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47 drivers that have been replaced by something else, and/or are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 || 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
327 config TREE_PREEMPT_RCU
328 bool "Preemptable tree-based hierarchical RCU"
331 This option selects the RCU implementation that is
332 designed for very large SMP systems with hundreds or
333 thousands of CPUs, but for which real-time response
334 is also required. It also scales down nicely to
338 bool "UP-only small-memory-footprint RCU"
341 This option selects the RCU implementation that is
342 designed for UP systems from which real-time response
343 is not required. This option greatly reduces the
344 memory footprint of RCU.
349 bool "Enable tracing for RCU"
350 depends on TREE_RCU || TREE_PREEMPT_RCU
352 This option provides tracing in RCU which presents stats
353 in debugfs for debugging RCU implementation.
355 Say Y here if you want to enable RCU tracing
356 Say N if you are unsure.
359 int "Tree-based hierarchical RCU fanout value"
362 depends on TREE_RCU || TREE_PREEMPT_RCU
366 This option controls the fanout of hierarchical implementations
367 of RCU, allowing RCU to work efficiently on machines with
368 large numbers of CPUs. This value must be at least the cube
369 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
370 systems and up to 262,144 for 64-bit systems.
372 Select a specific number if testing RCU itself.
373 Take the default if unsure.
375 config RCU_FANOUT_EXACT
376 bool "Disable tree-based hierarchical RCU auto-balancing"
377 depends on TREE_RCU || TREE_PREEMPT_RCU
380 This option forces use of the exact RCU_FANOUT value specified,
381 regardless of imbalances in the hierarchy. This is useful for
382 testing RCU itself, and might one day be useful on systems with
383 strong NUMA behavior.
385 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
389 config TREE_RCU_TRACE
390 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
393 This option provides tracing for the TREE_RCU and
394 TREE_PREEMPT_RCU implementations, permitting Makefile to
395 trivially select kernel/rcutree_trace.c.
397 endmenu # "RCU Subsystem"
400 tristate "Kernel .config support"
402 This option enables the complete Linux kernel ".config" file
403 contents to be saved in the kernel. It provides documentation
404 of which kernel options are used in a running kernel or in an
405 on-disk kernel. This information can be extracted from the kernel
406 image file with the script scripts/extract-ikconfig and used as
407 input to rebuild the current kernel or to build another kernel.
408 It can also be extracted from a running kernel by reading
409 /proc/config.gz if enabled (below).
412 bool "Enable access to .config through /proc/config.gz"
413 depends on IKCONFIG && PROC_FS
415 This option enables access to the kernel configuration file
416 through /proc/config.gz.
419 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
423 Select kernel log buffer size as a power of 2.
433 # Architectures with an unreliable sched_clock() should select this:
435 config HAVE_UNSTABLE_SCHED_CLOCK
439 bool "Group CPU scheduler"
440 depends on EXPERIMENTAL
443 This feature lets CPU scheduler recognize task groups and control CPU
444 bandwidth allocation to such task groups.
445 In order to create a group from arbitrary set of processes, use
446 CONFIG_CGROUPS. (See Control Group support.)
448 config FAIR_GROUP_SCHED
449 bool "Group scheduling for SCHED_OTHER"
450 depends on GROUP_SCHED
453 config RT_GROUP_SCHED
454 bool "Group scheduling for SCHED_RR/FIFO"
455 depends on EXPERIMENTAL
456 depends on GROUP_SCHED
459 This feature lets you explicitly allocate real CPU bandwidth
460 to users or control groups (depending on the "Basis for grouping tasks"
461 setting below. If enabled, it will also make it impossible to
462 schedule realtime tasks for non-root users until you allocate
463 realtime bandwidth for them.
464 See Documentation/scheduler/sched-rt-group.txt for more information.
467 depends on GROUP_SCHED
468 prompt "Basis for grouping tasks"
474 This option will choose userid as the basis for grouping
475 tasks, thus providing equal CPU bandwidth to each user.
