7 option env="KERNELVERSION"
13 default "/lib/modules/$UNAME_RELEASE/.config"
14 default "/etc/kernel-config"
15 default "/boot/config-$UNAME_RELEASE"
16 default "$ARCH_DEFCONFIG"
17 default "arch/$ARCH/defconfig"
27 bool "Prompt for development and/or incomplete code/drivers"
29 Some of the various things that Linux supports (such as network
30 drivers, file systems, network protocols, etc.) can be in a state
31 of development where the functionality, stability, or the level of
32 testing is not yet high enough for general use. This is usually
33 known as the "alpha-test" phase among developers. If a feature is
34 currently in alpha-test, then the developers usually discourage
35 uninformed widespread use of this feature by the general public to
36 avoid "Why doesn't this work?" type mail messages. However, active
37 testing and use of these systems is welcomed. Just be aware that it
38 may not meet the normal level of reliability or it may fail to work
39 in some special cases. Detailed bug reports from people familiar
40 with the kernel internals are usually welcomed by the developers
41 (before submitting bug reports, please read the documents
42 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
43 <file:Documentation/BUG-HUNTING>, and
44 <file:Documentation/oops-tracing.txt> in the kernel source).
46 This option will also make obsoleted drivers available. These are
47 drivers that have been replaced by something else, and/or are
48 scheduled to be removed in a future kernel release.
50 Unless you intend to help test and develop a feature or driver that
51 falls into this category, or you have a situation that requires
52 using these features, you should probably say N here, which will
53 cause the configurator to present you with fewer choices. If
54 you say Y here, you will be offered the choice of using features or
55 drivers that are currently considered to be in the alpha-test phase.
62 depends on BROKEN || !SMP
67 depends on SMP || PREEMPT
70 config INIT_ENV_ARG_LIMIT
75 Maximum of each of the number of arguments and environment
76 variables passed to init from the kernel command line.
80 string "Local version - append to kernel release"
82 Append an extra string to the end of your kernel version.
83 This will show up when you type uname, for example.
84 The string you set here will be appended after the contents of
85 any files with a filename matching localversion* in your
86 object and source tree, in that order. Your total string can
87 be a maximum of 64 characters.
89 config LOCALVERSION_AUTO
90 bool "Automatically append version information to the version string"
93 This will try to automatically determine if the current tree is a
94 release tree by looking for git tags that belong to the current
97 A string of the format -gxxxxxxxx will be added to the localversion
98 if a git-based tree is found. The string generated by this will be
99 appended after any matching localversion* files, and after the value
100 set in CONFIG_LOCALVERSION.
102 (The actual string used here is the first eight characters produced
103 by running the command:
105 $ git rev-parse --verify HEAD
107 which is done within the script "scripts/setlocalversion".)
109 config HAVE_KERNEL_GZIP
112 config HAVE_KERNEL_BZIP2
115 config HAVE_KERNEL_LZMA
119 prompt "Kernel compression mode"
121 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA
123 The linux kernel is a kind of self-extracting executable.
124 Several compression algorithms are available, which differ
125 in efficiency, compression and decompression speed.
126 Compression speed is only relevant when building a kernel.
127 Decompression speed is relevant at each boot.
129 If you have any problems with bzip2 or lzma compressed
130 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
131 version of this functionality (bzip2 only), for 2.4, was
132 supplied by Christian Ludwig)
134 High compression options are mostly useful for users, who
135 are low on disk space (embedded systems), but for whom ram
138 If in doubt, select 'gzip'
142 depends on HAVE_KERNEL_GZIP
144 The old and tried gzip compression. Its compression ratio is
145 the poorest among the 3 choices; however its speed (both
146 compression and decompression) is the fastest.
150 depends on HAVE_KERNEL_BZIP2
152 Its compression ratio and speed is intermediate.
153 Decompression speed is slowest among the three. The kernel
154 size is about 10% smaller with bzip2, in comparison to gzip.
155 Bzip2 uses a large amount of memory. For modern kernels you
156 will need at least 8MB RAM or more for booting.
160 depends on HAVE_KERNEL_LZMA
162 The most recent compression algorithm.
163 Its ratio is best, decompression speed is between the other
164 two. Compression is slowest. The kernel size is about 33%
165 smaller with LZMA in comparison to gzip.
