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47 drivers that have been replaced by something else, and/or are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"
120 default KERNEL_LZO if ARCH_RK29
122 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
124 The linux kernel is a kind of self-extracting executable.
125 Several compression algorithms are available, which differ
126 in efficiency, compression and decompression speed.
127 Compression speed is only relevant when building a kernel.
128 Decompression speed is relevant at each boot.
130 If you have any problems with bzip2 or lzma compressed
131 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
132 version of this functionality (bzip2 only), for 2.4, was
133 supplied by Christian Ludwig)
135 High compression options are mostly useful for users, who
136 are low on disk space (embedded systems), but for whom ram
139 If in doubt, select 'gzip'
143 depends on HAVE_KERNEL_GZIP
145 The old and tried gzip compression. Its compression ratio is
146 the poorest among the 3 choices; however its speed (both
147 compression and decompression) is the fastest.
151 depends on HAVE_KERNEL_BZIP2
153 Its compression ratio and speed is intermediate.
154 Decompression speed is slowest among the three. The kernel
155 size is about 10% smaller with bzip2, in comparison to gzip.
156 Bzip2 uses a large amount of memory. For modern kernels you
157 will need at least 8MB RAM or more for booting.
161 depends on HAVE_KERNEL_LZMA
163 The most recent compression algorithm.
164 Its ratio is best, decompression speed is between the other
165 two. Compression is slowest. The kernel size is about 33%
166 smaller with LZMA in comparison to gzip.
171 bool "Support for paging of anonymous memory (swap)"
172 depends on MMU && BLOCK
175 This option allows you to choose whether you want to have support
176 for so called swap devices or swap files in your kernel that are
177 used to provide more virtual memory than the actual RAM present
178 in your computer. If unsure say Y.
183 Inter Process Communication is a suite of library functions and
184 system calls which let processes (running programs) synchronize and
185 exchange information. It is generally considered to be a good thing,
186 and some programs won't run unless you say Y here. In particular, if
187 you want to run the DOS emulator dosemu under Linux (read the
188 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
189 you'll need to say Y here.
191 You can find documentation about IPC with "info ipc" and also in
192 section 6.4 of the Linux Programmer's Guide, available from
193 <http://www.tldp.org/guides.html>.
195 config SYSVIPC_SYSCTL
202 bool "POSIX Message Queues"
203 depends on NET && EXPERIMENTAL
205 POSIX variant of message queues is a part of IPC. In POSIX message
206 queues every message has a priority which decides about succession
207 of receiving it by a process. If you want to compile and run
208 programs written e.g. for Solaris with use of its POSIX message
209 queues (functions mq_*) say Y here.
211 POSIX message queues are visible as a filesystem called 'mqueue'
212 and can be mounted somewhere if you want to do filesystem
213 operations on message queues.
217 config POSIX_MQUEUE_SYSCTL
219 depends on POSIX_MQUEUE
223 config BSD_PROCESS_ACCT
224 bool "BSD Process Accounting"
226 If you say Y here, a user level program will be able to instruct the
227 kernel (via a special system call) to write process accounting
228 information to a file: whenever a process exits, information about
229 that process will be appended to the file by the kernel. The
230 information includes things such as creation time, owning user,
231 command name, memory usage, controlling terminal etc. (the complete
232 list is in the struct acct in <file:include/linux/acct.h>). It is
233 up to the user level program to do useful things with this
234 information. This is generally a good idea, so say Y.
236 config BSD_PROCESS_ACCT_V3
237 bool "BSD Process Accounting version 3 file format"
238 depends on BSD_PROCESS_ACCT
241 If you say Y here, the process accounting information is written
242 in a new file format that also logs the process IDs of each
243 process and it's parent. Note that this file format is incompatible
244 with previous v0/v1/v2 file formats, so you will need updated tools
245 for processing it. A preliminary version of these tools is available
246 at <http://www.gnu.org/software/acct/>.
249 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
253 Export selected statistics for tasks/processes through the
254 generic netlink interface. Unlike BSD process accounting, the
255 statistics are available during the lifetime of tasks/processes as
256 responses to commands. Like BSD accounting, they are sent to user
261 config TASK_DELAY_ACCT
262 bool "Enable per-task delay accounting (EXPERIMENTAL)"
265 Collect information on time spent by a task waiting for system
266 resources like cpu, synchronous block I/O completion and swapping
267 in pages. Such statistics can help in setting a task's priorities
268 relative to other tasks for cpu, io, rss limits etc.
