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
33 bool "Prompt for development and/or incomplete code/drivers"
35 Some of the various things that Linux supports (such as network
36 drivers, file systems, network protocols, etc.) can be in a state
37 of development where the functionality, stability, or the level of
38 testing is not yet high enough for general use. This is usually
39 known as the "alpha-test" phase among developers. If a feature is
40 currently in alpha-test, then the developers usually discourage
41 uninformed widespread use of this feature by the general public to
42 avoid "Why doesn't this work?" type mail messages. However, active
43 testing and use of these systems is welcomed. Just be aware that it
44 may not meet the normal level of reliability or it may fail to work
45 in some special cases. Detailed bug reports from people familiar
46 with the kernel internals are usually welcomed by the developers
47 (before submitting bug reports, please read the documents
48 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
49 <file:Documentation/BUG-HUNTING>, and
50 <file:Documentation/oops-tracing.txt> in the kernel source).
52 This option will also make obsoleted drivers available. These are
53 drivers that have been replaced by something else, and/or are
54 scheduled to be removed in a future kernel release.
56 Unless you intend to help test and develop a feature or driver that
57 falls into this category, or you have a situation that requires
58 using these features, you should probably say N here, which will
59 cause the configurator to present you with fewer choices. If
60 you say Y here, you will be offered the choice of using features or
61 drivers that are currently considered to be in the alpha-test phase.
68 depends on BROKEN || !SMP
71 config INIT_ENV_ARG_LIMIT
76 Maximum of each of the number of arguments and environment
77 variables passed to init from the kernel command line.
79 config INIT_PASS_ALL_PARAMS
80 bool "Pass all (known and unknown) kernel parameters to init"
83 Pass all kernel command line parameters to init, this includes
84 those consumed by kernel modules. This is useful for upstart
85 based systems. If in doubt say N.
88 string "Cross-compiler tool prefix"
90 Same as running 'make CROSS_COMPILE=prefix-' but stored for
91 default make runs in this kernel build directory. You don't
92 need to set this unless you want the configured kernel build
93 directory to select the cross-compiler automatically.
96 string "Local version - append to kernel release"
98 Append an extra string to the end of your kernel version.
99 This will show up when you type uname, for example.
100 The string you set here will be appended after the contents of
101 any files with a filename matching localversion* in your
102 object and source tree, in that order. Your total string can
103 be a maximum of 64 characters.
105 config LOCALVERSION_AUTO
106 bool "Automatically append version information to the version string"
109 This will try to automatically determine if the current tree is a
110 release tree by looking for git tags that belong to the current
111 top of tree revision.
113 A string of the format -gxxxxxxxx will be added to the localversion
114 if a git-based tree is found. The string generated by this will be
115 appended after any matching localversion* files, and after the value
116 set in CONFIG_LOCALVERSION.
118 (The actual string used here is the first eight characters produced
119 by running the command:
121 $ git rev-parse --verify HEAD
123 which is done within the script "scripts/setlocalversion".)
125 config HAVE_KERNEL_GZIP
128 config HAVE_KERNEL_BZIP2
131 config HAVE_KERNEL_LZMA
134 config HAVE_KERNEL_XZ
137 config HAVE_KERNEL_LZO
141 prompt "Kernel compression mode"
143 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
145 The linux kernel is a kind of self-extracting executable.
146 Several compression algorithms are available, which differ
147 in efficiency, compression and decompression speed.
148 Compression speed is only relevant when building a kernel.
149 Decompression speed is relevant at each boot.
151 If you have any problems with bzip2 or lzma compressed
152 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
153 version of this functionality (bzip2 only), for 2.4, was
154 supplied by Christian Ludwig)
156 High compression options are mostly useful for users, who
157 are low on disk space (embedded systems), but for whom ram
160 If in doubt, select 'gzip'
164 depends on HAVE_KERNEL_GZIP
166 The old and tried gzip compression. It provides a good balance
167 between compression ratio and decompression speed.
171 depends on HAVE_KERNEL_BZIP2
173 Its compression ratio and speed is intermediate.
174 Decompression speed is slowest among the three. The kernel
175 size is about 10% smaller with bzip2, in comparison to gzip.
176 Bzip2 uses a large amount of memory. For modern kernels you
177 will need at least 8MB RAM or more for booting.
181 depends on HAVE_KERNEL_LZMA
183 The most recent compression algorithm.
184 Its ratio is best, decompression speed is between the other
185 two. Compression is slowest. The kernel size is about 33%
186 smaller with LZMA in comparison to gzip.
190 depends on HAVE_KERNEL_XZ
192 XZ uses the LZMA2 algorithm and instruction set specific
193 BCJ filters which can improve compression ratio of executable
194 code. The size of the kernel is about 30% smaller with XZ in
195 comparison to gzip. On architectures for which there is a BCJ
196 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
197 will create a few percent smaller kernel than plain LZMA.
