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
29 config THREAD_INFO_IN_TASK
32 Select this to move thread_info off the stack into task_struct. To
33 make this work, an arch will need to remove all thread_info fields
34 except flags and fix any runtime bugs.
36 One subtle change that will be needed is to use try_get_task_stack()
37 and put_task_stack() in save_thread_stack_tsk() and get_wchan().
46 depends on BROKEN || !SMP
49 config INIT_ENV_ARG_LIMIT
54 Maximum of each of the number of arguments and environment
55 variables passed to init from the kernel command line.
59 string "Cross-compiler tool prefix"
61 Same as running 'make CROSS_COMPILE=prefix-' but stored for
62 default make runs in this kernel build directory. You don't
63 need to set this unless you want the configured kernel build
64 directory to select the cross-compiler automatically.
67 bool "Compile also drivers which will not load"
70 Some drivers can be compiled on a different platform than they are
71 intended to be run on. Despite they cannot be loaded there (or even
72 when they load they cannot be used due to missing HW support),
73 developers still, opposing to distributors, might want to build such
74 drivers to compile-test them.
76 If you are a developer and want to build everything available, say Y
77 here. If you are a user/distributor, say N here to exclude useless
78 drivers to be distributed.
81 string "Local version - append to kernel release"
83 Append an extra string to the end of your kernel version.
84 This will show up when you type uname, for example.
85 The string you set here will be appended after the contents of
86 any files with a filename matching localversion* in your
87 object and source tree, in that order. Your total string can
88 be a maximum of 64 characters.
90 config LOCALVERSION_AUTO
91 bool "Automatically append version information to the version string"
94 This will try to automatically determine if the current tree is a
95 release tree by looking for git tags that belong to the current
98 A string of the format -gxxxxxxxx will be added to the localversion
99 if a git-based tree is found. The string generated by this will be
100 appended after any matching localversion* files, and after the value
101 set in CONFIG_LOCALVERSION.
103 (The actual string used here is the first eight characters produced
104 by running the command:
106 $ git rev-parse --verify HEAD
108 which is done within the script "scripts/setlocalversion".)
110 config HAVE_KERNEL_GZIP
113 config HAVE_KERNEL_BZIP2
116 config HAVE_KERNEL_LZMA
119 config HAVE_KERNEL_XZ
122 config HAVE_KERNEL_LZO
125 config HAVE_KERNEL_LZ4
129 prompt "Kernel compression mode"
131 depends on HAVE_KERNEL_GZIP || HAVE_KERNEL_BZIP2 || HAVE_KERNEL_LZMA || HAVE_KERNEL_XZ || HAVE_KERNEL_LZO || HAVE_KERNEL_LZ4
133 The linux kernel is a kind of self-extracting executable.
134 Several compression algorithms are available, which differ
135 in efficiency, compression and decompression speed.
136 Compression speed is only relevant when building a kernel.
137 Decompression speed is relevant at each boot.
139 If you have any problems with bzip2 or lzma compressed
140 kernels, mail me (Alain Knaff) <alain@knaff.lu>. (An older
141 version of this functionality (bzip2 only), for 2.4, was
142 supplied by Christian Ludwig)
144 High compression options are mostly useful for users, who
145 are low on disk space (embedded systems), but for whom ram
148 If in doubt, select 'gzip'
152 depends on HAVE_KERNEL_GZIP
154 The old and tried gzip compression. It provides a good balance
155 between compression ratio and decompression speed.
159 depends on HAVE_KERNEL_BZIP2
161 Its compression ratio and speed is intermediate.
162 Decompression speed is slowest among the choices. The kernel
163 size is about 10% smaller with bzip2, in comparison to gzip.
164 Bzip2 uses a large amount of memory. For modern kernels you
165 will need at least 8MB RAM or more for booting.
169 depends on HAVE_KERNEL_LZMA
171 This compression algorithm's ratio is best. Decompression speed
172 is between gzip and bzip2. Compression is slowest.
173 The kernel size is about 33% smaller with LZMA in comparison to gzip.
177 depends on HAVE_KERNEL_XZ
179 XZ uses the LZMA2 algorithm and instruction set specific
180 BCJ filters which can improve compression ratio of executable
181 code. The size of the kernel is about 30% smaller with XZ in
182 comparison to gzip. On architectures for which there is a BCJ
183 filter (i386, x86_64, ARM, IA-64, PowerPC, and SPARC), XZ
184 will create a few percent smaller kernel than plain LZMA.
186 The speed is about the same as with LZMA: The decompression
187 speed of XZ is better than that of bzip2 but worse than gzip
188 and LZO. Compression is slow.
192 depends on HAVE_KERNEL_LZO
194 Its compression ratio is the poorest among the choices. The kernel
195 size is about 10% bigger than gzip; however its speed
196 (both compression and decompression) is the fastest.
200 depends on HAVE_KERNEL_LZ4
202 LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding.
203 A preliminary version of LZ4 de/compression tool is available at
204 <https://code.google.com/p/lz4/>.
206 Its compression ratio is worse than LZO. The size of the kernel
207 is about 8% bigger than LZO. But the decompression speed is
212 config DEFAULT_HOSTNAME
213 string "Default hostname"
216 This option determines the default system hostname before userspace
217 calls sethostname(2). The kernel traditionally uses "(none)" here,
218 but you may wish to use a different default here to make a minimal
219 system more usable with less configuration.
222 bool "Support for paging of anonymous memory (swap)"
223 depends on MMU && BLOCK
226 This option allows you to choose whether you want to have support
227 for so called swap devices or swap files in your kernel that are
228 used to provide more virtual memory than the actual RAM present
229 in your computer. If unsure say Y.
234 Inter Process Communication is a suite of library functions and
235 system calls which let processes (running programs) synchronize and
236 exchange information. It is generally considered to be a good thing,
237 and some programs won't run unless you say Y here. In particular, if
238 you want to run the DOS emulator dosemu under Linux (read the
239 DOSEMU-HOWTO, available from <http://www.tldp.org/docs.html#howto>),
240 you'll need to say Y here.
242 You can find documentation about IPC with "info ipc" and also in
243 section 6.4 of the Linux Programmer's Guide, available from
244 <http://www.tldp.org/guides.html>.
246 config SYSVIPC_SYSCTL
253 bool "POSIX Message Queues"
256 POSIX variant of message queues is a part of IPC. In POSIX message
257 queues every message has a priority which decides about succession
258 of receiving it by a process. If you want to compile and run
259 programs written e.g. for Solaris with use of its POSIX message
260 queues (functions mq_*) say Y here.
262 POSIX message queues are visible as a filesystem called 'mqueue'
263 and can be mounted somewhere if you want to do filesystem
264 operations on message queues.
268 config POSIX_MQUEUE_SYSCTL
270 depends on POSIX_MQUEUE
274 config CROSS_MEMORY_ATTACH
275 bool "Enable process_vm_readv/writev syscalls"
279 Enabling this option adds the system calls process_vm_readv and
280 process_vm_writev which allow a process with the correct privileges
281 to directly read from or write to another process' address space.
282 See the man page for more details.
285 bool "open by fhandle syscalls"
288 If you say Y here, a user level program will be able to map
289 file names to handle and then later use the handle for
290 different file system operations. This is useful in implementing
291 userspace file servers, which now track files using handles instead
292 of names. The handle would remain the same even if file names
293 get renamed. Enables open_by_handle_at(2) and name_to_handle_at(2)
297 bool "uselib syscall"
300 This option enables the uselib syscall, a system call used in the
301 dynamic linker from libc5 and earlier. glibc does not use this
302 system call. If you intend to run programs built on libc5 or
303 earlier, you may need to enable this syscall. Current systems
304 running glibc can safely disable this.
