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47 drivers that have been replaced by something else, and/or are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,
327 depends on AUDITSYSCALL
332 depends on AUDITSYSCALL
338 prompt "RCU Implementation"
342 bool "Tree-based hierarchical RCU"
343 depends on !PREEMPT && SMP
345 This option selects the RCU implementation that is
346 designed for very large SMP system with hundreds or
347 thousands of CPUs. It also scales down nicely to
350 config TREE_PREEMPT_RCU
351 bool "Preemptible tree-based hierarchical RCU"
354 This option selects the RCU implementation that is
355 designed for very large SMP systems with hundreds or
356 thousands of CPUs, but for which real-time response
357 is also required. It also scales down nicely to
361 bool "UP-only small-memory-footprint RCU"
364 This option selects the RCU implementation that is
365 designed for UP systems from which real-time response
366 is not required. This option greatly reduces the
367 memory footprint of RCU.
369 config TINY_PREEMPT_RCU
370 bool "Preemptible UP-only small-memory-footprint RCU"
371 depends on !SMP && PREEMPT
373 This option selects the RCU implementation that is designed
374 for real-time UP systems. This option greatly reduces the
375 memory footprint of RCU.
380 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
382 This option enables preemptible-RCU code that is common between
383 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
386 bool "Enable tracing for RCU"
388 This option provides tracing in RCU which presents stats
389 in debugfs for debugging RCU implementation.
391 Say Y here if you want to enable RCU tracing
392 Say N if you are unsure.
395 int "Tree-based hierarchical RCU fanout value"
398 depends on TREE_RCU || TREE_PREEMPT_RCU
402 This option controls the fanout of hierarchical implementations
403 of RCU, allowing RCU to work efficiently on machines with
404 large numbers of CPUs. This value must be at least the fourth
405 root of NR_CPUS, which allows NR_CPUS to be insanely large.
406 The default value of RCU_FANOUT should be used for production
407 systems, but if you are stress-testing the RCU implementation
408 itself, small RCU_FANOUT values allow you to test large-system
409 code paths on small(er) systems.
411 Select a specific number if testing RCU itself.
412 Take the default if unsure.
414 config RCU_FANOUT_EXACT
415 bool "Disable tree-based hierarchical RCU auto-balancing"
416 depends on TREE_RCU || TREE_PREEMPT_RCU
419 This option forces use of the exact RCU_FANOUT value specified,
420 regardless of imbalances in the hierarchy. This is useful for
421 testing RCU itself, and might one day be useful on systems with
422 strong NUMA behavior.
424 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
428 config RCU_FAST_NO_HZ
429 bool "Accelerate last non-dyntick-idle CPU's grace periods"
430 depends on TREE_RCU && NO_HZ && SMP
433 This option causes RCU to attempt to accelerate grace periods
434 in order to allow the final CPU to enter dynticks-idle state
435 more quickly. On the other hand, this option increases the
436 overhead of the dynticks-idle checking, particularly on systems
437 with large numbers of CPUs.
439 Say Y if energy efficiency is critically important, particularly
440 if you have relatively few CPUs.
442 Say N if you are unsure.
444 config TREE_RCU_TRACE
445 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
448 This option provides tracing for the TREE_RCU and
449 TREE_PREEMPT_RCU implementations, permitting Makefile to
450 trivially select kernel/rcutree_trace.c.
453 bool "Enable RCU priority boosting"
454 depends on RT_MUTEXES && TINY_PREEMPT_RCU
457 This option boosts the priority of preempted RCU readers that
458 block the current preemptible RCU grace period for too long.
459 This option also prevents heavy loads from blocking RCU
460 callback invocation for all flavors of RCU.
462 Say Y here if you are working with real-time apps or heavy loads
463 Say N here if you are unsure.
465 config RCU_BOOST_PRIO
466 int "Real-time priority to boost RCU readers to"
471 This option specifies the real-time priority to which preempted
472 RCU readers are to be boosted. If you are working with CPU-bound
473 real-time applications, you should specify a priority higher then
474 the highest-priority CPU-bound application.
476 Specify the real-time priority, or take the default if unsure.
478 config RCU_BOOST_DELAY
479 int "Milliseconds to delay boosting after RCU grace-period start"
484 This option specifies the time to wait after the beginning of
485 a given grace period before priority-boosting preempted RCU
486 readers blocking that grace period. Note that any RCU reader
487 blocking an expedited RCU grace period is boosted immediately.
