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47 drivers that have been replaced by something else, and/or are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
118 config HAVE_KERNEL_LZO
122 prompt "Kernel compression mode"
124 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
126 The linux kernel is a kind of self-extracting executable.
127 Several compression algorithms are available, which differ
128 in efficiency, compression and decompression speed.
129 Compression speed is only relevant when building a kernel.
130 Decompression speed is relevant at each boot.
132 If you have any problems with bzip2 or lzma compressed
133 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
134 version of this functionality (bzip2 only), for 2.4, was
135 supplied by Christian Ludwig)
137 High compression options are mostly useful for users, who
138 are low on disk space (embedded systems), but for whom ram
141 If in doubt, select 'gzip'
145 depends on HAVE_KERNEL_GZIP
147 The old and tried gzip compression. It provides a good balance
148 between compression ratio and decompression speed.
152 depends on HAVE_KERNEL_BZIP2
154 Its compression ratio and speed is intermediate.
155 Decompression speed is slowest among the three. The kernel
156 size is about 10% smaller with bzip2, in comparison to gzip.
157 Bzip2 uses a large amount of memory. For modern kernels you
158 will need at least 8MB RAM or more for booting.
162 depends on HAVE_KERNEL_LZMA
164 The most recent compression algorithm.
165 Its ratio is best, decompression speed is between the other
166 two. Compression is slowest. The kernel size is about 33%
167 smaller with LZMA in comparison to gzip.
171 depends on HAVE_KERNEL_LZO
173 Its compression ratio is the poorest among the 4. The kernel
174 size is about about 10% bigger than gzip; however its speed
175 (both compression and decompression) is the fastest.
180 bool "Support for paging of anonymous memory (swap)"
181 depends on MMU && BLOCK
184 This option allows you to choose whether you want to have support
185 for so called swap devices or swap files in your kernel that are
186 used to provide more virtual memory than the actual RAM present
187 in your computer. If unsure say Y.
192 Inter Process Communication is a suite of library functions and
193 system calls which let processes (running programs) synchronize and
194 exchange information. It is generally considered to be a good thing,
195 and some programs won't run unless you say Y here. In particular, if
196 you want to run the DOS emulator dosemu under Linux (read the
197 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
198 you'll need to say Y here.
200 You can find documentation about IPC with "info ipc" and also in
201 section 6.4 of the Linux Programmer's Guide, available from
202 <http://www.tldp.org/guides.html>.
204 config SYSVIPC_SYSCTL
211 bool "POSIX Message Queues"
212 depends on NET && EXPERIMENTAL
214 POSIX variant of message queues is a part of IPC. In POSIX message
215 queues every message has a priority which decides about succession
216 of receiving it by a process. If you want to compile and run
217 programs written e.g. for Solaris with use of its POSIX message
218 queues (functions mq_*) say Y here.
220 POSIX message queues are visible as a filesystem called 'mqueue'
221 and can be mounted somewhere if you want to do filesystem
222 operations on message queues.
226 config POSIX_MQUEUE_SYSCTL
228 depends on POSIX_MQUEUE
232 config BSD_PROCESS_ACCT
233 bool "BSD Process Accounting"
235 If you say Y here, a user level program will be able to instruct the
236 kernel (via a special system call) to write process accounting
237 information to a file: whenever a process exits, information about
238 that process will be appended to the file by the kernel. The
239 information includes things such as creation time, owning user,
240 command name, memory usage, controlling terminal etc. (the complete
241 list is in the struct acct in <file:include/linux/acct.h>). It is
242 up to the user level program to do useful things with this
243 information. This is generally a good idea, so say Y.
245 config BSD_PROCESS_ACCT_V3
246 bool "BSD Process Accounting version 3 file format"
247 depends on BSD_PROCESS_ACCT
250 If you say Y here, the process accounting information is written
251 in a new file format that also logs the process IDs of each
252 process and it's parent. Note that this file format is incompatible
253 with previous v0/v1/v2 file formats, so you will need updated tools
254 for processing it. A preliminary version of these tools is available
255 at <http://www.gnu.org/software/acct/>.