199 The speed is about the same as with LZMA: The decompression
200 speed of XZ is better than that of bzip2 but worse than gzip
201 and LZO. Compression is slow.
205 depends on HAVE_KERNEL_LZO
207 Its compression ratio is the poorest among the 4. The kernel
208 size is about 10% bigger than gzip; however its speed
209 (both compression and decompression) is the fastest.
213 config DEFAULT_HOSTNAME
214 string "Default hostname"
217 This option determines the default system hostname before userspace
218 calls sethostname(2). The kernel traditionally uses "(none)" here,
219 but you may wish to use a different default here to make a minimal
220 system more usable with less configuration.
222 config VERSION_SIGNATURE
223 string "Arbitrary version signature"
225 This string will be created in a file, /proc/version_signature. It
226 is useful in determining arbitrary data about your kernel. For instance,
227 if you have several kernels of the same version, but need to keep track
228 of a revision of the same kernel, but not affect it's ability to load
229 compatible modules, this is the easiest way to do that.
232 bool "Support for paging of anonymous memory (swap)"
233 depends on MMU && BLOCK
236 This option allows you to choose whether you want to have support
237 for so called swap devices or swap files in your kernel that are
238 used to provide more virtual memory than the actual RAM present
239 in your computer. If unsure say Y.
244 Inter Process Communication is a suite of library functions and
245 system calls which let processes (running programs) synchronize and
246 exchange information. It is generally considered to be a good thing,
247 and some programs won't run unless you say Y here. In particular, if
248 you want to run the DOS emulator dosemu under Linux (read the
249 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
250 you'll need to say Y here.
252 You can find documentation about IPC with "info ipc" and also in
253 section 6.4 of the Linux Programmer's Guide, available from
254 <http://www.tldp.org/guides.html>.
256 config SYSVIPC_SYSCTL
263 bool "POSIX Message Queues"
264 depends on NET && EXPERIMENTAL
266 POSIX variant of message queues is a part of IPC. In POSIX message
267 queues every message has a priority which decides about succession
268 of receiving it by a process. If you want to compile and run
269 programs written e.g. for Solaris with use of its POSIX message
270 queues (functions mq_*) say Y here.
272 POSIX message queues are visible as a filesystem called 'mqueue'
273 and can be mounted somewhere if you want to do filesystem
274 operations on message queues.
278 config POSIX_MQUEUE_SYSCTL
280 depends on POSIX_MQUEUE
284 config BSD_PROCESS_ACCT
285 bool "BSD Process Accounting"
287 If you say Y here, a user level program will be able to instruct the
288 kernel (via a special system call) to write process accounting
289 information to a file: whenever a process exits, information about
290 that process will be appended to the file by the kernel. The
291 information includes things such as creation time, owning user,
292 command name, memory usage, controlling terminal etc. (the complete
293 list is in the struct acct in <file:include/linux/acct.h>). It is
294 up to the user level program to do useful things with this
295 information. This is generally a good idea, so say Y.
297 config BSD_PROCESS_ACCT_V3
298 bool "BSD Process Accounting version 3 file format"
299 depends on BSD_PROCESS_ACCT
302 If you say Y here, the process accounting information is written
303 in a new file format that also logs the process IDs of each
304 process and it's parent. Note that this file format is incompatible
305 with previous v0/v1/v2 file formats, so you will need updated tools
306 for processing it. A preliminary version of these tools is available
307 at <http://www.gnu.org/software/acct/>.
310 bool "open by fhandle syscalls"
313 If you say Y here, a user level program will be able to map
314 file names to handle and then later use the handle for
315 different file system operations. This is useful in implementing
316 userspace file servers, which now track files using handles instead
317 of names. The handle would remain the same even if file names
318 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
322 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
326 Export selected statistics for tasks/processes through the
327 generic netlink interface. Unlike BSD process accounting, the
328 statistics are available during the lifetime of tasks/processes as
329 responses to commands. Like BSD accounting, they are sent to user
334 config TASK_DELAY_ACCT
335 bool "Enable per-task delay accounting (EXPERIMENTAL)"
338 Collect information on time spent by a task waiting for system
339 resources like cpu, synchronous block I/O completion and swapping
340 in pages. Such statistics can help in setting a task's priorities
341 relative to other tasks for cpu, io, rss limits etc.
346 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
349 Collect extended task accounting data and send the data
350 to userland for processing over the taskstats interface.
