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53 drivers that have been replaced by something else, and/or are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.
81 string "Cross-compiler tool prefix"
83 Same as running 'make CROSS_COMPILE=prefix-' but stored for
84 default make runs in this kernel build directory. You don't
85 need to set this unless you want the configured kernel build
86 directory to select the cross-compiler automatically.
89 string "Local version - append to kernel release"
91 Append an extra string to the end of your kernel version.
92 This will show up when you type uname, for example.
93 The string you set here will be appended after the contents of
94 any files with a filename matching localversion* in your
95 object and source tree, in that order. Your total string can
96 be a maximum of 64 characters.
98 config LOCALVERSION_AUTO
99 bool "Automatically append version information to the version string"
102 This will try to automatically determine if the current tree is a
103 release tree by looking for git tags that belong to the current
104 top of tree revision.
106 A string of the format -gxxxxxxxx will be added to the localversion
107 if a git-based tree is found. The string generated by this will be
108 appended after any matching localversion* files, and after the value
109 set in CONFIG_LOCALVERSION.
111 (The actual string used here is the first eight characters produced
112 by running the command:
114 $ git rev-parse --verify HEAD
116 which is done within the script "scripts/setlocalversion".)
118 config HAVE_KERNEL_GZIP
121 config HAVE_KERNEL_BZIP2
124 config HAVE_KERNEL_LZMA
127 config HAVE_KERNEL_XZ
130 config HAVE_KERNEL_LZO
134 prompt "Kernel compression mode"
136 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
138 The linux kernel is a kind of self-extracting executable.
139 Several compression algorithms are available, which differ
140 in efficiency, compression and decompression speed.
141 Compression speed is only relevant when building a kernel.
142 Decompression speed is relevant at each boot.
144 If you have any problems with bzip2 or lzma compressed
145 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
146 version of this functionality (bzip2 only), for 2.4, was
147 supplied by Christian Ludwig)
149 High compression options are mostly useful for users, who
150 are low on disk space (embedded systems), but for whom ram
153 If in doubt, select 'gzip'
157 depends on HAVE_KERNEL_GZIP
159 The old and tried gzip compression. It provides a good balance
160 between compression ratio and decompression speed.
164 depends on HAVE_KERNEL_BZIP2
166 Its compression ratio and speed is intermediate.
167 Decompression speed is slowest among the three. The kernel
168 size is about 10% smaller with bzip2, in comparison to gzip.
169 Bzip2 uses a large amount of memory. For modern kernels you
170 will need at least 8MB RAM or more for booting.
174 depends on HAVE_KERNEL_LZMA
176 The most recent compression algorithm.
177 Its ratio is best, decompression speed is between the other
178 two. Compression is slowest. The kernel size is about 33%
179 smaller with LZMA in comparison to gzip.
183 depends on HAVE_KERNEL_XZ
185 XZ uses the LZMA2 algorithm and instruction set specific
186 BCJ filters which can improve compression ratio of executable
187 code. The size of the kernel is about 30% smaller with XZ in
188 comparison to gzip. On architectures for which there is a BCJ
189 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
190 will create a few percent smaller kernel than plain LZMA.
192 The speed is about the same as with LZMA: The decompression
193 speed of XZ is better than that of bzip2 but worse than gzip
194 and LZO. Compression is slow.
198 depends on HAVE_KERNEL_LZO
200 Its compression ratio is the poorest among the 4. The kernel
201 size is about 10% bigger than gzip; however its speed
202 (both compression and decompression) is the fastest.
206 config DEFAULT_HOSTNAME
207 string "Default hostname"
210 This option determines the default system hostname before userspace
211 calls sethostname(2). The kernel traditionally uses "(none)" here,
212 but you may wish to use a different default here to make a minimal
213 system more usable with less configuration.
216 bool "Support for paging of anonymous memory (swap)"
217 depends on MMU && BLOCK
220 This option allows you to choose whether you want to have support
221 for so called swap devices or swap files in your kernel that are
222 used to provide more virtual memory than the actual RAM present
223 in your computer. If unsure say Y.
228 Inter Process Communication is a suite of library functions and
229 system calls which let processes (running programs) synchronize and
230 exchange information. It is generally considered to be a good thing,
231 and some programs won't run unless you say Y here. In particular, if
232 you want to run the DOS emulator dosemu under Linux (read the
233 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
234 you'll need to say Y here.
