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47 drivers that have been replaced by something else, and/or are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 "Local version - append to kernel release"
82 Append an extra string to the end of your kernel version.
83 This will show up when you type uname, for example.
84 The string you set here will be appended after the contents of
85 any files with a filename matching localversion* in your
86 object and source tree, in that order. Your total string can
87 be a maximum of 64 characters.
89 config LOCALVERSION_AUTO
90 bool "Automatically append version information to the version string"
93 This will try to automatically determine if the current tree is a
94 release tree by looking for git tags that belong to the current
97 A string of the format -gxxxxxxxx will be added to the localversion
98 if a git-based tree is found. The string generated by this will be
99 appended after any matching localversion* files, and after the value
100 set in CONFIG_LOCALVERSION.
102 (The actual string used here is the first eight characters produced
103 by running the command:
105 $ git rev-parse --verify HEAD
107 which is done within the script "scripts/setlocalversion".)
109 config HAVE_KERNEL_GZIP
112 config HAVE_KERNEL_BZIP2
115 config HAVE_KERNEL_LZMA
118 config HAVE_KERNEL_LZO
122 prompt "Kernel compression mode"
124 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
126 The linux kernel is a kind of self-extracting executable.
127 Several compression algorithms are available, which differ
128 in efficiency, compression and decompression speed.
129 Compression speed is only relevant when building a kernel.
130 Decompression speed is relevant at each boot.
132 If you have any problems with bzip2 or lzma compressed
133 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
134 version of this functionality (bzip2 only), for 2.4, was
135 supplied by Christian Ludwig)
137 High compression options are mostly useful for users, who
138 are low on disk space (embedded systems), but for whom ram
141 If in doubt, select 'gzip'
145 depends on HAVE_KERNEL_GZIP
147 The old and tried gzip compression. It provides a good balance
148 between compression ratio and decompression speed.
152 depends on HAVE_KERNEL_BZIP2
154 Its compression ratio and speed is intermediate.
155 Decompression speed is slowest among the three. The kernel
156 size is about 10% smaller with bzip2, in comparison to gzip.
157 Bzip2 uses a large amount of memory. For modern kernels you
158 will need at least 8MB RAM or more for booting.
162 depends on HAVE_KERNEL_LZMA
164 The most recent compression algorithm.
165 Its ratio is best, decompression speed is between the other
166 two. Compression is slowest. The kernel size is about 33%
167 smaller with LZMA in comparison to gzip.
171 depends on HAVE_KERNEL_LZO
173 Its compression ratio is the poorest among the 4. The kernel
174 size is about about 10% bigger than gzip; however its speed
175 (both compression and decompression) is the fastest.
180 bool "Support for paging of anonymous memory (swap)"
181 depends on MMU && BLOCK
184 This option allows you to choose whether you want to have support
185 for so called swap devices or swap files in your kernel that are
186 used to provide more virtual memory than the actual RAM present
187 in your computer. If unsure say Y.
192 Inter Process Communication is a suite of library functions and
193 system calls which let processes (running programs) synchronize and
194 exchange information. It is generally considered to be a good thing,
195 and some programs won't run unless you say Y here. In particular, if
196 you want to run the DOS emulator dosemu under Linux (read the
197 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
198 you'll need to say Y here.
200 You can find documentation about IPC with "info ipc" and also in
201 section 6.4 of the Linux Programmer's Guide, available from
202 <http://www.tldp.org/guides.html>.
204 config SYSVIPC_SYSCTL
211 bool "POSIX Message Queues"
212 depends on NET && EXPERIMENTAL
214 POSIX variant of message queues is a part of IPC. In POSIX message
215 queues every message has a priority which decides about succession
216 of receiving it by a process. If you want to compile and run
217 programs written e.g. for Solaris with use of its POSIX message
218 queues (functions mq_*) say Y here.
220 POSIX message queues are visible as a filesystem called 'mqueue'
221 and can be mounted somewhere if you want to do filesystem
222 operations on message queues.
