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"
27 bool "Prompt for development and/or incomplete code/drivers"
29 Some of the various things that Linux supports (such as network
30 drivers, file systems, network protocols, etc.) can be in a state
31 of development where the functionality, stability, or the level of
32 testing is not yet high enough for general use. This is usually
33 known as the "alpha-test" phase among developers. If a feature is
34 currently in alpha-test, then the developers usually discourage
35 uninformed widespread use of this feature by the general public to
36 avoid "Why doesn't this work?" type mail messages. However, active
37 testing and use of these systems is welcomed. Just be aware that it
38 may not meet the normal level of reliability or it may fail to work
39 in some special cases. Detailed bug reports from people familiar
40 with the kernel internals are usually welcomed by the developers
41 (before submitting bug reports, please read the documents
42 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
43 <file:Documentation/BUG-HUNTING>, and
44 <file:Documentation/oops-tracing.txt> in the kernel source).
46 This option will also make obsoleted drivers available. These are
47 drivers that have been replaced by something else, and/or are
48 scheduled to be removed in a future kernel release.
50 Unless you intend to help test and develop a feature or driver that
51 falls into this category, or you have a situation that requires
52 using these features, you should probably say N here, which will
53 cause the configurator to present you with fewer choices. If
54 you say Y here, you will be offered the choice of using features or
55 drivers that are currently considered to be in the alpha-test phase.
62 depends on BROKEN || !SMP
67 depends on SMP || PREEMPT
70 config INIT_ENV_ARG_LIMIT
75 Maximum of each of the number of arguments and environment
76 variables passed to init from the kernel command line.
80 string "Cross-compiler tool prefix"
82 Same as running 'make CROSS_COMPILE=prefix-' but stored for
83 default make runs in this kernel build directory. You don't
84 need to set this unless you want the configured kernel build
85 directory to select the cross-compiler automatically.
88 string "Local version - append to kernel release"
90 Append an extra string to the end of your kernel version.
91 This will show up when you type uname, for example.
92 The string you set here will be appended after the contents of
93 any files with a filename matching localversion* in your
94 object and source tree, in that order. Your total string can
95 be a maximum of 64 characters.
97 config LOCALVERSION_AUTO
98 bool "Automatically append version information to the version string"
101 This will try to automatically determine if the current tree is a
102 release tree by looking for git tags that belong to the current
103 top of tree revision.
105 A string of the format -gxxxxxxxx will be added to the localversion
106 if a git-based tree is found. The string generated by this will be
107 appended after any matching localversion* files, and after the value
108 set in CONFIG_LOCALVERSION.
110 (The actual string used here is the first eight characters produced
111 by running the command:
113 $ git rev-parse --verify HEAD
115 which is done within the script "scripts/setlocalversion".)
117 config HAVE_KERNEL_GZIP
120 config HAVE_KERNEL_BZIP2
123 config HAVE_KERNEL_LZMA
126 config HAVE_KERNEL_LZO
130 prompt "Kernel compression mode"
132 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
134 The linux kernel is a kind of self-extracting executable.
135 Several compression algorithms are available, which differ
136 in efficiency, compression and decompression speed.
137 Compression speed is only relevant when building a kernel.
138 Decompression speed is relevant at each boot.
140 If you have any problems with bzip2 or lzma compressed
141 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
142 version of this functionality (bzip2 only), for 2.4, was
143 supplied by Christian Ludwig)
145 High compression options are mostly useful for users, who
146 are low on disk space (embedded systems), but for whom ram
149 If in doubt, select 'gzip'
153 depends on HAVE_KERNEL_GZIP
155 The old and tried gzip compression. It provides a good balance
156 between compression ratio and decompression speed.
160 depends on HAVE_KERNEL_BZIP2
162 Its compression ratio and speed is intermediate.
163 Decompression speed is slowest among the three. The kernel
164 size is about 10% smaller with bzip2, in comparison to gzip.
165 Bzip2 uses a large amount of memory. For modern kernels you
166 will need at least 8MB RAM or more for booting.
170 depends on HAVE_KERNEL_LZMA
172 The most recent compression algorithm.
173 Its ratio is best, decompression speed is between the other
174 two. Compression is slowest. The kernel size is about 33%
175 smaller with LZMA in comparison to gzip.
