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47 drivers that have been replaced by something else, and/or are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"
387 depends on TREE_RCU || TREE_PREEMPT_RCU
389 This option provides tracing in RCU which presents stats
390 in debugfs for debugging RCU implementation.
392 Say Y here if you want to enable RCU tracing
393 Say N if you are unsure.
396 int "Tree-based hierarchical RCU fanout value"
399 depends on TREE_RCU || TREE_PREEMPT_RCU
403 This option controls the fanout of hierarchical implementations
404 of RCU, allowing RCU to work efficiently on machines with
405 large numbers of CPUs. This value must be at least the fourth
406 root of NR_CPUS, which allows NR_CPUS to be insanely large.
407 The default value of RCU_FANOUT should be used for production
408 systems, but if you are stress-testing the RCU implementation
409 itself, small RCU_FANOUT values allow you to test large-system
410 code paths on small(er) systems.
412 Select a specific number if testing RCU itself.
413 Take the default if unsure.
415 config RCU_FANOUT_EXACT
416 bool "Disable tree-based hierarchical RCU auto-balancing"
417 depends on TREE_RCU || TREE_PREEMPT_RCU
420 This option forces use of the exact RCU_FANOUT value specified,
421 regardless of imbalances in the hierarchy. This is useful for
422 testing RCU itself, and might one day be useful on systems with
423 strong NUMA behavior.
425 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
429 config RCU_FAST_NO_HZ
430 bool "Accelerate last non-dyntick-idle CPU's grace periods"
431 depends on TREE_RCU && NO_HZ && SMP
434 This option causes RCU to attempt to accelerate grace periods
435 in order to allow the final CPU to enter dynticks-idle state
436 more quickly. On the other hand, this option increases the
437 overhead of the dynticks-idle checking, particularly on systems
438 with large numbers of CPUs.
440 Say Y if energy efficiency is critically important, particularly
441 if you have relatively few CPUs.
443 Say N if you are unsure.
445 config TREE_RCU_TRACE
446 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
449 This option provides tracing for the TREE_RCU and
450 TREE_PREEMPT_RCU implementations, permitting Makefile to
451 trivially select kernel/rcutree_trace.c.
453 endmenu # "RCU Subsystem"
456 tristate "Kernel .config support"
458 This option enables the complete Linux kernel ".config" file
459 contents to be saved in the kernel. It provides documentation
460 of which kernel options are used in a running kernel or in an
461 on-disk kernel. This information can be extracted from the kernel
462 image file with the script scripts/extract-ikconfig and used as
463 input to rebuild the current kernel or to build another kernel.
464 It can also be extracted from a running kernel by reading
465 /proc/config.gz if enabled (below).
468 bool "Enable access to .config through /proc/config.gz"
469 depends on IKCONFIG && PROC_FS
471 This option enables access to the kernel configuration file
472 through /proc/config.gz.
475 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
479 Select kernel log buffer size as a power of 2.
489 # Architectures with an unreliable sched_clock() should select this:
491 config HAVE_UNSTABLE_SCHED_CLOCK
495 boolean "Control Group support"
498 This option adds support for grouping sets of processes together, for
499 use with process control subsystems such as Cpusets, CFS, memory
500 controls or device isolation.
502 - Documentation/scheduler/sched-design-CFS.txt (CFS)
503 - Documentation/cgroups/ (features for grouping, isolation
504 and resource control)
511 bool "Example debug cgroup subsystem"
515 This option enables a simple cgroup subsystem that
516 exports useful debugging information about the cgroups
522 bool "Namespace cgroup subsystem"
525 Provides a simple namespace cgroup subsystem to
526 provide hierarchical naming of sets of namespaces,
527 for instance virtual servers and checkpoint/restart
530 config CGROUP_FREEZER
531 bool "Freezer cgroup subsystem"
534 Provides a way to freeze and unfreeze all tasks in a
538 bool "Device controller for cgroups"
539 depends on CGROUPS && EXPERIMENTAL
541 Provides a cgroup implementing whitelists for devices which
542 a process in the cgroup can mknod or open.