226 config POSIX_MQUEUE_SYSCTL
228 depends on POSIX_MQUEUE
232 config BSD_PROCESS_ACCT
233 bool "BSD Process Accounting"
235 If you say Y here, a user level program will be able to instruct the
236 kernel (via a special system call) to write process accounting
237 information to a file: whenever a process exits, information about
238 that process will be appended to the file by the kernel. The
239 information includes things such as creation time, owning user,
240 command name, memory usage, controlling terminal etc. (the complete
241 list is in the struct acct in <file:include/linux/acct.h>). It is
242 up to the user level program to do useful things with this
243 information. This is generally a good idea, so say Y.
245 config BSD_PROCESS_ACCT_V3
246 bool "BSD Process Accounting version 3 file format"
247 depends on BSD_PROCESS_ACCT
250 If you say Y here, the process accounting information is written
251 in a new file format that also logs the process IDs of each
252 process and it's parent. Note that this file format is incompatible
253 with previous v0/v1/v2 file formats, so you will need updated tools
254 for processing it. A preliminary version of these tools is available
255 at <http://www.gnu.org/software/acct/>.
258 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
262 Export selected statistics for tasks/processes through the
263 generic netlink interface. Unlike BSD process accounting, the
264 statistics are available during the lifetime of tasks/processes as
265 responses to commands. Like BSD accounting, they are sent to user
270 config TASK_DELAY_ACCT
271 bool "Enable per-task delay accounting (EXPERIMENTAL)"
274 Collect information on time spent by a task waiting for system
275 resources like cpu, synchronous block I/O completion and swapping
276 in pages. Such statistics can help in setting a task's priorities
277 relative to other tasks for cpu, io, rss limits etc.
282 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
285 Collect extended task accounting data and send the data
286 to userland for processing over the taskstats interface.
290 config TASK_IO_ACCOUNTING
291 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
292 depends on TASK_XACCT
294 Collect information on the number of bytes of storage I/O which this
300 bool "Auditing support"
303 Enable auditing infrastructure that can be used with another
304 kernel subsystem, such as SELinux (which requires this for
305 logging of avc messages output). Does not do system-call
306 auditing without CONFIG_AUDITSYSCALL.
309 bool "Enable system-call auditing support"
310 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
311 default y if SECURITY_SELINUX
313 Enable low-overhead system-call auditing infrastructure that
314 can be used independently or with another kernel subsystem,
315 such as SELinux. To use audit's filesystem watch feature, please
316 ensure that INOTIFY is configured.
320 depends on AUDITSYSCALL
326 prompt "RCU Implementation"
330 bool "Tree-based hierarchical RCU"
332 This option selects the RCU implementation that is
333 designed for very large SMP system with hundreds or
334 thousands of CPUs. It also scales down nicely to
337 config TREE_PREEMPT_RCU
338 bool "Preemptable tree-based hierarchical RCU"
341 This option selects the RCU implementation that is
342 designed for very large SMP systems with hundreds or
343 thousands of CPUs, but for which real-time response
344 is also required. It also scales down nicely to
348 bool "UP-only small-memory-footprint RCU"
351 This option selects the RCU implementation that is
352 designed for UP systems from which real-time response
353 is not required. This option greatly reduces the
354 memory footprint of RCU.
359 bool "Enable tracing for RCU"
360 depends on TREE_RCU || TREE_PREEMPT_RCU
362 This option provides tracing in RCU which presents stats
363 in debugfs for debugging RCU implementation.
365 Say Y here if you want to enable RCU tracing
366 Say N if you are unsure.
369 int "Tree-based hierarchical RCU fanout value"
372 depends on TREE_RCU || TREE_PREEMPT_RCU
376 This option controls the fanout of hierarchical implementations
377 of RCU, allowing RCU to work efficiently on machines with
378 large numbers of CPUs. This value must be at least the cube
379 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
380 systems and up to 262,144 for 64-bit systems.