179 depends on HAVE_KERNEL_LZO
181 Its compression ratio is the poorest among the 4. The kernel
182 size is about about 10% bigger than gzip; however its speed
183 (both compression and decompression) is the fastest.
188 bool "Support for paging of anonymous memory (swap)"
189 depends on MMU && BLOCK
192 This option allows you to choose whether you want to have support
193 for so called swap devices or swap files in your kernel that are
194 used to provide more virtual memory than the actual RAM present
195 in your computer. If unsure say Y.
200 Inter Process Communication is a suite of library functions and
201 system calls which let processes (running programs) synchronize and
202 exchange information. It is generally considered to be a good thing,
203 and some programs won't run unless you say Y here. In particular, if
204 you want to run the DOS emulator dosemu under Linux (read the
205 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
206 you'll need to say Y here.
208 You can find documentation about IPC with "info ipc" and also in
209 section 6.4 of the Linux Programmer's Guide, available from
210 <http://www.tldp.org/guides.html>.
212 config SYSVIPC_SYSCTL
219 bool "POSIX Message Queues"
220 depends on NET && EXPERIMENTAL
222 POSIX variant of message queues is a part of IPC. In POSIX message
223 queues every message has a priority which decides about succession
224 of receiving it by a process. If you want to compile and run
225 programs written e.g. for Solaris with use of its POSIX message
226 queues (functions mq_*) say Y here.
228 POSIX message queues are visible as a filesystem called 'mqueue'
229 and can be mounted somewhere if you want to do filesystem
230 operations on message queues.
234 config POSIX_MQUEUE_SYSCTL
236 depends on POSIX_MQUEUE
240 config BSD_PROCESS_ACCT
241 bool "BSD Process Accounting"
243 If you say Y here, a user level program will be able to instruct the
244 kernel (via a special system call) to write process accounting
245 information to a file: whenever a process exits, information about
246 that process will be appended to the file by the kernel. The
247 information includes things such as creation time, owning user,
248 command name, memory usage, controlling terminal etc. (the complete
249 list is in the struct acct in <file:include/linux/acct.h>). It is
250 up to the user level program to do useful things with this
251 information. This is generally a good idea, so say Y.
253 config BSD_PROCESS_ACCT_V3
254 bool "BSD Process Accounting version 3 file format"
255 depends on BSD_PROCESS_ACCT
258 If you say Y here, the process accounting information is written
259 in a new file format that also logs the process IDs of each
260 process and it's parent. Note that this file format is incompatible
261 with previous v0/v1/v2 file formats, so you will need updated tools
262 for processing it. A preliminary version of these tools is available
263 at <http://www.gnu.org/software/acct/>.
266 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
270 Export selected statistics for tasks/processes through the
271 generic netlink interface. Unlike BSD process accounting, the
272 statistics are available during the lifetime of tasks/processes as
273 responses to commands. Like BSD accounting, they are sent to user
278 config TASK_DELAY_ACCT
279 bool "Enable per-task delay accounting (EXPERIMENTAL)"
282 Collect information on time spent by a task waiting for system
283 resources like cpu, synchronous block I/O completion and swapping
284 in pages. Such statistics can help in setting a task's priorities
285 relative to other tasks for cpu, io, rss limits etc.
290 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
293 Collect extended task accounting data and send the data
294 to userland for processing over the taskstats interface.
298 config TASK_IO_ACCOUNTING
299 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
300 depends on TASK_XACCT
302 Collect information on the number of bytes of storage I/O which this
308 bool "Auditing support"
311 Enable auditing infrastructure that can be used with another
312 kernel subsystem, such as SELinux (which requires this for
313 logging of avc messages output). Does not do system-call
314 auditing without CONFIG_AUDITSYSCALL.
317 bool "Enable system-call auditing support"
318 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
319 default y if SECURITY_SELINUX
321 Enable low-overhead system-call auditing infrastructure that
322 can be used independently or with another kernel subsystem,
323 such as SELinux. To use audit's filesystem watch feature, please
324 ensure that INOTIFY is configured.
