7 option env="KERNELVERSION"
13 default "/lib/modules/$UNAME_RELEASE/.config"
14 default "/etc/kernel-config"
15 default "/boot/config-$UNAME_RELEASE"
16 default "$ARCH_DEFCONFIG"
17 default "arch/$ARCH/defconfig"
28 depends on HAVE_IRQ_WORK
30 config BUILDTIME_EXTABLE_SORT
36 bool "Prompt for development and/or incomplete code/drivers"
38 Some of the various things that Linux supports (such as network
39 drivers, file systems, network protocols, etc.) can be in a state
40 of development where the functionality, stability, or the level of
41 testing is not yet high enough for general use. This is usually
42 known as the "alpha-test" phase among developers. If a feature is
43 currently in alpha-test, then the developers usually discourage
44 uninformed widespread use of this feature by the general public to
45 avoid "Why doesn't this work?" type mail messages. However, active
46 testing and use of these systems is welcomed. Just be aware that it
47 may not meet the normal level of reliability or it may fail to work
48 in some special cases. Detailed bug reports from people familiar
49 with the kernel internals are usually welcomed by the developers
50 (before submitting bug reports, please read the documents
51 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
52 <file:Documentation/BUG-HUNTING>, and
53 <file:Documentation/oops-tracing.txt> in the kernel source).
55 This option will also make obsoleted drivers available. These are
56 drivers that have been replaced by something else, and/or are
57 scheduled to be removed in a future kernel release.
59 Unless you intend to help test and develop a feature or driver that
60 falls into this category, or you have a situation that requires
61 using these features, you should probably say N here, which will
62 cause the configurator to present you with fewer choices. If
63 you say Y here, you will be offered the choice of using features or
64 drivers that are currently considered to be in the alpha-test phase.
71 depends on BROKEN || !SMP
74 config INIT_ENV_ARG_LIMIT
79 Maximum of each of the number of arguments and environment
80 variables passed to init from the kernel command line.
84 string "Cross-compiler tool prefix"
86 Same as running 'make CROSS_COMPILE=prefix-' but stored for
87 default make runs in this kernel build directory. You don't
88 need to set this unless you want the configured kernel build
89 directory to select the cross-compiler automatically.
92 string "Local version - append to kernel release"
94 Append an extra string to the end of your kernel version.
95 This will show up when you type uname, for example.
96 The string you set here will be appended after the contents of
97 any files with a filename matching localversion* in your
98 object and source tree, in that order. Your total string can
99 be a maximum of 64 characters.
101 config LOCALVERSION_AUTO
102 bool "Automatically append version information to the version string"
105 This will try to automatically determine if the current tree is a
106 release tree by looking for git tags that belong to the current
107 top of tree revision.
109 A string of the format -gxxxxxxxx will be added to the localversion
110 if a git-based tree is found. The string generated by this will be
111 appended after any matching localversion* files, and after the value
112 set in CONFIG_LOCALVERSION.
114 (The actual string used here is the first eight characters produced
115 by running the command:
117 $ git rev-parse --verify HEAD
119 which is done within the script "scripts/setlocalversion".)
121 config HAVE_KERNEL_GZIP
124 config HAVE_KERNEL_BZIP2
127 config HAVE_KERNEL_LZMA
130 config HAVE_KERNEL_XZ
133 config HAVE_KERNEL_LZO
137 prompt "Kernel compression mode"
139 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
141 The linux kernel is a kind of self-extracting executable.
142 Several compression algorithms are available, which differ
143 in efficiency, compression and decompression speed.
144 Compression speed is only relevant when building a kernel.
145 Decompression speed is relevant at each boot.
147 If you have any problems with bzip2 or lzma compressed
148 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
149 version of this functionality (bzip2 only), for 2.4, was
150 supplied by Christian Ludwig)
152 High compression options are mostly useful for users, who
153 are low on disk space (embedded systems), but for whom ram
156 If in doubt, select 'gzip'
160 depends on HAVE_KERNEL_GZIP
162 The old and tried gzip compression. It provides a good balance
163 between compression ratio and decompression speed.
167 depends on HAVE_KERNEL_BZIP2
169 Its compression ratio and speed is intermediate.
170 Decompression speed is slowest among the choices. The kernel
171 size is about 10% smaller with bzip2, in comparison to gzip.
172 Bzip2 uses a large amount of memory. For modern kernels you
173 will need at least 8MB RAM or more for booting.
177 depends on HAVE_KERNEL_LZMA
179 This compression algorithm's ratio is best. Decompression speed
180 is between gzip and bzip2. Compression is slowest.
181 The kernel size is about 33% smaller with LZMA in comparison to gzip.
185 depends on HAVE_KERNEL_XZ
187 XZ uses the LZMA2 algorithm and instruction set specific
188 BCJ filters which can improve compression ratio of executable
189 code. The size of the kernel is about 30% smaller with XZ in
190 comparison to gzip. On architectures for which there is a BCJ
191 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
192 will create a few percent smaller kernel than plain LZMA.
194 The speed is about the same as with LZMA: The decompression
195 speed of XZ is better than that of bzip2 but worse than gzip
196 and LZO. Compression is slow.
200 depends on HAVE_KERNEL_LZO
202 Its compression ratio is the poorest among the choices. The kernel
203 size is about 10% bigger than gzip; however its speed
204 (both compression and decompression) is the fastest.
