7 option env="KERNELVERSION"
13 default "/lib/modules/$UNAME_RELEASE/.config"
14 default "/etc/kernel-config"
15 default "/boot/config-$UNAME_RELEASE"
16 default "$ARCH_DEFCONFIG"
17 default "arch/$ARCH/defconfig"
27 bool "Prompt for development and/or incomplete code/drivers"
29 Some of the various things that Linux supports (such as network
30 drivers, file systems, network protocols, etc.) can be in a state
31 of development where the functionality, stability, or the level of
32 testing is not yet high enough for general use. This is usually
33 known as the "alpha-test" phase among developers. If a feature is
34 currently in alpha-test, then the developers usually discourage
35 uninformed widespread use of this feature by the general public to
36 avoid "Why doesn't this work?" type mail messages. However, active
37 testing and use of these systems is welcomed. Just be aware that it
38 may not meet the normal level of reliability or it may fail to work
39 in some special cases. Detailed bug reports from people familiar
40 with the kernel internals are usually welcomed by the developers
41 (before submitting bug reports, please read the documents
42 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
43 <file:Documentation/BUG-HUNTING>, and
44 <file:Documentation/oops-tracing.txt> in the kernel source).
46 This option will also make obsoleted drivers available. These are
47 drivers that have been replaced by something else, and/or are
48 scheduled to be removed in a future kernel release.
50 Unless you intend to help test and develop a feature or driver that
51 falls into this category, or you have a situation that requires
52 using these features, you should probably say N here, which will
53 cause the configurator to present you with fewer choices. If
54 you say Y here, you will be offered the choice of using features or
55 drivers that are currently considered to be in the alpha-test phase.
62 depends on BROKEN || !SMP
67 depends on SMP || PREEMPT
70 config INIT_ENV_ARG_LIMIT
75 Maximum of each of the number of arguments and environment
76 variables passed to init from the kernel command line.
80 string "Local version - append to kernel release"
82 Append an extra string to the end of your kernel version.
83 This will show up when you type uname, for example.
84 The string you set here will be appended after the contents of
85 any files with a filename matching localversion* in your
86 object and source tree, in that order. Your total string can
87 be a maximum of 64 characters.
89 config LOCALVERSION_AUTO
90 bool "Automatically append version information to the version string"
93 This will try to automatically determine if the current tree is a
94 release tree by looking for git tags that belong to the current
97 A string of the format -gxxxxxxxx will be added to the localversion
98 if a git-based tree is found. The string generated by this will be
99 appended after any matching localversion* files, and after the value
100 set in CONFIG_LOCALVERSION.
102 (The actual string used here is the first eight characters produced
103 by running the command:
105 $ git rev-parse --verify HEAD
107 which is done within the script "scripts/setlocalversion".)
109 config HAVE_KERNEL_GZIP
112 config HAVE_KERNEL_BZIP2
115 config HAVE_KERNEL_LZMA
118 config HAVE_KERNEL_LZO
122 prompt "Kernel compression mode"
124 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_LZO
126 The linux kernel is a kind of self-extracting executable.
127 Several compression algorithms are available, which differ
128 in efficiency, compression and decompression speed.
129 Compression speed is only relevant when building a kernel.
130 Decompression speed is relevant at each boot.
132 If you have any problems with bzip2 or lzma compressed
133 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
134 version of this functionality (bzip2 only), for 2.4, was
135 supplied by Christian Ludwig)
137 High compression options are mostly useful for users, who
138 are low on disk space (embedded systems), but for whom ram
141 If in doubt, select 'gzip'
145 depends on HAVE_KERNEL_GZIP
147 The old and tried gzip compression. It provides a good balance
148 between compression ratio and decompression speed.
152 depends on HAVE_KERNEL_BZIP2
154 Its compression ratio and speed is intermediate.
155 Decompression speed is slowest among the three. The kernel
156 size is about 10% smaller with bzip2, in comparison to gzip.
157 Bzip2 uses a large amount of memory. For modern kernels you
158 will need at least 8MB RAM or more for booting.
