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"
22 bool "Prompt for development and/or incomplete code/drivers"
24 Some of the various things that Linux supports (such as network
25 drivers, file systems, network protocols, etc.) can be in a state
26 of development where the functionality, stability, or the level of
27 testing is not yet high enough for general use. This is usually
28 known as the "alpha-test" phase among developers. If a feature is
29 currently in alpha-test, then the developers usually discourage
30 uninformed widespread use of this feature by the general public to
31 avoid "Why doesn't this work?" type mail messages. However, active
32 testing and use of these systems is welcomed. Just be aware that it
33 may not meet the normal level of reliability or it may fail to work
34 in some special cases. Detailed bug reports from people familiar
35 with the kernel internals are usually welcomed by the developers
36 (before submitting bug reports, please read the documents
37 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
38 <file:Documentation/BUG-HUNTING>, and
39 <file:Documentation/oops-tracing.txt> in the kernel source).
41 This option will also make obsoleted drivers available. These are
42 drivers that have been replaced by something else, and/or are
43 scheduled to be removed in a future kernel release.
45 Unless you intend to help test and develop a feature or driver that
46 falls into this category, or you have a situation that requires
47 using these features, you should probably say N here, which will
48 cause the configurator to present you with fewer choices. If
49 you say Y here, you will be offered the choice of using features or
50 drivers that are currently considered to be in the alpha-test phase.
57 depends on BROKEN || !SMP
62 depends on SMP || PREEMPT
65 config INIT_ENV_ARG_LIMIT
70 Maximum of each of the number of arguments and environment
71 variables passed to init from the kernel command line.
75 string "Local version - append to kernel release"
77 Append an extra string to the end of your kernel version.
78 This will show up when you type uname, for example.
79 The string you set here will be appended after the contents of
80 any files with a filename matching localversion* in your
81 object and source tree, in that order. Your total string can
82 be a maximum of 64 characters.
84 config LOCALVERSION_AUTO
85 bool "Automatically append version information to the version string"
88 This will try to automatically determine if the current tree is a
89 release tree by looking for git tags that belong to the current
92 A string of the format -gxxxxxxxx will be added to the localversion
93 if a git-based tree is found. The string generated by this will be
94 appended after any matching localversion* files, and after the value
95 set in CONFIG_LOCALVERSION.
97 (The actual string used here is the first eight characters produced
98 by running the command:
100 $ git rev-parse --verify HEAD
102 which is done within the script "scripts/setlocalversion".)
104 config HAVE_KERNEL_GZIP
107 config HAVE_KERNEL_BZIP2
110 config HAVE_KERNEL_LZMA
114 prompt "Kernel compression mode"
116 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
118 The linux kernel is a kind of self-extracting executable.
119 Several compression algorithms are available, which differ
120 in efficiency, compression and decompression speed.
121 Compression speed is only relevant when building a kernel.
122 Decompression speed is relevant at each boot.
124 If you have any problems with bzip2 or lzma compressed
125 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
126 version of this functionality (bzip2 only), for 2.4, was
127 supplied by Christian Ludwig)
129 High compression options are mostly useful for users, who
130 are low on disk space (embedded systems), but for whom ram
133 If in doubt, select 'gzip'
137 depends on HAVE_KERNEL_GZIP
139 The old and tried gzip compression. Its compression ratio is
140 the poorest among the 3 choices; however its speed (both
141 compression and decompression) is the fastest.
145 depends on HAVE_KERNEL_BZIP2
147 Its compression ratio and speed is intermediate.
148 Decompression speed is slowest among the three. The kernel
149 size is about 10% smaller with bzip2, in comparison to gzip.
150 Bzip2 uses a large amount of memory. For modern kernels you
151 will need at least 8MB RAM or more for booting.
155 depends on HAVE_KERNEL_LZMA
157 The most recent compression algorithm.
158 Its ratio is best, decompression speed is between the other
159 two. Compression is slowest. The kernel size is about 33%
160 smaller with LZMA in comparison to gzip.
