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"
29 depends on HAVE_IRQ_WORK
34 bool "Prompt for development and/or incomplete code/drivers"
36 Some of the various things that Linux supports (such as network
37 drivers, file systems, network protocols, etc.) can be in a state
38 of development where the functionality, stability, or the level of
39 testing is not yet high enough for general use. This is usually
40 known as the "alpha-test" phase among developers. If a feature is
41 currently in alpha-test, then the developers usually discourage
42 uninformed widespread use of this feature by the general public to
43 avoid "Why doesn't this work?" type mail messages. However, active
44 testing and use of these systems is welcomed. Just be aware that it
45 may not meet the normal level of reliability or it may fail to work
46 in some special cases. Detailed bug reports from people familiar
47 with the kernel internals are usually welcomed by the developers
48 (before submitting bug reports, please read the documents
49 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
50 <file:Documentation/BUG-HUNTING>, and
51 <file:Documentation/oops-tracing.txt> in the kernel source).
53 This option will also make obsoleted drivers available. These are
54 drivers that have been replaced by something else, and/or are
55 scheduled to be removed in a future kernel release.
57 Unless you intend to help test and develop a feature or driver that
58 falls into this category, or you have a situation that requires
59 using these features, you should probably say N here, which will
60 cause the configurator to present you with fewer choices. If
61 you say Y here, you will be offered the choice of using features or
62 drivers that are currently considered to be in the alpha-test phase.
69 depends on BROKEN || !SMP
74 depends on (SMP || PREEMPT) && BKL
77 config INIT_ENV_ARG_LIMIT
82 Maximum of each of the number of arguments and environment
83 variables passed to init from the kernel command line.
87 string "Cross-compiler tool prefix"
89 Same as running 'make CROSS_COMPILE=prefix-' but stored for
90 default make runs in this kernel build directory. You don't
91 need to set this unless you want the configured kernel build
92 directory to select the cross-compiler automatically.
95 string "Local version - append to kernel release"
97 Append an extra string to the end of your kernel version.
98 This will show up when you type uname, for example.
99 The string you set here will be appended after the contents of
100 any files with a filename matching localversion* in your
101 object and source tree, in that order. Your total string can
102 be a maximum of 64 characters.
104 config LOCALVERSION_AUTO
105 bool "Automatically append version information to the version string"
108 This will try to automatically determine if the current tree is a
109 release tree by looking for git tags that belong to the current
110 top of tree revision.
112 A string of the format -gxxxxxxxx will be added to the localversion
113 if a git-based tree is found. The string generated by this will be
114 appended after any matching localversion* files, and after the value
115 set in CONFIG_LOCALVERSION.
117 (The actual string used here is the first eight characters produced
118 by running the command:
120 $ git rev-parse --verify HEAD
122 which is done within the script "scripts/setlocalversion".)
124 config HAVE_KERNEL_GZIP
127 config HAVE_KERNEL_BZIP2
130 config HAVE_KERNEL_LZMA
133 config HAVE_KERNEL_LZO
137 prompt "Kernel compression mode"
139 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || 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 three. 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 The most recent compression algorithm.
180 Its ratio is best, decompression speed is between the other
181 two. Compression is slowest. The kernel size is about 33%
182 smaller with LZMA in comparison to gzip.
186 depends on HAVE_KERNEL_LZO
188 Its compression ratio is the poorest among the 4. The kernel
189 size is about 10% bigger than gzip; however its speed
190 (both compression and decompression) is the fastest.
195 bool "Support for paging of anonymous memory (swap)"
196 depends on MMU && BLOCK
199 This option allows you to choose whether you want to have support
200 for so called swap devices or swap files in your kernel that are
201 used to provide more virtual memory than the actual RAM present
202 in your computer. If unsure say Y.
207 Inter Process Communication is a suite of library functions and
208 system calls which let processes (running programs) synchronize and
209 exchange information. It is generally considered to be a good thing,
210 and some programs won't run unless you say Y here. In particular, if
211 you want to run the DOS emulator dosemu under Linux (read the
212 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
213 you'll need to say Y here.
