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"
26 config BUILDTIME_EXTABLE_SORT
36 depends on BROKEN || !SMP
39 config INIT_ENV_ARG_LIMIT
44 Maximum of each of the number of arguments and environment
45 variables passed to init from the kernel command line.
49 string "Cross-compiler tool prefix"
51 Same as running 'make CROSS_COMPILE=prefix-' but stored for
52 default make runs in this kernel build directory. You don't
53 need to set this unless you want the configured kernel build
54 directory to select the cross-compiler automatically.
57 bool "Compile also drivers which will not load"
60 Some drivers can be compiled on a different platform than they are
61 intended to be run on. Despite they cannot be loaded there (or even
62 when they load they cannot be used due to missing HW support),
63 developers still, opposing to distributors, might want to build such
64 drivers to compile-test them.
66 If you are a developer and want to build everything available, say Y
67 here. If you are a user/distributor, say N here to exclude useless
68 drivers to be distributed.
71 string "Local version - append to kernel release"
73 Append an extra string to the end of your kernel version.
74 This will show up when you type uname, for example.
75 The string you set here will be appended after the contents of
76 any files with a filename matching localversion* in your
77 object and source tree, in that order. Your total string can
78 be a maximum of 64 characters.
80 config LOCALVERSION_AUTO
81 bool "Automatically append version information to the version string"
84 This will try to automatically determine if the current tree is a
85 release tree by looking for git tags that belong to the current
88 A string of the format -gxxxxxxxx will be added to the localversion
89 if a git-based tree is found. The string generated by this will be
90 appended after any matching localversion* files, and after the value
91 set in CONFIG_LOCALVERSION.
93 (The actual string used here is the first eight characters produced
94 by running the command:
96 $ git rev-parse --verify HEAD
98 which is done within the script "scripts/setlocalversion".)
100 config HAVE_KERNEL_GZIP
103 config HAVE_KERNEL_BZIP2
106 config HAVE_KERNEL_LZMA
109 config HAVE_KERNEL_XZ
112 config HAVE_KERNEL_LZO
115 config HAVE_KERNEL_LZ4
119 prompt "Kernel compression mode"
121 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
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. It provides a good balance
145 between compression ratio and decompression speed.
149 depends on HAVE_KERNEL_BZIP2
151 Its compression ratio and speed is intermediate.
152 Decompression speed is slowest among the choices. The kernel
153 size is about 10% smaller with bzip2, in comparison to gzip.
154 Bzip2 uses a large amount of memory. For modern kernels you
155 will need at least 8MB RAM or more for booting.
159 depends on HAVE_KERNEL_LZMA
161 This compression algorithm's ratio is best. Decompression speed
162 is between gzip and bzip2. Compression is slowest.
163 The kernel size is about 33% smaller with LZMA in comparison to gzip.
167 depends on HAVE_KERNEL_XZ
169 XZ uses the LZMA2 algorithm and instruction set specific
170 BCJ filters which can improve compression ratio of executable
171 code. The size of the kernel is about 30% smaller with XZ in
172 comparison to gzip. On architectures for which there is a BCJ
173 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
174 will create a few percent smaller kernel than plain LZMA.
176 The speed is about the same as with LZMA: The decompression
177 speed of XZ is better than that of bzip2 but worse than gzip
178 and LZO. Compression is slow.
182 depends on HAVE_KERNEL_LZO
184 Its compression ratio is the poorest among the choices. The kernel
185 size is about 10% bigger than gzip; however its speed
186 (both compression and decompression) is the fastest.
190 depends on HAVE_KERNEL_LZ4
192 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
193 A preliminary version of LZ4 de/compression tool is available at
194 <https://code.google.com/p/lz4/>.
196 Its compression ratio is worse than LZO. The size of the kernel
197 is about 8% bigger than LZO. But the decompression speed is
202 config DEFAULT_HOSTNAME
203 string "Default hostname"
206 This option determines the default system hostname before userspace
207 calls sethostname(2). The kernel traditionally uses "(none)" here,
208 but you may wish to use a different default here to make a minimal
209 system more usable with less configuration.
212 bool "Support for paging of anonymous memory (swap)"
213 depends on MMU && BLOCK
216 This option allows you to choose whether you want to have support
217 for so called swap devices or swap files in your kernel that are
218 used to provide more virtual memory than the actual RAM present
219 in your computer. If unsure say Y.
224 Inter Process Communication is a suite of library functions and
225 system calls which let processes (running programs) synchronize and
226 exchange information. It is generally considered to be a good thing,
227 and some programs won't run unless you say Y here. In particular, if
228 you want to run the DOS emulator dosemu under Linux (read the
229 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
230 you'll need to say Y here.
232 You can find documentation about IPC with "info ipc" and also in
233 section 6.4 of the Linux Programmer's Guide, available from
234 <http://www.tldp.org/guides.html>.
236 config SYSVIPC_SYSCTL
243 bool "POSIX Message Queues"
246 POSIX variant of message queues is a part of IPC. In POSIX message
247 queues every message has a priority which decides about succession
248 of receiving it by a process. If you want to compile and run
249 programs written e.g. for Solaris with use of its POSIX message
250 queues (functions mq_*) say Y here.
252 POSIX message queues are visible as a filesystem called 'mqueue'
253 and can be mounted somewhere if you want to do filesystem
254 operations on message queues.
258 config POSIX_MQUEUE_SYSCTL
260 depends on POSIX_MQUEUE
265 tristate "kdbus interprocess communication"
268 D-Bus is a system for low-latency, low-overhead, easy to use
269 interprocess communication (IPC).
271 See the man-pages and HTML files in Documentation/kdbus/
272 that are generated by 'make mandocs' and 'make htmldocs'.
274 If you have an ordinary machine, select M here. The module
275 will be called kdbus.
277 config CROSS_MEMORY_ATTACH
278 bool "Enable process_vm_readv/writev syscalls"
282 Enabling this option adds the system calls process_vm_readv and
283 process_vm_writev which allow a process with the correct privileges
284 to directly read from or write to another process' address space.
285 See the man page for more details.
288 bool "open by fhandle syscalls"
291 If you say Y here, a user level program will be able to map
292 file names to handle and then later use the handle for
293 different file system operations. This is useful in implementing
294 userspace file servers, which now track files using handles instead
295 of names. The handle would remain the same even if file names
296 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
300 bool "uselib syscall"
303 This option enables the uselib syscall, a system call used in the
304 dynamic linker from libc5 and earlier. glibc does not use this
305 system call. If you intend to run programs built on libc5 or
306 earlier, you may need to enable this syscall. Current systems
307 running glibc can safely disable this.
310 bool "Auditing support"
313 Enable auditing infrastructure that can be used with another
314 kernel subsystem, such as SELinux (which requires this for
315 logging of avc messages output). Does not do system-call
316 auditing without CONFIG_AUDITSYSCALL.