165 bool "Support for paging of anonymous memory (swap)"
166 depends on MMU && BLOCK
169 This option allows you to choose whether you want to have support
170 for so called swap devices or swap files in your kernel that are
171 used to provide more virtual memory than the actual RAM present
172 in your computer. If unsure say Y.
177 Inter Process Communication is a suite of library functions and
178 system calls which let processes (running programs) synchronize and
179 exchange information. It is generally considered to be a good thing,
180 and some programs won't run unless you say Y here. In particular, if
181 you want to run the DOS emulator dosemu under Linux (read the
182 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
183 you'll need to say Y here.
185 You can find documentation about IPC with "info ipc" and also in
186 section 6.4 of the Linux Programmer's Guide, available from
187 <http://www.tldp.org/guides.html>.
189 config SYSVIPC_SYSCTL
196 bool "POSIX Message Queues"
197 depends on NET && EXPERIMENTAL
199 POSIX variant of message queues is a part of IPC. In POSIX message
200 queues every message has a priority which decides about succession
201 of receiving it by a process. If you want to compile and run
202 programs written e.g. for Solaris with use of its POSIX message
203 queues (functions mq_*) say Y here.
205 POSIX message queues are visible as a filesystem called 'mqueue'
206 and can be mounted somewhere if you want to do filesystem
207 operations on message queues.
211 config BSD_PROCESS_ACCT
212 bool "BSD Process Accounting"
214 If you say Y here, a user level program will be able to instruct the
215 kernel (via a special system call) to write process accounting
216 information to a file: whenever a process exits, information about
217 that process will be appended to the file by the kernel. The
218 information includes things such as creation time, owning user,
219 command name, memory usage, controlling terminal etc. (the complete
220 list is in the struct acct in <file:include/linux/acct.h>). It is
221 up to the user level program to do useful things with this
222 information. This is generally a good idea, so say Y.
224 config BSD_PROCESS_ACCT_V3
225 bool "BSD Process Accounting version 3 file format"
226 depends on BSD_PROCESS_ACCT
229 If you say Y here, the process accounting information is written
230 in a new file format that also logs the process IDs of each
231 process and it's parent. Note that this file format is incompatible
232 with previous v0/v1/v2 file formats, so you will need updated tools
233 for processing it. A preliminary version of these tools is available
234 at <http://www.gnu.org/software/acct/>.
237 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
241 Export selected statistics for tasks/processes through the
242 generic netlink interface. Unlike BSD process accounting, the
243 statistics are available during the lifetime of tasks/processes as
244 responses to commands. Like BSD accounting, they are sent to user
249 config TASK_DELAY_ACCT
250 bool "Enable per-task delay accounting (EXPERIMENTAL)"
253 Collect information on time spent by a task waiting for system
254 resources like cpu, synchronous block I/O completion and swapping
255 in pages. Such statistics can help in setting a task's priorities
256 relative to other tasks for cpu, io, rss limits etc.
261 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
264 Collect extended task accounting data and send the data
265 to userland for processing over the taskstats interface.
269 config TASK_IO_ACCOUNTING
270 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
271 depends on TASK_XACCT
273 Collect information on the number of bytes of storage I/O which this
279 bool "Auditing support"
282 Enable auditing infrastructure that can be used with another
283 kernel subsystem, such as SELinux (which requires this for
284 logging of avc messages output). Does not do system-call
285 auditing without CONFIG_AUDITSYSCALL.
288 bool "Enable system-call auditing support"
289 depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
290 default y if SECURITY_SELINUX
292 Enable low-overhead system-call auditing infrastructure that
293 can be used independently or with another kernel subsystem,
294 such as SELinux. To use audit's filesystem watch feature, please
295 ensure that INOTIFY is configured.