354 config TASK_IO_ACCOUNTING
355 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
356 depends on TASK_XACCT
358 Collect information on the number of bytes of storage I/O which this
364 bool "Auditing support"
367 Enable auditing infrastructure that can be used with another
368 kernel subsystem, such as SELinux (which requires this for
369 logging of avc messages output). Does not do system-call
370 auditing without CONFIG_AUDITSYSCALL.
373 bool "Enable system-call auditing support"
374 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
375 default y if SECURITY_SELINUX
377 Enable low-overhead system-call auditing infrastructure that
378 can be used independently or with another kernel subsystem,
383 depends on AUDITSYSCALL
388 depends on AUDITSYSCALL
391 source "kernel/irq/Kconfig"
396 prompt "RCU Implementation"
400 bool "Tree-based hierarchical RCU"
401 depends on !PREEMPT && SMP
403 This option selects the RCU implementation that is
404 designed for very large SMP system with hundreds or
405 thousands of CPUs. It also scales down nicely to
408 config TREE_PREEMPT_RCU
409 bool "Preemptible tree-based hierarchical RCU"
410 depends on PREEMPT && SMP
412 This option selects the RCU implementation that is
413 designed for very large SMP systems with hundreds or
414 thousands of CPUs, but for which real-time response
415 is also required. It also scales down nicely to
419 bool "UP-only small-memory-footprint RCU"
420 depends on !PREEMPT && !SMP
422 This option selects the RCU implementation that is
423 designed for UP systems from which real-time response
424 is not required. This option greatly reduces the
425 memory footprint of RCU.
427 config TINY_PREEMPT_RCU
428 bool "Preemptible UP-only small-memory-footprint RCU"
429 depends on PREEMPT && !SMP
431 This option selects the RCU implementation that is designed
432 for real-time UP systems. This option greatly reduces the
433 memory footprint of RCU.
438 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
440 This option enables preemptible-RCU code that is common between
441 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
444 bool "Enable tracing for RCU"
446 This option provides tracing in RCU which presents stats
447 in debugfs for debugging RCU implementation.
449 Say Y here if you want to enable RCU tracing
450 Say N if you are unsure.
453 int "Tree-based hierarchical RCU fanout value"
456 depends on TREE_RCU || TREE_PREEMPT_RCU
460 This option controls the fanout of hierarchical implementations
461 of RCU, allowing RCU to work efficiently on machines with
462 large numbers of CPUs. This value must be at least the fourth
463 root of NR_CPUS, which allows NR_CPUS to be insanely large.
464 The default value of RCU_FANOUT should be used for production
465 systems, but if you are stress-testing the RCU implementation
466 itself, small RCU_FANOUT values allow you to test large-system
467 code paths on small(er) systems.
469 Select a specific number if testing RCU itself.
470 Take the default if unsure.
472 config RCU_FANOUT_EXACT
473 bool "Disable tree-based hierarchical RCU auto-balancing"
474 depends on TREE_RCU || TREE_PREEMPT_RCU
477 This option forces use of the exact RCU_FANOUT value specified,
478 regardless of imbalances in the hierarchy. This is useful for
479 testing RCU itself, and might one day be useful on systems with
480 strong NUMA behavior.
482 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
486 config RCU_FAST_NO_HZ
487 bool "Accelerate last non-dyntick-idle CPU's grace periods"
488 depends on TREE_RCU && NO_HZ && SMP
491 This option causes RCU to attempt to accelerate grace periods
492 in order to allow the final CPU to enter dynticks-idle state
493 more quickly. On the other hand, this option increases the
494 overhead of the dynticks-idle checking, particularly on systems
495 with large numbers of CPUs.
497 Say Y if energy efficiency is critically important, particularly
498 if you have relatively few CPUs.
500 Say N if you are unsure.
502 config TREE_RCU_TRACE
503 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
506 This option provides tracing for the TREE_RCU and
507 TREE_PREEMPT_RCU implementations, permitting Makefile to
508 trivially select kernel/rcutree_trace.c.
511 bool "Enable RCU priority boosting"
512 depends on RT_MUTEXES && PREEMPT_RCU
515 This option boosts the priority of preempted RCU readers that
516 block the current preemptible RCU grace period for too long.
517 This option also prevents heavy loads from blocking RCU
518 callback invocation for all flavors of RCU.
520 Say Y here if you are working with real-time apps or heavy loads
521 Say N here if you are unsure.
523 config RCU_BOOST_PRIO
524 int "Real-time priority to boost RCU readers to"
529 This option specifies the real-time priority to which preempted
530 RCU readers are to be boosted. If you are working with CPU-bound
531 real-time applications, you should specify a priority higher then
532 the highest-priority CPU-bound application.
534 Specify the real-time priority, or take the default if unsure.
536 config RCU_BOOST_DELAY
537 int "Milliseconds to delay boosting after RCU grace-period start"
542 This option specifies the time to wait after the beginning of
543 a given grace period before priority-boosting preempted RCU
544 readers blocking that grace period. Note that any RCU reader
545 blocking an expedited RCU grace period is boosted immediately.