208 config DEFAULT_HOSTNAME
209 string "Default hostname"
212 This option determines the default system hostname before userspace
213 calls sethostname(2). The kernel traditionally uses "(none)" here,
214 but you may wish to use a different default here to make a minimal
215 system more usable with less configuration.
218 bool "Support for paging of anonymous memory (swap)"
219 depends on MMU && BLOCK
222 This option allows you to choose whether you want to have support
223 for so called swap devices or swap files in your kernel that are
224 used to provide more virtual memory than the actual RAM present
225 in your computer. If unsure say Y.
230 Inter Process Communication is a suite of library functions and
231 system calls which let processes (running programs) synchronize and
232 exchange information. It is generally considered to be a good thing,
233 and some programs won't run unless you say Y here. In particular, if
234 you want to run the DOS emulator dosemu under Linux (read the
235 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
236 you'll need to say Y here.
238 You can find documentation about IPC with "info ipc" and also in
239 section 6.4 of the Linux Programmer's Guide, available from
240 <http://www.tldp.org/guides.html>.
242 config SYSVIPC_SYSCTL
249 bool "POSIX Message Queues"
250 depends on NET && EXPERIMENTAL
252 POSIX variant of message queues is a part of IPC. In POSIX message
253 queues every message has a priority which decides about succession
254 of receiving it by a process. If you want to compile and run
255 programs written e.g. for Solaris with use of its POSIX message
256 queues (functions mq_*) say Y here.
258 POSIX message queues are visible as a filesystem called 'mqueue'
259 and can be mounted somewhere if you want to do filesystem
260 operations on message queues.
264 config POSIX_MQUEUE_SYSCTL
266 depends on POSIX_MQUEUE
270 config BSD_PROCESS_ACCT
271 bool "BSD Process Accounting"
273 If you say Y here, a user level program will be able to instruct the
274 kernel (via a special system call) to write process accounting
275 information to a file: whenever a process exits, information about
276 that process will be appended to the file by the kernel. The
277 information includes things such as creation time, owning user,
278 command name, memory usage, controlling terminal etc. (the complete
279 list is in the struct acct in <file:include/linux/acct.h>). It is
280 up to the user level program to do useful things with this
281 information. This is generally a good idea, so say Y.
283 config BSD_PROCESS_ACCT_V3
284 bool "BSD Process Accounting version 3 file format"
285 depends on BSD_PROCESS_ACCT
288 If you say Y here, the process accounting information is written
289 in a new file format that also logs the process IDs of each
290 process and it's parent. Note that this file format is incompatible
291 with previous v0/v1/v2 file formats, so you will need updated tools
292 for processing it. A preliminary version of these tools is available
293 at <http://www.gnu.org/software/acct/>.
296 bool "open by fhandle syscalls"
299 If you say Y here, a user level program will be able to map
300 file names to handle and then later use the handle for
301 different file system operations. This is useful in implementing
302 userspace file servers, which now track files using handles instead
303 of names. The handle would remain the same even if file names
304 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
308 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
312 Export selected statistics for tasks/processes through the
313 generic netlink interface. Unlike BSD process accounting, the
314 statistics are available during the lifetime of tasks/processes as
315 responses to commands. Like BSD accounting, they are sent to user
320 config TASK_DELAY_ACCT
321 bool "Enable per-task delay accounting (EXPERIMENTAL)"
324 Collect information on time spent by a task waiting for system
325 resources like cpu, synchronous block I/O completion and swapping
326 in pages. Such statistics can help in setting a task's priorities
327 relative to other tasks for cpu, io, rss limits etc.
332 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
335 Collect extended task accounting data and send the data
336 to userland for processing over the taskstats interface.
340 config TASK_IO_ACCOUNTING
341 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
342 depends on TASK_XACCT
344 Collect information on the number of bytes of storage I/O which this
350 bool "Auditing support"
353 Enable auditing infrastructure that can be used with another
354 kernel subsystem, such as SELinux (which requires this for
355 logging of avc messages output). Does not do system-call
356 auditing without CONFIG_AUDITSYSCALL.
359 bool "Enable system-call auditing support"
360 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || (ARM && AEABI && !OABI_COMPAT))
361 default y if SECURITY_SELINUX
363 Enable low-overhead system-call auditing infrastructure that
364 can be used independently or with another kernel subsystem,
369 depends on AUDITSYSCALL
374 depends on AUDITSYSCALL
377 config AUDIT_LOGINUID_IMMUTABLE
378 bool "Make audit loginuid immutable"
381 The config option toggles if a task setting its loginuid requires
382 CAP_SYS_AUDITCONTROL or if that task should require no special permissions
383 but should instead only allow setting its loginuid if it was never
384 previously set. On systems which use systemd or a similar central
385 process to restart login services this should be set to true. On older
386 systems in which an admin would typically have to directly stop and
387 start processes this should be set to false. Setting this to true allows
388 one to drop potentially dangerous capabilites from the login tasks,
389 but may not be backwards compatible with older init systems.