299 depends on AUDITSYSCALL && INOTIFY
302 tristate "Kernel .config support"
304 This option enables the complete Linux kernel ".config" file
305 contents to be saved in the kernel. It provides documentation
306 of which kernel options are used in a running kernel or in an
307 on-disk kernel. This information can be extracted from the kernel
308 image file with the script scripts/extract-ikconfig and used as
309 input to rebuild the current kernel or to build another kernel.
310 It can also be extracted from a running kernel by reading
311 /proc/config.gz if enabled (below).
314 bool "Enable access to .config through /proc/config.gz"
315 depends on IKCONFIG && PROC_FS
317 This option enables access to the kernel configuration file
318 through /proc/config.gz.
321 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
325 Select kernel log buffer size as a power of 2.
335 bool "Control Group support"
337 This option will let you use process cgroup subsystems
343 bool "Example debug cgroup subsystem"
347 This option enables a simple cgroup subsystem that
348 exports useful debugging information about the cgroups
354 bool "Namespace cgroup subsystem"
357 Provides a simple namespace cgroup subsystem to
358 provide hierarchical naming of sets of namespaces,
359 for instance virtual servers and checkpoint/restart
362 config CGROUP_FREEZER
363 bool "control group freezer subsystem"
366 Provides a way to freeze and unfreeze all tasks in a
370 bool "Device controller for cgroups"
371 depends on CGROUPS && EXPERIMENTAL
373 Provides a cgroup implementing whitelists for devices which
374 a process in the cgroup can mknod or open.
377 bool "Cpuset support"
378 depends on SMP && CGROUPS
380 This option will let you create and manage CPUSETs which
381 allow dynamically partitioning a system into sets of CPUs and
382 Memory Nodes and assigning tasks to run only within those sets.
383 This is primarily useful on large SMP or NUMA systems.
388 # Architectures with an unreliable sched_clock() should select this:
390 config HAVE_UNSTABLE_SCHED_CLOCK
394 bool "Group CPU scheduler"
395 depends on EXPERIMENTAL
398 This feature lets CPU scheduler recognize task groups and control CPU
399 bandwidth allocation to such task groups.
401 config FAIR_GROUP_SCHED
402 bool "Group scheduling for SCHED_OTHER"
403 depends on GROUP_SCHED
406 config RT_GROUP_SCHED
407 bool "Group scheduling for SCHED_RR/FIFO"
408 depends on EXPERIMENTAL
409 depends on GROUP_SCHED
412 This feature lets you explicitly allocate real CPU bandwidth
413 to users or control groups (depending on the "Basis for grouping tasks"
414 setting below. If enabled, it will also make it impossible to
415 schedule realtime tasks for non-root users until you allocate
416 realtime bandwidth for them.
417 See Documentation/scheduler/sched-rt-group.txt for more information.
420 depends on GROUP_SCHED
421 prompt "Basis for grouping tasks"
427 This option will choose userid as the basis for grouping
428 tasks, thus providing equal CPU bandwidth to each user.
431 bool "Control groups"
434 This option allows you to create arbitrary task groups
435 using the "cgroup" pseudo filesystem and control
436 the cpu bandwidth allocated to each such task group.
437 Refer to Documentation/cgroups.txt for more information
438 on "cgroup" pseudo filesystem.
442 config CGROUP_CPUACCT
443 bool "Simple CPU accounting cgroup subsystem"
446 Provides a simple Resource Controller for monitoring the
447 total CPU consumed by the tasks in a cgroup
449 config RESOURCE_COUNTERS
450 bool "Resource counters"
452 This option enables controller independent resource accounting
453 infrastructure that works with cgroups
459 config CGROUP_MEM_RES_CTLR
460 bool "Memory Resource Controller for Control Groups"
461 depends on CGROUPS && RESOURCE_COUNTERS
464 Provides a memory resource controller that manages both anonymous
465 memory and page cache. (See Documentation/controllers/memory.txt)
467 Note that setting this option increases fixed memory overhead
468 associated with each page of memory in the system. By this,
469 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
470 usage tracking struct at boot. Total amount of this is printed out
473 Only enable when you're ok with these trade offs and really
474 sure you need the memory resource controller. Even when you enable
475 this, you can set "cgroup_disable=memory" at your boot option to
476 disable memory resource controller and you can avoid overheads.