307 bool "Auditing support"
310 Enable auditing infrastructure that can be used with another
311 kernel subsystem, such as SELinux (which requires this for
312 logging of avc messages output). Does not do system-call
313 auditing without CONFIG_AUDITSYSCALL.
315 config HAVE_ARCH_AUDITSYSCALL
319 bool "Enable system-call auditing support"
320 depends on AUDIT && HAVE_ARCH_AUDITSYSCALL
321 default y if SECURITY_SELINUX
323 Enable low-overhead system-call auditing infrastructure that
324 can be used independently or with another kernel subsystem,
329 depends on AUDITSYSCALL
334 depends on AUDITSYSCALL
337 source "kernel/irq/Kconfig"
338 source "kernel/time/Kconfig"
340 menu "CPU/Task time and stats accounting"
342 config VIRT_CPU_ACCOUNTING
346 prompt "Cputime accounting"
347 default TICK_CPU_ACCOUNTING if !PPC64
348 default VIRT_CPU_ACCOUNTING_NATIVE if PPC64
350 # Kind of a stub config for the pure tick based cputime accounting
351 config TICK_CPU_ACCOUNTING
352 bool "Simple tick based cputime accounting"
353 depends on !S390 && !NO_HZ_FULL
355 This is the basic tick based cputime accounting that maintains
356 statistics about user, system and idle time spent on per jiffies
361 config VIRT_CPU_ACCOUNTING_NATIVE
362 bool "Deterministic task and CPU time accounting"
363 depends on HAVE_VIRT_CPU_ACCOUNTING && !NO_HZ_FULL
364 select VIRT_CPU_ACCOUNTING
366 Select this option to enable more accurate task and CPU time
367 accounting. This is done by reading a CPU counter on each
368 kernel entry and exit and on transitions within the kernel
369 between system, softirq and hardirq state, so there is a
370 small performance impact. In the case of s390 or IBM POWER > 5,
371 this also enables accounting of stolen time on logically-partitioned
374 config VIRT_CPU_ACCOUNTING_GEN
375 bool "Full dynticks CPU time accounting"
376 depends on HAVE_CONTEXT_TRACKING
377 depends on HAVE_VIRT_CPU_ACCOUNTING_GEN
378 select VIRT_CPU_ACCOUNTING
379 select CONTEXT_TRACKING
381 Select this option to enable task and CPU time accounting on full
382 dynticks systems. This accounting is implemented by watching every
383 kernel-user boundaries using the context tracking subsystem.
384 The accounting is thus performed at the expense of some significant
387 For now this is only useful if you are working on the full
388 dynticks subsystem development.
392 config IRQ_TIME_ACCOUNTING
393 bool "Fine granularity task level IRQ time accounting"
394 depends on HAVE_IRQ_TIME_ACCOUNTING && !NO_HZ_FULL
396 Select this option to enable fine granularity task irq time
397 accounting. This is done by reading a timestamp on each
398 transitions between softirq and hardirq state, so there can be a
399 small performance impact.
401 If in doubt, say N here.
405 config BSD_PROCESS_ACCT
406 bool "BSD Process Accounting"
409 If you say Y here, a user level program will be able to instruct the
410 kernel (via a special system call) to write process accounting
411 information to a file: whenever a process exits, information about
412 that process will be appended to the file by the kernel. The
413 information includes things such as creation time, owning user,
414 command name, memory usage, controlling terminal etc. (the complete
415 list is in the struct acct in <file:include/linux/acct.h>). It is
416 up to the user level program to do useful things with this
417 information. This is generally a good idea, so say Y.
419 config BSD_PROCESS_ACCT_V3
420 bool "BSD Process Accounting version 3 file format"
421 depends on BSD_PROCESS_ACCT
424 If you say Y here, the process accounting information is written
425 in a new file format that also logs the process IDs of each
426 process and it's parent. Note that this file format is incompatible
427 with previous v0/v1/v2 file formats, so you will need updated tools
428 for processing it. A preliminary version of these tools is available
429 at <http://www.gnu.org/software/acct/>.
432 bool "Export task/process statistics through netlink"
437 Export selected statistics for tasks/processes through the
438 generic netlink interface. Unlike BSD process accounting, the
439 statistics are available during the lifetime of tasks/processes as
440 responses to commands. Like BSD accounting, they are sent to user
445 config TASK_DELAY_ACCT
446 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"
481 default y if !PREEMPT && SMP
483 This option selects the RCU implementation that is
484 designed for very large SMP system with hundreds or
485 thousands of CPUs. It also scales down nicely to
492 This option selects the RCU implementation that is
493 designed for very large SMP systems with hundreds or
494 thousands of CPUs, but for which real-time response
495 is also required. It also scales down nicely to
498 Select this option if you are unsure.
502 default y if !PREEMPT && !SMP
504 This option selects the RCU implementation that is
505 designed for UP systems from which real-time response
506 is not required. This option greatly reduces the
507 memory footprint of RCU.
510 bool "Make expert-level adjustments to RCU configuration"
513 This option needs to be enabled if you wish to make
514 expert-level adjustments to RCU configuration. By default,
515 no such adjustments can be made, which has the often-beneficial
516 side-effect of preventing "make oldconfig" from asking you all
517 sorts of detailed questions about how you would like numerous
518 obscure RCU options to be set up.
520 Say Y if you need to make expert-level adjustments to RCU.
522 Say N if you are unsure.
527 This option selects the sleepable version of RCU. This version
528 permits arbitrary sleeping or blocking within RCU read-side critical
536 This option enables a task-based RCU implementation that uses
537 only voluntary context switch (not preemption!), idle, and
538 user-mode execution as quiescent states.
540 config RCU_STALL_COMMON
541 def_bool ( TREE_RCU || PREEMPT_RCU || RCU_TRACE )
543 This option enables RCU CPU stall code that is common between
544 the TINY and TREE variants of RCU. The purpose is to allow
545 the tiny variants to disable RCU CPU stall warnings, while
546 making these warnings mandatory for the tree variants.
548 config CONTEXT_TRACKING
551 config CONTEXT_TRACKING_FORCE
552 bool "Force context tracking"
553 depends on CONTEXT_TRACKING
554 default y if !NO_HZ_FULL
556 The major pre-requirement for full dynticks to work is to
557 support the context tracking subsystem. But there are also
558 other dependencies to provide in order to make the full
561 This option stands for testing when an arch implements the
562 context tracking backend but doesn't yet fullfill all the
563 requirements to make the full dynticks feature working.
564 Without the full dynticks, there is no way to test the support
565 for context tracking and the subsystems that rely on it: RCU
566 userspace extended quiescent state and tickless cputime
567 accounting. This option copes with the absence of the full
568 dynticks subsystem by forcing the context tracking on all
571 Say Y only if you're working on the development of an
572 architecture backend for the context tracking.
574 Say N otherwise, this option brings an overhead that you
575 don't want in production.
579 int "Tree-based hierarchical RCU fanout value"
582 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
586 This option controls the fanout of hierarchical implementations
587 of RCU, allowing RCU to work efficiently on machines with
588 large numbers of CPUs. This value must be at least the fourth
589 root of NR_CPUS, which allows NR_CPUS to be insanely large.
590 The default value of RCU_FANOUT should be used for production
591 systems, but if you are stress-testing the RCU implementation
592 itself, small RCU_FANOUT values allow you to test large-system
593 code paths on small(er) systems.