215 You can find documentation about IPC with "info ipc" and also in
216 section 6.4 of the Linux Programmer's Guide, available from
217 <http://www.tldp.org/guides.html>.
219 config SYSVIPC_SYSCTL
226 bool "POSIX Message Queues"
227 depends on NET && EXPERIMENTAL
229 POSIX variant of message queues is a part of IPC. In POSIX message
230 queues every message has a priority which decides about succession
231 of receiving it by a process. If you want to compile and run
232 programs written e.g. for Solaris with use of its POSIX message
233 queues (functions mq_*) say Y here.
235 POSIX message queues are visible as a filesystem called 'mqueue'
236 and can be mounted somewhere if you want to do filesystem
237 operations on message queues.
241 config POSIX_MQUEUE_SYSCTL
243 depends on POSIX_MQUEUE
247 config BSD_PROCESS_ACCT
248 bool "BSD Process Accounting"
250 If you say Y here, a user level program will be able to instruct the
251 kernel (via a special system call) to write process accounting
252 information to a file: whenever a process exits, information about
253 that process will be appended to the file by the kernel. The
254 information includes things such as creation time, owning user,
255 command name, memory usage, controlling terminal etc. (the complete
256 list is in the struct acct in <file:include/linux/acct.h>). It is
257 up to the user level program to do useful things with this
258 information. This is generally a good idea, so say Y.
260 config BSD_PROCESS_ACCT_V3
261 bool "BSD Process Accounting version 3 file format"
262 depends on BSD_PROCESS_ACCT
265 If you say Y here, the process accounting information is written
266 in a new file format that also logs the process IDs of each
267 process and it's parent. Note that this file format is incompatible
268 with previous v0/v1/v2 file formats, so you will need updated tools
269 for processing it. A preliminary version of these tools is available
270 at <http://www.gnu.org/software/acct/>.
273 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
277 Export selected statistics for tasks/processes through the
278 generic netlink interface. Unlike BSD process accounting, the
279 statistics are available during the lifetime of tasks/processes as
280 responses to commands. Like BSD accounting, they are sent to user
285 config TASK_DELAY_ACCT
286 bool "Enable per-task delay accounting (EXPERIMENTAL)"
289 Collect information on time spent by a task waiting for system
290 resources like cpu, synchronous block I/O completion and swapping
291 in pages. Such statistics can help in setting a task's priorities
292 relative to other tasks for cpu, io, rss limits etc.
297 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
300 Collect extended task accounting data and send the data
301 to userland for processing over the taskstats interface.
305 config TASK_IO_ACCOUNTING
306 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
307 depends on TASK_XACCT
309 Collect information on the number of bytes of storage I/O which this
315 bool "Auditing support"
318 Enable auditing infrastructure that can be used with another
319 kernel subsystem, such as SELinux (which requires this for
320 logging of avc messages output). Does not do system-call
321 auditing without CONFIG_AUDITSYSCALL.
324 bool "Enable system-call auditing support"
325 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
326 default y if SECURITY_SELINUX
328 Enable low-overhead system-call auditing infrastructure that
329 can be used independently or with another kernel subsystem,
334 depends on AUDITSYSCALL
339 depends on AUDITSYSCALL
342 source "kernel/irq/Kconfig"
347 prompt "RCU Implementation"
351 bool "Tree-based hierarchical RCU"
352 depends on !PREEMPT && SMP
354 This option selects the RCU implementation that is
355 designed for very large SMP system with hundreds or
356 thousands of CPUs. It also scales down nicely to
359 config TREE_PREEMPT_RCU
360 bool "Preemptible tree-based hierarchical RCU"
363 This option selects the RCU implementation that is
364 designed for very large SMP systems with hundreds or
365 thousands of CPUs, but for which real-time response
366 is also required. It also scales down nicely to
370 bool "UP-only small-memory-footprint RCU"
373 This option selects the RCU implementation that is
374 designed for UP systems from which real-time response
375 is not required. This option greatly reduces the
376 memory footprint of RCU.