391 source "kernel/irq/Kconfig"
392 source "kernel/time/Kconfig"
397 prompt "RCU Implementation"
401 bool "Tree-based hierarchical RCU"
402 depends on !PREEMPT && SMP
404 This option selects the RCU implementation that is
405 designed for very large SMP system with hundreds or
406 thousands of CPUs. It also scales down nicely to
409 config TREE_PREEMPT_RCU
410 bool "Preemptible tree-based hierarchical RCU"
411 depends on PREEMPT && SMP
413 This option selects the RCU implementation that is
414 designed for very large SMP systems with hundreds or
415 thousands of CPUs, but for which real-time response
416 is also required. It also scales down nicely to
420 bool "UP-only small-memory-footprint RCU"
421 depends on !PREEMPT && !SMP
423 This option selects the RCU implementation that is
424 designed for UP systems from which real-time response
425 is not required. This option greatly reduces the
426 memory footprint of RCU.
428 config TINY_PREEMPT_RCU
429 bool "Preemptible UP-only small-memory-footprint RCU"
430 depends on PREEMPT && !SMP
432 This option selects the RCU implementation that is designed
433 for real-time UP systems. This option greatly reduces the
434 memory footprint of RCU.
439 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
441 This option enables preemptible-RCU code that is common between
442 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
445 int "Tree-based hierarchical RCU fanout value"
448 depends on TREE_RCU || TREE_PREEMPT_RCU
452 This option controls the fanout of hierarchical implementations
453 of RCU, allowing RCU to work efficiently on machines with
454 large numbers of CPUs. This value must be at least the fourth
455 root of NR_CPUS, which allows NR_CPUS to be insanely large.
456 The default value of RCU_FANOUT should be used for production
457 systems, but if you are stress-testing the RCU implementation
458 itself, small RCU_FANOUT values allow you to test large-system
459 code paths on small(er) systems.
461 Select a specific number if testing RCU itself.
462 Take the default if unsure.
464 config RCU_FANOUT_LEAF
465 int "Tree-based hierarchical RCU leaf-level fanout value"
466 range 2 RCU_FANOUT if 64BIT
467 range 2 RCU_FANOUT if !64BIT
468 depends on TREE_RCU || TREE_PREEMPT_RCU
471 This option controls the leaf-level fanout of hierarchical
472 implementations of RCU, and allows trading off cache misses
473 against lock contention. Systems that synchronize their
474 scheduling-clock interrupts for energy-efficiency reasons will
475 want the default because the smaller leaf-level fanout keeps
476 lock contention levels acceptably low. Very large systems
477 (hundreds or thousands of CPUs) will instead want to set this
478 value to the maximum value possible in order to reduce the
479 number of cache misses incurred during RCU's grace-period
480 initialization. These systems tend to run CPU-bound, and thus
481 are not helped by synchronized interrupts, and thus tend to
482 skew them, which reduces lock contention enough that large
483 leaf-level fanouts work well.
485 Select a specific number if testing RCU itself.
487 Select the maximum permissible value for large systems.
489 Take the default if unsure.
491 config RCU_FANOUT_EXACT
492 bool "Disable tree-based hierarchical RCU auto-balancing"
493 depends on TREE_RCU || TREE_PREEMPT_RCU
496 This option forces use of the exact RCU_FANOUT value specified,
497 regardless of imbalances in the hierarchy. This is useful for
498 testing RCU itself, and might one day be useful on systems with
499 strong NUMA behavior.
501 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
505 config RCU_FAST_NO_HZ
506 bool "Accelerate last non-dyntick-idle CPU's grace periods"
507 depends on NO_HZ && SMP
510 This option causes RCU to attempt to accelerate grace periods
511 in order to allow CPUs to enter dynticks-idle state more
512 quickly. On the other hand, this option increases the overhead
513 of the dynticks-idle checking, particularly on systems with
514 large numbers of CPUs.
516 Say Y if energy efficiency is critically important, particularly
517 if you have relatively few CPUs.
519 Say N if you are unsure.
521 config TREE_RCU_TRACE
522 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
525 This option provides tracing for the TREE_RCU and
526 TREE_PREEMPT_RCU implementations, permitting Makefile to
527 trivially select kernel/rcutree_trace.c.
530 bool "Enable RCU priority boosting"
531 depends on RT_MUTEXES && PREEMPT_RCU
534 This option boosts the priority of preempted RCU readers that
535 block the current preemptible RCU grace period for too long.
536 This option also prevents heavy loads from blocking RCU
537 callback invocation for all flavors of RCU.
539 Say Y here if you are working with real-time apps or heavy loads
540 Say N here if you are unsure.
542 config RCU_BOOST_PRIO
543 int "Real-time priority to boost RCU readers to"
548 This option specifies the real-time priority to which long-term
549 preempted RCU readers are to be boosted. If you are working
550 with a real-time application that has one or more CPU-bound
551 threads running at a real-time priority level, you should set
552 RCU_BOOST_PRIO to a priority higher then the highest-priority
553 real-time CPU-bound thread. The default RCU_BOOST_PRIO value
554 of 1 is appropriate in the common case, which is real-time
555 applications that do not have any CPU-bound threads.
557 Some real-time applications might not have a single real-time
558 thread that saturates a given CPU, but instead might have
559 multiple real-time threads that, taken together, fully utilize
560 that CPU. In this case, you should set RCU_BOOST_PRIO to
561 a priority higher than the lowest-priority thread that is
562 conspiring to prevent the CPU from running any non-real-time
563 tasks. For example, if one thread at priority 10 and another
564 thread at priority 5 are between themselves fully consuming
565 the CPU time on a given CPU, then RCU_BOOST_PRIO should be
566 set to priority 6 or higher.