382 Select a specific number if testing RCU itself.
383 Take the default if unsure.
385 config RCU_FANOUT_EXACT
386 bool "Disable tree-based hierarchical RCU auto-balancing"
387 depends on TREE_RCU || TREE_PREEMPT_RCU
390 This option forces use of the exact RCU_FANOUT value specified,
391 regardless of imbalances in the hierarchy. This is useful for
392 testing RCU itself, and might one day be useful on systems with
393 strong NUMA behavior.
395 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
399 config RCU_FAST_NO_HZ
400 bool "Accelerate last non-dyntick-idle CPU's grace periods"
401 depends on TREE_RCU && NO_HZ && SMP
404 This option causes RCU to attempt to accelerate grace periods
405 in order to allow the final CPU to enter dynticks-idle state
406 more quickly. On the other hand, this option increases the
407 overhead of the dynticks-idle checking, particularly on systems
408 with large numbers of CPUs.
410 Say Y if energy efficiency is critically important, particularly
411 if you have relatively few CPUs.
413 Say N if you are unsure.
415 config TREE_RCU_TRACE
416 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
419 This option provides tracing for the TREE_RCU and
420 TREE_PREEMPT_RCU implementations, permitting Makefile to
421 trivially select kernel/rcutree_trace.c.
423 endmenu # "RCU Subsystem"
426 tristate "Kernel .config support"
428 This option enables the complete Linux kernel ".config" file
429 contents to be saved in the kernel. It provides documentation
430 of which kernel options are used in a running kernel or in an
431 on-disk kernel. This information can be extracted from the kernel
432 image file with the script scripts/extract-ikconfig and used as
433 input to rebuild the current kernel or to build another kernel.
434 It can also be extracted from a running kernel by reading
435 /proc/config.gz if enabled (below).
438 bool "Enable access to .config through /proc/config.gz"
439 depends on IKCONFIG && PROC_FS
441 This option enables access to the kernel configuration file
442 through /proc/config.gz.
445 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
449 Select kernel log buffer size as a power of 2.
459 # Architectures with an unreliable sched_clock() should select this:
461 config HAVE_UNSTABLE_SCHED_CLOCK
465 boolean "Control Group support"
468 This option adds support for grouping sets of processes together, for
469 use with process control subsystems such as Cpusets, CFS, memory
470 controls or device isolation.
472 - Documentation/scheduler/sched-design-CFS.txt (CFS)
473 - Documentation/cgroups/ (features for grouping, isolation
474 and resource control)
481 bool "Example debug cgroup subsystem"
485 This option enables a simple cgroup subsystem that
486 exports useful debugging information about the cgroups
492 bool "Namespace cgroup subsystem"
495 Provides a simple namespace cgroup subsystem to
496 provide hierarchical naming of sets of namespaces,
497 for instance virtual servers and checkpoint/restart
500 config CGROUP_FREEZER
501 bool "Freezer cgroup subsystem"
504 Provides a way to freeze and unfreeze all tasks in a
508 bool "Device controller for cgroups"
509 depends on CGROUPS && EXPERIMENTAL
511 Provides a cgroup implementing whitelists for devices which
512 a process in the cgroup can mknod or open.
515 bool "Cpuset support"
518 This option will let you create and manage CPUSETs which
519 allow dynamically partitioning a system into sets of CPUs and
520 Memory Nodes and assigning tasks to run only within those sets.
521 This is primarily useful on large SMP or NUMA systems.
525 config PROC_PID_CPUSET
526 bool "Include legacy /proc/<pid>/cpuset file"
530 config CGROUP_CPUACCT
531 bool "Simple CPU accounting cgroup subsystem"
534 Provides a simple Resource Controller for monitoring the
535 total CPU consumed by the tasks in a cgroup.
537 config RESOURCE_COUNTERS
538 bool "Resource counters"
540 This option enables controller independent resource accounting
541 infrastructure that works with cgroups.