162 depends on HAVE_KERNEL_LZMA
164 The most recent compression algorithm.
165 Its ratio is best, decompression speed is between the other
166 two. Compression is slowest. The kernel size is about 33%
167 smaller with LZMA in comparison to gzip.
171 depends on HAVE_KERNEL_LZO
173 Its compression ratio is the poorest among the 4. The kernel
174 size is about about 10% bigger than gzip; however its speed
175 (both compression and decompression) is the fastest.
180 bool "Support for paging of anonymous memory (swap)"
181 depends on MMU && BLOCK
184 This option allows you to choose whether you want to have support
185 for so called swap devices or swap files in your kernel that are
186 used to provide more virtual memory than the actual RAM present
187 in your computer. If unsure say Y.
192 Inter Process Communication is a suite of library functions and
193 system calls which let processes (running programs) synchronize and
194 exchange information. It is generally considered to be a good thing,
195 and some programs won't run unless you say Y here. In particular, if
196 you want to run the DOS emulator dosemu under Linux (read the
197 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
198 you'll need to say Y here.
200 You can find documentation about IPC with "info ipc" and also in
201 section 6.4 of the Linux Programmer's Guide, available from
202 <http://www.tldp.org/guides.html>.
204 config SYSVIPC_SYSCTL
211 bool "POSIX Message Queues"
212 depends on NET && EXPERIMENTAL
214 POSIX variant of message queues is a part of IPC. In POSIX message
215 queues every message has a priority which decides about succession
216 of receiving it by a process. If you want to compile and run
217 programs written e.g. for Solaris with use of its POSIX message
218 queues (functions mq_*) say Y here.
220 POSIX message queues are visible as a filesystem called 'mqueue'
221 and can be mounted somewhere if you want to do filesystem
222 operations on message queues.
226 config POSIX_MQUEUE_SYSCTL
228 depends on POSIX_MQUEUE
232 config BSD_PROCESS_ACCT
233 bool "BSD Process Accounting"
235 If you say Y here, a user level program will be able to instruct the
236 kernel (via a special system call) to write process accounting
237 information to a file: whenever a process exits, information about
238 that process will be appended to the file by the kernel. The
239 information includes things such as creation time, owning user,
240 command name, memory usage, controlling terminal etc. (the complete
241 list is in the struct acct in <file:include/linux/acct.h>). It is
242 up to the user level program to do useful things with this
243 information. This is generally a good idea, so say Y.
245 config BSD_PROCESS_ACCT_V3
246 bool "BSD Process Accounting version 3 file format"
247 depends on BSD_PROCESS_ACCT
250 If you say Y here, the process accounting information is written
251 in a new file format that also logs the process IDs of each
252 process and it's parent. Note that this file format is incompatible
253 with previous v0/v1/v2 file formats, so you will need updated tools
254 for processing it. A preliminary version of these tools is available
255 at <http://www.gnu.org/software/acct/>.
258 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
262 Export selected statistics for tasks/processes through the
263 generic netlink interface. Unlike BSD process accounting, the
264 statistics are available during the lifetime of tasks/processes as
265 responses to commands. Like BSD accounting, they are sent to user
270 config TASK_DELAY_ACCT
271 bool "Enable per-task delay accounting (EXPERIMENTAL)"
274 Collect information on time spent by a task waiting for system
275 resources like cpu, synchronous block I/O completion and swapping
276 in pages. Such statistics can help in setting a task's priorities
277 relative to other tasks for cpu, io, rss limits etc.
282 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
285 Collect extended task accounting data and send the data
286 to userland for processing over the taskstats interface.
290 config TASK_IO_ACCOUNTING
291 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
292 depends on TASK_XACCT
294 Collect information on the number of bytes of storage I/O which this
300 bool "Auditing support"
303 Enable auditing infrastructure that can be used with another
304 kernel subsystem, such as SELinux (which requires this for
305 logging of avc messages output). Does not do system-call
306 auditing without CONFIG_AUDITSYSCALL.