568 Specify the real-time priority, or take the default if unsure.
570 config RCU_BOOST_DELAY
571 int "Milliseconds to delay boosting after RCU grace-period start"
576 This option specifies the time to wait after the beginning of
577 a given grace period before priority-boosting preempted RCU
578 readers blocking that grace period. Note that any RCU reader
579 blocking an expedited RCU grace period is boosted immediately.
581 Accept the default if unsure.
583 endmenu # "RCU Subsystem"
586 tristate "Kernel .config support"
588 This option enables the complete Linux kernel ".config" file
589 contents to be saved in the kernel. It provides documentation
590 of which kernel options are used in a running kernel or in an
591 on-disk kernel. This information can be extracted from the kernel
592 image file with the script scripts/extract-ikconfig and used as
593 input to rebuild the current kernel or to build another kernel.
594 It can also be extracted from a running kernel by reading
595 /proc/config.gz if enabled (below).
598 bool "Enable access to .config through /proc/config.gz"
599 depends on IKCONFIG && PROC_FS
601 This option enables access to the kernel configuration file
602 through /proc/config.gz.
605 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
609 Select kernel log buffer size as a power of 2.
619 # Architectures with an unreliable sched_clock() should select this:
621 config HAVE_UNSTABLE_SCHED_CLOCK
625 boolean "Control Group support"
628 This option adds support for grouping sets of processes together, for
629 use with process control subsystems such as Cpusets, CFS, memory
630 controls or device isolation.
632 - Documentation/scheduler/sched-design-CFS.txt (CFS)
633 - Documentation/cgroups/ (features for grouping, isolation
634 and resource control)
641 bool "Example debug cgroup subsystem"
644 This option enables a simple cgroup subsystem that
645 exports useful debugging information about the cgroups
650 config CGROUP_FREEZER
651 bool "Freezer cgroup subsystem"
653 Provides a way to freeze and unfreeze all tasks in a
657 bool "Device controller for cgroups"
659 Provides a cgroup implementing whitelists for devices which
660 a process in the cgroup can mknod or open.
663 bool "Cpuset support"
665 This option will let you create and manage CPUSETs which
666 allow dynamically partitioning a system into sets of CPUs and
667 Memory Nodes and assigning tasks to run only within those sets.
668 This is primarily useful on large SMP or NUMA systems.
672 config PROC_PID_CPUSET
673 bool "Include legacy /proc/<pid>/cpuset file"
677 config CGROUP_CPUACCT
678 bool "Simple CPU accounting cgroup subsystem"
680 Provides a simple Resource Controller for monitoring the
681 total CPU consumed by the tasks in a cgroup.
683 config RESOURCE_COUNTERS
684 bool "Resource counters"
686 This option enables controller independent resource accounting
687 infrastructure that works with cgroups.
690 bool "Memory Resource Controller for Control Groups"
691 depends on RESOURCE_COUNTERS
694 Provides a memory resource controller that manages both anonymous
695 memory and page cache. (See Documentation/cgroups/memory.txt)
697 Note that setting this option increases fixed memory overhead
698 associated with each page of memory in the system. By this,
699 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
700 usage tracking struct at boot. Total amount of this is printed out
703 Only enable when you're ok with these trade offs and really
704 sure you need the memory resource controller. Even when you enable
705 this, you can set "cgroup_disable=memory" at your boot option to
706 disable memory resource controller and you can avoid overheads.
707 (and lose benefits of memory resource controller)
709 This config option also selects MM_OWNER config option, which
710 could in turn add some fork/exit overhead.
713 bool "Memory Resource Controller Swap Extension"
714 depends on MEMCG && SWAP
716 Add swap management feature to memory resource controller. When you
717 enable this, you can limit mem+swap usage per cgroup. In other words,
718 when you disable this, memory resource controller has no cares to
719 usage of swap...a process can exhaust all of the swap. This extension
720 is useful when you want to avoid exhaustion swap but this itself
721 adds more overheads and consumes memory for remembering information.
722 Especially if you use 32bit system or small memory system, please
723 be careful about enabling this. When memory resource controller
724 is disabled by boot option, this will be automatically disabled and
725 there will be no overhead from this. Even when you set this config=y,
726 if boot option "swapaccount=0" is set, swap will not be accounted.
727 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
728 size is 4096bytes, 512k per 1Gbytes of swap.
729 config MEMCG_SWAP_ENABLED
730 bool "Memory Resource Controller Swap Extension enabled by default"
731 depends on MEMCG_SWAP
734 Memory Resource Controller Swap Extension comes with its price in
735 a bigger memory consumption. General purpose distribution kernels
736 which want to enable the feature but keep it disabled by default
737 and let the user enable it by swapaccount boot command line
738 parameter should have this option unselected.
739 For those who want to have the feature enabled by default should
740 select this option (if, for some reason, they need to disable it
741 then swapaccount=0 does the trick).
743 bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
744 depends on MEMCG && EXPERIMENTAL
747 The Kernel Memory extension for Memory Resource Controller can limit
748 the amount of memory used by kernel objects in the system. Those are
749 fundamentally different from the entities handled by the standard
750 Memory Controller, which are page-based, and can be swapped. Users of
751 the kmem extension can use it to guarantee that no group of processes
752 will ever exhaust kernel resources alone.