258 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
262 Export selected statistics for tasks/processes through the
263 generic netlink interface. Unlike BSD process accounting, the
264 statistics are available during the lifetime of tasks/processes as
265 responses to commands. Like BSD accounting, they are sent to user
270 config TASK_DELAY_ACCT
271 bool "Enable per-task delay accounting (EXPERIMENTAL)"
274 Collect information on time spent by a task waiting for system
275 resources like cpu, synchronous block I/O completion and swapping
276 in pages. Such statistics can help in setting a task's priorities
277 relative to other tasks for cpu, io, rss limits etc.
282 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
285 Collect extended task accounting data and send the data
286 to userland for processing over the taskstats interface.
290 config TASK_IO_ACCOUNTING
291 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
292 depends on TASK_XACCT
294 Collect information on the number of bytes of storage I/O which this
300 bool "Auditing support"
303 Enable auditing infrastructure that can be used with another
304 kernel subsystem, such as SELinux (which requires this for
305 logging of avc messages output). Does not do system-call
306 auditing without CONFIG_AUDITSYSCALL.
309 bool "Enable system-call auditing support"
310 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
311 default y if SECURITY_SELINUX
313 Enable low-overhead system-call auditing infrastructure that
314 can be used independently or with another kernel subsystem,
315 such as SELinux. To use audit's filesystem watch feature, please
316 ensure that INOTIFY is configured.
320 depends on AUDITSYSCALL
326 prompt "RCU Implementation"
330 bool "Tree-based hierarchical RCU"
332 This option selects the RCU implementation that is
333 designed for very large SMP system with hundreds or
334 thousands of CPUs. It also scales down nicely to
337 config TREE_PREEMPT_RCU
338 bool "Preemptable tree-based hierarchical RCU"
341 This option selects the RCU implementation that is
342 designed for very large SMP systems with hundreds or
343 thousands of CPUs, but for which real-time response
344 is also required. It also scales down nicely to
348 bool "UP-only small-memory-footprint RCU"
351 This option selects the RCU implementation that is
352 designed for UP systems from which real-time response
353 is not required. This option greatly reduces the
354 memory footprint of RCU.
359 bool "Enable tracing for RCU"
360 depends on TREE_RCU || TREE_PREEMPT_RCU
362 This option provides tracing in RCU which presents stats
363 in debugfs for debugging RCU implementation.
365 Say Y here if you want to enable RCU tracing
366 Say N if you are unsure.
369 int "Tree-based hierarchical RCU fanout value"
372 depends on TREE_RCU || TREE_PREEMPT_RCU
376 This option controls the fanout of hierarchical implementations
377 of RCU, allowing RCU to work efficiently on machines with
378 large numbers of CPUs. This value must be at least the cube
379 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
380 systems and up to 262,144 for 64-bit systems.
382 Select a specific number if testing RCU itself.
383 Take the default if unsure.
385 config RCU_FANOUT_EXACT
386 bool "Disable tree-based hierarchical RCU auto-balancing"
387 depends on TREE_RCU || TREE_PREEMPT_RCU
390 This option forces use of the exact RCU_FANOUT value specified,
391 regardless of imbalances in the hierarchy. This is useful for
392 testing RCU itself, and might one day be useful on systems with
393 strong NUMA behavior.
395 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
399 config RCU_FAST_NO_HZ
400 bool "Accelerate last non-dyntick-idle CPU's grace periods"
401 depends on TREE_RCU && NO_HZ && SMP
404 This option causes RCU to attempt to accelerate grace periods
405 in order to allow the final CPU to enter dynticks-idle state
406 more quickly. On the other hand, this option increases the
407 overhead of the dynticks-idle checking, particularly on systems
408 with large numbers of CPUs.