378 config TINY_PREEMPT_RCU
379 bool "Preemptible UP-only small-memory-footprint RCU"
380 depends on !SMP && PREEMPT
382 This option selects the RCU implementation that is designed
383 for real-time UP systems. This option greatly reduces the
384 memory footprint of RCU.
389 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
391 This option enables preemptible-RCU code that is common between
392 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
395 bool "Enable tracing for RCU"
396 depends on TREE_RCU || TREE_PREEMPT_RCU
398 This option provides tracing in RCU which presents stats
399 in debugfs for debugging RCU implementation.
401 Say Y here if you want to enable RCU tracing
402 Say N if you are unsure.
405 int "Tree-based hierarchical RCU fanout value"
408 depends on TREE_RCU || TREE_PREEMPT_RCU
412 This option controls the fanout of hierarchical implementations
413 of RCU, allowing RCU to work efficiently on machines with
414 large numbers of CPUs. This value must be at least the fourth
415 root of NR_CPUS, which allows NR_CPUS to be insanely large.
416 The default value of RCU_FANOUT should be used for production
417 systems, but if you are stress-testing the RCU implementation
418 itself, small RCU_FANOUT values allow you to test large-system
419 code paths on small(er) systems.
421 Select a specific number if testing RCU itself.
422 Take the default if unsure.
424 config RCU_FANOUT_EXACT
425 bool "Disable tree-based hierarchical RCU auto-balancing"
426 depends on TREE_RCU || TREE_PREEMPT_RCU
429 This option forces use of the exact RCU_FANOUT value specified,
430 regardless of imbalances in the hierarchy. This is useful for
431 testing RCU itself, and might one day be useful on systems with
432 strong NUMA behavior.
434 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
438 config RCU_FAST_NO_HZ
439 bool "Accelerate last non-dyntick-idle CPU's grace periods"
440 depends on TREE_RCU && NO_HZ && SMP
443 This option causes RCU to attempt to accelerate grace periods
444 in order to allow the final CPU to enter dynticks-idle state
445 more quickly. On the other hand, this option increases the
446 overhead of the dynticks-idle checking, particularly on systems
447 with large numbers of CPUs.
449 Say Y if energy efficiency is critically important, particularly
450 if you have relatively few CPUs.
452 Say N if you are unsure.
454 config TREE_RCU_TRACE
455 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
458 This option provides tracing for the TREE_RCU and
459 TREE_PREEMPT_RCU implementations, permitting Makefile to
460 trivially select kernel/rcutree_trace.c.
462 endmenu # "RCU Subsystem"
465 tristate "Kernel .config support"
467 This option enables the complete Linux kernel ".config" file
468 contents to be saved in the kernel. It provides documentation
469 of which kernel options are used in a running kernel or in an
470 on-disk kernel. This information can be extracted from the kernel
471 image file with the script scripts/extract-ikconfig and used as
472 input to rebuild the current kernel or to build another kernel.
473 It can also be extracted from a running kernel by reading
474 /proc/config.gz if enabled (below).
477 bool "Enable access to .config through /proc/config.gz"
478 depends on IKCONFIG && PROC_FS
480 This option enables access to the kernel configuration file
481 through /proc/config.gz.
484 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
488 Select kernel log buffer size as a power of 2.
498 # Architectures with an unreliable sched_clock() should select this:
500 config HAVE_UNSTABLE_SCHED_CLOCK
504 boolean "Control Group support"
507 This option adds support for grouping sets of processes together, for
508 use with process control subsystems such as Cpusets, CFS, memory
509 controls or device isolation.
511 - Documentation/scheduler/sched-design-CFS.txt (CFS)
512 - Documentation/cgroups/ (features for grouping, isolation
513 and resource control)
520 bool "Example debug cgroup subsystem"
523 This option enables a simple cgroup subsystem that
524 exports useful debugging information about the cgroups
530 bool "Namespace cgroup subsystem"
532 Provides a simple namespace cgroup subsystem to
533 provide hierarchical naming of sets of namespaces,
534 for instance virtual servers and checkpoint/restart
537 config CGROUP_FREEZER
538 bool "Freezer cgroup subsystem"
540 Provides a way to freeze and unfreeze all tasks in a
544 bool "Device controller for cgroups"
545 depends on EXPERIMENTAL
547 Provides a cgroup implementing whitelists for devices which
548 a process in the cgroup can mknod or open.
