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
264 config CROSS_MEMORY_ATTACH
265 bool "Enable process_vm_readv/writev syscalls"
269 Enabling this option adds the system calls process_vm_readv and
270 process_vm_writev which allow a process with the correct privileges
271 to directly read from or write to another process' address space.
272 See the man page for more details.
275 bool "open by fhandle syscalls"
278 If you say Y here, a user level program will be able to map
279 file names to handle and then later use the handle for
280 different file system operations. This is useful in implementing
281 userspace file servers, which now track files using handles instead
282 of names. The handle would remain the same even if file names
283 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
287 bool "uselib syscall"
290 This option enables the uselib syscall, a system call used in the
291 dynamic linker from libc5 and earlier. glibc does not use this
292 system call. If you intend to run programs built on libc5 or
293 earlier, you may need to enable this syscall. Current systems
294 running glibc can safely disable this.
297 bool "Auditing support"
300 Enable auditing infrastructure that can be used with another
301 kernel subsystem, such as SELinux (which requires this for
302 logging of avc messages output). Does not do system-call
303 auditing without CONFIG_AUDITSYSCALL.
305 config HAVE_ARCH_AUDITSYSCALL
309 bool "Enable system-call auditing support"
310 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
311 default y if SECURITY_SELINUX
313 Enable low-overhead system-call auditing infrastructure that
314 can be used independently or with another kernel subsystem,
319 depends on AUDITSYSCALL
324 depends on AUDITSYSCALL
327 source "kernel/irq/Kconfig"
328 source "kernel/time/Kconfig"
330 menu "CPU/Task time and stats accounting"
332 config VIRT_CPU_ACCOUNTING
336 prompt "Cputime accounting"
337 default TICK_CPU_ACCOUNTING if !PPC64
338 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
340 # Kind of a stub config for the pure tick based cputime accounting
341 config TICK_CPU_ACCOUNTING
342 bool "Simple tick based cputime accounting"
343 depends on !S390 && !NO_HZ_FULL
345 This is the basic tick based cputime accounting that maintains
346 statistics about user, system and idle time spent on per jiffies
351 config VIRT_CPU_ACCOUNTING_NATIVE
352 bool "Deterministic task and CPU time accounting"
353 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
354 select VIRT_CPU_ACCOUNTING
356 Select this option to enable more accurate task and CPU time
357 accounting. This is done by reading a CPU counter on each
358 kernel entry and exit and on transitions within the kernel
359 between system, softirq and hardirq state, so there is a
360 small performance impact. In the case of s390 or IBM POWER > 5,
361 this also enables accounting of stolen time on logically-partitioned
364 config VIRT_CPU_ACCOUNTING_GEN
365 bool "Full dynticks CPU time accounting"
366 depends on HAVE_CONTEXT_TRACKING
367 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
368 select VIRT_CPU_ACCOUNTING
369 select CONTEXT_TRACKING
371 Select this option to enable task and CPU time accounting on full
372 dynticks systems. This accounting is implemented by watching every
373 kernel-user boundaries using the context tracking subsystem.
374 The accounting is thus performed at the expense of some significant
377 For now this is only useful if you are working on the full
378 dynticks subsystem development.
382 config IRQ_TIME_ACCOUNTING
383 bool "Fine granularity task level IRQ time accounting"
384 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
386 Select this option to enable fine granularity task irq time
387 accounting. This is done by reading a timestamp on each
388 transitions between softirq and hardirq state, so there can be a
389 small performance impact.
391 If in doubt, say N here.
395 config BSD_PROCESS_ACCT
396 bool "BSD Process Accounting"
399 If you say Y here, a user level program will be able to instruct the
400 kernel (via a special system call) to write process accounting
401 information to a file: whenever a process exits, information about
402 that process will be appended to the file by the kernel. The
403 information includes things such as creation time, owning user,
404 command name, memory usage, controlling terminal etc. (the complete
405 list is in the struct acct in <file:include/linux/acct.h>). It is
406 up to the user level program to do useful things with this
407 information. This is generally a good idea, so say Y.
409 config BSD_PROCESS_ACCT_V3
410 bool "BSD Process Accounting version 3 file format"
411 depends on BSD_PROCESS_ACCT
414 If you say Y here, the process accounting information is written
415 in a new file format that also logs the process IDs of each
416 process and it's parent. Note that this file format is incompatible
417 with previous v0/v1/v2 file formats, so you will need updated tools
418 for processing it. A preliminary version of these tools is available
419 at <http://www.gnu.org/software/acct/>.
422 bool "Export task/process statistics through netlink"
427 Export selected statistics for tasks/processes through the
428 generic netlink interface. Unlike BSD process accounting, the
429 statistics are available during the lifetime of tasks/processes as
430 responses to commands. Like BSD accounting, they are sent to user
435 config TASK_DELAY_ACCT
436 bool "Enable per-task delay accounting"
440 Collect information on time spent by a task waiting for system
441 resources like cpu, synchronous block I/O completion and swapping
442 in pages. Such statistics can help in setting a task's priorities
443 relative to other tasks for cpu, io, rss limits etc.
448 bool "Enable extended accounting over taskstats"
451 Collect extended task accounting data and send the data
452 to userland for processing over the taskstats interface.
456 config TASK_IO_ACCOUNTING
457 bool "Enable per-task storage I/O accounting"
458 depends on TASK_XACCT
460 Collect information on the number of bytes of storage I/O which this
465 endmenu # "CPU/Task time and stats accounting"
471 default y if !PREEMPT && SMP
473 This option selects the RCU implementation that is
474 designed for very large SMP system with hundreds or
475 thousands of CPUs. It also scales down nicely to
482 This option selects the RCU implementation that is
483 designed for very large SMP systems with hundreds or
484 thousands of CPUs, but for which real-time response
485 is also required. It also scales down nicely to
488 Select this option if you are unsure.
492 default y if !PREEMPT && !SMP
494 This option selects the RCU implementation that is
495 designed for UP systems from which real-time response
496 is not required. This option greatly reduces the
497 memory footprint of RCU.
500 bool "Make expert-level adjustments to RCU configuration"
503 This option needs to be enabled if you wish to make
504 expert-level adjustments to RCU configuration. By default,
505 no such adjustments can be made, which has the often-beneficial
506 side-effect of preventing "make oldconfig" from asking you all
507 sorts of detailed questions about how you would like numerous
508 obscure RCU options to be set up.
