593 !!!WARNING!!! If you enable this option, you MUST make sure that the
1594 module DOES NOT get stripped after being signed. This includes the
1595 debuginfo strip done by some packagers (such as rpmbuild) and
1596 inclusion into an initramfs that wants the module size reduced.
1598 config MODULE_SIG_FORCE
1599 bool "Require modules to be validly signed"
1600 depends on MODULE_SIG
1602 Reject unsigned modules or signed modules for which we don't have a
1603 key. Without this, such modules will simply taint the kernel.
1606 prompt "Which hash algorithm should modules be signed with?"
1607 depends on MODULE_SIG
1609 This determines which sort of hashing algorithm will be used during
1610 signature generation. This algorithm _must_ be built into the kernel
1611 directly so that signature verification can take place. It is not
1612 possible to load a signed module containing the algorithm to check
1613 the signature on that module.
1615 config MODULE_SIG_SHA1
1616 bool "Sign modules with SHA-1"
1619 config MODULE_SIG_SHA224
1620 bool "Sign modules with SHA-224"
1621 select CRYPTO_SHA256
1623 config MODULE_SIG_SHA256
1624 bool "Sign modules with SHA-256"
1625 select CRYPTO_SHA256
1627 config MODULE_SIG_SHA384
1628 bool "Sign modules with SHA-384"
1629 select CRYPTO_SHA512
1631 config MODULE_SIG_SHA512
1632 bool "Sign modules with SHA-512"
1633 select CRYPTO_SHA512
1639 config INIT_ALL_POSSIBLE
1642 Back when each arch used to define their own cpu_online_mask and
1643 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1644 with all 1s, and others with all 0s. When they were centralised,
1645 it was better to provide this option than to break all the archs
1646 and have several arch maintainers pursuing me down dark alleys.
1651 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1653 Need stop_machine() primitive.
1655 source "block/Kconfig"
1657 config PREEMPT_NOTIFIERS
1664 # Can be selected by architectures with broken toolchains
1665 # that get confused by correct const<->read_only section
1667 config BROKEN_RODATA
1673 Build a simple ASN.1 grammar compiler that produces a bytecode output
1674 that can be interpreted by the ASN.1 stream decoder and used to
1675 inform it as to what tags are to be expected in a stream and what
1676 functions to call on what tags.
1678 source "kernel/Kconfig.locks"
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