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47 drivers that have been replaced by something else, and/or are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 "Local version - append to kernel release"
82 Append an extra string to the end of your kernel version.
83 This will show up when you type uname, for example.
84 The string you set here will be appended after the contents of
85 any files with a filename matching localversion* in your
86 object and source tree, in that order. Your total string can
87 be a maximum of 64 characters.
89 config LOCALVERSION_AUTO
90 bool "Automatically append version information to the version string"
93 This will try to automatically determine if the current tree is a
94 release tree by looking for git tags that belong to the current
97 A string of the format -gxxxxxxxx will be added to the localversion
98 if a git-based tree is found. The string generated by this will be
99 appended after any matching localversion* files, and after the value
100 set in CONFIG_LOCALVERSION.
102 (The actual string used here is the first eight characters produced
103 by running the command:
105 $ git rev-parse --verify HEAD
107 which is done within the script "scripts/setlocalversion".)
109 config HAVE_KERNEL_GZIP
112 config HAVE_KERNEL_BZIP2
115 config HAVE_KERNEL_LZMA
119 prompt "Kernel compression mode"
121 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
123 The linux kernel is a kind of self-extracting executable.
124 Several compression algorithms are available, which differ
125 in efficiency, compression and decompression speed.
126 Compression speed is only relevant when building a kernel.
127 Decompression speed is relevant at each boot.
129 If you have any problems with bzip2 or lzma compressed
130 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
131 version of this functionality (bzip2 only), for 2.4, was
132 supplied by Christian Ludwig)
134 High compression options are mostly useful for users, who
135 are low on disk space (embedded systems), but for whom ram
138 If in doubt, select 'gzip'
142 depends on HAVE_KERNEL_GZIP
144 The old and tried gzip compression. Its compression ratio is
145 the poorest among the 3 choices; however its speed (both
146 compression and decompression) is the fastest.
150 depends on HAVE_KERNEL_BZIP2
152 Its compression ratio and speed is intermediate.
153 Decompression speed is slowest among the three. The kernel
154 size is about 10% smaller with bzip2, in comparison to gzip.
155 Bzip2 uses a large amount of memory. For modern kernels you
156 will need at least 8MB RAM or more for booting.
160 depends on HAVE_KERNEL_LZMA
162 The most recent compression algorithm.
163 Its ratio is best, decompression speed is between the other
164 two. Compression is slowest. The kernel size is about 33%
165 smaller with LZMA in comparison to gzip.
170 bool "Support for paging of anonymous memory (swap)"
171 depends on MMU && BLOCK
174 This option allows you to choose whether you want to have support
175 for so called swap devices or swap files in your kernel that are
176 used to provide more virtual memory than the actual RAM present
177 in your computer. If unsure say Y.
182 Inter Process Communication is a suite of library functions and
183 system calls which let processes (running programs) synchronize and
184 exchange information. It is generally considered to be a good thing,
185 and some programs won't run unless you say Y here. In particular, if
186 you want to run the DOS emulator dosemu under Linux (read the
187 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
188 you'll need to say Y here.
190 You can find documentation about IPC with "info ipc" and also in
191 section 6.4 of the Linux Programmer's Guide, available from
192 <http://www.tldp.org/guides.html>.
194 config SYSVIPC_SYSCTL
201 bool "POSIX Message Queues"
202 depends on NET && EXPERIMENTAL
204 POSIX variant of message queues is a part of IPC. In POSIX message
205 queues every message has a priority which decides about succession
206 of receiving it by a process. If you want to compile and run
207 programs written e.g. for Solaris with use of its POSIX message
208 queues (functions mq_*) say Y here.
210 POSIX message queues are visible as a filesystem called 'mqueue'
211 and can be mounted somewhere if you want to do filesystem
212 operations on message queues.
216 config POSIX_MQUEUE_SYSCTL
218 depends on POSIX_MQUEUE
222 config BSD_PROCESS_ACCT
223 bool "BSD Process Accounting"
225 If you say Y here, a user level program will be able to instruct the
226 kernel (via a special system call) to write process accounting
227 information to a file: whenever a process exits, information about
228 that process will be appended to the file by the kernel. The
229 information includes things such as creation time, owning user,
230 command name, memory usage, controlling terminal etc. (the complete
231 list is in the struct acct in <file:include/linux/acct.h>). It is
232 up to the user level program to do useful things with this
233 information. This is generally a good idea, so say Y.