510 Say Y if you need to make expert-level adjustments to RCU.
512 Say N if you are unsure.
517 This option selects the sleepable version of RCU. This version
518 permits arbitrary sleeping or blocking within RCU read-side critical
526 This option enables a task-based RCU implementation that uses
527 only voluntary context switch (not preemption!), idle, and
528 user-mode execution as quiescent states.
530 config RCU_STALL_COMMON
531 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
533 This option enables RCU CPU stall code that is common between
534 the TINY and TREE variants of RCU. The purpose is to allow
535 the tiny variants to disable RCU CPU stall warnings, while
536 making these warnings mandatory for the tree variants.
538 config CONTEXT_TRACKING
544 This option sets hooks on kernel / userspace boundaries and
545 puts RCU in extended quiescent state when the CPU runs in
546 userspace. It means that when a CPU runs in userspace, it is
547 excluded from the global RCU state machine and thus doesn't
548 try to keep the timer tick on for RCU.
550 config CONTEXT_TRACKING_FORCE
551 bool "Force context tracking"
552 depends on CONTEXT_TRACKING
553 default y if !NO_HZ_FULL
555 The major pre-requirement for full dynticks to work is to
556 support the context tracking subsystem. But there are also
557 other dependencies to provide in order to make the full
560 This option stands for testing when an arch implements the
561 context tracking backend but doesn't yet fullfill all the
562 requirements to make the full dynticks feature working.
563 Without the full dynticks, there is no way to test the support
564 for context tracking and the subsystems that rely on it: RCU
565 userspace extended quiescent state and tickless cputime
566 accounting. This option copes with the absence of the full
567 dynticks subsystem by forcing the context tracking on all
570 Say Y only if you're working on the development of an
571 architecture backend for the context tracking.
573 Say N otherwise, this option brings an overhead that you
574 don't want in production.
578 int "Tree-based hierarchical RCU fanout value"
581 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
585 This option controls the fanout of hierarchical implementations
586 of RCU, allowing RCU to work efficiently on machines with
587 large numbers of CPUs. This value must be at least the fourth
588 root of NR_CPUS, which allows NR_CPUS to be insanely large.
589 The default value of RCU_FANOUT should be used for production
590 systems, but if you are stress-testing the RCU implementation
591 itself, small RCU_FANOUT values allow you to test large-system
592 code paths on small(er) systems.
594 Select a specific number if testing RCU itself.
595 Take the default if unsure.
597 config RCU_FANOUT_LEAF
598 int "Tree-based hierarchical RCU leaf-level fanout value"
601 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
604 This option controls the leaf-level fanout of hierarchical
605 implementations of RCU, and allows trading off cache misses
606 against lock contention. Systems that synchronize their
607 scheduling-clock interrupts for energy-efficiency reasons will
608 want the default because the smaller leaf-level fanout keeps
609 lock contention levels acceptably low. Very large systems
610 (hundreds or thousands of CPUs) will instead want to set this
611 value to the maximum value possible in order to reduce the
612 number of cache misses incurred during RCU's grace-period
613 initialization. These systems tend to run CPU-bound, and thus
614 are not helped by synchronized interrupts, and thus tend to
615 skew them, which reduces lock contention enough that large
616 leaf-level fanouts work well.
618 Select a specific number if testing RCU itself.
620 Select the maximum permissible value for large systems.
622 Take the default if unsure.
624 config RCU_FAST_NO_HZ
625 bool "Accelerate last non-dyntick-idle CPU's grace periods"
626 depends on NO_HZ_COMMON && SMP && RCU_EXPERT
629 This option permits CPUs to enter dynticks-idle state even if
630 they have RCU callbacks queued, and prevents RCU from waking
631 these CPUs up more than roughly once every four jiffies (by
632 default, you can adjust this using the rcutree.rcu_idle_gp_delay
633 parameter), thus improving energy efficiency. On the other
634 hand, this option increases the duration of RCU grace periods,
635 for example, slowing down synchronize_rcu().
637 Say Y if energy efficiency is critically important, and you
638 don't care about increased grace-period durations.
640 Say N if you are unsure.
642 config TREE_RCU_TRACE
643 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
646 This option provides tracing for the TREE_RCU and
647 PREEMPT_RCU implementations, permitting Makefile to
648 trivially select kernel/rcutree_trace.c.
651 bool "Enable RCU priority boosting"
652 depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
655 This option boosts the priority of preempted RCU readers that
656 block the current preemptible RCU grace period for too long.
657 This option also prevents heavy loads from blocking RCU
658 callback invocation for all flavors of RCU.
660 Say Y here if you are working with real-time apps or heavy loads
661 Say N here if you are unsure.
663 config RCU_KTHREAD_PRIO
664 int "Real-time priority to use for RCU worker threads"
665 range 1 99 if RCU_BOOST
666 range 0 99 if !RCU_BOOST
667 default 1 if RCU_BOOST
668 default 0 if !RCU_BOOST
669 depends on RCU_EXPERT
671 This option specifies the SCHED_FIFO priority value that will be
672 assigned to the rcuc/n and rcub/n threads and is also the value
673 used for RCU_BOOST (if enabled). If you are working with a
674 real-time application that has one or more CPU-bound threads
675 running at a real-time priority level, you should set
676 RCU_KTHREAD_PRIO to a priority higher than the highest-priority
677 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
678 value of 1 is appropriate in the common case, which is real-time
679 applications that do not have any CPU-bound threads.
681 Some real-time applications might not have a single real-time
682 thread that saturates a given CPU, but instead might have
683 multiple real-time threads that, taken together, fully utilize
684 that CPU. In this case, you should set RCU_KTHREAD_PRIO to
685 a priority higher than the lowest-priority thread that is
686 conspiring to prevent the CPU from running any non-real-time
687 tasks. For example, if one thread at priority 10 and another
688 thread at priority 5 are between themselves fully consuming
689 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
690 set to priority 6 or higher.
692 Specify the real-time priority, or take the default if unsure.
694 config RCU_BOOST_DELAY
695 int "Milliseconds to delay boosting after RCU grace-period start"
700 This option specifies the time to wait after the beginning of
701 a given grace period before priority-boosting preempted RCU
702 readers blocking that grace period. Note that any RCU reader
703 blocking an expedited RCU grace period is boosted immediately.
