7 option env="KERNELVERSION"
13 default "/lib/modules/$UNAME_RELEASE/.config"
14 default "/etc/kernel-config"
15 default "/boot/config-$UNAME_RELEASE"
16 default "$ARCH_DEFCONFIG"
17 default "arch/$ARCH/defconfig"
29 depends on HAVE_IRQ_WORK
34 bool "Prompt for development and/or incomplete code/drivers"
36 Some of the various things that Linux supports (such as network
37 drivers, file systems, network protocols, etc.) can be in a state
38 of development where the functionality, stability, or the level of
39 testing is not yet high enough for general use. This is usually
40 known as the "alpha-test" phase among developers. If a feature is
41 currently in alpha-test, then the developers usually discourage
42 uninformed widespread use of this feature by the general public to
43 avoid "Why doesn't this work?" type mail messages. However, active
44 testing and use of these systems is welcomed. Just be aware that it
45 may not meet the normal level of reliability or it may fail to work
46 in some special cases. Detailed bug reports from people familiar
47 with the kernel internals are usually welcomed by the developers
48 (before submitting bug reports, please read the documents
49 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
50 <file:Documentation/BUG-HUNTING>, and
51 <file:Documentation/oops-tracing.txt> in the kernel source).
53 This option will also make obsoleted drivers available. These are
54 drivers that have been replaced by something else, and/or are
55 scheduled to be removed in a future kernel release.
57 Unless you intend to help test and develop a feature or driver that
58 falls into this category, or you have a situation that requires
59 using these features, you should probably say N here, which will
60 cause the configurator to present you with fewer choices. If
61 you say Y here, you will be offered the choice of using features or
62 drivers that are currently considered to be in the alpha-test phase.
69 depends on BROKEN || !SMP
74 depends on (SMP || PREEMPT) && BKL
77 config INIT_ENV_ARG_LIMIT
82 Maximum of each of the number of arguments and environment
83 variables passed to init from the kernel command line.
87 string "Cross-compiler tool prefix"
89 Same as running 'make CROSS_COMPILE=prefix-' but stored for
90 default make runs in this kernel build directory. You don't
91 need to set this unless you want the configured kernel build
92 directory to select the cross-compiler automatically.
95 string "Local version - append to kernel release"
97 Append an extra string to the end of your kernel version.
98 This will show up when you type uname, for example.
99 The string you set here will be appended after the contents of
100 any files with a filename matching localversion* in your
101 object and source tree, in that order. Your total string can
102 be a maximum of 64 characters.
104 config LOCALVERSION_AUTO
105 bool "Automatically append version information to the version string"
108 This will try to automatically determine if the current tree is a
109 release tree by looking for git tags that belong to the current
110 top of tree revision.
112 A string of the format -gxxxxxxxx will be added to the localversion
113 if a git-based tree is found. The string generated by this will be
114 appended after any matching localversion* files, and after the value
115 set in CONFIG_LOCALVERSION.
117 (The actual string used here is the first eight characters produced
118 by running the command:
120 $ git rev-parse --verify HEAD
122 which is done within the script "scripts/setlocalversion".)
124 config HAVE_KERNEL_GZIP
127 config HAVE_KERNEL_BZIP2
130 config HAVE_KERNEL_LZMA
133 config HAVE_KERNEL_LZO
137 prompt "Kernel compression mode"
139 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
141 The linux kernel is a kind of self-extracting executable.
142 Several compression algorithms are available, which differ
143 in efficiency, compression and decompression speed.
144 Compression speed is only relevant when building a kernel.
145 Decompression speed is relevant at each boot.
147 If you have any problems with bzip2 or lzma compressed
148 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
149 version of this functionality (bzip2 only), for 2.4, was
150 supplied by Christian Ludwig)
152 High compression options are mostly useful for users, who
153 are low on disk space (embedded systems), but for whom ram
156 If in doubt, select 'gzip'
160 depends on HAVE_KERNEL_GZIP
162 The old and tried gzip compression. It provides a good balance
163 between compression ratio and decompression speed.
167 depends on HAVE_KERNEL_BZIP2
169 Its compression ratio and speed is intermediate.
170 Decompression speed is slowest among the three. The kernel
171 size is about 10% smaller with bzip2, in comparison to gzip.
172 Bzip2 uses a large amount of memory. For modern kernels you
173 will need at least 8MB RAM or more for booting.
177 depends on HAVE_KERNEL_LZMA
179 The most recent compression algorithm.
180 Its ratio is best, decompression speed is between the other
181 two. Compression is slowest. The kernel size is about 33%
182 smaller with LZMA in comparison to gzip.