754 config CGROUP_HUGETLB
755 bool "HugeTLB Resource Controller for Control Groups"
756 depends on RESOURCE_COUNTERS && HUGETLB_PAGE && EXPERIMENTAL
759 Provides a cgroup Resource Controller for HugeTLB pages.
760 When you enable this, you can put a per cgroup limit on HugeTLB usage.
761 The limit is enforced during page fault. Since HugeTLB doesn't
762 support page reclaim, enforcing the limit at page fault time implies
763 that, the application will get SIGBUS signal if it tries to access
764 HugeTLB pages beyond its limit. This requires the application to know
765 beforehand how much HugeTLB pages it would require for its use. The
766 control group is tracked in the third page lru pointer. This means
767 that we cannot use the controller with huge page less than 3 pages.
770 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
771 depends on PERF_EVENTS && CGROUPS
773 This option extends the per-cpu mode to restrict monitoring to
774 threads which belong to the cgroup specified and run on the
779 menuconfig CGROUP_SCHED
780 bool "Group CPU scheduler"
783 This feature lets CPU scheduler recognize task groups and control CPU
784 bandwidth allocation to such task groups. It uses cgroups to group
788 config FAIR_GROUP_SCHED
789 bool "Group scheduling for SCHED_OTHER"
790 depends on CGROUP_SCHED
794 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
795 depends on EXPERIMENTAL
796 depends on FAIR_GROUP_SCHED
799 This option allows users to define CPU bandwidth rates (limits) for
800 tasks running within the fair group scheduler. Groups with no limit
801 set are considered to be unconstrained and will run with no
803 See tip/Documentation/scheduler/sched-bwc.txt for more information.
805 config RT_GROUP_SCHED
806 bool "Group scheduling for SCHED_RR/FIFO"
807 depends on EXPERIMENTAL
808 depends on CGROUP_SCHED
811 This feature lets you explicitly allocate real CPU bandwidth
812 to task groups. If enabled, it will also make it impossible to
813 schedule realtime tasks for non-root users until you allocate
814 realtime bandwidth for them.
815 See Documentation/scheduler/sched-rt-group.txt for more information.
820 bool "Block IO controller"
824 Generic block IO controller cgroup interface. This is the common
825 cgroup interface which should be used by various IO controlling
828 Currently, CFQ IO scheduler uses it to recognize task groups and
829 control disk bandwidth allocation (proportional time slice allocation)
830 to such task groups. It is also used by bio throttling logic in
831 block layer to implement upper limit in IO rates on a device.
833 This option only enables generic Block IO controller infrastructure.
834 One needs to also enable actual IO controlling logic/policy. For
835 enabling proportional weight division of disk bandwidth in CFQ, set
836 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
837 CONFIG_BLK_DEV_THROTTLING=y.
839 See Documentation/cgroups/blkio-controller.txt for more information.
841 config DEBUG_BLK_CGROUP
842 bool "Enable Block IO controller debugging"
843 depends on BLK_CGROUP
846 Enable some debugging help. Currently it exports additional stat
847 files in a cgroup which can be useful for debugging.
851 config CHECKPOINT_RESTORE
852 bool "Checkpoint/restore support" if EXPERT
855 Enables additional kernel features in a sake of checkpoint/restore.
856 In particular it adds auxiliary prctl codes to setup process text,
857 data and heap segment sizes, and a few additional /proc filesystem
860 If unsure, say N here.
862 menuconfig NAMESPACES
863 bool "Namespaces support" if EXPERT
866 Provides the way to make tasks work with different objects using
867 the same id. For example same IPC id may refer to different objects
868 or same user id or pid may refer to different tasks when used in
869 different namespaces.
877 In this namespace tasks see different info provided with the
882 depends on (SYSVIPC || POSIX_MQUEUE)
885 In this namespace tasks work with IPC ids which correspond to
886 different IPC objects in different namespaces.
889 bool "User namespace (EXPERIMENTAL)"
890 depends on EXPERIMENTAL
891 depends on UIDGID_CONVERTED
892 select UIDGID_STRICT_TYPE_CHECKS
896 This allows containers, i.e. vservers, to use user namespaces
897 to provide different user info for different servers.
901 bool "PID Namespaces"
904 Support process id namespaces. This allows having multiple
905 processes with the same pid as long as they are in different
906 pid namespaces. This is a building block of containers.
909 bool "Network namespace"
913 Allow user space to create what appear to be multiple instances
914 of the network stack.
918 config UIDGID_CONVERTED
919 # True if all of the selected software conmponents are known
920 # to have uid_t and gid_t converted to kuid_t and kgid_t
921 # where appropriate and are otherwise safe to use with
922 # the user namespace.