236 You can find documentation about IPC with "info ipc" and also in
237 section 6.4 of the Linux Programmer's Guide, available from
238 <http://www.tldp.org/guides.html>.
240 config SYSVIPC_SYSCTL
247 bool "POSIX Message Queues"
248 depends on NET && EXPERIMENTAL
250 POSIX variant of message queues is a part of IPC. In POSIX message
251 queues every message has a priority which decides about succession
252 of receiving it by a process. If you want to compile and run
253 programs written e.g. for Solaris with use of its POSIX message
254 queues (functions mq_*) say Y here.
256 POSIX message queues are visible as a filesystem called 'mqueue'
257 and can be mounted somewhere if you want to do filesystem
258 operations on message queues.
262 config POSIX_MQUEUE_SYSCTL
264 depends on POSIX_MQUEUE
268 config BSD_PROCESS_ACCT
269 bool "BSD Process Accounting"
271 If you say Y here, a user level program will be able to instruct the
272 kernel (via a special system call) to write process accounting
273 information to a file: whenever a process exits, information about
274 that process will be appended to the file by the kernel. The
275 information includes things such as creation time, owning user,
276 command name, memory usage, controlling terminal etc. (the complete
277 list is in the struct acct in <file:include/linux/acct.h>). It is
278 up to the user level program to do useful things with this
279 information. This is generally a good idea, so say Y.
281 config BSD_PROCESS_ACCT_V3
282 bool "BSD Process Accounting version 3 file format"
283 depends on BSD_PROCESS_ACCT
286 If you say Y here, the process accounting information is written
287 in a new file format that also logs the process IDs of each
288 process and it's parent. Note that this file format is incompatible
289 with previous v0/v1/v2 file formats, so you will need updated tools
290 for processing it. A preliminary version of these tools is available
291 at <http://www.gnu.org/software/acct/>.
294 bool "open by fhandle syscalls"
297 If you say Y here, a user level program will be able to map
298 file names to handle and then later use the handle for
299 different file system operations. This is useful in implementing
300 userspace file servers, which now track files using handles instead
301 of names. The handle would remain the same even if file names
302 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
306 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
310 Export selected statistics for tasks/processes through the
311 generic netlink interface. Unlike BSD process accounting, the
312 statistics are available during the lifetime of tasks/processes as
313 responses to commands. Like BSD accounting, they are sent to user
318 config TASK_DELAY_ACCT
319 bool "Enable per-task delay accounting (EXPERIMENTAL)"
322 Collect information on time spent by a task waiting for system
323 resources like cpu, synchronous block I/O completion and swapping
324 in pages. Such statistics can help in setting a task's priorities
325 relative to other tasks for cpu, io, rss limits etc.
330 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
333 Collect extended task accounting data and send the data
334 to userland for processing over the taskstats interface.
338 config TASK_IO_ACCOUNTING
339 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
340 depends on TASK_XACCT
342 Collect information on the number of bytes of storage I/O which this
348 bool "Auditing support"
351 Enable auditing infrastructure that can be used with another
352 kernel subsystem, such as SELinux (which requires this for
353 logging of avc messages output). Does not do system-call
354 auditing without CONFIG_AUDITSYSCALL.
357 bool "Enable system-call auditing support"
358 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || ARM)
359 default y if SECURITY_SELINUX
361 Enable low-overhead system-call auditing infrastructure that
362 can be used independently or with another kernel subsystem,
367 depends on AUDITSYSCALL
372 depends on AUDITSYSCALL
375 config AUDIT_LOGINUID_IMMUTABLE
376 bool "Make audit loginuid immutable"
379 The config option toggles if a task setting its loginuid requires
380 CAP_SYS_AUDITCONTROL or if that task should require no special permissions
381 but should instead only allow setting its loginuid if it was never
382 previously set. On systems which use systemd or a similar central
383 process to restart login services this should be set to true. On older
384 systems in which an admin would typically have to directly stop and
385 start processes this should be set to false. Setting this to true allows
386 one to drop potentially dangerous capabilites from the login tasks,
387 but may not be backwards compatible with older init systems.