186 depends on HAVE_KERNEL_LZO
188 Its compression ratio is the poorest among the 4. The kernel
189 size is about 10% bigger than gzip; however its speed
190 (both compression and decompression) is the fastest.
195 bool "Support for paging of anonymous memory (swap)"
196 depends on MMU && BLOCK
199 This option allows you to choose whether you want to have support
200 for so called swap devices or swap files in your kernel that are
201 used to provide more virtual memory than the actual RAM present
202 in your computer. If unsure say Y.
207 Inter Process Communication is a suite of library functions and
208 system calls which let processes (running programs) synchronize and
209 exchange information. It is generally considered to be a good thing,
210 and some programs won't run unless you say Y here. In particular, if
211 you want to run the DOS emulator dosemu under Linux (read the
212 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
213 you'll need to say Y here.
215 You can find documentation about IPC with "info ipc" and also in
216 section 6.4 of the Linux Programmer's Guide, available from
217 <http://www.tldp.org/guides.html>.
219 config SYSVIPC_SYSCTL
226 bool "POSIX Message Queues"
227 depends on NET && EXPERIMENTAL
229 POSIX variant of message queues is a part of IPC. In POSIX message
230 queues every message has a priority which decides about succession
231 of receiving it by a process. If you want to compile and run
232 programs written e.g. for Solaris with use of its POSIX message
233 queues (functions mq_*) say Y here.
235 POSIX message queues are visible as a filesystem called 'mqueue'
236 and can be mounted somewhere if you want to do filesystem
237 operations on message queues.
241 config POSIX_MQUEUE_SYSCTL
243 depends on POSIX_MQUEUE
247 config BSD_PROCESS_ACCT
248 bool "BSD Process Accounting"
250 If you say Y here, a user level program will be able to instruct the
251 kernel (via a special system call) to write process accounting
252 information to a file: whenever a process exits, information about
253 that process will be appended to the file by the kernel. The
254 information includes things such as creation time, owning user,
255 command name, memory usage, controlling terminal etc. (the complete
256 list is in the struct acct in <file:include/linux/acct.h>). It is
257 up to the user level program to do useful things with this
258 information. This is generally a good idea, so say Y.
260 config BSD_PROCESS_ACCT_V3
261 bool "BSD Process Accounting version 3 file format"
262 depends on BSD_PROCESS_ACCT
265 If you say Y here, the process accounting information is written
266 in a new file format that also logs the process IDs of each
267 process and it's parent. Note that this file format is incompatible
268 with previous v0/v1/v2 file formats, so you will need updated tools
269 for processing it. A preliminary version of these tools is available
270 at <http://www.gnu.org/software/acct/>.
273 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
277 Export selected statistics for tasks/processes through the
278 generic netlink interface. Unlike BSD process accounting, the
279 statistics are available during the lifetime of tasks/processes as
280 responses to commands. Like BSD accounting, they are sent to user
285 config TASK_DELAY_ACCT
286 bool "Enable per-task delay accounting (EXPERIMENTAL)"
289 Collect information on time spent by a task waiting for system
290 resources like cpu, synchronous block I/O completion and swapping
291 in pages. Such statistics can help in setting a task's priorities
292 relative to other tasks for cpu, io, rss limits etc.
297 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
300 Collect extended task accounting data and send the data
301 to userland for processing over the taskstats interface.
305 config TASK_IO_ACCOUNTING
306 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
307 depends on TASK_XACCT
309 Collect information on the number of bytes of storage I/O which this
315 bool "Auditing support"
318 Enable auditing infrastructure that can be used with another
319 kernel subsystem, such as SELinux (which requires this for
320 logging of avc messages output). Does not do system-call
321 auditing without CONFIG_AUDITSYSCALL.
324 bool "Enable system-call auditing support"
325 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
326 default y if SECURITY_SELINUX
328 Enable low-overhead system-call auditing infrastructure that
329 can be used independently or with another kernel subsystem,
334 depends on AUDITSYSCALL
339 depends on AUDITSYSCALL
342 source "kernel/irq/Kconfig"
347 prompt "RCU Implementation"
351 bool "Tree-based hierarchical RCU"
352 depends on !PREEMPT && SMP
354 This option selects the RCU implementation that is
355 designed for very large SMP system with hundreds or
356 thousands of CPUs. It also scales down nicely to
359 config TREE_PREEMPT_RCU
360 bool "Preemptible tree-based hierarchical RCU"
363 This option selects the RCU implementation that is
364 designed for very large SMP systems with hundreds or
365 thousands of CPUs, but for which real-time response
366 is also required. It also scales down nicely to
370 bool "UP-only small-memory-footprint RCU"
373 This option selects the RCU implementation that is
374 designed for UP systems from which real-time response
375 is not required. This option greatly reduces the
376 memory footprint of RCU.
