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54 drivers that have been replaced by something else, and/or are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
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 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
345 prompt "RCU Implementation"
349 bool "Tree-based hierarchical RCU"
350 depends on !PREEMPT && SMP
352 This option selects the RCU implementation that is
353 designed for very large SMP system with hundreds or
354 thousands of CPUs. It also scales down nicely to
357 config TREE_PREEMPT_RCU
358 bool "Preemptible tree-based hierarchical RCU"
361 This option selects the RCU implementation that is
362 designed for very large SMP systems with hundreds or
363 thousands of CPUs, but for which real-time response
364 is also required. It also scales down nicely to
368 bool "UP-only small-memory-footprint RCU"
371 This option selects the RCU implementation that is
372 designed for UP systems from which real-time response
373 is not required. This option greatly reduces the
374 memory footprint of RCU.
376 config TINY_PREEMPT_RCU
377 bool "Preemptible UP-only small-memory-footprint RCU"
378 depends on !SMP && PREEMPT
380 This option selects the RCU implementation that is designed
381 for real-time UP systems. This option greatly reduces the
382 memory footprint of RCU.
387 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
389 This option enables preemptible-RCU code that is common between
390 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
393 bool "Enable tracing for RCU"
394 depends on TREE_RCU || TREE_PREEMPT_RCU
396 This option provides tracing in RCU which presents stats
397 in debugfs for debugging RCU implementation.
399 Say Y here if you want to enable RCU tracing
400 Say N if you are unsure.
403 int "Tree-based hierarchical RCU fanout value"
406 depends on TREE_RCU || TREE_PREEMPT_RCU
410 This option controls the fanout of hierarchical implementations
411 of RCU, allowing RCU to work efficiently on machines with
412 large numbers of CPUs. This value must be at least the fourth
413 root of NR_CPUS, which allows NR_CPUS to be insanely large.
414 The default value of RCU_FANOUT should be used for production
415 systems, but if you are stress-testing the RCU implementation
416 itself, small RCU_FANOUT values allow you to test large-system
417 code paths on small(er) systems.
419 Select a specific number if testing RCU itself.
420 Take the default if unsure.
422 config RCU_FANOUT_EXACT
423 bool "Disable tree-based hierarchical RCU auto-balancing"
424 depends on TREE_RCU || TREE_PREEMPT_RCU
427 This option forces use of the exact RCU_FANOUT value specified,
428 regardless of imbalances in the hierarchy. This is useful for
429 testing RCU itself, and might one day be useful on systems with
430 strong NUMA behavior.
432 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
436 config RCU_FAST_NO_HZ
437 bool "Accelerate last non-dyntick-idle CPU's grace periods"
438 depends on TREE_RCU && NO_HZ && SMP
441 This option causes RCU to attempt to accelerate grace periods
442 in order to allow the final CPU to enter dynticks-idle state
443 more quickly. On the other hand, this option increases the
444 overhead of the dynticks-idle checking, particularly on systems
445 with large numbers of CPUs.
447 Say Y if energy efficiency is critically important, particularly
448 if you have relatively few CPUs.
450 Say N if you are unsure.
452 config TREE_RCU_TRACE
453 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
456 This option provides tracing for the TREE_RCU and
457 TREE_PREEMPT_RCU implementations, permitting Makefile to
458 trivially select kernel/rcutree_trace.c.
460 endmenu # "RCU Subsystem"
463 tristate "Kernel .config support"
465 This option enables the complete Linux kernel ".config" file
466 contents to be saved in the kernel. It provides documentation
467 of which kernel options are used in a running kernel or in an
468 on-disk kernel. This information can be extracted from the kernel
469 image file with the script scripts/extract-ikconfig and used as
470 input to rebuild the current kernel or to build another kernel.
471 It can also be extracted from a running kernel by reading
472 /proc/config.gz if enabled (below).
475 bool "Enable access to .config through /proc/config.gz"
476 depends on IKCONFIG && PROC_FS
478 This option enables access to the kernel configuration file
479 through /proc/config.gz.