170 bool "Support for paging of anonymous memory (swap)"
171 depends on MMU && BLOCK
174 This option allows you to choose whether you want to have support
175 for so called swap devices or swap files in your kernel that are
176 used to provide more virtual memory than the actual RAM present
177 in your computer. If unsure say Y.
182 Inter Process Communication is a suite of library functions and
183 system calls which let processes (running programs) synchronize and
184 exchange information. It is generally considered to be a good thing,
185 and some programs won't run unless you say Y here. In particular, if
186 you want to run the DOS emulator dosemu under Linux (read the
187 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
188 you'll need to say Y here.
190 You can find documentation about IPC with "info ipc" and also in
191 section 6.4 of the Linux Programmer's Guide, available from
192 <http://www.tldp.org/guides.html>.
194 config SYSVIPC_SYSCTL
201 bool "POSIX Message Queues"
202 depends on NET && EXPERIMENTAL
204 POSIX variant of message queues is a part of IPC. In POSIX message
205 queues every message has a priority which decides about succession
206 of receiving it by a process. If you want to compile and run
207 programs written e.g. for Solaris with use of its POSIX message
208 queues (functions mq_*) say Y here.
210 POSIX message queues are visible as a filesystem called 'mqueue'
211 and can be mounted somewhere if you want to do filesystem
212 operations on message queues.
216 config POSIX_MQUEUE_SYSCTL
218 depends on POSIX_MQUEUE
222 config BSD_PROCESS_ACCT
223 bool "BSD Process Accounting"
225 If you say Y here, a user level program will be able to instruct the
226 kernel (via a special system call) to write process accounting
227 information to a file: whenever a process exits, information about
228 that process will be appended to the file by the kernel. The
229 information includes things such as creation time, owning user,
230 command name, memory usage, controlling terminal etc. (the complete
231 list is in the struct acct in <file:include/linux/acct.h>). It is
232 up to the user level program to do useful things with this
233 information. This is generally a good idea, so say Y.
235 config BSD_PROCESS_ACCT_V3
236 bool "BSD Process Accounting version 3 file format"
237 depends on BSD_PROCESS_ACCT
240 If you say Y here, the process accounting information is written
241 in a new file format that also logs the process IDs of each
242 process and it's parent. Note that this file format is incompatible
243 with previous v0/v1/v2 file formats, so you will need updated tools
244 for processing it. A preliminary version of these tools is available
245 at <http://www.gnu.org/software/acct/>.
248 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
252 Export selected statistics for tasks/processes through the
253 generic netlink interface. Unlike BSD process accounting, the
254 statistics are available during the lifetime of tasks/processes as
255 responses to commands. Like BSD accounting, they are sent to user
260 config TASK_DELAY_ACCT
261 bool "Enable per-task delay accounting (EXPERIMENTAL)"
264 Collect information on time spent by a task waiting for system
265 resources like cpu, synchronous block I/O completion and swapping
266 in pages. Such statistics can help in setting a task's priorities
267 relative to other tasks for cpu, io, rss limits etc.
272 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
275 Collect extended task accounting data and send the data
276 to userland for processing over the taskstats interface.
280 config TASK_IO_ACCOUNTING
281 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
282 depends on TASK_XACCT
284 Collect information on the number of bytes of storage I/O which this
290 bool "Auditing support"
293 Enable auditing infrastructure that can be used with another
294 kernel subsystem, such as SELinux (which requires this for
295 logging of avc messages output). Does not do system-call
296 auditing without CONFIG_AUDITSYSCALL.
299 bool "Enable system-call auditing support"
300 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH)
301 default y if SECURITY_SELINUX
303 Enable low-overhead system-call auditing infrastructure that
304 can be used independently or with another kernel subsystem,
305 such as SELinux. To use audit's filesystem watch feature, please
306 ensure that INOTIFY is configured.
310 depends on AUDITSYSCALL
316 prompt "RCU Implementation"
320 bool "Tree-based hierarchical RCU"
322 This option selects the RCU implementation that is
323 designed for very large SMP system with hundreds or
324 thousands of CPUs. It also scales down nicely to
327 config TREE_PREEMPT_RCU
328 bool "Preemptable tree-based hierarchical RCU"
331 This option selects the RCU implementation that is
332 designed for very large SMP systems with hundreds or
333 thousands of CPUs, but for which real-time response
334 is also required. It also scales down nicely to
340 bool "Enable tracing for RCU"
341 depends on TREE_RCU || TREE_PREEMPT_RCU
343 This option provides tracing in RCU which presents stats
344 in debugfs for debugging RCU implementation.