389 source "kernel/irq/Kconfig"
390 source "kernel/time/Kconfig"
395 prompt "RCU Implementation"
399 bool "Tree-based hierarchical RCU"
400 depends on !PREEMPT && SMP
402 This option selects the RCU implementation that is
403 designed for very large SMP system with hundreds or
404 thousands of CPUs. It also scales down nicely to
407 config TREE_PREEMPT_RCU
408 bool "Preemptible tree-based hierarchical RCU"
409 depends on PREEMPT && SMP
411 This option selects the RCU implementation that is
412 designed for very large SMP systems with hundreds or
413 thousands of CPUs, but for which real-time response
414 is also required. It also scales down nicely to
418 bool "UP-only small-memory-footprint RCU"
419 depends on !PREEMPT && !SMP
421 This option selects the RCU implementation that is
422 designed for UP systems from which real-time response
423 is not required. This option greatly reduces the
424 memory footprint of RCU.
426 config TINY_PREEMPT_RCU
427 bool "Preemptible UP-only small-memory-footprint RCU"
428 depends on PREEMPT && !SMP
430 This option selects the RCU implementation that is designed
431 for real-time UP systems. This option greatly reduces the
432 memory footprint of RCU.
437 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
439 This option enables preemptible-RCU code that is common between
440 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
443 int "Tree-based hierarchical RCU fanout value"
446 depends on TREE_RCU || TREE_PREEMPT_RCU
450 This option controls the fanout of hierarchical implementations
451 of RCU, allowing RCU to work efficiently on machines with
452 large numbers of CPUs. This value must be at least the fourth
453 root of NR_CPUS, which allows NR_CPUS to be insanely large.
454 The default value of RCU_FANOUT should be used for production
455 systems, but if you are stress-testing the RCU implementation
456 itself, small RCU_FANOUT values allow you to test large-system
457 code paths on small(er) systems.
459 Select a specific number if testing RCU itself.
460 Take the default if unsure.
462 config RCU_FANOUT_EXACT
463 bool "Disable tree-based hierarchical RCU auto-balancing"
464 depends on TREE_RCU || TREE_PREEMPT_RCU
467 This option forces use of the exact RCU_FANOUT value specified,
468 regardless of imbalances in the hierarchy. This is useful for
469 testing RCU itself, and might one day be useful on systems with
470 strong NUMA behavior.
472 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
476 config RCU_FAST_NO_HZ
477 bool "Accelerate last non-dyntick-idle CPU's grace periods"
478 depends on NO_HZ && SMP
481 This option causes RCU to attempt to accelerate grace periods
482 in order to allow CPUs to enter dynticks-idle state more
483 quickly. On the other hand, this option increases the overhead
484 of the dynticks-idle checking, particularly on systems with
485 large numbers of CPUs.
487 Say Y if energy efficiency is critically important, particularly
488 if you have relatively few CPUs.
490 Say N if you are unsure.
492 config TREE_RCU_TRACE
493 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
496 This option provides tracing for the TREE_RCU and
497 TREE_PREEMPT_RCU implementations, permitting Makefile to
498 trivially select kernel/rcutree_trace.c.
501 bool "Enable RCU priority boosting"
502 depends on RT_MUTEXES && PREEMPT_RCU
505 This option boosts the priority of preempted RCU readers that
506 block the current preemptible RCU grace period for too long.
507 This option also prevents heavy loads from blocking RCU
508 callback invocation for all flavors of RCU.
510 Say Y here if you are working with real-time apps or heavy loads
511 Say N here if you are unsure.
513 config RCU_BOOST_PRIO
514 int "Real-time priority to boost RCU readers to"
519 This option specifies the real-time priority to which preempted
520 RCU readers are to be boosted. If you are working with CPU-bound
521 real-time applications, you should specify a priority higher then
522 the highest-priority CPU-bound application.
524 Specify the real-time priority, or take the default if unsure.
526 config RCU_BOOST_DELAY
527 int "Milliseconds to delay boosting after RCU grace-period start"
532 This option specifies the time to wait after the beginning of
533 a given grace period before priority-boosting preempted RCU
534 readers blocking that grace period. Note that any RCU reader
535 blocking an expedited RCU grace period is boosted immediately.
537 Accept the default if unsure.
539 endmenu # "RCU Subsystem"
542 tristate "Kernel .config support"
544 This option enables the complete Linux kernel ".config" file
545 contents to be saved in the kernel. It provides documentation
546 of which kernel options are used in a running kernel or in an
547 on-disk kernel. This information can be extracted from the kernel
548 image file with the script scripts/extract-ikconfig and used as
549 input to rebuild the current kernel or to build another kernel.