378 config TINY_PREEMPT_RCU
379 bool "Preemptible UP-only small-memory-footprint RCU"
380 depends on !SMP && PREEMPT
382 This option selects the RCU implementation that is designed
383 for real-time UP systems. This option greatly reduces the
384 memory footprint of RCU.
389 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
391 This option enables preemptible-RCU code that is common between
392 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
395 bool "Enable tracing for RCU"
397 This option provides tracing in RCU which presents stats
398 in debugfs for debugging RCU implementation.
400 Say Y here if you want to enable RCU tracing
401 Say N if you are unsure.
404 int "Tree-based hierarchical RCU fanout value"
407 depends on TREE_RCU || TREE_PREEMPT_RCU
411 This option controls the fanout of hierarchical implementations
412 of RCU, allowing RCU to work efficiently on machines with
413 large numbers of CPUs. This value must be at least the fourth
414 root of NR_CPUS, which allows NR_CPUS to be insanely large.
415 The default value of RCU_FANOUT should be used for production
416 systems, but if you are stress-testing the RCU implementation
417 itself, small RCU_FANOUT values allow you to test large-system
418 code paths on small(er) systems.
420 Select a specific number if testing RCU itself.
421 Take the default if unsure.
423 config RCU_FANOUT_EXACT
424 bool "Disable tree-based hierarchical RCU auto-balancing"
425 depends on TREE_RCU || TREE_PREEMPT_RCU
428 This option forces use of the exact RCU_FANOUT value specified,
429 regardless of imbalances in the hierarchy. This is useful for
430 testing RCU itself, and might one day be useful on systems with
431 strong NUMA behavior.
433 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
437 config RCU_FAST_NO_HZ
438 bool "Accelerate last non-dyntick-idle CPU's grace periods"
439 depends on TREE_RCU && NO_HZ && SMP
442 This option causes RCU to attempt to accelerate grace periods
443 in order to allow the final CPU to enter dynticks-idle state
444 more quickly. On the other hand, this option increases the
445 overhead of the dynticks-idle checking, particularly on systems
446 with large numbers of CPUs.
448 Say Y if energy efficiency is critically important, particularly
449 if you have relatively few CPUs.
451 Say N if you are unsure.
453 config TREE_RCU_TRACE
454 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
457 This option provides tracing for the TREE_RCU and
458 TREE_PREEMPT_RCU implementations, permitting Makefile to
459 trivially select kernel/rcutree_trace.c.
462 bool "Enable RCU priority boosting"
463 depends on RT_MUTEXES && TINY_PREEMPT_RCU
466 This option boosts the priority of preempted RCU readers that
467 block the current preemptible RCU grace period for too long.
468 This option also prevents heavy loads from blocking RCU
469 callback invocation for all flavors of RCU.
471 Say Y here if you are working with real-time apps or heavy loads
472 Say N here if you are unsure.
474 config RCU_BOOST_PRIO
475 int "Real-time priority to boost RCU readers to"
480 This option specifies the real-time priority to which preempted
481 RCU readers are to be boosted. If you are working with CPU-bound
482 real-time applications, you should specify a priority higher then
483 the highest-priority CPU-bound application.
485 Specify the real-time priority, or take the default if unsure.
487 config RCU_BOOST_DELAY
488 int "Milliseconds to delay boosting after RCU grace-period start"
493 This option specifies the time to wait after the beginning of
494 a given grace period before priority-boosting preempted RCU
495 readers blocking that grace period. Note that any RCU reader
496 blocking an expedited RCU grace period is boosted immediately.
498 Accept the default if unsure.
500 config SRCU_SYNCHRONIZE_DELAY
501 int "Microseconds to delay before waiting for readers"
505 This option controls how long SRCU delays before entering its
506 loop waiting on SRCU readers. The purpose of this loop is
507 to avoid the unconditional context-switch penalty that would
508 otherwise be incurred if there was an active SRCU reader,
509 in a manner similar to adaptive locking schemes. This should
510 be set to be a bit longer than the common-case SRCU read-side
511 critical-section overhead.
