7 option env="KERNELVERSION"
13 default "/lib/modules/$UNAME_RELEASE/.config"
14 default "/etc/kernel-config"
15 default "/boot/config-$UNAME_RELEASE"
16 default "$ARCH_DEFCONFIG"
17 default "arch/$ARCH/defconfig"
27 bool "Prompt for development and/or incomplete code/drivers"
29 Some of the various things that Linux supports (such as network
30 drivers, file systems, network protocols, etc.) can be in a state
31 of development where the functionality, stability, or the level of
32 testing is not yet high enough for general use. This is usually
33 known as the "alpha-test" phase among developers. If a feature is
34 currently in alpha-test, then the developers usually discourage
35 uninformed widespread use of this feature by the general public to
36 avoid "Why doesn't this work?" type mail messages. However, active
37 testing and use of these systems is welcomed. Just be aware that it
38 may not meet the normal level of reliability or it may fail to work
39 in some special cases. Detailed bug reports from people familiar
40 with the kernel internals are usually welcomed by the developers
41 (before submitting bug reports, please read the documents
42 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
43 <file:Documentation/BUG-HUNTING>, and
44 <file:Documentation/oops-tracing.txt> in the kernel source).
46 This option will also make obsoleted drivers available. These are
47 drivers that have been replaced by something else, and/or are
48 scheduled to be removed in a future kernel release.
50 Unless you intend to help test and develop a feature or driver that
51 falls into this category, or you have a situation that requires
52 using these features, you should probably say N here, which will
53 cause the configurator to present you with fewer choices. If
54 you say Y here, you will be offered the choice of using features or
55 drivers that are currently considered to be in the alpha-test phase.
62 depends on BROKEN || !SMP
67 depends on SMP || PREEMPT
70 config INIT_ENV_ARG_LIMIT
75 Maximum of each of the number of arguments and environment
76 variables passed to init from the kernel command line.
80 string "Local version - append to kernel release"
82 Append an extra string to the end of your kernel version.
83 This will show up when you type uname, for example.
84 The string you set here will be appended after the contents of
85 any files with a filename matching localversion* in your
86 object and source tree, in that order. Your total string can
87 be a maximum of 64 characters.
89 config LOCALVERSION_AUTO
90 bool "Automatically append version information to the version string"
93 This will try to automatically determine if the current tree is a
94 release tree by looking for git tags that belong to the current
97 A string of the format -gxxxxxxxx will be added to the localversion
98 if a git-based tree is found. The string generated by this will be
99 appended after any matching localversion* files, and after the value
100 set in CONFIG_LOCALVERSION.
102 (The actual string used here is the first eight characters produced
103 by running the command:
105 $ git rev-parse --verify HEAD
107 which is done within the script "scripts/setlocalversion".)
109 config HAVE_KERNEL_GZIP
112 config HAVE_KERNEL_BZIP2
115 config HAVE_KERNEL_LZMA
119 prompt "Kernel compression mode"
121 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
123 The linux kernel is a kind of self-extracting executable.
124 Several compression algorithms are available, which differ
125 in efficiency, compression and decompression speed.
126 Compression speed is only relevant when building a kernel.
127 Decompression speed is relevant at each boot.
129 If you have any problems with bzip2 or lzma compressed
130 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
131 version of this functionality (bzip2 only), for 2.4, was
132 supplied by Christian Ludwig)
134 High compression options are mostly useful for users, who
135 are low on disk space (embedded systems), but for whom ram
138 If in doubt, select 'gzip'
142 depends on HAVE_KERNEL_GZIP
144 The old and tried gzip compression. Its compression ratio is
145 the poorest among the 3 choices; however its speed (both
146 compression and decompression) is the fastest.
150 depends on HAVE_KERNEL_BZIP2
152 Its compression ratio and speed is intermediate.
153 Decompression speed is slowest among the three. The kernel
154 size is about 10% smaller with bzip2, in comparison to gzip.
155 Bzip2 uses a large amount of memory. For modern kernels you
156 will need at least 8MB RAM or more for booting.
160 depends on HAVE_KERNEL_LZMA
162 The most recent compression algorithm.
163 Its ratio is best, decompression speed is between the other
164 two. Compression is slowest. The kernel size is about 33%
165 smaller with LZMA in comparison to gzip.