551 bool "Cpuset support"
553 This option will let you create and manage CPUSETs which
554 allow dynamically partitioning a system into sets of CPUs and
555 Memory Nodes and assigning tasks to run only within those sets.
556 This is primarily useful on large SMP or NUMA systems.
560 config PROC_PID_CPUSET
561 bool "Include legacy /proc/<pid>/cpuset file"
565 config CGROUP_CPUACCT
566 bool "Simple CPU accounting cgroup subsystem"
568 Provides a simple Resource Controller for monitoring the
569 total CPU consumed by the tasks in a cgroup.
571 config RESOURCE_COUNTERS
572 bool "Resource counters"
574 This option enables controller independent resource accounting
575 infrastructure that works with cgroups.
577 config CGROUP_MEM_RES_CTLR
578 bool "Memory Resource Controller for Control Groups"
579 depends on RESOURCE_COUNTERS
582 Provides a memory resource controller that manages both anonymous
583 memory and page cache. (See Documentation/cgroups/memory.txt)
585 Note that setting this option increases fixed memory overhead
586 associated with each page of memory in the system. By this,
587 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
588 usage tracking struct at boot. Total amount of this is printed out
591 Only enable when you're ok with these trade offs and really
592 sure you need the memory resource controller. Even when you enable
593 this, you can set "cgroup_disable=memory" at your boot option to
594 disable memory resource controller and you can avoid overheads.
595 (and lose benefits of memory resource controller)
597 This config option also selects MM_OWNER config option, which
598 could in turn add some fork/exit overhead.
600 config CGROUP_MEM_RES_CTLR_SWAP
601 bool "Memory Resource Controller Swap Extension"
602 depends on CGROUP_MEM_RES_CTLR && SWAP
604 Add swap management feature to memory resource controller. When you
605 enable this, you can limit mem+swap usage per cgroup. In other words,
606 when you disable this, memory resource controller has no cares to
607 usage of swap...a process can exhaust all of the swap. This extension
608 is useful when you want to avoid exhaustion swap but this itself
609 adds more overheads and consumes memory for remembering information.
610 Especially if you use 32bit system or small memory system, please
611 be careful about enabling this. When memory resource controller
612 is disabled by boot option, this will be automatically disabled and
613 there will be no overhead from this. Even when you set this config=y,
614 if boot option "noswapaccount" is set, swap will not be accounted.
615 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
616 size is 4096bytes, 512k per 1Gbytes of swap.
618 menuconfig CGROUP_SCHED
619 bool "Group CPU scheduler"
620 depends on EXPERIMENTAL
623 This feature lets CPU scheduler recognize task groups and control CPU
624 bandwidth allocation to such task groups. It uses cgroups to group
628 config FAIR_GROUP_SCHED
629 bool "Group scheduling for SCHED_OTHER"
630 depends on CGROUP_SCHED
633 config RT_GROUP_SCHED
634 bool "Group scheduling for SCHED_RR/FIFO"
635 depends on EXPERIMENTAL
636 depends on CGROUP_SCHED
639 This feature lets you explicitly allocate real CPU bandwidth
640 to task groups. If enabled, it will also make it impossible to
641 schedule realtime tasks for non-root users until you allocate
642 realtime bandwidth for them.
643 See Documentation/scheduler/sched-rt-group.txt for more information.
648 tristate "Block IO controller"
652 Generic block IO controller cgroup interface. This is the common
653 cgroup interface which should be used by various IO controlling
656 Currently, CFQ IO scheduler uses it to recognize task groups and
657 control disk bandwidth allocation (proportional time slice allocation)
658 to such task groups. It is also used by bio throttling logic in
659 block layer to implement upper limit in IO rates on a device.