273 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
276 Collect extended task accounting data and send the data
277 to userland for processing over the taskstats interface.
281 config TASK_IO_ACCOUNTING
282 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
283 depends on TASK_XACCT
285 Collect information on the number of bytes of storage I/O which this
291 bool "Auditing support"
294 Enable auditing infrastructure that can be used with another
295 kernel subsystem, such as SELinux (which requires this for
296 logging of avc messages output). Does not do system-call
297 auditing without CONFIG_AUDITSYSCALL.
300 bool "Enable system-call auditing support"
301 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
302 default y if SECURITY_SELINUX
304 Enable low-overhead system-call auditing infrastructure that
305 can be used independently or with another kernel subsystem,
306 such as SELinux. To use audit's filesystem watch feature, please
307 ensure that INOTIFY is configured.
311 depends on AUDITSYSCALL
317 prompt "RCU Implementation"
321 bool "Tree-based hierarchical RCU"
323 This option selects the RCU implementation that is
324 designed for very large SMP system with hundreds or
325 thousands of CPUs. It also scales down nicely to
328 config TREE_PREEMPT_RCU
329 bool "Preemptable tree-based hierarchical RCU"
332 This option selects the RCU implementation that is
333 designed for very large SMP systems with hundreds or
334 thousands of CPUs, but for which real-time response
335 is also required. It also scales down nicely to
341 bool "Enable tracing for RCU"
342 depends on TREE_RCU || TREE_PREEMPT_RCU
344 This option provides tracing in RCU which presents stats
345 in debugfs for debugging RCU implementation.
347 Say Y here if you want to enable RCU tracing
348 Say N if you are unsure.
351 int "Tree-based hierarchical RCU fanout value"
354 depends on TREE_RCU || TREE_PREEMPT_RCU
358 This option controls the fanout of hierarchical implementations
359 of RCU, allowing RCU to work efficiently on machines with
360 large numbers of CPUs. This value must be at least the cube
361 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
362 systems and up to 262,144 for 64-bit systems.
364 Select a specific number if testing RCU itself.
365 Take the default if unsure.
367 config RCU_FANOUT_EXACT
368 bool "Disable tree-based hierarchical RCU auto-balancing"
369 depends on TREE_RCU || TREE_PREEMPT_RCU
372 This option forces use of the exact RCU_FANOUT value specified,
373 regardless of imbalances in the hierarchy. This is useful for
374 testing RCU itself, and might one day be useful on systems with
375 strong NUMA behavior.
377 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
381 config TREE_RCU_TRACE
382 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
385 This option provides tracing for the TREE_RCU and
386 TREE_PREEMPT_RCU implementations, permitting Makefile to
387 trivially select kernel/rcutree_trace.c.
389 endmenu # "RCU Subsystem"
392 tristate "Kernel .config support"
394 This option enables the complete Linux kernel ".config" file
395 contents to be saved in the kernel. It provides documentation
396 of which kernel options are used in a running kernel or in an
397 on-disk kernel. This information can be extracted from the kernel
398 image file with the script scripts/extract-ikconfig and used as
399 input to rebuild the current kernel or to build another kernel.
400 It can also be extracted from a running kernel by reading
401 /proc/config.gz if enabled (below).
404 bool "Enable access to .config through /proc/config.gz"
405 depends on IKCONFIG && PROC_FS
407 This option enables access to the kernel configuration file
408 through /proc/config.gz.
411 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
415 Select kernel log buffer size as a power of 2.
425 # Architectures with an unreliable sched_clock() should select this:
427 config HAVE_UNSTABLE_SCHED_CLOCK
431 bool "Group CPU scheduler"
432 depends on EXPERIMENTAL
435 This feature lets CPU scheduler recognize task groups and control CPU
436 bandwidth allocation to such task groups.