170 bool "Support for paging of anonymous memory (swap)"
171 depends on MMU && BLOCK
174 This option allows you to choose whether you want to have support
175 for so called swap devices or swap files in your kernel that are
176 used to provide more virtual memory than the actual RAM present
177 in your computer. If unsure say Y.
182 Inter Process Communication is a suite of library functions and
183 system calls which let processes (running programs) synchronize and
184 exchange information. It is generally considered to be a good thing,
185 and some programs won't run unless you say Y here. In particular, if
186 you want to run the DOS emulator dosemu under Linux (read the
187 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
188 you'll need to say Y here.
190 You can find documentation about IPC with "info ipc" and also in
191 section 6.4 of the Linux Programmer's Guide, available from
192 <http://www.tldp.org/guides.html>.
194 config SYSVIPC_SYSCTL
201 bool "POSIX Message Queues"
202 depends on NET && EXPERIMENTAL
204 POSIX variant of message queues is a part of IPC. In POSIX message
205 queues every message has a priority which decides about succession
206 of receiving it by a process. If you want to compile and run
207 programs written e.g. for Solaris with use of its POSIX message
208 queues (functions mq_*) say Y here.
210 POSIX message queues are visible as a filesystem called 'mqueue'
211 and can be mounted somewhere if you want to do filesystem
212 operations on message queues.
216 config POSIX_MQUEUE_SYSCTL
218 depends on POSIX_MQUEUE
222 config BSD_PROCESS_ACCT
223 bool "BSD Process Accounting"
225 If you say Y here, a user level program will be able to instruct the
226 kernel (via a special system call) to write process accounting
227 information to a file: whenever a process exits, information about
228 that process will be appended to the file by the kernel. The
229 information includes things such as creation time, owning user,
230 command name, memory usage, controlling terminal etc. (the complete
231 list is in the struct acct in <file:include/linux/acct.h>). It is
232 up to the user level program to do useful things with this
233 information. This is generally a good idea, so say Y.
235 config BSD_PROCESS_ACCT_V3
236 bool "BSD Process Accounting version 3 file format"
237 depends on BSD_PROCESS_ACCT
240 If you say Y here, the process accounting information is written
241 in a new file format that also logs the process IDs of each
242 process and it's parent. Note that this file format is incompatible
243 with previous v0/v1/v2 file formats, so you will need updated tools
244 for processing it. A preliminary version of these tools is available
245 at <http://www.gnu.org/software/acct/>.
248 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
252 Export selected statistics for tasks/processes through the
253 generic netlink interface. Unlike BSD process accounting, the
254 statistics are available during the lifetime of tasks/processes as
255 responses to commands. Like BSD accounting, they are sent to user
260 config TASK_DELAY_ACCT
261 bool "Enable per-task delay accounting (EXPERIMENTAL)"
264 Collect information on time spent by a task waiting for system
265 resources like cpu, synchronous block I/O completion and swapping
266 in pages. Such statistics can help in setting a task's priorities
267 relative to other tasks for cpu, io, rss limits etc.
272 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
275 Collect extended task accounting data and send the data
276 to userland for processing over the taskstats interface.
280 config TASK_IO_ACCOUNTING
281 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
282 depends on TASK_XACCT
284 Collect information on the number of bytes of storage I/O which this
290 bool "Auditing support"
293 Enable auditing infrastructure that can be used with another
294 kernel subsystem, such as SELinux (which requires this for
295 logging of avc messages output). Does not do system-call
296 auditing without CONFIG_AUDITSYSCALL.
299 bool "Enable system-call auditing support"
300 depends on AUDIT && (X86 || PPC || PPC64 || S390 || IA64 || UML || SPARC64|| SUPERH)
301 default y if SECURITY_SELINUX
303 Enable low-overhead system-call auditing infrastructure that
304 can be used independently or with another kernel subsystem,
305 such as SELinux. To use audit's filesystem watch feature, please
306 ensure that INOTIFY is configured.
310 depends on AUDITSYSCALL
316 prompt "RCU Implementation"
322 This option selects the classic RCU implementation that is
323 designed for best read-side performance on non-realtime
326 Select this option if you are unsure.
329 bool "Tree-based hierarchical RCU"
331 This option selects the RCU implementation that is
332 designed for very large SMP system with hundreds or
336 bool "Preemptible RCU"
339 This option reduces the latency of the kernel by making certain
340 RCU sections preemptible. Normally RCU code is non-preemptible, if
341 this option is selected then read-only RCU sections become
342 preemptible. This helps latency, but may expose bugs due to
343 now-naive assumptions about each RCU read-side critical section
344 remaining on a given CPU through its execution.