478 bool "Control groups"
481 This option allows you to create arbitrary task groups
482 using the "cgroup" pseudo filesystem and control
483 the cpu bandwidth allocated to each such task group.
484 Refer to Documentation/cgroups/cgroups.txt for more
485 information on "cgroup" pseudo filesystem.
490 boolean "Control Group support"
492 This option adds support for grouping sets of processes together, for
493 use with process control subsystems such as Cpusets, CFS, memory
494 controls or device isolation.
496 - Documentation/scheduler/sched-design-CFS.txt (CFS)
497 - Documentation/cgroups/ (features for grouping, isolation
498 and resource control)
505 bool "Example debug cgroup subsystem"
509 This option enables a simple cgroup subsystem that
510 exports useful debugging information about the cgroups
516 bool "Namespace cgroup subsystem"
519 Provides a simple namespace cgroup subsystem to
520 provide hierarchical naming of sets of namespaces,
521 for instance virtual servers and checkpoint/restart
524 config CGROUP_FREEZER
525 bool "Freezer cgroup subsystem"
528 Provides a way to freeze and unfreeze all tasks in a
532 bool "Device controller for cgroups"
533 depends on CGROUPS && EXPERIMENTAL
535 Provides a cgroup implementing whitelists for devices which
536 a process in the cgroup can mknod or open.
539 bool "Cpuset support"
542 This option will let you create and manage CPUSETs which
543 allow dynamically partitioning a system into sets of CPUs and
544 Memory Nodes and assigning tasks to run only within those sets.
545 This is primarily useful on large SMP or NUMA systems.
549 config PROC_PID_CPUSET
550 bool "Include legacy /proc/<pid>/cpuset file"
554 config CGROUP_CPUACCT
555 bool "Simple CPU accounting cgroup subsystem"
558 Provides a simple Resource Controller for monitoring the
559 total CPU consumed by the tasks in a cgroup.
561 config RESOURCE_COUNTERS
562 bool "Resource counters"
564 This option enables controller independent resource accounting
565 infrastructure that works with cgroups.
568 config CGROUP_MEM_RES_CTLR
569 bool "Memory Resource Controller for Control Groups"
570 depends on CGROUPS && RESOURCE_COUNTERS
573 Provides a memory resource controller that manages both anonymous
574 memory and page cache. (See Documentation/cgroups/memory.txt)
576 Note that setting this option increases fixed memory overhead
577 associated with each page of memory in the system. By this,
578 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
579 usage tracking struct at boot. Total amount of this is printed out
582 Only enable when you're ok with these trade offs and really
583 sure you need the memory resource controller. Even when you enable
584 this, you can set "cgroup_disable=memory" at your boot option to
585 disable memory resource controller and you can avoid overheads.
586 (and lose benefits of memory resource controller)
588 This config option also selects MM_OWNER config option, which
589 could in turn add some fork/exit overhead.
591 config CGROUP_MEM_RES_CTLR_SWAP
592 bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
593 depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
595 Add swap management feature to memory resource controller. When you
596 enable this, you can limit mem+swap usage per cgroup. In other words,
597 when you disable this, memory resource controller has no cares to
598 usage of swap...a process can exhaust all of the swap. This extension
599 is useful when you want to avoid exhaustion swap but this itself
600 adds more overheads and consumes memory for remembering information.
601 Especially if you use 32bit system or small memory system, please
602 be careful about enabling this. When memory resource controller
603 is disabled by boot option, this will be automatically disabled and
604 there will be no overhead from this. Even when you set this config=y,
605 if boot option "noswapaccount" is set, swap will not be accounted.
606 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
607 size is 4096bytes, 512k per 1Gbytes of swap.
614 config SYSFS_DEPRECATED
617 config SYSFS_DEPRECATED_V2
618 bool "enable deprecated sysfs features which may confuse old userspace tools"
621 select SYSFS_DEPRECATED
623 This option switches the layout of sysfs to the deprecated
624 version. Do not use it on recent distributions.