309 bool "Enable system-call auditing support"
310 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
311 default y if SECURITY_SELINUX
313 Enable low-overhead system-call auditing infrastructure that
314 can be used independently or with another kernel subsystem,
315 such as SELinux. To use audit's filesystem watch feature, please
316 ensure that INOTIFY is configured.
320 depends on AUDITSYSCALL
326 prompt "RCU Implementation"
330 bool "Tree-based hierarchical RCU"
332 This option selects the RCU implementation that is
333 designed for very large SMP system with hundreds or
334 thousands of CPUs. It also scales down nicely to
337 config TREE_PREEMPT_RCU
338 bool "Preemptable tree-based hierarchical RCU"
341 This option selects the RCU implementation that is
342 designed for very large SMP systems with hundreds or
343 thousands of CPUs, but for which real-time response
344 is also required. It also scales down nicely to
350 bool "Enable tracing for RCU"
351 depends on TREE_RCU || TREE_PREEMPT_RCU
353 This option provides tracing in RCU which presents stats
354 in debugfs for debugging RCU implementation.
356 Say Y here if you want to enable RCU tracing
357 Say N if you are unsure.
360 int "Tree-based hierarchical RCU fanout value"
363 depends on TREE_RCU || TREE_PREEMPT_RCU
367 This option controls the fanout of hierarchical implementations
368 of RCU, allowing RCU to work efficiently on machines with
369 large numbers of CPUs. This value must be at least the cube
370 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
371 systems and up to 262,144 for 64-bit systems.
373 Select a specific number if testing RCU itself.
374 Take the default if unsure.
376 config RCU_FANOUT_EXACT
377 bool "Disable tree-based hierarchical RCU auto-balancing"
378 depends on TREE_RCU || TREE_PREEMPT_RCU
381 This option forces use of the exact RCU_FANOUT value specified,
382 regardless of imbalances in the hierarchy. This is useful for
383 testing RCU itself, and might one day be useful on systems with
384 strong NUMA behavior.
386 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
390 config TREE_RCU_TRACE
391 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
394 This option provides tracing for the TREE_RCU and
395 TREE_PREEMPT_RCU implementations, permitting Makefile to
396 trivially select kernel/rcutree_trace.c.
398 endmenu # "RCU Subsystem"
401 tristate "Kernel .config support"
403 This option enables the complete Linux kernel ".config" file
404 contents to be saved in the kernel. It provides documentation
405 of which kernel options are used in a running kernel or in an
406 on-disk kernel. This information can be extracted from the kernel
407 image file with the script scripts/extract-ikconfig and used as
408 input to rebuild the current kernel or to build another kernel.
409 It can also be extracted from a running kernel by reading
410 /proc/config.gz if enabled (below).
413 bool "Enable access to .config through /proc/config.gz"
414 depends on IKCONFIG && PROC_FS
416 This option enables access to the kernel configuration file
417 through /proc/config.gz.
420 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
424 Select kernel log buffer size as a power of 2.
434 # Architectures with an unreliable sched_clock() should select this:
436 config HAVE_UNSTABLE_SCHED_CLOCK
440 boolean "Control Group support"
442 This option adds support for grouping sets of processes together, for
443 use with process control subsystems such as Cpusets, CFS, memory
444 controls or device isolation.
446 - Documentation/scheduler/sched-design-CFS.txt (CFS)
447 - Documentation/cgroups/ (features for grouping, isolation
448 and resource control)
455 bool "Example debug cgroup subsystem"
459 This option enables a simple cgroup subsystem that
460 exports useful debugging information about the cgroups
466 bool "Namespace cgroup subsystem"
469 Provides a simple namespace cgroup subsystem to
470 provide hierarchical naming of sets of namespaces,
471 for instance virtual servers and checkpoint/restart
474 config CGROUP_FREEZER
475 bool "Freezer cgroup subsystem"
478 Provides a way to freeze and unfreeze all tasks in a
482 bool "Device controller for cgroups"
483 depends on CGROUPS && EXPERIMENTAL
485 Provides a cgroup implementing whitelists for devices which
486 a process in the cgroup can mknod or open.