349 bool "Enable tracing for RCU"
350 depends on TREE_RCU || 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"
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"
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
393 This option provides tracing for the TREE_RCU implementation,
394 permitting Makefile to trivially select kernel/rcutree_trace.c.
396 config PREEMPT_RCU_TRACE
397 def_bool RCU_TRACE && PREEMPT_RCU
400 This option provides tracing for the PREEMPT_RCU implementation,
401 permitting Makefile to trivially select kernel/rcupreempt_trace.c.
403 endmenu # "RCU Subsystem"
406 tristate "Kernel .config support"
408 This option enables the complete Linux kernel ".config" file
409 contents to be saved in the kernel. It provides documentation
410 of which kernel options are used in a running kernel or in an
411 on-disk kernel. This information can be extracted from the kernel
412 image file with the script scripts/extract-ikconfig and used as
413 input to rebuild the current kernel or to build another kernel.
414 It can also be extracted from a running kernel by reading
415 /proc/config.gz if enabled (below).
418 bool "Enable access to .config through /proc/config.gz"
419 depends on IKCONFIG && PROC_FS
421 This option enables access to the kernel configuration file
422 through /proc/config.gz.
425 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
429 Select kernel log buffer size as a power of 2.
439 # Architectures with an unreliable sched_clock() should select this:
441 config HAVE_UNSTABLE_SCHED_CLOCK
445 bool "Group CPU scheduler"
446 depends on EXPERIMENTAL
449 This feature lets CPU scheduler recognize task groups and control CPU
450 bandwidth allocation to such task groups.
451 In order to create a group from arbitrary set of processes, use
452 CONFIG_CGROUPS. (See Control Group support.)
454 config FAIR_GROUP_SCHED
455 bool "Group scheduling for SCHED_OTHER"
456 depends on GROUP_SCHED
459 config RT_GROUP_SCHED
460 bool "Group scheduling for SCHED_RR/FIFO"
461 depends on EXPERIMENTAL
462 depends on GROUP_SCHED
465 This feature lets you explicitly allocate real CPU bandwidth
466 to users or control groups (depending on the "Basis for grouping tasks"
467 setting below. If enabled, it will also make it impossible to
468 schedule realtime tasks for non-root users until you allocate
469 realtime bandwidth for them.
470 See Documentation/scheduler/sched-rt-group.txt for more information.
473 depends on GROUP_SCHED
474 prompt "Basis for grouping tasks"
480 This option will choose userid as the basis for grouping
481 tasks, thus providing equal CPU bandwidth to each user.
484 bool "Control groups"
487 This option allows you to create arbitrary task groups
488 using the "cgroup" pseudo filesystem and control
489 the cpu bandwidth allocated to each such task group.
490 Refer to Documentation/cgroups/cgroups.txt for more
491 information on "cgroup" pseudo filesystem.
496 boolean "Control Group support"
498 This option adds support for grouping sets of processes together, for
499 use with process control subsystems such as Cpusets, CFS, memory
500 controls or device isolation.
502 - Documentation/scheduler/sched-design-CFS.txt (CFS)
503 - Documentation/cgroups/ (features for grouping, isolation
504 and resource control)
511 bool "Example debug cgroup subsystem"
515 This option enables a simple cgroup subsystem that
516 exports useful debugging information about the cgroups
522 bool "Namespace cgroup subsystem"
525 Provides a simple namespace cgroup subsystem to
526 provide hierarchical naming of sets of namespaces,
527 for instance virtual servers and checkpoint/restart
530 config CGROUP_FREEZER
531 bool "Freezer cgroup subsystem"
534 Provides a way to freeze and unfreeze all tasks in a
538 bool "Device controller for cgroups"
539 depends on CGROUPS && EXPERIMENTAL
541 Provides a cgroup implementing whitelists for devices which
542 a process in the cgroup can mknod or open.