926 # List of kernel pieces that need user namespace work
932 depends on NET_9P = n
936 depends on AFFS_FS = n
937 depends on AFS_FS = n
938 depends on AUTOFS4_FS = n
939 depends on BFS_FS = n
940 depends on BTRFS_FS = n
941 depends on CEPH_FS = n
943 depends on CODA_FS = n
944 depends on FUSE_FS = n
945 depends on GFS2_FS = n
946 depends on HPFS_FS = n
947 depends on JFFS2_FS = n
948 depends on JFS_FS = n
949 depends on NCP_FS = n
951 depends on NFS_FS = n
952 depends on OCFS2_FS = n
953 depends on REISERFS_FS = n
954 depends on SQUASHFS = n
955 depends on UBIFS_FS = n
956 depends on UDF_FS = n
957 depends on UFS_FS = n
958 depends on XFS_FS = n
960 depends on !UML || HOSTFS = n
962 # The rare drivers that won't build
963 depends on ANDROID_BINDER_IPC = n
966 depends on SECURITY_TOMOYO = n
968 config UIDGID_STRICT_TYPE_CHECKS
969 bool "Require conversions between uid/gids and their internal representation"
970 depends on UIDGID_CONVERTED
973 While the nececessary conversions are being added to all subsystems this option allows
974 the code to continue to build for unconverted subsystems.
976 Say Y here if you want the strict type checking enabled
978 config SCHED_AUTOGROUP
979 bool "Automatic process group scheduling"
983 select FAIR_GROUP_SCHED
985 This option optimizes the scheduler for common desktop workloads by
986 automatically creating and populating task groups. This separation
987 of workloads isolates aggressive CPU burners (like build jobs) from
988 desktop applications. Task group autogeneration is currently based
994 config SYSFS_DEPRECATED
995 bool "Enable deprecated sysfs features to support old userspace tools"
999 This option adds code that switches the layout of the "block" class
1000 devices, to not show up in /sys/class/block/, but only in
1003 This switch is only active when the sysfs.deprecated=1 boot option is
1004 passed or the SYSFS_DEPRECATED_V2 option is set.
1006 This option allows new kernels to run on old distributions and tools,
1007 which might get confused by /sys/class/block/. Since 2007/2008 all
1008 major distributions and tools handle this just fine.
1010 Recent distributions and userspace tools after 2009/2010 depend on
1011 the existence of /sys/class/block/, and will not work with this
1014 Only if you are using a new kernel on an old distribution, you might
1017 config SYSFS_DEPRECATED_V2
1018 bool "Enable deprecated sysfs features by default"
1021 depends on SYSFS_DEPRECATED
1023 Enable deprecated sysfs by default.
1025 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1028 Only if you are using a new kernel on an old distribution, you might
1029 need to say Y here. Even then, odds are you would not need it
1030 enabled, you can always pass the boot option if absolutely necessary.
1033 bool "Kernel->user space relay support (formerly relayfs)"
1035 This option enables support for relay interface support in
1036 certain file systems (such as debugfs).
1037 It is designed to provide an efficient mechanism for tools and
1038 facilities to relay large amounts of data from kernel space to
1043 config BLK_DEV_INITRD
1044 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1045 depends on BROKEN || !FRV
1047 The initial RAM filesystem is a ramfs which is loaded by the
1048 boot loader (loadlin or lilo) and that is mounted as root
1049 before the normal boot procedure. It is typically used to
1050 load modules needed to mount the "real" root file system,
1051 etc. See <file:Documentation/initrd.txt> for details.
1053 If RAM disk support (BLK_DEV_RAM) is also included, this
1054 also enables initial RAM disk (initrd) support and adds
1055 15 Kbytes (more on some other architectures) to the kernel size.
1061 source "usr/Kconfig"
1065 config CC_OPTIMIZE_FOR_SIZE
1066 bool "Optimize for size"
1068 Enabling this option will pass "-Os" instead of "-O2" to gcc
1069 resulting in a smaller kernel.
1080 bool "Configure standard kernel features (expert users)"
1081 # Unhide debug options, to make the on-by-default options visible
1084 This option allows certain base kernel options and settings
1085 to be disabled or tweaked. This is for specialized
1086 environments which can tolerate a "non-standard" kernel.
1087 Only use this if you really know what you are doing.
1090 bool "Enable 16-bit UID system calls" if EXPERT
1091 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
1094 This enables the legacy 16-bit UID syscall wrappers.
1096 config SYSCTL_SYSCALL
1097 bool "Sysctl syscall support" if EXPERT
1098 depends on PROC_SYSCTL
1102 sys_sysctl uses binary paths that have been found challenging
1103 to properly maintain and use. The interface in /proc/sys
1104 using paths with ascii names is now the primary path to this
1107 Almost nothing using the binary sysctl interface so if you are
1108 trying to save some space it is probably safe to disable this,
1109 making your kernel marginally smaller.
1111 If unsure say N here.
1114 bool "Load all symbols for debugging/ksymoops" if EXPERT
1117 Say Y here to let the kernel print out symbolic crash information and
1118 symbolic stack backtraces. This increases the size of the kernel
1119 somewhat, as all symbols have to be loaded into the kernel image.
1122 bool "Include all symbols in kallsyms"
1123 depends on DEBUG_KERNEL && KALLSYMS
1125 Normally kallsyms only contains the symbols of functions for nicer
1126 OOPS messages and backtraces (i.e., symbols from the text and inittext
1127 sections). This is sufficient for most cases. And only in very rare
1128 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1129 names of variables from the data sections, etc).
1131 This option makes sure that all symbols are loaded into the kernel
1132 image (i.e., symbols from all sections) in cost of increased kernel
1133 size (depending on the kernel configuration, it may be 300KiB or
1134 something like this).