346 Say Y here if you want to enable RCU tracing
347 Say N if you are unsure.
350 int "Tree-based hierarchical RCU fanout value"
353 depends on TREE_RCU || TREE_PREEMPT_RCU
357 This option controls the fanout of hierarchical implementations
358 of RCU, allowing RCU to work efficiently on machines with
359 large numbers of CPUs. This value must be at least the cube
360 root of NR_CPUS, which allows NR_CPUS up to 32,768 for 32-bit
361 systems and up to 262,144 for 64-bit systems.
363 Select a specific number if testing RCU itself.
364 Take the default if unsure.
366 config RCU_FANOUT_EXACT
367 bool "Disable tree-based hierarchical RCU auto-balancing"
368 depends on TREE_RCU || TREE_PREEMPT_RCU
371 This option forces use of the exact RCU_FANOUT value specified,
372 regardless of imbalances in the hierarchy. This is useful for
373 testing RCU itself, and might one day be useful on systems with
374 strong NUMA behavior.
376 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
380 config TREE_RCU_TRACE
381 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
384 This option provides tracing for the TREE_RCU and
385 TREE_PREEMPT_RCU implementations, permitting Makefile to
386 trivially select kernel/rcutree_trace.c.
388 endmenu # "RCU Subsystem"
391 tristate "Kernel .config support"
393 This option enables the complete Linux kernel ".config" file
394 contents to be saved in the kernel. It provides documentation
395 of which kernel options are used in a running kernel or in an
396 on-disk kernel. This information can be extracted from the kernel
397 image file with the script scripts/extract-ikconfig and used as
398 input to rebuild the current kernel or to build another kernel.
399 It can also be extracted from a running kernel by reading
400 /proc/config.gz if enabled (below).
403 bool "Enable access to .config through /proc/config.gz"
404 depends on IKCONFIG && PROC_FS
406 This option enables access to the kernel configuration file
407 through /proc/config.gz.
410 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
414 Select kernel log buffer size as a power of 2.
424 # Architectures with an unreliable sched_clock() should select this:
426 config HAVE_UNSTABLE_SCHED_CLOCK
430 boolean "Control Group support"
432 This option adds support for grouping sets of processes together, for
433 use with process control subsystems such as Cpusets, CFS, memory
434 controls or device isolation.
436 - Documentation/scheduler/sched-design-CFS.txt (CFS)
437 - Documentation/cgroups/ (features for grouping, isolation
438 and resource control)
445 bool "Example debug cgroup subsystem"
449 This option enables a simple cgroup subsystem that
450 exports useful debugging information about the cgroups
456 bool "Namespace cgroup subsystem"
459 Provides a simple namespace cgroup subsystem to
460 provide hierarchical naming of sets of namespaces,
461 for instance virtual servers and checkpoint/restart
464 config CGROUP_FREEZER
465 bool "Freezer cgroup subsystem"
468 Provides a way to freeze and unfreeze all tasks in a
472 bool "Device controller for cgroups"
473 depends on CGROUPS && EXPERIMENTAL
475 Provides a cgroup implementing whitelists for devices which
476 a process in the cgroup can mknod or open.
479 bool "Cpuset support"
482 This option will let you create and manage CPUSETs which
483 allow dynamically partitioning a system into sets of CPUs and
484 Memory Nodes and assigning tasks to run only within those sets.
485 This is primarily useful on large SMP or NUMA systems.
489 config PROC_PID_CPUSET
490 bool "Include legacy /proc/<pid>/cpuset file"
494 config CGROUP_CPUACCT
495 bool "Simple CPU accounting cgroup subsystem"
498 Provides a simple Resource Controller for monitoring the
499 total CPU consumed by the tasks in a cgroup.
501 config RESOURCE_COUNTERS
502 bool "Resource counters"
504 This option enables controller independent resource accounting
505 infrastructure that works with cgroups.
508 config CGROUP_MEM_RES_CTLR
509 bool "Memory Resource Controller for Control Groups"
510 depends on CGROUPS && RESOURCE_COUNTERS
513 Provides a memory resource controller that manages both anonymous
514 memory and page cache. (See Documentation/cgroups/memory.txt)
516 Note that setting this option increases fixed memory overhead
517 associated with each page of memory in the system. By this,
518 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
519 usage tracking struct at boot. Total amount of this is printed out
522 Only enable when you're ok with these trade offs and really
523 sure you need the memory resource controller. Even when you enable
524 this, you can set "cgroup_disable=memory" at your boot option to
525 disable memory resource controller and you can avoid overheads.