410 Say Y if energy efficiency is critically important, particularly
411 if you have relatively few CPUs.
413 Say N if you are unsure.
415 config TREE_RCU_TRACE
416 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
419 This option provides tracing for the TREE_RCU and
420 TREE_PREEMPT_RCU implementations, permitting Makefile to
421 trivially select kernel/rcutree_trace.c.
423 endmenu # "RCU Subsystem"
426 tristate "Kernel .config support"
428 This option enables the complete Linux kernel ".config" file
429 contents to be saved in the kernel. It provides documentation
430 of which kernel options are used in a running kernel or in an
431 on-disk kernel. This information can be extracted from the kernel
432 image file with the script scripts/extract-ikconfig and used as
433 input to rebuild the current kernel or to build another kernel.
434 It can also be extracted from a running kernel by reading
435 /proc/config.gz if enabled (below).
438 bool "Enable access to .config through /proc/config.gz"
439 depends on IKCONFIG && PROC_FS
441 This option enables access to the kernel configuration file
442 through /proc/config.gz.
445 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
449 Select kernel log buffer size as a power of 2.
459 # Architectures with an unreliable sched_clock() should select this:
461 config HAVE_UNSTABLE_SCHED_CLOCK
465 bool "Group CPU scheduler"
466 depends on EXPERIMENTAL
469 This feature lets CPU scheduler recognize task groups and control CPU
470 bandwidth allocation to such task groups.
471 In order to create a group from arbitrary set of processes, use
472 CONFIG_CGROUPS. (See Control Group support.)
474 config FAIR_GROUP_SCHED
475 bool "Group scheduling for SCHED_OTHER"
476 depends on GROUP_SCHED
479 config RT_GROUP_SCHED
480 bool "Group scheduling for SCHED_RR/FIFO"
481 depends on EXPERIMENTAL
482 depends on GROUP_SCHED
485 This feature lets you explicitly allocate real CPU bandwidth
486 to users or control groups (depending on the "Basis for grouping tasks"
487 setting below. If enabled, it will also make it impossible to
488 schedule realtime tasks for non-root users until you allocate
489 realtime bandwidth for them.
490 See Documentation/scheduler/sched-rt-group.txt for more information.
493 depends on GROUP_SCHED
494 prompt "Basis for grouping tasks"
500 This option will choose userid as the basis for grouping
501 tasks, thus providing equal CPU bandwidth to each user.
504 bool "Control groups"
507 This option allows you to create arbitrary task groups
508 using the "cgroup" pseudo filesystem and control
509 the cpu bandwidth allocated to each such task group.
510 Refer to Documentation/cgroups/cgroups.txt for more
511 information on "cgroup" pseudo filesystem.
516 boolean "Control Group support"
518 This option adds support for grouping sets of processes together, for
519 use with process control subsystems such as Cpusets, CFS, memory
520 controls or device isolation.
522 - Documentation/scheduler/sched-design-CFS.txt (CFS)
523 - Documentation/cgroups/ (features for grouping, isolation
524 and resource control)
531 bool "Example debug cgroup subsystem"
535 This option enables a simple cgroup subsystem that
536 exports useful debugging information about the cgroups
542 bool "Namespace cgroup subsystem"
545 Provides a simple namespace cgroup subsystem to
546 provide hierarchical naming of sets of namespaces,
547 for instance virtual servers and checkpoint/restart
550 config CGROUP_FREEZER
551 bool "Freezer cgroup subsystem"
554 Provides a way to freeze and unfreeze all tasks in a
558 bool "Device controller for cgroups"
559 depends on CGROUPS && EXPERIMENTAL
561 Provides a cgroup implementing whitelists for devices which
562 a process in the cgroup can mknod or open.