318 config HAVE_ARCH_AUDITSYSCALL
322 bool "Enable system-call auditing support"
323 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
324 default y if SECURITY_SELINUX
326 Enable low-overhead system-call auditing infrastructure that
327 can be used independently or with another kernel subsystem,
332 depends on AUDITSYSCALL
337 depends on AUDITSYSCALL
340 source "kernel/irq/Kconfig"
341 source "kernel/time/Kconfig"
343 menu "CPU/Task time and stats accounting"
345 config VIRT_CPU_ACCOUNTING
349 prompt "Cputime accounting"
350 default TICK_CPU_ACCOUNTING if !PPC64
351 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
353 # Kind of a stub config for the pure tick based cputime accounting
354 config TICK_CPU_ACCOUNTING
355 bool "Simple tick based cputime accounting"
356 depends on !S390 && !NO_HZ_FULL
358 This is the basic tick based cputime accounting that maintains
359 statistics about user, system and idle time spent on per jiffies
364 config VIRT_CPU_ACCOUNTING_NATIVE
365 bool "Deterministic task and CPU time accounting"
366 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
367 select VIRT_CPU_ACCOUNTING
369 Select this option to enable more accurate task and CPU time
370 accounting. This is done by reading a CPU counter on each
371 kernel entry and exit and on transitions within the kernel
372 between system, softirq and hardirq state, so there is a
373 small performance impact. In the case of s390 or IBM POWER > 5,
374 this also enables accounting of stolen time on logically-partitioned
377 config VIRT_CPU_ACCOUNTING_GEN
378 bool "Full dynticks CPU time accounting"
379 depends on HAVE_CONTEXT_TRACKING
380 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
381 select VIRT_CPU_ACCOUNTING
382 select CONTEXT_TRACKING
384 Select this option to enable task and CPU time accounting on full
385 dynticks systems. This accounting is implemented by watching every
386 kernel-user boundaries using the context tracking subsystem.
387 The accounting is thus performed at the expense of some significant
390 For now this is only useful if you are working on the full
391 dynticks subsystem development.
395 config IRQ_TIME_ACCOUNTING
396 bool "Fine granularity task level IRQ time accounting"
397 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
399 Select this option to enable fine granularity task irq time
400 accounting. This is done by reading a timestamp on each
401 transitions between softirq and hardirq state, so there can be a
402 small performance impact.
404 If in doubt, say N here.
408 config BSD_PROCESS_ACCT
409 bool "BSD Process Accounting"
411 If you say Y here, a user level program will be able to instruct the
412 kernel (via a special system call) to write process accounting
413 information to a file: whenever a process exits, information about
414 that process will be appended to the file by the kernel. The
415 information includes things such as creation time, owning user,
416 command name, memory usage, controlling terminal etc. (the complete
417 list is in the struct acct in <file:include/linux/acct.h>). It is
418 up to the user level program to do useful things with this
419 information. This is generally a good idea, so say Y.
421 config BSD_PROCESS_ACCT_V3
422 bool "BSD Process Accounting version 3 file format"
423 depends on BSD_PROCESS_ACCT
426 If you say Y here, the process accounting information is written
427 in a new file format that also logs the process IDs of each
428 process and it's parent. Note that this file format is incompatible
429 with previous v0/v1/v2 file formats, so you will need updated tools
430 for processing it. A preliminary version of these tools is available
431 at <http://www.gnu.org/software/acct/>.
434 bool "Export task/process statistics through netlink"
438 Export selected statistics for tasks/processes through the
439 generic netlink interface. Unlike BSD process accounting, the
440 statistics are available during the lifetime of tasks/processes as
441 responses to commands. Like BSD accounting, they are sent to user
446 config TASK_DELAY_ACCT
447 bool "Enable per-task delay accounting"
450 Collect information on time spent by a task waiting for system
451 resources like cpu, synchronous block I/O completion and swapping
452 in pages. Such statistics can help in setting a task's priorities
453 relative to other tasks for cpu, io, rss limits etc.
458 bool "Enable extended accounting over taskstats"
461 Collect extended task accounting data and send the data
462 to userland for processing over the taskstats interface.
466 config TASK_IO_ACCOUNTING
467 bool "Enable per-task storage I/O accounting"
468 depends on TASK_XACCT
470 Collect information on the number of bytes of storage I/O which this
475 endmenu # "CPU/Task time and stats accounting"
480 prompt "RCU Implementation"
484 bool "Tree-based hierarchical RCU"
485 depends on !PREEMPT && SMP
487 This option selects the RCU implementation that is
488 designed for very large SMP system with hundreds or
489 thousands of CPUs. It also scales down nicely to
493 bool "Preemptible tree-based hierarchical RCU"
496 This option selects the RCU implementation that is
497 designed for very large SMP systems with hundreds or
498 thousands of CPUs, but for which real-time response
499 is also required. It also scales down nicely to
502 Select this option if you are unsure.
505 bool "UP-only small-memory-footprint RCU"
506 depends on !PREEMPT && !SMP
508 This option selects the RCU implementation that is
509 designed for UP systems from which real-time response
510 is not required. This option greatly reduces the
511 memory footprint of RCU.
518 This option selects the sleepable version of RCU. This version
519 permits arbitrary sleeping or blocking within RCU read-side critical
523 bool "Task_based RCU implementation using voluntary context switch"
527 This option enables a task-based RCU implementation that uses
528 only voluntary context switch (not preemption!), idle, and
529 user-mode execution as quiescent states.
533 config RCU_STALL_COMMON
534 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
536 This option enables RCU CPU stall code that is common between
537 the TINY and TREE variants of RCU. The purpose is to allow
538 the tiny variants to disable RCU CPU stall warnings, while
539 making these warnings mandatory for the tree variants.
541 config CONTEXT_TRACKING
545 bool "Consider userspace as in RCU extended quiescent state"
546 depends on HAVE_CONTEXT_TRACKING && SMP
547 select CONTEXT_TRACKING
549 This option sets hooks on kernel / userspace boundaries and
550 puts RCU in extended quiescent state when the CPU runs in
551 userspace. It means that when a CPU runs in userspace, it is
552 excluded from the global RCU state machine and thus doesn't
553 try to keep the timer tick on for RCU.
555 Unless you want to hack and help the development of the full
556 dynticks mode, you shouldn't enable this option. It also
557 adds unnecessary overhead.
561 config CONTEXT_TRACKING_FORCE
562 bool "Force context tracking"
563 depends on CONTEXT_TRACKING
564 default y if !NO_HZ_FULL
566 The major pre-requirement for full dynticks to work is to
567 support the context tracking subsystem. But there are also
568 other dependencies to provide in order to make the full
571 This option stands for testing when an arch implements the
572 context tracking backend but doesn't yet fullfill all the
573 requirements to make the full dynticks feature working.
574 Without the full dynticks, there is no way to test the support
575 for context tracking and the subsystems that rely on it: RCU
576 userspace extended quiescent state and tickless cputime
577 accounting. This option copes with the absence of the full
578 dynticks subsystem by forcing the context tracking on all
581 Say Y only if you're working on the development of an
582 architecture backend for the context tracking.
584 Say N otherwise, this option brings an overhead that you
585 don't want in production.
589 int "Tree-based hierarchical RCU fanout value"
592 depends on TREE_RCU || PREEMPT_RCU
596 This option controls the fanout of hierarchical implementations
597 of RCU, allowing RCU to work efficiently on machines with
598 large numbers of CPUs. This value must be at least the fourth
599 root of NR_CPUS, which allows NR_CPUS to be insanely large.