550 It can also be extracted from a running kernel by reading
551 /proc/config.gz if enabled (below).
554 bool "Enable access to .config through /proc/config.gz"
555 depends on IKCONFIG && PROC_FS
557 This option enables access to the kernel configuration file
558 through /proc/config.gz.
561 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
565 Select kernel log buffer size as a power of 2.
575 # Architectures with an unreliable sched_clock() should select this:
577 config HAVE_UNSTABLE_SCHED_CLOCK
581 boolean "Control Group support"
584 This option adds support for grouping sets of processes together, for
585 use with process control subsystems such as Cpusets, CFS, memory
586 controls or device isolation.
588 - Documentation/scheduler/sched-design-CFS.txt (CFS)
589 - Documentation/cgroups/ (features for grouping, isolation
590 and resource control)
597 bool "Example debug cgroup subsystem"
600 This option enables a simple cgroup subsystem that
601 exports useful debugging information about the cgroups
606 config CGROUP_FREEZER
607 bool "Freezer cgroup subsystem"
609 Provides a way to freeze and unfreeze all tasks in a
613 bool "Device controller for cgroups"
615 Provides a cgroup implementing whitelists for devices which
616 a process in the cgroup can mknod or open.
619 bool "Cpuset support"
621 This option will let you create and manage CPUSETs which
622 allow dynamically partitioning a system into sets of CPUs and
623 Memory Nodes and assigning tasks to run only within those sets.
624 This is primarily useful on large SMP or NUMA systems.
628 config PROC_PID_CPUSET
629 bool "Include legacy /proc/<pid>/cpuset file"
633 config CGROUP_CPUACCT
634 bool "Simple CPU accounting cgroup subsystem"
636 Provides a simple Resource Controller for monitoring the
637 total CPU consumed by the tasks in a cgroup.
639 config RESOURCE_COUNTERS
640 bool "Resource counters"
642 This option enables controller independent resource accounting
643 infrastructure that works with cgroups.
645 config CGROUP_MEM_RES_CTLR
646 bool "Memory Resource Controller for Control Groups"
647 depends on RESOURCE_COUNTERS
650 Provides a memory resource controller that manages both anonymous
651 memory and page cache. (See Documentation/cgroups/memory.txt)
653 Note that setting this option increases fixed memory overhead
654 associated with each page of memory in the system. By this,
655 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
656 usage tracking struct at boot. Total amount of this is printed out
659 Only enable when you're ok with these trade offs and really
660 sure you need the memory resource controller. Even when you enable
661 this, you can set "cgroup_disable=memory" at your boot option to
662 disable memory resource controller and you can avoid overheads.
663 (and lose benefits of memory resource controller)
665 This config option also selects MM_OWNER config option, which
666 could in turn add some fork/exit overhead.
668 config CGROUP_MEM_RES_CTLR_SWAP
669 bool "Memory Resource Controller Swap Extension"
670 depends on CGROUP_MEM_RES_CTLR && SWAP
672 Add swap management feature to memory resource controller. When you
673 enable this, you can limit mem+swap usage per cgroup. In other words,
674 when you disable this, memory resource controller has no cares to
675 usage of swap...a process can exhaust all of the swap. This extension
676 is useful when you want to avoid exhaustion swap but this itself
677 adds more overheads and consumes memory for remembering information.
678 Especially if you use 32bit system or small memory system, please
679 be careful about enabling this. When memory resource controller
680 is disabled by boot option, this will be automatically disabled and
681 there will be no overhead from this. Even when you set this config=y,
682 if boot option "swapaccount=0" is set, swap will not be accounted.
683 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
684 size is 4096bytes, 512k per 1Gbytes of swap.
685 config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
686 bool "Memory Resource Controller Swap Extension enabled by default"
687 depends on CGROUP_MEM_RES_CTLR_SWAP
690 Memory Resource Controller Swap Extension comes with its price in
691 a bigger memory consumption. General purpose distribution kernels
692 which want to enable the feature but keep it disabled by default
693 and let the user enable it by swapaccount boot command line
694 parameter should have this option unselected.
695 For those who want to have the feature enabled by default should
696 select this option (if, for some reason, they need to disable it
697 then swapaccount=0 does the trick).
