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"
28 depends on HAVE_IRQ_WORK
33 bool "Prompt for development and/or incomplete code/drivers"
35 Some of the various things that Linux supports (such as network
36 drivers, file systems, network protocols, etc.) can be in a state
37 of development where the functionality, stability, or the level of
38 testing is not yet high enough for general use. This is usually
39 known as the "alpha-test" phase among developers. If a feature is
40 currently in alpha-test, then the developers usually discourage
41 uninformed widespread use of this feature by the general public to
42 avoid "Why doesn't this work?" type mail messages. However, active
43 testing and use of these systems is welcomed. Just be aware that it
44 may not meet the normal level of reliability or it may fail to work
45 in some special cases. Detailed bug reports from people familiar
46 with the kernel internals are usually welcomed by the developers
47 (before submitting bug reports, please read the documents
48 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
49 <file:Documentation/BUG-HUNTING>, and
50 <file:Documentation/oops-tracing.txt> in the kernel source).
52 This option will also make obsoleted drivers available. These are
53 drivers that have been replaced by something else, and/or are
54 scheduled to be removed in a future kernel release.
56 Unless you intend to help test and develop a feature or driver that
57 falls into this category, or you have a situation that requires
58 using these features, you should probably say N here, which will
59 cause the configurator to present you with fewer choices. If
60 you say Y here, you will be offered the choice of using features or
61 drivers that are currently considered to be in the alpha-test phase.
68 depends on BROKEN || !SMP
71 config INIT_ENV_ARG_LIMIT
76 Maximum of each of the number of arguments and environment
77 variables passed to init from the kernel command line.
81 string "Cross-compiler tool prefix"
83 Same as running 'make CROSS_COMPILE=prefix-' but stored for
84 default make runs in this kernel build directory. You don't
85 need to set this unless you want the configured kernel build
86 directory to select the cross-compiler automatically.
89 string "Local version - append to kernel release"
91 Append an extra string to the end of your kernel version.
92 This will show up when you type uname, for example.
93 The string you set here will be appended after the contents of
94 any files with a filename matching localversion* in your
95 object and source tree, in that order. Your total string can
96 be a maximum of 64 characters.
98 config LOCALVERSION_AUTO
99 bool "Automatically append version information to the version string"
102 This will try to automatically determine if the current tree is a
103 release tree by looking for git tags that belong to the current
104 top of tree revision.
106 A string of the format -gxxxxxxxx will be added to the localversion
107 if a git-based tree is found. The string generated by this will be
108 appended after any matching localversion* files, and after the value
109 set in CONFIG_LOCALVERSION.
111 (The actual string used here is the first eight characters produced
112 by running the command:
114 $ git rev-parse --verify HEAD
116 which is done within the script "scripts/setlocalversion".)
118 config HAVE_KERNEL_GZIP
121 config HAVE_KERNEL_BZIP2
124 config HAVE_KERNEL_LZMA
127 config HAVE_KERNEL_XZ
130 config HAVE_KERNEL_LZO
134 prompt "Kernel compression mode"
136 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
138 The linux kernel is a kind of self-extracting executable.
139 Several compression algorithms are available, which differ
140 in efficiency, compression and decompression speed.
141 Compression speed is only relevant when building a kernel.
142 Decompression speed is relevant at each boot.
144 If you have any problems with bzip2 or lzma compressed
145 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
146 version of this functionality (bzip2 only), for 2.4, was
147 supplied by Christian Ludwig)
149 High compression options are mostly useful for users, who
150 are low on disk space (embedded systems), but for whom ram
153 If in doubt, select 'gzip'
157 depends on HAVE_KERNEL_GZIP
159 The old and tried gzip compression. It provides a good balance
160 between compression ratio and decompression speed.
164 depends on HAVE_KERNEL_BZIP2
166 Its compression ratio and speed is intermediate.
167 Decompression speed is slowest among the three. The kernel
168 size is about 10% smaller with bzip2, in comparison to gzip.
169 Bzip2 uses a large amount of memory. For modern kernels you
170 will need at least 8MB RAM or more for booting.
174 depends on HAVE_KERNEL_LZMA
176 The most recent compression algorithm.
177 Its ratio is best, decompression speed is between the other
178 two. Compression is slowest. The kernel size is about 33%
179 smaller with LZMA in comparison to gzip.
183 depends on HAVE_KERNEL_XZ
185 XZ uses the LZMA2 algorithm and instruction set specific
186 BCJ filters which can improve compression ratio of executable
187 code. The size of the kernel is about 30% smaller with XZ in
188 comparison to gzip. On architectures for which there is a BCJ
189 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
190 will create a few percent smaller kernel than plain LZMA.