489 bool "Cpuset support"
492 This option will let you create and manage CPUSETs which
493 allow dynamically partitioning a system into sets of CPUs and
494 Memory Nodes and assigning tasks to run only within those sets.
495 This is primarily useful on large SMP or NUMA systems.
499 config PROC_PID_CPUSET
500 bool "Include legacy /proc/<pid>/cpuset file"
504 config CGROUP_CPUACCT
505 bool "Simple CPU accounting cgroup subsystem"
508 Provides a simple Resource Controller for monitoring the
509 total CPU consumed by the tasks in a cgroup.
511 config RESOURCE_COUNTERS
512 bool "Resource counters"
514 This option enables controller independent resource accounting
515 infrastructure that works with cgroups.
518 config CGROUP_MEM_RES_CTLR
519 bool "Memory Resource Controller for Control Groups"
520 depends on CGROUPS && RESOURCE_COUNTERS
523 Provides a memory resource controller that manages both anonymous
524 memory and page cache. (See Documentation/cgroups/memory.txt)
526 Note that setting this option increases fixed memory overhead
527 associated with each page of memory in the system. By this,
528 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
529 usage tracking struct at boot. Total amount of this is printed out
532 Only enable when you're ok with these trade offs and really
533 sure you need the memory resource controller. Even when you enable
534 this, you can set "cgroup_disable=memory" at your boot option to
535 disable memory resource controller and you can avoid overheads.
536 (and lose benefits of memory resource controller)
538 This config option also selects MM_OWNER config option, which
539 could in turn add some fork/exit overhead.
541 config CGROUP_MEM_RES_CTLR_SWAP
542 bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
543 depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
545 Add swap management feature to memory resource controller. When you
546 enable this, you can limit mem+swap usage per cgroup. In other words,
547 when you disable this, memory resource controller has no cares to
548 usage of swap...a process can exhaust all of the swap. This extension
549 is useful when you want to avoid exhaustion swap but this itself
550 adds more overheads and consumes memory for remembering information.
551 Especially if you use 32bit system or small memory system, please
552 be careful about enabling this. When memory resource controller
553 is disabled by boot option, this will be automatically disabled and
554 there will be no overhead from this. Even when you set this config=y,
555 if boot option "noswapaccount" is set, swap will not be accounted.
556 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
557 size is 4096bytes, 512k per 1Gbytes of swap.
559 menuconfig CGROUP_SCHED
560 bool "Group CPU scheduler"
561 depends on EXPERIMENTAL && CGROUPS
564 This feature lets CPU scheduler recognize task groups and control CPU
565 bandwidth allocation to such task groups. It uses cgroups to group
569 config FAIR_GROUP_SCHED
570 bool "Group scheduling for SCHED_OTHER"
571 depends on CGROUP_SCHED
574 config RT_GROUP_SCHED
575 bool "Group scheduling for SCHED_RR/FIFO"
576 depends on EXPERIMENTAL
577 depends on CGROUP_SCHED
580 This feature lets you explicitly allocate real CPU bandwidth
581 to task groups. If enabled, it will also make it impossible to
582 schedule realtime tasks for non-root users until you allocate
583 realtime bandwidth for them.
584 See Documentation/scheduler/sched-rt-group.txt for more information.
593 config SYSFS_DEPRECATED
596 config SYSFS_DEPRECATED_V2
597 bool "enable deprecated sysfs features which may confuse old userspace tools"
600 select SYSFS_DEPRECATED
602 This option switches the layout of sysfs to the deprecated
603 version. Do not use it on recent distributions.
605 The current sysfs layout features a unified device tree at
606 /sys/devices/, which is able to express a hierarchy between
607 class devices. If the deprecated option is set to Y, the
608 unified device tree is split into a bus device tree at
609 /sys/devices/ and several individual class device trees at
610 /sys/class/. The class and bus devices will be connected by
611 "<subsystem>:<name>" and the "device" links. The "block"
612 class devices, will not show up in /sys/class/block/. Some
613 subsystems will suppress the creation of some devices which
614 depend on the unified device tree.