526 (and lose benefits of memory resource controller)
528 This config option also selects MM_OWNER config option, which
529 could in turn add some fork/exit overhead.
531 config CGROUP_MEM_RES_CTLR_SWAP
532 bool "Memory Resource Controller Swap Extension(EXPERIMENTAL)"
533 depends on CGROUP_MEM_RES_CTLR && SWAP && EXPERIMENTAL
535 Add swap management feature to memory resource controller. When you
536 enable this, you can limit mem+swap usage per cgroup. In other words,
537 when you disable this, memory resource controller has no cares to
538 usage of swap...a process can exhaust all of the swap. This extension
539 is useful when you want to avoid exhaustion swap but this itself
540 adds more overheads and consumes memory for remembering information.
541 Especially if you use 32bit system or small memory system, please
542 be careful about enabling this. When memory resource controller
543 is disabled by boot option, this will be automatically disabled and
544 there will be no overhead from this. Even when you set this config=y,
545 if boot option "noswapaccount" is set, swap will not be accounted.
546 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
547 size is 4096bytes, 512k per 1Gbytes of swap.
549 menuconfig CGROUP_SCHED
550 bool "Group CPU scheduler"
551 depends on EXPERIMENTAL && CGROUPS
554 This feature lets CPU scheduler recognize task groups and control CPU
555 bandwidth allocation to such task groups. It uses cgroups to group
559 config FAIR_GROUP_SCHED
560 bool "Group scheduling for SCHED_OTHER"
561 depends on CGROUP_SCHED
564 config RT_GROUP_SCHED
565 bool "Group scheduling for SCHED_RR/FIFO"
566 depends on EXPERIMENTAL
567 depends on CGROUP_SCHED
570 This feature lets you explicitly allocate real CPU bandwidth
571 to users or control groups (depending on the "Basis for grouping tasks"
572 setting below. If enabled, it will also make it impossible to
573 schedule realtime tasks for non-root users until you allocate
574 realtime bandwidth for them.
575 See Documentation/scheduler/sched-rt-group.txt for more information.
584 config SYSFS_DEPRECATED
587 config SYSFS_DEPRECATED_V2
588 bool "enable deprecated sysfs features which may confuse old userspace tools"
591 select SYSFS_DEPRECATED
593 This option switches the layout of sysfs to the deprecated
594 version. Do not use it on recent distributions.
596 The current sysfs layout features a unified device tree at
597 /sys/devices/, which is able to express a hierarchy between
598 class devices. If the deprecated option is set to Y, the
599 unified device tree is split into a bus device tree at
600 /sys/devices/ and several individual class device trees at
601 /sys/class/. The class and bus devices will be connected by
602 "<subsystem>:<name>" and the "device" links. The "block"
603 class devices, will not show up in /sys/class/block/. Some
604 subsystems will suppress the creation of some devices which
605 depend on the unified device tree.
607 This option is not a pure compatibility option that can
608 be safely enabled on newer distributions. It will change the
609 layout of sysfs to the non-extensible deprecated version,
610 and disable some features, which can not be exported without
611 confusing older userspace tools. Since 2007/2008 all major
612 distributions do not enable this option, and ship no tools which
613 depend on the deprecated layout or this option.
615 If you are using a new kernel on an older distribution, or use
616 older userspace tools, you might need to say Y here. Do not say Y,
617 if the original kernel, that came with your distribution, has
618 this option set to N.
621 bool "Kernel->user space relay support (formerly relayfs)"
623 This option enables support for relay interface support in
624 certain file systems (such as debugfs).
625 It is designed to provide an efficient mechanism for tools and
626 facilities to relay large amounts of data from kernel space to
632 bool "Namespaces support" if EMBEDDED
635 Provides the way to make tasks work with different objects using
636 the same id. For example same IPC id may refer to different objects
637 or same user id or pid may refer to different tasks when used in
638 different namespaces.
642 depends on NAMESPACES
644 In this namespace tasks see different info provided with the
649 depends on NAMESPACES && (SYSVIPC || POSIX_MQUEUE)
651 In this namespace tasks work with IPC ids which correspond to
652 different IPC objects in different namespaces.