595 Select a specific number if testing RCU itself.
596 Take the default if unsure.
598 config RCU_FANOUT_LEAF
599 int "Tree-based hierarchical RCU leaf-level fanout value"
602 depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT
605 This option controls the leaf-level fanout of hierarchical
606 implementations of RCU, and allows trading off cache misses
607 against lock contention. Systems that synchronize their
608 scheduling-clock interrupts for energy-efficiency reasons will
609 want the default because the smaller leaf-level fanout keeps
610 lock contention levels acceptably low. Very large systems
611 (hundreds or thousands of CPUs) will instead want to set this
612 value to the maximum value possible in order to reduce the
613 number of cache misses incurred during RCU's grace-period
614 initialization. These systems tend to run CPU-bound, and thus
615 are not helped by synchronized interrupts, and thus tend to
616 skew them, which reduces lock contention enough that large
617 leaf-level fanouts work well.
619 Select a specific number if testing RCU itself.
621 Select the maximum permissible value for large systems.
623 Take the default if unsure.
625 config RCU_FAST_NO_HZ
626 bool "Accelerate last non-dyntick-idle CPU's grace periods"
627 depends on NO_HZ_COMMON && SMP && RCU_EXPERT
630 This option permits CPUs to enter dynticks-idle state even if
631 they have RCU callbacks queued, and prevents RCU from waking
632 these CPUs up more than roughly once every four jiffies (by
633 default, you can adjust this using the rcutree.rcu_idle_gp_delay
634 parameter), thus improving energy efficiency. On the other
635 hand, this option increases the duration of RCU grace periods,
636 for example, slowing down synchronize_rcu().
638 Say Y if energy efficiency is critically important, and you
639 don't care about increased grace-period durations.
641 Say N if you are unsure.
643 config TREE_RCU_TRACE
644 def_bool RCU_TRACE && ( TREE_RCU || PREEMPT_RCU )
647 This option provides tracing for the TREE_RCU and
648 PREEMPT_RCU implementations, permitting Makefile to
649 trivially select kernel/rcutree_trace.c.
652 bool "Enable RCU priority boosting"
653 depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
656 This option boosts the priority of preempted RCU readers that
657 block the current preemptible RCU grace period for too long.
658 This option also prevents heavy loads from blocking RCU
659 callback invocation for all flavors of RCU.
661 Say Y here if you are working with real-time apps or heavy loads
662 Say N here if you are unsure.
664 config RCU_KTHREAD_PRIO
665 int "Real-time priority to use for RCU worker threads"
666 range 1 99 if RCU_BOOST
667 range 0 99 if !RCU_BOOST
668 default 1 if RCU_BOOST
669 default 0 if !RCU_BOOST
670 depends on RCU_EXPERT
672 This option specifies the SCHED_FIFO priority value that will be
673 assigned to the rcuc/n and rcub/n threads and is also the value
674 used for RCU_BOOST (if enabled). If you are working with a
675 real-time application that has one or more CPU-bound threads
676 running at a real-time priority level, you should set
677 RCU_KTHREAD_PRIO to a priority higher than the highest-priority
678 real-time CPU-bound application thread. The default RCU_KTHREAD_PRIO
679 value of 1 is appropriate in the common case, which is real-time
680 applications that do not have any CPU-bound threads.
682 Some real-time applications might not have a single real-time
683 thread that saturates a given CPU, but instead might have
684 multiple real-time threads that, taken together, fully utilize
685 that CPU. In this case, you should set RCU_KTHREAD_PRIO to
686 a priority higher than the lowest-priority thread that is
687 conspiring to prevent the CPU from running any non-real-time
688 tasks. For example, if one thread at priority 10 and another
689 thread at priority 5 are between themselves fully consuming
690 the CPU time on a given CPU, then RCU_KTHREAD_PRIO should be
691 set to priority 6 or higher.
693 Specify the real-time priority, or take the default if unsure.
695 config RCU_BOOST_DELAY
696 int "Milliseconds to delay boosting after RCU grace-period start"
701 This option specifies the time to wait after the beginning of
702 a given grace period before priority-boosting preempted RCU
703 readers blocking that grace period. Note that any RCU reader
704 blocking an expedited RCU grace period is boosted immediately.
706 Accept the default if unsure.
709 bool "Offload RCU callback processing from boot-selected CPUs"
710 depends on TREE_RCU || PREEMPT_RCU
711 depends on RCU_EXPERT || NO_HZ_FULL
714 Use this option to reduce OS jitter for aggressive HPC or
715 real-time workloads. It can also be used to offload RCU
716 callback invocation to energy-efficient CPUs in battery-powered
717 asymmetric multiprocessors.
719 This option offloads callback invocation from the set of
720 CPUs specified at boot time by the rcu_nocbs parameter.
721 For each such CPU, a kthread ("rcuox/N") will be created to
722 invoke callbacks, where the "N" is the CPU being offloaded,
723 and where the "x" is "b" for RCU-bh, "p" for RCU-preempt, and
724 "s" for RCU-sched. Nothing prevents this kthread from running
725 on the specified CPUs, but (1) the kthreads may be preempted
726 between each callback, and (2) affinity or cgroups can be used
727 to force the kthreads to run on whatever set of CPUs is desired.
729 Say Y here if you want to help to debug reduced OS jitter.
730 Say N here if you are unsure.
733 prompt "Build-forced no-CBs CPUs"
734 default RCU_NOCB_CPU_NONE
735 depends on RCU_NOCB_CPU
737 This option allows no-CBs CPUs (whose RCU callbacks are invoked
738 from kthreads rather than from softirq context) to be specified
739 at build time. Additional no-CBs CPUs may be specified by
740 the rcu_nocbs= boot parameter.
742 config RCU_NOCB_CPU_NONE
743 bool "No build_forced no-CBs CPUs"
745 This option does not force any of the CPUs to be no-CBs CPUs.
746 Only CPUs designated by the rcu_nocbs= boot parameter will be
747 no-CBs CPUs, whose RCU callbacks will be invoked by per-CPU
748 kthreads whose names begin with "rcuo". All other CPUs will
749 invoke their own RCU callbacks in softirq context.
751 Select this option if you want to choose no-CBs CPUs at
752 boot time, for example, to allow testing of different no-CBs
753 configurations without having to rebuild the kernel each time.
755 config RCU_NOCB_CPU_ZERO
756 bool "CPU 0 is a build_forced no-CBs CPU"
758 This option forces CPU 0 to be a no-CBs CPU, so that its RCU
759 callbacks are invoked by a per-CPU kthread whose name begins
760 with "rcuo". Additional CPUs may be designated as no-CBs
761 CPUs using the rcu_nocbs= boot parameter will be no-CBs CPUs.
762 All other CPUs will invoke their own RCU callbacks in softirq
765 Select this if CPU 0 needs to be a no-CBs CPU for real-time
766 or energy-efficiency reasons, but the real reason it exists
767 is to ensure that randconfig testing covers mixed systems.
769 config RCU_NOCB_CPU_ALL
770 bool "All CPUs are build_forced no-CBs CPUs"
772 This option forces all CPUs to be no-CBs CPUs. The rcu_nocbs=
773 boot parameter will be ignored. All CPUs' RCU callbacks will
774 be executed in the context of per-CPU rcuo kthreads created for
775 this purpose. Assuming that the kthreads whose names start with
776 "rcuo" are bound to "housekeeping" CPUs, this reduces OS jitter
777 on the remaining CPUs, but might decrease memory locality during
778 RCU-callback invocation, thus potentially degrading throughput.
780 Select this if all CPUs need to be no-CBs CPUs for real-time
781 or energy-efficiency reasons.
