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54 drivers that have been replaced by something else, and/or are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
72 config INIT_ENV_ARG_LIMIT
77 Maximum of each of the number of arguments and environment
78 variables passed to init from the kernel command line.
82 string "Cross-compiler tool prefix"
84 Same as running 'make CROSS_COMPILE=prefix-' but stored for
85 default make runs in this kernel build directory. You don't
86 need to set this unless you want the configured kernel build
87 directory to select the cross-compiler automatically.
90 string "Local version - append to kernel release"
92 Append an extra string to the end of your kernel version.
93 This will show up when you type uname, for example.
94 The string you set here will be appended after the contents of
95 any files with a filename matching localversion* in your
96 object and source tree, in that order. Your total string can
97 be a maximum of 64 characters.
99 config LOCALVERSION_AUTO
100 bool "Automatically append version information to the version string"
103 This will try to automatically determine if the current tree is a
104 release tree by looking for git tags that belong to the current
105 top of tree revision.
107 A string of the format -gxxxxxxxx will be added to the localversion
108 if a git-based tree is found. The string generated by this will be
109 appended after any matching localversion* files, and after the value
110 set in CONFIG_LOCALVERSION.
112 (The actual string used here is the first eight characters produced
113 by running the command:
115 $ git rev-parse --verify HEAD
117 which is done within the script "scripts/setlocalversion".)
119 config HAVE_KERNEL_GZIP
122 config HAVE_KERNEL_BZIP2
125 config HAVE_KERNEL_LZMA
128 config HAVE_KERNEL_XZ
131 config HAVE_KERNEL_LZO
135 prompt "Kernel compression mode"
137 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
139 The linux kernel is a kind of self-extracting executable.
140 Several compression algorithms are available, which differ
141 in efficiency, compression and decompression speed.
142 Compression speed is only relevant when building a kernel.
143 Decompression speed is relevant at each boot.
145 If you have any problems with bzip2 or lzma compressed
146 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
147 version of this functionality (bzip2 only), for 2.4, was
148 supplied by Christian Ludwig)
150 High compression options are mostly useful for users, who
151 are low on disk space (embedded systems), but for whom ram
154 If in doubt, select 'gzip'
158 depends on HAVE_KERNEL_GZIP
160 The old and tried gzip compression. It provides a good balance
161 between compression ratio and decompression speed.
165 depends on HAVE_KERNEL_BZIP2
167 Its compression ratio and speed is intermediate.
168 Decompression speed is slowest among the three. The kernel
169 size is about 10% smaller with bzip2, in comparison to gzip.
170 Bzip2 uses a large amount of memory. For modern kernels you
171 will need at least 8MB RAM or more for booting.
175 depends on HAVE_KERNEL_LZMA
177 The most recent compression algorithm.
178 Its ratio is best, decompression speed is between the other
179 two. Compression is slowest. The kernel size is about 33%
180 smaller with LZMA in comparison to gzip.
184 depends on HAVE_KERNEL_XZ
186 XZ uses the LZMA2 algorithm and instruction set specific
187 BCJ filters which can improve compression ratio of executable
188 code. The size of the kernel is about 30% smaller with XZ in
189 comparison to gzip. On architectures for which there is a BCJ
190 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
191 will create a few percent smaller kernel than plain LZMA.
193 The speed is about the same as with LZMA: The decompression
194 speed of XZ is better than that of bzip2 but worse than gzip
195 and LZO. Compression is slow.
199 depends on HAVE_KERNEL_LZO
201 Its compression ratio is the poorest among the 4. The kernel
202 size is about 10% bigger than gzip; however its speed
203 (both compression and decompression) is the fastest.
208 bool "Support for paging of anonymous memory (swap)"
209 depends on MMU && BLOCK
212 This option allows you to choose whether you want to have support
213 for so called swap devices or swap files in your kernel that are
214 used to provide more virtual memory than the actual RAM present
215 in your computer. If unsure say Y.
220 Inter Process Communication is a suite of library functions and
221 system calls which let processes (running programs) synchronize and
222 exchange information. It is generally considered to be a good thing,
223 and some programs won't run unless you say Y here. In particular, if
224 you want to run the DOS emulator dosemu under Linux (read the
225 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
226 you'll need to say Y here.
228 You can find documentation about IPC with "info ipc" and also in
229 section 6.4 of the Linux Programmer's Guide, available from
230 <http://www.tldp.org/guides.html>.