545 bool "Cpuset support"
548 This option will let you create and manage CPUSETs which
549 allow dynamically partitioning a system into sets of CPUs and
550 Memory Nodes and assigning tasks to run only within those sets.
551 This is primarily useful on large SMP or NUMA systems.
555 config PROC_PID_CPUSET
556 bool "Include legacy /proc/<pid>/cpuset file"
560 config CGROUP_CPUACCT
561 bool "Simple CPU accounting cgroup subsystem"
564 Provides a simple Resource Controller for monitoring the
565 total CPU consumed by the tasks in a cgroup.
567 config RESOURCE_COUNTERS
568 bool "Resource counters"
570 This option enables controller independent resource accounting
571 infrastructure that works with cgroups.
574 config CGROUP_MEM_RES_CTLR
575 bool "Memory Resource Controller for Control Groups"
576 depends on CGROUPS && RESOURCE_COUNTERS
579 Provides a memory resource controller that manages both anonymous
580 memory and page cache. (See Documentation/cgroups/memory.txt)
582 Note that setting this option increases fixed memory overhead
583 associated with each page of memory in the system. By this,
584 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
585 usage tracking struct at boot. Total amount of this is printed out
588 Only enable when you're ok with these trade offs and really
589 sure you need the memory resource controller. Even when you enable
590 this, you can set "cgroup_disable=memory" at your boot option to
591 disable memory resource controller and you can avoid overheads.
592 (and lose benefits of memory resource controller)
594 This config option also selects MM_OWNER config option, which
595 could in turn add some fork/exit overhead.
597 config CGROUP_MEM_RES_CTLR_SWAP
598 bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
599 depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
601 Add swap management feature to memory resource controller. When you
602 enable this, you can limit mem+swap usage per cgroup. In other words,
603 when you disable this, memory resource controller has no cares to
604 usage of swap...a process can exhaust all of the swap. This extension
605 is useful when you want to avoid exhaustion swap but this itself
606 adds more overheads and consumes memory for remembering information.
607 Especially if you use 32bit system or small memory system, please
608 be careful about enabling this. When memory resource controller
609 is disabled by boot option, this will be automatically disabled and
610 there will be no overhead from this. Even when you set this config=y,
611 if boot option "noswapaccount" is set, swap will not be accounted.
612 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
613 size is 4096bytes, 512k per 1Gbytes of swap.
620 config SYSFS_DEPRECATED
623 config SYSFS_DEPRECATED_V2
624 bool "remove sysfs features which may confuse old userspace tools"
627 select SYSFS_DEPRECATED
629 This option switches the layout of sysfs to the deprecated
630 version. Do not use it on recent distributions.
632 The current sysfs layout features a unified device tree at
633 /sys/devices/, which is able to express a hierarchy between
634 class devices. If the deprecated option is set to Y, the
635 unified device tree is split into a bus device tree at
636 /sys/devices/ and several individual class device trees at
637 /sys/class/. The class and bus devices will be connected by
638 "<subsystem>:<name>" and the "device" links. The "block"
639 class devices, will not show up in /sys/class/block/. Some
640 subsystems will suppress the creation of some devices which
641 depend on the unified device tree.
643 This option is not a pure compatibility option that can
644 be safely enabled on newer distributions. It will change the
645 layout of sysfs to the non-extensible deprecated version,
646 and disable some features, which can not be exported without
647 confusing older userspace tools. Since 2007/2008 all major
648 distributions do not enable this option, and ship no tools which
649 depend on the deprecated layout or this option.
651 If you are using a new kernel on an older distribution, or use
652 older userspace tools, you might need to say Y here. Do not say Y,
653 if the original kernel, that came with your distribution, has
654 this option set to N.
657 bool "Kernel->user space relay support (formerly relayfs)"
659 This option enables support for relay interface support in
660 certain file systems (such as debugfs).
661 It is designed to provide an efficient mechanism for tools and
662 facilities to relay large amounts of data from kernel space to
668 bool "Namespaces support" if EMBEDDED
671 Provides the way to make tasks work with different objects using
672 the same id. For example same IPC id may refer to different objects
673 or same user id or pid may refer to different tasks when used in
674 different namespaces.
678 depends on NAMESPACES
680 In this namespace tasks see different info provided with the
685 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
687 In this namespace tasks work with IPC ids which correspond to
688 different IPC objects in different namespaces.