785 config RCU_EXPEDITE_BOOT
789 This option enables expedited grace periods at boot time,
790 as if rcu_expedite_gp() had been invoked early in boot.
791 The corresponding rcu_unexpedite_gp() is invoked from
792 rcu_end_inkernel_boot(), which is intended to be invoked
793 at the end of the kernel-only boot sequence, just before
796 Accept the default if unsure.
798 endmenu # "RCU Subsystem"
805 tristate "Kernel .config support"
808 This option enables the complete Linux kernel ".config" file
809 contents to be saved in the kernel. It provides documentation
810 of which kernel options are used in a running kernel or in an
811 on-disk kernel. This information can be extracted from the kernel
812 image file with the script scripts/extract-ikconfig and used as
813 input to rebuild the current kernel or to build another kernel.
814 It can also be extracted from a running kernel by reading
815 /proc/config.gz if enabled (below).
818 bool "Enable access to .config through /proc/config.gz"
819 depends on IKCONFIG && PROC_FS
821 This option enables access to the kernel configuration file
822 through /proc/config.gz.
825 int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
826 range 12 25 if !H8300
831 Select the minimal kernel log buffer size as a power of 2.
832 The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
833 parameter, see below. Any higher size also might be forced
834 by "log_buf_len" boot parameter.
844 config LOG_CPU_MAX_BUF_SHIFT
845 int "CPU kernel log buffer size contribution (13 => 8 KB, 17 => 128KB)"
848 default 12 if !BASE_SMALL
849 default 0 if BASE_SMALL
852 This option allows to increase the default ring buffer size
853 according to the number of CPUs. The value defines the contribution
854 of each CPU as a power of 2. The used space is typically only few
855 lines however it might be much more when problems are reported,
858 The increased size means that a new buffer has to be allocated and
859 the original static one is unused. It makes sense only on systems
860 with more CPUs. Therefore this value is used only when the sum of
861 contributions is greater than the half of the default kernel ring
862 buffer as defined by LOG_BUF_SHIFT. The default values are set
863 so that more than 64 CPUs are needed to trigger the allocation.
865 Also this option is ignored when "log_buf_len" kernel parameter is
866 used as it forces an exact (power of two) size of the ring buffer.
868 The number of possible CPUs is used for this computation ignoring
869 hotplugging making the compuation optimal for the the worst case
870 scenerio while allowing a simple algorithm to be used from bootup.
872 Examples shift values and their meaning:
873 17 => 128 KB for each CPU
874 16 => 64 KB for each CPU
875 15 => 32 KB for each CPU
876 14 => 16 KB for each CPU
877 13 => 8 KB for each CPU
878 12 => 4 KB for each CPU
881 # Architectures with an unreliable sched_clock() should select this:
883 config HAVE_UNSTABLE_SCHED_CLOCK
886 config GENERIC_SCHED_CLOCK
890 # For architectures that want to enable the support for NUMA-affine scheduler
893 config ARCH_SUPPORTS_NUMA_BALANCING
897 # For architectures that prefer to flush all TLBs after a number of pages
898 # are unmapped instead of sending one IPI per page to flush. The architecture
899 # must provide guarantees on what happens if a clean TLB cache entry is
900 # written after the unmap. Details are in mm/rmap.c near the check for
901 # should_defer_flush. The architecture should also consider if the full flush
902 # and the refill costs are offset by the savings of sending fewer IPIs.
903 config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
907 # For architectures that know their GCC __int128 support is sound
909 config ARCH_SUPPORTS_INT128
912 # For architectures that (ab)use NUMA to represent different memory regions
913 # all cpu-local but of different latencies, such as SuperH.
915 config ARCH_WANT_NUMA_VARIABLE_LOCALITY
918 config NUMA_BALANCING
919 bool "Memory placement aware NUMA scheduler"
920 depends on ARCH_SUPPORTS_NUMA_BALANCING
921 depends on !ARCH_WANT_NUMA_VARIABLE_LOCALITY
922 depends on SMP && NUMA && MIGRATION
924 This option adds support for automatic NUMA aware memory/task placement.
925 The mechanism is quite primitive and is based on migrating memory when
926 it has references to the node the task is running on.
928 This system will be inactive on UMA systems.
930 config NUMA_BALANCING_DEFAULT_ENABLED
931 bool "Automatically enable NUMA aware memory/task placement"
933 depends on NUMA_BALANCING
935 If set, automatic NUMA balancing will be enabled if running on a NUMA
939 bool "Control Group support"
942 This option adds support for grouping sets of processes together, for
943 use with process control subsystems such as Cpusets, CFS, memory
944 controls or device isolation.
946 - Documentation/scheduler/sched-design-CFS.txt (CFS)
947 - Documentation/cgroups/ (features for grouping, isolation
948 and resource control)
955 bool "Example debug cgroup subsystem"
958 This option enables a simple cgroup subsystem that
959 exports useful debugging information about the cgroups
964 config CGROUP_FREEZER
965 bool "Freezer cgroup subsystem"
967 Provides a way to freeze and unfreeze all tasks in a
971 bool "PIDs cgroup subsystem"
973 Provides enforcement of process number limits in the scope of a
974 cgroup. Any attempt to fork more processes than is allowed in the
975 cgroup will fail. PIDs are fundamentally a global resource because it
976 is fairly trivial to reach PID exhaustion before you reach even a
977 conservative kmemcg limit. As a result, it is possible to grind a
978 system to halt without being limited by other cgroup policies. The
979 PIDs cgroup subsystem is designed to stop this from happening.
981 It should be noted that organisational operations (such as attaching
982 to a cgroup hierarchy will *not* be blocked by the PIDs subsystem),
983 since the PIDs limit only affects a process's ability to fork, not to
987 bool "Device controller for cgroups"
989 Provides a cgroup implementing whitelists for devices which
990 a process in the cgroup can mknod or open.
993 bool "Cpuset support"
995 This option will let you create and manage CPUSETs which
996 allow dynamically partitioning a system into sets of CPUs and
997 Memory Nodes and assigning tasks to run only within those sets.
998 This is primarily useful on large SMP or NUMA systems.
1002 config PROC_PID_CPUSET
1003 bool "Include legacy /proc/<pid>/cpuset file"
1007 config CGROUP_CPUACCT
1008 bool "Simple CPU accounting cgroup subsystem"
1010 Provides a simple Resource Controller for monitoring the
1011 total CPU consumed by the tasks in a cgroup.
1017 bool "Memory Resource Controller for Control Groups"
1021 Provides a memory resource controller that manages both anonymous
1022 memory and page cache. (See Documentation/cgroups/memory.txt)
1025 bool "Memory Resource Controller Swap Extension"
1026 depends on MEMCG && SWAP
1028 Add swap management feature to memory resource controller. When you
1029 enable this, you can limit mem+swap usage per cgroup. In other words,
1030 when you disable this, memory resource controller has no cares to
1031 usage of swap...a process can exhaust all of the swap. This extension
1032 is useful when you want to avoid exhaustion swap but this itself
1033 adds more overheads and consumes memory for remembering information.
1034 Especially if you use 32bit system or small memory system, please
1035 be careful about enabling this. When memory resource controller
1036 is disabled by boot option, this will be automatically disabled and
1037 there will be no overhead from this. Even when you set this config=y,
1038 if boot option "swapaccount=0" is set, swap will not be accounted.