232 config SYSVIPC_SYSCTL
239 bool "POSIX Message Queues"
240 depends on NET && EXPERIMENTAL
242 POSIX variant of message queues is a part of IPC. In POSIX message
243 queues every message has a priority which decides about succession
244 of receiving it by a process. If you want to compile and run
245 programs written e.g. for Solaris with use of its POSIX message
246 queues (functions mq_*) say Y here.
248 POSIX message queues are visible as a filesystem called 'mqueue'
249 and can be mounted somewhere if you want to do filesystem
250 operations on message queues.
254 config POSIX_MQUEUE_SYSCTL
256 depends on POSIX_MQUEUE
260 config BSD_PROCESS_ACCT
261 bool "BSD Process Accounting"
263 If you say Y here, a user level program will be able to instruct the
264 kernel (via a special system call) to write process accounting
265 information to a file: whenever a process exits, information about
266 that process will be appended to the file by the kernel. The
267 information includes things such as creation time, owning user,
268 command name, memory usage, controlling terminal etc. (the complete
269 list is in the struct acct in <file:include/linux/acct.h>). It is
270 up to the user level program to do useful things with this
271 information. This is generally a good idea, so say Y.
273 config BSD_PROCESS_ACCT_V3
274 bool "BSD Process Accounting version 3 file format"
275 depends on BSD_PROCESS_ACCT
278 If you say Y here, the process accounting information is written
279 in a new file format that also logs the process IDs of each
280 process and it's parent. Note that this file format is incompatible
281 with previous v0/v1/v2 file formats, so you will need updated tools
282 for processing it. A preliminary version of these tools is available
283 at <http://www.gnu.org/software/acct/>.
286 bool "open by fhandle syscalls"
289 If you say Y here, a user level program will be able to map
290 file names to handle and then later use the handle for
291 different file system operations. This is useful in implementing
292 userspace file servers, which now track files using handles instead
293 of names. The handle would remain the same even if file names
294 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
298 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
302 Export selected statistics for tasks/processes through the
303 generic netlink interface. Unlike BSD process accounting, the
304 statistics are available during the lifetime of tasks/processes as
305 responses to commands. Like BSD accounting, they are sent to user
310 config TASK_DELAY_ACCT
311 bool "Enable per-task delay accounting (EXPERIMENTAL)"
314 Collect information on time spent by a task waiting for system
315 resources like cpu, synchronous block I/O completion and swapping
316 in pages. Such statistics can help in setting a task's priorities
317 relative to other tasks for cpu, io, rss limits etc.
322 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
325 Collect extended task accounting data and send the data
326 to userland for processing over the taskstats interface.
330 config TASK_IO_ACCOUNTING
331 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
332 depends on TASK_XACCT
334 Collect information on the number of bytes of storage I/O which this
340 bool "Auditing support"
343 Enable auditing infrastructure that can be used with another
344 kernel subsystem, such as SELinux (which requires this for
345 logging of avc messages output). Does not do system-call
346 auditing without CONFIG_AUDITSYSCALL.
349 bool "Enable system-call auditing support"
350 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
351 default y if SECURITY_SELINUX
353 Enable low-overhead system-call auditing infrastructure that
354 can be used independently or with another kernel subsystem,
359 depends on AUDITSYSCALL
364 depends on AUDITSYSCALL
367 source "kernel/irq/Kconfig"
372 prompt "RCU Implementation"
376 bool "Tree-based hierarchical RCU"
377 depends on !PREEMPT && SMP
379 This option selects the RCU implementation that is
380 designed for very large SMP system with hundreds or
381 thousands of CPUs. It also scales down nicely to
384 config TREE_PREEMPT_RCU
385 bool "Preemptible tree-based hierarchical RCU"
388 This option selects the RCU implementation that is
389 designed for very large SMP systems with hundreds or
390 thousands of CPUs, but for which real-time response
391 is also required. It also scales down nicely to
395 bool "UP-only small-memory-footprint RCU"
398 This option selects the RCU implementation that is
399 designed for UP systems from which real-time response
400 is not required. This option greatly reduces the
401 memory footprint of RCU.
403 config TINY_PREEMPT_RCU
404 bool "Preemptible UP-only small-memory-footprint RCU"
405 depends on !SMP && PREEMPT
407 This option selects the RCU implementation that is designed
408 for real-time UP systems. This option greatly reduces the
409 memory footprint of RCU.