691 bool "User namespace (EXPERIMENTAL)"
692 depends on NAMESPACES && EXPERIMENTAL
694 This allows containers, i.e. vservers, to use user namespaces
695 to provide different user info for different servers.
699 bool "PID Namespaces (EXPERIMENTAL)"
701 depends on NAMESPACES && EXPERIMENTAL
703 Support process id namespaces. This allows having multiple
704 processes with the same pid as long as they are in different
705 pid namespaces. This is a building block of containers.
707 Unless you want to work with an experimental feature
711 bool "Network namespace"
713 depends on NAMESPACES && EXPERIMENTAL && NET
715 Allow user space to create what appear to be multiple instances
716 of the network stack.
718 config BLK_DEV_INITRD
719 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
720 depends on BROKEN || !FRV
722 The initial RAM filesystem is a ramfs which is loaded by the
723 boot loader (loadlin or lilo) and that is mounted as root
724 before the normal boot procedure. It is typically used to
725 load modules needed to mount the "real" root file system,
726 etc. See <file:Documentation/initrd.txt> for details.
728 If RAM disk support (BLK_DEV_RAM) is also included, this
729 also enables initial RAM disk (initrd) support and adds
730 15 Kbytes (more on some other architectures) to the kernel size.
740 config CC_OPTIMIZE_FOR_SIZE
741 bool "Optimize for size"
744 Enabling this option will pass "-Os" instead of "-O2" to gcc
745 resulting in a smaller kernel.
756 bool "Configure standard kernel features (for small systems)"
758 This option allows certain base kernel options and settings
759 to be disabled or tweaked. This is for specialized
760 environments which can tolerate a "non-standard" kernel.
761 Only use this if you really know what you are doing.
764 bool "Enable 16-bit UID system calls" if EMBEDDED
765 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
768 This enables the legacy 16-bit UID syscall wrappers.
770 config SYSCTL_SYSCALL
771 bool "Sysctl syscall support" if EMBEDDED
775 sys_sysctl uses binary paths that have been found challenging
776 to properly maintain and use. The interface in /proc/sys
777 using paths with ascii names is now the primary path to this
780 Almost nothing using the binary sysctl interface so if you are
781 trying to save some space it is probably safe to disable this,
782 making your kernel marginally smaller.
784 If unsure say Y here.
787 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
790 Say Y here to let the kernel print out symbolic crash information and
791 symbolic stack backtraces. This increases the size of the kernel
792 somewhat, as all symbols have to be loaded into the kernel image.
795 bool "Include all symbols in kallsyms"
796 depends on DEBUG_KERNEL && KALLSYMS
798 Normally kallsyms only contains the symbols of functions, for nicer
799 OOPS messages. Some debuggers can use kallsyms for other
800 symbols too: say Y here to include all symbols, if you need them
801 and you don't care about adding 300k to the size of your kernel.
805 config KALLSYMS_EXTRA_PASS
806 bool "Do an extra kallsyms pass"
809 If kallsyms is not working correctly, the build will fail with
810 inconsistent kallsyms data. If that occurs, log a bug report and
811 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
812 Always say N here unless you find a bug in kallsyms, which must be
813 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
814 you wait for kallsyms to be fixed.
818 bool "Support for hot-pluggable devices" if EMBEDDED
821 This option is provided for the case where no hotplug or uevent
822 capabilities is wanted by the kernel. You should only consider
823 disabling this option for embedded systems that do not use modules, a
824 dynamic /dev tree, or dynamic device discovery. Just say Y.
828 bool "Enable support for printk" if EMBEDDED
830 This option enables normal printk support. Removing it
831 eliminates most of the message strings from the kernel image
832 and makes the kernel more or less silent. As this makes it
833 very difficult to diagnose system problems, saying N here is
834 strongly discouraged.
837 bool "BUG() support" if EMBEDDED
840 Disabling this option eliminates support for BUG and WARN, reducing
841 the size of your kernel image and potentially quietly ignoring
842 numerous fatal conditions. You should only consider disabling this
843 option for embedded systems with no facilities for reporting errors.
848 bool "Enable ELF core dumps" if EMBEDDED
850 Enable support for generating core dumps. Disabling saves about 4k.
852 config PCSPKR_PLATFORM
853 bool "Enable PC-Speaker support" if EMBEDDED
854 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
857 This option allows to disable the internal PC-Speaker
858 support, saving some memory.