235 config BSD_PROCESS_ACCT_V3
236 bool "BSD Process Accounting version 3 file format"
237 depends on BSD_PROCESS_ACCT
240 If you say Y here, the process accounting information is written
241 in a new file format that also logs the process IDs of each
242 process and it's parent. Note that this file format is incompatible
243 with previous v0/v1/v2 file formats, so you will need updated tools
244 for processing it. A preliminary version of these tools is available
245 at <http://www.gnu.org/software/acct/>.
248 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
252 Export selected statistics for tasks/processes through the
253 generic netlink interface. Unlike BSD process accounting, the
254 statistics are available during the lifetime of tasks/processes as
255 responses to commands. Like BSD accounting, they are sent to user
260 config TASK_DELAY_ACCT
261 bool "Enable per-task delay accounting (EXPERIMENTAL)"
264 Collect information on time spent by a task waiting for system
265 resources like cpu, synchronous block I/O completion and swapping
266 in pages. Such statistics can help in setting a task's priorities
267 relative to other tasks for cpu, io, rss limits etc.
272 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
275 Collect extended task accounting data and send the data
276 to userland for processing over the taskstats interface.
280 config TASK_IO_ACCOUNTING
281 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
282 depends on TASK_XACCT
284 Collect information on the number of bytes of storage I/O which this
290 bool "Auditing support"
293 Enable auditing infrastructure that can be used with another
294 kernel subsystem, such as SELinux (which requires this for
295 logging of avc messages output). Does not do system-call
296 auditing without CONFIG_AUDITSYSCALL.
299 bool "Enable system-call auditing support"
300 depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
301 default y if SECURITY_SELINUX
303 Enable low-overhead system-call auditing infrastructure that
304 can be used independently or with another kernel subsystem,
305 such as SELinux. To use audit's filesystem watch feature, please
306 ensure that INOTIFY is configured.
310 depends on AUDITSYSCALL
316 prompt "RCU Implementation"
320 bool "Tree-based hierarchical RCU"
322 This option selects the RCU implementation that is
323 designed for very large SMP system with hundreds or
324 thousands of CPUs. It also scales down nicely to
328 bool "Preemptible RCU"
331 This option reduces the latency of the kernel by making certain
332 RCU sections preemptible. Normally RCU code is non-preemptible, if
333 this option is selected then read-only RCU sections become
334 preemptible. This helps latency, but may expose bugs due to
335 now-naive assumptions about each RCU read-side critical section
336 remaining on a given CPU through its execution.
338 config TREE_PREEMPT_RCU
339 bool "Preemptable tree-based hierarchical RCU"
342 This option selects the RCU implementation that is
343 designed for very large SMP systems with hundreds or
344 thousands of CPUs, but for which real-time response
350 bool "Enable tracing for RCU"
351 depends on TREE_RCU || PREEMPT_RCU || TREE_PREEMPT_RCU
353 This option provides tracing in RCU which presents stats
354 in debugfs for debugging RCU implementation.
356 Say Y here if you want to enable RCU tracing
357 Say N if you are unsure.
360 int "Tree-based hierarchical RCU fanout value"
363 depends on TREE_RCU || TREE_PREEMPT_RCU
367 This option controls the fanout of hierarchical implementations
368 of RCU, allowing RCU to work efficiently on machines with
369 large numbers of CPUs. This value must be at least the cube
370 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
371 systems and up to 262,144 for 64-bit systems.
373 Select a specific number if testing RCU itself.
374 Take the default if unsure.
376 config RCU_FANOUT_EXACT
377 bool "Disable tree-based hierarchical RCU auto-balancing"
378 depends on TREE_RCU || TREE_PREEMPT_RCU
381 This option forces use of the exact RCU_FANOUT value specified,
382 regardless of imbalances in the hierarchy. This is useful for
383 testing RCU itself, and might one day be useful on systems with
384 strong NUMA behavior.
386 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
390 config TREE_RCU_TRACE
391 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
394 This option provides tracing for the TREE_RCU and
395 TREE_PREEMPT_RCU implementations, permitting Makefile to
396 trivially select kernel/rcutree_trace.c.