545 bool "Cpuset support"
548 This option will let you create and manage CPUSETs which
549 allow dynamically partitioning a system into sets of CPUs and
550 Memory Nodes and assigning tasks to run only within those sets.
551 This is primarily useful on large SMP or NUMA systems.
555 config PROC_PID_CPUSET
556 bool "Include legacy /proc/<pid>/cpuset file"
560 config CGROUP_CPUACCT
561 bool "Simple CPU accounting cgroup subsystem"
564 Provides a simple Resource Controller for monitoring the
565 total CPU consumed by the tasks in a cgroup.
567 config RESOURCE_COUNTERS
568 bool "Resource counters"
570 This option enables controller independent resource accounting
571 infrastructure that works with cgroups.
574 config CGROUP_MEM_RES_CTLR
575 bool "Memory Resource Controller for Control Groups"
576 depends on CGROUPS && RESOURCE_COUNTERS
579 Provides a memory resource controller that manages both anonymous
580 memory and page cache. (See Documentation/cgroups/memory.txt)
582 Note that setting this option increases fixed memory overhead
583 associated with each page of memory in the system. By this,
584 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
585 usage tracking struct at boot. Total amount of this is printed out
588 Only enable when you're ok with these trade offs and really
589 sure you need the memory resource controller. Even when you enable
590 this, you can set "cgroup_disable=memory" at your boot option to
591 disable memory resource controller and you can avoid overheads.
592 (and lose benefits of memory resource controller)
594 This config option also selects MM_OWNER config option, which
595 could in turn add some fork/exit overhead.
597 config CGROUP_MEM_RES_CTLR_SWAP
598 bool "Memory Resource Controller Swap Extension"
599 depends on CGROUP_MEM_RES_CTLR && SWAP
601 Add swap management feature to memory resource controller. When you
602 enable this, you can limit mem+swap usage per cgroup. In other words,
603 when you disable this, memory resource controller has no cares to
604 usage of swap...a process can exhaust all of the swap. This extension
605 is useful when you want to avoid exhaustion swap but this itself
606 adds more overheads and consumes memory for remembering information.
607 Especially if you use 32bit system or small memory system, please
608 be careful about enabling this. When memory resource controller
609 is disabled by boot option, this will be automatically disabled and
610 there will be no overhead from this. Even when you set this config=y,
611 if boot option "noswapaccount" is set, swap will not be accounted.
612 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
613 size is 4096bytes, 512k per 1Gbytes of swap.
615 menuconfig CGROUP_SCHED
616 bool "Group CPU scheduler"
617 depends on EXPERIMENTAL && CGROUPS
620 This feature lets CPU scheduler recognize task groups and control CPU
621 bandwidth allocation to such task groups. It uses cgroups to group
625 config FAIR_GROUP_SCHED
626 bool "Group scheduling for SCHED_OTHER"
627 depends on CGROUP_SCHED
630 config RT_GROUP_SCHED
631 bool "Group scheduling for SCHED_RR/FIFO"
632 depends on EXPERIMENTAL
633 depends on CGROUP_SCHED
636 This feature lets you explicitly allocate real CPU bandwidth
637 to task groups. If enabled, it will also make it impossible to
638 schedule realtime tasks for non-root users until you allocate
639 realtime bandwidth for them.
640 See Documentation/scheduler/sched-rt-group.txt for more information.
645 tristate "Block IO controller"
646 depends on CGROUPS && BLOCK
649 Generic block IO controller cgroup interface. This is the common
650 cgroup interface which should be used by various IO controlling
653 Currently, CFQ IO scheduler uses it to recognize task groups and
654 control disk bandwidth allocation (proportional time slice allocation)
657 This option only enables generic Block IO controller infrastructure.
658 One needs to also enable actual IO controlling logic in CFQ for it
659 to take effect. (CONFIG_CFQ_GROUP_IOSCHED=y).
661 See Documentation/cgroups/blkio-controller.txt for more information.
663 config DEBUG_BLK_CGROUP
664 bool "Enable Block IO controller debugging"
665 depends on BLK_CGROUP
668 Enable some debugging help. Currently it exports additional stat
669 files in a cgroup which can be useful for debugging.