513 Accept the default if unsure.
515 endmenu # "RCU Subsystem"
518 tristate "Kernel .config support"
520 This option enables the complete Linux kernel ".config" file
521 contents to be saved in the kernel. It provides documentation
522 of which kernel options are used in a running kernel or in an
523 on-disk kernel. This information can be extracted from the kernel
524 image file with the script scripts/extract-ikconfig and used as
525 input to rebuild the current kernel or to build another kernel.
526 It can also be extracted from a running kernel by reading
527 /proc/config.gz if enabled (below).
530 bool "Enable access to .config through /proc/config.gz"
531 depends on IKCONFIG && PROC_FS
533 This option enables access to the kernel configuration file
534 through /proc/config.gz.
537 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
541 Select kernel log buffer size as a power of 2.
551 # Architectures with an unreliable sched_clock() should select this:
553 config HAVE_UNSTABLE_SCHED_CLOCK
557 boolean "Control Group support"
560 This option adds support for grouping sets of processes together, for
561 use with process control subsystems such as Cpusets, CFS, memory
562 controls or device isolation.
564 - Documentation/scheduler/sched-design-CFS.txt (CFS)
565 - Documentation/cgroups/ (features for grouping, isolation
566 and resource control)
573 bool "Example debug cgroup subsystem"
576 This option enables a simple cgroup subsystem that
577 exports useful debugging information about the cgroups
583 bool "Namespace cgroup subsystem"
585 Provides a simple namespace cgroup subsystem to
586 provide hierarchical naming of sets of namespaces,
587 for instance virtual servers and checkpoint/restart
590 config CGROUP_FREEZER
591 bool "Freezer cgroup subsystem"
593 Provides a way to freeze and unfreeze all tasks in a
597 bool "Device controller for cgroups"
599 Provides a cgroup implementing whitelists for devices which
600 a process in the cgroup can mknod or open.
603 bool "Cpuset support"
605 This option will let you create and manage CPUSETs which
606 allow dynamically partitioning a system into sets of CPUs and
607 Memory Nodes and assigning tasks to run only within those sets.
608 This is primarily useful on large SMP or NUMA systems.
612 config PROC_PID_CPUSET
613 bool "Include legacy /proc/<pid>/cpuset file"
617 config CGROUP_CPUACCT
618 bool "Simple CPU accounting cgroup subsystem"
620 Provides a simple Resource Controller for monitoring the
621 total CPU consumed by the tasks in a cgroup.
623 config RESOURCE_COUNTERS
624 bool "Resource counters"
626 This option enables controller independent resource accounting
627 infrastructure that works with cgroups.
629 config CGROUP_MEM_RES_CTLR
630 bool "Memory Resource Controller for Control Groups"
631 depends on RESOURCE_COUNTERS
634 Provides a memory resource controller that manages both anonymous
635 memory and page cache. (See Documentation/cgroups/memory.txt)
637 Note that setting this option increases fixed memory overhead
638 associated with each page of memory in the system. By this,
639 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
640 usage tracking struct at boot. Total amount of this is printed out
643 Only enable when you're ok with these trade offs and really
644 sure you need the memory resource controller. Even when you enable
645 this, you can set "cgroup_disable=memory" at your boot option to
646 disable memory resource controller and you can avoid overheads.
647 (and lose benefits of memory resource controller)
649 This config option also selects MM_OWNER config option, which
650 could in turn add some fork/exit overhead.
652 config CGROUP_MEM_RES_CTLR_SWAP
653 bool "Memory Resource Controller Swap Extension"
654 depends on CGROUP_MEM_RES_CTLR && SWAP
656 Add swap management feature to memory resource controller. When you
657 enable this, you can limit mem+swap usage per cgroup. In other words,
658 when you disable this, memory resource controller has no cares to
659 usage of swap...a process can exhaust all of the swap. This extension
660 is useful when you want to avoid exhaustion swap but this itself
661 adds more overheads and consumes memory for remembering information.
662 Especially if you use 32bit system or small memory system, please
663 be careful about enabling this. When memory resource controller
664 is disabled by boot option, this will be automatically disabled and
665 there will be no overhead from this. Even when you set this config=y,
666 if boot option "noswapaccount" is set, swap will not be accounted.
667 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
668 size is 4096bytes, 512k per 1Gbytes of swap.
669 config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
670 bool "Memory Resource Controller Swap Extension enabled by default"
671 depends on CGROUP_MEM_RES_CTLR_SWAP
674 Memory Resource Controller Swap Extension comes with its price in
675 a bigger memory consumption. General purpose distribution kernels
676 which want to enable the feautre but keep it disabled by default
677 and let the user enable it by swapaccount boot command line
678 parameter should have this option unselected.