477 (and lose benefits of memory resource contoller)
479 This config option also selects MM_OWNER config option, which
480 could in turn add some fork/exit overhead.
482 config SYSFS_DEPRECATED
485 config SYSFS_DEPRECATED_V2
486 bool "Create deprecated sysfs files"
489 select SYSFS_DEPRECATED
491 This option creates deprecated symlinks such as the
492 "device"-link, the <subsystem>:<name>-link, and the
493 "bus"-link. It may also add deprecated key in the
495 None of these features or values should be used today, as
496 they export driver core implementation details to userspace
497 or export properties which can't be kept stable across kernel
500 If enabled, this option will also move any device structures
501 that belong to a class, back into the /sys/class hierarchy, in
502 order to support older versions of udev and some userspace
505 If you are using a distro with the most recent userspace
506 packages, it should be safe to say N here.
508 config PROC_PID_CPUSET
509 bool "Include legacy /proc/<pid>/cpuset file"
514 bool "Kernel->user space relay support (formerly relayfs)"
516 This option enables support for relay interface support in
517 certain file systems (such as debugfs).
518 It is designed to provide an efficient mechanism for tools and
519 facilities to relay large amounts of data from kernel space to
525 bool "Namespaces support" if EMBEDDED
528 Provides the way to make tasks work with different objects using
529 the same id. For example same IPC id may refer to different objects
530 or same user id or pid may refer to different tasks when used in
531 different namespaces.
535 depends on NAMESPACES
537 In this namespace tasks see different info provided with the
542 depends on NAMESPACES && SYSVIPC
544 In this namespace tasks work with IPC ids which correspond to
545 different IPC objects in different namespaces
548 bool "User namespace (EXPERIMENTAL)"
549 depends on NAMESPACES && EXPERIMENTAL
551 This allows containers, i.e. vservers, to use user namespaces
552 to provide different user info for different servers.
556 bool "PID Namespaces (EXPERIMENTAL)"
558 depends on NAMESPACES && EXPERIMENTAL
560 Support process id namespaces. This allows having multiple
561 process with the same pid as long as they are in different
562 pid namespaces. This is a building block of containers.
564 Unless you want to work with an experimental feature
567 config BLK_DEV_INITRD
568 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
569 depends on BROKEN || !FRV
571 The initial RAM filesystem is a ramfs which is loaded by the
572 boot loader (loadlin or lilo) and that is mounted as root
573 before the normal boot procedure. It is typically used to
574 load modules needed to mount the "real" root file system,
575 etc. See <file:Documentation/initrd.txt> for details.
577 If RAM disk support (BLK_DEV_RAM) is also included, this
578 also enables initial RAM disk (initrd) support and adds
579 15 Kbytes (more on some other architectures) to the kernel size.
589 config CC_OPTIMIZE_FOR_SIZE
590 bool "Optimize for size"
593 Enabling this option will pass "-Os" instead of "-O2" to gcc
594 resulting in a smaller kernel.
602 bool "Configure standard kernel features (for small systems)"
604 This option allows certain base kernel options and settings
605 to be disabled or tweaked. This is for specialized
606 environments which can tolerate a "non-standard" kernel.
607 Only use this if you really know what you are doing.
610 bool "Enable 16-bit UID system calls" if EMBEDDED
611 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
614 This enables the legacy 16-bit UID syscall wrappers.
616 config SYSCTL_SYSCALL
617 bool "Sysctl syscall support" if EMBEDDED
621 sys_sysctl uses binary paths that have been found challenging
622 to properly maintain and use. The interface in /proc/sys
623 using paths with ascii names is now the primary path to this
626 Almost nothing using the binary sysctl interface so if you are
627 trying to save some space it is probably safe to disable this,
628 making your kernel marginally smaller.