437 In order to create a group from arbitrary set of processes, use
438 CONFIG_CGROUPS. (See Control Group support.)
440 config FAIR_GROUP_SCHED
441 bool "Group scheduling for SCHED_OTHER"
442 depends on GROUP_SCHED
445 config RT_GROUP_SCHED
446 bool "Group scheduling for SCHED_RR/FIFO"
447 depends on EXPERIMENTAL
448 depends on GROUP_SCHED
451 This feature lets you explicitly allocate real CPU bandwidth
452 to users or control groups (depending on the "Basis for grouping tasks"
453 setting below. If enabled, it will also make it impossible to
454 schedule realtime tasks for non-root users until you allocate
455 realtime bandwidth for them.
456 See Documentation/scheduler/sched-rt-group.txt for more information.
459 depends on GROUP_SCHED
460 prompt "Basis for grouping tasks"
466 This option will choose userid as the basis for grouping
467 tasks, thus providing equal CPU bandwidth to each user.
470 bool "Control groups"
473 This option allows you to create arbitrary task groups
474 using the "cgroup" pseudo filesystem and control
475 the cpu bandwidth allocated to each such task group.
476 Refer to Documentation/cgroups/cgroups.txt for more
477 information on "cgroup" pseudo filesystem.
482 boolean "Control Group support"
484 This option adds support for grouping sets of processes together, for
485 use with process control subsystems such as Cpusets, CFS, memory
486 controls or device isolation.
488 - Documentation/scheduler/sched-design-CFS.txt (CFS)
489 - Documentation/cgroups/ (features for grouping, isolation
490 and resource control)
497 bool "Example debug cgroup subsystem"
501 This option enables a simple cgroup subsystem that
502 exports useful debugging information about the cgroups
508 bool "Namespace cgroup subsystem"
511 Provides a simple namespace cgroup subsystem to
512 provide hierarchical naming of sets of namespaces,
513 for instance virtual servers and checkpoint/restart
516 config CGROUP_FREEZER
517 bool "Freezer cgroup subsystem"
520 Provides a way to freeze and unfreeze all tasks in a
524 bool "Device controller for cgroups"
525 depends on CGROUPS && EXPERIMENTAL
527 Provides a cgroup implementing whitelists for devices which
528 a process in the cgroup can mknod or open.
531 bool "Cpuset support"
534 This option will let you create and manage CPUSETs which
535 allow dynamically partitioning a system into sets of CPUs and
536 Memory Nodes and assigning tasks to run only within those sets.
537 This is primarily useful on large SMP or NUMA systems.
541 config PROC_PID_CPUSET
542 bool "Include legacy /proc/<pid>/cpuset file"
546 config CGROUP_CPUACCT
547 bool "Simple CPU accounting cgroup subsystem"
550 Provides a simple Resource Controller for monitoring the
551 total CPU consumed by the tasks in a cgroup.
553 config RESOURCE_COUNTERS
554 bool "Resource counters"
556 This option enables controller independent resource accounting
557 infrastructure that works with cgroups.
560 config CGROUP_MEM_RES_CTLR
561 bool "Memory Resource Controller for Control Groups"
562 depends on CGROUPS && RESOURCE_COUNTERS
565 Provides a memory resource controller that manages both anonymous
566 memory and page cache. (See Documentation/cgroups/memory.txt)
568 Note that setting this option increases fixed memory overhead
569 associated with each page of memory in the system. By this,
570 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
571 usage tracking struct at boot. Total amount of this is printed out
574 Only enable when you're ok with these trade offs and really
575 sure you need the memory resource controller. Even when you enable
576 this, you can set "cgroup_disable=memory" at your boot option to
577 disable memory resource controller and you can avoid overheads.
578 (and lose benefits of memory resource controller)
580 This config option also selects MM_OWNER config option, which
581 could in turn add some fork/exit overhead.
583 config CGROUP_MEM_RES_CTLR_SWAP
584 bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
585 depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
587 Add swap management feature to memory resource controller. When you
588 enable this, you can limit mem+swap usage per cgroup. In other words,
589 when you disable this, memory resource controller has no cares to
590 usage of swap...a process can exhaust all of the swap. This extension
591 is useful when you want to avoid exhaustion swap but this itself
592 adds more overheads and consumes memory for remembering information.
