4 config ENTERPRISE_SUPPORT
5 bool "Enable enterprise support facility"
8 This feature enables the handling of the "supported" module flag.
9 This flag can be used to report unsupported module loads or even
10 refuse them entirely. It is useful when ensuring that the kernel
11 remains in a state that Novell Technical Services, or its
12 technical partners, is prepared to support.
14 Modules in the list of supported modules will be marked supported
15 on build. The default enforcement mode is to report, but not
16 deny, loading of unsupported modules.
18 If you aren't building a kernel for an enterprise distribution,
22 bool "Split the kernel package into multiple RPMs"
23 depends on SUSE_KERNEL && MODULES
25 This is an option used by the kernel packaging infrastructure
26 to split kernel modules into different packages. It isn't used
27 by the kernel itself, but allows the the packager to make
28 decisions on a per-config basis.
30 If you aren't packaging a kernel for distribution, it's safe to
34 bool "Kernel to suit desktop workloads"
36 This is an option used to tune kernel parameters to better suit
45 option env="KERNELVERSION"
51 default "/lib/modules/$UNAME_RELEASE/.config"
52 default "/etc/kernel-config"
53 default "/boot/config-$UNAME_RELEASE"
54 default "$ARCH_DEFCONFIG"
55 default "arch/$ARCH/defconfig"
66 depends on HAVE_IRQ_WORK
71 bool "Prompt for development and/or incomplete code/drivers"
73 Some of the various things that Linux supports (such as network
74 drivers, file systems, network protocols, etc.) can be in a state
75 of development where the functionality, stability, or the level of
76 testing is not yet high enough for general use. This is usually
77 known as the "alpha-test" phase among developers. If a feature is
78 currently in alpha-test, then the developers usually discourage
79 uninformed widespread use of this feature by the general public to
80 avoid "Why doesn't this work?" type mail messages. However, active
81 testing and use of these systems is welcomed. Just be aware that it
82 may not meet the normal level of reliability or it may fail to work
83 in some special cases. Detailed bug reports from people familiar
84 with the kernel internals are usually welcomed by the developers
85 (before submitting bug reports, please read the documents
86 <file:README>, <file:MAINTAINERS>, <file:REPORTING-BUGS>,
87 <file:Documentation/BUG-HUNTING>, and
88 <file:Documentation/oops-tracing.txt> in the kernel source).
90 This option will also make obsoleted drivers available. These are
91 drivers that have been replaced by something else, and/or are
92 scheduled to be removed in a future kernel release.
94 Unless you intend to help test and develop a feature or driver that
95 falls into this category, or you have a situation that requires
96 using these features, you should probably say N here, which will
97 cause the configurator to present you with fewer choices. If
98 you say Y here, you will be offered the choice of using features or
99 drivers that are currently considered to be in the alpha-test phase.
106 depends on BROKEN || !SMP
109 config INIT_ENV_ARG_LIMIT
114 Maximum of each of the number of arguments and environment
115 variables passed to init from the kernel command line.
119 string "Cross-compiler tool prefix"
121 Same as running 'make CROSS_COMPILE=prefix-' but stored for
122 default make runs in this kernel build directory. You don't
123 need to set this unless you want the configured kernel build
124 directory to select the cross-compiler automatically.
127 string "Local version - append to kernel release"
129 Append an extra string to the end of your kernel version.
130 This will show up when you type uname, for example.
131 The string you set here will be appended after the contents of
132 any files with a filename matching localversion* in your
133 object and source tree, in that order. Your total string can
134 be a maximum of 64 characters.
136 config LOCALVERSION_AUTO
137 bool "Automatically append version information to the version string"
140 This will try to automatically determine if the current tree is a
141 release tree by looking for git tags that belong to the current
142 top of tree revision.
144 A string of the format -gxxxxxxxx will be added to the localversion
145 if a git-based tree is found. The string generated by this will be
146 appended after any matching localversion* files, and after the value
147 set in CONFIG_LOCALVERSION.
149 (The actual string used here is the first eight characters produced
150 by running the command:
152 $ git rev-parse --verify HEAD
154 which is done within the script "scripts/setlocalversion".)
156 config HAVE_KERNEL_GZIP
159 config HAVE_KERNEL_BZIP2
162 config HAVE_KERNEL_LZMA
165 config HAVE_KERNEL_XZ
168 config HAVE_KERNEL_LZO
172 prompt "Kernel compression mode"
174 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO
176 The linux kernel is a kind of self-extracting executable.
177 Several compression algorithms are available, which differ
178 in efficiency, compression and decompression speed.
179 Compression speed is only relevant when building a kernel.
180 Decompression speed is relevant at each boot.
182 If you have any problems with bzip2 or lzma compressed
183 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
184 version of this functionality (bzip2 only), for 2.4, was
185 supplied by Christian Ludwig)
187 High compression options are mostly useful for users, who
188 are low on disk space (embedded systems), but for whom ram
191 If in doubt, select 'gzip'
195 depends on HAVE_KERNEL_GZIP
197 The old and tried gzip compression. It provides a good balance
198 between compression ratio and decompression speed.