676 config SYSFS_DEPRECATED
679 config SYSFS_DEPRECATED_V2
680 bool "enable deprecated sysfs features to support old userspace tools"
683 select SYSFS_DEPRECATED
685 This option switches the layout of sysfs to the deprecated
686 version. Do not use it on recent distributions.
688 The current sysfs layout features a unified device tree at
689 /sys/devices/, which is able to express a hierarchy between
690 class devices. If the deprecated option is set to Y, the
691 unified device tree is split into a bus device tree at
692 /sys/devices/ and several individual class device trees at
693 /sys/class/. The class and bus devices will be connected by
694 "<subsystem>:<name>" and the "device" links. The "block"
695 class devices, will not show up in /sys/class/block/. Some
696 subsystems will suppress the creation of some devices which
697 depend on the unified device tree.
699 This option is not a pure compatibility option that can
700 be safely enabled on newer distributions. It will change the
701 layout of sysfs to the non-extensible deprecated version,
702 and disable some features, which can not be exported without
703 confusing older userspace tools. Since 2007/2008 all major
704 distributions do not enable this option, and ship no tools which
705 depend on the deprecated layout or this option.
707 If you are using a new kernel on an older distribution, or use
708 older userspace tools, you might need to say Y here. Do not say Y,
709 if the original kernel, that came with your distribution, has
710 this option set to N.
713 bool "Kernel->user space relay support (formerly relayfs)"
715 This option enables support for relay interface support in
716 certain file systems (such as debugfs).
717 It is designed to provide an efficient mechanism for tools and
718 facilities to relay large amounts of data from kernel space to
724 bool "Namespaces support" if EMBEDDED
727 Provides the way to make tasks work with different objects using
728 the same id. For example same IPC id may refer to different objects
729 or same user id or pid may refer to different tasks when used in
730 different namespaces.
734 depends on NAMESPACES
736 In this namespace tasks see different info provided with the
741 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
743 In this namespace tasks work with IPC ids which correspond to
744 different IPC objects in different namespaces.
747 bool "User namespace (EXPERIMENTAL)"
748 depends on NAMESPACES && EXPERIMENTAL
750 This allows containers, i.e. vservers, to use user namespaces
751 to provide different user info for different servers.
755 bool "PID Namespaces (EXPERIMENTAL)"
757 depends on NAMESPACES && EXPERIMENTAL
759 Support process id namespaces. This allows having multiple
760 processes with the same pid as long as they are in different
761 pid namespaces. This is a building block of containers.
763 Unless you want to work with an experimental feature
767 bool "Network namespace"
769 depends on NAMESPACES && EXPERIMENTAL && NET
771 Allow user space to create what appear to be multiple instances
772 of the network stack.
774 config BLK_DEV_INITRD
775 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
776 depends on BROKEN || !FRV
778 The initial RAM filesystem is a ramfs which is loaded by the
779 boot loader (loadlin or lilo) and that is mounted as root
780 before the normal boot procedure. It is typically used to
781 load modules needed to mount the "real" root file system,
782 etc. See <file:Documentation/initrd.txt> for details.
784 If RAM disk support (BLK_DEV_RAM) is also included, this
785 also enables initial RAM disk (initrd) support and adds
786 15 Kbytes (more on some other architectures) to the kernel size.
796 config CC_OPTIMIZE_FOR_SIZE
797 bool "Optimize for size"
800 Enabling this option will pass "-Os" instead of "-O2" to gcc
801 resulting in a smaller kernel.
812 bool "Configure standard kernel features (for small systems)"
814 This option allows certain base kernel options and settings
815 to be disabled or tweaked. This is for specialized
816 environments which can tolerate a "non-standard" kernel.