661 This option only enables generic Block IO controller infrastructure.
662 One needs to also enable actual IO controlling logic/policy. For
663 enabling proportional weight division of disk bandwidth in CFQ seti
664 CONFIG_CFQ_GROUP_IOSCHED=y and for enabling throttling policy set
665 CONFIG_BLK_THROTTLE=y.
667 See Documentation/cgroups/blkio-controller.txt for more information.
669 config DEBUG_BLK_CGROUP
670 bool "Enable Block IO controller debugging"
671 depends on BLK_CGROUP
674 Enable some debugging help. Currently it exports additional stat
675 files in a cgroup which can be useful for debugging.
682 config SYSFS_DEPRECATED
683 bool "enable deprecated sysfs features to support old userspace tools"
687 This option adds code that switches the layout of the "block" class
688 devices, to not show up in /sys/class/block/, but only in
691 This switch is only active when the sysfs.deprecated=1 boot option is
692 passed or the SYSFS_DEPRECATED_V2 option is set.
694 This option allows new kernels to run on old distributions and tools,
695 which might get confused by /sys/class/block/. Since 2007/2008 all
696 major distributions and tools handle this just fine.
698 Recent distributions and userspace tools after 2009/2010 depend on
699 the existence of /sys/class/block/, and will not work with this
702 Only if you are using a new kernel on an old distribution, you might
705 config SYSFS_DEPRECATED_V2
706 bool "enabled deprecated sysfs features by default"
709 depends on SYSFS_DEPRECATED
711 Enable deprecated sysfs by default.
713 See the CONFIG_SYSFS_DEPRECATED option for more details about this
716 Only if you are using a new kernel on an old distribution, you might
717 need to say Y here. Even then, odds are you would not need it
718 enabled, you can always pass the boot option if absolutely necessary.
721 bool "Kernel->user space relay support (formerly relayfs)"
723 This option enables support for relay interface support in
724 certain file systems (such as debugfs).
725 It is designed to provide an efficient mechanism for tools and
726 facilities to relay large amounts of data from kernel space to
731 menuconfig NAMESPACES
732 bool "Namespaces support" if EMBEDDED
735 Provides the way to make tasks work with different objects using
736 the same id. For example same IPC id may refer to different objects
737 or same user id or pid may refer to different tasks when used in
738 different namespaces.
746 In this namespace tasks see different info provided with the
751 depends on (SYSVIPC || POSIX_MQUEUE)
754 In this namespace tasks work with IPC ids which correspond to
755 different IPC objects in different namespaces.
758 bool "User namespace (EXPERIMENTAL)"
759 depends on EXPERIMENTAL
762 This allows containers, i.e. vservers, to use user namespaces
763 to provide different user info for different servers.
767 bool "PID Namespaces"
770 Support process id namespaces. This allows having multiple
771 processes with the same pid as long as they are in different
772 pid namespaces. This is a building block of containers.
775 bool "Network namespace"
779 Allow user space to create what appear to be multiple instances
780 of the network stack.
784 config BLK_DEV_INITRD
785 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
786 depends on BROKEN || !FRV
788 The initial RAM filesystem is a ramfs which is loaded by the
789 boot loader (loadlin or lilo) and that is mounted as root
790 before the normal boot procedure. It is typically used to
791 load modules needed to mount the "real" root file system,
792 etc. See <file:Documentation/initrd.txt> for details.
794 If RAM disk support (BLK_DEV_RAM) is also included, this
795 also enables initial RAM disk (initrd) support and adds
796 15 Kbytes (more on some other architectures) to the kernel size.
806 config CC_OPTIMIZE_FOR_SIZE
807 bool "Optimize for size"
810 Enabling this option will pass "-Os" instead of "-O2" to gcc
811 resulting in a smaller kernel.
822 bool "Configure standard kernel features (for small systems)"
824 This option allows certain base kernel options and settings
825 to be disabled or tweaked. This is for specialized
826 environments which can tolerate a "non-standard" kernel.