202 depends on HAVE_KERNEL_BZIP2
204 Its compression ratio and speed is intermediate.
205 Decompression speed is slowest among the three. The kernel
206 size is about 10% smaller with bzip2, in comparison to gzip.
207 Bzip2 uses a large amount of memory. For modern kernels you
208 will need at least 8MB RAM or more for booting.
212 depends on HAVE_KERNEL_LZMA
214 The most recent compression algorithm.
215 Its ratio is best, decompression speed is between the other
216 two. Compression is slowest. The kernel size is about 33%
217 smaller with LZMA in comparison to gzip.
221 depends on HAVE_KERNEL_XZ
223 XZ uses the LZMA2 algorithm and instruction set specific
224 BCJ filters which can improve compression ratio of executable
225 code. The size of the kernel is about 30% smaller with XZ in
226 comparison to gzip. On architectures for which there is a BCJ
227 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
228 will create a few percent smaller kernel than plain LZMA.
230 The speed is about the same as with LZMA: The decompression
231 speed of XZ is better than that of bzip2 but worse than gzip
232 and LZO. Compression is slow.
236 depends on HAVE_KERNEL_LZO
238 Its compression ratio is the poorest among the 4. The kernel
239 size is about 10% bigger than gzip; however its speed
240 (both compression and decompression) is the fastest.
244 config DEFAULT_HOSTNAME
245 string "Default hostname"
248 This option determines the default system hostname before userspace
249 calls sethostname(2). The kernel traditionally uses "(none)" here,
250 but you may wish to use a different default here to make a minimal
251 system more usable with less configuration.
254 bool "Support for paging of anonymous memory (swap)"
255 depends on MMU && BLOCK
258 This option allows you to choose whether you want to have support
259 for so called swap devices or swap files in your kernel that are
260 used to provide more virtual memory than the actual RAM present
261 in your computer. If unsure say Y.
266 Inter Process Communication is a suite of library functions and
267 system calls which let processes (running programs) synchronize and
268 exchange information. It is generally considered to be a good thing,
269 and some programs won't run unless you say Y here. In particular, if
270 you want to run the DOS emulator dosemu under Linux (read the
271 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
272 you'll need to say Y here.
274 You can find documentation about IPC with "info ipc" and also in
275 section 6.4 of the Linux Programmer's Guide, available from
276 <http://www.tldp.org/guides.html>.
278 config SYSVIPC_SYSCTL
285 bool "POSIX Message Queues"
286 depends on NET && EXPERIMENTAL
288 POSIX variant of message queues is a part of IPC. In POSIX message
289 queues every message has a priority which decides about succession
290 of receiving it by a process. If you want to compile and run
291 programs written e.g. for Solaris with use of its POSIX message
292 queues (functions mq_*) say Y here.
294 POSIX message queues are visible as a filesystem called 'mqueue'
295 and can be mounted somewhere if you want to do filesystem
296 operations on message queues.
300 config POSIX_MQUEUE_SYSCTL
302 depends on POSIX_MQUEUE
306 config BSD_PROCESS_ACCT
307 bool "BSD Process Accounting"
309 If you say Y here, a user level program will be able to instruct the
310 kernel (via a special system call) to write process accounting
311 information to a file: whenever a process exits, information about
312 that process will be appended to the file by the kernel. The
313 information includes things such as creation time, owning user,
314 command name, memory usage, controlling terminal etc. (the complete
315 list is in the struct acct in <file:include/linux/acct.h>). It is
316 up to the user level program to do useful things with this
317 information. This is generally a good idea, so say Y.
319 config BSD_PROCESS_ACCT_V3
320 bool "BSD Process Accounting version 3 file format"
321 depends on BSD_PROCESS_ACCT
324 If you say Y here, the process accounting information is written
325 in a new file format that also logs the process IDs of each
326 process and it's parent. Note that this file format is incompatible
327 with previous v0/v1/v2 file formats, so you will need updated tools
328 for processing it. A preliminary version of these tools is available
329 at <http://www.gnu.org/software/acct/>.
332 bool "open by fhandle syscalls"
335 If you say Y here, a user level program will be able to map
336 file names to handle and then later use the handle for
337 different file system operations. This is useful in implementing
338 userspace file servers, which now track files using handles instead
339 of names. The handle would remain the same even if file names
340 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
344 bool "Export task/process statistics through netlink (EXPERIMENTAL)"
348 Export selected statistics for tasks/processes through the
349 generic netlink interface. Unlike BSD process accounting, the
350 statistics are available during the lifetime of tasks/processes as
351 responses to commands. Like BSD accounting, they are sent to user
356 config TASK_DELAY_ACCT
357 bool "Enable per-task delay accounting (EXPERIMENTAL)"
360 Collect information on time spent by a task waiting for system
361 resources like cpu, synchronous block I/O completion and swapping
362 in pages. Such statistics can help in setting a task's priorities
363 relative to other tasks for cpu, io, rss limits etc.
368 bool "Enable extended accounting over taskstats (EXPERIMENTAL)"
371 Collect extended task accounting data and send the data
372 to userland for processing over the taskstats interface.