679 For those who want to have the feature enabled by default should
680 select this option (if, for some reason, they need to disable it
681 then noswapaccount does the trick).
683 menuconfig CGROUP_SCHED
684 bool "Group CPU scheduler"
685 depends on EXPERIMENTAL
688 This feature lets CPU scheduler recognize task groups and control CPU
689 bandwidth allocation to such task groups. It uses cgroups to group
693 config FAIR_GROUP_SCHED
694 bool "Group scheduling for SCHED_OTHER"
695 depends on CGROUP_SCHED
698 config RT_GROUP_SCHED
699 bool "Group scheduling for SCHED_RR/FIFO"
700 depends on EXPERIMENTAL
701 depends on CGROUP_SCHED
704 This feature lets you explicitly allocate real CPU bandwidth
705 to task groups. If enabled, it will also make it impossible to
706 schedule realtime tasks for non-root users until you allocate
707 realtime bandwidth for them.
708 See Documentation/scheduler/sched-rt-group.txt for more information.
713 tristate "Block IO controller"
717 Generic block IO controller cgroup interface. This is the common
718 cgroup interface which should be used by various IO controlling
721 Currently, CFQ IO scheduler uses it to recognize task groups and
722 control disk bandwidth allocation (proportional time slice allocation)
723 to such task groups. It is also used by bio throttling logic in
724 block layer to implement upper limit in IO rates on a device.
726 This option only enables generic Block IO controller infrastructure.
727 One needs to also enable actual IO controlling logic/policy. For
728 enabling proportional weight division of disk bandwidth in CFQ seti
729 CONFIG_CFQ_GROUP_IOSCHED=y and for enabling throttling policy set
730 CONFIG_BLK_THROTTLE=y.
732 See Documentation/cgroups/blkio-controller.txt for more information.
734 config DEBUG_BLK_CGROUP
735 bool "Enable Block IO controller debugging"
736 depends on BLK_CGROUP
739 Enable some debugging help. Currently it exports additional stat
740 files in a cgroup which can be useful for debugging.
744 menuconfig NAMESPACES
745 bool "Namespaces support" if EMBEDDED
748 Provides the way to make tasks work with different objects using
749 the same id. For example same IPC id may refer to different objects
750 or same user id or pid may refer to different tasks when used in
751 different namespaces.
759 In this namespace tasks see different info provided with the
764 depends on (SYSVIPC || POSIX_MQUEUE)
767 In this namespace tasks work with IPC ids which correspond to
768 different IPC objects in different namespaces.
771 bool "User namespace (EXPERIMENTAL)"
772 depends on EXPERIMENTAL
775 This allows containers, i.e. vservers, to use user namespaces
776 to provide different user info for different servers.
780 bool "PID Namespaces"
783 Support process id namespaces. This allows having multiple
784 processes with the same pid as long as they are in different
785 pid namespaces. This is a building block of containers.
788 bool "Network namespace"
792 Allow user space to create what appear to be multiple instances
793 of the network stack.
800 config SYSFS_DEPRECATED
801 bool "enable deprecated sysfs features to support old userspace tools"
805 This option adds code that switches the layout of the "block" class
806 devices, to not show up in /sys/class/block/, but only in
809 This switch is only active when the sysfs.deprecated=1 boot option is
810 passed or the SYSFS_DEPRECATED_V2 option is set.
812 This option allows new kernels to run on old distributions and tools,
813 which might get confused by /sys/class/block/. Since 2007/2008 all
814 major distributions and tools handle this just fine.
816 Recent distributions and userspace tools after 2009/2010 depend on
817 the existence of /sys/class/block/, and will not work with this
820 Only if you are using a new kernel on an old distribution, you might
823 config SYSFS_DEPRECATED_V2
824 bool "enabled deprecated sysfs features by default"
827 depends on SYSFS_DEPRECATED
829 Enable deprecated sysfs by default.
831 See the CONFIG_SYSFS_DEPRECATED option for more details about this
834 Only if you are using a new kernel on an old distribution, you might
835 need to say Y here. Even then, odds are you would not need it
836 enabled, you can always pass the boot option if absolutely necessary.
839 bool "Kernel->user space relay support (formerly relayfs)"
841 This option enables support for relay interface support in
842 certain file systems (such as debugfs).