328 depends on AUDITSYSCALL
334 prompt "RCU Implementation"
338 bool "Tree-based hierarchical RCU"
340 This option selects the RCU implementation that is
341 designed for very large SMP system with hundreds or
342 thousands of CPUs. It also scales down nicely to
345 config TREE_PREEMPT_RCU
346 bool "Preemptable tree-based hierarchical RCU"
349 This option selects the RCU implementation that is
350 designed for very large SMP systems with hundreds or
351 thousands of CPUs, but for which real-time response
352 is also required. It also scales down nicely to
356 bool "UP-only small-memory-footprint RCU"
359 This option selects the RCU implementation that is
360 designed for UP systems from which real-time response
361 is not required. This option greatly reduces the
362 memory footprint of RCU.
367 bool "Enable tracing for RCU"
368 depends on TREE_RCU || TREE_PREEMPT_RCU
370 This option provides tracing in RCU which presents stats
371 in debugfs for debugging RCU implementation.
373 Say Y here if you want to enable RCU tracing
374 Say N if you are unsure.
377 int "Tree-based hierarchical RCU fanout value"
380 depends on TREE_RCU || TREE_PREEMPT_RCU
384 This option controls the fanout of hierarchical implementations
385 of RCU, allowing RCU to work efficiently on machines with
386 large numbers of CPUs. This value must be at least the cube
387 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
388 systems and up to 262,144 for 64-bit systems.
390 Select a specific number if testing RCU itself.
391 Take the default if unsure.
393 config RCU_FANOUT_EXACT
394 bool "Disable tree-based hierarchical RCU auto-balancing"
395 depends on TREE_RCU || TREE_PREEMPT_RCU
398 This option forces use of the exact RCU_FANOUT value specified,
399 regardless of imbalances in the hierarchy. This is useful for
400 testing RCU itself, and might one day be useful on systems with
401 strong NUMA behavior.
403 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
407 config TREE_RCU_TRACE
408 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
411 This option provides tracing for the TREE_RCU and
412 TREE_PREEMPT_RCU implementations, permitting Makefile to
413 trivially select kernel/rcutree_trace.c.
415 endmenu # "RCU Subsystem"
418 tristate "Kernel .config support"
420 This option enables the complete Linux kernel ".config" file
421 contents to be saved in the kernel. It provides documentation
422 of which kernel options are used in a running kernel or in an
423 on-disk kernel. This information can be extracted from the kernel
424 image file with the script scripts/extract-ikconfig and used as
425 input to rebuild the current kernel or to build another kernel.
426 It can also be extracted from a running kernel by reading
427 /proc/config.gz if enabled (below).
430 bool "Enable access to .config through /proc/config.gz"
431 depends on IKCONFIG && PROC_FS
433 This option enables access to the kernel configuration file
434 through /proc/config.gz.
437 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
441 Select kernel log buffer size as a power of 2.
451 # Architectures with an unreliable sched_clock() should select this:
453 config HAVE_UNSTABLE_SCHED_CLOCK
457 bool "Group CPU scheduler"
458 depends on EXPERIMENTAL
461 This feature lets CPU scheduler recognize task groups and control CPU
462 bandwidth allocation to such task groups.
463 In order to create a group from arbitrary set of processes, use
464 CONFIG_CGROUPS. (See Control Group support.)
466 config FAIR_GROUP_SCHED
467 bool "Group scheduling for SCHED_OTHER"
468 depends on GROUP_SCHED
471 config RT_GROUP_SCHED
472 bool "Group scheduling for SCHED_RR/FIFO"
473 depends on EXPERIMENTAL
474 depends on GROUP_SCHED
477 This feature lets you explicitly allocate real CPU bandwidth
478 to users or control groups (depending on the "Basis for grouping tasks"
479 setting below. If enabled, it will also make it impossible to
480 schedule realtime tasks for non-root users until you allocate
481 realtime bandwidth for them.
482 See Documentation/scheduler/sched-rt-group.txt for more information.
485 depends on GROUP_SCHED
486 prompt "Basis for grouping tasks"
492 This option will choose userid as the basis for grouping
493 tasks, thus providing equal CPU bandwidth to each user.