630 If unsure say Y here.
633 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
636 Say Y here to let the kernel print out symbolic crash information and
637 symbolic stack backtraces. This increases the size of the kernel
638 somewhat, as all symbols have to be loaded into the kernel image.
641 bool "Include all symbols in kallsyms"
642 depends on DEBUG_KERNEL && KALLSYMS
644 Normally kallsyms only contains the symbols of functions, for nicer
645 OOPS messages. Some debuggers can use kallsyms for other
646 symbols too: say Y here to include all symbols, if you need them
647 and you don't care about adding 300k to the size of your kernel.
651 config KALLSYMS_STRIP_GENERATED
652 bool "Strip machine generated symbols from kallsyms"
653 depends on KALLSYMS_ALL
656 Say N if you want kallsyms to retain even machine generated symbols.
658 config KALLSYMS_EXTRA_PASS
659 bool "Do an extra kallsyms pass"
662 If kallsyms is not working correctly, the build will fail with
663 inconsistent kallsyms data. If that occurs, log a bug report and
664 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
665 Always say N here unless you find a bug in kallsyms, which must be
666 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
667 you wait for kallsyms to be fixed.
671 bool "Support for hot-pluggable devices" if EMBEDDED
674 This option is provided for the case where no hotplug or uevent
675 capabilities is wanted by the kernel. You should only consider
676 disabling this option for embedded systems that do not use modules, a
677 dynamic /dev tree, or dynamic device discovery. Just say Y.
681 bool "Enable support for printk" if EMBEDDED
683 This option enables normal printk support. Removing it
684 eliminates most of the message strings from the kernel image
685 and makes the kernel more or less silent. As this makes it
686 very difficult to diagnose system problems, saying N here is
687 strongly discouraged.
690 bool "BUG() support" if EMBEDDED
693 Disabling this option eliminates support for BUG and WARN, reducing
694 the size of your kernel image and potentially quietly ignoring
695 numerous fatal conditions. You should only consider disabling this
696 option for embedded systems with no facilities for reporting errors.
701 bool "Enable ELF core dumps" if EMBEDDED
703 Enable support for generating core dumps. Disabling saves about 4k.
705 config PCSPKR_PLATFORM
706 bool "Enable PC-Speaker support" if EMBEDDED
707 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
710 This option allows to disable the internal PC-Speaker
711 support, saving some memory.
714 bool "Disable heap randomization"
717 Randomizing heap placement makes heap exploits harder, but it
718 also breaks ancient binaries (including anything libc5 based).
719 This option changes the bootup default to heap randomization
720 disabled, and can be overriden runtime by setting
721 /proc/sys/kernel/randomize_va_space to 2.
723 On non-ancient distros (post-2000 ones) N is usually a safe choice.
727 bool "Enable full-sized data structures for core" if EMBEDDED
729 Disabling this option reduces the size of miscellaneous core
730 kernel data structures. This saves memory on small machines,
731 but may reduce performance.
734 bool "Enable futex support" if EMBEDDED
738 Disabling this option will cause the kernel to be built without
739 support for "fast userspace mutexes". The resulting kernel may not
740 run glibc-based applications correctly.
746 bool "Enable eventpoll support" if EMBEDDED
750 Disabling this option will cause the kernel to be built without
751 support for epoll family of system calls.
754 bool "Enable signalfd() system call" if EMBEDDED
758 Enable the signalfd() system call that allows to receive signals
759 on a file descriptor.
764 bool "Enable timerfd() system call" if EMBEDDED
768 Enable the timerfd() system call that allows to receive timer
769 events on a file descriptor.
774 bool "Enable eventfd() system call" if EMBEDDED
778 Enable the eventfd() system call that allows to receive both
779 kernel notification (ie. KAIO) or userspace notifications.