705 Accept the default if unsure.
708 bool "Offload RCU callback processing from boot-selected CPUs"
709 depends on TREE_RCU || PREEMPT_RCU
712 Use this option to reduce OS jitter for aggressive HPC or
713 real-time workloads. It can also be used to offload RCU
714 callback invocation to energy-efficient CPUs in battery-powered
715 asymmetric multiprocessors.
717 This option offloads callback invocation from the set of
718 CPUs specified at boot time by the rcu_nocbs parameter.
719 For each such CPU, a kthread ("rcuox/N") will be created to
720 invoke callbacks, where the "N" is the CPU being offloaded,
721 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
722 "s" for RCU-sched. Nothing prevents this kthread from running
723 on the specified CPUs, but (1) the kthreads may be preempted
724 between each callback, and (2) affinity or cgroups can be used
725 to force the kthreads to run on whatever set of CPUs is desired.
727 Say Y here if you want to help to debug reduced OS jitter.
728 Say N here if you are unsure.
731 prompt "Build-forced no-CBs CPUs"
732 default RCU_NOCB_CPU_NONE
733 depends on RCU_NOCB_CPU
735 This option allows no-CBs CPUs (whose RCU callbacks are invoked
736 from kthreads rather than from softirq context) to be specified
737 at build time. Additional no-CBs CPUs may be specified by
738 the rcu_nocbs= boot parameter.
740 config RCU_NOCB_CPU_NONE
741 bool "No build_forced no-CBs CPUs"
743 This option does not force any of the CPUs to be no-CBs CPUs.
744 Only CPUs designated by the rcu_nocbs= boot parameter will be
745 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
746 kthreads whose names begin with "rcuo". All other CPUs will
747 invoke their own RCU callbacks in softirq context.
749 Select this option if you want to choose no-CBs CPUs at
750 boot time, for example, to allow testing of different no-CBs
751 configurations without having to rebuild the kernel each time.
753 config RCU_NOCB_CPU_ZERO
754 bool "CPU 0 is a build_forced no-CBs CPU"
756 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
757 callbacks are invoked by a per-CPU kthread whose name begins
758 with "rcuo". Additional CPUs may be designated as no-CBs
759 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
760 All other CPUs will invoke their own RCU callbacks in softirq
763 Select this if CPU 0 needs to be a no-CBs CPU for real-time
764 or energy-efficiency reasons, but the real reason it exists
765 is to ensure that randconfig testing covers mixed systems.
767 config RCU_NOCB_CPU_ALL
768 bool "All CPUs are build_forced no-CBs CPUs"
770 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
771 boot parameter will be ignored. All CPUs' RCU callbacks will
772 be executed in the context of per-CPU rcuo kthreads created for
773 this purpose. Assuming that the kthreads whose names start with
774 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
775 on the remaining CPUs, but might decrease memory locality during
776 RCU-callback invocation, thus potentially degrading throughput.
778 Select this if all CPUs need to be no-CBs CPUs for real-time
779 or energy-efficiency reasons.
783 config RCU_EXPEDITE_BOOT
787 This option enables expedited grace periods at boot time,
788 as if rcu_expedite_gp() had been invoked early in boot.
789 The corresponding rcu_unexpedite_gp() is invoked from
790 rcu_end_inkernel_boot(), which is intended to be invoked
791 at the end of the kernel-only boot sequence, just before
794 Accept the default if unsure.
796 endmenu # "RCU Subsystem"
803 tristate "Kernel .config support"
806 This option enables the complete Linux kernel ".config" file
807 contents to be saved in the kernel. It provides documentation
808 of which kernel options are used in a running kernel or in an
809 on-disk kernel. This information can be extracted from the kernel
810 image file with the script scripts/extract-ikconfig and used as
811 input to rebuild the current kernel or to build another kernel.
812 It can also be extracted from a running kernel by reading
813 /proc/config.gz if enabled (below).
816 bool "Enable access to .config through /proc/config.gz"
817 depends on IKCONFIG && PROC_FS
819 This option enables access to the kernel configuration file
820 through /proc/config.gz.
823 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
828 Select the minimal kernel log buffer size as a power of 2.
829 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
830 parameter, see below. Any higher size also might be forced
831 by "log_buf_len" boot parameter.
841 config LOG_CPU_MAX_BUF_SHIFT
842 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
845 default 12 if !BASE_SMALL
846 default 0 if BASE_SMALL
849 This option allows to increase the default ring buffer size
850 according to the number of CPUs. The value defines the contribution
851 of each CPU as a power of 2. The used space is typically only few
852 lines however it might be much more when problems are reported,
855 The increased size means that a new buffer has to be allocated and
856 the original static one is unused. It makes sense only on systems
857 with more CPUs. Therefore this value is used only when the sum of
858 contributions is greater than the half of the default kernel ring
859 buffer as defined by LOG_BUF_SHIFT. The default values are set
860 so that more than 64 CPUs are needed to trigger the allocation.
862 Also this option is ignored when "log_buf_len" kernel parameter is
863 used as it forces an exact (power of two) size of the ring buffer.
865 The number of possible CPUs is used for this computation ignoring
866 hotplugging making the compuation optimal for the the worst case
867 scenerio while allowing a simple algorithm to be used from bootup.
869 Examples shift values and their meaning:
870 17 => 128 KB for each CPU
871 16 => 64 KB for each CPU
872 15 => 32 KB for each CPU
873 14 => 16 KB for each CPU
874 13 => 8 KB for each CPU
875 12 => 4 KB for each CPU
878 # Architectures with an unreliable sched_clock() should select this:
880 config HAVE_UNSTABLE_SCHED_CLOCK
883 config GENERIC_SCHED_CLOCK
887 # For architectures that want to enable the support for NUMA-affine scheduler
890 config ARCH_SUPPORTS_NUMA_BALANCING
894 # For architectures that know their GCC __int128 support is sound
896 config ARCH_SUPPORTS_INT128
899 # For architectures that (ab)use NUMA to represent different memory regions
900 # all cpu-local but of different latencies, such as SuperH.