616 This option is not a pure compatibility option that can
617 be safely enabled on newer distributions. It will change the
618 layout of sysfs to the non-extensible deprecated version,
619 and disable some features, which can not be exported without
620 confusing older userspace tools. Since 2007/2008 all major
621 distributions do not enable this option, and ship no tools which
622 depend on the deprecated layout or this option.
624 If you are using a new kernel on an older distribution, or use
625 older userspace tools, you might need to say Y here. Do not say Y,
626 if the original kernel, that came with your distribution, has
627 this option set to N.
630 bool "Kernel->user space relay support (formerly relayfs)"
632 This option enables support for relay interface support in
633 certain file systems (such as debugfs).
634 It is designed to provide an efficient mechanism for tools and
635 facilities to relay large amounts of data from kernel space to
641 bool "Namespaces support" if EMBEDDED
644 Provides the way to make tasks work with different objects using
645 the same id. For example same IPC id may refer to different objects
646 or same user id or pid may refer to different tasks when used in
647 different namespaces.
651 depends on NAMESPACES
653 In this namespace tasks see different info provided with the
658 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
660 In this namespace tasks work with IPC ids which correspond to
661 different IPC objects in different namespaces.
664 bool "User namespace (EXPERIMENTAL)"
665 depends on NAMESPACES && EXPERIMENTAL
667 This allows containers, i.e. vservers, to use user namespaces
668 to provide different user info for different servers.
672 bool "PID Namespaces (EXPERIMENTAL)"
674 depends on NAMESPACES && EXPERIMENTAL
676 Support process id namespaces. This allows having multiple
677 processes with the same pid as long as they are in different
678 pid namespaces. This is a building block of containers.
680 Unless you want to work with an experimental feature
684 bool "Network namespace"
686 depends on NAMESPACES && EXPERIMENTAL && NET
688 Allow user space to create what appear to be multiple instances
689 of the network stack.
691 config BLK_DEV_INITRD
692 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
693 depends on BROKEN || !FRV
695 The initial RAM filesystem is a ramfs which is loaded by the
696 boot loader (loadlin or lilo) and that is mounted as root
697 before the normal boot procedure. It is typically used to
698 load modules needed to mount the "real" root file system,
699 etc. See <file:Documentation/initrd.txt> for details.
701 If RAM disk support (BLK_DEV_RAM) is also included, this
702 also enables initial RAM disk (initrd) support and adds
703 15 Kbytes (more on some other architectures) to the kernel size.
713 config CC_OPTIMIZE_FOR_SIZE
714 bool "Optimize for size"
717 Enabling this option will pass "-Os" instead of "-O2" to gcc
718 resulting in a smaller kernel.
729 int "Default panic timeout"
732 Set default panic timeout.
735 bool "Configure standard kernel features (for small systems)"
737 This option allows certain base kernel options and settings
738 to be disabled or tweaked. This is for specialized
739 environments which can tolerate a "non-standard" kernel.
740 Only use this if you really know what you are doing.
743 bool "Enable 16-bit UID system calls" if EMBEDDED
744 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
747 This enables the legacy 16-bit UID syscall wrappers.
749 config SYSCTL_SYSCALL
750 bool "Sysctl syscall support" if EMBEDDED
754 sys_sysctl uses binary paths that have been found challenging
755 to properly maintain and use. The interface in /proc/sys
756 using paths with ascii names is now the primary path to this
759 Almost nothing using the binary sysctl interface so if you are
760 trying to save some space it is probably safe to disable this,
761 making your kernel marginally smaller.
763 If unsure say Y here.
766 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
769 Say Y here to let the kernel print out symbolic crash information and
770 symbolic stack backtraces. This increases the size of the kernel
771 somewhat, as all symbols have to be loaded into the kernel image.