192 The speed is about the same as with LZMA: The decompression
193 speed of XZ is better than that of bzip2 but worse than gzip
194 and LZO. Compression is slow.
198 depends on HAVE_KERNEL_LZO
200 Its compression ratio is the poorest among the 4. The kernel
201 size is about 10% bigger than gzip; however its speed
202 (both compression and decompression) is the fastest.
206 config DEFAULT_HOSTNAME
207 string "Default hostname"
210 This option determines the default system hostname before userspace
211 calls sethostname(2). The kernel traditionally uses "(none)" here,
212 but you may wish to use a different default here to make a minimal
213 system more usable with less configuration.
216 bool "Support for paging of anonymous memory (swap)"
217 depends on MMU && BLOCK
220 This option allows you to choose whether you want to have support
221 for so called swap devices or swap files in your kernel that are
222 used to provide more virtual memory than the actual RAM present
223 in your computer. If unsure say Y.
228 Inter Process Communication is a suite of library functions and
229 system calls which let processes (running programs) synchronize and
230 exchange information. It is generally considered to be a good thing,
231 and some programs won't run unless you say Y here. In particular, if
232 you want to run the DOS emulator dosemu under Linux (read the
233 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
234 you'll need to say Y here.
236 You can find documentation about IPC with "info ipc" and also in
237 section 6.4 of the Linux Programmer's Guide, available from
238 <http://www.tldp.org/guides.html>.
240 config SYSVIPC_SYSCTL
247 bool "POSIX Message Queues"
248 depends on NET && EXPERIMENTAL
250 POSIX variant of message queues is a part of IPC. In POSIX message
251 queues every message has a priority which decides about succession
252 of receiving it by a process. If you want to compile and run
253 programs written e.g. for Solaris with use of its POSIX message
254 queues (functions mq_*) say Y here.
256 POSIX message queues are visible as a filesystem called 'mqueue'
257 and can be mounted somewhere if you want to do filesystem
258 operations on message queues.
262 config POSIX_MQUEUE_SYSCTL
264 depends on POSIX_MQUEUE
268 config BSD_PROCESS_ACCT
269 bool "BSD Process Accounting"
271 If you say Y here, a user level program will be able to instruct the
272 kernel (via a special system call) to write process accounting
273 information to a file: whenever a process exits, information about
274 that process will be appended to the file by the kernel. The
275 information includes things such as creation time, owning user,
276 command name, memory usage, controlling terminal etc. (the complete
277 list is in the struct acct in <file:include/linux/acct.h>). It is
278 up to the user level program to do useful things with this
279 information. This is generally a good idea, so say Y.
281 config BSD_PROCESS_ACCT_V3
282 bool "BSD Process Accounting version 3 file format"
283 depends on BSD_PROCESS_ACCT
286 If you say Y here, the process accounting information is written
287 in a new file format that also logs the process IDs of each
288 process and it's parent. Note that this file format is incompatible
289 with previous v0/v1/v2 file formats, so you will need updated tools
290 for processing it. A preliminary version of these tools is available
291 at <http://www.gnu.org/software/acct/>.
294 bool "open by fhandle syscalls"
297 If you say Y here, a user level program will be able to map
298 file names to handle and then later use the handle for
299 different file system operations. This is useful in implementing
300 userspace file servers, which now track files using handles instead
301 of names. The handle would remain the same even if file names
302 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
306 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
310 Export selected statistics for tasks/processes through the
311 generic netlink interface. Unlike BSD process accounting, the
312 statistics are available during the lifetime of tasks/processes as
313 responses to commands. Like BSD accounting, they are sent to user
318 config TASK_DELAY_ACCT
319 bool "Enable per-task delay accounting (EXPERIMENTAL)"
322 Collect information on time spent by a task waiting for system
323 resources like cpu, synchronous block I/O completion and swapping
324 in pages. Such statistics can help in setting a task's priorities
325 relative to other tasks for cpu, io, rss limits etc.
330 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
333 Collect extended task accounting data and send the data
334 to userland for processing over the taskstats interface.
338 config TASK_IO_ACCOUNTING
339 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
340 depends on TASK_XACCT
342 Collect information on the number of bytes of storage I/O which this
348 bool "Auditing support"
351 Enable auditing infrastructure that can be used with another
352 kernel subsystem, such as SELinux (which requires this for
353 logging of avc messages output). Does not do system-call
354 auditing without CONFIG_AUDITSYSCALL.