547 Accept the default if unsure.
549 endmenu # "RCU Subsystem"
552 tristate "Kernel .config support"
554 This option enables the complete Linux kernel ".config" file
555 contents to be saved in the kernel. It provides documentation
556 of which kernel options are used in a running kernel or in an
557 on-disk kernel. This information can be extracted from the kernel
558 image file with the script scripts/extract-ikconfig and used as
559 input to rebuild the current kernel or to build another kernel.
560 It can also be extracted from a running kernel by reading
561 /proc/config.gz if enabled (below).
564 bool "Enable access to .config through /proc/config.gz"
565 depends on IKCONFIG && PROC_FS
567 This option enables access to the kernel configuration file
568 through /proc/config.gz.
571 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
575 Select kernel log buffer size as a power of 2.
585 # Architectures with an unreliable sched_clock() should select this:
587 config HAVE_UNSTABLE_SCHED_CLOCK
591 boolean "Control Group support"
594 This option adds support for grouping sets of processes together, for
595 use with process control subsystems such as Cpusets, CFS, memory
596 controls or device isolation.
598 - Documentation/scheduler/sched-design-CFS.txt (CFS)
599 - Documentation/cgroups/ (features for grouping, isolation
600 and resource control)
607 bool "Example debug cgroup subsystem"
610 This option enables a simple cgroup subsystem that
611 exports useful debugging information about the cgroups
616 config CGROUP_FREEZER
617 bool "Freezer cgroup subsystem"
619 Provides a way to freeze and unfreeze all tasks in a
623 bool "Device controller for cgroups"
625 Provides a cgroup implementing whitelists for devices which
626 a process in the cgroup can mknod or open.
629 bool "Cpuset support"
631 This option will let you create and manage CPUSETs which
632 allow dynamically partitioning a system into sets of CPUs and
633 Memory Nodes and assigning tasks to run only within those sets.
634 This is primarily useful on large SMP or NUMA systems.
638 config PROC_PID_CPUSET
639 bool "Include legacy /proc/<pid>/cpuset file"
643 config CGROUP_CPUACCT
644 bool "Simple CPU accounting cgroup subsystem"
646 Provides a simple Resource Controller for monitoring the
647 total CPU consumed by the tasks in a cgroup.
649 config RESOURCE_COUNTERS
650 bool "Resource counters"
652 This option enables controller independent resource accounting
653 infrastructure that works with cgroups.
655 config CGROUP_MEM_RES_CTLR
656 bool "Memory Resource Controller for Control Groups"
657 depends on RESOURCE_COUNTERS
660 Provides a memory resource controller that manages both anonymous
661 memory and page cache. (See Documentation/cgroups/memory.txt)
663 Note that setting this option increases fixed memory overhead
664 associated with each page of memory in the system. By this,
665 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
666 usage tracking struct at boot. Total amount of this is printed out
669 Only enable when you're ok with these trade offs and really
670 sure you need the memory resource controller. Even when you enable
671 this, you can set "cgroup_disable=memory" at your boot option to
672 disable memory resource controller and you can avoid overheads.
673 (and lose benefits of memory resource controller)
675 This config option also selects MM_OWNER config option, which
676 could in turn add some fork/exit overhead.
678 config CGROUP_MEM_RES_CTLR_SWAP
679 bool "Memory Resource Controller Swap Extension"
680 depends on CGROUP_MEM_RES_CTLR && SWAP
682 Add swap management feature to memory resource controller. When you
683 enable this, you can limit mem+swap usage per cgroup. In other words,
684 when you disable this, memory resource controller has no cares to
685 usage of swap...a process can exhaust all of the swap. This extension
686 is useful when you want to avoid exhaustion swap but this itself
687 adds more overheads and consumes memory for remembering information.
688 Especially if you use 32bit system or small memory system, please
689 be careful about enabling this. When memory resource controller
690 is disabled by boot option, this will be automatically disabled and
691 there will be no overhead from this. Even when you set this config=y,
692 if boot option "swapaccount=0" is set, swap will not be accounted.
693 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
694 size is 4096bytes, 512k per 1Gbytes of swap.
695 config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
696 bool "Memory Resource Controller Swap Extension enabled by default"
697 depends on CGROUP_MEM_RES_CTLR_SWAP
700 Memory Resource Controller Swap Extension comes with its price in
701 a bigger memory consumption. General purpose distribution kernels
702 which want to enable the feature but keep it disabled by default
703 and let the user enable it by swapaccount boot command line
704 parameter should have this option unselected.