482 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
486 Select kernel log buffer size as a power of 2.
496 # Architectures with an unreliable sched_clock() should select this:
498 config HAVE_UNSTABLE_SCHED_CLOCK
502 boolean "Control Group support"
505 This option adds support for grouping sets of processes together, for
506 use with process control subsystems such as Cpusets, CFS, memory
507 controls or device isolation.
509 - Documentation/scheduler/sched-design-CFS.txt (CFS)
510 - Documentation/cgroups/ (features for grouping, isolation
511 and resource control)
518 bool "Example debug cgroup subsystem"
522 This option enables a simple cgroup subsystem that
523 exports useful debugging information about the cgroups
529 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"
541 Provides a way to freeze and unfreeze all tasks in a
545 bool "Device controller for cgroups"
546 depends on CGROUPS && EXPERIMENTAL
548 Provides a cgroup implementing whitelists for devices which
549 a process in the cgroup can mknod or open.
552 bool "Cpuset support"
555 This option will let you create and manage CPUSETs which
556 allow dynamically partitioning a system into sets of CPUs and
557 Memory Nodes and assigning tasks to run only within those sets.
558 This is primarily useful on large SMP or NUMA systems.
562 config PROC_PID_CPUSET
563 bool "Include legacy /proc/<pid>/cpuset file"
567 config CGROUP_CPUACCT
568 bool "Simple CPU accounting cgroup subsystem"
571 Provides a simple Resource Controller for monitoring the
572 total CPU consumed by the tasks in a cgroup.
574 config RESOURCE_COUNTERS
575 bool "Resource counters"
577 This option enables controller independent resource accounting
578 infrastructure that works with cgroups.
581 config CGROUP_MEM_RES_CTLR
582 bool "Memory Resource Controller for Control Groups"
583 depends on CGROUPS && RESOURCE_COUNTERS
586 Provides a memory resource controller that manages both anonymous
587 memory and page cache. (See Documentation/cgroups/memory.txt)
589 Note that setting this option increases fixed memory overhead
590 associated with each page of memory in the system. By this,
591 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
592 usage tracking struct at boot. Total amount of this is printed out
595 Only enable when you're ok with these trade offs and really
596 sure you need the memory resource controller. Even when you enable
597 this, you can set "cgroup_disable=memory" at your boot option to
598 disable memory resource controller and you can avoid overheads.
599 (and lose benefits of memory resource controller)
601 This config option also selects MM_OWNER config option, which
602 could in turn add some fork/exit overhead.
604 config CGROUP_MEM_RES_CTLR_SWAP
605 bool "Memory Resource Controller Swap Extension"
606 depends on CGROUP_MEM_RES_CTLR && SWAP
608 Add swap management feature to memory resource controller. When you
609 enable this, you can limit mem+swap usage per cgroup. In other words,
610 when you disable this, memory resource controller has no cares to
611 usage of swap...a process can exhaust all of the swap. This extension
612 is useful when you want to avoid exhaustion swap but this itself
613 adds more overheads and consumes memory for remembering information.
614 Especially if you use 32bit system or small memory system, please
615 be careful about enabling this. When memory resource controller
616 is disabled by boot option, this will be automatically disabled and
617 there will be no overhead from this. Even when you set this config=y,
618 if boot option "noswapaccount" is set, swap will not be accounted.
619 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
620 size is 4096bytes, 512k per 1Gbytes of swap.
622 menuconfig CGROUP_SCHED
623 bool "Group CPU scheduler"
624 depends on EXPERIMENTAL && CGROUPS
627 This feature lets CPU scheduler recognize task groups and control CPU
628 bandwidth allocation to such task groups. It uses cgroups to group
632 config FAIR_GROUP_SCHED
633 bool "Group scheduling for SCHED_OTHER"
634 depends on CGROUP_SCHED
637 config RT_GROUP_SCHED
638 bool "Group scheduling for SCHED_RR/FIFO"
639 depends on EXPERIMENTAL
640 depends on CGROUP_SCHED
643 This feature lets you explicitly allocate real CPU bandwidth
644 to task groups. If enabled, it will also make it impossible to
645 schedule realtime tasks for non-root users until you allocate
646 realtime bandwidth for them.