357 bool "Enable system-call auditing support"
358 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
359 default y if SECURITY_SELINUX
361 Enable low-overhead system-call auditing infrastructure that
362 can be used independently or with another kernel subsystem,
367 depends on AUDITSYSCALL
372 depends on AUDITSYSCALL
375 source "kernel/irq/Kconfig"
380 prompt "RCU Implementation"
384 bool "Tree-based hierarchical RCU"
385 depends on !PREEMPT && SMP
387 This option selects the RCU implementation that is
388 designed for very large SMP system with hundreds or
389 thousands of CPUs. It also scales down nicely to
392 config TREE_PREEMPT_RCU
393 bool "Preemptible tree-based hierarchical RCU"
394 depends on PREEMPT && SMP
396 This option selects the RCU implementation that is
397 designed for very large SMP systems with hundreds or
398 thousands of CPUs, but for which real-time response
399 is also required. It also scales down nicely to
403 bool "UP-only small-memory-footprint RCU"
404 depends on !PREEMPT && !SMP
406 This option selects the RCU implementation that is
407 designed for UP systems from which real-time response
408 is not required. This option greatly reduces the
409 memory footprint of RCU.
411 config TINY_PREEMPT_RCU
412 bool "Preemptible UP-only small-memory-footprint RCU"
413 depends on PREEMPT && !SMP
415 This option selects the RCU implementation that is designed
416 for real-time UP systems. This option greatly reduces the
417 memory footprint of RCU.
422 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
424 This option enables preemptible-RCU code that is common between
425 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
428 bool "Enable tracing for RCU"
430 This option provides tracing in RCU which presents stats
431 in debugfs for debugging RCU implementation.
433 Say Y here if you want to enable RCU tracing
434 Say N if you are unsure.
437 int "Tree-based hierarchical RCU fanout value"
440 depends on TREE_RCU || TREE_PREEMPT_RCU
444 This option controls the fanout of hierarchical implementations
445 of RCU, allowing RCU to work efficiently on machines with
446 large numbers of CPUs. This value must be at least the fourth
447 root of NR_CPUS, which allows NR_CPUS to be insanely large.
448 The default value of RCU_FANOUT should be used for production
449 systems, but if you are stress-testing the RCU implementation
450 itself, small RCU_FANOUT values allow you to test large-system
451 code paths on small(er) systems.
453 Select a specific number if testing RCU itself.
454 Take the default if unsure.
456 config RCU_FANOUT_EXACT
457 bool "Disable tree-based hierarchical RCU auto-balancing"
458 depends on TREE_RCU || TREE_PREEMPT_RCU
461 This option forces use of the exact RCU_FANOUT value specified,
462 regardless of imbalances in the hierarchy. This is useful for
463 testing RCU itself, and might one day be useful on systems with
464 strong NUMA behavior.
466 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
470 config RCU_FAST_NO_HZ
471 bool "Accelerate last non-dyntick-idle CPU's grace periods"
472 depends on NO_HZ && SMP
475 This option causes RCU to attempt to accelerate grace periods
476 in order to allow CPUs to enter dynticks-idle state more
477 quickly. On the other hand, this option increases the overhead
478 of the dynticks-idle checking, particularly on systems with
479 large numbers of CPUs.
481 Say Y if energy efficiency is critically important, particularly
482 if you have relatively few CPUs.
484 Say N if you are unsure.
486 config TREE_RCU_TRACE
487 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
490 This option provides tracing for the TREE_RCU and
491 TREE_PREEMPT_RCU implementations, permitting Makefile to
492 trivially select kernel/rcutree_trace.c.
495 bool "Enable RCU priority boosting"
496 depends on RT_MUTEXES && PREEMPT_RCU
499 This option boosts the priority of preempted RCU readers that
500 block the current preemptible RCU grace period for too long.
501 This option also prevents heavy loads from blocking RCU
502 callback invocation for all flavors of RCU.
504 Say Y here if you are working with real-time apps or heavy loads
505 Say N here if you are unsure.
507 config RCU_BOOST_PRIO
508 int "Real-time priority to boost RCU readers to"
513 This option specifies the real-time priority to which preempted
514 RCU readers are to be boosted. If you are working with CPU-bound
515 real-time applications, you should specify a priority higher then
516 the highest-priority CPU-bound application.
518 Specify the real-time priority, or take the default if unsure.
520 config RCU_BOOST_DELAY
521 int "Milliseconds to delay boosting after RCU grace-period start"
526 This option specifies the time to wait after the beginning of
527 a given grace period before priority-boosting preempted RCU
528 readers blocking that grace period. Note that any RCU reader
529 blocking an expedited RCU grace period is boosted immediately.