827 Only use this if you really know what you are doing.
830 bool "Enable 16-bit UID system calls" if EMBEDDED
831 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
834 This enables the legacy 16-bit UID syscall wrappers.
836 config SYSCTL_SYSCALL
837 bool "Sysctl syscall support" if EMBEDDED
838 depends on PROC_SYSCTL
842 sys_sysctl uses binary paths that have been found challenging
843 to properly maintain and use. The interface in /proc/sys
844 using paths with ascii names is now the primary path to this
847 Almost nothing using the binary sysctl interface so if you are
848 trying to save some space it is probably safe to disable this,
849 making your kernel marginally smaller.
851 If unsure say Y here.
854 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
857 Say Y here to let the kernel print out symbolic crash information and
858 symbolic stack backtraces. This increases the size of the kernel
859 somewhat, as all symbols have to be loaded into the kernel image.
862 bool "Include all symbols in kallsyms"
863 depends on DEBUG_KERNEL && KALLSYMS
865 Normally kallsyms only contains the symbols of functions, for nicer
866 OOPS messages. Some debuggers can use kallsyms for other
867 symbols too: say Y here to include all symbols, if you need them
868 and you don't care about adding 300k to the size of your kernel.
872 config KALLSYMS_EXTRA_PASS
873 bool "Do an extra kallsyms pass"
876 If kallsyms is not working correctly, the build will fail with
877 inconsistent kallsyms data. If that occurs, log a bug report and
878 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
879 Always say N here unless you find a bug in kallsyms, which must be
880 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
881 you wait for kallsyms to be fixed.
885 bool "Support for hot-pluggable devices" if EMBEDDED
888 This option is provided for the case where no hotplug or uevent
889 capabilities is wanted by the kernel. You should only consider
890 disabling this option for embedded systems that do not use modules, a
891 dynamic /dev tree, or dynamic device discovery. Just say Y.
895 bool "Enable support for printk" if EMBEDDED
897 This option enables normal printk support. Removing it
898 eliminates most of the message strings from the kernel image
899 and makes the kernel more or less silent. As this makes it
900 very difficult to diagnose system problems, saying N here is
901 strongly discouraged.
904 bool "BUG() support" if EMBEDDED
907 Disabling this option eliminates support for BUG and WARN, reducing
908 the size of your kernel image and potentially quietly ignoring
909 numerous fatal conditions. You should only consider disabling this
910 option for embedded systems with no facilities for reporting errors.
915 bool "Enable ELF core dumps" if EMBEDDED
917 Enable support for generating core dumps. Disabling saves about 4k.
919 config PCSPKR_PLATFORM
920 bool "Enable PC-Speaker support" if EMBEDDED
921 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
924 This option allows to disable the internal PC-Speaker
925 support, saving some memory.
929 bool "Enable full-sized data structures for core" if EMBEDDED
931 Disabling this option reduces the size of miscellaneous core
932 kernel data structures. This saves memory on small machines,
933 but may reduce performance.
936 bool "Enable futex support" if EMBEDDED
940 Disabling this option will cause the kernel to be built without
941 support for "fast userspace mutexes". The resulting kernel may not
942 run glibc-based applications correctly.
945 bool "Enable eventpoll support" if EMBEDDED
949 Disabling this option will cause the kernel to be built without
950 support for epoll family of system calls.
953 bool "Enable signalfd() system call" if EMBEDDED
957 Enable the signalfd() system call that allows to receive signals
958 on a file descriptor.
963 bool "Enable timerfd() system call" if EMBEDDED
967 Enable the timerfd() system call that allows to receive timer
968 events on a file descriptor.
973 bool "Enable eventfd() system call" if EMBEDDED
977 Enable the eventfd() system call that allows to receive both
978 kernel notification (ie. KAIO) or userspace notifications.
983 bool "Use full shmem filesystem" if EMBEDDED
987 The shmem is an internal filesystem used to manage shared memory.
988 It is backed by swap and manages resource limits. It is also exported
989 to userspace as tmpfs if TMPFS is enabled. Disabling this
990 option replaces shmem and tmpfs with the much simpler ramfs code,
991 which may be appropriate on small systems without swap.
994 bool "Enable AIO support" if EMBEDDED
997 This option enables POSIX asynchronous I/O which may by used
998 by some high performance threaded applications. Disabling
999 this option saves about 7k.