774 bool "Include all symbols in kallsyms"
775 depends on DEBUG_KERNEL && KALLSYMS
777 Normally kallsyms only contains the symbols of functions, for nicer
778 OOPS messages. Some debuggers can use kallsyms for other
779 symbols too: say Y here to include all symbols, if you need them
780 and you don't care about adding 300k to the size of your kernel.
784 config KALLSYMS_EXTRA_PASS
785 bool "Do an extra kallsyms pass"
788 If kallsyms is not working correctly, the build will fail with
789 inconsistent kallsyms data. If that occurs, log a bug report and
790 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
791 Always say N here unless you find a bug in kallsyms, which must be
792 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
793 you wait for kallsyms to be fixed.
797 bool "Support for hot-pluggable devices" if EMBEDDED
800 This option is provided for the case where no hotplug or uevent
801 capabilities is wanted by the kernel. You should only consider
802 disabling this option for embedded systems that do not use modules, a
803 dynamic /dev tree, or dynamic device discovery. Just say Y.
807 bool "Enable support for printk" if EMBEDDED
809 This option enables normal printk support. Removing it
810 eliminates most of the message strings from the kernel image
811 and makes the kernel more or less silent. As this makes it
812 very difficult to diagnose system problems, saying N here is
813 strongly discouraged.
816 bool "BUG() support" if EMBEDDED
819 Disabling this option eliminates support for BUG and WARN, reducing
820 the size of your kernel image and potentially quietly ignoring
821 numerous fatal conditions. You should only consider disabling this
822 option for embedded systems with no facilities for reporting errors.
827 bool "Enable ELF core dumps" if EMBEDDED
829 Enable support for generating core dumps. Disabling saves about 4k.
831 config PCSPKR_PLATFORM
832 bool "Enable PC-Speaker support" if EMBEDDED
833 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
836 This option allows to disable the internal PC-Speaker
837 support, saving some memory.
841 bool "Enable full-sized data structures for core" if EMBEDDED
843 Disabling this option reduces the size of miscellaneous core
844 kernel data structures. This saves memory on small machines,
845 but may reduce performance.
848 bool "Enable futex support" if EMBEDDED
852 Disabling this option will cause the kernel to be built without
853 support for "fast userspace mutexes". The resulting kernel may not
854 run glibc-based applications correctly.
857 bool "Enable eventpoll support" if EMBEDDED
861 Disabling this option will cause the kernel to be built without
862 support for epoll family of system calls.
865 bool "Enable signalfd() system call" if EMBEDDED
869 Enable the signalfd() system call that allows to receive signals
870 on a file descriptor.
875 bool "Enable timerfd() system call" if EMBEDDED
879 Enable the timerfd() system call that allows to receive timer
880 events on a file descriptor.
885 bool "Enable eventfd() system call" if EMBEDDED
889 Enable the eventfd() system call that allows to receive both
890 kernel notification (ie. KAIO) or userspace notifications.
895 bool "Use full shmem filesystem" if EMBEDDED
899 The shmem is an internal filesystem used to manage shared memory.
900 It is backed by swap and manages resource limits. It is also exported
901 to userspace as tmpfs if TMPFS is enabled. Disabling this
902 option replaces shmem and tmpfs with the much simpler ramfs code,
903 which may be appropriate on small systems without swap.
906 bool "Enable the Anonymous Shared Memory Subsystem"
908 depends on SHMEM || TINY_SHMEM
910 The ashmem subsystem is a new shared memory allocator, similar to
911 POSIX SHM but with different behavior and sporting a simpler
915 bool "Enable AIO support" if EMBEDDED
918 This option enables POSIX asynchronous I/O which may by used
919 by some high performance threaded applications. Disabling
920 this option saves about 7k.
922 config HAVE_PERF_EVENTS
925 See tools/perf/design.txt for details.
927 config PERF_USE_VMALLOC
930 See tools/perf/design.txt for details
932 menu "Kernel Performance Events And Counters"
935 bool "Kernel performance events and counters"
936 default y if (PROFILING || PERF_COUNTERS)
937 depends on HAVE_PERF_EVENTS
940 Enable kernel support for various performance events provided
941 by software and hardware.