376 config TASK_IO_ACCOUNTING
377 bool "Enable per-task storage I/O accounting (EXPERIMENTAL)"
378 depends on TASK_XACCT
380 Collect information on the number of bytes of storage I/O which this
386 bool "Auditing support"
389 Enable auditing infrastructure that can be used with another
390 kernel subsystem, such as SELinux (which requires this for
391 logging of avc messages output). Does not do system-call
392 auditing without CONFIG_AUDITSYSCALL.
395 bool "Enable system-call auditing support"
396 depends on AUDIT && (X86 || PPC || S390 || IA64 || UML || SPARC64 || SUPERH || ARM)
397 default y if SECURITY_SELINUX
399 Enable low-overhead system-call auditing infrastructure that
400 can be used independently or with another kernel subsystem,
405 depends on AUDITSYSCALL
410 depends on AUDITSYSCALL
413 config AUDIT_LOGINUID_IMMUTABLE
414 bool "Make audit loginuid immutable"
417 The config option toggles if a task setting its loginuid requires
418 CAP_SYS_AUDITCONTROL or if that task should require no special permissions
419 but should instead only allow setting its loginuid if it was never
420 previously set. On systems which use systemd or a similar central
421 process to restart login services this should be set to true. On older
422 systems in which an admin would typically have to directly stop and
423 start processes this should be set to false. Setting this to true allows
424 one to drop potentially dangerous capabilites from the login tasks,
425 but may not be backwards compatible with older init systems.
427 source "kernel/irq/Kconfig"
432 prompt "RCU Implementation"
436 bool "Tree-based hierarchical RCU"
437 depends on !PREEMPT && SMP
439 This option selects the RCU implementation that is
440 designed for very large SMP system with hundreds or
441 thousands of CPUs. It also scales down nicely to
444 config TREE_PREEMPT_RCU
445 bool "Preemptible tree-based hierarchical RCU"
446 depends on PREEMPT && SMP
448 This option selects the RCU implementation that is
449 designed for very large SMP systems with hundreds or
450 thousands of CPUs, but for which real-time response
451 is also required. It also scales down nicely to
455 bool "UP-only small-memory-footprint RCU"
456 depends on !PREEMPT && !SMP
458 This option selects the RCU implementation that is
459 designed for UP systems from which real-time response
460 is not required. This option greatly reduces the
461 memory footprint of RCU.
463 config TINY_PREEMPT_RCU
464 bool "Preemptible UP-only small-memory-footprint RCU"
465 depends on PREEMPT && !SMP
467 This option selects the RCU implementation that is designed
468 for real-time UP systems. This option greatly reduces the
469 memory footprint of RCU.
474 def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
476 This option enables preemptible-RCU code that is common between
477 the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.
480 int "Tree-based hierarchical RCU fanout value"
483 depends on TREE_RCU || TREE_PREEMPT_RCU
487 This option controls the fanout of hierarchical implementations
488 of RCU, allowing RCU to work efficiently on machines with
489 large numbers of CPUs. This value must be at least the fourth
490 root of NR_CPUS, which allows NR_CPUS to be insanely large.
491 The default value of RCU_FANOUT should be used for production
492 systems, but if you are stress-testing the RCU implementation
493 itself, small RCU_FANOUT values allow you to test large-system
494 code paths on small(er) systems.
496 Select a specific number if testing RCU itself.
497 Take the default if unsure.
499 config RCU_FANOUT_EXACT
500 bool "Disable tree-based hierarchical RCU auto-balancing"
501 depends on TREE_RCU || TREE_PREEMPT_RCU
504 This option forces use of the exact RCU_FANOUT value specified,
505 regardless of imbalances in the hierarchy. This is useful for
506 testing RCU itself, and might one day be useful on systems with
507 strong NUMA behavior.
509 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
513 config RCU_FAST_NO_HZ
514 bool "Accelerate last non-dyntick-idle CPU's grace periods"
515 depends on NO_HZ && SMP
518 This option causes RCU to attempt to accelerate grace periods
519 in order to allow CPUs to enter dynticks-idle state more
520 quickly. On the other hand, this option increases the overhead
521 of the dynticks-idle checking, particularly on systems with
522 large numbers of CPUs.
524 Say Y if energy efficiency is critically important, particularly
525 if you have relatively few CPUs.
527 Say N if you are unsure.
529 config TREE_RCU_TRACE
530 def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU )
533 This option provides tracing for the TREE_RCU and
534 TREE_PREEMPT_RCU implementations, permitting Makefile to
535 trivially select kernel/rcutree_trace.c.
538 bool "Enable RCU priority boosting"
539 depends on RT_MUTEXES && PREEMPT_RCU
542 This option boosts the priority of preempted RCU readers that
543 block the current preemptible RCU grace period for too long.
544 This option also prevents heavy loads from blocking RCU
545 callback invocation for all flavors of RCU.