600 The default value of RCU_FANOUT should be used for production
601 systems, but if you are stress-testing the RCU implementation
602 itself, small RCU_FANOUT values allow you to test large-system
603 code paths on small(er) systems.
605 Select a specific number if testing RCU itself.
606 Take the default if unsure.
608 config RCU_FANOUT_LEAF
609 int "Tree-based hierarchical RCU leaf-level fanout value"
610 range 2 RCU_FANOUT if 64BIT
611 range 2 RCU_FANOUT if !64BIT
612 depends on TREE_RCU || PREEMPT_RCU
615 This option controls the leaf-level fanout of hierarchical
616 implementations of RCU, and allows trading off cache misses
617 against lock contention. Systems that synchronize their
618 scheduling-clock interrupts for energy-efficiency reasons will
619 want the default because the smaller leaf-level fanout keeps
620 lock contention levels acceptably low. Very large systems
621 (hundreds or thousands of CPUs) will instead want to set this
622 value to the maximum value possible in order to reduce the
623 number of cache misses incurred during RCU's grace-period
624 initialization. These systems tend to run CPU-bound, and thus
625 are not helped by synchronized interrupts, and thus tend to
626 skew them, which reduces lock contention enough that large
627 leaf-level fanouts work well.
629 Select a specific number if testing RCU itself.
631 Select the maximum permissible value for large systems.
633 Take the default if unsure.
635 config RCU_FANOUT_EXACT
636 bool "Disable tree-based hierarchical RCU auto-balancing"
637 depends on TREE_RCU || PREEMPT_RCU
640 This option forces use of the exact RCU_FANOUT value specified,
641 regardless of imbalances in the hierarchy. This is useful for
642 testing RCU itself, and might one day be useful on systems with
643 strong NUMA behavior.
645 Without RCU_FANOUT_EXACT, the code will balance the hierarchy.
649 config RCU_FAST_NO_HZ
650 bool "Accelerate last non-dyntick-idle CPU's grace periods"
651 depends on NO_HZ_COMMON && SMP
654 This option permits CPUs to enter dynticks-idle state even if
655 they have RCU callbacks queued, and prevents RCU from waking
656 these CPUs up more than roughly once every four jiffies (by
657 default, you can adjust this using the rcutree.rcu_idle_gp_delay
658 parameter), thus improving energy efficiency. On the other
659 hand, this option increases the duration of RCU grace periods,
660 for example, slowing down synchronize_rcu().
662 Say Y if energy efficiency is critically important, and you
663 don't care about increased grace-period durations.
665 Say N if you are unsure.
667 config TREE_RCU_TRACE
668 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
671 This option provides tracing for the TREE_RCU and
672 PREEMPT_RCU implementations, permitting Makefile to
673 trivially select kernel/rcutree_trace.c.
676 bool "Enable RCU priority boosting"
677 depends on RT_MUTEXES && PREEMPT_RCU
680 This option boosts the priority of preempted RCU readers that
681 block the current preemptible RCU grace period for too long.
682 This option also prevents heavy loads from blocking RCU
683 callback invocation for all flavors of RCU.
685 Say Y here if you are working with real-time apps or heavy loads
686 Say N here if you are unsure.
688 config RCU_KTHREAD_PRIO
689 int "Real-time priority to use for RCU worker threads"
690 range 1 99 if RCU_BOOST
691 range 0 99 if !RCU_BOOST
692 default 1 if RCU_BOOST
693 default 0 if !RCU_BOOST
695 This option specifies the SCHED_FIFO priority value that will be
696 assigned to the rcuc/n and rcub/n threads and is also the value
697 used for RCU_BOOST (if enabled). If you are working with a
698 real-time application that has one or more CPU-bound threads
699 running at a real-time priority level, you should set
700 RCU_KTHREAD_PRIO to a priority higher than the highest-priority
701 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
702 value of 1 is appropriate in the common case, which is real-time
703 applications that do not have any CPU-bound threads.
705 Some real-time applications might not have a single real-time
706 thread that saturates a given CPU, but instead might have
707 multiple real-time threads that, taken together, fully utilize
708 that CPU. In this case, you should set RCU_KTHREAD_PRIO to
709 a priority higher than the lowest-priority thread that is
710 conspiring to prevent the CPU from running any non-real-time
711 tasks. For example, if one thread at priority 10 and another
712 thread at priority 5 are between themselves fully consuming
713 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
714 set to priority 6 or higher.
716 Specify the real-time priority, or take the default if unsure.
718 config RCU_BOOST_DELAY
719 int "Milliseconds to delay boosting after RCU grace-period start"
724 This option specifies the time to wait after the beginning of
725 a given grace period before priority-boosting preempted RCU
726 readers blocking that grace period. Note that any RCU reader
727 blocking an expedited RCU grace period is boosted immediately.
729 Accept the default if unsure.
732 bool "Offload RCU callback processing from boot-selected CPUs"
733 depends on TREE_RCU || PREEMPT_RCU
736 Use this option to reduce OS jitter for aggressive HPC or
737 real-time workloads. It can also be used to offload RCU
738 callback invocation to energy-efficient CPUs in battery-powered
739 asymmetric multiprocessors.
741 This option offloads callback invocation from the set of
742 CPUs specified at boot time by the rcu_nocbs parameter.
743 For each such CPU, a kthread ("rcuox/N") will be created to
744 invoke callbacks, where the "N" is the CPU being offloaded,
745 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
746 "s" for RCU-sched. Nothing prevents this kthread from running
747 on the specified CPUs, but (1) the kthreads may be preempted
748 between each callback, and (2) affinity or cgroups can be used
749 to force the kthreads to run on whatever set of CPUs is desired.
751 Say Y here if you want to help to debug reduced OS jitter.
752 Say N here if you are unsure.
755 prompt "Build-forced no-CBs CPUs"
756 default RCU_NOCB_CPU_NONE
757 depends on RCU_NOCB_CPU
759 This option allows no-CBs CPUs (whose RCU callbacks are invoked
760 from kthreads rather than from softirq context) to be specified
761 at build time. Additional no-CBs CPUs may be specified by
762 the rcu_nocbs= boot parameter.
764 config RCU_NOCB_CPU_NONE
765 bool "No build_forced no-CBs CPUs"
767 This option does not force any of the CPUs to be no-CBs CPUs.
768 Only CPUs designated by the rcu_nocbs= boot parameter will be
769 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
770 kthreads whose names begin with "rcuo". All other CPUs will
771 invoke their own RCU callbacks in softirq context.
773 Select this option if you want to choose no-CBs CPUs at
774 boot time, for example, to allow testing of different no-CBs
775 configurations without having to rebuild the kernel each time.
777 config RCU_NOCB_CPU_ZERO
778 bool "CPU 0 is a build_forced no-CBs CPU"
780 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
781 callbacks are invoked by a per-CPU kthread whose name begins
782 with "rcuo". Additional CPUs may be designated as no-CBs
783 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
784 All other CPUs will invoke their own RCU callbacks in softirq
787 Select this if CPU 0 needs to be a no-CBs CPU for real-time
788 or energy-efficiency reasons, but the real reason it exists
789 is to ensure that randconfig testing covers mixed systems.