843 It is designed to provide an efficient mechanism for tools and
844 facilities to relay large amounts of data from kernel space to
849 config BLK_DEV_INITRD
850 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
851 depends on BROKEN || !FRV
853 The initial RAM filesystem is a ramfs which is loaded by the
854 boot loader (loadlin or lilo) and that is mounted as root
855 before the normal boot procedure. It is typically used to
856 load modules needed to mount the "real" root file system,
857 etc. See <file:Documentation/initrd.txt> for details.
859 If RAM disk support (BLK_DEV_RAM) is also included, this
860 also enables initial RAM disk (initrd) support and adds
861 15 Kbytes (more on some other architectures) to the kernel size.
871 config CC_OPTIMIZE_FOR_SIZE
872 bool "Optimize for size"
875 Enabling this option will pass "-Os" instead of "-O2" to gcc
876 resulting in a smaller kernel.
887 bool "Configure standard kernel features (for small systems)"
889 This option allows certain base kernel options and settings
890 to be disabled or tweaked. This is for specialized
891 environments which can tolerate a "non-standard" kernel.
892 Only use this if you really know what you are doing.
895 bool "Enable 16-bit UID system calls" if EMBEDDED
896 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
899 This enables the legacy 16-bit UID syscall wrappers.
901 config SYSCTL_SYSCALL
902 bool "Sysctl syscall support" if EMBEDDED
903 depends on PROC_SYSCTL
907 sys_sysctl uses binary paths that have been found challenging
908 to properly maintain and use. The interface in /proc/sys
909 using paths with ascii names is now the primary path to this
912 Almost nothing using the binary sysctl interface so if you are
913 trying to save some space it is probably safe to disable this,
914 making your kernel marginally smaller.
916 If unsure say Y here.
919 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
922 Say Y here to let the kernel print out symbolic crash information and
923 symbolic stack backtraces. This increases the size of the kernel
924 somewhat, as all symbols have to be loaded into the kernel image.
927 bool "Include all symbols in kallsyms"
928 depends on DEBUG_KERNEL && KALLSYMS
930 Normally kallsyms only contains the symbols of functions, for nicer
931 OOPS messages. Some debuggers can use kallsyms for other
932 symbols too: say Y here to include all symbols, if you need them
933 and you don't care about adding 300k to the size of your kernel.
937 config KALLSYMS_EXTRA_PASS
938 bool "Do an extra kallsyms pass"
941 If kallsyms is not working correctly, the build will fail with
942 inconsistent kallsyms data. If that occurs, log a bug report and
943 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
944 Always say N here unless you find a bug in kallsyms, which must be
945 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
946 you wait for kallsyms to be fixed.
950 bool "Support for hot-pluggable devices" if EMBEDDED
953 This option is provided for the case where no hotplug or uevent
954 capabilities is wanted by the kernel. You should only consider
955 disabling this option for embedded systems that do not use modules, a
956 dynamic /dev tree, or dynamic device discovery. Just say Y.
960 bool "Enable support for printk" if EMBEDDED
962 This option enables normal printk support. Removing it
963 eliminates most of the message strings from the kernel image
964 and makes the kernel more or less silent. As this makes it
965 very difficult to diagnose system problems, saying N here is
966 strongly discouraged.
969 bool "BUG() support" if EMBEDDED
972 Disabling this option eliminates support for BUG and WARN, reducing
973 the size of your kernel image and potentially quietly ignoring
974 numerous fatal conditions. You should only consider disabling this
975 option for embedded systems with no facilities for reporting errors.
980 bool "Enable ELF core dumps" if EMBEDDED
982 Enable support for generating core dumps. Disabling saves about 4k.
984 config PCSPKR_PLATFORM
985 bool "Enable PC-Speaker support" if EMBEDDED
986 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
989 This option allows to disable the internal PC-Speaker
990 support, saving some memory.
994 bool "Enable full-sized data structures for core" if EMBEDDED
996 Disabling this option reduces the size of miscellaneous core
997 kernel data structures. This saves memory on small machines,
998 but may reduce performance.
1001 bool "Enable futex support" if EMBEDDED
1005 Disabling this option will cause the kernel to be built without
1006 support for "fast userspace mutexes". The resulting kernel may not
1007 run glibc-based applications correctly.
1010 bool "Enable eventpoll support" if EMBEDDED
1014 Disabling this option will cause the kernel to be built without
1015 support for epoll family of system calls.
1018 bool "Enable signalfd() system call" if EMBEDDED
1022 Enable the signalfd() system call that allows to receive signals
1023 on a file descriptor.