647 See Documentation/scheduler/sched-rt-group.txt for more information.
652 tristate "Block IO controller"
653 depends on CGROUPS && BLOCK
656 Generic block IO controller cgroup interface. This is the common
657 cgroup interface which should be used by various IO controlling
660 Currently, CFQ IO scheduler uses it to recognize task groups and
661 control disk bandwidth allocation (proportional time slice allocation)
664 This option only enables generic Block IO controller infrastructure.
665 One needs to also enable actual IO controlling logic in CFQ for it
666 to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
668 See Documentation/cgroups/blkio-controller.txt for more information.
670 config DEBUG_BLK_CGROUP
671 bool "Enable Block IO controller debugging"
672 depends on BLK_CGROUP
675 Enable some debugging help. Currently it exports additional stat
676 files in a cgroup which can be useful for debugging.
683 config SYSFS_DEPRECATED
686 config SYSFS_DEPRECATED_V2
687 bool "enable deprecated sysfs features to support old userspace tools"
690 select SYSFS_DEPRECATED
692 This option switches the layout of sysfs to the deprecated
693 version. Do not use it on recent distributions.
695 The current sysfs layout features a unified device tree at
696 /sys/devices/, which is able to express a hierarchy between
697 class devices. If the deprecated option is set to Y, the
698 unified device tree is split into a bus device tree at
699 /sys/devices/ and several individual class device trees at
700 /sys/class/. The class and bus devices will be connected by
701 "<subsystem>:<name>" and the "device" links. The "block"
702 class devices, will not show up in /sys/class/block/. Some
703 subsystems will suppress the creation of some devices which
704 depend on the unified device tree.
706 This option is not a pure compatibility option that can
707 be safely enabled on newer distributions. It will change the
708 layout of sysfs to the non-extensible deprecated version,
709 and disable some features, which can not be exported without
710 confusing older userspace tools. Since 2007/2008 all major
711 distributions do not enable this option, and ship no tools which
712 depend on the deprecated layout or this option.
714 If you are using a new kernel on an older distribution, or use
715 older userspace tools, you might need to say Y here. Do not say Y,
716 if the original kernel, that came with your distribution, has
717 this option set to N.
720 bool "Kernel->user space relay support (formerly relayfs)"
722 This option enables support for relay interface support in
723 certain file systems (such as debugfs).
724 It is designed to provide an efficient mechanism for tools and
725 facilities to relay large amounts of data from kernel space to
731 bool "Namespaces support" if EMBEDDED
734 Provides the way to make tasks work with different objects using
735 the same id. For example same IPC id may refer to different objects
736 or same user id or pid may refer to different tasks when used in
737 different namespaces.
741 depends on NAMESPACES
743 In this namespace tasks see different info provided with the
748 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
750 In this namespace tasks work with IPC ids which correspond to
751 different IPC objects in different namespaces.
754 bool "User namespace (EXPERIMENTAL)"
755 depends on NAMESPACES && EXPERIMENTAL
757 This allows containers, i.e. vservers, to use user namespaces
758 to provide different user info for different servers.
762 bool "PID Namespaces (EXPERIMENTAL)"
764 depends on NAMESPACES && EXPERIMENTAL
766 Support process id namespaces. This allows having multiple
767 processes with the same pid as long as they are in different
768 pid namespaces. This is a building block of containers.
770 Unless you want to work with an experimental feature
774 bool "Network namespace"
776 depends on NAMESPACES && EXPERIMENTAL && NET
778 Allow user space to create what appear to be multiple instances
779 of the network stack.
781 config BLK_DEV_INITRD
782 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
783 depends on BROKEN || !FRV
785 The initial RAM filesystem is a ramfs which is loaded by the
786 boot loader (loadlin or lilo) and that is mounted as root
787 before the normal boot procedure. It is typically used to
788 load modules needed to mount the "real" root file system,
789 etc. See <file:Documentation/initrd.txt> for details.
791 If RAM disk support (BLK_DEV_RAM) is also included, this
792 also enables initial RAM disk (initrd) support and adds
793 15 Kbytes (more on some other architectures) to the kernel size.
803 config CC_OPTIMIZE_FOR_SIZE
804 bool "Optimize for size"
807 Enabling this option will pass "-Os" instead of "-O2" to gcc
808 resulting in a smaller kernel.