943 Software events are supported either built-in or via the
944 use of generic tracepoints.
946 Most modern CPUs support performance events via performance
947 counter registers. These registers count the number of certain
948 types of hw events: such as instructions executed, cachemisses
949 suffered, or branches mis-predicted - without slowing down the
950 kernel or applications. These registers can also trigger interrupts
951 when a threshold number of events have passed - and can thus be
952 used to profile the code that runs on that CPU.
954 The Linux Performance Event subsystem provides an abstraction of
955 these software and hardware event capabilities, available via a
956 system call and used by the "perf" utility in tools/perf/. It
957 provides per task and per CPU counters, and it provides event
958 capabilities on top of those.
963 bool "Tracepoint profiling sources"
964 depends on PERF_EVENTS && EVENT_TRACING
967 Allow the use of tracepoints as software performance events.
969 When this is enabled, you can create perf events based on
970 tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID
971 found in debugfs://tracing/events/*/*/id. (The -e/--events
972 option to the perf tool can parse and interpret symbolic
973 tracepoints, in the subsystem:tracepoint_name format.)
976 bool "Kernel performance counters (old config option)"
977 depends on HAVE_PERF_EVENTS
979 This config has been obsoleted by the PERF_EVENTS
980 config option - please see that one for details.
982 It has no effect on the kernel whether you enable
983 it or not, it is a compatibility placeholder.
987 config DEBUG_PERF_USE_VMALLOC
989 bool "Debug: use vmalloc to back perf mmap() buffers"
990 depends on PERF_EVENTS && DEBUG_KERNEL
991 select PERF_USE_VMALLOC
993 Use vmalloc memory to back perf mmap() buffers.
995 Mostly useful for debugging the vmalloc code on platforms
996 that don't require it.
1002 config VM_EVENT_COUNTERS
1004 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
1006 VM event counters are needed for event counts to be shown.
1007 This option allows the disabling of the VM event counters
1008 on EMBEDDED systems. /proc/vmstat will only show page counts
1009 if VM event counters are disabled.
1013 bool "Enable PCI quirk workarounds" if EMBEDDED
1016 This enables workarounds for various PCI chipset
1017 bugs/quirks. Disable this only if your target machine is
1018 unaffected by PCI quirks.
1022 bool "Enable SLUB debugging support" if EMBEDDED
1023 depends on SLUB && SYSFS
1025 SLUB has extensive debug support features. Disabling these can
1026 result in significant savings in code size. This also disables
1027 SLUB sysfs support. /sys/slab will not exist and there will be
1028 no support for cache validation etc.
1031 bool "Disable heap randomization"
1034 Randomizing heap placement makes heap exploits harder, but it
1035 also breaks ancient binaries (including anything libc5 based).
1036 This option changes the bootup default to heap randomization
1037 disabled, and can be overridden at runtime by setting
1038 /proc/sys/kernel/randomize_va_space to 2.
1040 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1043 prompt "Choose SLAB allocator"
1046 This option allows to select a slab allocator.
1051 The regular slab allocator that is established and known to work
1052 well in all environments. It organizes cache hot objects in
1053 per cpu and per node queues.
1056 depends on BROKEN || NUMA || !DISCONTIGMEM
1057 bool "SLUB (Unqueued Allocator)"
1059 SLUB is a slab allocator that minimizes cache line usage
1060 instead of managing queues of cached objects (SLAB approach).
1061 Per cpu caching is realized using slabs of objects instead
1062 of queues of objects. SLUB can use memory efficiently
1063 and has enhanced diagnostics. SLUB is the default choice for
1068 bool "SLOB (Simple Allocator)"
1070 SLOB replaces the stock allocator with a drastically simpler
1071 allocator. SLOB is generally more space efficient but
1072 does not perform as well on large systems.