626 The current sysfs layout features a unified device tree at
627 /sys/devices/, which is able to express a hierarchy between
628 class devices. If the deprecated option is set to Y, the
629 unified device tree is split into a bus device tree at
630 /sys/devices/ and several individual class device trees at
631 /sys/class/. The class and bus devices will be connected by
632 "<subsystem>:<name>" and the "device" links. The "block"
633 class devices, will not show up in /sys/class/block/. Some
634 subsystems will suppress the creation of some devices which
635 depend on the unified device tree.
637 This option is not a pure compatibility option that can
638 be safely enabled on newer distributions. It will change the
639 layout of sysfs to the non-extensible deprecated version,
640 and disable some features, which can not be exported without
641 confusing older userspace tools. Since 2007/2008 all major
642 distributions do not enable this option, and ship no tools which
643 depend on the deprecated layout or this option.
645 If you are using a new kernel on an older distribution, or use
646 older userspace tools, you might need to say Y here. Do not say Y,
647 if the original kernel, that came with your distribution, has
648 this option set to N.
651 bool "Kernel->user space relay support (formerly relayfs)"
653 This option enables support for relay interface support in
654 certain file systems (such as debugfs).
655 It is designed to provide an efficient mechanism for tools and
656 facilities to relay large amounts of data from kernel space to
662 bool "Namespaces support" if EMBEDDED
665 Provides the way to make tasks work with different objects using
666 the same id. For example same IPC id may refer to different objects
667 or same user id or pid may refer to different tasks when used in
668 different namespaces.
672 depends on NAMESPACES
674 In this namespace tasks see different info provided with the
679 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
681 In this namespace tasks work with IPC ids which correspond to
682 different IPC objects in different namespaces.
685 bool "User namespace (EXPERIMENTAL)"
686 depends on NAMESPACES && EXPERIMENTAL
688 This allows containers, i.e. vservers, to use user namespaces
689 to provide different user info for different servers.
693 bool "PID Namespaces (EXPERIMENTAL)"
695 depends on NAMESPACES && EXPERIMENTAL
697 Support process id namespaces. This allows having multiple
698 processes with the same pid as long as they are in different
699 pid namespaces. This is a building block of containers.
701 Unless you want to work with an experimental feature
705 bool "Network namespace"
707 depends on NAMESPACES && EXPERIMENTAL && NET
709 Allow user space to create what appear to be multiple instances
710 of the network stack.
712 config BLK_DEV_INITRD
713 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
714 depends on BROKEN || !FRV
716 The initial RAM filesystem is a ramfs which is loaded by the
717 boot loader (loadlin or lilo) and that is mounted as root
718 before the normal boot procedure. It is typically used to
719 load modules needed to mount the "real" root file system,
720 etc. See <file:Documentation/initrd.txt> for details.
722 If RAM disk support (BLK_DEV_RAM) is also included, this
723 also enables initial RAM disk (initrd) support and adds
724 15 Kbytes (more on some other architectures) to the kernel size.
734 config CC_OPTIMIZE_FOR_SIZE
735 bool "Optimize for size"
738 Enabling this option will pass "-Os" instead of "-O2" to gcc
739 resulting in a smaller kernel.
750 bool "Configure standard kernel features (for small systems)"
752 This option allows certain base kernel options and settings
753 to be disabled or tweaked. This is for specialized
754 environments which can tolerate a "non-standard" kernel.
755 Only use this if you really know what you are doing.
758 bool "Enable 16-bit UID system calls" if EMBEDDED
759 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
762 This enables the legacy 16-bit UID syscall wrappers.
764 config SYSCTL_SYSCALL
765 bool "Sysctl syscall support" if EMBEDDED
769 sys_sysctl uses binary paths that have been found challenging
770 to properly maintain and use. The interface in /proc/sys
771 using paths with ascii names is now the primary path to this
774 Almost nothing using the binary sysctl interface so if you are
775 trying to save some space it is probably safe to disable this,
776 making your kernel marginally smaller.