489 Accept the default if unsure.
491 endmenu # "RCU Subsystem"
494 tristate "Kernel .config support"
496 This option enables the complete Linux kernel ".config" file
497 contents to be saved in the kernel. It provides documentation
498 of which kernel options are used in a running kernel or in an
499 on-disk kernel. This information can be extracted from the kernel
500 image file with the script scripts/extract-ikconfig and used as
501 input to rebuild the current kernel or to build another kernel.
502 It can also be extracted from a running kernel by reading
503 /proc/config.gz if enabled (below).
506 bool "Enable access to .config through /proc/config.gz"
507 depends on IKCONFIG && PROC_FS
509 This option enables access to the kernel configuration file
510 through /proc/config.gz.
513 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
517 Select kernel log buffer size as a power of 2.
527 # Architectures with an unreliable sched_clock() should select this:
529 config HAVE_UNSTABLE_SCHED_CLOCK
533 boolean "Control Group support"
536 This option adds support for grouping sets of processes together, for
537 use with process control subsystems such as Cpusets, CFS, memory
538 controls or device isolation.
540 - Documentation/scheduler/sched-design-CFS.txt (CFS)
541 - Documentation/cgroups/ (features for grouping, isolation
542 and resource control)
549 bool "Example debug cgroup subsystem"
553 This option enables a simple cgroup subsystem that
554 exports useful debugging information about the cgroups
560 bool "Namespace cgroup subsystem"
563 Provides a simple namespace cgroup subsystem to
564 provide hierarchical naming of sets of namespaces,
565 for instance virtual servers and checkpoint/restart
568 config CGROUP_FREEZER
569 bool "Freezer cgroup subsystem"
572 Provides a way to freeze and unfreeze all tasks in a
576 bool "Device controller for cgroups"
577 depends on CGROUPS && EXPERIMENTAL
579 Provides a cgroup implementing whitelists for devices which
580 a process in the cgroup can mknod or open.
583 bool "Cpuset support"
586 This option will let you create and manage CPUSETs which
587 allow dynamically partitioning a system into sets of CPUs and
588 Memory Nodes and assigning tasks to run only within those sets.
589 This is primarily useful on large SMP or NUMA systems.
593 config PROC_PID_CPUSET
594 bool "Include legacy /proc/<pid>/cpuset file"
598 config CGROUP_CPUACCT
599 bool "Simple CPU accounting cgroup subsystem"
602 Provides a simple Resource Controller for monitoring the
603 total CPU consumed by the tasks in a cgroup.
605 config RESOURCE_COUNTERS
606 bool "Resource counters"
608 This option enables controller independent resource accounting
609 infrastructure that works with cgroups.
612 config CGROUP_MEM_RES_CTLR
613 bool "Memory Resource Controller for Control Groups"
614 depends on CGROUPS && RESOURCE_COUNTERS
617 Provides a memory resource controller that manages both anonymous
618 memory and page cache. (See Documentation/cgroups/memory.txt)
620 Note that setting this option increases fixed memory overhead
621 associated with each page of memory in the system. By this,
622 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
623 usage tracking struct at boot. Total amount of this is printed out
626 Only enable when you're ok with these trade offs and really
627 sure you need the memory resource controller. Even when you enable
628 this, you can set "cgroup_disable=memory" at your boot option to
629 disable memory resource controller and you can avoid overheads.
630 (and lose benefits of memory resource controller)
632 This config option also selects MM_OWNER config option, which
633 could in turn add some fork/exit overhead.
635 config CGROUP_MEM_RES_CTLR_SWAP
636 bool "Memory Resource Controller Swap Extension"
637 depends on CGROUP_MEM_RES_CTLR && SWAP
639 Add swap management feature to memory resource controller. When you
640 enable this, you can limit mem+swap usage per cgroup. In other words,
641 when you disable this, memory resource controller has no cares to
642 usage of swap...a process can exhaust all of the swap. This extension
643 is useful when you want to avoid exhaustion swap but this itself
644 adds more overheads and consumes memory for remembering information.
645 Especially if you use 32bit system or small memory system, please
646 be careful about enabling this. When memory resource controller
647 is disabled by boot option, this will be automatically disabled and
648 there will be no overhead from this. Even when you set this config=y,
649 if boot option "noswapaccount" is set, swap will not be accounted.
650 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
651 size is 4096bytes, 512k per 1Gbytes of swap.