902 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
905 config NUMA_BALANCING
906 bool "Memory placement aware NUMA scheduler"
907 depends on ARCH_SUPPORTS_NUMA_BALANCING
908 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
909 depends on SMP && NUMA && MIGRATION
911 This option adds support for automatic NUMA aware memory/task placement.
912 The mechanism is quite primitive and is based on migrating memory when
913 it has references to the node the task is running on.
915 This system will be inactive on UMA systems.
917 config NUMA_BALANCING_DEFAULT_ENABLED
918 bool "Automatically enable NUMA aware memory/task placement"
920 depends on NUMA_BALANCING
922 If set, automatic NUMA balancing will be enabled if running on a NUMA
926 bool "Control Group support"
930 This option adds support for grouping sets of processes together, for
931 use with process control subsystems such as Cpusets, CFS, memory
932 controls or device isolation.
934 - Documentation/scheduler/sched-design-CFS.txt (CFS)
935 - Documentation/cgroups/ (features for grouping, isolation
936 and resource control)
943 bool "Example debug cgroup subsystem"
946 This option enables a simple cgroup subsystem that
947 exports useful debugging information about the cgroups
952 config CGROUP_FREEZER
953 bool "Freezer cgroup subsystem"
955 Provides a way to freeze and unfreeze all tasks in a
959 bool "PIDs cgroup subsystem"
961 Provides enforcement of process number limits in the scope of a
962 cgroup. Any attempt to fork more processes than is allowed in the
963 cgroup will fail. PIDs are fundamentally a global resource because it
964 is fairly trivial to reach PID exhaustion before you reach even a
965 conservative kmemcg limit. As a result, it is possible to grind a
966 system to halt without being limited by other cgroup policies. The
967 PIDs cgroup subsystem is designed to stop this from happening.
969 It should be noted that organisational operations (such as attaching
970 to a cgroup hierarchy will *not* be blocked by the PIDs subsystem),
971 since the PIDs limit only affects a process's ability to fork, not to
975 bool "Device controller for cgroups"
977 Provides a cgroup implementing whitelists for devices which
978 a process in the cgroup can mknod or open.
981 bool "Cpuset support"
983 This option will let you create and manage CPUSETs which
984 allow dynamically partitioning a system into sets of CPUs and
985 Memory Nodes and assigning tasks to run only within those sets.
986 This is primarily useful on large SMP or NUMA systems.
990 config PROC_PID_CPUSET
991 bool "Include legacy /proc/<pid>/cpuset file"
995 config CGROUP_CPUACCT
996 bool "Simple CPU accounting cgroup subsystem"
998 Provides a simple Resource Controller for monitoring the
999 total CPU consumed by the tasks in a cgroup.
1005 bool "Memory Resource Controller for Control Groups"
1009 Provides a memory resource controller that manages both anonymous
1010 memory and page cache. (See Documentation/cgroups/memory.txt)
1013 bool "Memory Resource Controller Swap Extension"
1014 depends on MEMCG && SWAP
1016 Add swap management feature to memory resource controller. When you
1017 enable this, you can limit mem+swap usage per cgroup. In other words,
1018 when you disable this, memory resource controller has no cares to
1019 usage of swap...a process can exhaust all of the swap. This extension
1020 is useful when you want to avoid exhaustion swap but this itself
1021 adds more overheads and consumes memory for remembering information.
1022 Especially if you use 32bit system or small memory system, please
1023 be careful about enabling this. When memory resource controller
1024 is disabled by boot option, this will be automatically disabled and
1025 there will be no overhead from this. Even when you set this config=y,
1026 if boot option "swapaccount=0" is set, swap will not be accounted.
1027 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1028 size is 4096bytes, 512k per 1Gbytes of swap.
1029 config MEMCG_SWAP_ENABLED
1030 bool "Memory Resource Controller Swap Extension enabled by default"
1031 depends on MEMCG_SWAP
1034 Memory Resource Controller Swap Extension comes with its price in
1035 a bigger memory consumption. General purpose distribution kernels
1036 which want to enable the feature but keep it disabled by default
1037 and let the user enable it by swapaccount=1 boot command line
1038 parameter should have this option unselected.
1039 For those who want to have the feature enabled by default should
1040 select this option (if, for some reason, they need to disable it
1041 then swapaccount=0 does the trick).
1043 bool "Memory Resource Controller Kernel Memory accounting"
1045 depends on SLUB || SLAB
1047 The Kernel Memory extension for Memory Resource Controller can limit
1048 the amount of memory used by kernel objects in the system. Those are
1049 fundamentally different from the entities handled by the standard
1050 Memory Controller, which are page-based, and can be swapped. Users of
1051 the kmem extension can use it to guarantee that no group of processes
1052 will ever exhaust kernel resources alone.
1054 config CGROUP_HUGETLB
1055 bool "HugeTLB Resource Controller for Control Groups"
1056 depends on HUGETLB_PAGE
1060 Provides a cgroup Resource Controller for HugeTLB pages.
1061 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1062 The limit is enforced during page fault. Since HugeTLB doesn't
1063 support page reclaim, enforcing the limit at page fault time implies
1064 that, the application will get SIGBUS signal if it tries to access
1065 HugeTLB pages beyond its limit. This requires the application to know
1066 beforehand how much HugeTLB pages it would require for its use. The
1067 control group is tracked in the third page lru pointer. This means
1068 that we cannot use the controller with huge page less than 3 pages.
1071 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1072 depends on PERF_EVENTS && CGROUPS
1074 This option extends the per-cpu mode to restrict monitoring to
1075 threads which belong to the cgroup specified and run on the
1080 menuconfig CGROUP_SCHED
1081 bool "Group CPU scheduler"
1084 This feature lets CPU scheduler recognize task groups and control CPU
1085 bandwidth allocation to such task groups. It uses cgroups to group
1089 config FAIR_GROUP_SCHED
1090 bool "Group scheduling for SCHED_OTHER"
1091 depends on CGROUP_SCHED
1092 default CGROUP_SCHED
1094 config CFS_BANDWIDTH
1095 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1096 depends on FAIR_GROUP_SCHED
1099 This option allows users to define CPU bandwidth rates (limits) for
1100 tasks running within the fair group scheduler. Groups with no limit
1101 set are considered to be unconstrained and will run with no
1103 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1105 config RT_GROUP_SCHED
1106 bool "Group scheduling for SCHED_RR/FIFO"
1107 depends on CGROUP_SCHED
1110 This feature lets you explicitly allocate real CPU bandwidth
1111 to task groups. If enabled, it will also make it impossible to
1112 schedule realtime tasks for non-root users until you allocate
1113 realtime bandwidth for them.