778 If unsure say Y here.
781 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
784 Say Y here to let the kernel print out symbolic crash information and
785 symbolic stack backtraces. This increases the size of the kernel
786 somewhat, as all symbols have to be loaded into the kernel image.
789 bool "Include all symbols in kallsyms"
790 depends on DEBUG_KERNEL && KALLSYMS
792 Normally kallsyms only contains the symbols of functions, for nicer
793 OOPS messages. Some debuggers can use kallsyms for other
794 symbols too: say Y here to include all symbols, if you need them
795 and you don't care about adding 300k to the size of your kernel.
799 config KALLSYMS_EXTRA_PASS
800 bool "Do an extra kallsyms pass"
803 If kallsyms is not working correctly, the build will fail with
804 inconsistent kallsyms data. If that occurs, log a bug report and
805 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
806 Always say N here unless you find a bug in kallsyms, which must be
807 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
808 you wait for kallsyms to be fixed.
812 bool "Support for hot-pluggable devices" if EMBEDDED
815 This option is provided for the case where no hotplug or uevent
816 capabilities is wanted by the kernel. You should only consider
817 disabling this option for embedded systems that do not use modules, a
818 dynamic /dev tree, or dynamic device discovery. Just say Y.
822 bool "Enable support for printk" if EMBEDDED
824 This option enables normal printk support. Removing it
825 eliminates most of the message strings from the kernel image
826 and makes the kernel more or less silent. As this makes it
827 very difficult to diagnose system problems, saying N here is
828 strongly discouraged.
831 bool "BUG() support" if EMBEDDED
834 Disabling this option eliminates support for BUG and WARN, reducing
835 the size of your kernel image and potentially quietly ignoring
836 numerous fatal conditions. You should only consider disabling this
837 option for embedded systems with no facilities for reporting errors.
842 bool "Enable ELF core dumps" if EMBEDDED
844 Enable support for generating core dumps. Disabling saves about 4k.
846 config PCSPKR_PLATFORM
847 bool "Enable PC-Speaker support" if EMBEDDED
848 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
851 This option allows to disable the internal PC-Speaker
852 support, saving some memory.
856 bool "Enable full-sized data structures for core" if EMBEDDED
858 Disabling this option reduces the size of miscellaneous core
859 kernel data structures. This saves memory on small machines,
860 but may reduce performance.
863 bool "Enable futex support" if EMBEDDED
867 Disabling this option will cause the kernel to be built without
868 support for "fast userspace mutexes". The resulting kernel may not
869 run glibc-based applications correctly.
872 bool "Enable eventpoll support" if EMBEDDED
876 Disabling this option will cause the kernel to be built without
877 support for epoll family of system calls.
880 bool "Enable signalfd() system call" if EMBEDDED
884 Enable the signalfd() system call that allows to receive signals
885 on a file descriptor.
890 bool "Enable timerfd() system call" if EMBEDDED
894 Enable the timerfd() system call that allows to receive timer
895 events on a file descriptor.
900 bool "Enable eventfd() system call" if EMBEDDED
904 Enable the eventfd() system call that allows to receive both
905 kernel notification (ie. KAIO) or userspace notifications.
910 bool "Use full shmem filesystem" if EMBEDDED
914 The shmem is an internal filesystem used to manage shared memory.
915 It is backed by swap and manages resource limits. It is also exported
916 to userspace as tmpfs if TMPFS is enabled. Disabling this
917 option replaces shmem and tmpfs with the much simpler ramfs code,
918 which may be appropriate on small systems without swap.
921 bool "Enable AIO support" if EMBEDDED
924 This option enables POSIX asynchronous I/O which may by used
925 by some high performance threaded applications. Disabling
926 this option saves about 7k.
928 config HAVE_PERF_EVENTS
931 See tools/perf/design.txt for details.
933 config PERF_USE_VMALLOC
936 See tools/perf/design.txt for details
938 menu "Kernel Performance Events And Counters"
941 bool "Kernel performance events and counters"
942 default y if (PROFILING || PERF_COUNTERS)
943 depends on HAVE_PERF_EVENTS
946 Enable kernel support for various performance events provided
947 by software and hardware.