784 bool "Use full shmem filesystem" if EMBEDDED
788 The shmem is an internal filesystem used to manage shared memory.
789 It is backed by swap and manages resource limits. It is also exported
790 to userspace as tmpfs if TMPFS is enabled. Disabling this
791 option replaces shmem and tmpfs with the much simpler ramfs code,
792 which may be appropriate on small systems without swap.
795 bool "Enable AIO support" if EMBEDDED
798 This option enables POSIX asynchronous I/O which may by used
799 by some high performance threaded applications. Disabling
800 this option saves about 7k.
802 config VM_EVENT_COUNTERS
804 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
806 VM event counters are needed for event counts to be shown.
807 This option allows the disabling of the VM event counters
808 on EMBEDDED systems. /proc/vmstat will only show page counts
809 if VM event counters are disabled.
813 bool "Enable PCI quirk workarounds" if EMBEDDED
816 This enables workarounds for various PCI chipset
817 bugs/quirks. Disable this only if your target machine is
818 unaffected by PCI quirks.
822 bool "Enable SLUB debugging support" if EMBEDDED
823 depends on SLUB && SYSFS
825 SLUB has extensive debug support features. Disabling these can
826 result in significant savings in code size. This also disables
827 SLUB sysfs support. /sys/slab will not exist and there will be
828 no support for cache validation etc.
831 prompt "Choose SLAB allocator"
834 This option allows to select a slab allocator.
839 The regular slab allocator that is established and known to work
840 well in all environments. It organizes cache hot objects in
841 per cpu and per node queues.
844 bool "SLUB (Unqueued Allocator)"
846 SLUB is a slab allocator that minimizes cache line usage
847 instead of managing queues of cached objects (SLAB approach).
848 Per cpu caching is realized using slabs of objects instead
849 of queues of objects. SLUB can use memory efficiently
850 and has enhanced diagnostics. SLUB is the default choice for
855 bool "SLOB (Simple Allocator)"
857 SLOB replaces the stock allocator with a drastically simpler
858 allocator. SLOB is generally more space efficient but
859 does not perform as well on large systems.
864 bool "Profiling support (EXPERIMENTAL)"
866 Say Y here to enable the extended profiling support mechanisms used
867 by profilers such as OProfile.
870 # Place an empty function call at each tracepoint site. Can be
871 # dynamically changed for a probe function.
877 bool "Activate markers"
878 depends on TRACEPOINTS
880 Place an empty function call at each marker site. Can be
881 dynamically changed for a probe function.
883 source "arch/Kconfig"
885 endmenu # General setup
887 config HAVE_GENERIC_DMA_COHERENT
894 depends on SLAB || SLUB_DEBUG
907 default 0 if BASE_FULL
908 default 1 if !BASE_FULL
911 bool "Enable loadable module support"
913 Kernel modules are small pieces of compiled code which can
914 be inserted in the running kernel, rather than being
915 permanently built into the kernel. You use the "modprobe"
916 tool to add (and sometimes remove) them. If you say Y here,
917 many parts of the kernel can be built as modules (by
918 answering M instead of Y where indicated): this is most
919 useful for infrequently used options which are not required
920 for booting. For more information, see the man pages for
921 modprobe, lsmod, modinfo, insmod and rmmod.
923 If you say Y here, you will need to run "make
924 modules_install" to put the modules under /lib/modules/
925 where modprobe can find them (you may need to be root to do
932 config MODULE_FORCE_LOAD
933 bool "Forced module loading"
936 Allow loading of modules without version information (ie. modprobe
937 --force). Forced module loading sets the 'F' (forced) taint flag and
938 is usually a really bad idea.
941 bool "Module unloading"
943 Without this option you will not be able to unload any
944 modules (note that some modules may not be unloadable
945 anyway), which makes your kernel smaller, faster
946 and simpler. If unsure, say Y.