705 For those who want to have the feature enabled by default should
706 select this option (if, for some reason, they need to disable it
707 then swapaccount=0 does the trick).
710 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
711 depends on PERF_EVENTS && CGROUPS
713 This option extends the per-cpu mode to restrict monitoring to
714 threads which belong to the cgroup specified and run on the
719 menuconfig CGROUP_SCHED
720 bool "Group CPU scheduler"
721 depends on EXPERIMENTAL
724 This feature lets CPU scheduler recognize task groups and control CPU
725 bandwidth allocation to such task groups. It uses cgroups to group
729 config FAIR_GROUP_SCHED
730 bool "Group scheduling for SCHED_OTHER"
731 depends on CGROUP_SCHED
735 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
736 depends on EXPERIMENTAL
737 depends on FAIR_GROUP_SCHED
740 This option allows users to define CPU bandwidth rates (limits) for
741 tasks running within the fair group scheduler. Groups with no limit
742 set are considered to be unconstrained and will run with no
744 See tip/Documentation/scheduler/sched-bwc.txt for more information.
746 config RT_GROUP_SCHED
747 bool "Group scheduling for SCHED_RR/FIFO"
748 depends on EXPERIMENTAL
749 depends on CGROUP_SCHED
752 This feature lets you explicitly allocate real CPU bandwidth
753 to task groups. If enabled, it will also make it impossible to
754 schedule realtime tasks for non-root users until you allocate
755 realtime bandwidth for them.
756 See Documentation/scheduler/sched-rt-group.txt for more information.
761 tristate "Block IO controller"
765 Generic block IO controller cgroup interface. This is the common
766 cgroup interface which should be used by various IO controlling
769 Currently, CFQ IO scheduler uses it to recognize task groups and
770 control disk bandwidth allocation (proportional time slice allocation)
771 to such task groups. It is also used by bio throttling logic in
772 block layer to implement upper limit in IO rates on a device.
774 This option only enables generic Block IO controller infrastructure.
775 One needs to also enable actual IO controlling logic/policy. For
776 enabling proportional weight division of disk bandwidth in CFQ, set
777 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
778 CONFIG_BLK_DEV_THROTTLING=y.
780 See Documentation/cgroups/blkio-controller.txt for more information.
782 config DEBUG_BLK_CGROUP
783 bool "Enable Block IO controller debugging"
784 depends on BLK_CGROUP
787 Enable some debugging help. Currently it exports additional stat
788 files in a cgroup which can be useful for debugging.
792 menuconfig NAMESPACES
793 bool "Namespaces support" if EXPERT
796 Provides the way to make tasks work with different objects using
797 the same id. For example same IPC id may refer to different objects
798 or same user id or pid may refer to different tasks when used in
799 different namespaces.
807 In this namespace tasks see different info provided with the
812 depends on (SYSVIPC || POSIX_MQUEUE)
815 In this namespace tasks work with IPC ids which correspond to
816 different IPC objects in different namespaces.
819 bool "User namespace (EXPERIMENTAL)"
820 depends on EXPERIMENTAL
823 This allows containers, i.e. vservers, to use user namespaces
824 to provide different user info for different servers.
828 bool "PID Namespaces"
831 Support process id namespaces. This allows having multiple
832 processes with the same pid as long as they are in different
833 pid namespaces. This is a building block of containers.
836 bool "Network namespace"
840 Allow user space to create what appear to be multiple instances
841 of the network stack.
845 config SCHED_AUTOGROUP
846 bool "Automatic process group scheduling"
850 select FAIR_GROUP_SCHED
852 This option optimizes the scheduler for common desktop workloads by
853 automatically creating and populating task groups. This separation
854 of workloads isolates aggressive CPU burners (like build jobs) from
855 desktop applications. Task group autogeneration is currently based
861 config SYSFS_DEPRECATED
862 bool "Enable deprecated sysfs features to support old userspace tools"
866 This option adds code that switches the layout of the "block" class
867 devices, to not show up in /sys/class/block/, but only in
870 This switch is only active when the sysfs.deprecated=1 boot option is
871 passed or the SYSFS_DEPRECATED_V2 option is set.
873 This option allows new kernels to run on old distributions and tools,
874 which might get confused by /sys/class/block/. Since 2007/2008 all
875 major distributions and tools handle this just fine.
877 Recent distributions and userspace tools after 2009/2010 depend on
878 the existence of /sys/class/block/, and will not work with this
881 Only if you are using a new kernel on an old distribution, you might
884 config SYSFS_DEPRECATED_V2
885 bool "Enable deprecated sysfs features by default"
888 depends on SYSFS_DEPRECATED
890 Enable deprecated sysfs by default.
892 See the CONFIG_SYSFS_DEPRECATED option for more details about this
895 Only if you are using a new kernel on an old distribution, you might
896 need to say Y here. Even then, odds are you would not need it
897 enabled, you can always pass the boot option if absolutely necessary.