862 bool "Enable full-sized data structures for core" if EMBEDDED
864 Disabling this option reduces the size of miscellaneous core
865 kernel data structures. This saves memory on small machines,
866 but may reduce performance.
869 bool "Enable futex support" if EMBEDDED
873 Disabling this option will cause the kernel to be built without
874 support for "fast userspace mutexes". The resulting kernel may not
875 run glibc-based applications correctly.
878 bool "Enable eventpoll support" if EMBEDDED
882 Disabling this option will cause the kernel to be built without
883 support for epoll family of system calls.
886 bool "Enable signalfd() system call" if EMBEDDED
890 Enable the signalfd() system call that allows to receive signals
891 on a file descriptor.
896 bool "Enable timerfd() system call" if EMBEDDED
900 Enable the timerfd() system call that allows to receive timer
901 events on a file descriptor.
906 bool "Enable eventfd() system call" if EMBEDDED
910 Enable the eventfd() system call that allows to receive both
911 kernel notification (ie. KAIO) or userspace notifications.
916 bool "Use full shmem filesystem" if EMBEDDED
920 The shmem is an internal filesystem used to manage shared memory.
921 It is backed by swap and manages resource limits. It is also exported
922 to userspace as tmpfs if TMPFS is enabled. Disabling this
923 option replaces shmem and tmpfs with the much simpler ramfs code,
924 which may be appropriate on small systems without swap.
927 bool "Enable AIO support" if EMBEDDED
930 This option enables POSIX asynchronous I/O which may by used
931 by some high performance threaded applications. Disabling
932 this option saves about 7k.
934 config HAVE_PERF_COUNTERS
937 See tools/perf/design.txt for details.
939 menu "Performance Counters"
942 bool "Kernel Performance Counters"
943 depends on HAVE_PERF_COUNTERS
946 Enable kernel support for performance counter hardware.
948 Performance counters are special hardware registers available
949 on most modern CPUs. These registers count the number of certain
950 types of hw events: such as instructions executed, cachemisses
951 suffered, or branches mis-predicted - without slowing down the
952 kernel or applications. These registers can also trigger interrupts
953 when a threshold number of events have passed - and can thus be
954 used to profile the code that runs on that CPU.
956 The Linux Performance Counter subsystem provides an abstraction of
957 these hardware capabilities, available via a system call. It
958 provides per task and per CPU counters, and it provides event
959 capabilities on top of those.
964 bool "Tracepoint profile sources"
965 depends on PERF_COUNTERS && EVENT_TRACER
970 config VM_EVENT_COUNTERS
972 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
974 VM event counters are needed for event counts to be shown.
975 This option allows the disabling of the VM event counters
976 on EMBEDDED systems. /proc/vmstat will only show page counts
977 if VM event counters are disabled.
981 bool "Enable PCI quirk workarounds" if EMBEDDED
984 This enables workarounds for various PCI chipset
985 bugs/quirks. Disable this only if your target machine is
986 unaffected by PCI quirks.
990 bool "Enable SLUB debugging support" if EMBEDDED
991 depends on SLUB && SYSFS
993 SLUB has extensive debug support features. Disabling these can
994 result in significant savings in code size. This also disables
995 SLUB sysfs support. /sys/slab will not exist and there will be
996 no support for cache validation etc.
998 config STRIP_ASM_SYMS
999 bool "Strip assembler-generated symbols during link"
1002 Strip internal assembler-generated symbols during a link (symbols
1003 that look like '.Lxxx') so they don't pollute the output of
1004 get_wchan() and suchlike.
1007 bool "Disable heap randomization"
1010 Randomizing heap placement makes heap exploits harder, but it
1011 also breaks ancient binaries (including anything libc5 based).
1012 This option changes the bootup default to heap randomization
1013 disabled, and can be overridden at runtime by setting
1014 /proc/sys/kernel/randomize_va_space to 2.
1016 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1019 prompt "Choose SLAB allocator"
1022 This option allows to select a slab allocator.
1027 The regular slab allocator that is established and known to work
1028 well in all environments. It organizes cache hot objects in
1029 per cpu and per node queues.
1032 bool "SLUB (Unqueued Allocator)"
1034 SLUB is a slab allocator that minimizes cache line usage
1035 instead of managing queues of cached objects (SLAB approach).