414 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
416 This option enables preemptible-RCU code that is common between
417 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
420 bool "Enable tracing for RCU"
422 This option provides tracing in RCU which presents stats
423 in debugfs for debugging RCU implementation.
425 Say Y here if you want to enable RCU tracing
426 Say N if you are unsure.
429 int "Tree-based hierarchical RCU fanout value"
432 depends on TREE_RCU || TREE_PREEMPT_RCU
436 This option controls the fanout of hierarchical implementations
437 of RCU, allowing RCU to work efficiently on machines with
438 large numbers of CPUs. This value must be at least the fourth
439 root of NR_CPUS, which allows NR_CPUS to be insanely large.
440 The default value of RCU_FANOUT should be used for production
441 systems, but if you are stress-testing the RCU implementation
442 itself, small RCU_FANOUT values allow you to test large-system
443 code paths on small(er) systems.
445 Select a specific number if testing RCU itself.
446 Take the default if unsure.
448 config RCU_FANOUT_EXACT
449 bool "Disable tree-based hierarchical RCU auto-balancing"
450 depends on TREE_RCU || TREE_PREEMPT_RCU
453 This option forces use of the exact RCU_FANOUT value specified,
454 regardless of imbalances in the hierarchy. This is useful for
455 testing RCU itself, and might one day be useful on systems with
456 strong NUMA behavior.
458 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
462 config RCU_FAST_NO_HZ
463 bool "Accelerate last non-dyntick-idle CPU's grace periods"
464 depends on TREE_RCU && NO_HZ && SMP
467 This option causes RCU to attempt to accelerate grace periods
468 in order to allow the final CPU to enter dynticks-idle state
469 more quickly. On the other hand, this option increases the
470 overhead of the dynticks-idle checking, particularly on systems
471 with large numbers of CPUs.
473 Say Y if energy efficiency is critically important, particularly
474 if you have relatively few CPUs.
476 Say N if you are unsure.
478 config TREE_RCU_TRACE
479 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
482 This option provides tracing for the TREE_RCU and
483 TREE_PREEMPT_RCU implementations, permitting Makefile to
484 trivially select kernel/rcutree_trace.c.
487 bool "Enable RCU priority boosting"
488 depends on RT_MUTEXES && PREEMPT_RCU
491 This option boosts the priority of preempted RCU readers that
492 block the current preemptible RCU grace period for too long.
493 This option also prevents heavy loads from blocking RCU
494 callback invocation for all flavors of RCU.
496 Say Y here if you are working with real-time apps or heavy loads
497 Say N here if you are unsure.
499 config RCU_BOOST_PRIO
500 int "Real-time priority to boost RCU readers to"
505 This option specifies the real-time priority to which preempted
506 RCU readers are to be boosted. If you are working with CPU-bound
507 real-time applications, you should specify a priority higher then
508 the highest-priority CPU-bound application.
510 Specify the real-time priority, or take the default if unsure.
512 config RCU_BOOST_DELAY
513 int "Milliseconds to delay boosting after RCU grace-period start"
518 This option specifies the time to wait after the beginning of
519 a given grace period before priority-boosting preempted RCU
520 readers blocking that grace period. Note that any RCU reader
521 blocking an expedited RCU grace period is boosted immediately.
523 Accept the default if unsure.
525 endmenu # "RCU Subsystem"
528 tristate "Kernel .config support"
530 This option enables the complete Linux kernel ".config" file
531 contents to be saved in the kernel. It provides documentation
532 of which kernel options are used in a running kernel or in an
533 on-disk kernel. This information can be extracted from the kernel
534 image file with the script scripts/extract-ikconfig and used as
535 input to rebuild the current kernel or to build another kernel.
536 It can also be extracted from a running kernel by reading
537 /proc/config.gz if enabled (below).
540 bool "Enable access to .config through /proc/config.gz"
541 depends on IKCONFIG && PROC_FS
543 This option enables access to the kernel configuration file
544 through /proc/config.gz.
547 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
551 Select kernel log buffer size as a power of 2.
561 # Architectures with an unreliable sched_clock() should select this:
563 config HAVE_UNSTABLE_SCHED_CLOCK
567 boolean "Control Group support"
570 This option adds support for grouping sets of processes together, for
571 use with process control subsystems such as Cpusets, CFS, memory
572 controls or device isolation.