547 Say Y here if you are working with real-time apps or heavy loads
548 Say N here if you are unsure.
550 config RCU_BOOST_PRIO
551 int "Real-time priority to boost RCU readers to"
556 This option specifies the real-time priority to which preempted
557 RCU readers are to be boosted. If you are working with CPU-bound
558 real-time applications, you should specify a priority higher then
559 the highest-priority CPU-bound application.
561 Specify the real-time priority, or take the default if unsure.
563 config RCU_BOOST_DELAY
564 int "Milliseconds to delay boosting after RCU grace-period start"
569 This option specifies the time to wait after the beginning of
570 a given grace period before priority-boosting preempted RCU
571 readers blocking that grace period. Note that any RCU reader
572 blocking an expedited RCU grace period is boosted immediately.
574 Accept the default if unsure.
576 endmenu # "RCU Subsystem"
579 tristate "Kernel .config support"
581 This option enables the complete Linux kernel ".config" file
582 contents to be saved in the kernel. It provides documentation
583 of which kernel options are used in a running kernel or in an
584 on-disk kernel. This information can be extracted from the kernel
585 image file with the script scripts/extract-ikconfig and used as
586 input to rebuild the current kernel or to build another kernel.
587 It can also be extracted from a running kernel by reading
588 /proc/config.gz if enabled (below).
591 bool "Enable access to .config through /proc/config.gz"
592 depends on IKCONFIG && PROC_FS
594 This option enables access to the kernel configuration file
595 through /proc/config.gz.
598 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
602 Select kernel log buffer size as a power of 2.
612 # Architectures with an unreliable sched_clock() should select this:
614 config HAVE_UNSTABLE_SCHED_CLOCK
618 boolean "Control Group support"
620 default !KERNEL_DESKTOP
622 This option adds support for grouping sets of processes together, for
623 use with process control subsystems such as Cpusets, CFS, memory
624 controls or device isolation.
626 - Documentation/scheduler/sched-design-CFS.txt (CFS)
627 - Documentation/cgroups/ (features for grouping, isolation
628 and resource control)
635 bool "Example debug cgroup subsystem"
638 This option enables a simple cgroup subsystem that
639 exports useful debugging information about the cgroups
644 config CGROUP_FREEZER
645 bool "Freezer cgroup subsystem"
647 Provides a way to freeze and unfreeze all tasks in a
651 bool "Device controller for cgroups"
653 Provides a cgroup implementing whitelists for devices which
654 a process in the cgroup can mknod or open.
657 bool "Cpuset support"
659 This option will let you create and manage CPUSETs which
660 allow dynamically partitioning a system into sets of CPUs and
661 Memory Nodes and assigning tasks to run only within those sets.
662 This is primarily useful on large SMP or NUMA systems.
666 config PROC_PID_CPUSET
667 bool "Include legacy /proc/<pid>/cpuset file"
671 config CGROUP_CPUACCT
672 bool "Simple CPU accounting cgroup subsystem"
674 Provides a simple Resource Controller for monitoring the
675 total CPU consumed by the tasks in a cgroup.
677 config RESOURCE_COUNTERS
678 bool "Resource counters"
680 This option enables controller independent resource accounting
681 infrastructure that works with cgroups.
683 config CGROUP_MEM_RES_CTLR
684 bool "Memory Resource Controller for Control Groups"
685 depends on RESOURCE_COUNTERS
688 Provides a memory resource controller that manages both anonymous
689 memory and page cache. (See Documentation/cgroups/memory.txt)
691 Note that setting this option increases fixed memory overhead
692 associated with each page of memory in the system. By this,
693 20(40)bytes/PAGE_SIZE on 32(64)bit system will be occupied by memory
694 usage tracking struct at boot. Total amount of this is printed out
697 Only enable when you're ok with these trade offs and really
698 sure you need the memory resource controller. Even when you enable
699 this, you can set "cgroup_disable=memory" at your boot option to
700 disable memory resource controller and you can avoid overheads.
701 (and lose benefits of memory resource controller)
703 This config option also selects MM_OWNER config option, which
704 could in turn add some fork/exit overhead.
706 config CGROUP_MEM_RES_CTLR_SWAP
707 bool "Memory Resource Controller Swap Extension"
708 depends on CGROUP_MEM_RES_CTLR && SWAP
710 Add swap management feature to memory resource controller. When you
711 enable this, you can limit mem+swap usage per cgroup. In other words,
712 when you disable this, memory resource controller has no cares to
713 usage of swap...a process can exhaust all of the swap. This extension
714 is useful when you want to avoid exhaustion swap but this itself
715 adds more overheads and consumes memory for remembering information.
716 Especially if you use 32bit system or small memory system, please
717 be careful about enabling this. When memory resource controller
718 is disabled by boot option, this will be automatically disabled and
719 there will be no overhead from this. Even when you set this config=y,
720 if boot option "swapaccount=0" is set, swap will not be accounted.
721 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
722 size is 4096bytes, 512k per 1Gbytes of swap.