1001 config HAVE_PERF_EVENTS
1004 See tools/perf/design.txt for details.
1006 config PERF_USE_VMALLOC
1009 See tools/perf/design.txt for details
1011 menu "Kernel Performance Events And Counters"
1014 bool "Kernel performance events and counters"
1015 default y if (PROFILING || PERF_COUNTERS)
1016 depends on HAVE_PERF_EVENTS
1020 Enable kernel support for various performance events provided
1021 by software and hardware.
1023 Software events are supported either built-in or via the
1024 use of generic tracepoints.
1026 Most modern CPUs support performance events via performance
1027 counter registers. These registers count the number of certain
1028 types of hw events: such as instructions executed, cachemisses
1029 suffered, or branches mis-predicted - without slowing down the
1030 kernel or applications. These registers can also trigger interrupts
1031 when a threshold number of events have passed - and can thus be
1032 used to profile the code that runs on that CPU.
1034 The Linux Performance Event subsystem provides an abstraction of
1035 these software and hardware event capabilities, available via a
1036 system call and used by the "perf" utility in tools/perf/. It
1037 provides per task and per CPU counters, and it provides event
1038 capabilities on top of those.
1042 config PERF_COUNTERS
1043 bool "Kernel performance counters (old config option)"
1044 depends on HAVE_PERF_EVENTS
1046 This config has been obsoleted by the PERF_EVENTS
1047 config option - please see that one for details.
1049 It has no effect on the kernel whether you enable
1050 it or not, it is a compatibility placeholder.
1054 config DEBUG_PERF_USE_VMALLOC
1056 bool "Debug: use vmalloc to back perf mmap() buffers"
1057 depends on PERF_EVENTS && DEBUG_KERNEL
1058 select PERF_USE_VMALLOC
1060 Use vmalloc memory to back perf mmap() buffers.
1062 Mostly useful for debugging the vmalloc code on platforms
1063 that don't require it.
1069 config VM_EVENT_COUNTERS
1071 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1073 VM event counters are needed for event counts to be shown.
1074 This option allows the disabling of the VM event counters
1075 on EMBEDDED systems. /proc/vmstat will only show page counts
1076 if VM event counters are disabled.
1080 bool "Enable PCI quirk workarounds" if EMBEDDED
1083 This enables workarounds for various PCI chipset
1084 bugs/quirks. Disable this only if your target machine is
1085 unaffected by PCI quirks.
1089 bool "Enable SLUB debugging support" if EMBEDDED
1090 depends on SLUB && SYSFS
1092 SLUB has extensive debug support features. Disabling these can
1093 result in significant savings in code size. This also disables
1094 SLUB sysfs support. /sys/slab will not exist and there will be
1095 no support for cache validation etc.
1098 bool "Disable heap randomization"
1101 Randomizing heap placement makes heap exploits harder, but it
1102 also breaks ancient binaries (including anything libc5 based).
1103 This option changes the bootup default to heap randomization
1104 disabled, and can be overridden at runtime by setting
1105 /proc/sys/kernel/randomize_va_space to 2.
1107 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1110 prompt "Choose SLAB allocator"
1113 This option allows to select a slab allocator.
1118 The regular slab allocator that is established and known to work
1119 well in all environments. It organizes cache hot objects in
1120 per cpu and per node queues.
1123 bool "SLUB (Unqueued Allocator)"
1125 SLUB is a slab allocator that minimizes cache line usage
1126 instead of managing queues of cached objects (SLAB approach).
1127 Per cpu caching is realized using slabs of objects instead
1128 of queues of objects. SLUB can use memory efficiently
1129 and has enhanced diagnostics. SLUB is the default choice for
1134 bool "SLOB (Simple Allocator)"
1136 SLOB replaces the stock allocator with a drastically simpler
1137 allocator. SLOB is generally more space efficient but
1138 does not perform as well on large systems.