1039 Now, memory usage of swap_cgroup is 2 bytes per entry. If swap page
1040 size is 4096bytes, 512k per 1Gbytes of swap.
1041 config MEMCG_SWAP_ENABLED
1042 bool "Memory Resource Controller Swap Extension enabled by default"
1043 depends on MEMCG_SWAP
1046 Memory Resource Controller Swap Extension comes with its price in
1047 a bigger memory consumption. General purpose distribution kernels
1048 which want to enable the feature but keep it disabled by default
1049 and let the user enable it by swapaccount=1 boot command line
1050 parameter should have this option unselected.
1051 For those who want to have the feature enabled by default should
1052 select this option (if, for some reason, they need to disable it
1053 then swapaccount=0 does the trick).
1055 bool "Memory Resource Controller Kernel Memory accounting"
1057 depends on SLUB || SLAB
1059 The Kernel Memory extension for Memory Resource Controller can limit
1060 the amount of memory used by kernel objects in the system. Those are
1061 fundamentally different from the entities handled by the standard
1062 Memory Controller, which are page-based, and can be swapped. Users of
1063 the kmem extension can use it to guarantee that no group of processes
1064 will ever exhaust kernel resources alone.
1066 config CGROUP_HUGETLB
1067 bool "HugeTLB Resource Controller for Control Groups"
1068 depends on HUGETLB_PAGE
1072 Provides a cgroup Resource Controller for HugeTLB pages.
1073 When you enable this, you can put a per cgroup limit on HugeTLB usage.
1074 The limit is enforced during page fault. Since HugeTLB doesn't
1075 support page reclaim, enforcing the limit at page fault time implies
1076 that, the application will get SIGBUS signal if it tries to access
1077 HugeTLB pages beyond its limit. This requires the application to know
1078 beforehand how much HugeTLB pages it would require for its use. The
1079 control group is tracked in the third page lru pointer. This means
1080 that we cannot use the controller with huge page less than 3 pages.
1083 bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
1084 depends on PERF_EVENTS && CGROUPS
1086 This option extends the per-cpu mode to restrict monitoring to
1087 threads which belong to the cgroup specified and run on the
1092 menuconfig CGROUP_SCHED
1093 bool "Group CPU scheduler"
1096 This feature lets CPU scheduler recognize task groups and control CPU
1097 bandwidth allocation to such task groups. It uses cgroups to group
1101 config FAIR_GROUP_SCHED
1102 bool "Group scheduling for SCHED_OTHER"
1103 depends on CGROUP_SCHED
1104 default CGROUP_SCHED
1106 config CFS_BANDWIDTH
1107 bool "CPU bandwidth provisioning for FAIR_GROUP_SCHED"
1108 depends on FAIR_GROUP_SCHED
1111 This option allows users to define CPU bandwidth rates (limits) for
1112 tasks running within the fair group scheduler. Groups with no limit
1113 set are considered to be unconstrained and will run with no
1115 See tip/Documentation/scheduler/sched-bwc.txt for more information.
1117 config RT_GROUP_SCHED
1118 bool "Group scheduling for SCHED_RR/FIFO"
1119 depends on CGROUP_SCHED
1122 This feature lets you explicitly allocate real CPU bandwidth
1123 to task groups. If enabled, it will also make it impossible to
1124 schedule realtime tasks for non-root users until you allocate
1125 realtime bandwidth for them.
1126 See Documentation/scheduler/sched-rt-group.txt for more information.
1131 bool "Block IO controller"
1135 Generic block IO controller cgroup interface. This is the common
1136 cgroup interface which should be used by various IO controlling
1139 Currently, CFQ IO scheduler uses it to recognize task groups and
1140 control disk bandwidth allocation (proportional time slice allocation)
1141 to such task groups. It is also used by bio throttling logic in
1142 block layer to implement upper limit in IO rates on a device.
1144 This option only enables generic Block IO controller infrastructure.
1145 One needs to also enable actual IO controlling logic/policy. For
1146 enabling proportional weight division of disk bandwidth in CFQ, set
1147 CONFIG_CFQ_GROUP_IOSCHED=y; for enabling throttling policy, set
1148 CONFIG_BLK_DEV_THROTTLING=y.
1150 See Documentation/cgroups/blkio-controller.txt for more information.
1152 config DEBUG_BLK_CGROUP
1153 bool "Enable Block IO controller debugging"
1154 depends on BLK_CGROUP
1157 Enable some debugging help. Currently it exports additional stat
1158 files in a cgroup which can be useful for debugging.
1160 config CGROUP_WRITEBACK
1162 depends on MEMCG && BLK_CGROUP
1167 config CHECKPOINT_RESTORE
1168 bool "Checkpoint/restore support" if EXPERT
1169 select PROC_CHILDREN
1172 Enables additional kernel features in a sake of checkpoint/restore.
1173 In particular it adds auxiliary prctl codes to setup process text,
1174 data and heap segment sizes, and a few additional /proc filesystem
1177 If unsure, say N here.
1179 menuconfig NAMESPACES
1180 bool "Namespaces support" if EXPERT
1181 depends on MULTIUSER
1184 Provides the way to make tasks work with different objects using
1185 the same id. For example same IPC id may refer to different objects
1186 or same user id or pid may refer to different tasks when used in
1187 different namespaces.
1192 bool "UTS namespace"
1195 In this namespace tasks see different info provided with the
1199 bool "IPC namespace"
1200 depends on (SYSVIPC || POSIX_MQUEUE)
1203 In this namespace tasks work with IPC ids which correspond to
1204 different IPC objects in different namespaces.
1207 bool "User namespace"
1210 This allows containers, i.e. vservers, to use user namespaces
1211 to provide different user info for different servers.
1213 When user namespaces are enabled in the kernel it is
1214 recommended that the MEMCG and MEMCG_KMEM options also be
1215 enabled and that user-space use the memory control groups to
1216 limit the amount of memory a memory unprivileged users can
1222 bool "PID Namespaces"
1225 Support process id namespaces. This allows having multiple
1226 processes with the same pid as long as they are in different
1227 pid namespaces. This is a building block of containers.
1230 bool "Network namespace"
1234 Allow user space to create what appear to be multiple instances
1235 of the network stack.
1239 config SCHED_AUTOGROUP
1240 bool "Automatic process group scheduling"
1243 select FAIR_GROUP_SCHED
1245 This option optimizes the scheduler for common desktop workloads by
1246 automatically creating and populating task groups. This separation
1247 of workloads isolates aggressive CPU burners (like build jobs) from
1248 desktop applications. Task group autogeneration is currently based
1251 config SYSFS_DEPRECATED
1252 bool "Enable deprecated sysfs features to support old userspace tools"
1256 This option adds code that switches the layout of the "block" class
1257 devices, to not show up in /sys/class/block/, but only in
1260 This switch is only active when the sysfs.deprecated=1 boot option is
1261 passed or the SYSFS_DEPRECATED_V2 option is set.
1263 This option allows new kernels to run on old distributions and tools,
1264 which might get confused by /sys/class/block/. Since 2007/2008 all
1265 major distributions and tools handle this just fine.
1267 Recent distributions and userspace tools after 2009/2010 depend on
1268 the existence of /sys/class/block/, and will not work with this
1271 Only if you are using a new kernel on an old distribution, you might
1274 config SYSFS_DEPRECATED_V2
1275 bool "Enable deprecated sysfs features by default"
1278 depends on SYSFS_DEPRECATED
1280 Enable deprecated sysfs by default.
1282 See the CONFIG_SYSFS_DEPRECATED option for more details about this
1285 Only if you are using a new kernel on an old distribution, you might
1286 need to say Y here. Even then, odds are you would not need it
1287 enabled, you can always pass the boot option if absolutely necessary.