531 Accept the default if unsure.
533 endmenu # "RCU Subsystem"
536 tristate "Kernel .config support"
538 This option enables the complete Linux kernel ".config" file
539 contents to be saved in the kernel. It provides documentation
540 of which kernel options are used in a running kernel or in an
541 on-disk kernel. This information can be extracted from the kernel
542 image file with the script scripts/extract-ikconfig and used as
543 input to rebuild the current kernel or to build another kernel.
544 It can also be extracted from a running kernel by reading
545 /proc/config.gz if enabled (below).
548 bool "Enable access to .config through /proc/config.gz"
549 depends on IKCONFIG && PROC_FS
551 This option enables access to the kernel configuration file
552 through /proc/config.gz.
555 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
559 Select kernel log buffer size as a power of 2.
569 # Architectures with an unreliable sched_clock() should select this:
571 config HAVE_UNSTABLE_SCHED_CLOCK
575 boolean "Control Group support"
578 This option adds support for grouping sets of processes together, for
579 use with process control subsystems such as Cpusets, CFS, memory
580 controls or device isolation.
582 - Documentation/scheduler/sched-design-CFS.txt (CFS)
583 - Documentation/cgroups/ (features for grouping, isolation
584 and resource control)
591 bool "Example debug cgroup subsystem"
594 This option enables a simple cgroup subsystem that
595 exports useful debugging information about the cgroups
600 config CGROUP_FREEZER
601 bool "Freezer cgroup subsystem"
603 Provides a way to freeze and unfreeze all tasks in a
607 bool "Device controller for cgroups"
609 Provides a cgroup implementing whitelists for devices which
610 a process in the cgroup can mknod or open.
613 bool "Cpuset support"
615 This option will let you create and manage CPUSETs which
616 allow dynamically partitioning a system into sets of CPUs and
617 Memory Nodes and assigning tasks to run only within those sets.
618 This is primarily useful on large SMP or NUMA systems.
622 config PROC_PID_CPUSET
623 bool "Include legacy /proc/<pid>/cpuset file"
627 config CGROUP_CPUACCT
628 bool "Simple CPU accounting cgroup subsystem"
630 Provides a simple Resource Controller for monitoring the
631 total CPU consumed by the tasks in a cgroup.
633 config RESOURCE_COUNTERS
634 bool "Resource counters"
636 This option enables controller independent resource accounting
637 infrastructure that works with cgroups.
639 config CGROUP_MEM_RES_CTLR
640 bool "Memory Resource Controller for Control Groups"
641 depends on RESOURCE_COUNTERS
644 Provides a memory resource controller that manages both anonymous
645 memory and page cache. (See Documentation/cgroups/memory.txt)
647 Note that setting this option increases fixed memory overhead
648 associated with each page of memory in the system. By this,
649 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
650 usage tracking struct at boot. Total amount of this is printed out
653 Only enable when you're ok with these trade offs and really
654 sure you need the memory resource controller. Even when you enable
655 this, you can set "cgroup_disable=memory" at your boot option to
656 disable memory resource controller and you can avoid overheads.
657 (and lose benefits of memory resource controller)
659 This config option also selects MM_OWNER config option, which
660 could in turn add some fork/exit overhead.
662 config CGROUP_MEM_RES_CTLR_SWAP
663 bool "Memory Resource Controller Swap Extension"
664 depends on CGROUP_MEM_RES_CTLR && SWAP
666 Add swap management feature to memory resource controller. When you
667 enable this, you can limit mem+swap usage per cgroup. In other words,
668 when you disable this, memory resource controller has no cares to
669 usage of swap...a process can exhaust all of the swap. This extension
670 is useful when you want to avoid exhaustion swap but this itself
671 adds more overheads and consumes memory for remembering information.
672 Especially if you use 32bit system or small memory system, please
673 be careful about enabling this. When memory resource controller
674 is disabled by boot option, this will be automatically disabled and
675 there will be no overhead from this. Even when you set this config=y,
676 if boot option "swapaccount=0" is set, swap will not be accounted.
677 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
678 size is 4096bytes, 512k per 1Gbytes of swap.
679 config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
680 bool "Memory Resource Controller Swap Extension enabled by default"
681 depends on CGROUP_MEM_RES_CTLR_SWAP
684 Memory Resource Controller Swap Extension comes with its price in
685 a bigger memory consumption. General purpose distribution kernels
686 which want to enable the feature but keep it disabled by default
687 and let the user enable it by swapaccount boot command line
688 parameter should have this option unselected.
689 For those who want to have the feature enabled by default should
690 select this option (if, for some reason, they need to disable it
691 then swapaccount=0 does the trick).