1114 See Documentation/scheduler/sched-rt-group.txt for more information.
1119 bool "Block IO controller"
1123 Generic block IO controller cgroup interface. This is the common
1124 cgroup interface which should be used by various IO controlling
1127 Currently, CFQ IO scheduler uses it to recognize task groups and
1128 control disk bandwidth allocation (proportional time slice allocation)
1129 to such task groups. It is also used by bio throttling logic in
1130 block layer to implement upper limit in IO rates on a device.
1132 This option only enables generic Block IO controller infrastructure.
1133 One needs to also enable actual IO controlling logic/policy. For
1134 enabling proportional weight division of disk bandwidth in CFQ, set
1135 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1136 CONFIG_BLK_DEV_THROTTLING=y.
1138 See Documentation/cgroups/blkio-controller.txt for more information.
1140 config DEBUG_BLK_CGROUP
1141 bool "Enable Block IO controller debugging"
1142 depends on BLK_CGROUP
1145 Enable some debugging help. Currently it exports additional stat
1146 files in a cgroup which can be useful for debugging.
1148 config CGROUP_WRITEBACK
1150 depends on MEMCG && BLK_CGROUP
1155 config CHECKPOINT_RESTORE
1156 bool "Checkpoint/restore support" if EXPERT
1157 select PROC_CHILDREN
1160 Enables additional kernel features in a sake of checkpoint/restore.
1161 In particular it adds auxiliary prctl codes to setup process text,
1162 data and heap segment sizes, and a few additional /proc filesystem
1165 If unsure, say N here.
1167 menuconfig NAMESPACES
1168 bool "Namespaces support" if EXPERT
1169 depends on MULTIUSER
1172 Provides the way to make tasks work with different objects using
1173 the same id. For example same IPC id may refer to different objects
1174 or same user id or pid may refer to different tasks when used in
1175 different namespaces.
1180 bool "UTS namespace"
1183 In this namespace tasks see different info provided with the
1187 bool "IPC namespace"
1188 depends on (SYSVIPC || POSIX_MQUEUE)
1191 In this namespace tasks work with IPC ids which correspond to
1192 different IPC objects in different namespaces.
1195 bool "User namespace"
1198 This allows containers, i.e. vservers, to use user namespaces
1199 to provide different user info for different servers.
1201 When user namespaces are enabled in the kernel it is
1202 recommended that the MEMCG and MEMCG_KMEM options also be
1203 enabled and that user-space use the memory control groups to
1204 limit the amount of memory a memory unprivileged users can
1210 bool "PID Namespaces"
1213 Support process id namespaces. This allows having multiple
1214 processes with the same pid as long as they are in different
1215 pid namespaces. This is a building block of containers.
1218 bool "Network namespace"
1222 Allow user space to create what appear to be multiple instances
1223 of the network stack.
1227 config SCHED_AUTOGROUP
1228 bool "Automatic process group scheduling"
1231 select FAIR_GROUP_SCHED
1233 This option optimizes the scheduler for common desktop workloads by
1234 automatically creating and populating task groups. This separation
1235 of workloads isolates aggressive CPU burners (like build jobs) from
1236 desktop applications. Task group autogeneration is currently based
1239 config SYSFS_DEPRECATED
1240 bool "Enable deprecated sysfs features to support old userspace tools"
1244 This option adds code that switches the layout of the "block" class
1245 devices, to not show up in /sys/class/block/, but only in
1248 This switch is only active when the sysfs.deprecated=1 boot option is
1249 passed or the SYSFS_DEPRECATED_V2 option is set.
1251 This option allows new kernels to run on old distributions and tools,
1252 which might get confused by /sys/class/block/. Since 2007/2008 all
1253 major distributions and tools handle this just fine.
1255 Recent distributions and userspace tools after 2009/2010 depend on
1256 the existence of /sys/class/block/, and will not work with this
1259 Only if you are using a new kernel on an old distribution, you might
1262 config SYSFS_DEPRECATED_V2
1263 bool "Enable deprecated sysfs features by default"
1266 depends on SYSFS_DEPRECATED
1268 Enable deprecated sysfs by default.
1270 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1273 Only if you are using a new kernel on an old distribution, you might
1274 need to say Y here. Even then, odds are you would not need it
1275 enabled, you can always pass the boot option if absolutely necessary.
1278 bool "Kernel->user space relay support (formerly relayfs)"
1280 This option enables support for relay interface support in
1281 certain file systems (such as debugfs).
1282 It is designed to provide an efficient mechanism for tools and
1283 facilities to relay large amounts of data from kernel space to
1288 config BLK_DEV_INITRD
1289 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1290 depends on BROKEN || !FRV
1292 The initial RAM filesystem is a ramfs which is loaded by the
1293 boot loader (loadlin or lilo) and that is mounted as root
1294 before the normal boot procedure. It is typically used to
1295 load modules needed to mount the "real" root file system,
1296 etc. See <file:Documentation/initrd.txt> for details.
1298 If RAM disk support (BLK_DEV_RAM) is also included, this
1299 also enables initial RAM disk (initrd) support and adds
1300 15 Kbytes (more on some other architectures) to the kernel size.
1306 source "usr/Kconfig"
1310 config CC_OPTIMIZE_FOR_SIZE
1311 bool "Optimize for size"
1313 Enabling this option will pass "-Os" instead of "-O2" to
1314 your compiler resulting in a smaller kernel.
1327 config SYSCTL_EXCEPTION_TRACE
1330 Enable support for /proc/sys/debug/exception-trace.
1332 config SYSCTL_ARCH_UNALIGN_NO_WARN
1335 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1336 Allows arch to define/use @no_unaligned_warning to possibly warn
1337 about unaligned access emulation going on under the hood.
1339 config SYSCTL_ARCH_UNALIGN_ALLOW
1342 Enable support for /proc/sys/kernel/unaligned-trap
1343 Allows arches to define/use @unaligned_enabled to runtime toggle
1344 the unaligned access emulation.