1290 bool "Kernel->user space relay support (formerly relayfs)"
1292 This option enables support for relay interface support in
1293 certain file systems (such as debugfs).
1294 It is designed to provide an efficient mechanism for tools and
1295 facilities to relay large amounts of data from kernel space to
1300 config BLK_DEV_INITRD
1301 bool "Initial RAM filesystem and RAM disk (initramfs/initrd) support"
1302 depends on BROKEN || !FRV
1304 The initial RAM filesystem is a ramfs which is loaded by the
1305 boot loader (loadlin or lilo) and that is mounted as root
1306 before the normal boot procedure. It is typically used to
1307 load modules needed to mount the "real" root file system,
1308 etc. See <file:Documentation/initrd.txt> for details.
1310 If RAM disk support (BLK_DEV_RAM) is also included, this
1311 also enables initial RAM disk (initrd) support and adds
1312 15 Kbytes (more on some other architectures) to the kernel size.
1318 source "usr/Kconfig"
1323 prompt "Compiler optimization level"
1324 default CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE
1326 config CC_OPTIMIZE_FOR_PERFORMANCE
1327 bool "Optimize for performance"
1329 This is the default optimization level for the kernel, building
1330 with the "-O2" compiler flag for best performance and most
1331 helpful compile-time warnings.
1333 config CC_OPTIMIZE_FOR_SIZE
1334 bool "Optimize for size"
1336 Enabling this option will pass "-Os" instead of "-O2" to
1337 your compiler resulting in a smaller kernel.
1352 config SYSCTL_EXCEPTION_TRACE
1355 Enable support for /proc/sys/debug/exception-trace.
1357 config SYSCTL_ARCH_UNALIGN_NO_WARN
1360 Enable support for /proc/sys/kernel/ignore-unaligned-usertrap
1361 Allows arch to define/use @no_unaligned_warning to possibly warn
1362 about unaligned access emulation going on under the hood.
1364 config SYSCTL_ARCH_UNALIGN_ALLOW
1367 Enable support for /proc/sys/kernel/unaligned-trap
1368 Allows arches to define/use @unaligned_enabled to runtime toggle
1369 the unaligned access emulation.
1370 see arch/parisc/kernel/unaligned.c for reference
1372 config HAVE_PCSPKR_PLATFORM
1375 # interpreter that classic socket filters depend on
1380 bool "Configure standard kernel features (expert users)"
1381 # Unhide debug options, to make the on-by-default options visible
1384 This option allows certain base kernel options and settings
1385 to be disabled or tweaked. This is for specialized
1386 environments which can tolerate a "non-standard" kernel.
1387 Only use this if you really know what you are doing.
1390 bool "Enable 16-bit UID system calls" if EXPERT
1391 depends on HAVE_UID16 && MULTIUSER
1394 This enables the legacy 16-bit UID syscall wrappers.
1397 bool "Multiple users, groups and capabilities support" if EXPERT
1400 This option enables support for non-root users, groups and
1403 If you say N here, all processes will run with UID 0, GID 0, and all
1404 possible capabilities. Saying N here also compiles out support for
1405 system calls related to UIDs, GIDs, and capabilities, such as setuid,
1408 If unsure, say Y here.
1410 config SGETMASK_SYSCALL
1411 bool "sgetmask/ssetmask syscalls support" if EXPERT
1412 def_bool PARISC || MN10300 || BLACKFIN || M68K || PPC || MIPS || X86 || SPARC || CRIS || MICROBLAZE || SUPERH
1414 sys_sgetmask and sys_ssetmask are obsolete system calls
1415 no longer supported in libc but still enabled by default in some
1418 If unsure, leave the default option here.
1420 config SYSFS_SYSCALL
1421 bool "Sysfs syscall support" if EXPERT
1424 sys_sysfs is an obsolete system call no longer supported in libc.
1425 Note that disabling this option is more secure but might break
1426 compatibility with some systems.
1428 If unsure say Y here.
1430 config SYSCTL_SYSCALL
1431 bool "Sysctl syscall support" if EXPERT
1432 depends on PROC_SYSCTL
1436 sys_sysctl uses binary paths that have been found challenging
1437 to properly maintain and use. The interface in /proc/sys
1438 using paths with ascii names is now the primary path to this
1441 Almost nothing using the binary sysctl interface so if you are
1442 trying to save some space it is probably safe to disable this,
1443 making your kernel marginally smaller.
1445 If unsure say N here.
1448 bool "Load all symbols for debugging/ksymoops" if EXPERT
1451 Say Y here to let the kernel print out symbolic crash information and
1452 symbolic stack backtraces. This increases the size of the kernel
1453 somewhat, as all symbols have to be loaded into the kernel image.
1456 bool "Include all symbols in kallsyms"
1457 depends on DEBUG_KERNEL && KALLSYMS
1459 Normally kallsyms only contains the symbols of functions for nicer
1460 OOPS messages and backtraces (i.e., symbols from the text and inittext
1461 sections). This is sufficient for most cases. And only in very rare
1462 cases (e.g., when a debugger is used) all symbols are required (e.g.,
1463 names of variables from the data sections, etc).
1465 This option makes sure that all symbols are loaded into the kernel
1466 image (i.e., symbols from all sections) in cost of increased kernel
1467 size (depending on the kernel configuration, it may be 300KiB or
1468 something like this).
1470 Say N unless you really need all symbols.
1474 bool "Enable support for printk" if EXPERT
1477 This option enables normal printk support. Removing it
1478 eliminates most of the message strings from the kernel image
1479 and makes the kernel more or less silent. As this makes it
1480 very difficult to diagnose system problems, saying N here is
1481 strongly discouraged.
1484 bool "BUG() support" if EXPERT
1487 Disabling this option eliminates support for BUG and WARN, reducing
1488 the size of your kernel image and potentially quietly ignoring
1489 numerous fatal conditions. You should only consider disabling this
1490 option for embedded systems with no facilities for reporting errors.
1496 bool "Enable ELF core dumps" if EXPERT
1498 Enable support for generating core dumps. Disabling saves about 4k.
1501 config PCSPKR_PLATFORM
1502 bool "Enable PC-Speaker support" if EXPERT
1503 depends on HAVE_PCSPKR_PLATFORM
1507 This option allows to disable the internal PC-Speaker
1508 support, saving some memory.
1512 bool "Enable full-sized data structures for core" if EXPERT
1514 Disabling this option reduces the size of miscellaneous core
1515 kernel data structures. This saves memory on small machines,
1516 but may reduce performance.
1519 bool "Enable futex support" if EXPERT
1523 Disabling this option will cause the kernel to be built without
1524 support for "fast userspace mutexes". The resulting kernel may not
1525 run glibc-based applications correctly.
1527 config HAVE_FUTEX_CMPXCHG
1531 Architectures should select this if futex_atomic_cmpxchg_inatomic()
1532 is implemented and always working. This removes a couple of runtime
1536 bool "Enable eventpoll support" if EXPERT
1540 Disabling this option will cause the kernel to be built without
1541 support for epoll family of system calls.
1544 bool "Enable signalfd() system call" if EXPERT
1548 Enable the signalfd() system call that allows to receive signals
1549 on a file descriptor.
1554 bool "Enable timerfd() system call" if EXPERT
1558 Enable the timerfd() system call that allows to receive timer
1559 events on a file descriptor.