819 bool "Configure standard kernel features (for small systems)"
821 This option allows certain base kernel options and settings
822 to be disabled or tweaked. This is for specialized
823 environments which can tolerate a "non-standard" kernel.
824 Only use this if you really know what you are doing.
827 bool "Enable 16-bit UID system calls" if EMBEDDED
828 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
831 This enables the legacy 16-bit UID syscall wrappers.
833 config SYSCTL_SYSCALL
834 bool "Sysctl syscall support" if EMBEDDED
835 depends on PROC_SYSCTL
839 sys_sysctl uses binary paths that have been found challenging
840 to properly maintain and use. The interface in /proc/sys
841 using paths with ascii names is now the primary path to this
844 Almost nothing using the binary sysctl interface so if you are
845 trying to save some space it is probably safe to disable this,
846 making your kernel marginally smaller.
848 If unsure say Y here.
851 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
854 Say Y here to let the kernel print out symbolic crash information and
855 symbolic stack backtraces. This increases the size of the kernel
856 somewhat, as all symbols have to be loaded into the kernel image.
859 bool "Include all symbols in kallsyms"
860 depends on DEBUG_KERNEL && KALLSYMS
862 Normally kallsyms only contains the symbols of functions, for nicer
863 OOPS messages. Some debuggers can use kallsyms for other
864 symbols too: say Y here to include all symbols, if you need them
865 and you don't care about adding 300k to the size of your kernel.
869 config KALLSYMS_EXTRA_PASS
870 bool "Do an extra kallsyms pass"
873 If kallsyms is not working correctly, the build will fail with
874 inconsistent kallsyms data. If that occurs, log a bug report and
875 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
876 Always say N here unless you find a bug in kallsyms, which must be
877 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
878 you wait for kallsyms to be fixed.
882 bool "Support for hot-pluggable devices" if EMBEDDED
885 This option is provided for the case where no hotplug or uevent
886 capabilities is wanted by the kernel. You should only consider
887 disabling this option for embedded systems that do not use modules, a
888 dynamic /dev tree, or dynamic device discovery. Just say Y.
892 bool "Enable support for printk" if EMBEDDED
894 This option enables normal printk support. Removing it
895 eliminates most of the message strings from the kernel image
896 and makes the kernel more or less silent. As this makes it
897 very difficult to diagnose system problems, saying N here is
898 strongly discouraged.
901 bool "BUG() support" if EMBEDDED
904 Disabling this option eliminates support for BUG and WARN, reducing
905 the size of your kernel image and potentially quietly ignoring
906 numerous fatal conditions. You should only consider disabling this
907 option for embedded systems with no facilities for reporting errors.
912 bool "Enable ELF core dumps" if EMBEDDED
914 Enable support for generating core dumps. Disabling saves about 4k.
916 config PCSPKR_PLATFORM
917 bool "Enable PC-Speaker support" if EMBEDDED
918 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
921 This option allows to disable the internal PC-Speaker
922 support, saving some memory.
926 bool "Enable full-sized data structures for core" if EMBEDDED
928 Disabling this option reduces the size of miscellaneous core
929 kernel data structures. This saves memory on small machines,
930 but may reduce performance.
933 bool "Enable futex support" if EMBEDDED
937 Disabling this option will cause the kernel to be built without
938 support for "fast userspace mutexes". The resulting kernel may not
939 run glibc-based applications correctly.
942 bool "Enable eventpoll support" if EMBEDDED
946 Disabling this option will cause the kernel to be built without
947 support for epoll family of system calls.
950 bool "Enable signalfd() system call" if EMBEDDED
954 Enable the signalfd() system call that allows to receive signals
955 on a file descriptor.
960 bool "Enable timerfd() system call" if EMBEDDED
964 Enable the timerfd() system call that allows to receive timer
965 events on a file descriptor.
970 bool "Enable eventfd() system call" if EMBEDDED
974 Enable the eventfd() system call that allows to receive both
975 kernel notification (ie. KAIO) or userspace notifications.
980 bool "Use full shmem filesystem" if EMBEDDED
984 The shmem is an internal filesystem used to manage shared memory.
985 It is backed by swap and manages resource limits. It is also exported
986 to userspace as tmpfs if TMPFS is enabled. Disabling this
987 option replaces shmem and tmpfs with the much simpler ramfs code,
988 which may be appropriate on small systems without swap.
