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"
22 bool "Prompt for development and/or incomplete code/drivers"
24 Some of the various things that Linux supports (such as network
25 drivers, file systems, network protocols, etc.) can be in a state
26 of development where the functionality, stability, or the level of
27 testing is not yet high enough for general use. This is usually
28 known as the "alpha-test" phase among developers. If a feature is
29 currently in alpha-test, then the developers usually discourage
30 uninformed widespread use of this feature by the general public to
31 avoid "Why doesn't this work?" type mail messages. However, active
32 testing and use of these systems is welcomed. Just be aware that it
33 may not meet the normal level of reliability or it may fail to work
34 in some special cases. Detailed bug reports from people familiar
35 with the kernel internals are usually welcomed by the developers
36 (before submitting bug reports, please read the documents
37 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
38 <file:Documentation/BUG-HUNTING>, and
39 <file:Documentation/oops-tracing.txt> in the kernel source).
41 This option will also make obsoleted drivers available. These are
42 drivers that have been replaced by something else, and/or are
43 scheduled to be removed in a future kernel release.
45 Unless you intend to help test and develop a feature or driver that
46 falls into this category, or you have a situation that requires
47 using these features, you should probably say N here, which will
48 cause the configurator to present you with fewer choices. If
49 you say Y here, you will be offered the choice of using features or
50 drivers that are currently considered to be in the alpha-test phase.
57 depends on BROKEN || !SMP
62 depends on SMP || PREEMPT
65 config INIT_ENV_ARG_LIMIT
70 Maximum of each of the number of arguments and environment
71 variables passed to init from the kernel command line.
75 string "Local version - append to kernel release"
77 Append an extra string to the end of your kernel version.
78 This will show up when you type uname, for example.
79 The string you set here will be appended after the contents of
80 any files with a filename matching localversion* in your
81 object and source tree, in that order. Your total string can
82 be a maximum of 64 characters.
84 config LOCALVERSION_AUTO
85 bool "Automatically append version information to the version string"
88 This will try to automatically determine if the current tree is a
89 release tree by looking for git tags that belong to the current
92 A string of the format -gxxxxxxxx will be added to the localversion
93 if a git-based tree is found. The string generated by this will be
94 appended after any matching localversion* files, and after the value
95 set in CONFIG_LOCALVERSION.
97 (The actual string used here is the first eight characters produced
98 by running the command:
100 $ git rev-parse --verify HEAD
102 which is done within the script "scripts/setlocalversion".)
104 config HAVE_KERNEL_GZIP
107 config HAVE_KERNEL_BZIP2
110 config HAVE_KERNEL_LZMA
114 prompt "Kernel compression mode"
116 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
118 The linux kernel is a kind of self-extracting executable.
119 Several compression algorithms are available, which differ
120 in efficiency, compression and decompression speed.
121 Compression speed is only relevant when building a kernel.
122 Decompression speed is relevant at each boot.
124 If you have any problems with bzip2 or lzma compressed
125 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
126 version of this functionality (bzip2 only), for 2.4, was
127 supplied by Christian Ludwig)
129 High compression options are mostly useful for users, who
130 are low on disk space (embedded systems), but for whom ram
133 If in doubt, select 'gzip'
137 depends on HAVE_KERNEL_GZIP
139 The old and tried gzip compression. Its compression ratio is
140 the poorest among the 3 choices; however its speed (both
141 compression and decompression) is the fastest.
145 depends on HAVE_KERNEL_BZIP2
147 Its compression ratio and speed is intermediate.
148 Decompression speed is slowest among the three. The kernel
149 size is about 10% smaller with bzip2, in comparison to gzip.
150 Bzip2 uses a large amount of memory. For modern kernels you
151 will need at least 8MB RAM or more for booting.
155 depends on HAVE_KERNEL_LZMA
157 The most recent compression algorithm.
158 Its ratio is best, decompression speed is between the other
159 two. Compression is slowest. The kernel size is about 33%
160 smaller with LZMA in comparison to gzip.