817 Only use this if you really know what you are doing.
820 bool "Enable 16-bit UID system calls" if EMBEDDED
821 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
824 This enables the legacy 16-bit UID syscall wrappers.
826 config SYSCTL_SYSCALL
827 bool "Sysctl syscall support" if EMBEDDED
828 depends on PROC_SYSCTL
832 sys_sysctl uses binary paths that have been found challenging
833 to properly maintain and use. The interface in /proc/sys
834 using paths with ascii names is now the primary path to this
837 Almost nothing using the binary sysctl interface so if you are
838 trying to save some space it is probably safe to disable this,
839 making your kernel marginally smaller.
841 If unsure say Y here.
844 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
847 Say Y here to let the kernel print out symbolic crash information and
848 symbolic stack backtraces. This increases the size of the kernel
849 somewhat, as all symbols have to be loaded into the kernel image.
852 bool "Include all symbols in kallsyms"
853 depends on DEBUG_KERNEL && KALLSYMS
855 Normally kallsyms only contains the symbols of functions, for nicer
856 OOPS messages. Some debuggers can use kallsyms for other
857 symbols too: say Y here to include all symbols, if you need them
858 and you don't care about adding 300k to the size of your kernel.
862 config KALLSYMS_EXTRA_PASS
863 bool "Do an extra kallsyms pass"
866 If kallsyms is not working correctly, the build will fail with
867 inconsistent kallsyms data. If that occurs, log a bug report and
868 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
869 Always say N here unless you find a bug in kallsyms, which must be
870 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
871 you wait for kallsyms to be fixed.
875 bool "Support for hot-pluggable devices" if EMBEDDED
878 This option is provided for the case where no hotplug or uevent
879 capabilities is wanted by the kernel. You should only consider
880 disabling this option for embedded systems that do not use modules, a
881 dynamic /dev tree, or dynamic device discovery. Just say Y.
885 bool "Enable support for printk" if EMBEDDED
887 This option enables normal printk support. Removing it
888 eliminates most of the message strings from the kernel image
889 and makes the kernel more or less silent. As this makes it
890 very difficult to diagnose system problems, saying N here is
891 strongly discouraged.
894 bool "BUG() support" if EMBEDDED
897 Disabling this option eliminates support for BUG and WARN, reducing
898 the size of your kernel image and potentially quietly ignoring
899 numerous fatal conditions. You should only consider disabling this
900 option for embedded systems with no facilities for reporting errors.
905 bool "Enable ELF core dumps" if EMBEDDED
907 Enable support for generating core dumps. Disabling saves about 4k.
909 config PCSPKR_PLATFORM
910 bool "Enable PC-Speaker support" if EMBEDDED
911 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
914 This option allows to disable the internal PC-Speaker
915 support, saving some memory.
919 bool "Enable full-sized data structures for core" if EMBEDDED
921 Disabling this option reduces the size of miscellaneous core
922 kernel data structures. This saves memory on small machines,
923 but may reduce performance.
926 bool "Enable futex support" if EMBEDDED
930 Disabling this option will cause the kernel to be built without
931 support for "fast userspace mutexes". The resulting kernel may not
932 run glibc-based applications correctly.
935 bool "Enable eventpoll support" if EMBEDDED
939 Disabling this option will cause the kernel to be built without
940 support for epoll family of system calls.
943 bool "Enable signalfd() system call" if EMBEDDED
947 Enable the signalfd() system call that allows to receive signals
948 on a file descriptor.
953 bool "Enable timerfd() system call" if EMBEDDED
957 Enable the timerfd() system call that allows to receive timer
958 events on a file descriptor.
963 bool "Enable eventfd() system call" if EMBEDDED
967 Enable the eventfd() system call that allows to receive both
968 kernel notification (ie. KAIO) or userspace notifications.
973 bool "Use full shmem filesystem" if EMBEDDED
977 The shmem is an internal filesystem used to manage shared memory.
978 It is backed by swap and manages resource limits. It is also exported
979 to userspace as tmpfs if TMPFS is enabled. Disabling this
980 option replaces shmem and tmpfs with the much simpler ramfs code,
981 which may be appropriate on small systems without swap.
984 bool "Enable AIO support" if EMBEDDED
987 This option enables POSIX asynchronous I/O which may by used
988 by some high performance threaded applications. Disabling
989 this option saves about 7k.