791 config RCU_NOCB_CPU_ALL
792 bool "All CPUs are build_forced no-CBs CPUs"
794 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
795 boot parameter will be ignored. All CPUs' RCU callbacks will
796 be executed in the context of per-CPU rcuo kthreads created for
797 this purpose. Assuming that the kthreads whose names start with
798 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
799 on the remaining CPUs, but might decrease memory locality during
800 RCU-callback invocation, thus potentially degrading throughput.
802 Select this if all CPUs need to be no-CBs CPUs for real-time
803 or energy-efficiency reasons.
807 config RCU_EXPEDITE_BOOT
811 This option enables expedited grace periods at boot time,
812 as if rcu_expedite_gp() had been invoked early in boot.
813 The corresponding rcu_unexpedite_gp() is invoked from
814 rcu_end_inkernel_boot(), which is intended to be invoked
815 at the end of the kernel-only boot sequence, just before
818 Accept the default if unsure.
820 endmenu # "RCU Subsystem"
827 tristate "Kernel .config support"
830 This option enables the complete Linux kernel ".config" file
831 contents to be saved in the kernel. It provides documentation
832 of which kernel options are used in a running kernel or in an
833 on-disk kernel. This information can be extracted from the kernel
834 image file with the script scripts/extract-ikconfig and used as
835 input to rebuild the current kernel or to build another kernel.
836 It can also be extracted from a running kernel by reading
837 /proc/config.gz if enabled (below).
840 bool "Enable access to .config through /proc/config.gz"
841 depends on IKCONFIG && PROC_FS
843 This option enables access to the kernel configuration file
844 through /proc/config.gz.
847 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
852 Select the minimal kernel log buffer size as a power of 2.
853 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
854 parameter, see below. Any higher size also might be forced
855 by "log_buf_len" boot parameter.
865 config LOG_CPU_MAX_BUF_SHIFT
866 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
869 default 12 if !BASE_SMALL
870 default 0 if BASE_SMALL
873 This option allows to increase the default ring buffer size
874 according to the number of CPUs. The value defines the contribution
875 of each CPU as a power of 2. The used space is typically only few
876 lines however it might be much more when problems are reported,
879 The increased size means that a new buffer has to be allocated and
880 the original static one is unused. It makes sense only on systems
881 with more CPUs. Therefore this value is used only when the sum of
882 contributions is greater than the half of the default kernel ring
883 buffer as defined by LOG_BUF_SHIFT. The default values are set
884 so that more than 64 CPUs are needed to trigger the allocation.
886 Also this option is ignored when "log_buf_len" kernel parameter is
887 used as it forces an exact (power of two) size of the ring buffer.
889 The number of possible CPUs is used for this computation ignoring
890 hotplugging making the compuation optimal for the the worst case
891 scenerio while allowing a simple algorithm to be used from bootup.
893 Examples shift values and their meaning:
894 17 => 128 KB for each CPU
895 16 => 64 KB for each CPU
896 15 => 32 KB for each CPU
897 14 => 16 KB for each CPU
898 13 => 8 KB for each CPU
899 12 => 4 KB for each CPU
902 # Architectures with an unreliable sched_clock() should select this:
904 config HAVE_UNSTABLE_SCHED_CLOCK
907 config GENERIC_SCHED_CLOCK
911 # For architectures that want to enable the support for NUMA-affine scheduler
914 config ARCH_SUPPORTS_NUMA_BALANCING
918 # For architectures that know their GCC __int128 support is sound
920 config ARCH_SUPPORTS_INT128
923 # For architectures that (ab)use NUMA to represent different memory regions
924 # all cpu-local but of different latencies, such as SuperH.
926 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
929 config NUMA_BALANCING
930 bool "Memory placement aware NUMA scheduler"
931 depends on ARCH_SUPPORTS_NUMA_BALANCING
932 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
933 depends on SMP && NUMA && MIGRATION
935 This option adds support for automatic NUMA aware memory/task placement.
936 The mechanism is quite primitive and is based on migrating memory when
937 it has references to the node the task is running on.
939 This system will be inactive on UMA systems.
941 config NUMA_BALANCING_DEFAULT_ENABLED
942 bool "Automatically enable NUMA aware memory/task placement"
944 depends on NUMA_BALANCING
946 If set, automatic NUMA balancing will be enabled if running on a NUMA
950 bool "Control Group support"
953 This option adds support for grouping sets of processes together, for
954 use with process control subsystems such as Cpusets, CFS, memory
955 controls or device isolation.
957 - Documentation/scheduler/sched-design-CFS.txt (CFS)
958 - Documentation/cgroups/ (features for grouping, isolation
959 and resource control)
966 bool "Example debug cgroup subsystem"
969 This option enables a simple cgroup subsystem that
970 exports useful debugging information about the cgroups
975 config CGROUP_FREEZER
976 bool "Freezer cgroup subsystem"
978 Provides a way to freeze and unfreeze all tasks in a
982 bool "Device controller for cgroups"
984 Provides a cgroup implementing whitelists for devices which
985 a process in the cgroup can mknod or open.
988 bool "Cpuset support"
990 This option will let you create and manage CPUSETs which
991 allow dynamically partitioning a system into sets of CPUs and
992 Memory Nodes and assigning tasks to run only within those sets.
993 This is primarily useful on large SMP or NUMA systems.
997 config PROC_PID_CPUSET
998 bool "Include legacy /proc/<pid>/cpuset file"
1002 config CGROUP_CPUACCT
1003 bool "Simple CPU accounting cgroup subsystem"
1005 Provides a simple Resource Controller for monitoring the
1006 total CPU consumed by the tasks in a cgroup.
1012 bool "Memory Resource Controller for Control Groups"
1016 Provides a memory resource controller that manages both anonymous
1017 memory and page cache. (See Documentation/cgroups/memory.txt)
1020 bool "Memory Resource Controller Swap Extension"
1021 depends on MEMCG && SWAP
1023 Add swap management feature to memory resource controller. When you
1024 enable this, you can limit mem+swap usage per cgroup. In other words,
1025 when you disable this, memory resource controller has no cares to
1026 usage of swap...a process can exhaust all of the swap. This extension
1027 is useful when you want to avoid exhaustion swap but this itself
1028 adds more overheads and consumes memory for remembering information.
1029 Especially if you use 32bit system or small memory system, please
1030 be careful about enabling this. When memory resource controller
1031 is disabled by boot option, this will be automatically disabled and
1032 there will be no overhead from this. Even when you set this config=y,
1033 if boot option "swapaccount=0" is set, swap will not be accounted.
1034 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1035 size is 4096bytes, 512k per 1Gbytes of swap.
1036 config MEMCG_SWAP_ENABLED
1037 bool "Memory Resource Controller Swap Extension enabled by default"
1038 depends on MEMCG_SWAP
1041 Memory Resource Controller Swap Extension comes with its price in
1042 a bigger memory consumption. General purpose distribution kernels
1043 which want to enable the feature but keep it disabled by default
1044 and let the user enable it by swapaccount=1 boot command line
1045 parameter should have this option unselected.
1046 For those who want to have the feature enabled by default should
1047 select this option (if, for some reason, they need to disable it
1048 then swapaccount=0 does the trick).