948 config MODULE_FORCE_UNLOAD
949 bool "Forced module unloading"
950 depends on MODULE_UNLOAD && EXPERIMENTAL
952 This option allows you to force a module to unload, even if the
953 kernel believes it is unsafe: the kernel will remove the module
954 without waiting for anyone to stop using it (using the -f option to
955 rmmod). This is mainly for kernel developers and desperate users.
959 bool "Module versioning support"
961 Usually, you have to use modules compiled with your kernel.
962 Saying Y here makes it sometimes possible to use modules
963 compiled for different kernels, by adding enough information
964 to the modules to (hopefully) spot any changes which would
965 make them incompatible with the kernel you are running. If
968 config MODULE_SRCVERSION_ALL
969 bool "Source checksum for all modules"
971 Modules which contain a MODULE_VERSION get an extra "srcversion"
972 field inserted into their modinfo section, which contains a
973 sum of the source files which made it. This helps maintainers
974 see exactly which source was used to build a module (since
975 others sometimes change the module source without updating
976 the version). With this option, such a "srcversion" field
977 will be created for all modules. If unsure, say N.
982 This is being removed soon. These days, CONFIG_MODULES
983 implies CONFIG_KMOD, so use that instead.
987 config INIT_ALL_POSSIBLE
990 Back when each arch used to define their own cpu_online_map and
991 cpu_possible_map, some of them chose to initialize cpu_possible_map
992 with all 1s, and others with all 0s. When they were centralised,
993 it was better to provide this option than to break all the archs
994 and have several arch maintainers persuing me down dark alleys.
999 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1001 Need stop_machine() primitive.
1003 source "block/Kconfig"
1005 config PREEMPT_NOTIFIERS
1009 prompt "RCU Implementation"
1015 This option selects the classic RCU implementation that is
1016 designed for best read-side performance on non-realtime
1019 Select this option if you are unsure.
1022 bool "Tree-based hierarchical RCU"
1024 This option selects the RCU implementation that is
1025 designed for very large SMP system with hundreds or
1029 bool "Preemptible RCU"
1032 This option reduces the latency of the kernel by making certain
1033 RCU sections preemptible. Normally RCU code is non-preemptible, if
1034 this option is selected then read-only RCU sections become
1035 preemptible. This helps latency, but may expose bugs due to
1036 now-naive assumptions about each RCU read-side critical section
1037 remaining on a given CPU through its execution.
1042 bool "Enable tracing for RCU"
1043 depends on TREE_RCU || PREEMPT_RCU
1045 This option provides tracing in RCU which presents stats
1046 in debugfs for debugging RCU implementation.
1048 Say Y here if you want to enable RCU tracing
1049 Say N if you are unsure.
1052 int "Tree-based hierarchical RCU fanout value"
1054 range 2 32 if !64BIT
1057 default 32 if !64BIT
1059 This option controls the fanout of hierarchical implementations
1060 of RCU, allowing RCU to work efficiently on machines with
1061 large numbers of CPUs. This value must be at least the cube
1062 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
1063 systems and up to 262,144 for 64-bit systems.
1065 Select a specific number if testing RCU itself.
1066 Take the default if unsure.
1068 config RCU_FANOUT_EXACT
1069 bool "Disable tree-based hierarchical RCU auto-balancing"
1073 This option forces use of the exact RCU_FANOUT value specified,
1074 regardless of imbalances in the hierarchy. This is useful for
1075 testing RCU itself, and might one day be useful on systems with
1076 strong NUMA behavior.
1078 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
1082 config TREE_RCU_TRACE
1083 def_bool RCU_TRACE && TREE_RCU
1086 This option provides tracing for the TREE_RCU implementation,
1087 permitting Makefile to trivially select kernel/rcutree_trace.c.
1089 config PREEMPT_RCU_TRACE
1090 def_bool RCU_TRACE && PREEMPT_RCU
1093 This option provides tracing for the PREEMPT_RCU implementation,
1094 permitting Makefile to trivially select kernel/rcupreempt_trace.c.