655 bool "User namespace (EXPERIMENTAL)"
656 depends on NAMESPACES && EXPERIMENTAL
658 This allows containers, i.e. vservers, to use user namespaces
659 to provide different user info for different servers.
663 bool "PID Namespaces (EXPERIMENTAL)"
665 depends on NAMESPACES && EXPERIMENTAL
667 Support process id namespaces. This allows having multiple
668 processes with the same pid as long as they are in different
669 pid namespaces. This is a building block of containers.
671 Unless you want to work with an experimental feature
675 bool "Network namespace"
677 depends on NAMESPACES && EXPERIMENTAL && NET
679 Allow user space to create what appear to be multiple instances
680 of the network stack.
682 config BLK_DEV_INITRD
683 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
684 depends on BROKEN || !FRV
686 The initial RAM filesystem is a ramfs which is loaded by the
687 boot loader (loadlin or lilo) and that is mounted as root
688 before the normal boot procedure. It is typically used to
689 load modules needed to mount the "real" root file system,
690 etc. See <file:Documentation/initrd.txt> for details.
692 If RAM disk support (BLK_DEV_RAM) is also included, this
693 also enables initial RAM disk (initrd) support and adds
694 15 Kbytes (more on some other architectures) to the kernel size.
704 config CC_OPTIMIZE_FOR_SIZE
705 bool "Optimize for size"
708 Enabling this option will pass "-Os" instead of "-O2" to gcc
709 resulting in a smaller kernel.
720 bool "Configure standard kernel features (for small systems)"
722 This option allows certain base kernel options and settings
723 to be disabled or tweaked. This is for specialized
724 environments which can tolerate a "non-standard" kernel.
725 Only use this if you really know what you are doing.
728 bool "Enable 16-bit UID system calls" if EMBEDDED
729 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
732 This enables the legacy 16-bit UID syscall wrappers.
734 config SYSCTL_SYSCALL
735 bool "Sysctl syscall support" if EMBEDDED
739 sys_sysctl uses binary paths that have been found challenging
740 to properly maintain and use. The interface in /proc/sys
741 using paths with ascii names is now the primary path to this
744 Almost nothing using the binary sysctl interface so if you are
745 trying to save some space it is probably safe to disable this,
746 making your kernel marginally smaller.
748 If unsure say Y here.
751 bool "Load all symbols for debugging/ksymoops" if EMBEDDED
754 Say Y here to let the kernel print out symbolic crash information and
755 symbolic stack backtraces. This increases the size of the kernel
756 somewhat, as all symbols have to be loaded into the kernel image.
759 bool "Include all symbols in kallsyms"
760 depends on DEBUG_KERNEL && KALLSYMS
762 Normally kallsyms only contains the symbols of functions, for nicer
763 OOPS messages. Some debuggers can use kallsyms for other
764 symbols too: say Y here to include all symbols, if you need them
765 and you don't care about adding 300k to the size of your kernel.
769 config KALLSYMS_EXTRA_PASS
770 bool "Do an extra kallsyms pass"
773 If kallsyms is not working correctly, the build will fail with
774 inconsistent kallsyms data. If that occurs, log a bug report and
775 turn on KALLSYMS_EXTRA_PASS which should result in a stable build.
776 Always say N here unless you find a bug in kallsyms, which must be
777 reported. KALLSYMS_EXTRA_PASS is only a temporary workaround while
778 you wait for kallsyms to be fixed.
782 bool "Support for hot-pluggable devices" if EMBEDDED
785 This option is provided for the case where no hotplug or uevent
786 capabilities is wanted by the kernel. You should only consider
787 disabling this option for embedded systems that do not use modules, a
788 dynamic /dev tree, or dynamic device discovery. Just say Y.
792 bool "Enable support for printk" if EMBEDDED
794 This option enables normal printk support. Removing it
795 eliminates most of the message strings from the kernel image
796 and makes the kernel more or less silent. As this makes it
797 very difficult to diagnose system problems, saying N here is
798 strongly discouraged.
801 bool "BUG() support" if EMBEDDED
804 Disabling this option eliminates support for BUG and WARN, reducing
805 the size of your kernel image and potentially quietly ignoring
806 numerous fatal conditions. You should only consider disabling this
807 option for embedded systems with no facilities for reporting errors.