1036 Per cpu caching is realized using slabs of objects instead
1037 of queues of objects. SLUB can use memory efficiently
1038 and has enhanced diagnostics. SLUB is the default choice for
1043 bool "SLOB (Simple Allocator)"
1045 SLOB replaces the stock allocator with a drastically simpler
1046 allocator. SLOB is generally more space efficient but
1047 does not perform as well on large systems.
1052 bool "Profiling support (EXPERIMENTAL)"
1054 Say Y here to enable the extended profiling support mechanisms used
1055 by profilers such as OProfile.
1058 # Place an empty function call at each tracepoint site. Can be
1059 # dynamically changed for a probe function.
1065 bool "Activate markers"
1068 Place an empty function call at each marker site. Can be
1069 dynamically changed for a probe function.
1071 source "arch/Kconfig"
1077 The slow work thread pool provides a number of dynamically allocated
1078 threads that can be used by the kernel to perform operations that
1079 take a relatively long time.
1081 An example of this would be CacheFiles doing a path lookup followed
1082 by a series of mkdirs and a create call, all of which have to touch
1085 See Documentation/slow-work.txt.
1087 endmenu # General setup
1089 config HAVE_GENERIC_DMA_COHERENT
1096 depends on SLAB || SLUB_DEBUG
1104 default 0 if BASE_FULL
1105 default 1 if !BASE_FULL
1108 bool "Enable loadable module support"
1110 Kernel modules are small pieces of compiled code which can
1111 be inserted in the running kernel, rather than being
1112 permanently built into the kernel. You use the "modprobe"
1113 tool to add (and sometimes remove) them. If you say Y here,
1114 many parts of the kernel can be built as modules (by
1115 answering M instead of Y where indicated): this is most
1116 useful for infrequently used options which are not required
1117 for booting. For more information, see the man pages for
1118 modprobe, lsmod, modinfo, insmod and rmmod.
1120 If you say Y here, you will need to run "make
1121 modules_install" to put the modules under /lib/modules/
1122 where modprobe can find them (you may need to be root to do
1129 config MODULE_FORCE_LOAD
1130 bool "Forced module loading"
1133 Allow loading of modules without version information (ie. modprobe
1134 --force). Forced module loading sets the 'F' (forced) taint flag and
1135 is usually a really bad idea.
1137 config MODULE_UNLOAD
1138 bool "Module unloading"
1140 Without this option you will not be able to unload any
1141 modules (note that some modules may not be unloadable
1142 anyway), which makes your kernel smaller, faster
1143 and simpler. If unsure, say Y.
1145 config MODULE_FORCE_UNLOAD
1146 bool "Forced module unloading"
1147 depends on MODULE_UNLOAD && EXPERIMENTAL
1149 This option allows you to force a module to unload, even if the
1150 kernel believes it is unsafe: the kernel will remove the module
1151 without waiting for anyone to stop using it (using the -f option to
1152 rmmod). This is mainly for kernel developers and desperate users.
1156 bool "Module versioning support"
1158 Usually, you have to use modules compiled with your kernel.
1159 Saying Y here makes it sometimes possible to use modules
1160 compiled for different kernels, by adding enough information
1161 to the modules to (hopefully) spot any changes which would
1162 make them incompatible with the kernel you are running. If
1165 config MODULE_SRCVERSION_ALL
1166 bool "Source checksum for all modules"
1168 Modules which contain a MODULE_VERSION get an extra "srcversion"
1169 field inserted into their modinfo section, which contains a
1170 sum of the source files which made it. This helps maintainers
1171 see exactly which source was used to build a module (since
1172 others sometimes change the module source without updating
1173 the version). With this option, such a "srcversion" field
1174 will be created for all modules. If unsure, say N.
1178 config INIT_ALL_POSSIBLE
1181 Back when each arch used to define their own cpu_online_map and
1182 cpu_possible_map, some of them chose to initialize cpu_possible_map
1183 with all 1s, and others with all 0s. When they were centralised,
1184 it was better to provide this option than to break all the archs
1185 and have several arch maintainers pursuing me down dark alleys.
1190 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1192 Need stop_machine() primitive.
1194 source "block/Kconfig"
1196 config PREEMPT_NOTIFIERS
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