1136 Say N unless you really need all symbols.
1139 bool "Support for hot-pluggable devices" if EXPERT
1142 This option is provided for the case where no hotplug or uevent
1143 capabilities is wanted by the kernel. You should only consider
1144 disabling this option for embedded systems that do not use modules, a
1145 dynamic /dev tree, or dynamic device discovery. Just say Y.
1149 bool "Enable support for printk" if EXPERT
1151 This option enables normal printk support. Removing it
1152 eliminates most of the message strings from the kernel image
1153 and makes the kernel more or less silent. As this makes it
1154 very difficult to diagnose system problems, saying N here is
1155 strongly discouraged.
1158 bool "BUG() support" if EXPERT
1161 Disabling this option eliminates support for BUG and WARN, reducing
1162 the size of your kernel image and potentially quietly ignoring
1163 numerous fatal conditions. You should only consider disabling this
1164 option for embedded systems with no facilities for reporting errors.
1169 bool "Enable ELF core dumps" if EXPERT
1171 Enable support for generating core dumps. Disabling saves about 4k.
1174 config PCSPKR_PLATFORM
1175 bool "Enable PC-Speaker support" if EXPERT
1176 depends on HAVE_PCSPKR_PLATFORM
1180 This option allows to disable the internal PC-Speaker
1181 support, saving some memory.
1183 config HAVE_PCSPKR_PLATFORM
1188 bool "Enable full-sized data structures for core" if EXPERT
1190 Disabling this option reduces the size of miscellaneous core
1191 kernel data structures. This saves memory on small machines,
1192 but may reduce performance.
1195 bool "Enable futex support" if EXPERT
1199 Disabling this option will cause the kernel to be built without
1200 support for "fast userspace mutexes". The resulting kernel may not
1201 run glibc-based applications correctly.
1204 bool "Enable eventpoll support" if EXPERT
1208 Disabling this option will cause the kernel to be built without
1209 support for epoll family of system calls.
1212 bool "Enable signalfd() system call" if EXPERT
1216 Enable the signalfd() system call that allows to receive signals
1217 on a file descriptor.
1222 bool "Enable timerfd() system call" if EXPERT
1226 Enable the timerfd() system call that allows to receive timer
1227 events on a file descriptor.
1232 bool "Enable eventfd() system call" if EXPERT
1236 Enable the eventfd() system call that allows to receive both
1237 kernel notification (ie. KAIO) or userspace notifications.
1242 bool "Use full shmem filesystem" if EXPERT
1246 The shmem is an internal filesystem used to manage shared memory.
1247 It is backed by swap and manages resource limits. It is also exported
1248 to userspace as tmpfs if TMPFS is enabled. Disabling this
1249 option replaces shmem and tmpfs with the much simpler ramfs code,
1250 which may be appropriate on small systems without swap.
1253 bool "Enable AIO support" if EXPERT
1256 This option enables POSIX asynchronous I/O which may by used
1257 by some high performance threaded applications. Disabling
1258 this option saves about 7k.
1261 bool "Embedded system"
1264 This option should be enabled if compiling the kernel for
1265 an embedded system so certain expert options are available
1268 config HAVE_PERF_EVENTS
1271 See tools/perf/design.txt for details.
1273 config PERF_USE_VMALLOC
1276 See tools/perf/design.txt for details
1278 menu "Kernel Performance Events And Counters"
1281 bool "Kernel performance events and counters"
1282 default y if PROFILING
1283 depends on HAVE_PERF_EVENTS
1287 Enable kernel support for various performance events provided
1288 by software and hardware.
1290 Software events are supported either built-in or via the
1291 use of generic tracepoints.
1293 Most modern CPUs support performance events via performance
1294 counter registers. These registers count the number of certain
1295 types of hw events: such as instructions executed, cachemisses
1296 suffered, or branches mis-predicted - without slowing down the
1297 kernel or applications. These registers can also trigger interrupts
1298 when a threshold number of events have passed - and can thus be
1299 used to profile the code that runs on that CPU.
1301 The Linux Performance Event subsystem provides an abstraction of
1302 these software and hardware event capabilities, available via a
1303 system call and used by the "perf" utility in tools/perf/. It
1304 provides per task and per CPU counters, and it provides event
1305 capabilities on top of those.
1309 config DEBUG_PERF_USE_VMALLOC
1311 bool "Debug: use vmalloc to back perf mmap() buffers"
1312 depends on PERF_EVENTS && DEBUG_KERNEL
1313 select PERF_USE_VMALLOC
1315 Use vmalloc memory to back perf mmap() buffers.
1317 Mostly useful for debugging the vmalloc code on platforms
1318 that don't require it.
1324 config VM_EVENT_COUNTERS
1326 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1328 VM event counters are needed for event counts to be shown.
1329 This option allows the disabling of the VM event counters
1330 on EXPERT systems. /proc/vmstat will only show page counts
1331 if VM event counters are disabled.
1335 bool "Enable PCI quirk workarounds" if EXPERT
1338 This enables workarounds for various PCI chipset
1339 bugs/quirks. Disable this only if your target machine is
1340 unaffected by PCI quirks.
1344 bool "Enable SLUB debugging support" if EXPERT
1345 depends on SLUB && SYSFS
1347 SLUB has extensive debug support features. Disabling these can
1348 result in significant savings in code size. This also disables
1349 SLUB sysfs support. /sys/slab will not exist and there will be
1350 no support for cache validation etc.