949 Software events are supported either built-in or via the
950 use of generic tracepoints.
952 Most modern CPUs support performance events via performance
953 counter registers. These registers count the number of certain
954 types of hw events: such as instructions executed, cachemisses
955 suffered, or branches mis-predicted - without slowing down the
956 kernel or applications. These registers can also trigger interrupts
957 when a threshold number of events have passed - and can thus be
958 used to profile the code that runs on that CPU.
960 The Linux Performance Event subsystem provides an abstraction of
961 these software and hardware event capabilities, available via a
962 system call and used by the "perf" utility in tools/perf/. It
963 provides per task and per CPU counters, and it provides event
964 capabilities on top of those.
969 bool "Tracepoint profiling sources"
970 depends on PERF_EVENTS && EVENT_TRACING
973 Allow the use of tracepoints as software performance events.
975 When this is enabled, you can create perf events based on
976 tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID
977 found in debugfs://tracing/events/*/*/id. (The -e/--events
978 option to the perf tool can parse and interpret symbolic
979 tracepoints, in the subsystem:tracepoint_name format.)
982 bool "Kernel performance counters (old config option)"
983 depends on HAVE_PERF_EVENTS
985 This config has been obsoleted by the PERF_EVENTS
986 config option - please see that one for details.
988 It has no effect on the kernel whether you enable
989 it or not, it is a compatibility placeholder.
993 config DEBUG_PERF_USE_VMALLOC
995 bool "Debug: use vmalloc to back perf mmap() buffers"
996 depends on PERF_EVENTS && DEBUG_KERNEL
997 select PERF_USE_VMALLOC
999 Use vmalloc memory to back perf mmap() buffers.
1001 Mostly useful for debugging the vmalloc code on platforms
1002 that don't require it.
1008 config VM_EVENT_COUNTERS
1010 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1012 VM event counters are needed for event counts to be shown.
1013 This option allows the disabling of the VM event counters
1014 on EMBEDDED systems. /proc/vmstat will only show page counts
1015 if VM event counters are disabled.
1019 bool "Enable PCI quirk workarounds" if EMBEDDED
1022 This enables workarounds for various PCI chipset
1023 bugs/quirks. Disable this only if your target machine is
1024 unaffected by PCI quirks.
1028 bool "Enable SLUB debugging support" if EMBEDDED
1029 depends on SLUB && SYSFS
1031 SLUB has extensive debug support features. Disabling these can
1032 result in significant savings in code size. This also disables
1033 SLUB sysfs support. /sys/slab will not exist and there will be
1034 no support for cache validation etc.
1037 bool "Disable heap randomization"
1040 Randomizing heap placement makes heap exploits harder, but it
1041 also breaks ancient binaries (including anything libc5 based).
1042 This option changes the bootup default to heap randomization
1043 disabled, and can be overridden at runtime by setting
1044 /proc/sys/kernel/randomize_va_space to 2.
1046 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1049 prompt "Choose SLAB allocator"
1052 This option allows to select a slab allocator.
1057 The regular slab allocator that is established and known to work
1058 well in all environments. It organizes cache hot objects in
1059 per cpu and per node queues.
1062 bool "SLUB (Unqueued Allocator)"
1064 SLUB is a slab allocator that minimizes cache line usage
1065 instead of managing queues of cached objects (SLAB approach).
1066 Per cpu caching is realized using slabs of objects instead
1067 of queues of objects. SLUB can use memory efficiently
1068 and has enhanced diagnostics. SLUB is the default choice for
1073 bool "SLOB (Simple Allocator)"
1075 SLOB replaces the stock allocator with a drastically simpler
1076 allocator. SLOB is generally more space efficient but
1077 does not perform as well on large systems.