544 config CGROUP_MEM_RES_CTLR
545 bool "Memory Resource Controller for Control Groups"
546 depends on CGROUPS && RESOURCE_COUNTERS
549 Provides a memory resource controller that manages both anonymous
550 memory and page cache. (See Documentation/cgroups/memory.txt)
552 Note that setting this option increases fixed memory overhead
553 associated with each page of memory in the system. By this,
554 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
555 usage tracking struct at boot. Total amount of this is printed out
558 Only enable when you're ok with these trade offs and really
559 sure you need the memory resource controller. Even when you enable
560 this, you can set "cgroup_disable=memory" at your boot option to
561 disable memory resource controller and you can avoid overheads.
562 (and lose benefits of memory resource controller)
564 This config option also selects MM_OWNER config option, which
565 could in turn add some fork/exit overhead.
567 config CGROUP_MEM_RES_CTLR_SWAP
568 bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
569 depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
571 Add swap management feature to memory resource controller. When you
572 enable this, you can limit mem+swap usage per cgroup. In other words,
573 when you disable this, memory resource controller has no cares to
574 usage of swap...a process can exhaust all of the swap. This extension
575 is useful when you want to avoid exhaustion swap but this itself
576 adds more overheads and consumes memory for remembering information.
577 Especially if you use 32bit system or small memory system, please
578 be careful about enabling this. When memory resource controller
579 is disabled by boot option, this will be automatically disabled and
580 there will be no overhead from this. Even when you set this config=y,
581 if boot option "noswapaccount" is set, swap will not be accounted.
582 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
583 size is 4096bytes, 512k per 1Gbytes of swap.
585 menuconfig CGROUP_SCHED
586 bool "Group CPU scheduler"
587 depends on EXPERIMENTAL && CGROUPS
590 This feature lets CPU scheduler recognize task groups and control CPU
591 bandwidth allocation to such task groups. It uses cgroups to group
595 config FAIR_GROUP_SCHED
596 bool "Group scheduling for SCHED_OTHER"
597 depends on CGROUP_SCHED
600 config RT_GROUP_SCHED
601 bool "Group scheduling for SCHED_RR/FIFO"
602 depends on EXPERIMENTAL
603 depends on CGROUP_SCHED
606 This feature lets you explicitly allocate real CPU bandwidth
607 to users or control groups (depending on the "Basis for grouping tasks"
608 setting below. If enabled, it will also make it impossible to
609 schedule realtime tasks for non-root users until you allocate
610 realtime bandwidth for them.
611 See Documentation/scheduler/sched-rt-group.txt for more information.
616 tristate "Block IO controller"
617 depends on CGROUPS && BLOCK
620 Generic block IO controller cgroup interface. This is the common
621 cgroup interface which should be used by various IO controlling
624 Currently, CFQ IO scheduler uses it to recognize task groups and
625 control disk bandwidth allocation (proportional time slice allocation)
628 This option only enables generic Block IO controller infrastructure.
629 One needs to also enable actual IO controlling logic in CFQ for it
630 to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
632 See Documentation/cgroups/blkio-controller.txt for more information.
634 config DEBUG_BLK_CGROUP
635 bool "Enable Block IO controller debugging"
636 depends on BLK_CGROUP
639 Enable some debugging help. Currently it exports additional stat
640 files in a cgroup which can be useful for debugging.
647 config SYSFS_DEPRECATED
650 config SYSFS_DEPRECATED_V2
651 bool "enable deprecated sysfs features to support old userspace tools"
654 select SYSFS_DEPRECATED
656 This option switches the layout of sysfs to the deprecated
657 version. Do not use it on recent distributions.
659 The current sysfs layout features a unified device tree at
660 /sys/devices/, which is able to express a hierarchy between
661 class devices. If the deprecated option is set to Y, the
662 unified device tree is split into a bus device tree at
663 /sys/devices/ and several individual class device trees at
664 /sys/class/. The class and bus devices will be connected by
665 "<subsystem>:<name>" and the "device" links. The "block"
666 class devices, will not show up in /sys/class/block/. Some
667 subsystems will suppress the creation of some devices which
668 depend on the unified device tree.