593 Especially if you use 32bit system or small memory system, please
594 be careful about enabling this. When memory resource controller
595 is disabled by boot option, this will be automatically disabled and
596 there will be no overhead from this. Even when you set this config=y,
597 if boot option "noswapaccount" is set, swap will not be accounted.
598 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
599 size is 4096bytes, 512k per 1Gbytes of swap.
606 config SYSFS_DEPRECATED
609 config SYSFS_DEPRECATED_V2
610 bool "enable deprecated sysfs features which may confuse old userspace tools"
613 select SYSFS_DEPRECATED
615 This option switches the layout of sysfs to the deprecated
616 version. Do not use it on recent distributions.
618 The current sysfs layout features a unified device tree at
619 /sys/devices/, which is able to express a hierarchy between
620 class devices. If the deprecated option is set to Y, the
621 unified device tree is split into a bus device tree at
622 /sys/devices/ and several individual class device trees at
623 /sys/class/. The class and bus devices will be connected by
624 "<subsystem>:<name>" and the "device" links. The "block"
625 class devices, will not show up in /sys/class/block/. Some
626 subsystems will suppress the creation of some devices which
627 depend on the unified device tree.
629 This option is not a pure compatibility option that can
630 be safely enabled on newer distributions. It will change the
631 layout of sysfs to the non-extensible deprecated version,
632 and disable some features, which can not be exported without
633 confusing older userspace tools. Since 2007/2008 all major
634 distributions do not enable this option, and ship no tools which
635 depend on the deprecated layout or this option.
637 If you are using a new kernel on an older distribution, or use
638 older userspace tools, you might need to say Y here. Do not say Y,
639 if the original kernel, that came with your distribution, has
640 this option set to N.
643 bool "Kernel->user space relay support (formerly relayfs)"
645 This option enables support for relay interface support in
646 certain file systems (such as debugfs).
647 It is designed to provide an efficient mechanism for tools and
648 facilities to relay large amounts of data from kernel space to
654 bool "Namespaces support" if EMBEDDED
657 Provides the way to make tasks work with different objects using
658 the same id. For example same IPC id may refer to different objects
659 or same user id or pid may refer to different tasks when used in
660 different namespaces.
664 depends on NAMESPACES
666 In this namespace tasks see different info provided with the
671 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
673 In this namespace tasks work with IPC ids which correspond to
674 different IPC objects in different namespaces.
677 bool "User namespace (EXPERIMENTAL)"
678 depends on NAMESPACES && EXPERIMENTAL
680 This allows containers, i.e. vservers, to use user namespaces
681 to provide different user info for different servers.
685 bool "PID Namespaces (EXPERIMENTAL)"
687 depends on NAMESPACES && EXPERIMENTAL
689 Support process id namespaces. This allows having multiple
690 processes with the same pid as long as they are in different
691 pid namespaces. This is a building block of containers.
693 Unless you want to work with an experimental feature
697 bool "Network namespace"
699 depends on NAMESPACES && EXPERIMENTAL && NET
701 Allow user space to create what appear to be multiple instances
702 of the network stack.
704 config BLK_DEV_INITRD
705 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
706 depends on BROKEN || !FRV
708 The initial RAM filesystem is a ramfs which is loaded by the
709 boot loader (loadlin or lilo) and that is mounted as root
710 before the normal boot procedure. It is typically used to
711 load modules needed to mount the "real" root file system,
712 etc. See <file:Documentation/initrd.txt> for details.
714 If RAM disk support (BLK_DEV_RAM) is also included, this
715 also enables initial RAM disk (initrd) support and adds
716 15 Kbytes (more on some other architectures) to the kernel size.
726 config CC_OPTIMIZE_FOR_SIZE
727 bool "Optimize for size"
730 Enabling this option will pass "-Os" instead of "-O2" to gcc
731 resulting in a smaller kernel.
742 int "Default panic timeout"
745 Set default panic timeout.
748 bool "Configure standard kernel features (for small systems)"
750 This option allows certain base kernel options and settings
751 to be disabled or tweaked. This is for specialized
752 environments which can tolerate a "non-standard" kernel.