574 - Documentation/scheduler/sched-design-CFS.txt (CFS)
575 - Documentation/cgroups/ (features for grouping, isolation
576 and resource control)
583 bool "Example debug cgroup subsystem"
586 This option enables a simple cgroup subsystem that
587 exports useful debugging information about the cgroups
592 config CGROUP_FREEZER
593 bool "Freezer cgroup subsystem"
595 Provides a way to freeze and unfreeze all tasks in a
599 bool "Device controller for cgroups"
601 Provides a cgroup implementing whitelists for devices which
602 a process in the cgroup can mknod or open.
605 bool "Cpuset support"
607 This option will let you create and manage CPUSETs which
608 allow dynamically partitioning a system into sets of CPUs and
609 Memory Nodes and assigning tasks to run only within those sets.
610 This is primarily useful on large SMP or NUMA systems.
614 config PROC_PID_CPUSET
615 bool "Include legacy /proc/<pid>/cpuset file"
619 config CGROUP_CPUACCT
620 bool "Simple CPU accounting cgroup subsystem"
622 Provides a simple Resource Controller for monitoring the
623 total CPU consumed by the tasks in a cgroup.
625 config RESOURCE_COUNTERS
626 bool "Resource counters"
628 This option enables controller independent resource accounting
629 infrastructure that works with cgroups.
631 config CGROUP_MEM_RES_CTLR
632 bool "Memory Resource Controller for Control Groups"
633 depends on RESOURCE_COUNTERS
636 Provides a memory resource controller that manages both anonymous
637 memory and page cache. (See Documentation/cgroups/memory.txt)
639 Note that setting this option increases fixed memory overhead
640 associated with each page of memory in the system. By this,
641 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
642 usage tracking struct at boot. Total amount of this is printed out
645 Only enable when you're ok with these trade offs and really
646 sure you need the memory resource controller. Even when you enable
647 this, you can set "cgroup_disable=memory" at your boot option to
648 disable memory resource controller and you can avoid overheads.
649 (and lose benefits of memory resource controller)
651 This config option also selects MM_OWNER config option, which
652 could in turn add some fork/exit overhead.
654 config CGROUP_MEM_RES_CTLR_SWAP
655 bool "Memory Resource Controller Swap Extension"
656 depends on CGROUP_MEM_RES_CTLR && SWAP
658 Add swap management feature to memory resource controller. When you
659 enable this, you can limit mem+swap usage per cgroup. In other words,
660 when you disable this, memory resource controller has no cares to
661 usage of swap...a process can exhaust all of the swap. This extension
662 is useful when you want to avoid exhaustion swap but this itself
663 adds more overheads and consumes memory for remembering information.
664 Especially if you use 32bit system or small memory system, please
665 be careful about enabling this. When memory resource controller
666 is disabled by boot option, this will be automatically disabled and
667 there will be no overhead from this. Even when you set this config=y,
668 if boot option "noswapaccount" is set, swap will not be accounted.
669 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
670 size is 4096bytes, 512k per 1Gbytes of swap.
671 config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
672 bool "Memory Resource Controller Swap Extension enabled by default"
673 depends on CGROUP_MEM_RES_CTLR_SWAP
676 Memory Resource Controller Swap Extension comes with its price in
677 a bigger memory consumption. General purpose distribution kernels
678 which want to enable the feature but keep it disabled by default
679 and let the user enable it by swapaccount boot command line
680 parameter should have this option unselected.
681 For those who want to have the feature enabled by default should
682 select this option (if, for some reason, they need to disable it
683 then noswapaccount does the trick).
686 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
687 depends on PERF_EVENTS && CGROUPS
689 This option extends the per-cpu mode to restrict monitoring to
690 threads which belong to the cgroup specified and run on the
695 menuconfig CGROUP_SCHED
696 bool "Group CPU scheduler"
697 depends on EXPERIMENTAL
700 This feature lets CPU scheduler recognize task groups and control CPU
701 bandwidth allocation to such task groups. It uses cgroups to group
705 config FAIR_GROUP_SCHED
706 bool "Group scheduling for SCHED_OTHER"
707 depends on CGROUP_SCHED
710 config RT_GROUP_SCHED
711 bool "Group scheduling for SCHED_RR/FIFO"
712 depends on EXPERIMENTAL
713 depends on CGROUP_SCHED
716 This feature lets you explicitly allocate real CPU bandwidth
717 to task groups. If enabled, it will also make it impossible to
718 schedule realtime tasks for non-root users until you allocate
719 realtime bandwidth for them.