670 This option is not a pure compatibility option that can
671 be safely enabled on newer distributions. It will change the
672 layout of sysfs to the non-extensible deprecated version,
673 and disable some features, which can not be exported without
674 confusing older userspace tools. Since 2007/2008 all major
675 distributions do not enable this option, and ship no tools which
676 depend on the deprecated layout or this option.
678 If you are using a new kernel on an older distribution, or use
679 older userspace tools, you might need to say Y here. Do not say Y,
680 if the original kernel, that came with your distribution, has
681 this option set to N.
684 bool "Kernel->user space relay support (formerly relayfs)"
686 This option enables support for relay interface support in
687 certain file systems (such as debugfs).
688 It is designed to provide an efficient mechanism for tools and
689 facilities to relay large amounts of data from kernel space to
695 bool "Namespaces support" if EMBEDDED
698 Provides the way to make tasks work with different objects using
699 the same id. For example same IPC id may refer to different objects
700 or same user id or pid may refer to different tasks when used in
701 different namespaces.
705 depends on NAMESPACES
707 In this namespace tasks see different info provided with the
712 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
714 In this namespace tasks work with IPC ids which correspond to
715 different IPC objects in different namespaces.
718 bool "User namespace (EXPERIMENTAL)"
719 depends on NAMESPACES && EXPERIMENTAL
721 This allows containers, i.e. vservers, to use user namespaces
722 to provide different user info for different servers.
726 bool "PID Namespaces (EXPERIMENTAL)"
728 depends on NAMESPACES && EXPERIMENTAL
730 Support process id namespaces. This allows having multiple
731 processes with the same pid as long as they are in different
732 pid namespaces. This is a building block of containers.
734 Unless you want to work with an experimental feature
738 bool "Network namespace"
740 depends on NAMESPACES && EXPERIMENTAL && NET
742 Allow user space to create what appear to be multiple instances
743 of the network stack.
745 config BLK_DEV_INITRD
746 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
747 depends on BROKEN || !FRV
749 The initial RAM filesystem is a ramfs which is loaded by the
750 boot loader (loadlin or lilo) and that is mounted as root
751 before the normal boot procedure. It is typically used to
752 load modules needed to mount the "real" root file system,
753 etc. See <file:Documentation/initrd.txt> for details.
755 If RAM disk support (BLK_DEV_RAM) is also included, this
756 also enables initial RAM disk (initrd) support and adds
757 15 Kbytes (more on some other architectures) to the kernel size.
767 config CC_OPTIMIZE_FOR_SIZE
768 bool "Optimize for size"
771 Enabling this option will pass "-Os" instead of "-O2" to gcc
772 resulting in a smaller kernel.
783 bool "Configure standard kernel features (for small systems)"
785 This option allows certain base kernel options and settings
786 to be disabled or tweaked. This is for specialized
787 environments which can tolerate a "non-standard" kernel.
788 Only use this if you really know what you are doing.
791 bool "Enable 16-bit UID system calls" if EMBEDDED
792 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
795 This enables the legacy 16-bit UID syscall wrappers.
797 config SYSCTL_SYSCALL
798 bool "Sysctl syscall support" if EMBEDDED
799 depends on PROC_SYSCTL
803 sys_sysctl uses binary paths that have been found challenging
804 to properly maintain and use. The interface in /proc/sys
805 using paths with ascii names is now the primary path to this
808 Almost nothing using the binary sysctl interface so if you are
809 trying to save some space it is probably safe to disable this,
810 making your kernel marginally smaller.
812 If unsure say Y here.
815 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
818 Say Y here to let the kernel print out symbolic crash information and
819 symbolic stack backtraces. This increases the size of the kernel
820 somewhat, as all symbols have to be loaded into the kernel image.
823 bool "Include all symbols in kallsyms"
824 depends on DEBUG_KERNEL && KALLSYMS
826 Normally kallsyms only contains the symbols of functions, for nicer
827 OOPS messages. Some debuggers can use kallsyms for other
828 symbols too: say Y here to include all symbols, if you need them
829 and you don't care about adding 300k to the size of your kernel.