398 config PREEMPT_RCU_TRACE
399 def_bool RCU_TRACE && PREEMPT_RCU
402 This option provides tracing for the PREEMPT_RCU implementation,
403 permitting Makefile to trivially select kernel/rcupreempt_trace.c.
405 endmenu # "RCU Subsystem"
408 tristate "Kernel .config support"
410 This option enables the complete Linux kernel ".config" file
411 contents to be saved in the kernel. It provides documentation
412 of which kernel options are used in a running kernel or in an
413 on-disk kernel. This information can be extracted from the kernel
414 image file with the script scripts/extract-ikconfig and used as
415 input to rebuild the current kernel or to build another kernel.
416 It can also be extracted from a running kernel by reading
417 /proc/config.gz if enabled (below).
420 bool "Enable access to .config through /proc/config.gz"
421 depends on IKCONFIG && PROC_FS
423 This option enables access to the kernel configuration file
424 through /proc/config.gz.
427 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
431 Select kernel log buffer size as a power of 2.
441 # Architectures with an unreliable sched_clock() should select this:
443 config HAVE_UNSTABLE_SCHED_CLOCK
447 bool "Group CPU scheduler"
448 depends on EXPERIMENTAL
451 This feature lets CPU scheduler recognize task groups and control CPU
452 bandwidth allocation to such task groups.
453 In order to create a group from arbitrary set of processes, use
454 CONFIG_CGROUPS. (See Control Group support.)
456 config FAIR_GROUP_SCHED
457 bool "Group scheduling for SCHED_OTHER"
458 depends on GROUP_SCHED
461 config RT_GROUP_SCHED
462 bool "Group scheduling for SCHED_RR/FIFO"
463 depends on EXPERIMENTAL
464 depends on GROUP_SCHED
467 This feature lets you explicitly allocate real CPU bandwidth
468 to users or control groups (depending on the "Basis for grouping tasks"
469 setting below. If enabled, it will also make it impossible to
470 schedule realtime tasks for non-root users until you allocate
471 realtime bandwidth for them.
472 See Documentation/scheduler/sched-rt-group.txt for more information.
475 depends on GROUP_SCHED
476 prompt "Basis for grouping tasks"
482 This option will choose userid as the basis for grouping
483 tasks, thus providing equal CPU bandwidth to each user.
486 bool "Control groups"
489 This option allows you to create arbitrary task groups
490 using the "cgroup" pseudo filesystem and control
491 the cpu bandwidth allocated to each such task group.
492 Refer to Documentation/cgroups/cgroups.txt for more
493 information on "cgroup" pseudo filesystem.
498 boolean "Control Group support"
500 This option adds support for grouping sets of processes together, for
501 use with process control subsystems such as Cpusets, CFS, memory
502 controls or device isolation.
504 - Documentation/scheduler/sched-design-CFS.txt (CFS)
505 - Documentation/cgroups/ (features for grouping, isolation
506 and resource control)
513 bool "Example debug cgroup subsystem"
517 This option enables a simple cgroup subsystem that
518 exports useful debugging information about the cgroups
524 bool "Namespace cgroup subsystem"
527 Provides a simple namespace cgroup subsystem to
528 provide hierarchical naming of sets of namespaces,
529 for instance virtual servers and checkpoint/restart
532 config CGROUP_FREEZER
533 bool "Freezer cgroup subsystem"
536 Provides a way to freeze and unfreeze all tasks in a
540 bool "Device controller for cgroups"
541 depends on CGROUPS && EXPERIMENTAL
543 Provides a cgroup implementing whitelists for devices which
544 a process in the cgroup can mknod or open.
547 bool "Cpuset support"
550 This option will let you create and manage CPUSETs which
551 allow dynamically partitioning a system into sets of CPUs and
552 Memory Nodes and assigning tasks to run only within those sets.
553 This is primarily useful on large SMP or NUMA systems.
557 config PROC_PID_CPUSET
558 bool "Include legacy /proc/<pid>/cpuset file"
562 config CGROUP_CPUACCT
563 bool "Simple CPU accounting cgroup subsystem"
566 Provides a simple Resource Controller for monitoring the
567 total CPU consumed by the tasks in a cgroup.