723 config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
724 bool "Memory Resource Controller Swap Extension enabled by default"
725 depends on CGROUP_MEM_RES_CTLR_SWAP
728 Memory Resource Controller Swap Extension comes with its price in
729 a bigger memory consumption. General purpose distribution kernels
730 which want to enable the feature but keep it disabled by default
731 and let the user enable it by swapaccount boot command line
732 parameter should have this option unselected.
733 For those who want to have the feature enabled by default should
734 select this option (if, for some reason, they need to disable it
735 then swapaccount=0 does the trick).
736 config CGROUP_MEM_RES_CTLR_KMEM
737 bool "Memory Resource Controller Kernel Memory accounting (EXPERIMENTAL)"
738 depends on CGROUP_MEM_RES_CTLR && EXPERIMENTAL
741 The Kernel Memory extension for Memory Resource Controller can limit
742 the amount of memory used by kernel objects in the system. Those are
743 fundamentally different from the entities handled by the standard
744 Memory Controller, which are page-based, and can be swapped. Users of
745 the kmem extension can use it to guarantee that no group of processes
746 will ever exhaust kernel resources alone.
749 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
750 depends on PERF_EVENTS && CGROUPS
752 This option extends the per-cpu mode to restrict monitoring to
753 threads which belong to the cgroup specified and run on the
758 menuconfig CGROUP_SCHED
759 bool "Group CPU scheduler"
760 default !KERNEL_DESKTOP
762 This feature lets CPU scheduler recognize task groups and control CPU
763 bandwidth allocation to such task groups. It uses cgroups to group
767 config FAIR_GROUP_SCHED
768 bool "Group scheduling for SCHED_OTHER"
769 depends on CGROUP_SCHED
773 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
774 depends on EXPERIMENTAL
775 depends on FAIR_GROUP_SCHED
778 This option allows users to define CPU bandwidth rates (limits) for
779 tasks running within the fair group scheduler. Groups with no limit
780 set are considered to be unconstrained and will run with no
782 See tip/Documentation/scheduler/sched-bwc.txt for more information.
784 config RT_GROUP_SCHED
785 bool "Group scheduling for SCHED_RR/FIFO"
786 depends on EXPERIMENTAL
787 depends on CGROUP_SCHED
790 This feature lets you explicitly allocate real CPU bandwidth
791 to task groups. If enabled, it will also make it impossible to
792 schedule realtime tasks for non-root users until you allocate
793 realtime bandwidth for them.
794 See Documentation/scheduler/sched-rt-group.txt for more information.
799 tristate "Block IO controller"
803 Generic block IO controller cgroup interface. This is the common
804 cgroup interface which should be used by various IO controlling
807 Currently, CFQ IO scheduler uses it to recognize task groups and
808 control disk bandwidth allocation (proportional time slice allocation)
809 to such task groups. It is also used by bio throttling logic in
810 block layer to implement upper limit in IO rates on a device.
812 This option only enables generic Block IO controller infrastructure.
813 One needs to also enable actual IO controlling logic/policy. For
814 enabling proportional weight division of disk bandwidth in CFQ, set
815 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
816 CONFIG_BLK_DEV_THROTTLING=y.
818 See Documentation/cgroups/blkio-controller.txt for more information.
820 config DEBUG_BLK_CGROUP
821 bool "Enable Block IO controller debugging"
822 depends on BLK_CGROUP
825 Enable some debugging help. Currently it exports additional stat
826 files in a cgroup which can be useful for debugging.
830 config CHECKPOINT_RESTORE
831 bool "Checkpoint/restore support" if EXPERT
834 Enables additional kernel features in a sake of checkpoint/restore.
835 In particular it adds auxiliary prctl codes to setup process text,
836 data and heap segment sizes, and a few additional /proc filesystem
839 If unsure, say N here.
841 menuconfig NAMESPACES
842 bool "Namespaces support" if EXPERT
845 Provides the way to make tasks work with different objects using
846 the same id. For example same IPC id may refer to different objects
847 or same user id or pid may refer to different tasks when used in
848 different namespaces.
856 In this namespace tasks see different info provided with the
861 depends on (SYSVIPC || POSIX_MQUEUE)
864 In this namespace tasks work with IPC ids which correspond to
865 different IPC objects in different namespaces.
868 bool "User namespace (EXPERIMENTAL)"
869 depends on EXPERIMENTAL
872 This allows containers, i.e. vservers, to use user namespaces
873 to provide different user info for different servers.
877 bool "PID Namespaces"
880 Support process id namespaces. This allows having multiple
881 processes with the same pid as long as they are in different
882 pid namespaces. This is a building block of containers.
885 bool "Network namespace"
889 Allow user space to create what appear to be multiple instances
890 of the network stack.
894 config SCHED_AUTOGROUP
895 bool "Automatic process group scheduling"
899 select FAIR_GROUP_SCHED
901 This option optimizes the scheduler for common desktop workloads by
902 automatically creating and populating task groups. This separation
903 of workloads isolates aggressive CPU burners (like build jobs) from
904 desktop applications. Task group autogeneration is currently based
910 config SYSFS_DEPRECATED
911 bool "Enable deprecated sysfs features to support old userspace tools"
915 This option adds code that switches the layout of the "block" class
916 devices, to not show up in /sys/class/block/, but only in
919 This switch is only active when the sysfs.deprecated=1 boot option is
920 passed or the SYSFS_DEPRECATED_V2 option is set.