833 config KALLSYMS_EXTRA_PASS
834 bool "Do an extra kallsyms pass"
837 If kallsyms is not working correctly, the build will fail with
838 inconsistent kallsyms data. If that occurs, log a bug report and
839 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
840 Always say N here unless you find a bug in kallsyms, which must be
841 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
842 you wait for kallsyms to be fixed.
846 bool "Support for hot-pluggable devices" if EMBEDDED
849 This option is provided for the case where no hotplug or uevent
850 capabilities is wanted by the kernel. You should only consider
851 disabling this option for embedded systems that do not use modules, a
852 dynamic /dev tree, or dynamic device discovery. Just say Y.
856 bool "Enable support for printk" if EMBEDDED
858 This option enables normal printk support. Removing it
859 eliminates most of the message strings from the kernel image
860 and makes the kernel more or less silent. As this makes it
861 very difficult to diagnose system problems, saying N here is
862 strongly discouraged.
865 bool "BUG() support" if EMBEDDED
868 Disabling this option eliminates support for BUG and WARN, reducing
869 the size of your kernel image and potentially quietly ignoring
870 numerous fatal conditions. You should only consider disabling this
871 option for embedded systems with no facilities for reporting errors.
876 bool "Enable ELF core dumps" if EMBEDDED
878 Enable support for generating core dumps. Disabling saves about 4k.
880 config PCSPKR_PLATFORM
881 bool "Enable PC-Speaker support" if EMBEDDED
882 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
885 This option allows to disable the internal PC-Speaker
886 support, saving some memory.
890 bool "Enable full-sized data structures for core" if EMBEDDED
892 Disabling this option reduces the size of miscellaneous core
893 kernel data structures. This saves memory on small machines,
894 but may reduce performance.
897 bool "Enable futex support" if EMBEDDED
901 Disabling this option will cause the kernel to be built without
902 support for "fast userspace mutexes". The resulting kernel may not
903 run glibc-based applications correctly.
906 bool "Enable eventpoll support" if EMBEDDED
910 Disabling this option will cause the kernel to be built without
911 support for epoll family of system calls.
914 bool "Enable signalfd() system call" if EMBEDDED
918 Enable the signalfd() system call that allows to receive signals
919 on a file descriptor.
924 bool "Enable timerfd() system call" if EMBEDDED
928 Enable the timerfd() system call that allows to receive timer
929 events on a file descriptor.
934 bool "Enable eventfd() system call" if EMBEDDED
938 Enable the eventfd() system call that allows to receive both
939 kernel notification (ie. KAIO) or userspace notifications.
944 bool "Use full shmem filesystem" if EMBEDDED
948 The shmem is an internal filesystem used to manage shared memory.
949 It is backed by swap and manages resource limits. It is also exported
950 to userspace as tmpfs if TMPFS is enabled. Disabling this
951 option replaces shmem and tmpfs with the much simpler ramfs code,
952 which may be appropriate on small systems without swap.
955 bool "Enable AIO support" if EMBEDDED
958 This option enables POSIX asynchronous I/O which may by used
959 by some high performance threaded applications. Disabling
960 this option saves about 7k.
962 config HAVE_PERF_EVENTS
965 See tools/perf/design.txt for details.
967 config PERF_USE_VMALLOC
970 See tools/perf/design.txt for details
972 menu "Kernel Performance Events And Counters"
975 bool "Kernel performance events and counters"
976 default y if (PROFILING || PERF_COUNTERS)
977 depends on HAVE_PERF_EVENTS
980 Enable kernel support for various performance events provided
981 by software and hardware.
983 Software events are supported either built-in or via the
984 use of generic tracepoints.
986 Most modern CPUs support performance events via performance
987 counter registers. These registers count the number of certain
988 types of hw events: such as instructions executed, cachemisses
989 suffered, or branches mis-predicted - without slowing down the
990 kernel or applications. These registers can also trigger interrupts
991 when a threshold number of events have passed - and can thus be
992 used to profile the code that runs on that CPU.