653 menuconfig CGROUP_SCHED
654 bool "Group CPU scheduler"
655 depends on EXPERIMENTAL && CGROUPS
658 This feature lets CPU scheduler recognize task groups and control CPU
659 bandwidth allocation to such task groups. It uses cgroups to group
663 config FAIR_GROUP_SCHED
664 bool "Group scheduling for SCHED_OTHER"
665 depends on CGROUP_SCHED
668 config RT_GROUP_SCHED
669 bool "Group scheduling for SCHED_RR/FIFO"
670 depends on EXPERIMENTAL
671 depends on CGROUP_SCHED
674 This feature lets you explicitly allocate real CPU bandwidth
675 to task groups. If enabled, it will also make it impossible to
676 schedule realtime tasks for non-root users until you allocate
677 realtime bandwidth for them.
678 See Documentation/scheduler/sched-rt-group.txt for more information.
683 tristate "Block IO controller"
684 depends on CGROUPS && BLOCK
687 Generic block IO controller cgroup interface. This is the common
688 cgroup interface which should be used by various IO controlling
691 Currently, CFQ IO scheduler uses it to recognize task groups and
692 control disk bandwidth allocation (proportional time slice allocation)
695 This option only enables generic Block IO controller infrastructure.
696 One needs to also enable actual IO controlling logic in CFQ for it
697 to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
699 See Documentation/cgroups/blkio-controller.txt for more information.
701 config DEBUG_BLK_CGROUP
702 bool "Enable Block IO controller debugging"
703 depends on BLK_CGROUP
706 Enable some debugging help. Currently it exports additional stat
707 files in a cgroup which can be useful for debugging.
714 config SYSFS_DEPRECATED
717 config SYSFS_DEPRECATED_V2
718 bool "enable deprecated sysfs features to support old userspace tools"
721 select SYSFS_DEPRECATED
723 This option switches the layout of sysfs to the deprecated
724 version. Do not use it on recent distributions.
726 The current sysfs layout features a unified device tree at
727 /sys/devices/, which is able to express a hierarchy between
728 class devices. If the deprecated option is set to Y, the
729 unified device tree is split into a bus device tree at
730 /sys/devices/ and several individual class device trees at
731 /sys/class/. The class and bus devices will be connected by
732 "<subsystem>:<name>" and the "device" links. The "block"
733 class devices, will not show up in /sys/class/block/. Some
734 subsystems will suppress the creation of some devices which
735 depend on the unified device tree.
737 This option is not a pure compatibility option that can
738 be safely enabled on newer distributions. It will change the
739 layout of sysfs to the non-extensible deprecated version,
740 and disable some features, which can not be exported without
741 confusing older userspace tools. Since 2007/2008 all major
742 distributions do not enable this option, and ship no tools which
743 depend on the deprecated layout or this option.
745 If you are using a new kernel on an older distribution, or use
746 older userspace tools, you might need to say Y here. Do not say Y,
747 if the original kernel, that came with your distribution, has
748 this option set to N.
751 bool "Kernel->user space relay support (formerly relayfs)"
753 This option enables support for relay interface support in
754 certain file systems (such as debugfs).
755 It is designed to provide an efficient mechanism for tools and
756 facilities to relay large amounts of data from kernel space to
762 bool "Namespaces support" if EMBEDDED
765 Provides the way to make tasks work with different objects using
766 the same id. For example same IPC id may refer to different objects
767 or same user id or pid may refer to different tasks when used in
768 different namespaces.
772 depends on NAMESPACES
774 In this namespace tasks see different info provided with the
779 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
781 In this namespace tasks work with IPC ids which correspond to
782 different IPC objects in different namespaces.
785 bool "User namespace (EXPERIMENTAL)"
786 depends on NAMESPACES && EXPERIMENTAL
788 This allows containers, i.e. vservers, to use user namespaces
789 to provide different user info for different servers.
793 bool "PID Namespaces (EXPERIMENTAL)"
795 depends on NAMESPACES && EXPERIMENTAL
797 Support process id namespaces. This allows having multiple
798 processes with the same pid as long as they are in different
799 pid namespaces. This is a building block of containers.
801 Unless you want to work with an experimental feature
805 bool "Network namespace"
807 depends on NAMESPACES && EXPERIMENTAL && NET
809 Allow user space to create what appear to be multiple instances
810 of the network stack.