1028 bool "Enable timerfd() system call" if EMBEDDED
1032 Enable the timerfd() system call that allows to receive timer
1033 events on a file descriptor.
1038 bool "Enable eventfd() system call" if EMBEDDED
1042 Enable the eventfd() system call that allows to receive both
1043 kernel notification (ie. KAIO) or userspace notifications.
1048 bool "Use full shmem filesystem" if EMBEDDED
1052 The shmem is an internal filesystem used to manage shared memory.
1053 It is backed by swap and manages resource limits. It is also exported
1054 to userspace as tmpfs if TMPFS is enabled. Disabling this
1055 option replaces shmem and tmpfs with the much simpler ramfs code,
1056 which may be appropriate on small systems without swap.
1059 bool "Enable AIO support" if EMBEDDED
1062 This option enables POSIX asynchronous I/O which may by used
1063 by some high performance threaded applications. Disabling
1064 this option saves about 7k.
1066 config HAVE_PERF_EVENTS
1069 See tools/perf/design.txt for details.
1071 config PERF_USE_VMALLOC
1074 See tools/perf/design.txt for details
1076 menu "Kernel Performance Events And Counters"
1079 bool "Kernel performance events and counters"
1080 default y if (PROFILING || PERF_COUNTERS)
1081 depends on HAVE_PERF_EVENTS
1085 Enable kernel support for various performance events provided
1086 by software and hardware.
1088 Software events are supported either built-in or via the
1089 use of generic tracepoints.
1091 Most modern CPUs support performance events via performance
1092 counter registers. These registers count the number of certain
1093 types of hw events: such as instructions executed, cachemisses
1094 suffered, or branches mis-predicted - without slowing down the
1095 kernel or applications. These registers can also trigger interrupts
1096 when a threshold number of events have passed - and can thus be
1097 used to profile the code that runs on that CPU.
1099 The Linux Performance Event subsystem provides an abstraction of
1100 these software and hardware event capabilities, available via a
1101 system call and used by the "perf" utility in tools/perf/. It
1102 provides per task and per CPU counters, and it provides event
1103 capabilities on top of those.
1107 config PERF_COUNTERS
1108 bool "Kernel performance counters (old config option)"
1109 depends on HAVE_PERF_EVENTS
1111 This config has been obsoleted by the PERF_EVENTS
1112 config option - please see that one for details.
1114 It has no effect on the kernel whether you enable
1115 it or not, it is a compatibility placeholder.
1119 config DEBUG_PERF_USE_VMALLOC
1121 bool "Debug: use vmalloc to back perf mmap() buffers"
1122 depends on PERF_EVENTS && DEBUG_KERNEL
1123 select PERF_USE_VMALLOC
1125 Use vmalloc memory to back perf mmap() buffers.
1127 Mostly useful for debugging the vmalloc code on platforms
1128 that don't require it.
1134 config VM_EVENT_COUNTERS
1136 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1138 VM event counters are needed for event counts to be shown.
1139 This option allows the disabling of the VM event counters
1140 on EMBEDDED systems. /proc/vmstat will only show page counts
1141 if VM event counters are disabled.
1145 bool "Enable PCI quirk workarounds" if EMBEDDED
1148 This enables workarounds for various PCI chipset
1149 bugs/quirks. Disable this only if your target machine is
1150 unaffected by PCI quirks.
1154 bool "Enable SLUB debugging support" if EMBEDDED
1155 depends on SLUB && SYSFS
1157 SLUB has extensive debug support features. Disabling these can
1158 result in significant savings in code size. This also disables
1159 SLUB sysfs support. /sys/slab will not exist and there will be
1160 no support for cache validation etc.
1163 bool "Disable heap randomization"
1166 Randomizing heap placement makes heap exploits harder, but it
1167 also breaks ancient binaries (including anything libc5 based).
1168 This option changes the bootup default to heap randomization
1169 disabled, and can be overridden at runtime by setting
1170 /proc/sys/kernel/randomize_va_space to 2.
1172 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1175 prompt "Choose SLAB allocator"
1178 This option allows to select a slab allocator.
1183 The regular slab allocator that is established and known to work
1184 well in all environments. It organizes cache hot objects in
1185 per cpu and per node queues.
1188 bool "SLUB (Unqueued Allocator)"
1190 SLUB is a slab allocator that minimizes cache line usage
1191 instead of managing queues of cached objects (SLAB approach).