812 bool "Enable ELF core dumps" if EMBEDDED
814 Enable support for generating core dumps. Disabling saves about 4k.
816 config PCSPKR_PLATFORM
817 bool "Enable PC-Speaker support" if EMBEDDED
818 depends on ALPHA || X86 || MIPS || PPC_PREP || PPC_CHRP || PPC_PSERIES
821 This option allows to disable the internal PC-Speaker
822 support, saving some memory.
826 bool "Enable full-sized data structures for core" if EMBEDDED
828 Disabling this option reduces the size of miscellaneous core
829 kernel data structures. This saves memory on small machines,
830 but may reduce performance.
833 bool "Enable futex support" if EMBEDDED
837 Disabling this option will cause the kernel to be built without
838 support for "fast userspace mutexes". The resulting kernel may not
839 run glibc-based applications correctly.
842 bool "Enable eventpoll support" if EMBEDDED
846 Disabling this option will cause the kernel to be built without
847 support for epoll family of system calls.
850 bool "Enable signalfd() system call" if EMBEDDED
854 Enable the signalfd() system call that allows to receive signals
855 on a file descriptor.
860 bool "Enable timerfd() system call" if EMBEDDED
864 Enable the timerfd() system call that allows to receive timer
865 events on a file descriptor.
870 bool "Enable eventfd() system call" if EMBEDDED
874 Enable the eventfd() system call that allows to receive both
875 kernel notification (ie. KAIO) or userspace notifications.
880 bool "Use full shmem filesystem" if EMBEDDED
884 The shmem is an internal filesystem used to manage shared memory.
885 It is backed by swap and manages resource limits. It is also exported
886 to userspace as tmpfs if TMPFS is enabled. Disabling this
887 option replaces shmem and tmpfs with the much simpler ramfs code,
888 which may be appropriate on small systems without swap.
891 bool "Enable AIO support" if EMBEDDED
894 This option enables POSIX asynchronous I/O which may by used
895 by some high performance threaded applications. Disabling
896 this option saves about 7k.
898 config HAVE_PERF_EVENTS
901 See tools/perf/design.txt for details.
903 config PERF_USE_VMALLOC
906 See tools/perf/design.txt for details
908 menu "Kernel Performance Events And Counters"
911 bool "Kernel performance events and counters"
912 default y if (PROFILING || PERF_COUNTERS)
913 depends on HAVE_PERF_EVENTS
916 Enable kernel support for various performance events provided
917 by software and hardware.
919 Software events are supported either built-in or via the
920 use of generic tracepoints.
922 Most modern CPUs support performance events via performance
923 counter registers. These registers count the number of certain
924 types of hw events: such as instructions executed, cachemisses
925 suffered, or branches mis-predicted - without slowing down the
926 kernel or applications. These registers can also trigger interrupts
927 when a threshold number of events have passed - and can thus be
928 used to profile the code that runs on that CPU.
930 The Linux Performance Event subsystem provides an abstraction of
931 these software and hardware event capabilities, available via a
932 system call and used by the "perf" utility in tools/perf/. It
933 provides per task and per CPU counters, and it provides event
934 capabilities on top of those.
939 bool "Tracepoint profiling sources"
940 depends on PERF_EVENTS && EVENT_TRACING
943 Allow the use of tracepoints as software performance events.
945 When this is enabled, you can create perf events based on
946 tracepoints using PERF_TYPE_TRACEPOINT and the tracepoint ID
947 found in debugfs://tracing/events/*/*/id. (The -e/--events
948 option to the perf tool can parse and interpret symbolic
949 tracepoints, in the subsystem:tracepoint_name format.)
952 bool "Kernel performance counters (old config option)"
953 depends on HAVE_PERF_EVENTS
955 This config has been obsoleted by the PERF_EVENTS
956 config option - please see that one for details.
958 It has no effect on the kernel whether you enable
959 it or not, it is a compatibility placeholder.
963 config DEBUG_PERF_USE_VMALLOC
965 bool "Debug: use vmalloc to back perf mmap() buffers"
966 depends on PERF_EVENTS && DEBUG_KERNEL
967 select PERF_USE_VMALLOC
969 Use vmalloc memory to back perf mmap() buffers.
971 Mostly useful for debugging the vmalloc code on platforms
972 that don't require it.
978 config VM_EVENT_COUNTERS
980 bool "Enable VM event counters for /proc/vmstat" if EMBEDDED
982 VM event counters are needed for event counts to be shown.
983 This option allows the disabling of the VM event counters
984 on EMBEDDED systems. /proc/vmstat will only show page counts
985 if VM event counters are disabled.