900 bool "Kernel->user space relay support (formerly relayfs)"
902 This option enables support for relay interface support in
903 certain file systems (such as debugfs).
904 It is designed to provide an efficient mechanism for tools and
905 facilities to relay large amounts of data from kernel space to
910 config BLK_DEV_INITRD
911 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
912 depends on BROKEN || !FRV
914 The initial RAM filesystem is a ramfs which is loaded by the
915 boot loader (loadlin or lilo) and that is mounted as root
916 before the normal boot procedure. It is typically used to
917 load modules needed to mount the "real" root file system,
918 etc. See <file:Documentation/initrd.txt> for details.
920 If RAM disk support (BLK_DEV_RAM) is also included, this
921 also enables initial RAM disk (initrd) support and adds
922 15 Kbytes (more on some other architectures) to the kernel size.
932 config CC_OPTIMIZE_FOR_SIZE
933 bool "Optimize for size"
935 Enabling this option will pass "-Os" instead of "-O2" to gcc
936 resulting in a smaller kernel.
947 bool "Configure standard kernel features (expert users)"
948 # Unhide debug options, to make the on-by-default options visible
951 This option allows certain base kernel options and settings
952 to be disabled or tweaked. This is for specialized
953 environments which can tolerate a "non-standard" kernel.
954 Only use this if you really know what you are doing.
957 bool "Enable 16-bit UID system calls" if EXPERT
958 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
961 This enables the legacy 16-bit UID syscall wrappers.
963 config SYSCTL_SYSCALL
964 bool "Sysctl syscall support" if EXPERT
965 depends on PROC_SYSCTL
969 sys_sysctl uses binary paths that have been found challenging
970 to properly maintain and use. The interface in /proc/sys
971 using paths with ascii names is now the primary path to this
974 Almost nothing using the binary sysctl interface so if you are
975 trying to save some space it is probably safe to disable this,
976 making your kernel marginally smaller.
978 If unsure say N here.
981 bool "Load all symbols for debugging/ksymoops" if EXPERT
984 Say Y here to let the kernel print out symbolic crash information and
985 symbolic stack backtraces. This increases the size of the kernel
986 somewhat, as all symbols have to be loaded into the kernel image.
989 bool "Include all symbols in kallsyms"
990 depends on DEBUG_KERNEL && KALLSYMS
992 Normally kallsyms only contains the symbols of functions for nicer
993 OOPS messages and backtraces (i.e., symbols from the text and inittext
994 sections). This is sufficient for most cases. And only in very rare
995 cases (e.g., when a debugger is used) all symbols are required (e.g.,
996 names of variables from the data sections, etc).
998 This option makes sure that all symbols are loaded into the kernel
999 image (i.e., symbols from all sections) in cost of increased kernel
1000 size (depending on the kernel configuration, it may be 300KiB or
1001 something like this).
1003 Say N unless you really need all symbols.
1006 bool "Support for hot-pluggable devices" if EXPERT
1009 This option is provided for the case where no hotplug or uevent
1010 capabilities is wanted by the kernel. You should only consider
1011 disabling this option for embedded systems that do not use modules, a
1012 dynamic /dev tree, or dynamic device discovery. Just say Y.
1016 bool "Enable support for printk" if EXPERT
1018 This option enables normal printk support. Removing it
1019 eliminates most of the message strings from the kernel image
1020 and makes the kernel more or less silent. As this makes it
1021 very difficult to diagnose system problems, saying N here is
1022 strongly discouraged.
1025 bool "BUG() support" if EXPERT
1028 Disabling this option eliminates support for BUG and WARN, reducing
1029 the size of your kernel image and potentially quietly ignoring
1030 numerous fatal conditions. You should only consider disabling this
1031 option for embedded systems with no facilities for reporting errors.
1036 bool "Enable ELF core dumps" if EXPERT
1038 Enable support for generating core dumps. Disabling saves about 4k.
1041 config PCSPKR_PLATFORM
1042 bool "Enable PC-Speaker support" if EXPERT
1043 depends on HAVE_PCSPKR_PLATFORM
1047 This option allows to disable the internal PC-Speaker
1048 support, saving some memory.
1050 config HAVE_PCSPKR_PLATFORM
1055 bool "Enable full-sized data structures for core" if EXPERT
1057 Disabling this option reduces the size of miscellaneous core
1058 kernel data structures. This saves memory on small machines,
1059 but may reduce performance.
1062 bool "Enable futex support" if EXPERT
1066 Disabling this option will cause the kernel to be built without
1067 support for "fast userspace mutexes". The resulting kernel may not
1068 run glibc-based applications correctly.