753 Only use this if you really know what you are doing.
756 bool "Enable 16-bit UID system calls" if EMBEDDED
757 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
760 This enables the legacy 16-bit UID syscall wrappers.
762 config SYSCTL_SYSCALL
763 bool "Sysctl syscall support" if EMBEDDED
767 sys_sysctl uses binary paths that have been found challenging
768 to properly maintain and use. The interface in /proc/sys
769 using paths with ascii names is now the primary path to this
772 Almost nothing using the binary sysctl interface so if you are
773 trying to save some space it is probably safe to disable this,
774 making your kernel marginally smaller.
776 If unsure say Y here.
779 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
782 Say Y here to let the kernel print out symbolic crash information and
783 symbolic stack backtraces. This increases the size of the kernel
784 somewhat, as all symbols have to be loaded into the kernel image.
787 bool "Include all symbols in kallsyms"
788 depends on DEBUG_KERNEL && KALLSYMS
790 Normally kallsyms only contains the symbols of functions, for nicer
791 OOPS messages. Some debuggers can use kallsyms for other
792 symbols too: say Y here to include all symbols, if you need them
793 and you don't care about adding 300k to the size of your kernel.
797 config KALLSYMS_EXTRA_PASS
798 bool "Do an extra kallsyms pass"
801 If kallsyms is not working correctly, the build will fail with
802 inconsistent kallsyms data. If that occurs, log a bug report and
803 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
804 Always say N here unless you find a bug in kallsyms, which must be
805 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
806 you wait for kallsyms to be fixed.
810 bool "Support for hot-pluggable devices" if EMBEDDED
813 This option is provided for the case where no hotplug or uevent
814 capabilities is wanted by the kernel. You should only consider
815 disabling this option for embedded systems that do not use modules, a
816 dynamic /dev tree, or dynamic device discovery. Just say Y.
820 bool "Enable support for printk" if EMBEDDED
822 This option enables normal printk support. Removing it
823 eliminates most of the message strings from the kernel image
824 and makes the kernel more or less silent. As this makes it
825 very difficult to diagnose system problems, saying N here is
826 strongly discouraged.
829 bool "BUG() support" if EMBEDDED
832 Disabling this option eliminates support for BUG and WARN, reducing
833 the size of your kernel image and potentially quietly ignoring
834 numerous fatal conditions. You should only consider disabling this
835 option for embedded systems with no facilities for reporting errors.
840 bool "Enable ELF core dumps" if EMBEDDED
842 Enable support for generating core dumps. Disabling saves about 4k.
844 config PCSPKR_PLATFORM
845 bool "Enable PC-Speaker support" if EMBEDDED
846 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
849 This option allows to disable the internal PC-Speaker
850 support, saving some memory.
854 bool "Enable full-sized data structures for core" if EMBEDDED
856 Disabling this option reduces the size of miscellaneous core
857 kernel data structures. This saves memory on small machines,
858 but may reduce performance.
861 bool "Enable futex support" if EMBEDDED
865 Disabling this option will cause the kernel to be built without
866 support for "fast userspace mutexes". The resulting kernel may not
867 run glibc-based applications correctly.
870 bool "Enable eventpoll support" if EMBEDDED
874 Disabling this option will cause the kernel to be built without
875 support for epoll family of system calls.
878 bool "Enable signalfd() system call" if EMBEDDED
882 Enable the signalfd() system call that allows to receive signals
883 on a file descriptor.
888 bool "Enable timerfd() system call" if EMBEDDED
892 Enable the timerfd() system call that allows to receive timer
893 events on a file descriptor.
898 bool "Enable eventfd() system call" if EMBEDDED
902 Enable the eventfd() system call that allows to receive both
903 kernel notification (ie. KAIO) or userspace notifications.
908 bool "Use full shmem filesystem" if EMBEDDED
912 The shmem is an internal filesystem used to manage shared memory.
913 It is backed by swap and manages resource limits. It is also exported
914 to userspace as tmpfs if TMPFS is enabled. Disabling this
915 option replaces shmem and tmpfs with the much simpler ramfs code,
916 which may be appropriate on small systems without swap.