989 bool "Enable PCI quirk workarounds" if EMBEDDED
992 This enables workarounds for various PCI chipset
993 bugs/quirks. Disable this only if your target machine is
994 unaffected by PCI quirks.
998 bool "Enable SLUB debugging support" if EMBEDDED
999 depends on SLUB && SYSFS
1001 SLUB has extensive debug support features. Disabling these can
1002 result in significant savings in code size. This also disables
1003 SLUB sysfs support. /sys/slab will not exist and there will be
1004 no support for cache validation etc.
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.
1064 source "arch/Kconfig"
1070 The slow work thread pool provides a number of dynamically allocated
1071 threads that can be used by the kernel to perform operations that
1072 take a relatively long time.
1074 An example of this would be CacheFiles doing a path lookup followed
1075 by a series of mkdirs and a create call, all of which have to touch
1078 See Documentation/slow-work.txt.
1080 config SLOW_WORK_DEBUG
1081 bool "Slow work debugging through debugfs"
1083 depends on SLOW_WORK && DEBUG_FS
1085 Display the contents of the slow work run queue through debugfs,
1086 including items currently executing.
1088 See Documentation/slow-work.txt.
1090 endmenu # General setup
1092 config HAVE_GENERIC_DMA_COHERENT
1099 depends on SLAB || SLUB_DEBUG
1107 default 0 if BASE_FULL
1108 default 1 if !BASE_FULL
1111 bool "Enable loadable module support"
1113 Kernel modules are small pieces of compiled code which can
1114 be inserted in the running kernel, rather than being
1115 permanently built into the kernel. You use the "modprobe"
1116 tool to add (and sometimes remove) them. If you say Y here,
1117 many parts of the kernel can be built as modules (by
1118 answering M instead of Y where indicated): this is most
1119 useful for infrequently used options which are not required
1120 for booting. For more information, see the man pages for
1121 modprobe, lsmod, modinfo, insmod and rmmod.
1123 If you say Y here, you will need to run "make
1124 modules_install" to put the modules under /lib/modules/
1125 where modprobe can find them (you may need to be root to do
1132 config MODULE_FORCE_LOAD
1133 bool "Forced module loading"
1136 Allow loading of modules without version information (ie. modprobe
1137 --force). Forced module loading sets the 'F' (forced) taint flag and
1138 is usually a really bad idea.
1140 config MODULE_UNLOAD
1141 bool "Module unloading"
1143 Without this option you will not be able to unload any
1144 modules (note that some modules may not be unloadable
1145 anyway), which makes your kernel smaller, faster
1146 and simpler. If unsure, say Y.
1148 config MODULE_FORCE_UNLOAD
1149 bool "Forced module unloading"
1150 depends on MODULE_UNLOAD && EXPERIMENTAL
1152 This option allows you to force a module to unload, even if the
1153 kernel believes it is unsafe: the kernel will remove the module
1154 without waiting for anyone to stop using it (using the -f option to
1155 rmmod). This is mainly for kernel developers and desperate users.
1159 bool "Module versioning support"
1161 Usually, you have to use modules compiled with your kernel.
1162 Saying Y here makes it sometimes possible to use modules
1163 compiled for different kernels, by adding enough information
1164 to the modules to (hopefully) spot any changes which would
1165 make them incompatible with the kernel you are running. If
1168 config MODULE_SRCVERSION_ALL
1169 bool "Source checksum for all modules"
1171 Modules which contain a MODULE_VERSION get an extra "srcversion"
1172 field inserted into their modinfo section, which contains a
1173 sum of the source files which made it. This helps maintainers
1174 see exactly which source was used to build a module (since
1175 others sometimes change the module source without updating
1176 the version). With this option, such a "srcversion" field
1177 will be created for all modules. If unsure, say N.
1181 config INIT_ALL_POSSIBLE
1184 Back when each arch used to define their own cpu_online_map and
1185 cpu_possible_map, some of them chose to initialize cpu_possible_map
1186 with all 1s, and others with all 0s. When they were centralised,
1187 it was better to provide this option than to break all the archs
1188 and have several arch maintainers pursuing me down dark alleys.
1193 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1195 Need stop_machine() primitive.
1197 source "block/Kconfig"
1199 config PREEMPT_NOTIFIERS