1050 bool "Memory Resource Controller Kernel Memory accounting"
1052 depends on SLUB || SLAB
1054 The Kernel Memory extension for Memory Resource Controller can limit
1055 the amount of memory used by kernel objects in the system. Those are
1056 fundamentally different from the entities handled by the standard
1057 Memory Controller, which are page-based, and can be swapped. Users of
1058 the kmem extension can use it to guarantee that no group of processes
1059 will ever exhaust kernel resources alone.
1061 WARNING: Current implementation lacks reclaim support. That means
1062 allocation attempts will fail when close to the limit even if there
1063 are plenty of kmem available for reclaim. That makes this option
1064 unusable in real life so DO NOT SELECT IT unless for development
1067 config CGROUP_HUGETLB
1068 bool "HugeTLB Resource Controller for Control Groups"
1069 depends on HUGETLB_PAGE
1073 Provides a cgroup Resource Controller for HugeTLB pages.
1074 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1075 The limit is enforced during page fault. Since HugeTLB doesn't
1076 support page reclaim, enforcing the limit at page fault time implies
1077 that, the application will get SIGBUS signal if it tries to access
1078 HugeTLB pages beyond its limit. This requires the application to know
1079 beforehand how much HugeTLB pages it would require for its use. The
1080 control group is tracked in the third page lru pointer. This means
1081 that we cannot use the controller with huge page less than 3 pages.
1084 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1085 depends on PERF_EVENTS && CGROUPS
1087 This option extends the per-cpu mode to restrict monitoring to
1088 threads which belong to the cgroup specified and run on the
1093 menuconfig CGROUP_SCHED
1094 bool "Group CPU scheduler"
1097 This feature lets CPU scheduler recognize task groups and control CPU
1098 bandwidth allocation to such task groups. It uses cgroups to group
1102 config FAIR_GROUP_SCHED
1103 bool "Group scheduling for SCHED_OTHER"
1104 depends on CGROUP_SCHED
1105 default CGROUP_SCHED
1107 config CFS_BANDWIDTH
1108 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1109 depends on FAIR_GROUP_SCHED
1112 This option allows users to define CPU bandwidth rates (limits) for
1113 tasks running within the fair group scheduler. Groups with no limit
1114 set are considered to be unconstrained and will run with no
1116 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1118 config RT_GROUP_SCHED
1119 bool "Group scheduling for SCHED_RR/FIFO"
1120 depends on CGROUP_SCHED
1123 This feature lets you explicitly allocate real CPU bandwidth
1124 to task groups. If enabled, it will also make it impossible to
1125 schedule realtime tasks for non-root users until you allocate
1126 realtime bandwidth for them.
1127 See Documentation/scheduler/sched-rt-group.txt for more information.
1132 bool "Block IO controller"
1136 Generic block IO controller cgroup interface. This is the common
1137 cgroup interface which should be used by various IO controlling
1140 Currently, CFQ IO scheduler uses it to recognize task groups and
1141 control disk bandwidth allocation (proportional time slice allocation)
1142 to such task groups. It is also used by bio throttling logic in
1143 block layer to implement upper limit in IO rates on a device.
1145 This option only enables generic Block IO controller infrastructure.
1146 One needs to also enable actual IO controlling logic/policy. For
1147 enabling proportional weight division of disk bandwidth in CFQ, set
1148 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1149 CONFIG_BLK_DEV_THROTTLING=y.
1151 See Documentation/cgroups/blkio-controller.txt for more information.
1153 config DEBUG_BLK_CGROUP
1154 bool "Enable Block IO controller debugging"
1155 depends on BLK_CGROUP
1158 Enable some debugging help. Currently it exports additional stat
1159 files in a cgroup which can be useful for debugging.
1163 config CHECKPOINT_RESTORE
1164 bool "Checkpoint/restore support" if EXPERT
1167 Enables additional kernel features in a sake of checkpoint/restore.
1168 In particular it adds auxiliary prctl codes to setup process text,
1169 data and heap segment sizes, and a few additional /proc filesystem
1172 If unsure, say N here.
1174 menuconfig NAMESPACES
1175 bool "Namespaces support" if EXPERT
1178 Provides the way to make tasks work with different objects using
1179 the same id. For example same IPC id may refer to different objects
1180 or same user id or pid may refer to different tasks when used in
1181 different namespaces.
1186 bool "UTS namespace"
1189 In this namespace tasks see different info provided with the
1193 bool "IPC namespace"
1194 depends on (SYSVIPC || POSIX_MQUEUE)
1197 In this namespace tasks work with IPC ids which correspond to
1198 different IPC objects in different namespaces.
1201 bool "User namespace"
1204 This allows containers, i.e. vservers, to use user namespaces
1205 to provide different user info for different servers.
1207 When user namespaces are enabled in the kernel it is
1208 recommended that the MEMCG and MEMCG_KMEM options also be
1209 enabled and that user-space use the memory control groups to
1210 limit the amount of memory a memory unprivileged users can
1216 bool "PID Namespaces"
1219 Support process id namespaces. This allows having multiple
1220 processes with the same pid as long as they are in different
1221 pid namespaces. This is a building block of containers.
1224 bool "Network namespace"
1228 Allow user space to create what appear to be multiple instances
1229 of the network stack.
1233 config SCHED_AUTOGROUP
1234 bool "Automatic process group scheduling"
1237 select FAIR_GROUP_SCHED
1239 This option optimizes the scheduler for common desktop workloads by
1240 automatically creating and populating task groups. This separation
1241 of workloads isolates aggressive CPU burners (like build jobs) from
1242 desktop applications. Task group autogeneration is currently based
1245 config SYSFS_DEPRECATED
1246 bool "Enable deprecated sysfs features to support old userspace tools"
1250 This option adds code that switches the layout of the "block" class
1251 devices, to not show up in /sys/class/block/, but only in
1254 This switch is only active when the sysfs.deprecated=1 boot option is
1255 passed or the SYSFS_DEPRECATED_V2 option is set.
1257 This option allows new kernels to run on old distributions and tools,
1258 which might get confused by /sys/class/block/. Since 2007/2008 all
1259 major distributions and tools handle this just fine.
1261 Recent distributions and userspace tools after 2009/2010 depend on
1262 the existence of /sys/class/block/, and will not work with this
1265 Only if you are using a new kernel on an old distribution, you might
1268 config SYSFS_DEPRECATED_V2
1269 bool "Enable deprecated sysfs features by default"
1272 depends on SYSFS_DEPRECATED
1274 Enable deprecated sysfs by default.
1276 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1279 Only if you are using a new kernel on an old distribution, you might
1280 need to say Y here. Even then, odds are you would not need it
1281 enabled, you can always pass the boot option if absolutely necessary.
1284 bool "Kernel->user space relay support (formerly relayfs)"
1286 This option enables support for relay interface support in
1287 certain file systems (such as debugfs).
1288 It is designed to provide an efficient mechanism for tools and
1289 facilities to relay large amounts of data from kernel space to
1294 config BLK_DEV_INITRD
1295 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1296 depends on BROKEN || !FRV
1298 The initial RAM filesystem is a ramfs which is loaded by the
1299 boot loader (loadlin or lilo) and that is mounted as root
1300 before the normal boot procedure. It is typically used to
1301 load modules needed to mount the "real" root file system,
1302 etc. See <file:Documentation/initrd.txt> for details.