1345 see arch/parisc/kernel/unaligned.c for reference
1347 config HAVE_PCSPKR_PLATFORM
1350 # interpreter that classic socket filters depend on
1355 bool "Configure standard kernel features (expert users)"
1356 # Unhide debug options, to make the on-by-default options visible
1359 This option allows certain base kernel options and settings
1360 to be disabled or tweaked. This is for specialized
1361 environments which can tolerate a "non-standard" kernel.
1362 Only use this if you really know what you are doing.
1365 bool "Enable 16-bit UID system calls" if EXPERT
1366 depends on HAVE_UID16 && MULTIUSER
1369 This enables the legacy 16-bit UID syscall wrappers.
1372 bool "Multiple users, groups and capabilities support" if EXPERT
1375 This option enables support for non-root users, groups and
1378 If you say N here, all processes will run with UID 0, GID 0, and all
1379 possible capabilities. Saying N here also compiles out support for
1380 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1383 If unsure, say Y here.
1385 config SGETMASK_SYSCALL
1386 bool "sgetmask/ssetmask syscalls support" if EXPERT
1387 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1389 sys_sgetmask and sys_ssetmask are obsolete system calls
1390 no longer supported in libc but still enabled by default in some
1393 If unsure, leave the default option here.
1395 config SYSFS_SYSCALL
1396 bool "Sysfs syscall support" if EXPERT
1399 sys_sysfs is an obsolete system call no longer supported in libc.
1400 Note that disabling this option is more secure but might break
1401 compatibility with some systems.
1403 If unsure say Y here.
1405 config SYSCTL_SYSCALL
1406 bool "Sysctl syscall support" if EXPERT
1407 depends on PROC_SYSCTL
1411 sys_sysctl uses binary paths that have been found challenging
1412 to properly maintain and use. The interface in /proc/sys
1413 using paths with ascii names is now the primary path to this
1416 Almost nothing using the binary sysctl interface so if you are
1417 trying to save some space it is probably safe to disable this,
1418 making your kernel marginally smaller.
1420 If unsure say N here.
1423 bool "Load all symbols for debugging/ksymoops" if EXPERT
1426 Say Y here to let the kernel print out symbolic crash information and
1427 symbolic stack backtraces. This increases the size of the kernel
1428 somewhat, as all symbols have to be loaded into the kernel image.
1431 bool "Include all symbols in kallsyms"
1432 depends on DEBUG_KERNEL && KALLSYMS
1434 Normally kallsyms only contains the symbols of functions for nicer
1435 OOPS messages and backtraces (i.e., symbols from the text and inittext
1436 sections). This is sufficient for most cases. And only in very rare
1437 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1438 names of variables from the data sections, etc).
1440 This option makes sure that all symbols are loaded into the kernel
1441 image (i.e., symbols from all sections) in cost of increased kernel
1442 size (depending on the kernel configuration, it may be 300KiB or
1443 something like this).
1445 Say N unless you really need all symbols.
1449 bool "Enable support for printk" if EXPERT
1452 This option enables normal printk support. Removing it
1453 eliminates most of the message strings from the kernel image
1454 and makes the kernel more or less silent. As this makes it
1455 very difficult to diagnose system problems, saying N here is
1456 strongly discouraged.
1459 bool "BUG() support" if EXPERT
1462 Disabling this option eliminates support for BUG and WARN, reducing
1463 the size of your kernel image and potentially quietly ignoring
1464 numerous fatal conditions. You should only consider disabling this
1465 option for embedded systems with no facilities for reporting errors.
1471 bool "Enable ELF core dumps" if EXPERT
1473 Enable support for generating core dumps. Disabling saves about 4k.
1476 config PCSPKR_PLATFORM
1477 bool "Enable PC-Speaker support" if EXPERT
1478 depends on HAVE_PCSPKR_PLATFORM
1482 This option allows to disable the internal PC-Speaker
1483 support, saving some memory.
1487 bool "Enable full-sized data structures for core" if EXPERT
1489 Disabling this option reduces the size of miscellaneous core
1490 kernel data structures. This saves memory on small machines,
1491 but may reduce performance.
1494 bool "Enable futex support" if EXPERT
1498 Disabling this option will cause the kernel to be built without
1499 support for "fast userspace mutexes". The resulting kernel may not
1500 run glibc-based applications correctly.
1502 config HAVE_FUTEX_CMPXCHG
1506 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1507 is implemented and always working. This removes a couple of runtime
1511 bool "Enable eventpoll support" if EXPERT
1515 Disabling this option will cause the kernel to be built without
1516 support for epoll family of system calls.
1519 bool "Enable signalfd() system call" if EXPERT
1523 Enable the signalfd() system call that allows to receive signals
1524 on a file descriptor.
1529 bool "Enable timerfd() system call" if EXPERT
1533 Enable the timerfd() system call that allows to receive timer
1534 events on a file descriptor.
1539 bool "Enable eventfd() system call" if EXPERT
1543 Enable the eventfd() system call that allows to receive both
1544 kernel notification (ie. KAIO) or userspace notifications.
1548 # syscall, maps, verifier
1550 bool "Enable bpf() system call"
1555 Enable the bpf() system call that allows to manipulate eBPF
1556 programs and maps via file descriptors.
1559 bool "Use full shmem filesystem" if EXPERT
1563 The shmem is an internal filesystem used to manage shared memory.
1564 It is backed by swap and manages resource limits. It is also exported
1565 to userspace as tmpfs if TMPFS is enabled. Disabling this
1566 option replaces shmem and tmpfs with the much simpler ramfs code,
1567 which may be appropriate on small systems without swap.
1570 bool "Enable AIO support" if EXPERT
1573 This option enables POSIX asynchronous I/O which may by used
1574 by some high performance threaded applications. Disabling
1575 this option saves about 7k.
1577 config ADVISE_SYSCALLS
1578 bool "Enable madvise/fadvise syscalls" if EXPERT
1581 This option enables the madvise and fadvise syscalls, used by
1582 applications to advise the kernel about their future memory or file
1583 usage, improving performance. If building an embedded system where no
1584 applications use these syscalls, you can disable this option to save
1589 bool "Enable PCI quirk workarounds" if EXPERT
1592 This enables workarounds for various PCI chipset
1593 bugs/quirks. Disable this only if your target machine is
1594 unaffected by PCI quirks.