496 bool "Control groups"
499 This option allows you to create arbitrary task groups
500 using the "cgroup" pseudo filesystem and control
501 the cpu bandwidth allocated to each such task group.
502 Refer to Documentation/cgroups/cgroups.txt for more
503 information on "cgroup" pseudo filesystem.
508 boolean "Control Group support"
510 This option adds support for grouping sets of processes together, for
511 use with process control subsystems such as Cpusets, CFS, memory
512 controls or device isolation.
514 - Documentation/scheduler/sched-design-CFS.txt (CFS)
515 - Documentation/cgroups/ (features for grouping, isolation
516 and resource control)
523 bool "Example debug cgroup subsystem"
527 This option enables a simple cgroup subsystem that
528 exports useful debugging information about the cgroups
534 bool "Namespace cgroup subsystem"
537 Provides a simple namespace cgroup subsystem to
538 provide hierarchical naming of sets of namespaces,
539 for instance virtual servers and checkpoint/restart
542 config CGROUP_FREEZER
543 bool "Freezer cgroup subsystem"
546 Provides a way to freeze and unfreeze all tasks in a
550 bool "Device controller for cgroups"
551 depends on CGROUPS && EXPERIMENTAL
553 Provides a cgroup implementing whitelists for devices which
554 a process in the cgroup can mknod or open.
557 bool "Cpuset support"
560 This option will let you create and manage CPUSETs which
561 allow dynamically partitioning a system into sets of CPUs and
562 Memory Nodes and assigning tasks to run only within those sets.
563 This is primarily useful on large SMP or NUMA systems.
567 config PROC_PID_CPUSET
568 bool "Include legacy /proc/<pid>/cpuset file"
572 config CGROUP_CPUACCT
573 bool "Simple CPU accounting cgroup subsystem"
576 Provides a simple Resource Controller for monitoring the
577 total CPU consumed by the tasks in a cgroup.
579 config RESOURCE_COUNTERS
580 bool "Resource counters"
582 This option enables controller independent resource accounting
583 infrastructure that works with cgroups.
586 config CGROUP_MEM_RES_CTLR
587 bool "Memory Resource Controller for Control Groups"
588 depends on CGROUPS && RESOURCE_COUNTERS
591 Provides a memory resource controller that manages both anonymous
592 memory and page cache. (See Documentation/cgroups/memory.txt)
594 Note that setting this option increases fixed memory overhead
595 associated with each page of memory in the system. By this,
596 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
597 usage tracking struct at boot. Total amount of this is printed out
600 Only enable when you're ok with these trade offs and really
601 sure you need the memory resource controller. Even when you enable
602 this, you can set "cgroup_disable=memory" at your boot option to
603 disable memory resource controller and you can avoid overheads.
604 (and lose benefits of memory resource controller)
606 This config option also selects MM_OWNER config option, which
607 could in turn add some fork/exit overhead.
609 config CGROUP_MEM_RES_CTLR_SWAP
610 bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
611 depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
613 Add swap management feature to memory resource controller. When you
614 enable this, you can limit mem+swap usage per cgroup. In other words,
615 when you disable this, memory resource controller has no cares to
616 usage of swap...a process can exhaust all of the swap. This extension
617 is useful when you want to avoid exhaustion swap but this itself
618 adds more overheads and consumes memory for remembering information.
619 Especially if you use 32bit system or small memory system, please
620 be careful about enabling this. When memory resource controller
621 is disabled by boot option, this will be automatically disabled and
622 there will be no overhead from this. Even when you set this config=y,
623 if boot option "noswapaccount" is set, swap will not be accounted.
624 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
625 size is 4096bytes, 512k per 1Gbytes of swap.
632 config SYSFS_DEPRECATED
635 config SYSFS_DEPRECATED_V2
636 bool "enable deprecated sysfs features to support old userspace tools"
639 select SYSFS_DEPRECATED
641 This option switches the layout of sysfs to the deprecated
642 version. Do not use it on recent distributions.