1304 If RAM disk support (BLK_DEV_RAM) is also included, this
1305 also enables initial RAM disk (initrd) support and adds
1306 15 Kbytes (more on some other architectures) to the kernel size.
1312 source "usr/Kconfig"
1316 config CC_OPTIMIZE_FOR_SIZE
1317 bool "Optimize for size"
1319 Enabling this option will pass "-Os" instead of "-O2" to
1320 your compiler resulting in a smaller kernel.
1325 bool "Enable gcc link time optimization (LTO)"
1326 # Only tested on X86 for now. For other architectures you likely
1327 # have to fix some things first, like adding asmlinkages etc.
1329 # lto does not support excluding flags for specific files
1330 # right now. Can be removed if that is fixed.
1331 depends on !FUNCTION_TRACER
1333 With this option gcc will do whole program optimizations for
1334 the whole kernel and module. This increases compile time, but can
1335 lead to better code. It allows gcc to inline functions between
1336 different files and do other optimization. It might also trigger
1337 bugs due to more aggressive optimization. It allows gcc to drop unused
1338 code. On smaller monolithic kernel configurations
1339 it usually leads to smaller kernels, especially when modules
1342 With this option gcc will also do some global checking over
1343 different source files. It also disables a number of kernel
1346 This option is recommended for release builds. With LTO
1347 the kernel always has to be re-optimized (but not re-parsed)
1350 This requires a gcc 4.8 or later compiler and
1351 Linux binutils 2.21.51.0.3 or later. gcc 4.9 builds significantly
1352 faster than 4.8 It does not currently work with a FSF release of
1353 binutils or with the gold linker.
1355 On larger configurations this may need more than 4GB of RAM.
1356 It will likely not work on those with a 32bit compiler.
1358 When the toolchain support is not available this will (hopefully)
1359 be automatically disabled.
1361 For more information see Documentation/lto-build
1364 bool "Disable LTO again"
1368 This option is merely here so that allyesconfig or allmodconfig do
1369 not enable LTO. If you want to actually use LTO do not enable.
1374 depends on LTO_MENU && !LTO_DISABLE
1377 bool "Enable LTO compile time debugging"
1380 Enable LTO debugging in the compiler. The compiler dumps
1381 some log files that make it easier to figure out LTO
1382 behavior. The log files also allow to reconstruct
1383 the global inlining and a global callgraph.
1384 They however add some (single threaded) cost to the
1385 compilation. When in doubt do not enable.
1388 bool "Allow aggressive cloning for function specialization"
1391 Allow the compiler to clone and specialize functions for specific
1392 arguments when it determines these arguments are very commonly
1393 called. Experimential. Will increase text size.
1404 config SYSCTL_EXCEPTION_TRACE
1407 Enable support for /proc/sys/debug/exception-trace.
1409 config SYSCTL_ARCH_UNALIGN_NO_WARN
1412 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1413 Allows arch to define/use @no_unaligned_warning to possibly warn
1414 about unaligned access emulation going on under the hood.
1416 config SYSCTL_ARCH_UNALIGN_ALLOW
1419 Enable support for /proc/sys/kernel/unaligned-trap
1420 Allows arches to define/use @unaligned_enabled to runtime toggle
1421 the unaligned access emulation.
1422 see arch/parisc/kernel/unaligned.c for reference
1424 config HAVE_PCSPKR_PLATFORM
1427 # interpreter that classic socket filters depend on
1432 bool "Configure standard kernel features (expert users)"
1433 # Unhide debug options, to make the on-by-default options visible
1436 This option allows certain base kernel options and settings
1437 to be disabled or tweaked. This is for specialized
1438 environments which can tolerate a "non-standard" kernel.
1439 Only use this if you really know what you are doing.
1442 bool "Enable 16-bit UID system calls" if EXPERT
1443 depends on HAVE_UID16
1446 This enables the legacy 16-bit UID syscall wrappers.
1448 config SGETMASK_SYSCALL
1449 bool "sgetmask/ssetmask syscalls support" if EXPERT
1450 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1452 sys_sgetmask and sys_ssetmask are obsolete system calls
1453 no longer supported in libc but still enabled by default in some
1456 If unsure, leave the default option here.
1458 config SYSFS_SYSCALL
1459 bool "Sysfs syscall support" if EXPERT
1462 sys_sysfs is an obsolete system call no longer supported in libc.
1463 Note that disabling this option is more secure but might break
1464 compatibility with some systems.
1466 If unsure say Y here.
1468 config SYSCTL_SYSCALL
1469 bool "Sysctl syscall support" if EXPERT
1470 depends on PROC_SYSCTL
1474 sys_sysctl uses binary paths that have been found challenging
1475 to properly maintain and use. The interface in /proc/sys
1476 using paths with ascii names is now the primary path to this
1479 Almost nothing using the binary sysctl interface so if you are
1480 trying to save some space it is probably safe to disable this,
1481 making your kernel marginally smaller.
1483 If unsure say N here.
1486 bool "Load all symbols for debugging/ksymoops" if EXPERT
1489 Say Y here to let the kernel print out symbolic crash information and
1490 symbolic stack backtraces. This increases the size of the kernel
1491 somewhat, as all symbols have to be loaded into the kernel image.
1494 bool "Include all symbols in kallsyms"
1495 depends on DEBUG_KERNEL && KALLSYMS
1497 Normally kallsyms only contains the symbols of functions for nicer
1498 OOPS messages and backtraces (i.e., symbols from the text and inittext
1499 sections). This is sufficient for most cases. And only in very rare
1500 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1501 names of variables from the data sections, etc).
1503 This option makes sure that all symbols are loaded into the kernel
1504 image (i.e., symbols from all sections) in cost of increased kernel
1505 size (depending on the kernel configuration, it may be 300KiB or
1506 something like this).
1508 Say N unless you really need all symbols.
1512 bool "Enable support for printk" if EXPERT
1515 This option enables normal printk support. Removing it
1516 eliminates most of the message strings from the kernel image
1517 and makes the kernel more or less silent. As this makes it
1518 very difficult to diagnose system problems, saying N here is
1519 strongly discouraged.
1522 bool "BUG() support" if EXPERT
1525 Disabling this option eliminates support for BUG and WARN, reducing
1526 the size of your kernel image and potentially quietly ignoring
1527 numerous fatal conditions. You should only consider disabling this
1528 option for embedded systems with no facilities for reporting errors.
1534 bool "Enable ELF core dumps" if EXPERT
1536 Enable support for generating core dumps. Disabling saves about 4k.
1539 config PCSPKR_PLATFORM
1540 bool "Enable PC-Speaker support" if EXPERT
1541 depends on HAVE_PCSPKR_PLATFORM
1545 This option allows to disable the internal PC-Speaker
1546 support, saving some memory.
1550 bool "Enable full-sized data structures for core" if EXPERT
1552 Disabling this option reduces the size of miscellaneous core
1553 kernel data structures. This saves memory on small machines,
1554 but may reduce performance.
1557 bool "Enable futex support" if EXPERT
1561 Disabling this option will cause the kernel to be built without
1562 support for "fast userspace mutexes". The resulting kernel may not
1563 run glibc-based applications correctly.
1565 config HAVE_FUTEX_CMPXCHG
1569 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1570 is implemented and always working. This removes a couple of runtime
1574 bool "Enable eventpoll support" if EXPERT
1578 Disabling this option will cause the kernel to be built without
1579 support for epoll family of system calls.