720 See Documentation/scheduler/sched-rt-group.txt for more information.
725 tristate "Block IO controller"
729 Generic block IO controller cgroup interface. This is the common
730 cgroup interface which should be used by various IO controlling
733 Currently, CFQ IO scheduler uses it to recognize task groups and
734 control disk bandwidth allocation (proportional time slice allocation)
735 to such task groups. It is also used by bio throttling logic in
736 block layer to implement upper limit in IO rates on a device.
738 This option only enables generic Block IO controller infrastructure.
739 One needs to also enable actual IO controlling logic/policy. For
740 enabling proportional weight division of disk bandwidth in CFQ, set
741 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
742 CONFIG_BLK_DEV_THROTTLING=y.
744 See Documentation/cgroups/blkio-controller.txt for more information.
746 config DEBUG_BLK_CGROUP
747 bool "Enable Block IO controller debugging"
748 depends on BLK_CGROUP
751 Enable some debugging help. Currently it exports additional stat
752 files in a cgroup which can be useful for debugging.
756 menuconfig NAMESPACES
757 bool "Namespaces support" if EXPERT
760 Provides the way to make tasks work with different objects using
761 the same id. For example same IPC id may refer to different objects
762 or same user id or pid may refer to different tasks when used in
763 different namespaces.
771 In this namespace tasks see different info provided with the
776 depends on (SYSVIPC || POSIX_MQUEUE)
779 In this namespace tasks work with IPC ids which correspond to
780 different IPC objects in different namespaces.
783 bool "User namespace (EXPERIMENTAL)"
784 depends on EXPERIMENTAL
787 This allows containers, i.e. vservers, to use user namespaces
788 to provide different user info for different servers.
792 bool "PID Namespaces"
795 Support process id namespaces. This allows having multiple
796 processes with the same pid as long as they are in different
797 pid namespaces. This is a building block of containers.
800 bool "Network namespace"
804 Allow user space to create what appear to be multiple instances
805 of the network stack.
809 config SCHED_AUTOGROUP
810 bool "Automatic process group scheduling"
814 select FAIR_GROUP_SCHED
816 This option optimizes the scheduler for common desktop workloads by
817 automatically creating and populating task groups. This separation
818 of workloads isolates aggressive CPU burners (like build jobs) from
819 desktop applications. Task group autogeneration is currently based
825 config SYSFS_DEPRECATED
826 bool "Enable deprecated sysfs features to support old userspace tools"
830 This option adds code that switches the layout of the "block" class
831 devices, to not show up in /sys/class/block/, but only in
834 This switch is only active when the sysfs.deprecated=1 boot option is
835 passed or the SYSFS_DEPRECATED_V2 option is set.
837 This option allows new kernels to run on old distributions and tools,
838 which might get confused by /sys/class/block/. Since 2007/2008 all
839 major distributions and tools handle this just fine.
841 Recent distributions and userspace tools after 2009/2010 depend on
842 the existence of /sys/class/block/, and will not work with this
845 Only if you are using a new kernel on an old distribution, you might
848 config SYSFS_DEPRECATED_V2
849 bool "Enable deprecated sysfs features by default"
852 depends on SYSFS_DEPRECATED
854 Enable deprecated sysfs by default.
856 See the CONFIG_SYSFS_DEPRECATED option for more details about this
859 Only if you are using a new kernel on an old distribution, you might
860 need to say Y here. Even then, odds are you would not need it
861 enabled, you can always pass the boot option if absolutely necessary.
864 bool "Kernel->user space relay support (formerly relayfs)"
866 This option enables support for relay interface support in
867 certain file systems (such as debugfs).
868 It is designed to provide an efficient mechanism for tools and
869 facilities to relay large amounts of data from kernel space to
874 config BLK_DEV_INITRD
875 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
876 depends on BROKEN || !FRV
878 The initial RAM filesystem is a ramfs which is loaded by the
879 boot loader (loadlin or lilo) and that is mounted as root
880 before the normal boot procedure. It is typically used to
881 load modules needed to mount the "real" root file system,
882 etc. See <file:Documentation/initrd.txt> for details.
884 If RAM disk support (BLK_DEV_RAM) is also included, this
885 also enables initial RAM disk (initrd) support and adds
886 15 Kbytes (more on some other architectures) to the kernel size.