694 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
695 depends on PERF_EVENTS && CGROUPS
697 This option extends the per-cpu mode to restrict monitoring to
698 threads which belong to the cgroup specified and run on the
703 menuconfig CGROUP_SCHED
704 bool "Group CPU scheduler"
705 depends on EXPERIMENTAL
708 This feature lets CPU scheduler recognize task groups and control CPU
709 bandwidth allocation to such task groups. It uses cgroups to group
713 config FAIR_GROUP_SCHED
714 bool "Group scheduling for SCHED_OTHER"
715 depends on CGROUP_SCHED
719 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
720 depends on EXPERIMENTAL
721 depends on FAIR_GROUP_SCHED
724 This option allows users to define CPU bandwidth rates (limits) for
725 tasks running within the fair group scheduler. Groups with no limit
726 set are considered to be unconstrained and will run with no
728 See tip/Documentation/scheduler/sched-bwc.txt for more information.
730 config RT_GROUP_SCHED
731 bool "Group scheduling for SCHED_RR/FIFO"
732 depends on EXPERIMENTAL
733 depends on CGROUP_SCHED
736 This feature lets you explicitly allocate real CPU bandwidth
737 to task groups. If enabled, it will also make it impossible to
738 schedule realtime tasks for non-root users until you allocate
739 realtime bandwidth for them.
740 See Documentation/scheduler/sched-rt-group.txt for more information.
745 tristate "Block IO controller"
749 Generic block IO controller cgroup interface. This is the common
750 cgroup interface which should be used by various IO controlling
753 Currently, CFQ IO scheduler uses it to recognize task groups and
754 control disk bandwidth allocation (proportional time slice allocation)
755 to such task groups. It is also used by bio throttling logic in
756 block layer to implement upper limit in IO rates on a device.
758 This option only enables generic Block IO controller infrastructure.
759 One needs to also enable actual IO controlling logic/policy. For
760 enabling proportional weight division of disk bandwidth in CFQ, set
761 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
762 CONFIG_BLK_DEV_THROTTLING=y.
764 See Documentation/cgroups/blkio-controller.txt for more information.
766 config DEBUG_BLK_CGROUP
767 bool "Enable Block IO controller debugging"
768 depends on BLK_CGROUP
771 Enable some debugging help. Currently it exports additional stat
772 files in a cgroup which can be useful for debugging.
776 menuconfig NAMESPACES
777 bool "Namespaces support" if EXPERT
780 Provides the way to make tasks work with different objects using
781 the same id. For example same IPC id may refer to different objects
782 or same user id or pid may refer to different tasks when used in
783 different namespaces.
791 In this namespace tasks see different info provided with the
796 depends on (SYSVIPC || POSIX_MQUEUE)
799 In this namespace tasks work with IPC ids which correspond to
800 different IPC objects in different namespaces.
803 bool "User namespace (EXPERIMENTAL)"
804 depends on EXPERIMENTAL
807 This allows containers, i.e. vservers, to use user namespaces
808 to provide different user info for different servers.
812 bool "PID Namespaces"
815 Support process id namespaces. This allows having multiple
816 processes with the same pid as long as they are in different
817 pid namespaces. This is a building block of containers.
820 bool "Network namespace"
824 Allow user space to create what appear to be multiple instances
825 of the network stack.
829 config SCHED_AUTOGROUP
830 bool "Automatic process group scheduling"
834 select FAIR_GROUP_SCHED
836 This option optimizes the scheduler for common desktop workloads by
837 automatically creating and populating task groups. This separation
838 of workloads isolates aggressive CPU burners (like build jobs) from
839 desktop applications. Task group autogeneration is currently based
845 config SYSFS_DEPRECATED
846 bool "Enable deprecated sysfs features to support old userspace tools"
850 This option adds code that switches the layout of the "block" class
851 devices, to not show up in /sys/class/block/, but only in
854 This switch is only active when the sysfs.deprecated=1 boot option is
855 passed or the SYSFS_DEPRECATED_V2 option is set.
857 This option allows new kernels to run on old distributions and tools,
858 which might get confused by /sys/class/block/. Since 2007/2008 all
859 major distributions and tools handle this just fine.
861 Recent distributions and userspace tools after 2009/2010 depend on
862 the existence of /sys/class/block/, and will not work with this
865 Only if you are using a new kernel on an old distribution, you might
868 config SYSFS_DEPRECATED_V2
869 bool "Enable deprecated sysfs features by default"
872 depends on SYSFS_DEPRECATED
874 Enable deprecated sysfs by default.
876 See the CONFIG_SYSFS_DEPRECATED option for more details about this
879 Only if you are using a new kernel on an old distribution, you might
880 need to say Y here. Even then, odds are you would not need it
881 enabled, you can always pass the boot option if absolutely necessary.