991 bool "Enable AIO support" if EMBEDDED
994 This option enables POSIX asynchronous I/O which may by used
995 by some high performance threaded applications. Disabling
996 this option saves about 7k.
998 config HAVE_PERF_EVENTS
1001 See tools/perf/design.txt for details.
1003 config PERF_USE_VMALLOC
1006 See tools/perf/design.txt for details
1008 menu "Kernel Performance Events And Counters"
1011 bool "Kernel performance events and counters"
1012 default y if (PROFILING || PERF_COUNTERS)
1013 depends on HAVE_PERF_EVENTS
1017 Enable kernel support for various performance events provided
1018 by software and hardware.
1020 Software events are supported either built-in or via the
1021 use of generic tracepoints.
1023 Most modern CPUs support performance events via performance
1024 counter registers. These registers count the number of certain
1025 types of hw events: such as instructions executed, cachemisses
1026 suffered, or branches mis-predicted - without slowing down the
1027 kernel or applications. These registers can also trigger interrupts
1028 when a threshold number of events have passed - and can thus be
1029 used to profile the code that runs on that CPU.
1031 The Linux Performance Event subsystem provides an abstraction of
1032 these software and hardware event capabilities, available via a
1033 system call and used by the "perf" utility in tools/perf/. It
1034 provides per task and per CPU counters, and it provides event
1035 capabilities on top of those.
1039 config PERF_COUNTERS
1040 bool "Kernel performance counters (old config option)"
1041 depends on HAVE_PERF_EVENTS
1043 This config has been obsoleted by the PERF_EVENTS
1044 config option - please see that one for details.
1046 It has no effect on the kernel whether you enable
1047 it or not, it is a compatibility placeholder.
1051 config DEBUG_PERF_USE_VMALLOC
1053 bool "Debug: use vmalloc to back perf mmap() buffers"
1054 depends on PERF_EVENTS && DEBUG_KERNEL
1055 select PERF_USE_VMALLOC
1057 Use vmalloc memory to back perf mmap() buffers.
1059 Mostly useful for debugging the vmalloc code on platforms
1060 that don't require it.
1066 config VM_EVENT_COUNTERS
1068 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1070 VM event counters are needed for event counts to be shown.
1071 This option allows the disabling of the VM event counters
1072 on EMBEDDED systems. /proc/vmstat will only show page counts
1073 if VM event counters are disabled.
1077 bool "Enable PCI quirk workarounds" if EMBEDDED
1080 This enables workarounds for various PCI chipset
1081 bugs/quirks. Disable this only if your target machine is
1082 unaffected by PCI quirks.
1086 bool "Enable SLUB debugging support" if EMBEDDED
1087 depends on SLUB && SYSFS
1089 SLUB has extensive debug support features. Disabling these can
1090 result in significant savings in code size. This also disables
1091 SLUB sysfs support. /sys/slab will not exist and there will be
1092 no support for cache validation etc.
1095 bool "Disable heap randomization"
1098 Randomizing heap placement makes heap exploits harder, but it
1099 also breaks ancient binaries (including anything libc5 based).
1100 This option changes the bootup default to heap randomization
1101 disabled, and can be overridden at runtime by setting
1102 /proc/sys/kernel/randomize_va_space to 2.
1104 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1107 prompt "Choose SLAB allocator"
1110 This option allows to select a slab allocator.
1115 The regular slab allocator that is established and known to work
1116 well in all environments. It organizes cache hot objects in
1117 per cpu and per node queues.
1120 bool "SLUB (Unqueued Allocator)"
1122 SLUB is a slab allocator that minimizes cache line usage
1123 instead of managing queues of cached objects (SLAB approach).
1124 Per cpu caching is realized using slabs of objects instead
1125 of queues of objects. SLUB can use memory efficiently
1126 and has enhanced diagnostics. SLUB is the default choice for
1131 bool "SLOB (Simple Allocator)"
1133 SLOB replaces the stock allocator with a drastically simpler
1134 allocator. SLOB is generally more space efficient but
1135 does not perform as well on large systems.