569 config RESOURCE_COUNTERS
570 bool "Resource counters"
572 This option enables controller independent resource accounting
573 infrastructure that works with cgroups.
576 config CGROUP_MEM_RES_CTLR
577 bool "Memory Resource Controller for Control Groups"
578 depends on CGROUPS && RESOURCE_COUNTERS
581 Provides a memory resource controller that manages both anonymous
582 memory and page cache. (See Documentation/cgroups/memory.txt)
584 Note that setting this option increases fixed memory overhead
585 associated with each page of memory in the system. By this,
586 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
587 usage tracking struct at boot. Total amount of this is printed out
590 Only enable when you're ok with these trade offs and really
591 sure you need the memory resource controller. Even when you enable
592 this, you can set "cgroup_disable=memory" at your boot option to
593 disable memory resource controller and you can avoid overheads.
594 (and lose benefits of memory resource controller)
596 This config option also selects MM_OWNER config option, which
597 could in turn add some fork/exit overhead.
599 config CGROUP_MEM_RES_CTLR_SWAP
600 bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
601 depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
603 Add swap management feature to memory resource controller. When you
604 enable this, you can limit mem+swap usage per cgroup. In other words,
605 when you disable this, memory resource controller has no cares to
606 usage of swap...a process can exhaust all of the swap. This extension
607 is useful when you want to avoid exhaustion swap but this itself
608 adds more overheads and consumes memory for remembering information.
609 Especially if you use 32bit system or small memory system, please
610 be careful about enabling this. When memory resource controller
611 is disabled by boot option, this will be automatically disabled and
612 there will be no overhead from this. Even when you set this config=y,
613 if boot option "noswapaccount" is set, swap will not be accounted.
614 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
615 size is 4096bytes, 512k per 1Gbytes of swap.
622 config SYSFS_DEPRECATED
625 config SYSFS_DEPRECATED_V2
626 bool "remove sysfs features which may confuse old userspace tools"
629 select SYSFS_DEPRECATED
631 This option switches the layout of sysfs to the deprecated
632 version. Do not use it on recent distributions.
634 The current sysfs layout features a unified device tree at
635 /sys/devices/, which is able to express a hierarchy between
636 class devices. If the deprecated option is set to Y, the
637 unified device tree is split into a bus device tree at
638 /sys/devices/ and several individual class device trees at
639 /sys/class/. The class and bus devices will be connected by
640 "<subsystem>:<name>" and the "device" links. The "block"
641 class devices, will not show up in /sys/class/block/. Some
642 subsystems will suppress the creation of some devices which
643 depend on the unified device tree.
645 This option is not a pure compatibility option that can
646 be safely enabled on newer distributions. It will change the
647 layout of sysfs to the non-extensible deprecated version,
648 and disable some features, which can not be exported without
649 confusing older userspace tools. Since 2007/2008 all major
650 distributions do not enable this option, and ship no tools which
651 depend on the deprecated layout or this option.
653 If you are using a new kernel on an older distribution, or use
654 older userspace tools, you might need to say Y here. Do not say Y,
655 if the original kernel, that came with your distribution, has
656 this option set to N.
659 bool "Kernel->user space relay support (formerly relayfs)"
661 This option enables support for relay interface support in
662 certain file systems (such as debugfs).
663 It is designed to provide an efficient mechanism for tools and
664 facilities to relay large amounts of data from kernel space to
670 bool "Namespaces support" if EMBEDDED
673 Provides the way to make tasks work with different objects using
674 the same id. For example same IPC id may refer to different objects
675 or same user id or pid may refer to different tasks when used in
676 different namespaces.
680 depends on NAMESPACES
682 In this namespace tasks see different info provided with the
687 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
689 In this namespace tasks work with IPC ids which correspond to
690 different IPC objects in different namespaces.
693 bool "User namespace (EXPERIMENTAL)"
694 depends on NAMESPACES && EXPERIMENTAL
696 This allows containers, i.e. vservers, to use user namespaces
697 to provide different user info for different servers.
701 bool "PID Namespaces (EXPERIMENTAL)"
703 depends on NAMESPACES && EXPERIMENTAL
705 Support process id namespaces. This allows having multiple
706 processes with the same pid as long as they are in different
707 pid namespaces. This is a building block of containers.