644 The current sysfs layout features a unified device tree at
645 /sys/devices/, which is able to express a hierarchy between
646 class devices. If the deprecated option is set to Y, the
647 unified device tree is split into a bus device tree at
648 /sys/devices/ and several individual class device trees at
649 /sys/class/. The class and bus devices will be connected by
650 "<subsystem>:<name>" and the "device" links. The "block"
651 class devices, will not show up in /sys/class/block/. Some
652 subsystems will suppress the creation of some devices which
653 depend on the unified device tree.
655 This option is not a pure compatibility option that can
656 be safely enabled on newer distributions. It will change the
657 layout of sysfs to the non-extensible deprecated version,
658 and disable some features, which can not be exported without
659 confusing older userspace tools. Since 2007/2008 all major
660 distributions do not enable this option, and ship no tools which
661 depend on the deprecated layout or this option.
663 If you are using a new kernel on an older distribution, or use
664 older userspace tools, you might need to say Y here. Do not say Y,
665 if the original kernel, that came with your distribution, has
666 this option set to N.
669 bool "Kernel->user space relay support (formerly relayfs)"
671 This option enables support for relay interface support in
672 certain file systems (such as debugfs).
673 It is designed to provide an efficient mechanism for tools and
674 facilities to relay large amounts of data from kernel space to
680 bool "Namespaces support" if EMBEDDED
683 Provides the way to make tasks work with different objects using
684 the same id. For example same IPC id may refer to different objects
685 or same user id or pid may refer to different tasks when used in
686 different namespaces.
690 depends on NAMESPACES
692 In this namespace tasks see different info provided with the
697 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
699 In this namespace tasks work with IPC ids which correspond to
700 different IPC objects in different namespaces.
703 bool "User namespace (EXPERIMENTAL)"
704 depends on NAMESPACES && EXPERIMENTAL
706 This allows containers, i.e. vservers, to use user namespaces
707 to provide different user info for different servers.
711 bool "PID Namespaces (EXPERIMENTAL)"
713 depends on NAMESPACES && EXPERIMENTAL
715 Support process id namespaces. This allows having multiple
716 processes with the same pid as long as they are in different
717 pid namespaces. This is a building block of containers.
719 Unless you want to work with an experimental feature
723 bool "Network namespace"
725 depends on NAMESPACES && EXPERIMENTAL && NET
727 Allow user space to create what appear to be multiple instances
728 of the network stack.
730 config BLK_DEV_INITRD
731 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
732 depends on BROKEN || !FRV
734 The initial RAM filesystem is a ramfs which is loaded by the
735 boot loader (loadlin or lilo) and that is mounted as root
736 before the normal boot procedure. It is typically used to
737 load modules needed to mount the "real" root file system,
738 etc. See <file:Documentation/initrd.txt> for details.
740 If RAM disk support (BLK_DEV_RAM) is also included, this
741 also enables initial RAM disk (initrd) support and adds
742 15 Kbytes (more on some other architectures) to the kernel size.
752 config CC_OPTIMIZE_FOR_SIZE
753 bool "Optimize for size"
756 Enabling this option will pass "-Os" instead of "-O2" to gcc
757 resulting in a smaller kernel.
768 bool "Configure standard kernel features (for small systems)"
770 This option allows certain base kernel options and settings
771 to be disabled or tweaked. This is for specialized
772 environments which can tolerate a "non-standard" kernel.
773 Only use this if you really know what you are doing.
776 bool "Enable 16-bit UID system calls" if EMBEDDED
777 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
780 This enables the legacy 16-bit UID syscall wrappers.
782 config SYSCTL_SYSCALL
783 bool "Sysctl syscall support" if EMBEDDED
784 depends on PROC_SYSCTL
788 sys_sysctl uses binary paths that have been found challenging
789 to properly maintain and use. The interface in /proc/sys
790 using paths with ascii names is now the primary path to this
793 Almost nothing using the binary sysctl interface so if you are
794 trying to save some space it is probably safe to disable this,
795 making your kernel marginally smaller.
797 If unsure say Y here.
800 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
803 Say Y here to let the kernel print out symbolic crash information and
804 symbolic stack backtraces. This increases the size of the kernel
805 somewhat, as all symbols have to be loaded into the kernel image.