165 bool "Support for paging of anonymous memory (swap)"
166 depends on MMU && BLOCK
169 This option allows you to choose whether you want to have support
170 for so called swap devices or swap files in your kernel that are
171 used to provide more virtual memory than the actual RAM present
172 in your computer. If unsure say Y.
177 Inter Process Communication is a suite of library functions and
178 system calls which let processes (running programs) synchronize and
179 exchange information. It is generally considered to be a good thing,
180 and some programs won't run unless you say Y here. In particular, if
181 you want to run the DOS emulator dosemu under Linux (read the
182 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
183 you'll need to say Y here.
185 You can find documentation about IPC with "info ipc" and also in
186 section 6.4 of the Linux Programmer's Guide, available from
187 <http://www.tldp.org/guides.html>.
189 config SYSVIPC_SYSCTL
196 bool "POSIX Message Queues"
197 depends on NET && EXPERIMENTAL
199 POSIX variant of message queues is a part of IPC. In POSIX message
200 queues every message has a priority which decides about succession
201 of receiving it by a process. If you want to compile and run
202 programs written e.g. for Solaris with use of its POSIX message
203 queues (functions mq_*) say Y here.
205 POSIX message queues are visible as a filesystem called 'mqueue'
206 and can be mounted somewhere if you want to do filesystem
207 operations on message queues.
211 config POSIX_MQUEUE_SYSCTL
213 depends on POSIX_MQUEUE
217 config BSD_PROCESS_ACCT
218 bool "BSD Process Accounting"
220 If you say Y here, a user level program will be able to instruct the
221 kernel (via a special system call) to write process accounting
222 information to a file: whenever a process exits, information about
223 that process will be appended to the file by the kernel. The
224 information includes things such as creation time, owning user,
225 command name, memory usage, controlling terminal etc. (the complete
226 list is in the struct acct in <file:include/linux/acct.h>). It is
227 up to the user level program to do useful things with this
228 information. This is generally a good idea, so say Y.
230 config BSD_PROCESS_ACCT_V3
231 bool "BSD Process Accounting version 3 file format"
232 depends on BSD_PROCESS_ACCT
235 If you say Y here, the process accounting information is written
236 in a new file format that also logs the process IDs of each
237 process and it's parent. Note that this file format is incompatible
238 with previous v0/v1/v2 file formats, so you will need updated tools
239 for processing it. A preliminary version of these tools is available
240 at <http://www.gnu.org/software/acct/>.
243 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
247 Export selected statistics for tasks/processes through the
248 generic netlink interface. Unlike BSD process accounting, the
249 statistics are available during the lifetime of tasks/processes as
250 responses to commands. Like BSD accounting, they are sent to user
255 config TASK_DELAY_ACCT
256 bool "Enable per-task delay accounting (EXPERIMENTAL)"
259 Collect information on time spent by a task waiting for system
260 resources like cpu, synchronous block I/O completion and swapping
261 in pages. Such statistics can help in setting a task's priorities
262 relative to other tasks for cpu, io, rss limits etc.
267 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
270 Collect extended task accounting data and send the data
271 to userland for processing over the taskstats interface.
275 config TASK_IO_ACCOUNTING
276 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
277 depends on TASK_XACCT
279 Collect information on the number of bytes of storage I/O which this
285 bool "Auditing support"
288 Enable auditing infrastructure that can be used with another
289 kernel subsystem, such as SELinux (which requires this for
290 logging of avc messages output). Does not do system-call
291 auditing without CONFIG_AUDITSYSCALL.
294 bool "Enable system-call auditing support"
295 depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
296 default y if SECURITY_SELINUX
298 Enable low-overhead system-call auditing infrastructure that
299 can be used independently or with another kernel subsystem,
300 such as SELinux. To use audit's filesystem watch feature, please
301 ensure that INOTIFY is configured.