709 Unless you want to work with an experimental feature
713 bool "Network namespace"
715 depends on NAMESPACES && EXPERIMENTAL && NET
717 Allow user space to create what appear to be multiple instances
718 of the network stack.
720 config BLK_DEV_INITRD
721 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
722 depends on BROKEN || !FRV
724 The initial RAM filesystem is a ramfs which is loaded by the
725 boot loader (loadlin or lilo) and that is mounted as root
726 before the normal boot procedure. It is typically used to
727 load modules needed to mount the "real" root file system,
728 etc. See <file:Documentation/initrd.txt> for details.
730 If RAM disk support (BLK_DEV_RAM) is also included, this
731 also enables initial RAM disk (initrd) support and adds
732 15 Kbytes (more on some other architectures) to the kernel size.
742 config CC_OPTIMIZE_FOR_SIZE
743 bool "Optimize for size"
746 Enabling this option will pass "-Os" instead of "-O2" to gcc
747 resulting in a smaller kernel.
758 bool "Configure standard kernel features (for small systems)"
760 This option allows certain base kernel options and settings
761 to be disabled or tweaked. This is for specialized
762 environments which can tolerate a "non-standard" kernel.
763 Only use this if you really know what you are doing.
766 bool "Enable 16-bit UID system calls" if EMBEDDED
767 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
770 This enables the legacy 16-bit UID syscall wrappers.
772 config SYSCTL_SYSCALL
773 bool "Sysctl syscall support" if EMBEDDED
777 sys_sysctl uses binary paths that have been found challenging
778 to properly maintain and use. The interface in /proc/sys
779 using paths with ascii names is now the primary path to this
782 Almost nothing using the binary sysctl interface so if you are
783 trying to save some space it is probably safe to disable this,
784 making your kernel marginally smaller.
786 If unsure say Y here.
789 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
792 Say Y here to let the kernel print out symbolic crash information and
793 symbolic stack backtraces. This increases the size of the kernel
794 somewhat, as all symbols have to be loaded into the kernel image.
797 bool "Include all symbols in kallsyms"
798 depends on DEBUG_KERNEL && KALLSYMS
800 Normally kallsyms only contains the symbols of functions, for nicer
801 OOPS messages. Some debuggers can use kallsyms for other
802 symbols too: say Y here to include all symbols, if you need them
803 and you don't care about adding 300k to the size of your kernel.
807 config KALLSYMS_EXTRA_PASS
808 bool "Do an extra kallsyms pass"
811 If kallsyms is not working correctly, the build will fail with
812 inconsistent kallsyms data. If that occurs, log a bug report and
813 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
814 Always say N here unless you find a bug in kallsyms, which must be
815 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
816 you wait for kallsyms to be fixed.
820 bool "Support for hot-pluggable devices" if EMBEDDED
823 This option is provided for the case where no hotplug or uevent
824 capabilities is wanted by the kernel. You should only consider
825 disabling this option for embedded systems that do not use modules, a
826 dynamic /dev tree, or dynamic device discovery. Just say Y.
830 bool "Enable support for printk" if EMBEDDED
832 This option enables normal printk support. Removing it
833 eliminates most of the message strings from the kernel image
834 and makes the kernel more or less silent. As this makes it
835 very difficult to diagnose system problems, saying N here is
836 strongly discouraged.
839 bool "BUG() support" if EMBEDDED
842 Disabling this option eliminates support for BUG and WARN, reducing
843 the size of your kernel image and potentially quietly ignoring
844 numerous fatal conditions. You should only consider disabling this
845 option for embedded systems with no facilities for reporting errors.
850 bool "Enable ELF core dumps" if EMBEDDED
852 Enable support for generating core dumps. Disabling saves about 4k.
854 config PCSPKR_PLATFORM
855 bool "Enable PC-Speaker support" if EMBEDDED
856 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
859 This option allows to disable the internal PC-Speaker
860 support, saving some memory.
864 bool "Enable full-sized data structures for core" if EMBEDDED
866 Disabling this option reduces the size of miscellaneous core
867 kernel data structures. This saves memory on small machines,
868 but may reduce performance.
871 bool "Enable futex support" if EMBEDDED
875 Disabling this option will cause the kernel to be built without
876 support for "fast userspace mutexes". The resulting kernel may not
877 run glibc-based applications correctly.