994 The Linux Performance Event subsystem provides an abstraction of
995 these software and hardware event capabilities, available via a
996 system call and used by the "perf" utility in tools/perf/. It
997 provides per task and per CPU counters, and it provides event
998 capabilities on top of those.
1002 config PERF_COUNTERS
1003 bool "Kernel performance counters (old config option)"
1004 depends on HAVE_PERF_EVENTS
1006 This config has been obsoleted by the PERF_EVENTS
1007 config option - please see that one for details.
1009 It has no effect on the kernel whether you enable
1010 it or not, it is a compatibility placeholder.
1014 config DEBUG_PERF_USE_VMALLOC
1016 bool "Debug: use vmalloc to back perf mmap() buffers"
1017 depends on PERF_EVENTS && DEBUG_KERNEL
1018 select PERF_USE_VMALLOC
1020 Use vmalloc memory to back perf mmap() buffers.
1022 Mostly useful for debugging the vmalloc code on platforms
1023 that don't require it.
1029 config VM_EVENT_COUNTERS
1031 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1033 VM event counters are needed for event counts to be shown.
1034 This option allows the disabling of the VM event counters
1035 on EMBEDDED systems. /proc/vmstat will only show page counts
1036 if VM event counters are disabled.
1040 bool "Enable PCI quirk workarounds" if EMBEDDED
1043 This enables workarounds for various PCI chipset
1044 bugs/quirks. Disable this only if your target machine is
1045 unaffected by PCI quirks.
1049 bool "Enable SLUB debugging support" if EMBEDDED
1050 depends on SLUB && SYSFS
1052 SLUB has extensive debug support features. Disabling these can
1053 result in significant savings in code size. This also disables
1054 SLUB sysfs support. /sys/slab will not exist and there will be
1055 no support for cache validation etc.
1058 bool "Disable heap randomization"
1061 Randomizing heap placement makes heap exploits harder, but it
1062 also breaks ancient binaries (including anything libc5 based).
1063 This option changes the bootup default to heap randomization
1064 disabled, and can be overridden at runtime by setting
1065 /proc/sys/kernel/randomize_va_space to 2.
1067 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1070 prompt "Choose SLAB allocator"
1073 This option allows to select a slab allocator.
1078 The regular slab allocator that is established and known to work
1079 well in all environments. It organizes cache hot objects in
1080 per cpu and per node queues.
1083 bool "SLUB (Unqueued Allocator)"
1085 SLUB is a slab allocator that minimizes cache line usage
1086 instead of managing queues of cached objects (SLAB approach).
1087 Per cpu caching is realized using slabs of objects instead
1088 of queues of objects. SLUB can use memory efficiently
1089 and has enhanced diagnostics. SLUB is the default choice for
1094 bool "SLOB (Simple Allocator)"
1096 SLOB replaces the stock allocator with a drastically simpler
1097 allocator. SLOB is generally more space efficient but
1098 does not perform as well on large systems.
1102 config MMAP_ALLOW_UNINITIALIZED
1103 bool "Allow mmapped anonymous memory to be uninitialized"
1104 depends on EMBEDDED && !MMU
1107 Normally, and according to the Linux spec, anonymous memory obtained
1108 from mmap() has it's contents cleared before it is passed to
1109 userspace. Enabling this config option allows you to request that
1110 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1111 providing a huge performance boost. If this option is not enabled,
1112 then the flag will be ignored.
1114 This is taken advantage of by uClibc's malloc(), and also by
1115 ELF-FDPIC binfmt's brk and stack allocator.
1117 Because of the obvious security issues, this option should only be
1118 enabled on embedded devices where you control what is run in
1119 userspace. Since that isn't generally a problem on no-MMU systems,
1120 it is normally safe to say Y here.