305 depends on AUDITSYSCALL && INOTIFY
310 prompt "RCU Implementation"
316 This option selects the classic RCU implementation that is
317 designed for best read-side performance on non-realtime
320 Select this option if you are unsure.
323 bool "Tree-based hierarchical RCU"
325 This option selects the RCU implementation that is
326 designed for very large SMP system with hundreds or
330 bool "Preemptible RCU"
333 This option reduces the latency of the kernel by making certain
334 RCU sections preemptible. Normally RCU code is non-preemptible, if
335 this option is selected then read-only RCU sections become
336 preemptible. This helps latency, but may expose bugs due to
337 now-naive assumptions about each RCU read-side critical section
338 remaining on a given CPU through its execution.
343 bool "Enable tracing for RCU"
344 depends on TREE_RCU || PREEMPT_RCU
346 This option provides tracing in RCU which presents stats
347 in debugfs for debugging RCU implementation.
349 Say Y here if you want to enable RCU tracing
350 Say N if you are unsure.
353 int "Tree-based hierarchical RCU fanout value"
360 This option controls the fanout of hierarchical implementations
361 of RCU, allowing RCU to work efficiently on machines with
362 large numbers of CPUs. This value must be at least the cube
363 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
364 systems and up to 262,144 for 64-bit systems.
366 Select a specific number if testing RCU itself.
367 Take the default if unsure.
369 config RCU_FANOUT_EXACT
370 bool "Disable tree-based hierarchical RCU auto-balancing"
374 This option forces use of the exact RCU_FANOUT value specified,
375 regardless of imbalances in the hierarchy. This is useful for
376 testing RCU itself, and might one day be useful on systems with
377 strong NUMA behavior.
379 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
383 config TREE_RCU_TRACE
384 def_bool RCU_TRACE && TREE_RCU
387 This option provides tracing for the TREE_RCU implementation,
388 permitting Makefile to trivially select kernel/rcutree_trace.c.
390 config PREEMPT_RCU_TRACE
391 def_bool RCU_TRACE && PREEMPT_RCU
394 This option provides tracing for the PREEMPT_RCU implementation,
395 permitting Makefile to trivially select kernel/rcupreempt_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 "Create deprecated sysfs layout for older userspace tools"
621 select SYSFS_DEPRECATED
623 This option switches the layout of sysfs to the deprecated
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 VM_EVENT_COUNTERS
930 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
932 VM event counters are needed for event counts to be shown.
933 This option allows the disabling of the VM event counters
934 on EMBEDDED systems. /proc/vmstat will only show page counts
935 if VM event counters are disabled.
939 bool "Enable PCI quirk workarounds" if EMBEDDED
942 This enables workarounds for various PCI chipset
943 bugs/quirks. Disable this only if your target machine is
944 unaffected by PCI quirks.
948 bool "Enable SLUB debugging support" if EMBEDDED
949 depends on SLUB && SYSFS
951 SLUB has extensive debug support features. Disabling these can
952 result in significant savings in code size. This also disables
953 SLUB sysfs support. /sys/slab will not exist and there will be
954 no support for cache validation etc.
957 bool "Disable heap randomization"
960 Randomizing heap placement makes heap exploits harder, but it
961 also breaks ancient binaries (including anything libc5 based).
962 This option changes the bootup default to heap randomization
963 disabled, and can be overridden at runtime by setting
964 /proc/sys/kernel/randomize_va_space to 2.
966 On non-ancient distros (post-2000 ones) N is usually a safe choice.
969 prompt "Choose SLAB allocator"
972 This option allows to select a slab allocator.
977 The regular slab allocator that is established and known to work
978 well in all environments. It organizes cache hot objects in
979 per cpu and per node queues.
982 bool "SLUB (Unqueued Allocator)"
984 SLUB is a slab allocator that minimizes cache line usage
985 instead of managing queues of cached objects (SLAB approach).
986 Per cpu caching is realized using slabs of objects instead
987 of queues of objects. SLUB can use memory efficiently
988 and has enhanced diagnostics. SLUB is the default choice for
993 bool "SLOB (Simple Allocator)"
995 SLOB replaces the stock allocator with a drastically simpler
996 allocator. SLOB is generally more space efficient but
997 does not perform as well on large systems.