1139 config MMAP_ALLOW_UNINITIALIZED
1140 bool "Allow mmapped anonymous memory to be uninitialized"
1141 depends on EMBEDDED && !MMU
1144 Normally, and according to the Linux spec, anonymous memory obtained
1145 from mmap() has it's contents cleared before it is passed to
1146 userspace. Enabling this config option allows you to request that
1147 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1148 providing a huge performance boost. If this option is not enabled,
1149 then the flag will be ignored.
1151 This is taken advantage of by uClibc's malloc(), and also by
1152 ELF-FDPIC binfmt's brk and stack allocator.
1154 Because of the obvious security issues, this option should only be
1155 enabled on embedded devices where you control what is run in
1156 userspace. Since that isn't generally a problem on no-MMU systems,
1157 it is normally safe to say Y here.
1159 See Documentation/nommu-mmap.txt for more information.
1162 bool "Profiling support"
1164 Say Y here to enable the extended profiling support mechanisms used
1165 by profilers such as OProfile.
1168 # Place an empty function call at each tracepoint site. Can be
1169 # dynamically changed for a probe function.
1174 source "arch/Kconfig"
1176 endmenu # General setup
1178 config HAVE_GENERIC_DMA_COHERENT
1185 depends on SLAB || SLUB_DEBUG
1193 default 0 if BASE_FULL
1194 default 1 if !BASE_FULL
1197 bool "Enable loadable module support"
1199 Kernel modules are small pieces of compiled code which can
1200 be inserted in the running kernel, rather than being
1201 permanently built into the kernel. You use the "modprobe"
1202 tool to add (and sometimes remove) them. If you say Y here,
1203 many parts of the kernel can be built as modules (by
1204 answering M instead of Y where indicated): this is most
1205 useful for infrequently used options which are not required
1206 for booting. For more information, see the man pages for
1207 modprobe, lsmod, modinfo, insmod and rmmod.
1209 If you say Y here, you will need to run "make
1210 modules_install" to put the modules under /lib/modules/
1211 where modprobe can find them (you may need to be root to do
1218 config MODULE_FORCE_LOAD
1219 bool "Forced module loading"
1222 Allow loading of modules without version information (ie. modprobe
1223 --force). Forced module loading sets the 'F' (forced) taint flag and
1224 is usually a really bad idea.
1226 config MODULE_UNLOAD
1227 bool "Module unloading"
1229 Without this option you will not be able to unload any
1230 modules (note that some modules may not be unloadable
1231 anyway), which makes your kernel smaller, faster
1232 and simpler. If unsure, say Y.
1234 config MODULE_FORCE_UNLOAD
1235 bool "Forced module unloading"
1236 depends on MODULE_UNLOAD && EXPERIMENTAL
1238 This option allows you to force a module to unload, even if the
1239 kernel believes it is unsafe: the kernel will remove the module
1240 without waiting for anyone to stop using it (using the -f option to
1241 rmmod). This is mainly for kernel developers and desperate users.
1245 bool "Module versioning support"
1247 Usually, you have to use modules compiled with your kernel.
1248 Saying Y here makes it sometimes possible to use modules
1249 compiled for different kernels, by adding enough information
1250 to the modules to (hopefully) spot any changes which would
1251 make them incompatible with the kernel you are running. If
1254 config MODULE_SRCVERSION_ALL
1255 bool "Source checksum for all modules"
1257 Modules which contain a MODULE_VERSION get an extra "srcversion"
1258 field inserted into their modinfo section, which contains a
1259 sum of the source files which made it. This helps maintainers
1260 see exactly which source was used to build a module (since
1261 others sometimes change the module source without updating
1262 the version). With this option, such a "srcversion" field
1263 will be created for all modules. If unsure, say N.
1267 config INIT_ALL_POSSIBLE
1270 Back when each arch used to define their own cpu_online_map and
1271 cpu_possible_map, some of them chose to initialize cpu_possible_map
1272 with all 1s, and others with all 0s. When they were centralised,
1273 it was better to provide this option than to break all the archs
1274 and have several arch maintainers pursuing me down dark alleys.
1279 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1281 Need stop_machine() primitive.
1283 source "block/Kconfig"
1285 config PREEMPT_NOTIFIERS
1292 source "kernel/Kconfig.locks"