565 bool "Cpuset support"
568 This option will let you create and manage CPUSETs which
569 allow dynamically partitioning a system into sets of CPUs and
570 Memory Nodes and assigning tasks to run only within those sets.
571 This is primarily useful on large SMP or NUMA systems.
575 config PROC_PID_CPUSET
576 bool "Include legacy /proc/<pid>/cpuset file"
580 config CGROUP_CPUACCT
581 bool "Simple CPU accounting cgroup subsystem"
584 Provides a simple Resource Controller for monitoring the
585 total CPU consumed by the tasks in a cgroup.
587 config RESOURCE_COUNTERS
588 bool "Resource counters"
590 This option enables controller independent resource accounting
591 infrastructure that works with cgroups.
594 config CGROUP_MEM_RES_CTLR
595 bool "Memory Resource Controller for Control Groups"
596 depends on CGROUPS && RESOURCE_COUNTERS
599 Provides a memory resource controller that manages both anonymous
600 memory and page cache. (See Documentation/cgroups/memory.txt)
602 Note that setting this option increases fixed memory overhead
603 associated with each page of memory in the system. By this,
604 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
605 usage tracking struct at boot. Total amount of this is printed out
608 Only enable when you're ok with these trade offs and really
609 sure you need the memory resource controller. Even when you enable
610 this, you can set "cgroup_disable=memory" at your boot option to
611 disable memory resource controller and you can avoid overheads.
612 (and lose benefits of memory resource controller)
614 This config option also selects MM_OWNER config option, which
615 could in turn add some fork/exit overhead.
617 config CGROUP_MEM_RES_CTLR_SWAP
618 bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
619 depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
621 Add swap management feature to memory resource controller. When you
622 enable this, you can limit mem+swap usage per cgroup. In other words,
623 when you disable this, memory resource controller has no cares to
624 usage of swap...a process can exhaust all of the swap. This extension
625 is useful when you want to avoid exhaustion swap but this itself
626 adds more overheads and consumes memory for remembering information.
627 Especially if you use 32bit system or small memory system, please
628 be careful about enabling this. When memory resource controller
629 is disabled by boot option, this will be automatically disabled and
630 there will be no overhead from this. Even when you set this config=y,
631 if boot option "noswapaccount" is set, swap will not be accounted.
632 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
633 size is 4096bytes, 512k per 1Gbytes of swap.
640 config SYSFS_DEPRECATED
643 config SYSFS_DEPRECATED_V2
644 bool "enable deprecated sysfs features to support old userspace tools"
647 select SYSFS_DEPRECATED
649 This option switches the layout of sysfs to the deprecated
650 version. Do not use it on recent distributions.
652 The current sysfs layout features a unified device tree at
653 /sys/devices/, which is able to express a hierarchy between
654 class devices. If the deprecated option is set to Y, the
655 unified device tree is split into a bus device tree at
656 /sys/devices/ and several individual class device trees at
657 /sys/class/. The class and bus devices will be connected by
658 "<subsystem>:<name>" and the "device" links. The "block"
659 class devices, will not show up in /sys/class/block/. Some
660 subsystems will suppress the creation of some devices which
661 depend on the unified device tree.
663 This option is not a pure compatibility option that can
664 be safely enabled on newer distributions. It will change the
665 layout of sysfs to the non-extensible deprecated version,
666 and disable some features, which can not be exported without
667 confusing older userspace tools. Since 2007/2008 all major
668 distributions do not enable this option, and ship no tools which
669 depend on the deprecated layout or this option.
671 If you are using a new kernel on an older distribution, or use
672 older userspace tools, you might need to say Y here. Do not say Y,
673 if the original kernel, that came with your distribution, has
674 this option set to N.
677 bool "Kernel->user space relay support (formerly relayfs)"
679 This option enables support for relay interface support in
680 certain file systems (such as debugfs).