1071 bool "Enable eventpoll support" if EXPERT
1075 Disabling this option will cause the kernel to be built without
1076 support for epoll family of system calls.
1079 bool "Enable signalfd() system call" if EXPERT
1083 Enable the signalfd() system call that allows to receive signals
1084 on a file descriptor.
1089 bool "Enable timerfd() system call" if EXPERT
1093 Enable the timerfd() system call that allows to receive timer
1094 events on a file descriptor.
1099 bool "Enable eventfd() system call" if EXPERT
1103 Enable the eventfd() system call that allows to receive both
1104 kernel notification (ie. KAIO) or userspace notifications.
1109 bool "Use full shmem filesystem" if EXPERT
1113 The shmem is an internal filesystem used to manage shared memory.
1114 It is backed by swap and manages resource limits. It is also exported
1115 to userspace as tmpfs if TMPFS is enabled. Disabling this
1116 option replaces shmem and tmpfs with the much simpler ramfs code,
1117 which may be appropriate on small systems without swap.
1120 bool "Enable AIO support" if EXPERT
1123 This option enables POSIX asynchronous I/O which may by used
1124 by some high performance threaded applications. Disabling
1125 this option saves about 7k.
1128 bool "Embedded system"
1131 This option should be enabled if compiling the kernel for
1132 an embedded system so certain expert options are available
1135 config HAVE_PERF_EVENTS
1138 See tools/perf/design.txt for details.
1140 config PERF_USE_VMALLOC
1143 See tools/perf/design.txt for details
1145 menu "Kernel Performance Events And Counters"
1148 bool "Kernel performance events and counters"
1149 default y if (PROFILING || PERF_COUNTERS)
1150 depends on HAVE_PERF_EVENTS
1154 Enable kernel support for various performance events provided
1155 by software and hardware.
1157 Software events are supported either built-in or via the
1158 use of generic tracepoints.
1160 Most modern CPUs support performance events via performance
1161 counter registers. These registers count the number of certain
1162 types of hw events: such as instructions executed, cachemisses
1163 suffered, or branches mis-predicted - without slowing down the
1164 kernel or applications. These registers can also trigger interrupts
1165 when a threshold number of events have passed - and can thus be
1166 used to profile the code that runs on that CPU.
1168 The Linux Performance Event subsystem provides an abstraction of
1169 these software and hardware event capabilities, available via a
1170 system call and used by the "perf" utility in tools/perf/. It
1171 provides per task and per CPU counters, and it provides event
1172 capabilities on top of those.
1176 config PERF_COUNTERS
1177 bool "Kernel performance counters (old config option)"
1178 depends on HAVE_PERF_EVENTS
1180 This config has been obsoleted by the PERF_EVENTS
1181 config option - please see that one for details.
1183 It has no effect on the kernel whether you enable
1184 it or not, it is a compatibility placeholder.
1188 config DEBUG_PERF_USE_VMALLOC
1190 bool "Debug: use vmalloc to back perf mmap() buffers"
1191 depends on PERF_EVENTS && DEBUG_KERNEL
1192 select PERF_USE_VMALLOC
1194 Use vmalloc memory to back perf mmap() buffers.
1196 Mostly useful for debugging the vmalloc code on platforms
1197 that don't require it.
1203 config VM_EVENT_COUNTERS
1205 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1207 VM event counters are needed for event counts to be shown.
1208 This option allows the disabling of the VM event counters
1209 on EXPERT systems. /proc/vmstat will only show page counts
1210 if VM event counters are disabled.
1214 bool "Enable PCI quirk workarounds" if EXPERT
1217 This enables workarounds for various PCI chipset
1218 bugs/quirks. Disable this only if your target machine is
1219 unaffected by PCI quirks.
1223 bool "Enable SLUB debugging support" if EXPERT
1224 depends on SLUB && SYSFS
1226 SLUB has extensive debug support features. Disabling these can
1227 result in significant savings in code size. This also disables
1228 SLUB sysfs support. /sys/slab will not exist and there will be
1229 no support for cache validation etc.
1232 bool "Disable heap randomization"
1235 Randomizing heap placement makes heap exploits harder, but it
1236 also breaks ancient binaries (including anything libc5 based).
1237 This option changes the bootup default to heap randomization
1238 disabled, and can be overridden at runtime by setting
1239 /proc/sys/kernel/randomize_va_space to 2.
1241 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1244 prompt "Choose SLAB allocator"
1247 This option allows to select a slab allocator.
1252 The regular slab allocator that is established and known to work
1253 well in all environments. It organizes cache hot objects in
1254 per cpu and per node queues.
1257 bool "SLUB (Unqueued Allocator)"
1259 SLUB is a slab allocator that minimizes cache line usage
1260 instead of managing queues of cached objects (SLAB approach).