919 bool "Enable the Anonymous Shared Memory Subsystem"
921 depends on SHMEM || TINY_SHMEM
923 The ashmem subsystem is a new shared memory allocator, similar to
924 POSIX SHM but with different behavior and sporting a simpler
928 bool "Enable AIO support" if EMBEDDED
931 This option enables POSIX asynchronous I/O which may by used
932 by some high performance threaded applications. Disabling
933 this option saves about 7k.
935 config HAVE_PERF_EVENTS
938 See tools/perf/design.txt for details.
940 config PERF_USE_VMALLOC
943 See tools/perf/design.txt for details
945 menu "Kernel Performance Events And Counters"
948 bool "Kernel performance events and counters"
949 default y if (PROFILING || PERF_COUNTERS)
950 depends on HAVE_PERF_EVENTS
953 Enable kernel support for various performance events provided
954 by software and hardware.
956 Software events are supported either built-in or via the
957 use of generic tracepoints.
959 Most modern CPUs support performance events via performance
960 counter registers. These registers count the number of certain
961 types of hw events: such as instructions executed, cachemisses
962 suffered, or branches mis-predicted - without slowing down the
963 kernel or applications. These registers can also trigger interrupts
964 when a threshold number of events have passed - and can thus be
965 used to profile the code that runs on that CPU.
967 The Linux Performance Event subsystem provides an abstraction of
968 these software and hardware event capabilities, available via a
969 system call and used by the "perf" utility in tools/perf/. It
970 provides per task and per CPU counters, and it provides event
971 capabilities on top of those.
976 bool "Tracepoint profiling sources"
977 depends on PERF_EVENTS && EVENT_TRACING
980 Allow the use of tracepoints as software performance events.
982 When this is enabled, you can create perf events based on
983 tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID
984 found in debugfs://tracing/events/*/*/id. (The -e/--events
985 option to the perf tool can parse and interpret symbolic
986 tracepoints, in the subsystem:tracepoint_name format.)
989 bool "Kernel performance counters (old config option)"
990 depends on HAVE_PERF_EVENTS
992 This config has been obsoleted by the PERF_EVENTS
993 config option - please see that one for details.
995 It has no effect on the kernel whether you enable
996 it or not, it is a compatibility placeholder.
1000 config DEBUG_PERF_USE_VMALLOC
1002 bool "Debug: use vmalloc to back perf mmap() buffers"
1003 depends on PERF_EVENTS && DEBUG_KERNEL
1004 select PERF_USE_VMALLOC
1006 Use vmalloc memory to back perf mmap() buffers.
1008 Mostly useful for debugging the vmalloc code on platforms
1009 that don't require it.
1015 config VM_EVENT_COUNTERS
1017 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1019 VM event counters are needed for event counts to be shown.
1020 This option allows the disabling of the VM event counters
1021 on EMBEDDED systems. /proc/vmstat will only show page counts
1022 if VM event counters are disabled.
1026 bool "Enable PCI quirk workarounds" if EMBEDDED
1029 This enables workarounds for various PCI chipset
1030 bugs/quirks. Disable this only if your target machine is
1031 unaffected by PCI quirks.
1035 bool "Enable SLUB debugging support" if EMBEDDED
1036 depends on SLUB && SYSFS
1038 SLUB has extensive debug support features. Disabling these can
1039 result in significant savings in code size. This also disables
1040 SLUB sysfs support. /sys/slab will not exist and there will be
1041 no support for cache validation etc.
1044 bool "Disable heap randomization"
1047 Randomizing heap placement makes heap exploits harder, but it
1048 also breaks ancient binaries (including anything libc5 based).
1049 This option changes the bootup default to heap randomization
1050 disabled, and can be overridden at runtime by setting
1051 /proc/sys/kernel/randomize_va_space to 2.
1053 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1056 prompt "Choose SLAB allocator"
1059 This option allows to select a slab allocator.
1064 The regular slab allocator that is established and known to work
1065 well in all environments. It organizes cache hot objects in
1066 per cpu and per node queues.
1069 bool "SLUB (Unqueued Allocator)"
1071 SLUB is a slab allocator that minimizes cache line usage
1072 instead of managing queues of cached objects (SLAB approach).