1597 bool "Embedded system"
1598 option allnoconfig_y
1601 This option should be enabled if compiling the kernel for
1602 an embedded system so certain expert options are available
1605 config HAVE_PERF_EVENTS
1608 See tools/perf/design.txt for details.
1610 config PERF_USE_VMALLOC
1613 See tools/perf/design.txt for details
1615 menu "Kernel Performance Events And Counters"
1618 bool "Kernel performance events and counters"
1619 default y if PROFILING
1620 depends on HAVE_PERF_EVENTS
1625 Enable kernel support for various performance events provided
1626 by software and hardware.
1628 Software events are supported either built-in or via the
1629 use of generic tracepoints.
1631 Most modern CPUs support performance events via performance
1632 counter registers. These registers count the number of certain
1633 types of hw events: such as instructions executed, cachemisses
1634 suffered, or branches mis-predicted - without slowing down the
1635 kernel or applications. These registers can also trigger interrupts
1636 when a threshold number of events have passed - and can thus be
1637 used to profile the code that runs on that CPU.
1639 The Linux Performance Event subsystem provides an abstraction of
1640 these software and hardware event capabilities, available via a
1641 system call and used by the "perf" utility in tools/perf/. It
1642 provides per task and per CPU counters, and it provides event
1643 capabilities on top of those.
1647 config DEBUG_PERF_USE_VMALLOC
1649 bool "Debug: use vmalloc to back perf mmap() buffers"
1650 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1651 select PERF_USE_VMALLOC
1653 Use vmalloc memory to back perf mmap() buffers.
1655 Mostly useful for debugging the vmalloc code on platforms
1656 that don't require it.
1662 config VM_EVENT_COUNTERS
1664 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1666 VM event counters are needed for event counts to be shown.
1667 This option allows the disabling of the VM event counters
1668 on EXPERT systems. /proc/vmstat will only show page counts
1669 if VM event counters are disabled.
1673 bool "Enable SLUB debugging support" if EXPERT
1674 depends on SLUB && SYSFS
1676 SLUB has extensive debug support features. Disabling these can
1677 result in significant savings in code size. This also disables
1678 SLUB sysfs support. /sys/slab will not exist and there will be
1679 no support for cache validation etc.
1682 bool "Disable heap randomization"
1685 Randomizing heap placement makes heap exploits harder, but it
1686 also breaks ancient binaries (including anything libc5 based).
1687 This option changes the bootup default to heap randomization
1688 disabled, and can be overridden at runtime by setting
1689 /proc/sys/kernel/randomize_va_space to 2.
1691 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1694 prompt "Choose SLAB allocator"
1697 This option allows to select a slab allocator.
1702 The regular slab allocator that is established and known to work
1703 well in all environments. It organizes cache hot objects in
1704 per cpu and per node queues.
1707 bool "SLUB (Unqueued Allocator)"
1709 SLUB is a slab allocator that minimizes cache line usage
1710 instead of managing queues of cached objects (SLAB approach).
1711 Per cpu caching is realized using slabs of objects instead
1712 of queues of objects. SLUB can use memory efficiently
1713 and has enhanced diagnostics. SLUB is the default choice for
1718 bool "SLOB (Simple Allocator)"
1720 SLOB replaces the stock allocator with a drastically simpler
1721 allocator. SLOB is generally more space efficient but
1722 does not perform as well on large systems.
1726 config SLUB_CPU_PARTIAL
1728 depends on SLUB && SMP
1729 bool "SLUB per cpu partial cache"
1731 Per cpu partial caches accellerate objects allocation and freeing
1732 that is local to a processor at the price of more indeterminism
1733 in the latency of the free. On overflow these caches will be cleared
1734 which requires the taking of locks that may cause latency spikes.
1735 Typically one would choose no for a realtime system.
1737 config MMAP_ALLOW_UNINITIALIZED
1738 bool "Allow mmapped anonymous memory to be uninitialized"
1739 depends on EXPERT && !MMU
1742 Normally, and according to the Linux spec, anonymous memory obtained
1743 from mmap() has it's contents cleared before it is passed to
1744 userspace. Enabling this config option allows you to request that
1745 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1746 providing a huge performance boost. If this option is not enabled,
1747 then the flag will be ignored.
1749 This is taken advantage of by uClibc's malloc(), and also by
1750 ELF-FDPIC binfmt's brk and stack allocator.
1752 Because of the obvious security issues, this option should only be
1753 enabled on embedded devices where you control what is run in
1754 userspace. Since that isn't generally a problem on no-MMU systems,
1755 it is normally safe to say Y here.
1757 See Documentation/nommu-mmap.txt for more information.
1759 config SYSTEM_TRUSTED_KEYRING
1760 bool "Provide system-wide ring of trusted keys"
1763 Provide a system keyring to which trusted keys can be added. Keys in
1764 the keyring are considered to be trusted. Keys may be added at will
1765 by the kernel from compiled-in data and from hardware key stores, but
1766 userspace may only add extra keys if those keys can be verified by
1767 keys already in the keyring.
1769 Keys in this keyring are used by module signature checking.
1772 bool "Profiling support"
1774 Say Y here to enable the extended profiling support mechanisms used
1775 by profilers such as OProfile.
1778 # Place an empty function call at each tracepoint site. Can be
1779 # dynamically changed for a probe function.
1784 source "arch/Kconfig"
1786 endmenu # General setup
1788 config HAVE_GENERIC_DMA_COHERENT
1795 depends on SLAB || SLUB_DEBUG
1803 default 0 if BASE_FULL
1804 default 1 if !BASE_FULL
1807 bool "Enable loadable module support"
1810 Kernel modules are small pieces of compiled code which can
1811 be inserted in the running kernel, rather than being
1812 permanently built into the kernel. You use the "modprobe"
1813 tool to add (and sometimes remove) them. If you say Y here,
1814 many parts of the kernel can be built as modules (by
1815 answering M instead of Y where indicated): this is most
1816 useful for infrequently used options which are not required
1817 for booting. For more information, see the man pages for
1818 modprobe, lsmod, modinfo, insmod and rmmod.