681 It is designed to provide an efficient mechanism for tools and
682 facilities to relay large amounts of data from kernel space to
688 bool "Namespaces support" if EMBEDDED
691 Provides the way to make tasks work with different objects using
692 the same id. For example same IPC id may refer to different objects
693 or same user id or pid may refer to different tasks when used in
694 different namespaces.
698 depends on NAMESPACES
700 In this namespace tasks see different info provided with the
705 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
707 In this namespace tasks work with IPC ids which correspond to
708 different IPC objects in different namespaces.
711 bool "User namespace (EXPERIMENTAL)"
712 depends on NAMESPACES && EXPERIMENTAL
714 This allows containers, i.e. vservers, to use user namespaces
715 to provide different user info for different servers.
719 bool "PID Namespaces (EXPERIMENTAL)"
721 depends on NAMESPACES && EXPERIMENTAL
723 Support process id namespaces. This allows having multiple
724 processes with the same pid as long as they are in different
725 pid namespaces. This is a building block of containers.
727 Unless you want to work with an experimental feature
731 bool "Network namespace"
733 depends on NAMESPACES && EXPERIMENTAL && NET
735 Allow user space to create what appear to be multiple instances
736 of the network stack.
738 config BLK_DEV_INITRD
739 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
740 depends on BROKEN || !FRV
742 The initial RAM filesystem is a ramfs which is loaded by the
743 boot loader (loadlin or lilo) and that is mounted as root
744 before the normal boot procedure. It is typically used to
745 load modules needed to mount the "real" root file system,
746 etc. See <file:Documentation/initrd.txt> for details.
748 If RAM disk support (BLK_DEV_RAM) is also included, this
749 also enables initial RAM disk (initrd) support and adds
750 15 Kbytes (more on some other architectures) to the kernel size.
760 config CC_OPTIMIZE_FOR_SIZE
761 bool "Optimize for size"
764 Enabling this option will pass "-Os" instead of "-O2" to gcc
765 resulting in a smaller kernel.
776 bool "Configure standard kernel features (for small systems)"
778 This option allows certain base kernel options and settings
779 to be disabled or tweaked. This is for specialized
780 environments which can tolerate a "non-standard" kernel.
781 Only use this if you really know what you are doing.
784 bool "Enable 16-bit UID system calls" if EMBEDDED
785 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
788 This enables the legacy 16-bit UID syscall wrappers.
790 config SYSCTL_SYSCALL
791 bool "Sysctl syscall support" if EMBEDDED
792 depends on PROC_SYSCTL
796 sys_sysctl uses binary paths that have been found challenging
797 to properly maintain and use. The interface in /proc/sys
798 using paths with ascii names is now the primary path to this
801 Almost nothing using the binary sysctl interface so if you are
802 trying to save some space it is probably safe to disable this,
803 making your kernel marginally smaller.
805 If unsure say Y here.
808 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
811 Say Y here to let the kernel print out symbolic crash information and
812 symbolic stack backtraces. This increases the size of the kernel
813 somewhat, as all symbols have to be loaded into the kernel image.
816 bool "Include all symbols in kallsyms"
817 depends on DEBUG_KERNEL && KALLSYMS
819 Normally kallsyms only contains the symbols of functions, for nicer
820 OOPS messages. Some debuggers can use kallsyms for other
821 symbols too: say Y here to include all symbols, if you need them
822 and you don't care about adding 300k to the size of your kernel.
826 config KALLSYMS_EXTRA_PASS
827 bool "Do an extra kallsyms pass"
830 If kallsyms is not working correctly, the build will fail with
831 inconsistent kallsyms data. If that occurs, log a bug report and
832 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
833 Always say N here unless you find a bug in kallsyms, which must be
834 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
835 you wait for kallsyms to be fixed.
839 bool "Support for hot-pluggable devices" if EMBEDDED
842 This option is provided for the case where no hotplug or uevent
843 capabilities is wanted by the kernel. You should only consider
844 disabling this option for embedded systems that do not use modules, a
845 dynamic /dev tree, or dynamic device discovery. Just say Y.