698 config CGROUP_MEM_RES_CTLR_KMEM
699 bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
700 depends on CGROUP_MEM_RES_CTLR && EXPERIMENTAL
703 The Kernel Memory extension for Memory Resource Controller can limit
704 the amount of memory used by kernel objects in the system. Those are
705 fundamentally different from the entities handled by the standard
706 Memory Controller, which are page-based, and can be swapped. Users of
707 the kmem extension can use it to guarantee that no group of processes
708 will ever exhaust kernel resources alone.
711 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
712 depends on PERF_EVENTS && CGROUPS
714 This option extends the per-cpu mode to restrict monitoring to
715 threads which belong to the cgroup specified and run on the
720 menuconfig CGROUP_SCHED
721 bool "Group CPU scheduler"
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 config CHECKPOINT_RESTORE
793 bool "Checkpoint/restore support" if EXPERT
796 Enables additional kernel features in a sake of checkpoint/restore.
797 In particular it adds auxiliary prctl codes to setup process text,
798 data and heap segment sizes, and a few additional /proc filesystem
801 If unsure, say N here.
803 menuconfig NAMESPACES
804 bool "Namespaces support" if EXPERT
807 Provides the way to make tasks work with different objects using
808 the same id. For example same IPC id may refer to different objects
809 or same user id or pid may refer to different tasks when used in
810 different namespaces.
818 In this namespace tasks see different info provided with the
823 depends on (SYSVIPC || POSIX_MQUEUE)
826 In this namespace tasks work with IPC ids which correspond to
827 different IPC objects in different namespaces.
830 bool "User namespace (EXPERIMENTAL)"
831 depends on EXPERIMENTAL
834 This allows containers, i.e. vservers, to use user namespaces
835 to provide different user info for different servers.
839 bool "PID Namespaces"
842 Support process id namespaces. This allows having multiple
843 processes with the same pid as long as they are in different
844 pid namespaces. This is a building block of containers.
847 bool "Network namespace"
851 Allow user space to create what appear to be multiple instances
852 of the network stack.
856 config SCHED_AUTOGROUP
857 bool "Automatic process group scheduling"
861 select FAIR_GROUP_SCHED
863 This option optimizes the scheduler for common desktop workloads by
864 automatically creating and populating task groups. This separation
865 of workloads isolates aggressive CPU burners (like build jobs) from
866 desktop applications. Task group autogeneration is currently based
872 config SYSFS_DEPRECATED
873 bool "Enable deprecated sysfs features to support old userspace tools"
877 This option adds code that switches the layout of the "block" class
878 devices, to not show up in /sys/class/block/, but only in
881 This switch is only active when the sysfs.deprecated=1 boot option is
882 passed or the SYSFS_DEPRECATED_V2 option is set.
884 This option allows new kernels to run on old distributions and tools,
885 which might get confused by /sys/class/block/. Since 2007/2008 all
886 major distributions and tools handle this just fine.
888 Recent distributions and userspace tools after 2009/2010 depend on
889 the existence of /sys/class/block/, and will not work with this
892 Only if you are using a new kernel on an old distribution, you might
895 config SYSFS_DEPRECATED_V2
896 bool "Enable deprecated sysfs features by default"
899 depends on SYSFS_DEPRECATED
901 Enable deprecated sysfs by default.
903 See the CONFIG_SYSFS_DEPRECATED option for more details about this
906 Only if you are using a new kernel on an old distribution, you might
907 need to say Y here. Even then, odds are you would not need it
908 enabled, you can always pass the boot option if absolutely necessary.
911 bool "Kernel->user space relay support (formerly relayfs)"
913 This option enables support for relay interface support in
914 certain file systems (such as debugfs).
915 It is designed to provide an efficient mechanism for tools and
916 facilities to relay large amounts of data from kernel space to
921 config BLK_DEV_INITRD
922 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
923 depends on BROKEN || !FRV
925 The initial RAM filesystem is a ramfs which is loaded by the
926 boot loader (loadlin or lilo) and that is mounted as root
927 before the normal boot procedure. It is typically used to
928 load modules needed to mount the "real" root file system,
929 etc. See <file:Documentation/initrd.txt> for details.
931 If RAM disk support (BLK_DEV_RAM) is also included, this
932 also enables initial RAM disk (initrd) support and adds
933 15 Kbytes (more on some other architectures) to the kernel size.