808 bool "Include all symbols in kallsyms"
809 depends on DEBUG_KERNEL && KALLSYMS
811 Normally kallsyms only contains the symbols of functions, for nicer
812 OOPS messages. Some debuggers can use kallsyms for other
813 symbols too: say Y here to include all symbols, if you need them
814 and you don't care about adding 300k to the size of your kernel.
818 config KALLSYMS_EXTRA_PASS
819 bool "Do an extra kallsyms pass"
822 If kallsyms is not working correctly, the build will fail with
823 inconsistent kallsyms data. If that occurs, log a bug report and
824 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
825 Always say N here unless you find a bug in kallsyms, which must be
826 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
827 you wait for kallsyms to be fixed.
831 bool "Support for hot-pluggable devices" if EMBEDDED
834 This option is provided for the case where no hotplug or uevent
835 capabilities is wanted by the kernel. You should only consider
836 disabling this option for embedded systems that do not use modules, a
837 dynamic /dev tree, or dynamic device discovery. Just say Y.
841 bool "Enable support for printk" if EMBEDDED
843 This option enables normal printk support. Removing it
844 eliminates most of the message strings from the kernel image
845 and makes the kernel more or less silent. As this makes it
846 very difficult to diagnose system problems, saying N here is
847 strongly discouraged.
850 bool "BUG() support" if EMBEDDED
853 Disabling this option eliminates support for BUG and WARN, reducing
854 the size of your kernel image and potentially quietly ignoring
855 numerous fatal conditions. You should only consider disabling this
856 option for embedded systems with no facilities for reporting errors.
861 bool "Enable ELF core dumps" if EMBEDDED
863 Enable support for generating core dumps. Disabling saves about 4k.
865 config PCSPKR_PLATFORM
866 bool "Enable PC-Speaker support" if EMBEDDED
867 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
870 This option allows to disable the internal PC-Speaker
871 support, saving some memory.
875 bool "Enable full-sized data structures for core" if EMBEDDED
877 Disabling this option reduces the size of miscellaneous core
878 kernel data structures. This saves memory on small machines,
879 but may reduce performance.
882 bool "Enable futex support" if EMBEDDED
886 Disabling this option will cause the kernel to be built without
887 support for "fast userspace mutexes". The resulting kernel may not
888 run glibc-based applications correctly.
891 bool "Enable eventpoll support" if EMBEDDED
895 Disabling this option will cause the kernel to be built without
896 support for epoll family of system calls.
899 bool "Enable signalfd() system call" if EMBEDDED
903 Enable the signalfd() system call that allows to receive signals
904 on a file descriptor.
909 bool "Enable timerfd() system call" if EMBEDDED
913 Enable the timerfd() system call that allows to receive timer
914 events on a file descriptor.
919 bool "Enable eventfd() system call" if EMBEDDED
923 Enable the eventfd() system call that allows to receive both
924 kernel notification (ie. KAIO) or userspace notifications.
929 bool "Use full shmem filesystem" if EMBEDDED
933 The shmem is an internal filesystem used to manage shared memory.
934 It is backed by swap and manages resource limits. It is also exported
935 to userspace as tmpfs if TMPFS is enabled. Disabling this
936 option replaces shmem and tmpfs with the much simpler ramfs code,
937 which may be appropriate on small systems without swap.
940 bool "Enable AIO support" if EMBEDDED
943 This option enables POSIX asynchronous I/O which may by used
944 by some high performance threaded applications. Disabling
945 this option saves about 7k.
947 config HAVE_PERF_EVENTS
950 See tools/perf/design.txt for details.
952 config PERF_USE_VMALLOC
955 See tools/perf/design.txt for details
957 menu "Kernel Performance Events And Counters"
960 bool "Kernel performance events and counters"
961 default y if (PROFILING || PERF_COUNTERS)
962 depends on HAVE_PERF_EVENTS
965 Enable kernel support for various performance events provided
966 by software and hardware.
968 Software events are supported either built-in or via the
969 use of generic tracepoints.
971 Most modern CPUs support performance events via performance
972 counter registers. These registers count the number of certain
973 types of hw events: such as instructions executed, cachemisses
974 suffered, or branches mis-predicted - without slowing down the
975 kernel or applications. These registers can also trigger interrupts
976 when a threshold number of events have passed - and can thus be
977 used to profile the code that runs on that CPU.