922 This option allows new kernels to run on old distributions and tools,
923 which might get confused by /sys/class/block/. Since 2007/2008 all
924 major distributions and tools handle this just fine.
926 Recent distributions and userspace tools after 2009/2010 depend on
927 the existence of /sys/class/block/, and will not work with this
930 Only if you are using a new kernel on an old distribution, you might
933 config SYSFS_DEPRECATED_V2
934 bool "Enable deprecated sysfs features by default"
937 depends on SYSFS_DEPRECATED
939 Enable deprecated sysfs by default.
941 See the CONFIG_SYSFS_DEPRECATED option for more details about this
944 Only if you are using a new kernel on an old distribution, you might
945 need to say Y here. Even then, odds are you would not need it
946 enabled, you can always pass the boot option if absolutely necessary.
949 bool "Kernel->user space relay support (formerly relayfs)"
951 This option enables support for relay interface support in
952 certain file systems (such as debugfs).
953 It is designed to provide an efficient mechanism for tools and
954 facilities to relay large amounts of data from kernel space to
959 config BLK_DEV_INITRD
960 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
961 depends on BROKEN || !FRV
963 The initial RAM filesystem is a ramfs which is loaded by the
964 boot loader (loadlin or lilo) and that is mounted as root
965 before the normal boot procedure. It is typically used to
966 load modules needed to mount the "real" root file system,
967 etc. See <file:Documentation/initrd.txt> for details.
969 If RAM disk support (BLK_DEV_RAM) is also included, this
970 also enables initial RAM disk (initrd) support and adds
971 15 Kbytes (more on some other architectures) to the kernel size.
981 config CC_OPTIMIZE_FOR_SIZE
982 bool "Optimize for size"
984 Enabling this option will pass "-Os" instead of "-O2" to gcc
985 resulting in a smaller kernel.
996 bool "Configure standard kernel features (expert users)"
997 # Unhide debug options, to make the on-by-default options visible
1000 This option allows certain base kernel options and settings
1001 to be disabled or tweaked. This is for specialized
1002 environments which can tolerate a "non-standard" kernel.
1003 Only use this if you really know what you are doing.
1006 bool "Enable 16-bit UID system calls" if EXPERT
1007 depends on ARM || BLACKFIN || CRIS || FRV || H8300 || X86_32 || M68K || (S390 && !64BIT) || SUPERH || SPARC32 || (SPARC64 && COMPAT) || UML || (X86_64 && IA32_EMULATION)
1010 This enables the legacy 16-bit UID syscall wrappers.
1012 config SYSCTL_SYSCALL
1013 bool "Sysctl syscall support" if EXPERT
1014 depends on PROC_SYSCTL
1018 sys_sysctl uses binary paths that have been found challenging
1019 to properly maintain and use. The interface in /proc/sys
1020 using paths with ascii names is now the primary path to this
1023 Almost nothing using the binary sysctl interface so if you are
1024 trying to save some space it is probably safe to disable this,
1025 making your kernel marginally smaller.
1027 If unsure say N here.
1030 bool "Load all symbols for debugging/ksymoops" if EXPERT
1033 Say Y here to let the kernel print out symbolic crash information and
1034 symbolic stack backtraces. This increases the size of the kernel
1035 somewhat, as all symbols have to be loaded into the kernel image.
1038 bool "Include all symbols in kallsyms"
1039 depends on DEBUG_KERNEL && KALLSYMS
1041 Normally kallsyms only contains the symbols of functions for nicer
1042 OOPS messages and backtraces (i.e., symbols from the text and inittext
1043 sections). This is sufficient for most cases. And only in very rare
1044 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1045 names of variables from the data sections, etc).
1047 This option makes sure that all symbols are loaded into the kernel
1048 image (i.e., symbols from all sections) in cost of increased kernel
1049 size (depending on the kernel configuration, it may be 300KiB or
1050 something like this).
1052 Say N unless you really need all symbols.
1055 bool "Support for hot-pluggable devices" if EXPERT
1058 This option is provided for the case where no hotplug or uevent
1059 capabilities is wanted by the kernel. You should only consider
1060 disabling this option for embedded systems that do not use modules, a
1061 dynamic /dev tree, or dynamic device discovery. Just say Y.
1065 bool "Enable support for printk" if EXPERT
1067 This option enables normal printk support. Removing it
1068 eliminates most of the message strings from the kernel image
1069 and makes the kernel more or less silent. As this makes it
1070 very difficult to diagnose system problems, saying N here is
1071 strongly discouraged.
1074 bool "BUG() support" if EXPERT
1077 Disabling this option eliminates support for BUG and WARN, reducing
1078 the size of your kernel image and potentially quietly ignoring
1079 numerous fatal conditions. You should only consider disabling this
1080 option for embedded systems with no facilities for reporting errors.