1002 bool "Profiling support (EXPERIMENTAL)"
1004 Say Y here to enable the extended profiling support mechanisms used
1005 by profilers such as OProfile.
1008 # Place an empty function call at each tracepoint site. Can be
1009 # dynamically changed for a probe function.
1015 bool "Activate markers"
1018 Place an empty function call at each marker site. Can be
1019 dynamically changed for a probe function.
1021 source "arch/Kconfig"
1027 The slow work thread pool provides a number of dynamically allocated
1028 threads that can be used by the kernel to perform operations that
1029 take a relatively long time.
1031 An example of this would be CacheFiles doing a path lookup followed
1032 by a series of mkdirs and a create call, all of which have to touch
1035 See Documentation/slow-work.txt.
1037 endmenu # General setup
1039 config HAVE_GENERIC_DMA_COHERENT
1046 depends on SLAB || SLUB_DEBUG
1054 default 0 if BASE_FULL
1055 default 1 if !BASE_FULL
1058 bool "Enable loadable module support"
1060 Kernel modules are small pieces of compiled code which can
1061 be inserted in the running kernel, rather than being
1062 permanently built into the kernel. You use the "modprobe"
1063 tool to add (and sometimes remove) them. If you say Y here,
1064 many parts of the kernel can be built as modules (by
1065 answering M instead of Y where indicated): this is most
1066 useful for infrequently used options which are not required
1067 for booting. For more information, see the man pages for
1068 modprobe, lsmod, modinfo, insmod and rmmod.
1070 If you say Y here, you will need to run "make
1071 modules_install" to put the modules under /lib/modules/
1072 where modprobe can find them (you may need to be root to do
1079 config MODULE_FORCE_LOAD
1080 bool "Forced module loading"
1083 Allow loading of modules without version information (ie. modprobe
1084 --force). Forced module loading sets the 'F' (forced) taint flag and
1085 is usually a really bad idea.
1087 config MODULE_UNLOAD
1088 bool "Module unloading"
1090 Without this option you will not be able to unload any
1091 modules (note that some modules may not be unloadable
1092 anyway), which makes your kernel smaller, faster
1093 and simpler. If unsure, say Y.
1095 config MODULE_FORCE_UNLOAD
1096 bool "Forced module unloading"
1097 depends on MODULE_UNLOAD && EXPERIMENTAL
1099 This option allows you to force a module to unload, even if the
1100 kernel believes it is unsafe: the kernel will remove the module
1101 without waiting for anyone to stop using it (using the -f option to
1102 rmmod). This is mainly for kernel developers and desperate users.
1106 bool "Module versioning support"
1108 Usually, you have to use modules compiled with your kernel.
1109 Saying Y here makes it sometimes possible to use modules
1110 compiled for different kernels, by adding enough information
1111 to the modules to (hopefully) spot any changes which would
1112 make them incompatible with the kernel you are running. If
1115 config MODULE_SRCVERSION_ALL
1116 bool "Source checksum for all modules"
1118 Modules which contain a MODULE_VERSION get an extra "srcversion"
1119 field inserted into their modinfo section, which contains a
1120 sum of the source files which made it. This helps maintainers
1121 see exactly which source was used to build a module (since
1122 others sometimes change the module source without updating
1123 the version). With this option, such a "srcversion" field
1124 will be created for all modules. If unsure, say N.
1128 config INIT_ALL_POSSIBLE
1131 Back when each arch used to define their own cpu_online_map and
1132 cpu_possible_map, some of them chose to initialize cpu_possible_map
1133 with all 1s, and others with all 0s. When they were centralised,
1134 it was better to provide this option than to break all the archs
1135 and have several arch maintainers pursuing me down dark alleys.
1140 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1142 Need stop_machine() primitive.
1144 source "block/Kconfig"
1146 config PREEMPT_NOTIFIERS
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