884 bool "Kernel->user space relay support (formerly relayfs)"
886 This option enables support for relay interface support in
887 certain file systems (such as debugfs).
888 It is designed to provide an efficient mechanism for tools and
889 facilities to relay large amounts of data from kernel space to
894 config BLK_DEV_INITRD
895 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
896 depends on BROKEN || !FRV
898 The initial RAM filesystem is a ramfs which is loaded by the
899 boot loader (loadlin or lilo) and that is mounted as root
900 before the normal boot procedure. It is typically used to
901 load modules needed to mount the "real" root file system,
902 etc. See <file:Documentation/initrd.txt> for details.
904 If RAM disk support (BLK_DEV_RAM) is also included, this
905 also enables initial RAM disk (initrd) support and adds
906 15 Kbytes (more on some other architectures) to the kernel size.
916 config CC_OPTIMIZE_FOR_SIZE
917 bool "Optimize for size"
919 Enabling this option will pass "-Os" instead of "-O2" to gcc
920 resulting in a smaller kernel.
931 bool "Configure standard kernel features (expert users)"
932 # Unhide debug options, to make the on-by-default options visible
935 This option allows certain base kernel options and settings
936 to be disabled or tweaked. This is for specialized
937 environments which can tolerate a "non-standard" kernel.
938 Only use this if you really know what you are doing.
941 bool "Enable 16-bit UID system calls" if EXPERT
942 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
945 This enables the legacy 16-bit UID syscall wrappers.
947 config SYSCTL_SYSCALL
948 bool "Sysctl syscall support" if EXPERT
949 depends on PROC_SYSCTL
953 sys_sysctl uses binary paths that have been found challenging
954 to properly maintain and use. The interface in /proc/sys
955 using paths with ascii names is now the primary path to this
958 Almost nothing using the binary sysctl interface so if you are
959 trying to save some space it is probably safe to disable this,
960 making your kernel marginally smaller.
962 If unsure say N here.
965 bool "Load all symbols for debugging/ksymoops" if EXPERT
968 Say Y here to let the kernel print out symbolic crash information and
969 symbolic stack backtraces. This increases the size of the kernel
970 somewhat, as all symbols have to be loaded into the kernel image.
973 bool "Include all symbols in kallsyms"
974 depends on DEBUG_KERNEL && KALLSYMS
976 Normally kallsyms only contains the symbols of functions for nicer
977 OOPS messages and backtraces (i.e., symbols from the text and inittext
978 sections). This is sufficient for most cases. And only in very rare
979 cases (e.g., when a debugger is used) all symbols are required (e.g.,
980 names of variables from the data sections, etc).
982 This option makes sure that all symbols are loaded into the kernel
983 image (i.e., symbols from all sections) in cost of increased kernel
984 size (depending on the kernel configuration, it may be 300KiB or
985 something like this).
987 Say N unless you really need all symbols.
990 bool "Support for hot-pluggable devices" if EXPERT
993 This option is provided for the case where no hotplug or uevent
994 capabilities is wanted by the kernel. You should only consider
995 disabling this option for embedded systems that do not use modules, a
996 dynamic /dev tree, or dynamic device discovery. Just say Y.
1000 bool "Enable support for printk" if EXPERT
1002 This option enables normal printk support. Removing it
1003 eliminates most of the message strings from the kernel image
1004 and makes the kernel more or less silent. As this makes it
1005 very difficult to diagnose system problems, saying N here is
1006 strongly discouraged.
1009 bool "BUG() support" if EXPERT
1012 Disabling this option eliminates support for BUG and WARN, reducing
1013 the size of your kernel image and potentially quietly ignoring
1014 numerous fatal conditions. You should only consider disabling this
1015 option for embedded systems with no facilities for reporting errors.
1020 bool "Enable ELF core dumps" if EXPERT
1022 Enable support for generating core dumps. Disabling saves about 4k.
1025 config PCSPKR_PLATFORM
1026 bool "Enable PC-Speaker support" if EXPERT
1027 depends on HAVE_PCSPKR_PLATFORM
1031 This option allows to disable the internal PC-Speaker
1032 support, saving some memory.
1034 config HAVE_PCSPKR_PLATFORM
1039 bool "Enable full-sized data structures for core" if EXPERT
1041 Disabling this option reduces the size of miscellaneous core
1042 kernel data structures. This saves memory on small machines,
1043 but may reduce performance.
1046 bool "Enable futex support" if EXPERT
1050 Disabling this option will cause the kernel to be built without
1051 support for "fast userspace mutexes". The resulting kernel may not
1052 run glibc-based applications correctly.
1055 bool "Enable eventpoll support" if EXPERT
1059 Disabling this option will cause the kernel to be built without
1060 support for epoll family of system calls.