1353 bool "Disable heap randomization"
1356 Randomizing heap placement makes heap exploits harder, but it
1357 also breaks ancient binaries (including anything libc5 based).
1358 This option changes the bootup default to heap randomization
1359 disabled, and can be overridden at runtime by setting
1360 /proc/sys/kernel/randomize_va_space to 2.
1362 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1365 prompt "Choose SLAB allocator"
1368 This option allows to select a slab allocator.
1373 The regular slab allocator that is established and known to work
1374 well in all environments. It organizes cache hot objects in
1375 per cpu and per node queues.
1378 bool "SLUB (Unqueued Allocator)"
1380 SLUB is a slab allocator that minimizes cache line usage
1381 instead of managing queues of cached objects (SLAB approach).
1382 Per cpu caching is realized using slabs of objects instead
1383 of queues of objects. SLUB can use memory efficiently
1384 and has enhanced diagnostics. SLUB is the default choice for
1389 bool "SLOB (Simple Allocator)"
1391 SLOB replaces the stock allocator with a drastically simpler
1392 allocator. SLOB is generally more space efficient but
1393 does not perform as well on large systems.
1397 config MMAP_ALLOW_UNINITIALIZED
1398 bool "Allow mmapped anonymous memory to be uninitialized"
1399 depends on EXPERT && !MMU
1402 Normally, and according to the Linux spec, anonymous memory obtained
1403 from mmap() has it's contents cleared before it is passed to
1404 userspace. Enabling this config option allows you to request that
1405 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1406 providing a huge performance boost. If this option is not enabled,
1407 then the flag will be ignored.
1409 This is taken advantage of by uClibc's malloc(), and also by
1410 ELF-FDPIC binfmt's brk and stack allocator.
1412 Because of the obvious security issues, this option should only be
1413 enabled on embedded devices where you control what is run in
1414 userspace. Since that isn't generally a problem on no-MMU systems,
1415 it is normally safe to say Y here.
1417 See Documentation/nommu-mmap.txt for more information.
1420 bool "Profiling support"
1422 Say Y here to enable the extended profiling support mechanisms used
1423 by profilers such as OProfile.
1426 # Place an empty function call at each tracepoint site. Can be
1427 # dynamically changed for a probe function.
1432 source "arch/Kconfig"
1434 endmenu # General setup
1436 config HAVE_GENERIC_DMA_COHERENT
1443 depends on SLAB || SLUB_DEBUG
1451 default 0 if BASE_FULL
1452 default 1 if !BASE_FULL
1455 bool "Enable loadable module support"
1457 Kernel modules are small pieces of compiled code which can
1458 be inserted in the running kernel, rather than being
1459 permanently built into the kernel. You use the "modprobe"
1460 tool to add (and sometimes remove) them. If you say Y here,
1461 many parts of the kernel can be built as modules (by
1462 answering M instead of Y where indicated): this is most
1463 useful for infrequently used options which are not required
1464 for booting. For more information, see the man pages for
1465 modprobe, lsmod, modinfo, insmod and rmmod.
1467 If you say Y here, you will need to run "make
1468 modules_install" to put the modules under /lib/modules/
1469 where modprobe can find them (you may need to be root to do
1476 config MODULE_FORCE_LOAD
1477 bool "Forced module loading"
1480 Allow loading of modules without version information (ie. modprobe
1481 --force). Forced module loading sets the 'F' (forced) taint flag and
1482 is usually a really bad idea.
1484 config MODULE_UNLOAD
1485 bool "Module unloading"
1487 Without this option you will not be able to unload any
1488 modules (note that some modules may not be unloadable
1489 anyway), which makes your kernel smaller, faster
1490 and simpler. If unsure, say Y.
1492 config MODULE_FORCE_UNLOAD
1493 bool "Forced module unloading"
1494 depends on MODULE_UNLOAD && EXPERIMENTAL
1496 This option allows you to force a module to unload, even if the
1497 kernel believes it is unsafe: the kernel will remove the module
1498 without waiting for anyone to stop using it (using the -f option to
1499 rmmod). This is mainly for kernel developers and desperate users.
1503 bool "Module versioning support"
1505 Usually, you have to use modules compiled with your kernel.
1506 Saying Y here makes it sometimes possible to use modules
1507 compiled for different kernels, by adding enough information
1508 to the modules to (hopefully) spot any changes which would
1509 make them incompatible with the kernel you are running. If
1512 config MODULE_SRCVERSION_ALL
1513 bool "Source checksum for all modules"
1515 Modules which contain a MODULE_VERSION get an extra "srcversion"
1516 field inserted into their modinfo section, which contains a
1517 sum of the source files which made it. This helps maintainers
1518 see exactly which source was used to build a module (since
1519 others sometimes change the module source without updating
1520 the version). With this option, such a "srcversion" field
1521 will be created for all modules. If unsure, say N.
1525 config INIT_ALL_POSSIBLE
1528 Back when each arch used to define their own cpu_online_mask and
1529 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1530 with all 1s, and others with all 0s. When they were centralised,
1531 it was better to provide this option than to break all the archs
1532 and have several arch maintainers pursuing me down dark alleys.
1537 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1539 Need stop_machine() primitive.
1541 source "block/Kconfig"
1543 config PREEMPT_NOTIFIERS
1550 source "kernel/Kconfig.locks"