979 The Linux Performance Event subsystem provides an abstraction of
980 these software and hardware event capabilities, available via a
981 system call and used by the "perf" utility in tools/perf/. It
982 provides per task and per CPU counters, and it provides event
983 capabilities on top of those.
988 bool "Tracepoint profiling sources"
989 depends on PERF_EVENTS && EVENT_TRACING
992 Allow the use of tracepoints as software performance events.
994 When this is enabled, you can create perf events based on
995 tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID
996 found in debugfs://tracing/events/*/*/id. (The -e/--events
997 option to the perf tool can parse and interpret symbolic
998 tracepoints, in the subsystem:tracepoint_name format.)
1000 config PERF_COUNTERS
1001 bool "Kernel performance counters (old config option)"
1002 depends on HAVE_PERF_EVENTS
1004 This config has been obsoleted by the PERF_EVENTS
1005 config option - please see that one for details.
1007 It has no effect on the kernel whether you enable
1008 it or not, it is a compatibility placeholder.
1012 config DEBUG_PERF_USE_VMALLOC
1014 bool "Debug: use vmalloc to back perf mmap() buffers"
1015 depends on PERF_EVENTS && DEBUG_KERNEL
1016 select PERF_USE_VMALLOC
1018 Use vmalloc memory to back perf mmap() buffers.
1020 Mostly useful for debugging the vmalloc code on platforms
1021 that don't require it.
1027 config VM_EVENT_COUNTERS
1029 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1031 VM event counters are needed for event counts to be shown.
1032 This option allows the disabling of the VM event counters
1033 on EMBEDDED systems. /proc/vmstat will only show page counts
1034 if VM event counters are disabled.
1038 bool "Enable PCI quirk workarounds" if EMBEDDED
1041 This enables workarounds for various PCI chipset
1042 bugs/quirks. Disable this only if your target machine is
1043 unaffected by PCI quirks.
1047 bool "Enable SLUB debugging support" if EMBEDDED
1048 depends on SLUB && SYSFS
1050 SLUB has extensive debug support features. Disabling these can
1051 result in significant savings in code size. This also disables
1052 SLUB sysfs support. /sys/slab will not exist and there will be
1053 no support for cache validation etc.
1056 bool "Disable heap randomization"
1059 Randomizing heap placement makes heap exploits harder, but it
1060 also breaks ancient binaries (including anything libc5 based).
1061 This option changes the bootup default to heap randomization
1062 disabled, and can be overridden at runtime by setting
1063 /proc/sys/kernel/randomize_va_space to 2.
1065 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1068 prompt "Choose SLAB allocator"
1071 This option allows to select a slab allocator.
1076 The regular slab allocator that is established and known to work
1077 well in all environments. It organizes cache hot objects in
1078 per cpu and per node queues.
1081 bool "SLUB (Unqueued Allocator)"
1083 SLUB is a slab allocator that minimizes cache line usage
1084 instead of managing queues of cached objects (SLAB approach).
1085 Per cpu caching is realized using slabs of objects instead
1086 of queues of objects. SLUB can use memory efficiently
1087 and has enhanced diagnostics. SLUB is the default choice for
1092 bool "SLOB (Simple Allocator)"
1094 SLOB replaces the stock allocator with a drastically simpler
1095 allocator. SLOB is generally more space efficient but
1096 does not perform as well on large systems.
1100 config MMAP_ALLOW_UNINITIALIZED
1101 bool "Allow mmapped anonymous memory to be uninitialized"
1102 depends on EMBEDDED && !MMU
1105 Normally, and according to the Linux spec, anonymous memory obtained
1106 from mmap() has it's contents cleared before it is passed to
1107 userspace. Enabling this config option allows you to request that
1108 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1109 providing a huge performance boost. If this option is not enabled,
1110 then the flag will be ignored.
1112 This is taken advantage of by uClibc's malloc(), and also by
1113 ELF-FDPIC binfmt's brk and stack allocator.
1115 Because of the obvious security issues, this option should only be
1116 enabled on embedded devices where you control what is run in
1117 userspace. Since that isn't generally a problem on no-MMU systems,
1118 it is normally safe to say Y here.