812 config BLK_DEV_INITRD
813 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
814 depends on BROKEN || !FRV
816 The initial RAM filesystem is a ramfs which is loaded by the
817 boot loader (loadlin or lilo) and that is mounted as root
818 before the normal boot procedure. It is typically used to
819 load modules needed to mount the "real" root file system,
820 etc. See <file:Documentation/initrd.txt> for details.
822 If RAM disk support (BLK_DEV_RAM) is also included, this
823 also enables initial RAM disk (initrd) support and adds
824 15 Kbytes (more on some other architectures) to the kernel size.
834 config CC_OPTIMIZE_FOR_SIZE
835 bool "Optimize for size"
838 Enabling this option will pass "-Os" instead of "-O2" to gcc
839 resulting in a smaller kernel.
850 bool "Configure standard kernel features (for small systems)"
852 This option allows certain base kernel options and settings
853 to be disabled or tweaked. This is for specialized
854 environments which can tolerate a "non-standard" kernel.
855 Only use this if you really know what you are doing.
858 bool "Enable 16-bit UID system calls" if EMBEDDED
859 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
862 This enables the legacy 16-bit UID syscall wrappers.
864 config SYSCTL_SYSCALL
865 bool "Sysctl syscall support" if EMBEDDED
866 depends on PROC_SYSCTL
870 sys_sysctl uses binary paths that have been found challenging
871 to properly maintain and use. The interface in /proc/sys
872 using paths with ascii names is now the primary path to this
875 Almost nothing using the binary sysctl interface so if you are
876 trying to save some space it is probably safe to disable this,
877 making your kernel marginally smaller.
879 If unsure say Y here.
882 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
885 Say Y here to let the kernel print out symbolic crash information and
886 symbolic stack backtraces. This increases the size of the kernel
887 somewhat, as all symbols have to be loaded into the kernel image.
890 bool "Include all symbols in kallsyms"
891 depends on DEBUG_KERNEL && KALLSYMS
893 Normally kallsyms only contains the symbols of functions, for nicer
894 OOPS messages. Some debuggers can use kallsyms for other
895 symbols too: say Y here to include all symbols, if you need them
896 and you don't care about adding 300k to the size of your kernel.
900 config KALLSYMS_EXTRA_PASS
901 bool "Do an extra kallsyms pass"
904 If kallsyms is not working correctly, the build will fail with
905 inconsistent kallsyms data. If that occurs, log a bug report and
906 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
907 Always say N here unless you find a bug in kallsyms, which must be
908 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
909 you wait for kallsyms to be fixed.
913 bool "Support for hot-pluggable devices" if EMBEDDED
916 This option is provided for the case where no hotplug or uevent
917 capabilities is wanted by the kernel. You should only consider
918 disabling this option for embedded systems that do not use modules, a
919 dynamic /dev tree, or dynamic device discovery. Just say Y.
923 bool "Enable support for printk" if EMBEDDED
925 This option enables normal printk support. Removing it
926 eliminates most of the message strings from the kernel image
927 and makes the kernel more or less silent. As this makes it
928 very difficult to diagnose system problems, saying N here is
929 strongly discouraged.
932 bool "BUG() support" if EMBEDDED
935 Disabling this option eliminates support for BUG and WARN, reducing
936 the size of your kernel image and potentially quietly ignoring
937 numerous fatal conditions. You should only consider disabling this
938 option for embedded systems with no facilities for reporting errors.
943 bool "Enable ELF core dumps" if EMBEDDED
945 Enable support for generating core dumps. Disabling saves about 4k.
947 config PCSPKR_PLATFORM
948 bool "Enable PC-Speaker support" if EMBEDDED
949 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
952 This option allows to disable the internal PC-Speaker
953 support, saving some memory.
957 bool "Enable full-sized data structures for core" if EMBEDDED
959 Disabling this option reduces the size of miscellaneous core
960 kernel data structures. This saves memory on small machines,
961 but may reduce performance.
964 bool "Enable futex support" if EMBEDDED
968 Disabling this option will cause the kernel to be built without
969 support for "fast userspace mutexes". The resulting kernel may not
970 run glibc-based applications correctly.
973 bool "Enable eventpoll support" if EMBEDDED
977 Disabling this option will cause the kernel to be built without
978 support for epoll family of system calls.
981 bool "Enable signalfd() system call" if EMBEDDED
985 Enable the signalfd() system call that allows to receive signals
986 on a file descriptor.
991 bool "Enable timerfd() system call" if EMBEDDED
995 Enable the timerfd() system call that allows to receive timer
996 events on a file descriptor.