896 config CC_OPTIMIZE_FOR_SIZE
897 bool "Optimize for size"
899 Enabling this option will pass "-Os" instead of "-O2" to gcc
900 resulting in a smaller kernel.
911 bool "Configure standard kernel features (expert users)"
913 This option allows certain base kernel options and settings
914 to be disabled or tweaked. This is for specialized
915 environments which can tolerate a "non-standard" kernel.
916 Only use this if you really know what you are doing.
919 bool "Enable 16-bit UID system calls" if EXPERT
920 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
923 This enables the legacy 16-bit UID syscall wrappers.
925 config SYSCTL_SYSCALL
926 bool "Sysctl syscall support" if EXPERT
927 depends on PROC_SYSCTL
931 sys_sysctl uses binary paths that have been found challenging
932 to properly maintain and use. The interface in /proc/sys
933 using paths with ascii names is now the primary path to this
936 Almost nothing using the binary sysctl interface so if you are
937 trying to save some space it is probably safe to disable this,
938 making your kernel marginally smaller.
940 If unsure say Y here.
943 bool "Load all symbols for debugging/ksymoops" if EXPERT
946 Say Y here to let the kernel print out symbolic crash information and
947 symbolic stack backtraces. This increases the size of the kernel
948 somewhat, as all symbols have to be loaded into the kernel image.
951 bool "Include all symbols in kallsyms"
952 depends on DEBUG_KERNEL && KALLSYMS
954 Normally kallsyms only contains the symbols of functions for nicer
955 OOPS messages and backtraces (i.e., symbols from the text and inittext
956 sections). This is sufficient for most cases. And only in very rare
957 cases (e.g., when a debugger is used) all symbols are required (e.g.,
958 names of variables from the data sections, etc).
960 This option makes sure that all symbols are loaded into the kernel
961 image (i.e., symbols from all sections) in cost of increased kernel
962 size (depending on the kernel configuration, it may be 300KiB or
963 something like this).
965 Say N unless you really need all symbols.
968 bool "Support for hot-pluggable devices" if EXPERT
971 This option is provided for the case where no hotplug or uevent
972 capabilities is wanted by the kernel. You should only consider
973 disabling this option for embedded systems that do not use modules, a
974 dynamic /dev tree, or dynamic device discovery. Just say Y.
978 bool "Enable support for printk" if EXPERT
980 This option enables normal printk support. Removing it
981 eliminates most of the message strings from the kernel image
982 and makes the kernel more or less silent. As this makes it
983 very difficult to diagnose system problems, saying N here is
984 strongly discouraged.
987 bool "BUG() support" if EXPERT
990 Disabling this option eliminates support for BUG and WARN, reducing
991 the size of your kernel image and potentially quietly ignoring
992 numerous fatal conditions. You should only consider disabling this
993 option for embedded systems with no facilities for reporting errors.
998 bool "Enable ELF core dumps" if EXPERT
1000 Enable support for generating core dumps. Disabling saves about 4k.
1002 config PCSPKR_PLATFORM
1003 bool "Enable PC-Speaker support" if EXPERT
1004 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
1007 This option allows to disable the internal PC-Speaker
1008 support, saving some memory.
1012 bool "Enable full-sized data structures for core" if EXPERT
1014 Disabling this option reduces the size of miscellaneous core
1015 kernel data structures. This saves memory on small machines,
1016 but may reduce performance.
1019 bool "Enable futex support" if EXPERT
1023 Disabling this option will cause the kernel to be built without
1024 support for "fast userspace mutexes". The resulting kernel may not
1025 run glibc-based applications correctly.
1028 bool "Enable eventpoll support" if EXPERT
1032 Disabling this option will cause the kernel to be built without
1033 support for epoll family of system calls.
1036 bool "Enable signalfd() system call" if EXPERT
1040 Enable the signalfd() system call that allows to receive signals
1041 on a file descriptor.
1046 bool "Enable timerfd() system call" if EXPERT
1050 Enable the timerfd() system call that allows to receive timer
1051 events on a file descriptor.
1056 bool "Enable eventfd() system call" if EXPERT
1060 Enable the eventfd() system call that allows to receive both
1061 kernel notification (ie. KAIO) or userspace notifications.