943 config CC_OPTIMIZE_FOR_SIZE
944 bool "Optimize for size"
946 Enabling this option will pass "-Os" instead of "-O2" to gcc
947 resulting in a smaller kernel.
958 bool "Configure standard kernel features (expert users)"
959 # Unhide debug options, to make the on-by-default options visible
962 This option allows certain base kernel options and settings
963 to be disabled or tweaked. This is for specialized
964 environments which can tolerate a "non-standard" kernel.
965 Only use this if you really know what you are doing.
968 bool "Enable 16-bit UID system calls" if EXPERT
969 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
972 This enables the legacy 16-bit UID syscall wrappers.
974 config SYSCTL_SYSCALL
975 bool "Sysctl syscall support" if EXPERT
976 depends on PROC_SYSCTL
980 sys_sysctl uses binary paths that have been found challenging
981 to properly maintain and use. The interface in /proc/sys
982 using paths with ascii names is now the primary path to this
985 Almost nothing using the binary sysctl interface so if you are
986 trying to save some space it is probably safe to disable this,
987 making your kernel marginally smaller.
989 If unsure say N here.
992 bool "Load all symbols for debugging/ksymoops" if EXPERT
995 Say Y here to let the kernel print out symbolic crash information and
996 symbolic stack backtraces. This increases the size of the kernel
997 somewhat, as all symbols have to be loaded into the kernel image.
1000 bool "Include all symbols in kallsyms"
1001 depends on DEBUG_KERNEL && KALLSYMS
1003 Normally kallsyms only contains the symbols of functions for nicer
1004 OOPS messages and backtraces (i.e., symbols from the text and inittext
1005 sections). This is sufficient for most cases. And only in very rare
1006 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1007 names of variables from the data sections, etc).
1009 This option makes sure that all symbols are loaded into the kernel
1010 image (i.e., symbols from all sections) in cost of increased kernel
1011 size (depending on the kernel configuration, it may be 300KiB or
1012 something like this).
1014 Say N unless you really need all symbols.
1017 bool "Support for hot-pluggable devices" if EXPERT
1020 This option is provided for the case where no hotplug or uevent
1021 capabilities is wanted by the kernel. You should only consider
1022 disabling this option for embedded systems that do not use modules, a
1023 dynamic /dev tree, or dynamic device discovery. Just say Y.
1027 bool "Enable support for printk" if EXPERT
1029 This option enables normal printk support. Removing it
1030 eliminates most of the message strings from the kernel image
1031 and makes the kernel more or less silent. As this makes it
1032 very difficult to diagnose system problems, saying N here is
1033 strongly discouraged.
1036 bool "BUG() support" if EXPERT
1039 Disabling this option eliminates support for BUG and WARN, reducing
1040 the size of your kernel image and potentially quietly ignoring
1041 numerous fatal conditions. You should only consider disabling this
1042 option for embedded systems with no facilities for reporting errors.
1047 bool "Enable ELF core dumps" if EXPERT
1049 Enable support for generating core dumps. Disabling saves about 4k.
1052 config PCSPKR_PLATFORM
1053 bool "Enable PC-Speaker support" if EXPERT
1054 depends on HAVE_PCSPKR_PLATFORM
1058 This option allows to disable the internal PC-Speaker
1059 support, saving some memory.
1061 config HAVE_PCSPKR_PLATFORM
1066 bool "Enable full-sized data structures for core" if EXPERT
1068 Disabling this option reduces the size of miscellaneous core
1069 kernel data structures. This saves memory on small machines,
1070 but may reduce performance.
1073 bool "Enable futex support" if EXPERT
1077 Disabling this option will cause the kernel to be built without
1078 support for "fast userspace mutexes". The resulting kernel may not
1079 run glibc-based applications correctly.
1082 bool "Enable eventpoll support" if EXPERT
1086 Disabling this option will cause the kernel to be built without
1087 support for epoll family of system calls.
1090 bool "Enable signalfd() system call" if EXPERT
1094 Enable the signalfd() system call that allows to receive signals
1095 on a file descriptor.
1100 bool "Enable timerfd() system call" if EXPERT
1104 Enable the timerfd() system call that allows to receive timer
1105 events on a file descriptor.
1110 bool "Enable eventfd() system call" if EXPERT
1114 Enable the eventfd() system call that allows to receive both
1115 kernel notification (ie. KAIO) or userspace notifications.