1082 bool "Profiling support (EXPERIMENTAL)"
1084 Say Y here to enable the extended profiling support mechanisms used
1085 by profilers such as OProfile.
1088 # Place an empty function call at each tracepoint site. Can be
1089 # dynamically changed for a probe function.
1094 source "arch/Kconfig"
1100 The slow work thread pool provides a number of dynamically allocated
1101 threads that can be used by the kernel to perform operations that
1102 take a relatively long time.
1104 An example of this would be CacheFiles doing a path lookup followed
1105 by a series of mkdirs and a create call, all of which have to touch
1108 See Documentation/slow-work.txt.
1110 config SLOW_WORK_DEBUG
1111 bool "Slow work debugging through debugfs"
1113 depends on SLOW_WORK && DEBUG_FS
1115 Display the contents of the slow work run queue through debugfs,
1116 including items currently executing.
1118 See Documentation/slow-work.txt.
1120 endmenu # General setup
1122 config HAVE_GENERIC_DMA_COHERENT
1129 depends on SLAB || SLUB_DEBUG
1137 default 0 if BASE_FULL
1138 default 1 if !BASE_FULL
1141 bool "Enable loadable module support"
1143 Kernel modules are small pieces of compiled code which can
1144 be inserted in the running kernel, rather than being
1145 permanently built into the kernel. You use the "modprobe"
1146 tool to add (and sometimes remove) them. If you say Y here,
1147 many parts of the kernel can be built as modules (by
1148 answering M instead of Y where indicated): this is most
1149 useful for infrequently used options which are not required
1150 for booting. For more information, see the man pages for
1151 modprobe, lsmod, modinfo, insmod and rmmod.
1153 If you say Y here, you will need to run "make
1154 modules_install" to put the modules under /lib/modules/
1155 where modprobe can find them (you may need to be root to do
1162 config MODULE_FORCE_LOAD
1163 bool "Forced module loading"
1166 Allow loading of modules without version information (ie. modprobe
1167 --force). Forced module loading sets the 'F' (forced) taint flag and
1168 is usually a really bad idea.
1170 config MODULE_UNLOAD
1171 bool "Module unloading"
1173 Without this option you will not be able to unload any
1174 modules (note that some modules may not be unloadable
1175 anyway), which makes your kernel smaller, faster
1176 and simpler. If unsure, say Y.
1178 config MODULE_FORCE_UNLOAD
1179 bool "Forced module unloading"
1180 depends on MODULE_UNLOAD && EXPERIMENTAL
1182 This option allows you to force a module to unload, even if the
1183 kernel believes it is unsafe: the kernel will remove the module
1184 without waiting for anyone to stop using it (using the -f option to
1185 rmmod). This is mainly for kernel developers and desperate users.
1189 bool "Module versioning support"
1191 Usually, you have to use modules compiled with your kernel.
1192 Saying Y here makes it sometimes possible to use modules
1193 compiled for different kernels, by adding enough information
1194 to the modules to (hopefully) spot any changes which would
1195 make them incompatible with the kernel you are running. If
1198 config MODULE_SRCVERSION_ALL
1199 bool "Source checksum for all modules"
1201 Modules which contain a MODULE_VERSION get an extra "srcversion"
1202 field inserted into their modinfo section, which contains a
1203 sum of the source files which made it. This helps maintainers
1204 see exactly which source was used to build a module (since
1205 others sometimes change the module source without updating
1206 the version). With this option, such a "srcversion" field
1207 will be created for all modules. If unsure, say N.
1211 config INIT_ALL_POSSIBLE
1214 Back when each arch used to define their own cpu_online_map and
1215 cpu_possible_map, some of them chose to initialize cpu_possible_map
1216 with all 1s, and others with all 0s. When they were centralised,
1217 it was better to provide this option than to break all the archs
1218 and have several arch maintainers pursuing me down dark alleys.
1223 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1225 Need stop_machine() primitive.
1227 source "block/Kconfig"
1229 config PREEMPT_NOTIFIERS
1232 source "kernel/Kconfig.locks"
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