991 config HAVE_PERF_EVENTS
994 See tools/perf/design.txt for details.
996 config PERF_USE_VMALLOC
999 See tools/perf/design.txt for details
1001 menu "Kernel Performance Events And Counters"
1004 bool "Kernel performance events and counters"
1005 default y if (PROFILING || PERF_COUNTERS)
1006 depends on HAVE_PERF_EVENTS
1009 Enable kernel support for various performance events provided
1010 by software and hardware.
1012 Software events are supported either built-in or via the
1013 use of generic tracepoints.
1015 Most modern CPUs support performance events via performance
1016 counter registers. These registers count the number of certain
1017 types of hw events: such as instructions executed, cachemisses
1018 suffered, or branches mis-predicted - without slowing down the
1019 kernel or applications. These registers can also trigger interrupts
1020 when a threshold number of events have passed - and can thus be
1021 used to profile the code that runs on that CPU.
1023 The Linux Performance Event subsystem provides an abstraction of
1024 these software and hardware event capabilities, available via a
1025 system call and used by the "perf" utility in tools/perf/. It
1026 provides per task and per CPU counters, and it provides event
1027 capabilities on top of those.
1031 config PERF_COUNTERS
1032 bool "Kernel performance counters (old config option)"
1033 depends on HAVE_PERF_EVENTS
1035 This config has been obsoleted by the PERF_EVENTS
1036 config option - please see that one for details.
1038 It has no effect on the kernel whether you enable
1039 it or not, it is a compatibility placeholder.
1043 config DEBUG_PERF_USE_VMALLOC
1045 bool "Debug: use vmalloc to back perf mmap() buffers"
1046 depends on PERF_EVENTS && DEBUG_KERNEL
1047 select PERF_USE_VMALLOC
1049 Use vmalloc memory to back perf mmap() buffers.
1051 Mostly useful for debugging the vmalloc code on platforms
1052 that don't require it.
1058 config VM_EVENT_COUNTERS
1060 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1062 VM event counters are needed for event counts to be shown.
1063 This option allows the disabling of the VM event counters
1064 on EMBEDDED systems. /proc/vmstat will only show page counts
1065 if VM event counters are disabled.
1069 bool "Enable PCI quirk workarounds" if EMBEDDED
1072 This enables workarounds for various PCI chipset
1073 bugs/quirks. Disable this only if your target machine is
1074 unaffected by PCI quirks.
1078 bool "Enable SLUB debugging support" if EMBEDDED
1079 depends on SLUB && SYSFS
1081 SLUB has extensive debug support features. Disabling these can
1082 result in significant savings in code size. This also disables
1083 SLUB sysfs support. /sys/slab will not exist and there will be
1084 no support for cache validation etc.
1087 bool "Disable heap randomization"
1090 Randomizing heap placement makes heap exploits harder, but it
1091 also breaks ancient binaries (including anything libc5 based).
1092 This option changes the bootup default to heap randomization
1093 disabled, and can be overridden at runtime by setting
1094 /proc/sys/kernel/randomize_va_space to 2.
1096 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1099 prompt "Choose SLAB allocator"
1102 This option allows to select a slab allocator.
1107 The regular slab allocator that is established and known to work
1108 well in all environments. It organizes cache hot objects in
1109 per cpu and per node queues.
1112 bool "SLUB (Unqueued Allocator)"
1114 SLUB is a slab allocator that minimizes cache line usage
1115 instead of managing queues of cached objects (SLAB approach).
1116 Per cpu caching is realized using slabs of objects instead
1117 of queues of objects. SLUB can use memory efficiently
1118 and has enhanced diagnostics. SLUB is the default choice for
1123 bool "SLOB (Simple Allocator)"
1125 SLOB replaces the stock allocator with a drastically simpler
1126 allocator. SLOB is generally more space efficient but
1127 does not perform as well on large systems.