1261 Per cpu caching is realized using slabs of objects instead
1262 of queues of objects. SLUB can use memory efficiently
1263 and has enhanced diagnostics. SLUB is the default choice for
1268 bool "SLOB (Simple Allocator)"
1270 SLOB replaces the stock allocator with a drastically simpler
1271 allocator. SLOB is generally more space efficient but
1272 does not perform as well on large systems.
1276 config MMAP_ALLOW_UNINITIALIZED
1277 bool "Allow mmapped anonymous memory to be uninitialized"
1278 depends on EXPERT && !MMU
1281 Normally, and according to the Linux spec, anonymous memory obtained
1282 from mmap() has it's contents cleared before it is passed to
1283 userspace. Enabling this config option allows you to request that
1284 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1285 providing a huge performance boost. If this option is not enabled,
1286 then the flag will be ignored.
1288 This is taken advantage of by uClibc's malloc(), and also by
1289 ELF-FDPIC binfmt's brk and stack allocator.
1291 Because of the obvious security issues, this option should only be
1292 enabled on embedded devices where you control what is run in
1293 userspace. Since that isn't generally a problem on no-MMU systems,
1294 it is normally safe to say Y here.
1296 See Documentation/nommu-mmap.txt for more information.
1299 bool "Profiling support"
1301 Say Y here to enable the extended profiling support mechanisms used
1302 by profilers such as OProfile.
1305 # Place an empty function call at each tracepoint site. Can be
1306 # dynamically changed for a probe function.
1311 source "arch/Kconfig"
1313 endmenu # General setup
1315 config HAVE_GENERIC_DMA_COHERENT
1322 depends on SLAB || SLUB_DEBUG
1330 default 0 if BASE_FULL
1331 default 1 if !BASE_FULL
1334 bool "Enable loadable module support"
1336 Kernel modules are small pieces of compiled code which can
1337 be inserted in the running kernel, rather than being
1338 permanently built into the kernel. You use the "modprobe"
1339 tool to add (and sometimes remove) them. If you say Y here,
1340 many parts of the kernel can be built as modules (by
1341 answering M instead of Y where indicated): this is most
1342 useful for infrequently used options which are not required
1343 for booting. For more information, see the man pages for
1344 modprobe, lsmod, modinfo, insmod and rmmod.
1346 If you say Y here, you will need to run "make
1347 modules_install" to put the modules under /lib/modules/
1348 where modprobe can find them (you may need to be root to do
1355 config MODULE_FORCE_LOAD
1356 bool "Forced module loading"
1359 Allow loading of modules without version information (ie. modprobe
1360 --force). Forced module loading sets the 'F' (forced) taint flag and
1361 is usually a really bad idea.
1363 config MODULE_UNLOAD
1364 bool "Module unloading"
1366 Without this option you will not be able to unload any
1367 modules (note that some modules may not be unloadable
1368 anyway), which makes your kernel smaller, faster
1369 and simpler. If unsure, say Y.
1371 config MODULE_FORCE_UNLOAD
1372 bool "Forced module unloading"
1373 depends on MODULE_UNLOAD && EXPERIMENTAL
1375 This option allows you to force a module to unload, even if the
1376 kernel believes it is unsafe: the kernel will remove the module
1377 without waiting for anyone to stop using it (using the -f option to
1378 rmmod). This is mainly for kernel developers and desperate users.
1382 bool "Module versioning support"
1384 Usually, you have to use modules compiled with your kernel.
1385 Saying Y here makes it sometimes possible to use modules
1386 compiled for different kernels, by adding enough information
1387 to the modules to (hopefully) spot any changes which would
1388 make them incompatible with the kernel you are running. If
1391 config MODULE_SRCVERSION_ALL
1392 bool "Source checksum for all modules"
1394 Modules which contain a MODULE_VERSION get an extra "srcversion"
1395 field inserted into their modinfo section, which contains a
1396 sum of the source files which made it. This helps maintainers
1397 see exactly which source was used to build a module (since
1398 others sometimes change the module source without updating
1399 the version). With this option, such a "srcversion" field
1400 will be created for all modules. If unsure, say N.
1404 config INIT_ALL_POSSIBLE
1407 Back when each arch used to define their own cpu_online_map and
1408 cpu_possible_map, some of them chose to initialize cpu_possible_map
1409 with all 1s, and others with all 0s. When they were centralised,
1410 it was better to provide this option than to break all the archs
1411 and have several arch maintainers pursuing me down dark alleys.
1416 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1418 Need stop_machine() primitive.
1420 source "block/Kconfig"
1422 config PREEMPT_NOTIFIERS
1429 source "kernel/Kconfig.locks"