1073 Per cpu caching is realized using slabs of objects instead
1074 of queues of objects. SLUB can use memory efficiently
1075 and has enhanced diagnostics. SLUB is the default choice for
1080 bool "SLOB (Simple Allocator)"
1082 SLOB replaces the stock allocator with a drastically simpler
1083 allocator. SLOB is generally more space efficient but
1084 does not perform as well on large systems.
1089 bool "Profiling support (EXPERIMENTAL)"
1091 Say Y here to enable the extended profiling support mechanisms used
1092 by profilers such as OProfile.
1095 # Place an empty function call at each tracepoint site. Can be
1096 # dynamically changed for a probe function.
1101 source "arch/Kconfig"
1107 The slow work thread pool provides a number of dynamically allocated
1108 threads that can be used by the kernel to perform operations that
1109 take a relatively long time.
1111 An example of this would be CacheFiles doing a path lookup followed
1112 by a series of mkdirs and a create call, all of which have to touch
1115 See Documentation/slow-work.txt.
1117 config SLOW_WORK_DEBUG
1118 bool "Slow work debugging through debugfs"
1120 depends on SLOW_WORK && DEBUG_FS
1122 Display the contents of the slow work run queue through debugfs,
1123 including items currently executing.
1125 See Documentation/slow-work.txt.
1127 endmenu # General setup
1129 config HAVE_GENERIC_DMA_COHERENT
1136 depends on SLAB || SLUB_DEBUG
1144 default 0 if BASE_FULL
1145 default 1 if !BASE_FULL
1148 bool "Enable loadable module support"
1150 Kernel modules are small pieces of compiled code which can
1151 be inserted in the running kernel, rather than being
1152 permanently built into the kernel. You use the "modprobe"
1153 tool to add (and sometimes remove) them. If you say Y here,
1154 many parts of the kernel can be built as modules (by
1155 answering M instead of Y where indicated): this is most
1156 useful for infrequently used options which are not required
1157 for booting. For more information, see the man pages for
1158 modprobe, lsmod, modinfo, insmod and rmmod.
1160 If you say Y here, you will need to run "make
1161 modules_install" to put the modules under /lib/modules/
1162 where modprobe can find them (you may need to be root to do
1169 config MODULE_FORCE_LOAD
1170 bool "Forced module loading"
1173 Allow loading of modules without version information (ie. modprobe
1174 --force). Forced module loading sets the 'F' (forced) taint flag and
1175 is usually a really bad idea.
1177 config MODULE_UNLOAD
1178 bool "Module unloading"
1180 Without this option you will not be able to unload any
1181 modules (note that some modules may not be unloadable
1182 anyway), which makes your kernel smaller, faster
1183 and simpler. If unsure, say Y.
1185 config MODULE_FORCE_UNLOAD
1186 bool "Forced module unloading"
1187 depends on MODULE_UNLOAD && EXPERIMENTAL
1189 This option allows you to force a module to unload, even if the
1190 kernel believes it is unsafe: the kernel will remove the module
1191 without waiting for anyone to stop using it (using the -f option to
1192 rmmod). This is mainly for kernel developers and desperate users.
1196 bool "Module versioning support"
1198 Usually, you have to use modules compiled with your kernel.
1199 Saying Y here makes it sometimes possible to use modules
1200 compiled for different kernels, by adding enough information
1201 to the modules to (hopefully) spot any changes which would
1202 make them incompatible with the kernel you are running. If
1205 config MODULE_SRCVERSION_ALL
1206 bool "Source checksum for all modules"
1208 Modules which contain a MODULE_VERSION get an extra "srcversion"
1209 field inserted into their modinfo section, which contains a
1210 sum of the source files which made it. This helps maintainers
1211 see exactly which source was used to build a module (since
1212 others sometimes change the module source without updating
1213 the version). With this option, such a "srcversion" field
1214 will be created for all modules. If unsure, say N.
1218 config INIT_ALL_POSSIBLE
1221 Back when each arch used to define their own cpu_online_map and
1222 cpu_possible_map, some of them chose to initialize cpu_possible_map
1223 with all 1s, and others with all 0s. When they were centralised,
1224 it was better to provide this option than to break all the archs
1225 and have several arch maintainers pursuing me down dark alleys.
1230 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1232 Need stop_machine() primitive.
1234 source "block/Kconfig"
1236 config PREEMPT_NOTIFIERS