1063 bool "Enable signalfd() system call" if EXPERT
1067 Enable the signalfd() system call that allows to receive signals
1068 on a file descriptor.
1073 bool "Enable timerfd() system call" if EXPERT
1077 Enable the timerfd() system call that allows to receive timer
1078 events on a file descriptor.
1083 bool "Enable eventfd() system call" if EXPERT
1087 Enable the eventfd() system call that allows to receive both
1088 kernel notification (ie. KAIO) or userspace notifications.
1093 bool "Use full shmem filesystem" if EXPERT
1097 The shmem is an internal filesystem used to manage shared memory.
1098 It is backed by swap and manages resource limits. It is also exported
1099 to userspace as tmpfs if TMPFS is enabled. Disabling this
1100 option replaces shmem and tmpfs with the much simpler ramfs code,
1101 which may be appropriate on small systems without swap.
1104 bool "Enable AIO support" if EXPERT
1107 This option enables POSIX asynchronous I/O which may by used
1108 by some high performance threaded applications. Disabling
1109 this option saves about 7k.
1112 bool "Embedded system"
1115 This option should be enabled if compiling the kernel for
1116 an embedded system so certain expert options are available
1119 config HAVE_PERF_EVENTS
1122 See tools/perf/design.txt for details.
1124 config PERF_USE_VMALLOC
1127 See tools/perf/design.txt for details
1129 menu "Kernel Performance Events And Counters"
1132 bool "Kernel performance events and counters"
1133 default y if (PROFILING || PERF_COUNTERS)
1134 depends on HAVE_PERF_EVENTS
1138 Enable kernel support for various performance events provided
1139 by software and hardware.
1141 Software events are supported either built-in or via the
1142 use of generic tracepoints.
1144 Most modern CPUs support performance events via performance
1145 counter registers. These registers count the number of certain
1146 types of hw events: such as instructions executed, cachemisses
1147 suffered, or branches mis-predicted - without slowing down the
1148 kernel or applications. These registers can also trigger interrupts
1149 when a threshold number of events have passed - and can thus be
1150 used to profile the code that runs on that CPU.
1152 The Linux Performance Event subsystem provides an abstraction of
1153 these software and hardware event capabilities, available via a
1154 system call and used by the "perf" utility in tools/perf/. It
1155 provides per task and per CPU counters, and it provides event
1156 capabilities on top of those.
1160 config PERF_COUNTERS
1161 bool "Kernel performance counters (old config option)"
1162 depends on HAVE_PERF_EVENTS
1164 This config has been obsoleted by the PERF_EVENTS
1165 config option - please see that one for details.
1167 It has no effect on the kernel whether you enable
1168 it or not, it is a compatibility placeholder.
1172 config DEBUG_PERF_USE_VMALLOC
1174 bool "Debug: use vmalloc to back perf mmap() buffers"
1175 depends on PERF_EVENTS && DEBUG_KERNEL
1176 select PERF_USE_VMALLOC
1178 Use vmalloc memory to back perf mmap() buffers.
1180 Mostly useful for debugging the vmalloc code on platforms
1181 that don't require it.
1187 config VM_EVENT_COUNTERS
1189 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1191 VM event counters are needed for event counts to be shown.
1192 This option allows the disabling of the VM event counters
1193 on EXPERT systems. /proc/vmstat will only show page counts
1194 if VM event counters are disabled.
1198 bool "Enable PCI quirk workarounds" if EXPERT
1201 This enables workarounds for various PCI chipset
1202 bugs/quirks. Disable this only if your target machine is
1203 unaffected by PCI quirks.
1207 bool "Enable SLUB debugging support" if EXPERT
1208 depends on SLUB && SYSFS
1210 SLUB has extensive debug support features. Disabling these can
1211 result in significant savings in code size. This also disables
1212 SLUB sysfs support. /sys/slab will not exist and there will be
1213 no support for cache validation etc.
1216 bool "Disable heap randomization"
1219 Randomizing heap placement makes heap exploits harder, but it
1220 also breaks ancient binaries (including anything libc5 based).
1221 This option changes the bootup default to heap randomization
1222 disabled, and can be overridden at runtime by setting
1223 /proc/sys/kernel/randomize_va_space to 2.
1225 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1228 prompt "Choose SLAB allocator"
1231 This option allows to select a slab allocator.
1236 The regular slab allocator that is established and known to work
1237 well in all environments. It organizes cache hot objects in
1238 per cpu and per node queues.
1241 bool "SLUB (Unqueued Allocator)"
1243 SLUB is a slab allocator that minimizes cache line usage
1244 instead of managing queues of cached objects (SLAB approach).