1085 bool "Enable ELF core dumps" if EXPERT
1087 Enable support for generating core dumps. Disabling saves about 4k.
1090 config PCSPKR_PLATFORM
1091 bool "Enable PC-Speaker support" if EXPERT
1092 depends on HAVE_PCSPKR_PLATFORM
1096 This option allows to disable the internal PC-Speaker
1097 support, saving some memory.
1099 config HAVE_PCSPKR_PLATFORM
1104 bool "Enable full-sized data structures for core" if EXPERT
1106 Disabling this option reduces the size of miscellaneous core
1107 kernel data structures. This saves memory on small machines,
1108 but may reduce performance.
1111 bool "Enable futex support" if EXPERT
1115 Disabling this option will cause the kernel to be built without
1116 support for "fast userspace mutexes". The resulting kernel may not
1117 run glibc-based applications correctly.
1120 bool "Enable eventpoll support" if EXPERT
1124 Disabling this option will cause the kernel to be built without
1125 support for epoll family of system calls.
1128 bool "Enable signalfd() system call" if EXPERT
1132 Enable the signalfd() system call that allows to receive signals
1133 on a file descriptor.
1138 bool "Enable timerfd() system call" if EXPERT
1142 Enable the timerfd() system call that allows to receive timer
1143 events on a file descriptor.
1148 bool "Enable eventfd() system call" if EXPERT
1152 Enable the eventfd() system call that allows to receive both
1153 kernel notification (ie. KAIO) or userspace notifications.
1158 bool "Use full shmem filesystem" if EXPERT
1162 The shmem is an internal filesystem used to manage shared memory.
1163 It is backed by swap and manages resource limits. It is also exported
1164 to userspace as tmpfs if TMPFS is enabled. Disabling this
1165 option replaces shmem and tmpfs with the much simpler ramfs code,
1166 which may be appropriate on small systems without swap.
1169 bool "Enable AIO support" if EXPERT
1172 This option enables POSIX asynchronous I/O which may by used
1173 by some high performance threaded applications. Disabling
1174 this option saves about 7k.
1177 bool "Embedded system"
1180 This option should be enabled if compiling the kernel for
1181 an embedded system so certain expert options are available
1184 config HAVE_PERF_EVENTS
1187 See tools/perf/design.txt for details.
1189 config PERF_USE_VMALLOC
1192 See tools/perf/design.txt for details
1194 menu "Kernel Performance Events And Counters"
1197 bool "Kernel performance events and counters"
1198 default y if (PROFILING || PERF_COUNTERS)
1199 depends on HAVE_PERF_EVENTS
1203 Enable kernel support for various performance events provided
1204 by software and hardware.
1206 Software events are supported either built-in or via the
1207 use of generic tracepoints.
1209 Most modern CPUs support performance events via performance
1210 counter registers. These registers count the number of certain
1211 types of hw events: such as instructions executed, cachemisses
1212 suffered, or branches mis-predicted - without slowing down the
1213 kernel or applications. These registers can also trigger interrupts
1214 when a threshold number of events have passed - and can thus be
1215 used to profile the code that runs on that CPU.
1217 The Linux Performance Event subsystem provides an abstraction of
1218 these software and hardware event capabilities, available via a
1219 system call and used by the "perf" utility in tools/perf/. It
1220 provides per task and per CPU counters, and it provides event
1221 capabilities on top of those.
1225 config PERF_COUNTERS
1226 bool "Kernel performance counters (old config option)"
1227 depends on HAVE_PERF_EVENTS
1229 This config has been obsoleted by the PERF_EVENTS
1230 config option - please see that one for details.
1232 It has no effect on the kernel whether you enable
1233 it or not, it is a compatibility placeholder.
1237 config DEBUG_PERF_USE_VMALLOC
1239 bool "Debug: use vmalloc to back perf mmap() buffers"
1240 depends on PERF_EVENTS && DEBUG_KERNEL
1241 select PERF_USE_VMALLOC
1243 Use vmalloc memory to back perf mmap() buffers.
1245 Mostly useful for debugging the vmalloc code on platforms
1246 that don't require it.
1252 config VM_EVENT_COUNTERS
1254 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1256 VM event counters are needed for event counts to be shown.
1257 This option allows the disabling of the VM event counters
1258 on EXPERT systems. /proc/vmstat will only show page counts
1259 if VM event counters are disabled.
1263 bool "Enable PCI quirk workarounds" if EXPERT
1266 This enables workarounds for various PCI chipset
1267 bugs/quirks. Disable this only if your target machine is
1268 unaffected by PCI quirks.
1272 bool "Enable SLUB debugging support" if EXPERT
1273 depends on SLUB && SYSFS
1275 SLUB has extensive debug support features. Disabling these can
1276 result in significant savings in code size. This also disables
1277 SLUB sysfs support. /sys/slab will not exist and there will be
1278 no support for cache validation etc.
1281 bool "Disable heap randomization"
1284 Randomizing heap placement makes heap exploits harder, but it
1285 also breaks ancient binaries (including anything libc5 based).
1286 This option changes the bootup default to heap randomization
1287 disabled, and can be overridden at runtime by setting
1288 /proc/sys/kernel/randomize_va_space to 2.