849 bool "Enable support for printk" if EMBEDDED
851 This option enables normal printk support. Removing it
852 eliminates most of the message strings from the kernel image
853 and makes the kernel more or less silent. As this makes it
854 very difficult to diagnose system problems, saying N here is
855 strongly discouraged.
858 bool "BUG() support" if EMBEDDED
861 Disabling this option eliminates support for BUG and WARN, reducing
862 the size of your kernel image and potentially quietly ignoring
863 numerous fatal conditions. You should only consider disabling this
864 option for embedded systems with no facilities for reporting errors.
869 bool "Enable ELF core dumps" if EMBEDDED
871 Enable support for generating core dumps. Disabling saves about 4k.
873 config PCSPKR_PLATFORM
874 bool "Enable PC-Speaker support" if EMBEDDED
875 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
878 This option allows to disable the internal PC-Speaker
879 support, saving some memory.
883 bool "Enable full-sized data structures for core" if EMBEDDED
885 Disabling this option reduces the size of miscellaneous core
886 kernel data structures. This saves memory on small machines,
887 but may reduce performance.
890 bool "Enable futex support" if EMBEDDED
894 Disabling this option will cause the kernel to be built without
895 support for "fast userspace mutexes". The resulting kernel may not
896 run glibc-based applications correctly.
899 bool "Enable eventpoll support" if EMBEDDED
903 Disabling this option will cause the kernel to be built without
904 support for epoll family of system calls.
907 bool "Enable signalfd() system call" if EMBEDDED
911 Enable the signalfd() system call that allows to receive signals
912 on a file descriptor.
917 bool "Enable timerfd() system call" if EMBEDDED
921 Enable the timerfd() system call that allows to receive timer
922 events on a file descriptor.
927 bool "Enable eventfd() system call" if EMBEDDED
931 Enable the eventfd() system call that allows to receive both
932 kernel notification (ie. KAIO) or userspace notifications.
937 bool "Use full shmem filesystem" if EMBEDDED
941 The shmem is an internal filesystem used to manage shared memory.
942 It is backed by swap and manages resource limits. It is also exported
943 to userspace as tmpfs if TMPFS is enabled. Disabling this
944 option replaces shmem and tmpfs with the much simpler ramfs code,
945 which may be appropriate on small systems without swap.
948 bool "Enable AIO support" if EMBEDDED
951 This option enables POSIX asynchronous I/O which may by used
952 by some high performance threaded applications. Disabling
953 this option saves about 7k.
955 config HAVE_PERF_EVENTS
958 See tools/perf/design.txt for details.
960 config PERF_USE_VMALLOC
963 See tools/perf/design.txt for details
965 menu "Kernel Performance Events And Counters"
968 bool "Kernel performance events and counters"
969 default y if (PROFILING || PERF_COUNTERS)
970 depends on HAVE_PERF_EVENTS
973 Enable kernel support for various performance events provided
974 by software and hardware.
976 Software events are supported either built-in or via the
977 use of generic tracepoints.
979 Most modern CPUs support performance events via performance
980 counter registers. These registers count the number of certain
981 types of hw events: such as instructions executed, cachemisses
982 suffered, or branches mis-predicted - without slowing down the
983 kernel or applications. These registers can also trigger interrupts
984 when a threshold number of events have passed - and can thus be
985 used to profile the code that runs on that CPU.
987 The Linux Performance Event subsystem provides an abstraction of
988 these software and hardware event capabilities, available via a
989 system call and used by the "perf" utility in tools/perf/. It
990 provides per task and per CPU counters, and it provides event
991 capabilities on top of those.
996 bool "Tracepoint profiling sources"
997 depends on PERF_EVENTS && EVENT_TRACING
1000 Allow the use of tracepoints as software performance events.
1002 When this is enabled, you can create perf events based on
1003 tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID
1004 found in debugfs://tracing/events/*/*/id. (The -e/--events
1005 option to the perf tool can parse and interpret symbolic
1006 tracepoints, in the subsystem:tracepoint_name format.)