1120 bool "Use full shmem filesystem" if EXPERT
1124 The shmem is an internal filesystem used to manage shared memory.
1125 It is backed by swap and manages resource limits. It is also exported
1126 to userspace as tmpfs if TMPFS is enabled. Disabling this
1127 option replaces shmem and tmpfs with the much simpler ramfs code,
1128 which may be appropriate on small systems without swap.
1131 bool "Enable AIO support" if EXPERT
1134 This option enables POSIX asynchronous I/O which may by used
1135 by some high performance threaded applications. Disabling
1136 this option saves about 7k.
1139 bool "Embedded system"
1142 This option should be enabled if compiling the kernel for
1143 an embedded system so certain expert options are available
1146 config HAVE_PERF_EVENTS
1149 See tools/perf/design.txt for details.
1151 config PERF_USE_VMALLOC
1154 See tools/perf/design.txt for details
1156 menu "Kernel Performance Events And Counters"
1159 bool "Kernel performance events and counters"
1160 default y if (PROFILING || PERF_COUNTERS)
1161 depends on HAVE_PERF_EVENTS
1165 Enable kernel support for various performance events provided
1166 by software and hardware.
1168 Software events are supported either built-in or via the
1169 use of generic tracepoints.
1171 Most modern CPUs support performance events via performance
1172 counter registers. These registers count the number of certain
1173 types of hw events: such as instructions executed, cachemisses
1174 suffered, or branches mis-predicted - without slowing down the
1175 kernel or applications. These registers can also trigger interrupts
1176 when a threshold number of events have passed - and can thus be
1177 used to profile the code that runs on that CPU.
1179 The Linux Performance Event subsystem provides an abstraction of
1180 these software and hardware event capabilities, available via a
1181 system call and used by the "perf" utility in tools/perf/. It
1182 provides per task and per CPU counters, and it provides event
1183 capabilities on top of those.
1187 config PERF_COUNTERS
1188 bool "Kernel performance counters (old config option)"
1189 depends on HAVE_PERF_EVENTS
1191 This config has been obsoleted by the PERF_EVENTS
1192 config option - please see that one for details.
1194 It has no effect on the kernel whether you enable
1195 it or not, it is a compatibility placeholder.
1199 config DEBUG_PERF_USE_VMALLOC
1201 bool "Debug: use vmalloc to back perf mmap() buffers"
1202 depends on PERF_EVENTS && DEBUG_KERNEL
1203 select PERF_USE_VMALLOC
1205 Use vmalloc memory to back perf mmap() buffers.
1207 Mostly useful for debugging the vmalloc code on platforms
1208 that don't require it.
1214 config VM_EVENT_COUNTERS
1216 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1218 VM event counters are needed for event counts to be shown.
1219 This option allows the disabling of the VM event counters
1220 on EXPERT systems. /proc/vmstat will only show page counts
1221 if VM event counters are disabled.
1225 bool "Enable PCI quirk workarounds" if EXPERT
1228 This enables workarounds for various PCI chipset
1229 bugs/quirks. Disable this only if your target machine is
1230 unaffected by PCI quirks.
1234 bool "Enable SLUB debugging support" if EXPERT
1235 depends on SLUB && SYSFS
1237 SLUB has extensive debug support features. Disabling these can
1238 result in significant savings in code size. This also disables
1239 SLUB sysfs support. /sys/slab will not exist and there will be
1240 no support for cache validation etc.
1243 bool "Disable heap randomization"
1246 Randomizing heap placement makes heap exploits harder, but it
1247 also breaks ancient binaries (including anything libc5 based).
1248 This option changes the bootup default to heap randomization
1249 disabled, and can be overridden at runtime by setting
1250 /proc/sys/kernel/randomize_va_space to 2.
1252 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1255 prompt "Choose SLAB allocator"
1258 This option allows to select a slab allocator.
1263 The regular slab allocator that is established and known to work
1264 well in all environments. It organizes cache hot objects in
1265 per cpu and per node queues.
1268 bool "SLUB (Unqueued Allocator)"
1270 SLUB is a slab allocator that minimizes cache line usage
1271 instead of managing queues of cached objects (SLAB approach).
1272 Per cpu caching is realized using slabs of objects instead
1273 of queues of objects. SLUB can use memory efficiently
1274 and has enhanced diagnostics. SLUB is the default choice for
1279 bool "SLOB (Simple Allocator)"
1281 SLOB replaces the stock allocator with a drastically simpler
1282 allocator. SLOB is generally more space efficient but
1283 does not perform as well on large systems.