1142 config MMAP_ALLOW_UNINITIALIZED
1143 bool "Allow mmapped anonymous memory to be uninitialized"
1144 depends on EMBEDDED && !MMU
1147 Normally, and according to the Linux spec, anonymous memory obtained
1148 from mmap() has it's contents cleared before it is passed to
1149 userspace. Enabling this config option allows you to request that
1150 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1151 providing a huge performance boost. If this option is not enabled,
1152 then the flag will be ignored.
1154 This is taken advantage of by uClibc's malloc(), and also by
1155 ELF-FDPIC binfmt's brk and stack allocator.
1157 Because of the obvious security issues, this option should only be
1158 enabled on embedded devices where you control what is run in
1159 userspace. Since that isn't generally a problem on no-MMU systems,
1160 it is normally safe to say Y here.
1162 See Documentation/nommu-mmap.txt for more information.
1165 bool "Profiling support"
1167 Say Y here to enable the extended profiling support mechanisms used
1168 by profilers such as OProfile.
1171 # Place an empty function call at each tracepoint site. Can be
1172 # dynamically changed for a probe function.
1177 source "arch/Kconfig"
1179 endmenu # General setup
1181 config HAVE_GENERIC_DMA_COHERENT
1188 depends on SLAB || SLUB_DEBUG
1196 default 0 if BASE_FULL
1197 default 1 if !BASE_FULL
1200 bool "Enable loadable module support"
1202 Kernel modules are small pieces of compiled code which can
1203 be inserted in the running kernel, rather than being
1204 permanently built into the kernel. You use the "modprobe"
1205 tool to add (and sometimes remove) them. If you say Y here,
1206 many parts of the kernel can be built as modules (by
1207 answering M instead of Y where indicated): this is most
1208 useful for infrequently used options which are not required
1209 for booting. For more information, see the man pages for
1210 modprobe, lsmod, modinfo, insmod and rmmod.
1212 If you say Y here, you will need to run "make
1213 modules_install" to put the modules under /lib/modules/
1214 where modprobe can find them (you may need to be root to do
1221 config MODULE_FORCE_LOAD
1222 bool "Forced module loading"
1225 Allow loading of modules without version information (ie. modprobe
1226 --force). Forced module loading sets the 'F' (forced) taint flag and
1227 is usually a really bad idea.
1229 config MODULE_UNLOAD
1230 bool "Module unloading"
1232 Without this option you will not be able to unload any
1233 modules (note that some modules may not be unloadable
1234 anyway), which makes your kernel smaller, faster
1235 and simpler. If unsure, say Y.
1237 config MODULE_FORCE_UNLOAD
1238 bool "Forced module unloading"
1239 depends on MODULE_UNLOAD && EXPERIMENTAL
1241 This option allows you to force a module to unload, even if the
1242 kernel believes it is unsafe: the kernel will remove the module
1243 without waiting for anyone to stop using it (using the -f option to
1244 rmmod). This is mainly for kernel developers and desperate users.
1248 bool "Module versioning support"
1250 Usually, you have to use modules compiled with your kernel.
1251 Saying Y here makes it sometimes possible to use modules
1252 compiled for different kernels, by adding enough information
1253 to the modules to (hopefully) spot any changes which would
1254 make them incompatible with the kernel you are running. If
1257 config MODULE_SRCVERSION_ALL
1258 bool "Source checksum for all modules"
1260 Modules which contain a MODULE_VERSION get an extra "srcversion"
1261 field inserted into their modinfo section, which contains a
1262 sum of the source files which made it. This helps maintainers
1263 see exactly which source was used to build a module (since
1264 others sometimes change the module source without updating
1265 the version). With this option, such a "srcversion" field
1266 will be created for all modules. If unsure, say N.
1270 config INIT_ALL_POSSIBLE
1273 Back when each arch used to define their own cpu_online_map and
1274 cpu_possible_map, some of them chose to initialize cpu_possible_map
1275 with all 1s, and others with all 0s. When they were centralised,
1276 it was better to provide this option than to break all the archs
1277 and have several arch maintainers pursuing me down dark alleys.
1282 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1284 Need stop_machine() primitive.
1286 source "block/Kconfig"
1288 config PREEMPT_NOTIFIERS
1295 source "kernel/Kconfig.locks"