1564 bool "Enable eventfd() system call" if EXPERT
1568 Enable the eventfd() system call that allows to receive both
1569 kernel notification (ie. KAIO) or userspace notifications.
1573 # syscall, maps, verifier
1575 bool "Enable bpf() system call"
1580 Enable the bpf() system call that allows to manipulate eBPF
1581 programs and maps via file descriptors.
1583 config BPF_JIT_ALWAYS_ON
1584 bool "Permanently enable BPF JIT and remove BPF interpreter"
1585 depends on BPF_SYSCALL && HAVE_EBPF_JIT && BPF_JIT
1587 Enables BPF JIT and removes BPF interpreter to avoid
1588 speculative execution of BPF instructions by the interpreter
1591 bool "Use full shmem filesystem" if EXPERT
1595 The shmem is an internal filesystem used to manage shared memory.
1596 It is backed by swap and manages resource limits. It is also exported
1597 to userspace as tmpfs if TMPFS is enabled. Disabling this
1598 option replaces shmem and tmpfs with the much simpler ramfs code,
1599 which may be appropriate on small systems without swap.
1602 bool "Enable AIO support" if EXPERT
1605 This option enables POSIX asynchronous I/O which may by used
1606 by some high performance threaded applications. Disabling
1607 this option saves about 7k.
1609 config ADVISE_SYSCALLS
1610 bool "Enable madvise/fadvise syscalls" if EXPERT
1613 This option enables the madvise and fadvise syscalls, used by
1614 applications to advise the kernel about their future memory or file
1615 usage, improving performance. If building an embedded system where no
1616 applications use these syscalls, you can disable this option to save
1620 bool "Enable userfaultfd() system call"
1624 Enable the userfaultfd() system call that allows to intercept and
1625 handle page faults in userland.
1629 bool "Enable PCI quirk workarounds" if EXPERT
1632 This enables workarounds for various PCI chipset
1633 bugs/quirks. Disable this only if your target machine is
1634 unaffected by PCI quirks.
1637 bool "Enable membarrier() system call" if EXPERT
1640 Enable the membarrier() system call that allows issuing memory
1641 barriers across all running threads, which can be used to distribute
1642 the cost of user-space memory barriers asymmetrically by transforming
1643 pairs of memory barriers into pairs consisting of membarrier() and a
1649 bool "Embedded system"
1650 option allnoconfig_y
1653 This option should be enabled if compiling the kernel for
1654 an embedded system so certain expert options are available
1657 config HAVE_PERF_EVENTS
1660 See tools/perf/design.txt for details.
1662 config PERF_USE_VMALLOC
1665 See tools/perf/design.txt for details
1667 menu "Kernel Performance Events And Counters"
1670 bool "Kernel performance events and counters"
1671 default y if PROFILING
1672 depends on HAVE_PERF_EVENTS
1677 Enable kernel support for various performance events provided
1678 by software and hardware.
1680 Software events are supported either built-in or via the
1681 use of generic tracepoints.
1683 Most modern CPUs support performance events via performance
1684 counter registers. These registers count the number of certain
1685 types of hw events: such as instructions executed, cachemisses
1686 suffered, or branches mis-predicted - without slowing down the
1687 kernel or applications. These registers can also trigger interrupts
1688 when a threshold number of events have passed - and can thus be
1689 used to profile the code that runs on that CPU.
1691 The Linux Performance Event subsystem provides an abstraction of
1692 these software and hardware event capabilities, available via a
1693 system call and used by the "perf" utility in tools/perf/. It
1694 provides per task and per CPU counters, and it provides event
1695 capabilities on top of those.
1699 config DEBUG_PERF_USE_VMALLOC
1701 bool "Debug: use vmalloc to back perf mmap() buffers"
1702 depends on PERF_EVENTS && DEBUG_KERNEL && !PPC
1703 select PERF_USE_VMALLOC
1705 Use vmalloc memory to back perf mmap() buffers.
1707 Mostly useful for debugging the vmalloc code on platforms
1708 that don't require it.
1714 config VM_EVENT_COUNTERS
1716 bool "Enable VM event counters for /proc/vmstat" if EXPERT
1718 VM event counters are needed for event counts to be shown.
1719 This option allows the disabling of the VM event counters
1720 on EXPERT systems. /proc/vmstat will only show page counts
1721 if VM event counters are disabled.
1725 bool "Enable SLUB debugging support" if EXPERT
1726 depends on SLUB && SYSFS
1728 SLUB has extensive debug support features. Disabling these can
1729 result in significant savings in code size. This also disables
1730 SLUB sysfs support. /sys/slab will not exist and there will be
1731 no support for cache validation etc.
1734 bool "Disable heap randomization"
1737 Randomizing heap placement makes heap exploits harder, but it
1738 also breaks ancient binaries (including anything libc5 based).
1739 This option changes the bootup default to heap randomization
1740 disabled, and can be overridden at runtime by setting
1741 /proc/sys/kernel/randomize_va_space to 2.
1743 On non-ancient distros (post-2000 ones) N is usually a safe choice.
1746 prompt "Choose SLAB allocator"
1749 This option allows to select a slab allocator.
1754 The regular slab allocator that is established and known to work
1755 well in all environments. It organizes cache hot objects in
1756 per cpu and per node queues.
1759 bool "SLUB (Unqueued Allocator)"
1761 SLUB is a slab allocator that minimizes cache line usage
1762 instead of managing queues of cached objects (SLAB approach).
1763 Per cpu caching is realized using slabs of objects instead
1764 of queues of objects. SLUB can use memory efficiently
1765 and has enhanced diagnostics. SLUB is the default choice for
1770 bool "SLOB (Simple Allocator)"
1772 SLOB replaces the stock allocator with a drastically simpler
1773 allocator. SLOB is generally more space efficient but
1774 does not perform as well on large systems.
1778 config SLUB_CPU_PARTIAL
1780 depends on SLUB && SMP
1781 bool "SLUB per cpu partial cache"
1783 Per cpu partial caches accellerate objects allocation and freeing
1784 that is local to a processor at the price of more indeterminism
1785 in the latency of the free. On overflow these caches will be cleared
1786 which requires the taking of locks that may cause latency spikes.
1787 Typically one would choose no for a realtime system.
1789 config MMAP_ALLOW_UNINITIALIZED
1790 bool "Allow mmapped anonymous memory to be uninitialized"
1791 depends on EXPERT && !MMU
1794 Normally, and according to the Linux spec, anonymous memory obtained
1795 from mmap() has it's contents cleared before it is passed to
1796 userspace. Enabling this config option allows you to request that
1797 mmap() skip that if it is given an MAP_UNINITIALIZED flag, thus
1798 providing a huge performance boost. If this option is not enabled,
1799 then the flag will be ignored.
1801 This is taken advantage of by uClibc's malloc(), and also by
1802 ELF-FDPIC binfmt's brk and stack allocator.
1804 Because of the obvious security issues, this option should only be
1805 enabled on embedded devices where you control what is run in
1806 userspace. Since that isn't generally a problem on no-MMU systems,
1807 it is normally safe to say Y here.
1809 See Documentation/nommu-mmap.txt for more information.
1811 config SYSTEM_DATA_VERIFICATION
1813 select SYSTEM_TRUSTED_KEYRING
1816 select ASYMMETRIC_KEY_TYPE
1817 select ASYMMETRIC_PUBLIC_KEY_SUBTYPE
1818 select PUBLIC_KEY_ALGO_RSA
1821 select X509_CERTIFICATE_PARSER
1822 select PKCS7_MESSAGE_PARSER
1824 Provide PKCS#7 message verification using the contents of the system
1825 trusted keyring to provide public keys. This then can be used for
1826 module verification, kexec image verification and firmware blob
1830 bool "Profiling support"
1832 Say Y here to enable the extended profiling support mechanisms used
1833 by profilers such as OProfile.