1008 config PERF_COUNTERS
1009 bool "Kernel performance counters (old config option)"
1010 depends on HAVE_PERF_EVENTS
1012 This config has been obsoleted by the PERF_EVENTS
1013 config option - please see that one for details.
1015 It has no effect on the kernel whether you enable
1016 it or not, it is a compatibility placeholder.
1020 config DEBUG_PERF_USE_VMALLOC
1022 bool "Debug: use vmalloc to back perf mmap() buffers"
1023 depends on PERF_EVENTS && DEBUG_KERNEL
1024 select PERF_USE_VMALLOC
1026 Use vmalloc memory to back perf mmap() buffers.
1028 Mostly useful for debugging the vmalloc code on platforms
1029 that don't require it.
1035 config VM_EVENT_COUNTERS
1037 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1039 VM event counters are needed for event counts to be shown.
1040 This option allows the disabling of the VM event counters
1041 on EMBEDDED systems. /proc/vmstat will only show page counts
1042 if VM event counters are disabled.
1046 bool "Enable PCI quirk workarounds" if EMBEDDED
1049 This enables workarounds for various PCI chipset
1050 bugs/quirks. Disable this only if your target machine is
1051 unaffected by PCI quirks.
1055 bool "Enable SLUB debugging support" if EMBEDDED
1056 depends on SLUB && SYSFS
1058 SLUB has extensive debug support features. Disabling these can
1059 result in significant savings in code size. This also disables
1060 SLUB sysfs support. /sys/slab will not exist and there will be
1061 no support for cache validation etc.
1064 bool "Disable heap randomization"
1067 Randomizing heap placement makes heap exploits harder, but it
1068 also breaks ancient binaries (including anything libc5 based).
1069 This option changes the bootup default to heap randomization
1070 disabled, and can be overridden at runtime by setting
1071 /proc/sys/kernel/randomize_va_space to 2.
1073 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1076 prompt "Choose SLAB allocator"
1079 This option allows to select a slab allocator.
1084 The regular slab allocator that is established and known to work
1085 well in all environments. It organizes cache hot objects in
1086 per cpu and per node queues.
1089 bool "SLUB (Unqueued Allocator)"
1091 SLUB is a slab allocator that minimizes cache line usage
1092 instead of managing queues of cached objects (SLAB approach).
1093 Per cpu caching is realized using slabs of objects instead
1094 of queues of objects. SLUB can use memory efficiently
1095 and has enhanced diagnostics. SLUB is the default choice for
1100 bool "SLOB (Simple Allocator)"
1102 SLOB replaces the stock allocator with a drastically simpler
1103 allocator. SLOB is generally more space efficient but
1104 does not perform as well on large systems.
1108 config MMAP_ALLOW_UNINITIALIZED
1109 bool "Allow mmapped anonymous memory to be uninitialized"
1110 depends on EMBEDDED && !MMU
1113 Normally, and according to the Linux spec, anonymous memory obtained
1114 from mmap() has it's contents cleared before it is passed to
1115 userspace. Enabling this config option allows you to request that
1116 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1117 providing a huge performance boost. If this option is not enabled,
1118 then the flag will be ignored.
1120 This is taken advantage of by uClibc's malloc(), and also by
1121 ELF-FDPIC binfmt's brk and stack allocator.
1123 Because of the obvious security issues, this option should only be
1124 enabled on embedded devices where you control what is run in
1125 userspace. Since that isn't generally a problem on no-MMU systems,
1126 it is normally safe to say Y here.
1128 See Documentation/nommu-mmap.txt for more information.
1131 bool "Profiling support (EXPERIMENTAL)"
1133 Say Y here to enable the extended profiling support mechanisms used
1134 by profilers such as OProfile.