1066 bool "Use full shmem filesystem" if EXPERT
1070 The shmem is an internal filesystem used to manage shared memory.
1071 It is backed by swap and manages resource limits. It is also exported
1072 to userspace as tmpfs if TMPFS is enabled. Disabling this
1073 option replaces shmem and tmpfs with the much simpler ramfs code,
1074 which may be appropriate on small systems without swap.
1077 bool "Enable AIO support" if EXPERT
1080 This option enables POSIX asynchronous I/O which may by used
1081 by some high performance threaded applications. Disabling
1082 this option saves about 7k.
1085 bool "Embedded system"
1088 This option should be enabled if compiling the kernel for
1089 an embedded system so certain expert options are available
1092 config HAVE_PERF_EVENTS
1095 See tools/perf/design.txt for details.
1097 config PERF_USE_VMALLOC
1100 See tools/perf/design.txt for details
1102 menu "Kernel Performance Events And Counters"
1105 bool "Kernel performance events and counters"
1106 default y if (PROFILING || PERF_COUNTERS)
1107 depends on HAVE_PERF_EVENTS
1111 Enable kernel support for various performance events provided
1112 by software and hardware.
1114 Software events are supported either built-in or via the
1115 use of generic tracepoints.
1117 Most modern CPUs support performance events via performance
1118 counter registers. These registers count the number of certain
1119 types of hw events: such as instructions executed, cachemisses
1120 suffered, or branches mis-predicted - without slowing down the
1121 kernel or applications. These registers can also trigger interrupts
1122 when a threshold number of events have passed - and can thus be
1123 used to profile the code that runs on that CPU.
1125 The Linux Performance Event subsystem provides an abstraction of
1126 these software and hardware event capabilities, available via a
1127 system call and used by the "perf" utility in tools/perf/. It
1128 provides per task and per CPU counters, and it provides event
1129 capabilities on top of those.
1133 config PERF_COUNTERS
1134 bool "Kernel performance counters (old config option)"
1135 depends on HAVE_PERF_EVENTS
1137 This config has been obsoleted by the PERF_EVENTS
1138 config option - please see that one for details.
1140 It has no effect on the kernel whether you enable
1141 it or not, it is a compatibility placeholder.
1145 config DEBUG_PERF_USE_VMALLOC
1147 bool "Debug: use vmalloc to back perf mmap() buffers"
1148 depends on PERF_EVENTS && DEBUG_KERNEL
1149 select PERF_USE_VMALLOC
1151 Use vmalloc memory to back perf mmap() buffers.
1153 Mostly useful for debugging the vmalloc code on platforms
1154 that don't require it.
1160 config VM_EVENT_COUNTERS
1162 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1164 VM event counters are needed for event counts to be shown.
1165 This option allows the disabling of the VM event counters
1166 on EXPERT systems. /proc/vmstat will only show page counts
1167 if VM event counters are disabled.
1171 bool "Enable PCI quirk workarounds" if EXPERT
1174 This enables workarounds for various PCI chipset
1175 bugs/quirks. Disable this only if your target machine is
1176 unaffected by PCI quirks.
1180 bool "Enable SLUB debugging support" if EXPERT
1181 depends on SLUB && SYSFS
1183 SLUB has extensive debug support features. Disabling these can
1184 result in significant savings in code size. This also disables
1185 SLUB sysfs support. /sys/slab will not exist and there will be
1186 no support for cache validation etc.
1189 bool "Disable heap randomization"
1192 Randomizing heap placement makes heap exploits harder, but it
1193 also breaks ancient binaries (including anything libc5 based).
1194 This option changes the bootup default to heap randomization
1195 disabled, and can be overridden at runtime by setting
1196 /proc/sys/kernel/randomize_va_space to 2.
1198 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1201 prompt "Choose SLAB allocator"
1204 This option allows to select a slab allocator.
1209 The regular slab allocator that is established and known to work
1210 well in all environments. It organizes cache hot objects in
1211 per cpu and per node queues.
1214 bool "SLUB (Unqueued Allocator)"
1216 SLUB is a slab allocator that minimizes cache line usage
1217 instead of managing queues of cached objects (SLAB approach).
1218 Per cpu caching is realized using slabs of objects instead
1219 of queues of objects. SLUB can use memory efficiently
1220 and has enhanced diagnostics. SLUB is the default choice for
1225 bool "SLOB (Simple Allocator)"
1227 SLOB replaces the stock allocator with a drastically simpler
1228 allocator. SLOB is generally more space efficient but
1229 does not perform as well on large systems.