1287 config MMAP_ALLOW_UNINITIALIZED
1288 bool "Allow mmapped anonymous memory to be uninitialized"
1289 depends on EXPERT && !MMU
1292 Normally, and according to the Linux spec, anonymous memory obtained
1293 from mmap() has it's contents cleared before it is passed to
1294 userspace. Enabling this config option allows you to request that
1295 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1296 providing a huge performance boost. If this option is not enabled,
1297 then the flag will be ignored.
1299 This is taken advantage of by uClibc's malloc(), and also by
1300 ELF-FDPIC binfmt's brk and stack allocator.
1302 Because of the obvious security issues, this option should only be
1303 enabled on embedded devices where you control what is run in
1304 userspace. Since that isn't generally a problem on no-MMU systems,
1305 it is normally safe to say Y here.
1307 See Documentation/nommu-mmap.txt for more information.
1310 bool "Profiling support"
1312 Say Y here to enable the extended profiling support mechanisms used
1313 by profilers such as OProfile.
1316 # Place an empty function call at each tracepoint site. Can be
1317 # dynamically changed for a probe function.
1322 source "arch/Kconfig"
1324 endmenu # General setup
1326 config HAVE_GENERIC_DMA_COHERENT
1333 depends on SLAB || SLUB_DEBUG
1341 default 0 if BASE_FULL
1342 default 1 if !BASE_FULL
1345 bool "Enable loadable module support"
1347 Kernel modules are small pieces of compiled code which can
1348 be inserted in the running kernel, rather than being
1349 permanently built into the kernel. You use the "modprobe"
1350 tool to add (and sometimes remove) them. If you say Y here,
1351 many parts of the kernel can be built as modules (by
1352 answering M instead of Y where indicated): this is most
1353 useful for infrequently used options which are not required
1354 for booting. For more information, see the man pages for
1355 modprobe, lsmod, modinfo, insmod and rmmod.
1357 If you say Y here, you will need to run "make
1358 modules_install" to put the modules under /lib/modules/
1359 where modprobe can find them (you may need to be root to do
1366 config MODULE_FORCE_LOAD
1367 bool "Forced module loading"
1370 Allow loading of modules without version information (ie. modprobe
1371 --force). Forced module loading sets the 'F' (forced) taint flag and
1372 is usually a really bad idea.
1374 config MODULE_UNLOAD
1375 bool "Module unloading"
1377 Without this option you will not be able to unload any
1378 modules (note that some modules may not be unloadable
1379 anyway), which makes your kernel smaller, faster
1380 and simpler. If unsure, say Y.
1382 config MODULE_FORCE_UNLOAD
1383 bool "Forced module unloading"
1384 depends on MODULE_UNLOAD && EXPERIMENTAL
1386 This option allows you to force a module to unload, even if the
1387 kernel believes it is unsafe: the kernel will remove the module
1388 without waiting for anyone to stop using it (using the -f option to
1389 rmmod). This is mainly for kernel developers and desperate users.
1393 bool "Module versioning support"
1395 Usually, you have to use modules compiled with your kernel.
1396 Saying Y here makes it sometimes possible to use modules
1397 compiled for different kernels, by adding enough information
1398 to the modules to (hopefully) spot any changes which would
1399 make them incompatible with the kernel you are running. If
1402 config MODULE_SRCVERSION_ALL
1403 bool "Source checksum for all modules"
1405 Modules which contain a MODULE_VERSION get an extra "srcversion"
1406 field inserted into their modinfo section, which contains a
1407 sum of the source files which made it. This helps maintainers
1408 see exactly which source was used to build a module (since
1409 others sometimes change the module source without updating
1410 the version). With this option, such a "srcversion" field
1411 will be created for all modules. If unsure, say N.
1415 config INIT_ALL_POSSIBLE
1418 Back when each arch used to define their own cpu_online_mask and
1419 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1420 with all 1s, and others with all 0s. When they were centralised,
1421 it was better to provide this option than to break all the archs
1422 and have several arch maintainers pursuing me down dark alleys.
1427 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1429 Need stop_machine() primitive.
1431 source "block/Kconfig"
1433 config PREEMPT_NOTIFIERS
1440 source "kernel/Kconfig.locks"