1192 Per cpu caching is realized using slabs of objects instead
1193 of queues of objects. SLUB can use memory efficiently
1194 and has enhanced diagnostics. SLUB is the default choice for
1199 bool "SLOB (Simple Allocator)"
1201 SLOB replaces the stock allocator with a drastically simpler
1202 allocator. SLOB is generally more space efficient but
1203 does not perform as well on large systems.
1207 config MMAP_ALLOW_UNINITIALIZED
1208 bool "Allow mmapped anonymous memory to be uninitialized"
1209 depends on EMBEDDED && !MMU
1212 Normally, and according to the Linux spec, anonymous memory obtained
1213 from mmap() has it's contents cleared before it is passed to
1214 userspace. Enabling this config option allows you to request that
1215 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1216 providing a huge performance boost. If this option is not enabled,
1217 then the flag will be ignored.
1219 This is taken advantage of by uClibc's malloc(), and also by
1220 ELF-FDPIC binfmt's brk and stack allocator.
1222 Because of the obvious security issues, this option should only be
1223 enabled on embedded devices where you control what is run in
1224 userspace. Since that isn't generally a problem on no-MMU systems,
1225 it is normally safe to say Y here.
1227 See Documentation/nommu-mmap.txt for more information.
1230 bool "Profiling support"
1232 Say Y here to enable the extended profiling support mechanisms used
1233 by profilers such as OProfile.
1236 # Place an empty function call at each tracepoint site. Can be
1237 # dynamically changed for a probe function.
1242 source "arch/Kconfig"
1244 endmenu # General setup
1246 config HAVE_GENERIC_DMA_COHERENT
1253 depends on SLAB || SLUB_DEBUG
1261 default 0 if BASE_FULL
1262 default 1 if !BASE_FULL
1265 bool "Enable loadable module support"
1267 Kernel modules are small pieces of compiled code which can
1268 be inserted in the running kernel, rather than being
1269 permanently built into the kernel. You use the "modprobe"
1270 tool to add (and sometimes remove) them. If you say Y here,
1271 many parts of the kernel can be built as modules (by
1272 answering M instead of Y where indicated): this is most
1273 useful for infrequently used options which are not required
1274 for booting. For more information, see the man pages for
1275 modprobe, lsmod, modinfo, insmod and rmmod.
1277 If you say Y here, you will need to run "make
1278 modules_install" to put the modules under /lib/modules/
1279 where modprobe can find them (you may need to be root to do
1286 config MODULE_FORCE_LOAD
1287 bool "Forced module loading"
1290 Allow loading of modules without version information (ie. modprobe
1291 --force). Forced module loading sets the 'F' (forced) taint flag and
1292 is usually a really bad idea.
1294 config MODULE_UNLOAD
1295 bool "Module unloading"
1297 Without this option you will not be able to unload any
1298 modules (note that some modules may not be unloadable
1299 anyway), which makes your kernel smaller, faster
1300 and simpler. If unsure, say Y.
1302 config MODULE_FORCE_UNLOAD
1303 bool "Forced module unloading"
1304 depends on MODULE_UNLOAD && EXPERIMENTAL
1306 This option allows you to force a module to unload, even if the
1307 kernel believes it is unsafe: the kernel will remove the module
1308 without waiting for anyone to stop using it (using the -f option to
1309 rmmod). This is mainly for kernel developers and desperate users.
1313 bool "Module versioning support"
1315 Usually, you have to use modules compiled with your kernel.
1316 Saying Y here makes it sometimes possible to use modules
1317 compiled for different kernels, by adding enough information
1318 to the modules to (hopefully) spot any changes which would
1319 make them incompatible with the kernel you are running. If
1322 config MODULE_SRCVERSION_ALL
1323 bool "Source checksum for all modules"
1325 Modules which contain a MODULE_VERSION get an extra "srcversion"
1326 field inserted into their modinfo section, which contains a
1327 sum of the source files which made it. This helps maintainers
1328 see exactly which source was used to build a module (since
1329 others sometimes change the module source without updating
1330 the version). With this option, such a "srcversion" field
1331 will be created for all modules. If unsure, say N.
1335 config INIT_ALL_POSSIBLE
1338 Back when each arch used to define their own cpu_online_map and
1339 cpu_possible_map, some of them chose to initialize cpu_possible_map
1340 with all 1s, and others with all 0s. When they were centralised,
1341 it was better to provide this option than to break all the archs
1342 and have several arch maintainers pursuing me down dark alleys.
1347 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1349 Need stop_machine() primitive.
1351 source "block/Kconfig"
1353 config PREEMPT_NOTIFIERS
1360 source "kernel/Kconfig.locks"