1001 bool "Enable eventfd() system call" if EMBEDDED
1005 Enable the eventfd() system call that allows to receive both
1006 kernel notification (ie. KAIO) or userspace notifications.
1011 bool "Use full shmem filesystem" if EMBEDDED
1015 The shmem is an internal filesystem used to manage shared memory.
1016 It is backed by swap and manages resource limits. It is also exported
1017 to userspace as tmpfs if TMPFS is enabled. Disabling this
1018 option replaces shmem and tmpfs with the much simpler ramfs code,
1019 which may be appropriate on small systems without swap.
1022 bool "Enable AIO support" if EMBEDDED
1025 This option enables POSIX asynchronous I/O which may by used
1026 by some high performance threaded applications. Disabling
1027 this option saves about 7k.
1029 config HAVE_PERF_EVENTS
1032 See tools/perf/design.txt for details.
1034 config PERF_USE_VMALLOC
1037 See tools/perf/design.txt for details
1039 menu "Kernel Performance Events And Counters"
1042 bool "Kernel performance events and counters"
1043 default y if (PROFILING || PERF_COUNTERS)
1044 depends on HAVE_PERF_EVENTS
1047 Enable kernel support for various performance events provided
1048 by software and hardware.
1050 Software events are supported either built-in or via the
1051 use of generic tracepoints.
1053 Most modern CPUs support performance events via performance
1054 counter registers. These registers count the number of certain
1055 types of hw events: such as instructions executed, cachemisses
1056 suffered, or branches mis-predicted - without slowing down the
1057 kernel or applications. These registers can also trigger interrupts
1058 when a threshold number of events have passed - and can thus be
1059 used to profile the code that runs on that CPU.
1061 The Linux Performance Event subsystem provides an abstraction of
1062 these software and hardware event capabilities, available via a
1063 system call and used by the "perf" utility in tools/perf/. It
1064 provides per task and per CPU counters, and it provides event
1065 capabilities on top of those.
1069 config PERF_COUNTERS
1070 bool "Kernel performance counters (old config option)"
1071 depends on HAVE_PERF_EVENTS
1073 This config has been obsoleted by the PERF_EVENTS
1074 config option - please see that one for details.
1076 It has no effect on the kernel whether you enable
1077 it or not, it is a compatibility placeholder.
1081 config DEBUG_PERF_USE_VMALLOC
1083 bool "Debug: use vmalloc to back perf mmap() buffers"
1084 depends on PERF_EVENTS && DEBUG_KERNEL
1085 select PERF_USE_VMALLOC
1087 Use vmalloc memory to back perf mmap() buffers.
1089 Mostly useful for debugging the vmalloc code on platforms
1090 that don't require it.
1096 config VM_EVENT_COUNTERS
1098 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1100 VM event counters are needed for event counts to be shown.
1101 This option allows the disabling of the VM event counters
1102 on EMBEDDED systems. /proc/vmstat will only show page counts
1103 if VM event counters are disabled.
1107 bool "Enable PCI quirk workarounds" if EMBEDDED
1110 This enables workarounds for various PCI chipset
1111 bugs/quirks. Disable this only if your target machine is
1112 unaffected by PCI quirks.
1116 bool "Enable SLUB debugging support" if EMBEDDED
1117 depends on SLUB && SYSFS
1119 SLUB has extensive debug support features. Disabling these can
1120 result in significant savings in code size. This also disables
1121 SLUB sysfs support. /sys/slab will not exist and there will be
1122 no support for cache validation etc.
1125 bool "Disable heap randomization"
1128 Randomizing heap placement makes heap exploits harder, but it
1129 also breaks ancient binaries (including anything libc5 based).
1130 This option changes the bootup default to heap randomization
1131 disabled, and can be overridden at runtime by setting
1132 /proc/sys/kernel/randomize_va_space to 2.
1134 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1137 prompt "Choose SLAB allocator"
1140 This option allows to select a slab allocator.
1145 The regular slab allocator that is established and known to work
1146 well in all environments. It organizes cache hot objects in
1147 per cpu and per node queues.
1150 bool "SLUB (Unqueued Allocator)"
1152 SLUB is a slab allocator that minimizes cache line usage
1153 instead of managing queues of cached objects (SLAB approach).
1154 Per cpu caching is realized using slabs of objects instead
1155 of queues of objects. SLUB can use memory efficiently
1156 and has enhanced diagnostics. SLUB is the default choice for
1161 bool "SLOB (Simple Allocator)"
1163 SLOB replaces the stock allocator with a drastically simpler
1164 allocator. SLOB is generally more space efficient but
1165 does not perform as well on large systems.