880 bool "Enable eventpoll support" if EMBEDDED
884 Disabling this option will cause the kernel to be built without
885 support for epoll family of system calls.
888 bool "Enable signalfd() system call" if EMBEDDED
892 Enable the signalfd() system call that allows to receive signals
893 on a file descriptor.
898 bool "Enable timerfd() system call" if EMBEDDED
902 Enable the timerfd() system call that allows to receive timer
903 events on a file descriptor.
908 bool "Enable eventfd() system call" if EMBEDDED
912 Enable the eventfd() system call that allows to receive both
913 kernel notification (ie. KAIO) or userspace notifications.
918 bool "Use full shmem filesystem" if EMBEDDED
922 The shmem is an internal filesystem used to manage shared memory.
923 It is backed by swap and manages resource limits. It is also exported
924 to userspace as tmpfs if TMPFS is enabled. Disabling this
925 option replaces shmem and tmpfs with the much simpler ramfs code,
926 which may be appropriate on small systems without swap.
929 bool "Enable AIO support" if EMBEDDED
932 This option enables POSIX asynchronous I/O which may by used
933 by some high performance threaded applications. Disabling
934 this option saves about 7k.
936 config HAVE_PERF_COUNTERS
939 See tools/perf/design.txt for details.
941 menu "Performance Counters"
944 bool "Kernel Performance Counters"
945 default y if PROFILING
946 depends on HAVE_PERF_COUNTERS
949 Enable kernel support for performance counter hardware.
951 Performance counters are special hardware registers available
952 on most modern CPUs. These registers count the number of certain
953 types of hw events: such as instructions executed, cachemisses
954 suffered, or branches mis-predicted - without slowing down the
955 kernel or applications. These registers can also trigger interrupts
956 when a threshold number of events have passed - and can thus be
957 used to profile the code that runs on that CPU.
959 The Linux Performance Counter subsystem provides an abstraction of
960 these hardware capabilities, available via a system call. It
961 provides per task and per CPU counters, and it provides event
962 capabilities on top of those.
967 bool "Tracepoint profiling sources"
968 depends on PERF_COUNTERS && EVENT_TRACING
971 Allow the use of tracepoints as software performance counters.
973 When this is enabled, you can create perf counters based on
974 tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID
975 found in debugfs://tracing/events/*/*/id. (The -e/--events
976 option to the perf tool can parse and interpret symbolic
977 tracepoints, in the subsystem:tracepoint_name format.)
981 config VM_EVENT_COUNTERS
983 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
985 VM event counters are needed for event counts to be shown.
986 This option allows the disabling of the VM event counters
987 on EMBEDDED systems. /proc/vmstat will only show page counts
988 if VM event counters are disabled.
992 bool "Enable PCI quirk workarounds" if EMBEDDED
995 This enables workarounds for various PCI chipset
996 bugs/quirks. Disable this only if your target machine is
997 unaffected by PCI quirks.
1001 bool "Enable SLUB debugging support" if EMBEDDED
1002 depends on SLUB && SYSFS
1004 SLUB has extensive debug support features. Disabling these can
1005 result in significant savings in code size. This also disables
1006 SLUB sysfs support. /sys/slab will not exist and there will be
1007 no support for cache validation etc.
1009 config STRIP_ASM_SYMS
1010 bool "Strip assembler-generated symbols during link"
1013 Strip internal assembler-generated symbols during a link (symbols
1014 that look like '.Lxxx') so they don't pollute the output of
1015 get_wchan() and suchlike.
1018 bool "Disable heap randomization"
1021 Randomizing heap placement makes heap exploits harder, but it
1022 also breaks ancient binaries (including anything libc5 based).
1023 This option changes the bootup default to heap randomization
1024 disabled, and can be overridden at runtime by setting
1025 /proc/sys/kernel/randomize_va_space to 2.
1027 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1030 prompt "Choose SLAB allocator"
1033 This option allows to select a slab allocator.
1038 The regular slab allocator that is established and known to work
1039 well in all environments. It organizes cache hot objects in
1040 per cpu and per node queues.
1043 bool "SLUB (Unqueued Allocator)"
1045 SLUB is a slab allocator that minimizes cache line usage
1046 instead of managing queues of cached objects (SLAB approach).