1233 config MMAP_ALLOW_UNINITIALIZED
1234 bool "Allow mmapped anonymous memory to be uninitialized"
1235 depends on EXPERT && !MMU
1238 Normally, and according to the Linux spec, anonymous memory obtained
1239 from mmap() has it's contents cleared before it is passed to
1240 userspace. Enabling this config option allows you to request that
1241 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1242 providing a huge performance boost. If this option is not enabled,
1243 then the flag will be ignored.
1245 This is taken advantage of by uClibc's malloc(), and also by
1246 ELF-FDPIC binfmt's brk and stack allocator.
1248 Because of the obvious security issues, this option should only be
1249 enabled on embedded devices where you control what is run in
1250 userspace. Since that isn't generally a problem on no-MMU systems,
1251 it is normally safe to say Y here.
1253 See Documentation/nommu-mmap.txt for more information.
1256 bool "Profiling support"
1258 Say Y here to enable the extended profiling support mechanisms used
1259 by profilers such as OProfile.
1262 # Place an empty function call at each tracepoint site. Can be
1263 # dynamically changed for a probe function.
1268 source "arch/Kconfig"
1270 endmenu # General setup
1272 config HAVE_GENERIC_DMA_COHERENT
1279 depends on SLAB || SLUB_DEBUG
1287 default 0 if BASE_FULL
1288 default 1 if !BASE_FULL
1291 bool "Enable loadable module support"
1293 Kernel modules are small pieces of compiled code which can
1294 be inserted in the running kernel, rather than being
1295 permanently built into the kernel. You use the "modprobe"
1296 tool to add (and sometimes remove) them. If you say Y here,
1297 many parts of the kernel can be built as modules (by
1298 answering M instead of Y where indicated): this is most
1299 useful for infrequently used options which are not required
1300 for booting. For more information, see the man pages for
1301 modprobe, lsmod, modinfo, insmod and rmmod.
1303 If you say Y here, you will need to run "make
1304 modules_install" to put the modules under /lib/modules/
1305 where modprobe can find them (you may need to be root to do
1312 config MODULE_FORCE_LOAD
1313 bool "Forced module loading"
1316 Allow loading of modules without version information (ie. modprobe
1317 --force). Forced module loading sets the 'F' (forced) taint flag and
1318 is usually a really bad idea.
1320 config MODULE_UNLOAD
1321 bool "Module unloading"
1323 Without this option you will not be able to unload any
1324 modules (note that some modules may not be unloadable
1325 anyway), which makes your kernel smaller, faster
1326 and simpler. If unsure, say Y.
1328 config MODULE_FORCE_UNLOAD
1329 bool "Forced module unloading"
1330 depends on MODULE_UNLOAD && EXPERIMENTAL
1332 This option allows you to force a module to unload, even if the
1333 kernel believes it is unsafe: the kernel will remove the module
1334 without waiting for anyone to stop using it (using the -f option to
1335 rmmod). This is mainly for kernel developers and desperate users.
1339 bool "Module versioning support"
1341 Usually, you have to use modules compiled with your kernel.
1342 Saying Y here makes it sometimes possible to use modules
1343 compiled for different kernels, by adding enough information
1344 to the modules to (hopefully) spot any changes which would
1345 make them incompatible with the kernel you are running. If
1348 config MODULE_SRCVERSION_ALL
1349 bool "Source checksum for all modules"
1351 Modules which contain a MODULE_VERSION get an extra "srcversion"
1352 field inserted into their modinfo section, which contains a
1353 sum of the source files which made it. This helps maintainers
1354 see exactly which source was used to build a module (since
1355 others sometimes change the module source without updating
1356 the version). With this option, such a "srcversion" field
1357 will be created for all modules. If unsure, say N.
1361 config INIT_ALL_POSSIBLE
1364 Back when each arch used to define their own cpu_online_map and
1365 cpu_possible_map, some of them chose to initialize cpu_possible_map
1366 with all 1s, and others with all 0s. When they were centralised,
1367 it was better to provide this option than to break all the archs
1368 and have several arch maintainers pursuing me down dark alleys.
1373 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1375 Need stop_machine() primitive.
1377 source "block/Kconfig"
1379 config PREEMPT_NOTIFIERS
1386 source "kernel/Kconfig.locks"