1122 See Documentation/nommu-mmap.txt for more information.
1125 bool "Profiling support"
1127 Say Y here to enable the extended profiling support mechanisms used
1128 by profilers such as OProfile.
1131 # Place an empty function call at each tracepoint site. Can be
1132 # dynamically changed for a probe function.
1137 source "arch/Kconfig"
1143 The slow work thread pool provides a number of dynamically allocated
1144 threads that can be used by the kernel to perform operations that
1145 take a relatively long time.
1147 An example of this would be CacheFiles doing a path lookup followed
1148 by a series of mkdirs and a create call, all of which have to touch
1151 See Documentation/slow-work.txt.
1153 config SLOW_WORK_DEBUG
1154 bool "Slow work debugging through debugfs"
1156 depends on SLOW_WORK && DEBUG_FS
1158 Display the contents of the slow work run queue through debugfs,
1159 including items currently executing.
1161 See Documentation/slow-work.txt.
1163 endmenu # General setup
1165 config HAVE_GENERIC_DMA_COHERENT
1172 depends on SLAB || SLUB_DEBUG
1180 default 0 if BASE_FULL
1181 default 1 if !BASE_FULL
1184 bool "Enable loadable module support"
1186 Kernel modules are small pieces of compiled code which can
1187 be inserted in the running kernel, rather than being
1188 permanently built into the kernel. You use the "modprobe"
1189 tool to add (and sometimes remove) them. If you say Y here,
1190 many parts of the kernel can be built as modules (by
1191 answering M instead of Y where indicated): this is most
1192 useful for infrequently used options which are not required
1193 for booting. For more information, see the man pages for
1194 modprobe, lsmod, modinfo, insmod and rmmod.
1196 If you say Y here, you will need to run "make
1197 modules_install" to put the modules under /lib/modules/
1198 where modprobe can find them (you may need to be root to do
1205 config MODULE_FORCE_LOAD
1206 bool "Forced module loading"
1209 Allow loading of modules without version information (ie. modprobe
1210 --force). Forced module loading sets the 'F' (forced) taint flag and
1211 is usually a really bad idea.
1213 config MODULE_UNLOAD
1214 bool "Module unloading"
1216 Without this option you will not be able to unload any
1217 modules (note that some modules may not be unloadable
1218 anyway), which makes your kernel smaller, faster
1219 and simpler. If unsure, say Y.
1221 config MODULE_FORCE_UNLOAD
1222 bool "Forced module unloading"
1223 depends on MODULE_UNLOAD && EXPERIMENTAL
1225 This option allows you to force a module to unload, even if the
1226 kernel believes it is unsafe: the kernel will remove the module
1227 without waiting for anyone to stop using it (using the -f option to
1228 rmmod). This is mainly for kernel developers and desperate users.
1232 bool "Module versioning support"
1234 Usually, you have to use modules compiled with your kernel.
1235 Saying Y here makes it sometimes possible to use modules
1236 compiled for different kernels, by adding enough information
1237 to the modules to (hopefully) spot any changes which would
1238 make them incompatible with the kernel you are running. If
1241 config MODULE_SRCVERSION_ALL
1242 bool "Source checksum for all modules"
1244 Modules which contain a MODULE_VERSION get an extra "srcversion"
1245 field inserted into their modinfo section, which contains a
1246 sum of the source files which made it. This helps maintainers
1247 see exactly which source was used to build a module (since
1248 others sometimes change the module source without updating
1249 the version). With this option, such a "srcversion" field
1250 will be created for all modules. If unsure, say N.
1254 config INIT_ALL_POSSIBLE
1257 Back when each arch used to define their own cpu_online_map and
1258 cpu_possible_map, some of them chose to initialize cpu_possible_map
1259 with all 1s, and others with all 0s. When they were centralised,
1260 it was better to provide this option than to break all the archs
1261 and have several arch maintainers pursuing me down dark alleys.
1266 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1268 Need stop_machine() primitive.
1270 source "block/Kconfig"
1272 config PREEMPT_NOTIFIERS
1279 source "kernel/Kconfig.locks"