1582 bool "Enable signalfd() system call" if EXPERT
1586 Enable the signalfd() system call that allows to receive signals
1587 on a file descriptor.
1592 bool "Enable timerfd() system call" if EXPERT
1596 Enable the timerfd() system call that allows to receive timer
1597 events on a file descriptor.
1602 bool "Enable eventfd() system call" if EXPERT
1606 Enable the eventfd() system call that allows to receive both
1607 kernel notification (ie. KAIO) or userspace notifications.
1611 # syscall, maps, verifier
1613 bool "Enable bpf() system call"
1618 Enable the bpf() system call that allows to manipulate eBPF
1619 programs and maps via file descriptors.
1622 bool "Use full shmem filesystem" if EXPERT
1626 The shmem is an internal filesystem used to manage shared memory.
1627 It is backed by swap and manages resource limits. It is also exported
1628 to userspace as tmpfs if TMPFS is enabled. Disabling this
1629 option replaces shmem and tmpfs with the much simpler ramfs code,
1630 which may be appropriate on small systems without swap.
1633 bool "Enable AIO support" if EXPERT
1636 This option enables POSIX asynchronous I/O which may by used
1637 by some high performance threaded applications. Disabling
1638 this option saves about 7k.
1640 config ADVISE_SYSCALLS
1641 bool "Enable madvise/fadvise syscalls" if EXPERT
1644 This option enables the madvise and fadvise syscalls, used by
1645 applications to advise the kernel about their future memory or file
1646 usage, improving performance. If building an embedded system where no
1647 applications use these syscalls, you can disable this option to save
1652 bool "Enable PCI quirk workarounds" if EXPERT
1655 This enables workarounds for various PCI chipset
1656 bugs/quirks. Disable this only if your target machine is
1657 unaffected by PCI quirks.
1660 bool "Embedded system"
1661 option allnoconfig_y
1664 This option should be enabled if compiling the kernel for
1665 an embedded system so certain expert options are available
1668 config HAVE_PERF_EVENTS
1671 See tools/perf/design.txt for details.
1673 config PERF_USE_VMALLOC
1676 See tools/perf/design.txt for details
1678 menu "Kernel Performance Events And Counters"
1681 bool "Kernel performance events and counters"
1682 default y if PROFILING
1683 depends on HAVE_PERF_EVENTS
1688 Enable kernel support for various performance events provided
1689 by software and hardware.
1691 Software events are supported either built-in or via the
1692 use of generic tracepoints.
1694 Most modern CPUs support performance events via performance
1695 counter registers. These registers count the number of certain
1696 types of hw events: such as instructions executed, cachemisses
1697 suffered, or branches mis-predicted - without slowing down the
1698 kernel or applications. These registers can also trigger interrupts
1699 when a threshold number of events have passed - and can thus be
1700 used to profile the code that runs on that CPU.
1702 The Linux Performance Event subsystem provides an abstraction of
1703 these software and hardware event capabilities, available via a
1704 system call and used by the "perf" utility in tools/perf/. It
1705 provides per task and per CPU counters, and it provides event
1706 capabilities on top of those.
1710 config DEBUG_PERF_USE_VMALLOC
1712 bool "Debug: use vmalloc to back perf mmap() buffers"
1713 depends on PERF_EVENTS && DEBUG_KERNEL
1714 select PERF_USE_VMALLOC
1716 Use vmalloc memory to back perf mmap() buffers.
1718 Mostly useful for debugging the vmalloc code on platforms
1719 that don't require it.
1725 config VM_EVENT_COUNTERS
1727 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1729 VM event counters are needed for event counts to be shown.
1730 This option allows the disabling of the VM event counters
1731 on EXPERT systems. /proc/vmstat will only show page counts
1732 if VM event counters are disabled.
1736 bool "Enable SLUB debugging support" if EXPERT
1737 depends on SLUB && SYSFS
1739 SLUB has extensive debug support features. Disabling these can
1740 result in significant savings in code size. This also disables
1741 SLUB sysfs support. /sys/slab will not exist and there will be
1742 no support for cache validation etc.
1745 bool "Disable heap randomization"
1748 Randomizing heap placement makes heap exploits harder, but it
1749 also breaks ancient binaries (including anything libc5 based).
1750 This option changes the bootup default to heap randomization
1751 disabled, and can be overridden at runtime by setting
1752 /proc/sys/kernel/randomize_va_space to 2.
1754 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1757 prompt "Choose SLAB allocator"
1760 This option allows to select a slab allocator.
1765 The regular slab allocator that is established and known to work
1766 well in all environments. It organizes cache hot objects in
1767 per cpu and per node queues.
1770 bool "SLUB (Unqueued Allocator)"
1772 SLUB is a slab allocator that minimizes cache line usage
1773 instead of managing queues of cached objects (SLAB approach).
1774 Per cpu caching is realized using slabs of objects instead
1775 of queues of objects. SLUB can use memory efficiently
1776 and has enhanced diagnostics. SLUB is the default choice for
1781 bool "SLOB (Simple Allocator)"
1783 SLOB replaces the stock allocator with a drastically simpler
1784 allocator. SLOB is generally more space efficient but
1785 does not perform as well on large systems.
1789 config SLUB_CPU_PARTIAL
1791 depends on SLUB && SMP
1792 bool "SLUB per cpu partial cache"
1794 Per cpu partial caches accellerate objects allocation and freeing
1795 that is local to a processor at the price of more indeterminism
1796 in the latency of the free. On overflow these caches will be cleared
1797 which requires the taking of locks that may cause latency spikes.
1798 Typically one would choose no for a realtime system.
1800 config MMAP_ALLOW_UNINITIALIZED
1801 bool "Allow mmapped anonymous memory to be uninitialized"
1802 depends on EXPERT && !MMU
1805 Normally, and according to the Linux spec, anonymous memory obtained
1806 from mmap() has it's contents cleared before it is passed to
1807 userspace. Enabling this config option allows you to request that
1808 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1809 providing a huge performance boost. If this option is not enabled,
1810 then the flag will be ignored.
1812 This is taken advantage of by uClibc's malloc(), and also by
1813 ELF-FDPIC binfmt's brk and stack allocator.
1815 Because of the obvious security issues, this option should only be
1816 enabled on embedded devices where you control what is run in
1817 userspace. Since that isn't generally a problem on no-MMU systems,
1818 it is normally safe to say Y here.
1820 See Documentation/nommu-mmap.txt for more information.
1822 config SYSTEM_TRUSTED_KEYRING
1823 bool "Provide system-wide ring of trusted keys"
1826 Provide a system keyring to which trusted keys can be added. Keys in
1827 the keyring are considered to be trusted. Keys may be added at will
1828 by the kernel from compiled-in data and from hardware key stores, but
1829 userspace may only add extra keys if those keys can be verified by
1830 keys already in the keyring.
1832 Keys in this keyring are used by module signature checking.
1835 bool "Profiling support"
1837 Say Y here to enable the extended profiling support mechanisms used
1838 by profilers such as OProfile.
1841 # Place an empty function call at each tracepoint site. Can be
1842 # dynamically changed for a probe function.