1047 Per cpu caching is realized using slabs of objects instead
1048 of queues of objects. SLUB can use memory efficiently
1049 and has enhanced diagnostics. SLUB is the default choice for
1054 bool "SLOB (Simple Allocator)"
1056 SLOB replaces the stock allocator with a drastically simpler
1057 allocator. SLOB is generally more space efficient but
1058 does not perform as well on large systems.
1063 bool "Profiling support (EXPERIMENTAL)"
1065 Say Y here to enable the extended profiling support mechanisms used
1066 by profilers such as OProfile.
1069 # Place an empty function call at each tracepoint site. Can be
1070 # dynamically changed for a probe function.
1076 bool "Activate markers"
1079 Place an empty function call at each marker site. Can be
1080 dynamically changed for a probe function.
1082 source "arch/Kconfig"
1088 The slow work thread pool provides a number of dynamically allocated
1089 threads that can be used by the kernel to perform operations that
1090 take a relatively long time.
1092 An example of this would be CacheFiles doing a path lookup followed
1093 by a series of mkdirs and a create call, all of which have to touch
1096 See Documentation/slow-work.txt.
1098 endmenu # General setup
1100 config HAVE_GENERIC_DMA_COHERENT
1107 depends on SLAB || SLUB_DEBUG
1115 default 0 if BASE_FULL
1116 default 1 if !BASE_FULL
1119 bool "Enable loadable module support"
1121 Kernel modules are small pieces of compiled code which can
1122 be inserted in the running kernel, rather than being
1123 permanently built into the kernel. You use the "modprobe"
1124 tool to add (and sometimes remove) them. If you say Y here,
1125 many parts of the kernel can be built as modules (by
1126 answering M instead of Y where indicated): this is most
1127 useful for infrequently used options which are not required
1128 for booting. For more information, see the man pages for
1129 modprobe, lsmod, modinfo, insmod and rmmod.
1131 If you say Y here, you will need to run "make
1132 modules_install" to put the modules under /lib/modules/
1133 where modprobe can find them (you may need to be root to do
1140 config MODULE_FORCE_LOAD
1141 bool "Forced module loading"
1144 Allow loading of modules without version information (ie. modprobe
1145 --force). Forced module loading sets the 'F' (forced) taint flag and
1146 is usually a really bad idea.
1148 config MODULE_UNLOAD
1149 bool "Module unloading"
1151 Without this option you will not be able to unload any
1152 modules (note that some modules may not be unloadable
1153 anyway), which makes your kernel smaller, faster
1154 and simpler. If unsure, say Y.
1156 config MODULE_FORCE_UNLOAD
1157 bool "Forced module unloading"
1158 depends on MODULE_UNLOAD && EXPERIMENTAL
1160 This option allows you to force a module to unload, even if the
1161 kernel believes it is unsafe: the kernel will remove the module
1162 without waiting for anyone to stop using it (using the -f option to
1163 rmmod). This is mainly for kernel developers and desperate users.
1167 bool "Module versioning support"
1169 Usually, you have to use modules compiled with your kernel.
1170 Saying Y here makes it sometimes possible to use modules
1171 compiled for different kernels, by adding enough information
1172 to the modules to (hopefully) spot any changes which would
1173 make them incompatible with the kernel you are running. If
1176 config MODULE_SRCVERSION_ALL
1177 bool "Source checksum for all modules"
1179 Modules which contain a MODULE_VERSION get an extra "srcversion"
1180 field inserted into their modinfo section, which contains a
1181 sum of the source files which made it. This helps maintainers
1182 see exactly which source was used to build a module (since
1183 others sometimes change the module source without updating
1184 the version). With this option, such a "srcversion" field
1185 will be created for all modules. If unsure, say N.
1189 config INIT_ALL_POSSIBLE
1192 Back when each arch used to define their own cpu_online_map and
1193 cpu_possible_map, some of them chose to initialize cpu_possible_map
1194 with all 1s, and others with all 0s. When they were centralised,
1195 it was better to provide this option than to break all the archs
1196 and have several arch maintainers pursuing me down dark alleys.
1201 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1203 Need stop_machine() primitive.
1205 source "block/Kconfig"
1207 config PREEMPT_NOTIFIERS