1131 config MMAP_ALLOW_UNINITIALIZED
1132 bool "Allow mmapped anonymous memory to be uninitialized"
1133 depends on EMBEDDED && !MMU
1136 Normally, and according to the Linux spec, anonymous memory obtained
1137 from mmap() has it's contents cleared before it is passed to
1138 userspace. Enabling this config option allows you to request that
1139 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1140 providing a huge performance boost. If this option is not enabled,
1141 then the flag will be ignored.
1143 This is taken advantage of by uClibc's malloc(), and also by
1144 ELF-FDPIC binfmt's brk and stack allocator.
1146 Because of the obvious security issues, this option should only be
1147 enabled on embedded devices where you control what is run in
1148 userspace. Since that isn't generally a problem on no-MMU systems,
1149 it is normally safe to say Y here.
1151 See Documentation/nommu-mmap.txt for more information.
1154 bool "Profiling support"
1156 Say Y here to enable the extended profiling support mechanisms used
1157 by profilers such as OProfile.
1160 # Place an empty function call at each tracepoint site. Can be
1161 # dynamically changed for a probe function.
1166 source "arch/Kconfig"
1168 endmenu # General setup
1170 config HAVE_GENERIC_DMA_COHERENT
1177 depends on SLAB || SLUB_DEBUG
1185 default 0 if BASE_FULL
1186 default 1 if !BASE_FULL
1189 bool "Enable loadable module support"
1191 Kernel modules are small pieces of compiled code which can
1192 be inserted in the running kernel, rather than being
1193 permanently built into the kernel. You use the "modprobe"
1194 tool to add (and sometimes remove) them. If you say Y here,
1195 many parts of the kernel can be built as modules (by
1196 answering M instead of Y where indicated): this is most
1197 useful for infrequently used options which are not required
1198 for booting. For more information, see the man pages for
1199 modprobe, lsmod, modinfo, insmod and rmmod.
1201 If you say Y here, you will need to run "make
1202 modules_install" to put the modules under /lib/modules/
1203 where modprobe can find them (you may need to be root to do
1210 config MODULE_FORCE_LOAD
1211 bool "Forced module loading"
1214 Allow loading of modules without version information (ie. modprobe
1215 --force). Forced module loading sets the 'F' (forced) taint flag and
1216 is usually a really bad idea.
1218 config MODULE_UNLOAD
1219 bool "Module unloading"
1221 Without this option you will not be able to unload any
1222 modules (note that some modules may not be unloadable
1223 anyway), which makes your kernel smaller, faster
1224 and simpler. If unsure, say Y.
1226 config MODULE_FORCE_UNLOAD
1227 bool "Forced module unloading"
1228 depends on MODULE_UNLOAD && EXPERIMENTAL
1230 This option allows you to force a module to unload, even if the
1231 kernel believes it is unsafe: the kernel will remove the module
1232 without waiting for anyone to stop using it (using the -f option to
1233 rmmod). This is mainly for kernel developers and desperate users.
1237 bool "Module versioning support"
1239 Usually, you have to use modules compiled with your kernel.
1240 Saying Y here makes it sometimes possible to use modules
1241 compiled for different kernels, by adding enough information
1242 to the modules to (hopefully) spot any changes which would
1243 make them incompatible with the kernel you are running. If
1246 config MODULE_SRCVERSION_ALL
1247 bool "Source checksum for all modules"
1249 Modules which contain a MODULE_VERSION get an extra "srcversion"
1250 field inserted into their modinfo section, which contains a
1251 sum of the source files which made it. This helps maintainers
1252 see exactly which source was used to build a module (since
1253 others sometimes change the module source without updating
1254 the version). With this option, such a "srcversion" field
1255 will be created for all modules. If unsure, say N.
1259 config INIT_ALL_POSSIBLE
1262 Back when each arch used to define their own cpu_online_map and
1263 cpu_possible_map, some of them chose to initialize cpu_possible_map
1264 with all 1s, and others with all 0s. When they were centralised,
1265 it was better to provide this option than to break all the archs
1266 and have several arch maintainers pursuing me down dark alleys.
1271 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1273 Need stop_machine() primitive.
1275 source "block/Kconfig"
1277 config PREEMPT_NOTIFIERS
1284 source "kernel/Kconfig.locks"