1836 # Place an empty function call at each tracepoint site. Can be
1837 # dynamically changed for a probe function.
1842 source "arch/Kconfig"
1844 endmenu # General setup
1846 config HAVE_GENERIC_DMA_COHERENT
1853 depends on SLAB || SLUB_DEBUG
1861 default 0 if BASE_FULL
1862 default 1 if !BASE_FULL
1865 bool "Enable loadable module support"
1868 Kernel modules are small pieces of compiled code which can
1869 be inserted in the running kernel, rather than being
1870 permanently built into the kernel. You use the "modprobe"
1871 tool to add (and sometimes remove) them. If you say Y here,
1872 many parts of the kernel can be built as modules (by
1873 answering M instead of Y where indicated): this is most
1874 useful for infrequently used options which are not required
1875 for booting. For more information, see the man pages for
1876 modprobe, lsmod, modinfo, insmod and rmmod.
1878 If you say Y here, you will need to run "make
1879 modules_install" to put the modules under /lib/modules/
1880 where modprobe can find them (you may need to be root to do
1887 config MODULE_FORCE_LOAD
1888 bool "Forced module loading"
1891 Allow loading of modules without version information (ie. modprobe
1892 --force). Forced module loading sets the 'F' (forced) taint flag and
1893 is usually a really bad idea.
1895 config MODULE_UNLOAD
1896 bool "Module unloading"
1898 Without this option you will not be able to unload any
1899 modules (note that some modules may not be unloadable
1900 anyway), which makes your kernel smaller, faster
1901 and simpler. If unsure, say Y.
1903 config MODULE_FORCE_UNLOAD
1904 bool "Forced module unloading"
1905 depends on MODULE_UNLOAD
1907 This option allows you to force a module to unload, even if the
1908 kernel believes it is unsafe: the kernel will remove the module
1909 without waiting for anyone to stop using it (using the -f option to
1910 rmmod). This is mainly for kernel developers and desperate users.
1914 bool "Module versioning support"
1916 Usually, you have to use modules compiled with your kernel.
1917 Saying Y here makes it sometimes possible to use modules
1918 compiled for different kernels, by adding enough information
1919 to the modules to (hopefully) spot any changes which would
1920 make them incompatible with the kernel you are running. If
1923 config MODULE_SRCVERSION_ALL
1924 bool "Source checksum for all modules"
1926 Modules which contain a MODULE_VERSION get an extra "srcversion"
1927 field inserted into their modinfo section, which contains a
1928 sum of the source files which made it. This helps maintainers
1929 see exactly which source was used to build a module (since
1930 others sometimes change the module source without updating
1931 the version). With this option, such a "srcversion" field
1932 will be created for all modules. If unsure, say N.
1935 bool "Module signature verification"
1937 select SYSTEM_DATA_VERIFICATION
1939 Check modules for valid signatures upon load: the signature
1940 is simply appended to the module. For more information see
1941 Documentation/module-signing.txt.
1943 Note that this option adds the OpenSSL development packages as a
1944 kernel build dependency so that the signing tool can use its crypto
1947 !!!WARNING!!! If you enable this option, you MUST make sure that the
1948 module DOES NOT get stripped after being signed. This includes the
1949 debuginfo strip done by some packagers (such as rpmbuild) and
1950 inclusion into an initramfs that wants the module size reduced.
1952 config MODULE_SIG_FORCE
1953 bool "Require modules to be validly signed"
1954 depends on MODULE_SIG
1956 Reject unsigned modules or signed modules for which we don't have a
1957 key. Without this, such modules will simply taint the kernel.
1959 config MODULE_SIG_ALL
1960 bool "Automatically sign all modules"
1962 depends on MODULE_SIG
1964 Sign all modules during make modules_install. Without this option,
1965 modules must be signed manually, using the scripts/sign-file tool.
1967 comment "Do not forget to sign required modules with scripts/sign-file"
1968 depends on MODULE_SIG_FORCE && !MODULE_SIG_ALL
1971 prompt "Which hash algorithm should modules be signed with?"
1972 depends on MODULE_SIG
1974 This determines which sort of hashing algorithm will be used during
1975 signature generation. This algorithm _must_ be built into the kernel
1976 directly so that signature verification can take place. It is not
1977 possible to load a signed module containing the algorithm to check
1978 the signature on that module.
1980 config MODULE_SIG_SHA1
1981 bool "Sign modules with SHA-1"
1984 config MODULE_SIG_SHA224
1985 bool "Sign modules with SHA-224"
1986 select CRYPTO_SHA256
1988 config MODULE_SIG_SHA256
1989 bool "Sign modules with SHA-256"
1990 select CRYPTO_SHA256
1992 config MODULE_SIG_SHA384
1993 bool "Sign modules with SHA-384"
1994 select CRYPTO_SHA512
1996 config MODULE_SIG_SHA512
1997 bool "Sign modules with SHA-512"
1998 select CRYPTO_SHA512
2002 config MODULE_SIG_HASH
2004 depends on MODULE_SIG
2005 default "sha1" if MODULE_SIG_SHA1
2006 default "sha224" if MODULE_SIG_SHA224
2007 default "sha256" if MODULE_SIG_SHA256
2008 default "sha384" if MODULE_SIG_SHA384
2009 default "sha512" if MODULE_SIG_SHA512
2011 config MODULE_COMPRESS
2012 bool "Compress modules on installation"
2016 Compresses kernel modules when 'make modules_install' is run; gzip or
2017 xz depending on "Compression algorithm" below.
2019 module-init-tools MAY support gzip, and kmod MAY support gzip and xz.
2021 Out-of-tree kernel modules installed using Kbuild will also be
2022 compressed upon installation.
2024 Note: for modules inside an initrd or initramfs, it's more efficient
2025 to compress the whole initrd or initramfs instead.
2027 Note: This is fully compatible with signed modules.
2032 prompt "Compression algorithm"
2033 depends on MODULE_COMPRESS
2034 default MODULE_COMPRESS_GZIP
2036 This determines which sort of compression will be used during
2037 'make modules_install'.
2039 GZIP (default) and XZ are supported.
2041 config MODULE_COMPRESS_GZIP
2044 config MODULE_COMPRESS_XZ
2051 config MODULES_TREE_LOOKUP
2053 depends on PERF_EVENTS || TRACING
2055 config INIT_ALL_POSSIBLE
2058 Back when each arch used to define their own cpu_online_mask and
2059 cpu_possible_mask, some of them chose to initialize cpu_possible_mask
2060 with all 1s, and others with all 0s. When they were centralised,
2061 it was better to provide this option than to break all the archs
2062 and have several arch maintainers pursuing me down dark alleys.
2064 source "block/Kconfig"
2066 config PREEMPT_NOTIFIERS
2073 # Can be selected by architectures with broken toolchains
2074 # that get confused by correct const<->read_only section
2076 config BROKEN_RODATA
2082 Build a simple ASN.1 grammar compiler that produces a bytecode output
2083 that can be interpreted by the ASN.1 stream decoder and used to
2084 inform it as to what tags are to be expected in a stream and what
2085 functions to call on what tags.
2087 source "kernel/Kconfig.locks"
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