1847 source "arch/Kconfig"
1849 endmenu # General setup
1851 config HAVE_GENERIC_DMA_COHERENT
1858 depends on SLAB || SLUB_DEBUG
1866 default 0 if BASE_FULL
1867 default 1 if !BASE_FULL
1870 bool "Enable loadable module support"
1873 Kernel modules are small pieces of compiled code which can
1874 be inserted in the running kernel, rather than being
1875 permanently built into the kernel. You use the "modprobe"
1876 tool to add (and sometimes remove) them. If you say Y here,
1877 many parts of the kernel can be built as modules (by
1878 answering M instead of Y where indicated): this is most
1879 useful for infrequently used options which are not required
1880 for booting. For more information, see the man pages for
1881 modprobe, lsmod, modinfo, insmod and rmmod.
1883 If you say Y here, you will need to run "make
1884 modules_install" to put the modules under /lib/modules/
1885 where modprobe can find them (you may need to be root to do
1892 config MODULE_FORCE_LOAD
1893 bool "Forced module loading"
1896 Allow loading of modules without version information (ie. modprobe
1897 --force). Forced module loading sets the 'F' (forced) taint flag and
1898 is usually a really bad idea.
1900 config MODULE_UNLOAD
1901 bool "Module unloading"
1903 Without this option you will not be able to unload any
1904 modules (note that some modules may not be unloadable
1905 anyway), which makes your kernel smaller, faster
1906 and simpler. If unsure, say Y.
1908 config MODULE_FORCE_UNLOAD
1909 bool "Forced module unloading"
1910 depends on MODULE_UNLOAD
1912 This option allows you to force a module to unload, even if the
1913 kernel believes it is unsafe: the kernel will remove the module
1914 without waiting for anyone to stop using it (using the -f option to
1915 rmmod). This is mainly for kernel developers and desperate users.
1919 bool "Module versioning support"
1920 # LTO should work with gcc 4.9
1923 Usually, you have to use modules compiled with your kernel.
1924 Saying Y here makes it sometimes possible to use modules
1925 compiled for different kernels, by adding enough information
1926 to the modules to (hopefully) spot any changes which would
1927 make them incompatible with the kernel you are running. If
1930 config MODULE_SRCVERSION_ALL
1931 bool "Source checksum for all modules"
1933 Modules which contain a MODULE_VERSION get an extra "srcversion"
1934 field inserted into their modinfo section, which contains a
1935 sum of the source files which made it. This helps maintainers
1936 see exactly which source was used to build a module (since
1937 others sometimes change the module source without updating
1938 the version). With this option, such a "srcversion" field
1939 will be created for all modules. If unsure, say N.
1942 bool "Module signature verification"
1944 select SYSTEM_TRUSTED_KEYRING
1947 select ASYMMETRIC_KEY_TYPE
1948 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1949 select PUBLIC_KEY_ALGO_RSA
1952 select X509_CERTIFICATE_PARSER
1954 Check modules for valid signatures upon load: the signature
1955 is simply appended to the module. For more information see
1956 Documentation/module-signing.txt.
1958 !!!WARNING!!! If you enable this option, you MUST make sure that the
1959 module DOES NOT get stripped after being signed. This includes the
1960 debuginfo strip done by some packagers (such as rpmbuild) and
1961 inclusion into an initramfs that wants the module size reduced.
1963 config MODULE_SIG_FORCE
1964 bool "Require modules to be validly signed"
1965 depends on MODULE_SIG
1967 Reject unsigned modules or signed modules for which we don't have a
1968 key. Without this, such modules will simply taint the kernel.
1970 config MODULE_SIG_ALL
1971 bool "Automatically sign all modules"
1973 depends on MODULE_SIG
1975 Sign all modules during make modules_install. Without this option,
1976 modules must be signed manually, using the scripts/sign-file tool.
1978 comment "Do not forget to sign required modules with scripts/sign-file"
1979 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1982 prompt "Which hash algorithm should modules be signed with?"
1983 depends on MODULE_SIG
1985 This determines which sort of hashing algorithm will be used during
1986 signature generation. This algorithm _must_ be built into the kernel
1987 directly so that signature verification can take place. It is not
1988 possible to load a signed module containing the algorithm to check
1989 the signature on that module.
1991 config MODULE_SIG_SHA1
1992 bool "Sign modules with SHA-1"
1995 config MODULE_SIG_SHA224
1996 bool "Sign modules with SHA-224"
1997 select CRYPTO_SHA256
1999 config MODULE_SIG_SHA256
2000 bool "Sign modules with SHA-256"
2001 select CRYPTO_SHA256
2003 config MODULE_SIG_SHA384
2004 bool "Sign modules with SHA-384"
2005 select CRYPTO_SHA512
2007 config MODULE_SIG_SHA512
2008 bool "Sign modules with SHA-512"
2009 select CRYPTO_SHA512
2013 config MODULE_SIG_HASH
2015 depends on MODULE_SIG
2016 default "sha1" if MODULE_SIG_SHA1
2017 default "sha224" if MODULE_SIG_SHA224
2018 default "sha256" if MODULE_SIG_SHA256
2019 default "sha384" if MODULE_SIG_SHA384
2020 default "sha512" if MODULE_SIG_SHA512
2022 config MODULE_COMPRESS
2023 bool "Compress modules on installation"
2026 This option compresses the kernel modules when 'make
2027 modules_install' is run.
2029 The modules will be compressed either using gzip or xz depend on the
2030 choice made in "Compression algorithm".
2032 module-init-tools has support for gzip format while kmod handle gzip
2033 and xz compressed modules.
2035 When a kernel module is installed from outside of the main kernel
2036 source and uses the Kbuild system for installing modules then that
2037 kernel module will also be compressed when it is installed.
2039 This option provides little benefit when the modules are to be used inside
2040 an initrd or initramfs, it generally is more efficient to compress the whole
2041 initrd or initramfs instead.
2043 This is fully compatible with signed modules while the signed module is
2044 compressed. module-init-tools or kmod handles decompression and provide to
2045 other layer the uncompressed but signed payload.
2048 prompt "Compression algorithm"
2049 depends on MODULE_COMPRESS
2050 default MODULE_COMPRESS_GZIP
2052 This determines which sort of compression will be used during
2053 'make modules_install'.
2055 GZIP (default) and XZ are supported.
2057 config MODULE_COMPRESS_GZIP
2060 config MODULE_COMPRESS_XZ
2067 config INIT_ALL_POSSIBLE
2070 Back when each arch used to define their own cpu_online_mask and
2071 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2072 with all 1s, and others with all 0s. When they were centralised,
2073 it was better to provide this option than to break all the archs
2074 and have several arch maintainers pursuing me down dark alleys.
2079 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
2081 Need stop_machine() primitive.
2083 source "block/Kconfig"
2085 config PREEMPT_NOTIFIERS
2092 # Can be selected by architectures with broken toolchains
2093 # that get confused by correct const<->read_only section
2095 config BROKEN_RODATA
2101 Build a simple ASN.1 grammar compiler that produces a bytecode output
2102 that can be interpreted by the ASN.1 stream decoder and used to
2103 inform it as to what tags are to be expected in a stream and what
2104 functions to call on what tags.
2106 source "kernel/Kconfig.locks"
projects / karo-tx-linux.git / blob