1290 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1293 prompt "Choose SLAB allocator"
1296 This option allows to select a slab allocator.
1301 The regular slab allocator that is established and known to work
1302 well in all environments. It organizes cache hot objects in
1303 per cpu and per node queues.
1306 bool "SLUB (Unqueued Allocator)"
1308 SLUB is a slab allocator that minimizes cache line usage
1309 instead of managing queues of cached objects (SLAB approach).
1310 Per cpu caching is realized using slabs of objects instead
1311 of queues of objects. SLUB can use memory efficiently
1312 and has enhanced diagnostics. SLUB is the default choice for
1317 bool "SLOB (Simple Allocator)"
1319 SLOB replaces the stock allocator with a drastically simpler
1320 allocator. SLOB is generally more space efficient but
1321 does not perform as well on large systems.
1325 config MMAP_ALLOW_UNINITIALIZED
1326 bool "Allow mmapped anonymous memory to be uninitialized"
1327 depends on EXPERT && !MMU
1330 Normally, and according to the Linux spec, anonymous memory obtained
1331 from mmap() has it's contents cleared before it is passed to
1332 userspace. Enabling this config option allows you to request that
1333 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1334 providing a huge performance boost. If this option is not enabled,
1335 then the flag will be ignored.
1337 This is taken advantage of by uClibc's malloc(), and also by
1338 ELF-FDPIC binfmt's brk and stack allocator.
1340 Because of the obvious security issues, this option should only be
1341 enabled on embedded devices where you control what is run in
1342 userspace. Since that isn't generally a problem on no-MMU systems,
1343 it is normally safe to say Y here.
1345 See Documentation/nommu-mmap.txt for more information.
1348 bool "Profiling support"
1350 Say Y here to enable the extended profiling support mechanisms used
1351 by profilers such as OProfile.
1354 # Place an empty function call at each tracepoint site. Can be
1355 # dynamically changed for a probe function.
1360 source "arch/Kconfig"
1362 endmenu # General setup
1364 config HAVE_GENERIC_DMA_COHERENT
1371 depends on SLAB || SLUB_DEBUG
1379 default 0 if BASE_FULL
1380 default 1 if !BASE_FULL
1383 bool "Enable loadable module support"
1385 Kernel modules are small pieces of compiled code which can
1386 be inserted in the running kernel, rather than being
1387 permanently built into the kernel. You use the "modprobe"
1388 tool to add (and sometimes remove) them. If you say Y here,
1389 many parts of the kernel can be built as modules (by
1390 answering M instead of Y where indicated): this is most
1391 useful for infrequently used options which are not required
1392 for booting. For more information, see the man pages for
1393 modprobe, lsmod, modinfo, insmod and rmmod.
1395 If you say Y here, you will need to run "make
1396 modules_install" to put the modules under /lib/modules/
1397 where modprobe can find them (you may need to be root to do
1404 config MODULE_FORCE_LOAD
1405 bool "Forced module loading"
1408 Allow loading of modules without version information (ie. modprobe
1409 --force). Forced module loading sets the 'F' (forced) taint flag and
1410 is usually a really bad idea.
1412 config MODULE_UNLOAD
1413 bool "Module unloading"
1415 Without this option you will not be able to unload any
1416 modules (note that some modules may not be unloadable
1417 anyway), which makes your kernel smaller, faster
1418 and simpler. If unsure, say Y.
1420 config MODULE_FORCE_UNLOAD
1421 bool "Forced module unloading"
1422 depends on MODULE_UNLOAD && EXPERIMENTAL
1424 This option allows you to force a module to unload, even if the
1425 kernel believes it is unsafe: the kernel will remove the module
1426 without waiting for anyone to stop using it (using the -f option to
1427 rmmod). This is mainly for kernel developers and desperate users.
1431 bool "Module versioning support"
1433 Usually, you have to use modules compiled with your kernel.
1434 Saying Y here makes it sometimes possible to use modules
1435 compiled for different kernels, by adding enough information
1436 to the modules to (hopefully) spot any changes which would
1437 make them incompatible with the kernel you are running. If
1440 config MODULE_SRCVERSION_ALL
1441 bool "Source checksum for all modules"
1443 Modules which contain a MODULE_VERSION get an extra "srcversion"
1444 field inserted into their modinfo section, which contains a
1445 sum of the source files which made it. This helps maintainers
1446 see exactly which source was used to build a module (since
1447 others sometimes change the module source without updating
1448 the version). With this option, such a "srcversion" field
1449 will be created for all modules. If unsure, say N.
1453 config INIT_ALL_POSSIBLE
1456 Back when each arch used to define their own cpu_online_mask and
1457 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
1458 with all 1s, and others with all 0s. When they were centralised,
1459 it was better to provide this option than to break all the archs
1460 and have several arch maintainers pursuing me down dark alleys.
1465 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
1467 Need stop_machine() primitive.
1469 source "block/Kconfig"
1471 config PREEMPT_NOTIFIERS
1478 source "kernel/Kconfig.locks"
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