1245 Per cpu caching is realized using slabs of objects instead
1246 of queues of objects. SLUB can use memory efficiently
1247 and has enhanced diagnostics. SLUB is the default choice for
1252 bool "SLOB (Simple Allocator)"
1254 SLOB replaces the stock allocator with a drastically simpler
1255 allocator. SLOB is generally more space efficient but
1256 does not perform as well on large systems.
1260 config MMAP_ALLOW_UNINITIALIZED
1261 bool "Allow mmapped anonymous memory to be uninitialized"
1262 depends on EXPERT && !MMU
1265 Normally, and according to the Linux spec, anonymous memory obtained
1266 from mmap() has it's contents cleared before it is passed to
1267 userspace. Enabling this config option allows you to request that
1268 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1269 providing a huge performance boost. If this option is not enabled,
1270 then the flag will be ignored.
1272 This is taken advantage of by uClibc's malloc(), and also by
1273 ELF-FDPIC binfmt's brk and stack allocator.
1275 Because of the obvious security issues, this option should only be
1276 enabled on embedded devices where you control what is run in
1277 userspace. Since that isn't generally a problem on no-MMU systems,
1278 it is normally safe to say Y here.
1280 See Documentation/nommu-mmap.txt for more information.
1283 bool "Profiling support"
1285 Say Y here to enable the extended profiling support mechanisms used
1286 by profilers such as OProfile.
1289 # Place an empty function call at each tracepoint site. Can be
1290 # dynamically changed for a probe function.
1295 source "arch/Kconfig"
1297 endmenu # General setup
1299 config HAVE_GENERIC_DMA_COHERENT
1306 depends on SLAB || SLUB_DEBUG
1314 default 0 if BASE_FULL
1315 default 1 if !BASE_FULL
1318 bool "Enable loadable module support"
1320 Kernel modules are small pieces of compiled code which can
1321 be inserted in the running kernel, rather than being
1322 permanently built into the kernel. You use the "modprobe"
1323 tool to add (and sometimes remove) them. If you say Y here,
1324 many parts of the kernel can be built as modules (by
1325 answering M instead of Y where indicated): this is most
1326 useful for infrequently used options which are not required
1327 for booting. For more information, see the man pages for
1328 modprobe, lsmod, modinfo, insmod and rmmod.
1330 If you say Y here, you will need to run "make
1331 modules_install" to put the modules under /lib/modules/
1332 where modprobe can find them (you may need to be root to do
1339 config MODULE_FORCE_LOAD
1340 bool "Forced module loading"
1343 Allow loading of modules without version information (ie. modprobe
1344 --force). Forced module loading sets the 'F' (forced) taint flag and
1345 is usually a really bad idea.
1347 config MODULE_UNLOAD
1348 bool "Module unloading"
1350 Without this option you will not be able to unload any
1351 modules (note that some modules may not be unloadable
1352 anyway), which makes your kernel smaller, faster
1353 and simpler. If unsure, say Y.
1355 config MODULE_FORCE_UNLOAD
1356 bool "Forced module unloading"
1357 depends on MODULE_UNLOAD && EXPERIMENTAL
1359 This option allows you to force a module to unload, even if the
1360 kernel believes it is unsafe: the kernel will remove the module
1361 without waiting for anyone to stop using it (using the -f option to
1362 rmmod). This is mainly for kernel developers and desperate users.
1366 bool "Module versioning support"
1368 Usually, you have to use modules compiled with your kernel.
1369 Saying Y here makes it sometimes possible to use modules
1370 compiled for different kernels, by adding enough information
1371 to the modules to (hopefully) spot any changes which would
1372 make them incompatible with the kernel you are running. If
1375 config MODULE_SRCVERSION_ALL
1376 bool "Source checksum for all modules"
1378 Modules which contain a MODULE_VERSION get an extra "srcversion"
1379 field inserted into their modinfo section, which contains a
1380 sum of the source files which made it. This helps maintainers
1381 see exactly which source was used to build a module (since
1382 others sometimes change the module source without updating
1383 the version). With this option, such a "srcversion" field
1384 will be created for all modules. If unsure, say N.
1388 config INIT_ALL_POSSIBLE
1391 Back when each arch used to define their own cpu_online_map and
1392 cpu_possible_map, some of them chose to initialize cpu_possible_map
1393 with all 1s, and others with all 0s. When they were centralised,
1394 it was better to provide this option than to break all the archs
1395 and have several arch maintainers pursuing me down dark alleys.
1400 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1402 Need stop_machine() primitive.
1404 source "block/Kconfig"
1406 config PREEMPT_NOTIFIERS
1413 source "kernel/Kconfig.locks"
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