1120 See Documentation/nommu-mmap.txt for more information.
1123 bool "Profiling support (EXPERIMENTAL)"
1125 Say Y here to enable the extended profiling support mechanisms used
1126 by profilers such as OProfile.
1129 # Place an empty function call at each tracepoint site. Can be
1130 # dynamically changed for a probe function.
1135 source "arch/Kconfig"
1141 The slow work thread pool provides a number of dynamically allocated
1142 threads that can be used by the kernel to perform operations that
1143 take a relatively long time.
1145 An example of this would be CacheFiles doing a path lookup followed
1146 by a series of mkdirs and a create call, all of which have to touch
1149 See Documentation/slow-work.txt.
1151 config SLOW_WORK_DEBUG
1152 bool "Slow work debugging through debugfs"
1154 depends on SLOW_WORK && DEBUG_FS
1156 Display the contents of the slow work run queue through debugfs,
1157 including items currently executing.
1159 See Documentation/slow-work.txt.
1161 endmenu # General setup
1163 config HAVE_GENERIC_DMA_COHERENT
1170 depends on SLAB || SLUB_DEBUG
1178 default 0 if BASE_FULL
1179 default 1 if !BASE_FULL
1182 bool "Enable loadable module support"
1184 Kernel modules are small pieces of compiled code which can
1185 be inserted in the running kernel, rather than being
1186 permanently built into the kernel. You use the "modprobe"
1187 tool to add (and sometimes remove) them. If you say Y here,
1188 many parts of the kernel can be built as modules (by
1189 answering M instead of Y where indicated): this is most
1190 useful for infrequently used options which are not required
1191 for booting. For more information, see the man pages for
1192 modprobe, lsmod, modinfo, insmod and rmmod.
1194 If you say Y here, you will need to run "make
1195 modules_install" to put the modules under /lib/modules/
1196 where modprobe can find them (you may need to be root to do
1203 config MODULE_FORCE_LOAD
1204 bool "Forced module loading"
1207 Allow loading of modules without version information (ie. modprobe
1208 --force). Forced module loading sets the 'F' (forced) taint flag and
1209 is usually a really bad idea.
1211 config MODULE_UNLOAD
1212 bool "Module unloading"
1214 Without this option you will not be able to unload any
1215 modules (note that some modules may not be unloadable
1216 anyway), which makes your kernel smaller, faster
1217 and simpler. If unsure, say Y.
1219 config MODULE_FORCE_UNLOAD
1220 bool "Forced module unloading"
1221 depends on MODULE_UNLOAD && EXPERIMENTAL
1223 This option allows you to force a module to unload, even if the
1224 kernel believes it is unsafe: the kernel will remove the module
1225 without waiting for anyone to stop using it (using the -f option to
1226 rmmod). This is mainly for kernel developers and desperate users.
1230 bool "Module versioning support"
1232 Usually, you have to use modules compiled with your kernel.
1233 Saying Y here makes it sometimes possible to use modules
1234 compiled for different kernels, by adding enough information
1235 to the modules to (hopefully) spot any changes which would
1236 make them incompatible with the kernel you are running. If
1239 config MODULE_SRCVERSION_ALL
1240 bool "Source checksum for all modules"
1242 Modules which contain a MODULE_VERSION get an extra "srcversion"
1243 field inserted into their modinfo section, which contains a
1244 sum of the source files which made it. This helps maintainers
1245 see exactly which source was used to build a module (since
1246 others sometimes change the module source without updating
1247 the version). With this option, such a "srcversion" field
1248 will be created for all modules. If unsure, say N.
1252 config INIT_ALL_POSSIBLE
1255 Back when each arch used to define their own cpu_online_map and
1256 cpu_possible_map, some of them chose to initialize cpu_possible_map
1257 with all 1s, and others with all 0s. When they were centralised,
1258 it was better to provide this option than to break all the archs
1259 and have several arch maintainers pursuing me down dark alleys.
1264 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1266 Need stop_machine() primitive.
1268 source "block/Kconfig"
1270 config PREEMPT_NOTIFIERS
1273 source "kernel/Kconfig.locks"
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