1077 bool "Profiling support (EXPERIMENTAL)"
1079 Say Y here to enable the extended profiling support mechanisms used
1080 by profilers such as OProfile.
1083 # Place an empty function call at each tracepoint site. Can be
1084 # dynamically changed for a probe function.
1089 source "arch/Kconfig"
1095 The slow work thread pool provides a number of dynamically allocated
1096 threads that can be used by the kernel to perform operations that
1097 take a relatively long time.
1099 An example of this would be CacheFiles doing a path lookup followed
1100 by a series of mkdirs and a create call, all of which have to touch
1103 See Documentation/slow-work.txt.
1105 config SLOW_WORK_DEBUG
1106 bool "Slow work debugging through debugfs"
1108 depends on SLOW_WORK && DEBUG_FS
1110 Display the contents of the slow work run queue through debugfs,
1111 including items currently executing.
1113 See Documentation/slow-work.txt.
1115 endmenu # General setup
1117 config HAVE_GENERIC_DMA_COHERENT
1124 depends on SLAB || SLUB_DEBUG
1132 default 0 if BASE_FULL
1133 default 1 if !BASE_FULL
1136 bool "Enable loadable module support"
1138 Kernel modules are small pieces of compiled code which can
1139 be inserted in the running kernel, rather than being
1140 permanently built into the kernel. You use the "modprobe"
1141 tool to add (and sometimes remove) them. If you say Y here,
1142 many parts of the kernel can be built as modules (by
1143 answering M instead of Y where indicated): this is most
1144 useful for infrequently used options which are not required
1145 for booting. For more information, see the man pages for
1146 modprobe, lsmod, modinfo, insmod and rmmod.
1148 If you say Y here, you will need to run "make
1149 modules_install" to put the modules under /lib/modules/
1150 where modprobe can find them (you may need to be root to do
1157 config MODULE_FORCE_LOAD
1158 bool "Forced module loading"
1161 Allow loading of modules without version information (ie. modprobe
1162 --force). Forced module loading sets the 'F' (forced) taint flag and
1163 is usually a really bad idea.
1165 config MODULE_UNLOAD
1166 bool "Module unloading"
1168 Without this option you will not be able to unload any
1169 modules (note that some modules may not be unloadable
1170 anyway), which makes your kernel smaller, faster
1171 and simpler. If unsure, say Y.
1173 config MODULE_FORCE_UNLOAD
1174 bool "Forced module unloading"
1175 depends on MODULE_UNLOAD && EXPERIMENTAL
1177 This option allows you to force a module to unload, even if the
1178 kernel believes it is unsafe: the kernel will remove the module
1179 without waiting for anyone to stop using it (using the -f option to
1180 rmmod). This is mainly for kernel developers and desperate users.
1184 bool "Module versioning support"
1186 Usually, you have to use modules compiled with your kernel.
1187 Saying Y here makes it sometimes possible to use modules
1188 compiled for different kernels, by adding enough information
1189 to the modules to (hopefully) spot any changes which would
1190 make them incompatible with the kernel you are running. If
1193 config MODULE_SRCVERSION_ALL
1194 bool "Source checksum for all modules"
1196 Modules which contain a MODULE_VERSION get an extra "srcversion"
1197 field inserted into their modinfo section, which contains a
1198 sum of the source files which made it. This helps maintainers
1199 see exactly which source was used to build a module (since
1200 others sometimes change the module source without updating
1201 the version). With this option, such a "srcversion" field
1202 will be created for all modules. If unsure, say N.
1206 config INIT_ALL_POSSIBLE
1209 Back when each arch used to define their own cpu_online_map and
1210 cpu_possible_map, some of them chose to initialize cpu_possible_map
1211 with all 1s, and others with all 0s. When they were centralised,
1212 it was better to provide this option than to break all the archs
1213 and have several arch maintainers pursuing me down dark alleys.
1218 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1220 Need stop_machine() primitive.
1222 source "block/Kconfig"
1224 config PREEMPT_NOTIFIERS