1820 If you say Y here, you will need to run "make
1821 modules_install" to put the modules under /lib/modules/
1822 where modprobe can find them (you may need to be root to do
1829 config MODULE_FORCE_LOAD
1830 bool "Forced module loading"
1833 Allow loading of modules without version information (ie. modprobe
1834 --force). Forced module loading sets the 'F' (forced) taint flag and
1835 is usually a really bad idea.
1837 config MODULE_UNLOAD
1838 bool "Module unloading"
1840 Without this option you will not be able to unload any
1841 modules (note that some modules may not be unloadable
1842 anyway), which makes your kernel smaller, faster
1843 and simpler. If unsure, say Y.
1845 config MODULE_FORCE_UNLOAD
1846 bool "Forced module unloading"
1847 depends on MODULE_UNLOAD
1849 This option allows you to force a module to unload, even if the
1850 kernel believes it is unsafe: the kernel will remove the module
1851 without waiting for anyone to stop using it (using the -f option to
1852 rmmod). This is mainly for kernel developers and desperate users.
1856 bool "Module versioning support"
1858 Usually, you have to use modules compiled with your kernel.
1859 Saying Y here makes it sometimes possible to use modules
1860 compiled for different kernels, by adding enough information
1861 to the modules to (hopefully) spot any changes which would
1862 make them incompatible with the kernel you are running. If
1865 config MODULE_SRCVERSION_ALL
1866 bool "Source checksum for all modules"
1868 Modules which contain a MODULE_VERSION get an extra "srcversion"
1869 field inserted into their modinfo section, which contains a
1870 sum of the source files which made it. This helps maintainers
1871 see exactly which source was used to build a module (since
1872 others sometimes change the module source without updating
1873 the version). With this option, such a "srcversion" field
1874 will be created for all modules. If unsure, say N.
1877 bool "Module signature verification"
1879 select SYSTEM_TRUSTED_KEYRING
1882 select ASYMMETRIC_KEY_TYPE
1883 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1884 select PUBLIC_KEY_ALGO_RSA
1887 select X509_CERTIFICATE_PARSER
1889 Check modules for valid signatures upon load: the signature
1890 is simply appended to the module. For more information see
1891 Documentation/module-signing.txt.
1893 !!!WARNING!!! If you enable this option, you MUST make sure that the
1894 module DOES NOT get stripped after being signed. This includes the
1895 debuginfo strip done by some packagers (such as rpmbuild) and
1896 inclusion into an initramfs that wants the module size reduced.
1898 config MODULE_SIG_FORCE
1899 bool "Require modules to be validly signed"
1900 depends on MODULE_SIG
1902 Reject unsigned modules or signed modules for which we don't have a
1903 key. Without this, such modules will simply taint the kernel.
1905 config MODULE_SIG_ALL
1906 bool "Automatically sign all modules"
1908 depends on MODULE_SIG
1910 Sign all modules during make modules_install. Without this option,
1911 modules must be signed manually, using the scripts/sign-file tool.
1913 comment "Do not forget to sign required modules with scripts/sign-file"
1914 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1917 prompt "Which hash algorithm should modules be signed with?"
1918 depends on MODULE_SIG
1920 This determines which sort of hashing algorithm will be used during
1921 signature generation. This algorithm _must_ be built into the kernel
1922 directly so that signature verification can take place. It is not
1923 possible to load a signed module containing the algorithm to check
1924 the signature on that module.
1926 config MODULE_SIG_SHA1
1927 bool "Sign modules with SHA-1"
1930 config MODULE_SIG_SHA224
1931 bool "Sign modules with SHA-224"
1932 select CRYPTO_SHA256
1934 config MODULE_SIG_SHA256
1935 bool "Sign modules with SHA-256"
1936 select CRYPTO_SHA256
1938 config MODULE_SIG_SHA384
1939 bool "Sign modules with SHA-384"
1940 select CRYPTO_SHA512
1942 config MODULE_SIG_SHA512
1943 bool "Sign modules with SHA-512"
1944 select CRYPTO_SHA512
1948 config MODULE_SIG_HASH
1950 depends on MODULE_SIG
1951 default "sha1" if MODULE_SIG_SHA1
1952 default "sha224" if MODULE_SIG_SHA224
1953 default "sha256" if MODULE_SIG_SHA256
1954 default "sha384" if MODULE_SIG_SHA384
1955 default "sha512" if MODULE_SIG_SHA512
1957 config MODULE_COMPRESS
1958 bool "Compress modules on installation"
1962 Compresses kernel modules when 'make modules_install' is run; gzip or
1963 xz depending on "Compression algorithm" below.
1965 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
1967 Out-of-tree kernel modules installed using Kbuild will also be
1968 compressed upon installation.
1970 Note: for modules inside an initrd or initramfs, it's more efficient
1971 to compress the whole initrd or initramfs instead.
1973 Note: This is fully compatible with signed modules.
1978 prompt "Compression algorithm"
1979 depends on MODULE_COMPRESS
1980 default MODULE_COMPRESS_GZIP
1982 This determines which sort of compression will be used during
1983 'make modules_install'.
1985 GZIP (default) and XZ are supported.
1987 config MODULE_COMPRESS_GZIP
1990 config MODULE_COMPRESS_XZ
1997 config MODULES_TREE_LOOKUP
1999 depends on PERF_EVENTS || TRACING
2001 config INIT_ALL_POSSIBLE
2004 Back when each arch used to define their own cpu_online_mask and
2005 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2006 with all 1s, and others with all 0s. When they were centralised,
2007 it was better to provide this option than to break all the archs
2008 and have several arch maintainers pursuing me down dark alleys.
2013 depends on (SMP && MODULE_UNLOAD) || HOTPLUG_CPU
2015 Need stop_machine() primitive.
2017 source "block/Kconfig"
2019 config PREEMPT_NOTIFIERS
2026 # Can be selected by architectures with broken toolchains
2027 # that get confused by correct const<->read_only section
2029 config BROKEN_RODATA
2035 Build a simple ASN.1 grammar compiler that produces a bytecode output
2036 that can be interpreted by the ASN.1 stream decoder and used to
2037 inform it as to what tags are to be expected in a stream and what
2038 functions to call on what tags.
2040 source "kernel/Kconfig.locks"
projects / cascardo / linux.git / blob