1169 config MMAP_ALLOW_UNINITIALIZED
1170 bool "Allow mmapped anonymous memory to be uninitialized"
1171 depends on EMBEDDED && !MMU
1174 Normally, and according to the Linux spec, anonymous memory obtained
1175 from mmap() has it's contents cleared before it is passed to
1176 userspace. Enabling this config option allows you to request that
1177 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1178 providing a huge performance boost. If this option is not enabled,
1179 then the flag will be ignored.
1181 This is taken advantage of by uClibc's malloc(), and also by
1182 ELF-FDPIC binfmt's brk and stack allocator.
1184 Because of the obvious security issues, this option should only be
1185 enabled on embedded devices where you control what is run in
1186 userspace. Since that isn't generally a problem on no-MMU systems,
1187 it is normally safe to say Y here.
1189 See Documentation/nommu-mmap.txt for more information.
1192 bool "Profiling support"
1194 Say Y here to enable the extended profiling support mechanisms used
1195 by profilers such as OProfile.
1198 # Place an empty function call at each tracepoint site. Can be
1199 # dynamically changed for a probe function.
1204 source "arch/Kconfig"
1206 endmenu # General setup
1208 config HAVE_GENERIC_DMA_COHERENT
1215 depends on SLAB || SLUB_DEBUG
1223 default 0 if BASE_FULL
1224 default 1 if !BASE_FULL
1227 bool "Enable loadable module support"
1229 Kernel modules are small pieces of compiled code which can
1230 be inserted in the running kernel, rather than being
1231 permanently built into the kernel. You use the "modprobe"
1232 tool to add (and sometimes remove) them. If you say Y here,
1233 many parts of the kernel can be built as modules (by
1234 answering M instead of Y where indicated): this is most
1235 useful for infrequently used options which are not required
1236 for booting. For more information, see the man pages for
1237 modprobe, lsmod, modinfo, insmod and rmmod.
1239 If you say Y here, you will need to run "make
1240 modules_install" to put the modules under /lib/modules/
1241 where modprobe can find them (you may need to be root to do
1248 config MODULE_FORCE_LOAD
1249 bool "Forced module loading"
1252 Allow loading of modules without version information (ie. modprobe
1253 --force). Forced module loading sets the 'F' (forced) taint flag and
1254 is usually a really bad idea.
1256 config MODULE_UNLOAD
1257 bool "Module unloading"
1259 Without this option you will not be able to unload any
1260 modules (note that some modules may not be unloadable
1261 anyway), which makes your kernel smaller, faster
1262 and simpler. If unsure, say Y.
1264 config MODULE_FORCE_UNLOAD
1265 bool "Forced module unloading"
1266 depends on MODULE_UNLOAD && EXPERIMENTAL
1268 This option allows you to force a module to unload, even if the
1269 kernel believes it is unsafe: the kernel will remove the module
1270 without waiting for anyone to stop using it (using the -f option to
1271 rmmod). This is mainly for kernel developers and desperate users.
1275 bool "Module versioning support"
1277 Usually, you have to use modules compiled with your kernel.
1278 Saying Y here makes it sometimes possible to use modules
1279 compiled for different kernels, by adding enough information
1280 to the modules to (hopefully) spot any changes which would
1281 make them incompatible with the kernel you are running. If
1284 config MODULE_SRCVERSION_ALL
1285 bool "Source checksum for all modules"
1287 Modules which contain a MODULE_VERSION get an extra "srcversion"
1288 field inserted into their modinfo section, which contains a
1289 sum of the source files which made it. This helps maintainers
1290 see exactly which source was used to build a module (since
1291 others sometimes change the module source without updating
1292 the version). With this option, such a "srcversion" field
1293 will be created for all modules. If unsure, say N.
1297 config INIT_ALL_POSSIBLE
1300 Back when each arch used to define their own cpu_online_map and
1301 cpu_possible_map, some of them chose to initialize cpu_possible_map
1302 with all 1s, and others with all 0s. When they were centralised,
1303 it was better to provide this option than to break all the archs
1304 and have several arch maintainers pursuing me down dark alleys.
1309 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1311 Need stop_machine() primitive.
1313 source "block/Kconfig"
1315 config PREEMPT_NOTIFIERS
1322 source "kernel/Kconfig.locks"