1137 # Place an empty function call at each tracepoint site. Can be
1138 # dynamically changed for a probe function.
1143 source "arch/Kconfig"
1149 The slow work thread pool provides a number of dynamically allocated
1150 threads that can be used by the kernel to perform operations that
1151 take a relatively long time.
1153 An example of this would be CacheFiles doing a path lookup followed
1154 by a series of mkdirs and a create call, all of which have to touch
1157 See Documentation/slow-work.txt.
1159 config SLOW_WORK_DEBUG
1160 bool "Slow work debugging through debugfs"
1162 depends on SLOW_WORK && DEBUG_FS
1164 Display the contents of the slow work run queue through debugfs,
1165 including items currently executing.
1167 See Documentation/slow-work.txt.
1169 endmenu # General setup
1171 config HAVE_GENERIC_DMA_COHERENT
1178 depends on SLAB || SLUB_DEBUG
1186 default 0 if BASE_FULL
1187 default 1 if !BASE_FULL
1190 bool "Enable loadable module support"
1192 Kernel modules are small pieces of compiled code which can
1193 be inserted in the running kernel, rather than being
1194 permanently built into the kernel. You use the "modprobe"
1195 tool to add (and sometimes remove) them. If you say Y here,
1196 many parts of the kernel can be built as modules (by
1197 answering M instead of Y where indicated): this is most
1198 useful for infrequently used options which are not required
1199 for booting. For more information, see the man pages for
1200 modprobe, lsmod, modinfo, insmod and rmmod.
1202 If you say Y here, you will need to run "make
1203 modules_install" to put the modules under /lib/modules/
1204 where modprobe can find them (you may need to be root to do
1211 config MODULE_FORCE_LOAD
1212 bool "Forced module loading"
1215 Allow loading of modules without version information (ie. modprobe
1216 --force). Forced module loading sets the 'F' (forced) taint flag and
1217 is usually a really bad idea.
1219 config MODULE_UNLOAD
1220 bool "Module unloading"
1222 Without this option you will not be able to unload any
1223 modules (note that some modules may not be unloadable
1224 anyway), which makes your kernel smaller, faster
1225 and simpler. If unsure, say Y.
1227 config MODULE_FORCE_UNLOAD
1228 bool "Forced module unloading"
1229 depends on MODULE_UNLOAD && EXPERIMENTAL
1231 This option allows you to force a module to unload, even if the
1232 kernel believes it is unsafe: the kernel will remove the module
1233 without waiting for anyone to stop using it (using the -f option to
1234 rmmod). This is mainly for kernel developers and desperate users.
1238 bool "Module versioning support"
1240 Usually, you have to use modules compiled with your kernel.
1241 Saying Y here makes it sometimes possible to use modules
1242 compiled for different kernels, by adding enough information
1243 to the modules to (hopefully) spot any changes which would
1244 make them incompatible with the kernel you are running. If
1247 config MODULE_SRCVERSION_ALL
1248 bool "Source checksum for all modules"
1250 Modules which contain a MODULE_VERSION get an extra "srcversion"
1251 field inserted into their modinfo section, which contains a
1252 sum of the source files which made it. This helps maintainers
1253 see exactly which source was used to build a module (since
1254 others sometimes change the module source without updating
1255 the version). With this option, such a "srcversion" field
1256 will be created for all modules. If unsure, say N.
1260 config INIT_ALL_POSSIBLE
1263 Back when each arch used to define their own cpu_online_map and
1264 cpu_possible_map, some of them chose to initialize cpu_possible_map
1265 with all 1s, and others with all 0s. When they were centralised,
1266 it was better to provide this option than to break all the archs
1267 and have several arch maintainers pursuing me down dark alleys.
1272 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1274 Need stop_machine() primitive.
1276 source "block/Kconfig"
1278 config PREEMPT_NOTIFIERS
1281 source "kernel/Kconfig.locks"
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